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Biomedical subjects

F C Tenover

Publications and source records attributed to F C Tenover.

At least 109 records · Page 6Linked to original sources
PubMed1995

Pulsed-field gel electrophoresis as a replacement for bacteriophage typing of Staphylococcus aureus.

Bacteriophage typing (BT) (World Health Organization method) has been used at the Centers for Disease Control and Prevention for over 30 years to type isolates of Staphylococcus aureus. Since studies have shown that BT patterns have poor reproducibility and because BT fails to type a high percentage (15 to 20%) of isolates, the Centers for Disease Control and Prevention has converted from using BT to using pulsed-field gel electrophoresis (PFGE) for strain typing S. aureus. We compared the results of BT with results of PFGE for typing 300 isolates of S. aureus, including strains from several well-characterized outbreaks. Ninety-six isolates were BT group I, 19 were group II, 82 were group III, 7 were group V, and 96 were nontypeable. PFGE identified subgroups within each phage group and thus was more discriminating than BT, which identified no subgroups. PFGE was able to type all isolates and distinguish related from unrelated strains of S. aureus. Our modified, standardized PFGE methodology should enable typing laboratories to obtain rapid, reliable results in 3 to 4 days when starting with an isolated colony on agar media.

Bacteriophage Typing↗
PubMed1995

Ability of commercial and reference antimicrobial susceptibility testing methods to detect vancomycin resistance in enterococci.

We evaluated the abilities of 10 commercially available antimicrobial susceptibility testing methods and four reference methods (agar dilution, broth microdilution, disk diffusion, and the agar screen plate) to classify enterococci correctly as vancomycin susceptible or resistant using 50 well-characterized strains of enterococci. There was a high level of agreement of category classification data obtained with broth-based systems (Sceptor, MicroMedia, Pasco, and Sensititre), agar dilution, and an antibiotic gradient method (E test) with data obtained by reference broth microdilution; no very major or major errors were seen, and minor errors were < or = 6%. Increased minor error rates were observed with disk diffusion (12%), Alamar (16%), Uniscept (16%), and conventional (overnight) MicroScan panels (16%). The errors were primarily with Enterococcus casseliflavus strains and organisms containing the vanB vancomycin resistance gene. Very major error rates of 10.3 and 20.7% were observed with Vitek and MicroScan Rapid (MS/Rapid) systems, respectively; however, only the MS/Rapid system produced major errors (13.3%). On repeat testing of discrepant isolates, the very major error rate with the Vitek system dropped to 3.4%, while the very major error rate with the MS/Rapid system increased to 27.6%; major errors with the MS/Rapid system were not resolved. Many of the commercial systems had only 4 dilutions of vancomycin, which resulted in up to 84% of values being off scale (e.g., Uniscept). Of the methods tested, most conventional broth- and agar-based methods proved to be highly accurate when incubation was done for a full 24 h, although several of the tests had high minor error rates. Automated systems continued to demonstrate problems in detecting low-level resistance.

Automation↗
PubMed1995

Detection of penicillin-resistant Streptococcus pneumoniae with commercially available broth microdilution panels.

We compared penicillin MICs obtained with three different commercially available broth microdilution panels (MicroScan, Sensititre, and Pasco) with MICs obtained with reference microdilution panels for 20 well-characterized pneumococci with decreased susceptibilities to penicillin (7 resistant and 13 intermediate). All panels were supplemented with 2 to 5% lysed horse blood (LHB) prepared in-house. Additional supplements included fastidious inoculum broth (FIB) for MicroScan panels and commercially prepared LHB (Difco) for Pasco panels. The percentages of penicillin-resistant strains (MIC 2 micrograms/ml) detected by the different methods follow: MicroScan-FIB, 0; MicroScan-LHB 0; Pasco in-house LHB, 71; and Sensititre-LHB, 100. The percentages of intermediate strains (MIC = 0.1 to 1.0 micrograms/ml) detected by the different methods follow: MicroScan-FIB, 31; MicroScan-LHB 23; Pasco in-house LHB, 46; and Sensititre-LHB, 85. Difco LHB supplement failed to support the growth of 86% of the strains in the Pasco panels. Of the commercially available panels evaluated, only Sensititre, supplemented with LHB prepared in-house could reliably detect penicillin-resistant pneumococci.

Culture Media↗
PubMed1995

An outbreak of gram-negative bloodstream infections in chronic hemodialysis patients.

Six chronic hemodialysis patients acquired bloodstream infections (BSIs) with Klebsiella pneumoniae of the same serotype and similar plasmid profile during an 11-day period. The 6 case-patients were more likely than noncase-patients to have received dialysis during the fourth shift (p < 0.05) and to have their dialyzers reprocessed for reuse after those of the noncase-patients (p = 0.05). Investigation identified a patient during the same shift with an arteriovenous fistula infected with K. pneumoniae. The dialyzer reprocessing technician did not change gloves between contacting patients and their dialyzers in the treatment area and reprocessing the case-patients' dialyzers at the end of the fourth shift. We conclude that the outbreak of BSIs was caused by cross-contamination of the case-patients' dialyzers with bacteria from the gloves of the reprocessing technician and by inadequate dialyzer disinfection. After revised dialyzer reprocessing techniques and glove-changing policies were instituted, no further clusters of BSIs occurred.

Arteriovenous Shunt, Surgical↗
PubMed1994

Emergence of drug-resistant pneumococcal infections in the United States.

OBJECTIVE: To estimate drug susceptibility patterns of Streptococcus pneumoniae in selected hospitals in the United States and to characterize the epidemiology of invasive drug-resistant pneumococcal infections. DESIGN: Minimum inhibitory concentrations (MICs) for a variety of commonly used antimicrobial drugs were determined for pneumococcal isolates submitted to the Centers for Disease Control and Prevention (CDC). Risk factors for drug-resistant pneumococcal infection were evaluated. SETTING: Hospital laboratories in the United States submitting pneumococcal isolates to the CDC between October 1, 1991, and September 30, 1992. PARTICIPANTS: A total of 544 persons with pneumococci isolated from normally sterile sites. RESULTS: A total of 13 hospitals in 12 states actively participated in an ongoing pneumococcal surveillance study. Resistance to penicillin was detected in 6.6% of isolates, including 1.3% of isolates with MICs of 2.0 micrograms/mL or more (compared with < 0.02% of isolates with MIC > or = 2.0 micrograms/mL identified by CDC surveillance from 1979 to 1987). A total of 16.4% were resistant to at least one of the following drugs or drug classes: penicillin, cephalosporins, macrolides, combination trimethoprim and sulfamethoxazole, and chloramphenicol. Six serotypes (6B, 23F, 14, 9V, 19A, and 19F) accounted for nearly 85% of strains resistant to at least one drug class. Children were more likely than adults to be infected with strains resistant to trimethoprim-sulfamethoxazole, erythromycin, or chloramphenicol. CONCLUSIONS: Emergence of drug-resistant pneumococcal infections will present critical challenges to clinicians for treating patients with pneumococcal disease. Widened and intensified surveillance is needed. These data suggest that current recommendations for use of 23-valent pneumococcal capsular polysaccharide vaccines should be aggressively promoted and that development and evaluation of new conjugate pneumococcal vaccines may be a crucial part of strategies for prevention.

Anti-Bacterial Agents↗
PubMed1994

Optimizing testing of methicillin-resistant Staphylococcus species.

Selection of the appropriate NaCl concentration for test medium for oxacillin susceptibility testing of Staphylococcus aureus and coagulase-negative staphylococci has been problematic when using different antimicrobial susceptibility testing methods. Broth microdilution, using cation-adjusted Mueller-Hinton broth + 2% NaCl, is the currently recommended reference method. There is currently no recommendation for the addition of NaCl to agar for dilution susceptibility tests when Staphylococcus species are tested with oxacillin. We examined the effects of adding 0, 2%, 4%, and 5% NaCl to Mueller-Hinton agar and broth for agar dilution, Etest, and broth microdilution tests. The results of these tests were compared with the reference broth microdilution results and with the results of a hybridization assay using a mec gene probe. We tested 223 strains of staphylococci, 128 of which were mec gene positive and had oxacillin minimum inhibitory concentrations (MICs) > or = 4 micrograms/ml. Seven strains of S. aureus were mec probe negative but were oxacillin resistant. Seven coagulase-negative strains (three S. epidermidis, one S. haemolyticus, and three S. simulans) were mec probe positive and were oxacillin susceptible. The MICs for oxacillin-resistant strains increased two- to fourfold with the addition of 2% NaCl, but the MICs for oxacillin-susceptible strains were unchanged. Major and very major interpretative rates ranged from 18.2% to 20.2% for agar dilution and Etest without NaCl added to the medium, and these rates decreased to < 1% with the addition of 2% NaCl to the medium. The addition of 4% or 5% NaCl caused major error rates of > 17% for all test methods.(ABSTRACT TRUNCATED AT 250 WORDS)

Culture Media↗
PubMed1994

Prevalence of Neisseria meningitidis relatively resistant to penicillin in the United States, 1991. Meningococcal Disease Study Group.

To estimate the prevalence of Neisseria meningitidis relatively resistant to penicillin in the United States, antimicrobial susceptibility testing was performed on all US meningococcal isolates submitted to the Centers for Disease Control and Prevention in 1991, including isolates identified through population-based surveillance for invasive meningococcal disease in selected areas of the United States. Three of the 100 isolates tested had MICs of penicillin of 0.125 microgram/mL. All were serogroup B, beta-lactamase-negative, and unique by multilocus enzyme electrophoresis subtyping. None of the 3 patients had been treated solely with penicillin; all recovered completely. About 4% of the isolates obtained from the population-based surveillance system were relatively penicillin-resistant. Given the low prevalence and uncertain clinical significance of infection with these organisms, routine susceptibility testing of meningococcal isolates is not indicated at this time; however, continued surveillance is necessary to monitor trends in antimicrobial susceptibility of meningococci in the United States.

Disease Outbreaks↗
PubMed1994

Epidemic Shigella dysenteriae type 1 in Burundi: panresistance and implications for prevention.

An epidemic of Shigella dysenteriae type 1 infections has affected Africa since 1979. Reported dysentery cases increase sharply in Burundi during September through December. Of stool samples from 189 patients reporting bloody diarrhea in November 1990, a pathogen was identified in 123 (65%). The pathogen was S. dysenteriae type 1 in 82 (67%). All S. dysenteriae type 1 isolates were resistant to ampicillin, chloramphenicol, nalidixic acid, streptomycin, sulfisoxazole, tetracycline, and trimethoprim-sulfamethoxazole. Thirty-two specimens (26%) yielded other Shigella species. Patients with S. dysenteriae type 1 were more likely than those with other Shigella infections to have abdominal pain, "lots of blood" in the stool, blood in the stool specimen examined by the interviewer, recent contact with a person with dysentery, or recent antimicrobial treatment. Thus, the seasonal increase in dysentery was due largely to multidrug-resistant S. dysenteriae type 1, clinical and epidemiologic features may predict such infection, and efforts to control this epidemic must focus on preventing transmission.

Adolescent↗
PubMed1994

The tet(Q) gene in bacteria isolated from patients with refractory periodontal disease.

Twenty-two tetracycline-resistant (tetr) anaerobic and facultative anaerobic bacteria isolated from periodontal pockets of 12 patients with refractory periodontitis were examined for the presence of the Tet Q determinant by DNA-DNA hybridization. Dot blots of bacterial DNA were tested with an intragenic digoxigenin-labelled tet(Q) probe consisting of a 1.45 kb EcoRI/PvuII fragment from plasmid pNFD13-2. Southern blots of chromosomal DNA digested with the restriction enzyme EcoRI were also examined. The tet(Q) probe hybridized with DNA from 8 of the 22 tetr strains, including 2 Prevotella intermedia strains and one strain each of Prevotella nigrescens, Prevotella loescheii, Prevotella veroralis and Prevotella melaninogenica. The tetr strains of Mitsuokella dentalis and Capnocytophaga ochracea also hybridized with the probe. The lack of discernible plasmid DNA in all the probe-positive isolates suggests that these tetracycline-resistance genes were chromosomally encoded. The probe hybridized with a different size fragment in all the isolates. This study extends the number of species that carry the tet(Q) gene to include several outside the genera Prevotella and Bacteroides.

Anti-Bacterial Agents↗
PubMed1994

Outbreak of vancomycin-, ampicillin-, and aminoglycoside-resistant Enterococcus faecium bacteremia in an adult oncology unit.

An outbreak of bacteremia caused by Enterococcus faecium with high-level resistance to vancomycin (MIC of > or = 256 micrograms/ml), ampicillin (MIC of > or = 64 micrograms/ml), and gentamicin or streptomycin (MIC of > or = 2,000 micrograms/ml) occurred in an adult oncology unit from June 1991 to May 1992. Active surveillance for the presence of this organism in stool or perianal cultures was begun in September 1991. Between June 1991 and May 1992, seven patients with bacteremia and 22 noninfected carriers of the organism in stool were identified. The vanA gene, tested for by PCR and gene probe, was present in all isolates evaluated. All bacteremic patients also had resistant E. faecium present in a stool or perianal culture; the stool isolates tested were closely related to the respective blood isolates as determined by pulsed-field gel electrophoresis. Antibiotic regimens using high-dose ampicillin and an aminoglycoside were ineffective with four patients. Five patients (71%) had multiple positive blood cultures; four of these patients died. Following a multiple logistic regression analysis, it was found that bacteremic patients received a significantly greater number of total antibiotic days compared with noninfected stool carriers (P = 0.019). The emergence of E. faecium with high-level resistance to vancomycin, ampicillin, and aminoglycosides underscores the importance of performing susceptibility testing on all clinically significant isolates. In the neutropenic adult oncology patient, bacteremia with this organism is of probable gastrointestinal origin, is often persistent, and is refractory to treatment with ampicillin in combination with an aminoglycoside. Prolonged use of antibiotics may predispose patients with gastrointestinal colonization to develop bacteremia.

Adult↗
PubMed1994

Detection of penicillin and extended-spectrum cephalosporin resistance among Streptococcus pneumoniae clinical isolates by use of the E test.

Increasing penicillin resistance and the initial recognition of resistance to extended-spectrum cephalosporins among Streptococcus pneumoniae isolates have placed greater emphasis on accurate methods for susceptibility testing of clinical isolates. This study has evaluated the use of the E test (AB Biodisk NA, Piscataway, N.J.) for the detection of penicillin and cefotaxime resistance among 147 pneumococcal clinical isolates in three geographically separate laboratories. These included 42 penicillin-resistant (MIC, > or = 2 micrograms/ml) and 14 cefotaxime-resistant (defined here as an MIC of > or = 2 micrograms/ml) isolates. E test strips were applied to the surface of Mueller-Hinton sheep blood agar plates and incubated at 35 degrees C in 5% CO2 for 20 to 24 h. E test MICs were compared with MICs determined with lysed horse blood-supplemented Mueller-Hinton broth in a microdilution format as recommended by the National Committee for Clinical Laboratory Standards. Penicillin MICs agreed within one log2 dilution for 136 of 147 (92.5%) isolates, and cefotaxime MICs agreed within one log2 dilution for 142 of 147 (96.6%) isolates. No very major or major interpretive errors occurred with either penicillin or cefotaxime E test MIC results. There were 9.5 and 5.4% minor interpretive category errors with penicillin and cefotaxime E test MICs, respectively. These data indicate that the E test represents a convenient and reliable method for the detection of penicillin or cephalosporin resistance in pneumococci.

Air↗
PubMed1994

Nosocomial epiglottitis associated with penicillin- and cephalosporin-resistant Streptococcus pneumoniae bacteremia.

We cared for a 4-year-old male with nosocomially acquired epiglottitis caused by Streptococcus pneumoniae. He had been receiving ceftazidime therapy when this infection was recognized. The S. pneumoniae isolate was of serotype 15B and was resistant to beta-lactam antibiotics, cephalosporins (including those with extended spectra), and trimethoprim-sulfamethoxazole. Clinicians and clinical microbiologists must be aware that cephalosporin susceptibility may no longer be assumed for penicillin-resistant S. pneumoniae isolates and that susceptibility testing for the extended-spectrum cephalosporins should be performed whenever this species is isolated from a normally sterile body fluid.

Bacteremia↗
PubMed1994

Development of interpretive criteria and quality control limits for broth microdilution and disk diffusion antimicrobial susceptibility testing of Streptococcus pneumoniae.

A five-center collaborative study was undertaken to develop quality control and specific interpretive criteria for susceptibility testing of Streptococcus pneumoniae against 12 antimicrobial agents. MICs were determined for 248 pneumococcal clinical isolates (with an emphasis on resistant strains) by use of the National Committee for Clinical Laboratory Standards (NCCLS)-recommended broth microdilution procedure incorporating lysed horse blood-supplemented Mueller-Hinton broth. NCCLS disk diffusion testing was also performed for each isolate by using Mueller-Hinton sheep blood agar incubated in 5% CO2. Repetitive testing of S. pneumoniae ATCC 49619 with different sources and lots of media and disks allowed development of quality control ranges which encompassed approximately 95% of MIC and zone size values observed in the study. Good intra- and interlaboratory reproducibilities were seen with these testing methods and all of the drugs examined. On the basis of the results of this study, MIC interpretive criteria are proposed for 11 agents. Comparisons of MICs and disk diffusion zone sizes allowed disk diffusion zone size interpretive criteria to be proposed for five drugs and confirmed the use of the oxacillin disk test for prediction of penicillin susceptibility among pneumococci. Excessive numbers of minor-category interpretive errors precludes recommendation at this time of the disk diffusion method for testing of pneumococci against five of the drugs. Use of these proposed quality control and interpretive criteria should provide for reproducible test results and allow recognition of recently emerging resistance among pneumococcal clinical isolates.

Diffusion↗
PubMed1994

Development of PCR assays to detect ampicillin resistance genes in cerebrospinal fluid samples containing Haemophilus influenzae.

We developed PCR primers specific for the blaTEM and blaROB ampicillin resistance genes. The specificity of the primers was confirmed by testing a series of Escherichia coli isolates containing a variety of ampicillin resistance genes and a series of ampicillin-resistant and ampicillin-susceptible Haemophilus influenzae isolates. There was a perfect correlation between ampicillin MICs, the presence of beta-lactamase (as determined by the nitrocefin test), and the results with the blaTEM and blaROB primers. Isolates of H. influenzae and Streptococcus pneumoniae obtained from 25 frozen cerebrospinal fluid (CSF) specimens were also tested. Four of 14 H. influenzae isolates were positive with the blaTEM primers; none were positive with the blaROB primers. Ampicillin MICs were determined for the H. influenzae isolates, and penicillin MICs were determined for the S. pneumoniae isolates. Only the four PCR-positive H. influenzae isolates had elevated MICs of ampicillin and were beta-lactamase positive. None of the H. influenzae isolates contained the blaROB gene, and none of the S. pneumoniae isolates produced positive reactions with either primer set. We then used universal primers directed to conserved regions of rRNA and a Haemophilus detection probe to identify which of the 25 frozen samples of CSF contained H. influenzae. Fourteen of the 25 CSF specimens were positive for H. influenzae, which correlated with the number of organisms obtained by culture of the CSF samples. Four of the CSF samples were positive with the blaTEM primer set, and these correlated with the four H. influenzae isolates that were positive when tested directly by PCR. The blaTEM assay required the use of native Taq polymerase because Amplitaq preparations were contaminated with vector DNA that contained the blaTEM-1 gene.

Ampicillin Resistance↗
PubMed1994

Evaluation and characterization of multiresistant Enterococcus faecium from 12 U.S. medical centers.

Forty-two Enterococcus faecium isolates resistant to ampicillin, penicillin, gentamicin, streptomycin, vancomycin, and teicoplanin (VanA phenotype) from 12 U.S. medical centers were analyzed by pulsed-field gel electrophoresis of chromosomal DNA. The isolates were tested for susceptibility to 12 alternative drugs. The results indicated both intrahospital and interhospital diversity among multiresistant vanA enterococcal isolates. Furthermore, the finding of isolates with identical pulsed-field gel electrophoresis patterns in different centers strongly suggests some interhospital clonal transmission.

DNA, Bacterial↗
PubMed1994

Comparison of traditional and molecular methods of typing isolates of Staphylococcus aureus.

Fifty-nine Staphylococcus aureus isolates and 1 isolate of Staphylococcus intermedius were typed by investigators at eight institutions by using either antibiograms, bacteriophage typing, biotyping, immunoblotting, insertion sequence typing with IS257/431, multilocus enzyme electrophoresis, restriction analysis of plasmid DNA, pulsed-field or field inversion gel electrophoresis, restriction analysis of PCR-amplified coagulase gene sequences, restriction fragment length polymorphism typing by using four staphylococcal genes as probes, or ribotyping. Isolates from four well-characterized outbreaks (n = 29) and a collection of organisms from two nursing homes were mixed with epidemiologically unrelated stock strains from the Centers for Disease Control and Prevention. Several isolates were included multiple times either within or between the sets of isolates to analyze the reproducibilities of the typing systems. Overall, the DNA-based techniques and immunoblotting were most effective in grouping outbreak-related strains, recognizing 27 to 29 of the 29 outbreak-related strains; however, they also tended to include 3 to 8 epidemiologically unrelated isolates in the same strain type. Restriction fragment length polymorphism methods with mec gene-associated loci were less useful than other techniques for typing oxacillin-susceptible isolates. Phage typing, plasmid DNA restriction analysis, and antibiogram analysis, the techniques most readily available to clinical laboratories, identified 23 to 26 of 29 outbreak-related isolates and assigned 0 to 6 unrelated isolates to outbreak strain types. No single technique was clearly superior to the others; however, biotyping, because it produced so many subtypes, did not effectively group outbreak-related strains of S. aureus.

Bacterial Typing Techniques↗