Prevalence of Virulence Genes of Diarrheagenic Escherichia coli in Fecal Samples Obtained from Cattle, Poultry and Diarrheic Patients in Bangladesh

Foodborne bacteria in milk and milk products along the water buffalo milk chain in Bangladesh

Controlling foodborne pathogens in buffalo milk is crucial for ensuring food safety. This study estimated the prevalence of nine target genes representing seven critical foodborne bacteria in milk and milk products, and identified factors associated with their presence in buffalo milk chain nodes in Bangladesh. One hundred and forty-three milk samples from bulk tank milk (n = 34), middlemen (n = 37), milk collection centers (n = 37), and milk product shops (n = 35) were collected and analyzed using RT-PCR. Escherichia (E.) coli, represented through yccT genes, was the most prevalent throughout the milk chain (81-97%). Chi-squared tests were performed to identify the potential risk factors associated with the presence of foodborne bacteria encoded for different genes. At the middleman level, the prevalence of E. coli was associated with the Mymensingh, Noakhali, and Bhola districts (P = 0.01). The prevalence of Listeria monocytogenes, represented through inlA genes, and Yersinia (Y.) enterocolitica, represented through yst genes, were the highest at the farm level (65-79%). The prevalence of both bacteria in bulk milk was associated with the Noakhali and Bhola districts (P < 0.05). The prevalence of Y. enterocolitica in bulk milk was also associated with late autumn and spring (P = 0.01) and was higher in buffalo-cow mixed milk than in pure buffalo milk at the milk collection center level (P < 0.01). The gene stx2 encoding for Shiga toxin-producing (STEC) E. coli was detected in 74% of the milk products. At the middleman level, the prevalence of STEC E. coli was associated with the use of cloths or tissues when drying milk containers (P = 0.01). Salmonella enterica, represented through the presence of invA gene, was most commonly detected (14%) at the milk collection center. The use of plastic milk containers was associated with a higher prevalence of Staphylococcus aureus, represented through htrA genes, at milk product shops (P < 0.05). These results suggest that raw milk consumers in Bangladesh are at risk if they purchase and consume unpasteurized milk.

Immunological pathogenesis of Bovine E. coli infection in a model of C. elegans

BACKGROUND

Cattle industry is critical for China's livestock industry, whereas E. coli infection and relevant diseases could lead huge economic loss. Traditional mammalian models would be costly, time consuming and complicated to study pathological changes of bovine E. coli. There is an urgent need for a simple but efficient animal model to quantitatively evaluate the pathological changes of bovine-derived E. coli in vivo. Caenorhabditis elegans (C. elegans) has a broad host range of diverse E. coli strains with advantages, including a short life cycle, a simple structure, a transparent body which is easily visualized, a well-studied genetic map, an intrinsic immune system which is conservable with more complicated mammalians.

RESULTS

Here, we considered that O126 was the dominant serotype, and a total of 19 virulence factors were identified from 41 common E. coli virulence factors. Different E. coli strains with diverse pathogenicity strengths were tested in C. elegans in E. coli with higher pathogenicity (EC3/10), Nsy-1, Sek-1 and Pmk-1 of the p38 MAPK signaling pathway cascade and the expression of the antimicrobial peptides Abf-3 and Clec-60 were significantly up-regulated comparing with other groups. E. coli with lower pathogenicity (EC5/13) only activated the expression of Nsy-1 and Sek-1 genes in the p38 MAPK signaling pathway, Additionally, both groups of E. coli strains caused significant upregulation of the antimicrobial peptide Spp-1.

CONCLUSION

Thirteen E. coli strains showed diverse pathogenicity in nematodes and the detection rate of virulence factors did not corresponding to the virulence in nematodes, indicating complex pathogenicity mechanisms. We approved that C. elegans is a fast and convenient detection model for pathogenic bacteria virulence examinations.

Genetic diversity and virulence gene profiles of Escherichia coli from diarrhoeal rabbits in Sichuan Province, China

Escherichia coli (E. coli) can cause diarrhoea in a wide range of hosts. Moreover, some trains with high virulence and drug resistance pose a serious threat to public health and livestock products. Diarrhoea caused by E. coli outbreaks in rabbitries result in serious economic losses. The aim of this study was to investigate the distribution of virulence genes and molecular genetic characteristics of E. coli from diarrhoeal rabbits in the main rearing areas of Sichuan province, China in 2015-2017. In total, 39 E. coli isolates were identified and undivided divided into 17 sequence types by multilocus sequence typing (MLST) and grouped in 22 clusters by pulsed-field gel electrophoresis. Polymerase chain reaction tests detected 6 virulence genes: eae (41.0%), ler (41.0%), ral (33.3%), afr2 (10.3%), irp2 (15.4%) and astA (7.7%) of the tested 17 virulence genes identifying 16 enteropathogenic E. coli (EPEC) isolates. The main sequence types U328, ST328 and ST20 carried rabbit EPEC associated virulence genes (eae, ler, ral and afr2). The results showed that the distribution of virulence genes varied by year and area; genotype had major types in local rearing areas but was of high diversity in Sichuan province.

Antimicrobial and antiadhesive effects of Lactobacillus isolates of healthy human gut origin on Enterotoxigenic Escherichia coli (ETEC) and Enteroaggregative Escherichia coli (EAEC)

PURPOSE

Diarrhea is one of the five leading causes of mortality in children under the age of five, especially in developing countries. Nowadays, by increasing the resistance of pathogens to antibiotics, employment of probiotics as novel therapeutic method, could be considered as a necessity.The aim of this study was to examine the features and antagonistic action of Lactobacillus strains, against the growth and adhesion of Enterotoxigenic Escherichia coli (ETEC) and Enteroaggregative Escherichia coli (EAEC) strains creating diarrhea in children. Then, we introduced new strains of Lactobacillus as probiotic candidates, to prevent diarrheal infections in children.

METHODS

Stool samples were collected from healthy individuals, and Lactobacillus strains were isolated. The antimicrobial effect of the isolates against ETEC and EAEC strains investigated by agar well diffusion method and their resistance to acidic and bile conditions. The potency of selected isolates in adhesion to HT-29 epithelial cells and their ability to inhibit the adhesion of ETEC and EAEC strains to this cell were measured. At the end, identification of the optimally efficient Lactobacillus isolates was performed by 16S rDNA sequencing and making Phylogenetic tree using MEGA (version 4.0) software.

RESULTS

In total, 157 isolates suspected to Lactobacillus were isolated from 115 stool samples. In antimicrobial activity test, ETEC and EAEC growth was inhibited by 132 and 84 isolates respectively, while 17 isolates showed resistance to Bile. Of 17 Bile resistant Lactobacillus isolates, 15 isolates were resistant to pH: 3.2. Further, among 15 isolates, only two isolates, were resistant to pH: 2.5. In the adhesion assay, five isolates had more adhesion tendency to HT-29 epithelial cells than L. rhamnosus GG, which was considered as a positive control. Investigation of isolates that inhibit adhesion of ETEC and EAEC strains to HT-29 cells showed that four isolates were able to inhibit ETEC adhesion. However, only one out of four isolates was relatively able to have an impact on EAEC adhesion.

CONCLUSION

In conclusion, three species of Lactobacillus including L. paracasei (two strain), L. fermentum (two strain) and L. plantarum showed good probiotic properties compared to other isolates that were identified by sequencing. In this study, strain L. fermentum 61.1 had the highest adhesion ability to HT-29 cells and strain L. paracasei 47.2 had the highest potency to inhibit ETEC adhesion to HT-29 cells. These isolates have good probiotic properties and are likely to be effective in preventing or treating diarrheal infections, especially in children.

Molecular Detection of Avian Pathogenic Escherichia coli (APEC) for the First Time in Layer Farms in Bangladesh and Their Antibiotic Resistance Patterns

Avian pathogenic Escherichia coli (APEC) causes significant economic losses in poultry industries. Here, we determined for the first time in Bangladesh, the prevalence of APEC-associated virulence genes in E. coli isolated from layer farms and their antibiotic resistance patterns. A total of 99 samples comprising internal organs, feces, and air were collected from 32 layer farms. Isolation was performed by culturing samples on eosin–methylene blue agar plates, while the molecular detection of APEC was performed by PCR, and antibiograms were performed by disk diffusion. Among the samples, 36 were positive for the APEC-associated virulence genes fimC, iucD, and papC. Out of 36 isolates, 7, 18, and 11 were positive, respectively, for three virulence genes (papC, fimC, and iucD), two virulence genes, and a single virulence gene. Although the detection of virulence genes was significantly higher in the internal organs, the air and feces were also positive. The antibiograms revealed that all the isolates (100%) were resistant to ampicillin and tetracycline; 97.2%, to chloramphenicol and erythromycin; 55.5%, to enrofloxacin; 50.0%, to norfloxacin and ciprofloxacin; 19.4%, to streptomycin; 11.1%, to colistin; and 8.33%, to gentamicin. Interestingly, all the isolates were multidrug-resistant (MDR). Spearman’s rank correlation coefficient analysis revealed the strongest significant correlation between norfloxacin and ciprofloxacin resistance. This is the first study in Bangladesh describing the molecular detection of APEC in layer farms. Isolated APEC can now be used for detailed genetic characterization and assessing the impact on public health.