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E. coli mastitis is a major production disease in dairy cattle and requires alternative treatments to antibiotics. In this context, phages are of growing interest, but their host specificity remains a challenge in therapy. This study aimed to characterize eight newly isolated phages for the control of E. coli mastitis, to assess their efficacy in milk and to investigate their specificity. Physicochemical characterization of the phages was performed, followed by in vitro stability and lytic activity assays in raw and heat-treated milks. Genome sequencing of phages and bacteria was performed to investigate phage attachment. Phage stability was maintained across physiological pH and temperature ranges, as well as in raw milk. Phage lytic activity demonstrated bacterial decreases below detection level, but regrowth occurred in raw milk after 5 h of incubation with 3/8 phages. A narrow host range was linked to the diversity of the bacterial collection and to the presence of two receptor-binding proteins among Tevenvirinae . Indeed, structural analysis of the proteins revealed a variable region in the long tail fiber and a conserved short tail fiber. In conclusion, phage specificity was mainly associated with the long tail fiber and milk components didn’t hinder the efficacy of phages to control bovine mastitis, although resistance should be investigated.

The objective of this study was to evaluate the longitudinal effect of enrofloxacin or tulathromycin use in calves at high risk of bovine respiratory disease (BRD) on antimicrobial resistance genes and mutation in quinolone resistance-determining regions (QRDR) in fecal E. coli . Calves at high risk of developing BRD were randomly enrolled in one of three groups receiving: (1) enrofloxacin (ENR; n = 22); (2) tulathromycin (TUL; n = 24); or (3) no treatment (CTL; n = 21). Fecal samples were collected at enrollment and at 7, 28, and 56 days after beginning treatment, cultured for Escherichia coli (EC) and DNA extracted. Isolates were screened for cephalosporin, quinolone and tetracycline resistance genes using PCR. QRDR screening was conducted using Sanger sequencing. The only resistance genes detected were aac(6′)Ib-cr (n = 13), bla -CTX-M (n = 51), bla -TEM (n = 117), tet A (n = 142) and tet B (n = 101). A significantly higher detection of gyr A mutated at position 248 at time points 7 (OR = 11.5; P value = 0.03) and 28 (OR = 9.0; P value = 0.05) was observed in the ENR group when compared to calves in the control group. Our findings support a better understanding of the potential impacts from the use of enrofloxacin in calves on the selection and persistence of resistance.

Avian pathogenic Escherichia coli (APEC) can cause colibacillosis in poultry, characterised by localised or systemic infections. Colibacillosis is considered one of the leading causes of economic losses in the poultry industry due to reduced performance, increased mortality, treatment costs and carcass condemnations. A live attenuated Escherichia coli O78 aroA gene mutant is widely used to prevent disease. However, no effective strategies to differentiate the vaccine strain from field strains are available, hampering follow-up of vaccination campaigns. In the current study, we report a PCR-based method to simultaneously detect the vaccine strain by targeting the vaccine-specific mutation in the aroA gene, as well as the wild type E . coli strains by targeting the xanQ gene. The specificity of this PCR was evaluated using 123 E . coli isolates, form which 5 WT aroA auxotrophic strains (WT strains with a natural aroA deficiency), as well as 7 non- Escherichia isolates. The PCR showed 100% sensitivity of the xanQ primers for E . coli detection and 100% sensitivity of the Δ aroA primers for the vaccine strain. In order to allow quantification of the vaccine strain in complex samples containing many different E . coli strains and other related organisms, such as chicken faeces, a probe-based duplex qPCR was developed. The limit of detection (LOD) of this duplex qPCR method was 8.4*10 3 copies/g faeces. The specificity of the duplex qPCR was confirmed by determining both the vaccine strain levels, and the total E . coli load in intestinal digesta from both vaccinated and non-vaccinated birds. E . coli could be detected in both vaccinated and non-vaccinated birds. The duplex qPCR was specific for the vaccine strain as this strain was detected in all vaccinated birds, whereas no signal was detected in non-vaccinated birds. The duplex qPCR is helpful in monitoring colonization and shedding of the vaccine strain.

Avian pathogenic Escherichia coli (APEC) strains cause severe respiratory and systemic disease, threatening food security and avian welfare worldwide. Intensification of poultry production and the quick expansion of free-range production systems will increase the incidence of colibacillosis through greater exposure of birds to pathogens and stress. Therapy is mainly based on antibiotherapy and current vaccines have poor efficacy. Serotyping remains the most frequently used diagnostic method, only allowing the identification of a limited number of APEC strains. Several studies have demonstrated that the most common virulence factors studied in APEC are rarely all present in the same isolate, showing that APEC strains constitute a heterogeneous group. Different isolates may harbor different associations of virulence factors, each one able to induce colibacillosis. Despite its economical relevance, pathogenesis of colibacillosis is poorly understood. Our knowledge on the host response to APEC is based in very descriptive studies, mostly restricted to bacteriological and histopathological analysis of infected organs, mostly lungs. Furthermore, only a small number of APEC isolates has been used in experimental studies. In the present review we discuss current knowledge on APEC diversity and virulence, including host-response to infection and the associated inflammatory response with a focus on pulmonary colibacillosis.

A randomized control trial on verocytotoxigenic Escherichia coli (VTEC)-infected farms found evidence that: (1) keeping animals in the same group; (2) maintaining dry bedding; (3) preventing direct contact with neighbouring cattle; and (4) maintaining a closed herd, were associated with a reduced risk of infection in youngstock aged 3—18 months. This study evaluated these interventions using a cost-effectiveness framework for UK dairy farms. Keeping animals in the same group was considered to have negligible cost and was feasible for herds containing over 77 dairy cows. Assuming equal efficacy of the remaining interventions, preventing direct contact between neighbouring cattle is most cost-effective with a median annual cost of £2.76 per cow. This compares to £4.18 for maintaining dry bedding and £17.42 for maintaining a closed herd using quarantine procedures. Further model validation and exploration of other potential benefits are required before making policy decisions on VTEC control.

Escherichia coli ST58 has recently emerged as a globally disseminated uropathogen that often progresses to sepsis. Unlike most pandemic extra-intestinal pathogenic E. coli (ExPEC), which belong to pathogenic phylogroup B2, ST58 belongs to the environmental/commensal phylogroup B1. Here, we present a pan-genomic analysis of a global collection of 752 ST58 isolates from diverse sources. We identify a large ST58 sub-lineage characterized by near ubiquitous carriage of ColV plasmids, which carry genes encoding virulence factors, and by a distinct accessory genome including genes typical of the Yersiniabactin High Pathogenicity Island. This sub-lineage includes three-quarters of all ExPEC sequences in our study and has a broad host range, although poultry and porcine sources predominate. By contrast, strains isolated from cattle often lack ColV plasmids. Our data indicate that ColV plasmid acquisition contributed to the divergence of the major ST58 sub-lineage, and different sub-lineages inhabit poultry, swine and cattle. Escherichia coli ST58 has recently emerged as a globally disseminated extra-intestinal pathogen. Here, Reid et al. present a pan-genomic analysis of a global collection of ST58 isolates from animal and human sources, showing that ColV plasmid acquisition likely contributed to the divergence of a major sub-lineage that has a broad host range but is more commonly found in poultry and swine.

This study aimed to characterize virulence and antibiotic resistance genes in multidrug-resistant (MDR) and extensively drug-resistant (XDR) Escherichia coli and Klebsiella pneumoniae isolated from cases of subclinical mastitis (SCM) in buffaloes. A cross-sectional study was conducted on 1540 quarter milk samples collected from 385 buffaloes. Milk samples were screened using the California Mastitis Test and Modified Whiteside Test. Positive samples underwent bacterial culture, biochemical tests, biofilm detection and molecular analysis for pathogen identification and detection of virulence, resistance, and extended-spectrum beta-lactamase (ESBL) genes. The prevalence of SCM was 67.9% (1046/1540) at the quarter level and 80.8% (311/385) at the animal level. E. coli was identified in 9.5% (146/1540) of the samples, while K. pneumoniae was detected in 9.09% (140/1540). Virulence genes, such as stx1 (27.4%), and resistance genes, including aac(3) -iv (77.4%) and tetA (76.7%), exhibited higher prevalence. Additionally, β -lactamase genes, notably bla TEM (67.1%), and ESBL genes, such as bla CTX-M1 , were detected. Biofilm formation was detected in 83.6% (122/146) of E. coli isolates and 75.7% (106/140) of K. pneumoniae isolates. Antimicrobial susceptibility testing revealed significant resistance to ampicillin, amoxicillin-clavulanic acid, and aminoglycosides. MDR was observed in 31.5% of E. coli and 39.3% of K. pneumoniae isolates, with XDR rates of 8.9% and 12.9%, respectively. These findings underscore the alarming spread of resistant pathogens in SCM-affected buffaloes, emphasizing the urgent need for ongoing surveillance and targeted intervention strategies.

Post-weaning diarrhea (PWD) due to Escherichia coli in pigs is a significant enteric disease in the U.S. Contemporary data about the main virulence factors, colony morphology, and distribution of virotypes of isolates associated with post-weaning colibacillosis (PWC) is essential information for swine veterinarians, producers, and stakeholders. This study reports the rate of PWC/PWD, frequency of detection of fimbrial types, pathotypes, toxins, virotypes, morphological characteristics, and temporal analysis of the most prevalent virotype of enterotoxigenic E. coli recovered from cases of PWD in pigs in the United States. There was a significant increase in PWC cases submitted to the diagnostic laboratory in 2013, 2014, and 2021, respectively. A greater frequency of detection of F18 fimbrial adhesin (69.87%) was observed compared to F4 (26.19%), F5 (0.25%), F41 (0.13%), AIDA (0.10%), and multiple adhesins (3.46%), respectively. Hybrid ETEC:STEC pathotype was greater than ETEC and STEC, and STb toxin was present in 93.33% of the detected isolates. The most frequently observed virotype was F18:LT:STa:STb:Stx2e (27.71%). Smooth:mucoid colony morphology was associated with a greater likelihood of PWC (0.758, 0.968, and 0.993) compared to smooth, intermediate, and rough, respectively. The frequency of the F18:LT:STa:STb:Stx2e virotype increased across all U.S. states from 2016 to 2023, greatest in the northwest and east of Iowa and northeast Indiana in 2022 and Iowa in 2023. The virulence factors and morphology of enterotoxigenic E. coli associated with PWC across different states in the U.S. from 2010 to 2023 were diverse; nevertheless, the virotype F18:LT:STa:STb:Stx2e predominated and increased in frequency during this time period.

Background Avian pathogenic Escherichia coli (APEC) is the principle cause of colibacillosis affecting poultry. The main challenge to the poultry industry is antimicrobial resistance and the emergence of multidrug resistant bacteria that threaten the safety of the food chain. Risk factors associated with emergence of antimicrobial resistance among avian pathogenic E. coli were correlated with the inappropriate use of antimicrobials along with inadequate hygienic practices, which encourages the selection pressure of antimicrobial resistant APEC. The aim of this study was to isolate, identify, serogroup and genotype APEC from broilers, assess their antibiotic resistance profile, expressed genes and the associated risk factors. Results APEC was isolated from the visceral organs of sick chickens with a prevalence of 53.4%. The most prevalent serotypes were O1, O2, O25 and O78, in percentage of 14.8, 12.6, 4.4 and 23.7%, respectively. Virulence Associated Genes; SitA, iss, iucD, iucC, astA, tsh cvi and irp2 were detected in rate of 97.4, 93.3, 75, 74, 71, 46.5, 39 and 34%, respectively and 186 (69.2%) isolates possess >  5–10 genes. The highest resistance was found against sulphamethoxazole-trimethoprim, florfenicol, amoxicillin, doxycycline and spectinomycin in percentage; 95.5, 93.7, 93.3, 92.2 and 92.2%, respectively. Sixty-eight percent of APEC isolates were found to have at least 5 out of 8 antimicrobial resistant genes. The most predominant genes were Int1 97%, tetA 78.4%, bla TEM 72.9%, Sul1 72.4%, Sul2 70.2%. Two risk factors were found to be associated with the presence of multi-drug resistant APEC in broiler chickens, with a P value ≤0.05; the use of ground water as source of drinking water and farms located in proximity to other farms. Conclusions This study characterized the VAGs of avian pathogenic E. coli and establish their antimicrobial resistance patterns. The widespread of antimicrobial resistance of APEC isolates and detection of ARGs highlighted the need to monitor the spread of ARGs in poultry farms and the environment in Jordan. Use of ground water and closely located farms were significant risk factors associated with the presence of MDR APEC in broiler chickens in Jordan.

Extraintestinal Pathogenic Escherichia coli (ExPEC) pose a significant threat to human and animal health. However, the diversity and antibiotic resistance of animal ExPEC, and their connection to human infections, remain largely unexplored. The study performs large-scale genome sequencing and antibiotic resistance testing of 499 swine-derived ExPEC isolates from China. Results show swine ExPEC are phylogenetically diverse, with over 80% belonging to phylogroups B1 and A. Importantly, 15 swine ExPEC isolates exhibit genetic relatedness to human-origin E. coli strains. Additionally, 49 strains harbor toxins typical of enteric E. coli pathotypes, implying hybrid pathotypes. Notably, 97% of the total strains are multidrug resistant, including resistance to critical human drugs like third- and fourth-generation cephalosporins. Correspondingly, genomic analysis unveils prevalent antibiotic resistance genes (ARGs), often associated with co-transfer mechanisms. Furthermore, analysis of 20 complete genomes illuminates the transmission pathways of ARGs within swine ExPEC and to human pathogens. For example, the transmission of plasmids co-harboring fosA3 , bla CTX-M-14 , and mcr-1 genes between swine ExPEC and human-origin Salmonella enterica is observed. These findings underscore the importance of monitoring and controlling ExPEC infections in animals, as they can serve as a reservoir of ARGs with the potential to affect human health or even be the origin of pathogens infecting humans. Extraintestinal pathogenic E. coli (ExPEC) is a significant cause of human and animal disease. Here, the authors compile a collection of 499 ExPEC samples from swine in China and characterise their phylogenetic population structure and antibiotic resistance profiles.