Nosocomial Infection by Gentamicin-ResistantStreptococcus faecalis

Abstract

Enterococci with high-level resistance to gentamicin account for 55% of clinical isolates of enterococci found in patients at the Ann Arbor Veterans Administration Medical Center. We prospectively studied cultures obtained from all 100 patients hospitalized from 1 December 1985 through 23 January 1986 on the surgical and thoracic intensive care units and a general medical floor. Ten patients' cultures grew colonies of gentamicin-resistant enterococci--six after admission to the intensive care units and four after hospitalization on the medical ward. The initial sites of colonization were the rectal and perineal areas in seven patients, sternal wound in one, urine in one, and the rectal and perineal areas as well as urine after Foley catheter insertion in one. Nine patients died and three of the deaths were associated with enterococcal infection. The acquisition of resistant strains was associated with previous and more frequent exposure to antimicrobial agents, and with geographic clustering of patients. Resistant enterococci were isolated from the hands of hospital personnel and were frequently isolated from environmental surfaces. Nosocomial acquisition and interhospital spread of gentamicin-resistant enterococci was shown to have occurred when plasmid content was used as an epidemiologic marker.

The epidemiology of enterococci

“…The authors concluded that nosocomial enterococcal bacteremia was usually caused by the patient's own endogenous fecal flora introduced into the bladder with instrumentation of the urinary tract and that there was no evidence of personto-person spread within the hospital (7). This study, which suggests that nosocomial transmission of enterococci may occur, was supported by a second prospective study of gentamicin resistant enterococci by the same authors (10). At the Ann Arbor Veterans Administration Medical Center all patients admitted to an index general medicine ward or surgical intensive care unit (SICU) over a two-month period were followed up with cultures.…”

“…Using antibiotic sensitivity patterns and plasmid profiles, however, they showed that the urinary tract isolate differed from the rectal or perineal isolate in two out of three cases, suggesting that colonization during catheter insertion, and not rectal or perineal colonization, predisposes to UTI (10). Bacteremia.…”

“…Traditionally, the source of enterococcal infections has been thought to be endogenous, arising from the patients own flora (7,8,9). Recent evidence, however, has suggested that nosocomial transmission and exogenous acquisition of enterococci may occur (10,11). The results of these studies indicate that patient-to-patient transfer and inter-hospital spread, well recognized in other bacterial species, can also occur with enterococci.…”

“…Using biochemical tests and antibiograms they showed that patients colonized with enterococci developed positive urine cultures with identical enterococci after urinary catheterization (7). This assumption must be reevaluted now in the light of the recent study of Zervos et al (10). These authors identified several patients with rectal or perineal enterococcal colonization who later developed UTI or wound infections with enterococci.…”

Antimicrobial resistance among enterococci

“…These strains were the first reported strains to be resistant to all aminoglycosides, since the French isolates were susceptible to high-level streptomycin. From 1981 to 1984, the frequency of isolation of E. faecalis strains resistant to high-level gentamicin at the University of Michigan Hospital rose from 0.04 to 3.7% and, by 1987, to 16% of all enterococcal isolates (65,66). Among 159 enterococcal isolates collected from eight U.S. tertiary-care hospitals in six geographic regions between July 1988 and March 1989, 24.5% demonstrated high-level gentamicin resistance (15).…”