You are here: Home Published Research Genotypically defined β-lactamase negative ampicillin resistant isolates of non-typeable Haemophilus influenzae are associated with increased invasion of bronchial epithelial cells in vitro.

Nicola A Atkins, Dale A Kunde, Graeme Zosky, and Stephen G Tristram (2014)

Genotypically defined β-lactamase negative ampicillin resistant isolates of non-typeable Haemophilus influenzae are associated with increased invasion of bronchial epithelial cells in vitro.

Journal of medical microbiology.

The aim of the study was to investigate the association between the presence of altered PBP3 in non-typeable Haemophilus influenzae (NTHi) and an increased capacity to invade bronchial epithelial cells in vitro. A collection of 40 clinical isolates of NTHi comprised of 20 with normal penicillin binding protein 3 (PBP3) and 20 with altered PBP3 (defined by an N526K substitution) was established. The isolates were tested for the ability to invade bronchial epithelial cells in vitro using a 4h gentamicin survival assay. Invasion was measured as the percentage of intracellular organisms relative to the initial inoculum. The mean invasion rate ranged from 0.00% to 14.79% in the normal PBP3 isolates and 0.02% to 36.69% in the altered PBP3 isolates. The altered PBP3 isolates had a higher (p = 0.003) mean invasion rate (6.86%, n = 20) than the normal PBP3 isolates (1.31%, n = 20). Subsequently, 2 variants of altered PBP3 (transformant 1 - N526K, transformant 2 - M377I, S385T, L389F and N526K) were cloned into 3 of the initial isolates (parents) with normal PBP3 and relatively low invasive ability, and the parents and transformants tested for invasion as above. There was no difference (p = 0.89) in the mean invasion rates for the parents (0.81%, n=3), transformants 1 (0.90%, n=3) and transformants 2 (1.38%, n=3). There is an association between the presence of altered PBP3 in NTHi and an increased capacity to invade BEAS-2B cells in vitro, but cloning experiments suggest that the altered PBP3 is not directly involved in enhanced invasion.

 
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