Molecular characterization of Panton-Valentine Leukocidin positive Staphylococcus aureus isolates obtained from clinical sample in Isfahan, Iran

Staphylococcus aureus is one of the main significant human pathogens which can produce various toxins such as Panton-Valentine Leukocidin (PVL) which is known as a prominent toxin associated with S. aureus infections. PVL-positive strains can cause a wide variety of skin, soft tissue, necrotizing pneumonia, fasciitis and life-threatening infections. Therefore, the aim of this study was evaluating the molecular characteristics of PVL-positive strains such as the presence of mecA, SCCmec types, agr types and exfoliative toxin genes. In this study, a total of 152 S. aureus strains were collected from clinical samples of patients who referred to Isfahan’s Alzahra hospital (Iran). The isolates were confirmed phenotypically by conventional methods and then PVL-positive isolates were identified by PCR molecular test. Thereafter, antibiotic resistance pattern, agr groups (I, II, III, and IV), exfoliative toxins (eta and etb), mecA gene and SCCmec various types were carried out. Totally, 52 (34.2%) of strains were positive for PVL. Six PVL-positive strains harbored mecA gene, one strain had SCCmec I, and 5 strains SCCmec type IV. The highest ratio of agr groups belonged to group (I) and the (eta) gene was also detected in 18 isolates. The PVL-positive S. aureus strains can cause more serious infections, so identification of the genetic characteristics and antibiotic resistance monitoring of these strains is necessary

Detection of Panton-valentine Leukocidin Gene Isoforms of Staphylococcus aureus Isolates in Al-Zahra Hospital, Isfahan-Iran

Background: Panton-Valentine leukocidin (PVL) is a gamma-toxin produced by Staphylococcus aureus encoded by genes lukS/lukF-PV with several single-nucleotide polymorphisms. A mutation at nucleotide position 527 results in substitution of histidine (H) to arginine (R) at amino acid 176. The groups defined based on the amino acid change, the “R isoform” group and the “H isoform” group. The purpose of this study was to determine the frequency of PVL gene isoforms in S. aureus strains isolated from patients at Al-Zahra Hospital Isfahan and molecular characterization of PVL-positive methicillin-resistant S. aureus(MRSA) strains including the detection of mecA gene and staphylococcal chromosomal cassette mec (SCCmec) typing. Materials and Methods: In this study, 130 isolates of S. aureus were collected from Al-Zahra Hospital. The PVL gene identified using polymerase chain reaction (PCR); PCR products were sequenced to identify the type of isoform. The molecular characterization of isolates of PVL-positive MRSA including detection of mecA gene by PCR and also SCCmec typing was performed by multiplex PCR. Results: Out of 130 isolates, 23% were positive for the presence of PVL genes. The PVL positive isolates were comprised 37% (11/30) of methicillin-resistant isolates and 63% (19/30) of methicillin-susceptible S. aureus (MSSA) isolates. The results showed that 17 isolated carrying isoform H and 13 isolated carrying the R isoform. Conclusion: The PVL gene was predominantly found in MSSA isolates. There was no relation between PVL isoforms and the presence of mecA and SCCmec types