Sequence analysis of two chromosomally mediated inducible β-lactamases from Aeromonas sobria, strain 163a, one a class D penicillinase, the other an AmpC cephalosporinase
Two β-lactamase genes from Aeromonas sobria, strain 163a, have been cloned and sequenced, one encoding a typical class C cephalosporinase, designated CepS, the other a class D penicillinase, designated AmpS. CepS is predicted to be a mature protein of 38 kDa with a pi value of 7.0. The amino acid sequence of CepS is most similar to that ofAmpC from Pseudomonas aeruginosa (54.7%). AmpS is predicted to be a mature protein of 27 kDa with a pi value of 7.9 that mostly closely resembles BLAD from Klebsiella pneumoniae (42.2%), and OXA-1from Escherichia coli (36.6%), β-lactamases that are encoded by genes carried on multiresistant transposons. AmpS differs significantly from the other class D β-lactamases in that it hydrolyses cloxacillin poorly and is inducible. Both genes exhibit a high overall GC content and possess a high NNC and NNG codon preference, similarto that of genes from Pseudomonas spp.