Antimicrobial susceptibility patterns and high-level gentamicin resistance among enterococci isolated in a Mexican tertiary care center.
OBJECTIVE
To describe the antimicrobial susceptibility pattern of enterococcal clinical isolates.


METHODS
A 200-bed tertiary-care center in Mexico City.


METHODS
Prospective surveillance of enterococcal clinical isolates identified according to Facklam's method since 1990. Susceptibility tests were performed by a commercial micromethod, agar diffusion and microbroth dilution. We present data from 1990 to 1992.


RESULTS
A total of 407 enterococci were recovered during the study period: 245 from inpatients and 162 from outpatients; 325 of the isolates were Enterococcus faecalis, 61 E. faecium, seven E. avium, four each for E. raffinosus and, E. hirae; two, E. pseudoavium; and one each E. gallinarum, E. durans; E. mundtii, and E. faecales var asacharolyticus. Resistance to ampicillin and imipenem among E. faecium was 59%. Among E. faecalis, 0.3% were resistant to ampicillin and 2% to imipenem; no beta-lactamase production was detected. All were susceptible to vancomycin. Overall, a 12% high-level gentamicin resistance (HLGR) was found without a difference between species; 25% of bloodstream clinical isolates were HLGR enterococci. More than half (63%) of the HLGR clinical isolates were susceptible to streptomycin; a-hemolysis in human blood agar as well as nitrofurantoin resistance were observed in all E. faecium isolates and in two E. avium.


CONCLUSIONS
In our center, HLGR has a prevalence of 12%. Streptomycin may be a therapeutic alternative in 63% of the HLGR cases. The pattern of hemolysis in human blood agar plus the susceptibility to nitrofurantoin could be used as an initial screening to identify enterococci.
Sifuentes-Osornio
J
J
Instituto Nacional de la Nutrición Salvador Zubirán, Col. Tlalpan, Mexico City.
Ponce-de-León
A
A
Muñoz-Trejo
T
T
Villalobos-Zapata
Y
Y
Ontiveros-Rodríguez
C
C
Gómez-Roldán
C
C
D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D004352:Drug Resistance, Microbial; D016983:Enterococcus / Q000187:drug effects*; D005839:Gentamicins / Q000494:pharmacology*; D006801:Humans; D008800:Mexico; D008826:Microbial Sensitivity Tests; D011446:Prospective Studies
D000900:Anti-Bacterial Agents; D005839:Gentamicins