Abstract
Panton-Valentine leukocidin (luk-pv) is a cytotoxin that causes leukocyte destruction and tissue necrosis. The aim of this study was to determine the prevalence of the pv1, mecA, and nuc genes in Staphylococcus aureus isolates obtained from anterior nares and superficial infection sites of skin in a slum population of West Bengal, India. Expression level of pv1 gene was also analysed. Twenty-two S. aureus strains were isolated, and phenotype and genotype specific examinations for S. aureus isolates were carried out. Molecular identification was done by PCR using species-specific 16S rRNA primer pairs and finally 22 isolates were found to be positive as S. aureus. The antibiotic responsiveness of all these isolates and the minimum inhibitory concentration (MIC) of MRSA isolates were determined using the broth dilution method with vancomycin. Antibiogram analysis of isolated S. aureus strains with respect to different antimicrobial agents revealed antibiotic resistance ranging from 27 to 91%. The results of MIC for vancomycin showed 95% of strains to be VSSA and 5% to be VISA. 68% isolates were resistant to methicillin. All the isolates were subjected to detection of pv1, mecA, and nuc genes, and 9%, 68%, and 27% were found to harbour pvl, mecA, and nuc genes, respectively. All the MRSA strains produced high to moderate levels of biofilm. pvl gene expression was carried out in vitro by Real-Time PCR. The low ∆Ct value (0.493) was indicative of high expression of pvl in one S. aureus strain. Thus, detection of pvl gene in community acquired S. aureus indicates the emergence of pathogenic S. aureus in community setup in the studied region. The existing exploration is extremely imperative and informative for the high level multi-drug resistant S. aureus infections inclusive of MRSA.
Highlights
To date, the major human pathogen, Staphylococcus aureus, has become a threat to our lives, because of elaboration of several different virulence factors
Panton-Valentine leukocidin (PVL) carrying S. aureus infects skin and soft tissues but the infection gradually spreads to the lung and disrupts the lung tissues, causing hemorrhagic necrotizing pneumonia, one of the most lethal diseases caused by S. aureus [5]
Resistance of S. aureus isolates to ampicillin (91%), nalidixic acid (91%), chloramphenicol (36%), streptomycin (27%), kanamycin (55%), cefoxitin (68%), novobiocin (64%), and erythromycin (82%) was found
Summary
The major human pathogen, Staphylococcus aureus, has become a threat to our lives, because of elaboration of several different virulence factors. Panton-Valentine leukocidin (PVL) is one of the most important virulence factors of S. aureus. This beta pore forming cytotoxin is associated with tissue necrosis and causes disruption of leukocyte membranes [1]. Pvl gene that encodes PVL cytotoxin comprises two exoprotein subunits, encoded by LukS-PV and LukF-PV [2, 3] These two co-transcribed genes act together as a subunit to form a pore by assembling in the cell membranes of host immune cells the white blood cells, monocytes, and macrophages [4]. PVL carrying S. aureus is responsible for different life-threatening invasive diseases, and skin and soft tissue infections. PVL carrying S. aureus infects skin and soft tissues but the infection gradually spreads to the lung and disrupts the lung tissues, causing hemorrhagic necrotizing pneumonia, one of the most lethal diseases caused by S. aureus [5]
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