Synergy between Sophorolipid Biosurfactant and SDS Increases the Efficiency of P. aeruginosa Biofilm Disruption.

Biofilms are communities of bacteria encased in self-secreted extracellular polymeric substances (EPS) that adhere stubbornly to submerged surfaces. Once established, these communities can cause serious chronic illnesses in medical settings, while they can promote corrosion and biofouling in industrial settings. Due to the difficulty of their removal, strongly oxidizing chemicals and detergents can be used to degrade and remove biofilms by killing the cells and degrading the matrix; however, the choice of compounds is limited in delicate environments due to the potential damage they may cause. In the case of detergents, most are synthesized from nonrenewable petrochemicals that have a degree of aquatic toxicity. There is a growing need to identify and characterize alternatives to synthetic surfactants. Biosurfactants, which are surfactants produced by microorganisms, are a promising alternative since they can be synthesized from renewable resources, have low environmental toxicity, and have been shown to have higher degrees of specificity in the mechanism of action. Sophorolipids are a class of glycolipid surfactants produced by yeast that have demonstrated great promise due to large yields from renewable feedstocks and for antimicrobial properties; however, the effect of the application of sophorolipids to Gram-negative bacterial biofilms has not been well studied. We investigate the antibiofilm properties of sophorolipids by demonstrating its ability to cause the catastrophic disruption of Pseudomonas aeruginosa PAO1 biofilms in microfluidic channels. We show that while sophorolipids inflict little damage to the bacteria, they weaken the EPS biofilm matrix, leading to surface-detachment and breakup of the biofilm. Furthermore, we find that sophorolipids act cooperatively with the widely used surfactant, sodium dodecyl sulfate. When combined, concentrations ∼100-fold lower than the minimum effective concentration, when used independently, recover potency. Biosurfactants are typically expensive to produce, thus our work demonstrates a means to improve efficacy while simultaneously reducing both cost and the amount of environmentally harmful substances used.

Prevalence and drug susceptibility of clinical Candida species in nasopharyngeal cancer patients in Vietnam.

In the nature, Candida species are normal inhabitants and can be observed in a wide variety of vertebrates. In humans, especially for cancer patients who fall prey to opportunistic pathogens, this group of susceptible multi-drug resistant and biofilm-forming yeasts, are among the commonest ones. In this study, Candida species in 76 oral lesion samples from Vietnamese nasopharyngeal-cancer patients were isolated, morphologically identified using CHROMagar™, germ tube formation, and chlamydospore formation tests, and molecularly confirmed by PCR-RFLP. The drug susceptibility of these isolates was then tested, and the gene ERG11 was DNA sequenced to investigate the mechanism of resistance. The results showed that Candida albicans remained the most prevalent species (63.16% of the cases), followed by Candida glabrata, Candida tropicalis, and Candida krusei. The rates of resistance of non-albicans Candida for tested drugs were 85.71%, 53.57%, and 57.14% to fluconazole, clotrimazole, and miconazole, respectively. Although the drug-resistance rate of Candida albicans was lower than that of non-albicans Candida, it was higher than expected, suggesting an emerging drug-resistance phenomenon. Furthermore, ERG11 DNA sequencing revealed different mutations (especially K128T), implying the presence of multiple resistance mechanisms. Altogether, the results indicate an alarming drug-resistance situation in Candida species in Vietnamese cancer patients and emphasize the importance of species identification and their drug susceptibility prior to treatment.