Immunosero quiz midterm review

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Gram-positive cocci in chains; catalase negative.

Streptococcus

Test that produces bubbles with H₂O₂ when positive.

Catalase test (bubbles = positive)

Hemolysis that gives a green discoloration (partial hemolysis).

Alpha (α) hemolysis

Hemolysis that gives a clear zone (complete hemolysis).

Beta (β) hemolysis

No hemolysis on blood agar (non-hemolytic).

Gamma (γ) hemolysis (non-hemolytic)

Classification based on C-carbohydrate (Groups A, B, D, etc.).

Lancefield grouping

Bacitracin sensitivity (A disk) — organism sensitive.

S. pyogenes (Group A)

CAMP test showing an arrowhead of enhanced hemolysis with S. aureus.

CAMP positive — S. agalactiae (Group B)

Optochin sensitivity (P disk) — organism sensitive.

S. pneumoniae (Optochin sensitive)

Organism that lyses in bile (bile solubility).

S. pneumoniae (bile soluble)

Bile esculin hydrolysis that darkens medium.

Enterococcus / Group D (bile esculin +)

Growth in 6.5% NaCl (salt tolerance).

Enterococcus (grows in 6.5% NaCl)

PYR test positive (red color).

S. pyogenes (and Enterococcus) — PYR positive

Hippurate hydrolysis positive.

S. agalactiae (Group B)

Alpha-hemolytic and optochin resistant, associated with dental origin.

Viridans streptococci (e.g., S. mutans)

Polysaccharide capsule that resists phagocytosis.

Capsule (S. pneumoniae has a polysaccharide capsule)

Surface M protein (major virulence factor).

M protein — S. pyogenes

Enzyme that breaks down blood clots (fibrin).

Streptokinase

Oxygen-labile toxin causing beta hemolysis.

Streptolysin O

Enzyme that digests connective tissue and aids spread.

Hyaluronidase

Post-streptococcal heart disease following untreated pharyngitis.

Rheumatic fever

Rapid, severe soft-tissue infection (necrotizing soft-tissue disease).

Necrotizing fasciitis (often S. pyogenes)

Common cause of neonatal sepsis and meningitis.

S. agalactiae (Group B)

Common cause of lobar pneumonia in adults.

S. pneumoniae

Streptococcus species associated with dental caries.

S. mutans (viridans group)

Enterococci group commonly found in GI tract.

Enterococcus spp. (e.g., E. faecalis)

Test using optochin disk to differentiate pneumococcus from others.

Optochin test (P disk)

Test that turns medium dark brown/black when esculin is hydrolyzed.

Bile esculin test (positive = esculin hydrolysis)

Beta-hemolytic + bacitracin sensitive + throat infection (cue).

S. pyogenes (Group A)

Quellung reaction (capsule swelling) as an identification clue.

Quellung reaction — capsule swelling (S. pneumoniae)

Thin, helical bacteria with axial filaments (endoflagella).

Spirochetes (Spirochaetes)

Spirochete that causes syphilis.

Treponema pallidum

Spirochete transmitted by Ixodes tick; causes Lyme disease.

Borrelia burgdorferi

Spirochete associated with Weil’s disease (icteric leptospirosis).

Leptospira interrogans

Microscopy method used to visualize very thin spirochetes.

Dark-field microscopy

Silver stain used to show spirochetes on tissue (e.g., skin biopsy).

Warthin–Starry (silver) stain

Non-treponemal serologic screening tests for syphilis.

VDRL and RPR

Specific treponemal confirmatory test for syphilis.

FTA-ABS (Fluorescent treponemal antibody absorption)

Classic early skin lesion of primary syphilis (painless ulcer).

Chancre (primary syphilis)

Rash involving palms and soles (secondary stage).

Secondary syphilis rash (palms & soles)

Late manifestations of untreated syphilis (gummas, aortitis, tabes dorsalis).

Tertiary syphilis

Skin lesion that expands in a bull’s-eye pattern (early Lyme sign).

Erythema migrans

Facial nerve palsy occurring in early Lyme disease.

Bell's palsy (can occur in Lyme disease)

Recurrent high-fever episodes due to antigenic variation (Borrelia).

Relapsing fever (Borrelia spp.)

Severe leptospirosis feature with jaundice and renal failure.

Weil's disease

Reservoir commonly linked to Leptospira spread (urine).

Rodents (and other animals) — reservoir; urine transmission

Culture medium often used to grow Leptospira in the lab.

EMJH medium

Diagnostic serology commonly used for Lyme disease (screening).

ELISA for Borrelia (followed by Western blot)

Reaction after starting antibiotics for spirochetal infections (fever, chills, myalgias).

Jarisch–Herxheimer reaction

Treponema pallidum characteristic: not cultivable on standard artificial media.

Not cultivable on standard media; diagnosed by serology or dark-field

Test showing specific antibodies to Treponema after infection/treatment.

FTA-ABS (treponemal test)

Vector for Borrelia relapsing fever (body louse for B. recurrentis).

Body louse (B. recurrentis — louse-borne relapsing fever)

Vector for Lyme disease (Ixodes tick).

Ixodes tick (deer tick)

Motility type in spirochetes produced by internal axial filaments.

Corkscrew motility

Lab stain used in tissue histology to show spirochetes (besides dark-field).

Silver stain (Warthin–Starry)

Diagnostic test that detects leptospiral antibodies in serum.

Microscopic agglutination test (MAT)

Important congenital signs of syphilis in newborns (skeletal/dental/skin findings).

Congenital syphilis: Hutchinson teeth, saddle nose, saber shins, rhagades, etc.

Borrelia species causing tick-borne relapsing fever.

Borrelia hermsii (and other tick-borne species)

Common outpatient antibiotic choice for early Lyme disease or leptospirosis.

Doxycycline (contraindicated in pregnancy/children <8)

Conjunctival suffusion as a clinical sign (disease association).

Leptospirosis (conjunctival suffusion)

BACk A-way (mnemonic).

Bacitracin → Group A (S. pyogenes)

CAMP up the Baby (mnemonic).

CAMP test → Group B (S. agalactiae)

OPTO = Ouch! (mnemonic).

Optochin sensitivity → S. pneumoniae

Entero = salt-tolerant ENTERs 6.5% NaCl (mnemonic).

Enterococcus grows in 6.5% NaCl

Alpha = Army (green camo) (mnemonic).

Alpha hemolysis = greenish partial hemolysis

DTS (mnemonic).

Dark-field; Too thin for Gram; Spirochete shape

Syphilis — P S T (mnemonic).

Primary chancre, Secondary rash, Tertiary gummas

BELL for Lyme (mnemonic).

Bell's palsy, Erythema migrans, Late arthritis/neurologic signs

URINE for Leptospira (mnemonic).

Urine transmission; Renal failure; Icterus; Need doxy/penicillin; Exposure to contaminated water

If catalase positive is mentioned, then…

Think Staphylococcus (not Streptococcus)

If optochin sensitivity is noted, then…

Think S. pneumoniae (pneumococcus)

If erythema migrans is described, then…

Think Lyme disease (Borrelia burgdorferi)