Frequency of prophage types and genes encoding β-lysin and staphylokinase among methicillin resistant Staphylococcus aureus strains isolated from patients in Tehran during 2017

Methicillin-resistant Staphylococcus aureus (MRSA) is a major opportunistic pathogen associated with nosocomial and community-acquired infections that causes significant morbidity and mortality. These bacteria have a high ability to acquire mobile genetic elements, such as bacteriophages, via horizontal gene transfer phenomenon. Bacteriophages are able to convert non-virulent strains to virulent ones through phage conversion which results in production of virulence factors such as β-lysin, staphylokinase, enterotoxins, toxic shock syndrome toxin-1 (TSST-1), lipase, exfoliative toxin A, and Panton-Valentine leukocidin (PVL). In this study we aimed to characterize the presence of different prophage types, β-lysin and staphylokinase virulence genes among MRSA strains isolated from patients in Tehran, Iran.

During 2017, a total of 50 suspected MRSA isolates were collected from patients in two referral hospitals in Tehran. All isolates were identified as S. aureus using specific primers for nucA gene and resistance to methicillin was determined by combination of disk diffusion method, according to the guidelines of Clinical Laboratory and Standard Institute (CLSI), and PCR by specific primers for mecA gene. A multiplex-PCR assay was employed for prophage typing of strains and all MRSA strains were tested for presence of hlb and sak virulence genes.

All 50 isolated strains from patients in 2 referral hospitals were confirmed as MRSA. Except for SGD and SGL all prophage types were identified among the strains in which SGF, SGFa and SGFb prophage types were present in all strains and the frequency of SGA and SGB prophage types was limited to 16 and 64% of strains, respectively. Moreover, 4 different prophage patterns were also identified among all, in which pattern 3 (consisted of SGB, SGF, SGFa and SGFb prophage types) was the dominant one. Furthermore, 100 and 82% of MRSA strains were positive for hlb and sak genes, respectively.

The results of the current study indicated the high prevalence of prophage types and virulence genes among MRSA strains in the studied hospitals. Such strains have a high potential to produce a variety of virulence factors and also different diseases.