Practice exam: chat my love <3 Flashcards by Paloma Loya

Which of the following respiratory viruses is the most common cause of the common cold?
a) Influenza A
b) Adenovirus
c) Parainfluenza
d) Rhinovirus

Answer: d) Rhinovirus
Explanation: Rhinovirus is the leading cause of the common cold. It is transmitted through direct contact or aerosols and replicates optimally at 33-35°C, favoring its growth in the upper respiratory tract.

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In influenza, what is the function of hemagglutinin (HA)?
a) Degrade respiratory mucus
b) Facilitate viral fusion with the host cell membrane
c) Allow the virus to exit the infected cell
d) Protect the virus from the immune response

Answer: b) Facilitate viral fusion with the host cell membrane
Explanation: Hemagglutinin (HA) is a surface glycoprotein that binds to sialic acid receptors on host cells, enabling viral entry via endocytosis.

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What clinical feature most commonly distinguishes influenza from other viral respiratory infections?
a) Severe odynophagia
b) Sudden onset of high fever
c) Persistent watery rhinorrhea
d) Hemorrhagic conjunctivitis

Answer: b) Sudden onset of high fever
Explanation: Influenza is characterized by an abrupt onset of high fever, accompanied by systemic symptoms such as myalgia, headache, and fatigue, distinguishing it from other viral respiratory infections, which tend to have a more gradual onset.

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Which of the following viruses is most commonly associated with croup in young children?
a) Rhinovirus
b) Adenovirus
c) Parainfluenza type 1
d) Coronavirus

Answer: c) Parainfluenza type 1
Explanation: Parainfluenza virus, particularly type 1, is the most common cause of laryngotracheobronchitis (croup), characterized by a barking cough, inspiratory stridor, and respiratory distress.

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Which respiratory virus is most commonly associated with conjunctivitis and gastroenteritis in addition to respiratory symptoms?
a) Influenza
b) Rhinovirus
c) Adenovirus
d) Parainfluenza

Answer: c) Adenovirus
Explanation: Adenovirus has multiple serotypes and can cause conjunctivitis, gastroenteritis, pneumonia, pharyngitis, and hemorrhagic cystitis. It spreads through direct contact, fomites, and contaminated water.

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What is the most common mode of transmission for SARS-CoV-2?
a) Contact with contaminated surfaces
b) Aerosols and respiratory droplets
c) Insect bites
d) Consumption of contaminated food

Answer: b) Aerosols and respiratory droplets
Explanation: Although surface contact is a possible transmission route, the primary mode of SARS-CoV-2 transmission is through inhalation of aerosols and respiratory droplets from infected individuals when speaking, coughing, or sneezing.

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What is the gold standard diagnostic test for viral respiratory infections?
a) ELISA
b) Viral culture
c) Reverse transcription polymerase chain reaction (RT-PCR)
d) Rapid antigen detection test

Answer: c) RT-PCR
Explanation: RT-PCR is the most sensitive and specific method for detecting viral RNA, making it the gold standard for diagnosing infections such as influenza, SARS-CoV-2, and other respiratory viruses.

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What feature of the influenza virus genome allows for its high antigenic variability?
a) Segmented single-stranded RNA
b) Linear double-stranded DNA
c) Circular single-stranded RNA
d) Presence of reverse transcriptase

Answer: a) Segmented single-stranded RNA
Explanation: The segmented RNA genome of the influenza virus enables genetic reassortment between strains, facilitating antigenic shift and increasing its variability.

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What severe complication can occur in children with influenza who are treated with aspirin?
a) Guillain-Barré syndrome
b) Reye syndrome
c) Aseptic meningitis
d) Thrombocytopenic purpura

Answer: b) Reye syndrome
Explanation: Reye syndrome is an acute encephalopathy associated with aspirin use in children with viral infections, particularly influenza and varicella.

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What is the first-line antiviral treatment for influenza within the first 48 hours of symptom onset?
a) Oseltamivir
b) Acyclovir
c) Ribavirin
d) Amantadine

Answer: a) Oseltamivir
Explanation: Oseltamivir is a neuraminidase inhibitor that reduces viral replication and shortens disease duration when administered within the first 48 hours of symptoms.

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Which respiratory virus is more likely to cause outbreaks in daycare centers and schools due to its resistance on surfaces?
a) Rhinovirus
b) Adenovirus
c) Coronavirus
d) Influenza

Answer: b) Adenovirus
Explanation: Adenovirus is highly resistant to disinfectants and can survive on surfaces for prolonged periods, facilitating transmission in closed environments.

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What is the primary natural reservoir of the influenza virus?
a) Humans
b) Pigs
c) Aquatic birds
d) Bats

Answer: c) Aquatic birds
Explanation: Aquatic birds are the primary reservoir of influenza virus, contributing to the emergence of new strains through genetic reassortment.

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What is the main structural difference between coronaviruses and rhinoviruses?
a) Genome type
b) Presence of an envelope
c) Type of RNA polymerase
d) Genome segmentation

Answer: b) Presence of an envelope
Explanation: Coronaviruses are enveloped viruses, whereas rhinoviruses are non-enveloped. This affects their environmental stability and mode of transmission.

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Which respiratory virus has a lytic cycle and can cause necrotizing pneumonia in children?
a) Rhinovirus
b) Adenovirus
c) Coronavirus
d) Parainfluenza

Answer: b) Adenovirus
Explanation: Adenovirus can cause necrotizing pneumonia, particularly in immunocompromised patients.

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Which of the following findings is most characteristic on chest X-ray in a patient with bronchiolitis caused by RSV or parainfluenza virus?
a) Bilateral interstitial infiltrates
b) Hyperinflation and patchy atelectasis
c) Lobar consolidations
d) Pleural effusion

Answer: b) Hyperinflation and patchy atelectasis
Explanation: Viral bronchiolitis is associated with air trapping, pulmonary hyperinflation, and secondary atelectasis due to small airway obstruction.

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What is the primary risk factor for severe RSV infection in infants?
a) Prematurity
b) Breastfeeding
c) Summer birth
d) Low birth weight

Answer: a) Prematurity
Explanation: Premature infants have immature lungs and lower levels of maternal antibodies, increasing the risk of severe RSV infection and hospitalization.

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What is the preferred prophylactic medication for high-risk infants against RSV?
a) Oseltamivir
b) Palivizumab
c) Ribavirin
d) Dexamethasone

Answer: b) Palivizumab
Explanation: Palivizumab is a monoclonal antibody given monthly to high-risk infants (e.g., premature, chronic lung disease, congenital heart disease) to prevent severe RSV infection.

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What is the most common cause of bronchiolitis in infants?
a) Influenza virus
b) Respiratory syncytial virus (RSV)
c) Rhinovirus
d) Adenovirus

Answer: b) Respiratory syncytial virus (RSV)
Explanation: RSV is the leading cause of bronchiolitis in infants, characterized by wheezing, tachypnea, and respiratory distress.

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A 4-year-old boy is brought to the emergency department in December with a 2-day history of fever (39.2°C/102.5°F), cough, and progressive difficulty breathing. His parents report that he initially had a “barking cough” and hoarseness, but over the past few hours, he has developed stridor at rest and intercostal retractions. His oxygen saturation is 95% on room air. A frontal neck X-ray reveals subglottic narrowing (steeple sign). Which of the following is the most likely causative pathogen?
a) Influenza A
b) Parainfluenza virus type 1
c) Adenovirus
d) Respiratory syncytial virus (RSV)
e) Rhinovirus

Answer: b) Parainfluenza virus type 1
Explanation: This child presents with croup (laryngotracheobronchitis), which is commonly caused by parainfluenza virus type 1. The key clinical features include barking cough, inspiratory stridor, and hoarseness, which worsen at night. The steeple sign on X-ray is a classic finding, indicating subglottic narrowing. The treatment includes humidified air, corticosteroids, and nebulized epinephrine in severe cases.

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A 67-year-old man with a history of COPD and hypertension presents with a 4-day history of fever (38.5°C/101.3°F), dry cough, and myalgia. He was prescribed oseltamivir by his primary physician two days ago. Today, he reports worsening dyspnea and productive cough with rust-colored sputum. His vitals are BP 110/65 mmHg, HR 105 bpm, RR 26/min, and SpO₂ 88% on room air. Chest auscultation reveals decreased breath sounds in the right lower lung field. A chest X-ray shows a right lower lobe consolidation. Which of the following is the most likely etiology of his current condition?
a) Secondary bacterial pneumonia due to Streptococcus pneumoniae
b) Oseltamivir-resistant influenza virus
c) Primary viral pneumonia due to influenza virus
d) Adenoviral pneumonia
e) Aspiration pneumonia

Answer: a) Secondary bacterial pneumonia due to Streptococcus pneumoniae
Explanation: This patient initially had influenza, but his clinical deterioration and development of rust-colored sputum, tachypnea, and lobar consolidation suggest secondary bacterial pneumonia, most commonly caused by Streptococcus pneumoniae. Other possible pathogens include Staphylococcus aureus (especially MRSA, which can cause necrotizing pneumonia) and Haemophilus influenzae. This is a well-known complication of influenza, especially in older adults and those with underlying lung disease (e.g., COPD). The best management includes empiric antibiotics covering typical and atypical pathogens (e.g., ceftriaxone + azithromycin or levofloxacin).

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Which of the following bacterial pathogens is the most common cause of community-acquired pneumonia (CAP) in adults?
a) Haemophilus influenzae
b) Moraxella catarrhalis
c) Mycoplasma pneumoniae
d) Streptococcus pneumoniae

Answer: d) Streptococcus pneumoniae
Explanation: S. pneumoniae is the most common cause of CAP, particularly in elderly and immunocompromised patients. It typically causes lobar pneumonia, characterized by rust-colored sputum, fever, and pleuritic chest pain.

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What is the main virulence factor of Streptococcus pneumoniae that allows it to evade the immune system?
a) Endotoxin
b) IgA protease
c) Capsule
d) Pili

Answer: c) Capsule
Explanation: The polysaccharide capsule is the major virulence factor of S. pneumoniae, helping it evade phagocytosis by preventing complement-mediated opsonization.

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Which of the following pathogens is a common cause of pneumonia in young adults and is associated with a prolonged dry cough and extrapulmonary manifestations (e.g., rash, hemolytic anemia)?
a) Haemophilus influenzae
b) Moraxella catarrhalis
c) Mycoplasma pneumoniae
d) Streptococcus pneumoniae

Answer: c) Mycoplasma pneumoniae
Explanation: M. pneumoniae causes “walking pneumonia,” which is milder but prolonged compared to typical bacterial pneumonias. It lacks a cell wall, making β-lactam antibiotics ineffective. It can also cause cold agglutinin disease (autoimmune hemolytic anemia) and erythema multiforme.

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Which bacterial pathogen is a common cause of otitis media, sinusitis, and pneumonia, particularly in patients with chronic lung disease (e.g., COPD)? a) Mycoplasma pneumoniae b) Moraxella catarrhalis c) Haemophilus influenzae d) Streptococcus pneumoniae

Answer: b) Moraxella catarrhalis Explanation: M. catarrhalis is a common cause of otitis media, sinusitis, and COPD exacerbations. It is a Gram-negative diplococcus that frequently produces β-lactamase, leading to resistance against penicillins.

Which of the following bacteria requires X (hemin) and V (NAD) factors for growth on chocolate agar? a) Mycoplasma pneumoniae b) Haemophilus influenzae c) Streptococcus pneumoniae d) Moraxella catarrhalis

Answer: b) Haemophilus influenzae Explanation: H. influenzae requires both X (hemin) and V (NAD) factors to grow on chocolate agar. It can cause pneumonia, meningitis (type b strain), epiglottitis, and otitis media.

What is the most common treatment for atypical pneumonia caused by Mycoplasma pneumoniae? a) Penicillin b) Ceftriaxone c) Azithromycin d) Amoxicillin

Answer: c) Azithromycin Explanation: M. pneumoniae lacks a cell wall, making β-lactams ineffective. Macrolides (e.g., azithromycin, erythromycin) or tetracyclines (e.g., doxycycline) are used instead.

What is the main virulence factor of Haemophilus influenzae type b that contributes to its pathogenicity? a) Endotoxin b) IgA protease c) Polyribosylribitol phosphate (PRP) capsule d) Pili

Answer: c) Polyribosylribitol phosphate (PRP) capsule Explanation: The capsule of H. influenzae type b, composed of polyribosylribitol phosphate (PRP), is its key virulence factor, allowing it to evade phagocytosis and cause invasive disease (e.g., meningitis, epiglottitis).

Which of the following vaccines provides protection against invasive infections caused by Haemophilus influenzae type b? a) Pneumococcal conjugate vaccine (PCV13) b) Hib vaccine c) DTaP vaccine d) MMR vaccine

Answer: b) Hib vaccine Explanation: The Hib vaccine contains the capsular PRP antigen conjugated to a protein, providing strong T-cell-dependent immunity and protecting against invasive H. influenzae type b infections.

A 72-year-old man with a history of COPD and smoking presents to the emergency department with fever, productive cough, and increased sputum production. His vitals include a temperature of 38.6°C (101.5°F), blood pressure 126/82 mmHg, heart rate 98 bpm, and oxygen saturation of 91% on room air. Physical examination reveals rhonchi and decreased breath sounds in the right lung base. Sputum culture shows Gram-negative diplococci. What is the most likely causative pathogen? a) Streptococcus pneumoniae b) Haemophilus influenzae c) Mycoplasma pneumoniae d) Moraxella catarrhalis

Answer: d) Moraxella catarrhalis Explanation: This patient has community-acquired pneumonia in the setting of COPD, which is commonly caused by M. catarrhalis, H. influenzae, and S. pneumoniae. The presence of Gram-negative diplococci strongly suggests Moraxella catarrhalis.

A 25-year-old college student presents with a two-week history of low-grade fever, persistent dry cough, and malaise. He denies chills or pleuritic chest pain. Physical examination reveals no rales or egophony, and chest X-ray shows diffuse interstitial infiltrates. A cold agglutinin test is positive. What is the most appropriate treatment? a) Amoxicillin b) Ceftriaxone c) Azithromycin d) Levofloxacin

Answer: c) Azithromycin Explanation: The patient’s presentation suggests "walking pneumonia" (atypical pneumonia) due to Mycoplasma pneumoniae. The positive cold agglutinin test supports this diagnosis. Macrolides (e.g., azithromycin) are the first-line treatment.

A 6-year-old unvaccinated boy is brought to the emergency department with fever, drooling, and difficulty breathing. He is sitting forward with his mouth open and refuses to lie down. Stridor is noted on examination. Lateral neck X-ray reveals a swollen epiglottis (thumbprint sign). What is the most likely causative pathogen? a) Streptococcus pneumoniae b) Haemophilus influenzae type b c) Mycoplasma pneumoniae d) Moraxella catarrhalis

Answer: b) Haemophilus influenzae type b Explanation: This child presents with epiglottitis, a life-threatening condition characterized by fever, drooling, stridor, and the "tripod position". The "thumbprint sign" on X-ray is diagnostic. H. influenzae type b (Hib) is the most common cause, particularly in unvaccinated children.

How does rotavirus cause diarrhea? A) It produces a cholera-like toxin that increases cAMP. B) It invades enterocytes, causing bloody diarrhea. C) It disrupts enterocyte absorption and produces NSP4 enterotoxin. D) It binds to M cells in Peyer’s patches, leading to systemic infection.

Correct answer: C Explanation: Rotavirus NSP4 acts as an enterotoxin, increasing chloride secretion and disrupting brush border enzyme function, leading to watery diarrhea.

Which of the following best describes the mechanism of ETEC diarrhea? A) Invasion of intestinal mucosa B) Heat-labile (LT) and heat-stable (ST) toxins increasing cAMP/cGMP C) Shiga-like toxin inhibiting protein synthesis D) Adhesion to Peyer’s patches, leading to ulcer formation

Correct answer: B Explanation: ETEC produces LT (activates cAMP) and ST (activates cGMP), leading to secretory diarrhea similar to cholera.

Which of the following conditions is most strongly associated with EHEC infection? A) Hemolytic uremic syndrome (HUS) B) Guillain-Barré syndrome C) Megacolon D) Septic arthritis

Correct answer: A Explanation: EHEC (especially O157:H7) produces Shiga-like toxin, leading to endothelial damage, thrombocytopenia, hemolysis, and renal failure (HUS).

What differentiates S. Typhi from non-typhoidal Salmonella infections? A) S. Typhi does not invade the bloodstream, while non-typhoidal Salmonella does. B) S. Typhi is associated with a rose spot rash and prolonged fever. C) Non-typhoidal Salmonella causes constipation more often than diarrhea. D) S. Typhi is a common cause of gastroenteritis in immunocompromised patients.

Correct answer: B Explanation: S. Typhi causes typhoid fever, characterized by prolonged fever, rose spots, hepatosplenomegaly, and systemic infection.

What is the main mechanism by which Vibrio cholerae causes severe watery diarrhea? A) Invasion of colonic epithelial cells B) Increased sodium absorption in the small intestine C) Activation of adenylate cyclase by cholera toxin, increasing cAMP D) Direct cytotoxicity leading to epithelial necrosis

Correct answer: C Explanation: Cholera toxin activates adenylate cyclase via Gs-protein, leading to massive chloride and water loss.

Which of the following diseases is H. pylori NOT strongly associated with? A) Gastric adenocarcinoma B) MALT lymphoma C) Duodenal ulcers D) Crohn’s disease

Correct answer: D Explanation: H. pylori causes peptic ulcers, gastric cancer, and MALT lymphoma but is not linked to Crohn’s disease.

Why is Shigella highly infectious even at low doses? A) It produces a heat-stable toxin that resists stomach acid. B) It invades directly via M cells in the gut epithelium. C) It has a protective capsule that prevents phagocytosis. D) It has a flagellum that enhances motility in the small intestine.

Correct answer: B Explanation: Shigella invades M cells, spreads cell-to-cell via actin polymerization, and causes dysentery with a very low infectious dose.

Which is the most common complication of E. histolytica infection? A) Reactive arthritis B) Hepatic abscess C) Intestinal perforation D) Bacteremia

Correct answer: B Explanation: E. histolytica can spread from the colon to the liver, causing abscesses filled with "anchovy paste"-like material.

Why can Yersinia enterocolitica mimic appendicitis? A) It produces a toxin that inflames the peritoneum. B) It primarily infects Peyer’s patches in the ileum. C) It invades the appendix directly. D) It spreads hematogenously to the appendix.

Correct answer: B Explanation: Y. enterocolitica infects Peyer’s patches, causing RLQ pain similar to appendicitis.

A 5-year-old child presents with bloody diarrhea and abdominal pain. Stool cultures grow E. coli O157:H7. What is the next step in management? A) Start ciprofloxacin immediately B) Supportive care and avoid antibiotics C) Treat with metronidazole D) Give vancomycin orally

Correct answer: B Explanation: Antibiotics can worsen EHEC by increasing toxin release, leading to HUS. Supportive care is preferred.

A 30-year-old traveler returns from Mexico with severe watery diarrhea. What is the most likely pathogen? A) Salmonella B) Shigella C) ETEC D) Entamoeba histolytica

Correct answer: C Explanation: ETEC is the most common cause of traveler’s diarrhea, causing secretory diarrhea via LT and ST toxins.

A 50-year-old male has recurrent gastric ulcers despite PPI therapy. What is the next step? A) Test for H. pylori and treat if positive B) Increase PPI dose C) Start steroids D) Prescribe a high-fiber diet

Correct answer: A Explanation: Persistent ulcers require H. pylori testing, as eradication prevents recurrence.

A 27-year-old male develops knee pain weeks after a bout of bloody diarrhea. Stool cultures were positive for Campylobacter jejuni. What is the most likely diagnosis? A) Rheumatoid arthritis B) Septic arthritis C) Reactive arthritis D) Osteoarthritis

Correct answer: C Explanation: C. jejuni can trigger reactive arthritis (Reiter’s syndrome) weeks after infection.

A 45-year-old man with HIV (CD4 count: 50 cells/µL) presents with 24 hours of fever, abdominal pain, and profuse, watery diarrhea. On exam, he is hypotensive (BP 85/50 mmHg), tachycardic (HR 120 bpm), and has diffuse abdominal tenderness without peritoneal signs. Laboratory tests show elevated lactate, leukopenia, and acute kidney injury. Stool culture reveals Gram-negative, oxidase-positive, comma-shaped rods. What is the most appropriate next step in management? A) Empiric vancomycin and cefepime B) IV fluids, doxycycline, and aggressive electrolyte replacement C) Metronidazole and oral vancomycin D) Immediate exploratory laparotomy Correct answer: B Explanation: This patient has severe cholera (Vibrio cholerae) in the setting of advanced HIV. Immunocompromised patients can develop life-threatening dehydration and sepsis from cholera due to rapid fluid loss. The priority is aggressive rehydration and electrolyte replacement, with doxycycline to shorten illness duration. Antibiotics alone will not be sufficient without massive fluid resuscitation.

A previously healthy 10-month-old infant is brought to the ED with lethargy, high fever (39.8°C), and bloody diarrhea. The parents report that symptoms began 48 hours ago, progressing from non-bloody diarrhea to grossly bloody stools with mucus. On exam, the child is pale, hypotensive, and has abdominal distension with tenderness. Labs show anemia, thrombocytopenia, elevated BUN/creatinine, and metabolic acidosis. Stool culture grows a non-motile, lactose-negative, Gram-negative rod. Which of the following is the best immediate management? A) Start ceftriaxone and administer IV fluids B) Begin empiric vancomycin and meropenem C) Supportive care only—antibiotics are contraindicated D) Immediate colectomy due to suspected toxic megacolon

Correct answer: C Explanation: This infant has hemolytic uremic syndrome (HUS) due to Shigella dysenteriae. Shigella produces Shiga toxin, which can cause HUS—a triad of microangiopathic hemolytic anemia, thrombocytopenia, and acute kidney injury. Antibiotics should not be given, as they can worsen toxin release and increase the risk of HUS. Management is supportive, including fluids, blood transfusions, and renal support if necessary.

Which of the following pathogens is the most common cause of uncomplicated cystitis? A) Klebsiella pneumoniae B) Enterococcus faecalis C) Escherichia coli D) Proteus mirabilis

Correct answer: C Explanation: E. coli causes 80–90% of uncomplicated cystitis, due to its uropathogenic virulence factors (fimbriae, adhesins).

Which of the following best differentiates acute pyelonephritis from uncomplicated cystitis? A) Hematuria B) Dysuria and frequency C) Costovertebral angle tenderness and fever D) Leukocyte esterase on urinalysis

Correct answer: C Explanation: Fever and flank pain (CVA tenderness) are the hallmark features of pyelonephritis, absent in simple cystitis.

Which is the first-line oral antibiotic for uncomplicated cystitis in an otherwise healthy, non-pregnant woman? A) Amoxicillin B) Ciprofloxacin C) Nitrofurantoin D) Clindamycin

Correct answer: C Explanation: Nitrofurantoin (5-day course) is a first-line option due to low resistance and good bladder penetration. Fluoroquinolones should be reserved for complicated infections.

A 27-year-old woman has four episodes of UTI in the past six months. What is the best strategy to reduce recurrence? A) Continuous prophylactic nitrofurantoin B) Single-dose postcoital antibiotics C) Cranberry extract supplementation D) Increase water intake

Correct answer: B Explanation: Postcoital antibiotics (nitrofurantoin, TMP-SMX) are effective for women with UTIs associated with sexual activity.

Which antibiotic is the best option for treating uncomplicated pyelonephritis in an outpatient setting? A) Nitrofurantoin B) Fosfomycin C) Ceftriaxone IM + oral fluoroquinolone D) Vancomycin

Correct answer: C Explanation: Outpatient pyelonephritis requires initial IV/IM ceftriaxone, followed by oral fluoroquinolones for 7–14 days.

Which antibiotic is contraindicated in a pregnant woman with UTI? A) Amoxicillin B) Nitrofurantoin C) TMP-SMX (trimethoprim-sulfamethoxazole) D) Cephalexin

Correct answer: C Explanation: TMP-SMX should be avoided in the first trimester (neural tube defects) and third trimester (kernicterus).

Which of the following is NOT considered a complicated UTI? A) UTI in a patient with an indwelling Foley catheter B) UTI in a diabetic patient C) UTI in a 35-year-old healthy, non-pregnant woman D) UTI in a patient with kidney stones

Correct answer: C Explanation: Uncomplicated UTIs occur in healthy, non-pregnant women without structural abnormalities or immunosuppression.

An 82-year-old woman with dementia is brought to the ER with confusion and lethargy. She has suprapubic tenderness, fever (39.2°C), and BP 85/50 mmHg. Labs show WBC 18,500, Cr 2.3 mg/dL (baseline 1.0), and lactate 3.5 mmol/L. Urinalysis shows leukocyte esterase, WBCs, and bacteriuria. What is the next best step? A) Start oral ciprofloxacin and discharge home B) IV cefepime + fluids + blood cultures C) Insert a Foley catheter and observe for 12 hours D) Wait for urine culture before starting antibiotics

Correct answer: B Explanation: This is urosepsis with hypotension and organ dysfunction (AKI, lactate elevation). Immediate IV broad-spectrum antibiotics (cefepime or piperacillin-tazobactam) + aggressive IV fluids are required.

A 35-year-old man with a history of spinal cord injury and chronic Foley catheter use presents with fever and chills. Urinalysis shows pyuria and bacteriuria. Urine culture grows carbapenem-resistant Klebsiella pneumoniae. What is the most appropriate treatment? A) IV meropenem B) IV colistin + tigecycline C) Oral nitrofurantoin D) Oral TMP-SMX

Correct answer: B Explanation: Carbapenem-resistant Klebsiella requires colistin, tigecycline, or ceftazidime-avibactam. Nitrofurantoin and TMP-SMX won’t work.

A 50-year-old woman with poorly controlled diabetes presents with fever, flank pain, and dysuria for 5 days. She was treated 2 weeks ago for a UTI with ciprofloxacin. Exam reveals CVA tenderness. CT abdomen shows a 4 cm perinephric abscess. What is the next best step? A) Continue oral fluoroquinolones for 4 weeks B) IV antibiotics + percutaneous drainage C) Immediate nephrectomy D) Switch to oral amoxicillin-clavulanate

Correct answer: B Explanation: Renal abscesses ≥3 cm require drainage + IV antibiotics (carbapenems, cefepime, or piperacillin-tazobactam).

Which cerebrospinal fluid (CSF) profile is most consistent with bacterial meningitis? A) Elevated WBC (lymphocytic), normal glucose, mildly elevated protein B) Elevated WBC (neutrophilic), low glucose, high protein C) Normal WBC, normal glucose, normal protein D) Slightly elevated WBC (mononuclear), high glucose, low protein

Correct answer: B Explanation: Bacterial meningitis presents with high WBC (neutrophilic predominance), low glucose (<40 mg/dL), and high protein due to increased permeability of the blood-brain barrier.

A 3-week-old neonate presents with fever, lethargy, and bulging fontanelle. Blood cultures are pending. What is the best empiric treatment? A) Ceftriaxone + vancomycin B) Cefotaxime + ampicillin + gentamicin C) Meropenem + linezolid D) Dexamethasone + acyclovir

Correct answer: B Explanation: Neonatal meningitis is commonly caused by Group B Streptococcus, E. coli, and Listeria monocytogenes. Ampicillin covers Listeria, and cefotaxime (not ceftriaxone) is preferred due to lower risk of kernicterus.

Which of the following is the best initial diagnostic test for suspected Cryptococcus neoformans meningitis in an HIV patient? A) CSF Gram stain B) India ink stain of CSF C) Serum cryptococcal antigen D) CSF PCR for Cryptococcus

Correct answer: C Explanation: Serum cryptococcal antigen is the most sensitive initial test. India ink stain has low sensitivity, and CSF PCR is not standard.

Which finding is more suggestive of autoimmune limbic encephalitis rather than viral encephalitis? A) Fever and altered mental status B) Temporal lobe hyperintensities on MRI C) Subacute memory loss with psychiatric symptoms D) CSF pleocytosis with positive HSV PCR

Correct answer: C Explanation: Autoimmune encephalitis (e.g., anti-NMDA receptor encephalitis) presents with subacute memory loss, psychiatric symptoms, and seizures rather than an acute febrile illness.

A 19-year-old college student is diagnosed with Neisseria meningitidis meningitis. His roommate is asymptomatic. What is the best prophylactic option for the roommate? A) No prophylaxis needed B) Azithromycin 5-day course C) Rifampin, ciprofloxacin, or ceftriaxone D) Amoxicillin-clavulanate

Correct answer: C Explanation: Close contacts of meningococcal cases require prophylaxis with rifampin, ciprofloxacin, or ceftriaxone to prevent secondary cases.

A 45-year-old man presents with fever, confusion, and new-onset seizures. He is disoriented and has aphasia. MRI shows bilateral temporal lobe hyperintensities. CSF findings: WBC: 120 (lymphocyte predominant) Glucose: 55 mg/dL Protein: 85 mg/dL CSF HSV PCR: Pending What is the best immediate step? A) Wait for HSV PCR results before starting treatment B) Start IV acyclovir immediately C) Start IV ceftriaxone + vancomycin + steroids D) Perform a brain biopsy for definitive diagnosis

Correct answer: B Explanation: This is classic HSV encephalitis (temporal lobe involvement, seizures, aphasia). Empiric IV acyclovir should be started immediately—delaying treatment worsens prognosis.

A 65-year-old man with HIV (CD4: 45) presents with headache, photophobia, and progressive confusion over 2 weeks. CSF analysis shows: WBC: 30 (mononuclear predominant) Glucose: 32 mg/dL Protein: 90 mg/dL India ink stain: Positive What is the best treatment? A) IV amphotericin B + flucytosine B) IV ceftriaxone + vancomycin + steroids C) IV acyclovir D) Oral fluconazole

Correct answer: A Explanation: This is cryptococcal meningitis in an HIV patient (CD4 <100). IV amphotericin B + flucytosine is the treatment of choice.

A 50-year-old man with alcoholic cirrhosis and chronic steroid use presents with fever, neck stiffness, and altered mental status. CSF analysis shows: WBC: 1,800 (neutrophils predominant) Glucose: 22 mg/dL Protein: 120 mg/dL What is the best initial treatment? A) IV ceftriaxone + vancomycin B) IV ceftriaxone + vancomycin + dexamethasone C) IV cefepime + vancomycin + ampicillin + dexamethasone D) IV meropenem + linezolid

Correct answer: C Explanation: Immunosuppressed patients (chronic steroids, cirrhosis) have increased risk for Listeria. Ampicillin must be added to cover Listeria monocytogenes.