Abstract
Molecular characterization of Staphylococcus aureus is of both clinical and infection control importance. Virulence determinants using PCR and multiple drug resistance profiles were studied in 130 S. aureus isolates. PCR-RFLP analysis of the 16S–23S DNA spacer region was done to investigate the level of 16S–23S ITS (internal transcribed spacer) polymorphism. Methicillin-resistant S. aureus (MRSA), which represented 72% of the studied isolates, showed multiple drug resistance with 18% being resistant to 10–18 of the drugs used compared to a maximum resistance to 9 antibiotics with the methicillin sensitive S. aureus (MSSA) isolates. Exfoliative toxin A (ETA) was more prevalent than B (ETB) with virulent determinants being additionally detected in multiple drug-resistant isolates. 16S–23S ITS PCR-RFLP combined with sequencing of the primary product was successful in generating molecular fingerprints of S. aureus and could be used for preliminary typing. This is the first study to demonstrate the incidence of virulent genes, ACME, and genetic diversity of S. aureus isolates in Lebanon. The data presented here epitomize a starting point defining the major genetic populations of both MRSA and MSSA in Lebanon and provide a basis for clinical epidemiological studies.
Highlights
Staphylococcus aureus are extremely versatile pathogenic bacteria that cause a wide range of syndromes, ranging from minor skin and soft tissue infections to life-threatening pneumonia and toxinoses [1]
This study aims at characterizing 130 S. aureus clinical isolates involved in human diseases based on the determination of antimicrobial resistance profiles, studying the prevalence of exfoliative toxins A and B, enterotoxins (SE) A- E and G- U, arginine catabolic mobile element (ACME), and toxic shock syndrome toxin-1 (TSST-1) and through typing the isolates based on the size of the 16S–23S DNA spacer region and on the patterns obtained by restriction digestion of the amplified spacer region
The sizes of amplicons obtained for the exotoxin genes were 119 and 200 bp for eta and etb genes, respectively, and 333 bp for the ACME, being same as those obtained for the reference strains TC7, TC-142, and BAA-1556D-5
Summary
Staphylococcus aureus are extremely versatile pathogenic bacteria that cause a wide range of syndromes, ranging from minor skin and soft tissue infections to life-threatening pneumonia and toxinoses [1]. The exoproteins or exotoxins include haemolysins, different enzymes, and a family of related pyrogenic toxins [4]. These pyrogenic toxins include staphylococcal enterotoxin (SE) A- E and G- U subtypes, toxic shock syndrome toxin-1 (TSST-1), and exfoliative toxins (ET) A and B [3]. DNA sequence analysis of the USA 300 clone identified a genetic region and designated the arginine catabolic mobile element (ACME). It was acquired horizontally from S. epidermidis or other coagulase-negative staphylococci [4] and inhibited polymorphonuclear cell production. ACME-encoded arcA gene encodes for an arginine deiminase pathway and an oligopeptide permease system enhancing colonization, virulence fitness of the strain, and is associated with invasive diseases (necrotizing pneumonia) [5]
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