Poultry and livestock are the most important reservoirs for pathogenic Escherichia coli and use of antimicrobials in animal farming is considered the most important factor promoting the emergence, selection and dissemination of antimicrobial-resistant microorganisms. The aim of our study was to investigate antimicrobial resistance in E. coli isolated from food animals in Jiangsu, China. The disc diffusion method was used to determine susceptibility to 18 antimicrobial agents in 862 clinical isolates collected from chickens, ducks, pigs, and cows between 2004 and 2012. Overall, 94% of the isolates showed resistance to at least one drug with 83% being resistance to at least three different classes of antimicrobials. The isolates from the different species were most commonly resistant to tetracycline, nalidixic acid, sulfamethoxazole, trimethoprim/sulfamethoxazole and ampicillin, and showed increasing resistance to amikacin, aztreonam, ceftazidime, cefotaxime, chloramphenicol, ciprofloxacin. They were least resistant to amoxicillin/clavulanic acid (3.4%) and ertapenem (0.2%). MDR was most common in isolates from ducks (44/44, 100%), followed by chickens (568/644, 88.2%), pigs (93/113, 82.3%) and cows (13/61, 21.3%). Our finding that clinical E. coli isolates from poultry and livestock are commonly resistant to multiple antibiotics should alert public health and veterinary authorities to limit and rationalize antimicrobial use in China.

Avian pathogenic Escherichia coli (APEC) causes colibacillosis in avian species, and new investigations have implicated APEC as a possible foodborne zoonotic pathogen. This review analyzes APEC's pathogenic and virulence features, assesses the zoonotic potential, provides an update on antibiotic resistance and vaccine research efforts, and outlines alternate management approaches. Aside from established virulence factors, various additional components, including 2-component systems (TCS), adhesins, secretion systems (SS), invasions, iron acquisition systems, quorum sensing systems (QS), transcriptional regulators (TR), toxins, and genes linked with metabolism, contribute to APEC pathogenesis. APEC may spread to diverse species of birds in all business sectors and can infect birds of varying ages. However, younger birds experience more severe sickness than mature ones, probably due to their developing immune systems, and stress factors such as vaccination, Mycoplasma Infections, poor housing circumstances, respiratory viruses, and other risk factors for secondary infections can all make APEC both primary and secondary pathogens. Understanding these factors will help in generating new and effective treatments. Moreover, APEC O145 was the most prevalent serotype recently reported in all of China. Thus, the APEC's zoonotic potential should not be underrated. Furthermore, it has already been noted that APEC is resistant to almost all antibiotic classes, including carbapenems. A robust vaccine capable of protecting against multiple APEC serotypes is urgently needed. Alternative medications, particularly virulence inhibitors, can provide a special method with a decreased likelihood of acquiring resistance.

Understanding the molecular parameters that regulate cross-species transmission and host adaptation of potential pathogens is crucial to control emerging infectious disease. Although microbial pathotype diversity is conventionally associated with gene gain or loss, the role of pathoadaptive nonsynonymous single-nucleotide polymorphisms (nsSNPs) has not been systematically evaluated. Here, our genome-wide analysis of core genes within Salmonella enterica serovar Typhimurium genomes reveals a high degree of allelic variation in surface-exposed molecules, including adhesins that promote host colonization. Subsequent multinomial logistic regression, MultiPhen and Random Forest analyses of known/suspected adhesins from 580 independent Typhimurium isolates identifies distinct host-specific nsSNP signatures. Moreover, population and functional analyses of host-associated nsSNPs for FimH, the type 1 fimbrial adhesin, highlights the role of key allelic residues in host-specific adherence in vitro. Together, our data provide the first concrete evidence that functional differences between allelic variants of bacterial proteins likely contribute to pathoadaption to diverse hosts.