Description

Image

Background

Urinary tract infections (UTIs) is an infection in any part of the urinary system. The urinary system includes kidney, ureter, bladder and urethra out of which it is observed that most of the infections is caused in the lower urinary tract- bladder and urethra.UTIs are the third most common bacterial infections in India, Nearly 150 million people get infected annually out of which about 73.57% are females and 35.46% are males.

UTIs don’t always show symptoms but some of the common symptoms that are observed during the infection periods are: burning feeling during urination, strong urge to urinate but urine doesn't go away, cloudy urine, strong smell in urine, presence of blood in urine hence the color of the urine appears to be red, brown or pink and pelvic pain in women.

The treatment is mostly done by the use of antibiotics based on the level of infection; some them are Trimethoprim and sulfamethoxazole (Bactrim, Bactrim DS), Fosfomycin (Monurol), Nitrofurantoin (Macrodantin, Macrobid, Furadantin), Cephalexin, Ceftriaxone. However these antibiotics are mostly used to cure the simple UTIs which show its effect within 1-3 days but the antibiotics are recommended to continue for 1-2 weeks. But if it is a frequent infection then the doses might be continued for 6 months or more. For severe UTIs hospitalization is required. There are two existing methods for diagnosis:

Existing methods for diagnosis:

Current detection methods of urinary tract infections (UTIs) can be categorized into two parts:

  1. Conventional culture based detection
  2. Molecular methods

Conventional culture based detection

  • Analyzing a urine sample

    Here a urine sample was asked from the patient where the patient has to collect the urine by wiping the genital area with an antiseptic pad and to collect the urine midstream. The process helps prevent the sample from being contaminated. The urine will be then looked at in a lab to check for white blood cells, red blood cells or bacteria.

  • Growing urinary tract bacteria in a lab

    Lab analysis of the urine is sometimes followed by a urine culture. This test tells about what bacteria are causing the infection and which medications will be most effective.

  • Creating images of the urinary tract

    Recurrent UTIs may be caused by a structural problem in the urinary tract. So an ultrasound, a CT scan or MRI is required to look for this issue. A contrast dye may be used to highlight structures in the urinary tract.

  • Using a scope to see inside the bladder

    If the patient has recurrent UTIs, then a cystoscopy may be performed. The test involves using a long, thin tube with a lens, called a cystoscope, to see inside the urethra and bladder. The cystoscope is inserted in the urethra and passed through to the bladder.

Molecular methods

  • Urine dipstick tests

    Dipstick tests are used to detect nitrites (bacteria convert urinary nitrates to nitrites) and leukocyte esterase (an enzyme produced by neutrophils, which presumptively associates pyuria with an UTI). They are advantageous in being simple and quick to use.

    These tests have several disadvantages, including low sensitivity. False negative nitrite tests are common due to insufficient bladder incubation time for converting nitrate to nitrite, reduced urinary excretion of nitrate, and the failure of certain pathogens, particularly Enterococcus faecalis, to convert nitrate to nitrite.

  • Microscopic urinalysis

    Flow cytometry can be used for the initial screening of urine samples. Depending on the sample, the concentration of bacteria required for a positive result may range from 40 to 1000/µL.

    The advantages of urine flow cytometry are that it is standardized, less expensive when compared to urine culture, and the results are rapid. The disadvantages are that flow cytometry is only a screen for bacteriuria; also, it does not provide either species identification or antimicrobial susceptibility testing (AST).

  • Urine Gram-staining

    The analysis of Gram-stained urine samples can be used as a screening technique for UTI. The sensitivity depends on whether the sample has been centrifuged or not. While the urine Gram-stain test provides quick information on the nature of the urinary pathogen, it is disadvantageous in that it is labor intensive and the sensitivity is poor. It is reliable only when the bacterial concentration in urine is >105 colony forming units per milliliter (CFU/mL).

  • MALDI-TOF mass spectrometry

    Matrix-assisted laser desorption ionization-time of flight (MALDI-TOF) mass spectrometry was initially approved for pathogen identification in UTIs, wherein the urine sample is cultured, the bacteria isolated, and a colony from the culture plate then analyzed. For the direct analysis of urine, several initial sample preparation steps are essential. These include the removal of cellular debris, leukocytes, and mucus, and the collection of bacteria. Best results are obtained when there is a high bacterial count (>105CFU/mL) and Gram-negative bacteria are involved. The main disadvantage is the inability to perform AST, for which conventional methods will still be required.

  • Fluorescence in situ hybridization (FISH)

    The target for bacterial detection in FISH is the 16S ribosomal RNA (rRNA), which is an integral constituent of bacterial genomes and is present in abundant quantities in the bacterial cell. Detection depends on the availability of specific probes. Rapid FISH assays are available that can give results within 20 minutes with high sensitivity and specificity. The main disadvantage is the inability to perform AST, for which conventional methods will still be required.

  • Multiplex PCR

    Multiplex PCR assays are increasingly being used in the clinical laboratory for the rapid detection and identification of uropathogens. The advantage is the ability to identify organisms that are not detected by routine culturing because they are considered fastidious. The disadvantage with currently available multiplex PCR assays is that they do not provide comprehensive or definitive phenotypic information about antibiotic susceptibility.

Our goal

We aim to develop a novel Aptamer based platform for point of care (POC) detection of pathogens causing Urinary Tract Infections. Urinary tract infections (UTIs) are the third most common bacterial infections in India. The conventional current diagnostic methods require bacterial culture from urea for antibody-based testing, which is a time-consuming procedure, with limited availability at the point of care and requirement of cold chain for Ab storage and assay. Owing to the limitation of cold chain and antibody assays, UTI detection at POC is a great challenge, thereby going undetected. Recurrent UTIs because of poor sanitary hygiene, aging and uncontrolled diabetes is becoming a reason for Antibiotic resistance. Looking at the challenge of timely and precise detection of UTI at POC, this year, our team aims to develop a novel, easy-to-use, cost-effective, sensitive point-of-care Aptamer-based diagnostic kit (Apt4UTI) that can precisely detect uropathogens.

  • References:

  1. Diagnosis of UTI:
    https://www.mayoclinic.org/diseases-conditions/urinary-tract-infection/diagnosis-treatment/drc-20353453
  2. Detection of UTI:
    https://www.clinicallab.com/trends/molecular-diagnostics/the-need-for-faster-uti-pathogen-detection-22132
  3. Schmiemann, G; Kniehl, E; Gebhardt, K; Matejczyk, M M; Hummers-Pradier, E. ‘The Diagnosis of Urinary Tract Infection’ 2010; 107(21): 361-7.
    DOI: 10.3238/arztebl.2010.0361

Image
Image
Image
Image
Image
Image
Loading...