Aerobic Gram Positive Bacilli and Corynebacterium

Flashcards covering the classification, morphology, pathogenesis, and laboratory identification of aerobic Gram-positive bacilli, with a focus on Genus Corynebacterium and diphtheria toxin.

Catalase Enzyme

An enzyme used as an indication that a group of gram (+) bacilli is aerobic, helping to separate them from anaerobic genera like clostridium.

$$FtsZ$$

A cytoskeletal structure associated with the default spherical or coccus shape of bacteria.

$$MreB$$

A cytoskeletal structure that allows a bacterial cell to elongate from a sphere to a rod or oblong shaped organism.

Crescentin ($Cres\,C$)

A cytoskeletal structure found in organisms like Crescentus caulobacter that characterizes spiral-shaped bacteria.

Aerobic Spore Former

A subgroup of gram (+) bacilli represented by the genus Bacillus (mnemonic: 'B' for 'bukas' or open/exposed).

Anaerobic Spore Former

A subgroup of gram (+) bacilli represented by the genus clostridia (mnemonic: 'C' for 'closed' or isolated).

Nocardia

A genus of aerobic, branching, fungus-like bacteria.

Rothia

A genus previously referred to as undesignated corynebacterium.

Pleomorphism

A characteristic where bacteria like Corynebacterium manifest in various shapes and arrangements (X, V, Y, L, or Chinese letters) due to incomplete binary fission.

Lipophilic Corynebacteria

Fastidious, slow-growing species such as C. jeikium and C. urealytium that require the addition of lipids (e.g., Tween 80 or rabbit serum) for growth.

Kleb-Löffler Bacillus

The common name for Corynebacterium diphtheriae, the causative agent of respiratory and cutaneous diphtheria.

Lysogenic Conversion

Also known as specialized transduction; the process by which Corynebacterium diphtheriae acquires the TOX gene from a $\beta$-phage.

Fragment A

The portion of the diphtheria exotoxin that splits NAD to nicotinamide and ADPR, eventually inactivating elongation factor 2 to stop protein biosynthesis.

Fragment B

The portion of the diphtheria exotoxin that facilitates entry into the host cell by binding to receptor domains CD-9 and HB-EGF.

Pseudomembrane

A grayish-black or grayish-white membrane formed in the throat during respiratory diphtheria, composed of pus, necrotic epithelial tissues, fibrin, and blood.

Bull’s Neck Appearance

A clinical manifestation of respiratory diphtheria characterized by swelling of the submandibular and cervical region (lymphadenopathy).

Veldt Sore

Also known as Barcoo root; a synonym for cutaneous diphtheria characterized by slow-healing ulcers with a dirty gray membrane.

Corynebacterium urealyticum

A lipophilic urinary pathogen known for rapid urease production, which results in alkaline urine and white crystals.

Erythrasma

A superficial, pruritic infection caused by Corynebacterium minutissimum.

Hoffman Bacillus

The common name for Corynebacterium pseudodiphtheriticum, a member of the indigenous microbiota of the human pharynx.

Cysteine Tellurite Blood Agar (CTBA)

The preferred isolation medium for C. diphtheriae; it produces black to brown colonies with a brown halo due to the breakdown of cysteine.

Löefflers Medium

A medium used to enhance the pleomorphism and formation of metachromatic granules in Corynebacterium species.

Babe’s – Ernst Granules

Metachromatic granules representing polyphosphate compounds seen in C. diphtheriae, often observed using Albert or Neisser stains.

Elek Test

An in vitro immunodiffusion test used to detect the production of diphtheria toxin by observing fine precipitin lines (arch of identity).

Schick Test

A skin test used to determine a person's susceptibility to the diphtheria toxin; a positive result is indicated by reddening.