Antimicrobial susceptibility pattern of oral viridans group Streptococci in children at risk of infective endocarditis

Abstract

Infective endocarditis (IE) is an important clinical disease in children with a mortality rate of 11.6%. Prophylaxis with antibiotics is one of the most commonly used methods in children at risk of IE; therefore, the evaluation of antibiotic resistance seems necessary in view of its increasing trend. This study aimed to determine the antibiotic susceptibility pattern of oral viridans group streptococci (VGS) isolated from the dental plaque of children at risk of IE. Fifty-one plaque samples were obtained from children aged 3 to 12 years old in the period from April to July 2018. Samples were obtained with sterile swabs and were transferred to the laboratory in Brain Heart Infusion (BHI) Broth. Samples were immediately cultivated on Columbia blood agar. After identifying VGS, antimicrobial susceptibility test (AST) was performed using Mueller-Hinton agar (MHA) with sheep's blood and E-test strips for selected antibiotics. The minimum inhibitory concentration (MIC) was determined for each isolate and the results were reported as sensitive, intermediate and resistant. Fifty-one VGS bacteria were isolated from children with an average age of 7.3 ± 2.5 years. The highest resistance was observed for azithromycin in 36 (70.6%) isolates and then cefazolin in 35 (68.6%) isolates. The highest susceptibility was observed for amoxicillin in 46 (90.2%) isolates. Based on the findings of this study, amoxicillin is the most effective option for prophylaxis in children. Furthermore, cefazolin should be used with caution because bacteria resistant to this antibiotic can transfer resistance genes to other bacteria.