Identification and Antimicrobial Susceptibility of Bacteria and Yeasts Isolated from Healthy Dogs and Dogs with Otitis Externa

Clinical safety and efficacy of a single-dose gentamicin, posaconazole and mometasone furoate otic suspension for treatment of canine otitis externa

BACKGROUND

A single-dose, in-clinic, veterinary professional-administered treatment for canine otitis externa was developed to improve compliance and canine welfare.

METHODS

This multicentre, controlled, examiner-masked, randomised field trial was conducted in 316 dogs over 42 days. Dogs were treated once, on day 0, with the investigational product containing gentamicin, posaconazole and mometasone furoate (Mometamax Ultra [MU]) or twice (days 0 and 7) with a control product containing florfenicol, terbinafine and betamethasone acetate (CP). The primary endpoint was a composite otitis index score of 4 or less (of 12) on day 14 and 3 or less (of 12) on day 28.

RESULTS

On day 28, treatment success was recorded in 128 of 143 MU-treated dogs (89.5%), significantly non-inferior to 116 of 133 (87.2%) CP-treated dogs (Farrington-Manning test, Z = 4.1351, p < 0.0001). For mixed cultures of Staphylococcus pseudintermedius and Malassezia pachydermatis, there was 100% treatment success in MU-treated dogs (n = 33), significantly non-inferior to 90.2% (37 of 41) in CP-treated dogs (Farrington-Manning test, Z = 3.1954, p = 0.0007).

LIMITATIONS

Efficacy in chronic otitis externa cases was not investigated. Cytology was not used to aid in diagnosis or for identification of secondary pathogens.

CONCLUSION

This unique combination, single-dose product is safe and effective in dogs with otitis externa. It offers enhanced compliance, canine welfare and quality of life by eliminating the owner burden of treating this painful condition.

Microbiological Survey and Evaluation of Antimicrobial Susceptibility Patterns of Microorganisms Obtained from Suspect Cases of Canine Otitis Externa in Gran Canaria, Spain

A retrospective study of microbiological laboratory results from 2020 to 2022, obtained from a veterinary diagnostic laboratory of the island of Gran Canaria, Spain, focused on canine otitis cases, was performed. The objective of this study was to analyze the pathogen distribution, antimicrobial susceptibility, prevalence of multidrug resistant phenotypes and the role of coinfections in otitis cases in order to provide up-to-date evidence that could support effective control strategies for this prevalent pathology. A total of 604 submissions were processed for the diagnosis of canine external otitis. Of the samples analyzed, 472 were positive for bacterial or fungal growth (78.1%; 95% CI: 74.8-81.4%). A total of 558 microbiological diagnoses were obtained, divided in 421 bacterial (75.4%; 95% CI: 71.8-79.0%) and 137 fungal (24.6%; 95% CI: 20.9-28.1%) identifications. Staphylococcus pseudintermedius, Malassezia pachydermatis and Pseudomonas aeruginosa were the most prevalent microorganisms detected in clinical cases of otitis. High level antimicrobial resistance was found for Pseudomonas aeruginosa (30.7%), Proteus mirabilis (29.4%), Staphylococcus pseudintermedius (25.1%) and Escherichia coli (19%). Multidrug-resistant phenotypes were observed in 47% of the bacteria isolated. In addition, a 26.4% prevalence of methicillin-resistant Staphylococcus pseudintermedius was detected. The high prevalence of antimicrobial resistant phenotypes in these bacteria highlights the current necessity for constant up-to-date prevalence and antimicrobial susceptibility data that can support evidence-based strategies to effectively tackle this animal and public health concern.

Identification of bacteria associated with canine otitis externa based on 16S rDNA high-throughput sequencing

Bacteria are regarded as predisposing and perpetuating factors causing otitis externa (OE), whereas auricular anatomy is a predisposing factor. This study aims to investigate bacterial populations in the external auditory canals of healthy dogs and dogs with OE. Four categories of ear swabs included healthy erect-ear dogs, erect-ear dogs with OE, healthy pendulous-ear dogs and pendulous-ear dogs with OE. After bacterial DNA extraction, 16S rDNAs were amplified using specific primers within a V3/V4 region. Following DNA library construction, high-throughput sequencing was performed on MiSeq (Illumina). CLC Microbial Genomics Module was used to determine the rarefaction curve, bacterial classification, relative abundance, richness and diversity index. The results demonstrated that healthy dogs had higher bacterial richness and diversity than the dogs with OE. Comparable with culture-dependent methods described previously, this study revealed predominant Corynebacterium spp., Pseudomonas spp., Staphylococcus spp., and Proteus spp. in OE cases. Furthermore, high-throughput sequencing might disclose some potential emerging pathogens including Tissierella spp., Acinetobacter spp., and Achromobacter spp., which have not been reported in previous canine OE cases. Nevertheless, larger sample sizes are further required for an extensive evidence-based investigation.

Pseudomonas spp. in Canine Otitis Externa

Canine otitis externa (OE) is a commonly diagnosed condition seen in veterinary practice worldwide. In this review, we discuss the mechanisms of the disease, with a particular focus on the biological characteristics of Pseudomonas aeruginosa and the impact that antibiotic resistance has on successful recovery from OE. We also consider potential alternatives to antimicrobial chemotherapy for the treatment of recalcitrant infections. P. aeruginosa is not a typical constituent of the canine ear microbiota, but is frequently isolated from cases of chronic OE, and the nature of this pathogen often makes treatment difficult. Biofilm formation is identified in 40-95% of P. aeruginosa from cases of OE and intrinsic and acquired antibiotic resistance, especially resistance to clinically important antibiotics, highlights the need for alternative treatments. The role of other virulence factors in OE remains relatively unexplored and further work is needed. The studies described in this work highlight several potential alternative treatments, including the use of bacteriophages. This review provides a summary of the aetiology of OE with particular reference to the dysbiosis that leads to colonisation by P. aeruginosa and highlights the need for novel treatments for the future management of P. aeruginosa otitis.

In Vitro Activity of Farnesol against Malassezia pachydermatis Isolates from Otitis Externa Cases in Dogs

Chronic otitis externa of dogs is a significant problem due to the prevalence and complexity of the treatment of such animals. There is evidence that in 60-80% of cases of infectious diseases microorganisms located in the biofilm phenotype play the main role. Microorganisms in the biofilm phenotype have a number of advantages, the most significant of which is considered to be increased resistance to various external factors. Among them, a special place is occupied by resistance to antibiotics. In recent decades, research has been conducted at an increasing scale on the role of biofilm infections in various pathologies in veterinary medicine. The etiology and therapy of dog otitis externa caused by Malassezia pachydermatis biofilm has not been fully studied. This is why we consider relevant the scientific and practical aspects of research on the etiology and therapy of dog otitis externa from the position of biofilm infection. In this work, it has been statistically proven that there is a relationship between the optical density of Malassezia pachydermatis biofilms and their sensitivity to drugs, and this relationship is statistically significant. In addition, we have demonstrated that Farnesol has a good antibiofilm effect at a concentration of more 1.6 μM/mL (24% OD decrease of biofilm), and its highest antibiofilm effect (71-55%-more than a half) was observed at a concentration of 200-12.5 μM/mL.

Evaluation of hypochlorous acid as an ear flush in dogs with chronic otitis externa

BACKGROUND

Chronic otitis externa (OE) in dogs frequently requires anaesthetised ear flushing.

OBJECTIVES

To evaluate hypochlorous acid as an ear flushing and antimicrobial agent in dogs with chronic OE.

ANIMALS

Twenty dogs with chronic OE caused by the same organisms bilaterally.

MATERIALS AND METHODS

One ear was flushed under anaesthesia with hypochlorous acid, the other with saline solution. Subsequently, the ear flushed with hypochlorous acid was cleaned with the same solution twice daily for 2 weeks, the other ear with a commercial ear cleaner. An ear medication containing miconazole, polymyxin B and prednisolone was used once daily in both ears. Clinical scores were determined before the flush. Ear cytological results were obtained, a hearing test was conducted before and after the ear flush, and a culture was taken directly after flushing. Ears were evaluated after 2 weeks of therapy.

RESULTS

Yeast was present in the ears of 11, cocci in one and a mixed infection in eight dogs. Five ears were negative on culture after flushing with hypochlorous acid, one after the saline flush. Clinical and cytological scores decreased significantly with both solutions after 2 weeks of treatment. There was no difference between treatments in any of the scores at any time point between treatments and in the results of the hearing test before and after the flushing procedure. Adverse effects were not seen.

CONCLUSIONS AND CLINICAL RELEVANCE

Hypochlorous acid is a suitable cleaning solution for canine OE.

Otitis Externa in Dogs: Distribution and Antimicrobial Susceptibility Patterns of Staphylococcus Spp. Isolates

The study aimed to investigate the Staphylococcus species from dogs with chronic otitis externa in Istanbul and to determine their antibiotic susceptibility patterns. Ear swab samples were collected from 100 dogs suspected of otitis externa admitted at the clinics of Istanbul University - Cerrahpaşa, Faculty of Veterinary Medicine. The dogs were of different age, gender, and breed. The bacterial isolation was performed by conventional methods. BD Phoenix Automated Microbiology System was used to confirm bacterial identification by conventional methods and to test antimicrobial susceptibility. Staphylococcus spp. were isolated from 36% of the samples collected from the dogs. S. pseudintermedius, S. aureus, S. epidermidis, S. hyicus and S. chromogenes were identified in 41.6%, 22.2%, 11.1%, 5.5%, and 5.5%. In Staphylococcus spp. isolates, enrofloxacin, penicillin, and ampicillin-sulbactam resistance was 8.3%, marbofloxacin resistance was 11.1%, doxycycline resistance was 16.6%, amoxicillin-clavulanic acid, erythromycin, and gentamicin resistance was 19.4%, tetracycline, clindamycin, and sulphonamide resistance was 25%. Methicillin resistance was not observed in any of the isolates. However, multiple drug resistance (MDR) was detected in 11 (30.5%) of 36 isolates. In conclusion, the early detection and antimicrobial sensitivity testing of Staphylococcus spp in dog otitis externa cases that do not respond to empiric therapy could be beneficial for appropriate antibiotic selection and treatment thus preventing MDR.

Antibiotic Resistance and Species Profile of Enterococcus Species in Dogs with Chronic Otitis Externa

Otitis externa, a common disease in dogs, has different etiologies. Enterococcus is a Gram-positive bacterium that frequently causes opportunistic ear infections. Here, we determined the distribution of Enterococcus in canine otitis externa via time-of-flight mass spectrometry and biochemical tests and evaluated their resistance patterns to 10 commonly used antibiotics. Among the 197 Enterococcus isolates, E. faecalis (48.7%; 96/197) was the most common, followed by E. faecium (21.3%; 42/197), E. casseliflavus (11.7%; 23/197), E. hirae (10.7%; 21/197), E. avium (3.6%; 7/197), E. gallinarum (2.5%; 5/197), E. canintestini (1.0%; 2/197), and E. durans (0.5%; 1/197). All isolates were tested for antibiotic resistance using the Kirby-Bauer disc diffusion method. Enterococcus faecalis strains were highly resistant to erythromycin (45.8%) and rifampin (34.3%) but were generally susceptible to penicillin class antibiotics. In contrast, E. faecium isolates were highly resistant to penicillin class antibiotics (ampicillin, 61.9%; penicillin, 71.4%). Most importantly, E. faecium demonstrated high resistance to most of the antibiotics used in this study. Multidrug resistance was found in 28.4% of the isolates (56/197). This study shows prevalence and antibiotics resistance profiles of Enterococcus species in canine chronic otitis externa. The results can contribute to establish therapeutic strategies of Enterococcus infections and be used as a comparable index of antibiotic resistance of Enterococcus in the future.

Bacterial Prevalence in Skin, Urine, Diarrheal Stool, and Respiratory Samples from Dogs

The emergence of bacterial infections in companion animals is a growing concern as humans can also be infected through the transmission of pathogenic bacteria. Because there have been few studies conducted on companion animals, the extent and significance of prevalence in veterinary practices remain unknown. This is the first nationwide surveillance report aimed at elucidating the prevalence pattern and associated infections of isolated bacteria from dogs in Korea. Bacterial isolates were collected from seven different laboratories participating in the Korean Veterinary Antimicrobial Resistance Monitoring System from 2018 to 2019. The samples were obtained from the diarrheal stool, skin/ear, urine, and respiratory samples of veterinary hospital-visited dogs. Isolation and identification of bacterial species was carried out using a bacterial culture approach and then confirmed with matrix-assisted laser desorption/ionization-time-of-flight mass spectrometry (MALDI-TOF) and polymerase chain reaction (PCR). Out of 3135 isolates in dogs, 1085, 1761, 171, and 118 were extracted from diarrheal stool, skin/ear, urine, and respiratory samples, respectively. The overall prevalence of bacteria was higher among two age groups (1-5 and 6-10 years) with a 66.5 percent prevalence. This study showed that Escherichia coli was the most prevalent species among isolated bacterial species of diarrheal and urine origin, whereas Staphylococcus pseudintermedius was the most prevalent among skin and respiratory sample isolates. The data on the prevalence of bacteria for each dog specimen could provide basic information to estimate the extent of bacterial infection and antimicrobial resistance development and to guide veterinarians in therapeutic decisions in clinical practices throughout Korea.

External Ear Canal Evaluation in Dogs with Chronic Suppurative Otitis Externa: Comparison of Direct Cytology, Bacterial Culture and 16S Amplicon Profiling

A discrepancy between cytology and bacterial culture methods is sometimes observed in canine otitis externa. The objective of this study was to compare results from cytology, bacterial culture and 16S amplicon profiling. Twenty samples from 16 dogs with chronic suppurative otitis externa were collected. A direct cytological evaluation was carried out during the consultations. Aerobic bacterial culture and susceptibility were performed by an external laboratory used in routine practice. For 16S amplicon profiling, DNA was extracted and the hypervariable segment V1−V3 of the 16S rDNA was amplified and then sequenced with a MiSeq Illumina sequence carried out by the Mothur software using the SILVA database. A good correlation between cytology and bacterial culture was observed in 60% of the samples. Some bacterial species revealed by bacterial culture were present with low relative abundance (<10%) in 16S amplicon profiling. Some bacterial species revealed by the 16S amplicon profiling analysis were not identified with culture; most of the time, the offending species was a Corynebacterium. To conclude, a careful interpretation of the results of bacterial culture should be made and always be in agreement with the cytology. The 16S amplicon profiling method appears to be a more sensitive method for detecting strains present in suppurative otitis but does not provide information on bacterial susceptibility.

Efficacy of afoxolaner for the treatment of ear mite infestation under field conditions

Otodectes cynotis is a commonly occurring surface mite that can be easily transmitted between suitable hosts, including dogs, causing otocariosis. The activity of the systemic insecticide afoxolaner against O. cynotis has been tested once under experimental conditions, showing a high efficacy. The present study aimed to i) assess the efficacy of two consecutive monthly oral administrations of afoxolaner (NexGard®) against O. cynotis in naturally infested dogs under field conditions and ii) evaluate its impact in reducing bacteria or fungal secondary infections. Dogs, positive for O. cynotis (n = 20), were included in the study and allocated in two groups of ten animals each (G1, control group, and G2, treated group). The first group of ear mite-infested dogs was treated with a placebo, while afoxolaner was administered orally to the second group of dogs at Day 0 (D0) and Day 30 (D30), following label instructions. Otoscopic assessments, deep-swab method and swab samples were performed on all dogs (Days 0, 30, 42) to evaluate the presence or absence of live mites and their number throughout the study, as well as to conduct bacterial and fungal assessments. No adverse events likely related were recorded throughout the study. By Day 42 (D42), all dog's ears were flushed to recover ear mites. All treated dogs became negative, as well as two dogs of the control group. The treatment efficacy of afoxolaner was 100 % based on the arithmetic means of the live mite counts. The clinical scores did not change significantly in the control group, whereas they significantly improved in the treated one from D0 to D30 (p-value = 5.47 10^-5). No live mites were present in the afoxolaner-treated group at D42 (p-value = 0.00073). In this field study, two oral administrations of afoxolaner at the recommended dose allowed a complete cure of the infestation. Bacterial and Malassezia pachydermatis infections were detected in both groups, although no significant trend was associated to the ear mite treatment.

Frequency and predisposing factors for canine otitis externa in the UK - a primary veterinary care epidemiological view

BACKGROUND

Otitis externa is a commonly diagnosed disorder in dogs and can carry a high welfare impact on affected animals. This study aimed to report the prevalence and explore the role of breed and aural conformation as predisposing factors for canine otitis externa in the UK. The study used a cohort design of dogs under UK primary veterinary care at clinics participating in the VetCompass Programme during 2016. Risk factor analysis used multivariable logistic regression modelling.

RESULTS

The study included a random sample of 22,333 dogs from an overall population of 905,554 dogs under veterinary care in 2016. The one-year period prevalence of otitis externa was 7.30% (95% confidence interval [CI]: 6.97 to 7.65). Breed and ear carriage were the highest ranked risk factors. Compared with crossbred dogs, sixteen breed types showed increased odds, including: Basset Hound (odds ratio [OR] 5.87), Chinese Shar Pei (OR 3.44), Labradoodle (OR 2.95), Beagle (OR 2.54) and Golden Retriever (OR 2.23). Four breeds showed protection (i.e. reduced odds) of otitis externa: Chihuahua (OR 0.20), Border Collie (OR 0.34), Yorkshire Terrier (OR 0.49) and Jack Russell Terrier (OR 0.52). Designer breed types overall had 1.63 times the odds (95% CI 1.31 to 2.03) compared with crossbred dogs. Compared with breeds with erect ear carriage, breeds with pendulous ear carriage had 1.76 times the odds (95% CI 1.48 to 2.10) and breeds with V-shaped drop ear carriage had 1.84 times the odds (95% CI 1.53 to 2.21) of otitis externa.

CONCLUSIONS

Breed itself and breed-associated ear carriage conformation are important predisposing factors for canine otitis externa. Greater awareness of these associations for both predisposed and protected breeds could support veterinary practitioners to promote cautious and low-harm approaches in their clinical advice on preventive care for otitis externa, especially in predisposed breeds.

On Gram-Positive- and Gram-Negative-Bacteria-Associated Canine and Feline Skin Infections: A 4-Year Retrospective Study of the University Veterinary Microbiology Diagnostic Laboratory of Naples, Italy

Simple Summary

Pet animals’ bacterial skin infections represent the main reason for presentation in small animal practice and are generally secondary complications of other pathological conditions. Pyoderma and otitis externa are generally caused by Staphylococcus spp., and particularly Staphylococcus pseudintermedius is often isolated from dogs and cats suffering from skin disorders. However, also Gram-negative bacteria, such as Pseudomonas aeruginosa and Escherichia coli, can be responsible for both otitis externa and pyoderma. Since multi-drug-resistant bacterial strains have become a relevant threat in veterinary medicine, this study aimed to identify the bacteria most frequently associated with the most common clinical cases of skin infections in dogs and cats attending the University Veterinary Teaching Hospital of Naples in the period from January 2016 to December 2019. Moreover, their antibiotic resistance profiles were evaluated, highlighting an increasing spread of multi-drug-resistant strains. It is worth noting that this spread may also concern humans because of their close contact with pets. Thus, it not only is of veterinary significance but also has zoonotic importance, with pets acting as reservoirs for humans, especially pet owners and veterinarians.

Abstract

A 4-year retrospective study (2016–2019) of selected routine bacteriological examinations of the veterinary microbiology laboratory of the University Veterinary Teaching Hospital of Naples (Italy) was carried out. A total of 189 bacteriological samples were collected from 171 dogs and 18 cats suffering from skin infections. In dogs, the most common cutaneous infection was otitis externa, while pyoderma was found to be prevalent in cats. The number of recorded Gram-positive strains over the study period did not vary considerably from year to year and was always significantly higher (p-value = 0.0007) in comparison with Gram-negative bacterial isolations. In dogs, Staphylococcus pseudintermedius was the most common identified Gram-positive bacterium (65%), while Pseudomonas aeruginosa (36%) was the one among the isolated Gram-negative bacteria. In cats, coagulase-negative staphylococci were the most predominant isolated bacteria (47%). The phenotypic profiles of antibiotic resistance showed that most of the strains were resistant to amoxicillin–clavulanate, penicillin, clindamycin, and trimethoprim–sulfamethoxazole. Several multi-drug-resistant strains (35%) were detected in canine isolates. An updating of antibiotic resistance profiles of the main Gram-positive and Gram-negative bacteria principally associated with skin infections of pet animals is necessary to improve stewardship programs of veterinary hospitals and clinics.

The Complex Diseases of Staphylococcus pseudintermedius in Canines: Where to Next?

Staphylococcus pseudintermedius is a pathogenic bacterium of concern within the veterinary sector and is involved in numerous infections in canines, including topical infections such as canine pyoderma and otitis externa, as well as systemic infections within the urinary, respiratory and reproductive tract. The high prevalence of methicillin-resistant Staphylococcus pseudintermedius (MRSP) within such infections is a growing concern. Therefore, it is crucial to understand the involvement of S. pseudintermedius in canine disease pathology to gain better insight into novel treatment avenues. Here, we review the literature focused on S. pseudintermedius infection in multiple anatomic locations in dogs and the role of MRSP in treatment outcomes at these niches. Multiple novel treatment avenues for MRSP have been pioneered in recent years and these are discussed with a specific focus on vaccines and phage therapy as potential therapeutic options. Whilst both undertakings are in their infancy, phage therapy is versatile and has shown high success in both animal and human medical use. It is clear that further research is required to combat the growing problems associated with MRSP in canines.

Cerumen microbial community shifts between healthy and otitis affected dogs

Otitis externa is a common multifactorial disease in dogs, characterized by broad and complex modifications of the ear microbiota. The goal of our study was to describe the ear cerumen microbiota of healthy dogs, within the same animal and between different animals, and to compare the cerumen microbiota of otitis affected dogs with that of healthy animals. The present study included 26 healthy dogs, 16 animals affected by bilateral otitis externa and 4 animals affected by monolateral otitis externa. For each animal cerumen samples from the right and left ear were separately collected with sterile swabs, and processed for DNA extraction and PCR amplification of the 16S rRNA gene. Amplicon libraries were sequenced using an Ion Torrent Personal Genome Machine (PGM), and taxonomical assignment and clustering were performed using QIIME 2 software. Our results indicate that the bacterial community of the cerumen in healthy dogs was characterized by extensive variability, with the most abundant phyla represented by Proteobacteria, Actinobacteria, Firmicutes, Bacteroidetes and Fusobacteria. The analysis of both alpha and beta diversity between pairs of left and right ear samples from the same dog within the group of affected animals displayed higher differences than between paired samples across healthy dogs. Moreover we observed reduced bacterial richness in the affected group as compared with controls and increased variability in population structure within otitis affected animals, often associated with the proliferation of a single bacterial taxon over the others. Moreover, Staphylococcus and Pseudomonas resulted to be the bacterial genera responsible for most distances between the two groups, in association with differences in the bacterial community structure. The cerumen microbiota in healthy dogs exhibits a complex bacterial population which undergoes significant modifications in otitis affected animals.

Changes in the ear canal microbiota of dogs with otitis externa

AIMS

Otitis externa (OE), one of the most common ear diseases in dogs, is caused by bacterial pathogens such as Staphylococcus sp. To understand the network of microbial communities in the canine ear canal affected with OE, we performed a cross-sectional study using next-generation sequencing.

METHODS AND RESULTS

Ear swab samples were collected from 23 OE-affected and 10 healthy control dogs, and the 16S rRNA gene sequenced using Illumina MiSeq. The otic microbiota in the OE-affected dogs showed significantly decreased alpha diversity compared to controls. The community composition also differed in the affected group, with significantly higher relative abundance of the phylum Firmicutes and the genus Staphylococcus (P = 0·01 and 0·04 respectively). Contrary to our expectations, the severity of the disease did not impact the otic microbiota in OE-affected dogs.

CONCLUSIONS

The ear canal microbiota of OE-affected dogs is distinct from that of healthy dogs, irrespective of disease status.

SIGNIFICANCE AND IMPACT OF THE STUDY

This study, one of the few detailed analyses of the otic microbiota, can provide practical information for the appropriate treatment of canine OE.

Preliminary evaluation of two commercial ear solutions in the treatment of canine otitis externa

OBJECTIVES

Preliminary evaluation of the efficacy of two commercial ear solutions composed of (1) chlorhexidine-Tris-ethylenediaminetetraacetic acid (EDTA) or (2) medical grade honey, for the treatment of otitis externa in dogs.

MATERIALS AND METHODS

Dogs affected with otitis externa housed in an animal shelter were eligible for inclusion. Treatment was applied daily for 10 days and effect was measured by otitis clinical scores and microbiological counts. One of the treatments was applied to affected left ears, while the other was applied to affected right ears.

RESULTS

A total of 24 ears from 13 dogs were included in the study. During the treatment period, with both treatments it was observed an improvement in clinical scores and a decrease in microbiological counts. At the end of the study 22 of 24 ears were deemed to have mild (4 ears), or no (18 ears) pain, with only two ears still showing pruritus.

CLINICAL SIGNIFICANCE

The application of ear solutions composed of chlorhexidine-Tris-EDTA or medical grade honey, in the absence of antimicrobial treatment, might be effective for the control of clinical signs and microbial colonisation in dogs with otitis externa. Additional randomised studies on clinical patients are required to validate these findings.

Antifungal Resistance Regarding Malassezia pachydermatis: Where Are We Now?

Malassezia pachydermatis is a yeast inhabiting the skin and ear canals in healthy dogs. In the presence of various predisposing conditions it can cause otitis and dermatitis, which are treated with multiple antifungal agents, mainly azole derivatives. This manuscript aims to review the available evidence regarding the occurrence of resistance phenomena in this organism. Various findings support the capacity of M. pachydermatis for developing resistance. These include some reports of treatment failure in dogs, the reduced antifungal activity found against yeast isolates sampled from dogs with exposure to antifungal drugs and strains exposed to antifungal agents in vitro, and the description of resistance mechanisms. At the same time, the data reviewed may suggest that the development of resistance is a rare eventuality in canine practice. For example, only three publications describe confirmed cases of treatment failure due to antifungal resistance, and most claims of resistance made by past studies are based on interpretive breakpoints that lack sound support from the clinical perspective. However, it is possible that resistant cases are underreported in literature, perhaps due to the difficulty of obtaining a laboratory confirmation given that a standard procedure for susceptibility testing of M. pachydermatis is still unavailable. These considerations highlight the need for maintaining surveillance for the possible emergence of clinically relevant resistance, hopefully through a shared strategy put in place by the scientific community.

Dogs Health Related to Ear Cropping

Ear cropping is a controversial subject with both supporters as well as detractors. Some consider that the procedure is cruel and unnecessary, while others consider it to be routine and harmless. The cropping of the ears of dogs for cosmetic reasons has no medical merit. It is a cosmetic, surgical procedure performed to achieve a specific appearance that matches the desired image and sometimes the standard of certain breeds of dogs. Cosmetic surgery offers the dog the desired look, but it is not a necessity. This procedure must be performed by a licensed veterinarian. Those interventions cause pain and anxiety and, like all surgical procedures, are associated with the risk of anaesthesia problems, blood loss and infection. There is only a thin line between what is convenient for the animal and what is good. Almost every community has legislation on animal welfare which includes amputation issues. If something is considered normal in some countries, this does not necessarily mean that it is also moral. The lack of legal consequences may lead some owners to produce certain breeds of dogs to their liking, but they should not be allowed to cripple their dog for their own personal benefit. Amputation can only be performed legally by a veterinarian and a new problem arises. This is because there are veterinarians who refuse to practice that kind of intervention. Some of them may think that since the legislation is unclear, they might be charged with a crime.

Antimicrobial resistance patterns of bacteria isolated from dogs with otitis

Antimicrobial-resistant bacteria in dogs can be transmitted to humans and close contact between dogs and people might foster dissemination of resistance determinants. The aim of our study was to describe the antimicrobial resistance (AMR) pattern of the major causative agents of canine otitis - one of the most common diseases in dogs - isolated in France. Data collected between 2012 and 2016 by the French national surveillance network for AMR, referred to as RESAPATH, were analysed. Resistance trends were investigated using non-linear analysis (generalised additive models). A total of 7021 antibiograms were analysed. The four major causative agents of canine otitis in France were coagulase-positive staphylococci, Pseudomonas aeruginosa, Proteus mirabilis and streptococci. Since 2013, resistance to fluoroquinolones has been on the decrease in both P. aeruginosa and Staphylococcus pseudintermedius isolates. For P. aeruginosa, 19.4% of isolates were resistant to both enrofloxacin and gentamicin. The levels of multidrug resistance (acquired resistance to at least one antibiotic in three or more antibiotic classes) ranged between 11.9% for P. mirabilis and 16.0% for S. pseudintermedius. These results are essential to guide prudent use of antibiotics in veterinary medicine. They will also help in designing efficient control strategies and in measuring their effectiveness.

Management of otitis externa with an led-illuminated gel: a randomized controlled clinical trial in dogs

BACKGROUND

Canine otitis externa is a painful condition which can be challenging to treat due to difficulties in the administration of otic medication. This can be due to lack of owner compliance in the application of ear drops or due to the resentment that some dogs demonstrate when attempts are made to administer topical medication into a sensitive ear canal. The aim of the study was to assess the efficacy of a topical LED-illuminated gel (LIG) in canine otitis externa in comparison to standard of care therapy. Dogs with spontaneous otitis externa were randomly allocated in three groups: groups QW received LIG once weekly; BW received LIG twice weekly; group C received enrofloxacin and silver sulfadiazine twice daily. LIG consists of a topical application of a gel containing chromophores that, when illuminated by a LED lamp, re-emit fluorescent light which can stimulate physiological responses, promoting healing and controlling bacteria. The evaluation protocol (T0 to T5) considered clinical assessment (OTIS-3-index-scoring-system; pruritus-severity-scale; pain-severity-score; aural temperature), cytological scoring system, quali-quantitative bacteriologic assessment.

RESULTS

All groups (QW, n = 21; BW, n = 23; C, n = 20) showed improvement during the study (QW: P < 0.02 for cytological and pain scores, P < 0.003 for bacteriologic assessment, P < 10- 4 for pruritus, total OTIS-3 and temperature assessments; BW: P < 10- 4 for all clinical, cytological and bacteriologic assessments; C: P < 0.02 for all clinical and cytological assessments, P < 10- 4 for bacteriologic assessment). The highest clinical score reduction occurred in Group BW (P < 0.014 in T3; P < 0.001 in T4 and P < 10- 4 in T5). BW reached the clinically relevant effect level at T3 (- 3.26 ± 1.21 levels), QW reached it at T4 (- 3.24 ± 0.99), C did not reach it. No differences between groups were seen in the reduction of CFU/mL (T0-T5).

CONCLUSIONS

All treatment groups showed a positive clinical effect. LIG administered twice-a-week was the most favourable protocol of the study. LIG may be considered beneficial in the management of canine otitis externa; it seems to be effective in controlling the clinical condition, including the signs of inflammation and local pain, the bacterial growth, and it may help increasing treatment compliance.

The otic microbiota and mycobiota in a referral population of dogs in eastern USA with otitis externa

BACKGROUND

Canine otitis externa (OE) is a common inflammatory disease that is frequently complicated by secondary bacterial and/or yeast infections. The otic microbial population is more complex than appreciated by cytological methods and aerobic culture alone.

HYPOTHESIS/OBJECTIVES

Differences in bacterial and fungal populations of the external ear canal will correlate with specific cytological and culture-based definitions of bacterial and Malassezia otitis.

ANIMALS

Forty client-owned dogs; 30 with OE and 10 with healthy ears.

METHODS AND MATERIALS

Prospective study comparing cytological samples, aerobic bacterial cultures and culture-independent sequencing-based analyses of the external ear canal. Subjects with OE included 10 dogs with only cocci [≥25/high power field (HPF)] on cytological evaluation and culture of Staphylococcus spp.; 10 dogs with rods (≥25/HPF) and exclusive culture of Pseudomonas aeruginosa; 10 dogs with only yeast on cytological results morphologically compatible with Malassezia spp. (≥5/HPF).

RESULTS

Staphylococcus was the most abundant taxa across all groups. Ears cytologically positive for cocci had decreased diversity, and all types of OE were associated with decreased fungal diversity compared to controls.

CONCLUSIONS AND CLINICAL IMPORTANCE

Cytological and culture-based assessment of the ear canal is not predictive of the diverse microbiota of the ear canal in cases of Pseudomonas or Malassezia otitis. Less abundant bacterial taxa in cases of staphylococcal OE are worth scrutiny for future biological therapy.

Susceptibility of Malassezia pachydermatis Clinical Isolates to Allopathic Antifungals and Brazilian Red, Green, and Brown Propolis Extracts

Clinical mycoses treatment is associated with issues such as negative side effects, high cost, prolonged treatment, and resistant strain selection. Malassezia pachydermatis is the most frequently isolated yeast in cases of canine otitis and dermatitis. The number of fungal strains exhibiting primary resistance to several drugs in vitro is increasing. Propolis has a diverse chemical composition and well-known therapeutic properties against mycoses. An alternative method for producing propolis extracts using supercritical fluid has higher selectivity, yielding extracts with fewer pollutant residues. This study therefore aimed to evaluate the in vitro susceptibility profile of M. pachydermatis clinical isolates to precharacterized supercritical and ethanolic extracts. Three types of Brazilian propolis extracts (green, red, and brown) and commercial allopathic antifungals were used in this investigation. We used the microdilution broth technique to evaluate the susceptibility profile of the yeasts. The minimum inhibitory concentration (MIC) of the brown propolis ethanolic extract was ≥16 μg/mL for all isolates. The MICs of fluconazole, ketoconazole, itraconazole, and amphotericin B ranged from 8 to >64 μg/mL, 0.032–4 μg/mL, 0.0313–16 μg/mL, and 1–2 μg/mL, respectively. The MICs of ethanolic red propolis extracts were lower than those of supercritical red propolis extracts. However, the green propolis ethanolic extract had more pronounced fungicidal activity. Isolates with lower susceptibility to commercial fungicides were inhibited by red and green propolis extracts. These results indicate that propolis can potentially be used in in vivo experiments as a promising therapeutic agent against M. pachydermatis infections.

Streptococcus canis multilocus sequence typing in a case series of dogs with ulcerative keratitis

OBJECTIVE

To determine whether four isolates of Streptococcus canis (S canis) recovered from dogs diagnosed with ulcerative keratitis at the Animal Health Trust (AHT) were genetically related to other ocular isolates that are registered in the online database.

ANIMAL STUDIED

Four S canis corneal isolates.

PROCEDURES

Clinical and laboratory records between 2016 and 2017 were searched for dogs with ulcerative keratitis for which microbiology analysis was consistent with the growth of S canis. Genomic DNA was extracted for sequencing (Illumina MiSeq), and multilocus sequence types (STs) were determined using MLST 1.8 relative to the 44 sequence types of S canis available. A neighbor-joining tree was constructed in MEGA v4.0. A two-sided Fisher's exact test was used to determine any associations between the isolated strains and ocular infections of dogs.

RESULTS

Four strains were isolated from pugs (cases 1-4) with ulcerative keratitis. Genome sequencing identified ST-27 (case 1), ST-9 (case 3), and ST-13 (cases 2 and 4). STs 13 and 27 are members of Clonal Complex (CC)-13. Analysis of the multilocus sequence typing database revealed that CC-13 strains accounted for six of the twelve isolates recovered from the eye exudates of dogs (P = .0078).

CONCLUSIONS

There is early evidence that the CC-13 group of S canis is associated with ocular infections in dogs. We provide draft genome sequences toward the future identification of virulence mechanisms associated with streptococcal keratitis in dogs.

Streptococcus hillyeri sp. nov., isolated from equine trachea

Strain 28462^T, which had Gram-stain-positive, catalase-negative coccus-shaped cells, was isolated from a routine tracheal sample from a 3 year old thoroughbred horse. 16S rRNA gene sequence analysis revealed it to be most closely related to, but distinct from, Streptococcus henryi (95.7 % identity), Streptococcusplurextorum (95.8 %), Streptococcusporci (96.4 %) and Streptococcus caprae (95.1 %). Similarity values derived from sequences from sodA and rpoB genes were consistent with strain 28462^T belonging to a species distinct from these four streptococci. At the whole genome level, strain 28462^T had an average nucleotide identity value <95 % and an inferred DNA-DNA hybridization value <70 % when compared to S. henryi, Streptococcus. plurextorum and S. porci with no S. caprae genome sequence being available. Finally, various phenotypic characteristics distinguish strain 28462^T from each of these species. Based on the genotypic and phenotypic results, it is proposed that strain 28462^T is a novel species, with the name Streptococcus hillyeri sp. nov. The type strain is 28462^T (=DSM 107591^T=CCUG 72762^T).

Antifungal Susceptibility of Malassezia pachydermatis Isolates from Dogs

The genus Malassezia belongs to Basidiomycota and includes 16 species, from which M. pachydermatis is the most common in dogs. M. pachydermatis is a member of the normal mycobiota of the skin and mucosal sites of dogs. Under certain conditions, these yeasts can be opportunistic pathogens and involved skin and ear canal infections of these animals. Topical and oral antifungal agents are used for the therapy of Malassezia dermatitis and otitis. With the expanding use of antifungal agents, resistant strains of Malassezia are increasingly detected. In this study, the susceptibility of 40 M. pachydermatis isolates to fluconazole, itraconazole, ketoconazole, clotrimazole and nystatin were evaluated in vitro based on the modified standard disk diffusion method M44-2A.

Streptococcus canis Are a Single Population Infecting Multiple Animal Hosts Despite the Diversity of the Universally Present M-Like Protein SCM

Streptococcus canis is an animal pathogen which occasionally causes infections in humans. The S. canis M-like protein (SCM) encoded by the scm gene, is its best characterized virulence factor but previous studies suggested it could be absent in a substantial fraction of isolates. We studied the distribution and variability of the scm gene in 188 S. canis isolates recovered from companion animals (n = 152), wild animal species (n = 20), and humans (n = 14). Multilocus sequence typing, including the first characterization of wildlife isolates, showed that the same lineages are present in all animal hosts, raising the possibility of extensive circulation between species. Whole-genome analysis revealed that emm-like genes found previously in S. canis correspond to divergent scm genes, indicating that what was previously believed to correspond to two genes is in fact the same scm locus. We designed primers allowing for the first time the successful amplification of the scm gene in all isolates. Analysis of the scm sequences identified 12 distinct types, which could be divided into two clusters: group I (76%, n = 142) and group II (24%, n = 46) sharing little sequence similarity. The predicted group I SCM showed extensive similarity with each other outside of the N-terminal hypervariable region and a conserved IgG binding domain. This domain was absent from group II SCM variants found in isolates previously thought to lack the scm gene, which also showed greater amino acid variability. Further studies are necessary to elucidate the possible host interacting partners of the group II SCM variants and their role in virulence.

Biofilm production of Pseudomonas spp. isolates from canine otitis in three different enrichment broths

BACKGROUND

Pseudomonas spp. are commonly isolated from dogs with clinical otitis and have been shown to produce biofilm. There is a paucity of studies demonstrating biofilm growth in veterinary medicine.

HYPOTHESIS/OBJECTIVES

To compare biofilm production of Pseudomonas spp. isolated from dogs with otitis using three different enrichment broths at two different time points. Speciation was performed.

ANIMALS

One hundred isolates from 98 dogs with clinical otitis were assessed for biofilm production.

METHODS AND MATERIALS

One hundred isolates were assessed for biofilm production using a microtitre plate assay. Biofilm production in Luria-Bertani Broth (LBB), Mueller-Hinton Broth (MHB) and Tryptic Soy Broth (TSB) were assessed after 18 and 24 h of incubation.

RESULTS

At 18 h, biofilm production was demonstrated in 87% of LBB, 91% of TSB and 93% of MHB grown isolates. By 24 h, this was 92% of LBB, 96% of TSB and 99% of MHB isolates. Biofilm production was significantly increased after 24 h incubation compared to 18 h. A significant difference was noted in biofilm production between LBB and MHB (P = 0.0349), but not between LBB and TSB (P = 0.3727) or MHB and TSB (P = 0.3687) at 24 h incubation. Two isolates were speciated as P. fluorescens and 98 as P. aeruginosa.

CONCLUSION AND CLINICAL IMPORTANCE

Not all enrichment broths were equivalent to one another and 24 h incubation was superior to 18 h. Biofilm production was high in this population of Pseudomonas spp. isolates.

Determination of minimum inhibitory concentrations for silver sulfadiazine and other topical antimicrobial agents against strains of Pseudomonas aeruginosa isolated from canine otitis externa

BACKGROUND

Otitis externa is a common presenting complaint in practice. Ear infections by Pseudomonas aeruginosa are particularly problematic due to the organism's high level of resistance and ability to damage the tympanum. Treatment should be based on susceptibility testing although minimum inhibitory concentrations (MICs) are not available for all treatment options. Silver sulfadiazine has been used in cases of recurrent P. aeruginosa otitis, although a MIC for silver sulfadiazine as a single agent has not been established.

OBJECTIVES

To describe susceptibility patterns of P. aeruginosa isolated from canine otitis externa and determine the MIC for silver sulfadiazine and other topical antimicrobials.

ANIMALS

Thirty-six P. aeruginosa isolates were collected from client-owned dogs, suffering from otitis externa.

METHODS AND MATERIALS

Susceptibility patterns were established using disc diffusion susceptibility testing against 17 antimicrobial agents. For determination of the MIC, selected strains were tested against increasing concentrations of marbofloxacin, enrofloxacin, gentamicin, polymyxin B and silver sulfadiazine using broth microdilution.

RESULTS

For nine of 17 antimicrobial agents, complete resistance was seen in all isolates tested via disk diffusion susceptibility testing. Approximately 94% and 96% of isolates were susceptible to gentamicin and imipenem, respectively. These findings were consistent with broth dilution, where all strains were susceptible to gentamicin. Resistance was higher against polymyxin B and the fluoroquinolones. Silver sulfadiazine was effective in vitro with a MIC ranging from 1 to 64 μg/mL.

CONCLUSIONS AND CLINICAL SIGNIFICANCE

As the MIC of silver sulfadiazine was lower than the concentration in a 1% preparation, such a product potentially represents a treatment option for dogs with P. aeruginosa otitis.

EFFECTIVENESS OF TOBRAMYCIN AND CIPROFLOXACIN AGAINST BACTERIAL ISOLATES IN CANINE OTITIS EXTERNA IN UBERABA, MINAS GERAIS

Abstract Canine otitis externa is a common and recurrent disease in domestic dogs. Although not being life threatening, it can result in the overuse of antibiotics, increased bacterial resistance and reduction of options for treatment. This study aimed to determine: the principal characteristics (age, race, and gender) of dogs affected by otitis externa; the most frequently bacteria identified as being associated with it and their antimicrobial resistance profiles. A total of 221 bacterial isolates were identified by morphological staining and biochemical processes and tested against eleven antibiotics. Among the 148 dogs diagnosed with otitis externa, 51.4% (76/148) were males and 48.6% (72/148) females. The cases were detected mainly in dogs with age above 7 years (54.7%; 81/148. Among the races examined, poodles were the most numerous (14.84%; 22/148). The most common bacteria found were: coagulase-negative Staphylococcus (StCN), 33.9% (75/221); coagulase-positive Staphylococcus (StCP), 19% (42/221); Proteus spp., 17.2% (38/221) and Pseudomonas aeruginosa, 9.5% (21/221). Simultaneous resistance to more than three classes of antimicrobials were most frequently detected in P. aeruginosa (61.9%; 13/21) and Proteus spp (39.47%; 15/38). According to data obtained from this study, two veterinary medications found to be most effective for topical treatment were tobramycin and ciprofloxacin.

Microbiological and antibacterial resistance profile in canine otitis externa – a comparative analysis

The aim of the present study was to compare the prevalence of microbial agents involved in canine otitis externa and their sensitivity to antibacterial drugs in two periods: 2007–2011 and 2013–2017. For 2013–2017, coagulase-positive staphylococci were the dominating bacterial species (186 isolates), followed by Pseudomonas aeruginosa (82 strains). The rate of isolated yeasts (mainly Malassezia pachydermatis) was substantially high (152 isolates). Compared to the earlier period (2007–2011) a tendency to more frequent occurrence of co-infections was noted – 61.7% and more than 80% of co-infections involved yeasts. Antibacterial resistance patterns showed a clear trend to increased resistance of coagulase-positive staphylococci and β-haemolytic streptococci to amoxicillin/clavulanic acid (42% and 50% respectively) and gentamicin (29%, 40%). Increased resistance of P. aeruginosa was established to gentamicin (16%) and amikacin (18%). The prevalence of pseudomonads resistant to enrofloxacin was lower (27%).

In vitro antimicrobial activity of seven adjuvants against common pathogens associated with canine otitis externa

BACKGROUND

An antibiotic adjuvant is a chemical substance used to modify or augment the effectiveness of primary antimicrobial agents against drug-resistant micro-organisms. Its use provides an alternative approach to address the global issue of antimicrobial resistance and enhance antimicrobial stewardship.

HYPOTHESIS/OBJECTIVES

To determine the antimicrobial activity of a panel of potential antimicrobial adjuvants against common pathogens associated with canine otitis externa (OE).

ANIMALS/ISOLATES

A number of type strains and clinical isolates (n = 110) from canine OE were tested including Staphylococcus pseudintermedius, β-haemolytic Streptococcus spp., Pseudomonas aeruginosa, Proteus mirabilis and Malassezia pachydermatis.

METHODS AND MATERIALS

Antimicrobial activities of monolaurin, monocaprin, N-acetylcysteine (NAC), polymyxin B nonapeptide, Tris-EDTA, Tris-HCL and disodium EDTA were tested using microdilution methodology according to CLSI guidelines.

RESULTS

N-acetylcysteine, Tris-EDTA and disodium EDTA had antimicrobial activity against both type strains and otic pathogens. The other adjuvants tested had limited to no efficacy. NAC had a minimal inhibitory concentration (MIC) range of 2,500-10,000 μg/mL for the various organisms. Pseudomonas aeruginosa isolates were eight times more susceptible to disodium EDTA in the presence of Tris-HCL in comparison to disodium EDTA alone. Malassezia pachydermatis isolates were most susceptible to Tris-EDTA (MIC₉₀  = 190/60 μg/mL) and disodium EDTA (MIC₉₀  = 120 μg/mL).

CONCLUSIONS AND CLINICAL RELEVANCE

N-acetylcysteine, Tris-EDTA and disodium EDTA have intrinsic antimicrobial activity and represent promising adjuvants that could be used to enhance the efficacy of existing antibiotics against Gram-negative and multidrug-resistant bacterial infections. These agents could be combined with other antimicrobial agents in a multimodal approach for mixed ear infections in dogs.

Treatment of Selected Canine Dermatological Conditions in Portugal - A Research Survey

INTRODUCTION

Staphylococcus pseudintermedius and Malassezia pachydermatis often cause skin diseases in dogs.

MATERIAL AND METHODS

An online survey was e-mailed to veterinary practices nationwide covering demographics, diagnosis methods, and oral and topical treatment options. Of the 740 surveys sent, 100 complete replies were obtained.

RESULTS

The majority of clinicians were unaware of the existence of the International Society for Companion Animal Infectious Diseases guidelines or did not follow them (53%). Oral antibiotics were used universally for superficial bacterial folliculitis treatment, particularly amoxicillin-clavulanic acid (100%), cephalexin (94%), enrofloxacin (67%), or marbofloxacin (60%). For fold dermatitis (FD) and otitis externa (OE), oral antibiotics were also given as treatment in 88% and 82% of cases, respectively. Oral antifungals were often prescribed for generalised Malassezia dermatitis (85%), FD (70%), and OE (59%). S. pseudintermedius and M. pachydermatis were frequently treated topically, particularly with antibacterials or antifungals only, or a combination of antibacterials, antifungals, and glucocorticoids. Alternative options such as honey-based products were not frequently used.

CONCLUSION

Our survey suggests that oral antibiotics are overused by Portuguese clinicians despite the spread of antibiotic resistant S. pseudintermedius. Oral antibiotics and antifungals are commonly prescribed for skin conditions manageable with topical treatments.

In vitro and in vivo efficacy of tea tree essential oil for bacterial and yeast ear infections in dogs

ABSTRACT: Otitis externa is a common complaint in dogs. Bacteria and yeasts are commonly involved and may perpetuate inflammatory reactions inside the ear canal. Otoscopy, cytological examination of secretion and microbiological culture embody forms of diagnosis. Cytology also has great use in accessing treatment evolution. Therapy usually consists of cleaning ear canals and subsequent use of antibiotics or antifungal products. As some of them may cause hypersensitivity and even ototoxicity, searching for new pharmacological bases is currently necessary and justifies this study, which aimed to evaluate in vitro and in vivo efficacy of tea tree essential oil for bacterial and yeast ear infections in dogs. Twenty-eight dogs from a particular shelter in Cuiabá (Mato Grosso, Brazil), presenting clinical signs of otitis externa, were enrolled in this clinical trial. In all of them, clinical and cytological evaluations, as well as culture and susceptibility testing of the affected ears were carried out. From each dog, one ear was treated with 5% tea tree essential oil lotion and the other with standard otic formulation, according to the type of infection (bacterial, yeast or both). In vitro susceptibility testings of all ear cultures, to the same drugs used in treatment, were also carried out. Culture results showed 62.5% bacterial and fungal infection, 33.9% bacterial infection and 3.6% fungal infection, from the 56 ear samples collected. The most common microorganisms isolated were Staphylococcus intermedius, Staphylococcus aureus, Proteus mirabilis and Malassezia pachydermatis. Gram-positive bacteria were susceptible to gentamycin in 60.5% and resistant in 16.3% of the samples. Five percent tea tree essential oil formulation produced a 5mm clear zone of inhibition around the disks in one of the 63 samples evaluated. Pure (100%) tea tree essential oil formulation produced a 10mm clear zone of inhibition around the disks in four of the 63 samples evaluated, a 9mm zone in three samples, an 8mm zone in 16 samples, a 7mm zone in seven samples, a 6mm zone in two samples and there was no clear zone in 31 samples. Inhibition zones were produced by strains of Staphylococcus intermedius, Staphylococcus hyicus, Corynebacterium sp., Proteus mirabilis and Enterobacter sp. tea tree essential oil ear solution significantly induced remission of clinical signs both in bacterial and yeast ear infections. It also reduced as much Malassezia pachydermatis ear infection as the nystatin solution used in this study, while gentamycin solution showed better antibacterial effect. More studies should be conducted to evaluate in vitro diffusion properties of tea tree essential oil. Good antimicrobial spectrum and the absence of adverse reactions confirm the importance of developing a tea tree formulation as an alternative therapy for ear infections in dogs.

In vitro antimicrobial activity of monensin against common clinical isolates associated with canine otitis externa

Antimicrobial resistance and antimicrobial stewardship are of ever-increasing importance in veterinary medicine. Multidrug-resistant infections of the canine skin and ear continue to emerge, but the use of antibiotic classes of critical importance to human medicine may not represent good antimicrobial stewardship. Repurposing of old drugs that are not used in human medicine is one approach that addresses both these issues. In this study, the minimal inhibitory concentration (MIC) of monensin for 111 bacterial and yeast canine otitis isolates was determined using microdilution methodology according to Clinical Laboratory Standards Institute (CLSI) guidelines. Monensin was effective against all Gram-positive bacteria including the multidrug-resistant staphylococcal strains with MICs ranging from 1 to 4 μg/ml, but lacked antimicrobial activity against Gram-negative bacteria and yeast isolates. Monensin has potential to be incorporated as one of the main components in an otic formulation.

Methodological Issues in Antifungal Susceptibility Testing of Malassezia pachydermatis

Reference methods for antifungal susceptibility testing of yeasts have been developed by the Clinical and Laboratory Standards Institute (CLSI) and the European Committee on Antibiotic Susceptibility Testing (EUCAST). These methods are intended to test the main pathogenic yeasts that cause invasive infections, namely Candida spp. and Cryptococcusneoformans, while testing other yeast species introduces several additional problems in standardization not addressed by these reference procedures. As a consequence, a number of procedures have been employed in the literature to test the antifungal susceptibility of Malassezia pachydermatis. This has resulted in conflicting results. The aim of the present study is to review the procedures and the technical parameters (growth media, inoculum preparation, temperature and length of incubation, method of reading) employed for susceptibility testing of M. pachydermatis, and when possible, to propose recommendations for or against their use. Such information may be useful for the future development of a reference assay.

Topical ear treatment - options, indications and limitations of current therapy

Topical otic products form an integral part of the overall management of otitis externa. With an ever increasing array of ear drops and cleaners to choose from, appropriate selection of therapy can be difficult. The investigation of all cases of otitis externa should consider primary and secondary causes and predisposing and perpetuating factors. This article considers topical therapy under these same broad headings and discusses, through literature review, the various properties of the components of the ear cleaning solutions and drops.

Clinical features, cytology and bacterial culture results in dogs with and without cheilitis and comparison of three sampling techniques

BACKGROUND

Cheilitis is a common presentation in dogs associated with a variety of skin diseases and often complicated by microbial infections.

OBJECTIVES

To describe and compare clinical and cytological features and bacterial culture results from the lower lips of dogs with cheilitis (as compared to healthy controls), and to evaluate three cytology sampling techniques for their abilities to differentiate between the groups.

ANIMALS

Fifty six dogs with cheilitis and 54 controls.

METHODS

Anatomy and clinical signs of the lower lip were recorded. Cytology samples taken by tape strip, direct impression and swabs rolled over skin were scored semiquantitatively for microorganisms, inflammatory cells and keratinocytes. Cytology scores were correlated with semiquantitative bacterial culture scores.

RESULTS

Pure breeds, frequency of lip folds and all cytology scores except keratinocytes were higher in dogs with cheilitis than in controls, but a substantial overlap was seen in all microorganisms between the groups. Hypersensitivity disorders were diagnosed in 40 of 56 dogs with cheilitis. The tape strip technique yielded the greatest differences between groups. Bacterial growth was reported in 100% of dogs with cheilitis and in 93% of the controls. Pathogens such as Staphylococcus pseudintermedius, Escherichia coli and Pseudomonas spp were found more frequently in dogs with cheilitis. Cytology and bacterial culture were poorly correlated.

CONCLUSION

Cheilitis was associated with primary hypersensitivity disorders and the presence of a lip fold was a predisposing factor. Results of aerobic culture were similar to prior studies on pyoderma of other body sites, except for higher rates of Pseudomonas spp. isolation.

First identification of methicillin-resistant Staphylococcus pseudintermedius strains among coagulase-positive staphylococci isolated from dogs with otitis externa in Trinidad, West Indies

BACKGROUND

Otitis externa is a common inflammatory ear disease in dogs caused by a variety of pathogens, and coagulase-positive staphylococci are frequently isolated from such infections.

OBJECTIVE

To identify antimicrobial susceptibility profiles and methicillin-resistant strains among coagulase-positive staphylococci isolated from otitis externa in dogs.

METHODS

A cross-sectional study was performed over 2 years on 114 client-owned dogs presented to the Veterinary Teaching Hospital with a primary complaint of ear infections. Swabs were obtained from both ears and cultured for staphylococci which were subsequently confirmed as coagulase-positive using rabbit plasma. Antimicrobial susceptibility assays were assessed on all isolates followed by subsequent genetic analysis for species identification and detection of the mecA gene.

RESULTS

Sixty-five coagulase-positive staphylococci were isolated from 114 client-owned dogs. The isolates exhibited resistance against neomycin (58.5%), streptomycin (49.2%), penicillin (49.2%), polymyxin B (44.6%), tetracycline (36.9%), sulphamethoxazole/trimethoprim (33.8%), kanamycin (33.8%), doxycycline (32.3%), norfloxacin (23.1%), amoxicillin/clavulanate (20%), ciprofloxacin (20%), enrofloxacin (18.5%), gentamicin (16.9%), and cephalothin (9.2%). Forty (61.5%) of the isolates were resistant to at least three or more antimicrobials and 10 were sensitive to all. Using a multiplex polymerase chain reaction assay based on species-specific regions of the thermonuclease (nuc) gene, 38/65 (58.5%) isolates were classified as Staphylococcus aureus, 23/65 (35.4%) as S. pseudintermedius, 2/65 (3.1%) as S. intermedius, and 2/65 (3.1%) as S. schleiferi. Analysis for the mecA gene revealed two positive isolates of S. pseudintermedius which were oxacillin-resistant, representing a first report of such organisms in the Caribbean.

CONCLUSION

Despite the relatively high prevalence of multidrug-resistant coagulase-positive staphylococci in Trinidad, these are largely susceptible to gentamicin consistent with use in clinical practice. The first detection of methicillin-resistant S. pseudintermedius (MRSP) in dogs is likely to have implications on the treatment options for otitis externa in dogs and potential public health significance.

Perfil clínico e microbiológico de cães com e sem otoacaríase

Os objetivos do estudo foram identificar a presença de microrganismos nos condutos auditivos dos cães através dos exames citológico e microbiológico, assim como avaliar a associação destes à otoacaríase e seus sinais clínicos. O diagnóstico da infestação por Otodectes cynotis foi realizado através de otoscopia bilateral e pela coleta de material e visualização do parasito sob microscópio esterioscópico, constituindo o exame parasitológico. Outras coletas de secreção otológica de cada orelha foram realizadas para confecção de lâminas para a citologia e para o isolamento microbiológico, sendo este último material coletado através de "swab" estéril. Dos 250 animais examinados, em 15 (6%) foi identificado o ácaro O. cynotis.Observou-se associação entre a presença do parasito e a ocorrência de otite clínica externa caracterizada especialmente por eritema auricular (P<0,001) e a produção excessiva de secreção otológica (P=0,0016), assim como a observação, pelos proprietários, de prurido ótico nos cães (P<0,001). Sugere-se a possibilidade de essas associações serem efeito da infestação. Houve também a associação (P<0,01) entre a otoacaríase e a ocorrência de microrganismos nos dois condutos auditivos de cada animal, detectados através da citologia. No entanto, não houve associação (P=0,04 e p=0,07) entre a presença do ácaro O. cynotis e a ocorrência de microrganismos no exame microbiológico das orelhas direita e esquerda, respectivamente.