Detection of newly defined superantigenic toxin genes and coagulase gene polymorphism in Staphylococcus aureus isolates

Emerging Challenges in Staphylococcus aureus Bloodstream Infections: Insights from Coagulase Typing, Toxin Genes, and Antibiotic Resistance Patterns

Background

The incidence of complications and mortality associated with Staphylococcus aureus (S. aureus) bloodstream infections has been increasing significantly, particularly in developing countries where control strategies against this virulent pathogen and its resistance to antibacterial agents are insufficient. The aim of this study was to investigate coagulase typing, the prevalence of toxin genes, and the antibiotic resistance profile of S. aureus isolated from bloodstream infections.

Methods

Antibiotic susceptibility of the isolates was determined by the disk diffusion method. The prevalence of toxin genes was determined using the polymerase chain reaction (PCR) method. Genetic variability of isolates was determined using multiplex PCR based on coagulase gene polymorphism.

Results

Out of 120 strains, 55 (46%) were methicillin-resistant S. aureus (MRSA) and 65 (54%) were methicillin-sensitive S. aureus (MSSA). All isolates were susceptible to linezolid and teicoplanin but showed varying levels of resistance to other antibiotics. The highest resistance was observed for ampicillin (92.5%), gentamicin (69.2%), and amikacin (68.3%). Multidrug resistance was observed in all isolates. PCR analysis revealed a higher prevalence of toxin genes in MRSA (tst: 38%, pvl: 29.1%, eta: 10%, and etb: 4.1%) than that in MSSA. According to the coa typing, the most prevalent types were coa III (29.2%), coa II (26.7%), and coa VI (10%).

Conclusion

The presence of genetic variability and widespread multidrug resistance in our hospitals emphasizes the circulation of various coa types. Therefore, it is crucial to implement antimicrobial stewardship and infection control measures to prevent and control the spread of these strains.

Comparative Genotypic Analysis of RAPD and RFLP Markers for Molecular Variation Detection of Methicillin-Resistant Staphylococcus aureus Clinical Isolates

Background and Objectives: Methicillin-resistant Staphylococcus aureus (MRSA) isolates are associated with various diseases ranged from mild superficial impairments to invasive infections. This study aimed to evaluate the ability of polymerase chain reaction (PCR) based methods namely, restriction fragment length polymorphism (RFLP) of the coa gene and random amplified polymorphic DNA (RAPD), to determine the genetic diversity of MRSA isolates. Materials and Methods: A total of 37 MRSA isolates were conventionally identified depending on their biochemical and microbiological culture characteristics. Genotypic confirmation was based on detection of the associated mecA gene. The genetic variation amongst MRSA isolates was evaluated following the coa gene-based RFLP and RAPD fingerprints. Results: Results illustrated that, the species specific coa gene was detected in all MRSA isolates. The irregular bands intensity, number, and molecular sizes of the PCR amplicons demonstrated the coa gene polymorphism. The incompatible AluI digestion patterns of these amplicons classified the tested MRSA isolates into 20 RFLP patterns which confirm the coa gene polymorphism. Additionally, the PCR-based RAPD analysis showed variable bands number with size range of approximately 130 bp to 4 kbp, which indicated the genetic variation of the tested MRSA isolates as it created 36 variable RAPD banding profiles. Conclusions: coa gene AluI enzymatic restriction sites, amongst the tested MRSA isolates, certify their genetic variation on the basis of the accurate but complicated and relatively expensive coa gene-based RFLP. Conversely, the results verified the excellent ability of the simple and cost-effective PCR-based RAPD analysis to discriminate between MRSA isolates without any preface data about the genome.

Nasal colonisation, antimicrobial susceptibility and genotypic pattern of Staphylococcus aureus among agricultural biotechnology students in Besut, Terengganu, east coast of Malaysia

BACKGROUND

This study aimed to profile the antimicrobial susceptibility and presence of resistance and virulence genes of methicillin-susceptible Staphylococcus aureus (MSSA) and MRSA nasal carriage, by means of genotypic analyses, in students of a tertiary institution in the state of Terengganu, east coast of Malaysia.

METHODS

A total of 370 agricultural biotechnology students from Universiti Sultan Zainal Abidin in Besut, Terengganu, were enrolled in this study. Antimicrobial susceptibility profiles were evaluated by standard methods. PCR detection of resistance and virulence genes was performed on S. aureus that were methicillin-resistant, macrolide-lincosamide-streptogramin B (MLS_B )-positive phenotype and/or positive for the leukocidin (pvl) gene followed by staphylococcal cassette chromosome mec (SCCmec), staphylococcal protein A (spa) and accessory gene regulator (agr) typing.

RESULTS

One hundred and nineteen of 370 students carried S. aureus (32%); 18 of the isolates were MRSA (15%). Erythromycin resistance was detected in 20% (24/119) of which 15% (18/119) were MRSA and 5% (6/119) MSSA. Among the 24 erythromycin-resistant isolates, D-test was positive in 29% (7/24) displaying inducible MLS_B , whereas the remaining 71% (17/24) showed constitutive MLS_B phenotypes. Nine (7.6%) of 119 isolates were pvl positive: 44% MRSA (4/9) and 56% MSSA (5/9). Staphylococcal surface protein sasX gene was present in 92% of MRSA and 8% of MSSA isolates. The majority of MRSA isolates were agr type I (15/18; 83%). Five spa types identified with spa t037 were predominant, followed by spa types (t304 and t8696) as newly reported Malaysian MRSA in a community setting.

CONCLUSION

The presence of MRSA with SCCmec of hospital-associated features and globally recognised spa types in community setting is worrisome. Furthermore, the presence of MLS_B strains among multidrug-resistant (MDR) S. aureus with sasX as well as pvl-positive isolates highlights the potential risk of a community setting in facilitating the dissemination of both virulence and resistance determinants.