Mec-A Positive Methicillin-Susceptible Staphylococcus Aureus as a Public Health Concern: A Case Series

Staphylococcus aureus, an opportunistic microorganism, is the leading cause of severe bloodstream infections, including sepsis and endocarditis, which can be life-threatening. Therefore, S. aureus infection poses a significant public health challenge, particularly in developing nations. mec-a is a genetic element commonly found in Methicillin-resistant Staphylococcus aureus (MRSA) strains that characterises the S. aureus resistance phenotype.

Clinical infection samples obtained from blood were collected and categorised as MRSA or Methicillin-sensitive Staphylococcus aureus (MSSA) using the VITEK-2 compact device. Subsequently, specific samples were gathered as case series owing to their unique characteristics. Resistance genes were detected using conventional polymerase chain reaction (PCR), followed by visualisation through electrophoresis.

Our findings were based on the identification of five instances of MSSA among samples obtained from a tertiary hospital's microbiology laboratory. Using the VITEK-2 antimicrobial susceptibility profile, these cases were determined to be MSSA. Subsequently, we conducted PCR, which revealed the presence of a mec-a-positive strain. Upon re-examination using Mueller-Hinton agar, the five strains were confirmed to be MSSA. Further analysis demonstrated that all strains were positive for Panton-Valentine leucocidin (pvl) and exfoliative toxin A (eta) gens.

The positive mec-A MSSA results should serve as a warning to clinicians that a resistant strain is forthcoming. mec-A continues to be the benchmark for confirming the resistance phenotype. Additional research is essential to explore this strain.