The Prevalence of Fecal Colonization of Enterococci, the Resistance of the Isolates to Ampicillin, Vancomycin, and High-Level Aminoglycosides, and the Clonal Relationship Among Isolates

The gastrointestinal tract carriage of enterococei was searched in 150 hospitalized patients and 100 outpa- tients, and clonal relatedness of the isolates and their resistance to ampicillin, vancomycin, and high-level streptomycin and gentamicin were investigated. A stool sample or rectal swab collected from each patient was inoculated into appropriate media within an hour. Enterococcus species were identified by using conventional biochemical tests, API-20 Strep assay, and BBL crystal kit. Antibiotic susceptibility tests were performed us- ing Kirby-Bauer disk diffusion method. A polymerase chain reaction (PCR) was used to detect vanA and vanB genes. Pulsed-field gel electrophoresis (PFGE) and arbitrarily primed-polymerase chain reaction (AP-PCR) methods were used for molecular typing of the strains. Enterococci were isolated from 90 (60%) of the spec- imens collected from 150 inpatients. Of these 90 isolates, 37 (41%) had high-level gentamicin resistance, 36 (40%) had high-level streptomycin resistance, and 50 (55.69%) had ampicillin resistance. Fecal colonization was found in 30% of the outpatients. Resistances to ampicillin, high-level streptomycin, and gentamicin were 13%, 10%, and 3%, in these patients' isolates, respectively. No vancomycin-resistant enterococci were de- tected by both agar diffusion and PCR assays in our study. Both typing procedures were applied on 78 En- terococcus strains isolated from inpatients. AP-PCR typing showed that 30 (50.8%) of the $9 E faecium and 5 (50%) of the 10 E. faecalis strains were clonally related. These values were found to be 12 (20.3%) and two (20%) by PFGE, respectively. The typing procedures did not find any clustered strains in the six E. durans and three E. avium isolates. Neither PFGE nor AP-PCR result was significantly different among the sensitive and resistant strains. Our results ipdicate that the high prevalence of colonization with ampicillin and higb- level aminoglycoside-resistant entecocci is an important problem in our medical center. The high clonal di- versity among the isolates indicates limited spread of antibiotic-resistant strains between patients.