Effect a of struvite dissolution diet on naturally occurring struvite urolithiasis
While uroliths are a less common cause of urinary tract signs in cats in the UK compared to the USA, studies have suggested that 10–15% of urinary tract infection (UTI) cases in the UK are due to urolithiasis. This recent paper by Tefft et al (2021), published in the Journal of Feline Medicine and Surgery, looked at the efficacy of a new diet with low struvite relative supersaturation for dissolution of feline struvite uroliths.
Of itself this is not a new approach, with diets designed to dissolve struvite uroliths first being used in 1983, but this paper has value in terms of using simple diagnostic criteria (radiographic moderately opaque, round to discoid uroliths in urine with a pH ≥6.5) to justify starting a struvite dissolution diet, when faced with at least 50% of uroliths being calcium oxalate in cats. Based on these criteria, 12/19 cats screened were enrolled and owners were supplied with the test dry diet to feed their cats exclusively.
Interestingly, 10/12 cats were deemed to be overweight or obese with a median weight of 6.15 kg. Nine cats completed the study (withdrawals resulted from being fed other foods, an obstructive urolith and systemic unwellness) with all cases showing complete (n=8) or partial resolution (n=1). For 7/8 cats, where there was complete resolution, time to dissolution was between 14 and 28 days (cats were re-evaluated at 2-week intervals) and one cat's condition resolved by 70 days. The cat with partial resolution had a mixed stone with a calcium oxalate core.
This study suggests that with simple investigation in cats with urolithiasis, it is possible to make a decision with good levels of confidence on whether the urolith is struvite and that the majority of cases will have a rapid response to diet, without need for surgery.
Antimicrobial resistance in canine urine samples
The development of antimicrobial resistance is a key issue in One Health, as this threatens the control of diseases affecting both humans and animals. This study by Guzmán Ramos et al (2020), published in the Journal of Small Animal Practice, looked at the in vitro resistance patterns of Enterobacteriaceae (Gram negative bacteria including Escherichia coli, Proteus spp., Klebsiella pneumoniae and Salmonella spp.) over a period of 8 years (2010–17). Of the 3420 canine urine samples submitted by a veterinary teaching hospital, 22.5% had a positive culture with E.coli being the most common isolate. During this period, antimicrobial resistance increased from 5.2 to 35.6%, with a significant increase in multidrug-resistant E.coli. Of the samples, 16.7% were resistant to cephalexin; 13% to amoxicillin clavulanate and 8.3% to enrofloxacin at the beginning of the study (2010), compared to 27.1%, 45.6% and 29.3% respectively at the end (2017). The authors note that the antimicrobial resistance seen in this study is concerning and has implications for veterinary and public health, while they reiterate the need for antibiotic stewardship programmes.
This study adds further support to the need for culture and sensitivity of urine being undertaken before antimicrobials are prescribed, even where there is a strong suspicion of a UTI, as it is likely that a significant percentage (approximately one third) of animals will not respond to empirical use of antimicrobials.
Diagnostic accuracy of point-of-care tests in detecting bacteria in the lower urinary tract
Diagnostic accuracy of point-of-care tests in detecting bacteria in the lower urinary tract. The barrier to urine culture in primary care practice for many owners is the fact that the cost of urine culture is higher than the cost of treatment, cystocentesis is generally required and the delay in the results makes a second trip necessary to collect medication. A study by Grant et al (2021), published in the Journal of Veterinary Internal Medicine, investigated the diagnostic performance of point-of-care testing of voided urine samples in 21 dogs showing signs that could be consistent with a UTI. The rapid immunoassay (RIA) was performed within 30 minutes of collection of the voided sample. The sensitivity, specificity, positive predictive value, and negative predictive value of the RIA were 89%, 100%, 100%, and 92%, respectively
Of the enrolled dogs, 43% (n=9) had a UTI confirmed on a cystocentesis, with the point-of-care test identifying eight of these with no false positives. Being able to test on a voided sample significantly reduces cost and has distinct advantages. Although it is not identifying the bacterium involved or antimicrobial sensitivity, it does provide an effective option for screening dogs for UTIs, before submitting a cystocentesis sample for culture, thereby reducing overall costs, risks and inconvenience. Unfortunately, this study did not look at cultures of these voided sample in practice against a selection of antimicrobials, to assess whether this method could also provide an inexpensive route to appropriate antimicrobial selection.