The aim of the present study was to determine the bioactive compounds in four essential oils (EO’s) from Origanum heracleoticum, Origanum vulgare, Thymus vulgaris and Thymus serpyllum and to assess their antimicrobial and anti-biofilm activity against Salmonella Enteritidis. Strains were previously characterized depending on the expression of the extracellular matrix components cellulose and curli fimbriae as rdar (red, dry and rough) and bdar morphotype (brown, dry and rough). This study revealed that the EO’s and EOC’s (carvacrol and thymol) investigated showed inhibition of biofilm formation at sub-minimum inhibitory concentration. Comparing the efficacy of EO’s and EOC’s in the inhibition of biofilm formation between the strains with different morphotype (rdar and bdar) did not show a statistically significant difference. Results related to the effectiveness of EO’s and EOC’s (the essential oil components, carvacrol and thymol) on eradication of preformed 48 h old biofilms indicated that biofilm reduction occurred in a dose-dependent manner over time.

Bacteria of the genus Salmonella, some Escherichia coli strains as well as other species of the family Enterobacteriaceae, manifest the ability to express a specific phenotype, which is commonly termed as the 'rdar' (red, dry and rough) morphotype. Both rdar and non-rdar phenotypes are commonly found in the nature; however, rdar is of essential importance for bacterial survival in the environment, outside of the host organisms. In that respect, it is comparable with the process of spore formation in Gram-positive bacteria. In laboratory conditions, rdar morphotype demonstrates growth of aforementioned organisms on agar containing diazo dye Congo Red, appearing as dark red (violet), rough and irregularly margined colonies. A coordinated expression of the number of genes mediated by major transcriptional regulators CsgD (curli subunit gene D) is the prerequisite for the formation of rdar morphotype colonies. The key point in this process is the activation of csgBAC operon transcription, which encodes the synthesis of curli fimbriae and activates the AgfD regulated gene (AdrA) involved in the cellulose biosynthesis. Curli fimbriae and cellulose are two basic structural components of the rdar morphotype. Curli fimbriae enable initial surface adhesion and intercellular aggregation of bacteria, whilst the cellulose (and other exopolysaccharides) promotes intercellular interactions. CsgD affects the overall cell physiology towards a 'bacterial multicellular behavior' pattern, such as biofilm formation. The colony growth on Congo Red agar is a widely accepted laboratory method used for bacteria from the family Enterobacteriaceae and highly conserved between Salmonella. However, repeated laboratory sub-passaging results in the substantial loss of rdar morphotype and the formation of smooth mutants, suggests the necessity for using wild isolates. In this article, the characteristics of rdar and non-rdar morphotypes of diverse Salmonella serotypes isolated from animal feed, as well as Escherichia coli isolates originating from cow's milk with clinical mastitis, were presented. The research indicates substantial importance of the rdar phenotype for the persistence of Salmonella in the environment and its entering the food chain as well as the potential role of rdar phenotype of Escherichia coli in the pathogenesis of recurrent coli mastitis in dairy cows.

Increased incidence of protothecal mastitis has been recorded in several countries in the past ten years. The main goal of this article is to draw the attention of scientific and professional community to the emerging issue of mammary protothecosis. The article collates currently known facts about infection reservoirs, predisposing factors for the development of mastitis, clinical manifestations of the disease, and potential transmission routes within the herd as well as the measures for control and eradication. We would like to point out that identification of protothecal mastitis on a dairy farm is associated with a range of problems. Early detection of infected animals can be difficult because of predominantly subclinical course of early-stage infection, which easily spreads between cows via the milking system. Spontaneous recovery has not been recorded and infected cows typically develop chronic mastitis with granulomatous infiltration and progressive loss of functional parenchyma of the mammary gland. Substantial economic losses and health damages associated with mammary protothecosis strongly emphasise the need for developing effective prevention strategies aimed at control of the infection.

Introduction Salmonella are one of the major foodborne pathogens, mainly due to their health and economic impact. About 93.8 million people worldwide are diagnosed with salmonellosis each year, which in 155,000 cases results in lethal outcome

For decades intensive husbandry has more or less been based on the use of antibiotics in sub-minimum inhibitory concentrations (sub-MIC) aimed at growth promotion. Continuous exposure of animal intestinal microbiota, including opportunistic zoonotic pathogens, to sub-MIC poses a pressure to selection and spread of bacteria strains with developed mechanism of antibiotic resistance. These bacteria may be transferred to people either by direct contact with farm animals or indirectly, via the food chain. Although in the EU a ban on the use of antibiotics as growth promoters was imposed in 2006, in many countries, including the largest producers and consumers of antibiotics in the world, it has yet to be done. Given that we are faced with a global problem of the loss of the efficacy of several antibiotic classes which are available for the treatment of human bacterial infections, it is unacceptable that antibiotic use in husbandry is not under global control. Reduction in antibiotic use in clinical practice in human medicine remains in dispute, but non-therapeutic use in husbandry remains a field in which much can be done to contribute substantially to the extension of antibiotic effectiveness and health care of future generations.