Biochemical characteristics, enterotoxigenicity and susceptibility to antimicrobial agents of clinical isolates of Aeromonas species encountered in the western region of Saudi Arabia.

The biochemical characteristics, enterotoxigenicity and susceptibility to antibiotics are reported for 22 strains of Aeromonas species isolated from clinical specimens in the Western Region of Saudi Arabia. Aeromonas caviae was the species most frequently observed; a high proportion of these strains fermented lactose, whereas lactose fermentation was not observed in strains of A. hydrophila and A. sobria. Enterotoxigenicity, as judged by cytotoxicity in tissue culture was observed in three of four A. hydrophila strains and six of seven A. sobria strains, but in only one of 11 A. caviae strains. Two schemes for the biochemical assessment of enterotoxigenicity were found to be in 91% and 86% agreement respectively with cytotoxicity studies and in 95% agreement with each other. No single biochemical test correlated fully with enterotoxigenicity, but 86% of strains that oxidized gluconate produced a cytotoxin. Most strains were inhibited by concentrations of gentamicin, amikacin, chloramphenicol and tetracycline achievable in plasma. Most strains were resistant to broad-spectrum penicillins and many were also resistant to cefuroxime and cefoxitin.