Contribution of AIDA-I to the pathogenicity of a porcine diarrheagenic Escherichia coli and to intestinal colonization through biofilm formation in pigs

In order to evaluate the role of the AIDA-I of porcine diarrheagenic Escherichia coli strain PD20 serogroup O143 (AIDA-I⁺, STb⁺), a mutant strain PD20M (AIDA-I⁻, STb⁺) was generated from strain PD20 by an allelic exchange procedure. In addition, the full-length aidA gene was reintroduced into strain PD20M to generate the complemented strain PD20C (pTaidA, AIDA-I⁺, STb⁺). A non-pathogenic E. coli strain PD71 was used as negative control. Each strain was inoculated to newborn pigs via stomach tube. Severity of diarrhea was evaluated clinically and intestinal colonization was assessed by histology, immunohistochemistry (IHC), and transmission electron microscopy (TEM) including immunogold electron microscopy (IGEM). The adhesion pattern to HeLa cells, bacterial auto-aggregation and biofilm formation were evaluated in vitro. Pigs infected with strains PD20 or PD20C developed diarrhea 16 and 28 h after inoculation, respectively, in contrast to pigs infected with strains PD20M or PD71. Histology, IHC, TEM and IGEM examinations showed heavy bacterial colonization with biofilm formation in the large intestine, and marked in vivo expression of AIDA-I protein in pigs infected with strains PD20 or PD20C in contrast to pigs infected with strains PD20M or PD71. The in vitro assays showed marked diffuse adherence to HeLa cells, enhanced bacterial auto-aggregation and significant biofilm formation (p < 0.05) by the AIDA-I⁺ strains, when compared to AIDA-I⁻ strains. These results demonstrate that expression of AIDA-I is essential for intestinal colonization and in vitro bacterial autoaggregation and biofilm formation. Thus, AIDA-I may be considered a significant virulence determinant in development of diarrhea caused by porcine diarrheagenic AIDA-I⁺ E. coli PD20 in piglets.     

Relationship between QT interval and heart rate in Alderley Park beagles.

The QT interval and heart rate were measured from the electrocardiogram of 1608 Alderley Park beagles, and the mean QT intervals for 28 values of heart rates between 84 and 192 beats per minute were calculated. These were analysed by linear regression and ranked by Pearson's correlation coefficient for each of eight equations, all of which have been proposed to describe the relationship between QT interval and heart rate. The equation QT=b(square root RR), upon which the calculation of QTc using Bazett's formula is based, did not adequately describe the relationship. QT=b(cube root RR) was a more adequate one-parameter equation. The first-ranked equation was 1/QT=a+b(HR), but its use presents practical and interpretational difficulties; consequently, the second-ranked equation, QT=a+b(log(e)HR), is recommended for routine use.     

Effectiveness of fish waste management strategies in reducing seabird attendance at a trawl vessel

The risk of seabird bycatch in trawl fisheries is increased by high numbers of seabirds attending vessels to feed on fish waste discharged. We conducted an experimental test of whether mincing fish waste prior to its discharge from a factory trawler reduced the number of seabirds attending the vessel. The trial was conducted on a mid-water trawler targeting hoki (Macruronus novaezelandiae) in New Zealand waters, and the experiment compared three treatments (1) discharging ‘unprocessed’ waste (fish offal and whole discards), (2) mincing all waste to a small particle size before discharge, or, (3) converting all waste to fishmeal and reducing discharge to sump water. The response to the experimental treatments was determined using seabird abundance within a 40 m-radius semi-circular area centred on the vessel stern. Mincing reduced the numbers of large albatrosses (Diomedea spp.) feeding astern of the vessel, but had no significant effect on other groups of seabirds. In contrast, reducing discharge to sump water resulted in a significant reduction in numbers of all groups of seabirds. In particular, the abundance of the small albatross group (principally Thalassarche spp.), and some smaller procellarids (e.g. sooty shearwater, Puffinus griseus, and white-chinned petrel, Procellaria aequinoctialis), was reduced to less than five percent of the number that were within the sweep area when unprocessed discharge was released. While mincing significantly reduced the abundance of large albatrosses at the vessel stern, relatively small numbers of these birds attend trawl vessels in New Zealand waters and associated bycatch rates are low. In contrast, reducing the quantity of fish waste discharge by mealing resulted in reduced abundances of a wide range of seabirds at the vessel. Therefore, compared to mincing, we recommend fish waste retention as a more effective management strategy for reducing seabird bycatch.     

Chloramphenicol toxicosis in cats

Six cats were given chloramphenicol orally at the dose level of 120/mg/kg/day in 3 divided doses for 14 days and were then observed for another 3 weeks after treatment. Five other cats were used as untreated controls for the first 14 days and subsequently were given 60 mg of chloramphenicol/kg/day for 21 days. Clinical signs of toxicosis, which were more severe in cats given the higher dose level, included central nervous system depression, dehydration, reduced food intake, body weight loss, sporadic diarrhea, and vomiting. In cats given the higher dose level, chloramphenicol caused reversible marrow suppression, with marrow hypoplasia, maturation arrest of erythroid cells, and inhibition of mitotic activity, and caused vacuolation of lymphocytes and of early myeloid and erythroid cells. Significant changes were evident in bone marrow after treatment for 1 week and in peripheral blood at the end of the 2nd week. Hematologic changes included decreased numbers of neutrophils, lymphocytes, reticulocytes, and platelets. In cats given the lower dose level, changes in blood and bone marrow were similar but less severe.     

Conservative management of a ruptured gastrocnemius muscle in a male llama.

Rupture of the gastrocnemius muscle was diagnosed in an obese llama using physical examination and ultrasound imaging. Conservative therapy consisting of the use of a cast to immobilize the affected limb permitted the muscle to heal. Only mild, residual gait abnormalities were observed on follow-up examination.     

Pulmonary hypertension and right-sided heart failure in an adult llama with hepatic disease

CASE DESCRIPTION: A 13-year-old llama was examined because of lethargy, inappetence, and syncope. CLINICAL FINDINGS: Physical examination revealed muffled heart and lung sounds and peripheral edema. Clinicopathologic abnormalities included lymphopenia, hyperglycemia, prerenal azotemia, mild hyponatremia, mild hypoalbuminemia, and high gamma-glutamyltransferase and creatine kinase activities. On ultrasonography, the liver appeared hyperechoic and ascites and pleural effusion were seen. Echocardiography revealed severe dilatation of the right atrium, right ventricle, and pulmonary artery; severe tricuspid regurgitation; and high right ventricular systolic pressure consistent with right-sided heart failure secondary to pulmonary hypertension. TREATMENT AND OUTCOME: Treatment with furosemide was attempted, but because of failing health, the llama was euthanized 4 weeks later. Macronodular cirrhosis of the liver, glomerulonephritis, and intimal fibrosis and medial hypertrophy of muscular pulmonary arteries were seen on histologic examination of postmortem specimens. CLINICAL RELEVANCE:Findings in this case were similar to those reported for human patients with portopulmonary hypertension secondary to hepatic cirrhosis. Pulmonary hypertension secondary to hepatic disease should be considered in the differential diagnosis of right-sided heart failure.