Aspergillus niger Culture Filtrate (ACF) Mediated Biocontrol of Enteric Pathogens in Wastewater

Harnessing the probiotic properties and immunomodulatory effects of fermented food-derived Limosilactobacillus fermentum strains: implications for environmental enteropathy

Introduction

Environmental enteropathy (EE), a chronic small intestine disease characterized by gut inflammation, is widely prevalent in low-income countries and is hypothesized to be caused by continuous exposure to fecal contamination. Targeted nutritional interventions using potential probiotic strains from fermented foods can be an effective strategy to inhibit enteric pathogens and prevent chronic gut inflammation.

Methods

We isolated potential strains from fermented rice water and lemon pickle and investigated their cell surface properties, antagonistic properties, adhesion to HT-29 cells, and inhibition of pathogen adherence to HT-29 cells. Bacteriocin-like inhibitory substances (BLIS) were purified, and in vivo, survival studies in Caenorhabditis elegans infected with Salmonella enterica MW116733 were performed. We further checked the expression pattern of pro and anti-inflammatory cytokines (IL-6, IL8, and IL-10) in HT-29 cells supplemented with strains.

Results

The strains isolated from rice water (RS) and lemon pickle (T1) were identified as Limosilactobacillus fermentum MN410703 and MN410702, respectively. Strains showed probiotic properties like tolerance to low pH (pH 3.0), bile salts up to 0.5%, simulated gastric juice at low pH, and binding to extracellular matrix molecules. Auto-aggregation of T1 was in the range of 85% and significantly co-aggregated with Klebsiella pneumoniae, S. enterica, and Escherichia coli at 48, 79, and 65%, respectively. Both strains had a higher binding affinity to gelatin and heparin compared to Bacillus clausii. Susceptibility to most aminoglycoside, cephalosporin, and macrolide classes of antibiotics was also observed. RS showed BLIS activity against K. pneumoniae, S. aureus, and S. enterica at 60, 48, and 30%, respectively, and the protective effects of BLIS from RS in the C. elegans infection model demonstrated a 70% survival rate of the worms infected with S. enterica. RS and T1 demonstrated binding efficiency to HT-29 cell lines in the 38-46% range, and both strains inhibited the adhesion of E. coli MDR and S. enterica. Upregulation of IL-6 and IL-10 and the downregulation of IL-8 were observed when HT-29 cells were treated with RS, indicating the immunomodulatory effects of the strain.

Discussion

The potential strains identified could effectively inhibit enteric pathogens and prevent environmental enteropathy.

Tetracycline resistance of Escherichia coli isolated from water, human stool, and fish gills from the Lake Sevan basin

The ecological state of Lake Sevan, the largest drinking water reservoir for the South Caucasus, formed under the influence of climatic and social changes. This study assesses the bacteriological quality of water in the rivers of the Lake Sevan basin and tetracycline-resistant bacteria isolated from fish and people living near the rivers of the Lake Sevan basin in Armenia in autumn 2019 and spring 2020. No differences have been shown for the tetracycline resistance of the investigated E. coli isolated from the human gut and the Masrik, Argichi, and Gavaraget Rivers. Horizontal gel electrophoresis revealed the same plasmid bands in most of the investigated E. coli with the same tetracycline resistance from the different sources of the Argichi River (obtained from people/fish/water sources where the fish were caught). The results also showed that most of the waters carried Edwardsiella spp., Erwinia spp., Morganella spp., and Proteus spp. in addition to E. coli; the coliform index did not exceed the standard level of 5 × 104 CFU mL-1 there. These findings highlight the importance of multidisciplinary studies of bacteria from "interacting" ecosystems, which might serve as a basis for the suggestion of microbial antibiotic resistance as another indicator of water pollution.

A novel and improved selective media for the isolation and enumeration of Klebsiella species

Bacterial pathogens are fostered in and transmitted through wastewater. Hence, monitoring their impact on sanitation and hygiene is imperative. As part of the monitoring process, culture-based methodologies are primarily used, which centre on the use of selective and differential media. Media available today are, at best, difficult to formulate and, at worst, prohibitively expensive. To address this lacuna, the study proposes a selective and differential medium for Klebsiella spp. Klebsiella blue agar (KBA) is completely selective against selected gram-positive bacteria (Bacillus spp., Staphylococcus aureus) and a few gram-negative bacteria (Acinetobacter baumanii, Serratia marcescens). On the other hand, it supports the growth of the chosen members of the Klebsiella pneumoniae species-complex with a characteristic green colouration. Methylene blue, tryptophan, and bile salt make up the selective components of KBA. Moreover, methylene blue, 0.6% NaCl, and glycerol render it differential. KBA was more selective than HiCrome™ Klebsiella Selective Agar Base (KSA) in replica plating experiments. KBA promoted only 157 CFUs against 209 CFUs in KSA when stamped with 253 CFUs grown on LB. The colonies so isolated were predominantly Klebsiella spp., on identification through colony polymerase chain reaction. Moreover, the differential nature of KBA distinguished Klebsiella aerogenes from other species. On the contrary, KSA lodged colonies indistinguishable from each other and Klebsiella spp. Due to its ease of formulation, high selectivity, differential nature, and cost-effective composition, KBA is a viable option for the routine culture of Klebsiella spp. in environmental and clinical settings. KEY POINTS: • Formulated a novel selective and differential media for Klebsiella spp., named Klebsiella Blue agar • Facile formulation methodology • Can be employed to isolate Klebsiella spp. from complex sources such as wastewater.