Phenotypic and Genotypic Identification of Typical and Atypical Staphylococcus aureus Isolated From Bovine Milk Samples

Abstract

This study aimed to determine the phenotypic and genotypic identification and differentiation of typical coagulase positive Staphylococcus aureus (CPSA) and atypical coagulase negative Staphylococcus aureus (CNSA) from other Staphylococci isolated form bovine milk. Out of 111 milk samples, 67 Staphylococcus strains were isolated, phenotypically, based on resistance to Acriflavine; Staphylococcus aureus (S. aureus) was detected in 44 isolates of them (30 CPSA strains and 14 CNSA strains). Twenty five from CPSA and 5 from CNSA isolates were positive for slime production on Congo red agar plates. Genotypically, the all five tested typical Staphylococcus aureus (CPSA) as well as three atypical Staphylococcus aureus (CNSA) strains encoded all investigated genes (nuc, spa-x and clfA), while the other two atypical CNSA strains, one encoded only nuc gene and the other encoded both nuc and clfA genes. Acriflavine sensitivity test must be included in the routine of phenotypic identification S. aureus as the gold method together with tube coagulase test. PCR analysis is most important confirmation method by detection of nuc gene. Genotypically both typical and atypical S. aureus isolates are virulent. Typical and atypical S. aureus isolated from isolated from bovine milk samples sold in dairy shops were with higher percentage than subclinical mastitic milk samples threating public health hazard. Attention must be paid toward detection and identification of atypical tube coagulase negative S. aureus strains.