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ENGR 1 > CommBactPathTable > Flashcards

CommBactPathTable Flashcards

1
Q

What are two genuses of gram positive cocci?

A

1) Staphylococcus (catalase +) 


2) Streptococcus (catalase -)

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2
Q

Generally describe staph aureus.

A
  • 1ary pathogenic species of genus
    
- gram (+) cocci in clusters
    
- Asymptomatic carriers => ~30% of healthy ppl —» potential for carriers to spread to pts
    
- Responsible for wide spectrum of diseases – depending on strain
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3
Q

What are the categories of the wide range of diseases caused by staph aureus?

A

1) Cutaneous infection 

2) Toxin-mediated disease 

3) Pneumonia 

4) Foreign-associated infections 

5) Bacteremia/endocarditis

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4
Q

Describe cutaneous infections caused by staph aureus

A

Characteristic lesion => Localized abscess

  • Bacterium + host wall off infection w/ fibrinous capsule
    
- Capsule prevents infiltration of phagocytes, Abs, antimicrobials 

  • Tx => draining abscess
    
- Often associated w/ presence of foreign body (splinter, suture)
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5
Q

Which enzyme helps form the fibrinous capsule involved in cutaneous infections caused by staph aureus?

A

Coagulase
- An essential virulence factor 
- Deposits fibrin on cell surface –» interferes w/ phagocytosis

Coagulase is used as a diagnostic factor when differentiating between different staphalococci

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6
Q

Which major cytotoxic agent is released by staph aureus during cutaneous infections?

A

Alpha-toxin

-First identified member of pore-forming beta-barrel toxin family

- Knock-out strains => reduces invasiveness and virulence of infection

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7
Q

What are different types of toxin-mediated diseases caused by staph aureus?

A

1) Scalded Skin Syndrome 

2) Toxic shock syndrome
3) Staph food poisoning

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8
Q

Describe Scalded Skin Syndrome

A
  • Local infection, toxin production => systemic effects 

  • Epidermis sloughs off (doesn’t necessary slough where the infection is) 

  • Adult slough —» more localized b/c of ^ presence of Ab 

  • Infant slough —» widespread b/c their immune system hasn’t seen the infection before (no Abs)
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9
Q

Describe Toxic Shock Syndrome

A
  • Most frequent in menstruating women (but 1/3 of cases are males)
    
- Local infection and toxin production
    
- Toxins requires O2, neutral pH, high protein environment (not changing a tampon often => ideal environment for staph aureus) «—IMPORTANT!! KNOW THIS
    
- Symptoms: High fever, shock, vomiting, muscle-pain, renal/hepatic injury
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10
Q

Describe staphylococcal food poisoning

A
  • Caused by contaminated food —» ingestion of superAg toxin 
- Vomiting and diarrhea
    YIPPEEEE!
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11
Q

What is a superantigen toxin?

A
  • Ag class => cause non-specific activation of T cells
    
- Polyclonal T cell activation and massive cytokine release
    
- Produced by pathogenic microbes

Normal Ags induce .001% of T cell response —- SuperAgs induce 25%!!

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12
Q

5

A
  • Prototype of SSNA (aka CNS) —» Staph species, not aureus - Coagulase-negative staph 

  • Normal skin flora, relatively non-pathogenic
    
- Allows slime/biofilm formation => adheres to implanted devices (catheters, shunts)
    
- Very difficult to treat! Usually have to remove device
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13
Q

Describe streptococcus pyogenes (Group A strep)

A
  • Can cause pharyngeal infection (LOCALIZED)
    
- Can cause skin/wound infections (SYSTEMIC) 

  • If untreated => post-strep probs (glomerulonephritis, rheumatic fever)
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14
Q

Describe streptococcal pharyngitis. What is the primary virulence factor associated w/ local infection?

A
  • Spreads via droplet/nasal secretions of infection person
    
- Several % of asymptomatic carriers
    
- Swollen tonsils w/ white, purulent exudate

Virulence factor

- M-protein => inhibits phagocytosis, kills PMNs, enhances adherence to epithelial cells 

- Produced by bacteria

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15
Q

Describe infective endocarditis

A
  • Caused by bacterial infection of heart valves

Three common bacteria:

1) Staph a.

2) Viridans Strept 

3) Coagulase-negative staph

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16
Q

Describe streptococcus pneumoniae

A
  • G(+) cocci in pairs
    
- In normal flora of 40% of healthy pop’n
    
- Pathogenesis related to ability to grow and evade host defenses:

1) Antiphagocytic polysaccharide capsule 

2) Recovery/immunity due to anticapsular Ab development 

3) Multiple antigenic types of capsule

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17
Q

What are the diseases caused by streptococcus pneumoniae? Classify according to invasiveness

A

Non-invasive: - Pneumonia 
- Sinusitis, otitis media, bronchitis

Invasive: 
- Meningitis 
- Bacteremia/septicemia

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18
Q

Which factors predispose a person to pneumonia?

A

1) Young and old 
2) Alcoholism 
3) Respiratory viral infection

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19
Q

Which types of vaccines exist against pneumonia? Separate according to age.

A

Adults: 
- 23-valent vx (you’ll hear pts call it the “pneumonia vaccine”)

- Technically also 13-valent, but Gill doesn’t say this (ACIP recommends in kids/adults)

Kids: 
- 7-valent vx (not recommended by ACIP anymore)

- 13-valent vx (recommended by ACIP)

Gill needs to update his vx info — recommendations have changed

20
Q

Describe enterococcus faecalis and E. faecium

A
  • Primary causes of enterococcal infections 
- Often nosocomial infections
    
- Common sites: urinary tract, surgical wounds, biliary tract
    
- Important to differentiate from other streptococci b/c of antibiotic tx resistance
21
Q

Which genus is classified as gram-positive rods?

A

Clostridium!!!

22
Q

How are Clostridia classified?

A

1) Strict anaerobes 
2) Endospore-formers

23
Q

Describe Clostridium difficile

A
  • Typically a nosocomial infection
    
- in normal flora of 10% of healthy ppl
    
- Resistant to most common antibiotics
    
- Spores NOT KILLED by alcohol-based hand sanitizers!! (HOLY FRICKIN MOLY!!!)
24
Q

How is C. Diff disease acquired?

A
  • In hospitals 

  • Associated w/ or follows antibiotic use (Clindamycin, etc.) b/c normal GI flora is suppressed => C. Diff grows!!
    
- Can also be transmitted from an infected person to another person
25
Q

Go read the C. Diff case history!!

A

It will help you understand the progression of C. Diff

SERIOUSLY!! GO READ IT! NOW

26
Q

Describe C. Tetani

A
  • Comes from soil/animals (think spore transmission)
    
- Local infection and toxin production 
- Retrograde transport of toxin to CNS 

  • Toxin blocks interneurons in CNS (Spastic paralysis!!! LOCK-JAW!)

Also, maternal and neonatal tetanus (b/c of unhygienic deliveries and umbilical cord care)

27
Q

Describe C. Botulinum

A
  • Comes from soil/animals (spore transmission)
    
- The preformed toxin in food circulated in body —» blocks Ach transmission at neuromuscular junctions => FLACID PARALYSIS
    
- Common in home-canned foods
28
Q

Describe C. perfringens

A
  • In wound infections (cellutis, fasciitis, myonecrosis) => bacteria produces alpha-toxin, and other damaging enzymes/toxins
    
- Alpha-toxin kills phagocytes and muscle tissue
  • In food poisoning: produce enterotoxin in vitro ==> disrupts tight junctions between endothelial cells in ilium (dysregulation of fluid transport)
29
Q

What are two types of gram-negative rods?

A

1) E. coli 
2) Pseudomonas aeruginosa

30
Q

Describe E. Coli

A
  • Many different strains 
- Normal in large intestine flora
    Causes GI disease:
    
- many strains vary in severity
    
- typically from contaminated food/water
    
- Antibiotics can/cannot be used (depends on strain)
    
- Traveler’s diarrhea (toxin disrupts electrolyte balance in gut, managed by fluid replacement
31
Q

Describe E. Coli in UTIs

A
  • Endogenous fro GI tract
    
- Access UT via uretha –» bladder —» kidney
    
- Certain strains can adhere to cells, interact w/ bladder epithelial cells, or are hemolytic
32
Q

Describe E. Coli in abdominal infections

A
  • Release/escape of contents of colon to peritoneal cavity/adjacent tissues 

  • B/c of surgery, wounds, colon cancer
    
- Often associated w/ anaerobic bacteria
33
Q

Describe Pseudomonas Aeruginosa

A
  • A very common environmental bacterium — most ppl are highly resistant to it 

  • Infections caused by traumatic injuries, surgical wounds, burns (especially BURNS)
    
- Also associated w/ chronic lung infection in pts w/ CF
34
Q

Describe Pseudomonas Aeruginosa in cystic fibrosis

A
  • Nearly all CF pts 15-20 yo are infected 

  • Facilitated by resistance to anti-staph drugs (makes it difficult to treat)
    
- Lung damage b/c of bacterial toxins
    
- PA is protected from phagocytes
    Frequently the COD in pts w/ CF
35
Q

What is a type of gram-negative (diplo)cocci?

A

Neisseria gonorrhoeae

36
Q

Describe Neisseria gonorrhoeae

A
  • Causes gonorrhea and conjunctivitis (leading to blindness) of infants born to gonorrhea (+) moms 

  • PILI: key to infectivity
    
- Pili interfere w/ killing of bacteria by PMNs — Ab develops to pili prevents infection
    
- Prolong infection => scarring/fibrosis (urethra (men/women), cervix => infertility in women)
37
Q

Describes anaerobes

A
  • Found in normal flora but killed by O2 
- Found in colon, mouth (e.g. gums, tongue), female genital tract, skin 
- Usually cause disease as a mixed infection (lung/colon abscesses)

Treatment:

More effective - metronidazole

Less effective – aminoglycosides

38
Q

Describe Bacteroides fragilis

A
  • Common in colon flora, aerotolerant
    
- Cultured from anaerobic abscess below diaphragm 

  • Considered to be a prototypical endogenous anaerobic pathogen
39
Q

What are the virulence factors associated w/ bacteroides fragilis?

A

1) Tissue-destructive enzymes 
2) Capsule 
3) Superoxide dismutase

40
Q

What is a type of intracellular bacteria?

A

Chlamydia trachomatis

41
Q

What is a type of bacteria w/o cell walls?

A

Mycoplasma pneumoniae

42
Q

Which diseases are caused by chlamydia trachomatis?

A

1) Trachoma 
2) Genital infections 
3) Neonatal infections

43
Q

Describe trachoma that is caused by chlamydia trachomatis

A
  • Chronic infection of conjunctiva
    
- Causes scarring and blindness 

  • Endemic in parts of Asia/Africa
44
Q

Describe the genital infections caused by chlamydia trachomatis

A
  • Common STI 
- Non-gonococcal urethritis (men) and urethritis, cervicitis, and PID (women)
    LEADS TO neonatal infections in mom is infected 

  • Neonatal conjunctivitis, pneumonia
    
- Screening and treatment in pregnant women decreases incidence
45
Q

Describe mycoplasma pneumoniae

A
  • Produces common form of pneumonia (10%): atypical pneumonia — found in younger ppl (5-20yo)
    
- Adheres to respiratory epithelial cells 
- Bacterial growth is extracellular 

  • Bacteria produce H2O2 and superoxide radical => UH OH! serious damage
46
Q

Describe mycoplasma pneumonia as it presents in pts

A
  • Generally mild 
- AKA: walking pneumonia 
- Spread by respiratory secretions 

  • Fever, headache, malaise, non-productive cough, check/body aches, fatigue
    
- Recovery slow — over 1-4 weeks
47
Q

Describe mycoplasma pneumonia on a cellular level

A
  • Culture difficult to grow => slow
    
- Causes inflammation/thickening of interstitium (tissue around air sacs of lungs)
    
- Lab diagnosis via serological tests 

  • Gram stain used primarily to RULE-OUT other bacteria

Treatment: b/c bacteria lack cell wall/shape => cell wall-active antibiotics not effective

ENGR 1 (29 decks)

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