EPIDEMIOLOGICALLY RELATED AND UNRELATED STRAINS OF PSEUDOMONAS-AERUGINOSA SEROTYPE O-12 CANNOT BE DISTINGUISHED BY PHENOTYPIC AND GENOTYPICTYPING

A clonal origin for European isolates of antibiotic multi-resistant Ps eudomonas aeruginosa serotype O12 has been suggested. This study was d esigned to assess the value and limitations of several typing methods for the investigation of outbreaks due to this serotype. In Hopital de Rodez, France, this organism is endemic, and a prospective clinical e pidemiological study was undertaken over a 15 month period, encompassi ng all patients at the hospital from whom P. aeruginosa O12 was isolat ed. All isolates were examined by auxanogram, antibiogram, phage-typin g, electrophoresis of esterases and pulsed-field gel electrophoresis o f DNA. The results suggest that (1) the methods used did not clearly d ifferentiate between clinically-related and epidemiologically-unrelate d European isolates, (2) in Hopital de Rodez, while some isolates were likely to have been transmitted from patient-to-patient, most infecti ons or colonizations with this organism were sporadic and their origin is unknown. The limits of typing methods for the investigation of out breaks of nosocomial infection with multi-resistant P. aeruginosa O12 are emphasized.