Abstract
In this study, we compared pulsed-field gel electrophoretic (PFGE), multilocus sequence typing (MLST), Staphylococcal cassette chromosome mec (SCCmec), spa typing, and virulence gene profiles of 19 Panton–Valentine leucocidin (PVL)-positive, multidrug-, and methicillin-resistant clinical Staphylococcus aureus (MRSA) isolates obtained from a hospital intensive care unit in Pakistan. The isolates exhibited 10 pulsotypes, contained eight adhesin genes (bbp, clfA, clfB, cna, fnbA, fnbB, map-eap, and spa), 10 toxin genes (hla, hlb, hld, hlg, pvl, sed, see, seg, seh, and tst), and two other virulence genes (cfb, v8) that were commonly present in all isolates. The spa-typing indicated seven known spa types (t030, t064, t138, t314, t987, t1509, and t5414) and three novel spa types. MLST analysis indicated eight ST types (ST8, ST15, ST30, ST239, ST291, ST503, ST772, and ST1413). All isolates belonged to the agr group 1. Most of the isolates possessed SCCmec type III, but some isolates had it in combination with types SCCmec IV and V. The presence of multidrug-resistant MRSA isolates in Pakistan indicates poor hygienic conditions, overuse of antibiotics, and a lack of rational antibiotic therapy that have led to the evolution and development of hypervirulent MRSA clones. The study warrants development of a robust epidemiological screening program and adoption of effective measures to stop their spread in hospitals and the community.
Highlights
Population-based studies of invasive methicillin-resistant clinical Staphylococcus aureus (MRSA) infections in the United States indicate that MRSA clones of ST5 (CC5) and ST8 (CC8) are the predominant causative strains in health care-associated bacteremia [29]
A few studies from Pakistan characterized MRSA isolates for the presence of Panton–Valentine leucocidin (PVL) genes and Staphylococcal cassette chromosome mec (SCCmec), pulsed-field gel electrophoretic (PFGE), and ST typing [30,31,32]; none of these studies explored the presence of virulence, adhesion, and enterotoxin genes among MRSA isolates from this geographical region
We used PFGE, multilocus sequence typing (MLST), spa, and SCCmec typing techniques to understand the genotypic diversity and relationship, evolutionary changes, distribution pattern of variable-number tandem repeat (VNTR) within the spa region, SCCmec, agr grouping, and distribution of various virulence, toxin, and antimicrobial resistance genes among 19 CA- and Hospital-acquired MRSA (HA-MRSA) isolates from Pakistan
Summary
MRSA is the major source of hospital-acquired infections and is of particular concern due to its involvement in high incidences of morbidity and mortality worldwide [1,2,3].Resistance to methicillin is conferred by a mecA gene that was first discovered in 1961 among nosocomial S. aureus isolates, and since it has been independently transferred multiple times into the S. aureus chromosome rather than originating from a single ancestral strain [4].While the incidence of MRSA infections and their epidemiology is well documented in western countries, data from the National Nosocomial Infections Surveillance System of Pakistan suggests that incidences of MRSA infections have increased from 35.9% to 66.7%in Pakistan during 2009–2019 [5,6,7]. The presence of other virulence factors, extracellular enterotoxin genes, and Panton–Valentine leucocidin cytotoxin (PVL) genes makes MRSA highly pathogenic and difficult to treat [8]. This organism causes a variety of infections, such as boils, furuncles, styes, impetigo, and other superficial infections, in humans [9,10]. Hospital-acquired MRSA (HA-MRSA) strains exhibit resistance to multiple antibiotics, including macrolides and fluoroquinolones, which poses serious challenges to the treatment of infections [13,14]. The association of Panton–Valentine leucocidin (PVL) genes in CA-MRSA causes infections in healthy young and immunocompetent hosts, sometimes with fatal outcomes [16].
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