1195 Statistical Evaluation of Streptococcus Resistance to Antibiotics in Children

Background and aims: The “European Surveillance” reported resistance of group A streptococci to macrolides as follows: 11% of isolates in Portugal and 32% in Italy. First clindamycin-resistant isolate was reported in 1999. The authors evaluated antibiotic resistance of pyogenic streptococci (serogroups A, C, G) for hospitalized children. Methods: There were realised 714 throat cultures during 30 days period: 56 isolates (7,84%) were positive (large-colony streptococci). Inclusion criteria (antibiogram performing): beta-hemolytic streptococci group A (GAS), C (GCS) and G (GGS). Exclusion criteria: small-colony streptococci. 34 isolates were selected for diffusimetric method (Mueller Hinton medium 5% sheep blood; S. pneumoniae ATCC 49619 strain as quality control) using penicillin, erythromycin and clindamycin disks. The cases were reevaluated after 10 days penicillin therapy. Results: 7 strains (20,58%) were erythromycin resistant (5 strains GAS, 1 GCS, 1 GGS), 2 strains (5,88%) clindamycin resistant beta-lactamases produced by (1 strain GAS,1 GGS). One case wasn't cured after penicillin therapy (antibiogram revealed resistance just for erythromycin), justifying Clindamycin treatment with good evolution. The other cases were successfully treated with penicillin. Conclusions: 1. The study confirmed macrolides resistance for 1/5 strains of streptococci pyogenes; 2. It isn't recommended routine antibiogram; 3. Clindamycin resistance was identified for 6% strains; 4. Penicillin is first choice treatment for streptococcal pharyngitis; 5. One case was penicillin resistant, probably due to bacterial adaptive mechanisms: the streptococcus “internalisation” or saprophytic bacteria from mouth or streptococcus persistance in lingual tonsils; 6. The persistence of Streptococcus in pharynx after penicillin treatment is different from concept of GAS resistance to penicillin.