Multiresistant serotype O 12 Pseudomonas aeruginosa: evidence for a common strain in Europe

A survey was made of serotype association and multiple antibiotic resistance in strains of Pseudomonas aeruginosa in Europe. Of 208 epidemiologically distinct strains from 16 laboratories in 10 countries, 48 were resistant to carbenicillin (MIC greater than 128 micrograms/ml) and gentamicin (MIC greater than 4 micrograms/ml), and 12 of these strains were of serotype O 12. Representative O 12 strains from different countries were compared with two multiresistant O 12 strains isolated 5 years apart, from a British burns unit and the antibiotic sensitive serotype reference strain. All O 12 strains were similar by phage and pyocin typing but lysogenic phage profiles indicated that two strains (the later burns isolate and the serotype strain) were distinct from the others. Electrophoretic characterization of outer membrane proteins, lipopolysaccharides and esterase enzymes corroborated the relationship of the strains and restriction fragment length polymorphism of DNA fragments hybridized with a cDNA probe copy of rRNA from P. aeruginosa provided further proof of their relatedness. We propose that the uniformity of characters of multiresistant O 12 P. aeruginosa in Europe is suggestive of a common origin for the strains.