Abstract
The performance of ribotyping and pulsed-field gel electrophoresis was compared in the differentiation of a collection of 44Pseudomonas aeruginosa serotype O11 strains isolated in seven hospitals in Singapore. Digestion of genomic DNA byEcoRI andSacI followed by Southern hybridization with thePseudomonas aeruginosa 16S and 23S rRNA gene revealed seven distinct ribotypes. Ribotyping using a combination of both enzymes revealed 11 ribotypes. In contrast, electrophoretic analysis differentiated 41 different strain types among the 44 clinical isolates using eitherSpeI orDraI. Pulsed-field gel electrophoresis demonstrated greater sensitivity than ribotyping in the differentiation ofPseudomonas aeruginosa strains of the same ribotype and could thus be used alone in epidemiological investigations of hospital outbreaks ofPseudomonas aeruginosa serotype O11 infection.