Nontypeable Haemophilus influenzae meningitis in children: phenotypic and genotypic characterization of isolates.
BACKGROUND
With the decline in the incidence of invasive Haemophilus influenzae type b disease as result of routine immunization of infants, the potential emergence of nontypeable H. influenzae (NTHi) strains as important pathogens has been suggested.


METHODS
From June 1997 to July 2006, 9 cases of NTHi meningitis in children aged < or =60 months were detected. The 9 NTHi isolates were characterized. Antimicrobial susceptibility patterns were determined by E-test. The transpeptidase domain of penicillin binding protein 3 of a beta-lactamase negative ampicillin-resistant strain was sequenced. Genetic relatedness among isolates was assessed by pulsed field gel electrophoresis and by multilocus sequence typing. The presence of HMW and Hia adhesins and hemagglutinating fimbriae was investigated by PCR and Western Blotting.


RESULTS
The 9 cases of NTHi meningitis did not occur in specific risk groups, except for one patient. Of the 9 NTHi isolates, 2 were beta-lactamase producers and 1 showed the beta-lactamase negative ampicillin-resistant phenotype. Sequencing of the penicillin binding protein 3 revealed novel amino acid substitutions. A high degree of genetic diversity among isolates was demonstrated by pulsed field gel electrophoresis. Multilocus sequence genotyping confirmed that the 9 NTHi isolates did not belong to related phylogenetic clusters. HMW adhesins were found in 2 isolates, and 5 strains possessed Hia. No hemagglutinating fimbriae were detected, even though 2 isolates contained hifA gene sequences.


CONCLUSIONS
NTHi isolates from cases of meningitis in children are genetically diverse. Distribution of adhesins among the isolates we examined is unusual: most strains express Hia that generally occurs in a minority of strains in NTHi, suggesting that this adhesin may play a role in virulence mechanisms of NTHi causing meningitis.
Cardines
Rita
R
Department of Infectious, Parasitic and Immune-mediated Diseases, Istituto Superiore di Sanità, Rome, Italy.
Giufrè
Maria
M
Mastrantonio
Paola
P
Ciofi degli Atti
Marta Luisa
ML
Cerquetti
Marina
M
D000900:Anti-Bacterial Agents / Q000494:pharmacology; D002675:Child, Preschool; D024901:Drug Resistance, Multiple, Bacterial; D005838:Genotype; D006193:Haemophilus influenzae / Q000145:classification* / Q000235:genetics* / Q000302:isolation & purification; D006801:Humans; D007223:Infant; D008583:Meningitis, Haemophilus / Q000382:microbiology*; D008826:Microbial Sensitivity Tests; D013997:Time Factors
D000900:Anti-Bacterial Agents