Prevalence and colonization of S.aureus in nasal cavity of domestic animals and of those who are taking care of them

Staphylococci can infect both mammals and humans; they are one of the most common bacterial pathogens and one of the most important factors for nosocomial infections. Therefore, the purpose of this study was to compare human and animal samples in relation to Staphylococci and to examine their resistance to antibiotics in Thessaly, Greece. Method: A total of 344 samples were collected; 74 from humans and 270 from domestic animals (cats, dogs, goats, horses, sheep). Sampling was performed using cotton swabs. All Staphylococci were isolated, identified and tested for their susceptibility to various antimicrobial agents using an automated system. Result: The majority of the samples collected were positive to a bacterium. The bacterium, which was isolated was mainly Staphylococcus sciuri. The isolates of S. aureus were detected in the human samples, as well as in the samples from dogs, and horses. Regarding the resistance to antibiotics, the highest rates were recorded against penicillin. In conclusion, humans, domestic animals and people who are taking care of them carried S.aureus.


Introduction
Until now, 47 species of bacteria belonging to the genus Staphylococcus have been identified, which can affect both humans and other kinds of mammals. The bacteria isolated in most cases from humans are S.aureus and Staphylococcus epidermidis [1][2][3]. S.aureus is the most pathogenic of the Staphylococcus genus [4,5]. It is characterized by its high resistance to antibiotics [6,7].
Bacteria of the Staphylococcus genus can also cause food poisoning, and S. aureus is the major factor. S. aureus food poisoning incidents are the most common food-borne diseases worldwide [8,9]. The aim of this research is to examine the nasal carriage of S.aureus in domestic animals and the people involved in their care in Thessaly, Greece

Material and method Sample collection and S. aureus identification
The survey was conducted in 2016 on a total of 344 samples, 74 of which were from humans and the remaining 270 from domestic animals such as cats, dogs, goats, horses and sheep. All samples were collected from houses that bred and kept domesticated animals and from the people who were taking care of them in Thessaly, Greece.
Sampling was performed using cotton swabs, while samples were collected from the participants' nasal cavity. The laboratory experiment was performed in the Microbiology Department of the University Hospital of Thessaly, Larissa.
The swab of each coating was initially inoculated into fresh nutrient broth (Tryptic Soy Broth) at 37°C for 24 hours in order to enrich the sample. A new cultivation of the broth in blood agar containing 5% sheep blood followed. From each culture, one or more colonies with different morphology (size, colour, haemolysis etc) were sub-cultured and were collected for further analysis.

S.xylosus:
All samples of Staphylococcus xylosus tested were susceptible to clindamycin, penicillin, oxacillin and cefoxitin.

S.simulans:The
Staphylococcus simulans sample was susceptible to all antibiotics apart from kanamycin in which it was not tested ( Table  4- 12).

Discussion
57% of the samples were positive to Staphylococcus.spp, while 8 of the 11 identified bacteria belonged to the Staphylococcus genus. The most common strain identified was S.sciuri (12.2%), followed by S.aureus and S.lentus (5.6% for each other) (Tables 1 and 2). Although most of the samples were taken from sheep, these animals showed less (34.2%) infected samples than horses (94.6%), humans (60.8%) and goats (85.7%) ( Table 1). The above results are consistent with the results of the research by Loeffler et al [10] where the most isolated bacteria were S. aureus and S. intemedius.
The rate of samples found infected with S.aureus (5.6%) is close to the respective percentage found in a survey conducted in Tunisia, where 6.5% of the samples carried the particular bacterium [11].Higher rates of positive samples have been recorded in the literature, such as in the research by Gömez-Sanz et al [12], where S.aureus strains were recorded in 12% of the samples. In addition, strains of S.aureus were found in 20% of dog samples, 17,8 of human samples and only 2.9% of horse samples ( Table 3). The results are quite similar to other surveys, that were carried out in different countries, as shown in Table 5.
As shown in the literature, various percentages of positive samples have been recorded. Differences from survey to survey are expected and may be due to both the different number of samples and the different region or time period ( Figure 1). Experiments performed to determine the positivity of the samples to catalase and to coagulase, showed that all samples were positive to catalase (100%), while 47,1% of samples were positive to both catalase and coagulase. 65,8% of samples was not identified ( Table 2). The lowest rates of coagulation positive samples were found in horses (22.9%) and the highest ones in cats (70%) and sheep (67.5%). 42% (human), 44,4% (dog) and 59.5% (goat) of the positive samples were positive to coagulase (Table 3 and Figure 2). Similar results were also shown by two more studies, where the percentage of samples from human was approximately 40%, while those from animals were 33-41%. A small deviation was found in dog samples and more than 30% deviation was found in cat samples [10][11][12]. Regarding the susceptibility of different samples to antibiotics, the rates recorded were quite high (47-100%).The highest rate was found against kanamycin, while 94,7% and 89,7% of the samples tested for their susceptibility to cefoxitin and oxacillin respectively were found susceptible to the corresponding antibiotic. 53,4% of the samples were resistant to penicillin. A significant difference was observed in the clindamycin, fusidic acid, penicillin and terracycline susceptibility     rates. In particular, the susceptibility rate of sheep to clindamycin was the lowest recorded, while the highest occurred in cats, dogs and horses. The sheep susceptibility rate to fusidic acid was lower than that of the cat, dog and horse. Goats and horses were more susceptible to penicillin comparing with other animals (Table 4 and Figure 3).
Regarding the bacteria, S. epidermidis samples were sensitive against clindamycin, penicillin, oxacillin, cefoxitin and tetracycline antibiotics, while all S. lentus samples were susceptible to oxacillin and cefoxitin substances. 60% of the S.lentus samples showed sensitivity to erythromycin, 66.7% to clindamycin, 90% to fusidic acid, and 80% to penicillin and tetracycline. Staphylococcus aureus strains were sensitive to erythromycin, clindamycin, fusidic acid, tetracycline and kanamycin. Half of them were susceptible to penicillin and 75% to oxacillin and cefoxitin. S.sciuri strains were susceptible to cefoxitin and tetracycline. 91.3% of S.sciuri samples were sensitive to erythromycin, 87.0% of them, to oxacillin and only 9.1% and 8.7% to clindamycin and penicillin respectively. The sample that was containing S. simulans was susceptible to all antibiotics apart from kanamycin, in which it was not tested. Strains of S. xylosus were susceptible to penicillin, clindamycin, oxacillin and cefoxitin and kanamycin. 20.0% of the S.xylosus samples were susceptible to fusidic acid and 40.0% to tetracycline. Finally, strains of S.intermedius were found to be sensitive to erythromycin, clindamycin, fusidic acid, oxacillin and cefoxitin. In addition, 33.3% of the S.intermedius samples were sensitive to tetracycline and all samples were resistant to penicillin (Tables 6-12). Generally speaking, S.aureus demonstrated high rates of susceptibility and sensitivity to the most antibiotics that were used, a data which is similar with the results of other surveys. Resistance to other antibiotics such as oxytetracycline, enroflaxin, methicillin, erythromycin, amoxicillin and clindamycin was demonstrated in quite high rates. The antibiotics in which S.aureus was more susceptible were tetracycline, ciprofloxacin, cefoxerazone and cefoxitin.

Conclusion
S.aureus is one of the most commonly corresponding bacteria in humans and animals, while new research is being carried out for a better and more direct addressing to its health impacts on organisms. The results indicated that Staphylococcus strains were detected in the samples, with S. sciuri occurring as the most common strain, while S.aureus was identified only in dogs, horses and humans. The antibiotic against which the highest levels of resistance from both S.aureus and other Staphylococci were recorded was penicillin, however, S.aureus showed susceptibility to most antibiotics. Further studies should be conducted to provide additional information on the ecology of S.aureus in both humans and domestic animals.