MRSA Case Study

Abstract

Background: Methicillin-resistant Staphylococcus aureus (MRSA) remains a major cause of nosocomial infections worldwide. This study aimed to explore the molecular evidence for MRSA transmission between staff and hospitalized patients in the critical care units of university hospital.

Material and methods: Nasal swabs were collected from 133 and 120 personnel and patients in اسم یونیتها؟high risk units such as …, respectively. All presumptive MRSA colonies were confirmed based on conventional biochemical assays and presence of mecA gene. The antimicrobial susceptibility test was performed by E-test and Kirby–Bauer disc diffusion method. Molecular typing and clonal relationships between isolates were determined by pulsed-field gel electrophoresis

Higher rates of MRSA carriage have been found among hospital staff (7), Nevertheless, transmission from person to person and from health care worker to patients is a primary health care concern. In the last few decades, MRSA has become an increasingly important cause of healthcare-associated infections (8). There are different molecular typing methods to investigate the clonal relationships between bacteria, Pulsed-Field Gel Electrophoresis (PFGE) has the highest discriminatory power of all of them (9). Molecular methods such as PFGE can help to decide on the prevention and proper treatment of patients and MRSA nasal carriage staff (10). This method is the current gold standard for use in epidemiological studies of MRSA (11, 12).

In Iran, few molecular studies are available on MRSA carriage and transmission of infection between patients and healthcare workers. This study aimed to determine the relationship between MRSA colonization in hospital staff and patients by pulsed-field gel electrophoresis (PFGE), Furthermore, the prevalence of MRSA nasal carriage studied among patients and hospital health care

Antibiotics tested included: gentamicin, teicoplanin, rifampicin, doxycycline, quinupristin/dalfopristin, cefoxitin, trimethoprim/sulfamethoxazole, chloramphenicol, linezolid and mupirocin.

2.3.2. Minimum inhibitory concentration (MIC) by Etest

Isolates resistant to cefoxitin were submitted to the Etest () to determine the sensitivity to vancomycin. S. aureus ATCC 29213 was used as the quality control in each set of tests. Isolates showing inhibition zones of 30 μg cefoxitin (Oxoid, Cambridge, UK) disk, and that were positive for mecA gene by PCR, were characterized as MRSA.

2.4. Molecular typing

PFGE was performed to analyze genetic relatedness of MRSA isolates collected from personnel and hospitalized patients in the high risk wards, with SmaI according to the protocol described previously ( ------). Briefly, after the SeaKem Gold Agarose embedded DNA was digested with 10 U of restriction endonuclease SmaI (Roche, Mannheim, Germany) for 1.5–2 h in water bath at 37 °C, DNA fragments were electrophoresed in 0.5 × TBE buffer at 14 °C for 24 h in Chef Mapper electrophoresis system (Biometra, Rotaphor system 6.0, 230V ), with pulse times of 5 s–60 s. Salmonella Braenderup H9812 was used as DNA ladder control strain. After DNAs were separated, the gel was stained with ethidium bromide, the DNA patterns were