Microbiology of Urinary Tract Infections

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Questions and Answers

Which medication is not typically used in empirical therapy for acute complicated urinary tract infections?

Amoxicillin-clavulanate (correct)

Vancomycin

Piperacillin-tazobactam

Ciprofloxacin

P fimbriae increase the susceptibility of bacteria to phagocytosis.

False

Which of the following microbial species is commonly associated with urinary tract infections?

Escherichia coli (correct)

Lactobacillus

Bacillus subtilis

Streptococcus

What is the role of flagella in bacterial virulence?

Enhanced motility Signup and view all the answers

Pregnant women do not require urine culture testing for urinary tract infections.

False Signup and view all the answers

___ is a siderophore produced by bacteria to acquire iron in the urinary tract.

Aerobactin Signup and view all the answers

What is one factor that predisposes women to urinary tract infections?

Short urethra Signup and view all the answers

The __________ test uses leukocyte esterase to detect the presence of infection in the urine.

urine dipstick Signup and view all the answers

Match the following beta-lactam agents with their dosages:

Amoxicillin-clavulanate = 500 mg twice daily Cefpodoxime = 100 mg twice daily Cefdinir = 300 mg twice daily Cefadroxil = 500 mg twice daily Signup and view all the answers

Match the following methods of evaluating the urinary tract with their indications:

Ultrasound = Nephrolithiasis or Neurogenic Bladder IVP = Men with 1st or 2nd infection CT scan = Bacteremic pyelonephritis not responding to therapy Urine culture = Pregnant women Signup and view all the answers

Which of the following is classified as an uncomplicated urinary tract infection (UTI)?

Simple cystitis of short duration Signup and view all the answers

Pyelonephritis is a type of lower urinary tract infection.

False Signup and view all the answers

What are two common clinical symptoms of cystitis in adults?

Dysuria and urinary frequency Signup and view all the answers

Asymptomatic bacteriuria is defined as the isolation of a specified quantitative count of bacteria in urine from an individual without symptoms of urinary tract infection when the count is greater than or equal to _____ CFU/mL.

105 Signup and view all the answers

Match the following types of urinary tract infections with their descriptions:

Uncomplicated UTI = Infection with structurally normal urinary tract Complicated UTI = Infection with structural or functional abnormalities Cystitis = Lower UTI symptoms like dysuria and frequency Pyelonephritis = Upper UTI symptoms like fever and flank pain Signup and view all the answers

Which of the following symptoms is NOT suggestive of upper tract disease (pyelonephritis)?

Persistent cough Signup and view all the answers

E.coli is the primary pathogen associated with cystitis.

True Signup and view all the answers

What are the two primary risk factors for recurrent uncomplicated urinary tract infections?

P1 blood group positive and postmenopausal status Signup and view all the answers

Urine culture is necessary in patients with __________ UTI or treatment failure.

complicated Signup and view all the answers

Match the following treatment options with their appropriate duration:

Short course therapy = 3 days Longer duration for complicated infections = 10-14 days Empiric therapy for acute simple cystitis = 3 days Signup and view all the answers

What is the generally recommended initial therapy for patients with pyelonephritis?

Intravenous antibiotics for 10-14 days Signup and view all the answers

Behavioral risk factors for UTIs may include spermicide use and having a new sexual partner.

True Signup and view all the answers

Which antibiotics are part of the empiric therapy for acute simple cystitis?

Trimethoprim (with or without sulfamethoxazole) Signup and view all the answers

Study Notes

Urinary Tract Infections in Adults

Urinary infections can be categorized as either acute uncomplicated cystitis or acute complicated UTI.
Acute simple cystitis is presumed confined to the bladder, with no signs or symptoms suggesting upper tract or systemic infection.
Acute complicated UTI presents with signs/symptoms indicating infection beyond the bladder, including fever (>99.9°F/37.7°C), chills, rigors, significant fatigue/malaise, flank pain, costovertebral angle tenderness, or pelvic/perineal pain in men.
Special populations warrant unique management considerations, including pregnant women and renal transplant recipients.

UTI Definitions

Lower UTI: Cystitis, urethritis, prostatitis.
Upper UTI: Pyelonephritis, intra-renal abscess, perinephric abscess (usually late complications of pyelonephritis).
Uncomplicated UTI: Infection in a structurally and neurologically normal urinary tract. Simple cystitis lasting 1-5 days.
Complicated UTI: Infection in a urinary tract with functional or structural abnormalities (e.g., indwelling catheters, renal calculi). Includes cystitis of long duration or hemorrhagic cystitis.

Asymptomatic Bacteriuria

Isolation of a specified quantitative count of bacteria in a properly collected urine specimen from an individual without urinary tract infection (UTI) symptoms.
A count of ≥10⁵ colony-forming units (CFU)/mL indicates asymptomatic bacteriuria.

Indications for Screening/Treating UTIs

Pregnancy
Patients undergoing urologic interventions
Renal transplant recipients
Patients with neurological or structural abnormalities of the urinary tract
Older patients
Patients with Diabetes Mellitus

Clinical Symptoms and Presentation

Cystitis: Dysuria, urinary urgency/frequency, bladder fullness/discomfort. Hemorrhagic cystitis (bloody urine) can occur in up to 10% of otherwise healthy women.
Pyelonephritis (upper UTI): Fever, sweating, nausea, vomiting, flank pain, dysuria, and signs/symptoms of dehydration and hypotension. A history of vaginal discharge may suggest vaginitis, cervicitis, or pelvic inflammatory disease as a possible cause for dysuria.

Diagnosis of UTI

Urinalysis (UA): Microscopic examination for WBCs, RBCs, and bacteria.
Urine dipstick test: Rapid screening test for leukocyte esterase and nitrite, although nitrites are only positive in ~25% of cases.
Urine culture: Indicated for pyelonephritis, children, pregnant women, and patients with urinary tract abnormalities.

Indications for Evaluating the Urinary Tract

Children: Ultrasound, intravenous pyelogram (IVP), or computed tomography (CT) scan.
Bacteremic pyelonephritis not responding to therapy: Ultrasound, IVP, or CT scan.
Nephrolithiasis or neurogenic bladder: Ultrasound, CT, or IVP with post-voiding films.
Men with 1st or 2nd infection: Careful prostate examination, ultrasound, or IVP with post-voiding films.

Differential Diagnosis

Vaginitis
Pelvic inflammatory disease
Painful bladder syndrome (Interstitial cystitis)

Microbial Species

Escherichia coli
Enterobacteriaceae (e.g., Klebsiella spp., Proteus spp)
Pseudomonas
Enterococci
Staphylococci (methicillin-sensitive Staphylococcus aureus [MSSA] and methicillin-resistant S. aureus [MRSA])
Candida spp

Pathogenesis of UTI

Hematogenous Route: Bacteria enter the bloodstream and travel to the kidneys.
Ascending Route: Bacteria enter the urinary tract via the urethra and ascend to the bladder and/or kidneys. This begins with colonization of the vaginal introitus and urethra before reaching the bladder.

Factors Predisposing to UTI in Women

Short urethra
Sexual intercourse without post-coital voiding
Use of diaphragms or spermicides
Estrogen deficiency

Host Factors Predisposing to UTI

Extra-renal obstruction (posterior urethral valves, urethral strictures)
Renal calculi
Incomplete bladder emptying
Neurogenic bladder
Immunocompromised individuals (e.g., diabetes, transplant recipients)

Virulence

Ability of microorganisms to overcome body defenses.
Factors include the number of infecting microorganisms, their route of entry, and the host's immune response.

Virulence Factors

Adhesion
Invasion
Resistance of host immunity
Secretion of toxins
Competition for iron and nutrients

Antibacterial Host Defenses

Urine flow and micturition
Urine osmolality and pH
Inflammatory response (PMNs, cytokines)
Inhibitors of bacterial adherence (e.g., bladder mucopolysaccharide, secretory immunoglobulin A)

UTI: Upper Tract Disease

Symptoms: Fever (>38°C), nausea, vomiting, costovertebral pain, urinary frequency, urgency, dysuria.
Evaluation: Urine culture, potentially blood cultures, imaging if no improvement. Microbiology (e.g., E. coli, Citrobacter, Pseudomonas aeruginosa, Enterococci, Staphylococcus spp).
Treatment: Intravenous antibiotics for 10-14 days (or longer for perinephric abscess).

Treatment: General Principles

Quantitative cultures may be unnecessary for typical uncomplicated cystitis.
Culture urine in cases of upper UTI, complicated UTI, or treatment failure.
Susceptibility testing needed for all recurrent or complicated infections; perhaps not uncomplicated cases.
Identify/correct predisposing factors (obstruction, calculi, diabetes).

Recurrent UTI

Risk factors: P1 blood group positive, post-menopausal status, diabetes, recent antimicrobial use, behavioral risks (spermicide use, new partner), first UTI before age 15.

Prevention Strategies

Alternative contraception methods.
Postcoital voiding and increased fluid intake.
Cranberry juice (for sexually active women with history of UTIs).
Antibiotic prophylaxis (>2 symptomatic UTIs within 6 months or >3 over 12 months).
Postcoital vs. continuous prophylaxis vs. self-treatment.

Empiric Antimicrobials

Choice of antimicrobial agents to reach high concentrations in urine and vaginal secretions to inhibit E. coli (the primary pathogen in cystitis).
Short course (3 days) for uncomplicated infections.
Longer duration (10-14 days) for complicated infections (e.g., pyelonephritis).

Empiric Therapy - Acute Simple Cystitis

Trimethoprim (with/without sulfamethoxazole)
Nitrofurantoin
Fosfomycin
Ciprofloxacin

Empiric Therapy - Acute Simple Cystitis - Beta-lactams

Amoxicillin-clavulanate (500 mg twice daily)
Cefpodoxime (100 mg twice daily) or (300 mg twice daily)
Cefadroxil (250 to 500 mg every six hours)

Empiric Therapy - Acute Complicated Urinary Tract Infection

Ceftriaxone (1 gram IV once daily)
Piperacillin-tazobactam (3.375 grams IV every six hours).
Fluoroquinolones (e.g., ciprofloxacin or levofloxacin), Imipenem (500 mg IV every 6 hours), Meropenem (1 gram IV every 6-8 hours), or Doripenem (500 mg IV every 8 hours).
Vancomycin (for MRSA)

Bacterial Virulence Factors-I

Enhanced adherence to uroepithelial cells (Type 1 & P fimbriae).
P fimbriae bind to galactose disaccharide on uroepithelial cells and P blood group antigens (D-galactose).
Phase variation (Type 1 down-regulated; Type P upregulated during upper tract infections).

Bacterial Virulence Factors-II

Flagella-enhanced motility
Production of hemolysins.
Production of aerobactin (iron acquisition in the iron-poor urinary tract).

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Description

This quiz tests your knowledge about the microbiology related to urinary tract infections, including empirical therapy, bacterial virulence factors, and specific medications. You'll explore common microbial species and specific tests used for diagnosis. Perfect for students studying microbiology or nursing.