Susceptibility of Candida albicans filamentation-defective mutants to clinical biocides

Candida auris: Disinfectants and Implications for Infection Control

Candida auris is a rapidly emerging pathogen and is able to cause severe infections with high mortality rates. It is frequently misidentified in most clinical laboratories, thus requiring more specialized identification techniques. Furthermore, several clinical isolates have been found to be multidrug resistant and there is evidence of nosocomial transmission in outbreak fashion. Appropriate infection control measures will play a major role in controlling the management and spread of this pathogen. Unfortunately, there are very few data available on the effectiveness of disinfectants against C. auris. Chlorine-based products appear to be the most effective for environmental surface disinfection. Other disinfectants, although less effective than chlorine-based products, may have a role as adjunctive disinfectants. A cleaning protocol will also need to be established as the use of disinfectants alone may not be sufficient for maximal decontamination of patient care areas. Furthermore, there are fewer data on the effectiveness of antiseptics against C. auris for patient decolonization and hand hygiene for healthcare personnel. Chlorhexidine gluconate has shown some efficacy in in vitro studies but there are reports of patients with persistent colonization despite twice daily body washes with this disinfectant. Hand hygiene using soap and water, with or without chlorhexidine gluconate, may require the subsequent use of alcohol-based hand sanitizer for maximal disinfection. Further studies will be needed to validate the currently studied disinfectants for use in real-world settings.

Filamentation protects Candida albicans from amphotericin B-induced programmed cell death via a mechanism involving the yeast metacaspase, MCA1

The budding yeast Candida albicans is one of the most significant fungal pathogens worldwide. It proliferates in two distinct cell types: blastopores and filaments. Only cells that are able to transform from one cell type into the other are virulent in mouse disease models. Programmed cell death is a controlled form of cell suicide that occurs when C. albicans cells are exposed to fungicidal drugs like amphotericin B and caspofungin, and to other stressful conditions. We now provide evidence that suggests that programmed cell death is cell-type specific in yeast: Filamentous C. albicans cells are more resistant to amphotericin B- and caspofungin-induced programmed cell death than their blastospore counterparts. Finally, our genetic data suggests that this phenomenon is mediated by a protective mechanism involving the yeast metacaspase, MCA1.

Biocide resistance of Candida and Escherichia coli biofilms is associated with higher antioxidative capacities

BACKGROUND

Most clinical guidelines for the use of biocides have been developed for planktonic micro-organisms, but in nature, most micro-organisms live as surface-adherent communities or biofilms.

AIM

To evaluate the effectiveness of commonly used biocides against Escherichia coli and Candida spp. in three distinct growth phases: planktonic, adhesion and biofilm.

METHODS

Ultrastructural, architectural and cellular viability changes following a 5 min exposure to biocide were monitored by scanning electron microscopy and confocal laser scanning microscopy using fluorescent dyes. Comparative transcript expression of the antioxidants SOD1 and CAT1 in the planktonic and biofilm phases was evaluated using quantitative real-time polymerase chain reaction.

FINDINGS

E. coli and Candida spp. in the planktonic phase were susceptible to all the tested biocides at the recommended concentrations. However, early adhesion and late biofilm phases of both were less susceptible to the biocides, and exceeded the recommended concentrations on several occasions. A short period of biocide exposure failed to fully eradicate the adherent microbial cells, and they recovered from the biocide challenge, forming biofilm on the biocide-treated surfaces. The biofilm phase showed higher expression of SOD1 and CAT1.

CONCLUSION

The recommended concentrations of biocides for clinical disinfection in the hospital setting may not fully eradicate the adhesion or biofilm phases of E. coli and Candida spp. Higher antioxidative capacities in microbial biofilms may be responsible for the resistance of biofilms against clinical biocides.