A Six-Year Surveillance of Nasal Methicillin-Resistant Staphylococcus aureus Colonization on Intensive Care Unit Admission: Do We Need Screening?

Background: Methicillin-resistant Staphylococcus aureus (MRSA) colonization is a risk factor for potential staphylococcal infection and outbreaks. Although it is recommended to obtain a swab culture to detect nasal colonization its necessity in low-prevalence countries is debated. The aim of this study was to determine the prevalence of MRSA nasal colonization, the rate of invasive infection development, and the risk factors for invasive infections in patients admitted to the intensive care unit. Materials and Methods: This retrospective study included patients who were followed up in one of the adult intensive care units at Kayseri City Training and Research Hospital between 1 January 2019 and 31 December 2024 (6 years) and from whom a culture was taken at the time of hospital admission to detect MRSA colonization in the nose. MRSA carriers were examined for the development of any invasive infection caused by MRSA within 28 days of their relevant admission. Results: Over a total period of six years, nasal swab samples were collected from 22,913 patients, and MRSA colonization was detected in 939 (4.0%). Of the patients with MRSA colonization, 32 (3.4%) were excluded from the analysis because they already had invasive MRSA infection. Additionally, 431 patients (45.8%) were excluded from the analysis because they were discharged or died within the first seven days of their admission. Consequently, invasive MRSA infection developed within 28 days in 29 of the 476 patients with MRSA colonization (6.0%). Patients who developed invasive infection had a higher rate of chronic renal failure (p < 0.001), hemodialysis (p < 0.001), central venous catheter (p = 0.028), staying in nursing home (p = 0.001), and a history of hospitalization within the last 90 days (p = 0.015). In the multivariable regression analysis, routine hemodialysis (OR: 5.216, p = 0.015), nursing home stay (OR: 3.668, p = 0.014), and a history of hospitalization within the last 90 days (OR: 2.458, p = 0.028) were found to be risk factors for developing invasive infection. The most common invasive infections were ventilator-associated pneumonia (n = 9), surgical site infection (n = 7), and catheter-related bloodstream infection (n = 6). All 29 strains were susceptible to vancomycin, linezolid, and daptomycin, while one strain was resistant to teicoplanin (3.5%). Conclusions: MRSA colonization has been detected in 4% of patients admitted to the intensive care unit. Screening should be performed because MRSA colonization may be a risk factor for invasive infections; however, screening all patients would be prohibitively expensive and labor-intensive. Instead, it may be more appropriate to identify risk factors and then screen select patients.