Campylobacter infection in wild artiodactyl species from southern Spain: Occurrence,risk factors and antimicrobial susceptibility

A cross-sectional study was performed to assess the occurrence of Campylobacter species and to identify potential associated risk factors for wild artiodactyl species in southern Spain. Campylobacter species were isolated in 55 of 363 (15.2%) faecal samples. Campylobacter was identified in faeces from wild boar (49/126; 38.9%), red deer (5/179; 2.8%) and mouflon (1/13; 7.7%) but not from fallow deer (0/45). The isolated Campylobacter species were identified as C. jejuni (2 isolates; 3.6%), C. coli (11 isolates; 20.0%) and C. lanienae (37 isolates; 67.3%). Five isolates (9.1%) could not be identified at the species level. This report is the first to describe C. lanienae infection in wild ruminant species. Resistance to erythromycin (4.8%), ciprofloxacin (37.5%), tetracycline (52.9%) and streptomycin (55%) were detected. C. lanienae presented a significantly higher number of susceptible isolates to ciprofloxacin and tetracycline than C. coli. Due to the low number of positive wild ruminants, a Generalised Estimating Equations model was only carried out for wild boar. The model indicated that the risk factors associated with Campylobacter infection were the density of wild boar (>10/100 ha) (OR: 3.05; CI_95%: 2.2–4.3), the presence of artificial waterholes (OR: 3.67; CI_95%: 1.3–10.5) and the winter season (OR: 3.30; CI_95%: 1.9–5.8). Campylobacter infection is widespread in wild boar populations in southern Spain. These findings suggest that wild artiodactyls, particularly wild boar, constitute a reservoir of Campylobacter species, including resistant and multi-resistant strains, which may be of public health concern.     

Helicobacter infection in dogs and cats: facts and fiction

The discovery of the spiral bacterium Helicobacter pylori and its causative role in gastric disease in humans has brought a dramatic change to gastroenterology. Although spiral bacteria have been known for more than a century to infect the stomachs of dogs and cats, recent research has been conducted mainly in the wake of interest in H. pylori. H. pylori has not been found in dogs and only very rarely in cats and zoonotic risk is minimal. A variety of other Helicobacter spp. can infect the stomach of pets; however, their pathogenic role is far from clear, and they have a small but real zoonotic potential. The prevalence of gastric Helicobacter spp. in dogs and cats is high, irrespective of clinical signs, and as in human medicine, mode of transmission is unclear. The relationship of Helicobacter spp. to gastric inflammation in cats and dogs is unresolved, with inflammation, glandular degeneration, and lymphoid follicle hyperplasia accompanying infection in some but not all subjects. Circulating anti-Helicobacter immunoglobulin G antibodies have been detected in 80% of dogs with naturally acquired infection and most dogs and cats with experimental infection. The gastric secretory axis is similar in infected and uninfected cats and dogs and no relationship of infection to gastrointestinal ulcers has been found. Differences in the pathogenicity of Helicobacter spp. are apparent, because infection with H pylori is associated with a more severe gastritis than infection with other Helicobacter spp. in both cats and dogs. Rapid urease test, histopathology, and touch cytology are all highly accurate invasive diagnostic tests for gastric Helicobacter-like organisms in dogs and cats, whereas culture and polymerase chain reaction are the only means to identify them to the species level. Urea breath and blood tests or serology can be used to diagnose Helicobacter spp. noninvasively in dogs and cats. Most therapeutic studies in pets have not shown long-term eradication of Helicobacter spp. Whether this is due to reinfection or recrudescence has not been established.     

Risk,prognosis and causality of parvo viral enteritis in dogs in Sri Lanka

We studied the causal variation, prognosis and risk factors of parvo viral enteritis using both molecular and statistical analysis. A multivariate factor analysis was performed to see the effect of the breed, age, vaccination status and the leukocyte counts on disease severity and survival. Twenty PCR amplicons (partial VP2 gene) from vaccinated dogs were sequenced to identify the variants. A total of 109 samples were positive for parvo viral DNA, 71 of which were from dogs who have received at least one dose of CPV-2 vaccine. Over 90% were leukopenic on 2^nd and 3^rd day of diarrhoea. Age < 6 months was negatively correlated with leukocyte count and the leukocyte count was negatively correlated with survival. Dobermans and Labradors showed significant negative correlation with survival. All variants of parvovirus affected dogs with the 2c being the predominant (2c = 12, 2a = 7, 2b = 1). All 20 strains harboured three additional amino acid substitutions (i.e. Phe267Tyr, Ser297Ala and Tyr324Ile) and warrant further studies on potential changes of the antigenicity of the virus.     

Multidrug-resistant extraintestinal pathogenic Escherichia coli of sequence type ST131 in animals and foods

Multidrug-resistant Escherichia coli sequence type 131 (ST131) has recently emerged as a globally distributed cause of extraintestinal infections in humans. Diverse factors have been investigated as explanations for ST131's rapid and successful dissemination, including transmission through animal contact and consumption of food, as suggested by the detection of ST131 in a number of nonhuman species. For example, ST131 has recently been identified as a cause of clinical infection in companion animals and poultry, and both host groups have been confirmed as faecal carriers of ST131. Moreover, a high degree of similarity has been shown among certain ST131 isolates from humans, companion animals, and poultry based on resistance characteristics and genomic background and human and companion animal ST131 isolates tend to exhibit similar virulence genotypes. However, most ST131 isolates from poultry appear to possess specific virulence genes that are typically absent from human and companion animal isolates, including genes associated with avian pathogenic E. coli. Since the number of reported animal and food-associated ST131 isolates is quite small, the role of nonhuman host species in the emergence, dissemination, and transmission of ST131 to humans remains unclear. Nevertheless, given the profound public health importance of the emergent ST131 clonal group, even the limited available evidence indicates a pressing need for further careful study of this significant question.     

Comparative assessment of genotypic and phenotypic correlates of Staphylococcus pseudintermedius strains isolated from dogs with otitis externa and healthy dogs

Staphylococcus pseudintermedius is considered a primary pathogen of canine skin and soft tissue infections, and the rapid emergence of methicillin-resistant S. pseudintermedius worldwide is a major issue. In the current study, genotypic and phenotypic correlates associated with S. pseudintermedius causing canine otitis externa were evaluated using 41 S. pseudintermedius strains isolated from dogs with otitis externa (n = 26) and healthy dogs (n = 15). The S. pseudintermedius strains were subjected to a comparative analysis of (i) genotypes (multilocus sequence typing, agr, and spa types), (ii) methicillin resistance and SCCmec types, (iii) multidrug resistance (MDR), (iv) biofilm formation, and (v) susceptibility to canine cathelicidin (K9CATH). A high degree of genetic diversity was observed in both groups of S. pseudintermedius strains, regardless of methicillin resistance. Almost all methicillin-resistant strains (>95%) harbored SCCmec V and displayed MDR. Although there was no difference in biofilm formation, S. pseudintermedius strains derived from otitis externa exhibited enhanced resistance to cationic antimicrobial peptide (K9CATH) compared with strains from healthy dogs. The high degree of heterogeneity in MLST, agr, and spa types prevented the identification of correlations between any specific genotype and virulence phenotype in otitis externa caused by S. pseudintermedius, These findings provide an important basis for monitoring and treating canine skin and soft tissue infections in Korea.     

A comprehensive study of dog bites in Spain, 1995-2004

Dog bites in humans are a complex problem embracing public health and animal welfare. To prevent dog bites it is necessary to have comprehensive epidemiological data that allow the identification of associated risk patterns. This study was aimed at investigating the problem posed by dog bites in Spain. The epidemiology of medically attended dog bite-related incidents reported in Aragón was analysed from 1995 to 2004. Bite incidents were mostly associated with: (1) low-population areas (71.3/100,000 inhabitants); (2) males and children, particularly those aged 5–9; (3) single injuries directed to the head and neck area in children and to the extremities in adults; (4) young, male, medium to large, owned dogs that were known to the victim; (5) summer months, and (6) specific circumstances such as human interference with knocked down and fighting dogs. In the light of these risk patterns, a wide range of specific preventive measures could be proposed.     

Antimicrobial resistance in faecal Escherichia coli isolates from farmed red deer and wild small mammals. Detection of a multiresistant E. coli producing extended-spectrum beta-lactamase

Eighty-nine Escherichia coli isolates recovered from faeces of red deer and small mammals, cohabiting the same area, were analyzed to determine the prevalence and mechanisms of antimicrobial resistance and molecular typing. Antimicrobial resistance was detected in 6.7% of isolates, with resistances to tetracycline and quinolones being the most common. An E. coli strain carrying bla_CTX-M-1 as well as other antibiotic resistant genes included in an unusual class 1 integron (Intl1-dfrA16–bla_PSE-1-aadA2-cmlA1-aadA1-qacH-IS440-sul3-orf1-mef(B)Δ-IS26) was isolated from a deer. The bla_CTX-M-1 gene was transferred by conjugation and transconjugants also acquired an IncN plasmid. This strain was typed as ST224, which seems to be well adapted to both clinical and environmental settings. The phylogenetic distribution of the 89 strains varied depending on the animal host. This work reveals low antimicrobial resistance levels among faecal E. coli from wild mammals, which reflects a lower selective pressure affecting these bacteria, compared to livestock. However, it is remarkable the detection of a multi-resistant ESBL-E. coli with an integron carrying clinically relevant antibiotic-resistance genes, which can contribute to the dissemination of resistance determinants among different ecosystems.     

A novel clinical scoring system for outcome prediction in dogs with acute kidney injury managed by hemodialysis

BACKGROUND: No reliable tool to predict outcome of acute kidney injury (AKI) exists. HYPOTHESIS: A statistically derived scoring system can accurately predict outcome in dogs with AKI managed with hemodialysis. ANIMALS: One hundred and eighty-two client-owned dogs with AKI. METHODS: Logistic regression analyses were performed initially on clinical variables available on the 1st day of hospitalization for relevance to outcome. Variables with P< or = .1 were considered for further analyses. Continuous variables outside the reference range were divided into quartiles to yield quartile-specific odds ratios (ORs) for survival. Models were developed by incorporating weighting factors assigned to each quartile based on the OR, using either the integer value of the OR (Model A) or the exact OR (Models B or C, when the etiology was known). A predictive score for each model was calculated for each dog by summing all weighting factors. In Model D, actual values for continuous variables were used in a logistic regression model. Receiver-operating curve analyses were performed to assess sensitivities, specificities, and optimal cutoff points for all models. RESULTS: Higher scores were associated with decreased probability of survival (P < .001). Models A, B, C, and D correctly classified outcomes in 81, 83, 87, and 76% of cases, respectively, and optimal sensitivities/specificities were 77/85, 81/85, 83/90 and 92/61%, respectively. CONCLUSIONS AND CLINICAL RELEVANCE: The models allowed outcome prediction that corresponded with actual outcome in our cohort. However, each model should be validated further in independent cohorts. The models may also be useful to assess AKI severity.     

Risk factors for Campylobacter infection in Norwegian cats and dogs

Rectal swabs from healthy cats and dogs, and from dogs and cats with clinical diarrhoea were collected approximately every third month from May 2000 to June 2001 from six small-animal practices throughout Norway. A questionnaire was filled in for each animal. Of the 301 healthy cats sampled, 54 (18%) were positive for Campylobacter, compared to 5 out of 31 (16%) cats with diarrhoea. Campylobacter jejuni was isolated from 11 (3%), C. upsaliensis from 42 (13%) and C. coli from 2 (0.6%) of the cats sampled. Isolates from four cats (1%) could not be specified. Of the 529 healthy dogs, 124 (23%) were positive for Campylobacter, compared to 18 of 66 (27%) dogs with diarrhoea. C. jejuni was isolated from 20 (3%) and C. upsaliensis from 117 (20%) of the dogs sampled. Isolates from five dogs (0.8%) could not be specified. Eighteen out of the 20 investigated C. upsaliensis samples were resistant to streptomycin. The clinically healthy animals were included in the analysis to identify factors associated with Campylobacter prevalence. The cat model had low classification ability. The dog-data model indicated increased odds of infection with Campylobacter for dogs ≤1 year, and in dogs sampled during the spring. No difference was observed between the prevalence of Campylobacter infections in cats and dogs with diarrhoea and healthy animals.     

Genotypic and phenotypic diversity differences of presumptive commensal and avian pathogenic E. coli

1. The objective of the experiment was to characterise the genotypic and phenotypic differences between presumptive commensal E. coli and avian pathogenic E. coli (APEC) of poultry.

2. DNA was extracted from 65 confirmed APEC E. coli from chicken, 100 presumptive commensal E. coli from healthy turkey and 35 from healthy chicken. Enterobacterial repetitive intergenic consensus PCR (ERIC-PCR) and virulence factors genotyping was performed to characterise genetic features.

3. Carbon source utilisation and antimicrobial susceptibility tests were performed to characterise phenotypic features of isolates.

4. The genetic divergence between E. coli strains tested by ERIC-PCR profiles and virulence-associated genes showed a clear genetic separation between E. coli APEC and turkey E. coli strains.

5. The carbon utilisation profile of turkey isolates was different from chicken and APEC strains; whereas antimicrobial susceptibility was highest for turkey isolates (53%), and lowest for APEC strains (33.8%).

6. The study showed a significant negative correlation between utilisation of arabitol and adonitol with different virulence determinants tested, which suggests that the ability to utilise some uncommon carbon sources may be used to discriminate between presumptive commensal E. coli and APEC.     

Canine superficial bacterial folliculitis: Current understanding of its etiology,diagnosis and treatment

Superficial bacterial folliculitis (SBF) is more common in the dog than other mammalian species. Until recently, a successful outcome in cases of canine SBF was possible by administering a potentiated amoxicillin, a first generation cephalosporin or a potentiated sulfonamide. Unfortunately, this predictable susceptibility has changed, because methicillin resistant Staphylococcus pseudintermedius (MRSP) and Staphylococcus aureus (MRSA) are becoming more prevalent in canine SBF cases. The increasing frequency of multidrug resistance complicates the selection of antimicrobial therapy. Antimicrobial agents that were once rarely used in cases of canine SBF, such as amikacin, rifampicin and chloramphenicol, are becoming the drugs of choice, based on bacterial culture and susceptibility testing. Furthermore, changes in antimicrobial susceptibility have helped to re-emphasize the importance of a multimodal approach to treatment of the disease, including topical therapy. Due to the increasing frequency of identification of highly resistant Staphylococcus spp., topical antimicrobial therapy, including the use of diluted sodium hypochlorite (bleach), is becoming necessary to successfully treat some cases of canine SBF. Other important antiseptics that can be used include chlorhexidine, benzoyl peroxide, ethyl lactate, triclosan and boric acid/acetic acid. This review discusses the diagnostic and therapeutic management of canine SBF, with a special emphasis on treating methicillin resistant staphylococcal infections.     

Granulomatous disease associated with Bartonella infection in 2 dogs

Shortly after removal of an engorged tick from the left ear, a 4-year-old Greyhound was referred for evaluation of fever and a rapidly enlarging mass in the region of the left submandibular lymph node. Histopathologic evaluation of the lymph node resulted in a diagnosis of severe granulomatous lymphadenitis. An 11-year-old mixed-breed dog was referred for evaluation of a 6-week history of serous nasal discharge. Histologic examination of a surgical biopsy from a nasal mass indicated multifocal granulomatous inflammation with fibrosis. Serum samples obtained from both dogs were reactive by immunofluorescent assay to Bartonella vinsonii subsp. berkhoffii antigens (reciprocal titers of 128). Although Bartonella organisms were not isolated by lysis centrifugation blood culture, Bartonella DNA was amplified from tissue samples obtained from each dog (lymph node biopsy from dog 1 and nasal biopsy from dog 2) using primers that amplify a portion of the 16S rRNA gene followed by Southern blot hybridization using a genus-specific probe. Additionally, restriction fragment length polymorphism (RFLP) analysis of a Bartonella-specific citrate synthase gene product obtained from dog 2 resulted in a restriction pattern identical to B. vinsonii subsp. berkhoffii. This is the 1st report of granulomatous disease in dogs associated with Bartonella infection.     

Plasma vascular endothelial growth factor concentrations in healthy dogs and dogs with hemangiosarcoma

Vascular endothelial growth factor (VEGF) is a dimeric glycosylated polypeptide growth factor with potent angiogenic, mitogenic, and vascular permeability-enhancing properties specific for endothelial cells. In humans, VEGF seems to play a major role in tumor growth, and plasma concentrations correlate with tumor burden, response to therapy, and disease progression. This study compared plasma VEGF concentrations in healthy client-owned dogs (n = 17) to dogs with hemangiosarcoma (HSA; n 16). Dogs with HSA were significantly more likely to have detectable concentrations of plasma VEGF (13/17) compared to healthy dogs (1/17; P < .001). The median plasma VEGF concentration for dogs with HSA was 17.2 pg/mL (range, < 1.0-66.7 pg/mL). Plasma VEGF concentrations in dogs with HSA did not correlate with stage of disease or tumor burden, but 1 dog had undetectable VEGF during chemotherapy that subsequently increased with disease progression.     

Canine echinococcosis in northwest Libya: assessment of coproantigen ELISA, and a survey of infection with analysis of risk-factors

In order to determine the prevalence and risk factors for canine echinococcosis in different endemic localities in the Tripoli area of northwest Libya, stray dogs were examined post-mortem, and owned dogs screened for Echinococcus granulosus infection using a standardised genus specific coproantigen ELISA. The prevalence of E. granulosus infection at necropsy in stray-dogs was 25.8% (15/58, 95% CI 15.3–39.0%), and 21.6% (72/334, 95% CI 17.3–26.4%) of owned dogs tested were positive by coproantigen ELISA. Sheepdogs appeared to have a significantly higher copro-positive prevalence (19/19 positive, p = 0.003), compared to 23.6% of other dog classes (e.g. 52/220 guard dogs and household pets). Worm burdens in necropsied dogs ranged from 29 to 2900 (mean 1064) and were positively correlated to coproantigen ELISA OD values (r_s = 0.87, p < 0.001), but negatively correlated with dog age (r_s = −0.69, p = 0.001). Dog age was a significant factor in copro-prevalence as there was an increasing coproantigen-positive tendency in younger dogs (≤5 years, p = 0.04). A total of 45/132 (34%, 95% CI 25.9–42.1%) of farms/homestead had at least one dog that was coproantigen positive. Overall copro-prevalence in dogs by locality varied, with Alkhums (Leptis-Magna) district having the highest copro-prevalence at 38.7% (24/62, 95% CI 26.6–50.8%) (p = 0.001). Coproantigen testing of a cohort of owned dogs before and approximately 15 months after praziquantel treatment showed a significant decrease in the coproantigen positive rate from 21.6% (72/334) to 9% (21/233) post-treatment. The overall E. granulosus coproantigen positive rate (‘re-infection rate’) within the same cohort of dogs was 22 % (10/45) by 15 months post-treatment. Significant risk factors for a copro-positive owned dog were associated with non-restraint of dogs, and owners that did not de-worm their dogs. Home slaughtering of livestock and lack of knowledge about E. granulosus transmission were also significant risk factors for a canine coproantigen positive result.     

Serum cardiac troponin I concentration in dogs with ehrlichiosis

Background: Ehrlichiosis is a multisystemic disease with the potential to cause cardiomyocyte injury in naturally infected dogs.
Hypothesis: Myocardial injury occurs in dogs infected with Ehrlichia canis .
Animals: One-hundred and ninety-four dogs from Brazil with clinical and laboratory abnormalities indicative of ehrlichiosis. Sixteen healthy dogs served as controls.
Methods: Electrocardiogram, echocardiogram, noninvasive blood pressure measurement, and serum cardiac troponin I (cTnI) concentrations were evaluated. Serologic assays and PCR determined the exposure and infection status for E. canis, Anaplasma spp., Babesia canis vogeli, Bartonella spp., Borrelia burgdorferi, Dirofilaria immitis, Ehrlichia chaffeensis, Ehrlichia ewingii, Leishmania chagasi , and spotted-fever group Rickettsia . Dogs were assigned to groups according to PCR status: E. canis infected, infected with other vector-borne organisms, sick dogs lacking PCR evidence for infection, and healthy controls.
Results: E. canis -infected dogs had higher serum cTnI concentrations than controls (median: 0.04 ng/dL; range 0.04–9.12 ng/dL; control median: 0.04 ng/dL; range: 0.04–0.10 ng/dL; P = .012), and acute E. canis infection was associated with myocardial injury (odds ratio [OR]: 2.67, confidence interval [CI] 95%: 1.12–6.40, P = .027). Severity of anemia was correlated with increased risk of cardiomyocyte damage ( r = 0.84, P < .001). Dogs with clinical signs of systemic inflammatory response syndrome (SIRS) were at higher risk for myocardial injury than were other sick dogs (OR: 2.55, CI 95%: 1.31–4.95, P = .005).
Conclusions and Clinical Importance: Acute infection with E. canis is a risk factor for myocardial injury in naturally infected Brazilian dogs. Severity of anemia and SIRS might contribute to the pathophysiology of myocardial damage.     

Prevalence of and risk factors for increased serum levels of allergen-specific IgE in a population of Norwegian dogs

Background

The importance of different allergens in association with IgE production and canine atopic dermatitis (CAD) has been poorly studied and few studies exist on factors influencing allergen-specific IgE antibodies in serum. The aim of this cross-sectional study was to investigate the prevalence of elevated IgE levels to different environmental allergens in Norwegian dogs with a suspicion of CAD. The secondary aim was to identify risk factors associated with elevated serum levels of allergen-specific IgE.

Results

The study sample consisted of serum from 1313 dogs of 161 different breeds. All samples were submitted for serologic IgE-testing (Fc epsilon R1 alpha-based ELISA) based on suspicion of CAD. Overall, 84.3% of the dogs had elevated IgE levels to one or more of the allergen(s). The predominant allergens amongst the positive results were the indoor allergens (Acarus siro 84.0%, Dermatophagoides farinae 80.2%, Tyrophagus putrescentiae 79.9%). Sheep sorrel was the most commonly encountered outdoor allergen (40.0%). Only 2.6% of the dogs with elevated IgE levels were positive to flea saliva.The test results varied significantly depending on when the serum samples were taken. Samples taken during summer and autumn more often came out positive than samples taken during winter and spring. Geographical variations were also demonstrated. A greater proportion of females than males had positive test results, and more females than males tested positive to outdoor allergens. The mean age was significantly higher in the dogs testing positive than amongst the dogs testing negative. The allergen-specific IgE levels varied with breed. The boxer was the only breed with a significantly higher proportion of positive test results compared to the other breeds. Boxers also had a higher prevalence of elevated IgE levels to outdoor allergens, whereas the Rottweiler had a higher prevalence of elevated IgE levels to indoor allergens compared to the other breeds.

Conclusions

IgE hypersensitivity was most often associated with indoor allergens. Outdoor allergens were of minor importance and IgE reactivity to flea saliva was rare. Breed differences in allergen-specific IgE levels were identified. Season of sampling, and the dogs’ geographical localisation, sex and age also affected the results of the IgE analysis.     

Serologic detection of Angiostrongylus vasorum infection in dogs

Angiostrongylus vasorum, French Heartworm, is a metastrongylid nematode infecting the pulmonary arteries and right heart of wild and domestic canids in various regions of the world. Infection in dogs can result in fatal cardiopulmonary disease. A single endemic focus of A. vasorum in North America occurs in the southeastern portion of Newfoundland, Canada. Dogs are currently diagnosed by detection of first-stage larvae shed in feces using the Baermann technique or fecal flotation. However, these procedures may lack sensitivity due to intermittent fecal larval shedding. The potential for using detection of circulating worm antigen for diagnosis was investigated by developing a sandwich-ELISA using rabbit anti-whole adult worm antiserum. This test detected circulating antigen in sera from 22/24 Baermann positive dogs naturally infected with A. vasorum. Negative results (0/52) were obtained from sera collected from Baermann negative dogs from outside of the endemic region, and from sera (0/30) from dogs from non-endemic regions that were infected with Crenosoma vulpis, the fox lung worm. Receiver operating curve analysis gave a specificity of 100% and a sensitivity of 92% for the sandwich-ELISA at an optical density cut-off of 0.19. Subsequently, 239 dogs from Newfoundland displaying clinical signs of cardiopulmonary disease, were examined using both the Baermann fecal examination and the sandwich-ELISA. Larvae were detected in 10% (24/239) of these dogs by fecal examination, whereas the sandwich-ELISA detected circulating antigen of A. vasorum in serum from 18.8% (45/239) of the dogs. This suggests that fecal diagnostics may have missed approximately half of the A. vasorum infected dogs, and that the sandwich-ELISA may be a useful tool in the diagnosis of this parasite.     

一株血清型O101多重耐药牛致病性大肠杆菌菌株的分离鉴定

试验对病料进行病原检测,并对分离到的病原菌进行分子生物学鉴定、血清学鉴定、药物敏感性试验、小鼠致病性试验研究,依据研究结果进行针对性治疗。试验结果:成功分离到一株牛致病性大肠杆菌,该株菌多重耐药,对小鼠具有高度致病性,其血清型为O101,使用该菌株的敏感药物对后续腹泻犊牛进行了及时治疗,成功控制了该养殖场犊牛腹泻的问题。