Discordant β-Lactam Susceptibility in Clinical Isolates: A Molecular and Phenotypical Exploration to Detect the BORSA/MODSA Isolates in Bogotá, Colombia.

is a human pathogen responsible for a wide range of diseases, such as skin and soft tissue infections, pneumonia, toxic shock syndrome, and urinary tract infections. Methicillin-resistant (MRSA) is a well-known pathogen with consistently high mortality rates. Detecting the resistance gene and phenotypical profile to β-lactams allows for the differentiation of MRSA from methicillin-susceptible (MSSA) isolates. In this study, we characterized 57 clinical isolates for β-lactam susceptibility and presence. We classified 52.63% as MRSA and 45.61% as MSSA. However, some isolates evidenced different oxacillin resistance profiles, such as borderline oxacillin-resistant or modified (BORSA/MODSA). The cefazolin inoculum effect (CzIE) was established for these samples, emphasizing the relevance of these isolates as a source of therapeutic failure. We also performed the detection of the Panton-Valentine Leucocidin virulence genes as well as the -type clonality. As expected, -types t002 and t008 were the most prevalent clones, demonstrating the success of well-established clones. These findings emphasize the importance of establishing sensitivity profiles, especially in isolates with poor resistance mechanisms, to determine their prevalence and their impact on public health.