5345. Bacterial culture. Nose. Methicillin-resistant Staphylococcus aureus (MRSA). Antimicrobial resistance profile with MIC (if methicillin-resistant Staphylococcus aureus is detected)

Nasal culture for MRSA is a microbiological test that allows the detection of methicillin-resistant Staphylococcus aureus (MRSA) – a strain of Staphylococcus aureus resistant to most β-lactam antibiotics.

If MRSA is detected, an antibiotic susceptibility test with MIC (minimal inhibitory concentration) is performed to determine antibiotic sensitivity and select effective treatment.

Automated identification of microorganisms is performed using MALDI-TOF mass spectrometry on the MALDI Biotyper sirius IVD System analyzer (Bruker, Germany).

Methicillin-resistant Staphylococcus aureus (MRSA) is a strain of Staphylococcus aureus that has acquired resistance to methicillin and most β-lactam antibiotics. It is one of the leading causes of hospital-acquired infections, particularly in immunocompromised patients, and in those with postoperative wounds, catheters, or implants.

MRSA can cause a wide range of infections, including skin and wound infections; abscesses, pyomyositis, necrotizing fasciitis; pneumonias (including hospital-acquired); sepsis, endocarditis, osteomyelitis, arthritis, and central nervous system involvement.

A person may be infected (showing clinical symptoms) or colonized, meaning the bacteria are present on the skin or mucous membranes without symptoms.

MRSA colonization most often occurs in the anterior nasal passages but can also be found in the throat, armpits, groin, skin, or perineal area. Transmission occurs through contact with biological fluids (blood, sputum, urine, wound exudate) or contaminated surfaces, such as toys, towels, sports equipment, door handles, and tables, particularly in hospital settings.

People at higher risk include:

• Newborns and breastfeeding women.
• Patients after surgical procedures.
• Individuals with catheters, implants, or skin injuries.
• Patients with diabetes, cancer, vascular or pulmonary diseases.
• People with immunodeficiency or injection drug use.

The primary method for MRSA detection is a nasal swab culture performed with a sterile swab. In suspected colonization or for epidemiological monitoring, serial testing is recommended – 2–3 samples collected several days apart. MRSA identification is based on the detection of resistance to oxacillin/cefoxitin according to EUCAST and CLSI standards.

Detection of MRSA requires medical evaluation because colonization may be asymptomatic but still poses a real risk of transmission, particularly in healthcare facilities. Self-administration of antibiotics without confirmed susceptibility testing is prohibited, as it may lead to resistance and complicate the course of infection.

Therefore, after receiving the bacterial culture results, consultation with an infectious disease specialist is required to determine the need for treatment, decolonization, or follow-up observation.

In cases of nasal carriage, the decision on decolonization is made individually, depending on the risk of transmission.

• Before hospitalization or surgical intervention (especially for high-risk departments – intensive care, oncohematology, neonatology).
• For healthcare workers and staff of childcare or nursing facilities – to detect asymptomatic carriage.
• For patients with frequent purulent-inflammatory conditions of the skin, wounds, or respiratory tract.
• In cases of recurrent infections unresponsive to standard antibiotic therapy.
• For epidemiological monitoring – in case of an MRSA outbreak in a healthcare facility or childcare group.
• For differential diagnosis of infections that do not respond to standard treatment.

• Various types of biological material depending on the test