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Biomedical subjects

F C Tenover

Publications and source records attributed to F C Tenover.

At least 73 records · Page 4Linked to original sources
PubMed1997

Surveillance for the emergence and dissemination of antimicrobial resistance in bacteria.

Effective surveillance of antimicrobial-resistant bacteria is important for developing rational empiric therapy guidelines and for guiding public health efforts to control and prevent the spread of infective agents. Surveillance must include a timely and thorough review of the test results generated in clinical microbiology laboratories because this data serves as the core of surveillance activities. Besides ensuring data accuracy and optimizing detection of emerging resistance, the role of clinical microbiology also includes supporting the production of informative surveillance reports, providing laboratory resources for outbreak investigations, and monitoring the performance of commonly used susceptibility testing methods. Once the accuracy of susceptibility results has been validated, the data are used by public health agencies and professional societies to monitor resistance trends on a local, state, national, and international level. This information is also used to develop policies for prudent antimicrobial use locally and nationally.

Anti-Bacterial Agents↗
PubMed1997

Society for Healthcare Epidemiology of America and Infectious Diseases Society of America Joint Committee on the Prevention of Antimicrobial Resistance: guidelines for the prevention of antimicrobial resistance in hospitals.

Antimicrobial resistance results in increased morbidity, mortality, and costs of health care. Prevention of the emergence of resistance and the dissemination of resistant microorganisms will reduce these adverse effects and their attendant costs. Appropriate antimicrobial stewardship that includes optimal selection, dose, and duration of treatment, as well as control of antibiotic use, will prevent or slow the emergence of resistance among microorganisms. A comprehensively applied infection control program will interdict the dissemination of resistant strains.

Anti-Bacterial Agents↗
PubMed1997

A global gene pool for high-level cephalosporin resistance in commensal Streptococcus species and Streptococcus pneumoniae.

Highly penicillin- and cephalosporin-resistant Streptococcus mitis and Streptococcus oralis were isolated in Spain, Hungary, and Berlin. With chromosomal DNA of these strains, resistant transformants of Streptococcus pneumoniae were obtained that expressed low-affinity variants of penicillin-binding proteins (PBPs) 2x, 1a, 2a, and 2b in different combinations, depending on the selective conditions. The transformants had cefotaxime MICs of up to 6 microg/mL, and those with a low-affinity PBP 2b were highly deficient in penicillin-induced lysis. Sequence analysis of the pbp2x genes confirmed the presence of a global gene pool of penicillin resistance determinants shared by commensal and pathogenic streptococci.

Amino Acid Sequence↗
PubMed1997

Society for Healthcare Epidemiology of America and Infectious Diseases Society of America Joint Committee on the Prevention of Antimicrobial Resistance: guidelines for the prevention of antimicrobial resistance in hospitals.

Antimicrobial resistance results in increased morbidity, mortality, and costs of health care. Prevention of the emergence of resistance and the dissemination of resistant microorganisms will reduce these adverse effects and their attendant costs. Appropriate antimicrobial stewardship that includes optimal selection, dose, and duration of treatment, as well as control of antibiotic use, will prevent or slow the emergence of resistance among microorganisms. A comprehensively applied infection control program will interdict the dissemination of resistant strains.

Anti-Bacterial Agents↗
PubMed1997

How to select and interpret molecular strain typing methods for epidemiological studies of bacterial infections: a review for healthcare epidemiologists. Molecular Typing Working Group of the Society for Healthcare Epidemiology of America.

Strain typing is an integral part of epidemiological investigations of nosocomial infections. Methods for distinguishing among bacterial strains have improved dramatically over the last 5 years, due mainly to the introduction of molecular technology. Although not all molecular techniques are equally effective for typing all organisms, pulsed-field gel electrophoresis is the technique currently favored for most nosocomial pathogens. Criteria to aid epidemiologists in interpreting results have been published. Nucleic acid amplification-based typing methods also are applicable to many organisms and can be completed within a single day, but interpretive criteria still are under debate. Strain typing cannot be used to replace a sound epidemiological investigation, but serves as a useful adjunct to such investigations.

Bacterial Typing Techniques↗
PubMed1997

Evidence of interhospital transmission of extended-spectrum beta-lactam-resistant Klebsiella pneumoniae in the United States, 1986 to 1993. The National Nosocomial Infections Surveillance System.

BACKGROUND: In addition to single-hospital outbreaks, interhospital transmission of extended-spectrum beta-lactam-resistant (ESBLR) Klebsiella pneumoniae has been suspected in some reports. However, these studies lacked sufficient epidemiological information to confirm such an occurrence. METHODS: We reviewed the surveillance data reported to the National Nosocomial Infections Surveillance (NNIS) System during 1986 to 1993 for K pneumoniae isolates and their susceptibility to either ceftazidime, cefotaxime, ceftriaxone, or aztreonam. Pulsed-field gel electrophoresis (PFGE) was used to study available ESBLR K pneumoniae isolates. RESULTS: Among 8,319 K pneumoniae isolates associated with nosocomial infections, 727 (8.7%) were resistant or had intermediate-level resistance to at least one of these antibiotics. One hospital (hospital A) accounted for 321 isolates (44.2%) of ESBLR K pneumoniae. During 1986 to 1993, the percentage of K pneumoniae isolates that were ESBLR increased from 0 to 57.7% in hospital A, from 0 to 35.6% in NNIS hospitals 0 to 20 miles from hospital A (area B), and from 1.6 to 7.3% in NNIS hospitals more than 20 miles from hospital A, including hospitals located throughout the United States. Analysis of PFGE restriction profiles showed a genetic relationship between a cluster of isolates from hospital A and some isolates from one hospital in area B, and consecutive admission in these two hospitals was confirmed for two patients from whom isolates were available. CONCLUSIONS: These data provide evidence of interhospital transmission of ESBLR K pneumoniae in one region of the United States and stress the interrelationship between hospitals when trying to control antimicrobial resistance.

Anti-Bacterial Agents↗
PubMed1997

Approaches to limiting emergence of antimicrobial resistance in bacteria in human populations.

Infectious diseases continue to be major threats to human health around the world. Within the past few years, several divergent groups of organisms have emerged as significant causes of morbidity and mortality. Included among these are bacteria that are refractory to therapy because of the development of resistance to multiple antimicrobial agents. Multidrug resistance in strains of Mycobacterium tuberculosis, Streptococcus pneumoniae, Shigella dysenteriae, Salmonella typhi, and Enterococcus faecium has been reported. Surveillance of resistant microorganisms in the United States and abroad is fragmentary and targets relatively few organisms. Surveillance is further hampered by the fact that detection of some novel resistance mechanisms is difficult by means of current laboratory methods. Both clinicians and public health officials are likely to continue to face a variety of challenges regarding surveillance, treatment, prevention, and control of drug-resistant infections.

Bacterial Infections↗
PubMed1997

Development of provisional disc diffusion breakpoints for testing quinupristin/dalfopristin.

Quinupristin/dalfopristin is an injectable streptogramin with broad activity against many Gram-positive bacteria, including Streptococcus pneumoniae, Staphylococcus aureus and Enterococcus faecium. Although a number of studies have reported the MICs of this compound against a variety of bacteria, there are no published reports of disc diffusion testing. We tested total disc masses of 7.5 and 15 micrograms with varying ratios of the component compounds, quinupristin and dalfopristin, combined in the following quinupristin: dalfopristin ratios (in microgram): 7.5:0, 0:7.5, 10:5, 5:10, 5:2.5 and 2.5:5. Zone diameters and MICs were determined in parallel for 44 isolates of staphylococci, 47 isolates pneumococci and 64 isolates of enterococci. Control strains were included for each species tested, including a strain of Enterococcus faecalis with known resistance to quinupristin/dalfopristin. Using tentative definitions for quinupristin/dalfopristin of < or = 2 mg/L as susceptible and > or = 4 mg/L as resistant, each of the four discs containing ratios of both component compounds separated presumptive susceptible organisms from resistant ones better than either quinupristin or dalfopristin alone. The best correlation of zone sizes and MICs for predicting susceptibility to quinupristin/dalfopristin at an MIC of < or = 2 mg/L was achieved with the 5 micrograms:10 micrograms disc and a zone diameter of > or = 18 mm. These criteria may be useful for identifying organisms that are presumptively susceptible to quinupristin/dalfopristin.

Anti-Bacterial Agents↗
PubMed1997

Evolution of extended-spectrum beta-lactam resistance (SHV-8) in a strain of Escherichia coli during multiple episodes of bacteremia.

Nine isolates of Escherichia coli were recovered from seven blood cultures over a period of 3 months from a 19-month-old female with aplastic anemia. Initial isolates were susceptible to extended-spectrum cephalosporins, including ceftazidime (MIC, < or = 0.25 microgram/ml), but gradually became resistant to this drug (MICs, > or = 128 micrograms/ml) and other cephalosporins and the monobactam aztreonam. Molecular typing methods, including plasmid profile analysis, pulsed-field gel electrophoresis, and arbitrarily primed PCR, indicated that the nine isolates were derived from a common ancestor. Dot blot hybridization and PCR analysis of total bacterial DNA using blaSHV- and blaTEM-specific DNA probes and primers identified the presence of a blaTEM beta-lactamase gene in all of the isolates and a blaSHV gene in the isolates with elevated ceftazidime MICs. Isoelectric focusing analysis of crude lysates showed that all nine isolates contained an enzyme with a pI of 5.4 corresponding to the TEM-1 beta-lactamase, and those isolates containing an SHV-type beta-lactamase demonstrated an additional band with a pI of 7.6. The first of the ceftazidime-resistant isolates appeared to hyperproduce the SHV enzyme compared to the other resistant isolates. DNA sequencing revealed a blaSHV-1 gene in the first ceftazidime-resistant isolate and a novel blaSHV gene, blaSHV-8, with an Asp-to-Asn substitution at amino acid position 179 in the remaining four isolates. Three of the ceftazidime-resistant isolates also showed a change in porin profile. The patient had received multiple courses of antimicrobial agents during her illness, including multiple courses of ceftazidime. This collection of blood isolates from the same patient appears to represent the in vivo evolution of resistance under selective pressure of treatment with various cephalosporins.

Amino Acid Sequence↗
PubMed1997

Are clinical laboratories in California accurately reporting vancomycin-resistant enterococci?

In order to determine whether hospital-based clinical laboratories conducting active surveillance for vancomycin-resistant enterococci in three San Francisco Bay area counties (San Francisco, Alameda, and Contra Costa counties) were accurately reporting vancomycin resistance, five vancomycin-resistant enterococcal strains and one vancomycin-susceptible beta-lactamase-producing enterococcus were sent to 31 of 32 (97%) laboratories conducting surveillance. Each strain was tested by the laboratory's routine antimicrobial susceptibility testing method. An Enterococcus faecium strain with high-level resistance to vancomycin (MIC, 512 microg/ml) was correctly reported as resistant by 100% of laboratories; an E. faecium strain with moderate-level resistance (MIC, 64 microg/ml) was correctly reported as resistant by 91% of laboratories; two Enterococcus faecalis strains with low-level resistance (MICs, 32 microg/ml) were correctly reported as resistant by 97 and 56% of laboratories, respectively. An Enterococcus gallinarum strain with intrinsic low-level resistance (MIC, 8 microg/ml) was correctly reported as intermediate by 50% of laboratories. A beta-lactamase-producing E. faecalis isolate was correctly identified as susceptible to vancomycin by 100% of laboratories and as resistant to penicillin and ampicillin by 68 and 44% of laboratories, respectively; all 23 (74%) laboratories that tested for beta-lactamase recognized that it was a beta-lactamase producer. This survey indicated that for clinically significant enterococcal isolates, laboratories in the San Francisco Bay area have problems in detecting low- to moderate-level but not high-level vancomycin resistance. Increasing accuracy of detection and prompt reporting of these isolates and investigation of cases are the next steps in the battle for control of the spread of vancomycin resistance.

Ampicillin↗
PubMed1997

Detection of vancomycin-resistant enterococci in fecal samples by PCR.

Surveillance cultures for vancomycin-resistant enterococci (VRE) are time-consuming and expensive for the laboratory to perform. Therefore, we investigated the use of PCR as an alternative method of detecting and identifying VRE directly in fecal samples. PCR primers directed to vanA, vanB, vanC1, vanC2, and enterococcal ligase genes were used to detect and identify VRE in fecal material obtained by rectal or perirectal swabbing. Although PCR-inhibitory substances were present in DNA prepared directly from the swabs, the inhibitory substances could be reduced by processing the nucleic acid with two commercially available DNA preparation columns. Fecal material from 333 swabs was cultured on several selective agar media before and after broth enrichment. DNA was extracted from the fecal material and was analyzed by PCR. By using all four primer sets, only 59 (67.8%) of the samples were positive for vanA. However, after retesting the negative samples with only the vanA primer set, 77 (88.5%) of 87 specimens that were culture positive for Enterococcus faecium containing vanA were positive by PCR. One specimen was PCR positive for the vanA gene but culture negative for enterococci. The specificity of the vanA assay was 99.6%. PCR analysis of enrichment broth samples with all four primers sets after 15 to 18 h of incubation detected 74 (85.1%) of the 87 culture-positive specimens. The specificity of the vanA assay after the enrichment step was 100%. No vanB-containing enterococci were recovered by culture. Since 16 samples can be tested by PCR in 4 h (including electrophoresis), identification of VRE is possible within 8 h of specimen submission at a cost of approximately $10.12/assay. Thus, PCR may be a cost-effective alternative to culture for surveillance of VRE in some hospitals.

Anti-Bacterial Agents↗
PubMed1996

Risk factors for carriage of drug-resistant Streptococcus pneumoniae among children in Memphis, Tennessee.

OBJECTIVES: To determine risk factors for carriage of drug-resistant Streptococcus pneumoniae to understand better the factors promoting spread of these isolates. STUDY DESIGN: We obtained medical and demographic information and nasopharyngeal swab specimens from 216 children less than 6 years old with upper respiratory tract infections, seeking medical care at five Memphis, Tenn, study sites. We evaluated risk factors for carriage of penicillin-nonsusceptible S. pneumoniae (NSSP) among 100 children with S. pneumoniae isolates. Patterns of antimicrobial prescription were recorded for enrolled children. RESULTS: Independent risk factors for carriage of NSSP included an increased number of antimicrobial treatment courses during the previous 3 months and white race. Day care attendance approached statistical significance (p = 0.07). Most children with upper respiratory tract infection received a prescription for antimicrobial drugs. These prescriptions were more common for white children than for black children. CONCLUSIONS: Increased use of antimicrobial drugs enhances the risk of carriage of NSSP. This may contribute to the higher risk among white children of NSSP infection; however, after control for antimicrobial use, white children were still at an increased risk of infection with NSSP, possibly through greater exposure to resistant strains.

Anti-Bacterial Agents↗
PubMed1996

Tentative interpretive criteria and quality control parameters for in-vitro susceptibility testing of Neisseria gonorrhoeae to two fluoroquinolones (PD 131628 and grepafloxacin (OPC 17116)).

The susceptibility of Neisseria gonorrhoeae to PD 131628 and grepafloxacin (OPC 17116) was evaluated by agar dilution and disc diffusion methods. A tentative susceptibility category for both fluoroquinolones included strains for which the MICs are < or = 0.06 mg/L and the zones of inhibition are > or = 38 mm for PD 131628 and > or = 37 mm for grepafloxacin. Quality control studies with N. gonorrhoeae ATCC 49226 suggested that agar dilution MIC limits were 0.002-0.008 mg/L and 0.004-0.03 mg/L for PD 131628 and grepafloxacin, respectively. The zone size limits were 50-58 mm for PD 131628 and 44-52 mm for grepafloxacin.

Anti-Infective Agents↗
PubMed1996

In-vitro susceptibility of Streptococcus pneumoniae to the d- and l-isomers of ofloxacin: interpretive criteria and quality control limits.

The l-isomer of ofloxacin (levofloxacin) was twice as active as ofloxacin and the d-isomer was inactive against 654 Streptococcus pneumoniae isolates. For disc susceptibility tests of pneumococci, 5 micrograms levofloxacin discs can be used with interpretive criteria of < or = 12 mm for resistant (MIC > or = 8.0 mg/L) and > or = 16 mm for susceptible (MIC < or = 2.0 mg/L). For quality control of levofloxacin tests, S. pneumoniae ATCC 49619 should give zones 20-25 mm in diameter and MICs 0.5-2.0 mg/L.

Anti-Infective Agents↗
PubMed1996

Reasons for the emergence of antibiotic resistance.

The ability of many different species of bacteria, including those that cause diseases in humans, to resist the inhibitory action of antimicrobial agents has become a global problem. Resistance continues to spread not only in nosocomial pathogens but in several key community-acquired organisms as well. 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. In addition, 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. In this article, the authors highlight some of the pathways leading to the development of resistance in bacteria, the importance of antimicrobial use, and the relevance of these mechanisms to measures for the control of resistant bacteria in hospital and community settings.

Anti-Bacterial Agents↗