Increasing antibiotic resistance in Streptococcus pneumoniae colonizing children attending day-care centres in Singapore.

Background and objective: Streptococcus pneumoniae is an important cause of morbidity and mortality in both the paediatric and adult population. This study aimed to define pneumococcal colonization rates, and antibiotic resistance patterns across two periods a decade apart, and also assess the serotypes of colonizing strains in children in the era of early pneumococcal conjugate vaccine uptake in Singapore. Methods: Two cross-sectional prevalence surveys were carried out in 1997 and 2007-2008 on children attending day-care centres across Singapore. Nasopharyngeal swabs were obtained and cultured for S. pneumoniae, and antibiotic susceptibility testing was performed. Serotyping was also done in the 2007-2008 survey. Results: Three hundred and ninety-five children participated in the first survey in 1997, and 418 in the 2007-2008 survey. Pneumococcal colonization rates were 25.8 and 14.1%, respectively. There was a marked increase in antimicrobial non-susceptibility (penicillin 27.4% vs 69.5%; erythromycin 33.4% vs 78%; clindamycin 24.5% vs 45.8%, tetracycline 48% vs 67.8%), and multi-drug resistance (defined as non-susceptibility to three or more classes of antibiotics) increased from 33.3 to 74.6%. In the 2007-2008 survey, serotypes 6B (16.9%), 23F (11.9%) and 19F (10.2%) were most commonly observed. The projected coverage of the 7 and 13-valent conjugate pneumococcal vaccine for colonizing serotypes were 61.9 and 67%, respectively. Conclusions: S. pneumoniae antibiotic resistance has risen dramatically over the last 10 years in Singapore. Wider conjugate vaccine uptake and improved antibiotic stewardship should be made priorities. Surveillance of sentinel sites like day-care centres provides important data with respect to shifts in pneumococcal ecology.