Effect of hydrogen peroxide on growth of Candida, Cryptococcus, and other yeasts in simulated blood culture bottles

Efficacy of antiseptics and disinfectants on clinical and environmental yeast isolates in planktonic and biofilm conditions

The aim of this study was to evaluate the efficacy of five antiseptics, three surface disinfectants and UV radiation against a wide range of clinical and environmental yeast isolates. Their efficacy against pure cultures, yeast mixtures and biofilms (prepared by culturing yeasts in Sabouraud broth containing a final concentration of 8% glucose) was tested. Three clinical isolates of Candida albicans, Cryptococcus neoformans and Rhodotorula rubra, and two environmental isolates of Candida albicans and Cryptococcus uniguttulatus were selected. For seven out of eight biocides tested (Betadine, Dermacide, Chlorhexidine, Dosisepsine, hydrogen peroxide, sodium hypochlorite, 70% alcohol, 0.5% Ecodiol) and for UV radiation, susceptibility did not differ according to genus, species or origin. Hydrogen peroxide, 0.25% Ecodiol and UV radiation were ineffective against the five isolates tested. On pure planktonic cultures, and, to a lesser extent, on free-living yeast mixtures, the other products were active and were then tested against biofilms: eight out of nine biocides were ineffective. Chlorhexidine at 0.5% was the only fungicidal agent on pure cultures, yeast mixtures and biofilms. The importance of the test method, including agent concentration, is discussed.

Value of extended agitation and subculture of BACTEC NR 660 aerobic resin blood culture bottles for clinical yeast isolates

From 10,351 blood cultures, we prospectively studied 1,000 BACTEC NR 660 aerobic resin blood culture bottles (26+ and Peds Plus) for patients suspected of having yeast septicemia to determine whether extended agitation and subculturing would increase the recovery of yeasts. Aerobic bottles were agitated continuously for 144 h. On day 7, 1,000 culture-negative aerobic bottles which had fungal blood culture requests were agitated for an additional 14 days. During this time they were subcultured twice and read twice by BACTEC NR 660. ON days 1 to 7, 81 bottles were cultured positive for yeasts from 36 patients, which included 44 isolates of Candida albicans, averaging 1.4 days to detection, and 12 isolates of Cryptococcus neoformans, averaging 3.8 days to detection. The average detection time for all yeasts was 2.2 days. On days 7 to 21, no yeasts were detected by BACTEC or recovered from the subcultures. We conclude that when continuously agitated for at least 5 full days (120 h), the BACTEC NR 660 aerobic resin bottles reliably isolate yeasts, and it is unnecessary to subculture or hold these bottles beyond 5 days. It also eliminates the need for an additional blood culture system for yeast detection, thus saving (i) confusion in the collection process, (ii) patients' blood and money, and (iii) laboratory technologists' time.