Salmonella Strain's Path to Virulence Uncovered

The occurence of salmonella in live poultry and poultry products is a common challenge the farmers and then the consumers are facing. The research has defined the organism very well; however much is to be defined yet, as this is a typical organism of poultry. Dr. Saadat Ali Changezi D.V.M.

There is direct evidence that antimicrobial use in animals selects for antimicrobial-resistant non-typhoid salmonella serotypes. These bacteria have been transmitted to humans in food or through direct contact with animals. Antimicrobial resistance limits the therapeutic options available to veterinarians and physicians for the subset of clinical cases of non-typhoid salmonella which require treatment. A recent example is a clone of S. typhimurium DT104, resistant to ampicillin, tetracycline, streptomycin, chloramphenicol and sulphonamides, which has become prevalent in many countries including the UK, Germany and the USA. Following the introduction of fluoroquinolones for use in food-producing animals, the emergence of salmonella serotypes with reduced susceptibility to fluoroquinolones in humans has become a cause for particular concern. This phenomenon has been observed in countries such as France, Germany, Ireland, the Netherlands, the Russia Federation, Spain and the UK. Many industry experts have realised that certain essential oils have antimicrobial effects and have tried to apply this knowledge to salmonellosis control in poultry farms. Amongst the various essential oils available as feed additives, natural phytobiotics such as oregano essential oils stand out, as they have been found to assist in controlling and preventing salmonellosis in poultry farms. This was recently proven in an experiment by Penalver et al. (2005), who studied the antimicrobial activity of five different essential oils against origin strains of the Enterobacteriaceae family described as follows. An in vitro assay measuring the antimicrobial activity of essential oils of Coridothymus capitatus (Spanish origanum), Satureja montana, Thymus mastichina (Spanish Origanum majorana), Thymus zygis (Spanish variety of Thymus vulgaris) and Origanum vulgare (Orego-Stim®) was carried out against poultry origin strains of Escherichia coli, Salmonella enteritidis and Salmonella essen, and pig origin strains of enterotoxigenic Escherichia coli (ETEC), Salmonella choleraesuis and Salmonella typhimurium. The essential oil that showed the highest antimicrobial activity against the four strains of salmonella was Origanum vulgare such as that found in Orego-Stim®. The results of this work confirm the antimicrobial activity of Origanum vulgare as well as its potential application in the treatment and prevention of poultry and pig diseases caused by salmonella. Reference: Penalver P, Huerta B, Borge C, Astorga R, Romero R, Perea A. Antimicrobial activity of five essential oils against animal origin strains of the Enterobacteriaceae family. APMIS 2005113:1–6.