Virulence profiles of Shiga toxin-producing Escherichia coli and other potentially diarrheagenic E.coli of bovine origin, in Mendoza, Argentina

This study described a group of strains obtained from a slaughter house in Mendoza, in terms of their pathogenic factors, serotype, antibiotype and molecular profile. Ninety one rectal swabs and one hundred eight plating samples taken from carcasses of healthy cattle intended for meat consumption were analyzed. Both the swab and the plate samples were processed to analyze the samples for the presence of virulence genes by PCR: stx1, stx2, eae and astA. The Stx positive strains were confirmed by citotoxicity assay in Vero cells. The isolates were subsequently investigated for their O:H serotype, antimicrobial susceptibility and molecular profile by Random Amplification of Polymorphic DNA (RAPD). Twelve E.coli strains were identified by their pathogenicity. Nine were from fecal origin and three from carcasses. Three strains carried the stx1 gene, three the stx2 gene, two carried eae and four the astA gene. The detected serotypes were: O172:H-; O150:H8; O91:H21; O178:H19 and O2:H5. The strains showed a similarity around 70% by RAPD. Some of the E.coli strains belonged to serogroups known for certain life-threatening diseases in humans. Their presence in carcasses indicates the high probability of bacterial spread during slaughter and processing.

Virulence profiles of Shiga toxin-producing Escherichia coli and other potentially diarrheagenic E.coli of bovine origin, in Mendoza, Argentina

This study described a group of strains obtained from a slaughter house in Mendoza, in terms of their pathogenic factors, serotype, antibiotype and molecular profile. Ninety one rectal swabs and one hundred eight plating samples taken from carcasses of healthy cattle intended for meat consumption were analyzed. Both the swab and the plate samples were processed to analyze the samples for the presence of virulence genes by PCR: stx1, stx2, eae and astA. The Stx positive strains were confirmed by citotoxicity assay in Vero cells. The isolates were subsequently investigated for their O:H serotype, antimicrobial susceptibility and molecular profile by Random Amplification of Polymorphic DNA (RAPD). Twelve E.coli strains were identified by their pathogenicity. Nine were from fecal origin and three from carcasses. Three strains carried the stx1 gene, three the stx2 gene, two carried eae and four the astA gene. The detected serotypes were: O172:H-; O150:H8; O91:H21; O178:H19 and O2:H5. The strains showed a similarity around 70% by RAPD. Some of the E.coli strains belonged to serogroups known for certain life-threatening diseases in humans. Their presence in carcasses indicates the high probability of bacterial spread during slaughter and processing.

Genetic similarity between APEC and Escherichia coli strains isolated from Guaruba guarouba in a survey on healthy captive psittacine birds / Similaridade genética entre APEC e cepas de Escherichia coli isoladas de Guaruba guarouba em um estudo com psitacídeos hígidos de cativeiro

The role of psittacine birds as a reservoir of avian pathogenic Escherichia coli (APEC) is not known but would be helpful in understanding the human animal interface, since the enteric microbiota of these birds consists of Gram positive bacteria. The aim of this study was to identify the presence of APEC in feces of clinically healthy Guaruba guarouba. To do this, we isolated and analyzed E. coli from cloacal fecal samples taken from 87 psittacine birds from six zoologic parks, three commercial breeders and one conservation breeder. Of the 87 birds examined, 46 (52.87%) presented E. coli in feces. The presence of the following eight virulence genes was determined by the polymerase chain reaction (PCR): irp2, iucD, iss, vat, cvi/cva, tsh, astA, and papC, and 29 (63.04%) of 46 E. coli isolates tested were positive at least one of the eight genes studied. The frequency of virulence genes observed in isolates of E. coli were 32.6% (15/46) irp2, 26% (12/46) iucD, 19.5% iss (9/46), 17.4% vat (8/46), 17.4% cvi/cva (8/46), 8.7% tsh (4/46), 4.4% astA (2/46) and 0% papC (0/46). The isolates were grouped in 13 genotypic profiles according to virulence gene combinations, but only 2 isolates were classified as APEC, with the pattern iuc, iss, cvi/cva, irp + and iuc, iss, cvi/cva, irp, tsh, vat +. This study reveals the presence of APEC in clinically healthy captive G. guarouba, suggesting that these psittacine birds may act as reservoir for pathogenic microorganisms. Epidemiological studies are needed to determine the relevance of this species as a reservoir and the implications for conservation of endangered species G. guarouba.(AU)

O papel dos psitacídeos como reservatório de Escherichia coli patogênicas para aves (APEC) não é conhecido, mas será útil para a compreensão da interface humano-animal, uma vez que a microbiota entérica destas aves é composta por bactérias Gram-positivas. O objetivo deste estudo foi identificar a presença de APEC em fezes de Guaruba guarouba clinicamente saudáveis. Para isso, foram isoladas e analisadas E. coli presentes em fezes cloacais coletadas de 87 psitacídeos, alojados em seis zoológicos, três criatórios comerciais e um criatório conservacionista. Das 87 aves examinadas, 46 (52,87%) apresentaram E. coli nas fezes. A presença de oito genes de virulência foi determinada pela reação em cadeia pela polimerase (PCR): irp2, iucD, iss, vat, cvi/cva, tsh, astA, e papC, e 29 (63,04%) dos 46 isolados foram positivos para pelo menos um dos oito genes estudados. A frequência dos genes de virulência observada nos isolados de E. coli foi 32.6% (15/46) irp2, 26% (12/46) iucD, 19.5% iss (9/46), 17.4% vat (8/46), 17.4% cvi/cva (8/46), 8.7% tsh (4/46), 4.4% astA (2/46) e 0% papC (0/46). Os isolados foram agrupados em 13 perfis genotípicos de acordo com combinações de genes de virulência, mas apenas duas amostras foram classificadas como APEC, com o perfil iuc, iss, cvi/cva, irp + e iuc, iss, cvi/cva, irp, tsh, iuc, iss, +. Este estudo revela a presença de APEC em aves de cativeiro (G. guarouba) clinicamente saudáveis, sugerindo que estes psitacídeos possam atuar como reservatórios de micro-organismos patogênicos. Estudos epidemiológicos são necessários para determinar a relevância desta espécie como reservatório e as implicações para a conservação da espécie ameaçada G. guarouba.(AU)

Putative new heat-stable cytotoxic and enterotoxic factors in culture supernatant of Escherichia coli isolated from drinking water

Enteric infections caused by the ingestion of contaminated water, especially by Escherichia coli, are important to define the virulence properties of these bacteria. Due to frequent infantile diarrhea in the city of Ouro Preto, Minas Gerais state, Brazil, the phenotypic and genotypic diarrheagenic properties of E. coli isolated from drinking water were studied. The culture supernatants of 39 (40 percent) among a total of 97 E. coli isolates from drinking water were positive by suckling mouse assay and induced cytotoxic effects on Vero cells. The enterotoxic and cytotoxic activities were present in the fraction with less than 10 kDa and were not lost when heated up to 60ºC and 100ºC for 30 minutes. PCR assays showed that among these 39 Vero cytotoxigenic E. coli, four (10.2 percent) were positive for ST II (estB) and two (5 percent) positive for αHly (hlyA). Gene amplification of SLT (stx 1, stx 2), ST I (estA), LT (eltI, eltII), EAST1 (astA), EHly (enhly) and plasmid-encoded enterotoxin (pet) were not observed. This heat-stable cytotoxic enterotoxin of E. coli is probably a new putative diarrheagenic virulence factor, as a toxin presenting these characteristics has not yet been described.(AU)

Indução de mutação por uma substância química em cepas de Escherichia coli para a atenuação e o desenvolvimento de vacina contra a colibacilose aviária / Mutations induced by a chemical in strains of Escherichia coli to the attenuation and vaccine development against avian colibacillosis

A colibacilose aviária caracteriza-se como uma infecção extra-intestinal secundária a outros agentes. É responsável por grandes perdas econômicas na criação de aves comerciais, sendo sua prevenção fundamental para minimizar prejuízos. O objetivo deste estudo foi atenuar cepas virulentas de Escherichia coli aviárias, por indução de mutagênese química. Foram selecionadas nove (09) cepas pertencentes à coleção de cultura do Laboratório de Ornitopatologia da FMVZ-USP. Todas as cepas estudadas foram resistentes à eritromicina, lincomicina, oxaciclina, penicilina, tiamulina e tilmicosin e sensíveis ao ácido nalidíxico, cloranfenicol, ciprofloxacina, colistina, enrofloxacina, florfenicol e gentamicina. Ocorreram resistências nas amostras analisadas de 33,33%, 22,22%, 11,11%, 55,55%, 66,66%, 77,77%, 33,33%, 22,22%, 22,22% e 33,33%, respectivamente, a amoxacilina, a ampicilina, a doxaciclina, a espectiomicina, a estreptomicina, a lincomicina-espectiomicina, a neomicina, a rifampicina, a tetraciclina e ao trimetropin-sulfa. Induziu-se resistência a estreptomicina ou rifampicina ou ácido nalidíxico como marcadores. Não houve o desenvolvimento de resistências a outros antimicrobianos testados, após a exposição a substância mutagênica. Os resultados da amplificação dos genes por PCR, mostraram que todas as cepas foram negativas para papC, cnf e astA e todas foram positivas para iuc e irp2. Duas cepas foram positivas para os genes vat, cinco para iss, quatro para o gene tsh, uma para cvi/cva, duas para sfaI e uma para astA. Após o uso da substância mutagênica duas cepas apresentaram reações negativas para os genes tsh, cvi/cva e sfaI e uma cepa para o gene astA. No teste de AFLP verificaram-se diferenças em similaridade de bandas em oito (08) das nove (09) cepas, quando comparadas com a amostra tratada com a substância mutagênica, sendo que este indice variou de 40% a 96,3%. Embora no teste de patogenicidade em pintinhos de um dia de idade não tenha ocorrido diferenças significativas na mortalidade nos diferentes grupos estudados, houve alteração de patogenicidade em cinco cepas expostas à substância mutagênica. Ocorreram reduções significativas em relação ao escore de lesões quando os grupos foram comparados (p<0,05), indicando atenuação pela substância mutagênica.

The avian colibacillosis is characterized as an extraintestinal infection which is secondary to other agents. It is responsible for considerable economic loss in the breeding of commercial birds, making its prevention essential to reducing damages. The aim of this study was to attenuate viral strains of avian Escherichia coli, using chemical mutagenesis induction. Nine (09) strains were selected from the culture collection of the Ornitopathology Laboratory of the School of Veterinary Medicine of the University of São Paulo. All analyzed strains were resistant to erythromycin, lincomicin, oxacillin, penicillin, tiamulin and tilmicosin and they were sensitive to nalidixic acid, chloramphenicol, ciprofloxacin, colistin, enrofloxacin, florfenicol and gentamicin. The analyzed samples presented the following resistance levels: 33.33%, 22.22%, 11.11%, 55.55%, 66.66%, 77.77%, 33.33%, 22.22%, 22.22% and 33.33% to, respectively, amoxicillin, ampicillin, doxycycline, spectinomycin, streptomycin, lincomycin-spectinomycin, neomycin, rifampicin, tetracycline and trimethoprim-sulfa. The resistance to streptomycin or rifampicin or nalidixic acid was induced as a marker. There was no development of resistance to other tested antimicrobials after the exposure to the mutagenic substance. The results of the PCR gene amplification showed that all strains were negative for papC, cnf and astA and they were all positive for iuc and irp2. Two strains were positive for the vat genes, five for iss, four for the tsh gene, one for cvi/cva, two for sfaI and one for astA. After using the mutagenic substance, two strains presented negative reactions for the tsh, cvi/cva and sfaI genes and one strain for the astA gene. In the AFLP test, differences were found for band similarity in eight (08) out of nine (09) strains, when compared with the samples treated with the mutagenic substance and this rate varied from 40% to 96.3%. Although the pathogenicity test in one-day-old chicks did not present significant differences in the mortality rate in the different analyzed groups, there was a pathogenicity alteration in five strains exposed to the mutagenic substance. There were significant reductions regarding the lesion scores when the groups were compared (p<0,05), indicating an attenuation due to the mutagenic substance.

Indução de mutação por uma substância química em cepas de Escherichia coli para a atenuação e o desenvolvimento de vacina contra a colibacilose aviária / Mutations induced by a chemical in strains of Escherichia coli to the attenuation and vaccine development against avian colibacillosis

A colibacilose aviária caracteriza-se como uma infecção extra-intestinal secundária a outros agentes. É responsável por grandes perdas econômicas na criação de aves comerciais, sendo sua prevenção fundamental para minimizar prejuízos. O objetivo deste estudo foi atenuar cepas virulentas de Escherichia coli aviárias, por indução de mutagênese química. Foram selecionadas nove (09) cepas pertencentes à coleção de cultura do Laboratório de Ornitopatologia da FMVZ-USP. Todas as cepas estudadas foram resistentes à eritromicina, lincomicina, oxaciclina, penicilina, tiamulina e tilmicosin e sensíveis ao ácido nalidíxico, cloranfenicol, ciprofloxacina, colistina, enrofloxacina, florfenicol e gentamicina. Ocorreram resistências nas amostras analisadas de 33,33%, 22,22%, 11,11%, 55,55%, 66,66%, 77,77%, 33,33%, 22,22%, 22,22% e 33,33%, respectivamente, a amoxacilina, a ampicilina, a doxaciclina, a espectiomicina, a estreptomicina, a lincomicina-espectiomicina, a neomicina, a rifampicina, a tetraciclina e ao trimetropin-sulfa. Induziu-se resistência a estreptomicina ou rifampicina ou ácido nalidíxico como marcadores. Não houve o desenvolvimento de resistências a outros antimicrobianos testados, após a exposição a substância mutagênica. Os resultados da amplificação dos genes por PCR, mostraram que todas as cepas foram negativas para papC, cnf e astA e todas foram positivas para iuc e irp2. Duas cepas foram positivas para os genes vat, cinco para iss, quatro para o gene tsh, uma para cvi/cva, duas para sfaI e uma para astA. Após o uso da substância mutagênica duas cepas apresentaram reações negativas para os genes tsh, cvi/cva e sfaI e uma cepa para o gene astA. No teste de AFLP verificaram-se diferenças em similaridade de bandas em oito (08) das nove (09) cepas, quando comparadas com a amostra tratada com a substância mutagênica, sendo que este indice variou de 40% a 96,3%. Embora no teste de patogenicidade em pintinhos de um dia de idade não tenha ocorrido diferenças significativas na mortalidade nos diferentes grupos estudados, houve alteração de patogenicidade em cinco cepas expostas à substância mutagênica. Ocorreram reduções significativas em relação ao escore de lesões quando os grupos foram comparados (p<0,05), indicando atenuação pela substância mutagênica. (AU)

The avian colibacillosis is characterized as an extraintestinal infection which is secondary to other agents. It is responsible for considerable economic loss in the breeding of commercial birds, making its prevention essential to reducing damages. The aim of this study was to attenuate viral strains of avian Escherichia coli, using chemical mutagenesis induction. Nine (09) strains were selected from the culture collection of the Ornitopathology Laboratory of the School of Veterinary Medicine of the University of São Paulo. All analyzed strains were resistant to erythromycin, lincomicin, oxacillin, penicillin, tiamulin and tilmicosin and they were sensitive to nalidixic acid, chloramphenicol, ciprofloxacin, colistin, enrofloxacin, florfenicol and gentamicin. The analyzed samples presented the following resistance levels: 33.33%, 22.22%, 11.11%, 55.55%, 66.66%, 77.77%, 33.33%, 22.22%, 22.22% and 33.33% to, respectively, amoxicillin, ampicillin, doxycycline, spectinomycin, streptomycin, lincomycin-spectinomycin, neomycin, rifampicin, tetracycline and trimethoprim-sulfa. The resistance to streptomycin or rifampicin or nalidixic acid was induced as a marker. There was no development of resistance to other tested antimicrobials after the exposure to the mutagenic substance. The results of the PCR gene amplification showed that all strains were negative for papC, cnf and astA and they were all positive for iuc and irp2. Two strains were positive for the vat genes, five for iss, four for the tsh gene, one for cvi/cva, two for sfaI and one for astA. After using the mutagenic substance, two strains presented negative reactions for the tsh, cvi/cva and sfaI genes and one strain for the astA gene. In the AFLP test, differences were found for band similarity in eight (08) out of nine (09) strains, when compared with the samples treated with the mutagenic substance and this rate varied from 40% to 96.3%. Although the pathogenicity test in one-day-old chicks did not present significant differences in the mortality rate in the different analyzed groups, there was a pathogenicity alteration in five strains exposed to the mutagenic substance. There were significant reductions regarding the lesion scores when the groups were compared (p<0,05), indicating an attenuation due to the mutagenic substance. (AU)

Expression of aggregative adherence to hela cells by Escherichia coli strains isolated from sick horses

The virulence attributes of 56 Escherichia coli strains isolated from sick horses (secretions of uterine cervices; gastrointestinal and lung fragments of necropsy; diarrheic feces, and tracheal washings) was examined by determining their adherence pattern to HeLa cells and searching for the presence of virulence genes of the various E. coli pathotypes. Two non-adherent strains presented astA, which encodes the enteroaggregative E. coli heat-stable toxin. Twenty-seven strains (48.2%) adhered to HeLa cells, 21 (77.8%) of which presented the aggregative adherence pattern (AA) that characterize the Enteroaggregative E. coli pathotype (EAEC). Nine of the strains presenting AA were isolated from secretions of uterine cervix, including one carrying virulence genes of the EAEC pathotype (aggR,aap,irp2, and pic). This is the first description of the AA phenotype amongst E. coli strains from sick horses. Such strains should be further evaluated regarding their potential role in the pathogenesis of diverse equine diseases and as reservoirs of human infections.

Características de virulência de 56 amostras de Escherichia coli isoladas de eqüinos doentes (secreção de colo uterino, fragmentos de necrópsia do trato gastrointestinal e de pulmões, fezes diarréicas e lavado traqueal) foram examinadas para determinar o padrão de aderência em células HeLa e pesquisar a presença de genes de virulência de vários patotipos de E. coli. Duas amostras não aderentes apresentaram astA, gene que codifica a toxina termo-estável de E. coli enteroagregativa. Das vinte e sete amostras (48,2%) que aderiram a células HeLa, 21 (77,8%) apresentaram o padrão de aderência agregativa (AA) que caracteriza o patotipo de E. coli Enteroagregativa (EAEC). Nove destas amostras que apresentaram AA foram isoladas de secreção de colo uterino, incluindo uma que apresentava genes de virulência de patotipos de EAEC (aggR,aap,irp2 e pic). Esta é a primeira descrição do fenótipo AA em amostras de cavalos doentes. Estas amostras deverão ser melhor avaliadas em relação a sua potencial função na patogênese de diferentes doenças eqüinas, bem como à possibilidade destes animais representarem um reservatório de infecções humanas causadas por esta bactéria.

Estudo dos fatores de virulência, sorogrupos, patogenicidade e susceptibilidade antimicrobiana das cepas de Escherichia coli isoladas de pintainhas de reposição de postura

Foram isoladas 90 estirpes de E. coli de fígados e de intestinos, de pintainhas de postura comercial, com sete dias de idade. Com o objetivo de caracterizar as estirpes isoladas, a patogenicidade das mesmas foi determinada, em inoculação ?in vivo?. O teste revelou 44 estirpes de alta ou de intermediária patogenicidade, que foram analisadas por PCR multiplex quanto á presença de oito genes de virulência (astA, iss, iucD, irp2, papC, tsh, vat e cva/cvi) e tiveram os sorotipos O:H identificados. Os resultados demonstraram que todas as estirpes analisadas continham pelo menos um dos oito genes pesquisados e que a maioria (93,20%) possuíam o gene iss. Foram detectados 17 perfis genéticos diferentes, sendo 15 deles com combinações de dois ou mais genes, representando 70,45% do total de estirpes analisadas. Onze sorogrupos e onze antígenos ?H? foram identificados, sendo O8 (15,89%) e o H17 (23,8%) os mais frequentes. Com o objetivo de verificar a susceptibilidade das estirpes aos antimicrobianos: ampicilina, enrofloxacina, eritromicina, espectinomicina, estreptomicina, fosfomicina, kanamicina, lincomicina, norfloxacina, sulfa+trimetoprim e tetraciclina, comumente utilizados na avicultura, todas as estirpes de E. coli isoladas foram analisadas. O antimicrobiano que apresentou maior atividade antibacteriana foi a espectinomicina (92,2%) e o de menor atividade foi a lincomicina. Nenhuma das estirpes foi sensível a todos os antimicrobianos testados. Os resultados demonstraram uma diversidade de sorotipos e de genes de virulência envolvidos no quadro clínico de colibacilose estudado, como também sorogrupos que não haviam sido relatados em APEC e a alta incidência de resistência antimicrobiana

A total of 90 strains of E. coli were isolated from the livers and intestines of seven-day-old commercial layer chicks. With the objective of characterising the isolated strains, their pathogenicity levels were determined by in vivo inoculation. These tests identified 44 strains with high or intermediate levels of pathogenicity, which were then analysed by multiplex PCR for the presence of eight virulence genes (astA, iss, iucD, irp2, papC, tsh, vat e cvi/cva) and the serotypes O:H were identified. The results demonstrated that these isolated strains contained at least one of the eight genes of interest, and the majority (93.20%) possessed the iss gene. Seventeen different genetic patterns were detected, 15 of which had combinations of two or more genes, representing 70.45% of all analysed strains. Eleven serogroups and eleven antigens ?H? were identified, O8 (15.89%) and H17 (23.80%) were most frequent. Aiming to verify the susceptibility of strains to antimicrobial agents: ampicillin, enrofloxacin, erythromycin, spectinomycin, streptomycin, fosfomycin, kanamycin, lincomycin, norfloxacin, trimethoprim sulfa and tetracycline, commonly used in poultry, all strains of E. coli isolates were analyzed. The antibiotics that showed the highest antibacterial activity was spectinomycin (92.2%) and less activity was the lincomycin (100%) strains were resistant. None of the strains were sensitive to all antibiotics tested. The results showed a diversity of serotypes and virulence genes involved in the clinical study of colibacillosis, as well as serogroups that had not been reported in APEC and the high incidence of antimicrobial resistance

East1 toxin and its presence in a changing microbial world

This review shows the structure, mode of action, and actual epidemiological data about EAST1 toxin. It is a particularly intriguing bacterial toxin that may subvert multiple cellular processes to yield intestinal epithelial cell secretion. EAST1 toxin was first described in strains of EAggEC that were associated with persistent diarrhea primarily in developing world countries. Molecular organization, mobility, and data in literature are suggesting that EAST1 could be a transposon. The insertion sequences in Escherichia coli and some of the usual transposition mechanisms as well as regulation are reviewed. This review emphasizes the presence of the gene astA in EPEC, EAggEC, A-EPEC, ETEC, DAEC, EIEC, and in non-diarrheagenic E. coli. It also discusses here the presence of the astA gene in Salmonella spp. and future perspectives for understanding its role in diarrheal disease in both bacterial genera.

Antibiotic resistance pattern and pathological features of avian pathogenic Escherichia coli O78: K80 in chickens / Padrão de resistência a antibióticos e características patológicas de Escherichia coli patogênica aviária O78: K80 em galinhas

Avian pathogenic Escherichia coli (APEC) induces colibacillosis, an acute and systemic disease, resulting in substantial economic losses in the poultry sector. This study aimed to investigate the antibiotic resistance pattern associated with frequent virulence gene distribution in APEC O78:K80 that may cause pathological alterations in chickens. The antibiogram profile showed high resistance to erythromycin, chloramphenicol, tetracycline, ampicillin, and co-trimoxazole, followed by intermediate resistance to ciprofloxacin, levofloxacin, enrofloxacin, norfloxacin, nitrofurantoin, and doxycycline hydrochloride, and sensitive to amikacin, streptomycin, gentamicin, and colistin. Virulence gene distribution identifies eight (irp-2, iutA, ompT, iss, iucD, astA, hlyF, iroN) genes through a conventional polymerase chain reaction. APEC O78:K80 caused significantly high liver enzyme concentrations, serum interleukin-6 and tumor necrosis factor-alpha levels in experimental birds. Also, infected birds have hypoproteinemia, hypoalbuminemia, and hyperglobulinemia. Necropsy examination revealed fibrinous perihepatitis and pericarditis, congested lungs, intestinal ecchymotic hemorrhages and necrotizing granulomatosis of the spleen. Histopathological examination depicted hepatocellular degeneration, myocardial necrosis, interstitial nephritis, intestinal hemorrhages and lymphopenia in the spleen. This study is the first evidence to assess the antibiotic resistance profile linked with virulence genes and clinicopathological potential of APEC O78:K80 in chickens in Pakistan, which could be a useful and rapid approach to prevent and control the disease by developing the control strategies.

A Escherichia coli patogênica aviária (APEC) induz a colibacilose, uma doença aguda e sistêmica, resultando em perdas econômicas substanciais no setor avícola. Este estudo teve como objetivo investigar o padrão de resistência a antibióticos associado à frequente distribuição de genes de virulência em APEC O78:K80 que podem causar alterações patológicas em galinhas. O perfil do antibiograma mostrou alta resistência à eritromicina, cloranfenicol, tetraciclina, ampicilina e cotrimoxazol; resistência intermediária à ciprofloxacina, levofloxacina, enrofloxacina, norfloxacina, nitrofurantoína e cloridrato de doxiciclina; e sensível à amicacina, estreptomicina, gentamicina e colistina . A distribuição de genes de virulência identificou oito genes (irp-2, iutA, ompT, iss, iucD, astA, hlyF e iroN) por meio de uma reação em cadeia da polimerase convencional. A APEC O78:K80 causou concentrações significativamente altas de enzimas hepáticas, níveis séricos de interleucina-6 e fator de necrose tumoral alfa em aves experimentais. Além disso, aves infectadas apresentaram hipoproteinemia, hipoalbuminemia e hiperglobulinemia. O exame de necropsia revelou peri-hepatite e pericardite fibrinosa, pulmões congestos, hemorragias equimóticas do intestino e granulomatose necrosante do baço. O exame histopatológico mostrou degeneração hepatocelular, necrose miocárdica, nefrite intersticial, hemorragias intestinais e linfopenia no baço. Este estudo é a primeira evidência para avaliar o perfil de resistência a antibióticos associado a genes de virulência e potencial clínico-patológico de APEC O78:K80 em galinhas no Paquistão, o que pode ser uma abordagem útil e rápida para prevenir e controlar a doença por meio do desenvolvimento de estratégias de controle.