ASM Microbe 2018

Headed to ASM Microbe 2018 this weekend?

Be sure to check out Dave’s talk on Sunday, June 10th ( B308-B309 and Lounge and Learn 3, Building B, Lobby) in the “What Makes a Commensal?” section.

His talk, entitled “Variation of Resident Escherichia coli in the Gastrointestinal Tract” will cover recent work in the lab investigating resident E. coli in Tanzanian children as well as the responses of the resident E. coli population to challenge with ETEC and antibiotics in a challenge trial (paper going public soon).

USA Science and Engineering Festival

If you are in the DC area April 7 and 8, be sure to check out the USA Science and Engineering Festival, a huge STEM education and career expo aimed and kids and families. While you are there, be sure to stop by the American Society for Microbiology booth on Sunday to say hi to Rasko lab postdoc Taylor, who will be there helping out (and bring questions for her for the Sunday afternoon Meet the Scientist session).

Goodbye BioPark building!

Lab work is slowing down this week as the Rasko lab (along with the rest of the Institute for Genome Sciences) prepares its move to the new building on campus. Preparing for a move is always a pain, but is going smoothly thanks to Jane’s expertise. We are looking forward to getting going again in the new space. Come visit us in our new location on the second floor of HSF III at the University of Maryland Baltimore (but maybe wait until all the boxes are unpacked)!

So many boxes!

Jane packing up lab supplies

How did this all fit in here?

New year, new digs!

In case you missed it: Transcriptional variation in EPEC

The latest paper by Tracy Hazen, “Transcriptional Variation of Diverse Enteropathogenic Escherichia coli Isolates under Virulence-Inducing Conditions”, confirms that the genomic diversity that has been recently identified among the EPEC pathovars corresponds with differences in their global transcription. This study expands upon previous work (including her 2015 paper “RNA-seq analysis of isolate- and growth phase-specific differences in the global transcriptomes of enterophatogenic Escherichia coli”), that showed that even well-studied EPEC strains exhibit isolate -, medium-, and growth phase-specific differences in their global transcription, including the expression of key virulence factors. The current study, by using EPEC isolates from more recent outbreaks and including those from three E. coli phylogroups, explores the transcriptional and biological diversity of a modern, disease-causing pathogen. Nine EPEC isolates from eight phylogenomic lineages and three phylogroups were selected for unbiased global RNA-seq following growth under a single set of virulence gene-inducing conditions. The results showed both lineage- and isolate-specific transcriptional profiles. This previously unexplored diversity within a single E. coli pathotype may contribute to isolate-specific variability in EPEC clinical presentation

Editor’s pick in mSystems!

Congratulations to Tracy Hazen for her paper “Transcriptional Variation of Diverse Enteropathogenic Escherichia coli Isolates under Virulence-Inducing Conditions” getting selected as the Editor’s Choice article.  See the editor’s summary of it here.

Welcome Rodrigo!

The Rasko Lab would like to welcome Rodrigo Hernandes, a scientist visiting the lab from Universidade Estadual Paulista in Sao Paulo, Brazil.  He will be with us for six months working on a project studying atypical EPEC.

A gene mosaic plasmid confers resistance in EPEC

Enteropathogenic E. coli (EPEC) is one of the leading causes of lethal diarrheal disease among infants in developing countries. As one of the attaching and effacing E. coli (AEEC, along with enterohemorrhagic E. coli or EHEC), EPEC is characterized, in part, by the locus of enterocyte effacement (LEE) pathogenicity island. This group of chromosomally-encoded genes are required for EPEC to cause disease and includes the intimin protein, used in adherence, and a type III secretion system that delivers effector proteins in to the host cell. Plasmid-encoded genes supplement the EPEC arsenal and virulence plasmids, such as the EPEC adherence factor (EAF) virulence plasmid, have been the focus of several studies. However, despite growing concerns about antibiotic resistance in human-associated bacteria, little is known about the diversity and gene content of resistance plasmids in EPEC and related pathogens.

A recent paper by Tracy Hazen and others seeks to correct this gap in knowledge. In it, she describes the sequence of the 90,229 bp resistance plasmid (called pB171_90) isolated from EPEC strain B171. This plasmid contains genes that confer resistance to antibiotics such as spectinomycin-streptomycin, tetracycline, and sulfonamides, as well as narrow spectrum mercury resistance. By comparing the gene content of the pB171_90 plasmid to genes in other E. coli, Tracy and colleagues found that the pB171_90 plasmid genes differed in their distributions. This mosaic plasmid combines genes common to AEEC strains with antibiotic resistance genes that are more frequently associated with non-AEEC strains. Genes found in this plasmid were more widespread than expected. Several genes thought to be unique to EPEC B171 were found throughout E. coli as well as other enteric bacteria. The high sequence similarity between this plasmid and those in other strains suggests that resistance plasmids have been exchanged between EPEC and other gastrointestinal pathogens EHEC O157:H7 and S. dysenteriae. This study highlights the need for sequence-based characterization of resistance plasmids to characterize the complex compositions and distributions of resistance plasmids in pathogenic bacteria.

Hazen, T. H. et al. (2017) Characterization of a large antibiotic resistance plasmid found in enteropathogenic Escherichia coli strain B171 and its relatedness to plasmids of diverse E. coli and Shigella. Antimicrob Agents Chemother doi:10.1128/AAC.00995-17

Using genome screening to identify new ETEC virulence factors

Enterotoxigenic E. coli (ETEC) causes watery diarrhea with the help of a group of adhesins known as colonization factors (CFs).  These CFs enable the bacteria to attach the intestinal cells, where they can colonize the intestine and produce the toxins that result in diarrhea.  As external structures essential to the development of disease, CFs have frequently been selected as candidate vaccine targets.  However, as many as 50% of investigated ETEC strains are lacking the any of the 22 known colonization factors, suggesting the presence of unknown CFs, and making it difficult to develop effective vaccine formulations.

A recent paper, with contributions by Dave Rasko, used bioinformatics techniques to identify previously undescribed CF loci.  Large-Scale BLAST Score Ratio (LS-BSR) analyses allowed for the identification of CF homologs in ETEC strains that were thought to be CF-negative based on previous methods.  These homologs, some of which belong to pili classes previously unknown in ETEC virulence, increase the understanding of the structural diversity of ETEC adhesins.  Further characterization of these adhesins may determine their usefulness as vaccine targets.

Del Canto, F. et al. (2016) Chaperone-Usher Pili Loci of Colonization Factor-Negative Human Enterotoxigenic Escherichia coli. Front Cell Infect Microbiol 6:200. doi:  10.3389/fcimb.2016.00200

ASM Microbe 2017

The Rasko Lab will be at ASM Microbe in New Orleans, LA!

Taylor will be presenting the following posters and rapid fire talks:

 Omics approach to enterotoxigenic E. coli and human gut microbiome
Rapid Fire Talk:  Friday 5:40-5:45 pm
Poster:  Saturday 12:15-2:15 pm


Responses of human gut E. coli population to pathogen and antibiotic disturbances
Rapid Fire Talk:  Friday 6:15-6:20 pm
Poster:  Saturday 12:15-2:15 pm


We’ll see you there!