Clinical and Molecular Epidemiology of Vancomycin-Resistant Enterococcus faecium During Its Emergence in a City in Southern Texas

Abstract

During a 19-month period from April 1993 to October 1994, 41 isolates of vancomycin-resistant Enterococcus faecium (VREF) were detected in seven different hospitals in a city in southern Texas. A case-control study to determine the risk factors for acquisition was done in the hospital in which the majority of isolates were detected. Pulsed-field gel electrophoresis (PFGE) of whole-cell DNA was used to determine strain identity. Thirty-five (85%) of the 41 VREF isolates were of the vanB phenotype. Of these, 32 (91%) of 35 were the same strain by PFGE typing. The same vanB strain was documented in five different hospitals in the city. In contrast, 4 (67%) of 6 of the vanA phenotype VREF isolates were distinct strains by PFGE typing. Significant risk factors for colonization or infection with VREF were prior exposure to antibiotics (P = .04), the previous use of third-generation cephalosporins (P = .03), and the previous use of parenteral vancomycin (P = .002). Infection-control and antibiotic-utilization measures were implemented to control cross-transmission and selection of VREF isolates. During the emergence of VREF in our city, clonal dissemination of a single strain of vanB VREF among six hospitals was documented. Limited cross-transmission of vanA phenotype VREF isolates occurred, but most vanA VREF isolates were distinct strains selected in individual hospital environments.

Occurrence of a Multidrug-Resistant Pseudomonas aeruginosa Clone in Different Hospitals in Rio de Janeiro, Brazil

“…Alternatively, isolates of genotype A might have emerged independently from a common ancestral strain of P. aeruginosa at these hospitals. The interhospital clonal spread of strains belonging to other bacterial species has been documented by PFGE analyses in the United States (6,15,21). Clonal spread of drug-resistant P. 3.…”

Application of Molecular Techniques to the Study of Hospital Infection

“…The cost savings realized by Northwestern Memorial Hospital and others (183,187) through the incorporation of molecular testing in the infection control program for endemic nosocomial infections is associated with the ability to enact early interventions following the identification of pathogen clonality, which could be an early indication of an outbreak. Conversely, the determination of the unrelatedness of isolates (sporadic infections), avoids triggering unneeded and costly epidemic investigations.…”

“…Several risk factors for acquiring an infection have been commonly cited, including the presence of underlying conditions (such as diabetes, renal failure, or malignancies), long hospitalizations, surgical procedures, receipt of prior antimicrobial therapy, and the presence of indwelling catheters. Major antimicrobial resistance problems are typically associated with gram-positive nosocomial pathogens, which include glycopeptide (vancomycin)-resistant enterococci (125,172,173,187,280,304), methicillin-resistant Staphylococcus aureus (MRSA) (15,229,253), and, more recently, glycopeptide-intermediate and -resistant S. aureus (255). Among the gram-negative bacilli, extended-spectrum-beta-lactamase-producing strains of Escherichia coli and Klebsiella pneumoniae and fluoroquinolone-resistant strains of Pseudomonas aeruginosa and E. coli have been the primary concerns (180,182,183,231,242,258,278,279,286).…”

Vancomycin-Resistant Enterococci

“…Such outbreaks may involve clonal dissemination of strains indistinguishable by pulsed-field gel electrophoresis (PFGE), not only within hospitals but also among several local hospitals (180). Multiple clones are often encountered, and sporadic isolates of unrelated strains may coexist with a predominant clone suspected of institutional spread (30,147).…”