Performance of a multiplex PCR for the determination of Haemophilus influenzae capsular types in the clinical microbiology laboratory

To improve tools for the surveillance of invasive H. influenzae in the context of the drastic decrease of type b infections following the implementation of vaccination, a two-step PCR technique was developed to detect the capsule and type specific regions of H. influenzae. The technique of Falla et al (1994) was modified to amplify in a first step the capsule and type b regions by multiplex PCR. For non-b capsulated strains, the type a, c, d, e, and f loci were afterward detected simultaneously by an optimized touch-down PCR technique. An internal control of extraction and amplification (16S rDNA) was included for both PCR techniques. Overall, this technique was shown to perform as efficiently or better than the slide agglutination without risks of interpretation errors. Of the 138 H. influenzae strains tested, seven that had given doubtful results by the agglutination technique were unequivocally typed by PCR.