ARBITRARILY PRIMED PCR, RIBOTYPING, AND PLASMID PATTERN-ANALYSIS APPLIED TO INVESTIGATION OF A NOSOCOMIAL OUTBREAK DUE TO ENTEROBACTER-CLOACAE IN A NEONATAL INTENSIVE-CARE UNIT

In December 1992, Enterobacter cloacae was isolated from the oropharyn x and respiratory tract of six ventilated neonates hospitalized in the intensive care unit (ICU) of our hospital. To establish the spread of the outbreak, 41 strains of E. cloacae were analyzed for genotypic ma rkers by three methods: plasmid profile analysis, ribotyping with EcoR I or PvuII endonuclease, and arbitrarily primed (AP) PCR. The tested s trains included 12 isolates from the 6 epidemic cases, 4 isolates from the respiratory tract of 4 children hospitalized in other wards durin g the same period, 13 isolates from 12 children hospitalized in pediat ric units before or after the outbreak, and 12 epidemiologically unrel ated isolates. Ribotyping and AP PCR demonstrated that each of the las t 12 strains exhibited distinct genomic patterns, as did each of the s trains isolated from neonates hospitalized before or after the epidemi c peak Conversely, two clones of strains were found among the isolates recovered in December, with concordant results being obtained by the three typing methods: the first clone included seven strains from five ventilated children in the ICU and two children from another ward; an other clone was shared by one neonate in the ICU and an infant from an other ward. These results indicate that ribotyping and AP PCR-the latt er applied, to our knowledge, ledge, for the first time to the genotyp ic analysis off. cloacae-represent very discriminatory tools for the i nvestigation of nosocomial outbreaks caused by this species.