Abstracts Book - IMRC 2018

• SWMC-O034
IS NANOSILVER BETTER THAN TRICLOSAN AS BIOCIDE?
Chengdong Zhang 1,2 , Jing Li 2
1 Beijing Normal University, School of Environmental Science, China. 2 Nankai University, College
of Environmental Science and Engineering, China.
Triclosan is a well-known biocide, which has been banned due to the potential
for co-selection on antibiotic resistance. As a new, promising biocide, silver
nanoparticle (AgNP) has been considered as a potential replacement for
triclosan. However, every few information is available about bacteria’s adaptive
response towards AgNP after low dose and chronic exposure and how such
adaptation could result in decreased susceptibility to one or more antibiotics.
Our results showed that E Coli decreased the susceptibility to AgNP after 100
generations of exposure as evidenced by the change of minimal inhibition
concentration (MIC) 1.3 to 3.2 mg/L. Interestingly, the MIC of E Coli to triclosan
increased dramatically 0.03 to 0.58 mg/L during the same period of exposure.
Transcriptomic and genomic analysis revealed that the adaptive mechanism to
triclosan involved in fatty acid synthesis, thus altering membrane permeability.
Nevertheless, the development of reduced susceptibility to AgNP was
associated with high mutation plus metabolic activity. As regarding to the coselection
on antibiotics, although the adaptive mechanisms are dissimilar, the
modifications of susceptibility to penicillin, kanamycin and ciprofloxacin were
similar. Particularly, AgNP-adapted E Coli showed selective resistance to
manganese ion, which possibly influence intracellular antioxidant activity.
Together, this outcome will allow us to address question concerning evolution
mechanism of bacteria towards AgNP, which also poses an important question
on the sustained use of AgNPs as “miracle” biocide.
Acknowledgment:
This work was supported under grants the National Natural Science Foundation
of China (grant number: 2177777) and the “973” program (grant number:
2014CB932000).
Keywords: triclosan, silver nanoparticle, adaptive response
Presenting authors email: zhangchengdong@nankai.edu.cn