Clinico-diagnosis and therapeutic management of bacterial and fungal infections of canine ear with special reference to molecular characterization of certain otic pathogens
Pundir, Sandeep (2007) Clinico-diagnosis and therapeutic management of bacterial and fungal infections of canine ear with special reference to molecular characterization of certain otic pathogens. Masters thesis, College of VeterinaryScience and Animal Husbandry, Anand Agricultural University, Anand, Gujarat, INDIA.
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On screening of 2620 dogs presented at the Teaching Veterinary Clinical Service Complex, Zaveri Clinic, Veterinary College, Anand, Gujarat during the period between August 1st, 2005 to July 31st, 2006, the overall incidence of dermatitis was observed to be 17.67 per cent (463 cases). Of all the dermatological afflictions in canine population, the incidence of otitis externa stood at 21.81 per cent. Out of all the maladies of dogs, the overall incidence of otitis externa stood at 3.85 per cent. Greater number of cases of otitis were observed during summer season (44.55 per cent). The dogs belonging to the age group of 3 years and above showed greater susceptibility (57.43 per cent). German shepherd (38.6 per cent), followed by Spitz and Labrador retrievers (16.83 per cent each) were the most frequently affected breeds. Male dogs showed greater (61.39 per cent) involvement than females. Thirty-seven dogs with apparently healthy ears were found to have yellow to brownish cerumen in the external ear canal. Seventy-six dogs suffering from otitis showed physical manifestations such as erythema, crust formation, foul smelling otic discharge, head shaking, scratching of ear pinnae with paws, pain on palpation of auricular cartilage, and ulceration of the inner aspect of external ear canal. The cytological examination of swabs from apparently healthy ears revealed presence of squamous cells, Gram-positive or Gram-negative micro-organisms, and leukocytes, whereas swabs from clinical cases of otitis showed either Gram-positive and/or Gram negative organisms. Cells of Malassezia pachydermatis were seen as oval to pea-nut Gram-positive unicellular yeast cells. Bacteriological culture examination of ear swabs collected from 37 dogs with apparently healthy ears resulted in the recovery of monomicrobic isolates from 7 dogs, whereas more than one organism (bacteria with fungal organism) were isolated from 15 dogs. Staphylococcus spp. accounted for 77.27 per cent isolates, followed by Streptococcus spp., Pseudomonas spp., and Escherichia coli. The ear exudate swabs from 76 dogs suffering from otitis on bacteriological culture examination resulted in the recovery of 66 isolates. Monomicrobic isolates were recovered from 41 dogs, whereas mixed infection was observed in 25 dogs suffering from otitis in association with other bacteria and/ or fungi viz. Malassezia pachydermatis, Aspergillus spp. Coagulase-positive staphylococci (CPS) accounted for highest number of isolates, followed by Pseudomonas spp., Streptococcus spp. and Escherichia coli. Mycological culture examination of ear swabs collected from 37 dogs with apparently healthy ears resulted in the recovery of the monomicrobic isolates from 7 dogs, whereas mixed culture was obtained from 15 dogs in conjunction with bacteria. Malassezia spp. accounted for 59.09 per cent isolates, followed by Aspergillus spp., and Candida spp. The otic exudate swabs from 76 dogs on mycological culture examination resulted in the recovery of 36 isolates. Malassezia pachydermatis was recovered as monomicrobic isolate from 10 dogs. Mixed infection was observed in 26 dogs suffering from otitis in association with bacteria viz. coagulase-positive staphylococci, Pseudomonas spp., Streptococcus spp. and Gram-negative coccobacilli, and/ or other fungi. On in-vitro drug sensitivity testing of bacterial isolates recovered from apparently healthy ears, all the isolates exhibited sensitivity to enrofloxacin and resistance against ampicillin. Similarly, bacterial isolates recovered on culture of otic exudate from clinical cases of otitis exhibited sensitivity to enrofloxacin, gentamicin, oxacillin, cephalothin, chloramphenicol, cotrimoxazole and amoxycillin, and resistance against other antibacterials. On in-vitro drug sensitivity testing of fungal isolates recovered from apparently healthy ears, all the isolates exhibited sensitivity to nystatin and clotrimazole, and resistance against fluconazole. Similarly, fungal isolates recovered on culture of otic exudate from clinical cases of otitis, elicited susceptibility to amphoterecin-B, followed by clotrimazole and nystatin, and resistance against fluconazole. DNA was extracted successfully from 33 bacterial and 35 fungal isolates. BOX-PCR yielded a total of 3 band patterns consisting of 19 bands of 470 to 1200 bp size in Escherichia coli, and 17 band patterns consisting of 23 bands ranging from 400 to 1000 bp size in Staphylococcus spp. BOX-PCR yielded 24 band patterns consisting of 24 bands of 400 to 1200 bp size in the 29 fungal isolates. ERIC-PCR yielded a total of 3 band patterns consisting of 5 bands ranging from 370 to 1100 bp size in Escherichia coli, and 8 band patterns consisting of 10 bands ranging from 350 to 1100 bp size in Staphylococcus spp. ERIC-PCR yielded a total of 16 band patterns consisting of 16 bands ranging from 250 to 1500 bp size in 17 fungal isolates. REP-PCR yielded a single band pattern consisting of 6 bands ranging from 70 to 305 bp size in all 58 isolates. BOX-PCR, ERIC-PCR, and REP-PCR pattern can not differentiate similar speciation or similar pathological conditions. The microorganisms could not be differentiated individually by using only one of the Rep-PCR DNA fingerprinting methods. But when used in tandem, all the three BOX-PCR, ERIC-PCR, and REPPCR were capable of differentiating the organisms individually. The treatment protocol found effective in the management of ear infections included cleaning the ear debris using ceruminolytic preparations/ ear wax dissolvent viz Otosaf (herbal) ear drop, dioctyl-sodium sulphosuccinate or para-dichlorobenzene, and subsequently instillation of ear preparations containing antibacterial drug (s) (in cases of bacterial infections) and antifungal agents (in case of fungal infection). The cases which did not show response to the treatment with topical medication, were treated with systemic antibacterial /antifungal drugs found effective on in-vitro drug sensitivity testing. Otosaf ear drop (herbal) in combination with antibiotics produced better results rather than when administered alone in cases of otitis in dogs. Chlorhexidine ear flushing was found to be the most effective flushing agent in treating dogs suffering from chronic otitis, followed by povidone iodine in efficacy. In the recurrent cases of otitis, especially with Pseudomonas spp., enrofloxacin and amoxycillin–clavulanic acid combination was found effective. The cases of otitis caused by Malassezia pachydermatis were treated by oral administration of ketoconazole and/or topical therapy with antifungal otic preparation. Cases of otitis with inflammed lesions and intense pruritus were also treated with systemic use of prednisolone in tapering dosage along side antibiotics.
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