Extended antimicrobial susceptibility assay for Staphylococcus aureus isolates from bovine mastitis growing in biofilms

Abstract

Staphylococcus aureus is one of the most prevalent causes of bovine mastitis. The antimicrobial treatment of this disease is currently based on antimicrobial susceptibility tests according to CLSI standards. However, various studies have shown that there is a discrepancy between the results of this standard susceptibility test and the actual cure rate of the applied antimicrobial treatment. Increasing evidence suggests that biofilm formation by S. aureus is associated with this problem. The currently available antimicrobial susceptibility assays for bacteria growing in biofilms, are not considered reliable enough for routine application. Therefore, the objective of this study was to further develop a susceptibility test for bacteria growing in biofilm, suitable for routine testing of the antimicrobial susceptibility of S. aureus. With the expansion of the available MBEC TM assay to an extended biofilm susceptibility test, that comprises 2 and 4 consecutive days of antimicrobial challenge, the antimicrobial susceptibility for S. aureus growing in biofilm was further analysed. The results showed clear differences between strains and various antimicrobial agents with respect to the effect of longer duration of the antimicrobial challenge on the eradication of S. aureus growing in biofilm. The extended biofilm susceptibility test also indicates that each bacterial strain requires a specific duration of antimicrobial therapy, which cannot be derived from a standard susceptibility test or from a 24-h biofilm susceptibility test. #

Genotypic and Phenotypic Characterization of Clinical Isolates of Staphylococcus Aureus for Biofilm Formation Ability

“…Biofilm production enables adhesion of bacteria to the epithelium of mammary glands. It also facilitates persistence of micro-organisms in the host tissue by protecting the bacterial cells against the mechanisms of the host defense (Melchior et al, 2006a(Melchior et al, , 2007. Production of biofilm requires the presence of the intracellular adhesion locus gene cluster icaADBC (Cramton et al, 1999) and strains harboring the icaADBC cluster are potential biofilm producers.…”

Detection of Biofilm Production by Staphylococcus Aureus and in-Vitro Inhibition of Biofilm Using Serum Antibodies

“…which because infections associated with biomedical devices in humans and chronic udder infections in animals [16,19]. The biofilm results in increased resistance to a wide range of antibiotics, disinfectants and also opposes the clearance of bacteria by the host immune system [9]. The increased use of antibiotics against mastitis in dairy animals results in drug residues in milk that causes different health related problems and is a matter of concern for human being as consumers.…”

“…It is now well established that S. aureus produces biofilm in the udder of infected cows which not only impair the immune system of the host but also resist to different antimicrobials thus results in persistent infection [9]. Biofilms also act as immunogenic structures and elicit a protective immune response against the invading bacteria.…”

Increase in biofilm formation by Escherichia coli under conditions that mimic the mastitic mammary gland

“…The mastitis treatment is based primarily on intramammary administration of antimicrobial agents to the animal, which may also be delivered by the parenteral route depending on the severity of the case. However, studies have shown that in many cases the success of the therapy is frustrated, being unable to eliminate the agent from the mammary gland, and allowing the development of persistent and recurrent cases of the disease (MELCHIOR et al, 2007;SIMOJOKI et al, 2012). One hypothesis to explain this fact is the ability of some microorganisms to form biofi lms on the surface of mammary gland tissue, thus presenting resistance to several antimicrobials (MELCHIOR et al, 2006).…”