Characterization of Escherichia coli and other bacteria isolated from condemned broilers at a Danish abattoir

Meat inspection is important to ensure food safety and protect public health. Visual inspection of slaughtered carcasses for pathological changes should be supported by bacteriological analysis to determine whether the entire carcass or parts of it should be condemned. The aim of this study was to determine the bacterial species present in different sample types from condemned broiler carcasses. Furthermore, we investigated the genetic characteristics, zoonotic potential, and relatedness of Escherichia coli, the predominant bacterial species isolated from the carcasses. A total of 400 broiler carcasses condemned because of cellulitis (100), scratches (100), hepatitis (100), and healthy control carcasses (100) were selected. Samples of meat, pathological lesion, and bone marrow of each carcass were obtained for microbial analysis. From the analyzed samples, 469 bacterial isolates were recovered with E. coli accounting for 45.8%, followed by Aeromonas spp. (27.9%), in particular A. veronii. The highest rate of bacterial isolation was observed in carcasses condemned with cellulitis, whereas carcasses with hepatitis had the lowest rate of bacterial isolation. Forty-four E. coli isolates originating from different sample types were selected for whole genome sequencing. A clonal relationship was shown between E. coli from different sample types of the same carcass condemned with cellulitis and scratches. A major clade of E. coli was found in carcasses condemned with cellulitis with isolates containing mdf(A), tet(A), and bla TEM-1B genes that confer resistance to macrolides, tetracycline, and ampicillin, respectively. E. coli in this clade all belonged to ST117 and clustered with E. coli isolates previously collected from dead chickens and carcasses condemned due to cellulitis in Denmark, Finland, and the United Kingdom. Bacterial evaluation results of carcasses condemned with cellulitis, scratches (moderate to severe skin lesion), and acute hepatitis confirmed the need for total condemnation of carcasses with these pathological findings. A similar evaluation should be done for carcasses affected with chronic hepatitis, and minor scratches lesions.

Animal-based welfare indicators of 4 slow-growing broiler genotypes for the approval in an animal welfare label program

For broiler genotypes to be merchandized under the animal welfare label of the German Animal Welfare Federation, several animal-based welfare indicators with upper limits are listed in a criteria catalog. We compared the prevalence of animal-based welfare indicators in 4 slow-growing broiler genotypes [Ranger Classic (RC), Ranger Gold (RG), Rowan Ranger (RoR), and Rambler Ranger (RaR)] in terms of potential approval of these genotypes for a German animal welfare label program. Chicks were housed in 16 floor pens, of which 8 had access to a winter garden. With 4 replications of each genotype, animal-based welfare indicators were assessed in 160 broilers (10 broilers per pen) on fattening days (FD) 36 and 44. The body weight of the 4 broiler genotypes differed on both examination days in decreasing order for RC, RG, RoR, and RaR (P < 0.001). The walking ability was within the scope of the animal welfare label in all genotypes; it was better in genotypes with a lower mean body weight and correlated positively with the body weight in RG, RoR, RaR, and in the pooled data of the 4 genotypes. Hock burns were only observed at a low severity score, with male broilers being affected more often than female broilers. A positive correlation of the development of hock burn with the weight of the broilers was observed on FD 44 when data of all genotypes were pooled. The footpads of all examined broilers were without lesions at both examinations. Skin scratches were observed in all genotypes at both examinations, and RC broilers differed on FD 36 from the other 3 genotypes by showing a higher prevalence of more severe scratches. Broilers of pens with access to a winter garden were affected by skin scratches more often than broilers without. With the exception of weight gain in 2 genotypes, the investigated indicators showed that all genotypes met the requirements of the animal welfare label.

Animal- and management-based welfare indicators for a conventional broiler strain in 2 barn types (Louisiana barn and closed barn)

The aim of this observational study was to describe health- and management-related welfare indicators for a conventional broiler strain housed in 2 barn types (Louisiana barn and closed barn) on the same farm and to assess the impact of age and housing conditions on these indicators. Broilers were examined 4 times in each of 7 fattening periods. Their weight gain, gait score, and further animal-based indicators did not differ between the barn types. On average 46% showed no sign, 51% a minor but visible, and 3% a profound lameness at the end of the fattening period (fattening day 39). Soiling of the plumage, skin scratches, foot pad dermatitis, and hock burns worsened with increasing age. Soiling of the plumage was correlated negatively with litter depth (Pearson, r = -0.549, P = 0.042) and positively with litter quality (Pearson, r = 0.641, P = 0.013). Skin scratches occurred in 89% of the broilers (32% deep with penetration of dermis) on fattening day 39 and were correlated positively with cumulative mortality (Pearson, r = 0.615, P = 0.019), indicating a severe animal welfare impact. Foot pad dermatitis did not correlate with health- or management-related indicators, whereas hock burn correlated positively with the broilers' weight (Pearson, r = 0.853, P < 0.001) and with ammonia concentrations (Pearson, r = 0.577, P = 0.031). Management-related indicators (antibiotic treatments, dead on arrival) and cumulative mortality did not differ between the barn types. At the end of the fattening period, the litter quality was worse and concentrations of ammonia and peaks of high carbon dioxide concentrations were higher in the Louisiana than in the closed barn. The light intensity was on average 20 times higher in the Louisiana than in the closed barn without any negative impact. Summarizing, the barn type did not seem to influence the investigated welfare indicators, but Louisiana barns might need a more precise management to maintain the required ranges of noxious gases and litter quality.

Gangrenous dermatitis in chickens and turkeys

Gangrenous dermatitis (GD) is a disease of chickens and turkeys that causes severe economic losses in the poultry industry worldwide. Clostridium septicum, Clostridium perfringens type A, and occasionally Clostridium sordellii are considered the main causes of GD, although Staphylococcus aureus and other aerobic bacteria may also be involved in some cases of the disease. GD has become one of the most significant diseases of commercial turkeys in the United States. Several infectious and/or environmental immunosuppressive factors can predispose to GD. Skin lesions are considered to be the main portal of entry of the microorganism(s) involved. GD is characterized by acute onset of mortality associated with gross skin and subcutaneous tissue lesions consisting of variable amounts of serosanguineous exudate together with emphysema and hemorrhages. The underlying skeletal muscle can also be involved. Ulceration of the epidermis may be also noticed in cases complicated with S. aureus. Microscopically, necrosis of the epidermis and dermis, and subcutaneous edema and emphysema are commonly observed. Gram-positive rods can be identified within the subcutis and skeletal muscles, usually associated with minimal inflammatory infiltrate. A presumptive diagnosis of GD can be made based on history, clinical signs, and gross anatomic and microscopic lesions. However, confirmation should be based on demonstration of the causative agents by culture, PCR, immunohistochemistry, and/or fluorescent antibody tests.

Colibacillosis in caged layer hens: characteristics of the disease and the aetiological agent

In Europe, outbreaks of acute mortality in layer flocks due to colisepticaemia have frequently been observed since the mid-1990s. The aims of this study were to describe the disease, to identify the serotypes of the avian pathogenic Escherichia coli (APEC) present in these outbreaks, and to detect the presence of F11 fimbriae and flagella in the isolates. For this purpose, 20 flocks with APEC-associated increased mortality and 20 control flocks matched for age were examined. Weekly mortality rates in the colibacillosis-affected flocks reached 1.71%, versus 0.30% in the control flocks. The maximum cumulative mortality over an entire colibacillosis outbreak reached 9.19%. The disease was often flock and hen house associated, with recurrent outbreaks within one round and in successive rounds in the same house. Disease was usually acute without clinical symptoms. Peritonitis with yolk material deposited in the peritoneal cavity and polyserositis were the main lesions at necropsy. O78 strains were isolated in 15 of the 20 colibacillosis flocks, and in only one of the control flocks. The majority of strains from the control flocks could not be serotyped by the 28 O-antisera used. In general, F11 fimbriae and flagella were present in the majority of the strains. F11 fimbriae were significantly more often found in O78 isolates than in the other serotypes, and are thus more often present in isolates from colibacillosis flocks. Strains positive for F11, and for F11 and flagella, were more frequently present in heart and liver of the colibacillosis-affected flocks.

Significance of interactions between Escherichia coli and respiratory pathogens in layer hen flocks suffering from colibacillosis-associated mortality

This study aimed to examine the significance of interactions between Escherichia coli and various respiratory pathogens during outbreaks of colibacillosis-associated mortality in layer hen flocks under field conditions. For this purpose, a case-control study involving 20 control flocks with baseline mortality and 20 flocks with increased mortality due to E. coli septicaemia and polyserositis, was conducted. In each colibacillosis flock, blood samples were taken from 20 hens at the onset of clinical disease and three times thereafter at 2-week intervals. Control flocks of comparable ages were sampled in the same way. Pooled sera, taken at the first and last sampling, were examined for antibody titres against infectious bronchitis virus (IBV) and Newcastle disease virus (NDV), and the individual sera from all four samplings were examined for the presence and/or titres of antibodies against avian pneumovirus (APV), Mycoplasma gallisepticum, Mycoplasma synoviae and Ornithobacterium rhinotracheale. Titre increases were seen for IBV D274 (one control flock) and O. rhinotracheale (one control and one colibacillosis flock). An increase in per cent reactors was seen for APV (one control flock), and for M. synoviae (one control and two colibacillosis flocks). The study failed to detect any consistent interactions between E. coli and the aforementioned pathogens. These results indicate that, at least as observed in this study, outbreaks of increased mortality resulting from colibacillosis are not necessarily associated with IBV, NDV, APV, M. gallisepticum, M. synoviae or O. rhinotracheale infections.

Risk factors associated with colibacillosis outbreaks in caged layer flocks

Colibacillosis appears to be of increasing significance in layer flocks, but there have been no studies of the risk factors associated with outbreaks. This study aimed to investigate the possible associations between risk factors of non-infectious nature and outbreaks of mortality due to colibacillosis in flocks of caged layer hens. Information on management, biosecurity measures and housing conditions was collected in 20 flocks suffering from the disease and in 20 clinically healthy control flocks. The data were processed using multiple logistic regression. The statistical analysis demonstrated that an increase in the distance to the nearest poultry farm by 1 km was associated with a six-fold decreased risk of an outbreak of colibacillosis (odds ratio=0.16). Furthermore, a 1 l increase in cage volume per hen was associated with a 33% decrease in the risk of an outbreak (odds ratio=0.75). It was concluded that the distance between poultry farms and the hen density in the cages are important risk factors for outbreaks of colibacillosis in flocks of layer hens.

ÍNDICE DE PATOGENICIDADE, PRODUÇÃO DE HEMOLISINA E SOROGRUPO DE AMOSTRAS DE ESCHERICHIA COLI ISOLADAS DE AVES DE POSTURA COMERCIAL

RESUMO Este estudo avaliou o índice de patogenicidade, a produção de hemolisina e a determinação de sorogrupos de cepas deEscherichia coli isoladas de fígado de aves de postura comercial com um dia de idade. Para este estudo, foram analisados 32 lotes, dos quais 15 foram positivos para o isolamento de E. coli no fígado, totalizando vinte e quatro amostras. A patogenicidade dos isolados foi determinada por inoculação no saco aéreo de pintinhos e classificada como alta, intermediária, baixa ou não-patogênica. Os sorogrupos foram identificados utilizando um conjunto de antissoros anti-O (O1 a O180). A produção de hemolisina foi determinada por semeadura em ágar sangue de galinha (8%) e em placas de ágar sangue de carneiro (8%). Do total de amostras estudadas, 17 (70,83%) foram classificadas como não patogênica, 6 (25%) como de baixa patogenicidade e 1 (4,17%) de alta patogenicidade. Foram identificados 14 sorogrupos diferentes: O1, O2, O5, O8, O15, O18, O22, O36, O64, O70, O75, O115, O132, O141. Cinco cepas não tiveram o sorogrupo identificado. Com relação ao teste de produção de hemolisina, todas as cepas foram consideradas negativas, tanto para o teste realizado com ágar sangue de galinha quanto para o de carneiro. Os resultados obtidos neste estudo demonstram a importância de se identificar as cepas prevalentes deE. colinas diferentes regiões produtoras, podendo ser utilizados em estudos epidemiológicos.

Virulence factors of avian pathogenic Escherichia coli (APEC)

Avian pathogenic Escherichia coli (APEC) strains cause a great diversity of diseases in birds and are responsible for great economic losses in the avian industry. To date, several studies have been carried out to better understand the APEC pathogenesis for a possible development of tools which could prevent the economics losses caused by these strains. This review discusses the virulence factors described do date to be expressed by these strains and the advances made to understand and identify virulence determinants present in APEC.

Prevalence of Pathogenic Escherichia coli in the Broiler House Environment

Matched sampling of Escherichia coli from broiler house litter and bird lesions of either cellulitis or colibacillosis was conducted to investigate the relationship of pathogenic E. coli to those found in the environment. Isolates were collected from six broiler flocks representing six geographically disparate ranches. Isolates were compared by flock for similarity in serotype and genotyped by pulsed-field gel electrophoresis. Serotyping revealed a considerable dissociation between the two groups of isolates. The prevalence of pathogenic E. coli that matched the environmental isolates from the same house was 0 to 3%. Statistical analysis of the serotype data showed a strong dependence of serotype on isolate source, indicating a high probability that a particular serotype would be found among lesions or litter but not in both groups. Genotyping of isolates on two farms supported the results of serotyping and provided differentiation of isolates that could not by typed by serology. These results suggested that the prevalence of pathogenic E. coli in the broiler house was independent of the prevalence of other commensal or environmental E. coli. Understanding the composition of E. coli populations in commercial poultry production may have bearing on the epidemiology and control of E. coli related diseases.

Trends in Cellulitis Condemnations in the Ontario Chicken Industry Between April 1998 and April 2001

We conducted a retrospective study to determine the prevalence of cellulitis condemnations in the Ontario chicken industry and the relative proportion of variation attributable to factors that vary between processors, producers, and lots and over time. The time span studied was April 1998 to April 2001. We obtained condemnation data randomly from the Chicken Farmers of Ontario and analyzed the data with a generalized mixed model. The (weighted) average prevalence of cellulitis in Ontario between April 1998 and 2001 was 0.94% (0.87%, 1.03%). The prevalence of cellulitis ranged from 0% to 14.9%, with one outlier at 30% and 95% of the data between 0 and 2.58%. The final mixed model we used to describe the variation in the prevalence of cellulitis between lots included random effect terms, the plant where the birds were processed, the producer, the quota period when the birds were processed, and the interaction term quota period by processing plant, as well as fixed effects terms, the type of inspection system and the average weight of the birds. The final model containing these variables explained approximately 78% of the total variation in the data. Our findings indicate all three random effects variables accounted for a significant amount of variation in the cellulitis data; however, the greatest source of variation was ascribed to the plants where the birds were processed. Some of the variation in cellulitis associated with processing plants was explained by the type of inspection system used by the plant, but even after controlling for this factor, there remained a relatively large amount of variation between processing plants (approximately 30%). These findings suggest there may be discrepancies in the diagnoses of the condition. Some of the variation in the prevalence of cellulitis (approximately 13%) was also attributed to the producer; however, more of the variation in the data was attributed to differences in lot-specific factors (approximately 22%). Therefore, future control efforts for cellulitis should focus on standardizing the classification of cellulitis at processing plants and identifying lot specific factors that may increase the risk of the condition.

Occurrence of the temperature-sensitive hemagglutinin among avian Escherichia coli

In this study, we determined the occurrence of the tsh gene among 305 Escherichia coli isolates from chickens by means of the polymerase chain reaction and agglutination of chicken erythrocytes; 200 of those isolates were obtained from chickens with colisepticemia, 52 isolates were from lesions of cellulitis, and 53 were from feces of normal chickens. The tsh gene was found in 79 (39.5%) isolates from colisepticemia, in 10 (19%) cellulitis-derived E. coli isolates, and in two (3.8%) fecal isolates. Among the tsh+ strains, 68 (86%) isolates from colisepticemia and nine (90%) from cellulitis agglutinated chicken erythrocytes in the presence of mannose, after growing the strains on colonization factor antigen agar plates at 26 C, which confirms a correlation between mannose-resistant hemagglutination and expression of hemagglutinin Tsh. These results show, for the first time, the presence of the gene tsh in cellulitis-derived E. coli isolates; the high frequency of this gene among avian pathogenic E. coli isolates in Brazil indicates that its putative role as a virulence factor should be studied more thoroughly.

Evaluation of the adhesive capacity of Escherichia coli isolates associated with avian cellulitis

It has been shown that Escherichia coli isolates from lesions of cellulitis belong to a limited number of clonal groups distinct from those of isolates found in the environment of these birds. In this study, different in vitro methods were used to evaluate adherence properties of E. coli isolates from cellulitis lesions and environments of high- and low-cellulitis prevalence broiler flocks. One hundred isolates were tested by hemagglutination. Adherence to frozen sections of chicken skin and binding to soluble fibronectin were examined for 40 of these 100 isolates by immunofluorescence and by immunocytofluorometry, respectively. Localization of bacterial adherence to skin tissues was confirmed by immunohistochemistry. It was demonstrated that O78:K80 isolates from cellulitis lesions adhered to skin sections to a much greater extent in deeper than in superficial tissue layers. A greater bacterial adherence following growth in TSB at 37 C was demonstrated for isolates from flocks with high prevalence of cellulitis than for isolates from flocks with low prevalence of cellulitis. MANOVA analysis results showed a significant difference between superficial and deep tissue layers only for one set of isolates from flocks with high prevalence of cellulitis. Hemagglutinating activity was variable among the O78:K80 isolates obtained from flocks with high prevalence of cellulitis. The results obtained for some O78:K80 isolates following growth in TSB suggest a role for type 1 fimbriae or F1 in adherence to skin sections. This was reinforced by the finding that adherence was inhibited by D-mannose. Poultry E. coli isolates that express F1 had no affinity for soluble fibronectin, although localization of the adherence in skin sections suggested a role for extracellular matrix components such as collagen and insoluble fibronectin.

Persistence of cellulitis-associated Escherichia coli DNA fingerprints in successive broiler chicken flocks

Avian cellulitis in broiler chickens is primarily caused by Escherichia coli. Previous research found that the E. coli isolates of cellulitis origin were unique to each ranch, suggesting that these E. coli were endemic within the ranch environment. To test the hypothesis that the E. coli associated with cellulitis are endemic in the litter of the broiler house, we designed a study to determine whether E. coli DNA fingerprints associated with cellulitis persist over successive flocks that are grown in the same house. In addition, we assessed the impact of different cleaning and disinfection strategies on this persistence. Two broiler houses were followed on each of five farms over 3-4 flocks. A total of 353 E. coli isolates from cellulitis lesions were analyzed in this study, and 314 of these isolates (89%) were DNA fingerprinted by PFGE. In each ranch, there were several DNA fingerprint patterns that were present over successive flocks, regardless of the cleaning and disinfection strategy utilized. Isolates persisted as long as 191 days, implying that these E. coli are capable of persisting in the broiler house environment for long periods of time. In addition, these E. coli isolates were associated with cellulitis lesions in successive flocks. Thus, the isolates of E. coli that are associated with cellulitis in broiler chickens appear to be endemic in the litter environment of the broiler house.

A statistical model for assessing sample size for bacterial colony selection: a case study of Escherichia coli and avian cellulitis

A general problem for microbiologists is determining the number of phenotypically similar colonies growing on an agar plate that must be analyzed in order to be confident of identifying all of the different strains present in the sample. If a specified number of colonies is picked from a plate on which the number of unique strains of bacteria is unknown, assigning a probability of correctly identifying all of the strains present on the plate is not a simple task. With Escherichia coli of avian cellulitis origin as a case study, a statistical model was designed that would delineate sample sizes for efficient and consistent identification of all the strains of phenotypically similar bacteria in a clinical sample. This model enables the microbiologist to calculate the probability that all of the strains contained within the sample are correctly identified and to generate probability-based sample sizes for colony identification. The probability of cellulitis lesions containing a single strain of E. coli was 95.4%. If one E. coli strain is observed out of three colonies randomly selected from a future agar plate, the probability is 98.8% that only one strain is on the plate. These results are specific for this cellulitis E. coli scenario. For systems in which the number of bacterial strains per sample is variable, this model provides a quantitative means by which sample sizes can be determined.

Incidence and characterization of integrons, genetic elements mediating multiple-drug resistance, in avian Escherichia coli

Antibiotic resistance among avian bacterial isolates is common and is of great concern to the poultry industry. Approximately 36% (n = 100) of avian, pathogenic Escherichia coli isolates obtained from diseased poultry exhibited multiple-antibiotic resistance to tetracycline, oxytetracycline, streptomycin, sulfonamides, and gentamicin. Clinical avian E. coli isolates were further screened for the presence of markers for class 1 integrons, the integron recombinase intI1 and the quaternary ammonium resistance gene qacEDelta1, in order to determine the contribution of integrons to the observed multiple-antibiotic resistance phenotypes. Sixty-three percent of the clinical isolates were positive for the class 1 integron markers intI1 and qacEDelta1. PCR analysis with the conserved class 1 integron primers yielded amplicons of approximately 1 kb from E. coli isolates positive for intI1 and qacEDelta1. These PCR amplicons contained the spectinomycin-streptomycin resistance gene aadA1. Further characterization of the identified integrons revealed that many were part of the transposon Tn21, a genetic element that encodes both antibiotic resistance and heavy-metal resistance to mercuric compounds. Fifty percent of the clinical isolates positive for the integron marker gene intI1 as well as for the qacEDelta1 and aadA1 cassettes also contained the mercury reductase gene merA. The correlation between the presence of the merA gene with that of the integrase and antibiotic resistance genes suggests that these integrons are located in Tn21. The presence of these elements among avian E. coli isolates of diverse genetic makeup as well as in Salmonella suggests the mobility of Tn21 among pathogens in humans as well as poultry.