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Key Facts: ABMM Exam

200

Total MCQ Items

Single-best-answer format

6 hrs

Total Exam Time

Single-session computer-based test

25%

Bacteriology Weight

Largest single content domain

$450 / $575

Application Fee

ASM member / non-member

12 states

CLIA Director Recognition

Direct CLIA recognition for high-complexity labs

3 yrs

Recertification Cycle

Continuing Maintenance Program

The ABMM exam (Diplomate, American Board of Medical Microbiology) is a 6-hour, 200-question single-best-answer computer-based test administered by ASM. Application is $450 (member) / $575 (non-member); a separate $400 exam registration fee applies if approved. Passing confers D(ABMM) — recognized under CLIA '88 for high-complexity clinical laboratory director qualification in 12 states. Recertification via the Continuing Maintenance Program every 3 years. Distinct from ABPath Medical Microbiology (MD-only) and ASCP M (BS-level technologist).

Sample ABMM Practice Questions

Try these sample questions to review concepts for the ABMM exam. Each question includes a detailed explanation. Start the interactive quiz above for the full 100+ question experience with AI tutoring.

1A Gram-positive coccus in clusters from a wound culture is catalase-positive and coagulase-positive. Which species is most likely?
A.Staphylococcus epidermidis
B.Staphylococcus aureus
C.Staphylococcus saprophyticus
D.Streptococcus pyogenes
Explanation: S. aureus is the catalase-positive, coagulase-positive Staphylococcus. Coagulase (clumping factor and free coagulase) reliably distinguishes S. aureus from coagulase-negative staphylococci in routine clinical workup of skin and soft tissue isolates.
2A coagulase-negative staphylococcus from a clean-catch urine in a young woman with cystitis is novobiocin-resistant. Which species is most likely?
A.Staphylococcus epidermidis
B.Staphylococcus saprophyticus
C.Staphylococcus lugdunensis
D.Staphylococcus haemolyticus
Explanation: S. saprophyticus is intrinsically resistant to novobiocin (5 µg disk zone <16 mm) and is a leading cause of uncomplicated cystitis in sexually active young women. Routine labs use the novobiocin disk to separate it from other CoNS.
3A blood culture isolate is a Gram-positive coccus in clusters, coagulase-negative, but ornithine decarboxylase positive and PYR positive. Which species should be suspected?
A.Staphylococcus epidermidis
B.Staphylococcus capitis
C.Staphylococcus lugdunensis
D.Staphylococcus warneri
Explanation: S. lugdunensis is unique among coagulase-negative staphylococci for being ornithine decarboxylase positive and PYR positive. It can cause aggressive endocarditis and abscesses similar to S. aureus and should not be dismissed as a contaminant.
4A throat culture grows beta-hemolytic colonies that are bacitracin-susceptible and PYR-positive. The most likely organism is:
A.Streptococcus agalactiae
B.Streptococcus pyogenes
C.Streptococcus dysgalactiae
D.Enterococcus faecalis
Explanation: S. pyogenes (group A Streptococcus) is bacitracin (taxo A) susceptible and PYR positive, and is the cause of acute streptococcal pharyngitis. Routine pharyngeal cultures use these markers along with Lancefield serology.
5A vaginal-rectal swab from a pregnant woman at 36 weeks grows beta-hemolytic colonies that are CAMP-positive and hippurate hydrolysis positive. Which Lancefield group does this organism belong to?
A.Group A
B.Group B
C.Group C
D.Group D
Explanation: Streptococcus agalactiae (group B Streptococcus, GBS) is CAMP-positive and hippurate-positive. Universal antenatal GBS screening at 35-37 weeks identifies colonized mothers for intrapartum penicillin prophylaxis to prevent neonatal sepsis.
6An alpha-hemolytic Gram-positive coccus from blood is optochin-susceptible and bile-soluble. The organism is:
A.Streptococcus pneumoniae
B.Streptococcus mitis
C.Streptococcus oralis
D.Enterococcus faecalis
Explanation: S. pneumoniae is optochin-susceptible (zone >=14 mm with 6 mm disk on sheep blood) and bile-soluble. Both tests are needed because some viridans streptococci can be falsely optochin-susceptible.
7A urinary isolate grows on bile-esculin agar with blackening and grows in 6.5% NaCl broth. PYR is positive. The most likely organism is:
A.Streptococcus bovis group
B.Enterococcus species
C.Group B Streptococcus
D.Aerococcus urinae
Explanation: Enterococcus species are PYR-positive, bile-esculin positive, and grow in 6.5% NaCl. The S. bovis group (now S. gallolyticus subsp.) is bile-esculin positive but does NOT grow in 6.5% NaCl and is PYR-negative.
8Which test best distinguishes Enterococcus faecium from Enterococcus faecalis in a clinical lab?
A.Bile-esculin
B.6.5% NaCl growth
C.PYR
D.Arabinose fermentation
Explanation: E. faecium ferments arabinose; E. faecalis does not. Both are PYR-positive, bile-esculin positive, and grow in 6.5% NaCl, so those tests cannot separate the two species. MALDI-TOF in modern labs replaces biochemical separation but arabinose remains a classic key.
9A urine isolate is a lactose-fermenting, indole-positive, motile Gram-negative rod that produces a green sheen on EMB. The organism is:
A.Klebsiella pneumoniae
B.Escherichia coli
C.Enterobacter cloacae
D.Citrobacter freundii
Explanation: E. coli is the classic lactose-fermenting, indole-positive Enterobacterales species and produces a metallic green sheen on EMB due to vigorous mixed-acid fermentation. IMViC for E. coli is ++--.
10A Gram-negative rod from a urine culture is urease-strongly-positive, swarms on blood agar, indole-negative, and produces H2S on TSI. The likely organism is:
A.Proteus mirabilis
B.Proteus vulgaris
C.Morganella morganii
D.Providencia stuartii
Explanation: P. mirabilis is urease-positive (rapid), swarms on non-selective agar, is indole-NEGATIVE, and produces H2S. Urease activity contributes to struvite stones in chronic UTI. P. vulgaris is the indole-positive Proteus.

About the ABMM Exam

The Diplomate, American Board of Medical Microbiology (D(ABMM)) certification validates doctoral-level expertise to direct a clinical microbiology laboratory. The 6-hour computer-based exam has 200 single-best-answer multiple-choice questions covering bacteriology, antimicrobial susceptibility testing, mycology, mycobacteriology, parasitology, virology, molecular diagnostics, and laboratory administration. Eligibility requires a doctorate (PhD, MD, DO, DVM, DDS/DMD, DrPH) plus 3 years post-doc experience, a 2-year CPEP postdoctoral fellowship, or an ACGME-accredited Medical Microbiology fellowship. CLIA recognizes D(ABMM) for high-complexity lab director qualification in 12 states.

Exam sponsor: American Society for Microbiology (ASM) — American Board of Medical Microbiology. The requirements and fees below concern the certification or admission exam, separate from our free practice resources.

Questions

200 questions

Time Limit

6 hours computer-based test (single session)

Passing Score

Criterion-referenced (modified Angoff); average item difficulty target ~0.70

Exam / Certification Fees

$450 (ASM member) / $575 (non-member) application + $400 exam registration if approved

Exam sponsor website

Reported exam pass rate: Not publicly published. ABMM uses a criterion-referenced cut score; candidates are evaluated against a fixed standard rather than a curve. Exam sponsor website

Fees, eligibility, and exam policies can change. Confirm them with the exam sponsor before applying or paying.

Our practice resources: topics covered

We aim to reflect publicly available exam outlines and topic information in our study resources. Coverage, format, and difficulty may differ from the actual exam, and we cannot guarantee that every detail is accurate or current. Confirm exam requirements, fees, and policies with the official exam sponsor.

25%

Bacteriology

Gram-positive cocci (Staph, Strep, Enterococcus), Enterobacterales, non-fermenters (Pseudomonas, Acinetobacter, Burkholderia, Stenotrophomonas), Neisseria/Moraxella, anaerobes, fastidious organisms (Haemophilus, Legionella, Bordetella, Brucella, Francisella, Bartonella), spirochetes (Treponema, Borrelia, Leptospira), Mycoplasma/Ureaplasma, Chlamydia, Rickettsia/Ehrlichia/Anaplasma/Coxiella. MALDI-TOF and 16S rRNA workflows.

10%

Antimicrobial Susceptibility Testing

CLSI M100 (current edition), broth microdilution, disk diffusion, gradient strip (Etest), automated systems, MIC interpretation and expert rules. ESBL (TEM/SHV/CTX-M), AmpC, carbapenemases (KPC, NDM, OXA-48-like, VIM, IMP), mecA/MRSA cefoxitin, vanA/vanB, MEF/ERM, qnr. mCIM/eCIM and CarbaNP confirmatory tests.

10%

Mycology

Yeasts including Candida auris, Cryptococcus neoformans/gattii, Trichosporon. Dimorphic fungi (Histoplasma, Blastomyces, Coccidioides, Paracoccidioides, Sporothrix, Talaromyces marneffei). Hyaline molds (Aspergillus, Fusarium, Scedosporium/Lomentospora), Mucorales, dematiaceous, dermatophytes, Pneumocystis jirovecii. CLSI M27/M38/M60 antifungal AST, galactomannan, β-D-glucan.

7%

Mycobacteriology

MTB complex, NTM (MAC, M. abscessus, M. kansasii, M. marinum, M. fortuitum), AFB stains, MGIT/Lowenstein-Jensen, MALDI-TOF mycobacteria, line probe assays, Xpert MTB/RIF and MTB/RIF Ultra, CLSI M24 AST, BSL-3 biosafety, IGRA vs TST.

7%

Parasitology

Protozoa (Giardia, Cryptosporidium, Cyclospora, Entamoeba, Plasmodium, Babesia, Trypanosoma, Leishmania, Toxoplasma, Naegleria, Acanthamoeba), helminths (Ascaris, Strongyloides, hookworm, Enterobius, Trichuris, Schistosoma, Taenia, Echinococcus, Diphyllobothrium). Stool O&P, Giemsa thick/thin smears, modified acid-fast, multiplex GI panels.

12%

Virology

Respiratory viruses (Influenza A/B, RSV, hMPV, parainfluenza, adenovirus, rhinovirus, SARS-CoV-2), GI viruses, herpes (HSV, VZV, CMV, EBV, HHV-6/7/8), hepatitis A-E, HIV diagnostic algorithm, HPV, arboviruses (West Nile, Zika, Dengue, chikungunya, EEE/WEE), VHF (BSL-4: Ebola, Lassa, Marburg).

15%

Molecular Diagnostics

PCR, real-time PCR, multiplex syndromic panels (BioFire, GenMark ePlex, NxTAG), NGS, MALDI-TOF, NAATs, isothermal amplification (LAMP, TMA, NEAR), 16S rRNA / ITS sequencing, FDA-cleared vs LDT regulations, validation/verification studies.

14%

Laboratory Administration & Consultation

CLIA '88 high-complexity testing, CAP and ISO 15189 accreditation, biosafety BSL-1 through BSL-4, HHS/USDA select agents, QA/QC and Westgard rules, proficiency testing, IQCP, LIS, billing/CPT, antimicrobial stewardship consultation, cumulative antibiograms, public health reporting.

Preparing for the ABMM Exam

What You Need to Know

  • Passing score: Criterion-referenced (modified Angoff); average item difficulty target ~0.70
  • Exam length: 200 questions
  • Time limit: 6 hours computer-based test (single session)
  • Exam / certification fees: $450 (ASM member) / $575 (non-member) application + $400 exam registration if approved Official sources

Using Our Practice Resources

  • Work through all 100 available questions
  • Review every answer and explanation
  • Track weak areas and revisit them
  • Use our AI tutor for tough concepts

ABMM: Suggested Study Strategy

1Master the CLSI M100 (current edition) breakpoint tables cold — ESBL phenotypic confirmation requires at least a 3-fold log2 dilution decrease in MIC of cefotaxime or ceftazidime when tested with vs without 4 µg/mL clavulanate. Modified carbapenem inactivation method (mCIM) detects carbapenemase activity; eCIM differentiates metallo (NDM, VIM, IMP) from serine carbapenemases (KPC, OXA)
2MRSA detection: cefoxitin disk (≤21 mm zone) or cefoxitin MIC ≥8 µg/mL is the preferred screen for mecA-mediated resistance — more sensitive than oxacillin. Vancomycin MIC creep — S. aureus isolates with MIC 1.5-2 µg/mL are at the edge of the susceptible breakpoint (≤2) and have been associated with clinical failure
3Candida auris: confirm by MALDI-TOF (with updated database) or D1/D2 28S rRNA sequencing; biochemical systems frequently misidentify it as C. haemulonii, C. famata, or Rhodotorula glutinis. Implement contact precautions and chlorhexidine bathing — environmental persistence is profound
4Mold morphology: Aspergillus shows septate hyphae with acute (~45°) dichotomous branching; Mucorales (Rhizopus, Mucor, Lichtheimia, Rhizomucor) show broad (10-20 µm) ribbon-like, pauciseptate hyphae with wide-angle (~90°) branching. Galactomannan is an Aspergillus biomarker; β-D-glucan is pan-fungal but NEGATIVE in Mucorales and Cryptococcus
5Validation vs verification (CLIA '88): an FDA-cleared assay used unmodified requires verification of accuracy, precision, reportable range, and reference intervals. An LDT or modified FDA-cleared assay requires full validation including analytical sensitivity, specificity, accuracy, precision, reportable range, reference intervals, and clinical performance

Frequently Asked Questions

What is the D(ABMM) credential?

D(ABMM) — Diplomate of the American Board of Medical Microbiology — is a doctoral-level certification awarded by the American Society for Microbiology (ASM) that validates expertise to direct a clinical microbiology laboratory. CLIA '88 recognizes D(ABMM) as a qualified high-complexity laboratory director in 12 U.S. states. The credential is held primarily by PhDs but is open to MDs, DOs, DVMs, DDS/DMDs, and DrPHs who meet the eligibility pathways.

Who is eligible to take the ABMM exam?

Candidates must hold an earned doctorate (PhD, MD, DO, DVM, DDS/DMD, or DrPH) and meet one of three experience pathways: (1) at least 3 years of post-doctoral experience in medical/clinical microbiology, (2) completion of a 2-year ASM CPEP-accredited postdoctoral fellowship in medical and public health microbiology, or (3) completion of an ACGME-accredited Medical Microbiology fellowship. The ABMM credentialing committee reviews each application before exam registration is permitted.

What is the format of the ABMM exam?

The ABMM exam is a 6-hour computer-based test of 200 single-best-answer multiple-choice questions delivered in a single session. The content blueprint covers Bacteriology (~25%), Virology (~12%), Mycology (~10%), Antimicrobial Susceptibility Testing (~10%), Mycobacteriology (~7%), Parasitology (~7%), Molecular Diagnostics (~15%), and Laboratory Administration (~14%). Pass status is criterion-referenced via the modified Angoff method; the average item difficulty target is approximately 0.70.

How much does the ABMM exam cost in 2026?

The application fee is $450 for ASM members and $575 for non-members, paid at submission and nonrefundable. If the credentialing committee approves the application, candidates pay an additional $400 exam registration fee before scheduling. Total first-attempt cost is approximately $850 (member) or $975 (non-member). Continuing Maintenance Program (CMP) fees apply every 3 years to maintain the credential.

How does ABMM differ from ABPath Medical Microbiology?

ABMM (D(ABMM)) is administered by ASM and is the doctoral-level credential primarily held by PhDs (open to all earned doctorates). ABPath Medical Microbiology is a subspecialty of the American Board of Pathology and is restricted to MDs/DOs who hold ABPath AP/CP or CP primary certification plus a 12-month ACGME Medical Microbiology fellowship. Both qualify the holder to direct a clinical microbiology lab; ABMM is the more common path for non-physician scientists.

Is D(ABMM) recognized by CLIA?

Yes. CLIA '88 explicitly recognizes D(ABMM) certification as qualifying a doctoral-level scientist to serve as a high-complexity clinical laboratory director in 12 states. State-specific licensure (e.g., New York Clinical Laboratory Technology Certificate of Qualification, California Laboratory Field Services) may impose additional requirements on top of D(ABMM).

What are the highest-yield topics?

Bacteriology (~25%) and Molecular Diagnostics (~15%) together cover 40% of the exam — master CLSI M100 breakpoint interpretation, ESBL/AmpC/carbapenemase detection (mCIM, CarbaNP), MRSA cefoxitin screen, vanA/vanB VRE, MALDI-TOF identification, multiplex syndromic panels (BioFire FilmArray), 16S rRNA sequencing applications, and FDA-cleared vs LDT validation. Lab Administration (~14%) is heavily weighted — know CLIA, CAP, ISO 15189, biosafety levels, and antimicrobial stewardship deeply.

How should I prepare for the ABMM exam?

Plan a 6-12 month focused review during or immediately after a CPEP/ACGME fellowship or ABMM-eligible directed practice. Work through the ASM Manual of Clinical Microbiology cover-to-cover, study the current CLSI M100/M24/M27/M38/M60 standards, complete thousands of board-style questions, and take at least two timed full-length 200-question mock exams. The ASM ABMM/CPEP study guide and the ASM Press 'Clinical Microbiology Procedures Handbook' are core references.