Comparative molecular analysis of Haemophilus influenzae isolates from young children with acute lower respiratory tract infections and meningitis in Hanoi, Vietnam

Abstract

Thirty-seven Haemophilus influenzae strains from nasopharyngeal swabs (NP) and 44 H. influenzae strains from cerebrospinal fluid (CSF) were investigated. Of the 37 H. influenzae isolates from NP, the serotypes of 30 isolates were nontypeable, 4 were type b, 2 were type c, and 1 was type a, whereas all of the 44 isolates from CSF were type b. The MICs of 16 antibiotics for the H. influenzae isolates from NP and CSF were similar, and no beta-lactamase-negative ampicillin-resistant strain was found. Molecular typing by pulsed-field gel electrophoresis (PFGE) showed that the 37 H. influenzae strains from NP had 22 PFGE patterns, with none predominating, and the 44 H. influenzae strains from CSF had 9 PFGE patterns, with patterns alpha (22 isolates) and beta (12 isolates) predominating. Our results indicate that two predominant types of H. influenzae type b strains have the potential to spread among children with meningitis in Hanoi, Vietnam.

FIG. 1.

PFGE patterns of SmaI-digested DNA from 37 H. influenzae isolates from NP of 37 children with acute lower respiratory tract infections. Molecular typing by PFGE demonstrated that 37 H. influenzae strains from the NP had 22 PFGE patterns (A to V), without any predominant pattern. The PFGE patterns of H. influenzae types a, b, and c were different from those of the nontypeable strains.

FIG. 2.

PFGE patterns of SmaI-digested DNA from 48 Hib isolates from the CSF of 44 children with meningitis and the NP of 4 children with acute lower respiratory tract infections. Molecular typing by PFGE demonstrated that the 44 Hib strains from the CSF had nine PFGE patterns (α to ι), with patterns α (22 isolates) and β (12 isolates) predominating. PFGE patterns of 4 Hib strains from the NP were quite different from those of 44 Hib strains from CSF.