In vivo typing of Escherichia coli obtained from laying chickens with the E. coli peritonitis syndrome

An insight into newly emerging avian pathogenic E. coli serogroups, biofilm formation, ESBLs and integron detection and in vivo pathogenicity in chicken

Bacterial diseases alone or in combination with other pathogens lead to significant economic losses in poultry globally including India. One of these diseases is avian colibacillosis which is caused by avian pathogenic Escherichia coli (APEC). The present study sought to isolate and characterize using in vivo and in vitro assays E. coli recovered from poultry diagnosed with colibacillosis. A total of 55 E. coli isolates were recovered from tissues of 55 broiler flocks affected with colibacillosis by using standard microbiological techniques, Vitek 2 Compact system and polymerase chain reaction. Out of 55 E. coli isolates, 50 (90.9 %) were characterized as APEC by multiplex PCR using a set of five virulence genes. On serotyping, 16 (32 %) APEC isolates were serogrouped as O26 followed by O98 (28 %), O120 (14 %), O11 (12 %), O135 (8 %) and O17 (4 %). The antimicrobial susceptibility testing of E. coli isolates revealed high antibiotic resistance against imipenem, tetracycline, ciprofloxacin and levofloxacin (96 % each). Interestingly all the 50 suspect APEC isolates were found to be multiple drug resistant (MDR) and the antimicrobial profiling indicated that these isolates could be classified into 38 resistotypes. Moreover, 10 (20 %) isolates were ESBL producers as per phenotypic characterization using combined disk diffusion test. On genotypic characterization of ESBLs, 31 (62 %) isolates were found positive for the blaTEM gene, whereas, 34 (68 %) isolates carried intI1 gene. On assessment for biofilm formation at 72 h incubation, thirteen (26 %) isolates were found to be strong biofilm producers, whereas nine (18 %) and twenty-eight (56 %) isolates were moderate and weak biofilm producers, respectively. Later, the LD50 of one MDR and strong biofilm producing isolate (APEC-P02) was calculated by in vivo oral challenge study in day old broiler chicks. The findings of this study demonstrated that LD50 of APEC-P02 isolate was 1.12 × 108 CFU/ml. The unexpectedly high prevalence of O11, O126, O98, O120 and O135 isolates suggest that there may be emergent serogroups causing colibacillosis in India. The current oral challenge study seems to be the first of its kind in India to estimate the LD50 of a multidrug resistant biofilm producer APEC isolate in day-old chicks.

Safety and efficacy of an inactivated tetravalent water-in-oil emulsion Escherichia coli vaccine against the E. coli peritonitis syndrome

RESEARCH HIGHLIGHTS

Protection against E. coli (EPS) challenge seems to be genotype-serotype-specific.Genotype B (O78:H4) gave (almost) full protection against genotypes B, F and H (all O78:H4).Genotype D (O11:H12) incited partial protection.Genotypes A (O1:H7) and C (O2:H1) were not protective.

Interference between Escherichia coli genotypes from the E. coli peritonitis syndrome given simultaneously to productive SPF White Leghorn hens by intratracheal inoculation

The purpose of the present study was to examine if potentiation of mortality occurred after simultaneous administration of several Escherichia coli genotypes, each capable of inducing the E. coli peritonitis syndrome, in comparison with single genotype application. Five groups of productive specified pathogen free White Leghorn hens were housed in isolators. Groups 1-4 consisted of 32 hens each, group 5 of 10 hens. At 32 weeks of age all groups were inoculated intratracheally. Groups 1 and 2 were inoculated with a mix of four E. coli genotypes and groups 3 and 4 with a mix of four other genotypes. Groups 1 and 3 were given 1 median lethal dose (LD50) of each genotype per hen and groups 2 and 4 had a dose of 0.1 LD50 per genotype per hen; group 5 was mock inoculated. The experiment ended one week after inoculations. In Group 5, no mortality occurred and gross lesions were absent at post-mortem examination. Mortality in groups 1 and 3 was 84% and 81%, respectively; in groups 2 and 4 59% and 66%, respectively. Although mortality in groups 1 and 3 exceeded the expected 50%, this could not be due to potentiation as cluster analysis of reisolates showed that in individual hens only one genotype was found, indicating interference between E. coli genotypes. In groups all four or only two genotypes were recovered, showing that not all genotypes will induce colibacillosis in all experimental groups. Therefore, broad protection can be best assessed by challenging with various single genotypes.RESEARCH HIGHLIGHTS All four or only two E. coli genotypes were found in groups of hens given mixes of four genotypes.In contrast, only one genotype was found in individual hens.E. coli genotypes interfere with each other in hens after given as a mix.Interference is likely based on a random process.Broad protection can best be assessed by challenging with single genotypes.

The synergy effect of matrine and berberine hydrochloride on treating colibacillosis caused by an avian highly pathogenic multidrug-resistant Escherichia coli

Infection by multidrug-resistant avian pathogenic Escherichia coli (APEC) in chickens always leads to the uselessness of antibiotics, highlighting the need for alternative antibacterial agents. Sophora flavescens and Coptis chinensis have been a classical combination used together in Traditional Chinese Medicine (TCM) formulas to treat diseases with similar symptoms to colibacillosis for an extended period, but the effect of their active ingredients' combination on APEC infection remains unstudied. The objective of this study was to explore the synergistic effect of matrine and berberine hydrochloride on colibacillosis caused by an isolated multidrug-resistant APEC. In this study, a highly pathogenic E. coli was isolated from the liver of a diseased chicken in a farm suspected of colibacillosis, and it was resistant to multiple antibiotics. The LD50 of the strain was approximately 3.759×108 CFU/mL. The strain harbored several antibiotic resistance genes and virulence genes. Matrine and berberine hydrochloride have synergistic antibacterial effect against the isolated strain in vitro. The combined use of matrine and berberine hydrochloride exhibited synergistic effects in the treatment of APEC infection by regulating the organ indices, improving the pathological situation, decreasing the bacterial load, and regulating the inflammatory factors to enhance the survival rate of chickens in vivo. These results provided a foundation for revealing the effective effects and possible mechanisms of matrine and berberine hydrochloride as potential antimicrobial agents on diseases caused by multidrug-resistant APEC in chickens.

Characterization of Escherichia coli pathogenicity and drug resistance in yolk peritonitis

Yolk Peritonitis can lead to a rapid decline in egg production, which seriously affects the health of laying hens and the profitability of chicken farms. Escherichia coli (E. coli) is the most common cause of yolk peritonitis in laying hens. In this study, bacterial samples were collected from the ovaries and fallopian tubes of laying hens with suspected yolk peritonitis from a laying farm in Jiangsu Province, and their pathogenicity and drug resistance were investigated. Initially, morphological and biochemical detection methods were employed to isolate and identify the pathogenic bacteria. The results showed that a total of 16 strains of E. coli were isolated from laying hens with yolk peritonitis. Subsequently, the drug resistance and pathogenicity of a randomly selected E. coli strain were analyzed and predicted by genome sequencing technology, and the drug resistance of E. coli was verified by drug sensitivity test and PCR. Finally, the virulence was verified by infection experiment in mice. The study revealed that the egg-yolk peritonitis in laying hens was caused by E. coli infection, and the genome sequencing analysis revealed that the bacteria had multidrug resistance and high virulence. The drug susceptibility testing indicates that E. coli exhibited resistance to aminoglycosides, β-lactam, macrolides, fluoroquinolones, and sulfonamides. In this study, resistance genes including KdpE, aadA5, APH(3 ")-ID, APH(6)-ID, and TEM-1 were identified, and their expression levels varied across different stages of bacterial growth. The results of virulence analysis indicated a mortality rate of 50% in mice infected with E. coli at a concentration of 2.985 × 107 CFU/mL. E. coli infection resulted in damage to various tissues and organs in mice, with the intestinal tissue structure being the most severely affected. This study provides a reference for the study of drug resistance mechanisms in E. coli and provides valuable insights into the selection of drugs for the treatment of vitelline peritonitis.

Phenotypic virulence characterization of avian pathogenic Escherichia coli (APEC) isolates from broiler breeders with colibacillosis in Mississippi

AIMS

In this study, we evaluated the phenotypic virulence characteristics of avian pathogenic Escherichia coli (APEC) isolates from broiler breeders with colibacillosis in Mississippi. Also, the relationship between phenotypic and genotypic virulence patterns was determined.

METHODS AND RESULTS

Twenty-eight APEC isolated from lesions of broiler breeders diagnosed with colibacillosis were used for embryo lethality assay and chick challenge study. The percentage of embryo mortality following embryo lethality assay and pathogenicity score following the chick challenge study were used to categorize the isolates based on virulence. Pearson correlation analysis was performed to determine the relationship between embryo mortality, chick pathogenicity, and the presence of virulence-associated genes in the isolates. Overall, 39.3% of the isolates were highly virulent and 3.5% were avirulent, following both assays. There existed a positive correlation between embryo mortality and chick pathogenicity (r = 0.73, P < .01), as well as percentage embryo mortality and pathogenicity score with the presence of some virulence genes.

CONCLUSIONS

Even though all the APEC were isolated from lesions of diseased breeders, the virulence potential varied from being avirulent to highly virulent. Further, we identified a positive relationship between phenotypic virulence and the frequency of virulence-associated genes.

A comprehensive study of colisepticaemia progression in layer chickens applying novel tools elucidates pathogenesis and transmission of Escherichia coli into eggs

Colisepticaemia caused by avian pathogenic Escherichia coli (APEC) is a challenging disease due to its high economic importance in poultry, dubious pathogenesis and potential link with zoonosis and food safety. The existing in vitro studies can't define hallmark traits of APEC isolates, suggesting a paradigm shift towards host response to understand pathogenesis. This study investigated the comprehensive pathological and microbial progression of colisepticaemia, and transmission of E. coli into eggs using novel tools. In total 48 hens were allocated into three groups and were inoculated intratracheally with ilux2-E. coli PA14/17480/5-/ovary (bioluminescent strain), E. coli PA14/17480/5-/ovary or phosphate buffered saline. Infection with both strains led to typical clinical signs and lesions of colibacillosis as in field outbreaks. Based on lung histopathology, colisepticaemia progression was divided into four disease stages as: stage I (1-3 days post infection (dpi)), stage II (6 dpi), stage III (9 dpi) and stage IV (16 dpi) that were histologically characterized by predominance of heterophils, mixed cells, pyogranuloma, and convalescence, respectively. As disease progressed, bacterial colonization in host organs also decreased, revealed by the quantification of bacterial bioluminescence, bacteriology, and quantitative immunohistochemistry. Furthermore, immunofluorescence, immunohistochemistry, and bacteria re-isolation showed that E. coli colonized the reproductive tract of infected hens and reached to egg yolk and albumen. In conclusion, the study provides novel insights into the pathogenesis of colisepticemia by characterizing microbial and pathological changes at different disease stages, and of the bacteria transmission to table eggs, which have serious consequences on poultry health and food safety.

Aerosol vaccination of chicken pullets with irradiated avian pathogenic Escherichia coli induces a local immunostimulatory effect

The present study investigated the expression of cytokines and cellular changes in chickens following vaccination with irradiated avian pathogenic Escherichia coli (APEC) and/or challenge. Four groups of 11-week-old pullets, each consisting of 16 birds were kept separately in isolators before they were sham inoculated (N), challenged only (C), vaccinated (V) or vaccinated and challenged (V+C). Vaccination was performed using irradiated APEC applied via aerosol. For challenge, the homologous strain was administered intratracheally. Birds were sacrificed on 3, 7, 14 and 21 days post challenge (dpc) to examine lesions, organ to body weight ratios and bacterial colonization. Lung and spleen were sampled for investigating gene expression of cytokines mediating inflammation by RT-qPCR and changes in the phenotype of subsets of mononuclear cells by flow cytometry. After re-stimulation of immune cells by co-cultivation with the pathogen, APEC-specific IFN-γ producing cells were determined. Challenged only birds showed more severe pathological and histopathological lesions, a higher probability of bacterial re-isolation and higher organ to body weight ratios compared to vaccinated and challenged birds. In the lung, an upregulation of IL-1β and IL-6 following vaccination and/or challenge at 3 dpc was observed, whereas in the spleen IL-1β was elevated. Changes were observed in macrophages and TCR-γδ⁺ cells within 7 dpc in spleen and lung of challenged birds. Furthermore, an increase of CD4⁺ cells in spleen and a rise of Bu-1⁺ cells in lung were present in vaccinated and challenged birds at 3 dpc. APEC re-stimulated lung and spleen mononuclear cells from only challenged pullets showed a significant increase of IFN-γ⁺CD8α⁺ and IFN-γ⁺TCR-γδ⁺ cells. Vaccinated and challenged chickens responded with a significant increase of IFN-γ⁺CD8α⁺ T cells in the lung and IFN-γ⁺TCR-γδ⁺ cells in the spleen. Re-stimulation of lung mononuclear cells from vaccinated birds resulted in a significant increase of both IFN-γ⁺CD8α⁺ and IFN-γ⁺TCR-γδ⁺ cells. In conclusion, vaccination with irradiated APEC caused enhanced pro-inflammatory response as well as the production of APEC-specific IFN-γ-producing γδ and CD8α T cells, which underlines the immunostimulatory effect of the vaccine in the lung. Hence, our study provides insights into the underlying immune mechanisms that account for the defense against APEC.

Longitudinal Study on Extended-Spectrum Beta-Lactamase-E. coli in Sentinel Mallard Ducks in an Important Baltic Stop-Over Site for Migratory Ducks in Germany

Antimicrobial resistance (AMR) is a serious global health threat with extended-spectrum beta-lactamase (ESBL)-producing Enterobacterales as the most critical ones. Studies on AMR in wild birds imply a possible dissemination function and indicate their potential role as sentinel animals. This study aimed to gain a deeper insight into the AMR burden of wild waterfowl by sampling semi-wild mallard ducks used as sentinels and to identify if AMR bacteria could be recommended to be added to the pathogens of public health risks to be screened for. In total, 376 cloacal and pooled fecal samples were collected from the sentinel plant over a period of two years. Samples were screened for ESBL-carrying E. coli and isolates found further analyzed using antimicrobial susceptibility testing and whole-genome sequencing. Over the sampling period, 4.26% (16/376) of the samples were positive for ESBL-producing E. coli. BlaCTX-M-1 and blaCTX-M-32 were the most abundant CTX-M types. Although none of the top global sequence types (ST) could be detected, poultry-derived ST115 and non-poultry-related STs were found and could be followed over time. The current study revealed low cases of ESBL-producing E. coli in semi-wild mallard ducks, which proves the suitability of sentinel surveillance for AMR detection in water-associated wildlife.

Assessment of the best inoculation route for virulotyping Enterococcus cecorum strains in a chicken embryo lethality assay

AbstractThe study aim was to determine the best inoculation route for virulotyping Enterococcus cecorum in a chicken embryo lethality assay (ELA). Twenty-eight genetically different strains were used. Fourteen strains were isolated from cloaca swabs of broiler reproduction chickens (cloaca strains) and fourteen strains from broilers with E. cecorum lesions (lesion strains). In all ELAs, 12 days incubated embryonated broiler eggs were inoculated with approximately 100 colony forming units of E. cecorum/egg. Twenty embryos per inoculation route and strain were used in each of three experiments. In Experiment 1, four cloaca and four lesion strains were inoculated via various routes, i.e. albumen, amniotic cavity, allantoic cavity, chorioallantoic membrane, intravenous or air chamber. The albumen inoculation route showed low mortality with cloaca strains, high mortality with lesion strains and the largest difference in mortality between these groups of strains (≥60%). This route was therefore used in subsequent experiments. In Experiment 2, the same strains were used to test reproducibility, which proved to be generally good. All 28 strains were thereafter used in Experiment 3. In the three experiments, mortality by cloaca and lesion strains ranged from 0 to 25% and from 15 to 100%, respectively. Recovery rates, assessed in all experiments after albumen inoculation, were significantly lower from eggs inoculated with cloaca strains, compared to lesion strains inoculated eggs (P <0.05). However, the bacterial load of eggs with positive recovery was similar in both groups. In conclusion: the albumen inoculation route appeared to be the best to virulotype E. cecorum strains.