23.2 Bacterial Infections of the Urinary System
4 min read•june 18, 2024
(UTIs) are a common bacterial menace. From E. coli to Klebsiella, various microbes can invade our plumbing system, causing symptoms like painful urination and fever. Understanding these culprits is key to effective treatment and prevention.
Beyond the usual suspects, some sneaky bacteria like and Chlamydia can also wreak havoc on our urinary system. These infections often require special diagnostic techniques and treatment approaches. Knowing their unique characteristics helps in tackling these less common but potentially serious threats.
Bacterial Pathogens and Infections of the Urinary System
Common bacterial pathogens in UTIs
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- (E. coli)
- Most frequently encountered cause of urinary tract infections (UTIs) accounting for a significant proportion of cases
- Commensal bacteria that typically resides in the gastrointestinal tract without causing disease
- Certain strains possess unique virulence factors enabling them to colonize and infect the urinary system
- Express adhesion molecules called that facilitate attachment to the uroepithelial cells lining the urinary tract (, )
- Secrete toxins such as which lyse red blood cells and damage the host tissue
- Can form biofilms, contributing to and persistent infections
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- Gram-negative rod-shaped bacteria that ranks as the second leading bacterial cause of UTIs after E. coli
- Possesses a prominent polysaccharide capsule contributing to its pathogenicity and antibiotic resistance
- Frequently implicated in hospital-acquired UTIs especially in catheterized patients or those with prolonged hospital stays (catheter-associated UTI or CAUTI)
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- Motile gram-negative rod exhibiting characteristic swarming motility on agar plates
- Elaborates the enzyme which hydrolyzes urea into carbon dioxide and ammonia
- Ammonia production raises urinary pH leading to precipitation of magnesium and calcium phosphate crystals (struvite stones)
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- Coagulase-negative staphylococcal species that does not produce the enzyme coagulase unlike S. aureus
- Major cause of uncomplicated UTIs in young women of reproductive age often following sexual intercourse
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- Gram-positive cocci that normally inhabit the gastrointestinal tract as part of the commensal flora
- Displays intrinsic resistance to several antibiotics () and can acquire resistance to vancomycin
- Frequently causes UTIs in patients with indwelling urinary catheters or other urologic instrumentation
Symptoms and diagnosis of urinary infections
- (infection of the urinary bladder)
- Patients experience:
- manifesting as a burning sensation during urination due to inflammation of the urethra and bladder
- Increased frequency and urgency of urination as the inflamed bladder becomes irritable and less distensible
- Discomfort or pain in the lower abdominal area (suprapubic region) where the bladder is located
- Presence of visible blood in the urine (gross ) or microscopic detectable on
- Diagnostic evaluation involves:
- to detect the presence of white blood cells (leukocytes), nitrites produced by certain bacteria, and bacteria on microscopy
- to isolate and identify the causative bacterial pathogen and determine its antibiotic susceptibility profile
- Patients experience:
- (infection of the kidney parenchyma)
- Patients manifest:
- High-grade fever often accompanied by chills and rigors due to the systemic inflammatory response
- Severe, unilateral flank pain overlying the affected kidney due to stretching of the renal capsule
- Gastrointestinal symptoms such as nausea and vomiting resulting from the inflammatory process
- Lower urinary tract symptoms of cystitis may also be present concurrently
- Diagnostic workup entails:
- Urinalysis and urine culture to confirm the presence of infection and identify the etiologic agent
- Blood cultures to assess for concomitant bloodstream invasion (bacteremia) by the urinary pathogen
- Radiologic imaging such as CT scan or ultrasound to evaluate for renal abscesses, obstruction, or other complications
- Patients manifest:
Leptospira and Chlamydia in urinary system
- Leptospira
- Thin, coiled, highly motile spirochete bacteria that infect both humans and animals (zoonosis)
- Acquired through contact with soil or water contaminated by the urine of infected animals (rodents, dogs, livestock) or through direct exposure to animal urine
- Penetrates intact mucous membranes or abraded skin and disseminates hematogenously to various organs
- In the kidneys, invades and multiplies within the renal tubular epithelial cells causing tubulointerstitial nephritis
- Severe cases progress to acute renal failure characterized by oliguria, azotemia, and electrolyte imbalances
- Diagnosis relies on serologic tests (microscopic agglutination test) to detect antibodies and to identify Leptospira DNA in clinical samples
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- Obligate intracellular bacteria that exclusively replicate within host cells and cannot be cultured on artificial media
- Most commonly transmitted through sexual contact making it one of the most prevalent sexually transmitted infections worldwide
- Primarily infects the genital tract (urethra, cervix) but can ascend to the upper genital and urinary tract
- In males, causes (urethral inflammation) and (inflammation of the epididymis)
- In females, can lead to pelvic inflammatory disease (PID) involving the uterus, fallopian tubes, and ovaries
- Nucleic acid amplification tests (NAATs) performed on urine samples or genital swabs are the diagnostic gold standard for detecting Chlamydia
Special considerations in urinary tract infections
- : Presence of bacteria in the urine without clinical symptoms, often requiring no treatment except in specific populations (e.g., pregnant women)
- Antibiotic resistance: Increasing prevalence of multidrug-resistant uropathogens, necessitating careful antibiotic selection based on local resistance patterns and susceptibility testing
- Recurrent UTIs: Some patients experience frequent infections due to factors like antibiotic resistance, , or anatomical abnormalities
Key Terms to Review (70)
Antibiotic Resistance: Antibiotic resistance is the ability of bacteria and other microorganisms to withstand the effects of antibiotics, rendering these drugs ineffective in treating infections. This phenomenon is a growing global health concern that has significant implications across various aspects of microbiology, including prokaryote habitats, antimicrobial discovery and chemotherapy, and the treatment of bacterial infections.
Antigenic variation: Antigenic variation is the process by which a pathogen alters its surface proteins to evade a host's immune response. This mechanism enables pathogens to persist in the host and cause chronic or recurrent infections.
Asymptomatic Bacteriuria: Asymptomatic bacteriuria refers to the presence of bacteria in the urine without any associated symptoms of a urinary tract infection. It is a common condition that is often observed in certain populations, such as the elderly and pregnant women, but does not necessarily require treatment.
Autotransporter proteins: Autotransporter proteins are a class of virulence factors used by Gram-negative bacteria to transport themselves across the outer membrane. They play a crucial role in bacterial pathogenesis, including adhesion, invasion, and evasion of host immune responses.
Biofilm Formation: Biofilm formation is the process by which microorganisms, such as bacteria and fungi, adhere to surfaces and develop into complex, structured communities encased in a self-produced extracellular matrix. This phenomenon is closely linked to the pathogenesis and persistence of various microbial infections, as well as the effectiveness of antimicrobial agents and disinfectants.
Bladder: The bladder is a hollow, muscular organ that serves as a reservoir for urine in the urinary system. It plays a crucial role in the normal functioning and health of the urogenital tract, as well as in the prevention and management of bacterial infections of the urinary system.
Bladder infections: Bladder infections, also known as cystitis, are bacterial infections that affect the bladder. They are commonly caused by Escherichia coli (E. coli) and can result in symptoms such as painful urination and frequent urges to urinate.
Carbapenems: Carbapenems are a class of broad-spectrum beta-lactam antibiotics highly effective against many gram-positive and gram-negative bacteria. They are often used as a last-resort treatment for severe or high-risk bacterial infections.
Catheter-Associated Urinary Tract Infection (CAUTI): Catheter-associated urinary tract infection (CAUTI) is a type of healthcare-associated infection that occurs when bacteria or other microorganisms enter the urinary tract through a urinary catheter, leading to an infection. Catheters are tubes inserted into the bladder to drain urine, and their use can increase the risk of developing a urinary tract infection (UTI).
Cephalosporins: Cephalosporins are a class of β-lactam antibiotics that inhibit bacterial cell wall synthesis and are used to treat a wide range of infections. They are structurally and functionally similar to penicillins but are often more resistant to β-lactamases.
Chlamydia trachomatis: Chlamydia trachomatis is a species of obligate intracellular bacteria that is the causative agent of several human diseases, including trachoma, lymphogranuloma venereum, and various sexually transmitted infections. It is a significant public health concern due to its ability to infect and impact multiple body systems.
Clean catch: A clean catch is a method of collecting a urine sample to avoid contamination by bacteria from the skin or genital area. It's crucial for accurate diagnosis of urinary infections.
Cystitis: Cystitis is an inflammation of the bladder, typically caused by a bacterial infection. It is a common urinary tract infection that can cause discomfort, pain, and other urinary symptoms.
Dysuria: Dysuria is the medical term for painful or difficult urination. It is commonly associated with infections of the urinary and reproductive systems.
Dysuria: Dysuria is the medical term for painful or difficult urination, a symptom that can arise from various conditions affecting the urogenital system. This term is particularly relevant in the context of understanding the anatomy and normal microbiota of the urogenital tract, bacterial infections of the urinary system, and protozoan infections of the urogenital system.
ELISA: ELISA (Enzyme-Linked Immunosorbent Assay) is a technique used to detect the presence of antibodies or antigens in a sample. It is widely used in microbiology for diagnostics and research.
Enterococcus faecalis: Enterococcus faecalis is a Gram-positive, facultatively anaerobic bacterium that is a common inhabitant of the human gastrointestinal tract. It is a significant cause of urinary tract infections and other nosocomial infections, particularly in immunocompromised individuals.
Epididymitis: Epididymitis is the inflammation of the epididymis, a tube at the back of the testicle that stores and carries sperm. It is commonly caused by bacterial infections, including sexually transmitted infections (STIs).
Epididymitis: Epididymitis is an inflammation of the epididymis, the coiled tube at the back of the testicle that stores and carries sperm. This condition can be caused by bacterial infections or, less commonly, by viral infections, and is often associated with urinary tract infections or sexually transmitted diseases.
Escherichia coli: Escherichia coli (E. coli) is a Gram-negative, rod-shaped bacterium commonly found in the intestines of warm-blooded organisms. While most strains are harmless, some can cause serious food poisoning and infections.
Glomerulonephritis: Glomerulonephritis is an inflammation of the glomeruli in the kidneys, often caused by immune system responses to infections or other diseases. It can lead to impaired kidney function and may result in chronic kidney disease if left untreated.
Hematuria: Hematuria is the presence of blood in urine, which can indicate underlying infections or other medical conditions. It can be visible (gross hematuria) or detected only by microscopic examination (microscopic hematuria).
Hematuria: Hematuria is the presence of red blood cells (RBCs) in the urine, resulting in a visibly red or pink-colored urine. It is an important clinical sign that can indicate various underlying conditions affecting the urogenital tract.
Hemolysin: Hemolysin is a toxin produced by certain bacteria that can disrupt and rupture red blood cells, causing them to release their hemoglobin content. This process is known as hemolysis and is an important virulence factor for many pathogenic bacteria.
Immunoglobulin α protease: Immunoglobulin α protease is an enzyme produced by certain bacteria that specifically cleaves immunoglobulin A (IgA) antibodies. This enzymatic action helps bacteria evade the host's immune response in mucosal areas, including the urinary system.
Injectisome: An injectisome is a needle-like protein appendage found in certain Gram-negative bacteria that facilitates the direct transfer of toxins into host cells. It plays a crucial role in bacterial pathogenicity, enabling bacteria to infect and manipulate host cellular processes.
Jaundice: Jaundice is a medical condition characterized by the yellowing of the skin and eyes due to elevated bilirubin levels in the blood. It often indicates underlying issues with the liver, bile ducts, or red blood cells.
Klebsiella pneumoniae: Klebsiella pneumoniae is a Gram-negative, encapsulated bacterium that can cause severe infections, particularly in the lungs and urinary tract. It is known for its resistance to multiple antibiotics, making infections difficult to treat.
Leptospira: Leptospira is a genus of spiral-shaped, motile bacteria that are the causative agents of the zoonotic disease leptospirosis. These bacteria primarily infect the kidneys of various animal hosts and can be transmitted to humans through contact with contaminated water or soil.
Leptospirosis: Leptospirosis is a bacterial infection caused by Leptospira species, primarily affecting the kidneys and urinary system. It is commonly transmitted through contact with water contaminated by the urine of infected animals.
Leukocyte esterase: Leukocyte esterase is an enzyme produced by white blood cells (leukocytes) and is used as a marker in urine tests to detect the presence of these cells, indicating inflammation or infection in the urinary tract. It is commonly utilized in diagnosing urinary tract infections (UTIs).
Moxifloxacin: Moxifloxacin is a broad-spectrum fluoroquinolone antibiotic used to treat various bacterial infections, including those of the urinary system. It works by inhibiting bacterial DNA gyrase and topoisomerase IV enzymes, preventing bacterial replication.
Multiple banded antigen: A multiple banded antigen is a type of protein marker found on the surface of certain bacteria that can generate multiple distinct immune responses. These antigens are often used to identify and differentiate bacterial strains in diagnostic tests.
Mycoplasma hominis: Mycoplasma hominis is a type of bacteria that lacks a cell wall and is commonly associated with urogenital tract infections. It is known for its role in bacterial vaginosis, pelvic inflammatory disease, and other urinary system infections.
Nitrate reductase: Nitrate reductase is an enzyme that reduces nitrate (NO3-) to nitrite (NO2-) during the process of anaerobic respiration in certain bacteria. It plays a crucial role in nitrogen metabolism and can be used as a diagnostic marker for bacterial infections.
Nitrofurantoin: Nitrofurantoin is an antibiotic specifically used to treat urinary tract infections. It works by inhibiting bacterial enzymes and interfering with cell wall synthesis.
Nongonococcal urethritis (NGU): Nongonococcal urethritis (NGU) is an inflammation of the urethra not caused by Neisseria gonorrhoeae. It is commonly associated with bacterial infections such as Chlamydia trachomatis and Mycoplasma genitalium.
P Fimbriae: P fimbriae are hair-like protein structures that extend from the surface of certain pathogenic bacteria, such as Escherichia coli. These adhesive structures allow the bacteria to attach to and colonize the epithelial cells lining the urinary tract, facilitating the development of urinary tract infections (UTIs).
PCR: Polymerase Chain Reaction (PCR) is a technique used to amplify small segments of DNA. It allows for the creation of millions of copies of a specific DNA sequence in a short period.
Penicillin: Penicillin is a group of antibiotics derived from Penicillium fungi. It is widely used to treat bacterial infections by inhibiting cell wall synthesis.
Penicillins: Penicillins are a group of antibiotics derived from Penicillium fungi, effective against many Gram-positive bacteria. They inhibit bacterial cell wall synthesis, leading to cell lysis and death.
Phospholipase A: Phospholipase A is an enzyme that hydrolyzes the sn-2 acyl bond of phospholipids, releasing fatty acids and lysophospholipids. It plays a role in bacterial pathogenesis by disrupting host cell membranes.
Phospholipase C: Phospholipase C is an enzyme that hydrolyzes phospholipids into diacylglycerol and inositol trisphosphate. It plays a key role in cell signaling pathways and can be a virulence factor for certain bacteria.
Proteus mirabilis: Proteus mirabilis is a Gram-negative, rod-shaped bacterium that is a common cause of urinary tract infections (UTIs), particularly in individuals with underlying urological abnormalities or who have been catheterized. It is known for its ability to swarm across surfaces and its tendency to form kidney stones.
Proteus vulgaris: Proteus vulgaris is a Gram-negative, rod-shaped bacterium commonly found in the intestines of humans and animals. It is known for its motility and ability to cause urinary tract infections (UTIs).
Pseudomonas aeruginosa: Pseudomonas aeruginosa is a Gram-negative, opportunistic pathogen that can cause serious infections in humans. It is known for its resistance to antibiotics and ability to thrive in various environments.
Pyelonephritis: Pyelonephritis is a type of urinary tract infection (UTI) that affects the kidneys. It can lead to severe complications if left untreated, including kidney damage and sepsis.
Pyelonephritis: Pyelonephritis is a type of urinary tract infection (UTI) that specifically affects the kidneys. It is an inflammation of the renal pelvis, the funnel-shaped part of the urinary tract that connects the kidneys to the ureters, often caused by a bacterial infection.
Pyuria: Pyuria is the presence of pus in the urine, a sign often indicative of a urinary tract infection (UTI). It is characterized by an elevated number of white blood cells in the urine.
Salpingitis: Salpingitis is the inflammation of the fallopian tubes, typically caused by bacterial infections. It can lead to serious reproductive complications if not treated promptly.
Staphylococcus saprophyticus: Staphylococcus saprophyticus is a Gram-positive, coagulase-negative bacterium that is a common cause of urinary tract infections, particularly in young, sexually active women. It is a normal part of the human skin and mucous membrane flora, but can opportunistically infect the urinary tract.
Streptococcus agalactiae: Streptococcus agalactiae, also known as Group B Streptococcus (GBS), is a Gram-positive bacterium that can cause severe infections in newborns, pregnant women, and immunocompromised individuals. It is a common cause of bacterial infections in the urogenital system and can also lead to meningitis and sepsis in neonates.
Streptococcus pyogenes: Streptococcus pyogenes is a Gram-positive bacterium responsible for various infections in humans. It is known for causing diseases such as strep throat, scarlet fever, and rheumatic fever.
Stress response proteins: Stress response proteins are a group of proteins that help bacteria survive under stressful conditions, such as high temperatures, oxidative stress, or the presence of antibiotics. These proteins play a crucial role in bacterial pathogenesis and survival within host environments.
Sulfamethoxazole: Sulfamethoxazole is a sulfonamide antibiotic that inhibits bacterial synthesis of dihydrofolic acid by competing with para-aminobenzoic acid (PABA). It is often used in combination with trimethoprim to treat various bacterial infections, including those of the urinary tract.
Trachoma: Trachoma is a bacterial infection of the eye caused by Chlamydia trachomatis, leading to inflammation and possible blindness if untreated. It is a significant cause of preventable blindness worldwide.
Trimethoprim: Trimethoprim is an antibiotic used primarily to treat bacterial infections, particularly in the urogenital and digestive systems. It works by inhibiting bacterial DNA synthesis.
Type III secretion effectors: Type III secretion effectors are proteins secreted by gram-negative bacteria directly into host cells via the Type III secretion system (T3SS). These effectors manipulate host cell functions to promote bacterial survival and infection.
Urease: Urease is an enzyme that catalyzes the hydrolysis of urea into carbon dioxide and ammonia. It is produced by certain bacteria and plays a crucial role in their survival and pathogenicity.
Urease: Urease is an enzyme produced by certain microorganisms that catalyzes the hydrolysis of urea into carbon dioxide and ammonia. This enzyme plays a crucial role in the nitrogen cycle and is particularly relevant in the context of prokaryote habitats, the urogenital tract, urinary system infections, and the digestive system.
Ureters: The ureters are a pair of narrow, muscular tubes that connect the kidneys to the bladder. They are responsible for transporting urine from the kidneys to the bladder for storage and eventual elimination from the body.
Urethritis: Urethritis is an inflammation of the urethra, the tube that carries urine from the bladder out of the body. This condition can be caused by bacterial or viral infections and is often associated with sexually transmitted diseases.
Urinalysis: Urinalysis is a diagnostic test that examines the content of urine to detect and manage various disorders, including infections of the urinary system. It involves physical, chemical, and microscopic analysis.
Urinalysis: Urinalysis is the physical, chemical, and microscopic examination of urine. It is a crucial diagnostic tool used to detect and monitor various health conditions, particularly those related to the urinary system and overall bodily function.
Urinary Tract Infection (UTI): A urinary tract infection (UTI) is a bacterial infection that affects any part of the urinary system, including the kidneys, ureters, bladder, and urethra. It is a common and often recurring condition that can cause significant discomfort and, if left untreated, can lead to more serious complications.
Urinary tract infections: Urinary tract infections (UTIs) are infections that affect any part of the urinary system, including the urethra, bladder, ureters, and kidneys. They are commonly caused by bacteria such as Escherichia coli.
Urine Culture: A urine culture is a laboratory test used to identify the presence and type of bacteria or other microorganisms in a urine sample. It is a crucial diagnostic tool for evaluating and managing bacterial infections of the urinary system.
Urine dipstick: A urine dipstick is a diagnostic tool used to detect abnormalities in a urine sample. It provides quick results for substances like proteins, glucose, and bacteria which can indicate infections or other medical conditions.
Weil’s disease: Weil's disease is a severe form of leptospirosis caused by the bacterium Leptospira interrogans. It primarily affects the kidneys and liver, leading to serious complications.
β-lactams: β-lactams are a class of broad-spectrum antibiotics that contain a β-lactam ring in their molecular structure. They work by inhibiting the synthesis of bacterial cell walls, leading to cell death.