Transcriptome changes and polymyxin resistance of acid-adapted Escherichia coli O157:H7 ATCC 43889

Daekeun Hwang,Hyun Jung Kim,Seung Min Kim

doi:10.1186/s13099-020-00390-5

Abstract

BackgroundAcid treatment is commonly used for controlling or killing pathogenic microorganisms on medical devices and environments; however, inadequate acid treatment may cause acid tolerance response (ATR) and offer cross-protection against environmental stresses, including antimicrobials. This study aimed to characterise an Escherichia coli strain that can survive in the acidic gastrointestinal environment.ResultsWe developed an acid-tolerant E. coli O157:H7 ATCC 43889 (ATCC 43889) strain that can survive at pH 2.75 via cell adaptation in low pH conditions. We also performed RNA sequencing and qRT-PCR to compare differentially expressed transcripts between acid-adapted and non-adapted cells. Genes related to stress resistance, including kdpA and bshA were upregulated in the acid-adapted ATCC 43889 strain. Furthermore, the polymyxin resistance gene arnA was upregulated in the acid-adapted cells, and resistance against polymyxin B and colistin (polymyxin E) was observed. As polymyxins are important antibiotics, effective against multidrug-resistant gram-negative bacterial infections, the emergence of polymyxin resistance in acid-adapted E. coli is a serious public health concern.ConclusionThe transcriptomic and phenotypic changes analysed in this study during the adaptation of E. coli to acid environments can provide useful information for developing intervention technologies and mitigating the risk associated with the emergence and spread of antimicrobial resistance.

Highlights

Acid treatment is commonly used for controlling or killing pathogenic microorganisms on medical devices and environments; inadequate acid treatment may cause acid tolerance response (ATR) and offer cross-protection against environmental stresses, including antimicrobials
Acid treatment is commonly used for the control or elimination of pathogenic microorganisms on the surface of medical devices or in environments, as well as in treatment of wastewater and food, as most microorganisms, including pathogenic bacteria, grow optimally at a pH range of 5–9 [1,2,3]
Improper or sub-lethal application of acids can induce acid tolerance response (ATR), which contributes to the survival of infectious foodborne pathogens such as enterohaemorrhagic Escherichia coli (EHEC), Salmonella, Shigella spp., and Listeria monocytogenes in acidic environments, including the human

Summary

Introduction

Acid treatment is commonly used for controlling or killing pathogenic microorganisms on medical devices and environments; inadequate acid treatment may cause acid tolerance response (ATR) and offer cross-protection against environmental stresses, including antimicrobials. In pharmaceutical and medical environments, hypochlorous acid is used as an antimicrobial agent against a wide range of improper or sub-lethal application of acids can induce acid tolerance response (ATR), which contributes to the survival of infectious foodborne pathogens such as enterohaemorrhagic Escherichia coli (EHEC), Salmonella, Shigella spp., and Listeria monocytogenes in acidic environments, including the human. 22–33% of commensal E. coli food isolates survived in gastric pH conditions of the Korean population, and the antimicrobial resistance gene can be transferred from the surviving cells to resident microbiota in the human gut [8]. ATR can affect the ability of pathogens to bind to surfaces and form biofilms, by increasing cell-surface hydrophobicity, which correlates with pathogenic adhesion to various surfaces in medical and food environments [10, 11]

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