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F C Tenover

Publications and source records attributed to F C Tenover.

At least 55 records · Page 3Linked to original sources

Surveillance of antimicrobial use and antimicrobial resistance in United States hospitals: project ICARE phase 2. Project Intensive Care Antimicrobial Resistance Epidemiology (ICARE) hospitals.

The search for the means to understand and control the emergence and spread of antimicrobial resistance has become a public health priority. Project ICARE (Intensive Care Antimicrobial Resistance Epidemiology) has established laboratory-based surveillance for antimicrobial resistance and antimicrobial use at a subset of hospitals participating in the National Nosocomial Infection Surveillance system. These data illustrate that for most antimicrobial-resistant organisms studied, rates of resistance were highest in the intensive care unit (ICU) areas and lowest in the outpatient areas. A notable exception was ciprofloxacin- or ofloxacin-resistant Pseudomonas aeruginosa, for which resistance rates were highest in the outpatient areas. For most of the antimicrobial agents associated with this resistance, the rate of use was highest in the ICU areas, in parallel to the pattern seen for resistance. These comparative data on use and resistance among similar areas (i.e., ICU or other inpatient areas) can be used as a benchmark by participating hospitals to focus their efforts at addressing antimicrobial resistance.

Anti-Bacterial Agents↗

Detection of a streptomycin/spectinomycin adenylyltransferase gene (aadA) in Enterococcus faecalis.

Genes encoding streptomycin/spectinomycin adenylyltransferases [ANT(3")(9)] have been reported to exist in gram-negative organisms and Staphylococcus aureus. During a study of high-level aminoglycoside resistance in enterococci, we encountered an isolate of Enterococcus faecalis that was streptomycin resistant but did not appear to contain the 6'-adenylyltransferase gene (aadE) when examined by PCR with specific primers. Phosphocellulose paper binding assays indicated the presence of an ANT(3")(9) enzyme. Streptomycin and spectinomycin MICs of 4,000 and 8,000 microg/ml, respectively, were observed for the isolate. PCR primers corresponding to a highly conserved region of the aadA gene were used to amplify a specific 284-bp product. The product hybridized with a digoxigenin-labeled PCR product from E. coli C600(pHP45Omega) known to contain the aadA gene. The aadA gene was transferred via filter matings from the E. faecalis donor to E. faecalis JH2-2. PCR primers designed for analysis of integrons were used to amplify a 1-kb product containing the aadA gene, which was cloned into the vector pCRII and transformed into Escherichia coli DH5-alpha competent cells. D-Rhodamine dye terminator cycle sequencing was used to determine the gene sequence, which was compared to previously reported sequences of aadA genes. We found the aadA gene in E. faecalis to be identical to the aadA genes reported by Sundstr om et al. for E. coli plasmid R6-5 (L. Sundström, P. Râdström, G. Swedberg, and O. Sköld, Mol. Gen. Genet. 213:191-201, 1988), by Fling et al. for the aadA within transposon Tn7 (M. E. Fling, J. Kopf, and C. Richards, Nucleic Acids Res. 13:7095-7106, 1985), and by Hollingshead and Vapnek for E. coli R538-1 (S. Hollingshead and D. Vapnek, Plasmid 13:17-30, 1985). Previous reports of the presence of the aadA gene in enterococci appear to be erroneous and probably describe an aadE gene, since the isolates were reported to be susceptible to spectinomycin.

Amino Acid Sequence↗

Activities of newer fluoroquinolones against Streptococcus pneumoniae clinical isolates including those with mutations in the gyrA, parC, and parE loci.

Resistance to fluoroquinolone (FQ) antibiotics in Streptococcus pneumoniae has been attributed primarily to specific mutations in the genes for DNA gyrase (gyrA and gyrB) and topoisomerase IV (parC and parE). Resistance to some FQs can result from a single mutation in one or more of the genes encoding these essential enzymes. A group of 160 clinical isolates of pneumococci was examined in this study, including 36 ofloxacin-resistant isolates (MICs, > or = 8 micrograms/ml) recovered from patients in North America, France, and Belgium. The susceptibilities of all isolates to clinafloxacin, grepafloxacin, levofloxacin, sparfloxacin, and trovafloxacin were examined by the National Committee for Clinical Laboratory Standards reference broth microdilution and disk diffusion susceptibility testing methods. Among the ofloxacin-resistant strains, 32 of 36 were also categorized as resistant to levofloxacin, 35 were resistant to sparfloxacin, 29 were resistant to grepafloxacin, and 19 were resistant to trovafloxacin. In vitro susceptibility to clinafloxacin appeared to be least affected by resistance to the other FQs. Eight isolates with high- and low-level resistance to the newer FQs were selected for DNA sequence analysis of the quinolone resistance-determining regions (QRDRs) of gyrA, gyrB, parC, and parE. The DNA and the inferred amino acid sequences of the resistant strains were compared with the analogous sequences of reference strain S. pneumoniae ATCC 49619 and FQ-susceptible laboratory strain R6. Reduced susceptibilities to grepafloxacin and sparfloxacin (MICs, 1 to 2 micrograms/ml) and trovafloxacin (MICs, 0.5 to 1 microgram/ml) were associated with either a mutation in parC that led to a single amino acid substitution (Ser-79 to Phe or Tyr) or double mutations that involved the genes for both GyrA (Ser-81 to Phe) and ParE (Asp-435 to Asn). High-level resistance to all of the compounds except clinafloxacin was associated with two or more amino acid substitutions involving both GyrA (Ser-81 to Phe) and ParC (Ser-79 to Phe or Ser-80 to Pro and Asp-83 to Tyr). No mutations were observed in the gyrB sequences of resistant strains. These data indicate that mutations in pneumococcal gyrA, parC, and parE genes all contribute to decreased susceptibility to the newer FQs, and genetic analysis of the QRDR of a single gene, either gyrA or parC, is not predictive of pneumococcal resistance to these agents.

Anti-Infective Agents↗

Glycopeptide-intermediate Staphylococcus aureus: evaluation of a novel screening method and results of a survey of selected U.S. hospitals.

Isolates of Staphylococcus aureus with decreased susceptibilities to glycopeptide antimicrobial agents, such as vancomycin and teicoplanin, have emerged in the United States and elsewhere. Commercially prepared brain heart infusion agar (BHIA) supplemented with 6 microg of vancomycin per ml was shown in a previous study to detect glycopeptide-intermediate S. aureus (GISA) with high sensitivity and specificity; however, this medium, when prepared in-house, occasionally showed growth of vancomycin-susceptible control organisms. This limitation could significantly impact laboratories that prepare media in-house, particularly if they wished to conduct large surveillance studies for GISA. Therefore, a pilot study to detect GISA was performed with vancomycin-containing Mueller-Hinton agar (MHA) prepared in-house in place of commercially prepared BHIA. MHA was selected for this study because this medium is widely available and well standardized. The results of the pilot study showed that supplementation of MHA with 5 microg of vancomycin per ml was both a sensitive and a specific method for screening for GISA isolates. This method was used to screen for GISA among 630 clinical isolates of methicillin-resistant S. aureus collected during 1997 from 33 U.S. hospitals. Although 14 S. aureus isolates grew on the screening agar, all were vancomycin susceptible (MICs were </=1 microg/ml) by broth microdilution testing. Population analyses of five isolates revealed two with a subpopulation for which vancomycin MICs were 8 microg/ml. In summary, the MHA screen plate containing 5 microg of vancomycin per ml prepared in-house provides a sensitive and cost-effective method for large-scale screening for GISA for which vancomycin MICs are 8 microg/ml. However, confirmation of isolates as vancomycin resistant is critical. This study suggests that GISA was not a widespread problem in the United States in 1997.

Anti-Bacterial Agents↗

Methods for improved detection of oxacillin resistance in coagulase-negative staphylococci: results of a multicenter study.

A multilaboratory study was undertaken to determine the accuracy of the current National Committee for Clinical Laboratory Standards (NCCLS) oxacillin breakpoints for broth microdilution and disk diffusion testing of coagulase-negative staphylococci (CoNS) by using a PCR assay for mecA as the reference method. Fifty well-characterized strains of CoNS were tested for oxacillin susceptibility by the NCCLS broth microdilution and disk diffusion procedures in 11 laboratories. In addition, organisms were inoculated onto a pair of commercially prepared oxacillin agar screen plates containing 6 microg of oxacillin per ml and 4% NaCl. The results of this study and of several other published reports suggest that, in order to reliably detect the presence of resistance mediated by mecA, the oxacillin MIC breakpoint for defining resistance in CoNS should be lowered from >/=4 to >/=0.5 microg/ml and the breakpoint for susceptibility should be lowered from </=2 to </=0.25 microg/ml. In addition, a single disk diffusion breakpoint of </=17 mm for resistance and >/=18 mm for susceptibility is suggested. Due to the poor sensitivity of the oxacillin agar screen plate for predicting resistance in this study, this test can no longer be recommended for use with CoNS. The proposed interpretive criteria for testing CoNS have been adopted by the NCCLS.

Bacterial Proteins↗

Detection and reporting of organisms producing extended-spectrum beta-lactamases: survey of laboratories in Connecticut.

Extended-spectrum beta-lactamases (ESBLs) are enzymes produced in some gram-negative bacilli that mediate resistance to extended-spectrum cephalosporins and aztreonam. They are most common in Klebsiella spp. and Escherichia coli but are present in a variety of Enterobacteriaceae. Resistance mediated by these enzymes can be difficult to detect depending on the antimicrobial agents tested. AmpC beta-lactamases are related to the chromosomal enzymes of Enterobacter and Citrobacter spp. and also mediate resistance to extended-spectrum cephalosporins and aztreonam in addition to cephamycins, such as cefoxitin. Unlike ESBLs, however, AmpC beta-lactamases are not inhibited by clavulanic acid or other similar compounds. To assess the abilities of various antimicrobial susceptibility testing methods to detect ESBLs, we sent three ESBL-producing organisms, one AmpC-producing organism, and a control strain that was susceptible to extended-spectrum cephalosporins to 38 laboratories in Connecticut for testing. Eight (21.0%) of 38 labs failed to detect extended-spectrum cephalosporin or aztreonam resistance in any of the ESBL- or AmpC-producing isolates. Errors were encountered with both automated and disk diffusion methods. Conversely, seven (18.4%) labs categorized at least some of the four resistant isolates as potential ESBL producers and reported the results with the extended-spectrum cephalosporins and aztreonam as resistant as suggested by current National Committee for Clinical Laboratory Standards (NCCLS) guidelines. The percentage of laboratories that failed to detect resistance in the ESBL or AmpC isolates ranged from 23.7 to 31.6% depending on the type of enzyme present in the test organism. This survey suggests that many laboratories have difficulty detecting resistance in ESBL and AmpC-producing organisms and may be unaware of the NCCLS guidelines on modifying susceptibility testing reports for ESBL-producing strains.

Aztreonam↗

Comparison of agar dilution, disk diffusion, MicroScan, and Vitek antimicrobial susceptibility testing methods to broth microdilution for detection of fluoroquinolone-resistant isolates of the family Enterobacteriaceae.

Fluoroquinolone resistance appears to be increasing in many species of bacteria, particularly in those causing nosocomial infections. However, the accuracy of some antimicrobial susceptibility testing methods for detecting fluoroquinolone resistance remains uncertain. Therefore, we compared the accuracy of the results of agar dilution, disk diffusion, MicroScan Walk Away Neg Combo 15 conventional panels, and Vitek GNS-F7 cards to the accuracy of the results of the broth microdilution reference method for detection of ciprofloxacin and ofloxacin resistance in 195 clinical isolates of the family Enterobacteriaceae collected from six U.S. hospitals for a national surveillance project (Project ICARE [Intensive Care Antimicrobial Resistance Epidemiology]). For ciprofloxacin, very major error rates were 0% (disk diffusion and MicroScan), 0.9% (agar dilution), and 2.7% (Vitek), while major error rates ranged from 0% (agar dilution) to 3.7% (MicroScan and Vitek). Minor error rates ranged from 12.3% (agar dilution) to 20.5% (MicroScan). For ofloxacin, no very major errors were observed, and major errors were noted only with MicroScan (3.7% major error rate). Minor error rates ranged from 8.2% (agar dilution) to 18.5% (Vitek). Minor errors for all methods were substantially reduced when results with MICs within +/-1 dilution of the broth microdilution reference MIC were excluded from analysis. However, the high number of minor errors by all test systems remains a concern.

Anti-Infective Agents↗

Antimicrobial use and resistance in eight US hospitals: complexities of analysis and modeling. Intensive Care Antimicrobial Resistance Epidemiology Project and National Nosocomial Infections Surveillance System Hospitals.

OBJECTIVE: To evaluate the relation between antimicrobial use and resistance in intensive-care unit (ICU) and non-ICU inpatient areas in eight US hospitals. METHODS: We determined antimicrobial use in terms of defined daily doses, antimicrobial-use density (defined daily doses/1,000 patient days), and percentage resistance for five antimicrobial-organism combinations in the ICU and non-ICU inpatient areas of eight US hospitals participating in project Intensive Care Antimicrobial Resistance Epidemiology. RESULTS: Antimicrobial resistance and use varied tremendously among the eight hospitals. Antimicrobial resistance among these five nosocomial pathogens was significantly higher within the inpatient setting of these hospitals, compared with the outpatient setting. One hospital consistently ranked highest for use of all classes of antimicrobials examined. High antimicrobial use was not associated necessarily with high resistance for a particular antimicrobial-organism pair. CONCLUSION: Antimicrobial use varied significantly across these hospitals, but generally was higher in ICUs. These results suggest that concomitant surveillance of both antimicrobial resistance and antimicrobial use is helpful in interpreting antimicrobial resistance in a hospital or ICU and that further analysis is required to determine the role of variables other than antimicrobial use in a statistical model for predicting antimicrobial resistance.

Anti-Bacterial Agents↗

gyrA mutations associated with fluoroquinolone resistance in eight species of Enterobacteriaceae.

Fluoroquinolone resistance (FQ-R) in clinical isolates of Enterobacteriaceae species has been reported with increasing frequency in recent years. Two mechanisms of FQ-R have been identified in gram-negative organisms: mutations in DNA gyrase and reduced intracellular drug accumulation. A single point mutation in gyrA has been shown to reduce susceptibility to fluoroquinolones. To determine the extent of gyrA mutations associated with FQ-R in enteric bacteria, one set of oligonucleotide primers was selected from conserved sequences in the flanking regions of the quinolone resistance-determining regions (QRDR) of Escherichia coli and Klebsiella pneumoniae. This set of primers was used to amplify and sequence the QRDRs from 8 Enterobacteriaceae type strains and 60 fluoroquinolone-resistant clinical isolates of Citrobacter freundii, Enterobacter aerogenes, Enterobacter cloacae, E. coli, K. pneumoniae, Klebsiella oxytoca, Providencia stuartii, and Serratia marcescens. Although similarity of the nucleotide sequences of seven species ranged from 80.8 to 93.3%, when compared with that of E. coli, the amino acid sequences of the gyrA QRDR were highly conserved. Conservative amino acid substitutions were detected in the QRDRs of the susceptible type strains of C. freundii, E. aerogenes, K. oxytoca (Ser-83 to Thr), and P. stuartii (Asp-87 to Glu). Strains with ciprofloxacin MICs of >2 microg/ml expressed amino acid substitutions primarily at the Gly-81, Ser-83, or Asp-87 position. Fluoroquinolone MICs varied significantly for strains exhibiting identical gyrA mutations, indicating that alterations outside gyrA contribute to resistance. The type and position of amino acid alterations also differed among these six genera. High-level FQ-R frequently was associated with single gyrA mutations in all species of Enterobacteriaceae in this study except E. coli.

Amino Acid Sequence↗

Characterization of erythromycin-resistant isolates of Staphylococcus aureus recovered in the United States from 1958 through 1969.

We tested 16 erythromycin-resistant clinical isolates of S. aureus, recovered from patients hospitalized in the United States from 1958 to 1969, for the presence of ermA, ermB, and ermC by using PCR. Fifteen of 16 isolates contained at least one copy of ermA; the remaining isolate, which was also clindamycin resistant, contained ermB. Eight of the 15 isolates harboring ermA, all of which were inducible, contained a single copy of the gene in the chromosome, while the remaining seven isolates had two copies of the gene. ermB was plasmid encoded and mediated constitutive resistance to erythromycin.

DNA, Bacterial↗

Detection of Tn917-like sequences within a Tn916-like conjugative transposon (Tn3872) in erythromycin-resistant isolates of Streptococcus pneumoniae.

A series of macrolide-lincosamide-streptogramin B (MLS)-resistant pneumococcal isolates of a variety of serotypes was examined and was found to contain Tn917-like elements by DNA-DNA hybridization. Like Tn1545, Tn917 also encodes an ermAM gene but does not mediate resistance to other antimicrobial agents. Furthermore, nucleotide sequence analyses of the DNAs flanking three of the Tn917-like elements revealed that they were inserted into orf9 of a Tn916-like element in a composite transposon-like structure (Tn3872). Other MLS-resistant strains appeared to contain Tn1545-like elements that had suffered a deletion of sequences including the aphA-3 sequences responsible for kanamycin resistance. Thus, the MLS resistance phenotype in pneumococci appears to be mediated by the ermAM present on a much wider variety of genetic elements than was previously appreciated.

Anti-Bacterial Agents↗

Comparison of restriction enzyme analysis, arbitrarily primed PCR, and protein profile analysis typing for epidemiologic investigation of an ongoing Clostridium difficile outbreak.

During an outbreak of diarrhea in a general hospital in 1992, 166 Clostridium difficile isolates from 102 patients were typed by restriction enzyme analysis (REA), arbitrarily primed PCR (AP-PCR), and protein profile analysis (PP) techniques. A total of 18 types and 5 subtypes were identified by REA, 32 types were identified by AP-PCR, and 9 types were identified by PP. Analysis of the data indicated the presence of a predominant strain among 76, 75, and 84% of the isolates by REA, AP-PCR, and PP, respectively. Subsequently, 45 C. difficile isolates which had been collected in 1990 from 33 patients in the same hospital following a significant increase in the number of cases of diarrhea caused by C. difficile were studied by REA, AP-PCR, and PP typing techniques. Thirteen types and one subtype were identified by REA, 12 types were identified by AP-PCR, and 5 types were identified by PP. As with the isolates from 1992, a dominant strain was identified. This strain was represented by 53, 64, and 70% of the total number of isolates when the strains were typed by REA, AP-PCR, and PP, respectively. Every isolate (210 of 211) from both 1990 and 1992 that was available for typing was typeable by all three methods. Furthermore, the same dominant strain was identified in both 1990 and 1992 by each method. This study demonstrates that each of the three typing methods can be useful in epidemiologic investigations of C. difficile outbreaks and that one strain can be dominant in an institution over a number of years.

Adult↗

Isolation of Enterobacter intermedium from the gallbladder of a patient with cholecystitis.

We describe the isolation and identification of Enterobacter intermedium from the gallbladder of a patient with cholecystitis. There have been only four documented isolations of this organism from humans; it normally occurs in surface water and unpolluted soils. The identification was initially made by a MicroScan Walk/Away system with a Neg Combo 18 conventional identification-susceptibility panel. The organism is susceptible to the aminoglycosides and imipenem but resistant to the cephalosporins and ciprofloxacin.

Anti-Bacterial Agents↗

Characterization of staphylococci with reduced susceptibilities to vancomycin and other glycopeptides.

During the last several years a series of staphylococcal isolates that demonstrated reduced susceptibility to vancomycin or other glycopeptides have been reported. We selected 12 isolates of staphylococci for which the vancomycin MICs were > or =4 microg/ml or for which the teicoplanin MICs were > or =8 microg/ml and 24 control strains for which the vancomycin MICs were < or =2 microg/ml or for which the teicoplanin MICs were < or =4 microg/ml to determine the ability of commercial susceptibility testing procedures and vancomycin agar screening methods to detect isolates with reduced glycopeptide susceptibility. By PCR analysis, none of the isolates with decreased glycopeptide susceptibility contained known vancomycin resistance genes. Broth microdilution tests held a full 24 h were best at detecting strains with reduced glycopeptide susceptibility. Disk diffusion did not differentiate the strains inhibited by 8 microg of vancomycin per ml from more susceptible isolates. Most of the isolates with reduced glycopeptide susceptibility were recognized by MicroScan conventional panels and Etest vancomycin strips. Sensititre panels read visually were more variable, although with some of the panels MICs of 8 microg/ml were noted for these isolates. Vitek results were 4 microg/ml for all strains for which the vancomycin MICs were > or =4 microg/ml. Vancomycin MICs on Rapid MicroScan panels were not predictive, giving MICs of either < or =2 or > or =16 microg/ml for these isolates. Commercial brain heart infusion vancomycin agar screening plates containing 6 microg of vancomycin per ml consistently differentiated those strains inhibited by 8 microg/ml from more susceptible strains. Vancomycin-containing media prepared in-house showed occasional growth of susceptible strains, Staphylococcus aureus ATCC 29213, and on occasion, Enterococcus faecalis ATCC 29212. Thus, strains of staphylococci with reduced susceptibility to glycopeptides, such as vancomycin, are best detected in the laboratory by nonautomated quantitative tests incubated for a full 24 h. Furthermore, it appears that commercial vancomycin agar screening plates can be used to detect these isolates.

Anti-Bacterial Agents↗

Detection and differentiation of vanC-1, vanC-2, and vanC-3 glycopeptide resistance genes in enterococci.

The VanC phenotype, as found in Enterococcus gallinarum, E. casseliflavus, and E. flavescens, is characterized by intrinsic low-level resistance to vancomycin. The nucleotide sequences of the vanC-1 gene in E. gallinarum, the vanC-2 gene in E. casseliflavus, and the vanC-3 gene in E. flavescens have been reported, although there is some disagreement as to whether E. flavescens is a legitimate enterococcal species. Previous attempts to differentiate the vanC-2 and vanC-3 genes by PCR analysis have been unsuccessful. The purpose of the present study was to detect and differentiate the three vanC determinants and examine the distribution of these genes in a collection of both typical and atypical enterococci. The 796-bp vanC-1 PCR product was amplified only from E. gallinarum isolates. As expected, due to the extensive homology in the vanC-2 and vanC-3 gene sequences, all of the E. casseliflavus and E. casseliflavus/flavescens isolates produced the 484-bp vanC-2 PCR product, although the E. gallinarum isolates were negative. Only the E. casseliflavus/flavescens isolates produced the 224-bp vanC-3 product. Using the three sets of primers, we were able to detect and distinguish the vanC-1, vanC-2, and vanC-3 genes from both typical and atypical enterococci strains. Antimicrobial susceptibility tests and analysis of genomic DNA by pulsed-field gel electrophoresis were also performed, but the results indicated that they were not able to distinguish among strains possessing the three vanC genotypes.

Anti-Bacterial Agents↗

Reproducibility of broth microdilution and disk diffusion susceptibility tests of nine antimicrobial agents against Streptococcus pneumoniae ATCC 49619.

Collaborative studies documented the reproducibility of broth microdilution susceptibility tests of Streptococcus pneumoniae against nine antimicrobial agents and of disk diffusion tests with six of those drugs. Replicate tests of Streptococcus pneumoniae ATCC 49619 in five different laboratories led to the following provisional quality control limits: cefdinir--0.03 to 0.25 microgram/ml and 26 to 31 mm; cefetamet--0.5 to 2 micrograms/ml and 20 to 25 mm; ciprofloxacin--0.25 to 1 microgram/ml and 20 to 26 mm; clinafloxacin--0.03 to 0.125 microgram/ml and 28 to 34 mm; grepafloxacin--0.06 to 0.5 microgram/ml and 21 to 28 mm; PD131628--0.125 to 0.5 microgram/ml and 24 to 29 mm; clindamycin--0.03 to 0.12 microgram/ml; cefpodoxime--0.03 to 0.12 microgram/ml; and trospectomycin--1 to 4 microgram/ml (disk tests were not evaluate for the latter three drugs).

Anti-Bacterial Agents↗

Control of antimicrobial resistance in the health care system.

Resistance continues to spread in nosocomial pathogens in acute care hospitals and other key settings of managed health care systems. Appropriate control measures for such resistant organisms depend, in part, on the pathways by which resistance has arisen. Unfortunately, these pathways differ greatly from organism to organism and setting to setting. Although the epidemiology of resistant organisms sometimes is similar to that of susceptible organisms of the same kind, in some situations it may be quite different. This article highlights some of the pathways leading to the development of resistance in bacteria and the relevance of these mechanisms to measures for the control of resistant bacteria in hospital and community settings.

Anti-Bacterial Agents↗