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Journal of Bacteriology  1963;85(4):918-926.
Bateman, J. B. (U.S. Army Biological Laboratories, Fort Detrick, Frederick, Md.) and F. Elizabeth White. Effect of relative humidity on the survival of Serratia marcescens in concentrated glycerol and sucrose solutions. J. Bacteriol. 85:918–926. 1963.—The effects of sucrose and glycerol upon the ability of Serratia marcescens to grow when restored to a normal medium after exposure to solutions of these substances were examined, with special attention to the prevailing thermodynamic activity of water in these solutions as a factor of supposed primary importance in influencing survival or death of cells. The data were notable for the absence of any zones of instability such as those found when the water activity is changed by exposure of washed cells to water vapor at controlled relative humidities (RH). The cells survived indefinitely at room temperature in concentrated sucrose solutions; in glycerol solutions of equilibrium RH values from 20 to 90, the first-order decay constants were about 0.03 to 0.1 hr−1. These results, considered together with the contrasting phenomenon of narrow lethal humidity zones found in vapor-phrase equilibration experiments, were explained generally in terms of competitive interactions involving concentrated intrinsic and adventitious solutes, the cell water, and the organized structures of the cell, whose integrity was considered to depend ultimately upon the net effect of these various interactions.
PMCID: PMC278245  PMID: 14044963
2.  Relative Humidity and the Killing of Bacteria 
Applied Microbiology  1961;9(6):567-571.
The viability of washed moist cells of Serratia marcescens after storage has been measured in relation to variations in the prior treatment of the cells and in conditions of storage. The factors considered were: (i) water content during storage; (ii) method of arriving at water content (partial drying in vacuum or freeze-drying and addition of water); (iii) presence or absence of air during storage.
Increasingly rapid decay occurs as the water content at which the cells are stored is diminished from above 90% to 20 or 30% (“critical” water content). It occurs in presence or absence of air and it occurs whether the final water content is approached by removal of water from wet cells or by addition of water to freeze-dried cells.
The rate of decay during storage at 20 to 30% water is somewhat diminished by the presence of air (“protective” effect of air).
As the water content is further reduced to less than 10%, the stability of cells stored in a vacuum approaches that of wet cells. In presence of air the reverse is true: the stability decreases until at less than 1% water, the decay rate is about as great as at the “critical” water content (“toxic” effect of air).
Particularly rapid decay of S. marcescens at the “critical” water content has escaped attention in aerosol studies because accurate control of relative humidity (RH) in this region, RH 94 to 99%, is virtually impossible in such studies. On the other hand, values of decay rates referred to measured water contents are quite unreliable in the 20 to 80% RH zone because the corresponding variation of water content is too small to measure reliably. Thus data of the kind reported in this paper cannot be directly compared to the published results of studies of air-borne bacteria, although they are relevant to the practical question of air-borne infection in humid atmospheres.
PMCID: PMC1057789  PMID: 13865722
3.  Survival of Microorganisms in Laundered Polyester-Cotton Sheeting1 
Applied Microbiology  1973;25(3):431-435.
The effects of wash-water temperature, cold-water or regular detergent, wash-cycle design, drying, and drying temperature on survival of four microorganisms on polyester-cotton sheeting were examined. Escherichia coli T3 bacteriophage survived washing at 24, 35, 46, and 57 C, but not at 68 C. Serratia marcescens survived only the lowest three wash temperatures. Levels of residual Staphylococcus aureus were diminished at the highest two wash temperatures, but survival was substantial even at 68 C. Counts of Bacillus stearothermophilus spores were not altered appreciably by wash temperature. Type of detergent had no practical effect on observed counts. The regular wash cycle was significantly more efficient in removal of microorganisms than the permanent-press cycle. Counts, especially of the bacteriophage and the gramnegative bacterium, were decreased by drying; after drying, the effects of wash-water temperature on S. aureus and B. stearothermophilus were not significantly different. Microorganisms were transferred from inoculated to sterilized sheeting during laundering. The public health significance of these observations is discussed.
PMCID: PMC380823  PMID: 4572894
4.  Preservation of Serratia marcescens by High-Vacuum Lyophilization 
Applied Microbiology  1966;14(4):561-567.
Water-washed Serratia marcescens (ATCC strain 14041) cells were lyophilized in an all-glass system capable of evacuation to pressures of less than 5 × 10-6 torr. Lyophilization at the lowest pressures resulted in 50 to 65% survival for unstabilized washed organisms compared with 10 to 20% when the cells were lyophilized at pressures of about 2.5 × 10-2 torr. At the latter pressures, 45 to 65% survival was obtained when NaCl or Naylor-Smith stabilizer was added to the cell suspensions before lyophilization. However, the stabilizers failed to increase significantly the levels of survival compared with water suspension when cells were lyophilized at pressures less than 10-5 torr. The high survival rates obtained by the high-vacuum technique may be attributed to the reduction of traces of molecular oxygen which has been reported to be destructive of the dried bacteria. Survival of unstabilized dried S. marcescens after 1-day storage increased markedly with decreasing sealing pressure. Under the highest vacuum attained, survival of the dried bacteria was not impaired by storage for up to 1 month at Dry Ice temperatures; at higher temperatures, viability losses occurred. Exposure of the dried unstabilized bacteria to dry air resulted in rapid viability loss. The inactivation could be stopped almost immediately by evacuation to pressures of less than 10-5 torr, but the evacuation failed to reverse the viability losses that occurred during exposure.
PMCID: PMC546782  PMID: 5332950
5.  Effects of Oxygen on Aerosolized Serratia marcescens 
Applied Microbiology  1965;13(5):781-787.
Suspensions of Serratia marcescens (ATCC strain 14041) in water were aerosolized in a rotating drum in the presence of various concentrations of oxygen. The colony-forming ability of aerosolized organisms was rapidly destroyed by contact with 0.25% or more oxygen at 40% relative humidity (RH) and 25 C, but was almost unimpaired for at least 5 hr in nitrogen containing not more than 10 ppm of oxygen. Completely hydrated organisms were insensitive to oxygen at pressures up to 100 psi for 4 hr. No loss in viability occurred in aerosols of washed cells in air at 97% RH. It is proposed that dehydration of the aerosolized cell results in sensitization to lethal effects of oxygen, but is not the primary cause of death. Mn++, Co++, glycerol, and thiourea enhanced the biological stability of aerosols in air. Numerous similarities between the effects of oxygen in this system and in systems using freeze-dried or irradiated organisms or cell-free enzymes support the hypothesis that closely related mechanisms are involved.
PMCID: PMC1058343  PMID: 5325941
6.  Kinetic properties of Serratia marcescens adenosine 5'-diphosphate glucose pyrophosphorylase. 
Journal of Bacteriology  1976;127(1):193-203.
The regulatory properties of partially purified adenosine 5'-diphosphate-(ADP) glucose pyrophosphorylase from two Serratia marcescens strains (ATCC 274 and ATCC 15365) have been studied. Slight or negligible activation by fructose-P2, pyridoxal-phosphate, or reduced nicotinamide adenine dinucleotide phosphate (NADPH) was observed. These compounds were previously shown to be potent activators of the ADPglucose pyrophosphorylases from the enterics, Salmonella typhimurium, Enterobacter aerogenes, Enterobacter cloacae, Citrobacter freundii, Escherichia aurescens, Shigella dysenteriae, and Escherichia coli. Phosphoenolpyruvate stimulated the rate of ADPglucose synthesis catalyzed by Serratia ADPglucose pyrophosphorylase about 1.5- to 2-fold but did not affect the S0.5 values (concentration of substrate required for 50% maximal stimulation) of the substrates, alpha-glucose-1-phosphate, and adenosine 5'-triphosphate. Adenosine 5'-monophosphate (AMP), a potent inhibitor of the enteric ADPglucose pyrophosphorylase, is an effective inhibitor of the S. marcescens enzyme. ADP also inhibits but is not as effective as AMP. Activators of the enteric enzyme counteract the inhibition caused by AMP. This is in contrast to what is observed for the S. marcescens enzyme. Neither phosphoenolpyruvate, fructose-diphosphate, pyridoxal-phosphate, NADPH, 3-phosphoglycerate, fructose-6-phosphate, nor pyruvate effect the inhibition caused by AMP. The properties of the S. marcescens HY strain and Serratia liquefaciens ADPglucose pyrophosphorylase were found to be similar to the above two S. marcescens enzymes with respect to activation and inhibition. These observations provide another example where the properties of an enzyme found in the genus Serratia have been found to be different from the properties of the same enzyme present in the enteric genera Escherichia, Salmonella, Shigella, Citrobacter, and Enterobacter.
PMCID: PMC233051  PMID: 6432
7.  Effects of sorption on biological degradation rates of (2,4-dichlorophenoxy) acetic acid in soils. 
Three mathematical models were proposed to describe the effects of sorption of both bacteria and the herbicide (2,4-dichlorophenoxy)acetic acid (2,4-D) on the biological degradation rates of 2,4-D in soils. Model 1 assumed that sorbed 2,4-D is not degraded, that only bacteria in solution are capable of degrading 2,4-D in solution, and that sorbed bacteria are not capable of degrading either sorbed or solution 2,4-D. Model 2 stated that only bacteria in the solution phase degrade 2,4-D in solution and that only sorbed bacteria degrade sorbed 2,4-D. Model 3 proposed that sorbed 2,4-D is completely protected from degradation and that both sorbed and solution bacteria are capable of degrading 2,4-D in solution. These models were tested by a series of controlled laboratory experiments. Models 1 and 2 did not describe the data satisfactorily and were rejected. Model 3 described the experimental results quite well, indicating that sorbed 2,4-D was completely protected from biological degradation and that sorbed- and solution-phase bacteria degraded solution-phase 2,4-D with almost equal efficiencies.
PMCID: PMC373553  PMID: 3994366
8.  Growth and survival of Serratia marcescens under aerobic and anaerobic conditions in the presence of materials from blood bags. 
Journal of Clinical Microbiology  1993;31(7):1826-1830.
Several patients receiving blood transfusions during the summer of 1991 developed bacteremia after the transfusion. In all cases, the infection was caused by Serratia marcescens. The same strain of Serratia marcescens was isolated from the patients and from the outer surface of unfilled blood bags. The transport containers for the blood bags were made anoxic by using a catalyst in order to prevent microbial growth. The survival and growth of S. marcescens K202, which was isolated from the blood bags, was studied at different oxygen concentrations in deionized water containing materials derived from the blood bags. The rate of survival and growth of S. marcescens was highest under anaerobic conditions, in which growth occurred with all materials and even in deionized water alone. In contrast, S. marcescens did not survive in control cultures under semi-anaerobic and aerobic conditions. Growth was observed, however, under both aerobic and semi-anaerobic conditions in the presence of each of the tested blood bag materials. These findings indicate that the conditions in the transport containers for the blood bags were favorable for the survival and growth of S. marcescens.
PMCID: PMC265640  PMID: 8349760
9.  Survival of Airborne Bacteria in a High Urban Concentration of Carbon Monoxide1 
Applied Microbiology  1973;25(1):86-91.
Vegetative cells of Serratia marcescens 8UK, Sarcina lutea, and spores of Bacillus subtilus var. niger were held in aerosols, with and without an urban concentration of CO (85 μliters per liter or ppm), for up to 6 hr at 15 C and a relative humidity (RH) of approximately 0, 25, 50, 75, and 95%. It was found that CO enhanced the death rate of S. marcescens 8UK at least four- to sevenfold at low RH (ca. 1 to 25%), but protected the cells at high RH (ca. 90%). Death rates of S. lutea, with or without added CO, were comparatively low over the entire RH range. However, in the first hour, airborne S. lutea held in CO-containing air were more stable than those in air without added CO (i.e., CO protection). A marked increase in the death rate (up to 70-fold) occurred in the subsequent 5 hr within the RH range of approximately 0 to 75%. Statistical analysis indicated that aerosol decay rates of B. subtilus var. niger spores decreased significantly, when held in a CO-containing as compared to a non-CO-containing atmosphere, in the 0 to 85% RH range. Thus, the data presented indicate that CO in the urban environment may have a protective or lethal effect on airborne bacteria, dependent upon at least the microbial species, aerosol age, and relative humidity. A mechanism for CO death enhancement and protection of airborne S. marcescens 8UK is suggested to involve CO uncoupling of an energy-requiring death mechanism and an energy-requiring maintenance mechanism at high and low RH, respectively.
PMCID: PMC380740  PMID: 4631439
10.  Sorption of Cadmium by Microorganisms in Competition with Other Soil Constituents † 
The fate of cadmium in soil is influenced to a great extent by microbial activity. Microorganisms were compared with abiotic soil components for their ability to sorb Cd from a liquid medium. When the same amount (on a dry weight basis) of bacterial cells (Serratia marcescens and Paracoccus sp.), clay (montmorillonite), or sand was separately incubated in 0.05 M phosphate buffer, pH 7.2, containing 10 ppm of Cd (10 μg/ml), bacterial cells removed the largest quantity of Cd. Dead cells sorbed much more Cd from the medium than live cells. A comparative study of Cd removal from the medium by seven soil bacteria and four fungi did not indicate appreciable differences. With increasing microbial biomass, the relative efficiency of 0.1 M NaOH as an extractant of sorbed Cd increased, whereas the extraction efficiency of 0.005 M DTPA (diethylenetriaminepentaacetic acid) decreased. It appeared that NaOH and DTPA extracted different chemical forms of Cd. This assumption was supported by vastly different correlation coefficients in the relative amount of Cd extracted by the two solvents.
PMCID: PMC244178  PMID: 16346002
11.  Population-genetic comparison of the Sorbian isolate population in Germany with the German KORA population using genome-wide SNP arrays 
BMC Genetics  2011;12:67.
The Sorbs are an ethnic minority in Germany with putative genetic isolation, making the population interesting for disease mapping. A sample of N = 977 Sorbs is currently analysed in several genome-wide meta-analyses. Since genetic differences between populations are a major confounding factor in genetic meta-analyses, we compare the Sorbs with the German outbred population of the KORA F3 study (N = 1644) and other publically available European HapMap populations by population genetic means. We also aim to separate effects of over-sampling of families in the Sorbs sample from effects of genetic isolation and compare the power of genetic association studies between the samples.
The degree of relatedness was significantly higher in the Sorbs. Principal components analysis revealed a west to east clustering of KORA individuals born in Germany, KORA individuals born in Poland or Czech Republic, Half-Sorbs (less than four Sorbian grandparents) and Full-Sorbs. The Sorbs cluster is nearest to the cluster of KORA individuals born in Poland. The number of rare SNPs is significantly higher in the Sorbs sample. FST between KORA and Sorbs is an order of magnitude higher than between different regions in Germany. Compared to the other populations, Sorbs show a higher proportion of individuals with runs of homozygosity between 2.5 Mb and 5 Mb. Linkage disequilibrium (LD) at longer range is also slightly increased but this has no effect on the power of association studies.
Oversampling of families in the Sorbs sample causes detectable bias regarding higher FST values and higher LD but the effect is an order of magnitude smaller than the observed differences between KORA and Sorbs. Relatedness in the Sorbs also influenced the power of uncorrected association analyses.
Sorbs show signs of genetic isolation which cannot be explained by over-sampling of relatives, but the effects are moderate in size. The Slavonic origin of the Sorbs is still genetically detectable.
Regarding LD structure, a clear advantage for genome-wide association studies cannot be deduced. The significant amount of cryptic relatedness in the Sorbs sample results in inflated variances of Beta-estimators which should be considered in genetic association analyses.
PMCID: PMC3199861  PMID: 21798003
12.  Kinetic Analysis of Growth Rate, ATP, and Pigmentation Suggests an Energy-Spilling Function for the Pigment Prodigiosin of Serratia marcescens▿  
Journal of Bacteriology  2008;190(22):7453-7463.
Serratia marcescens is a gram-negative environmental bacterium and opportunistic pathogen. S. marcescens expresses prodigiosin, a bright red and cell-associated pigment which has no known biological function for producing cells. We present here a kinetic model relating cell, ATP, and prodigiosin concentration changes for S. marcescens during cultivation in batch culture. Cells were grown in a variety of complex broth media at temperatures which either promoted or essentially prevented pigmentation. High growth rates were accompanied by large decreases in cellular prodigiosin concentration; low growth rates were associated with rapid pigmentation. Prodigiosin was induced most strongly during limited growth as the population transitioned to stationary phase, suggesting a negative effect of this pigment on biomass production. Mathematically, the combined rate of formation of biomass and bioenergy (as ATP) was shown to be equivalent to the rate of prodigiosin production. Studies with cyanide inhibition of both oxidative phosphorylation and pigment production indicated that rates of biomass and net ATP synthesis were actually higher in the presence of cyanide, further suggesting a negative regulatory role for prodigiosin in cell and energy production under aerobic growth conditions. Considered in the context of the literature, these results suggest that prodigiosin reduces ATP production by a process termed energy spilling. This process may protect the cell by limiting production of reactive oxygen compounds. Other possible functions for prodigiosin as a mediator of cell death at population stationary phase are discussed.
PMCID: PMC2576671  PMID: 18805986
Journal of Bacteriology  1963;85(5):1136-1140.
Blizzard, John L. (University of Houston, Houston, Texas) and G. E. Peterson. Selective inhibition of proline-induced pigmentation in washed cells of Serratia marcescens. J. Bacteriol. 85:1136–1140. 1963.—Streptomycin, chloramphenicol, and tetracyclines inhibited the synthesis of prodigiosin by Serratia marcescens strain D1. This occurred at concentrations of the antibiotic too low to inhibit the growth of the organism in either agar media or broth cultures. Nonpigmented cells were produced in broth by either adding streptomycin or incubating at 37 C. After being washed and resuspended in aqueous saline containing either casein hydrolysate, l-proline, or a glycine-succinate mixture and incubated at 27 C for 24 hr, these cells formed pigment. The appearance of pigment was preceded by a lag period of 10 hr. Prodigiosin production by these washed suspensions of cells was completely inhibited by either streptomycin or glucose, or by incubation at 37 C instead of 27 C. Even though pigmentation by washed-cell suspensions was induced by proline, the utilization of proline was not affected by streptomycin or glucose, or by incubation at 37 C. To block pigmentation completely, streptomycin had to be added to proline-supplemented cells before they were 10 hr old. Addition of the antibiotic after the end of the induction period caused either partial or no inhibition of pigment production. Streptomycin caused an increase in the endogenous respiration of S. marcescens but failed to affect the constitutive enzymes that oxidize glucose. The possible relationships of these phenomena are discussed.
Weil (1952) reported that low concentrations of chloramphenicol and certain tetracyclines inhibit the synthesis of prodigiosin while permitting growth by Serratia marcescens. He noted the potential value to “mode-of-action” studies of an organism having certain functions selectively inhibited by antibiotics. We confirmed Weil's (1952) observations and found that streptomycin at low concentration would also inhibit the synthesis of prodigiosin without impeding growth.
Further studies of the selective inhibition of prodigiosin synthesis by streptomycin were performed using nonproliferating suspensions of washed cells (Gott and Williams, 1961). Either a glycine-succinate mixture or l-proline could cause nonproliferating cells to form pigment. A period of induction preceded the formation of pigment. Either streptomycin or glucose, or an incubation temperature of 37 C, inhibited the proline-induced pigmentation by washed cells. Further investigations provided insights to these findings.
PMCID: PMC278295  PMID: 14044006
14.  Serum bactericidal activity and postantibiotic effect in serum of patients with urinary tract infection receiving high-dose amikacin. 
Ten patients received a 30-min infusion of amikacin (30 mg/kg) on day 1 and 15 mg/kg on day 2. Mean serum creatinine was 1.1 +/- 0.3 (standard deviation) mg/dl before and 1.0 +/- 0.3 mg/dl 3 days after the second infusion. Mean serum amikacin concentrations before, at the end of infusion, and 1, 6, 12, and 24 h after 30 and 15 mg/kg were 0, 157, 79, 31, 16, 5, 5, 85, 51, 19, 12, and 5 mg/liter, respectively. Five strains each of Staphylococcus aureus, Staphylococcus epidermidis susceptible and resistant to oxacillin, Streptococcus (Enterococcus) faecalis, corynebacterium sp. strain JK, Listeria monocytogenes, Mycobacterium fortuitum (three strains), Klebsiella pneumoniae, Serratia marcescens, Acinetobacter calcoaceticus, and Pseudomonas aeruginosa were tested. Serum bactericidal activities (SBAs) were greater than or equal to 1:8 in greater than or equal to 80% of the sera 1 and 6 h after 30 mg/kg and in greater than or equal to 60% of the sera 1 and 6 h after 15 mg/kg against Staphylococcus aureus and Staphylococcus epidermidis susceptible to oxacillin, A. calcoaceticus, and K. pneumoniae. L. monocytogenes, Serratia marcescens, and P. aeruginosa had lower SBAs. Very low or no activity was observed against oxacillin-resistant staphylococci and Streptococcus faecalis. The study of the killing rate in serum confirmed these results. Postantibiotic effect was studied by incubating a strain from each species in serum samples obtained 1 and 6 h after both regimens for 0.5, 1, or 2 h. The duration of postantibiotic effect depended on the duration of contact and the concentration of amikacin for the following organisms: oxacillin-susceptible staphylococci, L. monocytogenes, P. aeruginosa, A. calcoaceticus, K. pneumoniae, and Serratia marcescens. M. fortuitum was killed after 30 min of contact. No postantibiotic effect was observed with Streptococcus faecalis, Corynebacterium sp. strain JK, or oxacillin-resistant staphylococci. Amikacin at 30 mg/kg provided high levels and SBAs against susceptible pathogens. Prolonged postantibiotic effects were observed. No signs of nephrotoxicity occurred.
PMCID: PMC174872  PMID: 3116918
15.  Value of microbiology study in congenital nasolacrimal duct obstruction 
Saudi Journal of Ophthalmology  2012;26(2):223-228.
Evaluation of the effect of different microorganisms on congenital nasolacrimal duct obstruction (CNLDO) tightness and whether probing or silastic intubation is likely to fail in a particular microorganism infection.
The culture and sensitivity results of lacrimal drainage system (LDS) discharge samples from patients with CNLDO were reviewed. Different microorganisms were correlated with the severity of nasolacrimal duct (NLD) obstruction observed during surgical intervention. The success rates of probing and silastic intubation as a primary procedure for each identifiable microorganism were documented. Statistical analysis was conducted to correlate the type of microorganism with the tightness of CNLDO and treatment failure.
Out of 181 specimens, 22 had no growth (12.1%). LDS with positive culture had 76.6% successful probing (n = 49) and 82.1% successful silastic intubation (n = 78). Gram-positive and Gram-negative species were almost equally detected. The most prevalent organisms were Streptococcus pneumoniae and Hemophilus influenzae (48.1% and 39.2%, respectively). Tight CNLDO was more prevalent in Serratia marcescens (n = 2; 100%) and Staphylococcus aureus (n = 4; 33.3%) infections with a 7.75 Odds ratio [95% confidence interval (CI), 1.67–34.63]. Staphylococcus aureus had 37.5% successful probing; however, success was achieved in all cases with silastic intubation. Serratia marcescens infections had 100% successful silastic intubation.
Microbiology study can predict tight CNLDO and helps in choosing the most successful treatment option. CNLDO with Staphylococcus infection and Serratia marcescens were likely to have tight NLD obstruction and silastic intubation had better outcomes.
PMCID: PMC3729323  PMID: 23960996
Microbiology; Congenital; Nasolacrimal duct; Obstruction
16.  Water, Sanitation, Hygiene, and Soil-Transmitted Helminth Infection: A Systematic Review and Meta-Analysis 
PLoS Medicine  2014;11(3):e1001620.
In a systematic review and meta-analysis, Eric Strunz and colleagues examine whether improvements in water, sanitation, and hygiene (WASH) practices are associated with reduced risk of infections with soil-transmitted helminths.
Please see later in the article for the Editors' Summary
Preventive chemotherapy represents a powerful but short-term control strategy for soil-transmitted helminthiasis. Since humans are often re-infected rapidly, long-term solutions require improvements in water, sanitation, and hygiene (WASH). The purpose of this study was to quantitatively summarize the relationship between WASH access or practices and soil-transmitted helminth (STH) infection.
Methods and Findings
We conducted a systematic review and meta-analysis to examine the associations of improved WASH on infection with STH (Ascaris lumbricoides, Trichuris trichiura, hookworm [Ancylostoma duodenale and Necator americanus], and Strongyloides stercoralis). PubMed, Embase, Web of Science, and LILACS were searched from inception to October 28, 2013 with no language restrictions. Studies were eligible for inclusion if they provided an estimate for the effect of WASH access or practices on STH infection. We assessed the quality of published studies with the Grades of Recommendation, Assessment, Development and Evaluation (GRADE) approach. A total of 94 studies met our eligibility criteria; five were randomized controlled trials, whilst most others were cross-sectional studies. We used random-effects meta-analyses and analyzed only adjusted estimates to help account for heterogeneity and potential confounding respectively.
Use of treated water was associated with lower odds of STH infection (odds ratio [OR] 0.46, 95% CI 0.36–0.60). Piped water access was associated with lower odds of A. lumbricoides (OR 0.40, 95% CI 0.39–0.41) and T. trichiura infection (OR 0.57, 95% CI 0.45–0.72), but not any STH infection (OR 0.93, 95% CI 0.28–3.11). Access to sanitation was associated with decreased likelihood of infection with any STH (OR 0.66, 95% CI 0.57–0.76), T. trichiura (OR 0.61, 95% CI 0.50–0.74), and A. lumbricoides (OR 0.62, 95% CI 0.44–0.88), but not with hookworm infection (OR 0.80, 95% CI 0.61–1.06). Wearing shoes was associated with reduced odds of hookworm infection (OR 0.29, 95% CI 0.18–0.47) and infection with any STH (OR 0.30, 95% CI 0.11–0.83). Handwashing, both before eating (OR 0.38, 95% CI 0.26–0.55) and after defecating (OR 0.45, 95% CI 0.35–0.58), was associated with lower odds of A. lumbricoides infection. Soap use or availability was significantly associated with lower infection with any STH (OR 0.53, 95% CI 0.29–0.98), as was handwashing after defecation (OR 0.47, 95% CI 0.24–0.90).
Observational evidence constituted the majority of included literature, which limits any attempt to make causal inferences. Due to underlying heterogeneity across observational studies, the meta-analysis results reflect an average of many potentially distinct effects, not an average of one specific exposure-outcome relationship.
WASH access and practices are generally associated with reduced odds of STH infection. Pooled estimates from all meta-analyses, except for two, indicated at least a 33% reduction in odds of infection associated with individual WASH practices or access. Although most WASH interventions for STH have focused on sanitation, access to water and hygiene also appear to significantly reduce odds of infection. Overall quality of evidence was low due to the preponderance of observational studies, though recent randomized controlled trials have further underscored the benefit of handwashing interventions. Limited use of the Joint Monitoring Program's standardized water and sanitation definitions in the literature restricted efforts to generalize across studies. While further research is warranted to determine the magnitude of benefit from WASH interventions for STH control, these results call for multi-sectoral, integrated intervention packages that are tailored to social-ecological contexts.
Please see later in the article for the Editors' Summary
Editors' Summary
Worldwide, more than a billion people are infected with soil-transmitted helminths (STHs), parasitic worms that live in the human intestine (gut). These intestinal worms, including roundworm, hookworm, and whipworm, mainly occur in tropical and subtropical regions and are most common in developing countries, where personal hygiene is poor, there is insufficient access to clean water, and sanitation (disposal of human feces and urine) is inadequate or absent. STHs colonize the human intestine and their eggs are shed in feces and enter the soil. Humans ingest the eggs, either by touching contaminated ground or eating unwashed fruit and vegetables grown in such soil. Hookworm may enter the body by burrowing through the skin, most commonly when bare-footed individuals walk on infected soil. Repeated infection with STHs leads to a heavy parasite infestation of the gut, causing chronic diarrhea, intestinal bleeding, and abdominal pain. In addition the parasites compete with their human host for nutrients, leading to malnutrition, anemia, and, in heavily infected children, stunting of physical growth and slowing of mental development.
Why Was This Study Done?
While STH infections can be treated in the short-term with deworming medication, rapid re-infection is common, therefore a more comprehensive program of improved water, sanitation, and hygiene (WASH) is needed. WASH strategies include improvements in water access (e.g., water quality, water quantity, and distance to water), sanitation access (e.g., access to improved latrines, latrine maintenance, and fecal sludge management), and hygiene practices (e.g., handwashing before eating and/or after defecation, water treatment, soap use, wearing shoes, and water storage practices). WASH strategies have been shown to be effective for reducing rates of diarrhea and other neglected tropical diseases, such as trachoma; however, there is limited evidence linking specific WASH access or practices to STH infection rates. In this systematic review and meta-analysis, the researchers investigate whether WASH access or practices lower the risk of STH infections. A systematic review uses predefined criteria to identify all the research on a given topic; a meta-analysis is a statistical method that combines the results of several studies.
What Did the Researchers Do and Find?
The researchers identified 94 studies that included measurements of the relationship between WASH access and practices with one or more types of STHs. Meta-analyses of the data from 35 of these studies indicated that overall people with access to WASH strategies or practices were about half as likely to be infected with any STH. Specifically, a lower odds of infection with any STH was observed for those people who use treated water (odd ratio [OR] of 0.46), have access to sanitation (OR of 0.66), wear shoes (OR of 0.30), and use soap or have soap availability (OR of 0.53) compared to those without access to these practices or strategies. In addition, infection with roundworm was less than half as likely in those who practiced handwashing both before eating and after defecating than those who did not practice handwashing (OR of 0.38 and 0.45, respectively).
What Do These Findings Mean?
The studies included in this systematic review and meta-analysis have several shortcomings. For example, most were cross-sectional surveys—studies that examined the effect of WASH strategies on STH infections in a population at a single time point. Given this study design, people with access to WASH strategies may have shared other characteristics that were actually responsible for the observed reductions in the risk of STH infections. Consequently, the overall quality of the included studies was low and there was some evidence for publication bias (studies showing a positive association are more likely to be published than those that do not). Nevertheless, these findings confirm that WASH access and practices provide an effective control measure for STH. Controlling STHs in developing countries would have a huge positive impact on the physical and mental health of the population, especially children, therefore there should be more emphasis on expanding access to WASH as part of development guidelines and targets, in addition to short-term preventative chemotherapy currently used.
Additional Information
Please access these websites via the online version of this summary at
The US Centers for Disease Control and Prevention also provides detailed information on roundworm, whipworm, and hookworm infections
The World Health Organization provides information on soil-transmitted helminths, including a description of the current control strategy
Children Without Worms (CWW) partners with Johnson & Johnson, GlaxoSmithKline, the World Health Organization, national ministries of health and education, non-governmental organizations, and others to promote treatment and prevention of soil-transmitted helminthiasis. CWW advocates a four-pronged, comprehensive control strategy—Water, Sanitation, Hygiene Education, and Deworming (WASHED) to break the cycle of reinfection
The Global Network for Neglected Tropical Diseases, an advocacy initiative dedicated to raising the awareness, political will, and funding necessary to control and eliminate the most common neglected tropical diseases, provides information on infections with roundworm (ascariasis), whipworm (trichuriasis), and hookworm
WASH for the Neglected Tropical Diseases is a repository of information on WASH and the neglected tropical diseases (NTDs) such as soil-transmitted helminthiasis, and features a resource titled “WASH and the NTDs: A Manual for WASH Implementers.”
Two international programs promoting water sanitation are the World Health Organization Water Sanitation and Health program and the World Health Organization/United Nations Childrens Fund Joint Monitoring Programme for Water Supply and Sanitation
PMCID: PMC3965411  PMID: 24667810
17.  Relationship Between Atmospheric Temperature and Survival of Airborne Bacteria 
Applied Microbiology  1970;19(2):245-249.
Effects of temperatures ranging from −40 to 49 C on the behavior of airborne Serratia marcescens, Escherichia coli, and Bacillus subtilis var. niger were investigated. Aerosol decay rates of B. subtilis spores were not significantly affected by the temperature and remained approximately constant within the temperature range studied. The survival of airborne S. marcescens and E. coli was closely related to the temperature. An increase in temperature from −18 to 49 C resulted in a progressive increase of the biological death rate, and the relationship between the biological death rate and the temperature appeared to be linear. An increase in temperature from 24 to 49 C resulted in significantly reduced aerosol recoveries of the two vegetative organisms. At −40 C, the aerosol recovery of all three agents was consistently lower than at −18 to 24 C.
PMCID: PMC376659  PMID: 4985428
18.  Evaluation of RapID onE system for identification of 379 strains in the family Enterobacteriaceae and oxidase-negative, gram-negative nonfermenters. 
Journal of Clinical Microbiology  1994;32(4):931-934.
The ability of the RapID onE system (Innovative Diagnostic Systems, Inc., Norcross, Ga.) to identify 364 strains in the family Enterobacteriaceae and 15 oxidase-negative, gram-negative, nonfermentative rods was evaluated. Kits were inoculated with no. 2 McFarland standard suspensions, and reactions were interpreted after 4 h of incubation at 35 degrees C. Overall, the method correctly identified (to the species level or to the genus level for salmonellas and non-Shigella sonnei Shigella species) 363 strains (95.8%) without additional tests. For four strains (1.0%), additional tests were required to delineate the correct identification from a range of two or more possibilities; these included one Serratia liquefaciens (Serratia marcescens or Serratia liquefaciens), one Serratia rubidaea (Serratia rubidaea or Serratia odorifera), one Salmonella typhi (Leminorella richardii or Salmonella sp.) and one Yersinia enterocolitica (Yersinia frederiksenii, Yersinia intermedia, or Yersinia enterocolitica). Twelve strains (3.2%) were misidentified or yielded codes with no identification; these comprised one Citrobacter amalonaticus (no identification), three Enterobacter hormaechei (not in the RapID onE database; two Enterobacter amnigenus, one Enterobacter sp.), one Serratia liquefaciens (Enterobacter cloacae), one Serratia rubidaea (no identification), four Serratia fonticola (not in RapID onE database; two Enterobacter aerogenes, one Serratia marcescens, one not identified), one Proteus mirabilis (Proteus penneri), and one Proteus vulgaris (Providencia rustigianii). If the seven strains not included in the database had been excluded, correct identification rates would have risen to 97.6% without additional tests and 98.7% with additional tests, with misidentification rates dropping to 1.3%. The RapID onE system is easy to set up and the results are easy to read, and the system provides an accurate, nonautomated commercially available method for the same-day identification of members of the family Enterobacteriaceae and oxidase-negative, gram-negative nonfermenters.
PMCID: PMC263165  PMID: 8027345
19.  Size and UV Germicidal Irradiation Susceptibility of Serratia marcescens when Aerosolized from Different Suspending Media 
Experimental systems have been built in laboratories worldwide to investigate the influence of various environmental parameters on the efficacy of UV germicidal irradiation (UVGI) for deactivating airborne microorganisms. It is generally recognized that data from different laboratories might vary significantly due to differences in systems and experimental conditions. In this study we looked at the effect of the composition of the suspending medium on the size and UVGI susceptibility of Serratia marcescens in an experimental system built in our laboratory. S. marcescens was suspended in (i) distilled water, (ii) phosphate buffer, (iii) 10% fetal calf serum, (iv) phosphate-buffered saline (saline, 0.8% sodium chloride), and (v) synthetic saliva (phosphate-buffered saline with 10% fetal calf serum). At low humidity (36%), S. marcescens suspended in water-only medium was the most susceptible to UVGI, followed by those in serum-only medium. The count median diameters (CMDs) for culturable particles from water-only and serum-only media were 0.88 and 0.95 μm, respectively, with the measurements based on their aerodynamic behavior. The bacteria suspended in phosphate buffer, synthetic saliva, and phosphate-buffered saline had similar UVGI susceptibility and CMD at 1.0, 1.4, and 1.5 μm, respectively. At high humidity (68%) the CMD of the particles increased by 6 to 16%, and at the same time UVGI susceptibility decreased, with the magnitude of decrease related to the type of suspending medium. In conclusion, the choice of suspending medium influenced both size and UVGI susceptibility of S. marcescens. These data are valuable for making comparisons and deciding on the use of an appropriate medium for various applications.
PMCID: PMC383042  PMID: 15066792
20.  Alternative Hand Contamination Technique To Compare the Activities of Antimicrobial and Nonantimicrobial Soaps under Different Test Conditions▿  
Applied and Environmental Microbiology  2008;74(12):3739-3744.
Antimicrobial hand soaps provide a greater bacterial reduction than nonantimicrobial soaps. However, the link between greater bacterial reduction and a reduction of disease has not been definitively demonstrated. Confounding factors, such as compliance, soap volume, and wash time, may all influence the outcomes of studies. The aim of this work was to examine the effects of wash time and soap volume on the relative activities and the subsequent transfer of bacteria to inanimate objects for antimicrobial and nonantimicrobial soaps. Increasing the wash time from 15 to 30 seconds increased reduction of Shigella flexneri from 2.90 to 3.33 log10 counts (P = 0.086) for the antimicrobial soap, while nonantimicrobial soap achieved reductions of 1.72 and 1.67 log10 counts (P > 0.6). Increasing soap volume increased bacterial reductions for both the antimicrobial and the nonantimicrobial soaps. When the soap volume was normalized based on weight (∼3 g), nonantimicrobial soap reduced Serratia marcescens by 1.08 log10 counts, compared to the 3.83-log10 reduction caused by the antimicrobial soap (P < 0.001). The transfer of Escherichia coli to plastic balls following a 15-second hand wash with antimicrobial soap resulted in a bacterial recovery of 2.49 log10 counts, compared to the 4.22-log10 (P < 0.001) bacterial recovery on balls handled by hands washed with nonantimicrobial soap. This indicates that nonantimicrobial soap was less active and that the effectiveness of antimicrobial soaps can be improved with longer wash time and greater soap volume. The transfer of bacteria to objects was significantly reduced due to greater reduction in bacteria following the use of antimicrobial soap.
PMCID: PMC2446551  PMID: 18441107
21.  Serratia marcescens outbreak in a neonatal intensive care unit: crucial role of implementing hand hygiene among external consultants 
Serratia marcescens represents an important pathogen involved in hospital acquired infections. Outbreaks are frequently reported and are difficult to eradicate. The aim of this study is to describe an outbreak of Serratia marcescens occurred from May to November 2012 in a neonatal intensive care unit, to discuss the control measures adopted, addressing the role of molecular biology in routine investigations during the outbreak.
After an outbreak of Serratia marcescens involving 14 neonates, all admitted patients were screened for rectal and ocular carriage every two weeks. Extensive environmental sampling procedure and hand sampling of the staff were performed. Antimicrobial susceptibility pattern and molecular analysis of isolates were carried out. Effective hand hygiene measures involving all the external consultants has been implemented. Colonized and infected babies were cohorted. Dedicated staff was established to care for the colonized or infected babies.
During the surveillance, 65 newborns were sampled obtaining 297 ocular and rectal swabs in five times. Thirty-four Serratia marcescens isolates were collected: 11 out of 34 strains were isolated from eyes, being the remaining 23 isolated from rectal swabs. Two patients presented symptomatic conjunctivitis. Environmental and hand sampling resulted negative. During the fifth sampling procedure no colonized or infected patients have been identified. Two different clones have been identified.
Ocular and rectal colonization played an important role in spread of infections. Implementation of infection control measures, involving also external specialists, allowed to control a serious Serratia marcescens outbreak in a neonatal intensive care unit.
PMCID: PMC4301457  PMID: 25582674
Serratia marcescens; Outbreak; Neonatal intensive care unit; Molecular epidemiology; Ocular colonization; Rectal colonization; Hand hygiene
22.  New method for determination of efficacy of health care personnel hand wash products. 
Journal of Clinical Microbiology  1989;27(10):2295-2299.
A method of studying the effects of health care personnel hand wash products is described. The fingernail regions of the hands of volunteers are inoculated with a mixture of Escherichia coli and Serratia marcescens, and the areas are dried for a standard time. After routine hand washing, each fingernail region is individually scrubbed with an electric toothbrush which moves longitudinally to the handle into collection fluid contained in a petri dish. The test bacteria in the fluid are then enumerated. (Bacillus subtilis spores may be included as tracers to show degree of physical removal of the procedure.) This method has several advantages over the frequently used glove juice technique. Experimental designs with large numbers of volunteers, multiple sampling sites, and many hand wash products may be performed. Ten sampling sites (fingers) are available, versus the two gloved hands for testing products. (Efficiency is almost 100% in the recovery of spore tracers placed on the fingernails.) Many commercial health care personnel hand wash products containing antimicrobial agents substantive to the skin do not rapidly reduce numbers of inoculated bacteria in the fingernail regions to any greater extent than nonantimicrobial hand washes. Products containing isopropanol or ethanol are very effective in decreasing bacteria in areas around and under the fingernails.
PMCID: PMC267012  PMID: 2685028
23.  Case‐control analysis of endemic Serratia marcescens bacteremia in a neonatal intensive care unit 
Serratia marcescens is an opportunistic gram‐negative rod which typically infects compromised hosts.
To identify risk factors, signs, and outcomes associated with non‐epidemic S marcescens bacteremia in a neonatal intensive care unit (NICU).
The records of infants with S marcescens bacteremia while in the Yale‐New Haven Hospital NICU from 1980–2004 were reviewed. A matched case‐control study was performed by comparing each case of S marcescens to 2 uninfected controls and 2 cases of Escherichia coli bacteremia.
Twenty‐five sporadic cases of S marcescens bacteremia were identified. Eleven available isolates were determined to be different strains by pulse field gel electrophoresis. Infants with S marcescens bacteremia had median gestational age and birth weight of 28 weeks and 1235 grams, respectively. Compared to matched, uninfected controls, infants with S marcescens bacteremia were more likely to have had a central vascular catheter (OR = 4.33; 95% CI (1.41 to 13.36)) and surgery (OR = 5.67; 95% CI (1.81 to 17.37)), and had a higher overall mortality (44% vs 2%; OR = 38.50; 95% CI (4.57 to 324.47)). Compared to E coli matched controls, infants with S marcescens bacteremia had later onset of infection (median of 33 days of life vs 10; p<0.001), prolonged intubation (OR = 5.76; 95% CI (1.80 to 18.42)), and a higher rate of CVC (OR = 7.77; 95% CI (2.48 to 24.31)) use at the time of infection. A higher rate of meningitis (24% vs 7%; OR = 3.98; 95% CI (1.09 to 14.50)) was observed with S marcescens bacteremia compared to E coli.
S marcescens bacteremia occurs sporadically in the NICU, primarily in premature infants requiring support apparatus late in their hospital course. Associated meningitis is common and mortality high.
PMCID: PMC2675455  PMID: 17088342
24.  Sorption of Heavy Metals to the Filamentous Bacterium Thiothrix Strain A1 
A study was undertaken to determine the ability of the filamentous bacterium Thiothrix strain A1 to sorb heavy metals from solution. Cells of Thiothrix strain A1 were harvested, washed, and suspended in solutions of metals. After an equilibration period, biomass was separated from solution and the metal content in acid-digested cells and/or filtrates was determined by atomic absorption spectrophotometry. Sorption of nickel and zinc was very rapid; most of the sorbed metal was bound in less than 10 min. The sorption data for copper fit the Freundlich isotherm, and nickel and zinc data fit biphasic Freundlich isotherms. Sorption of both nickel and zinc was dependent on cell age. Cells harvested 24 h after inoculation sorbed approximately one-half of the amount of metal per gram cell protein than did cells harvested after 48, 72, or 96 h. Calcium and magnesium effectively competed with zinc for binding sites, whereas potassium had only a slight effect on the capacity of cells to sorb zinc. The primary mechanism of metal sorption apparently was ion exchange, because 66 to 75% of nickel or zinc could be desorbed by placing metal-laden cells in a solution of 5 mM CaCl2. A competition experiment with nickel and zinc indicated that both metals occupied the same sorption sites. The strong chelating agents EDTA and NTA effectively prevented metal uptake, but lactate enhanced the uptake of nickel. Thiothrix strain A1 grown in nickel-containing medium had a relatively low uptake of nickel compared with uptake by resting cells suspended in a simple buffer solution.
PMCID: PMC182077  PMID: 16348924
25.  Development of Quantitative Real-Time PCR Assays for Detection and Quantification of Surrogate Biological Warfare Agents in Building Debris and Leachate▿  
Applied and Environmental Microbiology  2007;73(20):6557-6565.
Evaluation of the fate and transport of biological warfare (BW) agents in landfills requires the development of specific and sensitive detection assays. The objective of the current study was to develop and validate SYBR green quantitative real-time PCR (Q-PCR) assays for the specific detection and quantification of surrogate BW agents in synthetic building debris (SBD) and leachate. Bacillus atrophaeus (vegetative cells and spores) and Serratia marcescens were used as surrogates for Bacillus anthracis (anthrax) and Yersinia pestis (plague), respectively. The targets for SYBR green Q-PCR assays were the 16S-23S rRNA intergenic transcribed spacer (ITS) region and recA gene for B. atrophaeus and the gyrB, wzm, and recA genes for S. marcescens. All assays showed high specificity when tested against 5 ng of closely related Bacillus and Serratia nontarget DNA from 21 organisms. Several spore lysis methods that include a combination of one or more of freeze-thaw cycles, chemical lysis, hot detergent treatment, bead beat homogenization, and sonication were evaluated. All methods tested showed similar threshold cycle values. The limit of detection of the developed Q-PCR assays was determined using DNA extracted from a pure bacterial culture and DNA extracted from sterile water, leachate, and SBD samples spiked with increasing quantities of surrogates. The limit of detection for B. atrophaeus genomic DNA using the ITS and B. atrophaeus recA Q-PCR assays was 7.5 fg per PCR. The limits of detection of S. marcescens genomic DNA using the gyrB, wzm, and S. marcescens recA Q-PCR assays were 7.5 fg, 75 fg, and 7.5 fg per PCR, respectively. Quantification of B. atrophaeus vegetative cells and spores was linear (R2 > 0.98) over a 7-log-unit dynamic range down to 101 B. atrophaeus cells or spores. Quantification of S. marcescens (R2 > 0.98) was linear over a 6-log-unit dynamic range down to 102 S. marcescens cells. The developed Q-PCR assays are highly specific and sensitive and can be used for monitoring the fate and transport of the BW surrogates B. atrophaeus and S. marcescens in building debris and leachate.
PMCID: PMC2075066  PMID: 17720820

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