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Trained dogs detect bacteria from urine samples
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Dogs trained to identify bacteriuria by smell appeared to accurately distinguish between urinary samples with and without various pathogens, according to a recent study.
“With severe [urinary tract] infection, prompt treatment minimizes morbidity and mortality,” the researchers wrote. “In many patients, early diagnosis is difficult to achieve and urine culture results cause further delays, taking up to 48 hours. Trained dogs may present a novel method for early UTI detection, potentially relevant to people with neurological impairment, hospitalized patients and the elderly.”
Figure 1. Sam, pictured above, is one of five dogs trained by the researchers to detect the presence of E. coli and other bacteria in urine.
Source: Ron Dahlquist Photography
Bacteria species, concentration does not affect accuracy
To test this approach, the researchers collected urine samples from adult patients cultured at a Hawaiian laboratory. Samples were obtained at either a hospital or a doctor’s office, and were considered to be bacterial culture-positive if more than 100,000 colony-forming units were detected per mL. Over the course of 8 weeks, five dogs were trained to identify positive samples contained in boxes, with blinded runs initiated and recorded once the animals’ accuracy exceeded 90%. The dogs were primarily trained to detect samples positive for Escherichia coli, but secondary tests — where samples were diluted with distilled water to 1% and 0.1% concentration or the bacteria were replaced with Klebsiella, Enterococcus and Staphylococcus aureus samples — also were performed.
Samples from 687 individuals aged 3 months to 92 years were collected for the study. Approximately two-thirds of these were considered negative, and the majority of positive cultures contained E. coli.
The dogs detected positive E. coli samples with 99.6% sensitivity and 91.5% specificity, the researchers wrote. Dilution at either concentration did not affect accuracy, and similar results were observed for the other three types of bacteria. Among the dogs, individual sensitivity ranged from 99% to 100%, while specificity ranged from 90.1% to 94.7%. In addition, the researchers noted an anecdotal incident 1 month after study completion where a dog spontaneously alerted a visitor to the training center of an unsuspected UTI.
“The results suggest that dogs may be taught to accurately detect bacterial infections at an early stage when less aggressive therapy is needed,” they wrote. “In our dilution experiments, we observed that the dogs were able to detect very low bacterial counts. Detecting negative cultures may also be clinically useful and help avoid overuse of antibiotic therapy.”
Dog identifies GI infection from samples, patients
Previous data also have suggested trained dogs may be able to identify a patient’s Clostridium difficile infection at an early stage.
In a 2012 study published in the British Medical Journal, a beagle was trained to detect C. difficile in stool samples as well as in patients. Consecutive patients from two hospitals who tested positive for C. difficile were included in this study, with each of the 30 patients having nine matched controls without C. difficile. The dog also was presented with 100 stool samples; half had C. difficile.
The dog correctly identified 25 of 30 cases and 265 of the 270 controls, translating to 83% sensitivity and 95% specificity. For the stool samples, the dog correctly identified all 50 of the positive samples (100% sensitivity) and 47 of 50 of the negative samples (100% specificity, if interpreting the three inconclusive responses as negative responses).
“In this proof of principle study, a trained dog was able to detect C. difficile with high estimated sensitivity and specificity, both in stool samples and in infected patients, in a hospital setting,” the researchers wrote. “This finding could have great potential for screening for C. difficile infection in health care facilities and thus contribute to the control and prevention of outbreaks.” – by Dave Muoio
Disclosure: The researchers report no relevant financial disclosures.
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