Zimbabwe offers the most recent example of the tragedy that befalls a country and its people when cholera strikes. The 2008–2009 outbreak rapidly spread across every province and brought rates of mortality similar to those witnessed as a consequence of cholera infections a hundred years ago. In this Review we highlight the advances that will help to unravel how interactions between the host, the bacterial pathogen and the lytic bacteriophage might propel and quench cholera outbreaks in endemic settings and in emergent epidemic regions such as Zimbabwe.
The use of tabletop exercises as a tool in emergency preparedness and response has proven to be an effective means of assessing readiness for unexpected events. Whereas most exercise developers target a population in a defined space (eg, state, county, metropolitan area, hospital), the Southeastern Center for Emerging Biologic Threats (SECEBT) conducted an innovative tabletop exercise involving an unusual foodborne outbreak pathogen, targeting public health agencies and academic institutions in 7 southeastern states. The exercise tested the ability of participants to respond to a simulated foodborne disease outbreak affecting the region. The attendees represented 4 federal agencies, 9 state agencies, 6 universities, 1 nonprofit organization, and 1 private corporation. The goals were to promote collaborative relationships among the players, identify gaps in plans and policies, and identify the unique contributions of each organization—and notably academic institutions—to outbreak recognition, investigation, and control. Participants discussed issues and roles related to outbreak detection and management, risk communication, and coordination of policies and responsibilities before, during, and after an emergency, with emphasis on assets of universities that could be mobilized during an outbreak response. The exercise generated several lessons and recommendations identified by participants and evaluators. Key recommendations included a need to establish trigger points and protocols for information sharing and alerts among public health, academic, and law enforcement; to establish relationships with local, state, and federal stakeholders to facilitate communications during an emergency; and to catalogue and leverage strengths, assets, and priorities of academic institutions to add value to outbreak responses.
A tabletop exercise simulated a foodborne outbreak and involved representatives from federal and state agencies, universities, a nonprofit organization, and a corporation. The exercise pointed up the need to establish working relationships before an emergency and suggested that the resources of academic institutions could be used to good advantage.
arbovirus; southeastern United States; arbovirus diseases; mosquitoes; viruses
Environmental triggers may lead to increases in Vibrio cholerae in environmental reservoirs, with spillover into human populations.
Cholera has affected humans for at least a millennium and persists as a major cause of illness and death worldwide, with recent epidemics in Zimbabwe (2008–2009) and Haiti (2010). Clinically, evidence exists of increasing severity of disease linked with emergence of atypical Vibrio cholerae organisms that have incorporated genetic material from classical biotype strains into an El Tor biotype background. A key element in transmission may be a recently recognized hyperinfectious phase, which persists for hours after passage in diarrheal feces. We propose a model of transmission in which environmental triggers (such as temperature) lead to increases in V. cholerae in environmental reservoirs, with spillover into human populations. However, once the microorganism is introduced into a human population, transmission occurs primary by “fast” transmission from person to person (taking advantage of the hyperinfectious state), without returning to the aquatic environment.
cholera; Vibrio cholerae; bacteria; hyperinfectious; mathematical models; reservoir; synopsis; pandemic; environmental; triggers; human; lineage
Methicillin-resistant Staphylococcus aureus (MRSA) is a leading cause of healthcare-associated infections and significant contributor to healthcare cost. Community-associated-MRSA (CA-MRSA) strains have now invaded healthcare settings. A convenience sample of 97 clinical MRSA isolates was obtained from seven hospitals during a one-week period in 2010. We employed a framework integrating Staphylococcus protein A typing and full-genome next-generation sequencing. Single nucleotide polymorphisms were analyzed using phylodynamics. Twenty-six t002, 48 t008, and 23 other strains were identified. Phylodynamic analysis of 30 t008 strains showed ongoing exponential growth of the effective population size the basic reproductive number (R0) ranging from 1.24 to 1.34. No evidence of hospital clusters was identified. The lack of phylogeographic clustering suggests that community introduction is a major contributor to emergence of CA-MRSA strains within hospitals. Phylodynamic analysis provides a powerful framework to investigate MRSA transmission between the community and hospitals, an understanding of which is essential for control.
Foodborne disease; disease burden; food attribution; United States; commentary
Background: Two decades ago, botulinum neurotoxin (BoNT) type A was introduced to the commercial market. Subsequently, the toxin was approved by the FDA to address several neurological syndromes, involving muscle, nerve, and gland hyperactivity. These syndromes have typically been associated with abnormalities in cholinergic transmission. Despite the multiplicity of botulinal serotypes (designated as types A through G), therapeutic preparations are currently only available for BoNT types A and B. However, other BoNT serotypes are under study for possible clinical use and new clinical indications; Objective: To review the current research on botulinum neurotoxin serotypes A-G, and to analyze potential applications within basic science and clinical settings; Conclusions: The increasing understanding of botulinal neurotoxin pathophysiology, including the neurotoxin’s effects on specific neuronal populations, will help us in tailoring treatments for specific diagnoses, symptoms and patients. Scientists and clinicians should be aware of the full range of available data involving neurotoxin subtypes A-G.
Botulinum toxin serotypes; neurotoxins subtypes; neuro-pharmacology toxins
In response to antibiotic and/or environmental stress, some species of bacteria shift to a “persister” phenotype. Although toxigenic Vibrio cholerae, responsible for the disease cholera, can be found in nutrient-poor aquatic environments in endemic areas, the underlying mechanism(s) by which culturable cells persist in these environmental reservoirs is largely unknown. Here we report that introduction of V. cholerae into a nutrient-poor filter sterilized lake water (FSLW) microcosm promoted a shift to what we have defined as a “persister” phenotype (PP) which was culturable for >700 days. Direct transfer of PP of V. cholerae from original microcosms to freshly prepared FSLW resulted in the same pattern of persistence seen in the original microcosms. Scanning electron microscopy of cells persisting for over 700 days demonstrated cell morphologies that were very small in size, with a high degree of aggregation associated with flagella emanating from all aspects of the cell. V. cholerae PP cells reverted to a typical V. cholerae morphology when transferred to nutrient-rich L- broth. Cell-free supernatants obtained from microcosms at 24 hours, 180 days, and 700 days all showed >2-fold increase in CAI-1 signaling molecules, consistent with quorum sensing activity, as has been described for Pseudomonas aeruginosa persister cells. Chitin and phosphate promoted cell growth. Our data suggest that nutrient stress can select a V. cholerae persister phenotype in environmental reservoirs, with these strains then seeding subsequent cholera epidemics in response to chitin and phosphate availability.
O-antigen biosynthetic (wbf) regions for Vibrio cholerae serogroups O5, O8, and O108 were isolated and sequenced. Sequences were compared to those of other published V. cholerae O-antigen regions. These wbf regions showed a high degree of heterogeneity both in gene content and in gene order. Genes identified frequently showed greater similarities to polysaccharide biosynthesis genes from species other than V. cholerae. Our results demonstrate the plasticity of O-antigen genes in V. cholerae, the diversity of the genetic pool from which they are drawn, and the likelihood that new pandemic serogroups will emerge.
To identify loci useful for species identification and to enhance our understanding of the population structure and genetic variability of the genus Mycobacterium, we conducted a multiple-genome comparison of a total of 27 sequenced genomes in the suborder of Corynebacterineae (18 from the Mycobacterium genus, 7 from the Corynebacterium genus, 1 each from the Nocardia and Rhodococcus genera). Our study revealed 26 informative loci for species identification in Mycobacterium. The sequences from these loci were used in a phylogenetic analysis to infer the evolutionary relations of the 18 mycobacterial genomes. Among the loci that we identified, rpoBC, dnaK, and hsp65 were amplified from 29 ATCC reference strains and 17 clinical isolates and sequenced. The phylogenetic trees generated from these loci show similar topologies. The newly identified dnaK locus is more discriminatory and more robust than the widely used hsp65 locus. The length-variable rpoBC locus is the first intergenic locus between two protein-encoding genes being used for mycobacterial species identification. A multilocus sequence analysis system including the rpoBC, dnaK, and hsp65 loci is a robust tool for accurate identification of Mycobacterium species.
Although public concern has focused on the environmental impact of the Deepwater Horizon oil spill, the public health impact on a broad range of coastal communities is minimally known.
We sought to determine the acute level of distress (depression, anxiety), mechanisms of adjustment (coping, resilience), and perceived risk in a community indirectly impacted by the oil spill and to identify the extent to which economic loss may explain these factors.
Using a community-based participatory model, we performed standardized assessments of psychological distress (mood, anxiety), coping, resilience, neurocognition, and perceived risk on residents of fishing communities who were indirectly impacted (n = 71, Franklin County, Florida) or directly exposed (n = 23, Baldwin County, Alabama) to coastal oil. We also compared findings for participants who reported income stability (n = 47) versus spill-related income loss (n = 47).
We found no significant differences between community groups in terms of psychological distress, adjustment, neurocognition, or environmental worry. Residents of both communities displayed clinically significant depression and anxiety. Relative to those with stable incomes, participants with spill-related income loss had significantly worse scores on tension/anxiety, depression, fatigue, confusion, and total mood disturbance scales; had higher rates of depression; were less resilient; and were more likely to use behavioral disengagement as a coping strategy.
Current estimates of human health impacts associated with the oil spill may underestimate the psychological impact in Gulf Coast communities that did not experience direct exposure to oil. Income loss after the spill may have a greater psychological health impact than the presence of oil on the immediately adjacent shoreline.
disasters; environmental epidemiology; occupational health; petroleum products; risk perception
Altered El Tor Vibrio cholerae O1, with classical cholera toxin B gene, was isolated from 16 patients with severe diarrhea at St. Mark’s Hospital, Arbonite, Haiti, <3 weeks after onset of the current cholera epidemic. Variable-number tandem-repeat typing of 187 isolates showed minimal diversity, consistent with a point source for the epidemic.
Cholera; Haiti; Vibrio cholerae; bacteria; variable-number tandem-repeat; molecular epidemiology; clonal origin; expedited; dispatch
Outbreaks of Vibrio vulnificus wound infections in Israel were previously attributed to tilapia aquaculture. In this study, V. vulnificus was frequently isolated from coastal but not freshwater aquaculture in Bangladesh. Phylogenetic analyses showed that strains from Bangladesh differed remarkably from isolates commonly recovered elsewhere from fish or oysters and were more closely related to strains of clinical origin.
Complete sequences of 9.5-kb pPCP1 plasmids in three Yersinia pestis strains from the former Soviet Union (FSU) were determined and compared with those of pPCP1 plasmids in three well-characterized, non-FSU Y. pestis strains (KIM, CO92, and 91001). Two of the FSU plasmids were from strains C2614 and C2944, isolated from plague foci in Russia, and one plasmid was from strain C790 from Kyrgyzstan. Sequence analyses identified four sequence types among the six plasmids. The pPCP1 plasmids in the FSU strains were most genetically related to the pPCP1 plasmid in the KIM strain and least related to the pPCP1 plasmid in Y. pestis 91001. The FSU strains generally had larger pPCP1 plasmid copy numbers compared to strain CO92. Expression of the plasmid's pla gene was significantly (P ≤ .05) higher in strain C2944 than in strain CO92. Given pla's role in Y. pestis virulence, this difference may have important implications for the strain's virulence.
Pandemic Vibrio parahaemolyticus has undergone rapid changes in both K- and O-antigens, making detection of outbreaks more difficult. In order to understand these rapid changes, the genetic regions encoding these antigens must be examined. In Vibrio cholerae and Vibrio vulnificus, both O-antigen and capsular polysaccharides are encoded in a single region on the large chromosome; a similar arrangement in pandemic V. parahaemolyticus would help explain the rapid serotype changes. However, previous reports on "capsule" genes are controversial. Therefore, we set out to clarify and characterize these regions in pandemic V. parahaemolyticus O3:K6 by gene deletion using a chitin based transformation strategy.
We generated different deletion mutants of putative polysaccharide genes and examined the mutants by immuno-blots with O and K specific antisera. Our results showed that O- and K-antigen genes are separated in V. parahaemolyticus O3:K6; the region encoding both O-antigen and capsule biosynthesis in other vibrios, i.e. genes between gmhD and rjg, determines the K6-antigen but not the O3-antigen in V. parahaemolyticus. The previously identified "capsule genes" on the smaller chromosome were related to exopolysaccharide synthesis, not K-antigen.
Understanding of the genetic basis of O- and K-antigens is critical to understanding the rapid changes in these polysaccharides seen in pandemic V. parahaemolyticus. This report confirms the genetic location of K-antigen synthesis in V. parahaemolyticus O3:K6 allowing us to focus future studies of the evolution of serotypes to this region.
A species-specific RNA colony blot hybridization protocol was developed for enumeration of culturable Vibrio cholerae and Vibrio mimicus bacteria in environmental water samples. Bacterial colonies on selective or nonselective plates were lysed by sodium dodecyl sulfate, and the lysates were immobilized on nylon membranes. A fluorescently labeled oligonucleotide probe targeting a phylogenetic signature sequence of 16S rRNA of V. cholerae and V. mimicus was hybridized to rRNA molecules immobilized on the nylon colony lift blots. The protocol produced strong positive signals for all colonies of the 15 diverse V. cholerae-V. mimicus strains tested, indicating 100% sensitivity of the probe for the targeted species. For visible colonies of 10 nontarget species, the specificity of the probe was calculated to be 90% because of a weak positive signal produced by Grimontia (Vibrio) hollisae, a marine bacterium. When both the sensitivity and specificity of the assay were evaluated using lake water samples amended with a bioluminescent V. cholerae strain, no false-negative or false-positive results were found, indicating 100% sensitivity and specificity for culturable bacterial populations in freshwater samples when G. hollisae was not present. When the protocol was applied to laboratory microcosms containing V. cholerae attached to live copepods, copepods were found to carry approximately 10,000 to 50,000 CFU of V. cholerae per copepod. The protocol was also used to analyze pond water samples collected in an area of cholera endemicity in Bangladesh over a 9-month period. Water samples collected from six ponds demonstrated a peak in abundance of total culturable V. cholerae bacteria 1 to 2 months prior to observed increases in pathogenic V. cholerae and in clinical cases recorded by the area health clinic. The method provides a highly specific and sensitive tool for monitoring the dynamics of V. cholerae in the environment. The RNA blot hybridization protocol can also be applied to detection of other gram-negative bacteria for taxon-specific enumeration.
Clinical and environmental Vibrio cholerae organisms collected from February 2004 through April 2005 were systematically isolated from 2 rural Bangladeshi locales. Their genetic relatedness was evaluated at 5 loci that contained a variable number of tandem repeats (VNTR). The observed minimal overlap in VNTR patterns between the 2 communities was consistent with sequential, small outbreaks from local sources.
Cholera; variable number of tandem repeats; epidemiology; outbreaks; genetic variation; dispatch
Vibrio cholerae NRT36S is a non-cholera toxin-producing, non-O1 strain that causes diarrhea in volunteers. The genome of NRT36S was sequenced to create a draft containing 174 contigs plus the superintegron region. Our analysis of the draft genome revealed several putative toxin genes and colonization factors. Besides confirming the existence of nonagglutinable heat-stable toxin, we also identified the genes for a type three secretion system, a putative exotoxin, two different RTX toxins, and four pilus systems.
Coexisting conditions and previous antimicrobial drug exposure predict colonization.
Extended-spectrum β-lactamase (ESBL)–producing bacteria are emerging pathogens. To analyze risk factors for colonization with ESBL-producing bacteria at intensive care unit (ICU) admission, we conducted a prospective study of a 3.5-year cohort of patients admitted to medical and surgical ICUs at the University of Maryland Medical Center. Over the study period, admission cultures were obtained from 5,209 patients. Of these, 117 were colonized with ESBL-producing Escherichia coli and Klebsiella spp., and 29 (25%) had a subsequent ESBL-positive clinical culture. Multivariable analysis showed the following to be statistically associated with ESBL colonization at admission: piperacillin-tazobactam (odds ratio [OR] 2.05, 95% confidence interval [CI] 1.36–3.10), vancomycin (OR 2.11, 95% CI 1.34–3.31), age >60 years (OR 1.79, 95% CI 1.24–2.60), and chronic disease score (OR 1.15; 95% CI 1.04–1.27). Coexisting conditions and previous antimicrobial drug exposure are thus predictive of colonization, and a large percentage of these patients have subsequent positive clinical cultures for ESBL-producing bacteria.
Drug-resistance microbial; risk factors; intensive care units; beta lactamases; Escherichia coli; Klebsiella; research
weather; climate; disease outbreaks; letter
Exposure to the dinoflagellate Pfiesteria has, under certain circumstances, been associated with deficits in human
learning and memory. However, uncertainties remain about the health
risk of chronic, low-level exposures (as seen among occupationally exposed
commercial fishermen), particularly in light of studies suggesting
that Pfiesteria strains are widespread in the estuarine environment in the U.S. mid-Atlantic
We selected an initial cohort of 152 persons, including 123 persons with
regular, occupational exposure to the Chesapeake Bay; 107 of the cohort
members were followed for the full four summer “seasons” of
the study. Cohort members were questioned biweekly about symptoms, and
data were collected about the areas of the bay in which they
worked. These latter data were matched with data on the presence or
absence of Pfiesteria in each area, based on polymerase chain reaction analysis of > 3,500 water
samples. Cohort members underwent neuropsychological testing at
the beginning and end of each summer season.
No correlation was found between work in an area where Pfiesteria was identified and specific symptomatology or changes on neuropsychological
Although high-level or outbreak-associated exposure to Pfiesteria species (or specific strains within a species) may have an effect on health, routine
occupational exposure to estuarine environments in which
these organisms are present does not appear to pose a significant health
commercial fishermen; dinoflagellates; environmental toxins; neuropsychological testing; occupational health
Cholera is an ancient disease that continues to cause epidemic and pandemic disease despite ongoing efforts to limit its spread. Mathematical models provide one means of assessing the utility of various proposed interventions. However, cholera models that have been developed to date have had limitations, suggesting that there are basic elements of cholera transmission that we still do not understand.
Methods and Findings
Recent laboratory findings suggest that passage of Vibrio cholerae O1 Inaba El Tor through the gastrointestinal tract results in a short-lived, hyperinfectious state of the organism that decays in a matter of hours into a state of lower infectiousness. Incorporation of this hyperinfectious state into our disease model provides a much better fit with the observed epidemic pattern of cholera. These findings help to substantiate the clinical relevance of laboratory observations regarding the hyperinfectious state, and underscore the critical importance of human-to-human versus environment-to-human transmission in the generation of epidemic and pandemic disease.
To have maximal impact on limiting epidemic spread of cholera, interventions should be targeted toward minimizing risk of transmission of the short-lived, hyperinfectious form of toxigenic Vibrio cholerae. The possibility of comparable hyperinfectious states in other major epidemic diseases also needs to be evaluated and, as appropriate, incorporated into models of disease prevention.
Adjusting cholera models to take into account a short-lived hyperinfectious state proposed by recent experimental data improves their fit with real outbreak data.
High prevalence of co-colonization increases risk for colonization or infection by vancomycin-resistant Staphylococcus aureus.
We assessed the prevalence, risk factors, and clinical outcomes of patients co-colonized with vancomycin-resistant enterococci (VRE) and methicillin-resistant Staphylococcus aureus (MRSA) upon admission to the medical and surgical intensive care units (ICUs) of a tertiary-care facility between January 1, 2002, and December 31, 2003. Co-colonization was defined as a VRE-positive perirectal surveillance culture with an MRSA-positive anterior nares surveillance culture collected concurrently. Among 2,440 patients, 65 (2.7%) were co-colonized. Independent risk factors included age (odds ratio [OR] 1.03, 95% confidence interval [CI] 1.01–1.05), admission to the medical ICU (OR 4.38, 95% CI 2.46–7.81), male sex (OR 1.93, 95% CI 1.14–3.30), and receiving antimicrobial drugs on a previous admission within 1 year (OR 3.06, 95% CI 1.85–5.07). None of the co-colonized patients would have been identified with clinical cultures alone. We report a high prevalence of VRE/MRSA co-colonization upon admission to ICUs at a tertiary-care hospital.
Vancomycin-resistant Staphylococcus aureus; Methicillin-resistant Staphylococcus aureus; Vancomycin-resistant enterococci; Intensive care unit; Colonization; Risk factors; Outcomes; Research
Smith and colleagues discuss evidence suggesting that antibiotic use in agriculture has contributed to antibiotic resistance in the pathogenic bacteria of humans.
Does antibiotic use in agriculture have a greater impact than hospital use?