Simultaneous nosocomial outbreaks caused by multiply resistant Klebsiella pneumoniae types 2 and 30.

Two simultaneous Klebsiella pneumoniae outbreaks resistant to multiple antibiotics are reported. The closely related strains were distinguished by comparing the zone diameters obtained by disk diffusion susceptibility testing but not by interpretations of susceptible, resistant, or intermediate. Similar conclusions were made when minimal inhibitory concentrations were considered. The separation was subsequently confirmed by capsular serotyping into types 2 and 30. The data presented suggest that routine antimicrobial susceptibility patterns obtained from disk diffusion and/or minimal inhibitory concentrations may serve as an inexpensive and reliable typing system for epidemiological investigations.