Bactericidal Spectrum of Baytril®

Various antimicrobial substances are available for the therapy of infectious diseases in cattle. Baytril® contains enrofloxacin, the first member of the class of modern fluoroquinolones exclusively developed for veterinary medicine. Baytril® shows quick bactericidal activity by inhibiting bacterial topoisomerases II (Gyrase) and IV. The action of these bacterial enzymes reseals the DNA during the bacterial multiplication process. Baytril® is registered for the therapy of several bacterial infections caused by susceptible microorganisms. Baytril® is bactericidal for different bacteria and mycoplasma at low concentrations.

Antimicrobial Products

Mod.: "Antimicrobial Medication in Domestic Poultry", Froyman R., 1996, in: "Poultry Diseases" 4th edition, ed. by Jordan F.T.W. and Pattison M., W.B. Saunders Company Ltd., pp. 486–487. Updated.
© 2002 Bayer AG, Germany

    No systemic activity; medication may reduce intestinal bacterial multiplication.
    Good susceptibility
    Moderate or variable susceptibility
    Present in normal gut flora
© 2002 Bayer AG, Germany

Antimicrobial Susceptilibity tests
Data collation of several antimicrobial susceptibility tests (published sources and data on file, Bayer Animal Health).
© 2002 Bayer AG, Germany

Bacterial Susceptibility

  • Confirmation of a pathogen's susceptibility to an antimicrobial is essential to achieve the right therapeutic approach.

  • The minimal inhibitory concentration (MIC) has been established as a standard for comparing the susceptibility of bacteria in vitro.

  • The unit is µg/ml and is given as MIC 50 or MIC 90 (indicating that the relevant concentration inhibits the growth of 50% or 90% of the bacteria of the tested population).

  • Results obtained from susceptibility testing (MIC tests and agar diffusion tests) always need careful interpretation. Contrary to these tests, which are performed under standardized conditions, nothing is static or standardized in the in vivo environment from which the pathogen was isolated. MICs and susceptibility follow their own dynamics and change over time. Bacterial isolates of a species may display different MICs even within a single animal or a group of animals. Despite these facts, the use of an antimicrobial classified as susceptible in in vitro testing has a high probability of successful therapy, whereas use of antimicrobial agents classified as resistant predicts a poor or no clinical response.

  • MIC values are particularly helpful when compared to the concentrations that a drug can achieve at the site of infection, in order to demonstrate the possibilities of successful therapy.

  • The high efficacy of Baytril® becomes evident when comparing enrofloxacin's MIC values for different pathogens with the achievable tissue concentrations and pharmacokinetic data.

Determination of MIC