Molecular basis of quinolone resistance in Escherichia coli from wild birds

Nine quinolone resistant (minimal inhibitory concentration [MIC] was > 32 microg/mL for nalidixic acid, > 1 microg/mL for ciprofloxacin) isolates of Escherichia coli have been found in wild birds with septicemia. All of the isolates were aerobactin positive. The mechanisms of resistance were characterised by sequencing the quinolone resistance-determining region (QRDR) of the gyrA, gyrB, parC, and parE genes. Sequence analysis of the gyrA gene in all isolates identified only 1 nucleotide substitution at codon Serine-83 for Leucine-83. Sequence analysis of the gyrB, parC, and parE QRDR genes revealed no mutations in any of the isolates. This study was conducted to determine the importance of these genes in the susceptibility of E. coli strains isolated from wild birds to quinolones.     

A simple random amplified polymorphic DNA genotyping method for field isolates of Dermatophilus congolensis

Dermatophilus congolensis is the pathogenic actinomycete that causes dermatophilosis in cattle, lumpy wool in sheep and rain scald in horses. Phenotypic variation between isolates has previously been described, but its genetic basis, extent and importance have not been investigated. Standard DNA extraction methods are not always successful for D. congolensis due to its complex life cycle, one stage of which is encapsulated. Here we describe the development of rapid and reliable DNA extraction and random amplified polymorphic DNA (RAPD) methods that can be used for genotyping D. congolensis field isolates. Our results suggest that genotypic variation between isolates correlates with host species. Several DNA extraction methods and RAPD protocols were compared. An extraction method based on incubation of the bacterium in lysozyme, sodium dodecyl sulphate (SDS) and proteinase K treatments and phenolic extraction yielded high-quality DNA, which was used to optimize RAPD-polymerase chain reaction (PCR) protocols for two random primers. An alternative rapid, non-phenolic extraction method based on proteinase K treatment and thermal shock was selected for routine RAPD typing of isolates. DNA extracted from reference strains from cattle, sheep and horse using either method gave reproducible banding patterns with different DNA batches and different thermal cyclers. The rapid DNA extraction method and RAPD-PCR were applied to 38 D. congolensis field isolates. The band patterns of the field and type isolates correlated with host species but not with geographical location.     

Facial swelling associated with impaction of the deciduous and permanent maxillary fourth premolars in a dog with patent ductus arteriosus

A three-year-old Labrador retriever was referred for decreased appetite, a painful swelling in the region of the maxillary right fourth premolar, and a heart murmur indicative of patent ductus arteriosus (PDA) diagnosed 1.5-weeks prior to presentation. Oral examination and intraoral dental radiographs showed impaction of the maxillary right fourth premolar surrounded by reactive alveolar bone. Necrotic bone, remnants of the deciduous maxillary right fourth premolar, and the impacted permanent maxillary right fourth premolar were removed following surgical exploration of the area. The PDA was repaired without complication 2-weeks following oral surgery. The extraction site was healing appropriately, and the dog's inappetence and painful facial swelling had resolved.     

The effect of vaccination with the PAV-250 strain classical swine fever (CSF) virus on the airborne transmission of CSF virus

The airborne transmission of Classical Swine Fever (CSF) virus to susceptible pigs, as well as the effect of vaccination with the CSF virus PAV-250 strain was investigated on this mode of transmission. Experiment I: four pigs were inoculated with the ALD CSFV strain (10(4.3) 50% TCID) by the intramuscular route, and at the onset of fever, they were introduced into an enclosed chamber. At the end of the experiment surviving pigs were sedated, anesthetized and euthanatized. Experiment II: four pigs were previously vaccinated with the CSF virus PAV-250 strain, and at 14 days post-vaccination they were challenged with the CSF virus ALD strain. In both experiments, four susceptible pigs were exposed to infectious aerosols by placing them in a chamber connected by a duct to the adjacent pen containing the infected animals and were kept there for 86 hs. In Experiment I, pigs exposed to contaminated air died as a result of infection with CSF virus on days 14, 21 and 28 post-inhalation. These four pigs seroconverted from day 12 post-inhalation. CSF virus was isolated from these animals, and the fluorescent antibody test on tonsils was positive. In Experiment II, a vaccinated pig exposed to contaminated air did not seroconvert, nor was CSF virus isolated from lymphoid tissues. However, mild fluorescence in tonsil sections from these pigs was observed. In conclusion, CSF virus was shown to be transmitted by air at a distance of 1 m to susceptible pigs. Vaccination with the PAV-250 CSF virus strain protected the pigs from clinical disease under the same conditions.     

Comparison of two heated gutta percha and sealer obturation techniques in canine teeth of dogs

The overall endodontic fill and apical seal achieved using two different obturation methods were compared. Twenty-six adult dog canine teeth were instrumented and obturated using either a warm vertical or heated lateral technique. Zinc oxide-eugenol sealer was applied by paper point in the warm vertical technique and by syringe injection in the heated lateral technique. The cadaver jaws were warmed to 35-37 degrees C (95-98.6 degrees F) during obturation using a circulating warm water bath. Obturation times were recorded and ventrodorsal, lateral, and oblique dental radiographs were taken of all teeth for comparison. Twenty-two of the canine teeth were extracted and an apical dye study was performed using a clearing technique. Apical dye leakage was linearly measured to evaluate the furthest ink penetration into the root canal. Although radiographically the heated lateral method appeared to have a better endodontic fill, there was significantly greater apical dye leakage in teeth obturated with that combination of sealer and gutta percha. There was also extrusion of sealer and root fracture associated with the heated lateral technique. The method of sealer application was different for each technique; this variable should be taken into consideration when interpreting our results, which suggest that the warm vertical compaction technique may provide a better apical seal in canine teeth of dogs in a shorter period of time, with fewer obturation complications when compared to the heated lateral technique.     

Odontoclastic resorptive lesion of a mandibular right first molar in a cougar

A two-year old neuteral/male cougar (Felis concolor) was presented because of abnormal eating habits and an irregularity of the mandibular right first molar that was noted by the caretaker. Oral examination and dental radiographs showed a lesion consistent with odontoclastic resorption of the mandibular right first molar, and a crown fracture and dilacerated root of the maxillary right first incisor. Exodontic therapy was performed on both teeth. The caretaker reported no problems associated with the patient's oral cavity 10-months following treatment.     

Aphid Transmission Alters the Genomic and Defective RNA Populations of Citrus tristeza virus Isolates

ABSTRACT A total of 14 Spanish isolates of Citrus tristeza virus (CTV) and 1 isolate from Japan were transmitted by Aphis gossypii, and the subisolates obtained were compared with the source isolates for symptom expression and double-stranded RNA (dsRNA) pattern. Of the 14 Spanish isolates, 9 showed altered dsRNA patterns after aphid transmission but only minor variations in the intensity of symptoms induced on Mexican lime. Northern blot hybridization with complementary DNA (cDNA) probes corresponding to both the 5' and the 3' termini of the CTV genomic RNA (gRNA) showed that the dsRNA bands that could be used to discriminate between the dsRNA pattern of the source and the aphid-transmitted isolates were the replicative forms of defective RNAs (D-RNAs). Conversely, the Japanese isolate and two subisolates obtained from it by aphid transmission had the same dsRNA pattern, but one of the subisolates induced milder symptoms in several hosts. Dot-blot hybridization with cDNA probes representing several regions of the gRNA showed that most of the aphid-transmitted isolates differed from the corresponding source isolate by their hybridization pattern. Our results indicate that aphid transmission often sorts the populations of gRNA variants and D-RNAs present in CTV isolates.