Is infectious disease high yield on the PEBC exam?

Yes. Antimicrobial therapy is a core clinical area, so common infections like UTI, pneumonia, and skin and soft tissue infections, along with the principles of antimicrobial selection and stewardship, come up often. The exact mix is randomized from one sitting to the next, but infectious disease is consistently worth strong preparation.

What infectious disease topics should I focus on for the PEBC?

Focus on empiric versus directed therapy, first-line antibiotics for the common community infections (UTI, pneumonia, cellulitis, otitis media, pharyngitis), spectrum of activity, penicillin allergy and cross-reactivity, treatment durations and the IV-to-oral switch, and the monitoring for vancomycin and aminoglycosides.

Which references should I use for infectious disease on the PEBC?

The Canadian standard references are Bugs and Drugs and the guidance from AMMI Canada (the Association of Medical Microbiology and Infectious Disease Canada), along with provincial antimicrobial stewardship resources. The PEBC expects the Canadian first-line choice, which is not always what a US source would recommend.

How should I study infectious disease for the PEBC?

Learn the first-line empiric therapy for the common infections cold, know the standard durations and when to switch from IV to oral, and always read the vignette for the patient factor (allergy, pregnancy, renal function) that changes the drug.

PEBC Infectious Disease Practice Questions

Infectious disease is one of the deepest areas on the PEBC exam. Antimicrobial selection, common community infections like UTI and pneumonia, HIV, endocarditis, and the principles of stewardship all show up, and most questions come down to matching the likely organism to the right Canadian first-line drug for that specific patient.

The questions below sample each of those areas. Each explanation argues every option, right and wrong, down to the organism, the allergy, or the patient factor that tipped the answer.

Written and reviewed against current Canadian guidelines and references.

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All 4

options explained

full clinical case

How to approach a PEBC infectious disease question

1Identify the infection and its most likely organisms first, then pick the drug. Most ID questions ask what bug first, and only then what drug.
2Check the patient for the factor that changes the choice: a penicillin allergy, pregnancy, renal function, or a resistance risk. That single detail usually decides the answer.
3Know first-line empiric therapy cold for the common community infections (UTI, pneumonia, cellulitis, otitis media, strep throat). The exam favours the Canadian first-line, so anchor on Bugs and Drugs and AMMI Canada.
4Watch the duration and the route. Many questions hinge on how long to treat or when to switch from IV to oral, not just which drug to start.
5For the drugs that need monitoring (vancomycin, aminoglycosides), know what you monitor and why.

Practice questions

Tap an answer to see why each option is right or wrong.

Question 1HIV & Opportunistic Infections

KL is a 38-year-old male recently diagnosed with HIV through routine screening. He is asymptomatic with no significant PMH. Baseline labs show CD4 320 cells/mm³, VL 85,000 copies/mL, HLA-B*5701 positive, HBV surface antigen negative, SCr 72 µmol/L. Which of the following is the most appropriate initial ART regimen?

Incorrect · Answer: B

PEBC Yield: Highdrug-selectioncontraindication-check

TDF/FTC backbone is acceptable with normal renal function, but efavirenz is no longer preferred first-line due to neuropsychiatric ADRs and has been replaced by INSTI-based regimens. Would be correct in settings where INSTIs are unavailable.

B) (Correct)

Correct — TAF/FTC plus dolutegravir is the preferred first-line regimen. HLA-B*5701 positive status excludes abacavir. DTG has a high genetic barrier to resistance, minimal DDIs, and excellent tolerability. TAF is preferred over TDF for reduced renal and bone toxicity.

TDF/FTC backbone is acceptable, but rilpivirine has lower efficacy when baseline VL exceeds 100,000 copies/mL. At VL 85,000, this patient is close to the threshold but still eligible; however, INSTI-based regimens are preferred over NNRTI-based regimens as first-line.

Tempting as a standard first-line backbone, but abacavir is absolutely contraindicated in HLA-B*5701 positive patients due to risk of fatal hypersensitivity reaction on rechallenge. Would be correct if HLA-B*5701 were negative.

Question 2Principles of Infection & Antimicrobial Therapy

A hospitalized patient with bacteremia requires a bactericidal antibiotic. Which of the following agents is bacteriostatic and would be LEAST appropriate for this indication?

Incorrect · Answer: D

PEBC Yield: Highempiric-therapydrug-selection

Vancomycin is not the regimen this stem is driving toward. Vancomycin is bactericidal and appropriate for high-burden infections including bacteremia, endocarditis, and CNS infections.

Meropenem is not the regimen this stem is driving toward. Meropenem (carbapenem) is a beta-lactam — bactericidal. Appropriate for serious Gram-negative bacteremia.

Ceftriaxone is not the regimen this stem is driving toward. Ceftriaxone (3rd-gen cephalosporin) is a beta-lactam — bactericidal. Commonly used for Gram-negative bacteremia.

D) (Correct)

Correct. For this regimen-selection item, Clindamycin is bacteriostatic. It inhibits bacterial protein synthesis (50S ribosomal subunit) and relies on host immune function to clear the infection. For high-burden infections like bacteremia, bactericidal agents are preferred because the patient's immune system may be insufficient to clear the remaining bacteria.

Question 3UTI

Which route most commonly explains bacterial entry in UTI pathophysiology?

Incorrect · Answer: A

PEBC Yield: Highdiagnosis-classificationpathogen-coverage

A) (Correct)

Correct -- the usual route is ascent from periurethral fecal flora.

Tempting because kidneys can become involved, but the usual direction is upward from the urethra.

Tempting because vaginal and bladder anatomy are close, but this is not the usual route described.

Tempting because hematogenous seeding can occur in selected infections, but it is not the usual UTI route.

Question 4Principles of Infection & Antimicrobial Therapy

Which oral antimicrobial option is the practical exception with activity against Pseudomonas aeruginosa when oral therapy is appropriate?

Incorrect · Answer: A

PEBC Yield: Highpathogen-coverageempiric-therapy

A) (Correct)

Correct. For this regimen-selection item, Ciprofloxacin is the practical oral exception in this option set because it can cover susceptible Pseudomonas aeruginosa when an oral regimen is appropriate. Most reliable antipseudomonal beta-lactams are IV agents, so oral step-down requires careful susceptibility confirmation.

Cefuroxime is not the regimen this stem is driving toward. Cefuroxime can be useful for selected respiratory, skin, and urinary pathogens, but it is not an antipseudomonal cephalosporin. If the organism named in the stem is the target, cefuroxime would leave Pseudomonas uncovered.

Cephalexin is not the regimen this stem is driving toward. Cephalexin is mainly used for susceptible streptococci and MSSA in uncomplicated skin or urinary syndromes. It has no reliable activity against Pseudomonas aeruginosa, so it misses the organism the stem specifically asks about.

Cefpodoxime is not the regimen this stem is driving toward. Cefpodoxime offers some oral gram-negative coverage in selected respiratory or urinary infections, but it is not used as an oral Pseudomonas agent. The oral option in this list with practical antipseudomonal activity is ciprofloxacin.

Question 5PEP & PrEP

JL is a 26-year-old male who presents to your pharmacy 6 hours after condomless receptive anal intercourse with a partner of unknown HIV status. He is HIV-negative on rapid testing. Which of the following is the most appropriate regimen?

Incorrect · Answer: C

PEBC Yield: Highdrug-selectionprophylaxis

Injectable cabotegravir is a PrEP option for ongoing risk prevention, not a PEP regimen. Additionally, cabotegravir monotherapy lacks the potency needed for post-exposure suppression.

Indefinite therapy is a PrEP approach (daily prevention before anticipated exposure). PEP is a 28-day course initiated after a specific exposure event.

C) (Correct)

Correct — this is a non-occupational PEP (nPEP) scenario: high-risk exposure (anal receptive = 1.38% per-event risk) within 72 hours, source status unknown. The 2025 preferred regimen is TAF/FTC/BIC (Biktarvy) PO daily for 28 days. The full course should be dispensed at the initial encounter.

Two-drug regimens (2 NRTIs) are for PrEP, not PEP. Post-exposure prophylaxis requires three drugs (2 NRTIs + INSTI) because viral burden in tissue immediately after exposure is higher and requires more aggressive suppression.

Question 6PEP & PrEP

BF is a 33-year-old HIV-negative male starting daily PrEP with TDF/FTC. Which of the following baseline tests is the LEAST important before initiation?

Incorrect · Answer: B

PEBC Yield: Highmonitoringscreening

Essential — Hepatitis A/B/C screening guides vaccination recommendations (Hep A/B if seronegative) and identifies co-infections. TDF/FTC has activity against HBV, and stopping PrEP in someone with undiagnosed HBV could trigger a flare.

B) (Correct)

Correct — resistance genotyping is performed in HIV-positive patients at diagnosis and treatment failure. It is not part of PrEP baseline workup because the patient is HIV-negative. There is no virus to genotype. If the patient were to seroconvert on PrEP, resistance testing would be done at that point.

Essential — must confirm HIV-negative status before starting PrEP. If the patient is already HIV-positive, PrEP would provide inadequate treatment and risk selecting for drug resistance.

Essential — establishes baseline renal function. TDF requires CrCl ≥ 60 mL/min, and urinalysis checks for proteinuria (early sign of renal tubular dysfunction).

Question 7UTI

Which organism is the most common UTI pathogen across sites and complexity?

Incorrect · Answer: B

PEBC Yield: Highpathogen-coverage

Tempting because Klebsiella is a common uropathogen, but it is less common than E. coli.

B) (Correct)

Correct -- E. coli is the most common pathogen regardless of site, severity, or complexity.

Tempting because Proteus is a common gram-negative uropathogen, but it is not the dominant organism.

Tempting because Enterococcus is important in complicated UTI, but it is not the most common overall.

Question 8HIV & Opportunistic Infections

GC is a 58-year-old male with HIV on darunavir/cobicistat plus tenofovir AF/emtricitabine. He is admitted for active PCP (Pneumocystis jirovecii pneumonia) confirmed by BAL. CD4 is 95 cells/mm³. Which of the following is the most appropriate treatment?

Incorrect · Answer: A

PEBC Yield: Highempiric-therapydrug-selection

A) (Correct)

Correct. GC has active PCP confirmed by BAL and is admitted to hospital with CD4 95 cells/mm3, so IV TMP-SMX for 21 days is the standard treatment approach. This is treatment dosing and duration, not prophylaxis.

Atovaquone by mouth is reserved for selected mild-to-moderate PCP or when TMP-SMX cannot be used. The stem describes confirmed active PCP requiring admission, so oral atovaquone is not the most appropriate first choice.

Dapsone 100 mg daily is a prophylaxis-style option, not adequate primary treatment for established PCP pneumonia. It would not match a BAL-confirmed active infection in a hospitalized patient.

Atovaquone 750 mg twice daily for 14 days has the wrong role and duration for this stem. Active PCP in HIV requires a 21-day treatment course, and hospitalized disease should be treated with TMP-SMX unless there is a compelling reason not to.

Question 9Infective Endocarditis

K.L. is a 74-year-old male with benign prostatic hyperplasia and recurrent urinary tract infections who develops subacute endocarditis. Blood cultures grow Enterococcus faecalis. He has a native aortic valve vegetation. His baseline eGFR is 42 mL/min/1.73m². Which of the following is the preferred antibiotic regimen?

Incorrect · Answer: C

PEBC Yield: Highdrug-selectiondose-adjustmentpathogen-coverage

Vancomycin plus gentamicin can be used when beta-lactams cannot be used, but it exposes this older patient with eGFR 42 to additive nephrotoxicity. It is not the preferred kidney-sparing regimen when ampicillin can be used.

Ampicillin alone is not enough for Enterococcus faecalis endocarditis because enterococci require synergistic bactericidal therapy to sterilize vegetations. Monotherapy would risk persistent infection.

C) (Correct)

Correct. Ampicillin plus ceftriaxone for 6 weeks provides synergistic activity against Enterococcus faecalis while avoiding prolonged aminoglycoside exposure. CPS Infective Endocarditis - Management and Prevention specifically highlights this approach when creatinine clearance is reduced.

Ceftriaxone alone does not provide reliable enterococcal coverage, and 4 weeks is not the regimen for this native-valve enterococcal case. Ceftriaxone is useful here only as the synergistic partner with ampicillin.

Question 10Fungal Infections

TN is a 62-year-old male with esophageal candidiasis being treated with fluconazole 200 mg PO daily. His past medical history includes hypertension, osteoarthritis, and GERD. He takes lisinopril 10 mg daily, acetaminophen 500 mg PRN, and pantoprazole 40 mg daily. His labs show SCr 210 µmol/L (baseline 85 µmol/L), eGFR 28 mL/min, K⁺ 4.8 mmol/L, and ALT 30 U/L. Which pharmacokinetic property of fluconazole is MOST relevant to this patient's clinical management?

Incorrect · Answer: B

PEBC Yield: Highfluconazolerenal eliminationdose adjustment

Fluconazole does undergo some hepatic CYP2C9 metabolism, and LFT monitoring is reasonable. However, the most clinically relevant property in a patient with acute kidney injury (SCr doubled, eGFR 28) is renal elimination, not hepatic metabolism. This would be the priority concern if the patient had elevated liver enzymes instead.

B) (Correct)

Correct — Fluconazole is 80% excreted unchanged in the urine, making it unique among azoles in requiring dose adjustment for renal dysfunction. With eGFR 28 mL/min, the dose must be reduced to prevent accumulation and toxicity.

Fluconazole's 12% protein binding is indeed low and provides good tissue distribution, but this is an advantage rather than a concern. Low protein binding would be clinically relevant if the question asked about which azole achieves the best CSF penetration.

Fluconazole is water soluble and well absorbed regardless of food or gastric pH. While accurate, this property is advantageous and does not require any clinical intervention. pH-dependent absorption would be relevant when counselling a patient on ketoconazole.

Want the full bank?

These are a sample. The full bank adds full-length cases and timed mock exams.

Sample full case

One patient with several linked questions, the format the real exam uses for case clusters.

Medications: Naproxen 500 mg PO BID prn (last dose 6 h ago). No other routine medications.

Labs on admission	Value	Reference
WBC	14.2 × 10⁹/L	4.0–11.0
Neutrophils	11.8 × 10⁹/L	2.0–7.5
Hgb	142 g/L	135–175
Platelets	285 × 10⁹/L	150–400
Serum creatinine	82 µmol/L	65–115
Random glucose	5.4 mmol/L	3.6–7.8
Plain film of foot	Periosteal reaction and early cortical lucency over the 3rd metatarsal head	—

Assessment: Acute contiguous-focus osteomyelitis of the right 3rd metatarsal from puncture-wound inoculation. Orthopaedics is consulted for surgical debridement; wound swab and bone biopsy cultures are pending. Empiric IV antibiotics are about to be initiated.

Question 1Osteomyelitis

Which serum laboratory value is most likely to be markedly elevated at this stage and most useful to follow serially as a marker of treatment response?

Incorrect · Answer: B

PEBC Yield: Highosteomyelitis-diagnosisesr-crp-monitoringinflammatory-markerstreatment-response-tracking

Incorrect. Serum calcium is not a marker of infection and is typically normal in osteomyelitis. It is not tracked for response to antimicrobial therapy.

B) (Correct)

Correct. ESR (and CRP) are the standard inflammatory markers followed serially in osteomyelitis. ESR is nearly always elevated at diagnosis (often >40 mm/h) and its trend downward over 2–4 weeks correlates with response to therapy. CRP tracks more rapidly (2–3 day half-life) and is often used together with ESR. Plain-film X-ray changes, in contrast, typically lag by 10–14 days from symptom onset and are not a good response marker.

Incorrect. ALP can be modestly elevated in high-bone-turnover states (e.g., Paget's disease, healing fracture, hepatic cholestasis), but it is not a primary marker of acute bacterial bone infection and is not used to follow treatment response in osteomyelitis.

Incorrect. Creatine kinase rises with skeletal muscle injury (rhabdomyolysis, myositis, heavy exertion) — not with bone infection. Osteomyelitis is a bone, not a muscle, pathology.

Question 2Osteomyelitis

Twenty-four hours after admission, the preliminary Gram stain from TG's bone biopsy returns Gram-positive cocci in clusters. Speciation and susceptibilities are still pending. Based on this finding and the clinical context of a nail-puncture-wound osteomyelitis, which organism is the most likely pathogen?

Incorrect · Answer: A

PEBC Yield: Highgram-stain-morphologys-aureus-osteomyelitispathogen-identificationpuncture-wound-microbiology

A) (Correct)

Correct. Gram-positive cocci in clusters is the signature Gram-stain morphology of Staphylococcus aureus (and coagulase-negative staphylococci, which are rarer in osteomyelitis). *S. aureus* is also the single most common cause of osteomyelitis across all contiguous-spread, hematogenous, and post-traumatic categories. Pending susceptibilities will classify MSSA vs MRSA and drive definitive therapy.

Incorrect. Pseudomonas aeruginosa is the textbook answer for nail-puncture-through-rubber-shoe osteomyelitis — but only as an empiric consideration. Once the Gram stain shows GPC in clusters, *Pseudomonas* (a Gram-negative rod) is ruled out by morphology. This distractor traps students who apply the epidemiologic rule without integrating the microbiology result.

Incorrect. *Streptococcus pyogenes* and other streptococci appear as Gram-positive cocci in chains (or pairs), not clusters. The clusters pattern specifically distinguishes staphylococci from streptococci on Gram stain.

Incorrect. *Enterococcus faecalis* is Gram-positive but appears as cocci in pairs or short chains, not clusters. Enterococci are also an uncommon primary pathogen in post-traumatic osteomyelitis of the foot.

Question 3Osteomyelitis

Final cultures return methicillin-susceptible Staphylococcus aureus (MSSA) that is susceptible to cloxacillin, cephalexin, clindamycin, doxycycline, and TMP-SMX. TG has completed 2 weeks of IV cefazolin, his inflammatory markers have fallen, and surgical debridement is complete. Which oral step-down regimen is most appropriate to complete his course?

Incorrect · Answer: A

PEBC Yield: Highmssa-oral-stepdowncephalosporin-pcn-allergyosteomyelitis-oral-therapyallergy-severity-assessment

A) (Correct)

Correct. Cephalexin (first-generation cephalosporin) is the preferred oral step-down for MSSA osteomyelitis: excellent *S. aureus* activity, good oral bioavailability, and adequate bone penetration. In a patient with a non-severe penicillin reaction (isolated maculopapular rash, no IgE-mediated or severe cutaneous features), cephalosporin cross-reactivity is <1% for first-generation agents with a different side chain, and IDSA/Choosing Wisely guidance supports using a cephalosporin rather than escalating to broader agents.

Incorrect. Amoxicillin/clavulanate contains amoxicillin, a penicillin. Even though the reaction history is non-severe, the amoxicillin side chain is specifically implicated in maculopapular drug rash and should be avoided when a safe non-penicillin β-lactam (e.g., cephalexin) is active against the organism.

Incorrect. Ciprofloxacin has poor reliability as MSSA monotherapy — *S. aureus* resistance emerges rapidly on fluoroquinolone monotherapy, and ciprofloxacin is not a first-line agent for staphylococcal bone infection. If a fluoroquinolone is used, it is combined with rifampin or an anti-staphylococcal agent, not given alone.

Incorrect. Doxycycline has some MSSA activity and is occasionally used for SSTI, but it is bacteriostatic and is not a preferred oral step-down for osteomyelitis when an active first-generation cephalosporin is available. Bactericidal agents are preferred for bone-and-joint infection where possible.

Question 4Osteomyelitis

TG transitions to oral cephalexin and continues to improve clinically. Orthopaedics and the ID team ask what total duration of effective antimicrobial therapy (IV + PO combined, counted from adequate surgical debridement) to plan for his acute contiguous-spread MSSA osteomyelitis with complete source control.

Incorrect · Answer: C

PEBC Yield: Highosteomyelitis-durationfour-to-six-week-rulesource-control-timingantibiotic-stewardship

Incorrect. 10–14 days is the duration used for uncomplicated skin and soft-tissue infection (SSTI) or uncomplicated *S. aureus* bacteremia without metastatic spread. It is far too short for bone-and-joint infection and would reliably relapse.

Incorrect. 2–3 weeks remains inadequate for acute osteomyelitis in adults. Some short-course regimens (≈3–4 weeks) are reported for pediatric acute hematogenous osteomyelitis with rapid response, but adult contiguous-spread osteomyelitis is not treated this way.

C) (Correct)

Correct. Adult acute osteomyelitis with adequate debridement: a minimum of 4–6 weeks of effective antimicrobial therapy (IDSA guidance). The clock starts from the date of adequate source control / debridement, and combined IV + PO duration counts toward the total. Longer courses (3 months+) are reserved for chronic osteomyelitis, retained hardware, inadequate debridement, or prosthetic-joint infection.

Incorrect. 3–6 months is reserved for chronic osteomyelitis, prosthetic-joint infection, or cases with retained hardware / incomplete debridement. TG has acute, contiguous, fully debrided MSSA osteomyelitis — extending therapy to months is not evidence-supported and increases adverse-event risk (C. diff, drug toxicity, resistance selection).

Full-length cases like this, across every PEBC domain, live in the question bank.

Frequently asked questions

Is infectious disease high yield on the PEBC exam?: Yes. Antimicrobial therapy is a core clinical area, so common infections like UTI, pneumonia, and skin and soft tissue infections, along with the principles of antimicrobial selection and stewardship, come up often. The exact mix is randomized from one sitting to the next, but infectious disease is consistently worth strong preparation.
What infectious disease topics should I focus on for the PEBC?: Focus on empiric versus directed therapy, first-line antibiotics for the common community infections (UTI, pneumonia, cellulitis, otitis media, pharyngitis), spectrum of activity, penicillin allergy and cross-reactivity, treatment durations and the IV-to-oral switch, and the monitoring for vancomycin and aminoglycosides.
Which references should I use for infectious disease on the PEBC?: The Canadian standard references are Bugs and Drugs and the guidance from AMMI Canada (the Association of Medical Microbiology and Infectious Disease Canada), along with provincial antimicrobial stewardship resources. The PEBC expects the Canadian first-line choice, which is not always what a US source would recommend.
How should I study infectious disease for the PEBC?: Learn the first-line empiric therapy for the common infections cold, know the standard durations and when to switch from IV to oral, and always read the vignette for the patient factor (allergy, pregnancy, renal function) that changes the drug.