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Antibiogram of Microbes Associated with Otitis in Canines.


The study was aimed at determining the microbial prevelance in 100 dogs of various breeds found positive for otitis based on history and clinical observations. Ear swabs were collected aseptically and subjected to microbiological examination. In all 96 bacterial isolates were recovered during microbiological screening of these Staphylococci sp. were 30 (31%), E. coli 25 (26%), Pseudomonas sp. 16 (16%), Proteus sp.10 (10%). Antibiogram pattern of Staphylococci sp. revealed highest sensitivity to Ciprofloxacin (76.66%) and least to Azithromycin (56.66%), E. coli was sensitive to Gentamicin (92%) and Pseudomonas sp. was highly sensitive to Polymixin-B (93.75%) followed by Ciprofloxacin (87.5%).

Keywords: Antibiogram; canine; etiology; otitis


Ear infections in dogs is commonly caused by multiple microbial agents and is estimated that 20% of dog population were affected by these disease (Senthel et al., 2010). Common organisms isolated from dogs with ear infections include Staphylococcus sp., Pseudomonas sp., Escherichia coli, Proteus sp etc. Otitis externa is an acute or chronic inflammation of external ear. The disease is more frequent in dogs than cats (Petrov et al., 2013). There have been no published surveys on antimicrobial susceptibilities of bacteria associated with otitis externa in dogs in Odisha. Although the antimicrobial therapy of ear infections in small animals has been reviewed. To ensure prudent use of antimicrobial drugs, a retrospective analysis was conducted from clinical cases of otitis externa of various breeds of dogs, including chronic cases.

Materials and Methods

The study was conducted in canine show pooch carnival held on 2nd October' 2015 organised by Odisha kennel club and 58 samples were collected. Similarly, 70 samples collected from dogs with history of dropping of ears, purulent greenish yellow discharge, pruritis, palpated erythema and swelling of ear presented with acute and chronic external otitis (Fig. 1 and 2). Thorough clinical examination of ear was carried out through bacteriological culture examination of otitic exudates for isolation of bacteria. Antibiotic sensitivity test was carried out in bacterial otitis to appropriate proper line of treatment. To isolate and identify bacteria, collected samples were grown on special culture media. Identification was based on various morphological and biochemical characters (Markey et al., 2013).

Microbiological tests: Samples were cultivated on blood agar containing 5% sheep blood and on Mc.conkey agar. Cultures were incubated aerobically for 24-48 hrs at 37[degrees]C. After incubation, isolates were identified according to conventional microbiological methods.The behavior of isolates to antimicrobial drugs was tested by disk diffusion methods in Muller Hinton agar medium loaded with antibiotic disc.

Results and Discussion

The microbial flora of ear canal of canines suffering from otitis has been studied by several workers and results differ widely. Similarly the present investigation revealed different microbial agents, details of recovered isolates are presented in Table-1. The microbiological tests conducted on 96 samples showed that 30 isolates with typical characteristic of Staphylococcus sp. (31.25%) followed by E. coli (26.04%), Streptococcus sp. (15.62%), Pseudomonas aeruginosa (16.66%) and Proteus (10.41%) which is close aggregation with Lakshmi et al. (2013).

Pseudomonas aeruginosa and Proteus mirabilis were isolated only from animals with chronic otitis or from dogs that failed to respond to any previous antibiotics treatment. p-haemolytic Streptococci and E. coli rarely caused otitis externa independently, but were rather seen in association with Staphylococci or Pseudomonas aeruginosa.

Antibiotic sensitivity test

Antibiotic sensitivity tests were conducted to evaluate the sensitivity of causative organisms for antibiotics and presented in Table 3 (Fig. 3). In-vitro antibiogram of Staphylococcus sp. indicated highest sensitivity to Ciprofloxacin 23 (76.66%) and least to Azithromycin 17 (56.66%). Next in order of effectiveness were Gentamicin 22 (73.33%), Ceftriaxone 20 (66.66%) and Cephalexin 19 (63.33%). In-vitro antibiogram of E. coli indicated highest 23 (92%) sensitivity to Gentamicin and least sensitivity to Lincomycin 7 (28%). Next in order of sensitivity was Erythromycin 18 (72%), Polymixin-B 17 (68%) and Ciprofloxacin 16 (64%). In-vitro antibiogram of Pseudomonas sp. indicated highest 15 (93.75%) sensitivity to Polymixin-B and next to Ciprofloxacin 14 (87.5%). The in-vitro antibiogram of Proteus sp. indicates highest 6 (60%) sensitive to Ciprofloxacin and least to 2 (20%) Enrofloxacin. Streptococcus sp. were sensitive to Ciprofloxacin 10 (66.66%) and least to 7 (46.66%) Cephalexin.

Ciprofloxacin is found to be effective against almost all bacterial isolates i.e. Staphylococcus sp., Streptococcus, E. coli, Pseudomonas sp. Proteus organism followed by Gentamicin. These findings are in agreement with Chaudhary et al. (2003) who observed similar sensitivity pattern of antibacterial agents to different bacterial isolates as Ciprofloxacin 86.67%, Norfloxacin 56.67% and Chloramphenicol 38%. Other antibiotics under study showed sensitivity to one or two bacterial isolates only. Chloramphenicol 15 (60%) and Erythromycin 18 (72%) were only sensitive to E.coli. Ampicillin did not shown sensitivity to any bacterial isolates justifying the rationality of Ciprofloxacin and Gentamicin in treatment of canine otitis. This finding is in akin with finding of Kumar and Rao (1997), Chaudhary et al. (2003) and Senthil Kumar (2010) who also recorded nearly same degree of sensitivity of Ciprofloxacin to isolates from otitic dogs.

As conclusion, it could be assumed that the commonest bacterial agents isolated from canine otitis externa were coagulase positive Staphylococci. However yeasts are also frequently involved in aetiology of ear canal inflammations that in many instances, clinical cases were caused by co-infections. Microbiological tests are always recommended for isolation and identification of microbial agents and for determination of their sensitivity to chemotherapeutics used for treatment of otitis externa in dogs.


Chaudhary, M., Mirakhur, K.K. and Jand, S.K. (2003). Antibiogram and microbiological patterns of external ear canal of dogs with reference to otitis. Indian Vet. J. 80: 951-52.

Lakshmi, K. and Tirumala Rao, D.S. (2013). Clinico-Microbiological and Therapeutic Studies on Canine Otitis Externa. Int J Pharm Bio Sci. 4: 1209-14.

Kumar, A. and Rao, P. (1997). Bacterial and fungal flora in otitis externa of dogs. Indian Vet. J. 79: 727-29.

Markey, B., F. Leonard, F., Archambault, M., Culinareand, A. and Maguire, D. (2013). Clinical Vet. Microbiology, 2nd Ed., Elsevier, p. 11-901.

Senthilkumar, K.P., Selveraj, S., Vairamuthu, M. and Shammiand D. Kathiresan (2010). Antibiogram pattern ofmicrobes isolated from otitis externa of dogs. Tamil Nadu J. Vet. Anim. Sci. 6: 145-47.

Petrov,V., Mihaylov,G., Tsachev,I., Zhelev, G., Marutsov,P. and Koev, K. (2013). Otitis Externa in Dogs Microbiology and Antimicrobial Susceptibility. Revue Med. Vet. 164: 18-22.

Sarita Behera (1), Rajashree Mishra, Prasanna Pati and Manoj K. Sahu

Department of Veterinary Microbiology College of Veterinary Science and Animal Husbandry Odisha University of Agriculture and Technology (OUAT) Bhubaneswar - 751003 (Odisha)

(1.) Corresponding author. E-mail: saritabehera1990@gmail.
Table 1 : Antibiotic disc used for AST

Antibiotics                    Concentration/disc

Ampicillin                         10 [micro]g
Cloxacillin                        30 [micro]g
Amoxicillin/ Clavulinic acid       30 [micro]g
Gentamicin                         30 [micro]g
Chloramphenicol                    30 [micro]g
Enrofloxacillin                    10 [micro]g
Ciprofloxacillin                   10 [micro]g
Erythromycin                       15 [micro]g
Ceftriaxone                        30 [micro]g
Amikacin                           30 [micro]g
Azithromycin                       30 [micro]g
Polymixin-B                        10 [micro]g
Lincomycin                         15 [micro]g
Cephalexin                         30 [micro]g

Table 2: Microbial prevelance in otitis

Dog breeds       No of    Bacteria             Isolated  Number and
                 samples                                 frequency(%)

Labrador          25       Staphylococci sp.    30         31.25
German shepherd   30       Streptococcus sp.    15         15.62
Spitz             35       Pseudomonas          16         16.66
Desi              10       Proteus sp.          10         10.41
Doberman          28       E. coli              25         26.04
Total            128                            96        100

Table 3: Antibiotic sensitivity against microbes isolated from Otitis

Antibiotics       Staphylococcus   Streptococcus   Pseudomonas
                   (N=30)           (N=15)          (N=16)

Ciprofloxacin     23 (76.66%)      10 (66.66%)      14 (87.5%)
Ceftriaxone       20 (66.66%)       8 (53.33%)      10 (62.5%)
Cephalexin        19 (63.33%)       7 (46.66%)      10 (62.5%)
Gentamicin        22 (73.33%)       9 (60%)         11 (68.75%)
Azithromycin      17 (56.66%)       8 (53.33%)      -
Polymyxin-B       -                 -               15 (93.75%)
Enrofloxacin      -                 -               10 (62.5%)
Amikacin          -                 -               -
Lincomycin        -                 -               11 (68.75%)
Chloramphenicol   -                 -               -
Erythromycin      -                 -               -

Antibiotics       Proteus   E.coli
                   (N=10)    (N=25)

Ciprofloxacin      6 (60%)   16 (64%)
Ceftriaxone        4 (40%)   14 (56%)
Cephalexin         -         13 (52%)
Gentamicin         5 (50%)   23 (92%)
Azithromycin       -         12 (48%)
Polymyxin-B        -         17 (68%)
Enrofloxacin       2 (20%)   12 (48%)
Amikacin           -         -
Lincomycin         -          7 (28%)
Chloramphenicol    -         15 (60%)
Erythromycin       -         18 (72%)
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Title Annotation:Research Article
Author:Behera, Sarita; Mishra, Rajashree; Pati, Prasanna; Sahu, Manoj K.
Publication:Intas Polivet
Article Type:Report
Date:Jul 1, 2016
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