Resistencia a la amoxicilina de cepas de Streptococcus mutans aisladas de individuos con antibioticoterapia previa y sin esta.

Background: Antimicrobial resistance is a natural phenomenon that microorganisms develop under selective pressures like exposure to antibiotics. This yields conventional antibiotic treatments ineffective. Purpose: To determine the frequency of amoxicillin-resistant Streptococcus mutans (S. mutans) in the mouth of individuals with and without previous treatment with β-lactam antibiotics. Methods: A descriptive cross-sectional study was performed, isolating S. mutans strains from the mouth of 200 healthy individuals with no history of recent antibiotic therapy, 100 persons who underwent antibiotic prophylactic treatment due to high risk of infectious endocarditis and 110 patients treated with β-lactam antibiotics for more than three weeks. Amoxicillin sensitivity was analyzed through Kirby-Bauer testing. Results: We found that of all individuals, 4.4% were carriers of amoxicillin-resistant strains: 2.2% in group I and group II, respectively. The analyses of individuals in which S. mutans was isolated (82% in group I and 60% in group II) showed that the percentage of carriers rose to 5.5% in group I and 7.1 % in group II. Conclusions: Treatment with β-lactam antibiotics remains effective for most oral infections and prophylaxis of infectious endocarditis; however, oral use changes ecosystems and reduces the recovery of S. mutans in the mouth. [ABSTRACT FROM AUTHOR]