Serotype 19A Disease Doesn't Outweigh PCV7 Benefit
Given these data, vancomycin remains first-line therapy for all suspected cases of pneumococcal meningitis, as well as for those who are severely ill. For the more common respiratory infections, we now need to consider serotype 19A as a potential etiology in a child who does not respond to traditional antibiotic therapy in 48–72 hours. In the case of AOM, tympanocentesis to identify the specific pathogen is the preferred approach. When that is not possible, a nasopharyngeal swab for identification of S. pneumoniae 19A is acceptable to identify children at risk for infection due to this multidrug resistant pathogen.
While waiting for the results in a child with respiratory tract infection who is well enough to be managed as an outpatient, ceftriaxone in doses of 75–100 mg/kg once per day, given either intramuscularly or intravenously for a minimum of 3 days is appropriate. Whether this will work depends on the level of resistance. If cultures reveal S. pneumoniae 19A and either the minimum inhibitory concentration is above 6–8 mg/mL or the child fails to respond to ceftriaxone, an alternative approach is necessary.
In that setting, I would use levofloxacin (the only fluoroquinolone available in a suspension). The American Academy of Pediatrics' recent guidelines on the use of fluoroquinolones in children (Pediatrics 2006;118:1287–92) did not specifically address this particular clinical scenario, but I agree with Dr. Pichichero and Dr. Casey that AOM caused by multidrug-resistant 19A S. pneumoniae is an appropriate off-label use once you have documentation that 19A is the likely pathogen. If the child can't tolerate levofloxacin or has a contraindication to a quinolone, surgical drainage of the ear with tube placement is the only remaining option.
Future vaccines may address the 19A problem. GlaxoSmithKline's 10-valent Synflorix will contain a 19F capsular polysaccharide that results in some functional activity against serotype 19A. Wyeth's 13-valent conjugate pneumococcal vaccine will actually contain serotype 19A capsular polysaccharide. Both vaccines are in phase III clinical trials and could be licensed in 2009–2010. While I don't expect IPD to ever completely disappear from the planet, these second-generation vaccines could further reduce the number of cases of IPD in children and potentially adults.
I am on the advisory board for both the GSK and Wyeth pneumococcal vaccine programs. I also have an investigator-initiated grant from Wyeth for statewide surveillance. I have no current relationship with the makers of levofloxacin.
