Drug susceptibility of bacteria isolated from pediatric respiratory infections at general practitioners' clinics to pediatric antibiotics

Four major causative bacteria (Streptococcus pneumoniae, Haemophilus influenzae, Moraxella catarrhalis, Streptococcus pyogenes) of pediatric respiratory infections, 295 clinical isolates in total, were isolated at general practitioners' clinics in Sendai city, and evaluated the drug susceptibility to seven antibiotics for pediatric. Penicillin-resistant S. pneumoniae and penicillin-intermediate S. pneumoniae (PRSP-PISP) were 55.8% of all S. pneumoniae isolates. The MIC₉₀ of penicillin and cephalosporin antibiotics in S. pneumoniae were good, 0.5∼1 μg/mL, however, macrolide-resistant strains remarkably increased. As for H. influenzae, 50.0% of all isolates were ampicillin-intermediate and -resistant (MIC: ≧2 μg/mL), the MIC₉₀s of cephalosporin antibiotics had large differences between 0.5 to 8 μg/mL, and generally less susceptibility was shown to other antibiotics. M. catarrhalis showed less susceptibility to amoxicillin which behaved unstably to penicillinase, on the other hand, the MIC₉₀s of other antibiotics were relatively good, 0.25 - 1 μg/mL. S. pyogenes remarkably tend to be resistant to macrolide antibiotics, however, the MIC ₉₀s of penicillin and cephalosporin antibiotics were very good, 0.03-0.06 μg/mL. Pediatric respiratory infections are required a treatment which results in inhibition of drug-resistant bacteria. Based on the results of drug susceptibility testing, we should make a proper selection of antibiotics by reference to disposition such as drug concentration in serum and transfer into cells.