Biofilm-Forming Potential of Staphylococcus aureus Isolated from Clinical Mastitis Cases in New Zealand.

Kristene Gedye,Gina Denicolo,Steve Flint,Norman Williamson,Shirli Notcovich,Alex Grinberg,Nicolas Lopez-Villalobos

doi:10.3390/vetsci5010008

Abstract

Biofilm formation is of growing concern in human and animal health. However, it is still unclear how biofilms are related to mastitis infections in dairy cattle. In this study, a comparison between two tests for biofilm formation and the association between biofilm and the presence of genes associated with biofilm formation were investigated for 92 Staphylococcus aureus isolates from intramammary infections. Congo red agar (CRA) and microtitre test assay (MTA) in vitro phenotypic tests were used to evaluate biofilm formation. The presence of icaA, icaD, and bap genes associated with biofilm formation was confirmed using the polymerase chain reaction. Results show that most of the S. aureus isolates, though not possessing one of the biofilm-forming genes, were able to produce biofilms. MTA was more frequently positive in identifying biofilm-forming isolates than CRA.

Highlights

Mastitis and its effects on milk quality have caused large economic losses due to the costs of animal treatment and reduced quality milk for the dairy industry over the last 50 years
Lack of success in treating some chronic or recurrent infections caused by S. aureus could be due to the presence of virulence mechanisms that allow the microorganisms to be protected against antimicrobials and the host immune response
This study aimed to examine the potential of S. aureus isolates from mastitis cases to form biofilm, compare methods for biofilm detection, and determine the presence of genes associated with biofilm formation

Summary

Introduction

Mastitis and its effects on milk quality have caused large economic losses due to the costs of animal treatment and reduced quality milk for the dairy industry over the last 50 years. In New. Zealand, around 25% of clinical mastitis cases in dairy cows are due to Staphylococcus aureus (S. aureus), resulting in recurrent and/or chronic infections [1]. Lack of success in treating some chronic or recurrent infections caused by S. aureus could be due to the presence of virulence mechanisms that allow the microorganisms to be protected against antimicrobials and the host immune response. Biofilm formation is a virulence mechanism that protects bacteria [2]. Biofilms are formed in a multi-step process that involves cell attachment and formation of an extracellular matrix, which is one of the factors that protects bacteria against a hostile environment. Elucidation of the mechanisms of biofilm formation by S. aureus may lead to new preventive or treatment measures for clinical, or subclinical, mastitis in dairy cows

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