Asymptomatic bacteriuria in pregnancy is a laboratory—determined pathological condition during gestation, in which repeated examination of urine with a break of 24 hours or more makes it possible to identify the same microorganism in the assays in a titer of 100,000 CFU/ml. There are no clinical symptoms. The disorder is diagnosed using a general urinalysis, bacteriological seeding, screening photocolorimetric TTX test. Treatment is carried out using phosphomycins, semi-synthetic penicillins, cephalosporins, synthetic nitrofurans, plant uroantiseptics.
O23 Infection of the genitourinary tract during pregnancy
Asymptomatic bacteriuria in pregnancy (ABP, asymptomatic or latent chronic bacteriuria) it is detected in 2.5-26% of pregnant women. In patients with low socio-economic status, the syndrome develops 5 times more often. Often, non-inflammatory bacterial colonization of the urinary tract precedes gestation. In 52.3% of pregnant women, asymptomatic bacteriuria is detected in the first trimester, in 35.4% — in the second and in 12.3% — in the third. According to WHO recommendations, it is clinically significant to increase the content of bacterial agents to 100 thousand or more CFU/ml. However, according to the observations of specialists in the field of urology, obstetrics and gynecology, the risk of complicated gestation occurs even with titers from 100 to 10000 CFU /ml.
Pathology of asymptomatic bacteriuria in pregnancy caused by commensal microorganisms that normally colonize the periurethral and perianal regions. Monoinfection is seeded in 95% of patients. In almost 2/3 of cases, etiopathogens are gram-negative: in 51.7% of pregnant women with asymptomatic bacteriuria, Escherichia coli is detected in tests, proteus, Klebsiella, enterobacter, citrobacter, pseudomonads, non-fermenting bacteria are less common. Gram-positive microflora is represented by staphylococci (epidermal, hemolytic, saprophytic), pyogenic streptococcus, fecal enterococcus.
The risk of developing a pathological condition increases in women with bacterial vaginosis, previously suffered urogenital infections, congenital abnormalities of the urinary tract, a history of nephrolithiasis, prolonged smoking, diabetes mellitus, frequent sore throats and acute respiratory infections. Specific factors contributing to the development of latent chronic bacteriuria in the gestational period are characteristic metabolic, urodynamic changes and mechanical effects:
- Stagnation and reverse casting of urine. In pregnant women, there is an expansion of the calyx-pelvic system, hypotension of the ureters and bladder, relaxation of the urethral sphincter caused by the reaction of smooth muscle fibers to an increase in the concentration of progesterone. Some patients have vesicoureteral and ureteral-pelvic reflux. The situation is aggravated by a 1.5-fold acceleration of glomerular filtration and mechanical compression of the urinary organs by an enlarged uterus.
- Changes in the chemical composition of urine. The influence of counterinsular hormones (cortisol, placental lactogen, chorionic gonadotropin) contributes to the development of physiological insulin resistance in pregnant women. In combination with increased glucose synthesis by the liver, this leads to the development of transient glucosuria, and with insufficient compensatory mechanisms, gestational diabetes. Glucose serves as a suitable substrate for the nutrition and growth of microorganisms trapped on the urothelium.
- Decreased immunity. The restructuring of the immune system of a pregnant woman is aimed at preserving gestation. To prevent rejection of a genetically alien fetus, the activity of T-suppressors in a woman’s body doubles, T-killers, phagocytic neutrophils of blood, macrophages are suppressed, the concentration of immunoglobulins G decreases. As a result, the patient’s susceptibility to bacterial infection increases, which contributes to asymptomatic activation of the commensals.
The mechanism of development of asymptomatic bacteriuria in pregnancy is based on the upward spread of commensal microorganisms through the urinary tract. It is extremely rare for infection to occur hematogenically. Usually, etiopathogens persisting on the mucous membranes of the periurethral zone enter the urinary system through the relaxed sphincter of the urethra. Insufficient immune response does not provide complete elimination of bacteria, the concentration of which is insufficient for the occurrence of a classical inflammatory reaction. Due to the presence of adhesins, hemolysin and other virulence factors, infectious agents colonize the urothelium. Accelerated bacterial growth is promoted by a physiological increase in the pH of urine and possible glucosuria.
Clinically latent bacteriuria does not manifest itself in any way, however, even with a low titer of microorganisms (100-10, 000 CFU / ml), complicated pregnancy is significantly more often observed. In 20-40% of cases, against the background of asymptomatic bacteriuria, acute gestational pyelonephritis develops in pregnant women. Increased local and systemic synthesis of prostaglandins, which are stimulators of the myometrium, provokes premature birth. The risk of gestosis, anemia of pregnant women, fetoplacental insufficiency, intrauterine fetal hypoxia, delayed development, infectious complications (chorioamnionitis, postpartum endometritis) increases. Indicators of prematurity and neonatal mortality in ABP increase 2-2.9 times. It is significant that the treatment of timely diagnosed asymptomatic bacteriuria significantly reduces the likelihood of complications.
The difficulty of detecting the syndrome is associated with the absence of symptoms and pathognomonic complaints. Asymptomatic bacteriuria in pregnancy is diagnosed in the laboratory. Diagnostic alertness is caused by concomitant disorders — increased urination due to possible transient or permanent glucosuria, vaginal discharge, pain, burning, pain, discomfort in the area of the external genitals, indicating a likely infectious and inflammatory process.
Taking into account the risk of complications, microbiological screening is indicated for all pregnant women when registering for a women’s consultation. The diagnosis of asymptomatic uroinfection is established only in cases when, when bacteria are detected in the urine, there are no clinical, laboratory and instrumental signs of infectious and inflammatory diseases of the urinary organs. The survey plan usually includes:
- General urinalysis. To exclude accidental contamination, an average portion of morning urine is examined. The analysis reveals bacteria, in some pregnant women – leukocytes. Elevated pH and glucose in the urine can also be determined.
- Sowing urine on microflora. The analysis is performed twice with an interval between studies of at least 24 hours. The diagnosis of bacteriuria is made with the repeated detection of the same bacterium in a concentration of 100 thousand. CFU/ml.
- TTX test. The photocolorimetric screening diagnostic method allows detecting an increased content of bacteria in the sample within 4 hours. The sensitivity of the reaction with triphenyltetrazolium chloride reaches 90%.
To exclude inflammatory urological diseases and assess the functional capabilities of the kidneys, urine analysis by Nechiporenko, renal tests (nephrological complex), general and biochemical blood tests, kidney ultrasound, Doppler ultrasound of renal vessels are recommended as additional studies. Radiological or endoscopic methods are used only in complex diagnostic cases, taking into account possible negative consequences for the woman or fetus. True asymptomatic uroinfection is differentiated with false bacteriuria due to contamination of the material, pyelonephritis, cystitis, urethritis. In addition to the obstetrician-gynecologist, the patient is examined by a therapist, urologist, nephrologist.
The detection of microorganisms in the urine during pregnancy, even in the absence of clinical symptoms and other signs of inflammation, is a sufficient reason for the appointment of antibacterial therapy. Treatment is usually carried out on an outpatient basis with an empirical choice of one of the recommended schemes. Pregnant women can be assigned:
- One-day course. A single dose of a broad-spectrum antibiotic from the group of fosfomycins makes it possible to eliminate most of the bacteria colonizing the urinary tract. Due to the ease of use, high efficiency, and safety, the method is considered preferable in pregnant women.
- Three-day course. Semi-synthetic beta-lactam penicillins, cephalosporins of the II-III generation are used as an antibacterial monopreparation. In the I-II trimester, the appointment of synthetic nitrofurans is permissible, in the III trimester they can provoke hemolytic disease of newborns.
14 days after the end of the course of taking the antibiotic, a repeated bacteriological examination of urine is performed. If there is no bacteriuria, dynamic monitoring of the pregnant woman continues. To consolidate the therapeutic effect, non-drug methods are used: increased urination due to heavy drinking, a decrease in pH through the use of acidic drinks (cranberry juice, etc.). If factors that increase the risk of asymptomatic uroinfection are identified, phytotherapy using herbal antiseptics of complex action is indicated. If latent bacteriuria is detected again, another antibacterial scheme or a drug selected taking into account the sensitivity of microorganisms is prescribed. The preferred method of delivery of pregnant women who have undergone ABP is natural childbirth. Caesarean section is performed only in the presence of obstetric or extragenital indications.
Prognosis and prevention
The effectiveness of short antibacterial courses in the treatment of asymptomatic bacteriuria reaches 79-90%. The prognosis of pregnancy and childbirth with timely detection and adequate therapy of the syndrome is favorable: in 70-80% of pregnant women with signs of ABP, it is possible to prevent the development of pyelonephritis, in 5-10% — prematurity of the child. Primary prevention of asymptomatic uroinfection is aimed at eliminating factors contributing to the occurrence of bacteriuria: pre-gravidar rehabilitation of urogenital organs, smoking cessation, weight correction to reduce the likelihood of developing insulin resistance, drinking mors to acidify urine, preventive intake of uroantiseptics by pregnant women at risk.