Pooled Antibiotic Susceptibility of Urinary Tract Infections
Margo Lee, Ph.D.
Urinary tract infections (UTIs) are common infections that are caused by bacteria that inhabit the kidneys, bladder, ureter, or urethra.1 These infections effect more than 150 million people globally per year and account for 25% of all infections in the elderly.2,3 Traditionally, they are identified by standard urine culture methodology which grow pathogens on an agar plate. Frequently if there are two or more organisms in the urine, the bacteria may not be able to be fully identified in a standard culture setting and may need to be identified separately.4 Bacteria that grow in culture separately versus together can modify their response to specific antibiotics.5 Standard culture may identify the antibiotic susceptibility of an individual pathogen but will not distinguish a polymicrobial response by multiple bacteria in an infection and as a result, does not provide an accurate prediction of what happens in the body.6
Polymicrobial infections are common in half of positive UTI cases.7 Bacteria from similar or different species (including gram positive and gram negative) in polymicrobial samples interact with each other to collectively change their susceptibility to antibiotics.8,9 These organisms communicate with each other and will often share resistance by transferring plasmid DNA to surrounding bacteria that are sensitive to an antibiotic.10,11 Through these bacterial interactions, pathogens can collectively modify their response in the presence of an antibiotic and increase or decrease antibiotic resistance for their survival. It is essential when determining susceptibility of a polymicrobial infection that these bacteria are examined comprehensively, not individually, to capture all these crucial bacterial interactions.
Pooled Antibiotic Susceptibility Testing (P-ASTTM) is a unique feature of Guidance® UTI that identifies the susceptibility of the comprehensive pool of pathogens in urine. By testing bacterial organisms together instead of each organism individually, P-ASTTM accounts for the essential interactions between bacteria in polymicrobial infections which occur as much as 50% of the time and directly impact susceptibility to antibiotics. P-ASTTM evaluates the collective expression of bacteria in an infection in the body, yielding valuable insight to the response of all the bacteria contained in a patient sample.12
Guidance® UTI is a precision diagnostic tool that evaluates the specimen’s pooled antibiotic susceptibility to 19 commonly prescribed antibiotics for UTI infections. This information helps guide antibiotic selection by identifying antibiotic susceptibility of all the pathogens and their interactions in the infection before treatment begins. By having this knowledge prior to treatment, providers have vital phenotypic guidance to help them with appropriate medication selection, lessen empiric approaches, and support patient antibiotic stewardship.
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6 Baunoch D, Luke N, Wang D, Vollstedt A, Zhao X, Ko DSC, Huang S, Cacdac P, Sirls LT. Concordance Between Antibiotic Resistance Genes and Susceptibility in Symptomatic Urinary Tract Infections. Infect Drug Resist. 2021 Aug 19;14:3275-3286. doi:10.2147/IDR.S323095. PMID:34447256; PMCID: PMC8382965.
7 Vollstedt, A & Baunoch, D & Wolfe, Alan & Luke, N & Wojno, K & Campbell, Meghan. (2020). Bacterial Interactions as Detected by Pooled Antibiotic Susceptibility Testing (P-AST) in Polymicrobial Urine Specimens. 101. 10.29011/JSU-101.100001.
8 Baunoch D, Luke N, Wang D, Vollstedt A, Zhao X, Ko DSC, Huang S, Cacdac P, Sirls LT. Concordance Between Antibiotic Resistance Genes and Susceptibility in Symptomatic Urinary Tract Infections. Infect Drug Resist. 2021 Aug 19;14:3275-3286. doi:10.2147/IDR.S323095. PMID:34447256; PMCID: PMC8382965.
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polymicrobial infections. Proc Natl Acad Sci U S A. 2017 Oct 3;114(40):10666-10671. doi: 10.1073/pnas.1713372114. Epub 2017 Sep 18. PMID:28923953; PMCID: PMC5635929.
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