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M K Hayden

Publications and source records attributed to M K Hayden.

At least 19 recordsLinked to original sources
PubMed2001

Effectiveness of gloves in the prevention of hand carriage of vancomycin-resistant enterococcus species by health care workers after patient care.

Gloving reduces acquisition of vancomycin-resistant Enterococcus species (VRE) on the hands, and it should be considered for routine inpatient care, even for contact with the intact skin of patients who may be colonized with VRE. However, gloving does not completely prevent contamination of the hands, and hand washing is necessary after glove removal.

Electrophoresis, Gel, Pulsed-Field↗
PubMed2000

Insights into the epidemiology and control of infection with vancomycin-resistant enterococci.

Despite control efforts, the incidence of nosocomial infections due to vancomycin-resistant enterococci (VRE) continues to increase in the United States. VRE are thought to spread primarily by cross-contamination. Recent molecular epidemiologic studies have refined our understanding of this phenomenon. If VRE are not controlled soon after introduction into a hospital, sporadic cases may evolve into a monoclonal outbreak, which may then evolve to polyclonal endemicity. An intervention that is effective in containing VRE in one setting may be ineffective in another. Control of VRE where they are endemic is particularly challenging. Although eradication of endemic VRE may not be possible, aggressive, multifaceted programs have been successful in diminishing the problem. A mathematical model of transmission of VRE and the effect of infection control measures in settings where they are endemic has been reported. The use of such a model may allow more precise determination of the impact of control strategies in the future.

Cross Infection↗
PubMed1999

The changing molecular epidemiology and establishment of endemicity of vancomycin resistance in enterococci at one hospital over a 6-year period.

The contributions of clonal spread, transfer of genetic elements, and introduction of new strains to the establishment of endemicity of vancomycin-resistant enterococci (VRE) were determined. The study took place at one hospital between 1990, when VRE were first detected, and 1996, when endemicity had become established. Isolates from 183 patients were categorized into 24 strain types by pulsed-field gel electrophoresis; the resistance genotype was determined by polymerase chain reaction. Between 1990 and 1993, 69% of patients were infected with the same vanB Enterococcus faecium strain. VanA resistance was not detected until 1993, but in 1996, the ratio of vanA to vanB was 2.2:1. Over time, 8 vanA strains were detected; a 35- or 40-kb conjugative vanA plasmid was found in 4 of the 8 strains. Clonal spread was a major factor in the establishment of endemicity. Transfer of genetic elements and introduction of new strain types were detected less often. However, these events may have been equally important evolutionarily.

Adult↗
PubMed1998

The role of "colonization pressure" in the spread of vancomycin-resistant enterococci: an important infection control variable.

OBJECTIVE: The spread of nosocomial multiresistant microorganisms is affected by compliance with infection control measures and antibiotic use. We hypothesized that "colonization pressure" (ie, the proportion of other patients colonized) also is an important variable. We studied the effect of colonization pressure, compliance with infection control measures, antibiotic use, and other previously identified risk factors on acquisition of colonization with vancomycin-resistant enterococci (VRE). METHODS: Rectal colonization was studied daily for 19 weeks in 181 consecutive patients who were admitted to a single medical intensive care unit. A statistical model was created using a Cox proportional hazards regression model including length of stay in the medical intensive care unit until acquisition of VRE, colonization pressure, personnel compliance with infection control measures (hand washing and glove use), APACHE (Acute Physiology and Chronic Health Evaluation) 11 scores, and the proportion of days that a patient received vancomycin or third-generation cephalosporins, sucralfate, and enteral feeding. RESULTS: With survival until colonization with VRE as the end point, colonization pressure was the most important variable affecting acquisition of VRE (hazard ratio [HR], 1.032; 95% confidence interval [C1], 1.012-1.052; P=.002). In addition, enteral feeding was associated with acquisition of VRE (HR, 1.009; 95% CI, 1.000-1.017; P=.05), and there was a trend toward association of third-generation cephalosporin use with acquisition (HR, 1.007; 95% CI, 0.999-1.015; P=.11). The effects of enteral feeding and third-generation cephalosporin use were more important when colonization pressure was less than 50%. Once colonization pressure was 50% or higher, these other variables hardly affected acquisition of VRE. CONCLUSIONS: Acquisition of VRE was affected by colonization pressure, the use of antibiotics, and the use of enteral feeding. However, once colonization pressure was high, it became the major variable affecting acquisition of VRE.

APACHE↗
PubMed1998

Stability of vancomycin-resistant enterococcal genotypes isolated from long-term-colonized patients.

Genotypic variation and stability of isolates of vancomycin-resistant enterococci (VRE) were studied to determine genetic diversity and whether strain definition based on pulsed-field gel electrophoresis (PFGE) is applicable to an endemic setting. Twenty-two PFGE types were identified among 455 VRE isolates. One-on-one comparisons of 10 vanA Enterococcus faecium strain types all yielded > 10 band differences. Variations among vanA and vanB E. faecium isolates from individual long-term-colonized (4-160 days) patients yielded < 3 band differences for > 85% of comparisons. Comparison of all strains without grouping by vancomycin resistance types yielded two peaks of band differences: one with < 3 and one with > 10 band differences. These data show that VRE isolates were genetically closely related or very different; demonstrate that within individual patients, VRE isolates show little genetic variation; and provide empirical evidence that PFGE can be used to study the epidemiology of VRE endemicity.

Anti-Bacterial Agents↗
PubMed1998

External sources of vancomycin-resistant enterococci for intensive care units.

OBJECTIVE: The incidence of colonization and infection with vancomycin-resistant enterococci (VRE) has increased dramatically in the last 5 yrs, especially in intensive care units (ICUs). We studied VRE-colonization in patients on admission to a medical ICU (MICU) where VRE colonization is endemic. DESIGN: Prospective, descriptive analysis. SETTING: An MICU of a public hospital. PATIENTS: Three hundred and one consecutively admitted patients. MEASUREMENTS AND MAIN RESULTS: Rectal swabs were obtained on admission from all patients. VRE isolates from all colonized patients were genetically fingerprinted by pulsed-field gel-electrophoresis (PFGE). Forty-three (14%) of 301 patients were colonized with VRE on MICU admission. Three (7%) of these 43 patients were admitted directly from the community without prior hospital contact. Risk of colonization on admission was related to the length of stay in the hospital before MICU-admission (odds ratio 4.65 for patients with a stay of at least 3 days) and previous in-hospital use of antibiotics. Of 22 VRE PFGE strain types recognized in the MICU during the study period, four (18%) were introduced by patients admitted directly from the community and ten (45%) were introduced by patients admitted from other hospital wards. CONCLUSIONS: These results show that although ICUs are considered epicenters for antibiotic resistance, sources extraneous to our MICU (e.g., other wards) contributed the majority of VRE strain types in the unit.

Anti-Bacterial Agents↗
PubMed1997

Skin colonization with vancomycin-resistant enterococci among hospitalized patients with bacteremia.

To assess the prevalence of skin and rectal colonization by vancomycin-resistant enterococci (VRE) in hospitalized bacteremic patients and to determine the relation between colonization and bacteremia, we compared 14 case patients who had bacteremia due to VRE with 30 control patients who had bacteremia due to other pathogens. Rectal colonization and skin (inguinal area and/or antecubital fossa) colonization with VRE were common among both case patients (100% had rectal colonization, and 86% had skin colonization) and control patients (37% had rectal colonization and 23% had skin colonization). Among patients with rectal colonization, skin colonization was more common when diarrhea or fecal incontinence was present. The bloodstream cleared without appropriate antimicrobial therapy in nine of the 14 patients with bacteremia due to VRE. The high prevalence of skin colonization with VRE may increase the risk of catheter-related sepsis, cross-infection, or blood culture contamination (which may explain the frequent spontaneous resolution of bacteremia due to VRE).

Anti-Bacterial Agents↗
PubMed1997

Heterogeneous expression of glycopeptide resistance in enterococci associated with transfer of vanB.

In mating experiments using a clinical strain that constitutively expresses vanB-encoded glycopeptide resistance, resistance transfer was detectable at a frequency of <10(-7) transconjugants/donor. Vancomycin MICs for transconjugants were 2- to 10-fold lower than those for the donor; both inducibly and constitutively resistant transconjugants were obtained. These findings demonstrate that the transfer of vanB among enterococci can be associated with substantial alterations in the level and control of glycopeptide resistance expression.

Anti-Bacterial Agents↗
PubMed1996

Epidemiology of colonisation of patients and environment with vancomycin-resistant enterococci.

BACKGROUND: Vancomycin-resistant enterococci (VRE) have emerged as nosocomial pathogens during the past 5 years, but little is known about the epidemiology of VRE. We investigated colonisation of patients and environmental contamination with VRE in an endemic setting to assess the importance of different sources of colonisation. METHODS: Between April 12, and May 29, 1995, cultures from body sites (rectum, groin, arm, oropharynx, trachea, and stomach) and from environmental surfaces (bedrails, drawsheet, blood-pressure cuff, urine containers, and enteral feed) were obtained daily from all newly admitted ventilated patients in our medical intensive-care unit (MICU). Rectal cultures were obtained from all non-ventilated patients in the MICU. Strain types of VRE were determined by pulsed-field gel electrophoresis. FINDINGS: There were 97 admissions of 92 patients, of whom 38 required mechanical ventilation. Colonisation with VRE on admission was more common in ventilated than in non-ventilated patients (nine [24%] vs three [6%], p < 0.05). Of the nine ventilated patients colonised with VRE on admission, one acquired a new strain of VRE in the MICU. Of the 29 ventilated patients who were not colonised with VRE on admission, 12 (41%) acquired VRE in the MICU. The median time to acquisition of VRE was 5 days (interquartile range 3-8). Of the 13 ventilated patients who acquired VRE, 11 (85%) were colonised with VRE by cross-colonisation. VRE were isolated from 157 (12%) of 1294 environmental cultures. The rooms of 13 patients were contaminated with VRE, but only three (23%) of these patients subsequently acquired colonisation with VRE. Pulsed-field gel electrophoresis of 262 isolates showed 20 unique strain types of VRE. INTERPRETATION: Frequent colonisation with VRE on MICU admission and subsequent cross-colonisation are important factors in the endemic spread of VRE. Persistent VRE colonisation in the gastrointestinal tract and on the skin, the presence of multiple-strain types of VRE, and environmental contamination may all contribute to the spread of VRE.

Adult↗
PubMed1996

A comparison of the effect of universal use of gloves and gowns with that of glove use alone on acquisition of vancomycin-resistant enterococci in a medical intensive care unit.

OBJECTIVE: To determine the efficacy of the use of gloves and gowns compared with that of the use of gloves alone for the prevention of nosocomial transmission of vancomycin-resistant enterococci. DESIGN: Epidemiologic study and controlled, nonrandomized clinical trial. SETTING: University-affiliated, 900-bed, urban teaching hospital in which vancomycin-resistant enterococci are endemic. PATIENTS: 181 consecutive patients admitted to the medical intensive care unit for 48 hours or more. INTERVENTION: It was determined that all hospital employees would always use gloves and gowns when attending 8 particular beds in the medical intensive care unit and would always use gloves alone when attending 8 others. Compliance with precautions was monitored weekly. Rectal surveillance cultures were taken from patients daily. Cultures of environmental surfaces, such as those of bed rails, bedside tables, and other frequently touched objects in patient rooms and common areas, were taken monthly. Pulsed-field gel electrophoresis was used for molecular epidemiologic typing of vancomycin-resistant enterococci. MEASUREMENTS: The number of patients becoming colonized by vancomycin-resistant enterococci; the number of days to acquisition of vancomycin-resistant enterococci; and other measurements, including nosocomial infections, length of hospital stay, and mortality rates. RESULTS: The 93 patients in glove-and-gown rooms and the 88 patients in glove-only rooms had similar demographic and clinical characteristics. Fifteen (16.1%) patients in the glove-and-gown group and 13 (14.8%) in the glove-only group had vancomycin-resistant enterococci on admission to the medical intensive care unit. Twenty-four (25.8%) patients in the glove-and-gown group and 21 (23.9%) in the glove-only group acquired vancomycin-resistant enterococci in the medical intensive care unit. The mean times to colonization among the patients who became colonized were 8.0 days in the glove-and-gown group and 7.1 days in the glove-only group. None of these comparisons were statistically significant. Risk factors for acquisition of vancomycin-resistant enterococci induced length of stay in the medical intensive care unit, use of enteral feeding, and use of sucralfate. Compliance with precautions was 79% in glove-and-gown rooms and 62% in glove-only rooms (P < 0.001). Only 25 of 397 (6.3%) environmental cultures were positive for vancomycin-resistant enterococci. Nineteen types of vancomycin-resistant enterococci were documented by pulsed-field gel electrophoresis during the study period. CONCLUSIONS: Universal use of gloves and gowns was no better than universal use of gloves only in preventing rectal colonization by vancomycin-resistant enterococci in a medical intensive care unit of a hospital in which vancomycin-resistant enterococci are endemic. Because the use of gowns and gloves together may be associated with better compliance and may help prevent transmission of other infectious agents, this finding may not be applicable to outbreaks caused by single strains or hospitals in which the prevalence of vancomycin-resistant enterococci is low.

Adult↗
PubMed1996

Ceftazidime-resistant Klebsiella pneumoniae and Escherichia coli bloodstream infection: a case-control and molecular epidemiologic investigation.

In a molecular, microbiologic, and case-control study to describe the epidemiology of ceftazidime-resistant Klebsiella pneumoniae and Escherichia coli bloodstream infection, 32 unique isolates were recovered over 31 months from the blood of patients hospitalized in a 900-bed hospital in Chicago. Multivariate analysis revealed cases occurred more frequently in debilitated nursing home patients with central venous catheters than in younger, healthier patients. Mortality rates were similar for cases and controls. Case-patients were less likely to die if they received appropriate antibiotic treatment within 3 days of bacteremia onset (P = .02). Pulsed-field gel electrophoresis analysis indicated a polyclonal outbreak, with strain-specific temporal and geographic clustering. Isoelectric focusing results suggested that a predominant enzyme, TEM-10, was responsible for the ceftazidime resistance. The resistance gene was usually carried on a large conjugative plasmid. The polyclonality of the resistant strains suggests that ceftazidime resistance due to TEM-10 is now endemic in Chicago.

Adolescent↗
PubMed1996

Rapid preparation of bacterial DNA for pulsed-field gel electrophoresis.

A disadvantage of genotyping bacterial strains by pulsed-field gel electrophoresis is that the procedure requires up to 6 days to complete. We modified a standard pulsed-field gel electrophoresis method (B.E. Murray, K.V. Singh, J.D. Health, B.R. Sharma, and G.M. Weinstock, J.Clin. Microbiol. 28:2059-2063, 1990) so that it could be completed in less than 3 days. We successfully applied this method to the analysis of a variety of gram-positive and gram-negative bacteria.

DNA, Bacterial↗
PubMed1995

Comparison of the in vitro activity of levofloxacin and other antimicrobial agents against vancomycin-susceptible and vancomycin-resistant Enterococcus species.

The in vitro activities of levofloxacin and other antibiotics against 133 clinical isolates of vancomycin-resistant and vancomycin-susceptible enterococci were evaluated. Only 14 (39%) of the vancomycin-susceptible isolates and 11 (11%) of the vancomycin-resistant isolates were susceptible to levofloxacin. Levofloxacin exhibited a marked inoculum effect for all enterococci tested. These results suggest that levofloxacin may be of limited use in the treatment of serious enterococcal infections.

Ampicillin↗
PubMed1995

Genotypic and phenotypic characterization of Borrelia burgdorferi isolated from ticks and small animals in Illinois.

We have characterized 33 isolates of Borrelia burgdorferi from northern Illinois (32 isolates) and Wisconsin (1 isolate) representing the largest series of midwestern isolates investigated to date. The techniques used for molecular analysis of strains included (i) genospecies typing with species-specific PCR primers, (ii) plasmid profiling by pulsed-field gel electrophoresis of total genomic DNA, (iii) large-restriction-fragment pattern (LRFP) analysis by pulsed-field gel electrophoresis of MluI-digested genomic DNA (J. Belfaiza, D. Postic, E. Bellenger, G. Baranton, and I. Saint Girons, J. Clin. Microbiol. 31:2873-2877, 1993), (iv) sodium dodecyl sulfate-polyacrylamide gel electrophoresis of total proteins, (v) microsequencing of high-performance liquid chromatography-purified peptides derived from proteins showing high levels of expression, (vi) amino acid composition analysis of proteins, and (vii) immunological analysis of proteins with a polyclonal antiserum of human origin. Five reference strains as well as two atypical tick isolates from California (DN127) and New York (25015) were included for comparison. All of the Illinois and Wisconsin isolates were typed as B. burgdorferi sensu stricto with genospecies-specific PCR primers. The isolates were found to be heterogeneous with regard to their plasmid and protein profiles. One isolate from Illinois possessed two large-molecular-size plasmids instead of the usual 49-kb plasmid. Fragment patterns resulting from MluI digestion of genomic DNA from the 33 isolates and strains DN127 and 25015 were separable into six distinct LRFPs, five of which have not previously been described. Strain 25015 and an isolate from Illinois (CT39) shared an unusual LRFP that is not typical of other B. burgdorferi sensu stricto strains, suggesting that they may represent a fifth species of B. burgdorferi sensu lato. Five of the 33 isolates and strains DN127 and 25015 showed high-level expression of proteins with molecular masses of approximately 22 kDa. Investigation of these proteins by microsequencing of individual peptides and total amino acid composition analysis indicated that the 22-kDa proteins expressed by the seven strains were polymorphic OspC proteins. By using a polyclonal serum of human origin, expression of OspC could be detected in all 33 Illinois and Wisconsin isolates.

Amino Acid Sequence↗
PubMed1994

Bactericidal activities of antibiotics against vancomycin-resistant Enterococcus faecium blood isolates and synergistic activities of combinations.

The effects of teicoplanin (8 micrograms/ml), ampicillin (64 micrograms/ml), imipenem (32 micrograms/ml), and gentamicin (4 micrograms/ml), alone and in combination, against 13 unique blood isolates of vancomycin-resistance (MIC for 90% of isolates tested [MIC90], 512 micrograms/ml), teicoplanin-susceptible (MIC90, 2.0 micrograms/ml), ampicillin-resistant (MIC90, 128 micrograms/ml), and non-beta-lactamase-producing Enterococcus facium (vancomycin-resistant enterococci [VRE] isolates) were evaluated by time-kill studies. All 13 isolates exhibited high-level resistance to streptomycin; 7 isolates exhibited high-level gentamicin resistance (HLGR). After 24 h of incubation, ampicillin (64 micrograms/ml) combined with gentamicin (4 micrograms/ml) was bactericidal against three of the VRE isolates that did not display HLGR. Synergy between ampicillin and gentamicin was not observed against these isolates. Teicoplanin (8 micrograms/ml) alone was bactericidal at 24 h against five of six VRE isolates that lacked HLGR, but was not bactericidal against any HLGR VRE isolate at that time point. The addition of ampicillin (64 micrograms/ml) or imipenem (32 micrograms/ml) to teicoplanin did not significantly enhance the killing of HLGR VRE isolates as a group (P = 0.335). However, there was a trend toward improved killing of some HLGR VRE isolates by teicoplanin plus imipenem. Vancomycin (32 micrograms/ml) combined with ampicillin (64 micrograms/ml) was neither bactericidal nor synergistic against HLGR VRE isolates. Overall, bactericidal activity was attainable against 7 of 13 VRE isolates at 24 h.

Ampicillin↗