Biofilm formation in bovine mastitis pathogens and the effect on them of antimicrobial drugs

The ability of bacteria to produce a biofilm is considered an important virulent property in pathogenesis of mastitis. The purpose of studies is to investigate the ability to form biofilms, their density, to determine and compare the sensitivity to antibacterial drugs of planktonic and biofilm forms of the main bovine mastitis pathogens on dairy farms of the Western region of Ukraine.Diagnosis of bovine mastitis, selection of milk samples and secretions of the mammary gland, microbiological studies were carried out in accordance with generally accepted methods. The performed studies have established that among pathogens, both acute and chronic forms of mastitis, the most productive film-forming ability had S. aureus strains, which on average 1.5 times more often formed the biofilm than Str. agalactiae and Str. dysgalactiae strains. It was revealed that S. aureus strains, isolated from cows under the subclinical form of mastitis and at carriage, 2.0 times (p <0.05) more often formed biofilms than in the clinical form of mastitis. The highest sensitivity of planktonic bacteria to pathogens of mastitis of streptococci and staphylococci was to ceftriaxone and doxycycline (100-80.9%). The least susceptible streptococci and staphylococci were to benzylpenicillin 32.3-45.4%, and the susceptibility of S. aureus strains was 19.0%.When determining the influence of antibiotics on biofilm forms of bacteria found that cells in the biofilm are more resistant to antibacterial drugs. It was found that antibiotic enrofloxacin completely inactivated streptococci and staphylococci in biofilms. Also, antibiotics ceftriaxone and doxycycline were also effective on bacteria in biofilms. At the same time, under the action of antibiotics penicillins, aminoglycosides and macrolides, the amount of microbial cells that survived in a biofilm was about lg 5.3 CFU/cm2 of area. Consequently, studies have shown that it is necessary to seek effective methods and develop new drugs that would influence the bacteria in biofilms to effectively treat bovine mastitis