Abstract
Escherichia coli is a bacterial species found ubiquitously in the intestinal flora of animals, although pathogenic variants cause major public health problems. Aptamers are short oligonucleotides that bind to targets with high affinity and specificity, and have great potential for use in diagnostics and therapy. We used cell-based Systematic Evolution of Ligands by EXponential enrichment (cell-SELEX) to isolate four single stranded DNA (ssDNA) aptamers that bind strongly to E. coli cells (ATCC generic strain 25922), with Kd values in the nanomolar range. Fluorescently labeled aptamers label the surface of E. coli cells, as viewed by fluorescent microscopy. Specificity tests with twelve different bacterial species showed that one of the aptamers–called P12-31—is highly specific for E. coli. Importantly, this aptamer binds to Meningitis/sepsis associated E. coli (MNEC) clinical isolates, and is the first aptamer described with potential for use in the diagnosis of MNEC-borne pathologies.
Highlights
Escherichia coli is a Gram-negative bacterial species found ubiquitously in the intestinal gut flora of animals, including humans, and can survive and multiply in abiotic environments
We chose to use in our experiments the E. coli strain ATCC 25922, because this strain—originally isolated from a human clinical sample (Seattle, WA, USA; 1946)—is commonly used for quality control of antibody sensitivity assays
We evaluated the specificity of aptamers to E. coli by comparing the ability of these molecules to bind to 12 different bacterial species, including nine Gram-negative and three Gram-positive strains (Fig 5)
Summary
Escherichia coli is a Gram-negative bacterial species found ubiquitously in the intestinal gut flora of animals, including humans, and can survive and multiply in abiotic environments. It colonizes the infant gastro-intestinal tract within hours after birth, with lifelong benefits to the host [1]. Used E. coli detection methods normally require an enrichment step of bacterial culturing, which usually takes 2 to 3 days to yield results. This method does not permit rapid bacterial detection, which requires bacterial identification either by the polymerase chain
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