Epidemiological typing of Pseudomonas aeruginosa

Current knowledge of the typing of Pseudomonas aeruginosa and new methods for characterizing strains are reviewed. A combination of serotyping as a primary screen with pyocin typing for finer discrimination between isolates gives valid epidemiological data, is within the scope of most clinical laboratories and is to be recommended. Phage typing and H typing do provide good discrimination but are not reproducible in practice because a reaction-difference rule has to be applied to phage patterns, and diphasic variation reduces the accuracy of the identification of flagellar antigens. A problem remains with cystic fibrosis isolates, which show considerable heterogeneity in surface properties. For these strains pyocin production typing by the revised method of Govan is indicated. Newer techniques such as isoenzyme profile and DNA probes of the chromosome require independent evaluation and due to their technical difficulty may not be adopted in a routine context for some years to come.