EMERGING MULTIPLY RESISTANT ENTEROCOCCI AMONG CLINICAL ISOLATES .1. PREVALENCE DATA FROM 97 MEDICAL-CENTER SURVEILLANCE STUDY IN THE UNITED-STATES

To assess the evolving problem of therapeutic drug resistances among e nterococci, we organized a comprehensive national (United States) surv eillance trial using 99 recruited microbiology laboratories in 48 of t he 49 contiguous stares or districts. AIL but two sites completed the protocol that generated information from nearly 2000 enterococci, usua lly isolated from blood cultures. All strains were speciated by the sa me method (API 20S) and were susceptibility tested by three methods (b roth microdilution, disk diffusion, and Etest) against ampicillin, pen icillin, vancomycin, teicoplanin, gentamicin, and streptomycin. Strain s resistant to a glycopeptide or penicillin, or possessing high-level aminoglycoside resistance were referred to the monitor's laboratory fo r validation and additional susceptibility testing against other alter native antimicrobial agents. The most common species were Enterococcus faecalis and Enterococcus faecium. However, antimicrobial resistance occurred most often among the E. faecium isolates. Twenty-three percen t of participant centers (22 sites) reported 87 vancomycin-resistant i solates, which accounts for 4.4% of the isolates evaluated. A recent a udit (March 1994) of the laboratories not reporting vancomycin resista nce during the study interval (October-December 1992) revealed that 61 % of sites have now recognized these strains, a threefold increase in 12-15 months. Teicoplanin remained active against 28% (Van B phenotype ) of vancomycin-resistant enterococci (10 E. faecalis, 13 E. faecium, and one Enterococcus spp.). Ampicillin-resistant beta-lactamase-positi ve strains were found only at one medical center (two strains, 0.2% of referred or validated strains); however, ampicillin-resistant strains represented 12% of all enterococcal, bur nearly 60% of E. faecium str ains. Aminoglycoside resistance was: gentamicin 27% and streptomycin 3 6% of strains. The susceptibility to alternative drugs was: ciprofloxa cin 25%, erythromycin 3%, trimethoprim/sulfamethoxazole 22%, and spect inomycin 97%. All National Committee for Clinical Laboratory Standards tests and interpretive criteria performed well. Other drugs worthy of therapeutic consideration include chloramphenicol, tetracyclines (esp ecially doxycycline), novobiocin, trospectomycin or kanamycin as a co- drug, and some newer fluoroquinolones (sparfloxacin and clinafloxacin) . Because of this rapidly evolving problem of drug-resistant invasive enterococcal infections, new alternative combination regimens require immediate consideration for structured clinical trials.