CLINICAL AND MOLECULAR EPIDEMIOLOGY OF ACINETOBACTER INFECTIONS SENSITIVE ONLY TO POLYMYXIN-B AND SULBACTAM

A nosocomial outbreak of infections due to imipenem-resistant Acinetob acter baumannii occurred in a New York hospital after increased use of imipenem for cephalosporin-resistant klebsiella infections. We identi fied all A baumannii isolates over 12 months, reviewed corresponding p atient records, and compared strains with different antibiotic suscept ibility patterns by restriction endonuclease analysis. Environmental s urveillance cultures were done before and after institution of control measures. 59 patients harboured imipenem-resistant A baumannii, and 1 8 were infected, isolates from patients were resistant to all routinel y tested antibiotics, including imipenem. Further studies showed susce ptibility to polymyxin B and sulbactam. These isolates were identical by restriction endonuclease analysis to A baumannii isolates susceptib le to imipenem alone, or to imipenem and amikacin, but differed from b roadly susceptible isolates. Surveillance cultures showed hand and env ironmental colonisation by imipenem-resistant strains. Infection and c olonisation were eliminated by intensive infection control measures, a nd irrigation of wounds with polymyxin B. Increased use of imipenem ag ainst cephalosporin-resistant klebsiella may lead to imipenem resistan ce among other species, particularly acinetobacter. Such resistance ap pears to derive from a prior multi-resistant clone, in contrast to one which retains susceptibility to several antibiotics.