Inducible Oxacillin-Hydrolyzing Penicillinase in Aeromonas hydrophila Isolated from Fish

Open Access
Publisher Website
Google Scholar
Abstract
An inducible penicillinase was shown to be present in a strain of Aeromonas hydrophila subsp. hydrophila isolated from freshwater fish. Enzyme induction was observed with benzylpenicillin or 6-aminopenicillanic acid, and the enzyme was cell bound. The penicillinase was purified 50-fold from a crude cell extract. The molecular weight was estimated to be 23,000 by gel filtration. The pH and temperature optima for the enzyme activity were 8.0 and 35°C, respectively. The penicillinase showed a unique substrate profile by hydrolyzing oxacillin about twice as rapidly as benzylpenicillin. The enzyme activity was weakly inhibited by sodium chloride but was not affected by p-chloromercuribenzoate. The property of penicillinase production by the A. hydrophila strain could not be transferred to Escherichia coli and also could not be eliminated from the bacteria by ethidium bromide treatment.