Predominance of nontypeable Haemophilus influenzae in children with otitis media following introduction of a 3+0 pneumococcal conjugate vaccine schedule.

In Australia the 7-valent pneumococcal conjugate vaccine (PCV7) is administered at 2, 4 and 6 months of age, with no booster dose. Information on bacterial carriage and the aetiology of recurrent acute otitis media (rAOM) after introduction of PCV7 using the 3+0 schedule is required to evaluate the potential impact of second generation pneumococcal vaccines. We found that 2-4 years after introduction of PCV7 in the National Immunisation Program, nontypeable Haemophilus influenzae (NTHi) was the predominant pathogen isolated from the nasopharynx and middle ear of children with a history of rAOM. Compared with healthy controls (n=81), NTHi and Streptococcus pneumoniae carriage rates were significantly higher in children with a history of rAOM (n=186) (19% vs. 56% p<0.0001 and 26% vs. 41%, p=0.02, respectively). Carriage of PCV7 pneumococcal serotypes was rare, whereas PCV7-related and non-PCV7 serotypes were isolated of 38% of cases and 24% of controls. Serotype 19A was the most common serotype isolated from the nasopharynx and middle ear and accounted for 36% (14/39) of total pneumococcal isolates with reduced susceptibility to cotrimoxazole. Of the 119 children carrying NTHi, 17% of isolates were ß-lactamase positive. The scarcity of PCV7 serotypes in children with and without a history of rAOM indicates that the 3+0 PCV7 schedule is preventing carriage and rAOM from PCV7 serotypes. Introduction of new vaccines in Australia with increased pneumococcal serotype and pathogen coverage, including 19A and NTHi, should decrease the circulation of antibiotic-resistant bacteria and reduce the burden of rAOM.

Nasopharyngeal carriage of Haemophilus haemolyticus in otitis-prone and healthy children.

Haemophilus haemolyticus is often incorrectly categorized as nontypeable Haemophilus influenzae (NTHI) upon culture. PCR analyses of 266 NTHI-like nasopharyngeal isolates from children with and without recurrent acute otitis media (rAOM) revealed that 11.7% were H. haemolyticus and 9.4% gave equivocal results. Children with rAOM were more likely to carry H. haemolyticus.

Antimicrobial susceptibility of Moraxella catarrhalis isolated from children in Kalgoorlie-Boulder, Western Australia.

AIM: To investigate antimicrobial susceptibility of Moraxella catarrhalis isolated from a cohort of children being followed in a study of the natural history of otitis media in a semi-arid region of Western Australia. METHODS: In the Kalgoorlie Otitis Media Research Project nasopharyngeal aspirates were collected from children up to seven times between the age of 1 week and 2 years. A total of 261 M. catarrhalis strains from 50 Aboriginal and 50 non-Aboriginal children were tested against 14 antibiotics using the Clinical and Laboratory Standards Institute (CLSI) agar dilution method. RESULTS: All strains were susceptible to amoxicillin/clavulanate, cefuroxime, azithromycin, ciprofloxacin, moxifloxacin, levofloxacin, erythromycin and minocycline. While no criteria exist for assessment of susceptibility to roxithromycin, minimum inhibitory concentrations (MICs) were low. Approximately 46% of strains from Aboriginal children and 27% from non-Aboriginal children appeared susceptible to ampicillin. A small number of strains was intermediately resistant to cefaclor (9/261, 3.4%), while the bulk of strains was intermediately resistant to co-trimoxazole. A low prevalence of tetracycline resistance (3/261, 1.1%) was noted. beta-lactamase production was observed in 97.7% of strains. CONCLUSIONS: While M. catarrhalis strains from children of the Kalgoorlie region were susceptible to many of the antibiotics used to treat respiratory tract infections, a large proportion of strains were resistant to ampicillin and/or co-trimoxazole. Current therapeutic guidelines, which recommend amoxicillin for treatment of otitis media, may need to be revised.

Comparison between nasal swabs and nasopharyngeal aspirates for, and effect of time in transit on, isolation of Streptococcus pneumoniae, Staphylococcus aureus, Haemophilus influenzae, and Moraxella catarrhalis.

We assessed the impact of the use of nasal swabs or nasopharyngeal aspirates and the time from specimen collection to storage at -70 degrees C on bacterial isolation. Haemophilus influenzae was isolated significantly less often from swabs than from nasopharyngeal aspirates. Samples in transit for >3 days were half as likely to grow Streptococcus pneumoniae and H. influenzae as those in transit for < or =3 days. There was no statistically significant difference for either Moraxella catarrhalis or Staphylococcus aureus.