Necrotic enteritis: effect of barley, wheat and corn diets on proliferation of Clostridium perfringens type A

Necrotic enteritis, caused by Clostridium perfringens type A, is more prevalent in broilers fed wheat or barley diets than in those fed a corn diet. We compared the effects of wheat, barley and corn diets on in vitro proliferation of C. perfringens type A. Bacteria were inoculated into the supernatants delivered from either digested or non-digested barley, wheat and corn diets mixed with thioglycollate medium (1:3). Colony forming units were counted following incubation for 6 h at 40 degrees C. There were no significant differences in clostridial proliferation among non-digested diets. Bacterial proliferation in the digested wheat and barley diets was significantly higher than in the digested corn diet. These findings suggest that the increased incidence of necrotic enteritis in broilers fed barley and wheat diets compared with those fed a corn diet may be due in part to increased clostridial proliferation associated with the wheat and barley diets, or to decreased proliferation associated with the corn diet.

Responses of broiler chickens orally challenged with Clostridium perfringens isolated from field cases of necrotic enteritis

The present study examines the responses of broiler chickens to oral administration of Clostridium perfringens freshly isolated from field cases of necrotic enteritis (NE). The challenge studies included long-term exposure and short-term exposure, factored in with dietary and management variables including high levels of dietary components such as fish meal, meat meal, abrupt change of feed, and fasting. In the long-term exposure trials, the birds were orally inoculated daily, with 1 ml (1.0 or 2 x 10(8) CFU/ml) of an overnight culture of C. perfringens for 7 days. Short-term exposure trials involved challenge with 1 ml (3 x 10(10) CFU/ml) administered as a single dose. The responses of broilers to orally administered C. perfingens under laboratory controlled conditions are presented and discussed in the context of authentic field cases of necrotic enteritis. None of the challenge trials produced overt clinical signs of NE and there were no mortalities associated with oral exposure to high doses of C. perfringens. However, many of the challenged birds showed distinctly pronounced pathological changes in the intestinal tissue. On gross examination the responses in birds challenged orally with C. perfringens could be placed into two categories: (1) no apparent pathological changes in the intestinal tissue and (2) sub-clinical inflammatory responses with focal, multi-focal, locally extensive, or disseminated distribution throughout various sections of duodenum, jejunum, ileum, and ceca. In birds that responded with intestinal lesions, hyperemia and occasional hemorrhages were the main gross changes. In some birds, the mucosa was covered with a brownish material, but typically, the mucosa was lined by yellow or greenish, loosely adherent material. Mild gross changes were seen in some control birds, but both qualitatively and quantitatively, the lesions were distinctly more pronounced in the challenged birds. Upon histological examination, none of the experimentally exposed birds showed overt mucosal necrosis typical of field cases of NE, but typically the lamina propria was hyperemic and infiltrated with numerous inflammatory cells. Most significant changes were seen at the interface of the basal domain of enterocytes and lamina propria. Multifocally, these areas were extensively edematous, allowing for the substantial disturbance of the structural integrity between the lamina propria and the enterocytes. The lesions observed in the present study were consistently reproduced in all of our challenge trials, hence these responses may signify newly emerging patterns of sub-clinical enteric disorders in contemporary strains of poultry. The pathological changes observed in broilers challenged orally with C. perfringens in the present study, differ significantly from those reported previously, and must be clearly differentiated from those described in cases of NE or ulcerative enteritis. Although no overt necrosis of the intestinal mucosa typical of field cases of NE were observed in the present study, the birds challenged with C. perfringens showed strong inflammatory reaction to the introduced pathogens. The distinct features of the microscopic lesions were changes involving apparently normal enterocytes at the interface of the basal domain of villar epithelia and lamina propria. Although the pathological changes in the intestinal tissues observed in our trials appear to be rather subtle when compared to field cases of NE, the nature of these lesions suggest a significant negative effect on the digestive physiology of intestinal mucosa.

Trends in antimicrobial resistance of Salmonella isolated from animals, foods of animal origin, and the environment of animal production in Canada, 1994-1997

The purpose of our study was to determine the occurrence, magnitude, trends, and relationships regarding antibiotic resistance of Salmonella isolated from animals, animal food products, and the environment of animals. We examined 621 strains of 67 different serovars isolated in 1994, 721 strains of 75 different serovars isolated in 1995, 1,219 strains of 83 different serovars isolated in 1996, and 1,336 Salmonella strains of 92 different serovars isolated in 1997, for resistance to 17 antibiotics at one to three different concentrations with the agar dilution method. The overall resistance magnitude regressed from 9.2% in 1994 to 8.1% in 1997. Resistance to streptomycin (30.4% of 3,897 isolates), tetracycline (27.3%), and sulfisoxazole (23.7%) was highest. Resistance to streptomycin, tetracycline, kanamycin, and gentamicin declined during the 4-year period. Notable increases in resistance to ampicillin, chloramphenicol, and neomycin occurred during the 1994-1997 years. None of the isolates was resistant to amikacin. None of the isolates was resistant to ciprofloxacin at 1, 2, and 4 microg/ml. Salmonella bredeney isolates from turkeys showed a decreased sensitivity to ciprofloxacin and were resistant at the low level of 0.125 microg/ml, but none of these isolates was resistant at 1 microg/ml. Resistance to nalidixic acid correlated significantly with decreased sensitivity to ciprofloxacin; 122 of 127 (96%) isolates resistant to nalidixic acid at 32 microg/ml were resistant to ciprofloxacin at 0.125 microg/ml but sensitive at 1 microg/ml. Resistance to S. typhimurium to each of the seven antibiotics ampicillin, chloramphenicol, kanamycin, neomycin, streptomycin, sulfisoxazole, and tetracycline increased persistently during each of the years 1994-1997, but none of the S. typhimurium isolates showed decreased sensitivity to ciprofloxacin. Clinical isolates of Salmonella were twice as frequently resistant to the antimicrobials in the test panel than isolates obtained during surveys. Salmonella isolates from turkeys were more frequently resistant than isolates from pigs, cattle, and chickens.

Presence of Clostridium difficile in pig faecal samples and wild animal species associated with pig farms

AIMS

To determine the presence of Clostridium difficile on fattening pig farms in north-eastern Spain.

METHODS AND RESULTS

Twenty-seven farms were sampled. Pools of pig faecal samples (n = 210), samples of intestinal content from common farm pest species (n = 95) and environment-related samples (n = 93) were collected. Isolates were tested for toxin genes of C. difficile, and typed by PCR-ribotyping and toxinotyping. The minimal inhibitory concentrations of six antimicrobial agents were determined using Etest. Thirty-four isolates were obtained from 12 farms, and 30 (88·2%) had toxin genes. Seven ribotypes were identified. Ribotype 078 and its variant 126 were predominant (52·9%). The same ribotypes were isolated from different animal species on the same farm. None of the isolates were resistant to metronidazole or vancomycin.

CONCLUSIONS

Clostridium difficile was common within the pig farm environment. Most of the positive samples came from pest species or were pest-related environmental samples.

SIGNIFICANCE AND IMPACT OF THE STUDY

Pest species were colonized with toxigenic and antimicrobial-resistant C. difficile strains of the same ribotypes that are found in humans and pigs. Rodents and pigeons may transmit toxigenic and antimicrobial-resistant C. difficile strains that are of the same ribotypes as those occuring in humans.

The Role of First Line of Defence Mechanisms in the Pathogenesis of Cellulitis in Broiler Chickens: Skin Structural, Physiological and Cellular Response Factors

The present study examined several basic attributes of first-line defence mechanisms in the skin as potential factors that may explain the susceptibility of broiler chickens to cellulitis. The variables including structural characteristics of the skin, physicochemical properties and cellular responses to the challenge with pathogens were compared between two categories of chickens, a strain of fast-growing commercial broiler chickens (susceptible to cellulitis) and leghorn chickens (resistant to cellulitis). There were substantial differences between leghorns and broilers with regard to physiological characteristics of the skin. Broiler skin was more amenable to injury and the wound-healing process was slow. Compared with leghorns, the lesions resulting from sub-dermal challenge in broilers were more severe and disseminated over a larger area. Mobilization of phagocytic cells (heterophils and macrophages) in leghorns was brisk even in the areas distant from the site of infection, whereas only few heterophils were recruited in the skin of broilers. The functional competence of heterophils in broilers was inferior when compared with leghorns. Based on the present finding, the predisposition of broilers to cellulitis appears to be primarily associated with the inferior first line of defence of their skin. Broilers in commercial situations may be at higher risk to succumb to even minor infection and eventually develop cellulitis because: (1) structural weaknesses of the skin may predispose broilers to skin injury and thus the risk of skin infection by pathogens is increased; (2) broiler skin surface is more likely to provide a conducive environment for colonization of Escherichia coli; (3) in the event of infection, poor recruitment of phagocytic cells to the site of infection may readily lead to widespread colonization of the tissue by pathogens causing cellulitis and (4) poor functional quality of the phagocytic cells that are mobilized compromise the ability of the host to contain the spread of infection.

Antimicrobial susceptibility of canine and human Staphylococcus aureus collected in Saskatoon, Canada

Staphylococcus aureus is one of the most common causes of infection in people and is increasingly recognized in dogs. The increasing prevalence of methicillin resistant S. aureus (MRSA) is complicating the treatment of these infections. Panton Valentine leukocidin (PVL), a toxin involved in the pathogenesis of necrotic syndromes in people may be partially responsible for the rise of MRSA. Canine and human S. aureus from the same geographic area are genetically similar, indicating a common population and likely transmission. The implications of increasing antimicrobial resistance complicated by interspecies transmission, necessitates including both dogs and humans in S. aureus resistance surveillance studies. A collection of 126 S. aureus isolates from people (n = 99) and dogs (n = 27) were included, minimum inhibitor concentrations to a panel of 33 antimicrobials used in human and veterinary medicine were determined. No resistance to vancomycin, linezolid, daptomycin, quinupristin/dalfopristin or nitrofurantoin was found. A wide range of antibiograms were found; including resistance to 0-12 drugs (0-6 drug classes). Outstanding antibiograms included a canine MRSA resistant to rifampin and a human MRSA resistant to chloramphenicol. Inducible clindamycin resistance was found among 78% and 4% of canine and human MRSA and 17% and 25% of canine colonizing and human methicillin susceptible S. aureus (MSSA), respectively. Resistance to mupirocin was only found among human isolates including 20% of MRSA and 4% of MSSA. While no canine isolates were PVL positive, 39% of human MRSA and 2% of MSSA carried the gene. The bidirectional transmission of S. aureus between people and dogs necessitates the inclusion of isolates from both species in future studies.

Update on treatment of vesiculitis in bulls

Four experiments were done to determine: (1) the effectiveness of early detection and treatment of vesiculitis in bulls; (2) whether antibiotic treatment at recommended dosages will result in adequate vesicular gland tissue concentrations of antibiotics to prevent in vitro bacterial growth; (3) whether intraglandular injection of antibiotics can be a successful alternative to systemic antibiotic treatment; and (4) the effectiveness of tilmicosin versus tulathromycin for treatment of clinical vesiculitis. In Experiment 1, there was a high rate of spontaneous remission from vesiculitis detected at 9-12 mo of age. Furthermore, there was no advantage for early antibiotic treatment versus no treatment for bulls of this age. In Experiment 2, bacteria on agar plates were exposed to fluid extracted from vesicular gland biopsies after antibiotic treatment of normal, healthy bulls. Although inadequate concentrations of antibiotics were achieved to inhibit bacterial growth when recommended dosages of various antibiotics were administered, doubling the antibiotic dosage increased in vitro bacterial growth inhibition. In Experiment 3, relatively nonirritating antibiotics were injected directly into the glands of bulls with clinical vesiculitis, demonstrating that intraglandular injections of antibiotic could be used as a successful alternative to systemic antibiotic treatment. Experiment 4 was a clinical field trial to compare the efficacy of tilmicosin versus tulathromide at recommended dosages for the treatment of clinical vesiculitis. Although the results favored tulathromycin, both antibiotics resulted in clinical cures of vesiculitis.

Molecular analysis of three Clostridium difficile strain genomes isolated from pig farm-related samples

Clostridium difficile is an anaerobic spore-forming bacillus that usually causes gastrointestinal disorders in man and other animal species. Most of the strains isolated from animals are toxigenic being the virulent ribotype (RT) 078 predominant in several animal species. Although C. difficile is pathogenic to both humans and animals, there is no direct evidence of zoonosis. Deep genome sequencing provides sufficient resolution to analyse which strains found in animals might be related to human pathogens. So far, there are only a few fully sequenced genomes of C. difficile strains isolated from domestic and wild animals. Using Illumina technology, we have sequenced the genome of three isolates; a strain isolated from the vagina of a sow (5754), one from rat (Rattus spp) intestinal content (RC10) and a third one isolated from environmental rat faeces (RF17). Both, rat and rat faeces were sampled in fattening pig farms. Our study reveals a close genetic relationship of two of these isolates with the virulent strain M120 (RT078) isolated from a human patient. The analysis of the sequences has revealed the presence of antibiotic resistance genes, mobile elements, including the transposon linked with virulence Tn6164, and the similarity of virulence factors between these isolates and human strains. This is the first study focused on the sequencing of C. difficile genomes obtained from wild animals like rats, which can be considered as potential reservoirs for humans and other animal species. This study can help to understand the genome composition and epidemiology of this bacterium species.

Survey on 'lumpy jaw' on deer farms in western Canada: prevalence and distribution, and identification of associated factors

AIM

To investigate the prevalence and geographical distribution of 'lumpy jaw' (LJ) in a population of white-tailed deer (WTD; Odocoileus virginianus) and mule deer (MD; Odocoileus hemionus) farms from the western Canadian provinces of Saskatchewan and Alberta, and to identify factors associated with its occurrence.

METHODS

A cross-sectional study, in which the target population was all farmers of WTD and MD registered in Saskatchewan and Alberta, was conducted between July 2004 and January 2005. A questionnaire was mailed to all farmers requesting information about the presence of LJ and other necrobacillosis- related syndromes (footrot and fawn death syndrome), and various farm characteristics, during 2002, 2003 and 2004. Herd and within-herd incidences of disease were estimated. Global and local spatial analyses were performed to identify possible clusters of occurrence of LJ in the region. Logistic regression analysis was used to identify factors associated with the occurrence of LJ.

RESULTS

A total of 139/268 (52%) deer farmers responded to the survey. Over the entire study period, 108/139 (78%) of farmers reported having cases of LJ in their herds, and in any given year the incidence amongst herds was about 40%. The presence of footrot was not associated with the presence of LJ. The proportion of fawns dying suddenly in 2004 was higher on farms affected by LJ than in those considered LJ-free (median of 11.1% and 0%, respectively; p<0.001). Two areas in Saskatchewan were identified as having a higher herd prevalence of LJ (clusters) than all other areas. Density of animals, moving and handling animals, lack of basic hygiene measures, and bottle- feeding of fawns increased the odds of a herd being affected by LJ.

CONCLUSIONS AND CLINICAL RELEVANCE

LJ should be considered a common disease in farmed deer in western Canada. The observed relationship between the occurrence of LJ and acute mortality of fawns emphasises the potential of this infection to result in significant economic loss. Intensive management of deer, characterised by high densities and frequent moving and handling of animals, may contribute significantly to the occurrence of LJ. Observed geographical clusters may reflect areas where management of deer was more intensive or the trading of deer more common.

Experimental reproduction of endocarditis with Pasteurella gallinarum in mature leghorn chickens

The pathogenicity of Pasteurella gallinarum for mature leghorn chickens was investigated by inoculating thirty 52-week-old chickens intravenously with live P. gallinarum. Each chicken was inoculated once daily for 5 days at one of three different dosage levels with either the type strain ATCC 13361 or a field isolate from a chicken with endocarditis. Chickens were necropsied after death or euthanasia. Valvular endocarditis was present in seven chickens given the field isolate and five chickens given the type strain. Other lesions detected were myocarditis, hepatic and splenic infarcts, nephritis, pneumonia, and encephalitis. At necropsy, P. gallinarum was reisolated from hearts, livers, spleens, lungs, kidneys, and blood. Controls injected with sterile broth had no lesions of endocarditis, nor was P. gallinarum isolated from them. The results confirm the pathogenicity of P. gallinarum for the heart valves of mature chickens.

Feedtrough dirt as a source of Clostridium botulinum type C intoxication in a group of farm horses

Four horses from the same farm developed clinical signs of botulism during the winter months; three of these horses died. One horse survived an initial attack and recovered over a three-week period, but died during a second attack. The horse that survived took six weeks to recover. Clinical and postmortem examination ruled out other causes of disease. Confirmation of the diagnosis was made by isolation of Clostridium botulinum type C toxin from the dirt in the bottom of an oak feedtrough used by all horses, and from the colonic contents of one of the horses that died. To our knowledge, this is the second case of C. botulinum type C intoxication reported in horses in North America. In both cases, soil and sand near aquatic environments were identified as the source of toxin.

Antimicrobial resistance and prevalence of canine uropathogens at the Western College of Veterinary Medicine Veterinary Teaching Hospital, 2002-2007

Between January 2002 and June 2007, uropathogens were isolated from 473 of 1557 canine urine samples submitted to Prairie Diagnostic Services from the Western College of Veterinary Medicine Veterinary Teaching Hospital. Culture and susceptibility results were analyzed, retrospectively, to estimate the prevalence of common bacterial uropathogens in dogs with urinary tract infections and to identify changes in antimicrobial resistance. The most common pathogens identified were Escherichia coli, Staphylococcus intermedius, Enterococcus spp., and Proteus spp. Antimicrobial resistance increased during the study period, particularly among recurrent E. coli isolates. Using the formula to help select rational antimicrobial therapy (FRAT), bacterial isolates were most likely to be susceptible to gentamicin, fluoroquinolones, amoxicillin-clavulanic acid, and groups 4 and 5 (third generation) cephalosporins.

The relationship between the presence of Helicobacter pylori, Clostridium perfringens type A, Campylobacter spp, or fungi and fatal abomasal ulcers in unweaned beef calves

A case-control study involving 30 unweaned beef calves was conducted to determine whether specific species of bacteria or fungi were associated with fatal abomasal ulcer formation. Special microbiological and histological techniques were used to detect Clostridium perfringens type A, Helicobacter pylori, or Campylobacter spp. It has been speculated that these bacteria are potential ulcerogenic agents of unweaned beef calves. Calves were recruited for the study at necropsy, with those dying of either a perforating or a hemorrhagic ulcer representing the cases, and calves of a similar age dying of a disease unrelated to the abomasum representing the controls. Helicobacter pylori was not visualized in or cultured from any of the abomasal tissue samples. Clostridium perfringens type A was isolated from 78.6% of the cases and 75% of the controls. These isolates were further dichotomized into "heavy" and "light" growth; no significant association was found between ulcers and the amount of growth. A light growth of Campylobacter spp. was recovered from 3 cases and 3 controls. There was no compelling evidence to suggest that Clostridium perfringens type A, Helicobacter pylori, or Campylobacter spp. were involved in ulcer formation.