A Virulent Nosocomial Klebsiella with a Transferable R Factor for Gentamicin: Emergence and Suppression

In February, 1970, at the District of Columbia General Hospital, there occurred a sudden outbreak of serious infections caused by gentamicin-resistant strains of gram-negative rods. All of 19 isolates from 14 medical patients were shown to be the same strain of Klebsiella type 22, resistant to all common antibiotics except cephalothin and the polymyxins. Control measures were instituted throughout the hospital that were designed to interrupt interpatient transmission (via the hands of personnel attending patients with indwelling urinary catheters) and to eliminate effects of selection pressure of topical gentamicin. Despite continued parenteral usage of gentamicin, the outbreak was successfully suppressed. The strain of Klebsiella type 22 was 10- to 40-fold more resistant to gentamicin than were sensitive strains of Klebsiella, both in vitro and in vivo. The strain possessed a transferable R factor for gentamicin which differs from those which mediate direct inactivation of other aminoglycosides.