Distribution and antibiotic-resistance of different species identified by matrix assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) isolated from the oral cavity.

Background: The use of antibiotics in dentistry is associated with the emergence and spread of antibiotic-resistant microorganisms, including commensal staphylococci.

Methods: A total of 367 oral samples were collected, from which staphylococci were isolated and identified by using matrix assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF). The antibiotic susceptibility of the isolates was determined and molecular characteristics for methicillin-resistant staphylococci was performed.

Results: A total of 103 coagulase-negative staphylococci (CoNS), among them , and , were confirmed by MALDI-TOF. Resistance to most tested antibiotics was statistically higher in CoNS than in isolates (-value < 0.05). CoNS isolates showed high resistance to penicillin ( 88.9%), erythromycin ( 84.6%), fusidic acid ( 77.8%), co-trimoxazole ( 71.4%), gentamicin ( 63.8%), and tetracycline ( 55.6%). Multidrug resistance was largely observed, especially among and species. Methicillin-resistance in (38.5%), (22.2%) and (13.5%) was associated with the presence of the A gene and SCC type IV or V.

Conclusion: Coagulase-negative staphylococci, especially and , seem to be a reservoir of methicillin resistance and multidrug resistance in the oral cavity.