Antibiotics sensitivity and characteristics of the esculin-positive Pseudomonas aeruginosa biovar]

Strains of Pseudomonas aeruginosa hydrolyzing esculin were isolated for the first time. They amount to 17.1 +/- 2.0% (60 from 325) of the investigated P. aeruginosa strains isolated from the clinical material in St. Petersburg. Esculin hydrolysis was measured by micromethod in plates, results were analysed after 3-hours incubation at 37 degrees C. Esculin-positive strains possesed biovar properties: they are widely spread, demonstrated other characteristic features (absence of triethylamine odour, specific colonies lysis), are stable on ability to hydrolyse esculin while culture storage and after repeated culturing. Typical strain of esculinolytica biovar was deposited into the culture collection of the National Research Institute of Agricultural Microbiology as P. aeruginosa ARRIAM 64-A. Susceptibility testing of the esculin-positive strains by disk-diffusion method revealed that most strains were inhibited by imipenem (86.6%), amikacin (75.0%), ceftazidime (65.0%), meropenem (60.0%), aztreonam (51.6%). The percent of strains susceptible to other antibiotics was lower: azlocillin--33.3%, netilmycin--33.3%, piperacillin--26.6%, ceftriaxon--18.3%. Only small number of strains were inhibited by ciprofloxacin (8.3%), gentamycin (3.4%), cefoperazone (1.7%) and carbenicillin (1.7%). The results may be used for empiric therapy before the isolated strain susceptibility is tested but only according to positive esculin-hydrolysis express-test evaluated in 3-hours period.