100+ Free ACVM Veterinary Microbiology Practice Questions

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Question 1

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A canine pyoderma swab yields gram-positive cocci in clusters that are catalase-positive and coagulase-positive. Which species is MOST likely?

Staphylococcus aureus

Staphylococcus pseudintermedius

Streptococcus canis

Enterococcus faecalis

to track

2026 Statistics

Key Facts: ACVM Veterinary Microbiology Exam

~100

Practice Questions

OpenExamPrep ACVM question bank (2026)

Subspecialty Tracks

Bacteriology/Mycology, Virology, Immunology, Parasitology

~15%

Clinical Bacteriology Weight

Largest domain in 2026 ACVM content outline (tied with ID, virology, parasitology)

~$1,500-$2,500

2026 Exam Fee

ACVM (verify current schedule at acvm.us)

3+ yr

Training Pathway

Residency or graduate training under ACVM diplomate mentor

Required Publication

Peer-reviewed publication in veterinary microbiology

The ACVM Certifying Examination is the multi-part written board examination of the American College of Veterinary Microbiologists leading to diplomate status in Bacteriology/Mycology, Virology, Immunology, or Parasitology. Content spans clinical bacteriology (~15%), bacterial identification (~15%), virology (~15%), parasitology (~15%), immunology (~10%), antimicrobial susceptibility testing (~10%), mycology (~8%), virology lab methods (~5%), molecular diagnostics (~4%), biosafety (~2%), and emerging diseases (~1%). Examination fee is approximately $1,500-$2,500; requires DVM/VMD plus completion of the ACVM training pathway with research experience and peer-reviewed publication.

Sample ACVM Veterinary Microbiology Practice Questions

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

1A canine pyoderma swab yields gram-positive cocci in clusters that are catalase-positive and coagulase-positive. Which species is MOST likely?

A.Staphylococcus aureus

B.Staphylococcus pseudintermedius

C.Streptococcus canis

D.Enterococcus faecalis

Explanation: S. pseudintermedius is the predominant commensal and opportunistic pathogen of canine skin and is catalase- and coagulase-positive. S. aureus can be isolated but is far less common in dogs. Streptococci are catalase-negative. Definitive differentiation from S. aureus requires MALDI-TOF or nuc PCR.

2Which selective and differential medium distinguishes lactose-fermenting from non-lactose-fermenting gram-negative enteric bacteria?

A.Blood agar

B.Chocolate agar

C.MacConkey agar

D.Sabouraud dextrose agar

Explanation: MacConkey contains bile salts and crystal violet to inhibit gram-positives, and lactose plus neutral red as a pH indicator. Lactose fermenters (E. coli, Klebsiella) form pink colonies; non-fermenters (Salmonella, Proteus, Pseudomonas) remain colorless.

3MALDI-TOF mass spectrometry identifies microbial isolates by analyzing which cellular component?

A.16S rRNA sequences

B.Ribosomal and other abundant proteins

C.Lipopolysaccharide side chains

D.Genomic GC content

Explanation: MALDI-TOF ionizes primarily ribosomal proteins and compares the resulting spectral fingerprint to a reference database. It provides species-level identification in minutes from a single colony and is now routine in veterinary diagnostic labs for bacteria and yeasts.

4Beta-hemolysis on blood agar is defined by which observation?

A.Greenish discoloration with partial RBC lysis

B.Complete clearing of red cells around colonies

C.No change in the medium

D.Black pigmentation of the colony

Explanation: Beta-hemolysis shows complete clearing from full RBC lysis (e.g., Streptococcus equi, S. aureus). Alpha-hemolysis is partial or greenish; gamma is no hemolysis. Patterns guide presumptive ID but must be confirmed biochemically or by MALDI-TOF.

5The oxidase test distinguishes which two groups of gram-negative rods most usefully?

A.Enterobacteriaceae (negative) from Pseudomonas/Pasteurella (positive)

B.Staphylococci from streptococci

C.Aerobes from anaerobes

D.Acid-fast from non-acid-fast

Explanation: Oxidase detects cytochrome c oxidase. Enterobacteriaceae are oxidase-negative, whereas Pseudomonas, Pasteurella, Aeromonas, Vibrio, and Neisseria are oxidase-positive. This is a first-line triage test on gram-negative rods after MacConkey growth.

616S rRNA gene sequencing is most valuable in veterinary microbiology for which application?

A.Quantifying antimicrobial MICs

B.Identifying fastidious or unculturable bacteria to genus or species level

C.Detecting fungal dermatophytes

D.Typing viral subtypes

Explanation: The 16S rRNA gene has conserved and variable regions that allow universal bacterial PCR followed by sequencing for identification when organisms are slow-growing, fastidious, or cannot be cultured. The analogous fungal target is the ITS region.

7Gram stain of bovine mastitic milk shows gram-positive cocci in chains, catalase-negative, narrowly beta-hemolytic, CAMP-positive. What is the MOST likely organism?

A.Staphylococcus aureus

B.Streptococcus agalactiae

C.Corynebacterium bovis

D.Trueperella pyogenes

Explanation: Strep agalactiae (Lancefield group B) is catalase-negative, forms chains, is narrowly beta-hemolytic, and is CAMP-test positive. It is a contagious mastitis pathogen adapted to the udder. S. aureus is catalase-positive; Trueperella and Corynebacterium are gram-positive rods.

8Which colony morphology feature is most useful in initial identification of Pseudomonas aeruginosa?

A.Metallic sheen with sulfur odor

B.Greenish-blue pyocyanin pigment with grape-like odor and beta-hemolysis

C.Pinpoint black colonies

D.Tiny alpha-hemolytic colonies with bile esculin hydrolysis

Explanation: P. aeruginosa produces pyocyanin (blue-green) and pyoverdine (fluorescent yellow-green) pigments with a characteristic grape-like odor. It is oxidase-positive, non-lactose-fermenting, and beta-hemolytic. It is a common cause of chronic otitis externa with multiple intrinsic resistance mechanisms.

9On the tube coagulase test, which substrate does coagulase activate to produce a visible clot?

A.Hyaluronic acid

B.Prothrombin (producing fibrin from fibrinogen)

C.Fibrinolysin

D.DNA

Explanation: Staphylococcal coagulase activates prothrombin, which cleaves fibrinogen into fibrin and clots plasma. Slide coagulase detects bound clumping factor; tube coagulase detects both forms and is more definitive. S. pseudintermedius, S. aureus, and S. intermedius are coagulase-positive.

10A small gram-negative rod from chronic feline otitis grows profusely on MacConkey with pink colonies, swarms on blood agar, and is urease-positive. Most likely organism?

A.Klebsiella pneumoniae

B.Proteus mirabilis

C.Escherichia coli

D.Pasteurella multocida

Explanation: Proteus mirabilis is strongly urease-positive, motile, and swarms across blood agar in concentric waves. It is a non-lactose fermenter (shows H2S on TSI). Klebsiella is non-motile with mucoid colonies; E. coli is lactose-positive and urease-negative; Pasteurella does not grow on MacConkey.

About the ACVM Veterinary Microbiology Exam

The ACVM Veterinary Microbiology Certifying Examination is administered by the American College of Veterinary Microbiologists and leads to board certification with subspecialty in Bacteriology/Mycology, Virology, Immunology, or Parasitology. Content spans clinical veterinary bacteriology (Staphylococcus/MRSP mecA, Mannheimia BRDC, Brucella, Mycobacterium, Clostridium toxinotyping), bacterial identification (MALDI-TOF, 16S rRNA sequencing, selective media, anaerobes), veterinary virology (BVDV Pestivirus with PI calves, CDV, CPV, FIV/FeLV, FIP with GS-441524, HPAI H5N1 clade 2.3.4.4b including the 2024 US dairy cattle outbreak, FMDV, ASFV, PRRSV, PCV2), parasitology (Haemonchus/FAMACHA, Dirofilaria heartworm, Cryptosporidium, Eimeria, Neospora, Babesia, Theileria, ticks and mites), veterinary immunology (colostrum and FPT, vaccines and DIVA, hypersensitivity, Coggins/AGID), mycology (Microsporum canis on DTM, Blastomyces broad-based budding, Cryptococcus India ink, Pythium oomycete), antimicrobial susceptibility testing (CLSI VET breakpoints, AMR mechanisms, AMDUCA, NARMS), molecular diagnostics (qPCR, RT-PCR, Nanopore WGS), and biosafety (BSL-3Ag, select agents, FAD reporting). Requires DVM/VMD plus the ACVM training pathway with research and publication.

Questions

100 scored questions

Time Limit

Multi-day written examination administered per ACVM schedule

Passing Score

Criterion-referenced passing standard set by the ACVM examination committee

Exam Fee

~$1,500-$2,500 ACVM Certifying Examination fee (ACVM 2026 — verify current schedule) (American College of Veterinary Microbiologists (ACVM))

ACVM Veterinary Microbiology Exam Content Outline

~15%

Clinical Bacteriology

Veterinary bacterial pathogens across species — Staphylococcus pseudintermedius MRSP (mecA), Streptococcus equi and S. agalactiae bovine mastitis, E. coli (ETEC K88/F4, F18), Salmonella (Typhimurium, Dublin, Newport DT104), Pasteurella multocida, Mannheimia haemolytica (BRDC), Mycoplasma bovis/hyopneumoniae/gallisepticum, Brucella (abortus, canis, melitensis — zoonotic), Leptospira, Campylobacter fetus venerealis, Clostridium perfringens A-E toxinotyping, C. chauvoei blackleg, C. botulinum, C. tetani, Rhodococcus equi, Mycobacterium bovis and M. avium paratuberculosis.

~15%

Bacterial Identification & Taxonomy

Gram staining, colony morphology, hemolysis, CAMP test, oxidase/catalase, coagulase, MALDI-TOF mass spectrometry (primary identification in modern veterinary labs), 16S rRNA gene sequencing for difficult isolates, MLST, whole-genome sequencing for outbreak investigation, selective/differential media (MacConkey, XLD, Hektoen, CIN, Columbia CNA), anaerobic culture (Clostridium, Bacteroides, Fusobacterium necrophorum), fastidious organisms (Taylorella equigenitalis CEM, Lawsonia intracellularis).

~15%

Veterinary Virology

BVDV (Pestivirus — type 1/2, cytopathic vs noncytopathic, persistent infection PI calves as reservoir, mucosal disease), BHV-1 (IBR), BRSV, PI-3, BCoV, rotavirus, FMDV (Aphthovirus — 7 serotypes), PPR, CSF, ASFV, PRRSV (type 1 EU, type 2 NA), PCV2 PMWS, SIV H1N1/H3N2, CDV (canine distemper), CPV-2 (2a/2b/2c), feline calicivirus, FHV-1, FIV/FeLV retroviruses, FIP (feline coronavirus biotype shift — GS-441524 antiviral), HPAI H5N1 clade 2.3.4.4b including the 2024 US dairy cattle outbreak, NDV, MDV, IBDV (Gumboro), rabies lyssavirus, West Nile virus, EEE/WEE/VEE.

~15%

Veterinary Parasitology

Nematodes — Haemonchus contortus (barber pole worm, FAMACHA scoring, ivermectin/benzimidazole resistance), Ostertagia, Dirofilaria immitis (heartworm — macrocyclic lactone prophylaxis, melarsomine adulticide), Toxocara, Parascaris equorum, Strongylus vulgaris; cestodes — Taenia, Echinococcus granulosus/multilocularis (zoonotic), Dipylidium; trematodes — Fasciola hepatica; protozoa — Giardia, Cryptosporidium parvum (calf scours, zoonotic), Eimeria (coccidiosis), Toxoplasma gondii (cats definitive host), Neospora caninum (bovine abortion), Babesia bigemina/bovis/canis, Theileria parva (ECF), Trypanosoma, Leishmania; ectoparasites — ticks (Rhipicephalus, Dermacentor, Ixodes, Amblyomma), mites (Sarcoptes, Demodex, Psoroptes).

~10%

Veterinary Immunology

Innate vs adaptive immunity, species-specific immunology (bovine gamma-delta T cells, equine NI — neonatal isoerythrolysis, SCID in Arabian foals), colostrum and passive transfer (FPT in foals with IgG <800 mg/dL), vaccine platforms (modified-live, killed, subunit, mRNA, vectored, recombinant DIVA vaccines), adjuvants, vaccine-associated sarcoma in cats (injection-site sarcoma), hypersensitivity types I-IV, autoimmune (IMHA, pemphigus, SLE), immunodeficiency, serology (ELISA, SNAP, HI, VN, AGID for EIA — Coggins test, IFA).

~10%

Antimicrobial Susceptibility Testing

CLSI VET standards (VET01, VET08, VET09) with veterinary-specific breakpoints, disk diffusion vs broth microdilution (MIC), interpretive categories (S/I/R, SDD), ECOFFs, Kirby-Bauer, intrinsic vs acquired resistance, AMR mechanisms (beta-lactamases — ESBLs, AmpC, carbapenemases; methicillin resistance mecA/mecC in MRSP; vancomycin vanA; fluoroquinolone gyrA/parC; colistin mcr-1 plasmid-mediated), antimicrobial stewardship (AMEG categories, WOAH critically important antimicrobials), extralabel drug use AMDUCA, withdrawal times, NARMS surveillance.

~8%

Mycology

Dermatophytes — Microsporum canis (most common in cats/dogs; dermatophyte test medium DTM with red color change in alkaline byproducts; Wood's lamp fluorescence variable), Trichophyton mentagrophytes, Microsporum gypseum; systemic mycoses — Blastomyces dermatitidis (broad-based budding yeast, endemic Ohio/Mississippi/Great Lakes — itraconazole), Histoplasma capsulatum (small intracellular yeast in macrophages), Coccidioides immitis/posadasii (spherules with endospores — SW US), Cryptococcus neoformans/gattii (narrow-based budding, capsule, India ink, latex agglutination — cats); opportunistic — Aspergillus fumigatus (canine sinonasal, equine guttural pouch mycosis, avian), Candida, Malassezia pachydermatis; Pythium insidiosum (oomycete — not a true fungus).

~5%

Virology Laboratory Methods

Cell culture (MDBK bovine, MDCK canine, Vero, primary cells), cytopathic effect (CPE) patterns, plaque assay, TCID50, hemagglutination and HI, virus neutralization (VN/SN), electron microscopy, antigen-capture ELISA, immunohistochemistry, fluorescent antibody testing (FAT for rabies — gold standard direct FA on brain), embryonated egg inoculation (avian viruses), biosafety considerations for FADs (FMD, CSF, ASF at Plum Island/NBAF).

~4%

Molecular Diagnostics

PCR (conventional, nested, multiplex), real-time qPCR (TaqMan, SYBR), RT-PCR for RNA viruses (BVDV, PRRSV, influenza, FMDV), digital PCR, LAMP (isothermal), sequencing (Sanger, next-generation — Illumina, Nanopore for field WGS), metagenomics, bioinformatics (BLAST, genome assembly), CRISPR-based diagnostics (SHERLOCK, DETECTR), validation parameters (analytical/diagnostic sensitivity/specificity, LoD, repeatability), quality management (ISO 17025, AAVLD accreditation).

~2%

Biosafety & Biosecurity

BSL-1 through BSL-4 (BSL-3Ag for large animal containment of FMDV, HPAI, Rift Valley fever), USDA APHIS/HHS select agents and toxins list, foreign animal disease (FAD) reporting chain, OIE/WOAH notifiable diseases, decontamination and PPE, shipping IATA category A/B infectious substances, reportable zoonoses.

~1%

Emerging & Transboundary Diseases

One Health approach, HPAI H5N1 2024 US dairy cattle outbreak (novel mammalian adaptation, within-herd transmission, milk shedding), SARS-CoV-2 spillover to mink/white-tailed deer/zoo felids, African swine fever global spread, novel tick-borne pathogens (Heartland virus, Bourbon virus), climate-driven vector expansion.

How to Pass the ACVM Veterinary Microbiology Exam

What You Need to Know

Passing score: Criterion-referenced passing standard set by the ACVM examination committee
Exam length: 100 questions
Time limit: Multi-day written examination administered per ACVM schedule
Exam fee: ~$1,500-$2,500 ACVM Certifying Examination fee (ACVM 2026 — verify current schedule)

Keys to Passing

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

ACVM Veterinary Microbiology Study Tips from Top Performers

1MALDI-TOF is the modern first-line bacterial identification method in veterinary diagnostic labs — rapid, accurate for most cultivable bacteria from primary culture. For organisms with underpopulated databases, unusual morphology, or closely related species (e.g., S. pseudintermedius vs S. intermedius vs S. delphini), confirm with 16S rRNA gene sequencing or targeted PCR. Whole-genome sequencing (Illumina short-read, Oxford Nanopore long-read) increasingly used for outbreak investigation and resistome/virulome profiling.

2BVDV high-yield: Pestivirus with two biotypes — cytopathic (cp) and noncytopathic (ncp). Transplacental infection with ncp before 125 days gestation creates persistently infected (PI) calves that are immunotolerant, shed virus lifelong, and are the major reservoir. Mucosal disease develops when a PI animal is superinfected with an antigenically similar cp strain. Diagnosis: ear-notch IHC or antigen-capture ELISA (skin), RT-PCR (whole blood or pooled). Control requires identification and removal of PI animals plus vaccination.

3CLSI VET breakpoints differ from human CLSI (M100) — always use VET01/VET08/VET09 for veterinary isolates with veterinary-specific drug-bug-host combinations. MRSP (methicillin-resistant S. pseudintermedius) carries mecA (or occasionally mecC) encoding PBP2a — oxacillin disk/MIC used for detection; cefoxitin is NOT reliable in S. pseudintermedius (unlike in S. aureus). Colistin resistance mcr-1 is plasmid-mediated and transferable — significant One Health concern especially in swine and poultry.

4HPAI H5N1 clade 2.3.4.4b goose/Guangdong lineage caused an unprecedented 2024 US dairy cattle outbreak with novel bovine adaptation, within-herd transmission via contaminated milking equipment, and high viral loads in milk (pasteurization inactivates). Affected cows show drop in milk production, thickened colostrum-like milk, and decreased appetite. Spillover to cats (often fatal neurologic disease) and farmworkers (mild conjunctivitis). Diagnosis by RT-PCR on milk and nasal swabs; reportable to USDA APHIS. Underscores One Health surveillance and biosecurity.

5Systemic mycoses by morphology: Blastomyces dermatitidis — large (8-15 μm) BROAD-based budding yeast, endemic Ohio/Mississippi/Great Lakes/St. Lawrence watersheds, itraconazole. Cryptococcus neoformans/gattii — NARROW-based budding with prominent polysaccharide capsule (India ink halo), cats and koalas, latex agglutination antigen test, fluconazole/amphotericin B. Histoplasma — SMALL (2-4 μm) intracellular yeast within macrophages. Coccidioides — tissue SPHERULES containing endospores, SW US/Mexico. Pythium insidiosum is an OOMYCETE (not a fungus) — no ergosterol, resistant to azoles.

Frequently Asked Questions

What is the ACVM Veterinary Microbiology Certifying Examination?

The ACVM Certifying Examination is administered by the American College of Veterinary Microbiologists and leads to diplomate (board-certified) status in veterinary microbiology. Candidates select a subspecialty — Bacteriology/Mycology, Virology, Immunology, or Parasitology — and sit a multi-part written examination covering general veterinary microbiology plus in-depth subspecialty content. Diplomates typically work in veterinary diagnostic laboratories, academic research, government (USDA APHIS, CDC, FDA), and the animal health industry.

Who is eligible to take the ACVM examination?

Candidates must hold a DVM, VMD, or equivalent veterinary degree and complete the ACVM training pathway — typically a residency or graduate program (3+ years) under ACVM diplomate mentors with documented experience in the chosen subspecialty. A peer-reviewed publication in veterinary microbiology (or closely related field) is required. The credentials package must be approved by the ACVM credentials committee before the candidate is admitted to the examination.

What is the format of the ACVM exam?

The ACVM Certifying Examination is a multi-part written examination administered per the ACVM schedule, covering general veterinary microbiology plus the candidate's chosen subspecialty (Bacteriology/Mycology, Virology, Immunology, or Parasitology). Items commonly include clinical scenarios, laboratory interpretation (MALDI-TOF, PCR, AST), organism identification from morphology/biochemistry, and epidemiology. Candidates must pass both general and subspecialty sections to earn diplomate status.

How much does the 2026 ACVM exam cost?

The 2026 ACVM Certifying Examination fee is approximately $1,500-$2,500 — always verify the current schedule on the ACVM website (acvm.us). There are also credentials application fees and annual ACVM dues after certification. Cancellation, refund, and retake policies follow the ACVM schedule. Retakes require re-registration and fee payment within the allowed eligibility window.

When is the 2026 ACVM exam administered?

The ACVM Certifying Examination is typically offered once annually. Credentials applications generally open months ahead with a defined submission deadline. Approved candidates sit the examination at the ACVM-designated venue and schedule. Exact 2026 dates and deadlines should be confirmed directly on the ACVM website.

How is the exam scored?

ACVM uses a criterion-referenced passing standard set by the examination committee. A candidate's pass/fail result depends on performance against a fixed content-expert cut-score, not on other candidates. Candidates must pass both the general veterinary microbiology section and their chosen subspecialty section. Score reports provide domain-level feedback to guide future attempts if needed.

What are the highest-yield topics?

Highest-yield topics include MALDI-TOF and 16S rRNA sequencing for bacterial identification, MRSP with mecA/mecC, CLSI VET breakpoints and AMR mechanisms (ESBL, AmpC, carbapenemases, mcr-1), BVDV with persistent infection and mucosal disease, CDV and CPV, FIV/FeLV, FIP and GS-441524 antiviral, HPAI H5N1 clade 2.3.4.4b with the 2024 US dairy cattle outbreak, FMDV and ASFV as FADs, Haemonchus with FAMACHA and anthelmintic resistance, Cryptosporidium parvum zoonosis, Babesia and Theileria hemoparasites, Microsporum canis on DTM, Blastomyces broad-based budding, Cryptococcus with India ink, AGID Coggins test, and BSL-3Ag containment.

How should I study for this exam?

Use a structured 18-36 month plan layered on residency or graduate training. Map to the ACVM content outline: start with classical and molecular bacteriology, then virology and cell culture/PCR methods, parasitology and mycology, immunology and serology, antimicrobial susceptibility testing and stewardship, biosafety, and emerging diseases. Integrate Quinn's Veterinary Microbiology, MacLachlan & Dubovi's Fenner's Veterinary Virology, Bowman's Georgis' Parasitology, Tizard's Veterinary Immunology, CLSI VET standards, WOAH Terrestrial Manual, and high-volume case-based practice. Complete 2-3 timed mock exams with subspecialty focus.