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*med3* > Infectious Disease - Bacteria > Flashcards

Infectious Disease - Bacteria Flashcards

1
Q

what is the feature that distinguishes staph from strep?

A

catalase+

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2
Q

what is the basic habitat for staph aureus?

A

nares

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3
Q

what kind of hemolysis will you see when staph aureus is plated on blood agar?

A

β

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4
Q

what is protein A?

A

main virulence factor for staph Aureus binds Fc IgG to block complement activation and phagocytosis

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5
Q

what are the toxin-mediated diseases caused by staph aureus?

A

toxic shock syndrome - TSST-1

food poisoning - enterotoxin

scalded skin syndrome - exfoliatin

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6
Q

what are the infectious diseases caused by staph aureus?

A

skin infections - impetigo

pneumonia

endocarditis

osteomyelitis

abscesses

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7
Q

how does toxic shock syndrome present?

A

fever, schock (hypoTN),

red rash = erythroderma****

after weeks - desquamation of palms/soles

diarrhea****

multi-organ system failure

****unusual for sepsis, so you know it’s TSST-1

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8
Q

what organism should you think of when a question has a person that has been using tampons or had a surgical wound packed?

A

staph aureus

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9
Q

how does staph cause food poisoning?

A

s. aureus contaminates food

food left at room temperature (PICNIC)

bacteria grow –> enterotoxin

ingestion of preformed toxin causes disease

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10
Q

multiple sick people at a picnic with mayo, egg salad,

A

s. aureus food poisoning

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11
Q

what is the incubation period for s. aureus enterotoxin?

A

3-6 hrs after ingestion of preformed toxin GI Sx develop

N/V - D is rare*

abdominal cramps

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12
Q

what causes scalded skin syndrome?

A

s. aureus exfoliative toxin (exfoliatin) toxin destroys keratinocyte attachments in stratum granulosum only - damage is intraepidermal so the skin can heal completely without leaving a scar

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13
Q

newborns 3-7 days old

fever

diffuse erythema starting at the mouth

sloughing of skin

A

scaled skin syndrome exfoliatin toxin of s. aureus

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14
Q

what is Nikolsky’s sign?

A

sign of scalded skin syndrome if the skin slips off with a gentle tug

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15
Q

what is imgetigo?

A

skin infection caused by group A strep or staph aureus

honey colored, crusted lesions

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16
Q

what population mostly gets bullous impetigo?

A

children

easly spread from child to child

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17
Q

what is bullous impetigo?

A

variant of impetigo with bullae

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18
Q

what causes bullous impetigo?

A

staph aureus exfoliative toxin strains

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19
Q

what is a rare cause of lobar pneumonia?

A

staph aureus

“post-infectious” - someone gets the influenza virus, recovers and then develops another infection caused by bacteria

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20
Q

classic cause of ACUTE endocarditis?

A

staph aureus

21
Q

acute vs. subacute endocarditis

A

(acute) staph aureus vs (subacute) strep viridans
onset: rapid vs slow
presentation: verry ill vs less sick

related condtions: none vs prior valve abnormality

22
Q

what predisposes someone to subacute endocarditis?

A

prior valve abnormaility in order to attach to the heart

Hx of mitral valve prolapse

23
Q

what is a common cause of staph bacteremia? how is it prevaentable?

A

central lines

sterile technique:

  • wash hands,
  • gloves
  • sterile insertion practices
24
Q

staph aureus is a common cause of what bone disease?

A

osteomyelitis

25
Q

where do children typically get osteomyelitis compared to adults?

A

children - long bones - femur, tibia, fibula

adults - spine

26
Q

how does s. aureus get to the bones to cause osteomyelitis?

A
  • hematogenous spread - bacteremia (also causes endocarditis)
  • spread from skin/soft tissue - pts who sit in bed all day get bed sores and the tissue breaks down and the staph can get direcly into th bone
  • trauma (surgery)
27
Q

Sx of osteomyelitis

A

localized pain +/- fever

28
Q

how is osteomyelitis Dx’d?

A

imaging - CXR, CT, MRI

29
Q

what are the classic causes of osteomyelitis?

A
  1. child = staph auerus = hematogenous spread
  2. sickle cell patient = salmonella = hematogenous spread
  3. TB patient = Pott’s disease (vertebrae/spine)
  4. diabetic - polymicrobial from foot ulcer - can result in amputation
  5. bedbound patients - polymicrobial from pressure sores
30
Q

what is cellulitis?

what causes it?

A

infection of deep dermis and subcutaneous fat - often after injury or cut to introduce bacteria

caused by β-hemolytic streptococci

also, less commonly, staph aureus => antibiotics must cover staph

31
Q

what are abscesses?

A

infections walled off in deep tissues that are filled with bacteria and inflammatory cells (pus)

32
Q

what are the types of abscesses commonly caused by staph aureus?

A

skin abscesses

  1. furuncle = boil; infectin of hair follicle
  2. carbuncle = multiple boils clistered together\

tonsillar abscesses - s. aureus lives in the nose! duhh

33
Q

what is the mainstay of treatment for an abscess?

A

incision and drainage

34
Q

what antibiotics are most strains of staph resistant to?

A

penicillin - staph produces β-lactamases = enzymes that inactivate penicillin

35
Q

what drug classes are used to treat staph?

A
  1. antistaphylococal penicillins
    1. dicloxacillin
    2. nafcillin
    3. oxacillin
  2. 1st gen cephalosporins
    1. cephalexin - opten given to patients with staph skin infection
  3. β-lactam + inhibitor
    1. amoxicillin/calvulanate - amoxicillin is a β-lactam antibiotic and clavulanate is a β-lactamase inhibitor = drug covers staph
36
Q

what is MRSA?

why is it dangerous?

how is it acquired?

A

methicillin-resistant-staph-aureus

resistant to all β-lactams bc they express altered penicillin binding proteins (PBPs)

hospital-acquired

37
Q

what drugs are used to treat MRSA?

A

vancomycin & daptomycin are the DOC

can also use linezolid

38
Q

what are the characteristics of staph epidermidis?

what are the 2 clinical scenarios it can cause?

what is the treatment?

A
  1. normal skin flora
  2. blood culture contaminant - needle/IV contaminated by staph epidermidis
  3. infects prosthetic materials in blood
  4. methicillin resistant
  5. tx is vancomycin
39
Q
A
40
Q

how does staph epidermidis infect prosthetic materials in blood?

what is the treatment?

A

surface molecules on bacteria aid in adherance => attach and produce biofilms

treat with vancomycin as if you were to treat for MRSA because of methicillin resistance

41
Q

what are likely places staph epidermidis can infect a prosthetic?

A

catheter in blood stream for CTX

packemakers

***prosthetic heart vaves

prosthetic joints

42
Q

how can you tell if blood cultures were contaminated with staph epidermidis or if it is true bacteremia?

A

sticking needle into vein causes staph epi contamination so 4 vials will be sent to lab and tested for staph epi

true bacteremia would result in growth in all 4 vials

43
Q

staph saprophyticus is a common cause of ______, especially in sexually active women.

A

UTIs

44
Q

What bug causes most UTIs? What other bugs can cause a UTI?

A

E. Coli

proteus, klebsiella, S. saprophyticus

very rare - enterococcus

45
Q

key features of what bacteria?

sexual activity young female - honeymooners cystitis

nitrite negative on urine dipstick

A

staph saprophyticus UTI

**E.Coli is nitrite positive

46
Q

how is staph saprophyticus treated?

A

UTI antibiotics:

  1. fluoroquinolones
  2. SMX-TMP
  3. Nitrofurantoin
47
Q

what antibiotics contain a β-lactam ring?

A

penicillins

carbapenems

aztreonam

cephalosporins

48
Q

what part of the penicillins structure is unique?

A

thiazolidine ring

49
Q

what are the layers of the skin?

A

*med3* (21 decks)

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