# Perinatal Occurrence and Epidemiological Significance of Staphylococcus aureus in Local Sheep Breeds

## TL;DR

This study shows that healthy sheep, especially during pregnancy, can carry dangerous antibiotic-resistant Staphylococcus aureus bacteria, which could pose a public health risk.

## Contribution

The study identifies new sequence types of MRSA in sheep and highlights the oral cavity as a key site for S. aureus sampling.

## Key findings

- Healthy sheep, including pregnant ones, are reservoirs of multi-drug resistant Staphylococcus aureus strains.
- The Świniarka breed shows higher resistance to colonization and infection due to less antibiotic use.
- Three new MRSA sequence types (ST 9313, ST 9314, ST 9315) were identified in the study.

## Abstract

Sheep are farm animals that provide numerous goods such as wool, meat, and milk, and animal-derived foods constitute an important part of the human diet. Staphylococcus aureus can spread between farm animals and humans, posing a public health threat and increasing the already high level of multi-drug resistant bacterial strains in both hospitals and the environment. This research shows that healthy sheep are a reservoir of S. aureus strains including methicillin-resistant strains (MRSA) and multi-drug resistance (MDR). The oral cavity should be considered the most representative site for sample collection. The level of S. aureus colonization is not constant and varies with the breed and physiological condition. During pregnancy, the level of S. aureus colonization significantly increases. In total, 46.6% of all tested strains met the criteria for multi-drug resistance. The primitive breed, Świniarka, is more resistant to both colonization and infection, which in turn is associated with less frequent antibiotic use in these breeds and lower levels of resistance in the colonizing strains. The presence of MRSA strains was detected at low levels in both breeds.

Staphylococcus are common bacteria that can be a component of the natural microbiota of the body of human and animal hosts or cause serious infections. The aim of this study was to analyze the presence of S. aureus in samples from two sheep breeds (Świniarka and Uhruska), assess the antimicrobial susceptibility and virulence profile of these microorganisms, and perform molecular comparative analysis of these bacteria. One hundred and three isolates of S. aureus strains were obtained (including five MRSA strains) and the highest phenotypic resistance to tetracycline (46.6%), clindamycin (45.6%), erythromycin (39.8%), and penicillin (31.1%) was confirmed. The tetL gene (27.2%) and the seB gene (44.7%) were the most frequently detected in strains. Three new sequence types in the MRSA isolates (ST 9313, ST 9314, ST 9315) were identified. In conclusion, our results confirm that sheep are significant reservoirs of S. aureus, especially MRSA strains, varying in terms of both resistance and virulence and with the potential to spread between individuals in the same herd, which may pose a potential health problem.