Hospital epidemiology and antimicrobial susceptibility of isolated methicillin-resistant Staphylococcus aureus: a 5-year retrospective study at a tertiary care centre in Aseer Region, Saudi Arabia.

Between 2019 and 2023, an analysis at the tertiary care centre revealed that 849 out of 1,951 Staphylococcus aureus isolates were methicillin-resistant (Staphylococcus aureus), commonly known as MRSA. According to statistical results, the rate of MRSA infection was markedly higher in patients who received inpatient department care (IPD) at 46.8% than in outpatient department (OPD) at 37.0% (p < 0.0001). Results showed males infected at a rate of 45.3% compared to females who had a rate of 39.4% (p = 0.0198) and age groups demonstrated no significant association (p > 0.05). The choice of specimen type affected MRSA detection rates as endotracheal tubes (32.5%, p = 0.004) together with 'Other' samples (e.g.: CSF, bone, bone marrow, bronchial lavage, abdominal aspirate, semen, ETT tip, femoral tip, jugular tip) (54.2%, p = 0.0068) presented higher proportions of infections. Individuals with benign prostatic hyperplasia showed an increased risk of MRSA infection (OR, 1.8; p < 0.0001) along with patients who had chronic lung disease (OR, 1.2; p = 0.048) or recent antibacterial substance use (OR, 2.5; p < 0.0001) while steroid use reduced the risk of MRSA infection (OR, 0.8; p = 0.002). MRSA showed complete resistance against β-lactam antibacterial substances, while all samples remained susceptible to Daptomycin, Linezolid, Nitrofurantoin, and Tigecycline. The sensitivity rate of vancomycin reached 95%, but MRSA displayed significantly reduced susceptibility to fluoroquinolones at 39.3% to 46.3% compared to MSSA, with rates at 81.5% to 85.5%. The percentage of macrolide-resistant bacteria was higher in MRSA, since they showed 28.3%-37.1% susceptibility rates, whereas MSSA had 61.3%-61.8% susceptibility rates. The anti-staphylococcal activity between MRSA and MSSA exceeded 94% for Rifampicin, Teicoplanin, and Fosfomycin. The antibacterial substances, Gentamicin and Tobramycin, showed high sensitivity against MSSA, since their sensitivity reached 92.3% and 91.3%, respectively. Both agents had good sensitivity against MRSA, with rates of 82.4% for gentamicin and 88.9% for tobramycin. Strict antimicrobial stewardship should be implemented as a priority to control the spread of MRSA. Last-line therapies such as vancomycin, daptomycin, and linezolid remain essential treatment options. Regular antimicrobial susceptibility testing is crucial for healthcare professionals to optimize therapy and prevent the development of drug resistance.