_applied_  
_sciences_  
_Article_  
**Methicillin-Resistant _Staphylococcus aureus_ in Diabetic Foot Infections: Protein Profiling, Virulence Determinants,**  
**and Antimicrobial Resistance**  
**[PERSON]\({}^{\text{1}}\)\({}^{\text{(c)}}\) and [PERSON]\({}^{\text{1,2,*}}\)**  
\({}^{\text{1}}\) Department of Public Health, College of Public Health and Health Informatics, Qassim University,  
Al-Bukairiyah 51941, Saudi Arabia  
\({}^{\text{2}}\) Department of Bacteriology, Mycology and Immunology, Faculty of Veterinary Medicine,  
University of Sadat City, Sadat City 32897, Egypt  
\({}^{\text{*}}\) Correspondence: [EMAIL_ADDRESS]  
**Abstract:** _Staphylococcus aureus (S. aureus)_ is one of the most prevalent bacterial pathogens recovered from diabetic foot infections (DFIs). Most _S. aureus_ isolates exhibit methicillin resistance, so treatment is recommended with antimicrobials active against methicillin-resistant S. aureus (MRSA) in patients who have risk factors associated with MRSA infections. The main goal of this study was to see if proteomics and molecular methods could be effective in identifying and distinguishing MRSA recovered from DFIs. Since MRSA is highly resistant to \(\beta\)-lactam antibiotics and usually does not respond to other antimicrobial drugs, we evaluated the resistance of MRSA isolates against different antibiotics. The standard procedures were followed for a culture of 250 skin swabs collected from diabetic foot patients. The phenotypic characteristics of 48 suspected 5. _ aureus_ cultures were determined via microscopic examination, Gram staining, a coagulales test, a BBL\({}^{\text{(c)}}\)Staphyloside\({}^{\text{(c)}}\) Latex test, a Staph ID 32 API system, and a Vitek 2 Compact system. Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) was used to examine the protein profile of all isolates, and real-time PCR was then used to identify _mcaA_ and _PVL_ virulence genes. _S aureus_ isolates were tested using the Vitek 2 Compact for antimicrobial susceptibility using Gram-positive cards (GP71). Among the 48 bacterial isolates tested, 45 (93.75%), 42 (87.5%), and 46 (95.83%) were positive in tube coagulase, the Staph ID 32 API system, and the Vitek 2 Compact system, respectively. We correctly identified all suspected _S. aureus_ isolates (100%) via MALDI TOF MS with a score value \(\geq\)2.00 and differentiated them into 22/48 MRSA (45.83%) and 26/48 MSSA (54.17%) isolates. A higher peak intensity at masses of 5530 Da, 6580 Da, 6710 Da, and 6820 Da was detected in MRSA, but not in MSSA. All MRSA isolates tested positive for the _mcaA_ gene, while all isolates tested negative for the _PVL_ gene. The antibiotic susceptibility results showed that 22 (100%), 20 (90.91%), 19 (86.36%), 18 (81.82%), 17 (77.27%), 15 (68.18%), 13 (59.1%), and 12 (54.55%) MRSA strains were resistant to cefoxitin, daptomycin, erythromycinocin, benzylpenicillin, ciprofloxacin, oxacillin, and clindamycin, respectively. In contrast, all MRSA strains were extremely susceptible (100%) to linezold, nitrofurantion, quiniprutin-dalforgristin, Gieycline, and vancomycin. Moreover, 20 (90.91%), 18 (81.82%), and 17 (77.27%) of the MRSA strains exhibited high sensitivity against rifamppin, trimethoprim--sulfamethoxazole, and gentamicin, respectively. In DFIs, MALDI-TOF MS is a powerful and accurate method of identifying and distinguishing both MRSA and MSA isolates. A high level of antimicrobial resistance was found in MRSA isolates, and antibiotic therapy based on antibiotic susceptibility patterns is essential for a successful outcome.  
**Keywords:** diabetic foot infections; MRSA; proteomics; virulent genes; antibiotic profiles