Restrictive Streptomycin Resistance Mutations Decrease the Formation of Attaching and Effacing Lesions in Escherichia coli O157:H7 Strains

Abstract

dStreptomycin binds to the bacterial ribosome and disrupts protein synthesis by promoting misreading of mRNA. Restrictive mutations on the ribosomal subunit protein S12 confer a streptomycin resistance (Str r ) phenotype and concomitantly increase the accuracy of the decoding process and decrease the rate of translation. Spontaneous Str r mutants of Escherichia coli O157:H7 have been generated for in vivo studies to promote colonization and to provide a selective marker for this pathogen. The locus of enterocyte effacement (LEE) of E. coli O157:H7 encodes a type III secretion system (T3SS), which is required for attaching and effacing to the intestinal epithelium. In this study, we observed decreases in both the expression and secretion levels of the T3SS translocated proteins EspA and EspB in E. coli O157:H7 Str r restrictive mutants, which have K42T or K42I mutations in S12. However, mildly restrictive (K87R) and nonrestrictive (K42R) mutants showed slight or indistinguishable changes in EspA and EspB secretion. Adherence and actin staining assays indicated that restrictive mutations compromised the formation of attaching and effacing lesions in E. coli O157:H7. Therefore, we suggest that E. coli O157:H7 strains selected for Str r should be thoroughly characterized before in vivo and in vitro experiments that assay for LEE-directed phenotypes and that strains carrying nonrestrictive mutations such as K42R make better surrogates of wild-type strains than those carrying restrictive mutations.

Pathogenic and non-pathogenic Escherichia coli colonization and host inflammatory response in a defined microbiota mouse model

“…Therefore, streptomycin treatment is commonly used to suppress facultative anaerobes to allow E . coli to overcome colonization resistance in mice ( Chen et al, 2013 ; Leatham et al, 2009 ; Mohawk and O'Brien, 2011 ). The exact mechanism of reduction of colonization resistance after streptomycin administration is unclear, but elimination of microbe-microbe interactions and a streptomycin-induced inflammatory response to support growth of E .…”

“…A limitation of using spontaneous streptomycin-resistant E . coli strains is that they may have slight to significant decreases in colonization factor expression that could influence host-pathogen interactions ( Chen et al, 2013 ). In addition, streptomycin treatment alone leads to a modest increase in histopathological changes, making the intestine more irritable ( Spees et al, 2013 ).…”

“…coli to colonize ( Allen et al, 2006 ; Leatham et al, 2009 ; Lindgren et al, 1993 ). Streptomycin-treated mice have a variable microbiota and require generation of streptomycin-resistant E. coli mutants, which can affect expression of bacterial virulence factors ( Chen et al, 2013 ). Other studies have used germ-free mouse models to study E .…”

Ribosomal mutations affecting the translation of genes that use non‐optimal codons

“…Two common rpsL mutations in E. coli that confer STR R are the replacement of the amino acid lysine 42 with threonine (referred to as K42T) and the replacement of the amino acid lysine 87 with arginine (referred to as K87R) . While the K42T mutation also results in error‐restrictive ribosomes , the K87R mutation results in semi error‐restrictive ribosomes, with a translational error rate that is lower than that of wild‐type strain yet higher than error‐restrictive strains such as the K42T mutant . On the other hand, it was demonstrated that a single amino acid substitution in the E. coli rpsE gene of a highly conserved glycine to an aspartate at position 28 (referred to G28D), which produces SPEC R , also resulted in error‐prone ribosomes .…”

Broadscale phage therapy is unlikely to select for widespread evolution of bacterial resistance to virus infection

“…This is because chromosomal resistance mutations frequently occur as molecular changes in the targets of antibiotics, and these targets are generally highly conserved structures that are central to bacterial metabolism, for example, the ribosomes and nucleic acid polymerases ( Munita and Arias 2016 ). Changes in these target sites often come at a high cost by reducing bacterial growth rate ( Chen et al. 2013 ; Cohan, King, and Zawadzki 1994 ; Gagneux et al.…”