Abstract
Listeria monocytogenes is a foodborne pathogen that is widely distributed in nature, having been isolated from a variety of sources such as soil, water, plant matter, and animals. In addition, L. monocytogenes is often detected in the regular sampling of food and food processing environments. The most common method for detecting L. monocytogenes is the use of selective enrichments. Both lithium chloride and esculin, in combination with ferric ammonium citrate, are utilized in several of the most commonly-employed selective enrichment schemes for L. monocytogenes. Here we report that transposon-based inactivation of lmo1930, one of the genes in the menaquinone biosynthesis operon, via transposon mutagenesis severely impaired the ability of L. monocytogenes to grow in the presence of lithium chloride or hydrolyze esculin, and conferred reduced growth and colony size. All phenotypes were restored upon genetic complementation. Thus, strains of L. monocytogenes with mutations leading to inactivation of lmo1930 may evade many commonly-used selective enrichment protocols employed in the detection of L. monocytogenes.
Highlights
Listeria monocytogenes is found ubiquitously in nature and is a facultative intracellular pathogen, capable of causing severe disease and death in susceptible individuals [1,2]
The ability to hydrolyze esculin has been observed in diverse microorganisms and esculin has been incorporated as a differential-selective agent into several selective enrichment protocols for L. monocytogenes
Esculin hydrolysis in the presence of ferric ammonium citrate results in a black precipitate that is detected with the naked eye in either liquid or solid media, allowing detection of putative L. monocytogenes or other Listeria spp. on agar media such as Modified Oxford (MOX) [7,8]
Summary
Listeria monocytogenes is found ubiquitously in nature and is a facultative intracellular pathogen, capable of causing severe disease and death in susceptible individuals [1,2]. For these reasons, the rapid and reliable detection of L. monocytogenes is a key factor in the surveillance of this pathogen. If esculin hydrolysis or lithium chloride tolerance were compromised, L. monocytogenes and other Listeria spp. would be undetectable in many of the currently employed enrichment protocols, with potentially important food safety and public health implications. We employed transposon mutagenesis and genetic complementation to identify and characterize a gene essential in esculin hydrolysis in L. monocytogenes strain 2010L-1723, implicated in an outbreak of listeriosis via contaminated celery
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
