Infections due to beta-lactamase-producing, high-level gentamicin-resistant Enterococcus faecalis.
OBJECTIVE
To investigate the risk factors, clinical features, molecular epidemiology, and treatment outcomes associated with an outbreak of infections due to beta-lactamase-producing, high-level gentamicin-resistant Enterococcus faecalis.


METHODS
Case-control and molecular genetics study.


METHODS
Tertiary care Veterans Affairs hospital.


METHODS
Sixty-five patients infected or colonized with beta-lactamase-producing high-level gentamicin-resistant E. faecalis (case patients) were matched and compared with 65 randomly selected patients infected or colonized with beta-lactamase-negative, gentamicin-susceptible E. faecalis.


RESULTS
During the 20-month study period, 124 of 1506 isolates (8.2%) of E. faecalis from 70 patients were found to produce beta-lactamase. Univariate analysis showed older age, higher APACHE II score, nosocomial acquisition, recent surgical procedure, total parenteral nutrition, and antibiotic treatment to be significantly associated with the acquisition of beta-lactamase-producing, high-level gentamicin-resistant E. faecalis. A multivariate analysis, done using stepwise multiple logistic regressions, showed that only two variables remained significant: an APACHE II score greater than 6 (odds ratio, 9.5; 95% CI, 4.4 to 20.3) and antibiotic treatment (odds ratio, 10.2; CI, 4.5 to 23.2). The mortality rate for case patients was 7.7% (5 of 65 patients; CI, 1.2% to 14.2%); no control patient died. Of 23 infections occurring in case patients, 13 were treated with "inappropriate" antibiotics (regimens that included a beta-lactamase-unstable antibiotic); 2 patients improved and 11 had complete resolution of disease. "Appropriate" treatments (regimens that included a beta-lactamase-stable antibiotic) were used in 10 patients; 5 of 10 infections were fatal. Restriction enzyme digests of total chromosomal DNA showed nearly identical patterns for selected isolates of beta-lactamase-producing, high-level gentamicin-resistant E. faecalis, suggesting dissemination through the hospital of a single strain of E. faecalis.


CONCLUSIONS
Fatal infections were observed despite treatment with beta-lactamase-stable antibiotics. The risk for infection or colonization with beta-lactamase-producing, high-level gentamicin-resistant E. faecalis was strongly associated with severe underlying disease (acute physiology and chronic health evaluation [APACHE] II score, greater than 6) and previous antibiotic treatment. These results may be useful in targeting high-risk patients for infection-control interventions.
Wells
V D
VD
Department of Veterans Affairs Medical Center, Richmond, VA 23249.
Wong
E S
ES
Murray
B E
BE
Coudron
P E
PE
Williams
D S
DS
Markowitz
S M
SM
D016022:Case-Control Studies; D003428:Cross Infection / Q000382:microbiology*; D004196:Disease Outbreaks; D004352:Drug Resistance, Microbial; D016521:Electrophoresis, Gel, Pulsed-Field; D013293:Enterococcus faecalis / Q000187:drug effects / Q000201:enzymology / Q000235:genetics; D005839:Gentamicins / Q000494:pharmacology*; D016908:Gram-Positive Bacterial Infections / Q000453:epidemiology / Q000382:microbiology*; D006746:Hospital Bed Capacity, 500 and over; D006787:Hospitals, Veterans; D006801:Humans; D008875:Middle Aged; D016896:Treatment Outcome; D014768:Virginia; D001618:beta-Lactamases / Q000096:biosynthesis*
D005839:Gentamicins; D001618:beta-Lactamases