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Phenotypic and genotypic characterization of Haemophilus influenzae strains isolated from children with cystic fibrosis

Abstract number: P1727

Cardines R., Giufrè M., Fiscarelli E., Accogli M., Cerquetti M.

Objectives: Patients suffering for the cystic fibrosis (CF) disease are prone to recurrent respiratory infections caused by a variety of bacterial pathogens including Haemophilus influenzae, Staphylococcus aureus, Pseudomonas aeruginosa and Burkholderia cepacia complex. H. influenzae commonly infects the respiratory tract of CF patients early in childhood. The objective of the study was to characterise H. influenzae isolates from CF patients included in a 5-year follow-up study (2004–2009).

Methods: Fifty-eight H. influenzae strains were recovered from the respiratory secretions of 45 CF patients attending the CF center of the "Bambino Gesù" paediatric hospital in Rome. Eleven of the 45 patients contributed two or more H. influenzae isolates over time. The median age of the patients was 5 years (range 0.25–27 years). The capsular serotype was identified by PCR. MICs were determined by E-test. Production of b-lactamase was detected by the cefinase disk test. Genetic relatedness among isolates was assessed by PFGE. The presence of the hia and hmw adhesin encoding genes was detected by PCR and colony blotting techniques, respectively.

Results: Of the 58 strains, 52 (89.7%) were nonencapsulated or nontypeable (NTHi), 4 type e and 2 type a. The rate of b-lactamase producers was 13.8%; 3 strains showed the b-lactamase negative ampicillin-resistant phenotype. Heterogeneous resistance to imipenem was identified in 11 strains (18.9%). No strains were found resistant to cephalosporins and amoxicillin–clavulanic acid. Resistance to azithromycin and chloramphenenicol was 13.8% and 5.2%, respectively. No increase in antibiotic resistance was observed in strains serially isolated from the same patient. By PFGE, the 52 NTHi isolates yielded 47 different profiles but 11 minor clusters were identified, each including from 2 to 6 strains. Of 11 patients with sequential isolates, 4 harboured strains exhibiting identical PFGE profiles, while 7 patients possessed strains without close genetic relationships. Some NTHi isolates from different patients shared related genotypes, but 16 isolates were totally unrelated to each other. A minority of the NTHi isolates harboured the hia and hmw genes, the former being the most frequent (16/58, 27.6%).

Conclusions: Resistance to imipenem in H. influenzae has emerged in Italy. Persistence of an identical clone was observed in 36% of patients. No apparent association between antimicrobial resistance and persistence was found.

Session Details

Date: 10/04/2010
Time: 00:00-00:00
Session name: Abstracts 20th European Congress of Clinical Microbiology and Infectious Diseases
Subject:
Location: Vienna, Austria, 10 - 13 April 2010
Presentation type:
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