Nosocomial acquisition of beta-lactamase--negative, ampicillin-resistant enterococcus
V. A. Chirurgi, S. E. Oster, A. A. Goldberg and R. E. McCabe
Medical Service, Department of Veterans Affairs Medical Center, Martinez, Calif.
BACKGROUND--A recent prospective study at the Department of Veterans
Affairs Medical Center, Martinez, Calif, revealed that 9% of enterococcal
clinical isolates were ampicillin resistant. We prospectively studied 100
patients hospitalized in one general medicine ward and in the medical
intensive care unit to study determinants of acquisition of
ampicillin-resistant enterococcus. METHODS--Rectal swabs and urine cultures
were obtained from patients within 72 hours of admission to the study ward
and twice weekly until discharge from the ward or the intensive care unit.
Cultures were obtained from the hands of personnel and from environmental
surfaces in the general medical ward and the intensive care unit.
Ampicillin-resistant enterococcal isolates were examined for molecular
relatedness by plasmid DNA analysis. RESULTS--The cultures from 23 patients
yielded ampicillin-resistant enterococci. The rectal swabs yielded
ampicillin-resistant enterococci before the urine cultures did except in
one patient whose urine and rectal cultures were both positive on the same
day. Acquisition of ampicillin-resistant enterococci was significantly
associated with previous antimicrobial agents, Foley catheterization, and
being bedridden. Resistant enterococci were not isolated from hospital
personnel or environmental surfaces. Plasmid analysis by gel
electrophoresis demonstrated nine strains, two of which predominated.
Rectal and urine isolates from the same patient had identical plasmid
electrophoresis patterns. CONCLUSIONS--We conclude that
ampicillin-resistant enterococci are common in the rectal flora, can spread
to the urinary system, are associated with patient characteristics that
predipose to nosocomial infection, and may become an emerging clinical
problem.
