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Biomedical subjects

J M Boyce

Publications and source records attributed to J M Boyce.

At least 37 records · Page 2Linked to original sources
PubMed1992

Emergence and nosocomial transmission of ampicillin-resistant enterococci.

Between 1986 and 1988, the incidence of ampicillin-resistant enterococci increased sevenfold at a university-affiliated hospital. Forty-three patients acquired nosocomial infections with ampicillin-resistant enterococci, most of which were also resistant to mezlocillin, piperacillin, and imipenem. An analysis of plasmid and chromosomal DNAs of isolates revealed that the increase was due to an epidemic of 19 nosocomial infections that yielded closely related strains of Enterococcus faecium and to a significant increase in the incidence of nonepidemic, largely unrelated strains of ampicillin-resistant enterococci. The nonepidemic strains were identified as E. faecium, E. raffinosus, E. durans, and E. gallinarum. A logistic regression analysis revealed that patients with nonepidemic resistant strains were 16 times more likely than controls to have received preceding therapy with imipenem. In our institution, the increase in the incidence of ampicillin-resistant enterococci appears to be due to the selection of various strains of resistant enterococci by the use of imipenem and to the nosocomial transmission of E. faecium and E. raffinosus.

Adult↗
PubMed1992

Molecular typing of ampicillin-resistant, non-beta-lactamase-producing Enterococcus faecium isolates from diverse geographic areas.

Molecular typing methods were compared by using 66 ampicillin-resistant, non-beta-lactamase-producing Enterococcus faecium clinical isolates from diverse geographic areas. Whole-plasmid analysis, restriction enzyme analysis of plasmid DNA with EcoRI and HindIII, and contour-clamped homogeneous electric field electrophoresis with digestion by SmaI and ApaI were performed on all isolates. Whole-plasmid analysis identified 47 different groups. Restriction enzyme analysis of plasmid DNA identified 50 groups when EcoRI was used and 51 groups when HindIII was used. Results with EcoRI and HindIII differed in 9 of 66 isolates. Grouping results with whole-plasmid analysis differed from results of restriction enzyme analysis of plasmid DNA (combining EcoRI and HindIII) in 20 of 66 isolates. Contour-clamped homogeneous electric field electrophoresis identified 46 groups when SmaI was used and 44 groups when ApaI was used. Results with SmaI and ApaI differed in 3 of 66 isolates. Grouping results with contour-clamped homogeneous electric field electrophoresis (combining SmaI and ApaI) differed from results of restriction enzyme analysis of plasmid DNA (combining EcoRI and HindIII) in 17 of 66 isolates. The combined use of whole-plasmid analysis, restriction enzyme analysis of plasmid DNA with two enzymes, and contour-clamped homogeneous electric field electrophoresis with two restriction enzymes should be considered when E. faecium is typed for epidemiologic investigation.

Ampicillin Resistance↗
PubMed1991

Nosocomial pneumonia in Medicare patients. Hospital costs and reimbursement patterns under the prospective payment system.

To determine the extent to which hospitals are reimbursed for Medicare patients who develop nosocomial pneumonia, we analyzed hospital accounting costs, reimbursements received, and the net income from 33 Medicare patients who developed nosocomial pneumonia. In 31 of the 33 cases, hospital costs for the entire admission exceeded reimbursements, with a median net loss of $5800 per case. Eleven randomly selected pneumonia cases were compared with control patients matched by diagnosis related group, age, sex, and service. Cases had significantly longer hospital stays, had greater total hospital costs, and caused greater net losses than did matched controls. We conclude that hospitals are seldom reimbursed adequately for Medicare patients who develop nosocomial pneumonia. With the advent of the prospective payment system, hospitals now have substantial financial incentives for implementing cost-effective measures for preventing nosocomial pneumonias.

Aged↗
PubMed1991

Should we vigorously try to contain and control methicillin-resistant Staphylococcus aureus?

OBJECTIVE: To review practices currently used to control transmission of methicillin-resistant Staphylococcus aureus (MRSA) in hospitals, determine the frequency of their use, and discuss the indications for implementing such measures. DESIGN: A questionnaire survey to determine how commonly selected control practices are used, and a literature review of the efficacy of control practices. PARTICIPANTS: Two hundred fifty-six of 360 hospital-based members fo the Society for Hospital Epidemiology of America, Inc. (SHEA) completed the survey questionnaire. RESULTS: Many different combinations of surveillance and control measures are used by hospitals with MRSA. Nine percent of hospitals stated that no special measures were used to control MRSA. The efficacy of commonly used control measures has not been established by controlled trials. CONCLUSIONS: Implementing control measures is warranted when MRSA causes a high incidence of serious nosocomial infections, and is desirable when MRSA has been newly introduced into a hospital or into an intensive care unit, or when MRSA accounts for more than 10% of nosocomial staphylococcal isolates. While the value of some practices is well established, measures such as routinely attempting to eradicate carriage of MRSA by colonized patients and personnel require further evaluation.

Carrier State↗
PubMed1991

Failure of routine susceptibility tests to detect imipenem resistance among strains of methicillin-resistant Staphylococcus aureus.

We tested 75 methicillin-resistant Staphylococcus aureus strains for susceptibility to imipenem by using disk diffusion tests and broth microdilution tests with standard and heavy inocula. Population analysis was performed on isolates that appeared to be susceptible by these methods. All of the strains contained subpopulations of cells that are phenotypically resistant to imipenem.

Drug Resistance, Microbial↗
PubMed1990

Increasing prevalence of methicillin-resistant Staphylococcus aureus in the United States.

In the period 1975 to 1981, methicillin-resistant Staphylococcus aureus (MRSA) emerged as an important nosocomial pathogen in tertiary care centers in the United States. To determine if the prevalence of this organism has continued to increase, a questionnaire was sent to hospital epidemiologists in 360 acute care hospitals. A total of 256 (71%) of the 360 individuals responded. Overall, 97% (246/256) of responding hospitals reported having patients with MRSA in the period 1987 through 1989. Respondents in 217 hospitals provided estimates of the number of cases seen in 1987, 1988 and 1989. The percentage of respondents reporting one or more patients with MRSA increased from 88% in 1987 to 96.3% in 1989 (p = .0008). The percent of respondents reporting large numbers (greater than or equal to 50) of cases per year increased from 18% in 1987 to 32% in 1989 (p = .0006). Increasing frequency of large outbreaks was observed in community, community-teaching, federal, municipal and university hospitals.

Cross Infection↗
PubMed1990

Hospital reimbursement patterns among patients with surgical wound infections following open heart surgery.

Of the more than 200,000 patients who undergo open heart surgery annually in the United States, 2% to 10% will develop a post-operative infection related to their surgery. The economic impact of such infections on hospitals under the prospective payment system is unclear. To study the effect of such infections on hospital costs and reimbursement patterns, we compared case patients with controls of similar age, sex, urgency of surgery and type of surgery. The postoperative stay for cases was significantly longer than for matched controls (26.8 days and 8.3 days, respectively; p = .0002). The mean hospital cost for case admissions ($25,957) was twice as high as for control admissions ($12,795) (p = .0002). Cases resulted in an average net loss to the hospital of $2,344 per patient, while controls yielded an average net gain of $3,196 per patient (p = .02). We conclude that hospitals have substantial financial incentives to minimize the incidence of postoperative wound infections associated with open heart surgery.

Adult↗
PubMed1990

A common-source outbreak of Staphylococcus epidermidis infections among patients undergoing cardiac surgery.

A single strain of Staphylococcus epidermidis caused an outbreak of postoperative wound infections and endocarditis during a 6-month period. Infections caused by the epidemic strain developed more frequently in valve surgery patients than in those undergoing coronary artery bypass graft surgery (P = .03) and occurred only in patients operated on by surgeon A. None of 17 members of the cardiac surgery team carried the epidemic strain in their anterior nares, axillae, or inguinal folds. Hand cultures were performed on 8 surgical personnel, and only surgeon A carried the epidemic strain on his hands. Isolates from cardiac surgery patients, bypass pump blood cultures, and the hands of the implicated surgeon all had identical antimicrobial susceptibility patterns, plasmid profiles, and EcoRI restriction endonuclease digest patterns. In the 24 months after control measures were implemented, no infections caused by the epidemic strain occurred among open heart surgery patients. The findings suggest that the common-source outbreak of infections among cardiac surgery patients was due to carriage of a strain S. epidermidis on the hands of a cardiac surgeon.

Adult↗
PubMed1990

Induction of beta-lactamase and methicillin resistance in unusual strains of methicillin-resistant Staphylococcus aureus.

Two unusual, heterogeneously-resistant, strains of Staphylococcus aureus appeared resistant to oxacillin, but susceptible to methicillin by disc diffusion methods. In agar dilution tests, both strains were oxacillin-resistant. One was susceptible to methicillin, and the other gave a paradoxical reaction, with growth only on plates containing low (0.5, 1 and 2 mg/l) and high (32 and 64 mg/l) concentrations of antibiotic. Induction of methicillin resistance was tested by inoculating each strain on to agar plates containing an inhibitory concentration of methicillin (8 mg/l), and then placing discs containing inducers (oxacillin, nafcillin, methicillin and CBAP [2-(2'-carboxyphenyl) benzoyl-6-aminopenicillanic acid]) on the agar surface. Colonies grew only around discs containing effective inducers. Oxacillin and CBAP were much more potent inducers of methicillin resistance and beta-lactamase than was nafcillin or methicillin. These data suggest that the mechanism that regulates induction of the low-affinity penicillin binding protein (PBP-2') may be altered in these strains. Similar mechanisms appear to induce both beta-lactamase and methicillin resistance.

Bacterial Proteins↗
PubMed1989

Modification of homogeneous resistance in a methicillin-resistant strain of Staphylococcus aureus by acquisition of a beta-lactamase encoding plasmid.

Nearly all clinical isolates of methicillin-resistant Staphylococcus aureus (MRSA) are heterogeneously resistant and produce beta-lactamases which generally are plasmid mediated. In order to study the role of beta-lactamase plasmids in the expression of methicillin resistance, a beta-lactamase plasmid from Enterococcus faecalis HH22 (pBEM10) was transferred into a homogeneously resistant, beta-lactamase-negative strain of MRSA (MUSC284). By single disc diffusion testing at 42 degrees C, beta-lactamase producing transconjugants (SA-MM1) were found to be more susceptible than the parent strain to methicillin, imipenem, SCH 34343 and cloxacillin, but more resistant to piperacillin. The heterogeneity observed in transconjugants was not affected by the addition of clavulanic acid, indicating that beta-lactamase itself was not responsible for this effect. By population analysis over 50% of MUSC284 colonies and less than 1% of SA-MM1 colonies remained viable after incubation at 42 degrees C in agar plates containing 25 mg/l of cloxacillin. Cured derivatives of SA-MM1 reverted to homogeneous resistance to beta-lactam antibiotics as observed in the initial parenteral strain MUSC284. Thus, the introduction of a beta-lactamase coding plasmid into a homogeneously resistant MRSA yielded transconjugants which resembled heterogeneously resistant strains of MRSA. These results suggest that regulatory genes, capable of altering the expression of methicillin resistance, may be located on beta-lactamase plasmids commonly found in these organisms.

Chromosomes, Bacterial↗
PubMed1989

Methicillin-resistant Staphylococcus aureus. Detection, epidemiology, and control measures.

MRSA are important nosocomial pathogens in many larger medical centers and are likely to find their way into hospitals that have not yet been affected. Prompt implementation of a variety of control measures shortly after the first few cases has been recognized as the approach most likely to result in the eradication of the organism. Once MRSA have become endemic, extraordinary efforts may be required to stop nosocomial transmission. For patients infected with MRSA, vancomycin is the drug of choice.

Cross Infection↗