Controversies in the laboratory diagnosis of community-acquired urinary tract infection

Abstract

Urine samples constitute the largest single category of specimens examined in most medical microbiology laboratories. The everyday nature and apparent simplicity of urinary tract infection belies the intense debate and controversy regarding the optimal methods of collection, transport and processing of urine specimens and reporting of results. There is considerable variation in the interpretation of quantitative culture results between laboratories and the etiology of abacterial cystitis remains unclear. Microscopy to detect pyuria provides information on an important indicator of inflammation and it has been proposed that detection of urinary antibody may provide similar information. Neither of these indices of host response is suitable for use in a screening test for urinary infection however, although they may usefully contribute to the interpretation of significance of culture results. The development of screening tests and automated systems continues, but at present microscopy and culture remain the most important techniques for laboratory diagnosis. However, these techniques have so far failed to provide an etiological diagnosis for abacterial cystitis and this remains a major area for research.

Viable but Nonculturable Bacteria Are Present in Mouse and Human Urine Specimens

“…One method of diagnosing a UTI is by culturing urine specimens; a threshold of 100,000 CFU/ml in clean-catch urine specimens is considered to indicate a UTI (4, 28). This threshold is not an absolute indicator, as both asymptomatic bacteriuria and patients with UTI symptoms having no culturable urine bacteria occur (29,32).Urine within the urinary tract is generally considered sterile (14). This conclusion is based upon a lack of culturable cells present in urine specimens obtained via clean-catch and catheterization methods.…”

“…Urinary tract infections (UTIs) affect as many as 50% of women at least once during their lifetime (29,32), and 25% of those who acquire a UTI will have another infection within the following 6 months (17). A UTI occurs when the urinary tract is infected with microorganisms, and uropathogenic Escherichia coli accounts for greater than 80% of all UTI cases (4,30).…”

“…One method of diagnosing a UTI is by culturing urine specimens; a threshold of 100,000 CFU/ml in clean-catch urine specimens is considered to indicate a UTI (4,28). This threshold is not an absolute indicator, as both asymptomatic bacteriuria and patients with UTI symptoms having no culturable urine bacteria occur (29,32).…”

Fluorescent Amplified Fragment Length Polymorphism Probabilistic Database for Identification of Bacterial Isolates from Urinary Tract Infections

“…All bacteria were collected from midstream urine samples. All isolates were typed by conventional biochemical tests as belonging to E. coli (25), Proteus mirabilis (11), enterococci (11), Klebsiella pneumoniae (9), Klebsiella oxytoca (2), Citrobacter freundii (2), Morganella morganii (3), Enterobacter agglomerans (2), Enterobacter cloacae (3), and Providencia rettgeri (1) ( Table 1 shows details). All isolates were stored at Ϫ80°C in 30% glycerol.…”

“…Routine diagnosis includes a quantitative microbial count of urine. Counts of Ͼ10 5 organisms/ml are regarded as showing significant bacteriuria (25). Diagnosis is followed by characterization of the causal agent and sometimes antibiotic sensitivity tests to determine appropriate courses of treatment, because the empirical choice of an effective treatment is becoming more difficult as urinary pathogens become increasingly resistant to commonly used antibiotics (15).…”