Diagnostic accuracy of a rapid immunoassay for point of-care detection of urinary tract infection in dogs

Evaluation of a rapid immunoassay for bacteriuria in dogs

BACKGROUND

The ability to detect bacteriuria in dogs with a point-of-care test might improve medical care and antimicrobial stewardship.

HYPOTHESIS AND OBJECTIVE

A rapid immunoassay (RIA; RapidBac) will provide acceptable sensitivity and specificity for diagnosis of bacteriuria.

ANIMALS

Forty-four client-owned dogs with a clinical indication for urinalysis and aerobic bacterial urine culture.

METHODS

Prospective study. Urine, collected by cystocentesis, was submitted for urinalysis and culture at a diagnostic laboratory. Owners completed an enrollment questionnaire regarding their dogs' clinical signs. The RIA was performed according to the manufacturer's guidelines. Results were compared to culture.

RESULTS

Forty-four urine specimens were evaluated from 44 dogs. The sensitivity and specificity of the RIA test to detect bacteriuria compared to urine culture were 81.8% (95% CI, 65.7%-97.9%) and 95.5% (95% CI, 86.8%-99.9%), respectively. For cultures yielding ≥10³  CFU/mL, sensitivity increased to 90.0% (95% CI, 76.9%-100%) and specificity was similar at 95.2% (95% CI, 86.1%-99.9%). Malodorous urine, bacteriuria, and pyuria were more likely to be present in dogs with positive RIA or urine culture results compared to dogs with negative results.

CONCLUSIONS AND CLINICAL IMPORTANCE

The RIA was easy to perform and had good sensitivity and excellent specificity in this group of dogs. The RIA might be a useful screening test for decision-making regarding antimicrobial therapy in dogs with a clinical indication for urine culture. Consideration could be given to amending the International Society for Companion Animal Infectious Disease definition of bacterial cystitis as the presence of signs of lower urinary tract disease together with positive culture or a positive RIA.

Characterization of the urogenital microbiome in Miniature Schnauzers with and without calcium oxalate urolithiasis

Background

Calcium oxalate (CaOx) uroliths are common in dogs. Humans with CaOx urolithiasis exhibit alterations of the urinary and urogenital microbiomes that might mediate urolith formation. Detection of urogenital microbes associated with CaOx in dogs could inform disease pathophysiology.

Objective

To identify compositional differences in the urogenital microbiome of Miniature Schnauzers with and without CaOx uroliths.

Animals

Nineteen midstream, voided urine samples from Miniature Schnauzers with (n = 9) and without (n = 10) a history of CaOx urolithiasis.

Methods

Analytical cross‐sectional study. Microbial DNA was extracted from previously frozen urine samples and sequenced for the bacterial 16S rRNA V3‐V4 hypervariable regions. Diversity and composition of microbial populations were compared between urolith formers and controls.

Results

Alpha and beta diversity measures were similar between groups. Five individual bacterial taxa differed in abundance (indicator values >0.5 and P < .05): Acinetobacter, 2 Geobacillus variants, and Hydrogenophaga were overrepresented in the urine of urolith formers, and Sphingopyxis was overrepresented in controls. Two distinct subtypes of urine microbial composition were observed based on beta diversity measures, independent of urolith status, and other clinical variables.

Conclusions and Clinical Importance

Although we did not detect a difference in the overall urogenital microbial composition between groups, observed differences in individual bacterial taxa might be clinically relevant. For example, Acinetobacter was overrepresented in urolith formers and is associated with CaOx urolithiasis in humans. Two unique clusters of the microbiome were identified, independent of urolith status, which may represent distinct urotypes present in Miniature Schnauzers.

Comparison of a Chromogenic Urine Culture Plate System (UTid+) and Conventional Urine Culture for Canine and Feline Specimens

In companion animal medicine, urinary tract infection (UTI) is one of the most common indications for antimicrobial therapy. Definitive diagnosis of UTI requires isolation of bacteria with routine urine culture from an animal with concurrent clinical signs. Urine culture is typically performed at reference laboratories where paired susceptibility testing can be performed, but delays in shipment or processing can affect results. This study evaluated the use of a selective chromogenic, point-of-care culture system (UTid+) compared to conventional urine culture. A total of 119 (73 canine and 46 feline) cystocentesis urine samples were evaluated. Conventional urine culture was positive for 28 (23.5%) of the 119 cultures and UTid+ culture was positive for 26 (21.8%). The overall sensitivity, specificity, positive predictive value, negative predictive value and accuracy were 92.3%, 97.8%, 92.3%, 97.8 and 96.6% for UTid+ respectively. Overall, the UTid+ culture system showed an acceptable level of accuracy when compared to conventional urine culture. Agreement of identification results was high (κ = 0.90) with an important exception being Proteus spp. which was only identified in 1/3 positive cultures. UTid+ may be useful in scenarios where a common UTI pathogen is expected and identification within 24 h is ideal; however, conventional urine culture remains the gold standard.

A feasibility study investigating the utility of a point-of-care rapid immunoassay for detecting septic peritoneal effusion in dogs

OBJECTIVE

To determine the sensitivity (SN), specificity (SP), positive predictive value (PPV), negative predictive value (NPV), and accuracy of a point-of-care urine bacterial rapid immunoassay (RIA) for a diagnosis of septic peritonitis, compared to more traditional diagnostic tools, such as cytology and bacterial culture.

DESIGN

Prospective, cross-sectional feasibility study conducted from October 2016 to June 2017.

SETTING

Four locations within a private practice referral hospital.

ANIMALS

Sixty-four dogs with peritoneal effusion of any etiology were enrolled. Four dogs were excluded due to absent RIA or bacterial culture results. Two additional dogs were excluded because of an inability to definitively classify them as having septic peritonitis.

INTERVENTIONS

Abdominocentesis was performed to obtain peritoneal effusion samples for aerobic and anaerobic bacterial culture, cytology, and RIA. Cytological slides were evaluated by a clinical pathologist following enrollment.

MEASUREMENTS AND MAIN RESULTS

Fifty-eight dogs were included in the study, 8 of which were classified as having septic peritonitis. Compared to final diagnosis of septic peritonitis, RIA had a low PPV (36.8%) but good NPV (97.4%) and was 77.5% accurate. SN of RIA (87.5%) to diagnose septic peritonitis was similar to cytology (85.7%) and bacterial culture (87.5%); however, SP was lower (76%, 100%, and 98%, respectively). Cytology had the best overall predictive values and accuracy for diagnosing septic peritonitis (PPV 100%, NPV 97.9%, and accuracy 98%) compared to RIA and bacterial culture.

CONCLUSIONS

RIA testing was similarly sensitive in identifying septic peritonitis compared to cytology and bacterial culture but was not very specific or accurate. As a stand-alone test, RIA commonly had false-positive test results, making it unreliable in identifying septic peritonitis. Cytology was the most accurate diagnostic test and had no false-positive results. Further investigation with a larger sample size and prevalence of septic peritonitis may prove beneficial.

Development of a method for creating antibiograms for use in companion animal private practices

OBJECTIVE

To identify a method for developing antibiograms for use in companion animal private practices (PPs).

SAMPLES

Reports (n = 532) of aerobic bacterial culture and antimicrobial susceptibility testing performed between January 1, 2018, and December 31, 2018, at 11 PPs and 1 academic primary care practice (APCP).

PROCEDURES

Data extracted from reports included patient identification number, laboratory accession number, patient signalment, collection method, body site, and results of bacterial culture and antimicrobial susceptibility testing. A custom antibiogram was then constructed with the help of commonly available software by adapting methods used by human hospitals. Susceptibility patterns of bacteria isolated by PPs and the APCP were compared to identify challenges associated with collating data from multiple laboratories.

RESULTS

4 bacterial species (Escherichia coli, Proteus mirabilis, Pseudomonas aeruginosa, and Staphylococcus pseudintermedius) and 3 bacterial groups (Enterobacteriaceae, Enterococcus spp, and coagulase-positive Staphylococcus spp) met the minimum requirement of ≥ 15 isolates for construction of an antibiogram. For urine samples, 3 bacterial species and 2 bacterial groups met the minimum requirement of ≥ 10 isolates. For samples from skin, 2 bacterial species and 2 bacterial groups met the minimum requirement of ≥ 10 isolates. Patient signalment, sample source, and distribution of bacterial isolates were similar between PP and APCP patients.

CONCLUSIONS AND CLINICAL RELEVANCE

Results demonstrated that it was feasible to adapt existing guidelines for developing antibiograms in human medicine to the veterinary outpatient setting. Use of antibiograms could aid in empirical antimicrobial drug selection in a manner that supports antimicrobial stewardship principles.

Assessment of bacterial and fungal populations in urine from clinically healthy dogs using next-generation sequencing

BACKGROUND

Urine from clinically healthy dogs is not sterile. Characterizing microbial diversity and abundance within this population of dogs is important to define normal reference ranges for healthy urine.

OBJECTIVES

To establish composition and relative representation of bacterial and fungal microbiomes in urine of clinically healthy dogs.

ANIMALS

Fifty clinically healthy dogs.

METHODS

Analytic study. Urine sampling via cystocentesis. Comprehensive evaluation of urine including standard urinalysis, culture and sensitivity, next-generation sequencing (NGS), and bioinformatics to define bacterial and fungal microbiome.

RESULTS

Culture did not yield positive results in any samples. Next-generation sequencing of urine established low presence of bacteria, fungi, or both in all samples. Diversity and abundance of bacterial and fungal communities varied between urine samples from different dogs. Struvite crystals were associated with bacterial community structure (P = .07) and there was a positive correlation between struvite crystals and pH.

CONCLUSIONS AND CLINICAL IMPORTANCE

The microbiome in urine of clinically healthy dogs has diverse bacterial and fungal species These findings highlight limitations of conventional culture testing and the need for culture-independent molecular diagnostics to detect microorganisms in urine.

Diagnostic accuracy of a point-of-care test using voided urine samples for detection of bacteriuria in dogs with signs of lower urinary tract disease

BACKGROUND

Bacterial urine culture is recommended in dogs suspected of having urinary tract infection (UTI), but there is expense and delay in obtaining such results.

HYPOTHESIS/OBJECTIVE

To determine the diagnostic performance of a rapid immunoassay (RIA) dipstick for detection of bacteriuria using voided urine from dogs with clinical signs of lower UTI.

ANIMALS

Twenty-four client-owned dogs.

METHODS

Voided urine was collected and the RIA performed within 30 minutes. Urine collected by cystocentesis was submitted for aerobic urine culture. McNemar's test and kappa coefficient were calculated to determine agreement between the 2 tests.

RESULTS

Nine of 21 dogs (43%) had UTI verified by aerobic urine culture. There was 1 false-negative and no false-positive RIA results. Sensitivity, specificity, positive predictive value, and negative predictive value of the RIA were 89%, 100%, 100%, and 92%, respectively.

CONCLUSIONS AND CLINICAL IMPORTANCE

This RIA is promising for correctly identifying whether or not voided urine samples from dogs with lower urinary tract clinical signs have true bacteriuria in a rapid, inexpensive manner. Additional patients should be enrolled in a similar study to determine if diagnostic performance is robust in a large population.

Diagnosis of bacterial urinary tract infection: Utility of urine myeloperoxidase concentration to predict urine culture results in dogs

Suspected bacterial urinary tract infections (UTI) are a common cause of overuse and misuse of antimicrobials. A bedside diagnostic test that could accurately predict urine culture results would prevent antimicrobial overuse, but accurate biomarkers have not yet been identified in veterinary medicine. The objective of this study was to evaluate urine myeloperoxidase (uMPO) as a rapidly available, accurate marker to predict urine culture results. We hypothesized that uMPO would be higher in dogs with a positive urine culture than in dogs with a negative urine culture, and that uMPO could be used to aid in the accurate diagnosis of significant bacteriuria. Urine samples were collected from a veterinary university clinical pathology lab. uMPO concentration was measured using a commercially available canine myeloperoxidase (MPO) enzyme-linked immunosorbent assay (ELISA). Following validation, samples from 98 dogs that had a urinalysis and urine culture performed as part of their diagnostic investigation were included. Forty-seven dogs had a negative urine culture and fifty-one dogs had a positive urine culture. uMPO levels were significantly higher in samples that had a positive culture (median 2.13 ng/ml; IQR 0.98–7.07) versus samples that had a negative culture (median 1.07 ng/ml; IQR 0.52–1.84)(p < 0.005). Based on receiver-operator characteristic, a cutoff of 0.55 ng/ml was chosen to maximize sensitivity and specificity. Using a cutoff of 0.55 ng/ml, uMPO had a sensitivity of 70% and specificity of 69% to determine the presence of a positive culture. However, the degree of overlap between groups may preclude the use of this test as a surrogate for urine culture in a clinical setting.

Successful medical management of perinephric abscess and urosepsis following urethral obstruction in a cat

OBJECTIVE

To describe the clinical presentation and medical management of a cat with perinephric abscessation and urosepsis following urethral obstruction and catheterization.

CASE SUMMARY

A 2-year-old intact male domestic shorthaired cat presented to an emergency and referral center for lethargy, vomiting, and hematuria. Severe azotemia and hyperkalemia were observed on a serum biochemistry panel. The patient was diagnosed with urethral obstruction and was treated with urethral catheterization, calcium gluconate, IV fluid therapy, buprenorphine, and prazosin. The patient's azotemia improved, and the hyperkalemia resolved. Urinary catheterization was discontinued. The patient developed pyrexia, worsening azotemia, hypoalbuminemia, hyperbilirubinemia, and dysuria. Urethral catheterization was repeated. Abdominal radiographs showed left renomegaly, and abdominal ultrasound revealed left perinephric fluid. Ultrasound-guided centesis of the perinephric fluid revealed septic inflammation, and the sample was consistent with urine based upon sample creatinine. Fluid from the perinephric abscess and urine from the bladder both grew Pasturella spp. The patient was treated with perinephric catheterization, saline lavage, and a continuous infusion of cefotaxime for 72 h. The patient's azotemia quickly resolved, and the patient was discharged after 6 days of hospitalization. The patient was reported to have made a full recovery.

NEW OR UNIQUE INFORMATION PROVIDED

This is the first described case of perinephric abscess and urosepsis following urethral obstruction in a cat and its successful medical management. Perinephric abscess not associated with intrarenal abscess has not previously been identified. Additionally, continuous antimicrobial infusion to treat overwhelming infection and the use of the RapidBac Vet immunoassay for point-of-care detection of urinary tract infection has not been described in cats.

Antimicrobial Stewardship in Veterinary Medicine

While antimicrobial resistance is already a public health crisis in human medicine, therapeutic failure in veterinary medicine due to antimicrobial resistance remains relatively uncommon. However, there are many pathways by which antimicrobial resistance determinants can travel between animals and humans: by close contact, through the food chain, or indirectly via the environment. Antimicrobial stewardship describes measures that can help mitigate the public health crisis and preserve the effectiveness of available antimicrobial agents. Antimicrobial stewardship programs have been principally developed, implemented, and studied in human hospitals but are beginning to be adapted for other applications in human medicine. Key learning from the experiences of antimicrobial stewardship programs in human medicine are summarized in this article-guiding the development of a stewardship framework suitable for adaptation and use in both companion animal and livestock practice. The antimicrobial stewardship program for veterinary use integrates infection prevention and control together with approaches emphasizing avoidance of antimicrobial agents. The 5R framework of continuous improvement that is described recognizes the importance of executive support; highly motivated organizations and teams (responsibility); the need to review the starting position, set objectives, and determine means of measuring progress and success; and a critical focus on reducing, replacing, and refining the use of antimicrobial agents. Significant issues that are currently the focus of intensive research include improved detection and diagnosis of infections, refined dosing regimens that are simultaneously effective while not selecting resistance, searches for alternatives to antimicrobial agents, and development of improved vaccines to enhance immunity and reduce disease.

Urinary Tract Infection

"Urinary tract infection (UTI) is a common diagnosis in companion animal practice and is responsible for a significant proportion of antimicrobial use in veterinary medicine. The veterinary community has begun to follow the standards of care in human medicine and shift its definition of an UTI based on culture results and toward the presence of lower urinary tract symptoms. An improved understanding of the pathophysiology of UTI, risk factors for clinical disease, and the implementation of more reliable in-house diagnostic testing can lead to improved outcomes for patients and reduce inappropriate treatment. Investigation of antibiotic-sparing therapies holds some promise as well."

Diagnostic microbiology in veterinary dermatology: present and future

BACKGROUND

The microbiology laboratory can be perceived as a service provider rather than an integral part of the healthcare team.

OBJECTIVES

The aim of this review is to discuss the current challenges of providing a state-of-the-art diagnostic veterinary microbiology service including the identification (ID) and antimicrobial susceptibility testing (AST) of key pathogens in veterinary dermatology.

METHODS

The Study Group for Veterinary Microbiology (ESGVM) of the European Society of Clinical Microbiology and Infectious Diseases (ESCMID) identified scientific, technological, educational and regulatory issues impacting the predictive value of AST and the quality of the service offered by microbiology laboratories.

RESULTS

The advent of mass spectrometry has significantly reduced the time required for ID of key pathogens such as Staphylococcus pseudintermedius. However, the turnaround time for validated AST methods has remained unchanged for many years. Beyond scientific and technological constraints, AST methods are not harmonized and clinical breakpoints for some antimicrobial drugs are either missing or inadequate. Small laboratories, including in-clinic laboratories, are usually not adequately equipped to run up-to-date clinical microbiologic diagnostic tests.

CONCLUSIONS AND CLINICAL IMPORTANCE

ESGVM recommends the use of laboratories employing mass spectrometry for ID and broth micro-dilution for AST, and offering assistance by expert microbiologists on pre- and post-analytical issues. Setting general standards for veterinary clinical microbiology, promoting antimicrobial stewardship, and the development of new, validated and rapid diagnostic methods, especially for AST, are among the missions of ESGVM.

Urine Cytology: Collection, Film Preparation, and Evaluation

Cytologic examination of the urine sediment in animals suspected of having urinary tract disease or lower urinary tract masses is one of the best means of distinguishing inflammation, infection, and neoplasia and can help determine if a positive dipstick result for hemoglobin/blood is due to hemorrhage or blood contamination. The quality of the specimen collection and handling plays an important role in the quality of results, the validity of interpretations, and selection of appropriate course of action. The method of sample collection aids localization of pathology. Air dry but do not heat fix, freeze, or expose films to formalin fumes, temperature extremes, or condensation.