Clinical characteristics and molecular epidemiology associated with imipenem-resistant Klebsiella pneumoniae

Eight patients were infected or colonized with imipenem-resistant Klebsiell a pneumoniae (IRKP) from December 1994 to November 1995. Initial Klebsiella isolates were susceptible to imipenem but resistant to all cephalosporins, aminoglycosides, and beta-lactam inhibitor combinations. All patients had been in the surgical intensive care unit and had undergone abdominal surger y or tracheostomy during hospitalization. The average age of the patients w as 71 years (range, 41-81 years). All patients were treated with imipenem f or 5 to 36 days, and IRKP was recovered from each during or after therapy, Pulsed-field gel electrophoresis (PFGE) of the IRKP isolates revealed three distinct clonal patterns. Paired sequential isolates of imipenem-susceptib le K. pneumoniae and IRKP from two patients had identical PFGE patterns, su ggesting the development of clonal stepwise resistance to imipenem during t herapy. Thus, imipenem resistance in Klebsiella may occur when this agent i s used for treatment of infection due to ceftazidime- and aminoglycoside-re sistant strains.