Risk factors for penicillin-resistant Streptococcus pneumoniae acquisition in patients in Bangkok

To identify risk factors for acquisition of penicillin-resistant Streptococcus pneumoniae (PRSP) in patients in Bangkok, using a case-control study, the study included patients with clinical specimens which grew S. pneumoniae during January to December 1997, treated at a teaching hospital in Bangkok. Penicillin susceptibility was determined by E-test and strains with MIC of > 0.1 microg/ml were considered resistant. Cases were the patients who had PRSP, and patients who had penicillin-susceptible S. pneumoniae (PSSP) were controls. The study variables included age 15 years or younger, immunocompromised status, ventilatory support, and antibiotic use or hospitalization within the previous 3 months. There were 73 cases and 51 controls. Their ages were 0 to 87 years, with median age of cases 4 and controls 49 years. Pneumonia was the most common type of infection, being 47% in cases and 45% in controls. Univariate analysis revealed significant association of PRSP acquisition with previous antibiotic use (p<0.0001), age < or = 15 years (p=0.001) and previous hospitalization (p=0.002). Logistic regression analysis in order to adjust for confounding effects showed that the only significant risk factor was previous antibiotic use (OR 18.4; 95% CI 6.2-54.6). The major risk factor for acquisition of PRSP in this study population is recent antibiotic use. Decreased antibiotic use would reduce risk of acquisition of PRSP.