Lawsonia intracellularis has been identified recently as the etiological agent of proliferative enteropathies, which are characterized by intestinal epithelial hyperplasia and associated moderate immune responses. This disease complex has been reported in a broad range of animals, prevalently in pigs, and L. intracellularis has been linked with ulcerative colitis in humans. L. intracellularis is an obligate intracellular bacterium, and the pathogenic mechanisms used to cause disease are unknown. Using in vitro-grown organisms as a source of genomic DNA, we identified a Lawsonia gene which encodes a surface antigen, LsaA (for Lawsonia surface antigen), associated with attachment to and entry into cells. The deduced amino acid sequence of this protein showed some similarity to members of a novel protein family identified in a number of other bacterial pathogens but for which roles are not fully defined. Transcription of this gene was detected by reverse transcription-PCR in L. intracellularis grown in vitro in IEC18 cells and in bacteria present in ileal tissue from infected animals. Immunohistochemistry with specific monoclonal antibody and immunoblotting with sera from infected animals demonstrated that LsaA protein is synthesized by L. intracellularis during infection. Expression of this gene during infection in vitro and in vivo suggests that this surface antigen is involved during infection, and phenotypic analysis indicated a role during L. intracellularis attachment to and entry into intestinal epithelial cellsA small number of bacterial pathogens have been identified as causative agents of gastrointestinal epithelial hyperplasia. These comprise Helicobacter species (gastric hyperplasia [3,20]), Citrobacter rodentium (murine colonic hyperplasia [15,16,26,36]), and Lawsonia intracellularis (proliferative enteropathy [23,40]). L. intracellularis was only recently recognized as a pathogen and remains poorly characterized in comparison to Helicobacter species and C. rodentium. L. intracellularis is phylogenetically unrelated to other pathogens (13, 34), but it is clearly the causative agent of proliferative enteropathies, which are infectious intestinal hyperplastic diseases of a variety of mammalian and avian species (6,8,23). Presently, the disease is recognized as most significant in pigs (23, 40); however, the broad host range of this bacterium includes primates (in which it was recently reported to cause fatal enteritis in captive L. intracellularis is an obligate intracellular bacterial enteropathogen which is most closely related to Desulfovibrio spp. (13) and Bilophila wadsworthia (41). This relationship is based solely on 16S rRNA sequence comparisons, and further similarities between L. intracellularis and these other species have not yet been reported. Pathogenesis of L. intracellularis has not been well investigated; however, organisms cultured in vitro have been used successfully to reproduce the disease in vivo (21,30,32,42,43). This bacterium has a tropism for intestinal epithelial cells, and the...
Background Middle ear effusion is common in brachycephalic dogs with similarities to otitis media with effusion in children. Association with the cranial and eustachian tube morphology and bacterial infection is suspected in both species. Hypothesis/objectives To determine cytological and bacteriological features of middle ear effusions in dogs, provide information on histological features, and further assess the dog as a model of the human disease. Animals Sixteen live dogs, 3 postmortem cases of middle ear effusion, and 2 postmortem controls. Methods Prospective; clinical investigation using computed tomography, magnetic resonance imaging, video‐otoscopy, myringotomy; cytological assessment of 30 and bacteriology of 28 effusions; histology and immunohistochemistry (CD3 for T‐lymphocytes, Pax5 for B lymphocytes and MAC387 for macrophages) of 10 middle ear sections. Results Effusions were associated with neurological deficits in 6/16 (38%) and concurrent atopic dermatitis and otitis externa in 9/16 (56%) of live cases. Neutrophils and macrophages predominated on cytology (median 60 [range 2%‐95.5%] and 27 [2%‐96.5%]) whether culture of effusions was positive or not. In histology sections, the mucosa was thickened in affected dogs but submucosal gland dilatation occurred in affected and unaffected dogs. There was no bacterial growth from 22/28 (79%) of effusions. Bacteria isolated from the other 6 (21%) were predominantly Staphylococcus pseudintermedius (4/6, 67%). Conclusions and Clinical Importance Clinical, morphological, and cytological findings in middle ear effusions of dogs and people suggest similar pathogeneses. Middle ear effusion of dogs could be a useful model of human otitis media with effusion. Such comparisons can improve understanding and management across species.
BackgroundTopical antimicrobials are recommended for first line treatment of surface and superficial infections in dogs. This is especially important given the increasing prevalence of antimicrobial resistant infections. Antimicrobial wipes have become popular, but there are a lack of controlled studies assessing their in vitro antimicrobial and in vivo residual activity. We aimed to assess the antimicrobial efficacy of two commercial antimicrobial wipes against frequently isolated pathogens.Ten clinical and one reference isolate each of meticillin-susceptible Staphylococcus pseudintermedius (MSSP), meticillin-resistant S. pseudintermedius (MRSP), Escherichia coli (EC), extended spectrum beta-lactamase (ESBL) producing E. coli (ESBL-EC), Pseudomonas aeruginosa (PA) and Malassezia pachydermatis (MP) were tested using a modified Kirby-Bauer technique. Each isolate was tested against 6 mm discs of chlorhexidine (CHX) and acetic acid/boric acid (AABA) wipes, and positive and negative controls either overnight (bacteria) or for 3 days (Malassezia).Healthy dogs were treated with the wipes and distilled water on a randomised flank (n = 5 each). Hair samples (1 cm; 0.1 g) taken at days 0, 1 and 3 were inoculated with an isolate of each organism. Zones of inhibition (ZI) were measured.ResultsAll isolates produced confluent growth with AABA and control wipes, except for the cleansing wipes and MP (median ZI 12 mm; 95% CI 8.2–15.8). The median (95% CI) CHX wipe ZIs (mm) were: MP 48.0 (47.0–49.0), MSSP 15.6 (14.2–17.0), MRSP 14.0 (13.6–14.4), EC 13.6 (12.0–15.2) and ESBL-EC 10.0 (9.4–10.6). PA showed confluent growth. The differences between the bacterial isolates was significant (Kruskal-Wallis p < 0.0001; post-tests MSSP = MRSP = EC > EBSL-EC > PA). Confluent growth was visible with all the hair samples.ConclusionCHX but not AABA showed in vitro efficacy against MSSP, MRSP, EC and MP. ESBL-EC were less susceptible and there was no activity against PA. There was no residual activity on hair. Additional studies are required to determine efficacy of these products in clinically affected patients.
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