Antimicrobial susceptibility of Escherichia coli from swine, horses, dogs and cats as determined in the BfT-GermVet monitoring program 2004-2006

A total of 417 isolates of Escherichia coli collected from five animal species/organ system combinations from swine [urinary/genital tract (UGT) incl. mastitis metritis agalactia syndrome], horses [genital tract (GT)] and dogs/cats [respiratory tract (RT), UGT and gastrointestinal tract (GIT)] were analysed quantitatively for their susceptibility against different antimicrobial agents by determination of minimum inhibitory concentrations. Regardless of which animal species the strains originated from, resistance appeared most frequently against sulfamethoxazole (18-59%), tetracycline (14-54 %), and ampicillin (14-39%). High percentages of intermediate isolates were observed for cephalothin (39-46 %). In general, low prevalences of resistance were detected for amoxicillin/clavulanic acid (1-4%), gentamicin (1-9%), and cefazolin (0-11%). Generally speaking, the antimicrobial resistance situation among E. coli isolates from horses and small animals is relatively good.     

Pathogenesis of infectious bronchitis virus in vaccinated chickens of two different major histocompatibility B complex genotypes

Infectious bronchitis (IB) disease progression in vaccinated chickens after challenge was evaluated in a single commercial line of layer chickens presenting two different major histocompatibility complex (MHC) B complex genotypes. MHC B genotypes were determined by DNA sequence-based typing of BF2 alleles. In total, 33 B2/B15 and 47 B2/B21 chickens were vaccinated with an Ark-type IB virus (IBV) attenuated vaccine and challenged with Ark-type IBV field isolate AL/4614/98 14 days later. Additional chickens of both genotypes served as unvaccinated/challenged and unvaccinated/nonchallenged controls. Clinical signs, histopathologic analysis, detection of IBV genomes in tears, and IBV-specific immunoglobulin A (IgA) in tears were used to evaluate disease progression and immune response. The incidence of IBV respiratory signs was significantly higher in B2/21 than in B2/B15 MHC genotype birds. However, neither the severity and duration of respiratory signs nor the severity and incidence of histologic lesions differed significantly with MHC genotype. The levels of IBV-specific IgA in tears of vaccinated and challenged chickens did not differ significantly between MHC genotypes. IBV genomes were present in the tears of vaccinated and challenged birds, and the incidence of detectable IBV genomes did not vary significantly with MHC B genotype. From an applied perspective, these results indicate that vaccinated commercial outbred chickens with these MHC genotypes are equally resistant to IBV.     

The effect of induced forelimb lameness on thoracolumbar kinematics during treadmill locomotion

REASONS FOR PERFORMING STUDY: Lameness has often been suggested to result in altered movement of the back, but there are no detailed studies describing such a relationship in quantitative terms. OBJECTIVES: To quantify the effect of induced subtle forelimb lameness on thoracolumbar kinematics in the horse. METHODS: Kinematics of 6 riding horses was measured at walk and at trot on a treadmill before and after the induction of reversible forelimb lameness grade 2 (AAEP scale 1-5). Ground reaction forces (GRF) for individual limbs were calculated from kinematics. RESULTS: The horses significantly unloaded the painful limb by 11.5% at trot, while unloading at walk was not significant. The overall flexion-extension range of back motion decreased on average by 0.2 degrees at walk and increased by 3.3 degrees at trot (P<0.05). Changes in angular motion patterns of vertebral joints were noted only at trot, with an increase in flexion of 0.9 degrees at T10 (i.e. angle between T6, T10 and T13) during the stance phase of the sound diagonal and an increase in extension of the thoracolumbar area during stance of the lame diagonal (0.7degrees at T13, 0.8 degres at T17, 0.5 degres at L1, 0.4 degrees at L3 and 0.3 degrees at L5) (P<0.05). Lameness further caused a lateral bending of the cranial thoracic vertebral column towards the lame side (1.3 degrees at T10 and 0.9 degrees at T13) (P<0.05) during stance of the lame diagonal. CONCLUSIONS: Both range of motion and vertebral angular motion patterns are affected by subtle forelimb lameness. At walk, the effect is minimal, at trot the horses increased the vertebral range of motion and changed the pattern of thoracolumbar motion in the sagittal and horizontal planes, presumably in an attempt to move the centre of gravity away from the lame side and reduce the force on the affected limb. POTENTIAL RELEVANCE: Subtle forelimb lameness affects thoracolumbar kinematics. Future studies should aim at elucidating whether the altered movement patterns lead to back and/or neck dysfunction in the case of chronic lameness.     

Comparison of mandibular motion in horses chewing hay and pellets

REASONS FOR PERFORMING STUDY: Previous studies have suggested that temporomandibular joint (TMJ) kinematics depend on the type of food being masticated, but accurate measurements of TMJ motion in horses chewing different feeds have not been published. HYPOTHESIS: The temporomandibular joint has a larger range of motion when horses chew hay compared to pellets. METHODS: An optical motion capture system was used to track skin markers on the skull and mandible of 7 horses as they chewed hay and pellets. A virtual marker was created on the midline between the mandibles at the level of the 4th premolar teeth to represent the overall motion of the mandible relative to the skull during the chewing cycle. RESULTS: Frequency of the chewing cycles was lower for hay than for pellets. Excursions of the virtual mandibular marker were significantly larger in all 3 directions when chewing hay compared to pellets. The mean velocity of the virtual mandibular marker during the chewing cycle was the same when chewing the 2 feeds. CONCLUSIONS: The range of mediolateral displacement of the mandible was sufficient to give full occlusal contact of the upper and lower dental arcades when chewing hay but not when chewing pellets. POTENTIAL RELEVANCE: These findings support the suggestion that horses receiving a diet high in concentrate feeds may require more frequent dental prophylactic examinations and treatments to avoid the development of dental irregularities associated with smaller mandibular excursions during chewing.     

Incisional complications following exploratory celiotomy: does an abdominal bandage reduce the risk?

REASONS FOR PERFORMING STUDY: Post operative complications following exploratory laparotomy can be potentially life-threatening, increase post operative morbidity and result in an increase in the length of hospitalisation of the affected individual. No study has evaluated the efficacy of specific strategies to reduce the incidence of post operative incisional complications. HYPOTHESIS: The use of an abdominal bandage following colic surgery through a celiotomy incision would significantly reduce the prevalence of post operative incisional complications. METHODS: A controlled, randomised clinical trial to test the hypothesis was devised. Horses eligible for inclusion in the study were assigned randomly either to the study or control group following recovery from general anaesthesia. Any post operative incisional complications occurring during hospitalisation were recorded. Long-term follow-up was obtained via telephone questionnaires. Absolute risk reduction (ARR) and number needed to treat (NNT) were calculated. Multivariable analyses were conducted for all outcomes of interest. RESULTS: There was an ARR of the likelihood of developing a post operative incisional complication of 45% when using compared to not using an abdominal bandage in the post operative period. Therefore, it would be necessary to treat 2.2 horses with an abdominal bandage in order to prevent one horse developing any post operative incisional complications. CONCLUSIONS: Although incisional complications continue to be a problem following an exploratory celiotomy for colic, the proportion of horses affected was significantly reduced by use of a bandage. POTENTIAL RELEVANCE: Using an abdominal bandage following an exploratory laparotomy may help reduce the prevalence of post operative incisional complications, and prevent the development of potentially life-threatening complications.     

High prevalence of methicillin resistant Staphylococcus aureus in pigs

Recently methicillin resistant Staphylococcus aureus (MRSA) was isolated from pigs and pig farmers in The Netherlands. In order to assess the dissemination of MRSA in the Dutch pig population, we screened 540 pigs in 9 slaughterhouses, where a representative portion of Dutch pigs (63%) was slaughtered in 2005. We found 209 (39%) of the pigs to carry MRSA in their nares. Forty-four of 54 groups of 10 consecutive pigs (81%), each group from a different farm, and all slaughterhouses were affected. All MRSA isolates belonged to 1 clonal group, showing Multi-Locus Sequence Type 398 and closely related spa types (mainly t011, t108 and t1254). Three types of the Staphylococcal Chromosome Cassette (SCCmec) were found: III (3%), IVa (39%) and V (57%). All 44 tested isolates (1 isolate per group) were resistant to tetracycline, reflecting the high and predominant use of tetracyclines in pig husbandry. Twenty-three percent of the isolates were resistant to both erythromycin and clindamycin and 36% to kanamycin, gentamicin and tobramycin but only a single isolate was resistant to co-trimoxazole and none to ciprofloxacin and several other antibiotics. The percentage of MRSA positive pigs was significantly different among slaughterhouses and among groups within slaughterhouses, indicating a high prevalence of MRSA in pigs delivered from the farms as well as cross contamination in the slaughterhouses.     

Central nervous system signs in chickens caused by a new avian reovirus strain: a pathogenesis study

The present study describes the pathogenesis of infection of chicks with a new avian reovirus strain, belonging to the so-called enteric reovirus strains (ERS) that is capable of causing central nervous system signs in SPF white leghorns. After intramuscular (IM) or oral inoculation birds were either observed for clinical signs or sacrificed for macroscopic, histological and virological examination for 21 days. Virus isolation was performed on the brain, leg muscle, hock joint, liver and spleen. For the detection of viral antigen the immunohistochemistry (IHC) technique was performed on the caudal part of the cerebrum, spinal cord including spinal ganglia and right N. Ischiadicus. High mortality (79% in 7 days) was seen in birds that were inoculated IM. Survivors were depressed and stayed small until the end of the experiment. One bird had tremor and showed torticollis at 9 days after IM inoculation. Birds that were inoculated orally were depressed from day 4 and stayed small until the end of the experiment. One bird showed a torticollis at 10 days after inoculation. After both IM and oral inoculation ERS was isolated from the brain between 3 and 10 days after inoculation. Other examined organs were positive for virus isolation from day 1 or 5 until day 21. IHC revealed viral antigen positive cells in the Plexus chorioideus (plexus epithelial cells or cells within the underlying connective tissue) and in a spinal ganglion. The results indicate that the pathogenesis of ERS infection in chickens bears some resemblance with that of the mammalian reoviruses serotype 1 in mice.     

Phenotypic and genotypic characterization of Paenibacillus larvae isolates

Paenibacillus larvae is the causative agent of American Foulbrood (AFB), a severe disease of honeybees (Apis melifera). The aim of this work was to develop a strategy for the subtyping and the epidemiological analysis of P. larvae. Phenotypic characterisation, susceptibility to several antibiotics, electrophoresis of whole bacterial proteins, rep-PCR, ribotyping and DGGE were assessed using a collection of P. larvae isolates from different Uruguayan and Argentinean locations. Results indicated that there are two P. larvae genotypes circulating in Uruguay ERIC I-BOX A (worldwide distributed) and ERIC I-BOX C (exclusively detected in Argentina until this study). These results suggest that P. larvae isolates had moved between Argentina and Uruguay, probably through the Uruguay River. Patterns of whole bacterial proteins, DGGE and ribotyping did not improve the P. larvae intraspecific discrimination. Antibiotic susceptibility assays showed that 100% isolates were OTC-sensitive and 22% (belonging to ERIC I-BOX A group) were sulfisoxazole-resistant. This work may contribute to the elucidation of basic aspects related to the epidemiology of AFB in Uruguay and in the region.