In-vitro proteinase production by oral isolates from patients with and without HIV infection (18 isolates from each group) was assessed by image analysis of a plate assay, with bovine serum albumin (BSA) as a substrate. The effect of sub-minimal inhibitory concentrations (sub-MICs) of nystatin, amphotericin B, clotrimazole and miconazole on in-vitro proteinase production by these yeast isolates was also investigated. Proteinase production by isolates from patients with HIV infection was significantly greater than production by those from individuals without infection. All 18 isolates from HIV-infected individuals produced proteinase, in comparison to 56% of isolates from uninfected individuals. Pre-exposure of isolates (seven proteinase producers from each group) to 1/4 and 1/16 MICs of nystatin, amphotericin B, clotrimazole and miconazole resulted in decreased proteinase production in all isolates tested. However, after exposure to the four antimycotic agents, proteinase production was decreased to a significantly greater extent in isolates from uninfected individuals than in those with HIV disease. Furthermore, when the relative concentration effect of antimycotic agents on proteinase production was compared, isolates from the HIV-free group demonstrated a salient dose-response relationship compared with the HIV-infected group. These results indicate that from patients with HIV infection are significantly more proteolytic than those from individuals without the infection, and that polyenes and imidazoles curtail the proteolytic activity of all isolates, albeit to a lesser extent in those from HIV-infected patients. It appears that HIV disease favours oral colonisation by more proteolytic isolates, with resilient proteolytic activity.


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