Purpose: The aim of this study was to gain a deeper genomics and bioinformatics understanding of diversification of accessory genetic elements (AGEs) in Providencia .
Methods: Herein, the complete genome sequences of five Providencia isolates from China were determined, and seven AGEs were identified from the chromosomes. Detailed genetic dissection and sequence comparison were applied to these seven AGEs, together with additional 10 chromosomal ones from GenBank (nine of them came from Providencia ).
Results: These 17 AGEs were divided into four groups: Tn 6512 and its six derivatives, Tn 6872 and its two derivatives, Tn 6875 and its one derivative, and Tn 7 and its four derivatives. These AGEs display high-level diversification in modular structures that had complex mosaic natures, and particularly different multidrug resistance (MDR) regions were presented in these AGEs. At least 52 drug resistance genes, involved in resistance to 15 different categories of antimicrobials and heavy metal, were found in 15 of these 17 AGEs.
Conclusion: Integration of these AGEs into the Providencia chromosomes would contribute to the accumulation and distribution of drug resistance genes and enhance the ability of Providencia isolates to survive under drug selection pressure.
Keywords: Providencia , integrative and conjugative elements, integrative and mobilizable elements, unit transposons, multidrug resistance