Genetic analysis of multidrug-resistant and AmpC-producing Citrobacter freundii

OBJECTIVE: During the last de-cade, antimicrobial resistance within pet animals has received worldwide concern owing to their close contact with humans and the possibility of animal-human co-transmission of multidrug-resistant bacteria. This study examined phenotypic as well as molecular mechanisms associated with antimicrobial resistance in a multidrug-resistant, and AmpC-producing Citrobacter freundii recovered from a dog suffering from kennel cough in.MATERIALS AND METHODS: The isolate was recovered from a two-year-old dog suffering from severe respiratory manifestations. Phenotypical-ly, the isolate was resistant to a wide range of an-timicrobial agents including, aztreonam, cipro-floxacin, levofloxacin, gentamicin, minocycline, piperacillin, sulfamethoxazole-trimethoprim, and tobramycin. PCR and sequencing confirmed that the isolate harbors multiple antibiotic resistance genes, such as bla(CMY-48) and bla(TEM-1B) which mediate resistance to B-lactams, and qnrB6 which mediate resistance to quinolone antibiotics.RESULTS: Multilocus sequence typing con-firmed that the isolate belongs to ST163. Due to the unique characteristics of this patho-gen, the whole genome sequencing was per-formed. In addition to the previously confirmed antibiotic resistance genes by PCR, the isolate was also confirmed to harbor other resistance genes which mediate resistance to aminoglyco-side (aac(3)-IId, aac(6')-Ib-cr, aadA16, aph(3'')-Ib, and aph(6)-Id), macrolides [mph(A)), pheni-cols (floR), rifampicin (ARR-3), sulphonamides (sul1 and sul2), trimethoprim (dfrA27), and tetra-cycline (tet(A) and tet(B)].CONCLUSIONS: The results presented in this study confirm that pets are possible sources of highly pathogenic multidrug-resistant microbes with unique genetic characteristics taking in-to consideration the high potential for their dis-semination to humans, which can undoubtedly develop of severe infections in these hosts.

Automated summary

This study examined a multidrug-resistant Citrobacter freundii recovered from a dog with kennel cough, and found that it harbored multiple antibiotic resistance genes, which could potentially lead to severe infections in humans.