Research Article
Austin J Vet Sci & Anim Husb. 2019; 6(3): 1061.
Ear Infections in Animals in Bareilly: Common causes and Effective Antimicrobials
Singh BR1*, Pawde AM2, Singh SV1, Agri H1, Sinha DK1, Vinodhkumar OR1, Zama MMS2, Kinjavdekar P2, Amarpal2 and Saxena AC2
1Division of Epidemiology, 438-MLB, Indian Veterinary Research Institute, Izatnagar-243 122, India
2Division of Surgery, ICAR-Indian Veterinary Research Institute, Izatnagar, India
*Corresponding author: Singh BR, Head Division of Epidemiology, 438-MLB, Indian Veterinary Research Institute, Izatnagar-243 122, India
Received: August 22, 2019; Accepted: October 16, 2019; Published: October 23, 2019
Abstract
Ear infections are one the most common ailments in pet dogs and sometimes in horses affecting their normal behaviour and utility. The study conducted on bacterial causes of ear infections and effective antimicrobials revealed that ear infections are more commonly reported in dogs than in other animals. Though bacteria belonging to 21 genera were isolated in an association of ear infections in animals, the most common were Staphylococcus spp., Pseudomonas spp. and Proteus spp. responsible for more than two-third cases. Isolation of Raoultella terrigena, Erwinia mallotivora, Sphingomonas echinoides, and Vibrio alginolyticus in association to ear infection in the study have rarely been reported earlier. Most of the antibiotics commonly prescribed to patients with ear infection were not effective and might be responsible for frequent treatment failure. Among the herbal antimicrobials cinnamon oil and ajowan oil have shown the potential for alternatives to antibiotics for formulations of ear drops and further studies are required to develop suitable formulations.
Keywords: Staphylococcus; Pseudomonas; Proteus; Raoultella; Erwinia; Sphingomonas echinoides; Vibrio alginolyticus
Introduction
Ear infections affect about 10-20 % of the dogs and are one of the most common health problems of the dogs [1]. Ear infections are usually caused by yeast, ear mites and bacteria, with bacteria being the most common cause. Ear problem in doge are usually identified by observing head shaking/ tilting, smelly ears, ear scratching, lack of balance, unusual back-and-forth eye movements, redness inside the ear, swelling of the ear and/or brown, yellow, or bloody discharge from the ear. The problem may be in one or both the ears at any age. Ear infections are usually caused by Staphylococcus, Pseudomonas and Streptococcus species [2,3]. Pseudomonas is not the only major cause of otorrhea in dogs [4] but also in other animals and humans, causing more than one-fourth of the ear infection cases [5]. The most common bacterial causes of otitis media in animals and human beings include Escherichia coli, Proteus spp., Staphylococcus aureus, Streptococcus pneumoniae, Moraxella (Branhamella) catarrhalis, and Haemophilus influenzae [6-8]. Besides Staphylococcus intermedius, Staphylococcus hyicus, Corynebacterium spp., and Enterobacter spp., isolates, Proteus mirabilis was identified as the most frequent cause of otitis in dogs [9].
In cases of bacterial infections of ear, antibiotics are often the first option to treat otorrhoea, mostly for local application and instillation and but in chronic cases oral or systemic antimicrobial therapy is recommended [10]. Besides antibiotics, herbal antimicrobials like oregano oil, apple cider [3] and tea tree oil [9] have been claimed effective. In a previous study [9], 60.5% Gram-positive and 70% Gram-negative bacteria isolated from cases of otitis in dogs were susceptible to gentamicin but all to tea tree oil. Another study revealed that 72% Staphylococcus aureus causing otitis were susceptible to tea tree oil, in concentrations lower than 2% [11]. In the present study, antimicrobial susceptibility testing data of 123 strains of bacteria isolated from cases of ear infections and otorrhea in animals was analysed to understand the causes and effective antimicrobials so that clinicians may get an overview of the problem in Bareilly region for instituting the most suitable antimicrobial treatment.
Materials and Methods
Antimicrobial susceptibility assay data of all 123 isolates of bacteria from cases of ear infections in animals in last three years were retrieved from Clinical Epidemiology Database of the Division of Epidemiology and transferred to Microsoft Office Excel 2007 worksheet for analysis.
In the study, deep ear swab samples collected by a clinician from referred ear infection cases of animals at Referral Veterinary Polyclinic of Indian Veterinary Research Institute were submitted within an hour of collection to Epidemiology Laboratory for identification and antibiotic susceptibility testing of the bacteria. Swab samples were processed as per standard protocol for isolation, identification and classification of the bacteria [12-14]; briefly, swab samples were inoculated into buffered peptone water (BBL, Diffco, USA) and incubated at 37°C for 6h, growth was streaked on to Blood agar and MacConkey agar (BBL, Diffco) and incubated at 37°C for 24- 48 h. Isolated colonies were picked up and tested for morphological, staining, growth and biochemical characteristics.
Characterised isolates were tested for their sensitivity to different conventional antimicrobials including amoxycillin, amoxycillin+clavulanic acid, amoxycillin+sulbactum, ampicillin, ampicillin+sulbactam, azithromycin, aztreonam, cefepime, cefixime, cefotaxime, cefoxitin, cefpodoxime, ceftriaxone+sulbactum, ceftazidime, ceftazidime+clavulanic acid, ceftriaxone, ceftriaxone+tazobactam, chloramphenicol, ciprofloxacin, cloxacillin, cotrimoxazole, ertapenem, erythromycin, gentamicin, imipenem, lincomycin, linezolid, meropenem, methicillin, moxalactam, nalidixic acid, nitrofurantoin, oxacillin, penicillin, piperacillin, piperacillin+tazobactam, polymyxin-B, spectinomycin, streptomycin, tetracycline, tigecycline and vancomycin through disc diffusion assay as per guidelines of CLSI [15,16]. All antimicrobial discs were purchased from BBL, Diffco. Bacterial isolates were also tested for their susceptibility to herbal antimicrobials using disc diffusion assay as described earlier [17]. For making discs of herbal antimicrobials ›98% pure herbal compounds were used to make 6mm discs cut from Whatman filter paper No.3, each disc contained 1mg of herbal compound [17]. In the study discs were prepared for carvacrol, cinnamaldehyde, citral, tea tree oil (from Sigma, USA), guggul oil (from ICAR-Indian Institute of Natural Resins and Gums, Namkum, Ranchi), Ageratum conizoides essential oil, ajowan oil, betel leaf essential oil, cinnamon oil, holy basil oil, lemongrass oil, patchouli (Pogostemon cablin) essential oil, sandalwood oil, thyme oil and Zanthoxylum rhetsa essential oil (from Shubh Flavours and Fragrance Ltd, New Delhi). A reference sensitive E. coli strain (E-382) available in the laboratory was used as control.
Determination of Minimum Inhibitory Concentration (MIC) of herbal antimicrobial for microbes
The MIC of Holy Basil Essential Oil (HBO), carvacrol, cinnamon oil, thyme oil, Sandalwood Oil (SWO), Tea Tree Essential Oil (TTO), Patchouli Essential Oil (PEO), citral, ajowan oil, lemongrass oil, guggul oil and Zanthoxylum rhetsa essential oil, for different bacteria was determined using agar well diffusion assay [18]. To determine MIC, nine wells of 6mm diameter each were cut in suitable MHA plates under sterile environment and bottoms of wells were sealed with the same medium. Culture prepared for antimicrobial sensitivity assay for test microbe (described earlier) was swab inoculated and wells were filled with 50μL of serially diluted herbal antimicrobial in sterile dimethyl sulphoxide (DMSO, SDFCL, India) so that well number one to nine contained 10, 20, 40, 80, 160, 320, 640, 1280μL and 2560μg of the PEO, respectively. Plates were incubated under appropriate growth conditions for 2h without inversion to get contents of the well absorbed in the medium and then overnight after inversion in an appropriate environment required for the optimum growth of the microbe. Measurable zone of growth inhibition around the well containing the highest dilution of herbal antimicrobial was marked as MIC value for the microbe. Tests were conducted in triplicate for confirmation.
The results were analysed in Microsoft Excel 2007 worksheet using shorting, filtration, correlation, and χ2 test tools.
Results and Discussion
The analysis of data revealed that the 10 most common bacteria associated with ear infections in dogs (117) and other animals (cat 1, horses 4 and rhino 1) were of Staphylococcus (56), Pseudomonas (16), Proteus (11), Bacillus (8), Streptococcus (6), Escherichia (5), Micrococcus (3), Acinetobacter (2), Enterobacter (2) and Sphingomonas (2) species (Table 1). In earlier studies too [6-9] similar types of bacteria have been reported to be associated with ear infections in animals. However, the most common causal organisms reported in earlier studies Pseudomonas species [6-8] or Proteus mirabilis [9], were outnumbered by Staphylococcus species in our study. It might be due to weather conditions, seasonality and geographic and several other social and biological variations in Bareilly in comparison to other areas targeted in earlier studies. Moreover, Staphylococcus being a skin commensal might have also come to samples as contamination during sample collection.
Genus
Species of bacteria (source animal)
MHARI
MARI
Carbapenem resistant
Acinetobacter (2)
A. ewofflii 2 (dogs)
0
0.087
1
Aerococcus (1)
A. sanguinus 1 (dogs)
0.6
0.419
1
Alcaligenes (1)
A. denitrificans 1 (dogs)
0.857
0.75
1
Avibacterium (1)
A. avium 1 (dogs)
0.077
0.455
1
Bacillus (8)
B. alvei 1, B. firmus 2, B. licheniformis 1, B. stearothermophilus 1, B. subtilis 1, Bacillus spp.2 (dogs)
0.283
0.306
2
Citrobacter (1)
C. amalonaticus 1 (dogs)
0.462
0.13
0
Enterobacter (2)
E. agglomerans 2 (dogs)
0.154
0.451
0
Enterococcus (1)
E. gallinarum 1 (dogs)
0.182
0.357
1
Erwinia (1)
E. mallotivora 1 (dogs)
0.308
0.261
0
Escherichia (5)
E. coli 5(dogs4, horse1)
0.443
0.415
0
Klebsiella (1)
K. pneumoniae 1 (dogs)
0.385
0.217
0
Micrococcus (3)
Micrococcus spp.3 (dogs)
0.477
0.201
0
Moraxella (1)
M. osloensis 1 (dogs)
1
0.077
0
Proteus (11)
P. mirabilis 10(dogs 9, horse 1), P. penneri 1 (dogs)
0.642
0.593
1
Providencia (1)
P. stuartii 1(horse)
0.6
0.5
1
Pseudomonas (16)
P. aeruginosa 12, Pseudomonas spp. 4 (dogs)
0.749
0.694
8
Raoultella (1)
R. terrigena 1 (dogs)
0.857
0.429
0
Sphingomonas (2)
S. echinoides 2 (dogs)
0.714
0.232
0
Staphylococcus (56)
S. aureus 5, S. auricularis 4(dogs 3, horse 1), (dogs), S. capitis 6(cat 1, dogs5), S. caseolyticus 2, S. delphini 1, S. epidermidis 2, S. felis 1, S. haemolyticus 8, S. hyicus 1, S. intermedius 16, S. lentus 2, S. lugdunerisii 1, S. schleiferi 2, S. sciuri 1, S. simulans 1 (dogs), Staphylococcus spp. 3(dogs3, Rhino1)
0.359
0.303
8
Streptococcus (6)
S. equi ssp. zooepidemicus 3, S. porcunus 1, S. pyogenes 2 (dogs)
0.227
0.113
0
Vibrio (2)
V. alginolyticus 2 (dogs)
0.357
0.138
0
Table 1: Bacteria associated with ear infections in animals and their multiple antimicrobial drug resistance indices (MARIs) and multiple herbal antimicrobial resistance indices (MHARIs).
In the study, few bacteria not reported or rarely reported in earlier studies were also identified causing otitis in dogs including Bacillus species (Table 1), Raoultella terrigena, Erwinia mallotivora, Sphingomonas echinoides, and Vibrio alginolyticus. These bacteria are known to cause several invasive and topical infections [14] but their isolation from cases of otorrhoea of dogs revealed the expanding plurality of causes.
Of the 123 isolates of bacteria identified, 25 had resistance to one or more carbapenem drugs (meropenem, imipenem, ertapenem). All the bacteria positive for Carbapenem Resistance (CR) were among the most common causes of ear infections reported earlier [1,6-9]. However, CR bacteria have rarely been reported earlier as a cause of ear infections [1,6-9,19].
High MARI and MHARI of pseudomonads indicated that ear infections associated with Pseudomonas spp., may lead to persistence of infection despite the best antimicrobial used. Nowadays chronic and persistent ear infections are becoming common [9] and might be due to high levels of drug resistance in bacteria. In the study, Alcaligenes denitrificans and Moraxella osloensis causing ear infection in dogs had the highest MARI and MHARI (Table 1) indicating that such infections may be even more dangerous than due to pseudomonads.
Of the 56 staphylococcal isolates, 7 (12.5%) were resistant to methicillin (MRS) and oxacillin and certainly a big threat as MRSA are grouped under ESKAPE pathogens commonly able to evade all the common treatments [20]. Methicillin-resistant staphylococci have been reported to be associated with otitis in dogs [9]. Of the 7 MRS strains, six were vancomycin-resistant (VRS) but none of Enterococcus and Streptococcus isolates from ear infections were resistant to vancomycin. Besides S. aureus, other members of ESKAPE group including E. agglomerans, K. pneumoniae and P. aeruginosa were also detected as an important cause of ear infections in dogs. Isolation of ESKAPE bacteria have been reported commonly associated with animal infections including in dogs, horses and cats in Bareilly area [20].
Antimicrobial susceptibility assays (Table 2) against 42 conventional antimicrobial preparations revealed that antibiotic susceptibility of different bacteria varied to a large extent. The most commonly used antimicrobials for treatment of bacterial otitis media are amoxycillin, amoxycillin+clavulanic acid, cephalospins (cefalexin, cefdinir, cefixime, ceftriaxone, cefuroxime), gentamicin and fluoroquinolones (ciprofloxacin, ofloxacin, levofloxacin) azithromycin, clarithromycin, neomycin, ploymyxin-B, and sulphamethoxazole+trimethoprim [21]. However, in our study one of the recommended drugs, ceftriaxone (inhibited about 75% isolates) could make to reach at the 9th place among the 10 most effective antimicrobials, it was preceded by imipenem, ceftriaxone+tazobactam, ceftriaxone+sulbactam, piperacillin+tazobactam, tigecycline, chloramphenicol, meropenem and ampicillin+sulbactam, Only piperacillin (inhibiting 73.8% isolates) was behind it. Among the recommended antibiotics cefixime inhibited only 30% isolates and was at the 36th place in efficacy on bacteria causing otitis. There was only a little variation between effective antibiotics on GPBs and GNBs (Table 2) as ceftriaxone failed to inhibit about 42% of GNBs but was effective on 86% GPBs. However, two of the recommended drugs in otitis [21], polymyxin B (70.3%) and ciprofloxacin (68.9%) stood at 8th and 9th place among the most effective 10 drugs for GNBs causing otitis and one of the most used antibiotic, gentamicin failed to inhibit 39% of the isolates. Proteus species isolates, the third most common cause of ear infection in this study and the most common cause at some places [9], 80% isolates were not inhibited by any of the recommended antibiotics for otitis treatment. However, many of the antibiotics in market including ampicillin+sulbactam, ceftriaxone+tazobactam, imipenem, ceftriaxone+sulbactam, meropenem, ceftazidime+clavulanic acid, piperacillin+tazobactam, tigecycline, moxalactam, and amoxycillin+sulbactum inhibited majority of the isolates of Proteus spp.
Antimicrobial tested
Number bacterial isolates resistant to different antibiotics with respect to their types and sources
Total (123)
GPBs (75)
GNBs (48)
Dogs (117)
Other animals (6)
E. coli (5)
Proteus (11)
Pseudo-monas (16)
Staphy-lococcus (56)
Strep tococcus (6)
Amoxycillin
62
25
37
59
3
5
6
15
18
1
Amoxycillin + clavulanic acid
44
16
28
39
5
4
5
12
14
0
Amoxycillin + sulbactam
28
6
22
27
1
2
1
15
5
0
Ampicillin
68
29
39
63
5
5
7
15
24
0
Ampicillin + sublactam
6
5
1
6
0
0
0
0
2
0
Azithromycin
38
16
22
34
4
2
8
7
14
0
Aztreonam
19
0
19
17
2
2
6
6
0
0
Cefepime
26
17
9
25
1
0
4
3
10
1
Cefixime
18
10
8
18
0
1
1
4
9
0
Cefotaxime
40
21
19
38
2
1
5
11
17
1
Cefoxitin
37
13
24
35
2
1
4
14
7
1
Cefpodoxime
24
12
12
24
0
1
2
6
10
0
Ceftriaxone + sulbactam
2
1
1
2
0
0
0
1
1
0
Ceftazidime
63
44
19
58
5
2
5
7
34
2
Ceftazidime + Clavulanic acid
42
34
8
39
3
1
0
5
24
4
Ceftriaxone
27
9
18
25
2
2
6
8
7
0
Ceftriaxone + tazobactam
1
0
1
1
0
0
0
1
0
0
Chloramphenicol
25
6
19
24
1
1
3
14
5
0
Table 2: Antimicrobial resistance pattern of common Gram-positive (GPBs) and Gram-negative (GNBs) bacteria isolated as cause of ear infections in animals in Bareilly area.
Ciprofloxacin
41
27
14
38
3
3
6
3
25
0
Cloxacillin
27
17
10
24
3
2
3
3
12
1
Cotrimoxazole
67
36
31
64
3
2
10
15
28
2
Ertapenem
12
7
5
12
0
0
1
4
5
0
Erythromycin
18
18
0
17
1
0
0
0
14
0
Gentamicin
39
21
18
36
3
3
8
4
20
1
Imipenem
0
0
0
0
0
0
0
0
0
0
Lincomycin
20
20
0
18
2
0
0
0
14
1
Linezolid
1
1
0
1
0
0
0
0
1
0
Meropenem
17
7
10
16
1
0
0
6
5
0
Methicillin
26
16
10
26
0
1
2
4
14
0
Moxalactam
30
17
13
26
4
1
1
8
11
1
Nalidixic acid
30
0
30
29
1
4
6
15
0
0
Nitrofurantoin
35
7
28
33
2
0
6
15
5
0
Oxacillin
42
30
12
40
2
1
3
4
22
0
Penicillin
52
27
25
48
4
3
4
11
23
1
Piperacillin
23
9
14
21
2
2
3
9
6
0
Piperacillin + tazobactam
14
6
8
13
1
2
1
5
6
0
Polymyxin-B
11
0
11
9
2
0
6
0
0
0
Spectinomycin
30
20
10
29
1
0
3
5
18
0
Streptomycin
18
6
12
16
2
2
2
8
5
0
Tetracycline
46
17
29
42
4
1
9
15
17
0
Tigecycline
14
0
14
13
1
0
1
11
0
0
Vancomycin
28
28
0
26
2
0
0
0
25
0
Table 2 of 1:
Staphylococcus isolates, the most common cause of ear infections in Bareilly region, ›83% could be managed with imipenem, tigecycline, linezolid, chloramphenicol, nitrofurantoin, cefriaxone+sulbactam, amoxycillin+sulbactam, piperacillin+tazobactam, ceftriaxone, piperacillin and cefoxitin. However, the most commonly prescribed amoxycillin+clavulanic acid, azithromycin and gentamicin in such cases [21] could inhibit the growth of only 75%, 75% and 64.3% staphylococcal isolates, respectively. The second most common cause, pseudomonads, were sensitive to five out of 10 most commonly prescribed antibiotics including polymyxin B, ciprofloxacin, gentamicin, cefepime, but only first three were able to inhibit ›80% isolates while later two failed on ›30% of the isolates.
Among herbal antimicrobials, cinnamaldehyde (an antimicrobial ingredient in cinnamon oil) and carvacrol (an antimicrobial ingredient in ajowan oil, thyme oil and oregano oil) inhibited ›93% of the total isolates (Table 3). However, 53% pseudomonads were resistant to carvacrol but 100% were sensitive to cinnamaldehyde. Similar herbal antimicrobial resistance pattern among pseudomonads of water and milk origin has been reported in Bareilly region [22]. Staphylococcal isolates were inhibited by carvacrol (100%), ajowan oil (100%), thyme oil (96.2%), cinnamaldehyde (88.5%), cinnamon oil (83.9%), citral (73.1%) and sandalwood oil (70.5%). However, Tea Tree Oil (TTO), often claimed highly effective on staphylococci causing ear infections [9,11] failed to inhibit ›91% of the isolates in the study. It might be due to lower TTO concentration used to determine the susceptibility of isolates in our study (1μL/disc) than 2% level used earlier [11] or due to a difference in resistance in isolates of different locality [16,19]. Our results with respect to carvacrol are in concurrence to reported effectiveness of oregano oil (source of carvacrol) in cases of ear infections [3]. In the study, cinnamon oil and cinnamaldehyde appeared as the most promising herbal antimicrobials inhibiting ›80% of the bacteria associated with an ear infection in animals and gives a window to explore further for the use of cinnamon oil or cinnamaldehyde in development of effective antimicrobial ear drops.
Herbal antimicrobial tested
Number of bacterial isolates resistant* to different herbal antimicrobial with respect to their types and sources
Total (123)
GPBs (75)
GNBs (48)
Dogs (117)
Other animals (6)
E.coli (5)
Proteus (11)
Pseudo-monas (16)
Staphy-lococcus (56)
Strep tococcus (6)
Ageratum conizoides oil
17
4
13
17
0
1
5
4
4
0
Ajowan oil
8
0
8
8
0
0
2
6
0
0
Betel leaf oil
21
13
8
21
0
0
1
7
11
0
Carvacrol
8
0
8
8
0
0
0
8
0
0
Cinnamaldehyde
3
3
0
3
0
0
0
0
3
0
Cinnamon oil
8
5
3
8
0
0
0
2
5
0
Citral
19
8
11
19
0
1
1
8
7
0
Guggul oil
86
45
41
81
5
5
11
16
33
2
Holy basil oil
27
15
12
25
2
1
1
9
10
1
Lemongrass oil
50
22
28
48
2
0
8
11
18
1
Patchouli (Pogostemon cablin) oil
64
27
37
62
2
5
10
14
20
1
Sandalwood oil
48
18
30
45
3
4
7
10
13
2
Tea Tree oil
40
28
12
35
5
2
3
5
20
2
Thyme oil
8
1
7
8
0
0
0
7
1
0
Zanthoxylum rhetsa essential oil
27
17
10
23
4
1
4
3
13
0
Minimum inhibitory concentration of resistant isolates for different herbal compounds varied from 1280μg/mL to >2560μg/mL.
Table 3: Herbal antimicrobial resistance pattern of common Gram-positive (GPBs) and Gram-negative (GNBs) bacteria isolated as cause of ear infections in animals in Bareilly area.
Observations on MIC of different herbal compounds (Table 4) revealed that MIC of different bacteria varied to a large extent even among strains of the same species and genus. However, MIC of thyme oil, ajowan oil, carvacrol and cinnamon oil was always ≤1280μg/mL (≤0.128%). The MIC of tea tree oil varied from 0.001% to ›0.256% and was one of the least efficacious oil on bacteria causing ear infections. In earlier studies [11] too, tea tree oil could inhibit all bacteria causing ear infections at 2% level. This study indicated that instead of tea tree oil options of adding thyme oil or ajowan oil or carvacrol, an active ingredient of thyme, oregano and ajowan oil or cinnamon oil may be better to be added to ear instillation preparations and these may act even at very low concentrations similar to many antibiotics.
Genus of bacteria (no. of isolates)
Minimum inhibitory concentration of different herbal compounds (μg/mL) determined through well diffusion assay
Holy basil oil
Carvacrol
Cinnamon oil
Thyme oil
Sandal wood oil
Tea tree oil
Patchouli oil
Citral
Ajowan oil
Lemon grass oil
Guggul oil
ZREO
Acinetobacter (2)
80, 320
10, 320
10, 640
80, 160
NT
10
NT
1280, 2560
10, 320
10, >2560
320, >2560
10-1280
Aerococcus (1)
NT
160
NT
NT
NT
NT
NT
NT
160
1280
>2560
640
Alcaligenes (1)
320
160
320
640
NT
NT
NT
640
320
640
>2560
>2560
Avibacterium (1)
NT
40
10
NT
NT
NT
NT
NT
320
20
40
80
Bacillus (8)
80-640
40-640
20-640
320-1280
320-1280
NT
10-1280
NT
320-1280
Oct-60
20->2560
80->2560
Citrobacter (1)
640
1280
1280
NT
NT
NT
NT
NT
1280
1280
>2560
2560
Enterobacter (2)
1280
320
320
320
NT
10, 40
NT
1280
320
>2560
>2560
>2560
Enterococcus (1)
1280
1280
640
640
NT
640
NT
>2560
1280
>2560
2560
640
Erwinia (1)
640
160
320
640
NT
640
NT
640
160
320
2560
2560
Escherichia (5)
640
160-640
160-1280
160-320
>2560
640->2560
160->2560
160-1280
160-1280
160->2560
2560->2560
640->2560
Klebsiella (1)
1280
320
640
320
NT
NT
NT
2560
320
2560
>2560
>2560
Micrococcus (3)
>2560
160
1280
320-1280
NT
2560
NT
>2560
NT
160->2560
80->2560
320->2560
Moraxella (1)
320
40
10
320
NT
640
NT
320
NT
320
320
320
Proteus (11)
160->2560
160-320
80-640
320-2560
NT
320->2560
NT
20->2560
10-1280
320-2560
320->2560
320->2560
Providencia (1)
NT
NT
NT
NT
NT
NT
NT
NT
NT
NT
2560
1280
Pseudomonas (16)
320->2560
10-1280
320-640
320-1280
NT
>2560
NT
1280->2560
160-1280
160->2560
640->2560
80->2560
Raoultella (1)
640
160
320
320
NT
>2560
NT
320
320
640
2560
2560
Sphingomonas (2)
NT
160, 320
NT
NT
NT
320
NT
NT
NT
320
NT
NT
Staphylococcus (56)
640->2560
80-2560
320-1280
40-1280
>2560
160->2560
160->2560
160->2560
320-1280
80-1280
10->2560
80->2560
Streptococcus (6)
320-1280
10-320
10-640
640-1280
640-2560
640->2560
10-1280
NT
320-1280
10-640
10->2560
40->2560
Vibrio (2)
NT
10 , 20
NT
NT
NT
NT
>2560
80, 640
NT
80, 640
2560, >2560
10, 1280
NT, not tested; ZREO, Zanthoxylum rhetsa essential oil.
Table 4: Minimum inhibitory concentration determined through well diffusion assay of different herbal compounds (μg/mL) for bacteria isolated from ear infection cases in animals.
Acknowledgement
Authors are thankful to the staff of Epidemiology (Mr. HC Joshi, Mr. Pratap Singh, Mr. Laiqur Rahman, Mr. Ram Das, Mr. Laxmi Prasad and Mr. Ashok Kumar) for assisting in testing of samples reaching in the laboratory and for helping in systematic data management. Besides, the authors also thank to all the clinicians of Referral Veterinary Polyclinic of the Institute for sending the samples for microbiology analysis. The Director and Joint Directors of the Institute are also acknowledged for the grant of funds for extending the ABST-services.
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