ANTIMICROBIAL SUSCEPTIBILITY PROFILES OF OROPHARYNGEAL VIRIDANS GROUPSTREPTOCOCCI ISOLATES FROM CYSTIC-FIBROSIS AND NON-CYSTIC FIBROSIS PATIENTS

The antimicrobial susceptibility profile of 77 oropharyngeal viridans streptococci isolates from 34 cystic fibrosis (CF) patients and 58 iso lates from 43 healthy non-CF patients were studied by the E-test and t he standard disk diffusion methods. Overall penicillin and cefotaxime resistances (intermediate plus resistant isolates) were significantly higher (p < 0.05) among CF isolates (72.7% and 45.5%, respectively) th an among non-CF isolates (51.7% and 15.5%, respectively), No significa nt difference was observed in overall (intermediate plus resistant) er ythromycin resistance rates, although high-level erythromycin resistan ce (greater than or equal to 32 mu g/mL) was more frequently found in CP isolates (24.6%) than in non-CF isolates (12.1%), An unexpected hig h percentage of isolates showed low level erythromycin resistance (MIC range, 0.5-15 mu g/mL): 41.5% in cystic fibrosis and 46.5% in non-CF isolates. No significant differences were observed regarding the perce ntage of colonized patients with at least one penicillin-resistant iso late. On the contrary, colonization with cefotaxime (p < 0.001) or ery thromycin (p = 0.014) resistant isolates were significantly more preva lent in CF patients. Similar tetracycline and chloramphenicol resistan ce rates were observed for both groups. Viridans isolates resistant to a single antibiotic were more prevalent among non-CF patients and mul tiple resistance was higher among CF patients. Prior antibiotic exposu re could result in differences in beta-lactam resistance and colonizat ion rates with resistant isolates between both groups. None of the non -CF patients was previously treated with antimicrobials for a period o f three months before sampling. In contrast, 94.1% of CF patients were treated with antimicrobials within the same period; 65.6% with beta-l actam antibiotics. Patients with CF disease, frequently exposed to ant imicrobials, may be a reservoir of viridans streptococci isolates with resistance determinants, particularly to beta-lactam antibiotics.