Veterinarija ir Zootechnika

Bovine mastitis is considered a problem that is impossible to eradicate, due to the indiscriminate use of antibiotics, mainly β-lactams. The aim of this study was to detect antimicrobial resistance genes in bacteria isolated from bovine mastitis in Western Nicaragua. The antimicrobial resistance profile of 30 bacterial strains was evaluated using the phenotypic method for the antibiotics amoxicillin/clavulanic acid (AMC), ceftriaxone (CRO), gentamicin (CN), cephalexin (CL), vancomycin (VA) for gram-positive bacteria, while the antibiotics amoxicillin/clavulanic acid (AMC), trimethoprim sulfamethoxazole (SXT), ceftriaxone (CRO), gentamicin (CN), cephalexin (CL) in gram negative bacteria. In addition, the evaluation of the genotypic method was carried out using the PCR (Polymerase Chain Reaction) technique for the detection of extended-spectrum β-lactamases (ESBL) in gram-negative bacteria and the mecA gene for bacteria of the Staphylococcus genus (MRS). It was possible to identify that the bacterial isolates presented a greater resistance to amoxicillin and oxacillin with 24/30 and 10/14, respectively. On the other hand, 100% of the bacterial strains showed sensitivity to the antibiotics gentamicin (CN) and sulfamethoxazole (SXT). In the present study, 2 antimicrobial resistance genes were detected in the gram-negative isolates related to ESBL, the blaSHV gene coding for the strains: Enterobacter, Serratia and E. coli, while the blaTEM gene was detected in the strains: Enterobacter and Serratia. The blaCTX gene in gram-negatives and the mecA gene in Staphylococcus were not detected.

The deficiency of tick control causes large economic losses for the health of animals and the risk of transmission of zoonotic diseases. Their control is based on the use of acaricides such as organophosphates, synthetic pyrethroids, amidines and macrocyclic lactones; however, its inappropriate use has favoured the presence of populations resistant to the main families of acaricides. This study was conducted with the objective to evaluate the resistance of Rhipicephalus (Boophilus) microplus against three widely used ixoidicides in Nicaragua, namely coumaphos, amitraz and cypermethrin, applied in the concentrations indicated by the manufacturer. For this, the techniques of Adult Immersion Test (AIT) and Larval Package Test (LPT) were applied, for which ticks were collected from farms in Western Nicaragua. The results obtained through the AIT show that coumaphos has a higher percentage of oviposition inhibition of 86%, while cypermethrin only demonstrated an oviposition of 12.9%. Mortality in adults treated with coumaphos was 97.72%, and in those treated with amitraz it was 48.8%, while cypermethrin only provided a mortality of 14.71%. In this study, the Rhipicephalus (Boophilus) microplus ticks collected from cattle were determined to have elevated levels of resistance to cypermethrin but low resistance to coumaphos.