Bacteria Review - Microbial Diseases 2

Vocabulary-style flashcards covering key bacteria, virulence factors, diagnostics, and treatments from the notes.

Staphylococcus aureus

Gram-positive cocci in clusters; catalase-positive; coagulase-positive; mannitol fermenter; human skin/nasopharynx reservoir; MRSA and PVL-associated tissue necrosis.

MRSA

Methicillin-resistant Staphylococcus aureus; mecA gene encodes PBP2a, conferring resistance to beta-lactam antibiotics.

MecA (PBP2a)

Alternative penicillin-binding protein with low affinity for beta-lactams; enables MRSA to synthesize cell wall in presence of beta-lactams.

PVL toxin

Pantone-Valentine Leukocidin; cytotoxin that destroys leukocytes and can cause necrotic skin infections, especially in community-associated S. aureus.

Protein A

Staphylococcus aureus surface protein that binds the Fc region of antibodies, hindering opsonization and phagocytosis.

Exfoliative toxin

Toxin causing loss of cell-to-cell adhesion in skin; linked to scalded skin syndrome and impetigo.

Catalase

Enzyme that breaks down hydrogen peroxide; Staphylococci are catalase-positive, helping differentiate from catalase-negative streptococci.

Coagulase

Enzyme that clots plasma; Staphylococcus aureus is coagulase-positive, distinguishing it from coagulase-negative staphylococci.

Staphylococcus epidermidis

Gram-positive cocci in clusters; coagulase-negative; forms slime layer/biofilms; common cause of prosthetic device and catheter infections.

Slime layer / glycocalyx / biofilms

Surface polysaccharide layer enabling tight adherence and protection; key in device-associated infections (e.g., S. epidermidis biofilms).

Cutibacterium acnes

Gram-positive rod; obligate anaerobe; skin commensal; acne vulgaris; can cause invasive, prosthesis-related infections via biofilms.

Bacillus anthracis

Gram-positive rod; spore-former; non-motile; gamma-hemolysis; capsule of poly-D-glutamic acid; inhalation or cutaneous transmission; virulence factors include protective antigen, lethal toxin, edema toxin.

Endospore

Dormant, resilient structure allowing survival in harsh environments; characteristic of Bacillus and Clostridium species.

Capsule (poly-D-glutamic acid)

Antiphagocytic capsule of Bacillus anthracis made of poly-D-glutamic acid.

Protective antigen

B component of anthrax toxin; facilitates delivery of lethal and edema toxins into host cells.

Lethal toxin

Anthrax AB toxin that disrupts MAPKK signaling, leading to cell death.

Edema toxin

Anthrax AB toxin that increases cAMP causing edema and fluid loss.

Clostridium perfringens

Gram-positive rod; obligate anaerobe; spore-former; double beta-hemolysis; gas gangrene (myonecrosis) with alpha toxin and other enzymes.

Alpha toxin (lecithinase)

Phospholipase C (lecithinase) toxin of C. perfringens that increases vascular permeability and tissue destruction.

Beta toxin

Cytotoxin of C. perfringens described as a 'hole puncher' in cells; contributes to tissue damage.

Gas gangrene (myonecrosis)

Rapid necrosis of muscle and tissue with gas production; caused by C. perfringens infection.

Neisseria gonorrhoeae

Gram-negative diplococci; intracellular in neutrophils; oxidase-positive; glucose-fermenting; sexually transmitted; can cause disseminated gonococcal infection.

Pasteurella multocida

Gram-negative coccobacillus; non-motile; zoonotic (cat/dog bites); rapid-onset cellulitis; possible septic arthritis/osteomyelitis; treated with amoxicillin-clavulanate.

Bartonella henselae

Gram-negative, intracellular rod; cat-scratch fever; bacillary angiomatosis in immunocompromised; Warthin-Starry stain; treated with macrolides if needed.

Pseudomonas aeruginosa

Gram-negative rod; oxidase-positive; obligate aerobe; non-fermenter; green pigment; biofilm formation; MDR potential; common in hospital infections; exotoxin A.

Exotoxin A

Pseudomonas toxin that inhibits protein synthesis by inactivating EF-2, contributing to tissue necrosis.

Vibrio vulnificus

Gram-negative curved rod; oxidase-positive; halophilic; wound infections after seawater exposure or shellfish ingestion; culture on TCBS agar; doxycycline + ceftriaxone treatment.

Borrelia burgdorferi

Spirochete transmitted by Ixodes ticks; causes Lyme disease; erythema migrans; disseminated disease; treated with doxycycline; OspA involved in transmission.

OspA

Borrelia outer surface protein A; helps bacteria attach to tick gut, facilitating transmission.

Rickettsia rickettsii

Obligate intracellular coccobacillus; tick-borne; causes Rocky Mountain Spotted Fever; endothelial cell infection leading to vasculitis; treated empirically with doxycycline.

RMSF (Rocky Mountain Spotted Fever)

Fever, headache, rash; severe vasculitis risk; treated promptly with doxycycline.

HACEK group

Fastidious gram-negative bacteria from oral flora (Haemophilus spp., Aggregatibacter actinomycetemcomitans, Cardiobacterium hominis, Eikenella corrodens, Kingella kingae); associated with culture-negative endocarditis.

Eikenella corrodens

Gram-negative short coccobacillus; oxidase-positive; non-motile; associated with human bites and endocarditis; treats with amoxicillin-clavulanate.

Kingella kingae

HACEK group member; pediatric septic arthritis/osteomyelitis; part of normal oropharyngeal flora; endocarditis risk.

Thayer-Martin agar

Selective chocolate agar with antibiotics to suppress commensals; used to culture Neisseria gonorrhoeae.

DGI (Disseminated Gonococcal Infection)

Dissemination of Neisseria gonorrhoeae leading to arthritis (usually one joint, knee) and possible other foci.

EIA/IFA and Western blot (Lyme testing)

Initial Lyme disease screen by EIA/IFA or immunofluorescence; confirmation with IgM/IgG western blot if positive or equivocal.

Erythema migrans

Bull’s-eye rash occurring 3–30 days after tick bite; hallmark early Lyme disease symptom.