Streptococcus and Enterococcus Lecture Notes

Comprehensive vocabulary flashcards covering the characteristics, pathogenesis, and laboratory identification methods for Genus Streptococcus and Enterococcus as discussed in the lecture.

Streptococcaceae

A family of catalase-negative, gram-positive cocci that include the genera Streptococcus and Enterococcus and are usually arranged in pairs or chains.

Capnophilic

Microorganisms that require an increased concentration of carbon dioxide, specifically between $5-10\%$, for growth.

Browns Classification

A system used to classify Streptococcus based on their ability to produce a specific hemolytic pattern on blood agar.

Lancefield Classification

A serologic grouping system for Streptococcus based on the antigenic carbohydrate classification found on their cell walls.

Streptococcus pyogenes (GAS)

Also known as Group A Streptococci, this species is not considered normal microbiota and is known for producing a large zone of B-hemolysis.

Streptolysin O

An $O_2$ labile hemolysin produced by Streptococcus pyogenes that is immunogenic and active against RBCs under anaerobic conditions.

Streptolysin S

An $O_2$ stable, nonimmunogenic cytolysin that is responsible for the lysis of leukocytes.

M protein

The best-defined virulence factor in Streptococcus pyogenes; it causes the bacterial cell to resist phagocytosis and assists in adherence to mucosal cells.

Non-Bullous Impetigo

A localized skin disease common in children characterized by small vesicles that progress to weeping lesions and eventually form honey-colored crusts.

Erysipelas

A rare skin infection frequently observed in elderly patients characterized by an intensely erythematous, acutely spreading skin lesion with a demarcated edge.

Necrotizing Fasciitis

An invasive infection, sometimes called 'flesh-eating disease,' characterized by rapidly progressing inflammation and necrosis of the skin, fat, and fascia.

Scarlet Fever

A pyrogenic infection caused by exotoxins $A-C$, appearing as a rash on the face and trunk, often accompanied by 'strawberry tongue.'

Acute Rheumatic Fever (ARF)

A serious post-streptococcal sequela that results in damage to heart muscle and valves due to cross-reactivity between bacterial antigens and human heart tissue.

Acute Glomerulonephritis

A sequela developing after S. pyogenes skin or pharyngeal infection where antigen-antibody complexes deposit in the glomeruli and impair kidney function.

Streptococcus agalactiae (GBS)

Also known as Group B Streptococci; it is normal microbiota in the female genital tract and a leading cause of meningitis and sepsis in newborns.

Streptococcus pneumoniae

A gram-positive, encapsulated coccus that is lancet-shaped or bullet-shaped and is the primary cause of community-associated bacterial pneumonia.

Pneumolysin O

A virulence factor of Streptococcus pneumoniae that activates the classic complement pathway and suppresses the oxidative burst in phagocytes.

Streptococcus mutans

A member of the Viridans group responsible for the formation of dental caries through the possession of insoluble dextran polymers.

Columbia agar with colistin and nalidixic acid (CNA)

A gram-positive selective medium used to inhibit gram-negative organisms like Staphylococci and Bacillus spp. during the isolation of Streptococcus.

LIM broth

A Todd-Hewitt broth base containing lincosamides and macrolides (such as gentamicin) used to suppress vaginal microbiota and detect Group B streptococci.

Enterococcosel agar

A selective and differential medium that uses oxgall to inhibit gram-positive organisms and sodium azide to inhibit gram-negatives, while identifying Group D streptococci via esculin hydrolysis.

Bacitracin Susceptibility Test (Taxo A)

A test used to differentiate S. pyogenes (susceptible) from other beta-hemolytic streptococci; a positive result is a zone of inhibition $> 10\,mm$.

CAMP Test

A test used to differentiate group B streptococci by producing an 'arrowhead' pattern of enhanced hemolysis when streaked perpendicular to Staphylococcus aureus.

Hippurate Hydrolysis Test

Specific for S. agalactiae, detecting the enzyme hippuricase which hydrolyzes hippuric acid to glycine and benzoic acid, resulting in a deep-purple product when ninhydrin is added.

PYR Test

Detects the enzyme L-PYRase to presumptively identify group A streptococci and enterococci via the production of a bright red precipitate.

Bile Esculin Test

Tests an organism's ability to hydrolyze esculin to esculetin in the presence of bile; a positive result is a dark brown to black precipitate.

Salt tolerance Test ($6.5\%$ NaCl)

Differentiates enterococci (growth/turbidity) from non-enterococci (no growth) based on the ability to survive in high salt concentrations.

Optochin Solubility Test (Taxo P)

Used to identify Streptococcus pneumoniae, ซึ่ง is susceptible to ethylhydrocupreine hydrochloride, creating a zone of inhibition between $14-16\,mm$.

Bile Solubility Test

A test where S. pneumoniae cells lyse and the solution becomes clear in the presence of sodium deoxycholate, while other alpha-hemolytic organisms remain turbid.

Neufeld quellung reaction

An immunoserologic test where the capsule of Streptococcus pneumoniae swells in the presence of specific antibodies.

Leucine Aminopeptidase (LAP) Test

A test used for the presumptive identification of catalase-negative gram-positive cocci such as Streptococcus, Enterococcus, and Pediococcus.

Anti-Streptolysin O Titer (ASO)

A serological test that uses latex immunoturbidimetry to document exposure to streptolysin O and diagnose post-streptococcal sequelae.