Study for biofilm formed by Haemophilus influenzae on human bronchial epithelial cells

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To evaluate the biofilm formation between Nontypeable Haemophilus influenzae (NTHi) and H. influenzae type b (Hib), we conducted the following comparative study. After serotyping and performing PCR to identify β-lactamase-negative ampicillin (AMP)-susceptible (BLNAS) NTHi, β-lactamase-negative AMP-resistant (BLNAR) NTHi, TEM-1 type β-lactamase-producing AMP-resistant (BLPAR) NTHi and Hib, we conducted biofilm production assays and scanning electron microscopy (SEM). The biofilm production assay and SEM showed that NTHi, including the BLNAR, BLNAS and BLPAR strains were similar in terms of forming biofilms, whereas in most of the Hib strains biofilm formation was decreased, compared to NTHi except for a few biofilm-producing strains. PCR to identify the type b cap gene and sequences indicated that 5 of the biofilm-producing Hib strains had lost their b capsule. Also, we compared anti-biofilm effect by several antibiotics between BLNAR and BLNAS strains using biofilm production assays. The assay indicates that penicillin and cephalosporin do not have anti-biofilm effect, but macrolide and quinolone have anti-biofilm effect against BLNAR and BLNAS strains dose-dependently. Our data indicate that most Hib strains form biofilms to a lesser extent than NTHi, whereas biofilm formation among BLNAR, BLNAS and BLPAR NTHi are variable and almost similar, and that the loss of b capsule expression in H. influenzae may result in enhanced biofilm formation. Also, our data demonstrate that macrolide and quinolone may inhibit biofilm formed by Haemophilus influenzae.