ABSTRACT
The antifungal antibiotic, ambruticin, inhibits growth of Candida parapsilosis and reduces its ability to take up amino acids. Increasing growth temperature from 30 degrees C to 39 degrees C leads to a 100-fold decrease in the minimum growth inhibitory concentration. Ambruticin is 20 times more effective at pH 5 than at pH 8 and exponentially growing cultures are much less susceptible than stationary phase cells. The activity of ambruticin is also dependent on the presence of certain exogenous nutrients. When acetate or succinate (10 mM) are included in the incubation medium, ambruticin has little effect on amino acid uptake. Glucose, mannose and glycerol do not decrease the efficacy of ambruticin. Ambruticin probably inhibits growth by reducing the utilization of exogenous and intracellular carbohydrates. This leads to a fall in energy production within the cell which can be monitored as a reduction in the activity of energy-dependent transport systems.
Subject(s)
Amino Acids/metabolism , Antifungal Agents/pharmacology , Candida/drug effects , Candida/growth & development , Candida/metabolism , Leucine/metabolism , Pyrans/pharmacologyABSTRACT
Total cellular DNA content, determined by a colorimetric method, was used as an index of ploidy in Candida albicans. Mononucleate hybrids were formed by fusion of spheroplasts derived from diploid parent strains. Five hybrids, of six studied, were taken to be tetraploid on the basis of estimated DNA content. One hybrid was taken to be hexaploid or near-hexaploid. Selection for increased resistance to 5-fluorocytosine in the hybrids, which were heterozygous for resistance, resulted in isolation of variants which were of lower ploidy than the hybrids from which they originated. Variants were obtained which corresponded (in measured DNA content) to aneuploid, triploid, and diploid states. These results may form the basis of a cyclic parasexual system (2n X 2n----4n----2n) for genetic analysis of this asexual species.
Subject(s)
Candida albicans/genetics , Candida albicans/drug effects , DNA, Fungal/genetics , Drug Resistance, Microbial , Flucytosine/toxicity , Genetic Linkage , Hybridization, GeneticABSTRACT
Optimal conditions for cryopreservation of nematode larvae have been established using Nematospiroides dubius. Ruminant nematode larvae were infective up to three and a half years after freezing if introduced by laporotomy (intestinal nematodes) or by oral challenge (abomasal nematodes). The advantages of cryopreservation over normal storage of larvae are discussed.
Subject(s)
Nematoda/physiology , Preservation, Biological/veterinary , Rumen/parasitology , Ancylostomatoidea/physiology , Animals , Cattle/parasitology , Freezing , Rats , Sheep/parasitologyABSTRACT
The resistance of the eggs of benzimidazole resistant Haemonchus contortus and Trichostrongylus colubriformis is not stable and will decrease in the absence of drug challenge. Dosing animals harbouring resistant H contortus with either thiabendazole or mebendazole selects for nematodes producing thiabendazole resistant eggs. The eggs of a thiabendazole selected strain of H contortus were more resistant to thiabendazole, parbendazole and oxibendazole but less resistant to cambendazole and mebendazole.
Subject(s)
Benzimidazoles/pharmacology , Nematoda/drug effects , Animals , Drug Resistance , Female , Haemonchus/drug effects , Ovum/drug effects , Trichostrongyloidea/drug effectsABSTRACT
Eggs of benzimidazole-resistant Haemonchus contortus and Trichostrongylus colubriformis are resistant to the ovicidal activity of benzimidazoles. The possiblity is raised of using this as a simple screen for detection of resistance in nematodes of domesticated animals.
