Enterococcus: an old pathogen with new tricks

Recent clinical enterococcal isolates from the Oklahoma City Department of Veterans Affairs Medical Center were screened for high-level aminoglycoside resistance, vancomycin resistance, beta-lactamase production, and hemolysin production. Twenty-nine of 53 (55%) enterococcal isolates had high-level resistance to gentamicin, kanamycin, or streptomycin; 27 of these isolates were from the blood and 16 (59%) showed high-level gentamicin resistance. Twenty-one percent of 259 enterococcal isolates from blood, urine, stool, and other sources were hemolytic. Of thirteen blood isolates tested for both high-level gentamicin resistance and hemolysin production, 6 (46%) showed both characteristics. Vancomycin-resistant or beta-lactamase-producing isolates were not found. Nineteen of 21 charts from patients with premortem enterococcal blood isolates were reviewed, and no correlation was found between appropriate antibiotic treatment for high-level gentamicin-resistant or susceptible enterococcal bacteremia and outcome. Enterococci with multiple high-level aminoglycoside resistance, but not vancomycin resistance or beta-lactamase production, are common at this referral medical center. Clinical microbiology laboratories in Oklahoma should routinely screen enterococcal isolates causing potentially serious infections (eg, from blood or cerebral spinal fluid) for high-level aminoglycoside resistance.