Staphylococcus Lecture Notes

Comprehensive vocabulary flashcards covering taxonomy, characteristics, pathogenesis, clinical diseases, and laboratory diagnosis of the Genus Staphylococcus as discussed in the lecture transcript.

Genus Staphylococcus

Gram (+) cocci that typically appear in clusters, are catalase positive, and are grouped under the Order Bacillales.

Catalase

An enzyme produced by aerobes and facultative anaerobes that converts hydrogen peroxide ($H_2O_2$) to water and oxygen ($O_2$).

Facultative anaerobe

Organisms that can live with or without the presence of oxygen; most staphylococci fall into this category, except for species like $S.\text{ anaerobius}$.

Brownian motion

The type of movement exhibited by encapsulated, non-motile bacteria like the Genus Staphylococcus.

CoPS

Coagulase-Positive Staphylococcus species which include $S.\text{ aureus}$ and $S.\text{ lugdunensis}$, characterized by the production of coagulase enzymes.

CoNS

Coagulase-Negative Staphylococcus species, such as $S.\text{ epidermidis}$, $S.\text{ haemolyticus}$, and $S.\text{ saprophyticus}$.

Novobiocin Susceptibility Testing

A test used to separate CoNS: $S.\text{ saprophyticus}$ is resistant, while $S.\text{ epidermidis}$ and $S.\text{ haemolyticus}$ are sensitive.

HAI

Hospital-acquired infection, a common route for antimicrobial resistant staphylococcal strains.

Persistent Carrier

A nasal carrier who carries a single strain of staphylococci for an extended period of time.

MRSA

Methicillin Resistant strain of $S.\text{ aureus}$, often carried by healthcare practitioners and transmitted to immunocompromised patients.

Protein A

A cell wall component of $S.\text{ aureus}$ that has an affinity for the Fc receptor of $IgG$ and complement, aiding in immune evasion.

Cytotoxin Gamma

A cytotoxin associated with Panton-Valentine Leukocidin (PVL) that is directed against WBCs and causes deep tissue infections.

Enterotoxin A

The most prominent pre-formed, heat-stable toxin resulting in gastrointestinal symptoms and food poisoning within $2 \text{ to } 8 \text{ hours}$.

TSST-1

Toxic shock syndrome toxin-1 (also known as Enterotoxin F or Pyrogenic Exotoxin C), which causes fever, desquamation, hypotension, and shock.

Hyaluronidase

Known as the "spreading factor," this enzyme degrades hyaluronic acid in tight junctions to allow bacterial invasion into other cells.

Staphylokinase

Also called fibrinolysin, it is an enzyme that removes fibrin clots, allowing bacteria to escape the clot and attach to host cells.

Folliculitis

A mild inflammation of a hair follicle or oil gland where the infected area is raised and red.

Furuncles

Also known as boils, these are large, raised, superficial abscesses that can be an extension of folliculitis.

Carbuncules

Large, invasive lesions developed from multiple furuncles that progress into deeper underlying tissues and present with multiple draining sinuses.

Ritter Disease

An extensive form of Scalded Skin Syndrome (SSS) in infants where approximately $90 \text{\%}$ of the body is affected by the exfoliative toxin.

Biofilm

A protective layer produced by organisms like $S.\text{ epidermidis}$ using an exopolysaccharide slime layer, often colonizing implants like catheters and prosthetic valves.

Poly-$\gamma$-DL-glutamic acid (PGA)

A bacterial factor involved in the adherence of $S.\text{ epidermidis}$ that provides protection against host defenses.

5\% Sheep's Blood Agar (BAP)

The most commonly employed initial plating medium for staphylococci, used to observe colonial growth and hemolytic patterns.

Columbia Nalidixic Agar (CNA)

A special plating medium highly selective for gram-positive organisms that contains inhibitors like nalidixic acid.

Mannitol Salt Agar (MSA)

A selective and differential medium containing $7.5 \text{\%}$ Sodium Chloride and mannitol; $S.\text{ aureus}$ ferments mannitol to produce yellow colonies with yellow halos.

CHROMagar

A selective and differential medium for the identification of MRSA that uses cefoxitin and chromogenic substrates to produce mauve-colored colonies.

Microdase Test

A rapid method using tetramethyl-paraphylene diamine hydrochloride to differentiate $Micrococcus \text{ spp.}$ (positive, blue/purple) from $Staphylococcus \text{ spp.}$ (negative, colorless).

DNase Test

A test used to distinguish $S.\text{ aureus}$ (positive, showing clearing) from other Staphylococcus species (negative, showing cloudy precipitate).

Bound Coagulase

Also called "clumping factor," this is bound to the bacterial cell wall and reacts directly with fibrinogen to form a fibrin clot in the slide test.

Mec-A Gene

A mobile DNA element that encodes for an altered penicillin-binding protein ($PBP \text{ 2a}$), providing methicillin resistance.

D-zone Test

A test used to detect inducible macrolide-lincosamide-streptogramin B ($MLSB$) resistance by placing clindamycin and erythromycin disks $15 \text{ mm}$ apart.

VRSA

Vancomycin-resistant $S.\text{ aureus}$, defined by a minimum inhibitory concentration ($MIC$) of $\ge 16 \text{ mg/mL}$.