Presence and diversity of the β-lactamase gene in cat and dog staphylococci

Staphylococci are part of the normal microflora of humans and animals and some are potential pathogens that have become resistant to almost all known antibiotics. Despite the widespread reports of penicillin resistance in cat and dog staphylococci, the mechanism underlying penicillin resistance has not been examined. This study was aimed at investigating the molecular basis of resistance to penicillin in cat and dog staphylococcal isolates that showed phenotypic resistance to β-lactam antibiotics. An 861 bp fragment of the structural blaZ gene which codes for β-lactamase production in staphylococci was amplified by polymerase chain reaction (PCR) and the products were sequenced. Sequenced fragments were analysed by protein signature typing and sequences were compared to published blaZ sequences of human and bovine staphylococcal strains held in a public database. Four known protein signature types (1, 3, 5 and 6) and one new type (12) were identified in this study. When sequences were compared with published blaZ sequences, gene phylogenetic analysis revealed three major groups. The four variants of β-lactamases types (A, B, C and D) belonged to each major group except for types A and D which were both in group II. These findings confirm that the blaZ gene is responsible for β-lactamase production leading to subsequent resistance to β-lactam antibiotics in feline and canine staphylococci and that the gene shows similar diversity and relatedness as found with blaZ sequences obtained from human and bovine staphylococci.