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TDK conference 2016

Virulence type of Staphylococcus strains originating from Hungarian rabbit farms
Vincze Noémi Laura - year 5
University of Veterinary Medicine, Department and Clinic of Food Animal Medicine
Supervisor: Dr. Zoltán László Német


Staphylococcus aureus is one of the most important opportunistic phatogens, which can infect both humans and animals, and which is widely disseminated. The staphylococcosis on industrial rabbit farms has a major economical impact worldwide. It can affect rabbits of any age, typically it is presented in a subacute or a chronic form. This agent can infect both the skin and the internal organs, purulent dermatitis, pododermatitis, mastitis, metritis, pneumonia, septicaemia, and abscess formation are the most commonly observed conditions.

Most of the rabbit farms are contaminated with this agent, but the damage caused, or the success of treatment shows significant differences between various units. It is known for decades that significantly different variants can be isolated from similar lesions. The low virulence strains (LV) usually cause sporadical disease, mainly in impaired individuals, so they do not have a notable economic importance. However, the high virulence (high virulence=HV) strains can cause significant losses, because it can infect a high number of animals in a short period of time. Despite of decades of research, we don’t have an effective treatment against the virulent variant, the only viable solution is to completely renew the entire infected flock. Thus the most effective defense strategy against HV strains is to prevent the contamination of the farm.

We can use a multiplex PCR system to differentiate between virulence types. With this technique we can identify LV and HV strains, and we can also recognize atypical high virulent (aHV) genotypes. From the chromosome of the HV and aHV strains we can detect a nucleotide sequence called flank. In case of HV strains we can also amplify the bbp (bone sialoprotein binding protein gene) and the selm gene, which is a part of the enterotoxin gene cluster (egc). We use the femA gene as an internal control, which is described to be specific for Staphylococcus aureus strains.

In the research presented here we examined 374 isolates of Staphylococcus genus, collected from 30 rabbit farms between 2009 and 2014.

84,2 % of the isolates belonged to the previously rarely detected aHV genotype, and only 6,1% of the isolates were typical HV strains. 6,4% of the strain collection belonged to the LV genotype, and 3,2 % were negative for femA gene as well, so these strains probably belong to other species of the Staphylococcus genus.

In addition we examined the connection between the virulence type and tissue tropism with statistical analysis. We used correspondence analysis and association plots in order to determine correlation between different virulence types and the organ systems they originated from. The most significant result was the connection between HV strains and septicaemia cases. It has been demonstrated, that LV strains and the isolates belonging to other Staphylococcus species mainly originated from cutaneous lesions.

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