Molecular epidemiology of vancomycin-resistant enterococci: a 2-year perspective.

OBJECTIVE: To determine the molecular epidemiology of vancomycin-resistant enterococci (VRE) at our medical center in order to identify the extent of strain clonality and possible transmission patterns of this pathogen. DESIGN: An important facet of our infection control program includes molecular typing of all clinical and surveillance isolates of VRE to determine transmission patterns in the hospital. Molecular strain typing is performed by restriction endonuclease analysis (REA) of genomic DNA. REA patterns are visually compared to categorize VRE strains into type and subtype designations. SETTING: A 588-bed, university-affiliated, tertiary-care hospital and a neighboring 155-bed rehabilitation facility. RESULTS: From January 1995 through December 1996, 379 VRE isolates were collected from 197 patients. Thirty-three genotypes were determined by REA typing; 15 genotypes were implicated in 29 instances of potential nosocomial transmission. Three major clusters of VRE involving patients on multiple nursing units and two adjacent hospitals were identified. The remaining instances of nosocomial transmission occurred in small patient clusters. CONCLUSIONS: In conclusion, the VRE epidemic at this medical center is polyclonal. VRE transmission patterns are complex, and, while large clusters do occur, the usual pattern of nosocomial acquisition of this pathogen occurs in the setting of "mini-clusters".

Medical and economic benefit of a comprehensive infection control program that includes routine determination of microbial clonality.

Nosocomial infections are a major part of the problem of reemerging pathogens causing infectious diseases, affecting 5% of patients hospitalized in the United States during 1995. We assessed the medical and economic effects on the overall nosocomial infection rate of an intervention that provided an enhanced, integrated infection control program, including an in-house molecular typing laboratory capability to rapidly assess microbial clonality. Data on nosocomial infections for 24 months prior to the change in approach to infection control were compared with data from the 24 months immediately following implementation of the new program. Infections per 1,000 patient-days and percentage of hospitalized patients in whom nosocomial infection developed were assessed. Overall, nosocomial infections per 1,000 patient-days decreased more than 10% (P = .027), and percentage of patients with nosocomial infection decreased 23% during the post-intervention period compared with the previous control 24 months. This translated to a mean reduction of some 270 patients per year with nosocomial infection, and lowering of actual health care costs for our institution by $4,368,100 over the 2 years of the intervention.

Comparison of genomic methods for differentiating strains of Enterococcus faecium: assessment using clinical epidemiologic data.

Genomic DNA extracted from 45 vancomycin-resistant Enterococcus faecium (VRE) isolates was cleaved with HindIII and HaeIII and subjected to agarose gel electrophoresis. The ability of this method (restriction endonuclease analysis [REA]) to distinguish strains at the subspecies level was compared with results previously determined by pulsed-field gel electrophoresis (PFGE). Chart reviews were performed to provide a clinical correlation of possible epidemiologic relatedness. A likely clinical association was found for 29 patients as part of two outbreaks. REA found 21 of 21 isolates were the same type in the first outbreak, with PFGE calling 19 strains the same type. In the second outbreak with eight patient isolates, HindIII found six were the same type and two were unique types. HaeIII found three strains were the same type, two strains were a separate type, and three more strains were unique types, while PFGE found three were the same type and five were unique types. No single "ideal" method can be used without clinical epidemiologic investigation, but any of these techniques is helpful in providing focus to infection control practitioners assessing possible outbreaks of nosocomial infection.

Comparative in vitro activity of l-ofloxacin and FK037 to other agents against 10,040 fresh clinical isolates.

Fresh clinical isolates collected from November 1, 1992 through November 1, 1993, were tested by agar dilution against 26 different antimicrobial agents including FK037 and l-ofloxacin. Among the 10 040 organisms tested were Staphylococcus aureus (n = 1222), methicillin-resistant Staphylococcus aureus (MRSA, n = 455), Staphylococcus epidermidis (n = 533), Staphylococcus hominis (n = 90), Staphylococcus hemolyticus (n = 89), Streptococcus pneumoniae (n = 144), Escherichia coli (n = 2326), Klebsiella pneumoniae (n = 745), Enterobacter cloacae (n = 258), Proteus mirabilis (n = 445), Pseudomonas aeruginosa (n = 998), and Stenotrophomonas (Xanthomonas) maltophilia (n = 102). Both l-ofloxacin and FK037 inhibited 98% of S. aureus strains at 4 mug/ml. FK037 was at least 4 times more effective than the third generation cephalosporins against MRSA, inhibiting 79% of the strains at 16 mug/ml. While the potency of these agents looks promising, their clinical utility will depend in part upon the maximal dosage that can be safely administered.