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I&I - M1T1 > Gram Positive Bacteria > Flashcards

Gram Positive Bacteria Flashcards

1
Q

This non-hemolytic staph is sensitive to novobiocin.

A

S. epidermidis

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2
Q

Who is at greatest risk of disease from Listeria monocytogenes infection?

A
  • Neonates
  • Pregnant women
  • Immunocompromised
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3
Q

What medically relevant Streptococcus spp. belongs to the Group B grouping?

A

S. agalactiae

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4
Q

What clinical diseases are associated with cutaneous exposure to B. anthracis?

A
  • Papules → Ulcers → Eschar
  • Lymphadenopathy
  • Edema
  • 20% mortality when untreated
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5
Q

What Enterococci spp. are clinically relevant?

A
  • E. faecalis
  • E. faecium
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6
Q

What types of infections does S. pyogenes cause?

A
  • Respiratory tract infections
  • Skin & soft tissue infections
  • Toxin-mediated infections
  • Immune-mediated infections
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7
Q

What risk factors are associated with Enterococci spp. infection?

A
  • Urinary or intravascular catheters
  • Hospitalization / nonsocomial infections
  • Broad spectrum antibiotic use
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8
Q

What diseases are associated with B. cereus infection?

A
  • Food poisoning (vomiting, diarrhea)
  • Ocular infections
  • Anthrax-like respiratory infection (rare)
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9
Q

What characteristics give Enterococci spp. their virulence?

A
  • Antibiotic resistance
  • Adherence & biofilms
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10
Q

What are the medically relevant gram-positive rods?

A
  • Bacillus anthracis
  • Bacillus cereus
  • Corynebacterium diphtheriae
  • Listeria monocytogenes
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11
Q

What term means pus-forming?

A

Pyogenic

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12
Q

What type of pathogen are Viridans streptococci?

A

Opportunistic pathogens - they are normal flora in the oropharynx, GI tract, and urinary tract

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13
Q

What gram-positive coccus is sensitive to optochin?

A

S. pneumoniae

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14
Q

What infections are associated with S. pyogenes?

A
  • Pharyngitis
  • Scarlet Fever (toxin-mediated following pharyngitis)
  • Skin & soft tissue infections
  • Bacteremia & sepsis
  • Pneumonia (less common)
  • Toxic shock syndrome
  • Rheumatic fever (immune-mediated)
  • Glomerulonephritis (immune-mediated)
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15
Q

What diseases are associated with C. diphtheria?

A
  • Diphtheria (toxin-mediated, A+B exotoxin, inhibits protein synthesis)
  • Exudative pharyngitis
  • Cervical lymphadenopathy
  • Psuedomembrane formation
  • Myocarditis
  • Neuropathy
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16
Q

What clinical diseases are associated with GI exposure to B. anthracis?

A
  • Ulcers at site of invasion
  • Lymphadenopathy
  • Edema
  • Sepsis
  • Mortality (100%)
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17
Q

What pyogenic infections may result from S. aureus infection?

A
  • Impetigo
  • Folliculitis, furuncles (boils), carbuncles
  • Cellulitis
  • Bacteremia & Endocarditis
  • Pneumonia & Empyema
  • Osteomyelitis & Septic Arthritis
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18
Q

What are the three medically relevant staphylococcus species? What features differentiate the species?

A

S. aureus - Coagulase, B hemolytic

S. epidermidis - Non-hemolytic, Novobicin sensitive

S. saprophyticus - Non-hemolytic, Novobicin resistant

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19
Q

What toxins may be produced by some S. aureus?

A
  • Cytolytic toxins (hemolysins)
  • Leukocidin (Panton-Valentine Factor) - Forms pores in WBCs, contributes to MRSA
  • Exfoliating toxins - cleve desmosomal protein in keratinocytes
  • Superantigens - Enterotoxin A (food poisoning), Enterotoxin B (most potent, pseudomembrane colitis, toxic shock syndrome), Toxin shock syndrome toxin (associated with menstruation)
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20
Q

What infection is most commonly associated with S. saprophyticus?

A

Urinary tract infections in women

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21
Q

What characteristic gives S. epidermidis its virulence?

A

Ability to form biofilms

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22
Q

What enzyme differentiates Staphylococcus from Streptococcus?

A

Catalase

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23
Q

What test is important in diagnosing rheumatic fever following pharyangitis?

A

ASO TIters (Anti-Streoptolysin O Antibodies)

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24
Q

This catalase and coagulase negative, beta-hemolytic, gram-positive coccus is sensitive to bacitracin.

A

S. pyogenes

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25
Q

How do the B. cerreus toxins differ in their mechanism and disease presentation?

A

The heat-stable toxin has a short incubation and symptom duration period. Symptoms include vomiting, nausea, and cramps. Ingestion is of the actual toxin.

The heat-liable toxin has a longer incubation and symptom duration period. Symptoms include diarrhea, cramps, and nausea. In this case, the bacterial organism is ingested, which then produces and releases the toxin within the body.

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26
Q

What are the disease processed of S. aureus?

A

Pyogenic & Toxigenic (only by some S. aureus)

27
Q

What toxin must S. pyogenes express in order to cause scarlet fever?

A

Spe toxin

28
Q

What diseases are associated with S. agalactiae?

A
  • Bacterimia & Pneumonia
  • Meningitis
  • Neonatl Sepsis
29
Q

What virulence factors are associated with S. pyogenes?

A
  • Capsule
  • M protein (blocks complement to prevent phagocytosis)
  • Lipoteichoic acid
  • F protein
  • Pyrogenic exotoxins (Spe toxins)
  • Steptolysin S (B hemolysis)
  • Steptokinase A & B (lyses blood clots)
30
Q

What characteristics describe Corynebacterium spp.?

A
  • Club-shaped
  • Aerobic or facultative anaerobes
  • Catalase positive
  • No flagella
  • Normal flora of skin, upper respiratory tract, GI tract, and urinary tract
31
Q

What are the medically relevant gram-positive cocci?

A

Staphylococcus, Streptococcus, Enterococcus

32
Q

What factors increase the virulence of S. aureus?

A
  • Capsule & Biofilm
  • Peptidoglycan - Edotoxin-like activity
  • Teichoic Acids - adherence
  • Staphylococcal protein A - binds IgG to inhibit opsonization
  • Microbial Surface Components Recognizing Adhesive Matrix Molecules (MSCRAMM) - Adherence and clumping
  • Toxins
  • Enzymes
33
Q

What diseases are associated with Listeria monocytogenes infection?

A
  • Gastroenteritis
  • Meningitis
  • Neonatal disease - Abortion, stillbirth, granulomatous infantispectic, meningitis, meningoencephalitis, septicemia
34
Q

This bacteria is catalase-positive, non-hemolytic, and resistant to novobiocin.

A

S. saprophyticus

35
Q

What skin infections are associated with S. pyogenes?

A
  • Impetigo
  • Erysipelas
  • Cellulitis
  • Necrotizing Fasciitis (“flesh-eating”)
36
Q

What characteristics describe Listeria monocytogenes?

A
  • Coccobacillus (short rods), in pairs or short chains
  • Intracellular pathogen
  • Can grow at low temperature
  • Halophilic
  • Normal flora of animals
37
Q

What is the most medically relevant Corynebacterium spp.?

A

C. diphtheriae - Humans are the only reservoir. Possible asymptomatic carriage on skin or oropharynx

38
Q

What are the virulence factors of B. anthracis?

A
  • Spore-forming
  • Polypeptide capsule (unusual as most capsules are made of polysaccharides)
  • Toxins (protective antigen, edema factor, lethal factor → exhibit A+B toxin structure)
39
Q

What diseases are associated with Viridans streptococci?

A
  • Cavities
  • Bacteremia
  • Abscesses in the brain, oropharynx, or peritoneal cavity
40
Q

What diseases are associated with S. pneumoniae infection?

A
  • Pneumonia
  • Otitis media (mostly children)
  • Sinusitis
  • Meningitis
  • Bacteremia
41
Q

What virulence factors are associated with S. pneumoniae?

A
  • Capsules (can exhibit recombination or point mutations to change surface antigens)
  • IgA protease at mucosal surfaces to escape mucus
  • Pneumolysin (lysis of Hb, cholesterol, epithelial cells, phagocytes)
  • Peptidoglycan & Teichoic Acid
42
Q

What clinical diseases are associated with inhaled exposure to B. anthracis?

A
  • Long incubation period if spread by spore
  • Initial nonspecific symptoms - fever, myalgia, cough, malaise
  • Progressive symptoms - worsening couch, fever, edema, enlargement of lymph nodes, respiratory failure, sepsis, shock
  • Death within 3 days of symptom onset when untreated
43
Q

Describe the mechanism of action for the diphtheria toxin.

A

A+B exotoxin. B subunit binds heparin-binding receptor. The A unit enters the cell and inactivates EF-2 to stop protein synthesis.

44
Q

This bacteria is resistant to optochin.

A

Enterococcus spp.

45
Q

What diseases/infections are associated with Enterococci spp.?

A
  • Urinary tract infections
  • Peritonitis
  • Bacteremia
  • Endocarditis
46
Q

What disease are associated with S. epidermidis infection?

A
  • Endocarditis
  • Infections of shunts and catheters
  • Infections of prosthetic joints
47
Q

Describe the mechanism of action for all three B. anthracis toxins.

A

Protective antigen - B subunit, binds to host cells for entry

Edema factor - A subunit, adenylate cyclase increases cAMP and causes tissue edema

Lethal factor - A subunit, zinc-dependent protease stimulates cytokine release by macrophages and macrophage lysis

48
Q

What population is especially at risk for S. agalactiae infection and why?

A

Neonates are especially at risk for S. agalactiae. Bacteria colonize the GI tract and urinary tract of mothers, which may be exposed to the neonate during childbirth. S. agalactiae is an important cause of neonatal sepsis.

49
Q

What is the staphylococcal chromosome cassette?

A

A mobile genetic element that houses the Mec gene, giving S. aureus methicillin resistance

50
Q

What are the medically relevant Streptoccus spp.?

A
  • S. pneumoniaw
  • S. pyogenes
  • S. agalctiae
  • Viridans streptococci
51
Q

What characteristic defines S. agalactiae serotypes?

A

Capsular polysaccharides, which provide protection against phagocytosis

52
Q

What types of infections are associated with B. anthracis?

A

Skin, lung, and GI infections

53
Q

What toxin-mediated infections are associated with S. aureus infection?

A
  • Bullous impetigo
  • Scaled skin syndrome (Ritter’s disease)
  • Food poisoning
  • Toxic shock syndrome
54
Q

What enzymes are associated with S. aureus virulence?

A
  • Coagulase - converts fibrinogen to fibrin (forms protective barrier around organism)
  • Catalase - prevents H2O2 toxicity
  • Hyaluronidase - Hydrolyzes hyaluronic acid in CT
  • Staphylokinase (Fibrinoylsin) - dissolves fibrin clots (promotes spread)
  • Lipase, Phospholipase, Nuclease, Protease (provides essential components for organism)
  • B-lactamase - penicillin resistance
55
Q

What are the general characteristics of Staphylococcus spp.?

A

Facultative aerobes, halophilic

Exposure through human-to-human contact or fomites

Normal flora on the skin and mucosal surfaces

S. aureus - Nasopharnyx

S. epidermidis - Skin

S. saprophyticus - GI Tract

56
Q

What are the virulence factors of Listeria monocytogenes?

A
  • Beta hemolytic
  • Listeriolysin O (cytolysin)
  • Internals (attachment proteins)
  • ActA (actin-enabled motility)
57
Q

What type of organism are Streptococci spp. and in what environment do they prefer to grow?

A

Aerotolerant anaerobes that prefer high CO2 (capnophilic)

58
Q

What is the mechanism for methicillin resistance in S. aureus?

A

The mecA/C gene encodes a penicillin binding protein (PBP2a) with lower affinity for methicillin. Because of this, the antibiotic is unable to bind with transpeptidase to disrupt cell wall structure.

59
Q

What virulence factors are associated with B. cereus?

A
  • Heat-stable enterotoxin
  • Heat-liable enterotoxin
  • Cytotoxic enzymes
60
Q

What genes encode in Methicillin resistance in S. aureus?

A

mecA (more common) & mecC

61
Q

What hemolysis mechanisms do each Steptococcus spp. exhibit?

A

S. pyogenes - beta hemolytic

S. agalactiae - beta hemolytic

S. pneumoniae - alpha hemolytic

Viridans streptococci - alpha or gamma hemolytic

62
Q

How is B. anthracis generally spread to humans?

A

The bacteria naturally exists in soil and commonly infects herbivores. Humans are then exposed through contaminated animal products. B. anthracis is also known to be a bioterrorism agent.

63
Q

To which grouping does S. pyogenes belong?

A

Group A

I&I - M1T1 (36 decks)

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