Genetic analysis of mec A homologues in Staphylococcus sciuri strains derived from mastitis in dairy cattle.
Methicillin-resistant Staphylococcus aureus (MRSA) is defined by the presence of the mec A gene, which is considered to have been transferred horizontally from unknown bacterial species to S. aureus. As a candidate of evolutionary precursor of the mec A, the mec A-like gene (mec A homologue), which is ubiquitously present in Staphylococcus sciuri has been proposed. In this study, sequences of the mec A homologue in four S. sciuri strains (SCBM 1-SCBM 4) derived from dairy cows were determined to analyze their genetic characteristics and relatedness to mec A and the mec A homologue reported so far. The mec A-like gene sequences of the four S. sciuri strains were identical with each other and were considered to encode a product comprising 665 amino acids that is one amino acid smaller in size than products of mec A-like gene reported previously for S. sciuri strains K1, K1 1, and K3 (mec A1). The mec A homologue of a representative strain SCBM 1 showed 79.3--79.8% sequence identity to MRSA mec A and 93.4--94.4% identity to mec A homologues reported for the three S. sciuri strains. Between S. sciuri strain SCBM 1 and strains K1, K1 1, or K3, amino acid sequence identities in transpeptidase domain of the mec A-like gene product (98.2--98.5%) were higher than those in the transglycosylase domain (92.1--94.3%). In addition, SCBM 1 showed extremely high sequence identities of hsp 60, sodA, and rpoB genes (more than 98.7%) to S. sciuri strains, while showing 70.3--94.2% identity of these genes to other staphylococcal species. These findings indicated that mec A homologues in S. sciuri may be genetically more divergent than mec A in MRSA and methicillin-resistant coagulase-negative staphylococci.
Rahman
Mohammed Tanvir
MT
Department of Microbiology and Hygiene, Faculty of Veterinary Science, Bangladesh Agriculture University, Mymensingh, Bangladesh.
Kobayashi
Nobumichi
N
Alam
Mohammed Mahbub
MM
Ishino
Masaho
M
D000595:Amino Acid Sequence; D000818:Animals; D001426:Bacterial Proteins / Q000235:genetics*; D002417:Cattle; D004269:DNA, Bacterial / Q000032:analysis; D014644:Genetic Variation; D008413:Mastitis / Q000382:microbiology* / Q000662:veterinary; D016106:Methicillin Resistance / Q000235:genetics*; D008969:Molecular Sequence Data; D013210:Staphylococcus / Q000235:genetics* / Q000302:isolation & purification
D001426:Bacterial Proteins; D004269:DNA, Bacterial