Sequential Outbreaks of Infection due to Klebsiella pneumoniae in a Neonatal Intensive Care Unit: Implication of a Conjugative R Plasmid

Abstract

Sequential outbreaks of infection in a [human] neonatal intensive care unit were due to multiple antibiotic-resistant strains of K. pneumoniae of different serotypes. In investigations of these outbreaks, the transfer of resistance to gentamicin, ampicillin, cephalothin, carbenicillin and kanamycin from gentamicin-resistant organisms to standard laboratory recipients and between recipients was observed. Purified plasmid DNA, isolated from all multiple antibiotic-resistant strains, was analyzed by agarose gel electrophoresis, which revealed a common, large plasmid component with a molecular size of 71 Mdaltons. Analysis of drug-resistant progeny suggested this plasmid encoded resistance to antibiotics and the information needed for its transmission. The identity of the plasmid from 3 different sources was established by the use of restriction-enzyme fingerprinting. The dissemination and persistence of this plasmid in environmental and fecal organisms, despite the disappearance of multiple antibiotic-resistant K. pneumoniae, provided a potential source for spread to other bacteria.