Pneumococcal Mastoiditis in Children Before and After the Introduction of Conjugate Pneumococcal Vaccines

OBJECTIVES:To determine whether serotype distribution and antibiotic resistance of Streptococcus pneumoniae acute mastoiditis (AM) in children have changed in the post pneumococcal conjugate vaccines (PCVs) era. METHODS:Medical records of pneumococcal AM cases, in a tertiary pediatric hospital were reviewed from January 1999 to December 2014. S. pneumoniae isolates were serotyped using the quellung reaction and tested for antibiotic susceptibility by E-test and for macrolide resistance genes by polymerase chain reaction. RESULTS:Among 334 children with AM, S. pneumoniae was isolated from 89 (26.6%) with median age 22 months (interquartile range12–30 months). S. pneumoniae was recovered from ear fluid (58%), mastoid specimens (35.2%) and blood (6.8%). Resistance to penicillin, erythromycin and clindamycin was 12.4%, 49.4% and 18%, respectively. Distribution of pneumococcal serotypes before (1999–2005), after the introduction of PCV7 (2006–2010) and after PCV13 (2011–2014) was foundfor the PCV7 serotypes 81%, 25% and 0% (P < 0.0001), for PCV13 additional serotypes 16.3%, 70.8% and 63.6% (P < 0.0001) and for non-PCV serotypes 2.3%, 4.1% and 36.3% (P = 0.0002), respectively. Significant increase was detected for the serotype 19A after PCV7, and this trend was not changed after PCV13 (2.3%, 50% and 50%, respectively; P < 0.0001). A significant proportion of resistant isolates to penicillin (54.5%) and erythromycin (34.8%) was identified as 19A. CONCLUSIONS:After the introduction of PCV7, a significant increase of serotype 19A and replacement of PCVs serotypes was identified. After PCV13, the overall proportion of pneumococcal mastoiditis and the incidence of serotype 19A were not significantly declined. A significant proportion of resistant isolates to penicillin and erythromycin is attributed to serotype 19A.