Colibacillosis is of the most common infectious bacterial diseases of poultry.A total of 170 Escherichia coli isolates obtained from broiler and layer flocks implicated with colibacillosis between 2011 and 2014 were subjected to phylogenetic analysis. Among 150 E. coli isolates from typical lesions of local and systemic colibacillosis, 54 (31.8%), 37 (21.7%), 36 (21.2%) and 43 (25.3%) isolates determined as belonged to groups A, B1, B2 and D, respectively. The distribution of phylogenetic types for 20 isolates, obtained from apparently healthy birds as controls, were 9 (45%), 5 (25%), 1 (5%) and 5 (25%) for A, B1, B2 and D, respectively. Overall, the phylogenetic Determination revealed the B2 groups as predominant isolates in diseased birds, whereas the A group was apparently predominant in healthy birds. Results of this study represent genotypic diversity among different manifestations of avian colibacillosis.

Seventy poultry farms’ drinking water was tested for Escherichia coli contamination in Qom province in Iran. The cases of colibacillosis from positive farms were also collected and tested. The isolates were examined for serotype، detection of virulence genes by multiplex PCR and antibiotic resistance. Thirty poultry farm water samples were E. coli positive (18. 57%)، although 13 E. coli isolates were recovered from carcasses of related farms. The isolates belonged to O2 serogroup and one O157، with approximately 29% of the strains being non-typeable. Two isolates from water and carcasses were serotyped O2 and one sample serotyped O157، which needs to be further studied. The PCR method was on the basis of showing virulence genes of espB، stx1، stx2 and eae. One sample from water and one from a carcass were shared espB، stx2 and eae genes. Stx1 and stx2 genes were common in a sample from both water and carcass، although five samples from both water and carcass shared a stx1 gene as well. All isolates showed maximum sensitivity and resistance to lincospectine and tetracycline، respectively.

The residue of antibiotics and other chemical compounds in chicken meat is one of main concerns in consumers of this protein source. In this research, for study of correlation between antibiotic consumption and chicken meat contamination, in summer of 2014, 10 chicken farms in Isfahan province that reared under conventional condition and 5 chicken farms that reared broilers under without antibiotic consumption were monitored from start of growing period. At end of growing period, in slaughter stage, one piece of breast muscle and cecum content were sampled. The percentage of carcass contamination and number of Escherichia coli (E.coli) in cecal content were determined in chickens reared under conventional and without antibiotic condition. Also, the shigatoxogenic E.coli was examined by PCR.Furthermore, the carcass contamination and E.coli colony count in cecal content in chickens with or without colibacillosis background were determined. The results showed that the chicken meat contamination to E.coli and the E.coli population in cecal content in chickens reared under conventional condition were not significant different from chickens reared without antibiotic, while these indices in chickens with colibacillosis history were significant higher than chickens without colibacillosis history. In this study the shigatoxogenic E.coli was not detected. In overall, this study revealed microbial infection in chicken farms that lead to antibiotic consumption could decrease hygienic quality of chicken meat. Therefore, in addition to controlling of withdrawal time for antibiotic consumption, the withdrawal time for infections incidence must be observed for decrease the risk of transmission of pathogens along the food chain of human.

The exploitation of virulence traits of Extra Pathogenic Escherichia coli (EXPEC) could be considered an applicable tool to describe the pathogenesis and design the new treatment and control methods.  This study aimed to investigate the frequency of pap G II, Sfa, and afa in Escherichia coli isolated from poultry colibacillosis as well as UTIs. Totally 320 Escherichia coli including 247 isolated from poultry colibacillosis from Semnan, Tehran and Gilan province, 53 isolated from the cloaca of apparently healthy birds from Semnan, and 20 from human UTI were evaluated for the presence of pap G II, Sfa, and afa by the colony hybridization assay. Statistical analysis was performed using the  test and the P-value was considered <0.05. The results of this study showed among three adhesion genes, pap GII was the most common adhesins in both human and poultry source strains. Frequency of pap GII was 21.05%, 13.2%, and 35% in Escherichia coli isolated from poultry colibacillosis, UTI, and apparently healthy birds respectively. It was found that Escherichia coli isolated from human UTIs contained a higher frequency of the Sfa than poultry colibacillosis and afa was not detected in any of the groups.   Escherichia coli isolated from poultry colibacillosis and human UTI showed high pap GII prevalence, which supports its role in the pathogenesis of EXPEC. Therefore, it can be an attractive target to develop novel anti-virulence therapeutics method and vaccine strategies.

Colibacillosis due to Escherichia coli is one of the most important infectious diseases in poultry. While the influence of E. coli virulence factor in birds may differ due to interactions with other influential factors، the sole presence of such factors in E. coli does not determine its pathogenicity. Therefore، it is necessary to test the pathogenic capability of E. coli isolates on susceptible birds. The purpose of this study was to determine the virulence of three E. coli isolates from colibacillosis and compare their effects on day-old chicks using a lethality test. Seventy 1-day-old chicks were divided into 3 treatment groups of 20 chicks and 2 control groups of 5 chicks. Each treatment group was assigned to one E. coli isolate and divided into 4 sub-groups of 5 chicks. The overnight broth culture of each E. coli isolate was washed with PBS three times and diluted. Then، 0. 5 ml of undiluted culture (~109 CFU/mL)، and the dilutions of 0. 1، 0. 01، and 0. 001 of each culture were injected subcutaneously to each of the 5 birds in each subgroup behind the neck. One group of 5 birds was injected by PBS while negative control group did not receive anything. The chicks were monitored every 12 hours for 6 days. The dead chicks during the course of the experiment and all survived ones were necropsied and samples were taken from hearts and livers for bacteriological culture. Virulence of each E. coli isolate was evaluated based on a scoring system developed on death time، gross pathological observations، and bacteriological findings. All E. coli isolates of this study were capable of causing mortalities and producing the lesions typical of colibacillosis. There were no significant differences among the three E. coli isolates in their in vivo virulence abilities but the difference between each of the three E. coli isolates and each of the two control groups was significant (p|||£|0. 05). This study determined that our E. coli isolates were able to cause mortalities in day-old chicks. These findings increased our knowledge on the virulence characteristics of three Iranian E. coli isolates originated from avian colibacillosis.

Avian Colibacillosis can lead to important economic losses in the poultry industry. Escherichia coli the causative agent of this disease has acquired resistance to different antibiotics, including tetracycline.
This study was carried out to detect the distribution of tetracycline Group І efflux genes genes among E.coli isolates from from avian colibacillosis in Iran by PCR assay .
A total of 50 E. coli isolates from chicken colibacillosis were characterized by cultural, biochemical and PCR methods. Kirby-Bauer disk diffusion method was used to define the resistance of isolates to tetracycline, then the Frequencies of tetracycline resistance genes (tetA, tetB, tetC, tetG, tetH, tetZ and tetE) were also determined using PCR method.
According to biochemical and molecular experiments, 50 isolates from 237 chicken samples were recognized as E. coli. Seventy six(76%) of the isolates, however, were resistant to tetracycline. The distribution of tetracycline-resistance genes among E. coli isolates included tetB(34%) , tetA(26%), tetE(16%), tetC(15%), tetH(12%), tetG(12%) and tetZ(6%).
The present study highlights the prevalence of tetracycline resistant E. coli among chickens which is due to extensive

Avian pathogenic Escherichia coli (APEC), which is the causative agent of colibacillosis, harbors several putative virulence genes. An important trait of APEC for both poultry and public health is antibiotic resistance. In the present study, some potential virulence genes of APECs isolated from Northeast of Iran and their resistance to the quinolones antibiotics were studied. The conventional polymerase chain reaction (PCR) was used to determine the presence of four virulence genes, including iss, cvi, iuc, and tsh, in 52 isolates of E. coli from avian colibacillosis and 11 isolates from feces of apparently healthy chicken. Disk diffusion method was used to also determine the resistance of all the isolates against nalidixic acid, norofloxacin, ciprofloxacin, and enrofloxacin. The presence of iss and tsh virulence genes in isolates from diseased chickens was significantly higher than isolates from healthy chickens. There was no significant difference between APEC and fecal E. coli when it comes to quinolone resistance. However, cvi and iuc genes were significantly higher in susceptible isolates of E. coli from healthy chickens. iss and tsh genes are more prevalent in APEC isolates than in fecal isolates. There is no association between lack of virulence and resistance to quinolones in E. coli isolates from diseased chickens.

In this study, to know about the phylogeny of Escherichia coli isolated from broilers with collibacillosis in Tabriz, 70 E. coli isolates recovered from broilers with collibacillosis were characterized for phylogenetic group (A, B1, B2, D) by multiplex PCR. Of the all 70 samples, 35 (50%) isolates were classified as type A, 32 (45%) as type D, 2 (2.8%) as type B1 and 1 (2.8%) as type B2. This study demonstrates the high prevalence of E. coli types A and D in infected broilers. This shows that the collibacilosis-causing E. coli bacteria are typical commensals, type A alongside pathogenic type, D in Iran. It is possible that this type of E. coli could acquire virulence genes from pathogenic types. Of course, such a claim needs further study.

Pathogenic Escherichia coli strains cause a wide range of extra intestinal infections including urinary tract infection in humans and colibacillosis in poultry. They are classified into uropathogenic E. coli (UPEC) and avian pathogenic E. coli (APEC) with genetic similarities and variations. Their pathogenicity is related to the virulence-encoding genes like sfa, papG II, ompT, iutA, and iss with zoonotic potentials. One hundred isolated E. coli from patients with urinary tract infection and 100 E. coli from chickens with colibacillosis were evaluated for the presence of the most common virulence-encoding genes including sfa, papG II, ompT, iutA, and iss by multiplex polymerase chain reaction. While the frequency of sfa, papG II, ompT, iutA and iss encoding genes in APEC isolates were respectively 0.00%, 67.00%, 63.00%, 89.00% and 89.00%, the frequency of these encoding genes in UPEC isolates were 18.00%, 40.00%, 40.00%, 74.00% and 48.00%, respectively. Except for sfa, the frequencies of other encoding genes in APEC were more than those in UPEC isolates. The iutA as the most common UPEC encoding gene and iss as the most common APEC encoding gene were the most prevalent virulence factors in the examined E. coli isolates. Finding out the distribution of virulence-associated genes could be helpful to identify similarities and differences between APEC and UPEC isolates in order to provide more substantial evidence of their common virulence traits and potential zoonotic threats.