Extended serogrouping scheme for motile, mesophilic Aeromonas species

A total of 1,255 strains of motile, mesophilic Aeromonas species isolated from clinical and environmental specimens in the United Kingdom and 258 strains isolated in Australia, Brazil, Peru, and the United States were examined by using antisera for serogroups O1 to O44 (R. Sakazaki and T. Shimada, Jpn. J. Med. Sci. 37:247-255, 1984) and for unpublished serogroup O45 (R. Sakazaki). The typeability rate for strains isolated in the United Kingdom was 35%; the strains isolated in other countries had typeability rates of between 14 and 43%. A total of 52 provisional new serogroups were identified, and the strains with unidentified O groups were examined by using antisera for these provisional new serogroups. The typeability rate for strains isolated in the United Kingdom was increased to 66% (70% of smooth strains). The typeability rates were 76% for A. hydrophila and 63% for both A. caviae and A. sobria. The 52 antisera for the provisional new serogroups increased the typeability rate for strains isolated outside the United Kingdom to between 43 and 68%. This extended serogrouping scheme would be of value in determining the importance of Aeromonas strains as human intestinal pathogens and in investigating the pathogenic mechanisms that may be involved in the production of diarrheal disease.