## 1 Introduction
Udder tissues host the most frequent pathogens and can be spread from animal to animal (contagious pathogens) or can be present in the livestock environment (known as environmental pathogens), including bedding, manure, or soil. Using conventional culture, more than 140 species were isolated in samples of milk derived from cows affected by mastitis [12]. The most reported etiological sources of mastitis are Staphylococci, and Coliform bacteria (_Escherichia coli_), independent of the origin of milk (cows, sheep, or goats) [12; 13; 14]. However, the most prevailing pathogen related to clinical and sub-clinical mastitis is _Staphylococcus aureus_ (_S. aureus_) [11; 15; 16], while _Klebsiella_ spp., _Enterobacter_ spp., and _Pseudomonas_ spp. have been associated with environmentally caused mastitis [17]. The detection of such pathogens is considered a definitive diagnosis of mastitis infections [18]. Nowadays, another great concern that has been raised is about the prevalence of multidrug resistance, particularly _S. aureus-resistant_ methicillin (MRSA), which has steadily increased in the EU [19], leading the European Food Safety Authority (EFSA) to suggest increased surveillance of MRSA both in food and livestock intended to be used for food production [16; 20]. Additionally, because antibiotics are often and inappropriately used in the medical sector, a broad range of pathogen species have emerged in many cases. Among them, _Klebsiella_ spp. serves as a vehicle for zoonotic pathogen resistance in multiple drugs that the World Health Organization (WHO) has put under surveillance [21]. _Klebsiella pneumoniae_ settles in different environmental recesses in water, plants, and the ground, and it has been extensively detected in dairy cattle mastitis cases [22]. It can be transmitted and invade the mammary epithelial cells in dairy cattle herds mostly through manure, through contiguity with the teats, and via the bedding and equipment used [23]. _K. pneumoniae_ strains which are multidrug resistant and hyper-virulent have been observed [24], leading to several illnesses, including meningitis, urinary tract infections, pneumonia, liver abscess, and septicmia [25]. Its pathogenesis as a procreator of dairy cattle mastitis has been scarcely studied especially when compared to the extensive studies on other bacterial pathogens [26]. Even more limited data can be retrieved for the occurrence of _K. pneumoniae_ in the milk of small ruminants (mostly caprine and ovine milk) or respective dairy products, as they share a limited segment of the global dairy market, although they significantly participate in the dairy economy of certain South European countries which correspond to major producers of sheep and goat milk. This preliminary study was performed to assess the presence of certain pathogens (such as _S. aureus_, _K. pneumoniae_, and _Enterobacter_ spp. ), which are associated with mastitis in samples of milk from various lactating ruminant species, namely cows, goats, and sheep using both conventional microbiological methods and PCR techniques and to further discuss the significance of the isolated pathogens to public health as well as to attract attention to emerging pathogens still not included in monitoring policies.