Differences in virulence of clinical isolates of Candida tropicalis and Candida albicans in mice

Abstract

Prior reports from this institution indicated that Candida tropicalis was more pathogenic than C. albicans in oncology patients. Pairs of clinical isolates of C. tropicalis and C. albicans recovered from similar patients at other institutions were examined to determine their relative virulence. After intravenous inoculation in normal mice, three pairs of isolates had no significant differences in the 50% lethal dose, and one C. tropicalis isolate was less virulent than its companion C. albicans isolate. In contrast, in mice treated with antibiotics and cytarabine, an antineoplastic drug which damages the gastrointestinal mucosa and produces granulocytopenia, oral inoculation of yeast cells produced striking differences in the 50% infective dose: each C. tropicalis isolate was more virulent than the companion C. albicans isolate from the same institution. The increased virulence of the C. tropicalis isolates compared with the C. albicans isolates when given orally to compromised mice parallels clinical observations in compromised patients.

Effects of extracellular DNA from Candida albicans and pneumonia-related pathogens on Candida biofilm formation and hyphal transformation

“…Candida tropicalis is considered an opportunistic yeastlike micro-organism that is common both in the environment and in normal human flora (Fromtling et al 1987). It has been reported that some C. tropicalis isolates were more virulent than C. albicans isolates obtained from the same institution (Wingard et al 1982). Our findings also showed that C. tropicalis biofilms were formed mainly with yeast-type cells although some long hyphae-type cells were also present ( Fig.…”

Pathogenic factors inCandidabiofilm-related infectious diseases

“…Candida tropicalis, an opportunistic yeast-like microorganism that is common both in the environment and in normal human flora (Fromtling et al 1987), has also been identified as the second or third most causative agent of candidaemia, mainly in oncology patients (Weinberger et al 2005;Nucci and Colombo 2007), and it is often associated with nosocomial urinary tract infections (Rho et al 2004). It has been reported that some C. tropicalis isolates were more virulent than C. albicans isolates obtained from the same institution (Wingard et al 1982). Our group also observed that C. tropicalis biofilms were formed mainly with yeast-type cells, although some Figure 3 Fluorescence microscopy images of Candida biofilms cultured with homogeneous eDNA (a; 1 mg ml À1 , b; 10 mg ml À1 ) for 48 h. The biofilms were comprised of metabolically active cells (blue, Hoechst 33342-stained intracellular DNA) and abundant extracellular DNA (red, stained with 7-hydroxyl-9H-(1,3-dichloro-9,9dimethylacridin-2-one; DDAO)) embedded in the extracellular matrix.…”

The contribution of mouse models to our understanding of systemic candidiasis

“…Mouse models have been invaluable in increasing our understanding of the behaviour of Candida species, particularly C. albicans, in the host. Assaying the virulence of clinical isolates in these models has demonstrated considerable variation, both between species and within species, which was not linked to the clinical source of the isolate (Wingard et al, 1982;Mellado et al, 2000;Brieland et al, 2001;Arendrup et al, 2002;Asmundsdottir et al, 2009;MacCallum et al, 2009b). Virulence differences have also been evident when the same strain, or isolate, has been compared in the two systemic infection mouse models (Wingard et al, 1982;de Repentigny et al, 1992;Bendel et al, 2003), suggesting that different virulence factors are required in the different models.…”