The emergence of drug-resistant Streptococcus pneumoniae and host risk factors for carriage of drug-resistant genes in northeastern Japan.

Our 2-year study includes research into the occurrence, molecular characteristics, and host risk factors for the carriage of drug-resistant strains of Streptococcus pneumoniae as a continuation of our previous report. From September 2001 to June 2003, strains of S. pneumoniae were isolated from the nasopharynx of children with respiratory tract infection in Soma General Hospital. Of the total of 949 strains, 761 (81%) had a decreased susceptibility to penicillin (MIC > 0.12 microg/ml), while 818 (86%) were resistant to erythromycin (MIC > 1 microg/ml) and 789 (83%) were resistant to clarithromycin (MIC > 1 microg/ml). More than half of the strains had decreased susceptibility to meropenem. Gene analysis of 226 randomly selected strains showed that 200 strains (88.5%) had one or more altered pbp genes and 191 strains (84.5%) had mef(A) and/or erm(B) genes. We reviewed the patient backgrounds for previous antibiotic use, age, daycare attendance, and siblings. Previous use of oral beta-lactams has shown a strong relationship with the carriage of altered pbp genes (P value < 0.01), and previous oral macrolide use has been related to the carriage of macrolide-resistant genes (P value < 0.01). The controlled use of antibiotics might be an important factor in preventing the emergence of S. pneumoniae with antibiotic-resistant genes.