Virulence genotyping of Escherichia coli isolates from avian cellulitis in relation to phylogeny

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.

Co-relationship between Escherichia coli in broiler cellulitis and liver lesions

Pathogenic strains of Escherichia coli may invade the subcutaneous tissue of poultry and cause cellulitis, whilst the pathogen may also cause lesions in internal organs such as the liver. Current paper co-relates Escherichia coli and virulence genes characteristic of Avian Pathogenic Escherichia coli (APEC) in broilers´ cellulitis and liver lesions. One hundred carcasses were retrieved from the production chain in an avian abattoir in the state of Bahia, Brazil, between August 2013 and January 2014, due to detection of cellulitis lesions. Cellulitis and liver samples were retrieved aseptically to quantify E. coli by Petrifilm™ count fast method (3M Company) (AOAC 998.8). Virulent genes iss and iutA were removed from E. coli isolates by Polymerase Chain Reaction (PCR). Escherichia coli was isolated from 82.0% of broilers removed from the production chain and the bacterium was concomitantly detected in cellulitis and liver lesions in 40.0% of broilers. E. coli counts ranged between 1.00 and 4.73 log CFU/g in liver lesions and between 2.00 and 9.00 log UFC/g in cellulitis lesions. Virulent genes iutA and iss were detected in 97.56% and 89.02% of E. coli isolates, respectively. Genotype analysis demonstrated the concomitant amplification of genes iutA and iss in 60.0% (n=40) of samples of cellulitis and liver lesions in which the simultaneous isolation of E. coli occurred. There was a positive and significant co-relationship (r=0.22; p<0.05) between the variables occurrence of E. coli isolated from liver samples and the occurrence of E. coli isolated from cellulitis lesions. There were also positive and significant co-relationships between populations of E. coli from liver isolates and cellulitis lesions (r=0.46; p<0.05) when E. coli isolated in the liver and in cellulitis lesions was detected. Since results showed a relationship between E. coli in cellulitis and liver lesions and possible systemic infection, the occurrence of cellulitis lesions as a criterion for total discarding of carcass may be suggested.

Escherichia coli vacuolating factor, involved in avian cellulitis, induces actin contraction and binds to cytoskeleton proteins in fibroblasts

Background

Avian pathogenic Escherichia coli (APEC) isolated from avian cellulitis lesions produces a toxin, named Escherichia coli vacuolating factor (ECVF), that causes cell vacuolization and induces inflammatory response in broiler chicken.

Methods

We investigated the intracellular activities of ECVF in avian fibroblasts using fluorescence staining, electron microscopy, MTT and LDH measurements. As ECVF act specifically in avian cells, we performed blotting assay followed by mass spectrometry to better understand its initial intracellular protein recognition.

Results

ECVF induced actin contraction, mitochondrial damage and membrane permeability alterations. Ultrastructural analysis showed intracellular alterations, as nuclear lobulation and the presence of degraded structures inside the vacuoles. Moreover, ECVF induced cell death in fibroblasts. ECVF-biotin associates to at least two proteins only in avian cell lysates: alpha-actinin 4 and vinculin, both involved in cytoskeleton structure.

Conclusion

These findings demonstrated that ECVF plays an important role in avian cellulitis, markedly in initial steps of infection. Taken together, the results place this toxin as a target for drug and/or vaccine development, instead of the use of large amounts antibiotics.

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

Avian pathogenic Escherichia coli (APEC) is an important respiratory pathogen of poultry. A variety of virulence-associated genes and serogroups are associated with avian colibacillosis caused by APEC strains. One hundred forty-eight E. coli isolates recovered from diagnosed cases of avian colibacillosis from Guangdong province between 2005 and 2008 were serotyped, and characterized for virulence-associated genes, phylogenetic backgrounds, antibiotic susceptibility, and genetic relatedness. Associations between virulence-associated genes and antimicrobial resistance were further analyzed. Although 148 APEC isolates belonged to 21 different serogroups, 81% were of one of eight serogroups: O65 (27%), O78 (10%), O8 (9%), O120 (9%), O2 (7%), O92 (6%), O108 (5%), and O26 (5%). Polymerase chain reaction analysis showed that the most prevalent gene was traT (90%), followed by iroN (63%), fimH (58%), hlyF (55%), cvaC (54%), and sitA (51%). The APEC strains mainly belonged to groups A (73%) and D (14%). Multiple antimicrobial-resistant phenotypes (greater than or equal to three antimicrobials) were detected in all E. coli isolates, with the majority of isolates displaying resistance to tetracycline (97%), sulfamethoxazole (93%) and fluoroquinolones (87% for ciprofloxacin and 84% for enrofloxacin), chloramphenicol (74%), and florfenicol (66%). All E. coli isolates were further genetically characterized by pulsed-field gel electrophoresis. A total of 125 different pulsed-field gel electrophoresis profiles were obtained, implying that the multiresistant E. coli isolates carrying virulence-associated genes and belonging to multiple serogroups were not derived from a specific clone, but represented a wide variety of chromosomal backgrounds. Statistical analysis showed that several virulence-associated genes were significantly present in APEC isolates susceptibility to multiple antimicrobials. The findings demonstrate that a wide variety of serogroups and potential virulence genes, multiple-resistances, and the clear association of susceptibility and virulence genes have commonly emerged in APEC strains, and these also suggest that antimicrobials should be prudently used to reduce the emergence and spread of resistant strains carrying virulence-associated genes.

Antimicrobial resistance, virulence genes, and phylogenetic background in Escherichia coli isolates from diseased pigs

Escherichia coli isolates from diseased pigs were examined for antimicrobial susceptibility to 12 antimicrobials and possession of virulence genes (VGs), and then grouped according to the phylogenetic background and genetic relatedness. Associations between antimicrobial resistance (AMR) and VGs and between AMR and phylogenetic group were subsequently assessed. The results showed that most isolates (91%) were epidemiologically unrelated. Multiple antimicrobial-resistant phenotypes (>or=5 antimicrobials) were observed in 89% of E. coli strains and the most frequent types of resistance were to sulfamethoxazole (95%), tetracycline (94%), chloramphenicol (89%), and streptomycin (84%). The majority of isolates belonged to phylogenetic group A (84%). The most prevalent VG was EAST1 (64%), followed by Stx2e (63%) and eae (47%). Resistance to ceftiofur was associated with the presence of certain VGs, whereas resistance to doxycycline and kanamycin was associated with the absence of certain VGs. These findings suggest that multidrug resistance phenotypes, a variety of VGs, and the clear associations between resistance and VGs are commonly present in E. coli strains from diseased pigs. These results indicate that there is a great need for surveillance programs in China to monitor AMR in pathogenic E. coli strains.