Potential clinical application of an automated fluorescent microbial cell counter in the detection of urinary tract infection

Abstract Background Urinary tract infections (UTI) account for millions of office visits and approximately 400 000 hospital admissions every year in the United States; as a result, the cost burden of UTI in the USA is estimated at approximately $2.8 billion. There is a great deal of interest in finding newer, faster, and more reliable methods for diagnosing UTI as compared to the standard urine culture. Methods An automated fluorescent microbial cell counter was used to compare urine samples found to be positive for Escherichia coli UTI via cell culturing (n = 11) with UTI‐negative samples (n = 10). Results Patients with a positive urine culture had significantly higher cell count results using the microbial cell counter (1.01 × 108 cells/mL) as compared to the negative samples (2.35 × 106 cells/mL; P = .0022). Conclusions These observations suggest that automated microbial cell counters may serve as a rapid, objective method for the detection of bacteriuria in urine samples submitted for evaluation of suspected UTI.

for urinary nitrites formed by bacterial oxidation, and microscopic quantification of microbial cells in a urine samples into "mild," "moderate," or "heavy" bacteriuria. 5 The sample is ideally cleancatch and mid-stream, and collected in the morning. This reduces contamination of the tested sample by the normal urinary tract or fecal flora.
A full urinalysis involves analyzing urine upon an abnormal result on a rapid urinalysis test. A full urinalysis involves screening the urine for abnormal color, odor, specific gravity, and chemical composition via dip-sticks and may involve a microscopic examination to identify bacteria, red blood cells, white blood cells, casts, and crystals. 5 A urinalysis suggestive of bacteriuria is followed by a urine culture to determine the specific infecting organism. The most common pathogen associated with UTI globally is Escherichia coli. 6,7 The appropriate treatment is administered depending on the type of infection detected.
Catheterization studies intended to localize the site of bacteriuria demonstrated notable bacterial concentrations (300-1000 bacteria/mL) in cytoscopic specimens collected following bladder irrigation from healthy subjects. 8 This finding suggests the importance of quantifying bacteria in the urinary tract, especially where UTI is concerned.
There is a great deal of interest in finding newer, faster, and more reliable methods for diagnosing UTI. Automated cell counters that This algorithm includes the ability to decluster stained objects to consider each tagged cell separately, providing an accurate cell count as compared to a subjective assessment of cells under the microscope.
The objective of this study was to determine the capacity for an automated microbial cell counter to detect microbial cells and robustly differentiate between urine samples previously identified as positive and negative for UTI via standard urinalysis culturing techniques. These results indicate a potential role for an automated microbial cell counter in a rapid clinical diagnostic setting. No demographic or personal information was provided with the samples.

| Statistical analysis
The statistical mean of the triplicated measurements for each sample was calculated. The statistical mean, range, and standard deviation for each group were then calculated using these values. Statistical significance (P < .5) was established using a heteroskedastic twosample t test.

| D ISCUSS I ON
The assessment of bacteriuria guides the treatment of suspected UTI based on clinical symptoms. Currently, bacteriuria is diagnosed indirectly by microscopic and chemical analysis of the urine. In the present study, the significant difference found be- Our findings may also suggest a potential for culture-independent methods of assessing UTI. In the present study, the microbial cell counter was not used to identify bacterial species present in urine. An important feature of standard urine culture techniques is the ability to identify the type of bacteria present in the urine and its sensitivity to antimicrobials, which allows for more specific treatment to be administered depending on the kind of infection.
However, with advances in nucleic acid-binding fluorescent chemistry, cellular quantification technology, and software, the ability to rapidly identify bacterial species may soon become reality.
Additional prospective controlled clinical trials are needed to define the precise role of the present state of this technology in the management of patients with UTI or other types of infection. Such studies should include analysis of samples associated with asymptomatic bacteriuria (ASB) to determine the extent to which total bacterial counts differ between ASB and symptomatic UTI.

| CON CLUS IONS
The automated microbial cell counter represents a significant step toward high throughput, reproducible microbial cell observation,