1. The increase in microbial resistance, and in particular multiple drug resistance (MDR), is an increasing threat to public health. The uncontrolled use of antibiotics and antibacterial chemotherapeutics in the poultry industry, especially in concentrations too low to cause inhibition, and the occurrence of residues in feed and in the environment play a significant role in the development of resistance among zoonotic food-borne microorganisms.
2. Determining the presence and transmission methods of resistance in bacteria is crucial for tracking and preventing antibiotic resistance. Horizontal transfer of genetic elements responsible for drug resistance is considered to be the main mechanism for the spread of antibiotic resistance.
3. Of the many well-known genetic elements responsible for horizontal gene transfer, integrons are among the most important factors contributing to multiple drug resistance. The mechanism of bacterial drug resistance acquisition through integrons is one of the essential elements of MDR prevention in animal production.
Hypothesis: Dogs that possess the ABCB1-1Δ mutation are more likely to develop hematologic toxicity associated with vincristine than ABCB1 wild-type dogs.
Animals: Thirty-four dogs diagnosed with lymphoma were included in this study.
Methods: Cheek swab samples were obtained from dogs diagnosed with lymphoma that were to be treated with vincristine. DNA was extracted from cheek swabs and the ABCB1 genotype was determined. Hematologic adverse drug reactions were recorded for each dog and graded according to the Veterinary Comparative Oncology Group's criteria for adverse event reporting (Consensus Document). In order to avoid possible bias, ABCB1 genotype results for a particular patient were not disclosed to oncologists until an initial adverse event report had been submitted.
Results: Dogs heterozygous or homozygous for the ABCB1-1Δ mutation were significantly more likely to develop hematologic toxicity, specifically neutropenia ( P = .0005) and thrombocytopenia ( P = .0001), after treatment with vincristine than ABCB1 wild-type dogs.
Conclusions and Clinical Implications: At currently recommended dosages (0.5–0.7 mg/M