Characterization of pseudomonal adherence to unwounded cornea

This study examined binding of Pseudomonas aeruginosa to unwounded postnatal day (P) 5 immature mouse cornea. To determine whether the receptor molecule was protein or lipid in nature, the eyes were incubated in vitro with trypsin or lipase before bacteria were applied. Trypsin significantly increased bacterial binding, whereas lipase had no effect. To determine if enhanced binding after trypsin indicated exposure of a lipid or a protein receptor, the eyes were treated sequentially with trypsin, then lipase. Subsequent binding did not differ significantly from trypsin alone, indicating that the exposed receptor was not a lipid. Incubation of the P 5 eye with neuraminidase to remove sialylated residues also significantly enhanced binding at all times, and premixing of the inoculum with the enzyme before adherence testing increased binding at 15 and 30 min. The effects of a monosialoganglioside (GM1) and gangliotetraosylceramide (asialo GM1) were also examined. Incubation of eyes with GM1 or asialo GM1 produced no significant inhibition of bacterial binding, but premixing of the bacterial inoculum with GM1 or asialo GM1 before corneal application transiently decreased adherence. Fibronectin (FN) treatment of the P 5 eye, premixing FN with the bacterial inoculum before its ocular application, or similar treatment with N-acetylneuraminic acid (NANA) transiently inhibited binding. These data demonstrate that pseudomonal binding to the unwounded eye is not lipase sensitive and is enhanced by trypsin treatment which exposes a lipase insensitive receptor and by neuraminidase which removes sialylated residues. It is not inhibited by pretreatment of the eye with either GM1 or asialo GM1 and is transiently inhibited by pretreatment of the eye or the inoculum with NANA or FN.