Molecular Differentiation and Detection of AMR Genes from Nosocomial Staphylococcus spp.

Staphylococcus spp. is a major nosocomial pathogen, particularly affecting immunocompromised patients and infants. It is associated with bacteremia, endocarditis, and co-infections. Methicillin-resistant Staphylococci (MRS) carry the mecA gene, encoding PBP2a, which confers resistance to beta-lactam antibiotics. The aim of this study is to investigate resistance profiles and develop a molecular method to identify nosocomial Staphylococcus spp. strains. A total of 64 strains from public hospitals in Rio de Janeiro were analyzed using phenotypic and molecular methods, with 17 classified as MDR. Different melting temperatures (Tm) were obtained through qPCR-HRM analysis, to identify S. aureus- (70.4 °C), S. haemolyticus- (79 °C), S. epidermidis- (74.1 °C) and mecA (70.5 °C)-positive strains (MRS). The mecA gene was detected in 51 strains, with 22 showing SCCmec type IV. The spread of MRSA and MDR Staphylococci, particularly MDR S. haemolyticus, is a growing concern. In our study, among 64 Staphylococci strains, only 11 were susceptible to methicillin, showing the continuous emergence of resistant strains. qPCR-HRM is a cost-effective, sensitive and fast method for rapid Staphylococcus spp. identification, aiding in nosocomial infection control.