Evaluación de la susceptibilidad antimicrobiana y del tratamiento del calostro para el control de las infecciones por Mycoplasma agalactiae y Mycoplasma mycoides subsp. capri

Abstract

In the present doctoral thesis, the different diagnostic methods of mastitis in dairy goats, as well as the conditions of the sampling and the analytical conditions of the sample, were addressed. All the studies that conform the thesis have, as a main objective, the syndrome known as contagious agalactia (CA) and its control. Specifically, the rest of the published works focused on the efficacy of some control methods of this disease in goat herds, such as the management of the colostrum intake and the antimicrobial therapy against the two main etiological agents of caprine CA. Objectives 1. To review and discuss the validity of the available diagnostic methods for caprine mastitis and contagious agalactia in dairy goats, according to the epidemiological situation of the herds. 2. To review and explain the goat pathogens potentially transmissible through the colostrum intake, the available methods for their inactivation and their effects over the quality of colostrum. 3. To study the viability of Mycoplasma agalactiae y Mycoplasma mycoides subsp. capri in goat colostrum subjected to heat treatment or added with sodium dodecyl sulfate. 4. To study in vitro the antimicrobial susceptibility to different antimicrobials of caprine isolates of Mycoplasma agalactiae obtained from asymptomatic animals or showing signs of contagious agalactia. 5. To study in vitro the antimicrobial susceptibility to different antimicrobials of caprine isolates of Mycoplasma mycoides subsp. capri obtained from different anatomic locations 6. To compare the results of antimicrobial susceptibility of Mycoplasma mycoides subsp. capri caprine isolates, obtained by two different methods. 7. To study the presence of mutations in quinolone resistance determining regions in Mycoplasma mycoides subsp. capri field isolates showing a low susceptibility to these compounds. Results and conclusions 1. The pasteurization of goat colostrum at 56 ºC or 60 ºC significantly reduces the concentration of Mycoplasma agalactiae, and Mycoplasma mycoides subsp. capri is inactivated after 60 minutes at 60 ºC. 2. The treatment of goat colostrum with sodium dodecyl sulfate at 0,1 % or 1 % for 10 minutes is insufficient to achieve the inactivation of Mycoplasma agalactiae or Mycoplasma mycoides subsp. capri. 3. The most effective antimicrobials against Mycoplasma agalactiae in vitro are fluoroquinolones, tetracyclines and macrolides, with the exception of erythromycin and spyramicin in the latter group, to which it seems to be resistant. 4. Mycoplasma agalactiae isolates obtained from animals with symptoms of contagious agalactia feature higher MIC90 values for most of the antimicrobials, with respect to those obtained from asymptomatic animals. 5. Enrofloxacin, ciprofloxacin, marbofloxacin, danofloxacin, moxifloxacin, doxycycline, tylosin and clindamycin are the most effective agents in vitro against Mycoplasma mycoides subsp. capri. Aminoglycosides, spiramycin and erithromycin seem not to be useful in the treatment of contagious agalactia caused by Mycoplasma mycoides subsp. capri. 6. The epsilometric test estimates the minimum inhibitory concentration in good agreement with the microdilution method for those antimicrobials with a low minimum inhibitory concentration, but the agreement decreases when this value, obtained by means of the microdilution method, is intermediate or high. 7. For the first time, it is confirmed the presence of mutations in quinolone resistance determining regions of the gene gyrA of Mycoplasma mycoides subsp. capri field isolates.