Urinary Tract Infections — MCQs
A patient presents with urethral discharge. Gram stain shows intracellular gram-negative diplococci. What is the causative organism?
Which of the following is typically seen on ultrasound in acute pyelonephritis?
What is the most common cause of urinary catheter induced infections?
Most common organism causing UTI:
A patient from the Ohio River valley presents with granulomatous prostatitis showing broad-based budding organisms on microscopy. What is the most likely infecting organism?
Which of the following disorders would be more likely associated with Staphylococcus saprophyticus rather than Staphylococcus aureus?
All of the following statements are true regarding central nervous system infections, except:
A 35-year-old woman presents with fever and abdominal pain. Blood culture shows gram-negative rods that ferment lactose and produce indole. What is the most likely pathogen?
A 6-year-old boy came with a history of recurrent urinary tract infections. Imaging was done and showed retrograde flow of urine from the bladder into the ureters. What is the most likely diagnosis based on the imaging findings?
Which antibiotic is the most appropriate choice for treating a bedridden patient with catheter-related urinary tract infection (UTI) and pneumonia?
Urinary Tract Infections Indian Medical PG Practice Questions and MCQs
Question 1: A patient presents with urethral discharge. Gram stain shows intracellular gram-negative diplococci. What is the causative organism?
- A. Mycoplasma genitalium
- B. Treponema pallidum
- C. Chlamydia trachomatis
- D. Neisseria gonorrhoeae (Correct Answer)
Explanation: ***Neisseria gonorrhoeae*** - The presence of **intracellular gram-negative diplococci** in urethral discharge is a classic microscopic finding for *Neisseria gonorrhoeae*. - This organism directly invades host cells, and its unique gram staining characteristic makes it readily identifiable in clinical samples. *Mycoplasma genitalium* - This organism does not have a **cell wall** and therefore will not gram stain. It cannot be identified by Gram stain. - Diagnosis typically requires molecular methods like **PCR**. *Treponema pallidum* - This spirochete is too thin to be visualized with standard Gram stain and is typically identified using **dark-field microscopy** or serological tests. - It does not present as gram-negative diplococci. *Chlamydia trachomatis* - *Chlamydia trachomatis* is an **obligate intracellular bacterium** but does not stain well with Gram stain due to its unique cell wall structure (lacks peptidoglycan). - It is often diagnosed using **nucleic acid amplification tests (NAATs)**.
Question 2: Which of the following is typically seen on ultrasound in acute pyelonephritis?
- A. Decreased vascularity
- B. Enlarged kidney with diffuse swelling (Correct Answer)
- C. Localized hypoechogenic areas in the kidney
- D. Fluid collection around the kidney
Explanation: ***Enlarged kidney with diffuse swelling*** - In **acute pyelonephritis**, the **most consistent ultrasound finding** is **renal enlargement** with **diffuse swelling** of the affected kidney. - This occurs due to **inflammatory edema** and increased fluid content within the renal parenchyma, representing the body's inflammatory response to infection. - **Diffuse enlargement** is present in the majority of cases and is often the **earliest sonographic manifestation**, making it the most typical finding. *Localized hypoechogenic areas in the kidney* - **Focal or multifocal hypoechoic areas** are indeed **highly characteristic** of acute pyelonephritis and represent zones of **parenchymal edema and inflammation**. - These are seen in approximately **20-80% of cases** and are considered a hallmark feature. - However, they may not be present in all cases, particularly in early or mild disease, whereas **renal enlargement is more consistently present**. - When visible, these areas have high specificity for the diagnosis. *Fluid collection around the kidney* - **Perinephric fluid collections** or abscesses indicate **complicated pyelonephritis** with extension of infection beyond the renal capsule. - These are **not typical findings in uncomplicated acute pyelonephritis** and suggest more severe or advanced infection requiring aggressive management. *Decreased vascularity* - Acute pyelonephritis typically shows **increased vascularity** on color Doppler due to **hyperemia and inflammatory vasodilation**. - **Decreased vascularity** is associated with **renal infarction**, severe ischemia, or chronic scarring—not acute bacterial infection.
Question 3: What is the most common cause of urinary catheter induced infections?
- A. Pseudomonas
- B. Staphylococcus epidermidis
- C. Proteus
- D. E. coli (Correct Answer)
Explanation: ***E. coli*** - **Uropathogenic E. coli (UPEC)** is the most frequent cause of both uncomplicated and complicated urinary tract infections, including those associated with catheter use, due to its **virulence factors** that promote colonization and invasion. - Its prevalence is linked to its presence in the **gut flora**, providing a common source for ascent into the urinary tract, especially with instrumentation. *Pseudomonas* - **Pseudomonas aeruginosa** is a significant pathogen in catheter-associated UTIs, particularly in hospitalized patients with prolonged catheterization or those who are immunocompromised. - While concerning due to its **antibiotic multi-resistance** and ability to form biofilms, it is not as common as E.coli in catheter-induced infections overall. *Staphylococcus epidermidis* - **Staphylococcus epidermidis** is a common cause of **catheter-related bloodstream infections** due to its presence on the skin and ability to form biofilms on indwelling devices. - However, in urinary catheters, while it can contribute to biofilm formation, it is not the primary cause of infection, with **E.coli** being much more prevalent in UTIs. *Proteus* - **Proteus mirabilis** is known for causing catheter-associated UTIs and is particularly concerning due to its ability to produce **urease**, which can lead to the formation of **struvite stones** and catheter encrustation. - Despite its pathological potential in the urinary tract, it remains less common than **E. coli** as the causative agent of catheter-induced infections.
Question 4: Most common organism causing UTI:
- A. E. coli (Correct Answer)
- B. Klebsiella
- C. Streptococci
- D. Staphylococcus saprophyticus
Explanation: ***E. coli*** - **Uropathogenic *E. coli*** (UPEC) is responsible for 75-95% of all urinary tract infections (UTIs) due to its virulence factors like **fimbriae** that allow adherence to uroepithelial cells. - Its presence in the urethra colonizes the region and ascends to the bladder, making it the most common causative agent. *Klebsiella* - **Klebsiella pneumoniae** is a common cause of UTIs, especially in complicated cases or in patients with indwelling catheters, but it is not the most frequent overall. - It ranks significantly lower than *E. coli* in incidence. *Streptococci* - While certain **Streptococcus species** can cause UTIs, they are a less common cause compared to gram-negative rods like *E. coli*. - For example, **Enterococcus faecalis** (a Group D Streptococcus) can cause UTIs, especially in hospital-acquired infections, but *E. coli* is still more prevalent. *Staphylococci saprophyticus* - **Staphylococcus saprophyticus** is a common cause of UTIs in young, sexually active women but is not the most common organism overall across all demographics. - Its incidence is significant in specific populations but doesn't rival that of *E. coli* generally.
Question 5: A patient from the Ohio River valley presents with granulomatous prostatitis showing broad-based budding organisms on microscopy. What is the most likely infecting organism?
- A. Escherichia coli
- B. Histoplasma capsulatum
- C. Pseudomonas aeruginosa
- D. Blastomyces dermatitidis (Correct Answer)
Explanation: ***Blastomyces dermatitidis*** - This organism is endemic to the **Ohio River valley** and is known to cause **granulomatous inflammation**, including in the prostate. - Its characteristic morphology is **broad-based budding yeast** on microscopy, fitting the description. *Escherichia coli* - While *E. coli* is a common cause of **bacterial prostatitis**, it does not present as granulomatous inflammation. - It is a **bacterium**, not a fungus, and would not show broad-based budding organisms. *Histoplasma capsulatum* - **Histoplasma** is also endemic to the Ohio River valley and causes granulomatous disease, but its yeast forms are **small**, intracellular, and do not exhibit broad-based budding. - It is often associated with a history of exposure to **bat or bird droppings** and commonly affects the lungs. *Pseudomonas aeruginosa* - *Pseudomonas aeruginosa* causes **bacterial infections**, often in immunocompromised individuals or associated with catheter use, and is not a fungus. - It causes **acute inflammation**, not chronic granulomatous inflammation, and does not show broad-based budding.
Question 6: Which of the following disorders would be more likely associated with Staphylococcus saprophyticus rather than Staphylococcus aureus?
- A. Burns
- B. Tension pneumothorax
- C. Osteomyelitis
- D. Acute cystitis (Correct Answer)
Explanation: ***Acute cystitis*** - **Staphylococcus saprophyticus** is a common cause of **urinary tract infections (UTIs)**, particularly acute cystitis, in young sexually active women. - This bacterium has a high affinity for **uroepithelial cells**, facilitating its colonization and subsequent infection of the bladder. *Tension pneumothorax* - A **tension pneumothorax** is a medical emergency characterized by air accumulation in the pleural space, leading to lung collapse and mediastinal shift. - It is typically caused by trauma or iatrogenic factors, not directly by bacterial infection from either *Staphylococcus saprophyticus* or *Staphylococcus aureus*. *Burns* - Burn wounds are highly susceptible to bacterial colonization and infection, with **Staphylococcus aureus** being a primary pathogen in this context. - *Staphylococcus saprophyticus* is rarely associated with burn wound infections. *Osteomyelitis* - **Osteomyelitis**, an infection of the bone, is most frequently caused by **Staphylococcus aureus** via hematogenous spread or direct inoculation. - *Staphylococcus saprophyticus* is not a common pathogen in osteomyelitis.
Question 7: All of the following statements are true regarding central nervous system infections, except:
- A. Prions infection causes spongiform encephalopathy
- B. JC virus is causative agent for progressive multifocal leucoencephalopathy
- C. Cytomegalovirus is a common cause of bilateral temporal lobe hemorrhagic infarction (Correct Answer)
- D. Measles virus is the causative agent for subacute sclerosing pan encephalitis (SSPE)
Explanation: ***Cytomegalovirus is a common cause of bilateral temporal lobe hemorrhagic infarction.*** - **Cytomegalovirus (CMV)** typically causes **ventriculoencephalitis or periventricular necrosis** and microglial nodules in immunocompromised patients, not bilateral temporal lobe hemorrhagic infarction. - **Herpes simplex virus type 1 (HSV-1)** is the classic infectious cause of **bilateral temporal lobe hemorrhagic infarction (necrotizing encephalitis)**. *Prions infection causes spongiform encephalopathy* - **Prions** are misfolded proteins that cause transmissible spongiform encephalopathies (TSEs), such as Creutzfeldt-Jakob disease, characterized by **neuronal loss** and vacuolation (spongiform changes). - These diseases are invariably fatal and lead to rapid neurological deterioration. *JC virus is causative agent for progressive multifocal leucoencephalopathy* - The **JC virus** specifically targets and destroys **oligodendrocytes**, the myelin-producing cells of the central nervous system. - This leads to **demyelination** in multiple areas of the brain, causing the characteristic lesions seen in progressive multifocal leukoencephalopathy (PML). *Measles virus is the causative agent for subacute sclerosing pan encephalitis (SSPE).* - **Subacute sclerosing panencephalitis (SSPE)** is a rare, fatal, progressive neurodegenerative disease caused by a persistent and defective **measles virus infection** in the brain. - It occurs years after the initial measles infection, leading to cognitive decline, seizures, and motor dysfunction.
Question 8: A 35-year-old woman presents with fever and abdominal pain. Blood culture shows gram-negative rods that ferment lactose and produce indole. What is the most likely pathogen?
- A. Escherichia coli (Correct Answer)
- B. Proteus mirabilis
- C. Klebsiella pneumoniae
- D. Salmonella enterica
Explanation: ***Escherichia coli*** - *Escherichia coli* is a **Gram-negative rod** that is a classic **lactose fermenter** and **indole positive**, fitting all the described microbiological characteristics. - It is a common cause of **bacteremia** originating from the gastrointestinal or genitourinary tracts, often presenting with fever and abdominal pain. *Proteus mirabilis* - *Proteus mirabilis* is a **Gram-negative rod** but it is typically a **non-lactose fermenter** and **indole negative**. - It is well-known for its **swarming motility** on agar and its association with **struvite kidney stones** due to urease production. *Klebsiella pneumoniae* - *Klebsiella pneumoniae* is a **Gram-negative rod** and a **lactose fermenter**, but it is typically **indole negative**. - It is characterized by its **prominent polysaccharide capsule**, which contributes to its virulence and mucoid colony appearance. *Salmonella enterica* - *Salmonella enterica* is a **Gram-negative rod** but it is a classic **non-lactose fermenter** and **indole negative**. - It is primarily associated with **gastroenteritis**, **typhoid fever**, and **bacteremia**, especially in immunocompromised individuals.
Question 9: A 6-year-old boy came with a history of recurrent urinary tract infections. Imaging was done and showed retrograde flow of urine from the bladder into the ureters. What is the most likely diagnosis based on the imaging findings?
- A. Vesicoureteric reflux (VUR) (Correct Answer)
- B. Urinary bladder diverticulum (UBD)
- C. Vesicocolic fistula (VCF)
- D. Urinary bladder hernia (UBH)
Explanation: ***Vesicoureteric reflux (VUR)*** - VUR is defined by the **retrograde flow of urine from the bladder into the ureters**, which directly matches the imaging finding described - This is the **most common cause of recurrent UTIs in children**, as reflux allows bacteria to ascend from the bladder to the kidneys - Diagnosed by **voiding cystourethrogram (VCUG)**, which shows contrast refluxing into ureters during micturition - Graded from I to V based on severity; can lead to **reflux nephropathy** and renal scarring if untreated *Urinary bladder diverticulum* - An **outpouching of the bladder wall** through weakened muscle layers - May predispose to UTIs due to urinary stasis within the diverticulum, but does **not cause retrograde flow into ureters** - Imaging would show a **saccular projection** from the bladder, not ureteral filling *Vesicocolic fistula* - An **abnormal communication between bladder and colon**, typically from inflammatory bowel disease, malignancy, or trauma in adults (rare in children) - Presents with **pneumaturia (air in urine)**, fecaluria, and recurrent UTIs - Would not demonstrate **retrograde ureteral flow** on imaging *Urinary bladder hernia* - Protrusion of bladder through a **hernial defect** (inguinal, femoral, or abdominal wall) - Presents as a **reducible mass** that may increase with Valsalva - Does not cause **ureteral reflux** and has a distinct clinical and radiological presentation
Question 10: Which antibiotic is the most appropriate choice for treating a bedridden patient with catheter-related urinary tract infection (UTI) and pneumonia?
- A. Amoxicillin
- B. Beta Lactam antibiotics with beta lactamase (Correct Answer)
- C. 3rd gen cephalosporins
- D. 2nd gen cephalosporins
Explanation: ***Beta Lactam antibiotics with beta lactamase*** - This combination provides a **broad spectrum of activity** against common pathogens causing both hospital-acquired UTIs and pneumonia, including those producing **beta-lactamase enzymes**. In many organisms, resistance is due to ̢-lactamase production, which can be overcome by the addition of ̢-lactamase inhibitors like clavulanic acid or tazobactam [1]. - Given the patient's bedridden status and catheter, there is a higher risk of **multidrug-resistant organisms**, making this broader coverage more appropriate. Ureidopenicillins combined with beta-lactamase inhibitors extend the spectrum to include Pseudomonas spp., which are often resistant to aminopenicillins [1]. *Amoxicillin* - **Amoxicillin** alone has a limited spectrum and is often ineffective against many hospital-acquired pathogens, especially those producing **beta-lactamase** [1]. - It would not adequately cover potential resistant bacteria in a bedridden patient with catheter-related infection. *3rd gen cephalosporins* - While **3rd generation cephalosporins** offer broader coverage than earlier generations, they may not adequately cover some **ESBL-producing organisms** or **Pseudomonas**, which are concerns in hospitalized, bedridden patients [1]. - They are suitable for many community-acquired infections but might be suboptimal for **nosocomial infections** without additional agents [2]. *2nd gen cephalosporins* - **Second-generation cephalosporins** have an even narrower spectrum compared to third-generation agents and would likely be insufficient for the broad range of potential pathogens in this clinical scenario. - They are typically used for specific indications and generally lack sufficient activity against many **gram-negative bacilli** and atypical pneumonia pathogens.
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