Candidemia in non-neutropenic patients with an intravenous hyperalimentation catheter: good prognosis of Candida parapsilosis infection

[Study on growth characteristics of Candida auris under different conditions in vitro and its in vivo toxicity]

OBJECTIVE

To investigate the characteristics of growth and metabolism and the in vivo toxicity of Candida auris under different conditions.

METHODS

We observed the growth of Candida auris and Candida albicans under routine culture conditions and in different pH and salt concentrations, and compared their activities of sugar fermentation using microbiochemical reaction tubes. Four-week-old nude mice were randomized into Candida auris infection group (n=5), Candida albicans infection group (n=5) and control group (n=5) for intragastric administration of 0.3 mL suspension the two Candida species (5×10⁹ cfu/mL) or 0.3 mL normal saline. Samples of the liver, kidney, intestine, feces and blood were taken for analysis of the in vivo distribution and toxicity of Candida albicans by fungal culture and histopathological examination.

RESULTS

Candida auris exhibited logarithmic growth at 8-24 h after inoculation and showed stable growth after 24 h. Candida auris showed optimal growth within the pH value range of 5-7 with a growth pattern identical to that of Candida albicans. Candida auris grew better than Candida albicans in media containing 5% and 10% NaCl, and could ferment glucose, sucrose, trehalose and sorbitol. Candida auris could be isolated from the feces, blood, liver and kidney of infected nude mice, and the liver had the highest fungal load (5.7 log₁₀ cfu/g). Candida auris could cause pathological changes in the liver and intestine of the mice, but with a lesser severity as compared with Candida albicans.

CONCLUSIONS

Candida auris exhibits optimal growth in mildly acidic or neutral conditions with a high salt tolerance, and can potentially penetrate the intestinal barrier into blood and lead to tissue injuries in hosts with immunosuppression.

Amino acids mediate colony and cell differentiation in the fungal pathogen Candida parapsilosis

Candida parapsilosis is responsible for severe cases of non-albicans systemic candidiasis and is one of the leading causes of mortality in neonates. The molecular mechanisms underlying this organism's virulence remain unknown. Unlike C. albicans, which can exist in several morphogenetic forms, C. parapsilosis exists in either the yeast or pseudohyphal forms. The environmental signals that trigger pseudohyphal differentiation and the signalling pathways that transduce these signals are unknown. This paper provides evidence for the role of amino acids in morphogenesis in C. parapsilosis. The cell and colony morphologies, pseudohyphal differentiation and invasive growth of five C. parapsilosis isolates were characterized in ammonium-rich minimal media lacking or supplemented with naturally occurring amino acids. C. parapsilosis underwent dramatic changes in cellular and colony morphology and formed pseudohyphae in response to a specific subset of amino acids. Transport studies showed that these amino acid inducers activate the transport of some, but not all, unrelated amino acids. Interestingly, citrulline, an amino acid that is not transported in the presence of ammonium, strongly induced pseudohyphal morphogenesis in C. parapsilosis under these conditions. Together the data suggest that amino acids are important morphogens in C. parapsilosis and that amino-acid-mediated morphogenesis in this organism does not require transport of the ligand across the plasma membrane.

Invasive candidiasis in cancer patients: observations from a randomized clinical trial

BACKGROUND

Invasive candidiasis is a common and serious complication of cancer and its therapy.

METHODS

We retrospectively identified patients with malignancies enrolled in a double-blind randomized trial of caspofungin (50 mg/day after a 70 mg loading dose) vs. conventional amphotericin B (0.6-1.0 mg/kg/day) as treatment of documented invasive candidiasis. A favorable response required complete resolution of signs and symptoms plus eradication of the Candida pathogen(s). The primary efficacy analysis used a modified intention-to-treat (MITT) approach that included all patients with a confirmed diagnosis of invasive candidiasis who received > or =1 dose of study medication.

RESULTS

74/224 (33%) patients in the MITT population had active malignancies. 25/30 (83%) hematological malignancies were acute or chronic leukaemias. 22/44 (50%) solid tumors were related to the gastrointestinal tract. Patients with hematological malignancies tended to be younger (median [range] age: 49 [19-74] vs. 59 [19-81] years) and have higher baseline acute physiology and chronic health evaluation (APACHE) II scores (mean [range]: 17 [0-28] vs. 15 [5-35]) than patients with solid tumors. Neutropenia [< or =500/microl] was present on entry in 23 (77%) patients with hematological malignancies and in one (3%) patient with a solid tumor. Candidemia was demonstrated in 56 (88%) cancer patients. C. albicans was the single most frequent isolate in cancer patients, although the majority of cases were caused by non-albicans species. Cancer patients in the caspofungin arm had more hematological malignancies (55 vs. 29%), higher baseline APACHE II scores (>20 in 36 vs. 15%), more frequent neutropenia (42 vs. 24%), and less C. albicans infections (27 vs. 49%) than the amphotericin B-treated cancer patients. Favorable response rates were 11/18 (61%) and 6/12 (50%) for patients with hematological malignancies treated with caspofungin or amphotericin B, respectively; the corresponding outcomes in patients with solid tumors were 12/15 (80%) and 17/29 (59%) for the 2 treatment arms. 7/14 (50%) caspofungin- and 4/10 (40%) amphotericin B-treated patients who were neutropenic on entry responded favorably. All-cause mortality rates during the study for caspofungin recipients were 11/18 (61%) with hematological malignancies and 6/15 (40%) with solid tumors, and for amphotericin recipients were 4/12 (33%) with hematological malignancies and 6/29 (21%) with solid tumors.

CONCLUSIONS

Underlying cancers, most commonly leukaemias and gastrointestinal tumors, were present in one-third of patients enrolled in this study of invasive candidiasis. Overall, 70% of caspofungin-treated and 56% of amphotericin B-treated cancer patients responded favorably. Response rates were lower for neutropenic leukaemic patients than for non-neutropenic patients with solid tumors in both treatment groups.

Translocation model of Candida albicans in DBA-2/J mice with protein calorie malnutrition mimics hematogenous candidiasis in humans

To elucidate the mechanism of translocation of Candida albicans from the intestine to the bloodstream, we attempted to establish a murine model for hematogenous translocation of C. albicans using DBA-2/J mice with protein calorie malnutrition (PCM). PCM severely affected the development of the intestinal epithelia; thereby, the keratin and mucinous layers became very thin. Oral inoculation with C. albicans resulted in long-term colonization in the intestine of the PCM mice but not the well-nourished animals. Chemotherapy with a combination of cyclophosphamide and methotrexate, which started four days after oral inoculation of C. albicans, resulted in the systemic dissemination of C. albicans from the intestine in the PCM mice. Among systemic organs, C. albicans was first isolated from the liver, in which focal necrosis, containing fungal balls of yeast-like forms and/or hyphae, was formed. Subsequently, C. albicans was first recovered from the blood of the infected PCM mice at one day after the isolation from the liver, and thereafter, candidemia continued to increase its intensity until death. Histological study indicated that C. albicans gained entry into the systemic organs from the epithelia of the esophago-cardiac junction as well as the Ileo-cecal portions of the infected mice. The results of our present study therefore suggest that this PCM mouse model may be useful for better understanding of the chemotherapy-induced translocation by C. albicans from the gut to the systemic organs in compromised humans.

Global distribution and outcomes for Candida species causing invasive candidiasis: results from an international randomized double-blind study of caspofungin versus amphotericin B for the treatment of invasive candidiasis

In a randomized study, caspofungin was compared with amphotericin B for the treatment of invasive candidiasis in a total of 239 adults from 56 sites in 20 countries. This study provided a unique opportunity to assess the frequency and outcome of invasive candidiasis caused by different Candida species worldwide, and the results are presented here. Efficacy was primarily assessed at the end of intravenous therapy using a modified intent-to-treat (MITT) analysis. This analysis was performed on 224 of the 239 patients enrolled in the study. Attempts were made to collect baseline Candida isolates from all patients for species identification at a central laboratory. Yeasts were identified to the species level using two commercial systems and microscopic examination. Viable baseline isolates were recovered from 210 of the 224 (94%) patients included in the MITT analysis. Candida albicans was the most frequently isolated species in all regions and was responsible for 45% of cases overall. Nevertheless, the majority of cases of infection were caused by non- albicans Candida species. In the USA and Canada, Candida glabrata was the second most commonly isolated pathogen (18%). In contrast, Candida parapsilosis and Candida tropicalis accounted for 55% of cases in Latin America. Outcomes were comparable for patients treated with caspofungin (74% overall; 64% and 80% for infections due to Candida albicans and non- albicans species) and amphotericin B (62% overall; 58% and 68% for infections due to Candida albicans and non- albicans species), and were generally similar across continents. The distribution of Candida species isolated from patients enrolled in a clinical trial may not be representative of pathogens causing invasive candidiasis in the general population. Nevertheless, our findings may affect the regional choice of empirical antifungal therapy for seriously ill patients with suspected or documented invasive candidiasis since different Candida species have varying susceptibility to conventional antifungal drugs.

Prophylaxis of fungal infections

Considering the high morbidity and mortality of deep-seated opportunistic mycoses in severely immunosuppressed patients, strategies for prophylaxis appear to be indicated. Exposure to Aspergillus spp. can be prevented by air filtration which has been shown to reduce the rate of infection. However, Candida infections are predominantly caused by colonizing fungi; therefore drug prophylaxis is more promising. Prospective randomized studies proved the effectiveness of fluconazole (FLU) to prevent infections in patients after bone marrow transplantation.