Double Detection: The Case for Including Wound Testing in UTI Labs

Urinary tract infections (UTIs) and wound infections are significant and rising global public health concerns. UTIs rank among the most common infections worldwide, with an estimated 404.61 million cases, 236,790 deaths, and 520,200 disability-adjusted life years (DALYs) in 2019 [1]. The global burden for wound infections may be even greater. A recent study in the U.S. found that 16% of Medicare beneficiaries (10.5 million) had at least one wound and that total Medicare spending to treat wounds could now be as high as $29.7 billion [2]. Chronic wounds are prone to infection, which can lead to even more dire medical consequences, particularly for the diabetic and geriatric populations most often afflicted. For example, 50%–60% of diabetic foot ulcers become infected, and approximately 20% of moderate or severe diabetic foot infections result in lower extremity amputations [3].

The challenges associated with UTI and wound infections are expected to climb significantly, spurred on by the world’s aging population, the increasing prevalence of diabetes and obesity, and the mounting threat of antimicrobial resistance [4]. That is why new strategies are needed to not only improve how infections like these are diagnosed, but also to better characterize pathogens, their resistance, and their role in disease.

Advanced molecular testing to improve how wound infections are diagnosed

While many complicated UTIs (cUTIs) are now addressed with a combination of culture and molecular tests, if a wound is suspected of being infected, it is typically only tested using conventional culture methods. This approach can have limitations, however. For instance, conventional culture testing for slow-growing anaerobic bacteria can take three days or more for results and even then, a culture test might miss low levels of a pathogen in the sample. In addition, culture testing is subjective, and that can be especially problematic for wounds since wound pathogens can be difficult to culture and identify. Put all of this together and it’s easy to see how a culture-only testing approach for wounds can be inaccurate, leading to misdiagnosis and unnecessary and/or inappropriate antibiotic prescribing.

The advent of advanced molecular testing is improving how wound infections are diagnosed. Compared to conventional culture tests, PCR-based molecular testing for wounds offers:

Faster time-to-results. Molecular testing for wounds can take less than two hours from extracted sample to results.
Higher sensitivity and specificity. Molecular diagnostics, such as nucleic acid amplification tests (NAATs) like real-time PCR, are not subjective and can detect pathogens even when the concentration in a sample is low. In addition, because they specifically target and amplify genetic material, NAATs have been shown to be highly specific. The combination of higher sensitivity and specificity can aid in pathogen identification, even for challenging anaerobic and polymicrobial wound infections, leading to more accurate diagnosis and treatment.
Better diagnostic information. Molecular tests can be used to determine specific pathogenic strains and other details that are useful for tracking the spread of infections and guiding public health measures.

These benefits mean molecular testing for wounds can not only support provider diagnoses in both in- and outpatient settings, but also improve both patient outcomes and antibiotic stewardship—by quickly and accurately ruling infections in or out, and helping to ensure each infection receives prompt, appropriate treatment.

Mixing UTI and wound application panels to optimize lab workflows

UTIs and wound infections have several overlapping pathogen and antimicrobial resistance (AMR) targets. That means another benefit of PCR testing for wounds is that samples can be added to application panels already in use for UTIs. In other words, the assay plate can be filled for different applications at the same time instead of having to run partially loaded plates when there is not sufficient volume for a single application. This strategy can maximize lab efficiency and margins, even with different sample types.

Table. Example of pathogen and AMR gene targets that overlap for UTI and wound applications.

Pathogen targets

Acinetobacter baumannii, Candida albicans, Candida auris, Candida glabrata, Candida parapsilosis, Citrobacter freundii , Citrobacter koseri, Enterobacter cloacae, Enterococcus faecalis, Enterococcus faecium, Escherichia coli, Klebsiella oxytoca, Klebsiella pneumoniae, Morganella morganii, Proteus mirabilis, Proteus vulgaris, Providencia stuartii, Pseudomonas aeruginosa, Serratia marcescens, Staphylococcus aureus, Staphylococcus epidermidis, Staphylococcus haemolyticus, Staphylococcus lugdunensis, Streptococcus agalactiae

AMR gene targets

blaACC, blaACT, blaCMY, blaCTX-M, blaDHA, blaFOX, blaGES, blaIMP, blaKPC, blaLAT, blaMOX, blaOXA, blaPER, blaSHV, blaTEM, blaVEB, blaVIM, dfrA1, dfrA5, mecA, qnrA, qnrB, qnrS, sul1, sul2, tetM, tetS, vanA, vanB

Mixing UTI and wound application panels to improve patient care

A small-scale pilot study found that bacterial species found in urine of nursing home residents would also be found within open wounds in the same patient at the same point in time [5].

Further investigation is needed to fully understand the relationship and clinical implications of this result; however, it suggests that mixing application panels could be a proactive step in wound care management and the prevention of wound contamination.

Molecular testing can improve diagnosis, enhance outcomes, and help mitigate the threat of antimicrobial resistance

Wound infections and UTIs are rising global public health concerns. Using well-designed, clinically relevant bacterial and fungal panels can improve how these infections are diagnosed, enhance outcomes, and help limit unnecessary and inappropriate antibiotic prescribing.

Learn more about the impact of PCR-based molecular testing on clinical outcomes at thermofisher.com/here.

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