Comparative Assessment of the Antimicrobial Susceptibility of Staphylococcus aureus Isolates from Bovine Mastitis in Biofilm Versus Planktonic Culture

• Published in: Journal of veterinary medicine. Series B Vol. 53; no. 7; pp. 326 - 332
• Main Authors: Melchior, M.B, Fink-Gremmels, J, Gaastra, W
• Format: Journal Article
• Language: English
• Published: Oxford, UK Oxford, UK : Blackwell Publishing Ltd 01-09-2006; Blackwell Publishing Ltd
• Subjects: Animals; Anti-Bacterial Agents - pharmacology; Anti-Bacterial Agents - therapeutic use; antibiotic resistance; antibiotics; Bacteria; bacterial infections; biofilm; Biofilms; Biofilms - growth & development; bovine mastitis; Cattle; cell culture; Colony Count, Microbial; Comparative analysis; culture media; dairy cows; disease control; Dose-Response Relationship, Drug; Drug Resistance, Bacterial; drug therapy; Female; Mastitis, Bovine - drug therapy; Mastitis, Bovine - microbiology; Microbial Sensitivity Tests - veterinary; minimum inhibitory concentration; Pathology; planktonic culture; Staphylococcal Infections - drug therapy; Staphylococcal Infections - microbiology; Staphylococcal Infections - veterinary; Staphylococcus aureus; Staphylococcus aureus - drug effects; Staphylococcus aureus - genetics; Staphylococcus aureus - physiology; subclinical infections
• ISSN: 0931-1793; 1863-1959; 1439-0450; 1863-2378
• DOI: 10.1111/j.1439-0450.2006.00962.x

Mastitis is one of the most important diseases in dairy cattle of which Staphylococcus aureus is a major pathogen. Despite an apparently good antimicrobial susceptibility in vitro, the cure of diseased animals from this bacteriological infection is often disappointing, which results in cases of recurrent clinical- and chronic subclinical infections. It has been suggested that these recurrent and chronic Staphylococcus infections can be attributed to the growth of bacteria in biofilm. The objective of this study was to compare the susceptibility for antimicrobial agents of S. aureus isolates obtained from bovine mastitis growing under different conditions. These conditions include a conventional conventional microbroth dilution assay in which minimal inhibitory concentration values are determined, the MBECTM assay which measures both the susceptibility in biofilm and the susceptibility of sequester cells released from the biofilm. A comparison of the susceptibility for antimicrobial agents of a number of representative S. aureus isolates grown in broth (representing in vitro growth conditions) or milk (representing in vivo growth conditions) is also made. The results indicate that S. aureus isolates obtained from bovine mastitis are highly resistant to antimicrobial agents when growing in biofilms.