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Abstract Pharyngeal carriage of H. influenzae type b (Hib) is important in the transmission of Hib organisms, the pathogenesis of Hib disease, and the development of immunity to the bacterium. The remarkable success of current vaccination programs against Hib has been due in part to the effect of conjugate Hib vaccines in decreasing carriage of Hib. This work presents the result of a study carried out between October 2004 and February 2006, in which nasopharyngeal specimens were obtained from 439 infants and children under the age of 6 years old and attending the outpatient clinics of Mansoura University Children?s Hospital (MUCH) to estimate the carriage rate of both H. influenzae and Hib. All samples were cultured on chocolate agar followed by colonial identification, Gram stain, microscopic examination, biochemical reactions and detection of X and V factors requirement for identification of H. influenzae. Biotyping was done according to the results of three biochemical reactions; indole production, urease activity and ornithine decarboxylase activity. H. influenzae type b was identified by slide agglutination test. Antimicrobial susceptibility testing was performed by the disc diffusion method according to KirbyBauer method. Betalactamase production by H. influenzae was tested by the use of nitrocefin gbslactamase discs This study revealed the following results: The overall carriage rate of H. influenzae was 22.3% and that of Hib was 7.3%, suggesting that Hib may be an important pathogen responsible for invasive infections in children. The predominant biotypes of H. influenzae isolates was type II (33.7%) and III (25.5%), whereas the predominant biotype of Hib isolates was type I (50%), which should be taken seriously as Hib isolates from invasive diseases are mainly biotype I. Resistance to ampicillin, chloramphenicol, and cotrimoxazole was 19.4%, 4.1%, and 22.4%, respectively for H. influenzae and 31.3%, 12.5% and 37.5% respectively for Hib. There was a trend toward increasing resistance for all three drugs. Resistance to ampicillin and chloramphenicol was almost universally coexistent. Cefuroxime, cefotaxime, ceftazidime, ceftrioxone, imipenem, amoxicillin/clavulanic acid and azithromycin were uniformly active to all strains. |