Molecular Epidemiologic Analysis of Enterobacter Isolated from Clinical Specimen

ABSTRACT

Eighty-nine isolates of Enterobacter spp. from two university hospitals were analyzed by phenotypic and genotypic characteristics for epidemiologic investigation. Most strains were isolated from sputum, urine, wound, pus and catheter tip. Most isolates of Enterobacter spp. were resistant to ampicillin, cefazolin and cefoxitin and 39% of E. cloacae isolates were also resistant to other cephalosporins and aminoglycoside antibiotics except amikacin but all strains were highly susceptible to imipenem and ciprofloxacin. Twenty-six antimicrobial resistance patterns were obtained from E. clacae, but E. aerogenes showed only 4 patterns. Fourty-two plasmid profiles were identified, but plasmid was not detected from 28.4% of E. cloacae and 58% of E. aerogenes. Six biotypes from E. cloacae and three biotypes from E. aerogenes were obtained by carbohydrate metabolism. Fourteen strains of E. cloacae carried conjugative R plasmids and these plasmids were further analyzed. Among them, ten plasmids showed identical antibiogram, molecular weight, and pI value by isoelectric focusing and nearly identical restriction endonuclease fragment pattern. Their parental strains had identical antibiogram, biotype, plasmid profile, and were isolated from 4 different specimens including 6 catheter tips of different patients. But most clinical isolates showed various types of combination and seemed to be different strains. These results indicate that the epidemic strain were present in this hospital and the combination of antibiogram and plasmid analysis can be used to discriminate the epidemic strains of multi-resistant E. cloacae.