Antibiotic Resistance Protocols (Methods in Molecular Biology)

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Stephen H. Gillespie (ed.), Antibiotic Resistance Protocols, Methods in Molecular Biology, vol. 1736,
https://doi.org/10.1007/978-1-4939-7638-6_10, © Springer Science+Business Media, LLC 2018

Chapter 10

Selection of ESBL-Producing E. coli in a Mouse Intestinal

Colonization Model

Frederik Boëtius Hertz, Karen Leth Nielsen, and Niels Frimodt-Møller

Abstract

Asymptomatic human carriage of antimicrobially drug-resistant pathogens prior to infection is increasing
worldwide. Further investigation into the role of this fecal reservoir is important for combatting the
increasing antimicrobial resistance problems. Additionally, the damage on the intestinal microflora due to
antimicrobial treatment is still not fully understood. Animal models are powerful tools to investigate bacte-
rial colonization subsequent to antibiotic treatment. In this chapter we present a mouse-intestinal coloni-
zation model designed to investigate how antibiotics select for an ESBL-producing E. coli isolate. The
model can be used to study how antibiotics with varying effect on the intestinal flora promote the estab-
lishment of the multidrug-resistant E. coli. Colonization is successfully investigated by sampling and cul-
turing stool during the days following administration of antibiotics. Following culturing, a precise
identification of the bacterial strain found in mice feces is applied to ensure that the isolate found is in fact
identical to the strain used for inoculation. For this purpose random amplified of polymorphic DNA
(RAPD) PCR specifically developed for E. coli is applied. This method allows us to distinguish E. coli with
more than 99.95% genome similarity using a duplex PCR method.

Key words Extended-spectrum beta-lactamase (ESBL), E. coli, Mouse model, Intestinal coloniza-

tion, RAPD, Typing, Selection, Antibiotics, Antibiotic resistance

1 Introduction

A major source for antimicrobial resistance in E. coli is plasmid-

borne Extended-Spectrum β-Lactamases (ESBL) [ 1 – 4 ]. The

majority of ESBLs belong to the four large families of SHV, TEM,

CTX-M and OXA [ 2 , 5 ]. ESBL CTX-M enzymes were first

described in Germany in 1989, but rapidly it became the dominat-

ing ESBL genotype during the early 2000s [ 6 ]. The rapid world-

wide dissemination has been known as the “CTX-M pandemic”

and the dominance of CTX-M types has largely been caused by

dissemination of E. coli lineages [ 7 – 9 ]. Now, community-onset

ESBL infections have become an important public health issue, as

community-onset infections caused by ESBL-producing E. coli pri-

marily are caused by CTX-M ESBLs [ 6 , 9 , 10 ].