A new technology emerges
Developed by Shariat in 2015, CRISPR-SeroSeq enables researchers to analyze all the types of salmonella present in a given sample. Traditional methods only examine one or two colonies of bacteria, potentially missing some strains of salmonella altogether. Shariat's technology identifies molecular signatures in salmonella's CRISPR regions, a specialized part of the bacteria's DNA. It also helps researchers identify which strains of the bacteria are most abundant.
In the current study, Shariat and colleagues found multiple salmonella strains in cattle feces before the animals were treated with the antibiotic tetracycline. After treatment, several of the dominant salmonella strains in the sample were wiped out, allowing Salmonella Reading to flourish.
Traditional culturing methods missed the antibiotic-resistant strain in the original samples. It was only once the antibiotic eliminated the more abundant strains that conventional methods were able to detect Salmonella Reading in the samples.
"This suggests that traditional tests have underestimated the amount of antibiotic-resistant bacteria in the past," said Shariat, an assistant professor of population health in the College of Veterinary Medicine.
But CRISPR-SeroSeq is a much more sensitive tool. It flagged the Salmonella Reading before antibiotic treatment.
"We need to know the antimicrobial resistance profiles of the bacteria that are present in animals," Shariat said. "That knowledge could make us change our choice of the type of antibiotic we use to treat ill animals. It can also help us select the best antibiotic for people who get sick from eating contaminated meat."
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