Enzyme profile of Haemophilus ducreyi strains isolated on different continents

Two hundred strains of Haemophilus ducreyi, isolated in different parts of the world, were investigated using the API-ZYM system, which included 95 different substrates. All strains produced aminopeptidase against beta-naphthylamide derivatives of L-lysine, glycine, L-arginine, L-alanine, D-L-methionine, glycyl-glycine, glycyl-L-alanine and L-leucine. All strains also produced alkaline and acid phosphatase and phosphohydrolase. Nearly all strains showed esterase activity against butyrate, valerate, caproate and caprylate, but the reactions were very weak. No glycosidase activity could be detected. Of the 47 aminopeptidase tests showing variable reactions, only the results for S-benzyl-L-cystine, L-ornithine, L-alanyl-L-phenyl-alanyl-L-proline, L-hystidyl-L-leucyl-L-histidine and L-histidyl-L-serine arylamidase obtained on strains from Asia, Africa and Europe were significantly different (p less than 0.05). On the basis of test results for L-ornithine arylamidase and L-alanyl-L-phenyl-alanyl-L-proline arylamidase, the distribution of three biovars found among the isolates of the different continents was significantly different (p less than 0.0001), whereas African strains isolated in Kenya and South Africa yielded the same enzymatic pattern. Thus, these enzymes may constitute a marker system for the epidemiological study of Haemophilus ducreyi.