Medical Bacteriology Practice Flashcards

A comprehensive set of vocabulary flashcards covering basic medical bacteriology concepts, staining methods, biochemical tests, and bacterial genetics based on the lecture transcript.

Medical Bacteriology

A branch of microbiology focusing on the study of bacteria that cause diseases in humans, including their structure, function, genetics, and pathogenic mechanisms.

Prokaryotes

Unicellular organisms, such as bacteria, that have no nuclear membrane, mitochondria, Golgi bodies, or endoplasmic reticulum, and reproduce by asexual division.

Microbiome

The thousands of different bacterial species that inhabit the human body, also known as normal flora.

Bacterial Cell Wall

A complex structure made up of a peptidoglycan layer used in the classification of bacteria.

Gram-positive Bacteria

Bacteria that stain dark blue or violet because of a high amount of peptidoglycan in their thick cell wall and the lack of an outer membrane.

Gram-negative Bacteria

Bacteria with a thinner peptidoglycan layer and an outer membrane containing lipopolysaccharide; they stain red or pink in a Gram stain test.

Acid-Fast Bacillus Test

Also known as the Ziehl-Neelsen method; a differential staining method used for bacteria that do not stain easily with Gram stain due to a lipid-rich (mycolic acid) cell wall.

Mycolic acid

A characteristic lipid-rich component of the cell wall in bacteria like the Mycobacterium genus that retains acid-fast stain.

Catalase Test

A biochemical test that detects the presence of the catalase enzyme by mixing a bacterial colony with hydrogen peroxide; bubbles indicate a positive result.

Coagulase Test

A test that detects the enzyme coagulase, which causes blood plasma to clot; it differentiates Staphylococcus aureus from other Staphylococci species.

Mannitol Salt Agar (MSA) Test

A test for the ability to ferment mannitol; yellow coloration on the media indicates a positive result, specific to Staphylococcus aureus.

Bile Esculin Test

A test for the ability to hydrolyze esculin in the presence of bile; blackening of the medium indicates a positive result for Enterococci and Group D Streptococci.

6.5% NaCl Test

Inoculation of bacteria in high-salt broth where turbidity indicates growth; used to differentiate Enterococci from non-Enterococci Streptococci.

Optochin Sensitivity Test

A test used to identify Streptococcus pneumoniae, which is sensitive to the antibiotic optochin, creating a zone of inhibition.

Bacitracin Sensitivity Test

Used to identify Group A Streptococci, which are sensitive to the antibiotic bacitracin.

PYR Test

A test for the enzyme pyrrolidinyl aryl-amidase; a red color indicates a positive result, distinguishing Enterococci from Group A Streptococci.

Alpha (α) Hemolysis

Partial hemolytic activity on blood agar appearing as a green coloration.

Beta (β) Hemolysis

Full hemolytic activity on blood agar appearing as a clear zone around the colonies.

Gamma (γ) Hemolysis

No hemolytic activity on blood agar.

Oxidase Test

A test to detect cytochrome c oxidase enzyme; a dark purple color change indicates a positive result, differentiating Pseudomonas and Neisseria from Enterobacteriaceae.

Indole Test

A test for the ability to produce indole from tryptophan; a red ring after adding Kovac’s reagent indicates a positive result (e.g., Escherichia coli).

Citrate Utilization Test

Detection of a bacteria's ability to use citrate as a sole carbon source; a blue color indicates a positive result.

Urease Test

A test for the production of the urease enzyme; a pink color indicates a positive result (e.g., Proteus).

Triple Sugar Iron (TSI) Agar Test

Tests for fermentation of glucose, lactose, and sucrose, and the production of hydrogen sulfide ($H_2S$) gas.

Analytical Profile Index (API)

A standardized panel of miniaturized biochemical tests in a plastic strip used for the identification of bacteria based on their biochemical profile.

Vitek System

An automated microbiology system used for rapid bacterial identification and antimicrobial susceptibility testing.

Serological Testing

Tests used to identify bacteria based on the interaction between specific antigens on their surface and corresponding antibodies.

Molecular Testing

Tests based on the detection of bacterial nucleic acids (DNA or RNA) in a sample, such as Polymerase Chain Reaction (PCR).

Minimum Inhibitory Concentration (MIC)

The lowest concentration of an antimicrobial agent that inhibits the visible growth of a bacterial isolate.

E-test (Epsilometer Test)

A gradient method for determining MIC using a plastic strip with a gradient of antibiotic concentrations placed on an inoculated agar plate.

Teichoic acids

Unique components of the Gram-positive cell wall that act as chelating agents and assist in adherence.

Nosocomial Infection

Healthcare-associated or hospital-acquired infection, such as MRSA or VRE.

MRSA

Methicillin-resistant Staphylococcus aureus, a Gram-positive bacterium of significant nosocomial importance.

Transformation

A mechanism of gene transfer where bacteria take up free DNA from the environment and incorporate it into their chromosome.

Transduction

Gene transfer mediated by bacteriophages (viruses) that package DNA from a donor bacterium and transfer it to a recipient.

Conjugation

A gene transfer mechanism where a plasmid is transferred from one bacterium to another through a sex pilus.

Atypical Bacteria

A collective term for organisms like Mycoplasma and Chlamydia that lack certain bacterial components and often require eukaryotic cells for reproduction.

Plasmids

Small, extra-chromosomal circular DNA molecules that often carry genes for antibiotic resistance and virulence factors.

Prodigiosin

The characteristic red pigment produced by members of the genus Serratia.

Lipopolysaccharide (LPS)

A component of the Gram-negative outer membrane consisting of lipid A, core polysaccharide, and O antigen.