Abstract
Simple SummaryPathogenic bacteria in poultry and the widespread use of antibiotics to manage them are costly in terms of production, environmental risk and human health. Probiotic and other low-cost, non-antibiotic treatments offer attractive alternatives to antibiotic applications, but relatively few of these options exist. In this research, we investigated the potential of an otherwise-useful industrial yeast, Metschnikowia pulcherrima, for the active suppression of poultry pathogenic bacteria. We tested multiple strains of yeast against several important bacterial pathogens and found that the more inhibitory strains of yeast supressed bacterial growth and actively killed the most recalcitrant bacteria. Less aggressive yeast strains could increase the growth of some bacterial strains in some environments. The yeast produced novel molecules in response to the presence of the bacteria and we identified several potential mechanisms by which the yeast inhibited or killed bacteria. Together, these results point towards a useful application of a novel yeast for enhanced, antibiotic-free pathogen control.Metschnikowia pulcherrima is a non-conventional yeast with potential to be used in biotechnological processes, especially those involving low-cost feedstock exploitation and biocontrol applications. The combination of traits that supports these industrial applications in M. pulcherrima also makes it an attractive option to study in the context of livestock health. In this study, we examined the specific interactions between M. pulcherrima and multiple avian pathogenic bacteria. We tested individual bacteria–yeast interactions and bacterial combinations in both solid and liquid media and in variable nutrient environments. Across multiple isolates of M. pulcherrima, we observed different levels of antimicrobial activity, varying from supporting the growth of competing bacteria through suppression and bacterial killing, and we found that these responses varied depending on the bacterial strains and media. We identified multiple molecular routes, including proteins produced by M. pulcherrima strains, that acted to control these microbial interactions. Furthermore, protein screening revealed that M. pulcherrima strains were induced to produce proteins specifically when exposed to bacterial strains, suggesting that fine-tuned mechanisms allow M. pulcherrima to function as a potential lynchpin in a microbial community.
Highlights
The use of antibiotics in animal farming is a global practice
To assess variation in antimicrobial activity across isolates, zone-of-inhibition (ZOI) assays were performed with 11 strains against 3 avian-derived pathogenic bacteria
S. aureus growth was the most inhibited by all yeast strains compared to inhibition of Salmonella and avian pathogenic E. coli (APEC) (Figure 1)
Summary
The use of antibiotics in animal farming is a global practice. Whether prescribed therapeutically when clinical symptoms appear or prophylactically for growth proportion and where farming conditions or methods predispose a population to disease outbreaks, the benefits of their use are important both financially and from an animal health perspective. Improved animal health measured by growth and overall productivity results from a variety of mechanisms associated with antibiotic use. The maintenance of a healthy commensal microbial population though prophylactic administration benefits animals by aiding the digestion and fermentation of plant polymers, the synthesis of vitamins and the conversion of toxins to non-toxic compounds and by forming an extra line of defence against pathogen colonisation [3]. For these reasons, approximately 80% of food animals receive antibiotic medication for some or most of their lives [4]
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