MOLECULAR EPIDEMIOLOGY OF XANTHOMONAS-MALTOPHILIA COLONIZATION AND INFECTION IN THE HOSPITAL ENVIRONMENT

Between April 1992 and December 1993, 80 Xanthomonas maltophilia isola tes were collected from 63 patients in three acute-care hospitals in C algary, Alberta, Canada. On the basis of Centers for Disease Control a nd Prevention definitions, 48 patients had nosocomial and 15 had commu nity-acquired X. maltophilia. Thirty-eight of the patients were coloni zed and 25 were infected. Sixty-four percent of patients who acquired X. maltophilia in the intensive care unit (ICU) became infected, where as 32% of patients in a non-ICU setting became infected. ICU patients tended to be hospitalized for a shorter period of time than non-ICU pa tients before the onset of X. maltophilia infection. Regardless of bei ng colonized or infected, all patients had debilitating conditions, wi th respiratory disease being the most common underlying illness (35%). Forty-two patients (88%) with hospital-acquired X. maltophilia receiv ed prior antibiotic therapy which included gentamicin, tobramycin, cef tazidime; piperacillin, and imipenem. Agar dilution MICs showed that p atient isolates were resistant to these antimicrobial agents that pati ents had received. Pulsed-field gel electrophoresis of SpeI-digested g enomic DNA revealed that six epidemiologically linked patient isolates from the ICU of one acute-care hospital had identical DNA profiles. I n contrast, isolates from patients from the other two hospitals had un ique genotype profiles (n = 57) regardless of the presence or absence of an epidemiologic association. In these patients there was genetic: evidence against the acquisition of a resident hospital clone. These r esults indicate that pulsed-field gel electrophoresis can resolve geno typically distinct Strains of X. maltophilia and, consequently, is a u seful tool for evaluating nosocomial infections caused by X. maltophil ia.