HAEMOPHILUS-INFLUENZAE INFECTION OF HUMAN RESPIRATORY MUCOSA IN LOW CONCENTRATIONS OF ANTIBIOTICS

We examined the effects of 0.25 and 0.5 minimal inhibitory concentrati ons (MIC) of amoxicillin, loracarbef, and ciprofloxacin on the interac tion of a clinical isolate of nontypable Haemophilus influenzae (NTHi) with human adenoid organ culture. Adenoid tissue was embedded in agar so that only the mucosal surface was exposed. Minimum essential mediu m containing NTHi with or without antibiotics was added to the organ c ulture and incubated with 5% CO2 at 37-degrees-C for 24 h. The organ c ultures (n = 6) were assessed for several parameters by light microsco py (LM) and transmission electron microscopy (TEM). Bacterial viable c ounts after 24 h were not significantly different in all organ culture s. Compared with uninfected controls at 24 h, infection with NTHi caus ed significant (p < 0.05) damage to epithelium as assessed by LM: redu ced ciliary beat frequency (CBF), disruption of epithelium integrity, and reduced number of ciliated sites. TEM showed extrusion of cells fr om the epithelial surface, loss of cilia from ciliated cells, cytoplas mic blebbing, and mitochondrial damage. In the presence of 0.25 and 0. 5 MIC of all three antibiotics, the mucosal damage was significantly l ess (p < 0.05). We conclude that in the presence of sub-MIC levels of amoxicillin, loracarbef, and ciprofloxacin, NTHi infection causes less functional (CBF) and structural damage.