Avian pathogenic Escherichia coli (APEC) causes colibacillosis in avian species, and recent reports have suggested APEC as a potential foodborne zoonotic pathogen. Herein, we discuss the virulence and pathogenesis factors of APEC, review the zoonotic potential, provide the current status of antibiotic resistance and progress in vaccine development, and summarize the alternative control measures being investigated. In addition to the known virulence factors, several other factors including quorum sensing system, secretion systems, two-component systems, transcriptional regulators, and genes associated with metabolism also contribute to APEC pathogenesis. The clear understanding of these factors will help in developing new effective treatments. The APEC isolates (particularly belonging to ST95 and ST131 or O1, O2, and O18) have genetic similarities and commonalities in virulence genes with human uropathogenic E. coli (UPEC) and neonatal meningitis E. coli (NMEC) and abilities to cause urinary tract infections and meningitis in humans. Therefore, the zoonotic potential of APEC cannot be undervalued. APEC resistance to almost all classes of antibiotics, including carbapenems, has been already reported. There is a need for an effective APEC vaccine that can provide protection against diverse APEC serotypes. Alternative therapies, especially the virulence inhibitors, can provide a novel solution with less likelihood of developing resistance.
Avian pathogenic E. coli (APEC), an extra-intestinal pathogenic E. coli (ExPEC), causes colibacillosis in chickens and is reportedly associated with urinary tract infections and meningitis in humans. Development of resistance is a major limitation of current ExPEC antibiotic therapy. New antibacterials that can circumvent resistance problem such as antimicrobial peptides (AMPs) are critically needed. Here, we evaluated the efficacy of Lactobacillus rhamnosus GG (LGG) derived peptides against APEC and uncovered their potential antibacterial targets. Three peptides (NPSRQERR: P1; PDENK: P2, and VHTAPK: P3) displayed inhibitory activity against APEC. These peptides were effective against APEC in biofilm and chicken macrophage HD11 cells. Treatment with these peptides reduced the cecum colonization (0.5 to 1.3 logs) of APEC in chickens. Microbiota analysis revealed two peptides (P1 and P2) decreased Enterobacteriaceae abundance with minimal impact on overall cecal microbiota of chickens. Bacterial cytological profiling showed peptides disrupt APEC membrane either by causing membrane shedding, rupturing or flaccidity. Further, gene expression analysis revealed that peptides downregulated the expression of omp C (>13.0 folds), omp F (>11.3 folds) and mla A (>4.9 folds) genes responsible for maintenance of outer membrane (OM) lipid asymmetry. Consistently, immunoblot analysis also showed decreased levels of OmpC and MlaA proteins in APEC treated with peptides. Alanine scanning studies revealed residues crucial (P1: N, E, R and P; P2: D and E; P3: T, P, and K) for their activity. Overall, our study identified peptides with new antibacterial target that can be developed to control APEC infections in chickens, thereby curtailing poultry-originated human ExPEC infections. Importance APEC is a subgroup of ExPEC and considered as a foodborne zoonotic pathogen transmitted through consumption of contaminated poultry products. APEC shares genetic similarities with human ExPECs, including uropathogenic E. coli (UPEC) and neonatal meningitis E. coli (NMEC). Our study identified LGG-derived peptides (P1: NPSRQERR, P2: PDENK, and P3: VHTAPK) effective in reducing APEC infection in chickens. Antimicrobial peptides (AMPs) are regarded as ideal candidates for antibacterial development because of their low propensity for resistance development and ability to kill resistant bacteria. Mechanistic studies showed peptides disrupt APEC membrane by affecting MlaA-OmpC/F system responsible for maintenance of OM lipid asymmetry, a promising new druggable target to overcome resistance problem in Gram-negative bacteria. Altogether, these peptides can provide a valuable approach for development of novel anti-ExPEC therapies, including APEC, human ExPECs and other related Gram-negative pathogens. Further, effective control of APEC infections in chickens can curb poultry-originated ExPEC infections in humans.
Gene frequencies for 23 genetic biochemical markers have been determined in one sample of Sherpas and two smaller samples, one of Tibetans living in Nepal and one of’mixed’ Nepalese. Sherpas presented a high GPT1 (0.71) and an appreciable incidence of HbE (about 2%). Variant phenotypes for PGM1; PHI, PepB and C were observed.
Pseudomonas leaf spot (PLS) disease in peppers caused by Pseudomonas syringae pv. syringae (Pss), is an emerging seed-borne phytopathogen. Pss infection can severely reduce the marketable yield of peppers in favorable environmental conditions and cause significant economic losses. The intensive use of copper-sulfate and streptomycin-sulfate to control PLS and other bacterial diseases is associated with antimicrobial-resistant-Pss strains, making these control methods less effective. Hence, there is an urgent need to develop novel antimicrobials effective against Pss in peppers. Several studies, including those done in our laboratory, have shown that small molecule (SM) antimicrobials are ideal candidates as they can be effective against multi-drug resistant bacteria. Therefore, our study aims to identify novel SM growth inhibitors of Pss, assess their safety, and evaluate their efficacy on Pss-infected pepper seeds and seedlings. Using high throughput screening we identified 10 SMs (PC1 to PC10) that inhibited the growth of Pss strains at 200 µM or lower concentrations. These SMs were effective against both copper- and streptomycin-resistant as well as biofilm-embedded Pss. These SMs were effective against other plant pathogens (n=22) at low concentrations (<200 µM) and had no impact on beneficial phytobacteria (n=12). Furthermore, these SMs showed better or equivalent antimicrobial activity against Pss in infested pepper seeds and inoculated seedlings, compared to copper-sulfate (200 µM) and streptomycin (200 µg/ml). Additionally, none of the SMs were toxic to pepper tissues (seeds, seedlings, or fruits), human Caco-2 cells, and pollinator honeybees at 200 µM. Overall, the SMs identified in this study are promising alternative antimicrobials for managing PLS in pepper production.
Understanding the functional role of bacterial genes in the persistent of Salmonella in plant organs can facilitate the development of agricultural practices to mitigate food safety risks associated with the consumption of fresh produce contaminated with Salmonella. Our study showed that Salmonella enterica subsp. enterica serotype Typhimurium (strain MDD14) persisted less in inoculated tomato plants than other S. Typhimurium strains tested (JSG210, JSG626, JSG634, JSG637, JSG3444, and EV030415; P<0.01). In vitro assays performed in limited-nutrient conditions (growth rate, biofilm production and motility) were inconclusive in explaining the in planta phenotype observed with MDD14. Whole genome sequencing combined with non-synonymous single nucleotide variations (nsSNVs) analysis was performed to identify genomic differences between MDD14 and the other S. Typhimurium strains. The genome of MDD14 contained a truncated version (123 bp N-terminal) of yicC and a mutated version of rpoS (two non-synonymous substitutions; G66E and R82C), which are two stress induced proteins involved in iron acquisition, environmental sensing and cell envelop integrity. The rpoS and yicC genes were deleted in S. Typhimurium JSG210 with the Lambda Red recombining system. Both mutants had limited persistence in tomato plant organs, similar to MDD14. In conclusion, we demonstrated that YicC and RpoS are involved in the persistence of Salmonella in tomato plants in greenhouse conditions, and thus, could represent potential targets to mitigate persistence of Salmonella spp. in planta.
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