Acute otitis media in infants younger than three months not vaccinated against Streptococcus pneumoniae.

UNLABELLED: The true incidence of acute otitis media (AOM) in neonates and infants younger than three months is unknown. In this population organisms causing AOM may disseminate leading to bacteremia, sepsis, and meningitis [1].

OBJECTIVES: To describe the clinical presentation, associated severe infections, bacteriologic etiology, and antibiotic resistance patterns of organisms isolated from the middle ear of infants younger than three months that were not vaccinated against Streptococcus pneumoniae.

METHODS: Otomicroscopy was performed in all children to confirm the suspected diagnosis of AOM. When purulent effusion retained in the middle ear was diagnosed, tympanocentesis and culture of middle-ear fluid was performed by conventional methods. Serotyping was done using the Quellung technique.

RESULTS: From May 2, 2009 to February 28, 2010, 52 infants met the inclusion criteria. Thirty-six were male (69.2%) and 16 were female (30.8%). From these 52 patients, 76 samples were obtained for culture. Bilateral acute suppurative otitis media was diagnosed in 24 (46.2%) infants. Of all infants, 18 (34.6%) had been treated with antibiotics before tympanocentesis. Eight patients (44.4%) had negative middle-ear fluid cultures. Sixty bacterial pathogens were isolated from the middle-ear fluid of 43 patients. Mixed infections were recorded in 14/52 patients (26.9%). Nine cultures were negative (17.3%), of which eight were from patients that had previously been treated with antibiotics. S. pneumoniae was isolated from middle-ear aspirates of 26/52 (50%) patients with acute suppurative otitis media. Twenty-two out of the 26 isolates were susceptible (84.7%) and four were intermediately susceptible to penicillin (15.3%). Streptococcus pyogenes was isolated in 3/52 (5.8%) and Haemophilus influenzae in 18/52 patients (34.6%). Five (27.8%) of these were beta-lactamase producers. Blood cultures, cerebrospinal fluid, and urine cultures were negative. Parenteral antimicrobial treatment was indicated in 29/52 (56%).

CONCLUSIONS: S. pneumoniae is the most frequent pathogen to cause AOM in this age group. Empirical treatment with amoxicillin or ceftriaxone should be considered depending on clinical suspicion of severe invasive infection.