Evaluation of Changes in Actin Filaments of RK13 Cells Infected with <i>Malassezia pachydermatis</i>

Background: Malassezia pachydermatis is the main causative agent of canine otitis and also of a myriad of dermatological problems in companion animals;its interaction mechanisms with host cells are still unclear. Objectives: To establish an in vitro infection model of M. pachydermatis-exposed RK13 cells in order to evaluate cell morphological changes as well as changes in the structure of actin filaments. Methods: Cultures of RK13 cells were infected with M. pachydermatis, alterations caused by the yeast were evaluated by optical and fluorescence microscopy. Results: M. pachydermatis adheres itself to the cell and produces the formation of multiple agglomerates that cause changes in cell morphology, formation of cell aggregates in overlays, presence of syncytia and destruction of cell culture structure. The damaged cells presented changes in the actin filaments consisting of thickening of the cell cortex and loss of stress fibers. On the other hand, the formation of perinuclear actin rings in the yeasts was observed. Conclusions: An in vitro infection model was established with M. pachydermatis and alterations in cell morphology were observed consisting of changes in the structure of the actin filaments, overgrowth of the cells and the presence of syncytia.

An update on microbiological causes of canine otitis externa in Campania Region,Italy

Objective: To update the recent knowledge of the microbiological causes of canine otitis externa in Campania Region(Italy) and the antibiotic susceptibility patterns of the isolated strains.Methods: A total of 122 dogs were examined by otoscopy, and auricular swab samples were collected from both ears in 74 dogs presenting clinical bilateral otitis and from single ears in 48 dogs displaying clinical unilateral otitis. Cytological examination,bacteriological analysis and antimicrobial susceptibility tests were performed.Results: Thirty-one out of 122 dogs were positive for yeast species(25.4%, 95% confidence interval(CI): 18.2%–34.2%) with a higher prevalence of Malassezia pachydermatis(21/31 isolates, 67.7%, CI: 48.5%–82.7%), and a total of 91 out of 122 dogs were positive for bacterial species(74.6%; CI: 65.8%–81.8%) with a higher prevalence of Staphylococcus pseudintermedius(45/143 isolates, 31.5%, CI: 24.1%–39.8%). These results are the first description of Streptococcus agalactiae-associated otitis. The yeasts isolated showed high levels of susceptibility to all antifungal agents tested; on the contrary all the isolated bacterial strains were highly resistant to at least four out of ten antimicrobial classes. Both Gram-positive and Gram-negative bacteria showed high resistance to amoxicillin/clavulanate and kanamycin hence they are not recommended as initial empirical therapy for the otitis treatment.Conclusions: This update illustrates an increase in antibiotic resistances providing an insight into the current knowledge of the therapeutic procedures followed on canine otitis externa in Italy. It also emphasizes the importance of considering the results of the microbiological and sensitivity tests to decide on an appropriate antibiotic therapy.