The Relationship of Phylogenetic Distribution and Integron Gene Presence with Multiple Antibiotic Resistance in Escherichia coli Isolates Obtained from Bovine Milk with Mastitis

Multiple antibiotic resistant (MDR) bacteria are one of the most important current threats to public health. Integrons are important mobile genetic mechanisms involved in the spread of resistance. Escherichia coli includes both commensal and pathogenic clones found in different phylogenetic groups. Revealing the distribution of phylogenetic groups and the presence of integrons in E. coli, which causes clinical mastitis ( CM), may assist in the development of specific strategies for the treatment and control of this pathogen. In this study, it was aimed to examine the relationship between phylogenetic distribution and integron related gene presence with multi-antibiotic resistance of bacteria in E. coli isolates obtained from bovine milk with clinical mastitis. The material of the study consisted of 73 E. coli (17.3%) isolates obtained from 422 milk samples. After bacterial isolation was performed with conventional biochemical tests; Identification, phylogeny and presence of integron genes were examined by Polymerase Chain Reaction (PCR). The resistance patterns of the isolates against nine antibiotics belonging to nine antimicrobial families were analyzed using the Kirby-Bauer disc diffusion method. Isolates resistant to at least three drugs from various antimicrobial drug classes were defined as multi-drug resistant (MDR). Chi-square (chi 2) test was used to calculate the relationship between multidrug resistance of isolates, their phylogenetic distribution and presence of integron genes (p<0.05). According to the antibiotic test results, the highest resistance was found against ampicillin (79.4%) and amoxicillin clavulanate (61.6%), while the highest sensitivity was against ciprofloxacin (86.3%) and cefoperazone (84.9%). 52.1% (38/73) of the isolates were MDR. The majority of isolated E. coli strains belonged to group A (37.0%), followed by group B1 (24.7%), group C (15.0%), group D (5.5%), group E (% 8.2%) and then group F (4.1%). It was determined that 31.5% of the isolates carried integron related genes. There was no significant relationship between MDR and phylogenetic distribution of the isolates. However, the relationship between MDR and the prevalence of integron related genes was significant (p=0.001). The high rate of multi-antibiotic resistance of isolates belonging to phylogroups A and B1, which are generally considered commensal, is a concern. The increase presence of MDR bacteria in animals can lead to the emergence of resistant bacteria that can be transferred to humans through direct contact or through the food chain, reducing the effectiveness of antibiotics used to treat human diseases.