Abstract:

In this study, we established a highly effective method to screen multiple-drug resistant (MDR) bacteria carrying
the integrative and conjugative elements (ICEs). Five Proteus vulgaris strains harboring SXT/R391 family of ICEs, isolated
from aquatic products in Shanghai, China, were obtained using the new method. Antimicrobial activity and heavy metal
susceptibility of the P. vulgaris strains were examined using standard Kirby-Bauer disk diffusion method and dilution
susceptibility tests according to the Clinical and Laboratory Standards Institute (CLSI, USA, 2012 Edition), all showing
distinct resistance to ten antimicrobial agents belonging to six drug classes tested. In addition, a wide heavy metal resistance
profile was also detected, displaying strong resistance to Cd, Cu, Zn and Hg. The conjugation experiments demonstrated the
capacities of active self-transmission of the SXT/R391-like ICEs between P. vulgaris and Escherichia coli MG1655 strains.
Our results will facilitate further research on collaborative selection mechanism of environmental antibiotics and heavy
metals, and early warning in prevalence of novel MDR bacteria or “super bacteria”.

Key words: integrative and conjugative elements (ICEs), SXT/R391 family, multiple-drug resistance, heavy metal tolerance