100+ Free ABPath Medical Microbiology Practice Questions

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Question 1

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A pleural fluid specimen shows Gram-positive cocci in chains on direct smear. After 24 hours on sheep blood agar, colonies are small with a narrow zone of beta-hemolysis and are catalase-negative. Lancefield grouping is positive for Group A. Which organism is most likely?

Streptococcus pyogenes

Streptococcus agalactiae

Enterococcus faecalis

Streptococcus pneumoniae

to track

2026 Statistics

Key Facts: ABPath Medical Microbiology Exam

305

Total MCQ Items

Single-best-answer format

6h 10m

Total Exam Time

1-day computer-based test

49%

Bacteriology Weight

Largest domain on 2026 blueprint

$2,100

2026 Exam Fee

Includes $200 admin fee

12 mo

Required Fellowship

ACGME Medical Microbiology fellowship

10 yr

Certification Validity

Time-limited; CC/MOC required

The ABPath Medical Microbiology exam is a 1-day 305-question computer-based test (6 hours 10 minutes) from the American Board of Pathology. The 2026 blueprint weights Bacteria 49%, Mycobacteria/Nocardia/Aerobic Actinomycetes 11%, Fungi 13%, Viruses & Prions 11%, Parasites 11%, and Management & Informatics — Medical Microbiology 5%. The 2026 application fee is $2,100 (includes $200 nonrefundable administrative fee). Testing window: September 8-28, 2026 at Pearson VUE centers. Pass score is criterion-referenced via modified Angoff.

Sample ABPath Medical Microbiology Practice Questions

Try these sample questions to test your ABPath Medical Microbiology exam readiness. Each question includes a detailed explanation. Start the interactive quiz above for the full 100+ question experience with AI tutoring.

1A pleural fluid specimen shows Gram-positive cocci in chains on direct smear. After 24 hours on sheep blood agar, colonies are small with a narrow zone of beta-hemolysis and are catalase-negative. Lancefield grouping is positive for Group A. Which organism is most likely?

A.Streptococcus pyogenes

B.Streptococcus agalactiae

C.Enterococcus faecalis

D.Streptococcus pneumoniae

Explanation: Streptococcus pyogenes is a catalase-negative, beta-hemolytic, Gram-positive coccus in chains that groups with Lancefield Group A. S. agalactiae is Group B, E. faecalis carries Group D antigen, and S. pneumoniae is alpha-hemolytic and bile-soluble. Bacitracin susceptibility and PYR positivity are additional confirmatory tests for S. pyogenes.

2A wound swab grows Gram-positive cocci in clusters. The isolate is catalase-positive and coagulase-positive. Which identification is most likely?

A.Staphylococcus epidermidis

B.Staphylococcus aureus

C.Staphylococcus saprophyticus

D.Micrococcus luteus

Explanation: Coagulase-positive, catalase-positive Gram-positive cocci in clusters define Staphylococcus aureus. S. epidermidis and S. saprophyticus are coagulase-negative staphylococci (CoNS); S. saprophyticus is novobiocin-resistant. Micrococcus is catalase-positive but is larger, yellow-pigmented, and modified oxidase-positive.

3An S. aureus isolate from a surgical wound is tested with a cefoxitin disk: a 19 mm zone is observed. Per current CLSI breakpoints, how should this be interpreted?

A.Susceptible to methicillin (MSSA)

B.Resistant to methicillin (MRSA)

C.Vancomycin-resistant

D.Inducible clindamycin resistance

Explanation: CLSI cefoxitin disk screen for S. aureus: ≤21 mm zone = MRSA (mecA positive), ≥22 mm = MSSA. Cefoxitin is a more sensitive inducer of mecA expression than oxacillin disks and is the CLSI-preferred phenotypic screen. PBP2a latex agglutination and mecA PCR are confirmatory.

4Which confirmatory test phenotypically detects ESBL (extended-spectrum beta-lactamase) production in Enterobacterales?

A.Modified carbapenem inactivation method (mCIM)

B.Nitrocefin chromogenic disk

C.Ceftazidime/cefotaxime MIC reduction ≥3 log2 dilutions with clavulanate

D.Cefoxitin disk screen

Explanation: CLSI ESBL confirmatory testing requires demonstration that ceftazidime (CAZ) or cefotaxime (CTX) MIC decreases by at least 3 log2 (8-fold) dilutions when combined with clavulanate (e.g., CTX MIC 64 → CTX/clav MIC 8 µg/mL). mCIM detects carbapenemase production, not ESBL. Nitrocefin detects general beta-lactamase (mostly staphylococcal penicillinase).

5A Klebsiella pneumoniae isolate is resistant to meropenem. Which test is the CLSI-recommended phenotypic method for carbapenemase detection?

A.Modified carbapenem inactivation method (mCIM) with or without EDTA-mCIM

B.Etest vancomycin gradient

C.Disk diffusion with cefoxitin

D.Standard broth microdilution alone

Explanation: CLSI recommends mCIM to detect carbapenemase production in Enterobacterales and Pseudomonas aeruginosa. Adding EDTA (eCIM) differentiates metallo-beta-lactamases (MBL — NDM, VIM, IMP) from serine carbapenemases (KPC, OXA-48). CarbaNP is an alternative rapid colorimetric method. Molecular tests (e.g., Xpert Carba-R) provide genotypic confirmation.

6Which organism produces a green pigment (pyocyanin), has a grape-like odor, and is the most common non-fermenting Gram-negative bacillus causing ventilator-associated pneumonia?

A.Pseudomonas aeruginosa

B.Acinetobacter baumannii

C.Burkholderia cepacia

D.Stenotrophomonas maltophilia

Explanation: Pseudomonas aeruginosa is an oxidase-positive, lactose-nonfermenting Gram-negative rod that produces pyocyanin (blue-green) and pyoverdine (fluorescent yellow-green) with a characteristic grape-like odor. Acinetobacter is oxidase-negative. Burkholderia cepacia is important in cystic fibrosis. Stenotrophomonas is oxidase-negative and intrinsically resistant to carbapenems (treat with TMP-SMX).

7A stool culture is set up on MacConkey agar. Which of the following would appear as lactose-fermenting (pink) colonies?

A.Salmonella enterica

B.Shigella flexneri

C.Escherichia coli

D.Yersinia enterocolitica

Explanation: E. coli is a lactose fermenter and produces pink colonies on MacConkey agar. Salmonella, Shigella, and Yersinia are lactose non-fermenters, producing colorless colonies. This is why selective/differential media like Hektoen enteric agar and XLD are used for enteric pathogen isolation from stool.

8An E. coli isolate is identified from a urine culture. The isolate demonstrates ESBL production. Which beta-lactam antibiotic class is most appropriate for serious infection?

A.Third-generation cephalosporins (ceftriaxone)

B.Carbapenems (meropenem)

C.Extended-penicillins (piperacillin-tazobactam)

D.First-generation cephalosporins (cefazolin)

Explanation: Carbapenems (meropenem, imipenem, ertapenem) are the drug of choice for serious ESBL-producing Enterobacterales infections because they are stable against ESBL hydrolysis. Piperacillin-tazobactam has historically been used but IDSA 2024 guidance and the MERINO trial favor carbapenems for bloodstream infection. Third-generation cephalosporins are hydrolyzed by ESBLs.

9Which of the following organisms is a member of the HACEK group causing culture-negative or slow-growing endocarditis?

A.Haemophilus influenzae

B.Aggregatibacter actinomycetemcomitans

C.Kingella kingae

D.Both B and C

Explanation: The HACEK group includes Haemophilus aphrophilus (now Aggregatibacter aphrophilus), Aggregatibacter actinomycetemcomitans, Cardiobacterium hominis, Eikenella corrodens, and Kingella kingae/K. denitrificans. These fastidious Gram-negative organisms cause slow-growing endocarditis. H. influenzae (not parainfluenzae/aphrophilus) is no longer in HACEK.

10Which of the following assays relies on the time-of-flight of protein ions to identify bacterial species from colony material within minutes?

A.MALDI-TOF mass spectrometry

B.16S rRNA gene sequencing

C.Multiplex PCR

D.Broth microdilution

Explanation: MALDI-TOF MS (Matrix-Assisted Laser Desorption/Ionization Time-Of-Flight) vaporizes and ionizes ribosomal proteins from bacterial colonies; the time-of-flight mass spectrum generates a species-specific fingerprint matched against a reference database. It has revolutionized routine bacterial ID from days to minutes. 16S sequencing is genotypic and slower. PCR is target-specific. Broth microdilution measures MICs.

About the ABPath Medical Microbiology Exam

The ABPath Medical Microbiology subspecialty certification validates expert-level knowledge of diagnostic microbiology — bacteriology, mycobacteriology, mycology, virology, parasitology, antimicrobial susceptibility testing, molecular diagnostics, and laboratory management. The 1-day computer-based exam has 305 single-best-answer multiple-choice items over 6 hours 10 minutes. Candidates must hold primary ABPath AP/CP or CP certification plus a 12-month ACGME-accredited Medical Microbiology fellowship (or CPEP-accredited equivalent for Clinical Microbiology Focused Practice).

Questions

305 scored questions

Time Limit

1-day computer-based (6 hours 10 minutes total)

Passing Score

Scaled criterion-referenced pass score (modified Angoff)

Exam Fee

$2,100 (includes $200 nonrefundable administrative fee) (American Board of Pathology (ABPath) / Pearson VUE)

ABPath Medical Microbiology Exam Content Outline

49%

Bacteria (non-mycobacterial)

Gram stain, aerobic/anaerobic culture, MALDI-TOF MS, 16S rRNA sequencing, Lancefield grouping, CoNS vs S. aureus, Enterobacterales, non-fermenters, HACEK, Brucella/Francisella/Bartonella, spirochetes (Treponema, Borrelia, Leptospira), CLSI MIC AST (disk diffusion, broth microdilution, Etest), ESBL confirmatory (clavulanate), AmpC, carbapenemase (mCIM, CarbaNP), MRSA cefoxitin, VRE, vancomycin MIC creep, β-lactamase detection.

11%

Mycobacteria, Nocardia & Aerobic Actinomycetes

MTB complex (AFB smear, Ziehl-Neelsen, auramine-rhodamine, Xpert MTB/RIF, MGIT, LJ), MAC, rapid-growers (M. abscessus/fortuitum/chelonae), M. leprae (Fite), CLSI M24 AST, Nocardia (partial acid-fast), Rhodococcus, Tropheryma whipplei, BSL-3.

13%

Fungi (Mycology)

Yeasts (Candida — germ tube for C. albicans, chromogenic agar), Cryptococcus (India ink, CrAg, mucicarmine), dimorphic fungi (Histoplasma, Blastomyces, Coccidioides, Paracoccidioides, Talaromyces), molds (Aspergillus 45° septate, Mucorales broad non-septate), dermatophytes, dematiaceous, Pneumocystis jirovecii, GMS/PAS/calcofluor stains, galactomannan & β-D-glucan.

11%

Viruses & Prions

Multiplex RT-PCR respiratory panels, viral culture/shell vial, serology (IgM/IgG, avidity), HSV/VZV/CMV/EBV (monospot, EBNA/VCA-IgM), hepatitis A/B/C/D/E (HBV windows, HCV RNA), HIV algorithm, arboviruses, hemorrhagic fever (BSL-4), rabies Negri bodies, hrHPV, prion disease (CJD — 14-3-3, RT-QuIC).

11%

Parasites (Parasitology)

Intestinal protozoa (Giardia, E. histolytica vs dispar, Cryptosporidium modified acid-fast, Cyclospora UV autofluorescence), blood/tissue protozoa (Plasmodium thick/thin — P. falciparum banana gametocyte, Babesia Maltese cross, Trypanosoma, Leishmania, Toxoplasma), helminths (Ascaris, hookworm, Strongyloides, Enterobius scotch tape, Schistosoma, tapeworms, Echinococcus), stool O&P, Giemsa.

Management & Informatics — Medical Microbiology

Biosafety levels (BSL-1 to BSL-4), select agents, CLIA regulations, quality control (Westgard), CAP proficiency testing, antimicrobial stewardship (ASP), rapid sepsis diagnostics, cumulative antibiograms, public health reporting, LIS, preanalytic quality, specimen rejection criteria.

How to Pass the ABPath Medical Microbiology Exam

What You Need to Know

Passing score: Scaled criterion-referenced pass score (modified Angoff)
Exam length: 305 questions
Time limit: 1-day computer-based (6 hours 10 minutes total)
Exam fee: $2,100 (includes $200 nonrefundable administrative fee)

Keys to Passing

Complete 500+ practice questions
Score 80%+ consistently before scheduling
Focus on highest-weighted sections
Use our AI tutor for tough concepts

ABPath Medical Microbiology Study Tips from Top Performers

1Master CLSI MIC breakpoints cold — ESBL confirmation requires ≥3 log2 dilution reduction in MIC with clavulanate vs without (e.g., cefotaxime MIC drops from 64 to 8 µg/mL); carbapenem-resistant Enterobacterales (CRE) screening uses meropenem MIC with mCIM (modified carbapenem inactivation method) or CarbaNP for carbapenemase confirmation

2MRSA detection: cefoxitin disk (≤21 mm or MIC ≥8 µg/mL) is more sensitive than oxacillin for mecA-mediated resistance. Vancomycin MIC creep — watch for S. aureus MIC 1.5-2 µg/mL approaching the susceptibility breakpoint (≤2); clinical failures associated with MIC 2

3C. difficile algorithm: NAAT (PCR) alone is highly sensitive but detects colonization — preferred algorithm is GDH antigen + toxin A/B EIA with NAAT as the tiebreaker, or toxin EIA-first to confirm active disease

4Germ tube test: Candida albicans and C. dubliniensis form germ tubes in serum at 37°C within 2-3 hours (positive). Chromogenic agar speciates most Candida; C. auris requires MALDI-TOF or sequencing — BSL-2 precautions and contact isolation mandatory due to multi-drug resistance

5Know the mold hyphal morphology pattern: Aspergillus shows septate hyphae with acute 45° dichotomous branching; Mucorales (Rhizopus, Mucor, Lichtheimia) show broad (10-20 µm) ribbon-like, pauciseptate non-septate hyphae with wide 90° angle branching. Galactomannan is an Aspergillus biomarker; β-D-glucan is a pan-fungal marker (negative in Mucorales and Cryptococcus)

Frequently Asked Questions

What is the ABPath Medical Microbiology subspecialty certification?

The ABPath Medical Microbiology subspecialty certification is awarded by the American Board of Pathology to diplomates who demonstrate expert-level knowledge of diagnostic clinical microbiology — including bacteriology, mycobacteriology, mycology, virology, parasitology, antimicrobial susceptibility testing, molecular diagnostics, and laboratory management. It qualifies pathologists to direct clinical microbiology laboratories and lead antimicrobial stewardship programs.

Who is eligible to take the ABPath Medical Microbiology exam?

Candidates must hold primary ABPath certification in good standing in AP/CP or CP and have completed 12 months of full-time training in an ACGME-accredited Medical Microbiology fellowship. An alternative Clinical Microbiology Focused Practice pathway exists via a CPEP-accredited 2-year training program or a practice pathway (≥30% Clinical Microbiology in 3 of last 5 years). A valid unrestricted medical license is required.

What is the format of the ABPath Medical Microbiology exam?

The exam is a 1-day computer-based examination administered at Pearson VUE. It consists of 305 single-best-answer multiple-choice questions delivered in 6 hours 10 minutes. All items are one-best-answer MCQs; there are no glass slides. The 2026 blueprint allocates 49% Bacteria, 11% Mycobacteria/Nocardia/Aerobic Actinomycetes, 13% Fungi, 11% Viruses & Prions, 11% Parasites, and 5% Management & Informatics.

How much does the 2026 ABPath Medical Microbiology exam cost?

The 2026 examination fee is $2,100, which includes a $200 nonrefundable administrative fee. Candidates who cancel by June 15 forfeit a $500 cancellation fee; cancellations after June 15 forfeit the full fee. Retakes within the 7-year qualification window require re-registration and full fee payment.

When is the 2026 exam administered?

The 2026 ABPath Medical Microbiology Subspecialty Certification Exam is offered September 8-28, 2026 at Pearson VUE Professional Testing Centers. Applications open February 16, 2026 and must be submitted by May 15, 2026 (11:59 PM EST). There are no late application deadlines. Scheduling with Pearson VUE opens in July after the application is complete.

How is the exam scored?

ABPath uses criterion-referenced scoring with a cut-score set in advance by subject-matter experts using the modified Angoff method, which estimates minimally-qualified-candidate performance on each item. A candidate's result depends only on performance relative to the cut-score, not on other candidates. Results are posted to the Board Correspondence tab in PATHway approximately 6 weeks after the final week of subspecialty exams.

What are the highest-yield topics?

Bacteriology (49%) dominates — master Gram stain morphology, MALDI-TOF identification, CLSI MIC breakpoints, ESBL/AmpC/carbapenemase detection (mCIM, CarbaNP), MRSA cefoxitin screen, vancomycin MIC creep, and VRE. Also know germ tube for C. albicans, septate vs non-septate molds (Aspergillus 45° vs Mucorales broad ribbon-like), Xpert MTB/RIF and MGIT mycobacteriology, multiplex respiratory PCR panels, HBV serology windows, Plasmodium thick/thin smear morphology, and C. difficile NAAT vs GDH/toxin EIA algorithms.

How should I study for this exam?

Use a structured 6-12 month plan during or immediately after fellowship. Start with bacteriology + CLSI antimicrobial susceptibility (largest domain), then mycology/virology/mycobacteriology molecular workup, then parasitology and lab management. Complete thousands of practice questions, build flashcards for CLSI MIC breakpoints and organism biochemical profiles, and take 2-3 timed full-length mock exams. Integrate ASM Manual of Clinical Microbiology, CLSI M100/M24/M60 standards, and relevant IDSA guidelines.