Testing for bacteriuria is usually performed in people with symptoms of a urinary tract infection. Certain populations that cannot feel or express symptoms of infection are also tested when showing nonspecific symptoms. For example, confusion or other changes in behaviour can be a sign of an infection in the elderly. Screening for asymptomatic bacteriuria in pregnancy is a common routine in many countries, but controversial. • The
gold standard for detecting bacteriuria is a
bacterial culture which identifies the concentration of bacterial cells in the urine. The culture is usually combined with subsequent testing using biochemical methods or
MALDI-TOF, which allows to identify the bacterial species, and
antibiotic susceptibility testing. Urine culture is quantitative and very reliable, but can take at least one day to obtain a result and it is expensive. Miniaturization of bacterial culture within dipstick format, Digital Dipstick, allows bacterial detection, identification and quantification for bacteriuria within 10–12 hours at the
point-of-care. Clinicians will often treat symptomatic bacteriuria based on the results of the
urine dipstick test while waiting for the culture results. • Bacteriuria can usually be detected using a
urine dipstick test. The
nitrite test detects nitrate-reducing bacteria if growing in high numbers in urine. A negative dipstick test does not exclude bacteriuria, as not all bacteria which can colonise the urinary tract are nitrate-reducing. The
leukocyte esterase test indirectly detects the presence of leukocytes (
white blood cells) in urine which can be associated with a urinary tract infection. In the elderly, the leukocyte esterase test is often positive even in the absence of an infection. The
urine dipstick test is readily available and provides fast, but often unreliable results. Some organisms such as chlamydia and
Ureaplasma urealyticum will produce a negative leukocyte esterase reaction. • Microscopy can also be used to detect bacteriuria. It is rarely used in clinical routine since it requires more time and equipment and does not allow reliable identification or quantification of the causal bacterial species. Bacteriuria is assumed if a single bacterial species is isolated in a concentration greater than 100,000
colony forming units per millilitre of urine in clean-catch midstream urine specimens. In urine samples obtained from women, there is a risk for bacterial contamination from the vaginal flora. Therefore, in research, usually a second specimen is analysed to confirm asymptomatic bacteriuria in women. For urine collected via bladder catheterization in men and women, a single urine specimen with greater than 100,000 colony forming units of a single species per millilitre is considered diagnostic. Using special techniques certain
non-disease causing bacteria have also been found in the urine of healthy people. These are part of the
resident microbiota. ==Treatment==