Risk Factors Associated With Methicillin-Resistant Staphylococcus aureus Infections in Patients With Diabetic Foot Ulcers in Tehran.

Abstract

Background: Foot ulcer is a common complication of diabetes mellitus, which is associated with high morbidity and mortality rates among diabetic patients. This study aimed to identify risk factors associated with methicillin-resistant Staphylococcus aureus (S. aureus) (MRSA) infections and their epidemiology among patients with diabetic foot ulcers (DFUs).

Methods: A total of 211 wound samples were collected from patients with DFUs in five educational hospitals in Tehran during 2017-2019. The presence of certain virulence markers (α-haemolysin (hlα), phenol-soluble modulins (psmα), accessory gene regulator (agr), exfoliative toxin A, B (eta etb) and toxic shock syndrome toxin-1 (tsst-1)) was investigated by polymerase chain reaction (PCR), and a multiplex PCR assay was used to screen for staphylococcal cassette chromosome (SCCmec) types. Antibiotic susceptibility testing (AST) was performed by the Kirby-Bauer disk diffusion method.

Results: A significant proportion of patients with DFUs had Type 2 diabetes. Grading of DFUs revealed that Grade 4 was the most common grade among patients. The majority of patients were infected with S. aureus (45.3%) and Escherichia coli (E. coli) (29.4%). A total of 59 S. aureus isolates were identified, of which 37 (62.7%) were MRSA, and 22 (37.2%) were methicillin-susceptible S. aureus (MSSA). MRSA isolates were mostly positive for the hlα (57.6%) and psmα (50.8%) genes. The tsst-1 gene was detected in 8.5% of MRSA strains, while the eta (3.4%) and etb (5.1%) genes had the lowest prevalence in MRSA isolates. According to the results, SCCmec Type III (48.6%) was the most common subtype among MRSA isolates, followed by SCCmec II (16.2%). The antimicrobial susceptibility testing results revealed that linezolid (66.1%), gentamycin (66.1%) and mupirocin (62.7%) were the most effective antibiotics against MRSA isolates, respectively. In contrast, MRSA strains showed the highest resistance to cefoxitin and penicillin. Finally, the risk factors in patients with DFU in this study were diastolic hypertension, cardiovascular diseases, renal failure, neuropathy disease and hospitalization history.

Conclusions: The findings underscore the critical importance of a comprehensive understanding of patients' medical records and underlying conditions. In addition, accurate assessment of microbial prevalence and antibiotic susceptibility is essential for the effective management of DFUs.