NOSOCOMIAL OUTBREAK OF KLEBSIELLA INFECTION RESISTANT TO LATE-GENERATION CEPHALOSPORINS

Objective: To describe the epidemiology, antimicrobial susceptibility, and control of widespread ceftazidime-resistant Klebsiella pneumoniae infections in a North American hospital and circumstances that led to delayed detection. Design: A 2-year epidemiologic, microbiologic, and clinical cohort study. Setting: A 487-bed general hospital in New Yor k City. Patients and Clinical Isolates: Patient records were reviewed retrospectively and prospectively. Isolates were obtained from the Cli nical Microbiology Laboratory. Results: Four hundred thirty-two isolat es of ceftazidime-resistant Klebsiella pneumoniae were recovered durin g a 19-month study period. The peak incidence reached 17.3% of all Kle bsiella isolates. One hundred fifty-five patients were colonized or in fected, representing more than 70 per 1000 average daily census. Infec tions occurred in 39% of patients from whom ceftazidime-resistant Kleb siella was isolated. These included 14 bacteremias and 17 pulmonary in fections among 52 infected patients. The outbreak coincided with incre asing use of ceftazidime therapy for multiresistant Acinetobacter infe ctions. Reduction in ceftazidime use and barrier precautions markedly reduced the incidence of colonization and infection. Ceftriaxone, ceft izoxime, cefotaxime, and cephamycins were inhibitory, but not bacteric idal, against ceftazidime-resistant Klebsiella and appeared effective by routine disc diffusion tests. In contrast, imipenem provided consis tent bactericidal activity. Preliminary studies indicated that the out break was caused by one or more plasmid-mediated beta lactamases. Conc lusions. Nosocomial ceftazidime-resistant Klebsiella pneumoniae may be resistant to the bactericidal activity of all cephalosporins and ceph amycins. Such isolates appear susceptible to cephalosporins other than ceftazidime by routine disc diffusion testing. Ineffective therapy, d elayed detection of resistance, and epidemic spread are potential cons equences. Imipenem provides consistent bactericidal activity. Ceftazid ime restriction and barrier precautions for colonized and infected pat ients are effective control measures.