Silent Nasal Carriers:
Nasal Colonization and Genetic Profiling of Methicillin-Resistant Coagulase Negative
Staphylococci among College Students
Ramachandiran Ramamoorthi, Kesavaram Padmavathy, Venkatachalam Pradeepa and Jebadass
Jasmine Vinshia
Res. J. Biotech.; Vol. 21(2); 230-234;
doi: https://doi.org/10.25303/212rjbt2300234; (2026)
Abstract
Coagulase-negative staphylococci (CoNS) have emerged as important opportunistic
pathogens and reservoirs of antimicrobial resistance, particularly methicillin resistance
mediated by the mecA gene. Their ability to colonize the anterior nares makes healthcare
students potential carriers, posing a risk of transmission in clinical environments.
This study aimed to assess nasal colonization of methicillin-resistant CoNS (MR-CoNS)
among preclinical dental students and to characterize the molecular mechanisms of
methicillin resistance including detection of the mecA gene and SCCmec typing. Nasal
swabs were collected from 71 students and processed using standard microbiological
techniques. Identification of CoNS isolates was carried out by biochemical tests
and VITEK-2, while methicillin resistance was determined using cefoxitin and oxacillin
susceptibility testing, confirmed by PCR amplification of the mecA gene. SCCmec
typing was performed through multiplex PCR.
Among the 71 isolates, 51 (71.83%) exhibited methicillin resistance, with Staphylococcus
epidermidis (43.13%) and Staphylococcus haemolyticus (25.4%) as predominant species.
The mecA gene was detected in 31 isolates including 28 MR-CoNS and 3 methicillin-susceptible
CoNS, suggesting silent mecA carriage. SCCmec analysis showed a predominance of
type 1 variant and type 5, especially in S. haemolyticus, while several isolates
remained non-typable, indicating possible novel SCCmec elements. These findings
demonstrate significant nasal carriage of genetically diverse MR-CoNS among dental
students, underscoring their role in the dissemination of antimicrobial resistance
within healthcare settings.
