The Urinary Tract Infections

Published Date: 02 Nov 2017

Epidemiologically, urinary tract infections are sub-divided into catheter associated or nosocomial infection or non-catheter associated community acquired infections. Infections in either category may be symptomatic or asymptomatic. Acute community infections are very common and account for more than 7 million Hospital visits annually in the United States. There infections occur in 1-3% of school girls and then increased markedly in incidence with the onset of sexual activity in adolescence. The vast majority of acute infections involve women. Acute symptomatic Urinary Tract Infections are unusual in men under the young age group of 50 yrs. The development of asymptomatic bacteriuria parallels that of symptomatic infections and in rare among men under 50 years but common among women between 20 and 50 years. Asymptomatic bacteriuria is more among elderly men and women with rates as high as 10-50% in some studies.

Causative organisms of Urinary Tract Infections are the most common organism is Gram Negative Bacilli

Escherichia coli – 70-80%

Klebsiella – 2-3%

Proteus – 2-4%

Enterococcus – 1-2%

Gram positive cocci

Staphylococcus saprophyticus – 10-15%

More commonly serratia and pseudomonas are known to cause recurrent infections and also in infections which are associated with urological manipulation, calculi or obstruction.

Proteus species and klebsiella species by virtue of urease production and through the production of polysaccharides and extracellular slime predispose to formation of stone and more frequently in patients with calculi.

Chlamydia trachomatis, Neisseria gonorrhoea, and herpes simplex virus are most frequently found in sexually active young women.

The causative role of non-bacterial pathogens in Urinary Tract Infection’s remains poorly defined. Urea plasma urealyticum has been frequently isolated from t urine of patients with acute dysuria and increased frequency but it is also found in specimens without urinary symptoms.

In patients with acute prostatitis and pyelonephritis species of mycoplasma hominis has been isolated from prostatic and renal tissues, and are probably irresponsible for some of the infections as well. Candida and other fungal infection are common and sometimes progressive to symptomatic invasive infection.

Mycobacterial infection of Urinary Tract Infection is also a common cause of Asymptomatic Bacteriuria.

PATHOGENESIS AND SOURCES OF INFECTION

The urinary tract should be viewed as a single anatomic unit that is united by a single column of urine extending from the urethra to the kidney.

Routes of Entry to the urinary tract

Ascending Infection

Mostly the infections of kidney units from organisms desired from gastrointestinal tract to the urethra and periurethra tissues into the bladder and then by the catheter to renal pelvis with subsequent invasion of renal medulla.

Haematogenous infection

It accounts for less than 3% cases of Urinary Tract Infection and pyelonephritis. The major cases of haematogenous infection are staphylococcus aureus, salmonella species, pseudomonas aeruginosa, and Enterococcus faecalis

Lymphatic spread

Spread of infection along the lymphatic channels connecting bowel and urinary tract is possible.

PREDISPOSING FACTORS

GENDER AND SEXUAL ACTIVITY

In females the urethra is prone for gram negative bacilli infection because it is close to the perineum and its short length and its termination beneath the labia. In addition UTI due to increased colonization of E.coli has been associated due to the use of spermicidal compounds with a diaphragm or a cervical cap or of spermicide coated condoms which dramatically alter the normal introital bacterial flora. In males who are a 50 years old and who have no H/o Heterosexual or Homosexual rectal intercourse, Urinary Tract Infection is exceedingly uncommon. Men & women who are infected with HIV are at increased risk of both bacteriuria and Urinary Tract Infection. Lack of circumcision has been identified as a risk factor for Urinary Tract Infection in both neonates & young men.

Pregnancy: 2-9 of Pregnant women 20-30% of pregnant women with Asymptomatic Bacteriuria subsequently develop pyelonephritis. Catheterization during or after delivery causes additional infections.

Obstruction: Any obstruction in free flow of urine due to tumour, stricture, stone, or prostatic hypertrophy results in increased frequency of Urinary Tract Infection.

NEUROGENIC BLADDER DYSFUNTION

Dysfunction that occurs due to interference with the nerve supply to the bladder which is seen in spinal cord injury, tabes dorsalis, multiple sclerosis. Diabetes and other diseases may be associated with Urinary Tract Infection. Other additional causes due to bone demineralization are from immobilization which leads to hypercalciuria, calculus formation & obstructive uropathy.

Vesicoureteral Reflux: Anatomically impaired vesicoureteral function facilities reflux of bacteria and thus Urinary Tract Infection.

BACTERIAL VIRULENCE FACTORS

Virulence factors of E.coli – surface antigen & toxins

Somatic Polysaccharide surface 0 antigens

Exerts endotoxic activity

Protects bacillus from phagocytosis

Protects bacillus from bactericidal effects of the complement system.

K antigens or envelop

P fimbriae bind specifically to the P blood group substance on human erythrocytes and uroepithelial cells.

The E.coli serotypes commonly responsible for Urinary tract infections are those normally found in the faces, o group 1, 2,4,6,7 strains carrying K antigens are more commonly responsible for pyelonephritis.

GENETIC FACTORS

A maternal History of Urinary Tract Infections is found more among women who have experienced recurrent Urinary Tract Infection’s than among controls. It has also been demonstrated that non-secretions of blood group antigens are at increased risk of Urinary Tract Infection.

DEFENSE MECHANISMS OF URINARY TRACT

Normal flora of the vagina

Flushing effect of urine flow and voiding

Phagocytosis

Bladder glycocalyx

Tomm-horsfall glycoprotein

Endotoxin

Immunological

IgA, IgM, IgG Antibodies