Genetic characterization, mechanisms and dissemination risk of antibiotic resistance of multidrug-resistant Rothia nasimurium.

Rothia nasimurium is part of the commensal flora of humans and other animals and has recently received increasing attention for its multidrug-resistance (MDR) and pathogenicity. Currently, no systematic reports characterize the genetics, mechanisms, and dissemination risks of antibiotic resistance in MDR R. nasimurium. Here, we present the first report outlining a MDR strain of R. nasimurium, E1706032a, isolated from ducks exhibiting clinical sickness. Phylogenetic analysis indicates that E1706032a mostly likely originated in the commensal bacteria of Amazona aestiva in Florida. E1706032a is resistant to beta-lactams, aminoglycosides, macrolides, sulfonamides, fluoroquinolones, rifamycins, tetracyclines, lincosamides and chloramphenicol. Genetic sequences related to drug resistance were detected, including resistance genes (aac(6')-Ib, ant(3″)-Ia, sul1, dfrA7, erm(X)), efflux pumps (tetZ, qacEΔ1, cmx, phosphate ABC transporter ATP-binding protein), and resistance-related proteins (hydrolase of the metallo-beta-lactamase (MBLs), mycinamicin resistance protein (myrA), DNA-directed RNA polymerase subunit beta (rpoB) variants, etc). E1706032a carries an IS481-like element, IS5564 and IS6-like elements, and IS6100 along with several novel transposases of the IS3 family. E1706032a also carries the class 1 integron gene IntI1, which is downstream adjacent to the gene cassettes aac(6')-Ib, tetZ, dfrA27, ant(3″)-Ia, qacEΔ1, sul1, cmx and upstream adjacent to gene tnpA of IS6100. Genetic analysis suggests that E1706032a carries wide antibiotic resistance and dissemination potential through movable elements and thus has the potential to cause difficult-to-treat infections in animals and humans. The dissemination of E1706032a from parrots in Florida to ducks in eastern China indicates a cross-regional public health infection risk that should be evaluated for risk of global spreading.