Frequency of genes encoding prophage-associated virulence factors among methicillin-resistant Staphylococcus aureus strains isolated from patients with diabetic foot infections in Tehran during 2021-2022

Foot ulcer is a common complication in diabetic subjects and infection of these wounds contributes to increased rates of morbidity and mortality. Diabetic foot infections (DFI) are caused by a multitude of microbes and methicillin resistant Staphylococcus aureus (S. aureus) (MRSA), a major nosocomial and community-associated pathogen, significantly contributes to wound infections as well. The aim of this study was to determine the frequency of genes encoding different virulence factors among MRSA strains isolated from patients with diabetic foot infection in Tehran.

In this study a total of 152 S. aureus isolated from patients with DFI in a laboratory of a hospital in Tehran were collected and confirmed by specific primers for nucA gene. The resistance of strains to oxacillin was determined using specific primers for mecA and mecC genes and separate multiplex-PCR assays were employed to type the MRSA strains. The presence of 6 enterotoxin (A, E, G, K, P and Q) genes and 5 virulence factors (hlb, sak, tsst-1, eta and PVL) among the strains were tested by specific primers.

A total of 58 (38%) mecA gene positive strains were selected as MRSA and 3 SCCmec types II (12%), III (69%) and V (19%) were detected among strains. Also, strains harbored 6 prophage types (SGA, SGB, SGF, SGFa, SGFb and SGL), in which SGF, SGFa and SGFb were the most prevalent types; and 4 prophage patterns were also determined, which pattern 3 (consisting of SGB, SGF, SGFa and SGFb) was the dominant one. All strains were positive for sea, sek and seq enterotoxin genes and hlb and sak virulence genes. Moreover, the frequency of see, seg, sep, eta, tsst-1 and pvl was limited to 24, 29, 36, 26, 14 and 11% of strains. On the other hand, community acquired MRSA (CA-MRSA) strains harbored SCCmec type V and were positive for SGA prophage type.

The results of the present study indicated the presence of prophage associated different virulence factor genes among MRSA strains isolated from patients with DFI, which enable them to produce a variety of diseases.