ABSTRACT
Background and Objective: Staphylococcus aureus is one of the major pathogens of nosocomial infections as wells as community-acquired (CA) infections worldwide. So far, large-scale comprehensive molecular and epidemiological characterisation of S. aureus from very diverse settings has not been carried out in India. The objective of this study is to evaluate the molecular, epidemiological and virulence characteristics of S. aureus in both community and hospital settings in Chennai, southern India. Methods: S. aureus isolates were obtained from four different groups (a) healthy individuals from closed community settings, (b) inpatients from hospitals, (c) outpatients from hospitals, representing isolates of hospital–community interface and (d) HIV-infected patients to define isolates associated with the immunocompromised. Antibiotic susceptibility testing, multiplex polymerase chain reactions for detection of virulence and resistance determinants, molecular typing including Staphylococcal cassette chromosome mec (SCCmec) and agr typing, were carried out. Sequencing-based typing was done using spa and multilocus sequence typing (MLST) methods. Clonal complexes (CC) of hospital and CA methicillin-resistant S. aureus (MRSA) were identified and compared for virulence and resistance. Results and Conclusion: A total of 769 isolates of S. aureus isolates were studied. The prevalence of MRSA was found to be 7.17%, 81.67%, 58.33% and 22.85% for groups a, b, c and d, respectively. Of the four SCCmec types (I, III, IV and V) detected, SCCmec V was found to be predominant. Panton-Valentine leucocidin toxin genes were detected among MRSA isolates harbouring SCCmec IV and V. A total of 78 spa types were detected, t657 being the most prevalent. 13 MLST types belonging to 9 CC were detected. CC1 (ST-772, ST-1) and CC8 (ST238, ST368 and ST1208) were found to be predominant among MRSA. CA-MRSA isolates with SCCmec IV and V were isolated from all study groups including hospitalised patients and were found to be similar by molecular tools. This shows that CA MRSA has probably infiltrated into the hospital settings.
ABSTRACT
Introduction: Panton–Valentine leucocidin (PVL) is a bicomponent pore‑forming cytolytic toxin encoded by the lukF‑PV and lukS‑PV genes. Community‑acquired methicillin‑resistant Staphylococcus aureus (CA‑MRSA) may carry the pvl genes which may be related to increased disease severity. This study aimed to characterise the PVL‑producing MRSA recovered from different Taif Hospitals, Saudi Arabia. Methods: The study included 45 hospital‑acquired‑MRSA (HA‑MRSA) and 26 CA‑MRSA strains which were identified from 445 S. aureus strains isolated from different clinical samples. MRSA strains were identified by standard oxacillin salt agar screening procedure and by the detection of the mecA gene by the polymerase chain reaction (PCR). Detection of the S. aureus‑specific femA, mecA and pvl genes was performed by multiplex PCR. PCR‑restriction fragment length polymorphism (PCR‑RFLP) analysis was done for coagulase (coa) gene. Results: The staphylococcal cassette chromosome mec types of the 45 HA‑MRSA strains were Type I (n = 24), Type II (n = 7) and Type III (n = 14) whereas the 26 CA‑MRSA strains were Type IV (n = 14), Type V (n = 11) and one isolate was non‑typeable. All the HA‑MRSA and six CA‑MRSA strains were PVL‑negative PCR‑RFLP analysis of coa gene showed that PVL‑positive MRSA (n = 20) isolates showed six different patterns, and five patterns were shared by PVL‑positive methicillin‑susceptible S. aureus (MSSA). The eighth pattern was the most frequent in both MRSA and MSSA. Conclusion: PVL is more frequent among CA‑MRSA than MSSA. All the HA‑MRSA and 25% of CA‑MRSA strains were negative for PVL. The pvl gene was related to the severity of infection but not related to coa gene RFLP pattern.