The genus Staphylococcus is a member of the family Micrococcaceae which includes three other general Micrococcus, Planococcus and Aerococcus. The four which have the same morphology and gram reaction may be distinguished from each other on the basis of arrangement, the utilization of glucose, the presence or abscence of cytochromes, oxygen requirements, motility and the G + C content of DNA. (Table I), The genus Staphylococcus includes three species; S. aureus, S. epidermidis and S. saprophyticus. These may be distinguished from each other on the basis of coagulase production, mannitol utilization, production of alpha toxin, presence of heat resistant endonucleases, requirement of biotin for growth, sensitivity to novobiocin and cell wall composition (Table II). In the early studies involving phages types and antibiotic susceptibilities, dilution methods (MIC) were used to determine susceptibility. With the adoption of the Kirby-Bauer technique, its wide clinical use, and the dynamic changes occurring in the staphylococci with respect to antibiotic susceptibility and phage patterns. Reexamination of these relationships becomes important and essential. Since no studies of this kind have ever been attempted on staphylococci from this community, it was decided to investigate the problem with respect to enzymatic activity, antibiogram and phage type and compare the findings with those from other geographic locations.

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Staphylococcal scalded skin syndrome (SSSS) is a life-threatening skin condition caused by Staphylococcus aureus (SA) strains producing exfoliative toxin. Most SSSS cases are associated with Exfoliative Toxin A, encoded by the eta gene and carried by a temperate bacteriophage phiETA (ΦETA). An estimated ~10% of strains containing ΦETA are methicillin-resistant SA (MRSA), raising questions about the factors associated with ΦETA susceptibility. Our study investigates the lysogenization susceptibility of ΦETA in a set of SA strains through lysogenic challenges. To this end, we first isolate phage lysates from a known epidemic strain containing eta. In lysogenic challenge assays, we demonstrate that MRSA strains are resistant to ΦETA acquisition. All the 4/89 (4.5%) strains that were successfully lysogenized with ΦETA were characterized as methicillin-susceptible SA (MSSA). While lysogenic conversion did not modify other phenotypic markers, it increased the biofilm production, indicating potential fitness advantages conferred by ΦETA lysogenization. We also hypothesized that phage sequences in challenged strains may provide immunity against ΦETA, thus prophage presence and diversity may correlate with ΦETA susceptibility. Among the 89 strains tested, we bioinformatically identified that 54 of them contained at least one intact prophage sequence. Interestingly, all successfully lysogenized strains lacked intact prophages in their native state which contradicts the poly-lysogenic nature of SA. Additionally, the enhancement of biofilm formation after lysogenic conversion by ΦETA could be associated with pathogenesis of SSSS, increased invasiveness and even emergence of clinically relevant strains. Further studies are needed to explain the genetic and transcriptional basis of phenotypic changes. Together, our results underscore the vital role of ΦETA prophages in shaping SA diversity and clinical outcomes. This study highlights the necessity of investigating the molecular mechanisms associated with bacteriophage lysogenization and host range expansion.

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