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 S. warneri, S. haemolyticus, S. saprophyticus, S. pasteuri, S. epidermidis, S. hominis, S. xylosus, S. equorum, S. kloosii, S. succinus, S. cohnii , and S. simulans, were confirmed by MALDI-TOF. Resistance to most tested antibiotics was statistically higher in CoNS than in S. aureus isolates ( P-value < 0.05). CoNS isolates showed high resistance to penicillin ( S. saprophyticus 88.9%), erythromycin ( S. haemolyticus 84.6%), fusidic acid ( S. saprophyticus 77.8%), co-trimoxazole ( S. epidermidis 71.4%), gentamicin ( S. warneri 63.8%), and tetracycline ( S. saprophyticus 55.6%). Multidrug resistance was largely observed, especially among S. haemolyticus and S. saprophyticus species. Methicillin-resistance in S. haemolyticus (38.5%), S. saprophyticus (22.2%) and S. aureus (13.5%) was associated with the presence of the mecA gene and SCC mec type IV or V.
Conclusion: Coagulase-negative staphylococci, especially S. haemolyticus and S. saprophyticus, seem to be a reservoir of methicillin resistance and multidrug resistance in the oral cavity.