MRSA/MSSA causing infections: prevalence of mecA gene

Abstract Introduction Staphylococcus aureus is part of the human flora, present in the skin and mucous membranes but can become pathogenic, causing a wide spectrum of infections that were initially treated with penicillin. However, were observed some strains with resistance to this antibiotic and, therefore was developed a new antibiotic, the methicillin. After its introduction, arose the first S. aureus with resistance to methicillin (MRSA) due to the presence of a gene known as mecA that encodes an altered penicillin binding protein (PBP2a). In Europe, it is estimated that MRSA are associated to 44% of hospital acquired infections and its mortality rate is around 20%. Objectives Prevalence of MRSA strains in different types of infection in Coimbra district. Methodology Were analysed a total of 539 isolates of S. aureus previously characterized to the antibiotic susceptibility profile in the Hospital and University Center of Coimbra. Through the minimum inhibitory concentration (MIC) of oxacillin we classified our strains into MRSA and S. aureus methicillin-sensitive (MSSA); simultaneously, the mecA gene was detected by Polymerase Chain Reaction (PCR). Results Of the 539 isolates, 49% were considered MRSA and 51% MSSA. All MRSA isolates express the mecA gene, but from the total of 276 MSSA, 191 show this gene but do not express it. MRSA isolates were mostly from respiratory tract samples (48%) and blood cultures (21%) while MSSA were isolated in skin and soft tissue samples (35%). Conclusion MRSA are considered one of the primary pathogens for the development of pneumonia and septicaemia due to its highly virulent potential and the increasing expression of genetic determinants of antimicrobial resistance. Therefore, infections caused by MRSA continue with highly representability in the clinical context and their dissemination is a public health problem.