Abstract
Problem
Streptococcus pneumoniae is the primary cause of pediatric mastoiditis. Since the 7-valent pneumococcal conjugate vaccine (PCV7) in 2000, the serotypes causing invasive infections have shifted. We are following the impact of PCV7 on pneumococcal mastoiditis at Texas Children's Hospital (TCH). Previously, a non-vaccine serotype, 19A and specifically a multidrug resistant clonotype, CC271, was identified as the predominant cause of mastoiditis during the 2006–07 academic year.
Methods
The medical records of children with pneumococcal mastoiditis between July 2007 and February 2008 (prospective through June 2008) were reviewed. Isolates were serotyped by the capsular swelling method and compared to previously collected data since January 1995.
Results
Six mastoiditis cases have been identified thus far in 2007–08; 19A has been the only isolated serotype. This is comparable to the number of cases identified at this point last year. Of the 15 total isolates in 2006–07, all but 2 were attributable to 19A. For comparison, prior to PCV7, the number of mastoiditis cases per year ranged from 0–3, none of which were 19A. This new data appears to continue a disturbing upward trend. Masoitiditis caused by 19A isolates was more likely to present with subperiosteal abscess (p=0.000002) and need mastoidectomy (p=0.007). The 2007–08 isolates differ from the 2006–07 group in drug resistance patterns. In the 2006–07 group 66% were non-susceptible to all antibiotics tested routinely; whereas 50% of the 2007–08 group were non-susceptible to those same antibiotics (p= 0.41). While not statistically significant, this does suggest a different clonal complex at work this season.
Conclusion
The data for this year confirms the trend identified in 2006–07: 19A is now the predominant serotype in mastoiditis at TCH.
Significance
The PCV7 vaccine has placed unexpected selective pressures on S.pneumoniae. Depending on the circulating clones, mastoiditis today may be more complicated to treat due to multi-drug resistance.
Support
Funding: supported, in part, by a Grant from Wyeth.
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