Rapid detection of Haemophilus influenzae and Haemophilus parainfluenzae in nasopharyngeal swabs by multiplex PCR

OBJECTIVE

To establish multiplex PCR-based assays for detecting H.influenzae and H.parainfluenzae. And the PCR-based assays were applied to detect the carriage rates of H.influenzae and H.parainfluenzae in nasopharyngeal swab specimens which were collected from healthy children.

METHODS

Multiplex primers for species-specific PCR were designed by using DNAstar soft based on the sequences of 16S rRNA genes from genus Haemophilus to detect H.influenzae and H.parainfluenzae.

RESULTS

The sensitivity of the 16S rRNA PCR assay for detecting H.influenzae and H.parainfluenzae was 97.53% and 100% respectively, and the specificity was 95.89% and 96.63% respectively. Youden's Index on the ability to detect H.influenzae and H.parainfluenzae was 0.9342 and 0.9663 respectively. 666 nasopharyngeal swab specimens were collected from healthy children. The detection rates of H.influenzae and H.parainfluenzae were 14.11% and 16.07% respectively by using isolation and culture methods. The detection rates of H.influenzae and H.parainfluenzae were 43.54% and 57.96% respectively by 16S rRNA PCR assays. The carriage rates of serotypes a, b, c, d, e, f and non-typeable isolates were 0% (0/666), 0.15% (1/666), 1.20% (8/666), 0.15% (1/666), 1.20% (8/666), 1.80% (12/666), 95.50% (636/666) respectively.

CONCLUSION

The multiplex PCR assays were very rapid, reliable and feasible methods for detection of H.influenzae and H.parainfluenzae in pharyngeal swab specimens which were compared to conventional isolation and culture methods. 95.5% of H.influenzae strains in healthy children were nontypeable. The encapsulated or typable strains were mainly three serotypes which was c, e, and f serotype.

Diversity of antibiotic resistance integrative and conjugative elements among haemophili

The objective of this study was to investigate the sequence diversity in a single country of a family of integrative and conjugative elements (ICEs) that are vectors of antibiotic resistance in Haemophilus influenzae and Haemophilus parainfluenzae, and test the hypothesis that they emerged from a single lineage. Sixty subjects aged 9 months – 13 years were recruited and oropharyngeal samples cultured. Up to 10 morphologically distinct Pasteurellaceae spp. were purified, and then the species were determined and differentiated by partial sequence analysis of 16S rDNA and mdh, respectively. ICEs were detected by PCR directed at five genes distributed evenly across the ICE. These amplicons were sequenced and aligned by the neighbour-joining algorithm. A total of 339 distinguishable isolates were cultured. ICEs with all 5 genes present were found in 9 of 110 (8 %) H. influenzae and 21 of 211 (10 %) H. parainfluenzae, respectively. ICEs were not detected among the other Pasteurellaceae. A total of 20 of 60 (33 %) children carried at least 1 oropharyngeal isolate with an ICE possessing all 5 genes. One of the five genes, integrase, however, consisted of two lineages, one of which was highly associated with H. influenzae. The topology of neighbour-joining trees of the remaining four ICE genes was compared and showed a lack of congruence; though, the genes form a common pool among H. influenzae and H. parainfluenzae. This family of antibiotic resistance ICEs was prevalent among the children studied, was genetically diverse, formed a large gene pool, transferred between H. influenzae and H. parainfluenzae, lacked population structure and possessed features suggestive of panmixia, all indicating it has not recently emerged from a single source.