ACVM Veterinary Microbiology flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

Lipid A endotoxin

The lipopolysaccharide component of Gram-negative outer membranes that activates TLR4, causing fever, hypotension, and disseminated intravascular coagulation. It is heat-stable and not converted to a toxoid.

Mycoplasma cell wall absence

Mycoplasmas lack peptidoglycan, so beta-lactam antibiotics are ineffective against them; they stain poorly and require enriched media for culture.

Bacterial capsule function

A polysaccharide or polypeptide layer outside the cell wall that impedes phagocytosis, enhancing virulence and serving as a serotyping determinant in organisms such as Klebsiella and Bacillus anthracis.

Bacterial spore resistance

Endospores of Bacillus and Clostridium resist heat, desiccation, and many disinfectants, allowing survival in the environment until favorable conditions trigger germination.

Facultative intracellular bacteria

Organisms such as Brucella, Salmonella, and Listeria that survive within host cells, shielding themselves from antibody and many antimicrobials and favoring chronic infection.

Antigenic shift versus drift

Shift is reassortment of segmented viral genomes producing major antigenic change; drift is gradual accumulation of point mutations. Shift can cause pandemics; drift drives vaccine updates.

Envelope and environmental stability

Enveloped viruses are inactivated by lipid solvents, detergents, and drying, whereas non-enveloped viruses such as parvovirus and calicivirus persist longer in the environment.

Viral latency

Herpesviruses establish latent infection, often in neurons or lymphoid cells, with the viral genome persisting silently and reactivating under stress or immunosuppression.

Viral replication cycle

The sequential steps of attachment, penetration, uncoating, genome replication and protein synthesis, assembly, and release by budding or cell lysis.

Retroviral provirus integration

Retroviruses transcribe their RNA genome into DNA using reverse transcriptase; integrase inserts the provirus into host DNA, enabling lifelong infection, as with bovine leukemia virus.

Ergosterol as antifungal target

Fungal membranes contain ergosterol; polyenes bind it to form pores, and azoles inhibit its synthesis. These selective targets underlie most antifungal therapy.

Dermatophyte identification

Microsporum, Trichophyton, and Epidermophyton digest keratin and are identified by macroconidia shape and colony morphology; they cause ringworm in animals and humans.

Cryptococcal capsule

Cryptococcus neoformans has a polysaccharide capsule that resists phagocytosis; capsular antigen is detectable by latex agglutination or lateral flow assays.

Dimorphic fungi

Fungi such as Blastomyces and Histoplasma grow as molds in the environment and as yeasts in tissue, switching form in response to temperature.

Echinocandin spectrum

Echinocandins inhibit beta-glucan synthase in fungal cell walls; they are ineffective against Mucorales, which lack the target, and are not used for that group.

Pattern recognition receptors

Innate immune receptors such as TLRs and NLRs that detect conserved pathogen molecules (LPS, flagellin, dsRNA) and trigger rapid inflammatory responses.

Immunoglobulin classes

IgM dominates the primary response, IgG the secondary response, IgA mucosal surfaces, IgE type I hypersensitivity, with species differences in placental transfer.

Fourfold antibody titer rise

A fourfold or greater increase in antibody titer between acute and convalescent sera indicates recent or active infection and is a standard serologic criterion.

Colostral antibody transfer

In ruminants and pigs, maternal antibody passes to offspring only through colostrum because there is no transplacental transfer; failure of colostral intake causes immunodeficiency.

Type IV hypersensitivity

A delayed, T-cell mediated reaction occurring 24 to 72 hours after antigen exposure, exemplified by the tuberculin skin test.

Koch's postulates

Criteria linking organism to disease: present in all diseased hosts, isolated in pure culture, disease reproduced on inoculation, and organism re-isolated from the experimental host.

Exotoxin properties

Protein toxins, often heat-labile and immunogenic, that can be converted to toxoids for vaccination; examples include tetanus and botulinum neurotoxins.

Carrier state

An infected host that sheds a pathogen without overt clinical signs, sustaining transmission within a population, as seen with Salmonella and Streptococcus equi.

Biofilm resistance

Surface-attached microbial communities embedded in matrix that resist antibiotics and host defenses, complicating treatment of infections involving Staphylococcus and Pseudomonas.

Gram stain principle

Crystal violet and iodine form a complex retained by thick peptidoglycan after decolorization; Gram-negative cells lose it and take the pink safranin counterstain.

Minimum inhibitory concentration

The lowest antimicrobial concentration that inhibits visible growth of an isolate under standardized conditions; it is compared with species-specific breakpoints to classify susceptibility.

Disk diffusion testing

Kirby-Bauer method measuring zone of inhibition diameter around an antibiotic disk; results are interpreted against standardized breakpoints and require quality control strains.

MALDI-TOF identification

Mass spectrometry method identifying bacterial isolates by their protein mass spectral fingerprints, providing rapid species-level identification compared with conventional biochemical testing.

Beta-lactam resistance

Beta-lactamase enzymes hydrolyze the drug, altered penicillin-binding proteins reduce binding, and efflux or reduced permeability lower intracellular concentrations, collectively conferring resistance.

Aminoglycoside action

These agents bind the 30S ribosomal subunit, causing concentration-dependent bacterial killing; nephrotoxicity and ototoxicity are important dose-limiting adverse effects.

Horizontal resistance gene transfer

Plasmids, transposons, and integrons move antimicrobial resistance genes between bacteria, enabling rapid spread of resistance across species and environments.

PCR cycle thresholds

Real-time PCR quantifies template by the cycle at which fluorescence exceeds threshold; a lower Ct value indicates a higher initial amount of target nucleic acid.