Further studies of transferable antibiotic resistance in strains of Pseudomonas aeruginosa from four clinical settings in three countries.

This paper describes transferability of antibiotic resistance determinants in clinical isolates of Pseudomonas aeruginosa resistant to imipenem, cefotaxime and ceftazidime obtained from different clinical settings in three different countries. Two strains of Enterobacteriaceae (Escherichia coli K-12 and Proteus mirabilis P-38) and two strains of P. aeruginosa (PAO and ML) were used as recipient strains. The conjugative transfer of resistance was very specific, i.e. donor strains of P. aeruginosa transferred individual resistance determinants either to recipient strains E. coli K-12 and P. mirabilis P-38, or to P. aeruginosa PAO or ML. In a case when three different species (P. aeruginosa, Acinetobacter calcoaceticus, Stenotrophomonas maltophilia) were isolated from a single patient, a block of resistance determinants was transferred both to Enterobacteriaceae and P. aeruginosa recipients. A single plasmid with rather specific properties was suspected of being exchanged among strains of these different species. It was recommended to study the overall situation of transferability of individual resistance determinants in bacterial strains belonging to various species of nosocomial bacteria, especially of P. aeruginosa, by using a rather specific methodology.