Characterization of Chloramphenicol and Florfenicol Abrasion in Escherichia coli Associated with Bovine Diarrhea

Florfenicol, a veterinary fluorinated analog of thiamphenicol, is acclimatized for appraisal of bovine respiratory bacilli in the United States. However, florfenicol abrasion has again emerged a allotment of veterinaryEscherichia coli isolates accusable in bovine diarrhea. The flo gene, which confers abrasion to florfenicol and chloramphenicol, has advanced been articular in Photobacterium piscicida and Salmonella entericaserovar Typhimurium DT104. The flo gene achievement is anxiously accompanying to the CmlA protein articular inPseudomonas aeruginosa.
The cmlA gene confers nonenzymatic chloramphenicol abrasion via an abode mechanism. Forty-eight E. coli isolates recovered from beasts with diarrhea, including 41 that were both chloramphenicol and florfenicol resistant, were assayed for the appearance of both flo and cmlA genes. Forty-two of the 44 isolates for which florfenicol MICs were ≥16 μg/ml were complete via PCR for the flo gene. AllE. coli isolates for which florfenicol MICs were ≤8 μg/ml were abrogating for the flo gene (n = 4). Twelve E. coli isolates were complete for cmlA, and chloramphenicol MICs for all 12 were ≥32 μg/ml.
Additionally, eight isolates were complete for both flo and cmlA, and both florfenicol and chloramphenicol MICs for these isolates were ≥64 μg/ml. DNA adjustment appraisal of the E. coli flo gene accustomed 98% appearance to the arise GenBank sequences of both serovar Typhimurium floSt and P. piscicida pp-flo. The flo gene was articular on high-molecular-weight plasmids of about 225 kb a allotment of the majority of florfenicol-resistant E. coli isolates. However, not all of the florfenicol-resistant E. coli isolates activated absolute the largeflo-positive plasmids. This suggests that several of the E. coli isolates may access a chromosomal flo gene. The E. coli flo gene specifies nonenzymatic cross-resistance to both florfenicol and chloramphenicol, and its appearance a allotment of bovine E. coli isolates of different abiogenetic backgrounds indicates a administering abounding added than advanced thought.