Evaluation of Haemophilus influenzae isolates from children with respiratory tract infections

Abstract number: 1733_1036

Makri A., Papavasileiou K., Panagiotaki E., Papavasileiou H., Varzakakos I., Voyatzi A.

Purpose: The aim of this study was to characterise isolates of Haemophilus influenzae (H.i) with respect to serotype and the in vitro susceptibility to first-line antibiotics used for lower respiratory tract infections.

Material and Methods: A total of 518 samples were collected during a three-year period (2004–2006) from the lower respiratory tract of children (327 sputum and 191 bronchoalveolar lavage). Isolates of H.i were confirmed by using conventional criteria and serotyping was performed by a slide agglutination procedure with all types antiserum (Denka seiken). Susceptibility testing was carried out by the disk diffusion method and the E test (AB Biodisk), while the interpretation was performed according to CLSI breakpoints. H.i ATCC 49247 and H.i ATCC 49766 were used as quality control strains. Beta-lactamase production was assessed by the nitrocefin stick assay.

Results: A total of 212 (40.9%) isolates of H.i were characterised in this study. Biotypes II and III were the most prevalent types (31.2% and 25.8% respectively) followed by biotypes I (20.5%), IV (12.9%), V (4.3%), VIII (3.3%), VI (1%) and VII (1%). The majority of these isolates (59.4%) were not typeable, whereas serogroups b, a, and d represented 18.9%, 7.9% and 6%, respectively. The serotypes c, e and f were rarely found (1%). All isolates were susceptible to amoxicillin-clavulanate, cefotaxime, meropenem and ciprofloxacin. Ampicillin resistance was observed in 36 strains (17%) and all isolates were identified as b-lactamase producers. Resistance to trimethoprim-sulfamethoxazole and clarithromycin was 26% and 13.7% respectively. The rank order of activity based on the MIC50 and MIC90 of the macrolide agents was: azithromycin (0.50–1.5 mg/L) > erythromycin (1.5–4 mg/L) > roxithromycin (2–4 mg/L) > clarithromycin (2–6 mg/L).

Conclusions: (1) Azithromycin was consistently four-fold more active than the others macrolides. (2) No BLNAR (b-lactamase-negative ampicillin resistance) isolates were found in our study. (3) The vast majority of our isolates were non-typeable after the widespread of conjugate vaccines. (4) Continued surveillance is necessary to monitor trends with the H.i disease.

Session Details

Date: 31/03/2007
Time: 00:00-00:00
Session name: European Society of Clinical Microbiology and Infectious Diseases
Location: ICC, Munich, Germany
Presentation type:
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