Emergence of a multiresistant serotype 19A pneumococcal strain not included in the 7-valent conjugate vaccine as an otopathogen in children

Abstract

Context: Concern has been raised about the possible emergence of a bacterial strain that is untreatable by US Food and Drug Administration (FDA)-approved antibiotics and that causes acute otitis media (AOM) in children.

Objective: To monitor continuing shifts in the strains of Streptococcus pneumoniae that cause AOM, with particular attention to capsular serotypes and antibiotic susceptibility, following the introduction of a pneumococcal 7-valent conjugate vaccine (PCV7).

Design, setting, and patients: Prospective cohort study using tympanocentesis to identify S pneumoniae strains that caused AOM in children receiving PCV7 between September 2003 and June 2006. All children were from a Rochester, New York, pediatric practice.

Main outcome measure: Determination of serotypes and antibiotic susceptibility of S pneumoniae causing AOM.

Results: Among 1816 children in whom AOM was diagnosed, tympanocentesis was performed in 212, yielding 59 cases of S pneumoniae infection. One strain of S pneumoniae belonging to serotype 19A was a new genotype and was resistant to all antibiotics approved by the FDA for use in children with AOM. This strain was identified in 9 cases (2 in 2003-2004, 2 in 2004-2005, and 5 in 2005-2006). Four children infected with this strain had been unsuccessfully treated with 2 or more antibiotics, including high-dose amoxicillin or amoxicillin-clavulanate and 3 injections of ceftriaxone; 3 had recurrent AOM; and for 2 others, the infection was their first in life. The first 4 cases required tympanostomy tube insertion after additional unsuccessful antibiotic therapies. Levofloxacin was used in the subsequent 5 cases, with resolution of infection without surgery.

Conclusion: In the years following introduction of PCV7, a strain of S pneumoniae has emerged in the United States as an otopathogen that is resistant to all FDA-approved antibiotics for treatment of AOM in children.