The fungistatic effect of histatin 5 and selection of pathogenic yeasts known to cause local and system infections
Madhira, Anuradha Beri
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It is well known that the human salivary protein histatin 5 exhibits fungicidal activity against the oral opportunistic pathogen Candida albicans. However, its fungistatic, or growth inhibitory, activity has been poorly investigated. One of the reasons for this is that growth inhibition assays are carried out in growth media in which the salt-sensitive histatins are in general inactive. In this manuscript we describe the development of an assay in which the fungistatic capacity of histatins could be established. The broth formulation contained a dilution of Muller-Hinton broth (MHB) or Sabouraud dextrose broth (SDB) supplemented with dialyzed yeast extract. The fungistatic activity of histatin 5 was investigated with 13 medically important fungi. In diluted supplemented MHB only some of the strains demonstrated growth whereas all strains grew in diluted supplemented SDB. ln the latter growth medium, the inhibitory concentrations (IC subscript 50 values) obtained for C. albicans strains ATCC 10231, 90028, 90029, 44505 and 32354 ranged between 10 and 20 [mega]g histatin 5 per ml. Cryptococci (clinical isolates) grew slower and were more sensitive with IC subscript 50 values of 5.2 and 5.6 [mega]/ml. Growth of C. kefyr (pseudotropicalis) (ATCC 4135), C. krusei (ATCC 6258) and C. parapsilosis (ATCC 90018) was inhibited by 50% at 11, 10 and 10[mega]/ml, respectively. In contrast, three C. glabrata strains (ATCC 90030, ATCC 2001 and ATCC 64677) were totally insensitive to histatin 5 (lC subscript 50 is [less or equal] 225 [mega]/ml). The insensitivity of C. glabrata toward histatin 5 was confirmed in killing assays. The data show that the employed growth inhibition assay allows for the rapid identification of oral fungal pathogens with reduced sensitivities to naturally occurring salivary antifungal proteins.
PLEASE NOTE: This work is protected by copyright. Downloading is restricted to the BU community: please click Download and log in with a valid BU account to access. If you are the author of this work and would like to make it publicly available, please contact email@example.com.Thesis (MSD)--Boston University, Goldman School of Dental Medicine, 2006 (Periodontics).Includes bibliographical references: leaves 54-64.
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