Department of Laboratory and Clinical Sciences, College of Pharmacy, Tikrit University, Iraq. · Department of Food Sciences, College of Agriculture, Tikrit University, Iraq. · Department of Biology, College of Science, Tikrit University, Iraq.
Background:Pharyngitis is a common upper respiratory infection that primarily affects children and adolescents.
Although Staphylococcus aureus is not considered a primary etiological agent, its role in chronic and recurrent
pharyngitis remains clinically relevant and underexplored.
Objective.This study aimed to assess the prevalence, antibiotic resistance, and virulence profile of S. aureus in
pharyngitis cases, and to evaluate its inflammatory impact on host immune cells.
Materials and Methods:A total of 122 throat swabs were collected from patients aged 4 to 17 years presenting with
pharyngitis across various healthcare centers. Patients were categorized into acute and chronic groups. S. aureus was
identified through morphological characteristics and biochemical assays (coagulase, DNase, mannitol fermentation),
with confirmation via the VITEK 2 system. Antimicrobial susceptibility was assessed using the disk diffusion method.
PCR analysis was conducted to detect the presence of mecA, femA, and LukE virulence genes. Furthermore,
splenocytes and lymph node cells were exposed to killed S. aureus, and the expression of inflammatory genes (NFκB, IL-6, TNF-α) was evaluated using RT-qPCR.
Results:S. aureus was detected in 70 out of 122 samples (57.3%). The isolates showed high resistance rates to oxacillin
(100%), amoxicillin (91%), vancomycin (85.7%), and ceftriaxone (80%), while resistance to levofloxacin and
clindamycin was lower (7.1% and 5.7%, respectively). Multidrug resistance (MDR) was observed in 5.7% of isolates.
PCR confirmed the presence of mecA, femA, and LukE genes in several MDR strains. Immune cell exposure to killed
S. aureus resulted in significant upregulation of NF-κB, IL-6, and TNF-α, indicating a pronounced pro-inflammatory
effect.
Conclusion:The study highlights the potential contribution of Staphylococcus aureus to pharyngeal inflammation,
particularly in persistent or recurrent infections. Its high resistance rates and capacity to induce immune activation
emphasize the need for targeted diagnostic and therapeutic strategies in managing pharyngitis.
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