Bacterial Diseases of the Urinary System

Urinary Tract Infection (UTI)

A urinary tract infection (UTI) is an infection affecting the urinary tract; about 150 million people develop UTIs each year.

Learning Objectives

Summarize the various categories of urinary tract infection (UTI): complicated, uncomplicated, upper and lower UTIs

Key Takeaways

Key Points

  • About 150 million people develop a urinary tract infection each year, and they are more common in women than men.
  • A urinary tract infection (UTI) is an infection that affects part of the urinary tract. When it affects the lower urinary tract it is known as a bladder infection ( cystitis ); when it affects the upper urinary tract it is known as kidney infection ( pyelonephritis ).
  • UTIs are generally treatable with antibiotics, though resistance to some of the medications is growing.

Key Terms

  • urinary tract infection: A bacterial infection that affects part of the urinary tract.

About 150 million people develop a urinary tract infection each year. They are more common in women than men. In women, they are the most common form of bacterial infection. Up to 10% of women have a urinary tract infection in a given year and half of women having at least one infection at some point in their lives. They occur most frequently between the ages of 16 and 35 years. Recurrences are common. Urinary tract infections have been described since ancient times with the first documented description in the Ebers Papyrus dated to c. 1550 BC.

A urinary tract infection (UTI) is an infection that affects part of the urinary tract. When it affects the lower urinary tract it is known as a bladder infection (cystitis); when it affects the upper urinary tract it is known as kidney infection (pyelonephritis). Symptoms from a lower urinary tract include pain with urination, frequent urination, and feeling the need to urinate despite having an empty bladder. Symptoms of a kidney infection include fever and flank pain usually in addition to the symptoms of a lower UTI. Rarely the urine may appear bloody. In the very old and the very young, symptoms may be vague or non-specific.

The most common cause of infection is Escherichia coli, though other bacteria or fungi may rarely be the cause. Risk factors include female anatomy, sexual intercourse, diabetes, obesity, and family history. Although sexual intercourse is a risk factor, UTIs are not classified as sexually transmitted infections (STIs). Kidney infection, if it occurs, usually follows a bladder infection but may also result from a blood-borne infection. Diagnosis in young healthy women can be based on symptoms alone. In those with vague symptoms, diagnosis can be difficult because bacteria may be present without there being an infection. In complicated cases or if treatment fails, a urine culture may be useful.

Categories of UTI

Uncomplicated UTIs

In uncomplicated cases, a diagnosis may be made and treatment given based on symptoms alone without further laboratory confirmation, and treatment involves a short course of antibiotics such as nitrofurantoin or trimethoprim / sulfamethoxazole. Resistance to many of the antibiotics used to treat this condition is increasing.

Complicated UTIs

In complicated cases, it may be useful to confirm the diagnosis via urinalysis, looking for the presence of urinary nitrites, white blood cells ( leukocytes ), or leukocyte esterase. Another test, urine microscopy, looks for the presence of red blood cells, white blood cells, or bacteria. A longer course or intravenous antibiotics may be needed. If symptoms do not improved in two or three days, further diagnostic testing may be needed. Phenazopyridine may help with symptoms. In those who have bacteria or white blood cells in their urine but have no symptoms, antibiotics are generally not needed, although during pregnancy is an exception. In those with frequent infections, a short course of antibiotics may be taken as soon as symptoms begin or long term antibiotics may be used as a preventative measure.

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Bacteriuria and Pyuria: Multiple bacilli (rod-shaped bacteria, here shown as black and bean-shaped) shown between white blood cells in urinary microscopy. These changes are indicative of a urinary tract infection.

Lower UTI

Lower urinary tract infection is also referred to as a bladder infection. The most common symptoms are burning with urination and having to urinate frequently (or an urge to urinate) in the absence of vaginal discharge and significant pain. These symptoms may vary from mild to severe and in healthy women last an average of six days. Some pain above the pubic bone or in the lower back may be present.

Upper UTI

People experiencing an upper urinary tract infection, or pyelonephritis, may experience flank pain, fever, or nausea and vomiting in addition to the classic symptoms of a lower urinary tract infection. Rarely the urine may appear bloody or contain visible pus in the urine.

Prevention

A number of measures have not been confirmed to affect UTI frequency including: urinating immediately after intercourse, the type of underwear used, personal hygiene methods used after urinating or defecating, or whether a person typically bathes or showers. There is similarly a lack of evidence surrounding the effect of holding one’s urine, tampon use, and douching. In those with frequent urinary tract infections who use spermicide or a diaphragm as a method of contraception, they are advised to use alternative methods. In those with benign prostatic hyperplasia urinating in a sitting position appears to improve bladder emptying which might decrease urinary tract infections in this group.

For those with recurrent infections, taking a short course of antibiotics when each infection occurs is associated with the lowest antibiotic use. A prolonged course of daily antibiotics is also effective. Medications frequently used include nitrofurantoin and trimethoprim/sulfamethoxazole (TMP/SMX). Methenamine is another agent used for this purpose as in the bladder where the acidity is low it produces formaldehyde to which resistance does not develop. Some recommend against prolonged use due to concerns of antibiotic resistance.

Cystitis

Cystitis is a urinary bladder inflammation that is most commonly caused by a bacterial infection of the lower urinary tract infection.

Learning Objectives

Differentiate among the distinct types of cystitis: traumatic, interstitial, eosinophilic, hemorrhagic cystitis, and cystitis cystica, recognizing their causes and risk factors

Key Takeaways

Key Points

  • Cystitis is a urinary bladder inflammation that is most commonly caused by a bacterial infection in which case it is referred to as a urinary tract infection. Symptoms from a lower urinary tract include painful urination and either frequent urination or urge to urinate (or both), but neither may be present.
  • Traumatic cystitis is probably the most common form of cystitis in the female. It is due to bruising of the bladder, usually by abnormally forceful sexual intercourse.
  • Interstitial cystitis (IC) is considered more of an injury to the bladder resulting in constant irritation and rarely involves the presence of infection.

Key Terms

  • cystitis: Cystitis is a urinary bladder inflammation that can result from any one of a number of distinct syndromes. It is most commonly caused by a bacterial infection in which case it is referred to as a urinary tract infection.

A urinary tract infection (UTI), a bacterial infection that affects the lower urinary tract, is also known as a simple cystitis (a bladder infection). Symptoms from a lower urinary tract infection include painful urination and either frequent urination or the urge to urinate (or both).

Cystitis is a urinary bladder inflammation that can result from any one of a number of distinct syndromes. It is most commonly caused by a bacterial infection in which case it is referred to as a urinary tract infection.

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Proteus vulgaris on MacConkey agar: After 24 hours, this inoculated MacConkey agar culture plate cultivated colonial growth of Gram-negative, rod-shaped, and facultatively anaerobic Proteus vulgaris bacteria. Normally found in the humans gastrointestinal tract, Proteus spp. are opportunistic pathogens, which means that they usually do not cause disease. However, under immunocompromised circumstances, i.e., weakened immunity, these bacteria can be found the culprit responsible for urinary tract infections such as cystitis and pyelonephritis.

Signs and Symptoms

  • Pressure in the lower pelvis
  • Painful urination (dysuria)
  • Frequent urination (polyuria) or urgent need to urinate (urinary urgency)
  • Need to urinate at night (nocturia)
  • Urine that contains traces of blood (haematuria)
  • Dark, cloudy or strong-smelling urine
  • Pain above the pubic bone, or in the lower back or abdomen
  • Feeling unwell, weak, or feverish

SUBTYPES

There are several medically distinct types of cystitis, each having a unique etiology and therapeutic approach:

  • Traumatic cystitis is probably the most common form of cystitis in the female. It is due to bruising of the bladder, usually by abnormally forceful sexual intercourse. This is often followed by bacterial cystitis, frequently by coliform bacteria being transferred from the bowel through the urethra into the bladder.
  • Interstitial cystitis (IC) is considered more of an injury to the bladder resulting in constant irritation and rarely involves the presence of infection. IC patients are often misdiagnosed with UTI/cystitis for years before they are told that their urine cultures are negative. Antibiotics are not used to treatment of IC. The cause of IC is unknown, although some suspect it may be autoimmune where the immune system attacks the bladder. Several therapies are now available.
  • Eosinophilic cystitis (EC) is a rare form of cystitis that is diagnosed via biopsy. In these cases, the bladder wall is infiltrated with a high number of eosinophils. The cause of EC may be attributed to infection by Schistosoma haematobium or by certain medications in afflicted children. Some consider it a form of interstitial cystitis.
  • Hemorrhagic cystitis can occur as a side effect of cyclophosphamide, ifosfamide, and radiation therapy. Radiation cystitis, one form of hemorrhagic cystitis is a rare consequence of patients undergoing radiation therapy for the treatment of cancer. Several adenovirus serotypes have been associated with an acute, self-limited hemorrhagic cystitis, which occurs primarily in boys. It is characterized by hematuria, and virus can usually be recovered from the urine. In sexually active women the most common cause of urinary tract infection is from E. coli and Staphylococcus saprophyticus.
  • Cystitis cystica is a chronic cystitis glandularis accompanied by the formation of cysts. This disease can cause chronic urinary tract infections. It appears as small cysts filled with fluid and lined by one or more layers of epithelial cells. These are due to hydropic degeneration in center of Brunn’s nests

Pyelonephritis

Pyelonephritis is an inflammation of the kidney tissue and surrounding area, commonly caused by a bacterial infection ascending up the upper urinary tract.

Learning Objectives

Identify the main symptoms of pyelonephritis

Key Takeaways

Key Points

  • Pyelonephritis is an inflammation of the kidney tissue and renal area of the pelvis.
  • Pyelonephritis is most commonly caused by a bacterial infection ascending up the upper urinary tract.
  • Severe cases of pyelonephritis can lead to sepsis, kidney failure, and death.
  • Pyelonephritis presents with fever, accelerated heart rate, painful urination, abdominal pain, and nausea.
  • Pyelonephritis requires antibiotic therapy, and sometimes surgical intervention, as well as treatment of any underlying causes to prevent recurrence.

Key Terms

  • pyelonephritis: An ascending urinary tract infection that has reached the pelvis or the kidney.
  • Urinary tract: The organ system that produces, stores, and eliminates urine. In humans it includes two kidneys, two ureters, the bladder, and the urethra.
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Urinary tract infection (UTI): White blood cells in the urine of someone with a UTI, seen under a microscope.

Pyelonephritis is an inflammation of the kidney tissue, calyces, and renal pelvis. It is commonly caused by bacterial infection that has spread up the urinary tract or travelled through the bloodstream to the kidneys.

A similar term is “pyelitis” which means inflammation of the pelvis and calyces. In other words, pyelitis together with nephritis is collectively known as pyelonephritis. Severe cases of pyelonephritis can lead to pyonephrosis (pus accumulation around the kidney), sepsis (a systemic inflammatory response of the body to infection), kidney failure and even death.

Pyelonephritis presents with fever, accelerated heart rate, painful urination, abdominal pain radiating to the back, nausea, and tenderness at the costovertebral angle on the affected side. Pyelonephritis that has progressed to urosepsis may be accompanied by signs of septic shock, including rapid breathing, decreased blood pressure, violent shivering, and occasionally delirium. Pyelonephritis requires antibiotic therapy, and sometimes surgical intervention, as well as treatment of any underlying causes to prevent its recurrence.

Leptospirosis

Leptospirosis is a rare and severe infection caused by Leptospira bacteria and usually transmitted to people from animals.

Learning Objectives

Generalize the causes and mode of transmission for leptospirosis

Key Takeaways

Key Points

  • Leptospirosis symptoms can range from none to mild such as headaches, muscle pains, and fevers; to severe with bleeding from the lungs or meningitis.
  • Outside of tropical areas, leptospirosis cases have a relatively distinct seasonality, with most cases occurring in spring and autumn.
  • Leptospirosis is transmitted by the urine of an infected animal and is contagious as long as it remains moist.
  • There is a direct correlation between the amount of rainfall and the incidence of leptospirosis, making it seasonal in temperate climates and year-round in tropical climates.

Key Terms

  • leptospirosis: an acute, infectious, febrile disease of both humans and animals, caused by spirochetes of the genus Leptospira

Symptoms of Leptospirosis

Leptospirosis (also known as Weil’s Syndrome, canicola fever, canefield fever, nanukayami fever, 7-day fever, Rat Catcher’s Yellows, Fort Bragg fever, black jaundice, and Pretibial fever) is caused by bacteria of the genus Leptospira, and affects humans as well as other animals. Symptoms can range from none to mild such as headaches, muscle pains, and fevers; to severe with bleeding from the lungs or meningitis. If the infection causes the person to turn yellow, have kidney failure and bleeding it is then known as Weil’s disease. If the infection causes lots of bleeding from the lungs it is known as severe pulmonary haemorrhage syndrome.

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Leptospira bactera that cause Leptospirosis: Scanning electron micrograph of a number of Leptospira sp. bacteria atop a 0.1 ┬Ám polycarbonate filter.

Cause and Transmission of Leptospirosis

Leptospirosis is among the world’s most common diseases transmitted to people from animals. The infection is commonly transmitted to humans by allowing water that has been contaminated by animal urine to come in contact with unhealed breaks in the skin, eyes, or mucous membranes. Outside of tropical areas, leptospirosis cases have a relatively distinct seasonality, with most cases occurring in spring and autumn.

Leptospirosis is caused by a spirochaete bacterium called Leptospira spp. There are at least five serotypes of importance in the United States and Canada, all of which cause disease in dogs (Icterohaemorrhagiae, Canicola, Pomona, Grippotyphosa, and Bratislava).There are other (less common) infectious strains as well. Leptospirosis is transmitted by the urine of an infected animal and is contagious as long as it is still moist. Although rats, mice, and moles are important primary hosts, a wide range of other mammals (including dogs, deer, rabbits, hedgehogs, cows, sheep, raccoons, opossums, skunks, and certain marine mammals) are able to carry and transmit the disease as secondary hosts. Dogs may lick the urine of an infected animal off the grass or soil or drink from an infected puddle.

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Leptospirosis in kidney: Photomicrograph of kidney tissue, using a silver staining technique, revealing the presence of Leptospira bacteria.

There have been reports of “house dogs” contracting leptospirosis from licking the urine of infected mice that enter the house. The type of habitats most likely to carry infectious bacteria are muddy riverbanks, ditches, gullies, and muddy livestock-rearing areas where there is regular passage of either wild or farm mammals. There is a direct correlation between the amount of rainfall and the incidence of leptospirosis, making it seasonal in temperate climates and year-round in tropical climates. Leptospirosis is also transmitted by the semen of infected animals. Humans become infected through contact with water, food, or soil containing urine from these infected animals. This may result from swallowing contaminated food and water or through skin contact. The disease is not known to be spread from person to person, and cases of bacterial dissemination in convalescence are extremely rare in humans. Leptospirosis is common among water-sport enthusiasts in specific areas, as prolonged immersion in water is known to promote the entry of the bacteria. Surfers and whitewater paddlers are at especially high risk in areas that have been shown to contain the bacteria, and can contract the disease by swallowing contaminated water, splashing contaminated water into their eyes or nose, or exposing open wounds to infected water.