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1.  Systematic Evaluation of Commercial Susceptibility Testing Methods for Determining the In Vitro Activity of Daptomycin versus Staphylococcus aureus and Enterococci 
Journal of Clinical Microbiology  2014;52(6):1877-1882.
We systematically evaluated 5 methods for testing daptomycin versus 48 Enterococcus faecalis, 51 Enterococcus faecium, and 50 Staphylococcus aureus isolates using (i and ii) broth microdilution (BMD) with 50-mg/liter calcium medium supplementation (reference method) and 30-mg/liter calcium medium supplementation (BMD30 method), (iii) Etest, and (iv and v) MicroScan panel 33 using 2 methods to prepare the bacterial inoculum (MicroScan turbidity and MicroScan Prompt). Isolates were categorized as susceptible (S) or nonsusceptible (NS) based on measured MICs. Essential (±1 dilution) agreement (EA) and categorical (S/NS) agreement (CA) for each method were compared to the reference method. For E. faecium, categorical agreement was poor between the reference method and BMD30 as well as with the three commercial methods, with frequent false-NS results (30 for BMD30, 18 for Etest, 22 for MicroScan Prompt, and 25 for MicroScan turbidity). All E. faecalis isolates were judged to be S by the reference method; two of these isolates were categorized as NS using the BMD30 method, and one was categorized as NS by all three commercial methods. All S. aureus isolates were judged to be S using all five methods. MIC values determined by the comparator methods tended to be higher than those for the reference method, especially for E. faecium isolates. EAs between the reference BMD and BMD30, Etest, MicroScan Prompt, and MicroScan turbidity were 63%, 63%, 63%, and 56%, respectively, for E. faecium, 87%, 83%, 98%, and 80%, respectively, for E. faecalis, and all 100% for S. aureus.
doi:10.1128/JCM.03439-13
PMCID: PMC4042769  PMID: 24648560
2.  A Guide to Utilization of the Microbiology Laboratory for Diagnosis of Infectious Diseases: 2013 Recommendations by the Infectious Diseases Society of America (IDSA) and the American Society for Microbiology (ASM)a 
The critical role of the microbiology laboratory in infectious disease diagnosis calls for a close, positive working relationship between the physician and the microbiologists who provide enormous value to the health care team. This document, developed by both laboratory and clinical experts, provides information on which tests are valuable and in which contexts, and on tests that add little or no value for diagnostic decisions. Sections are divided into anatomic systems, including Bloodstream Infections and Infections of the Cardiovascular System, Central Nervous System Infections, Ocular Infections, Soft Tissue Infections of the Head and Neck, Upper Respiratory Infections, Lower Respiratory Tract infections, Infections of the Gastrointestinal Tract, Intraabdominal Infections, Bone and Joint Infections, Urinary Tract Infections, Genital Infections, and Skin and Soft Tissue Infections; or into etiologic agent groups, including Tickborne Infections, Viral Syndromes, and Blood and Tissue Parasite Infections. Each section contains introductory concepts, a summary of key points, and detailed tables that list suspected agents; the most reliable tests to order; the samples (and volumes) to collect in order of preference; specimen transport devices, procedures, times, and temperatures; and detailed notes on specific issues regarding the test methods, such as when tests are likely to require a specialized laboratory or have prolonged turnaround times. There is redundancy among the tables and sections, as many agents and assay choices overlap. The document is intended to serve as a reference to guide physicians in choosing tests that will aid them to diagnose infectious diseases in their patients.
doi:10.1093/cid/cit278
PMCID: PMC3719886  PMID: 23845951
laboratory diagnosis; microbiology testing; specimen processing; physician-laboratory communication; medical laboratories
3.  Executive Summary: A Guide to Utilization of the Microbiology Laboratory for Diagnosis of Infectious Diseases: 2013 Recommendations by the Infectious Diseases Society of America (IDSA) and the American Society for Microbiology (ASM)a 
The critical role of the microbiology laboratory in infectious disease diagnosis calls for a close, positive working relationship between the physician and the microbiologists who provide enormous value to the health care team. This document, developed by both laboratory and clinical experts, provides information on which tests are valuable and in which contexts, and on tests that add little or no value for diagnostic decisions. Sections are divided into anatomic systems, including Bloodstream Infections and Infections of the Cardiovascular System, Central Nervous System Infections, Ocular Infections, Soft Tissue Infections of the Head and Neck, Upper Respiratory Infections, Lower Respiratory Tract infections, Infections of the Gastrointestinal Tract, Intraabdominal Infections, Bone and Joint Infections, Urinary Tract Infections, Genital Infections, and Skin and Soft Tissue Infections; or into etiologic agent groups, including Tickborne Infections, Viral Syndromes, and Blood and Tissue Parasite Infections. Each section contains introductory concepts, a summary of key points, and detailed tables that list suspected agents; the most reliable tests to order; the samples (and volumes) to collect in order of preference; specimen transport devices, procedures, times, and temperatures; and detailed notes on specific issues regarding the test methods, such as when tests are likely to require a specialized laboratory or have prolonged turnaround times. There is redundancy among the tables and sections, as many agents and assay choices overlap. The document is intended to serve as a reference to guide physicians in choosing tests that will aid them to diagnose infectious diseases in their patients.
doi:10.1093/cid/cit441
PMCID: PMC3719893  PMID: 23881727
laboratory diagnosis; microbiology testing; specimen processing; physician-laboratory communication; medical laboratories
4.  A Critical Appraisal of the Role of the Clinical Microbiology Laboratory in the Diagnosis of Bloodstream Infections 
Journal of Clinical Microbiology  2011;49(9 Suppl):S26-S29.
The detection of bloodstream infections is one of the most important functions of clinical microbiology laboratories. Despite advances in blood culture technology and clinical studies that have focused on the detection of bacteremia and fungemia, perfection has not been achieved and uncertainties persist. This review provides perspectives on a number of areas, including the recommended number of blood cultures, duration of incubation of blood cultures, use of anaerobic, in addition to aerobic, blood culture media, value of the lysis-centrifugation method, processing and reporting of probable blood culture contaminants, and limitations of current blood culture methods and systems. We also address the handling of blood cultures in point-of-care locations that lack full microbiology capabilities.
doi:10.1128/JCM.00765-11
PMCID: PMC3185849
6.  Characterisation of a Staphylococcus aureus strain with progressive loss of susceptibility to vancomycin and daptomycin during therapy✰ 
Following an initial response to vancomycin therapy, a patient with meticillin-resistant Staphylococcus aureus (MRSA) bacteraemia developed endocarditis, failed a second course of vancomycin and then failed daptomycin therapy. An increase in the vancomycin minimum inhibitory concentrations of four consecutive MRSA blood isolates from 2 μg/mL to 8 μg/mL was shown by Etest. Population analysis of four successive blood culture isolates recovered over the 10-week period showed that the MRSA strain became progressively less susceptible to both vancomycin and daptomycin. Retrospectively, the macro Etest method using teicoplanin indicated a decrease in vancomycin susceptibility in the second blood isolate. The patient improved after treatment with various courses of trimethoprim/sulphamethoxazole, quinupristin/dalfopristin and linezolid. Early detection of vancomycin-heteroresistant S. aureus isolates, which appeared to have clinical significance in this case, continues to be a challenge for the clinical laboratory. Development of suitable practical methods for this should be given priority. Concurrent development of resistance to vancomycin and daptomycin, whilst rare, must be considered in a patient who is unresponsive to daptomycin following vancomycin therapy.
doi:10.1016/j.ijantimicag.2008.12.010
PMCID: PMC2700752  PMID: 19233622
Staphylococci; Vancomycin; Teicoplanin; Heteroresistance
7.  First Descriptions of blaKPC in Raoultella spp. (R. planticola and R. ornithinolytica): Report from the SENTRY Antimicrobial Surveillance Program▿  
Journal of Clinical Microbiology  2009;47(12):4129-4130.
Two strains of Raoultella planticola and one of Raoultella ornithinolytica showing carbapenem resistance were recovered from patients hospitalized in New Jersey and Ohio. All patients had received previous antimicrobial treatment, including carbapenems. These strains harbored blaKPC-2 and blaKPC-3. Carbapenemase genes were embedded in isoforms of Tn4401 and were plasmidic and chromosomal in location.
doi:10.1128/JCM.01502-09
PMCID: PMC2786659  PMID: 19812278
8.  Discarding the Initial Aliquot of Blood Does Not Reduce Contamination Rates in Intravenous-Catheter-Drawn Blood Cultures ▿  
Journal of Clinical Microbiology  2009;47(9):2950-2951.
Although venipuncture is the preferred method for obtaining blood cultures, specimens often are obtained from intravenous catheters (IVC). For IVC-drawn blood cultures, some authorities recommend discarding the initial 5 to 10 ml of blood to reduce contamination and remove potential inhibitory substances. To determine whether this practice reduced contamination rates (CR), we assessed the results of IVC-drawn blood cultures for adults. Thirty milliliters of blood was obtained aseptically. The first 10 ml, rather than being discarded, was inoculated into an aerobic culture vial. Using a second sterile syringe, 20 ml of blood was obtained and inoculated in 10-ml aliquots to aerobic and anaerobic culture vials. Positive cultures were evaluated to assess clinical significance (true versus contaminant). Out of 653 IVC-drawn blood culture pairs, both vials were contaminated in 38 pairs (5.8%); only the “discard” vial was contaminated in 33 (5.1%); and only the “standard” vial was contaminated in 31 (4.7%). Overall CR were 10.9% for the discard vial versus 10.5% for the standard vial (P = 0.90). We conclude that discarding an initial aliquot of blood when obtaining blood cultures from IVCs does not reduce CR.
doi:10.1128/JCM.00292-09
PMCID: PMC2738108  PMID: 19641064
9.  Correlation of Cefoxitin MICs with the Presence of mecA in Staphylococcus spp.▿  
Journal of Clinical Microbiology  2009;47(6):1902-1905.
This report describes the results of an 11-laboratory study to determine if a cefoxitin broth microdilution MIC test could predict the presence of mecA in staphylococci. Using breakpoints of ≤4 μg/ml for mecA-negative and ≥6 or 8 μg/ml for mecA-positive isolates, sensitivity and specificity based on mecA or presumed mecA for Staphylococcus aureus at 18 h of incubation were 99.7 to 100% in three cation-adjusted Mueller-Hinton broths tested. For coagulase-negative strains at 24 h of incubation, breakpoints of ≤2 μg/ml for mecA-negative and ≥4 μg/ml for mecA-positive isolates gave sensitivity and specificity of 94 to 99% and 69 to 80%, respectively.
doi:10.1128/JCM.02304-08
PMCID: PMC2691132  PMID: 19357210
10.  Detection of Inducible Clindamycin Resistance in Staphylococci by Broth Microdilution Using Erythromycin-Clindamycin Combination Wells▿  
Journal of Clinical Microbiology  2007;45(12):3954-3957.
A study conducted by 11 laboratories investigated the ability of four combinations of erythromycin (ERY) and clindamycin (CC) (ERY and CC at 4 and 0.5, 6 and 1, 8 and 1.5, and 0.5 and 2 μg/ml) in a single well of a broth microdilution panel to predict the presence of inducible CC resistance. Each laboratory tested approximately 30 Staphylococcus aureus isolates and 20 coagulase-negative staphylococcus (CoNS) isolates in a panel using cation-adjusted Mueller-Hinton broth from three different manufacturers. Only the strains resistant to ERY and those susceptible or intermediate to CC were included in the analysis (S. aureus, n = 333; CoNS, n = 97). Results of the D-zone test were used as the gold standard. After an 18-h incubation, the combination of 4 μg/ml ERY and 0.5 μg/ml CC performed the best, with 98 to 100% sensitivity and 100% specificity for both organism groups. After a 24-h incubation, the ERY-CC combinations of 4 and 0.5, 6 and 1, and 8 and 1.5 μg/ml correlated well with the D-zone test.
doi:10.1128/JCM.01501-07
PMCID: PMC2168576  PMID: 17942655
11.  Detection of Bloodstream Infections in Adults: How Many Blood Cultures Are Needed?▿  
Journal of Clinical Microbiology  2007;45(11):3546-3548.
Although several reports have shown that two to three 20-ml blood cultures are adequate for the detection of bacteremia and fungemia in adults, a recent study (F. R. Cockerill et al., Clin. Infect. Dis. 38:1724-1730, 2004) found that two blood cultures detected only 80% of bloodstream infections and that three blood cultures detected 96% of episodes. We reviewed data at two university hospitals to determine whether the recent observations by Cockerill et al. are applicable more widely. We assessed all blood cultures obtained from adult inpatients from 1 January 2004 through 31 December 2005 at Robert Wood Johnson University Hospital and Duke University Medical Center. All instances in which ≥3 blood cultures per patient were obtained during a 24-h period were included. The medical records of patients who met the inclusion criteria were reviewed retrospectively to determine the clinical significance of the positive blood culture (true infection versus contamination). Data were analyzed to determine the cumulative sensitivity of blood cultures obtained sequentially during the 24-h time period. Of 629 unimicrobial episodes with ≥3 blood cultures obtained during the 24-h period, 460 (73.1%) were detected with the first blood culture, 564 (89.7%) were detected with the first two blood cultures, 618 (98.2%) were detected with the first three blood cultures, and 628 (99.8%) were detected with the first four blood cultures. Of 351 unimicrobial episodes with ≥4 blood cultures obtained during the 24-h period, 257 (73.2%) were detected with the first blood culture, 308 (93.9%) were detected with the first two blood cultures, 340 (96.9%) were detected with the first three blood cultures, and 350 (99.7%) were detected with the first four blood cultures. Among unimicrobial episodes, Staphylococcus aureus was more likely to be detected with the first blood culture (approximately 90% detected with the first blood culture). There were 58 polymicrobial episodes in which ≥3 blood cultures were obtained. Forty-seven (81.0%) were detected with the first blood culture, 54 (93.1%) were detected with the first two blood cultures, and 58 (100%) were detected with the first three blood cultures. The results of this study indicate that two blood cultures in a 24-h period will detect approximately 90% of bloodstream infections in adults. To achieve a detection rate of >99%, as many as four blood cultures may be needed. The previously held axiom that virtually all bloodstream infections can be detected with two to three blood cultures may no longer be valid but may also depend on the definition of the “first” blood culture obtained (see Materials and Methods and Discussion in the text).
doi:10.1128/JCM.01555-07
PMCID: PMC2168497  PMID: 17881544
12.  Multicenter Evaluation of the BD Phoenix Automated Microbiology System for Antimicrobial Susceptibility Testing of Streptococcus Species▿  
Journal of Clinical Microbiology  2007;45(9):2863-2871.
This multicenter study evaluated the BD Phoenix Automated Microbiology System STREP panel (BD Diagnostic Systems). Antimicrobial susceptibility testing (AST) with 13 agents was performed on 2,013 streptococci (938 Streptococcus pneumoniae isolates; 396 group B streptococci [GBS]; 369 viridans group streptococci [VGS]; 290 beta-hemolytic streptococcus groups A, C, and G; and 20 other streptococci) with the Phoenix system and a broth microdilution reference method. Clinical and challenge isolates were tested against cefepime, cefotaxime (CTX), ceftriaxone (CTR), clindamycin (CLI), erythromycin (ERY), gatifloxacin, levofloxacin, linezolid, meropenem, penicillin (PEN), tetracycline (TET), trimethoprim-sulfamethoxazole, and vancomycin. Clinical isolates with major errors or very major errors (VMEs) were retested in duplicate by both methods. The final results for clinical isolates showed the following trends. For all of the organism-antimicrobial agent combinations tested, categorical agreement (CA) was 92 to 100%, with one exception—VGS-PEN (87% CA; all errors were minor). For S. pneumoniae, there was one major error with CLI (0.1%) and one or two VMEs with CTX (4%), CTR (4.5%), ERY (0.9%), and TET (0.7%). For groups A, C, and G, the CA was 97 to 100% and the only VMEs were resolved by additional reference laboratory testing. For GBS, there was only one VME (TET, 0.3%) and D-zone testing of 23 isolates with CLI major errors (one isolate unavailable) revealed inducible CLI resistance. For VGS, the major error rates were 0 to 3% and VMEs occurred with seven agents (3.5 to 7.1%). The mean times required for organism groups to generate results ranged from 8.4 to 9.4 h. The Phoenix system provided reliable and rapid AST results for most of the organism-antimicrobial agent combinations tested.
doi:10.1128/JCM.00981-07
PMCID: PMC2045298  PMID: 17652483
13.  Utility of Extended Blood Culture Incubation for Isolation of Haemophilus, Actinobacillus, Cardiobacterium, Eikenella, and Kingella Organisms: a Retrospective Multicenter Evaluation 
Journal of Clinical Microbiology  2006;44(1):257-259.
The incidence of and average time to detection for Haemophilus, Actinobacillus, Cardiobacterium, Eikenella, and Kingella (HACEK) bacteria in blood cultures with standard incubation and the utility of extended incubation of blood culture bottles were reviewed at four tertiary care microbiology laboratories. HACEK organisms were isolated from 35 (<0.005%) of 59,203 positive blood cultures. None of 407 blood cultures with extended incubation grew HACEK or other bacteria. Bacteremia from HACEK bacteria is rare, and extended incubation of blood cultures to recover HACEK bacteria is unnecessary.
doi:10.1128/JCM.44.1.257-259.2006
PMCID: PMC1351967  PMID: 16390985
14.  Multicenter Evaluation of Use of Penicillin and Ampicillin as Surrogates for In Vitro Testing of Susceptibility of Enterococci to Imipenem 
Journal of Clinical Microbiology  2004;42(8):3747-3751.
Imipenem is approved by the U.S. Food and Drug Administration (FDA) for treatment of infections caused by Enterococcus faecalis. However, there are no NCCLS guidelines for testing susceptibility of enterococci against imipenem. To assess whether or not ampicillin or penicillin could be used as a surrogate for broth microdilution (BMD) testing of imipenem versus Enterococcus species, 633 strains of E. faecalis, E. faecium, and other enterococci isolated from blood cultures of patients at three geographically distinct university hospitals were tested by the NCCLS BMD and disk diffusion (DD) methods. Using FDA susceptibility breakpoints for imipenem and NCCLS breakpoints for penicillin and ampicillin, categorical agreement (CA) for penicillin-imipenem and ampicillin-imipenem tested with E. faecalis and E. faecium by BMD was ≥94% but was ≤90% for other enterococci. Using the DD method, CA for ampicillin-imipenem tested with E. faecalis and E. faecium was ≥98% and was 92% for other enterococci; CA for penicillin-imipenem was 91% for E. faecalis, 98% for E. faecium, and 87% for other enterococci. Further analysis showed that testing E. faecalis with ampicillin resulted in no false-susceptible (FS) or false-resistant (FR) results by BMD, no FS results by DD, and a single FR result by DD (0.2%), whereas testing with penicillin resulted in no FS results by BMD or DD and two FR results by BMD (0.4%). For E. faecium and other enterococci, the combination of FS and FR results was such that surrogate testing with penicillin or ampicillin appears not to be sufficiently reliable to be used clinically. We conclude that ampicillin is an accurate predictor of the in vitro activity of imipenem against E. faecalis.
doi:10.1128/JCM.42.8.3747-3751.2004
PMCID: PMC497596  PMID: 15297525
15.  Controlled Clinical Comparison of BacT/ALERT Standard Aerobic Medium with BACTEC Standard Aerobic Medium for Culturing Blood 
Journal of Clinical Microbiology  2003;41(6):2391-2394.
Standard aerobic media are widely used for culturing blood with the BacT/ALERT (BioMérieux, Inc., Durham, N.C.) (BM) and BACTEC 9240 (BD Diagnostic Systems, Sparks, Md.) (BD) automated continuously monitoring instrument systems. Although similarly composed of soybean-casein digest broths, the formulations of the standard aerobic media available for these instruments differ from each other in supplements and in sodium polyanetholesulfonate concentration. Therefore, we compared the standard aerobic media available for these systems at two university hospitals. Blood samples from adult patients with suspected bloodstream infection were inoculated at the bedside into nonvented BM and BD standard aerobic blood culture bottles and incubated in their respective instruments. The laboratories received 6,743 pairs of bottles that were each filled with 8 to 12 ml of blood. A total of 523 isolates representing true infections were recovered from 257 patients; of these isolates, 348 were recovered from both the BD and the BM bottles, 108 were recovered from the BM bottles only, and 67 were recovered from the BD bottles only (P < 0.005). More staphylococci (P < 0.05), especially coagulase-negative staphylococci (P < 0.05), and yeasts (P < 0.01) were recovered from BM bottles than from BD bottles. Of 291 unimicrobial episodes of bloodstream infection, 220 were detected with both bottles, 41 were detected with the BM bottles only, and 30 were detected with the BD bottles only (difference not significant). Among 335 cultures that were positive in both bottles within the first 72 h of incubation, the median times to detection were 14 h for BM bottles and 13 h for BD bottles. Rates for false-positive results were 0.5% for BM bottles and 0.1% for BD bottles. One BM bottle and seven BD bottles yielded false-negative results. We conclude that the BM medium provides improved recovery of microorganisms, especially staphylococci and yeasts, compared with that provided by the BD medium.
doi:10.1128/JCM.41.6.2391-2394.2003
PMCID: PMC156516  PMID: 12791854
16.  Blood Culture Contamination: Persisting Problems and Partial Progress 
Journal of Clinical Microbiology  2003;41(6):2275-2278.
doi:10.1128/JCM.41.6.2275-2278.2003
PMCID: PMC156489  PMID: 12791835
17.  Are Three Sputum Acid-Fast Bacillus Smears Necessary for Discontinuing Tuberculosis Isolation? 
Journal of Clinical Microbiology  2002;40(9):3482-3484.
To evaluate the efficacy of three sputum acid-fast bacillus (AFB) smears to rule out pulmonary tuberculosis, sputum AFB smear and culture results were analyzed at two university-affiliated teaching hospitals. The negative predictive value of the smear increased by only 0.2% on days 2 and 3 each, indicating that in low-prevalence populations, there is limited value in requiring three negative sputum AFB smears before discontinuing tuberculosis isolation.
doi:10.1128/JCM.40.9.3482-3484.2002
PMCID: PMC130719  PMID: 12202598
18.  Relevance of the Number of Positive Bottles in Determining Clinical Significance of Coagulase-Negative Staphylococci in Blood Cultures 
Journal of Clinical Microbiology  2001;39(9):3279-3281.
Coagulase-negative staphylococci (CNS) are the most commonly isolated contaminants from blood cultures, yet they frequently cause true infections. Determining the clinical significance of CNS is difficult, and clinicians often consider the number of positive bottles within a set of blood culture bottles in their assessment. Therefore, in three separate studies, we counted the number of positive bottles within blood culture sets comprising two, three, or four bottles in order to predict whether or not CNS were clinically significant isolates (CSI) in adult patients with suspected sepsis. Each culture was evaluated by independent, published clinical criteria to determine its clinical importance. Of 486 positive sets that included two adequately filled bottles, 127 (26%) CNS were CSI, 329 (67%) were contaminants, and 30 (6%) were indeterminate as a cause of sepsis. Among CSI, 39 and 61% were isolated from one and two bottles, respectively. The positive predictive value for sepsis was 18% when one bottle was positive and 37% when both bottles were positive. Of 235 positive sets that included three adequately filled bottles, 81 (34%) were CSI, 109 (46%) were contaminants, and 45 (19%) were indeterminate as a cause of sepsis. Of CSI, 43, 38, and 19% were found in one, two, and three bottles, respectively. The positive predictive value for sepsis was 28, 52, and 30% when one, two and three bottles were positive. Of 303 positive blood culture sets that included four adequately filled bottles, 64 (21%) were considered CSI, 197 (65%) were contaminants, and 42 (14%) were indeterminate as a cause of sepsis. Of CSI, 27, 28, 19, and 27% were found in one, two, three, and four bottles, respectively. The positive predictive value for sepsis was 11, 30, 34, and 37% when one, two, three, and four bottles were positive. We conclude that the number of culture bottles positive in a given culture set cannot reliably predict the clinical significance of the CNS isolated and, therefore, should not be used as a criterion for determining whether or not an isolate represents true infection or contamination.
doi:10.1128/JCM.39.9.3279-3281.2001
PMCID: PMC88331  PMID: 11526163
19.  Comparative Evaluation of Penicillin, Ampicillin, and Imipenem MICs and Susceptibility Breakpoints for Vancomycin-Susceptible and Vancomycin-Resistant Enterococcus faecalis and Enterococcus faecium 
Journal of Clinical Microbiology  2001;39(7):2729-2731.
Although imipenem has in vitro activity against Enterococcus faecalis and Food and Drug Administration-approved indications for treatment of infections caused by this microorganism, there are no NCCLS guidelines for susceptibility testing of imipenem versus enterococci. Therefore, the in vitro activities of penicillin, ampicillin, imipenem, and vancomycin against 201 blood isolates of E. faecalis and 24 blood isolates of Enterococcus faecium were compared. The susceptibility of isolates to penicillin or ampicillin accurately predicted the in vitro activity of imipenem. Since the susceptibility of enterococci to imipenem can be predicted by the results obtained by testing of penicillin or ampicillin, testing of imipenem by clinical laboratories probably is not necessary.
doi:10.1128/JCM.39.7.2729-2731.2001
PMCID: PMC88224  PMID: 11427608
20.  Controlled Clinical Comparison of BACTEC Plus Anaerobic/F to Standard Anaerobic/F as the Anaerobic Companion Bottle to Plus Aerobic/F Medium for Culturing Blood from Adults 
Journal of Clinical Microbiology  2001;39(3):983-989.
To determine the optimal anaerobic companion bottle to pair with BACTEC Plus Aerobic/F medium for recovery of pathogenic microorganisms from adult patients with bacteremia and fungemia, we compared Plus Anaerobic/F bottles with Standard Anaerobic/F bottles, each of which was filled with 4 to 6 ml of blood. The two bottles were paired with a Plus Aerobic/F bottle filled with 8 to 12 ml of blood. A total of 14,011 blood culture sets were obtained. Of these, 11,583 sets were received with all three bottles filled adequately and 12,257 were received with both anaerobic bottles filled adequately. Of 818 clinically important isolates detected in one or both adequately filled anaerobic bottles, significantly more staphylococci (P < 0.001), streptococci (P < 0.005), Escherichia coli isolates (P < 0.02), Klebsiella pneumoniae isolates (P < 0.005), and all microorganisms combined (P < 0.001) were detected in Plus Anaerobic/F bottles. In contrast, significantly more anaerobic gram-negative bacilli were detected in Standard Anaerobic/F bottles (P < 0.05). Of 397 unimicrobial episodes of septicemia, 354 were detected with both pairs, 30 were detected with Plus Aerobic/F–Plus Anaerobic/F pairs only, and 13 were detected with Plus Aerobic/F–Standard Anaerobic/F pairs only (P < 0.05). Significantly more episodes of bacteremia caused by members of the family Enterobacteriaceae (P < 0.05) and aerobic and facultative gram-positive bacteria (P < 0.025) were detected with Plus Anaerobic/F bottles only. In a paired-bottle analysis, 810 of 950 isolates were recovered from both pairs, 90 were recovered from Plus Aerobic/F–Plus Anaerobic/F pairs only, and 50 were recovered from Plus Aerobic/F–Standard Anaerobic/F pairs only (P < 0.001). Paired Plus Aerobic/F–Plus Anaerobic/F bottles yielded significantly more staphylococci (P < 0.001), streptococci (P < 0.05), and members of the family Enterobacteriaceae (P <0.001). We conclude that Plus Anaerobic/F bottles detect more microorganisms and episodes of bacteremia and fungemia than Standard Anaerobic/F bottles as companion bottles to Plus Aerobic/F bottles in the BACTEC 9240 blood culture system.
doi:10.1128/JCM.39.3.983-989.2001
PMCID: PMC87861  PMID: 11230415
21.  Controlled Comparison of BacT/ALERT FAN Aerobic Medium and BACTEC Fungal Blood Culture Medium for Detection of Fungemia 
Journal of Clinical Microbiology  2001;39(2):622-624.
Yeasts are an increasingly common cause of nosocomial bloodstream infections. Methods for their detection are many; controlled comparisons are few. The vented FAN aerobic blood culture medium has been shown to be superior to the standard BacT/ALERT aerobic medium for the detection of fungemia as well as bacteremia. The BACTEC selective fungal medium (FM) (BD Biosciences, Sparks, Md.) allowed detection of more episodes of fungemia than did a resin-containing medium with equal volumes of blood cultured. Therefore, we compared vented FAN to FM for the ability to recover fungi from the blood of patients who were at increased risk of having fungemia. From 5,109 cultures processed for which both FAN and FM bottles were adequately filled, fungi were recovered from 87 cultures. Of these, 47 were detected with both bottles, 12 were detected with FAN only, and 28 were detected with FM only (P < 0.05). FAN was the first bottle positive for 36 of the 47 cultures for which both bottles yielded the same fungus, whereas the FM bottle was the first bottle positive for 11 cultures (P < 0.001). A total of 54 episodes of fungemia were identified, with 40 detected by both media, 4 detected only by FAN, and 10 detected only by FM (P value, not significant). We conclude that the vented FAN aerobic bottle is comparable to the FM bottle for detection of episodes of yeast infection but has the added benefit of detecting bacteria.
doi:10.1128/JCM.39.2.622-624.2001
PMCID: PMC87787  PMID: 11158118
22.  Comparison of Iodophor and Alcohol Pledgets with the Medi-Flex Blood Culture Prep Kit II for Preventing Contamination of Blood Cultures 
Journal of Clinical Microbiology  2000;38(12):4665-4667.
Iodophor and alcohol pledgets were compared with the Medi-Flex Prep Kit II for skin disinfection before venipuncture. Of 12,367 blood cultures collected, 6,362 were done with conventional pledgets and 6,005 were done with Medi-Flex kits. Contamination occurred in 351 of 6,362 blood cultures (5.5%; range, 3.7 to 8.1%) with conventional pledgets versus 328 of 6,005 (5.5%; range, 3.5 to 7.5%) with Medi-Flex kits.
PMCID: PMC87661  PMID: 11101620
23.  Multilaboratory Validation of Rapid Spot Tests for Identification of Escherichia coli 
Journal of Clinical Microbiology  2000;38(9):3394-3398.
To validate the accuracy of rapid tests for identification of Escherichia coli, five laboratories sequentially collected 1,064 fresh, clinically significant strains with core criteria of indole-positive, oxidase-negative, nonspreading organisms on sheep blood agar plates (BAP), having typical gram-negative rod plate morphology, defined as good growth on gram-negative rod-selective media. An algorithm using beta-hemolysis on BAP, lactose reaction on eosin-methylene blue or MacConkey agar, l-pyrrolidonyl-β-naphthylamide (PYR), and 4-methylumbelliferyl-β-d-glucuronide (MUG) was evaluated. Identifications using the algorithm were compared to those obtained using commercial kit system identifications. One thousand strains were E. coli and 64 were not E. coli by kit identifications, which were supplemented with conventional biochemical testing of low probability profiles. Of the 1,064 isolates meeting the core criteria, 294 were beta-hemolytic and did not require further testing to be identified as E. coli. None of the 64 non-E. coli strains were hemolytic, although other indole-positive, lactose-negative species were found to be hemolytic when further strains were examined in a follow-up study. Of the remaining strains, 628 were identified as E. coli by a lactose-positive and PYR-negative reaction. For nonhemolytic, lactose-negative E. coli, PYR was not helpful, but a positive MUG reaction identified 65 of 78 isolates as E. coli. The remaining 13 E. coli strains required kit identifications. This scheme for E. coli identification misidentified three non-E. coli strains as E. coli, for an error rate of 0.3%. A total of 13 kit identifications, 657 PYR tests, and 113 MUG tests were needed to identify 1,000 E. coli strains with the algorithm. The use of this rapid system saves laboratory resources, provides timely identifications, and yields rare misidentifications.
PMCID: PMC87392  PMID: 10970389
24.  Controlled Clinical Comparison of bioMérieux VITAL and BACTEC NR-660 Blood Culture Systems for Detection of Bacteremia and Fungemia in Adults 
Journal of Clinical Microbiology  1999;37(6):1709-1713.
A total of 9,446 blood cultures were collected from adult patients at three university-affiliated hospitals. Of these, 8,943 cultures were received with both aerobic bottles filled adequately; 885 yielded 1,016 microorganisms, including 622 isolates (61%) that were the cause of sepsis, 337 isolates (33%) that were contaminants, and 57 isolates (6%) that were indeterminate as the cause of sepsis. With the exception of Staphylococcus aureus, which was recovered more often from VITAL aerobic bottles, more pathogenic microorganisms were recovered from BACTEC NR6 (aerobic) bottles than from VITAL aerobic bottles. Growth of pathogenic microorganisms was detected earlier in VITAL aerobic bottles. A total of 8,647 blood cultures were received with both anaerobic bottles filled adequately; 655 yielded 740 microorganisms, including 486 isolates (66%) that were the cause of sepsis, 215 isolates (29%) that were contaminants, and 39 isolates (6%) that were indeterminate as the cause of sepsis. More pathogenic microorganisms were recovered from VITAL anaerobic bottles than from BACTEC NR7 (anaerobic) bottles. Growth of pathogenic microorganisms was detected earlier in VITAL anaerobic bottles. In 8,500 sets all four bottles were received adequately filled. When paired aerobic and anaerobic bottle sets (systems) were compared, more pathogenic microorganisms (again with the exception of S. aureus) were recovered from the BACTEC system. For the 304 septic episodes (253 unimicrobial and 51 polymicrobial), significantly more were detected by the BACTEC system. We conclude that VITAL requires modification to improve recovery of pathogenic microorganisms to make it competitive with other commercially available blood culture systems.
PMCID: PMC84930  PMID: 10325312
25.  Clinical Importance of Identifying Coagulase-Negative Staphylococci Isolated from Blood Cultures: Evaluation of MicroScan Rapid and Dried Overnight Gram-Positive Panels versus a Conventional Reference Method 
Journal of Clinical Microbiology  1998;36(7):2089-2092.
We evaluated the clinical usefulness of species identification of blood isolates of coagulase-negative staphylococci as a predictor of the clinical significance of the isolates. In addition, we compared results of species identification obtained with MicroScan Rapid Gram-Positive Identification panels and Dried Overnight (Conventional) Gram-Positive Identification panels with those obtained by a tube reference method. Two hundred eighty-five blood isolates were tested, including 92 judged to represent true bacteremia and 193 judged to represent contamination. The most common species detected were Staphylococcus epidermidis, Staphylococcus hominis, and Staphylococcus haemolyticus. These three species accounted for nearly 98% of the clinically significant isolates and 89% of the contaminants. The isolation of other species almost always represented contamination. However, identification of the three most common species did not help distinguish pathogens from contaminants. Both the Rapid and the Dried Overnight Gram-Positive panels identified S. epidermidis strains accurately, but the panels performed less well for the other species. Analysis revealed that S. hominis was frequently misidentified due to the presence of a previously unknown subspecies. Based on the initial results, revised investigational Dried Overnight Gram-Positive Identification panels (CPID-2) were prepared and tested. The CPID-2 panels identified 85 to 95% of S. epidermidis strains, 76 to 86% of S. hominis strains, and 88 to 92% of S. haemolyticus strains with high probability (>85%) and, overall, represented a significant improvement over the other panels for identification of these staphylococcal species.
PMCID: PMC104986  PMID: 9650970

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