The in vitro proteolytic and saccharolytic activity of Candida species cultured in human saliva

Abstract

The proteolytic and saccharolytic activity of 4 Candida species was investigated in batch cultures of pooled, human mixed saliva supplemented with glucose. All the Candida species investigated (Candida albicans, Candida tropicalis, Candida glabrata and Candida krusei) demonstrated a marked growth in saliva with a concomitant reduction in pH from about 7.5 to 3.3, within 72 h. Isotachophoretic analysis of the culture supernatant revealed the presence of a variety of acid anions of which pyruvate and acetate were the most abundant. Proteolysis of salivary components, evaluated by a biochemical assay and sodium dodecyl sulfate-polyacrylamide gel electrophoresis, was exhibited by all 4 Candida species, although there was inter-species variation. Despite the similarity in growth rates, C. tropicalis and C. krusei demonstrated greater proteolytic activity than C. albicans and C. glabrata. Neither candidal growth nor proteolysis was observed in glucose-free control saliva samples. In contrast, the degree of saccharolytic and proteolytic activity of a single isolate of C. albicans in glucose-supplemented parotid saliva appeared to be relatively weak compared with mixed saliva. As the oral cavity provides ideal low pH niches periodically supplemented with dietary carbohydrates, the acidic proteinases of Candida species may play a role in the pathogenesis of oral candidiasis.

The Expression of Secreted Aspartyl Proteinases of Candida Species in Human Whole Saliva

“…Similar findings have been reported previously by Samaranayake et al [17] for both C. albicans and C. tropicalis in human whole saliva. The most likely explanation for this phenomenon is the differential rates of degradation of salivary proteins by the expressed candidal proteinases.…”

“…On the other hand, the proteolytic activity and the proteinase expression in the case of the latter two species were very similar. One reason for this could be the profuse growth of C. albicans in the test media as compared with non-albicans species, observed here as well as by others [17]. Despite this caveat, the results of the present study tend to confirm the recognised hierarchy of virulence in Candida spp.…”

“…l), all isolates demonstrated the same trend. Whilst the growth of C. albicans and C. tropicalis in human saliva culture has been reported by Samaranayake et al [17], this is the first study demonstrating C. parapsilosis growth in human saliva in vitro. These results together with previous work [ 17,231 convincingly demonstrate the ability of yeasts to grow in saliva while expressing their extracellular proteolytic activity.…”

“…One reason for this may be the salivary buffering action which neutralises the yeastderived carboxylic acids that have rapidly accumulated during the log phase of yeast growth. It is known that acid production in yeast-salivary cultures peaks at the log phase of growth and declines or abates thereafter [17,23]. An acidic pH is crucial for proteinase expression in Candida spp.…”

Candida krusei: biology, epidemiology, pathogenicity and clinical manifestations of an emerging pathogen

“…21 A complex variety of fatty acids has been demonstrated as metabolites when C. krusei is grown in culture media containing lactose,22 it is also able to produce a~e t o i n .~~ It also produces a number of shortchain carboxylic acids when cultured in saliva supplemented with glucose ; these include acetate, pyruvate, succinate, propionate, formate and lactate. 24 The biological role of these, if any, is as yet unknown.…”