Evolutionary genomic analyses of canine E. coli infections identify a relic capsular locus associated with resistance to multiple classes of antimicrobials.

Infections caused by antimicrobial-resistant Escherichia coli are the leading cause of death attributed to antimicrobial resistance (AMR) worldwide, and the known AMR mechanisms involve a range of functional proteins. Here, we employed a pan-genome wide association study (GWAS) approach on over 1,000 E. coli isolates from sick dogs collected across the US and Canada and identified a strong statistical association (empirical P < 0.01) of AMR, involving a range of antibiotics to a group 1 capsular (CPS) gene cluster. This cluster included genes under relaxed selection pressure, had several loci missing, and had pseudogenes for other key loci. Furthermore, this cluster is widespread in E. coli and Klebsiella clinical isolates across multiple host species. Earlier studies demonstrated that the octameric CPS polysaccharide export protein Wza can transmit macrolide antibiotics into the E. coli periplasm. We suggest that the CPS in question, and its highly divergent Wza, functions as an antibiotic trap, preventing antimicrobial penetration. We also highlight the high diversity of lineages circulating in dogs across all regions studied, the overlap with human lineages, and regional prevalence of resistance to multiple antimicrobial classes. IMPORTANCE: Much of the human genomic epidemiology data available for E. coli mechanism discovery studies has been heavily biased toward shiga-toxin producing strains from humans and livestock. E. coli occupies many niches and produces a wide variety of other significant pathotypes, including some implicated in chronic disease. We hypothesized that since dogs tend to share similar strains with their owners and are treated with similar antibiotics, their pathogenic isolates will harbor unexplored AMR mechanisms of importance to humans as well as animals. By comparing over 1,000 genomes with in vitro antimicrobial susceptibility data from sick dogs across the US and Canada, we identified a strong multidrug resistance association with an operon that appears to have once conferred a type 1 capsule production system.

A mutant fitness compendium in Bifidobacteria reveals molecular determinants of colonization and host-microbe interactions.

Bifidobacteria commonly represent a dominant constituent of human gut microbiomes during infancy, influencing nutrition, immune development, and resistance to infection. Despite interest as a probiotic therapy, predicting the nutritional requirements and health-promoting effects of Bifidobacteria is challenging due to major knowledge gaps. To overcome these deficiencies, we used large-scale genetics to create a compendium of mutant fitness in Bifidobacterium breve (Bb). We generated a high density, randomly barcoded transposon insertion pool in Bb, and used this pool to determine Bb fitness requirements during colonization of germ-free mice and chickens with multiple diets and in response to hundreds of in vitro perturbations. To enable mechanistic investigation, we constructed an ordered collection of insertion strains covering 1462 genes. We leveraged these tools to improve models of metabolic pathways, reveal unexpected host- and diet-specific requirements for colonization, and connect the production of immunomodulatory molecules to growth benefits. These resources will greatly reduce the barrier to future investigations of this important beneficial microbe.

Screening of Human Gut Bacterial Culture Collection Identifies Species That Biotransform Quercetin into Metabolites with Anticancer Properties.

We previously demonstrated that flavonoid metabolites inhibit cancer cell proliferation through both CDK-dependent and -independent mechanisms. The existing evidence suggests that gut microbiota is capable of flavonoid biotransformation to generate bioactive metabolites including 2,4,6-trihydroxybenzoic acid (2,4,6-THBA), 3,4-dihydroxybenzoic acid (3,4-DHBA), 3,4,5-trihyroxybenzoic acid (3,4,5-THBA) and 3,4-dihydroxyphenylacetic acid (DOPAC). In this study, we screened 94 human gut bacterial species for their ability to biotransform flavonoid quercetin into different metabolites. We demonstrated that five of these species were able to degrade quercetin including Bacillus glycinifermentans, Flavonifractor plautii, Bacteroides eggerthii, Olsenella scatoligenes and Eubacterium eligens. Additional studies showed that B. glycinifermentans could generate 2,4,6-THBA and 3,4-DHBA from quercetin while F. plautii generates DOPAC. In addition to the differences in the metabolites produced, we also observed that the kinetics of quercetin degradation was different between B. glycinifermentans and F. plautii, suggesting that the pathways of degradation are likely different between these strains. Similar to the antiproliferative effects of 2,4,6-THBA and 3,4-DHBA demonstrated previously, DOPAC also inhibited colony formation ex vivo in the HCT-116 colon cancer cell line. Consistent with this, the bacterial culture supernatant of F. plautii also inhibited colony formation in this cell line. Thus, as F. plautii and B. glycinifermentans generate metabolites possessing antiproliferative activity, we suggest that these strains have the potential to be developed into probiotics to improve human gut health.

Genomic analysis of Indian strains of Salmonella enterica subsp. enterica serovar Typhi indicates novel genetic repertoire for pathogenicity and adaptations.

In the era of emerging antibiotic resistance, Salmonella enterica subsp. enterica serovar Typhi the causative agent of typhoid, is a threat for healthcare systems in developing countries especially India, where the disease is highly endemic. Genetic diversity among different strains may be the cause of variable severity of disease in different regions of the world. To explore this genetic diversity, genome annotation by rapid annotation using subsystem technology (RAST) was carried out for genomes of four Salmonella Typhi strains from two distinct areas available in the public domain. Two clinical strains were from India (P-stx-12 and E02-1180) and the other two strains considered as reference strains were from the endemic regions of Papua New Guinea (UJ308A and UJ816A). We report that Indian clinical strains possess several similar genes responsible for virulence and pathogenicity as those present in the reference strains. Interestingly, Indian clinical strains also possess 34 additional potential virulence genes that are absent in the reference strains, suggesting the more dreadful nature of Indian clinical strains as compared to those causing endemic typhoid. Indian strains contained genes coding for; Colicin V and bacteriocin production; multidrug resistance efflux pumps; ABC transporters; Type III and Type VI secretion systems, siderophore aerobactin, pathogenicity islands and Vi polysaccharide biosynthesis and transport. These unique genes are also reported in the genomes of other six clinical strains of India analyzed through RAST and IslandViewer 4 for validation purpose. This study highlights the presence of potential genes as molecular targets to overcome the future endemic outbreaks in India.

Warburg micro syndrome in siblings from India.

Warburg syndrome is a rare disorder characterized by microcephaly, microcornea, congenital cataract, developmental delay, and hypogonadism. Here, we report two siblings from India who presented with developmental delay, microcornea, microphthalmia, and bilateral congenital cataracts, born to the third-degree consanguineously married couple. Both children had hypoplasia of corpus callosum. In this report, we aim to highlight and compare clinical features of these two cases with previously reported cases.