Frederick Adzitey1*, Nicholas Prah2, Hafiz Salifu2 , and David Yidana2
- Department of Animal Science, Faculty of Agriculture, Food and Consumer Sciences, University for Development Studies, P. O. Box TL 1882, Nyankpala Campus, Ghana
- Department of Veterinary Science, Faculty of Agriculture, Food and Consumer Sciences, University for Development Studies, P. O. Box TL 1882, Nyankpala Campus, Ghana
* Corresponding author: Frederick Adzitey, Department of Animal Science, Faculty of Agriculture, Food and Consumer Sciences, University for Development Studies, P. O. Box TL 1882, Nyankpala Campus, Ghana. Email: firstname.lastname@example.org
Introduction: Staphylococcus aureus is an important bacterium which induces a wide range of diseases. Its presence in dogs and resistance to antibiotics is a threat to public health due to the close association of humans with dogs. The objective of the present study was to determine the phenotypic resistance of Staphylococcus aureus (S. aureus) to antibiotics in dogs without any clinical manifestation of diseases in Tamale Metropolis, Ghana. The current study also examined microbial load in these dogs.
Materials and methods: A total of 120 samples from various parts of dogs, including the mouth, nose, anus, inner ear, and outer ear, were examined. Isolation and antibiotic resistance of S. aureus were determined using the USA Bacteriological Analytical Manual and the Disc Diffusion method, respectively.
Results: The presence of S. aureus in the dogs ranged from 8.3% (anus) to 58.3% (nose), averaging 40%. The microbial load also ranged from 2.9 log cfu/cm2 (mouth) to 3.4 log cfu/cm2 (outer ear) with an average of 3.2 log cfu/cm2. There were significant differences among the examined samples regarding the presence of S. aureus, but not the microbial load. The overall resistance, intermediate resistance, and susceptibility of S. aureus were 46.2%, 12.9%, and 42.2%, respectively. The S. aureus was highly resistant to teicoplanin (88.0%) and susceptible to chloramphenicol (72.0%). The multiple antibiotic indexes ranged from 0 to 0.9, and 89.1% of the isolates exhibited multidrug resistance.
Conclusion: The findings of the current study revealed that healthy dogs in Tamale Metropolis, Ghana, were carriers of S. aureus as well as other bacteria, and the S. aureus exhibited different resistance patterns to antibiotics.
Staphylococcus aureus (S. aureus) is a Gram-positive cocci-shaped bacterium that tends to be arranged in clusters, and is a member of the family Micrococcacae1,2. It is an important bacterium due to its capacity to induce a wide range of diseases and its ability to adapt to different environmental conditions2. The emergence of multidrug-resistant strains of S. aureus has contributed to the importance of this pathogen. Staphylococcus aureus could be acquired from human and animal hosts. Approximately 30% of humans bear S. aureus in their nasal cavities, which is the primary reservoir and the primary source of infection3. Strains of S. aureus have been reported to cause mastitis in cattle, botryomycosis in horses, dermatitis in dogs, septicemia, and arthritis in poultry4,5,6,7. Case reports of human infection or colonization from household pets have shown the high likelihood of animals acting as reservoirs for transmission of this pathogen8,9,10.
Pets can develop a social and emotional relationship with humans and their environment11. This has led to strong attachment between dogs and their owners or caretakers, and therefore, pets are treated as family members11. Dogs have been reported to be potential sources of various zoonotic pathogens, such as S. aureus, Escherichia coli, Salmonella enterica, Klebsiella species, and Bacillus species9,12,13,14 that are resistant to various antibiotics, including ampicillin, cephalosporin, gentamicin,
enrofloxacin, methicillin, and tetracycline10,15,16,17.
In Ghana, dogs are kept for different purposes, such as security, hunting, pets, and even food (meat). Although keeping dogs in Ghana is now rampant and currently raised due to the aforementioned reasons, the closeness between dogs and humans makes them potential sources for the transmission of zoonotic pathogens, such as S. aureus, to humans. However, information on the occurrence of S. aureus in dogs and their antibiotic resistance patterns in Ghana is limited. As these animals are in close contact with humans, the presence of antibiotic-resistant S. aureus can pose a health threat to humans. Therefore, the present study was conducted to determine the presence and antibiotic resistance of S. aureus in apparently healthy dogs in the Tamale Metropolis, Ghana. Furthermore, the microbial load of the various parts of the dogs was determined. To the best of the researchers’ knowledge, the current study is one of the first reports on the prevalence of antibiotic resistance S. aureus in dogs of Ghana.
2. Materials and Methods
2.1. Ethical approval
The present study did not cause any harm to humans or animals and was approved by Project Supervisors of the Department of Veterinary Science, University for Development Studies, Ghana.
2.2. Study area
The present study was carried out at the Tamale Metropolis of Ghana. Geographically, the Tamale Metropolis lies between latitudes 9o16 and 9o34 North and longitudes 0o36 and 0o57 South18. The Metropolis has an estimated total land area of 646.90180 sq km, and a population of 22325218.
2.3. Sample collection
A total of 120 samples were randomly collected from dogs without any clinical manifestation of diseases in the Tamale Metropolis, confirmed by a veterinarian. Houses that owned dogs were numbered, and the researchers randomly picked the numbers from a box. Houses picked were visited, and with the help of dog owners, such as the restrainers and a veterinary officer, swabs were taken from the various parts of the dogs. The dogs were randomly selected without emphasis on selecting a particular breed. Sterile cotton swabs were used to swab the anus, (n=24), mouth (n=24), nose (n=24), inner ear, (n=24), and outer ear (n=24) of the dogs at their homes with the help of dog owners and a veterinary officer. The swabbed samples were placed in an ice chest box containing ice blocks and transported to the Spanish Laboratory of the University for Development Studies, Nyankpala Campus, Ghana, where they were analyzed for S. aureus. Sampling was carried out from December 2019 to March 2020.
2.4. Enumeration of aerobic plate count
Enumeration of aerobic plate count was performed using a slightly modified procedure as previously done19,20. Swabs were soaked in 9 ml of 1% buffered peptone water (BPW), and serial dilutions from 10-1 to 10-5 were made using one ml of 1% BPW. It was then spread plated (0.1 ml) unto plate count agar and incubated at 37°C for 24 hours. Afterwards, the colonies were counted and expressed in colony-forming units. All media used were purchased from Oxoid, Basingstoke, the UK.
2.5. Isolation and identification of Staphylococcus aureus
Isolation and identification of S. aureus were performed using a slightly modified procedure21,22. Briefly, swabbed samples from healthy dogs were pre-enriched in BPW and incubated at 37°C for 24 hours. They were then streaked with mannitol salt agar (MSA) and incubated at 37°C for 24 hours. Presumptive S. aureus colonies formed yellow colonies on MSA surrounded by a yellow area. Two or three colonies were picked and purified on Trypticase soy agar and incubated for 24 hours at 37°C. Gram staining and Staphylase test were used to confirm the purified S. aureus colonies. All media and reagents used were purchased from Oxoid, Basingstoke, the UK.
2.6. Antibiotics susceptibility of Staphylococcus aureus
The disk diffusion method was used to determine the antimicrobial resistance of S. aureus against some antibiotics, including Amoxycillin/clavulanic acid (Amc, 30 μg), chloramphenicol (C, 30 μg), gentamicin (Cn, 10 μg), ceftriaxone (Cro, 30 μg), ciprofloxacin (Cip, 5 μg), azithromycin (Azm, 15 μg), sulphamethoxazole/ trimethoprim (Sxt, 22 μg), tetracycline (Te, 30 μg), and teicoplanin (Tec, 30 μg)23. Pure cultures of S. aureus were grown overnight in tryptic soy broth at 37°C, and the concentration was adjusted to 0.5 McFarland turbidity. About 0.5 ml of the culture was spread plated on Mueller Hinton agar. Four and five antimicrobial disks were placed on the surface of the agar plate at a distance to avoid overlapping inhibition zones. The plates were incubated at 37°C for 24 hours, and the results were interpreted according to a previous study24. All media and disks used were purchased from Oxoid, Basingstoke, the UK. The multiple antibiotic resistance (MAR) index was calculated and interpreted to use the formula a/b, where a represents the number of antibiotics to which a particular isolate was resistant, and b denotes the total number of antibiotics tested25.
2.7. Data analysis
The data obtained from microbial load was analyzed using ANOVA of GenStat Software 12.1 Edition. Data on the presence of S. aureus were analyzed using binary logistic of IBM Statistical Package for the Social Sciences (SPSS) Software Version 17. The statistical difference test was done using the Wald test in Chi-square. All differences were determined at a 5% significance level.