CHSE Odisha Voc. Microbiology & Serology flashcards

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

Koch's postulates

Four criteria proving a microbe causes a disease: found in all cases, isolated in pure culture, reproduces disease when inoculated, and re-isolated from the experimental host.

Biosafety level 2

Laboratory level for moderate-hazard agents such as Salmonella and hepatitis B virus; requires restricted access, biosafety cabinet for aerosols, and decontamination of waste.

Numerical aperture

Measure of the light-gathering ability of an objective lens; higher values improve resolution and brightness. Oil immersion raises it to about 1.25 by matching refractive index.

Dark-field microscopy

Technique that illuminates the specimen obliquely so objects appear bright against a dark background; used to view live spirochetes such as Treponema pallidum.

Autoclave standard cycle

Sterilisation with saturated steam at 121 degrees Celsius and 15 psi for 15 to 20 minutes; kills all microorganisms including bacterial spores by protein denaturation.

Selective and differential media

Selective media inhibit unwanted organisms, while differential media distinguish colonies by biochemical reaction; MacConkey agar is both, selecting Gram-negatives and differentiating lactose fermenters.

Generation time

Time required for a bacterial population to double during exponential growth; calculated as g = 1/k, where k is the growth rate constant.

Bacterial growth curve phases

Lag phase (adaptation), exponential or log phase (rapid division), stationary phase (growth equals death), and death phase (decline); generation time is measured in log phase.

Phenol coefficient

Ratio comparing the killing power of a disinfectant with that of phenol under the same conditions; a value above one indicates greater activity than phenol.

MRSA resistance mechanism

Methicillin-resistant Staphylococcus aureus carries mecA, encoding penicillin-binding protein 2a with low affinity for beta-lactams; vancomycin is a standard alternative therapy.

Innate versus acquired immunity

Innate immunity is non-specific and immediate with no memory; acquired immunity is specific, develops after exposure, and retains immunological memory through lymphocytes.

IgG and IgM

IgG is the most abundant immunoglobulin and crosses the placenta; IgM is the largest and appears first in acute infection, making it useful for recent-infection serology.

Hapten

A small molecule that is not immunogenic alone but becomes immunogenic when conjugated to a larger carrier protein; it can still bind specific antibodies.

Affinity versus avidity

Affinity is the binding strength between one epitope and one antibody site; avidity is the overall binding strength of a multivalent antibody with a multivalent antigen.

Prozone phenomenon

False-negative serological result caused by excess antibody preventing lattice formation; resolved by diluting the serum so antigen and antibody reach optimal proportions.

Sandwich ELISA

Assay in which capture antibody binds antigen, a second enzyme-labelled antibody detects it, and substrate produces a colour proportional to antigen concentration.

Ziehl-Neelsen stain

Acid-fast stain using carbol fuchsin with acid-alcohol decolourisation; Mycobacterium tuberculosis retains the red stain against a blue background.

Hepatitis B serology markers

HBsAg indicates infection, anti-HBs indicates immunity, HBeAg indicates high infectivity, and anti-HBc IgM indicates recent infection.

Midstream urine culture

Clean-catch urine collected after discarding the first portion; a count of 100,000 CFU/mL of one organism suggests infection, while mixed growth suggests contamination.

Blood culture collection

Collect 10 to 20 mL per set into aerobic and anaerobic bottles from two sites before antibiotics; timing at fever spikes improves recovery of bloodstream pathogens.

Most probable number method

Statistical estimate of coliform concentration in water using serial dilution tubes and probability tables; results are expressed per 100 mL of sample.

Biological oxygen demand

Amount of dissolved oxygen consumed by microorganisms decomposing organic matter in water; a key measure of organic pollution and sewage strength.

Gram stain decolourisation step

Acetone-alcohol briefly removes crystal violet from Gram-negative cells, which then take up safranin; Gram-positive cells retain the violet-iodine complex.

Phase-contrast microscopy

Converts differences in refractive index into brightness differences, allowing observation of unstained living cells and assessment of bacterial motility.

Membrane filtration sterilisation

Passing liquid through a filter with 0.22 micrometre pores removes bacteria and spores; used for heat-labile solutions such as serum and antibiotic preparations.

Facultative anaerobe

Organism that grows best with oxygen but can also grow without it by fermentation; it possesses superoxide dismutase and catalase to survive oxidative stress.

Beta-lactamase inhibitors

Compounds such as clavulanate, tazobactam, and sulbactam that bind and inactivate beta-lactamase enzymes, restoring activity of penicillins against resistant bacteria.

Complement membrane attack complex

C5b, C6, C7, C8, and C9 assemble into a pore in the microbial membrane, causing lysis; formed through classical, alternative, or lectin pathway activation.

Epitope

The specific antigenic determinant bound by an antibody or T-cell receptor; a single antigen may carry several different epitopes recognised by different antibodies.

Western blot

Confirmatory assay that separates proteins by gel electrophoresis, transfers them to a membrane, and detects specific bands with labelled antibody, such as in HIV confirmation.

Cryptococcus neoformans

Encapsulated yeast detected by India ink preparation and latex agglutination for capsular antigen; causes meningitis, especially in immunocompromised patients.

Cerebrospinal fluid processing

CSF is collected aseptically and processed immediately for cell count, Gram stain, culture, and PCR; it should not be refrigerated before culture.