Usefulness of the API ZYM system for the identification of Legionella sp.

BACKGROUND: The identification of Legionella genus is usually difficult, time consuming, and expensive. We decided to study the usefulness of API-ZYM system (Biomerieux) for Legionella species identification. METHODS: A total of 96 strains (82 from Legionella genus and 14 from other bacterial genus) were included. We studied 19 different enzyme activities and we proceed following the manufacturers directions, with an incubation time for galleries of 4 hours at 37 degrees C. RESULTS: Seventeen out of the 19 enzyme activities were uniformly positive or negative for Legionella sp. Thus, the sensitivity of these activities was 100% in identifying Legionella sp. Valine and cystine-arylamidase gave variable reactions for Legionella sp. strains. When the results of these enzyme test were compared to those of the control strains (Haemophilus influenzae, Pseudomonas aeruginosa) we observed that alkaline phosphatase, esterase, esterase-lipase, acid phosphatase and naphthol-AS-BI-phosphohydrolase in one side and esterase, esterase-lipase and leucin-arylamidase in the other side were able to differentiate Legionella sp. strains from P. aeruginosa and H. influenzae, respectively. CONCLUSION: API SYM system is a simple, accurate and reproducible method for the identification of Legionella sp.