title: Biofilm formation by coagulase-negative staphylococci: impact on the efficacy of antimicrobials and disinfectants commonly used on dairy farms.
abstract: Coagulase-negative staphylococci (CNS) have traditionally been considered minor mastitis pathogens and are the bacteria most frequently isolated from intramammary infection. Previously, our laboratory demonstrated that a majority of CNS isolated from Canadian milk were able to form biofilm and this was strongly and positively associated with days in milk. Biofilms offer protection against antibiotics and disinfectants, and the presence of CNS biofilms near the end of the lactation cycle could have an impact on the prevention and recurrence of CNS infections in the next lactation cycle. The objective of this study was to investigate the effect of biofilm formation on efficacy of commonly used antibiotics and disinfectants against CNS. The minimal inhibitory concentration (MIC) and minimal biofilm eradication concentration (MBEC) of several CNS isolates were determined using microdilution method and the MBEC device, respectively. Biofilm cells were more resistant to a penicillin G/novobiocin combination and to ceftiofur than their planktonic counterparts and the increase in resistance ranged from 4× to 2048×. For the disinfectants, we determined the minimum contact time required for different teat disinfectants to eradicated planktonic cells and biofilms. The chlorhexidine-based teat disinfectants eradicated planktonic cells and biofilms within 30s. For iodine-based teat disinfectants, it took 2-10× longer to eradicate the biofilms than planktonic cells. In conclusion, CNS biofilms were less susceptible to antibiotics; however, chlorhexidine-based teat disinfectants were still effective against CNS biofilms. This reinforces the use of post-milking teat disinfectants as a preventive measure of intramammary infections.
authors.affiliation: Département de pathologie et microbiologie Faculté de médecine vétérinaire, Université de Montréal, Canada; Canadian Bovine Mastitis and Milk Quality Research Network, C. P. 5000, St-Hyacinthe, Québec, Canada J2S 7C6.
authors.forename: Yannick D N
authors.initials: YD
authors.lastname: Tremblay
authors.affiliation: Département de pathologie et microbiologie Faculté de médecine vétérinaire, Université de Montréal, Canada.
authors.forename: Vincent
authors.initials: V
authors.lastname: Caron
authors.affiliation: Département de pathologie et microbiologie Faculté de médecine vétérinaire, Université de Montréal, Canada.
authors.forename: Andréanne
authors.initials: A
authors.lastname: Blondeau
authors.affiliation: Département de pathologie et microbiologie Faculté de médecine vétérinaire, Université de Montréal, Canada; Canadian Bovine Mastitis and Milk Quality Research Network, C. P. 5000, St-Hyacinthe, Québec, Canada J2S 7C6.
authors.forename: Serge
authors.initials: S
authors.lastname: Messier
authors.affiliation: Département de pathologie et microbiologie Faculté de médecine vétérinaire, Université de Montréal, Canada; Canadian Bovine Mastitis and Milk Quality Research Network, C. P. 5000, St-Hyacinthe, Québec, Canada J2S 7C6. Electronic address: mario.jacques@umontreal.ca.
authors.forename: Mario
authors.initials: M
authors.lastname: Jacques
mesh_terms: D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D018441:Biofilms / Q000254:growth & development*; D002170:Canada; D002417:Cattle; D004202:Disinfectants / Q000494:pharmacology*; D005260:Female; D007774:Lactation; D008414:Mastitis, Bovine / Q000382:microbiology; D008826:Microbial Sensitivity Tests / Q000662:veterinary; D008892:Milk / Q000382:microbiology; D013203:Staphylococcal Infections / Q000188:drug therapy / Q000382:microbiology / Q000662:veterinary*; D013210:Staphylococcus / Q000145:classification / Q000187:drug effects* / Q000502:physiology*
chemical_list: D000900:Anti-Bacterial Agents; D004202:Disinfectants
keywords: Antibiotic resistance; Biofilm; Coagulase negative staphylococci; Mastitis; Teat disinfectants