Bacteriuria is a laboratory symptom characterized by the presence of bacteria in the urine. Most often, this indicates an infection of the urinary tract (kidneys, bladder), but may be a harmless laboratory finding. Clinical manifestations can be diverse – from an absolutely asymptomatic course to pronounced signs (fever, lower back pain, urination disorders). The presence of bacterial flora in urine is investigated in several ways – physico-chemical, bacteriological, etc. Correction of bacteriuria is carried out by the appointment of antibacterial drugs.
Depending on the number of bacteria, some experts conditionally allocate insignificant and pronounced bacteriuria. In clinical practice, only one classification is used to determine the patient’s treatment tactics:
- Asymptomatic bacteriuria. It is characterized by the detection of bacteria in the urine in the absence of any complaints and other laboratory signs of urinary tract infections (leukocyturia, etc.) in the patient.
- Symptomatic bacteriuria. Combination of clinical symptoms and detection of bacteria in a urine sample.
Causes of bacteriuria
Violation of preparation for analysis
A fairly common cause of bacteriuria. Improper preparation for urinalysis, especially non-fulfillment or non-thorough toilet of the external genitalia can lead to false positive results. It is also considered incorrect to take a urine test during menstruation. Blood, being a nutrient medium for bacteria, creates a favorable environment for their reproduction.
When using non-sterile dishes for collecting urine, contamination of the sample by extraneous flora is possible. To donate urine to the bacteriological laboratory for sowing, it is recommended to use special test tubes with preservatives (boric acid, formate and sodium borate) that stabilize the bacterial composition of urine.
Detection of bacterial flora in urine without clinical and laboratory signs of infectious and inflammatory diseases of MVP occurs in 1-5% of healthy premenopausal women, in 2-10% of pregnant women, in 4-20% of healthy elderly men and women. Asymptomatic bacteriuria is almost never observed in young healthy men.
Such age-sexual characteristics of bacteriuria are associated with anatomical and physiological features of the female urogenital system, hormonal changes during pregnancy and menopause, as well as age-related changes in local immunity. Asymptomatic bacteriuria is a benign condition and does not require any intervention, with the exception of some patients who are at high risk of developing MVP infection.
Urinary tract infections
The most common cause of bacteriuria is acute, chronic and recurrent forms of MVP infections. The causative agents of these pathologies are mainly gram-negative enterobacteria – E. coli, Klebsiella, protei. Very rarely, infections of the genitourinary system are caused by gram-positive flora – staphylococci, enterococci. Infection occurs in several ways. The ascending path is recognized as the most common – through the urethra to the bladder and / or kidneys.
Less often, a hematogenic or lymphogenic pathway is possible. This option occurs if there is an additional source of infection in the body – pneumonia, infections of the oral cavity, ENT organs. The degree of bacteriuria can be different, it does not correlate with the severity of the disease and disappears almost from the first days of treatment with properly selected antibacterial drugs.
- Pyelonephritis. This is an infectious inflammation of the calyx-pelvic system of the kidneys with the involvement of interstitial tissue. It develops mainly in young women (5-6 times more often than in men).
- Cystitis. Inflammation of the mucous membrane of the bladder. A single episode of cystitis occurs in half of women worldwide.
- Nonspecific urethritis. Inflammation of the urethra, on the contrary, is more typical for men due to a longer and narrower urethra.
Bacteriuria in infections of male and female genital organs are very rare. They are caused by nonspecific conditionally pathogenic gram-negative and gram-positive flora (E. coli, enterococci, anaerobic bacteria) and often occur together with cystitis, urethritis. The severity of bacteriuria has nothing to do with the intensity of the inflammatory process.
- Infections of the male genital area. These include bacterial prostatitis (it takes about 10% of all cases of inflammation of the prostate gland), and extremely rarely, orchitis and epididymitis (inflammation of the testicle and its appendage), balanoposthitis (inflammation of the glans and foreskin of the penis).
- Infections of the female genital area. These infections include inflammation of the vagina and/or vulva (vaginitis, vulvovaginitis), cervix (cervicitis).
It is worth noting that in the case of infectious diseases of the genitals caused by bacteria that provoke venereal diseases, such as chlamydia, mycoplasmosis, gonorrhea, bacteriuria does not develop. These infections are diagnosed by other special research methods.
Risk factors for bacteriuria
This group includes diseases or conditions that contribute to the appearance of microorganisms in the urine:
- Glucosuria: poorly controlled hyperglycemia in diabetes mellitus, prolonged use of glucocorticosteroids, various endocrine disorders (Itsenko-Cushing’s disease / syndrome, pheochromocytoma, glucagonoma).
- Previously transferred UTIs.
- Violation of urine outflow: urolithiasis, congenital abnormalities of the structure of the urinary system, ureteral stenosis.
- Reverse casting of urine: urinary-ureteral-pelvic reflux.
- The presence of an installed urinary catheter.
- Urine pH shift to the alkaline side: nutritional characteristics, taking medications.
There are several diagnostic methods for detecting bacteriuria. The necessary proper preparation before passing the analysis. In a specific clinical situation, the attending physician selects a specific study or a combination of methods:
- Microscopy. Detection of bacteria by direct microscopic examination of the sediment of centrifuged urine. The method has extremely low diagnostic value. Microscopy may reveal signs of improper preparation of the patient – an abundance of diverse flora, a large amount of mucus and squamous epithelial cells.
- Nitrite test. In the process of vital activity, bacteria colonizing the genitourinary tract convert nitrates coming from food into nitrites. Urinary test strips have a special reagent zone that stains in the presence of nitrites. The test may be false negative in the absence of nitrates in the patient’s diet, infection with bacteria that do not form nitrites (streptococci), high content of ascorbic acid in the urine.
- Bacteriological sowing. This method is considered the gold standard for the diagnosis of bacteriuria. In the laboratory, a urine sample is seeded on nutrient media for certain bacteria. To confirm the diagnosis of “asymptomatic bacteriuria”, at least a 2-fold sowing with an interval of 24 hours is required. The disadvantage of the method is the long waiting time for the result – 2 or 3 days.
- Flow cytofluometry. Some modern automatic analyzers are able to carry out a detailed assessment of the cellular composition of a urine sample, including they count the number of bacteria.
- Microscopy, nitrite test and flow cytometry are considered indicative methods for detecting bacteriuria, and microbiological seeding is confirmatory. An important point is that in the case of bacterial growth reaching a clinically significant titer (above 10×5 colony-forming units per ml) during sowing, sensitivity to antibacterial drugs is necessarily determined. This is necessary for the selection of therapy.
In addition to the detection of bacteriuria, additional studies are required to differentiate the etiology of its occurrence:
- Urine analysis. OAM indicators help to find out the cause of bacteriuria. For example, the presence of leukocytes and the alkaline reaction of urine with a high probability excludes asymptomatic bacteriuria; an increase in the content of protein, erythrocytes may indicate pyelonephritis. Microscopy detection of transitional epithelial cells indicates damage to the bladder or urethra, and renal epithelium and a large number of cylinders – kidney damage.
- Ultrasound. On ultrasound of the kidneys with pyelonephritis, there is an expansion of the heart rate, it is also possible to identify abnormalities of the structure of the ureters. With prostatitis, ultrasound of the prostate gland reveals an increase in its size, a decrease in echogenicity. With epididymitis, an increase in the appendage and diffuse changes are visualized on the ultrasound of the testicle.
- Gynecologist’s examination. If you suspect a gynecological disease, you need to consult a gynecologist who conducts an examination of the genitals, bimanual vaginal examination, colposcopy. If necessary, a smear is taken from the mucous membranes or separated for cultural examination.
- Examination by a urologist. Similarly, if there are indications, men are prescribed a consultation with a urologist for finger rectal examination, collection of prostatic fluid or ejaculate.
If bacteriuria is detected, it is necessary to consult a doctor for correction. Asymptomatic bacteriuria in the vast majority of cases does not require treatment. The exceptions are pregnant women, patients with installed urinary catheters, patients with poorly controlled diabetes mellitus – these patients are shown antibacterial therapy. In symptomatic bacteriuria, the following treatment is recommended:
- Pyelonephritis. The first-line drugs are pecinillins (amoxicillin / quavulanate), cephalosporins (cefixime, ceftibutene). With strains resistant to them, fluoroquinolones (levofloxacin, ciprofloxacin), new generation cephalosporins (cefepim) are resorted to.
- Cystitis. Fosfomycin trometamol or nitrofurans (nitrofurantoin, furazolidone) are used. With recurrent cystitis, preparations based on cranberry extract, D-mannose, herbal remedies (kanefron) are prescribed. Also, in case of relapses, some experts recommend lyophilizate of bacterial lysate of E. coli.
- Infections of the genital tract. For prostatitis, epididymitis, fluoroquinolones, macrolides (azithromycin) are used, for vulvovaginitis, cervicitis – instillation with antiseptic solutions and antibiotics active against anaerobic flora (metronidazole, clindamycin).
Bacteriuria by itself cannot serve as a predictor of clinical outcome. The prognosis is directly determined by the underlying disease – the most favorable for asymptomatic bacteriuria, cystitis, urethritis. Often occurring pyelonephritis contributes to the formation of concretions in the kidneys. With severe bilateral pyelonephritis, serious life-threatening complications can develop – carbuncle, kidney abscess, hydronephrosis. An extremely rare and most fatal consequence of pyelonephritis is urosepsis.