Prevalence of serogroups, virulence genotypes, antimicrobial resistance, and phylogenetic background of avian pathogenic Escherichia coli in south of China

Effects of pomegranate (Punica granatum L.) peel on the growth performance and intestinal microbiota of broilers challenged with Escherichia coli

The effects of pomegranate peel on the growth performance, intestinal morphology, and the cecal microbial community were investigated in broilers challenged with avian pathogenic Escherichia coli (APEC) O78. A total of 240 one-day-old chicks (120 males and 120 females) were randomly and evenly allotted into 4 treatment groups (each with 6 biological replicates each of 10 chicks), i.e., negative control (NC), positive control (PC), and 2 experimental groups treated with 0.2% fermented pomegranate peel (FP) and 0.2% unfermented pomegranate peel (UFP), respectively, with PC, FP, and UFP groups challenged with APEC O78 (5 × 108 CFU) on day 14. Results showed that the challenge of APEC O78 decreased the body weight (BW) and average daily gain (ADG) of broilers from 1 to 28 d (P < 0.01). These broilers exhibited more pathological conditions in the heart and liver and higher mortality rates in 28 d compared to the NC group. Diet supplemented with pomegranate peel (either fermented or unfermented) significantly increased BW, ADG, and the villus height/crypt depth ratio (VCR) of small intestine in 28 d compared to the NC group (P < 0.05). Results of the taxonomic structure of the gut microbiota showed that compared to the NC group, the APEC challenge significantly decreased the relative abundance of Bacteroidetes and increased the relative abundance of Firmicutes (P < 0.01). Compared to the PC group, the relative abundance of Ruminococcus_torques_group in FP group was increased, while the relative abundance of Alistipes was decreased. In summary, our study showed that the dietary supplementation of pomegranate peel could maintain the intestinal microbiota at a state favorable to the host, effectively reduce the abnormal changes in the taxonomic structure of the intestinal microbiota, and improve the growth performance in broilers treated with APEC.

Recombinant Salmonella gallinarum (S. gallinarum) Vaccine Candidate Expressing Avian Pathogenic Escherichia coli Type I Fimbriae Provides Protections against APEC O78 and O161 Serogroups and S. gallinarum Infection

Avian pathogenic Escherichia coli (APEC) is one of the leading pathogens that cause devastating economic losses to the poultry industry. Type I fimbriae are essential adhesion factors of APEC, which can be targeted and developed as a vaccine candidate against multiple APEC serogroups due to their excellent immunogenicity and high homology. In this study, the recombinant strain SG102 was developed by expressing the APEC type I fimbriae gene cluster (fim) on the cell surface of an avirulent Salmonella gallinarum (S. gallinarum) vector strain using a chromosome-plasmid-balanced lethal system. The expression of APEC type I fimbriae was verified by erythrocyte hemagglutination assays and antigen-antibody agglutination tests. In vitro, the level of the SG102 strain adhering to leghorn male hepatoma (LMH) cells was significantly higher than that of the empty plasmid control strain, SG101. At two weeks after oral immunization, the SG102 strain remained detectable in the livers, spleens, and ceca of SG102-immunized chickens, while the SG101 strain was eliminated in SG101-immunized chickens. At 14 days after the secondary immunization with 5 × 109 CFU of the SG102 strain orally, highly antigen-specific humoral and mucosal immune responses against APEC type I fimbriae protein were detected in SG102-immunized chickens, with IgG and secretory IgA (sIgA) concentrations of 221.50 μg/mL and 1.68 μg/mL, respectively. The survival rates of SG102-immunized chickens were 65% (13/20) and 60% (12/20) after challenge with 50 LD50 doses of APEC virulent strains O78 and O161 serogroups, respectively. By contrast, 95% (19/20) and 100% (20/20) of SG101-immunized chickens died in challenge studies involving APEC O78 and O161 infections, respectively. In addition, the SG102 strain effectively provided protection against lethal challenges from the virulent S. gallinarum strain. These results demonstrate that the SG102 strain, which expresses APEC type I fimbriae, is a promising vaccine candidate against APEC O78 and O161 serogroups as well as S. gallinarum infections.

Exploring broilers and native fowls of Andaman and Nicobar Islands as a source of β-lactamase-producing Enterobacteriaceae even with limited anthropogenic activities and docking-based identification of catalytic domains in novel β-lactamase variants

Objectives

The present study was conducted to detect the occurrence of β-lactamase and biofilm-producing Escherichia coli, Salmonella, and Klebsiella in broilers and native fowl reared in the Andaman and Nicobar Islands, India. The study also included molecular docking experiments to confirm the nature of the catalytic domains found in the β-lactamase variants obtained and to reveal the clonal relationship of the isolates with human clinical strains from the database.

Materials and methods

A total of 199 cloacal swabs were collected from five poultry breeds/varieties (broiler, Vanraja, Desi, Nicobari, and layer) in three districts of the Andaman and Nicobar Islands. E. coli, Salmonella enterica, and Klebsiella pneumoniae were isolated by standard techniques and confirmed by PCR. Phenotypical β-lactamase producers were identified by a double-disc test. The genes (bla _CTX, bla _SHV, bla _TEM , and bla _AmpC) were screened, and selected sequences of β-lactamase variants were submitted to DDBJ. Homology modeling, model validation, and active site identification of different β-lactamase variants were done by the SWISS-MODEL. Molecular docking was performed to identify the catalytic domains of the β-lactamase variants. The selected β-lactamase sequences were compared with the Indian ESBL sequences from human clinical strains in NCBI-GenBank.

Results

In total, 425 Enterobacteriaceae strains were isolated from the collected samples. Klebsiella pneumoniae (42.58%) was found to be the most prevalent, followed by Salmonella enterica (30.82%) and E. coli (26.58%). The phenotypical antibiogram of all 425 isolates showed the highest resistance against oxytetracycline (61-76%) and the lowest against gentamicin (15-20%). Phenotypical production of β-lactamase enzymes was observed in 141 (33.38%) isolates. The isolation rate of β-lactamase producing E. coli, Salmonella enterica, and Klebsiella pneumoniae was significantly higher (p < 0.05) in the birds reared in the South Andaman district (25.6, 17.5, and 18.7%, respectively) than in Nicobar (11.5, 7.6, 7.1%, respectively). Genotyping of the β-lactamase-producing isolates revealed the maximum possession of bla _TEM, followed by bla _SHV and bla _{CTX - M}. The nucleotide sequences were found to be similar with bla _{CTX - M-15}, bla _{SHV - 11}, bla _{SHV - 27}, bla _{SHV - 228}, bla _{TEM - 1}, and bla _AmpC in BLAST search. Distribution of studied biofilm-associated genes in Enterobacteriaceae strains from different varieties of the birds revealed that the layer birds had the maximum possession, followed by Vanraja, Desi, broilers, and Nicobari fowls. The phylogenetic analysis of selected sequences revealed a partial clonal relationship with human clinical strains of the Indian subcontinent. Molecular docking depicted the Gibbs free energy release for 10 different macromolecules (proteins) and ligand (antibiotic) complexes, ranging from -8.1 (SHV-27 + cefotaxime) to -7 (TEM-1 + cefotaxime) kcal/mol.

Conclusion and relevance

The study revealed β-lactamase variants circulating in the fowl population of the Andaman and Nicobar Islands (India), even in remote places with low anthropogenic activity. Most of the strains possessed bla _{TEM - 1}, followed by bla _{CTX - M-15}. Possession of bla _{SHV - 11}, bla _{SHV - 27}, and bla _{SHV - 228} in poultry Enterobacteriaceae strains was not reported earlier from any part of the world. The phylogenetic analysis revealed a partial clonal relationship of β-lactamase sequences with the human clinical strains isolated from the Indian subcontinent.

Isolation, Molecular Characterization, and Antibiotic Resistance of Avian Pathogenic Escherichia coli in Eastern China

Avian pathogenic Escherichia coli (APEC) causes colibacillosis in avians, resulting in considerable losses in the poultry industry. APEC showed zoonotic potential initially related to the fact that APEC serves as the reservoir of virulence genes and antibiotic resistance genes for other E. coli. Thus, we determine the serotypes, phylogenetic groups, virulence genes distribution, and antibiotic resistance profiles of APEC isolates in eastern China. A total of 230 APEC were isolated from diseased chicken and duck with typical colibacillosis symptoms. Serotyping identified that O78 (44.78%) was the predominant serotype. The majority of APEC isolates were classified into B2 (29.57%), A (26.96%), D (20.00%), and B1 (18.26%), respectively. Among the 15 virulence genes, a high prevalence of ibeB (99.57%), fimC (91.74%), mat (91.30%), ompA (83.04%), and iss (80.43%) genes was observed. Except for low resistance rates for imipenem (1.7%) and polymyxin B (0.4%), most of the APEC isolates were resistant to erythromycin (98.7%), enrofloxacin (96.1%), tetracycline (95.2%), doxycycline (93.9%), lincomycin (90.0%), and streptomycin (90.0%). Moreover, all APEC exhibit multi-drug resistance. This study indicated that APEC isolates harbor a variety of virulence genes and showed multi-antibiotic resistance profiles, providing proof for understanding the epidemiological background and zoonotic potential of APEC in poultry farms.

Molecular characterization of blaNDM, blaOXA-48, mcr-1 and blaTEM-52 positive and concurrently carbapenem and colistin resistant and extended spectrum beta-lactamase producing Escherichia coli in chicken in Malaysia

Background

Antimicrobial resistance (AMR) is a global public health threat and the use of antibiotics growth promoters in food animals has been implicated as a potential contributing factor in the emergence and spread of AMR. This study was conducted to investigate colistin and carbapenem resistance and extended spectrum beta-lactamase producing E. coli from live broiler chicken and chicken meat in Kelantan, Malaysia.

Results

Among the E. coli isolates, 37.5% (27/72 were positive for at least one of the resistance genes and one isolate was positive for mcr-1, bla_TEM-52, bla_NDM and bla_OXA-48 whereas 4.17% (3/72) and 2.78% (2/72) were positive for mcr-1, bla_TEM-52 and bla_OXA-48, and mcr-1, bla_TEM-52 and bla_IMP. Multilocus sequence typing (MLST) results revealed the presence of widespread E. coli strains belonging to the sequence types ST410 and ST155 and other extra-intestinal E. coli (ExPEC) strains. Phylogroup A made up the majority 51.85% (14/27) followed by phylogroup B1 22.22% (6/27).

Conclusions

The findings imply the potential threats of colistin, extended-spectrum beta-lactamase producing and carbapenem resistant E. coli in food animals to the public health and underscores the need for judicious use of antibiotics in animal production and good hygiene practices to curb the rising risks of AMR.

Investigation of Serotype Prevalence of Escherichia coli Strains Isolated from Layer Poultry in Greece and Interactions with Other Infectious Agents

Colibacillosis is the most common bacterial disease in poultry and it is caused by avian pathogenic Escherichia coli (APEC), which is assigned to various O-serogroups. Previous studies have shown that APEC strains are more often related to certain O-serogroups such asO78, O2 and O1. E. coli has been reported to act either as a primary or secondary agent in complicating other infections. The aim of this study was to investigate the occurrence of and characterize the O-serogroups of E. coli strains isolated from commercial layer and layer breeder flocks showing macroscopic lesions of colibacillosis and increased or normal mortality in Greece. Furthermore, we attempted to assess the interaction between infectious agents such as Mycoplasma gallisepticum (MG), Mycoplasma synoviae (MS), infectious bronchitis (IBV) and infectious laryngotracheitis (ILT) with E. coli infections in layer flocks with increased mortality. Our study revealed that in addition to the common serogroups (O78, O2), many other, and less common serogroups were identified, including O111. The O78, O111 and O2 serogroups were frequently detected in flocks with lesions of colibacillosis and increased mortality whereas O2, O88 and O8 were reported more commonly in birds with colibacillosis lesions but normal mortality rates. These data provide important information for colibacillosis monitoring and define preventative measures, especially by using effective vaccination programs because E. coli vaccines are reported to mainly offer homologous protection. Finally, concerning the association of the four tested infectious agents with E. coli mortality, our study did not reveal a statistically significant effect of the above infectious agents tested with E. coli infection mortality.

Relationship between CRISPR sequence type and antimicrobial resistance in avian pathogenic Escherichia coli

Avian pathogenic Escherichia coli (APEC) is a primary cause of extraintestinal disease and respiratory infections in chickens; therefore, various antimicrobials applied via mass medication in farms to control APEC in Korea. In this study, we analyzed the relationship between CRISPR sequence type and antimicrobial resistance (AMR) in APEC isolates. Based on spacer distribution, a total of 103 CRISPR-positive APEC isolates were classified into 25 E. coli sequence types (ESTs), largely into two clusters that were correlated with phylogenetic groups: isolates appearing to have CRISPR 1 and/or 2 (93.2 %) and those having CRISPR 3 and 4 (6.8 %). Moreover, ESTs were divided into three AMR pattern-based groups: cephems-resistant group, non-cephems-resistant group, and antimicrobial sensitive group. There were significant differences among the groups (p < 0.05). Sixteen of the 25 ESTs had a significantly higher distribution of multidrug-resistant (MDR) isolates than the other ESTs (p < 0.05), and the ratio of MDR isolates was significantly higher than that of non-MDR isolates in the CRISPR 1 and 2 arrays (p < 0.05). A total of 9 protospacers were identified with protospacer, with protospacer 1 in CRISPR 1 being the most prevalent among the isolates (41.7 %). The protospacers of CRISPR 1 and 2 loci were associated with protection against external invaders such as bacteriophage or endogenous gene regulation. However, each protospacer of the CRISPR 3 and 4 loci originated from genes associated with AMR plasmids. These results indicate that CRISPR sequence type can improve AMR bacteria and enhance strategies for tackling the complexity of AMR in bacterial pathogens.

An Integrated Perspective on Virulence-Associated Genes (VAGs), Antimicrobial Resistance (AMR), and Phylogenetic Clusters of Pathogenic and Non-pathogenic Avian Escherichia coli

Avian pathogenic Escherichia coli (APEC) is an important bacterial pathogen that causes avian colibacillosis and leads to huge economic losses in the poultry industry. Different virulence traits contribute to pathogenesis of APEC infections, and antimicrobial resistance (AMR) has also been an overwhelming issue in poultry worldwide. In the present study, we aimed to investigate and compare the presence of virulence-associated genes (VAGs), AMR, and phylogenetic group's distribution among APEC and avian fecal E. coli (AFEC) strains. E. coli from birds with colisepticemia and yolk sac infection (YSI) (APEC) plus E. coli strains from the feces of healthy birds (AFEC) were compared by the aforementioned traits. In addition, the clonal relatedness was compared using Enterobacterial repetitive intergenic consensus PCR (ERIC-PCR). Although all strains were susceptible to fosfomycin, ceftriaxone, and cefixime, almost all strains (98%) were multi-drug resistant (MDR). All strains (except two) harbored at least three or more VAGs, and the virulence scores tended to be higher in pathogenic strains especially in the colisepticemic group. All phylogenetic groups were found in isolates from YSI, colisepticemia, and the feces of healthy birds; however, the frequency of phylogroups varied according to the source of the isolate. B1 and C phylogroups were statistically more likely to be found among APEC from YSI and colisepticemic E. coli groups, respectively, while phylogroup A was the most frequently occurring phylogroup among AFEC strains. Our findings also revealed that AMR and VAGs are not essentially co-evolved traits as in some instances AMR strains were more prevalent among AFEC. This reflects the divergent evolutionary pathways of resistance acquisition in pathogenic or non-pathogenic avian E. coli strains. Importantly, strains related to phylogenetic group C showed higher virulence score and AMR that requires further attention. To some extent, ERIC-PCR was able to group strains by isolation source, phylogroup, or virulence genes. Further integrated studies along with assessment of more detailed genotypic and phenotypic features could potentially lead to better understanding of virulence, resistance, and evolution of ExPEC.

Prevalence and Genetic Relationship of Predominant Escherichia coli Serotypes Isolated from Poultry, Wild Animals, and Environment in the Mekong Delta, Vietnam

Avian pathogenic Escherichia coli (APEC) is the main causative agent of avian colibacillosis, which is an important systemic disease of profound economic and clinical consequences for the poultry industry worldwide. In this study, 975 E. coli strains were isolated from 2,169 samples collected from cloacal swabs of chickens, in-farm wild animals (ants, geckos, flies, and rats), and environment. The highest proportion of E. coli isolation was obtained from chicken cloacal swabs with 71.05% (95% confidence interval (CI) 66.69-75.05%) followed by the proportions of 38.15% (95% CI 35.41-40.97%) and 38.11% (95% CI 34.15-42.24%) from wild animals or environment, respectively. Distribution of O-antigen serotypes of the E. coli isolates, including O1, O2, O18, and O78, was determined by PCR. The most predominant serotype was O18 (10.56%) followed by O2 (9.44%), O1 (7.79%), and O78 (6.56%). Of note, serotype O18 was more likely distributed in the examined wild animals, especially in geckos. Polymorphic DNA fingerprints, generated by ERIC-PCR, of representative E. coli strains of each serotype revealed genetic heterogeneity of the examined E. coli, and O18 was more divergent with 63 clusters formed from 66 isolates. Furthermore, several E. coli strains from different sample sources shared high DNA fingerprint relatedness, suggesting that there exists complex transmission of E. coli from chickens to wild animals and environment and vice versa in poultry husbandry settings. Although pathotypes of the examined E. coli were not determined in this study, our results provided important findings of epidemiological and genetic characteristics of E. coli in the Mekong Delta and highlighted the prerequisite of stricter biocontainment to reduce the prevalence and consequences of APEC in poultry production.

Prevalence and Antibiotic Resistance Characteristics of Extraintestinal Pathogenic Escherichia coli among Healthy Chickens from Farms and Live Poultry Markets in China

Simple Summary

Chicken meat has been proved to be a suspected source of extraintestinal pathogenic Escherichia coli (ExPEC), causing several diseases in humans, and bacteria in healthy chickens can contaminate chicken carcasses at the slaughter; however, reports about the prevalence and molecular characteristics of ExPEC in healthy chickens are still rare. In this study, among 926 E. coli isolates from healthy chickens in China, 22 (2.4%) were qualified as ExPEC and these ExPEC isolates were clonally unrelated. A total of six serogroups were identified in this study, with O78 being the most predominant type, and all the six serogroups had been frequently reported in human ExPEC isolates in many countries. All the 22 ExPEC isolates were multidrug-resistant and most isolates carried both bla_CTX-M and fosA3 resistance genes. Notably, plasmid-borne colistin resistance gene mcr-1 was identified in six ExPEC isolates, among which two carried additional carbapenemase gene bla_NDM, compromising both the efficacies of the two critically important drugs for humans, carbapenems and colistin. These results highlight that healthy chickens can serve as a potential reservoir for multidrug resistant ExPEC isolates, including mcr-1-containing ExPEC.

Abstract

Chicken products and chickens with colibacillosis are often reported to be a suspected source of extraintestinal pathogenic Escherichia coli (ExPEC) causing several diseases in humans. Such pathogens in healthy chickens can also contaminate chicken carcasses at the slaughter and then are transmitted to humans via food supply; however, reports about the ExPEC in healthy chickens are still rare. In this study, we determined the prevalence and characteristics of ExPEC isolates in healthy chickens in China. A total of 926 E. coli isolates from seven layer farms (371 isolates), one white-feather broiler farm (78 isolates) and 17 live poultry markets (477 isolates from yellow-feather broilers) in 10 cities in China, were isolated and analyzed for antibiotic resistance phenotypes and genotypes. The molecular detection of ExPEC among these healthy chicken E. coli isolates was performed by PCRs, and the serogroups and antibiotic resistance characteristics of ExPEC were also analyzed. Pulsed-field gel electrophoresis (PFGE) and Multilocus sequence typing (MLST) were used to analyze the genetic relatedness of these ExPEC isolates. We found that the resistance rate for each of the 15 antimicrobials tested among E. coli from white-feather broilers was significantly higher than that from brown-egg layers and that from yellow-feather broilers in live poultry markets (p < 0.05). A total of 22 of the 926 E. coli isolates (2.4%) from healthy chickens were qualified as ExPEC, and the detection rate (7.7%, 6/78) of ExPEC among white-feather broilers was significantly higher than that (1.6%, 6/371) from brown-egg layers and that (2.1%, 10/477) from yellow-feather broilers (p < 0.05). PFGE and MLST analysis indicated that clonal dissemination of these ExPEC isolates was unlikely. Serogroup O78 was the most predominant type among the six serogroups identified in this study, and all the six serogroups had been frequently reported in human ExPEC isolates in many countries. All the 22 ExPEC isolates were multidrug-resistant (MDR) and the resistance rates to ampicillin (100%) and sulfamethoxazole-trimethoprim (100%) were the highest, followed by tetracycline (95.5%) and doxycycline (90.9%). bla_CTX-M was found in 15 of the 22 ExPEC isolates including 10 harboring additional fosfomycin resistance gene fosA3. Notably, plasmid-borne colistin resistance gene mcr-1 was identified in six ExPEC isolates in this study. Worryingly, two ExPEC isolates were found to carry both mcr-1 and bla_NDM, compromising both the efficacies of carbapenems and colistin. The presence of ExPEC isolates in healthy chickens, especially those carrying mcr-1 and/or bla_NDM, is alarming and will pose a threat to the health of consumers. To our knowledge, this is the first report of mcr-1-positive ExPEC isolates harboring bla_NDM from healthy chickens.

Bacteriophage activity against and characterisation of avian pathogenic Escherichia coli isolated from colibacillosis cases in Uganda

Avian Pathogenic Escherichia coli (APEC) cause colibacillosis leading to significant economic losses in the poultry industry. This laboratory-based study aimed at establishing stocks of avian pathogenic Escherichia coli lytic bacteriophages, for future development of cocktail products for colibacillosis management. The study determined the antibiotic susceptibility; phylogenetic categories, occurrence of selected serotypes and virulence genes among Escherichia coli stock isolates from chicken colibacillosis cases; and evaluated bacteriophage activity against the bacteria. Escherichia coli characterization was done through phenotypic and multiplex PCR methods. Bacteriophage isolation and preliminary characterization was achieved using the spot assay and overlay plating techniques. Fifty-six (56) isolates were phenotypically confirmed as E. coli and all exhibited resistance to at least one antimicrobial agent; while multi-drug resistance (at least three drugs) was encountered in 50 (89.3%) isolates. The APEC isolates mainly belonged to phylogroups A and D, representing 44.6% and 39.3%, respectively; whereas serotypes O1, O2 and O78 were not detected. Of the 56 isolates, 69.6% harbored at least one virulence gene, while 50% had at least four virulence genes; hence confirmed as APEC. Virulence genes, ompT and iutA were the most frequent in 33 (58.9%) and 32 (57.1%) isolates respectively; while iroN least occurred in 23 (41.1%) isolates. Seven lytic bacteriophages were isolated and their host range, at 1×10⁸ PFU/ml, varied from 1.8% to 17.9% of the 56 APEC isolates, while the combined lytic spectrum was 25%. Phage stability was negatively affected by increasing temperatures with both UPEC04 and UPEC10 phages being undetectable at 70°C; whereas activity was detected between pH 2 and 12. The high occurrence of APEC isolates resistant against the commonly used antibiotics supports the need for alternative strategies of bacterial infections control in poultry. The low host range exhibited by the phages necessitates search for more candidates before in-depth phage characterization and application.

Longitudinal monitoring of multidrug resistance in Escherichia coli on broiler chicken fattening farms in Shandong, China

The extensive use of antibiotics has, in recent years, caused antimicrobial resistance and multidrug resistance in Escherichia coli to gradually develop into a worldwide problem. These resistant E. coli could be transmitted to humans through animal products and animal feces in the environment, thereby creating a problem for bacterial treatment for humans and animals and resulting in a public health issue. Monitoring the resistance of E. coli throughout the broiler fattening period is therefore of great significance for both the poultry industry and public health. In this longitudinal study, samples were taken from 6 conventional broiler fattening farms in Shandong Province, China, at 3 different times within 1 fattening period. The overall isolation rate of E. coli was 53.04% (375/707). Antibiotic resistance was very common in the E. coli isolated from these farms, and differed for different antibiotics, with ampicillin having the highest rate (92.86%) and cefoxitin the lowest (10.12%). Multidrug resistance was as high as 91.07%. More importantly, both the resistance rate of E. coli to the different drugs and the detection rate of drug resistance genes increased over time. The mobile colistin resistance (mcr-1) gene was detected in 24.40% of the strains, and these strains often carried other drug resistance genes, such as those conferring aminoglycoside, β-lactamase, tetracycline, and sulfonamide resistance. Antimicrobial resistance and drug resistance genes in E. coli were least common in the early fattening stage. The individual detection rates of sul1, sul3, aacC4, aphA3, and mcr-1 were significantly lower (P < 0.05) for the early fattening stage than for the middle and late stages. The rational use of antibiotics, in conjunction with the improvement of the breeding environment during the entire broiler fattening cycle, will be helpful in the development of the poultry industry and the protection of public health.

Serogrouping, phylotyping, and virulence genotyping of commensal and avian pathogenic Escherichia coli isolated from broilers in Hamedan, Iran

In the present study, 100 Avian-Pathogenic Escherichia coli (APEC) isolates from colibacillosis-suspected broilers and 100 Avian Faecal Escherichia coli (AFEC) isolates from healthy broilers in Iran were examined by PCR for confirmation of their serogroups and phylogenetic background, and their association with ten virulence-associated genes (VAG) including fimC, iutA, chuA, sitA, iss, cvaA/B, hylA, stx1, stx2, and yjaA. Serogroups O78, O1, O2 and O18 were the prominent strains including 54 % of the APEC and 23 % of the AFEC strains. At phylotyping, the majority of APEC strains belonged to phylogenetic group E (22 %) while for the AFEC strains, half of the isolates were not assigned to any group but the predominant phylogroup was E (27 %). Virulence genotyping, revealed that the predominant VAGs were iutA (97 %), fimC (87 %) and iss (84 %) among APEC strains, and fimC (95 %), iss (93 %) and sitA (87 %) in AFEC strains. This is the first time that phylogroup E is described as predominant phylogroup among APEC strains also, this is the first report on the presence of the stx1 gene in APEC strains isolated from broilers in Iran. The results of the present study indicate that VAGs are more prevalent in APEC strains belonging to O2 and O78 serogroups, also phylogroups E and D have more frequency of VAGs than other phylogroups. Therefore, the APEC strains belonging to O2 and O78 serogroups and phylogroups E and D probably have more pathogenicity to broilers.

Multidrug-Resistant Avian Pathogenic Escherichia coli Strains and Association of Their Virulence Genes in Bangladesh

The avian pathogenic Escherichia coli (APEC) strains are the chief etiology of colibacillosis worldwide. The present study investigated the circulating phylotypes, existence of virulence genes (VGs), and antimicrobial resistance (AMR) in 392 APEC isolates, obtained from 130 samples belonged to six farms using both phenotypic and PCR-based molecular approaches. Congo red binding (CRB) assay confirmed 174 APEC isolates which were segregated into ten, nine, and eight distinct genotypes by RAPD assay (discriminatory index, DI = 0.8707), BOX-PCR (DI = 0.8591) and ERIC-PCR (DI = 0.8371), respectively. The combination of three phylogenetic markers (chuA, yjaA and DNA fragment TspE4.C2) classified APEC isolates into B23 (37.36%), A1 (33.91%), D2 (11.49%), B22 (9.20%), and B1 (8.05%) phylotypes. Majority of the APEC isolates (75-100%) harbored VGs (ial, fimH, crl, papC, and cjrC). These VGs (papC and cjrC) and phylotypes (D2 and B2) of APEC had significant (p = 0.004) association with colibacillosis. Phylogenetic analysis showed two distinct clades (clade A and clade B) of APEC, where clade A had 98-100% similarity with E. coli APEC O78 and E. coli EHEC strains, and clade B had closest relationship with E. coli O169:H41 strain. Interestingly, phylogroups B2 and D2 were found in the APEC strains of both clades, while the strains from phylogroups A1 and B1 were found in clade A only. In this study, 81.71% of the isolates were biofilm formers, and possessed plasmids of varying ranges (1.0 to 54 kb). In vitro antibiogram profiling revealed that 100% isolates were resistant to ≥3 antibiotics, of which 61.96%, 55.24%, 53.85%, 51.16% and 45.58% isolates in phylotypes B1, D2, B22, B23, and A1, respectively, were resistant to these antimicrobials. The resistance patterns varied among different phylotypes, notably in phylotype B22, showing the highest resistance to ampicillin (90.91%), nalidixic acid (90.11%), tetracycline (83.72%), and nitrofurantoin (65.12%). Correspondence analysis also showed significant correlation among phylotypes with CRB (p = 0.008), biofilm formation (p = 0.02), drug resistance (p = 0.03), and VGs (p = 0.06). This report demonstrated that B2 and A1 phylotypes are dominantly circulating APEC phylotypes in Bangladesh; however, B2 and D2 are strongly associated with the pathogenicity. A high prevalence of antibiotic-resistant APEC strains from different phylotypes suggest the use of organic antimicrobial compounds, and/or metals, and the rotational use of antibiotics in poultry farms in Bangladesh.

Exploiting bacterial outer membrane vesicles as a cross-protective vaccine candidate against avian pathogenic Escherichia coli (APEC)

Background

The well-known fact that avian pathogenic Escherichia coli (APEC) is harder to prevent due to its numerous serogroups has promoted the development of biological immunostimulatory materials as new vaccine candidates in poultry farms. Bacterial outer membrane vesicles (OMVs), known as spherical nanovesicles enriched with various immunostimulants, are naturally secreted by Gram-negative bacteria, and have gained much attention for developing effective vaccine candidates. Recent report has demonstrated that OMVs of APEC O78 can induce protective immunity in chickens. Here, a novel multi-serogroup OMVs (MOMVs) vaccine was developed to achieve cross-protection against APEC infection in broiler chickens.

Results

In this study, OMVs produced by three APEC strains were isolated, purified and prepared into MOMVs by mixing these three OMVs. By using SDS-PAGE and LC–MS/MS, 159 proteins were identified in MOMVs and the subcellular location and biological functions of 20 most abundant proteins were analyzed. The immunogenicity of MOMVs was evaluated, and the results showed that MOMVs could elicit innate immune responses, including internalization by chicken macrophage and production of immunomodulatory cytokines. Vaccination with MOMVs induced specific broad-spectrum antibodies as well as Th1 and Th17 immune responses. The animal experiment has confirmed that immunization with an appropriate dose of MOMVs could not cause any adverse effect and was able to reduce bacteria loads and pro-inflammatory cytokines production, thus providing effective cross-protection against lethal infections induced by multi-serogroup APEC strains in chickens. Further experiments indicated that, although vesicular proteins were able to induce stronger protective efficiency than lipopolysaccharide, both vesicular proteins and lipopolysaccharide are crucial in MOMVs-mediated protection.

Conclusions

The multi-serogroup nanovesicles produced by APEC strains will open up a new way for the development of next generation vaccines with low toxicity and broad protection in the treatment and control of APEC infection.

Molecular characterization of avian pathogenic Escherichia coli from broiler chickens with colibacillosis

Avian pathogenic Escherichia coli (APEC) causes extensive mortality in poultry flocks, leading to extensive economic losses. The aim of this study was to investigate the phenotypic and genotypic characteristics and antimicrobial resistance of recent APEC isolates. Of the 79 APEC isolates, the most predominant serogroup was O78 (16 isolates, 20.3%), followed by O2 (7 isolates, 8.9%) and O53 (7 isolates, 8.9%). Thirty-seven (46.8%) and six (7.6%) of the isolates belonged to phylogenetic groups D and B2, respectively, and presented as virulent extraintestinal E. coli. Among 5 analyzed virulence genes, the highest frequency was observed in hlyF (74 isolates, 93.7%), followed by iutA (72 isolates, 91.9%) gene. The distribution of the iss gene was significantly different between groups A/B1 and B2/D (P < 0.05). All group B2 isolates carried all 5 virulence genes. APEC isolates showed high resistance to ampicillin (83.5%), nalidixic acid (65.8%), tetracycline (64.6%), cephalothin (46.8%), and ciprofloxacin (46.8%). The β-lactamases–encoding genes bla_TEM-1 (23 isolates, 29.1%), bla_CTX-M-1 (4 isolates, 5.1%), and bla_CTX-M-15 (3 isolates, 3.8%); the aminoglycoside-modifying enzyme gene aac(3)-II (4 isolates, 5.1%); and the plasmid-mediated quinolone genes qnrA (10 isolates, 12.7%) and qnrS (2 isolates, 2.5%) were identified in APEC isolates. The tetA (37 isolates, 46.8%) and sul2 (20 isolates, 25.3%) were the most prevalent among tetracycline and sulfonamide resistant isolates, respectively. This study indicates that APEC isolates harbor a variety of virulence and resistance genes; such genes are often associated with plasmids that facilitate their transmission between bacteria and should be continuously monitored to track APEC transmission in poultry farms.

Resistance and Virulence Mechanisms of Escherichia coli Selected by Enrofloxacin in Chicken

This study aimed to investigate the genetic characteristics, antibiotic resistance patterns, and novel mechanisms involved in fluoroquinolone (FQ) resistance in commensal Escherichia coli isolates. The E. coli isolates were recovered from a previous clinical study and subjected to antimicrobial susceptibility testing and molecular typing. Known mechanisms of FQ resistance (target site mutations, plasmid-mediated quinolone resistance [PMQR] genes, relative expression levels of efflux pumps and porins) were detected using DNA sequencing of PCR products and real-time quantitative PCR. Whole-genome shotgun sequencing was performed on 11 representative strains to screen for single nucleotide polymorphisms (SNPs). The function of a key SNP (A1541G) was investigated by site-directed mutagenesis and allelic exchange. The results showed that long-term enrofloxacin treatment selected multidrug-resistant (MDR) E. coli isolates in the chicken gut and that these E. coli isolates had diverse genetic backgrounds. Multiple genetic alterations, including double mutations on GyrA (S83L and D87N), a single mutation on ParC (S80I) and ParE (S458E), activation of efflux pumps, and the presence of the QnrS1 protein, contributed to the high-level FQ resistance (enrofloxacin MIC [MIC_ENR] ≥ 128 μg/ml), while the relatively low-level FQ resistance (MIC_ENR = 8 or 16 μg/ml) was commonly mediated by decreased expression of the porin OmpF, besides enhancement of the efflux pumps. No significant relationship was observed between resistance mechanisms and virulence genes. Introduction of the A1541G mutation on aegA was able to increase FQ susceptibility by 2-fold. This study contributes to a better understanding of the development of MDR and the differences underlying the mechanisms of high-level and low-level FQ resistance in E. coli.

Duck viral infection escalated the incidence of avian pathogenic Escherichia coli in China

Avian pathogenic Escherichia coli (APEC) causes high mortality in poultry flocks and often is complicated with viral infections, leading to large economic losses; however, little information is available on the epidemiological characteristics of this pathogen in ducks. Therefore, a systemic epidemiological investigation was performed on 325 duck farms from 13 provinces in China during the period of 1 April 2016 until 31 March 2018, covering 2 years. A total of 26 APEC strains were isolated from different farms in this study, and analysis showed that all of those isolates carried multiple virulence-associated genes and drug-resistance genes, which led to high pathogenicity (15/26), strong or moderate biofilm formation (24/26) and multidrug-resistant abilities (26/26). On the other hand, coinfection with APEC, H9 avian influenza virus (AIV) and Tembusu virus (TMUV) was very common on those farms (11/26), with APEC and TMUV sharing a similar morbidity peak (from May to September) and susceptibility (60% infections occurred in ducklings); thus, we speculated that the emerging TMUV infection escalated the APEC incidence in ducks. Finally, the data presented in this report enhance the current understanding of the epidemiology of APEC and different viral infections in ducks and provide additional insight into the critical factors that determine their pathogenicity. Meanwhile, the emergence of multidrug-resistant APEC strains and their coinfection with different viruses emphasize that preventive measures against such infections on poultry farms should be implemented immediately.

Serological diversity, molecular characterisation and antimicrobial sensitivity of avian pathogenic Escherichia coli (APEC) isolates from broiler chickens in Kashmir, India

The present study has determined the serological diversity, virulence-gene profile and in vitro antibiogram of avian pathogenic Escherichia coli (APEC) isolates from broiler chickens in India suspected to have died of colibacillosis. The virulence-gene profile of APEC was compared with that of the Escherichia coli isolates from faeces of apparently healthy chickens, called avian faecal E. coli (AFEC). In total, 90 representative isolates of APEC and 63 isolates of AFEC were investigated in the present study. The APEC were typed into 19 serogroups, while some isolates were rough and could not be typed. Most prevalent serogroup was O2 (24.44%). Among the eight virulence genes studied, the prevalence of seven genes (iss, iucD, tsh, cva/cvi, irp2, papC and vat) was significantly higher in APEC than in AFEC isolates. However, there was no significant difference between APEC and AFEC isolates for possession of astA gene. The most frequent gene detected among the two groups of organisms was iss, which was present in 98.88% and 44.44% of APEC and AFEC isolates respectively. The in vitro antibiogram showed that the majority (96.6%) of APEC isolates were resistant to tetracycline, while 82.2% were resistant to cephalexin, 78.8% to cotrimoxazole, 68.8% to streptomycin and 63.3% to ampicillin. However, most of them (84.45%) were sensitive to gentamicin. Thus, it is concluded that APEC from the broiler chickens carried putative virulence genes that attributed to their pathogenicity. Furthermore, the majority of APEC isolates were found to be multi-drug resistant, which, in addition to leading treatment failures in poultry, poses a public health threat.

Antimicrobial resistance genes in pathogenic Escherichia coli isolated from diseased broiler chickens in Egypt and their relationship with the phenotypic resistance characteristics

Aim:

The aim of this study was to determine the relationship between phenotypic resistance and genotypic resistance of isolated serotyped pathogenic Escherichia coli isolates from the clinically diseased broiler.

Materials and Methods:

A total of 160 samples (heart, liver, kidney, and lung) were collected from 18 to 34 days old clinically diseased broiler from 40 broiler farms (3-5 birds/farm) reared in Giza and Kaluobaia Governorates for the isolation of pathogenic E. coli. Various E. coli isolates were tested for the pathogenicity based on Congo red (CR) dye binding assay. The obtained CR-positive E. coli isolates were subjected to serological identification using slide agglutination test. Disc diffusion test was used to study the sensitivity pattern of E. coli isolates to available 12 antibiotics. Polymerase chain reaction was performed for the detection of antimicrobial resistance genes in the studied pathogenic E. coli isolates.

Results:

The results revealed that 56 samples (35 %) were positive for E. coli. The results of the CR assay indicates that 20 isolates of 56 (35.7%) were positive and 36 isolates (64.3%) were negative. Identified E. coli serotypes of CR-positive isolates were 1 (O24), 2 (O44), 2 (O55), 5 (O78), 2 (O86), 1 (124), 3 (O127), 1 (O158), and 3 untyped. Resistance rate in disc diffusion test was 85% to oxytetracycline and kanamycin; 80% to ampicillin (AMP), clindamycin, and streptomycin (S); 75% to enrofloxacin; 65% to chloramphenicol; 55% to cefotaxime and gentamicin (CN); 45% to trimethoprim+sulfamethoxazole; 35% to erythromycin (ERI); and 30% to oxacillin. All strains are multidrug-resistant (MDR). Antibacterial resistance genes CITM, ere, aac (3)-(IV), tet(A), tet(B), dfr(A1), and aad(A1) were detected in 14 (70%), 12 (60%), 12 (60%), 8 (40%), 11 (55%), 8 (40%), and 9 (45%) of tested 20 isolates, respectively. Multidrug resistance was detected in the form of resistance to 42%-83.3% of tested 12 antibiotics. Three isolates (15%) of 20 tested isolates showed a relationship between phenotype and genotype and 17 (85%) showed irregular relation. Strains are sensitive and show resistant gene (P-G+) presented in three isolates for AMP (beta-lactam), one for ERI (Macrolide), as well as five isolates for trimethoprim (pyrimidine inhibitor). E. coli isolates had resistance and lacked gene (P+ G-) reported meanly in one isolate for CN (aminoglycoside), two isolates for tetracycline, four isolates for ERI, seven isolates for trimethoprim, and eight isolates for S (aminoglycoside).

Conclusion:

The study demonstrates that E. coli is still a major pathogen responsible for disease conditions in broiler. E. coli isolates are pathogenic and MDR. Responsible gene was detected for six antibiotics in most of the isolates, but some do not show gene expression, this may be due to few numbers of resistance genes tested or other resistance factors not included in this study.

Phylogenetic Groups and Antimicrobial Susceptibility Patterns of Escherichia coli from Healthy Chicken in Eastern and Central Uganda

Antimicrobial resistance is an emerging problem in both humans and animals due to misuse and excessive use of drugs. Resistance in commensal E. coli isolates can be used to predict emergence of resistance in other gut microflora. The aim of this study is to determine the phylogenetic groups and antimicrobial resistance patterns of E. coli from healthy chickens in Uganda. The phylogenetic grouping of 120 fecal E. coli isolates from eastern and central Uganda was derived using the triplex PCR assay and their susceptibility patterns determined by agar disc diffusion method to 5 antimicrobial drugs. Most E. coli is segregated into phylogenetic group A comprising 84%, while 12% and 4% were in groups D and B1, respectively. Similarly most E. coli from central (87%) and eastern Uganda (82%) belonged to group A. Overall, 85 (70%) of E. coli were resistant to antimicrobial drugs, of which 72/101 (70%) are in PG A, 10 of 14 (71.4%) in PG D, and 3 of 5 (60%) in PG B1. Significantly, most of the isolates in PG A from both central (66.7%) and (60.6%) eastern Uganda were resistant to one antimicrobial. Resistance to tetracycline alone or in combination with other drugs for central and eastern Uganda in PG A is 51% and 55%, respectively. Multidrug resistance to tetracycline and ciprofloxacin or nalidixic acid was 10% and 18% in isolates from central and 10% and 12% in isolates from eastern region, respectively. Phylogenetic group A accounts for most of the E. coli in chicken from Uganda. No difference in the resistance rates between the phylogenetic groups of E. coli has been observed. The high prevalence of resistant E. coli strains from different phylogenetic groups in healthy chickens suggests antimicrobial drug selection pressure due to excessive drug in the rearing layer chickens.

A bivalent vaccine derived from attenuated Salmonella expressing O-antigen polysaccharide provides protection against avian pathogenic Escherichia coli O1 and O2 infection

Avian pathogenic Escherichia coli (APEC), a leading cause of avian airsacculitis and colibacillosis, is responsible for significant economic loss in the poultry industry. APEC serogroups O1, O2, and O78 are predominantly associated with disease. Lipopolysaccharide (LPS) O-antigen has been shown to be a potent antigen for inducing specific protective immune responses. Therefore, we sought to develop a multivalent polysaccharide vaccine to prevent most APEC infections. We previously reported the stable expression of plasmid pSS27 encoding the APEC O1 O-antigen gene cluster (10.8 kb) in attenuated Salmonella enterica serovar Typhimurium S740 provided excellent protection against APEC O1 challenge. In this study, the plasmid pSS28 harboring the APEC O2 O-antigen polysaccharide gene cluster (15.5 kb) was constructed. Biosynthesis of pSS28-encoded APEC O2 O-antigen in Salmonella vaccine strain S740 was validated by Western blot. The recombinant Salmonella vaccine strain S740 (pSS28) elicited homologous protection against virulent wild-type APEC O2 challenge in a chicken model. Furthermore, through equal-volume mixing the two monovalent vaccine strains S740 (pSS27) and S740 (pSS28), a bivalent vaccine candidate against both APEC O1 and O2 was developed. Immunization of chickens with the bivalent vaccine elicited production of serum IgG and mucosal sIgA antibodies against the LPS of both APEC O1 and O2. Moreover, antibodies induced by the bivalent vaccine promoted opsonization, provoked complement-mediated bactericidal activity, and elicited protection against lethal challenge with both virulent APEC O1 and O2 strains. These results demonstrate that the bivalent vaccine comprised of S740 (pSS27) and S740 (pSS28) is a promising vaccine candidate against APEC O1 and O2 infection.

Phylogenetic Group of Escherichia coli Isolates from Broilers in Brazilian Poultry Slaughterhouse

The aim of the study was to determine the phylogenetic groups of E. coli strains isolated from seemingly healthy broiler and broiler condemned suspected of colibacillosis in a Brazilian slaughterhouse. Samples from respiratory tract and edible giblets (liver and heart) of broilers with and without macroscopic lesions of colibacillosis were collected at slaughter. There were 84 strains isolated from broilers condemned of which 11 were obtained from swabs of the heart, 7 from the liver, and 66 from the respiratory tract. Of the 53 E. coli strains isolated from broilers not condemned, 5 were isolated from the heart, 4 from the liver, and 44 from the respiratory tract. E coli strains were tested via PCR for phylogenetic groups A, B1, B2, C, D, E, and F. Phylogroups A and B1 were the most common phylogroups of E. coli obtained from healthy and sick-appearing broiler carcasses. The results of the study showed that phylogroups B2 and E were associated with the heart samples and phylogroup A was associated with respiratory tract samples, phylogroup B1 with not condemned carcass, and phylogroup D with liver samples.

Autoinducer-2 of quorum sensing is involved in cell damage caused by avian pathogenic Escherichia coli

Avian pathogenic Escherichia coli (APEC) infections are responsible for great losses in the poultry industry. Quorum sensing (QS) acts as a global regulatory system that controls genes involved in bacterial pathogenesis, metabolism and protein biosynthesis. However, whether QS of APEC is related to cell damage has not been elucidated. In the present study, we explored the correlation between the damage of chicken type II pneumocytes induced by APEC and the autoinducer-2 (AI-2) activity of APEC. The results showed that when chicken type II pneumocytes were co-cultured with 10⁸ CFU/ml of APEC-O78 for 6 h, the release of LDH reached the highest level (192.5 ± 13.4 U/L) (P < 0.01), and the percentages of dead cells followed the same trend in trypan blue exclusion assay. In addition, the AI-2 activity of cell-free culture fluid (CF) reached the maximum value after 6 h co-culture with 10⁸ CFU/ml of APEC-O78. At the same time, the mRNA expressions of eight virulence genes (papC, fimA, fimC, hlyE, ompA, luxS, pfs, and qseA) of 10⁸ CFU/ml APEC-O78 were significantly increased compared with those of 10⁷ CFU/ml, and the mRNA expressions of four virulence genes (hlyE, tsh, iss, and luxS) of 10⁸ CFU/ml APEC-O78 were higher than those of 10⁹ CFU/ml (p < 0.05) after incubation for 6 h. These results suggested that AI-2-mediated QS is involved in the cell damage induced by APEC-O78, indicating AI-2 may be one new potential target for preventing chicken colibacillosis.

Characterization of avian pathogenic Escherichia coli isolated in eastern China

In order to investigate the biological characteristics of avian pathogenic Escherichia coli (APEC) isolated in eastern China, a total of 243 isolates were isolated from diseased poultry on different farms during the period from 2007 to 2014. These isolates were characterized for serogroups (polymerase chain reaction and agglutination), the presence of virulence-associated genes (fimC, iss, ompA, fyuA, stx2f, iroC, iucD, hlyE, tsh, cvaC, irp2, and papC) and class I integrons (polymerase chain reaction), drug susceptibilities (disk diffusion method) and the biofilm-forming abilities (semi-quantitative method). The results showed that the most predominant serogroups were O78 (87 isolates, 35.8%) and O2 (35 isolates, 14.4%). Gene profiling found that fimC and ompA were frequently distributed among the isolates and that 77.4% of the isolates were positive for class 1 integrons. Overall, isolates displayed resistance to tetracycline (97.5%), nalidixic acid (82.3%), ampicillin (81.1%), sulphafurazole (80.7%), streptomycin (79.0%), trimethoprim (78.2%) and cotrimoxazole (78.2%). Multiple-drug resistance was exhibited in 80.3% of the isolates, and the presence of class 1 integrons is associated with multidrug resistance. Finally, 151 isolates had the ability to form biofilms in vitro, and drug resistance seemed relative to biofilm-forming abilities.

Immune responses associated with homologous protection conferred by commercial vaccines for control of avian pathogenic Escherichia coli in turkeys

Avian pathogenic Escherichia coli (APEC) infections are a serious impediment to sustainable poultry production worldwide. Licensed vaccines are available, but the immunological basis of protection is ill-defined and a need exists to extend cross-serotype efficacy. Here, we analysed innate and adaptive responses induced by commercial vaccines in turkeys. Both a live-attenuated APEC O78 ΔaroA vaccine (Poulvac® E. coli) and a formalin-inactivated APEC O78 bacterin conferred significant protection against homologous intra-airsac challenge in a model of acute colibacillosis. Analysis of expression levels of signature cytokine mRNAs indicated that both vaccines induced a predominantly Th2 response in the spleen. Both vaccines resulted in increased levels of serum O78-specific IgY detected by ELISA and significant splenocyte recall responses to soluble APEC antigens at post-vaccination and post-challenge periods. Supplementing a non-adjuvanted inactivated vaccine with Th2-biasing (Titermax® Gold or aluminium hydroxide) or Th1-biasing (CASAC or CpG motifs) adjuvants, suggested that Th2-biasing adjuvants may give more protection. However, all adjuvants tested augmented humoral responses and protection relative to controls. Our data highlight the importance of both cell-mediated and antibody responses in APEC vaccine-mediated protection toward the control of a key avian endemic disease.

The luxS gene functions in the pathogenesis of avian pathogenic Escherichia coli

Avian pathogenic Escherichia coli (APEC) causes avian colibacillosis, the most significant infectious bacterial disease of poultry worldwide. LuxS, the product of the luxS gene, mediates the quorum sensing (QS) mechanism. This involves the production of autoinducer-2 (AI-2), which regulates important physiological traits and a variety of adaptive processes in different bacteria. In this study, a luxS gene deleted APEC mutant strain, ΔDE17, was constructed using strain DE17. Analysis of bioluminescence indicated that deletion of the luxS gene abolished the production of the QS signal AI-2 in the bacteria. Further studies showed that deletion of the luxS gene in DE17 reduced the bacterial virulence by 31.5-fold in ducklings, based on the measurement of the 50% lethal dose. The mutant strain reduced significantly the abilities of adherence and invasion, by 50.0% and 40.7% respectively, compared with the wild strain DE17. The mutant strain also showed reduced survival in vivo: the bacterial loads of the mutant strain in infected liver, spleen and blood were 46.4-fold, 5.2-fold, and 3.7-fold reduced, respectively, compared with the wild-type strain DE17. Real-time polymerase chain reaction (PCR) demonstrated further that the mRNA levels of the virulence-related genes iucD, fyuA, vat, ompA, iss, fimC and tsh were significantly decreased in the mutant strain ΔDE17, when compared with DE17 (p < 0.05). In addition, the deletion of the luxS gene reduced the motility of the bacterium. This study suggests that the luxS gene functions in the pathogenesis of diseases caused by avian pathogenic E. coli.

Prevalence of antimicrobial resistance in relation to virulence genes and phylogenetic origins among urogenital Escherichia coli isolates from dogs and cats in Japan

OBJECTIVE

To assess the status of antimicrobial resistance (AMR), identify extraintestinal virulence factors (VFs) and phylogenetic origins, and analyze relationships among these traits in extraintestinal pathogenic Escherichia coli (ExPEC) isolates from companion animals.

SAMPLE

104 E coli isolates obtained from urine or genital swab samples collected between 2003 and 2010 from 85 dogs and 19 cats with urogenital infections in Japan.

PROCEDURES

Antimicrobial susceptibility of isolates was determined by use of the agar dilution method; a multiplex PCR assay was used for VF gene detection and phylogenetic group assessment. Genetic diversity was evaluated via randomly amplified polymorphic DNA analysis.

RESULTS

Of the 104 isolates, 45 (43.3%) were resistant to > 2 antimicrobials. Phylogenetically, 64 (61.5%), 22 (21.2%), 13 (12.5%), and 5 (4.8%) isolates belonged to groups B2, D, B1, and A, respectively. Compared with other groups, group B2 isolates were less resistant to all tested antimicrobials and carried the pap, hly, and cnf genes with higher frequency and the aer gene with lower frequency. The aer gene was directly associated and the pap, sfa, hly, and cnf genes were inversely associated with AMR. Randomly amplified polymorphic DNA analysis revealed 3 major clusters, comprised mainly of group B1, B2, and D isolates; 2 subclusters of group B2 isolates had different VF and AMR status. CONCLUSIONS AND CLINICAL RELEVANCE; Prevalences of multidrug resistance and human-like phylogenetic origins among ExPEC isolates from companion animals in Japan were high. It is suggested that VFs, phylogenetic origins, and genetic diversity are significantly associated with AMR in ExPEC.

High prevalence of antibiotic resistance in pathogenic Escherichia coli from large- and small-scale poultry farms in Bangladesh

Antibiotic resistance in avian bacterial pathogens is a common problem in the Bangladesh poultry industry. The aim of the present study was to provide information on the present status of antibiotic resistance patterns in avian pathogenic Escherichia coli in Bangladesh. Of 279 dead or sick poultry of different ages, 101 pathogenic E coli strains isolated from broilers and layer hens with colibacillosis infections were screened to determine phenotypic expression of antimicrobial resistance against 13 antibiotics used in both veterinary and human medicine in Bangladesh. Of 101 pathogenic E. coli isolates, more than 55% were resistant to at least one or more of the tested compounds, and 36.6% of the isolates showed multiple-drug-resistant phenotypes. The most common resistances observed were against tetracycline (45.5%), trimethoprim-sulphamethoxazole (26.7%), nalidixic acid (25.7%), ampicillin (25.7%), and streptomycin (20.8%). Resistance to ciprofloxacin (12.9%), chlormaphenicol (8.9%), nitrofurantoin (2%), and gentamicin (2%) was also observed, and none of the isolates were resistant to tigecycline as well as extended spectrum beta-lactamase (ESBL) producers. One isolate was resistant to cefuroxime (1%), cefadroxil (1%), and mecillinam (1%) but was not an ESBL producer. Resistance rates, although significant in Bangladeshi isolates, were found to be lower than those reported for avian isolates from the Republic of Korea and clinical, avian, and environmental isolates from Bangladesh. The high level of antibiotic resistance in avian pathogens from Bangladesh is worrisome and indicates that widespread use of antibiotics as feed additives for growth promotion and disease prevention could have negative implications for human and animal health and the environment.

Association between antimicrobial resistance and virulence in Escherichia coli

Escherichia coli represents a major cause of morbidity and mortality worldwide. The treatment of E. coli infections is now threatened by the emergence of antimicrobial resistance. The dissemination of resistance is associated with genetic mobile elements, such as plasmids, that may also carry virulence determinants. A proficient pathogen should be virulent, resistant to antibiotics, and epidemic. However, the interplay between resistance and virulence is poorly understood. This review aims to critically discuss the association and linked transmission of both resistance and virulence traits in strains from extraintestinal infections in E. coli, and intestinal pathotypes. Despite the numerous controversies on this topic, findings from research published to date indicate that there is a link between resistance and virulence, as illustrated by the successful E. coli ST131 epidemic clone. Perhaps the most commonly accepted view is that resistance to quinolones is linked to a loss of virulence factors. However, the low virulent phylogenetic groups might be more prone to acquire resistance to quinolones. Specific characteristics of the E. coli genome that have yet to be identified may contribute to such genetic linkages. Research based on bacterial populations is sorely needed to help understand the molecular mechanisms underlying the association between resistance and virulence, that, in turn, may help manage the future disseminations of infectious diseases in their entirety.