Infectious Disease - Bacteria

Question 1

what is the feature that distinguishes staph from strep?

Answer 1

catalase+

Question 2

what is the basic habitat for staph aureus?

Answer 2

nares

Question 3

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

Answer 3

β

Question 4

what is protein A?

Answer 4

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

Question 5

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

Answer 5

toxic shock syndrome - TSST-1

food poisoning - enterotoxin

scalded skin syndrome - exfoliatin

Question 6

what are the infectious diseases caused by staph aureus?

Answer 6

skin infections - impetigo

pneumonia

endocarditis

osteomyelitis

abscesses

Question 7

how does toxic shock syndrome present?

Answer 7

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

Question 8

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

Answer 8

staph aureus

Question 9

how does staph cause food poisoning?

Answer 9

s. aureus contaminates food

food left at room temperature (PICNIC)

bacteria grow –> enterotoxin

ingestion of preformed toxin causes disease

Question 10

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

Answer 10

s. aureus food poisoning

Question 11

what is the incubation period for s. aureus enterotoxin?

Answer 11

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

N/V - D is rare*

abdominal cramps

Question 12

what causes scalded skin syndrome?

Answer 12

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

Question 13

newborns 3-7 days old

fever

diffuse erythema starting at the mouth

sloughing of skin

Answer 13

scaled skin syndrome exfoliatin toxin of s. aureus

Question 14

what is Nikolsky’s sign?

Answer 14

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

Question 15

what is imgetigo?

Answer 15

skin infection caused by group A strep or staph aureus

honey colored, crusted lesions

Question 16

what population mostly gets bullous impetigo?

Answer 16

children

easly spread from child to child

Question 17

what is bullous impetigo?

Answer 17

variant of impetigo with bullae

Question 18

what causes bullous impetigo?

Answer 18

staph aureus exfoliative toxin strains

Question 19

what is a rare cause of lobar pneumonia?

Answer 19

staph aureus

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

Question 20

classic cause of ACUTE endocarditis?

Answer 20

staph aureus

Question 21

acute vs. subacute endocarditis

Answer 21

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

related condtions: none vs prior valve abnormality

Question 22

what predisposes someone to subacute endocarditis?

Answer 22

prior valve abnormaility in order to attach to the heart

Hx of mitral valve prolapse

Question 23

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

Answer 23

central lines

sterile technique:

• wash hands,
• gloves
• sterile insertion practices

Question 24

staph aureus is a common cause of what bone disease?

Answer 24

osteomyelitis

Question 25

where do children typically get osteomyelitis compared to adults?

Answer 25

children - long bones - femur, tibia, fibula adults - spine

Question 26

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

Answer 26

* 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)

Question 27

Sx of osteomyelitis

Answer 27

localized pain +/- fever

Question 28

how is osteomyelitis Dx'd?

Answer 28

imaging - CXR, CT, MRI

Question 29

what are the classic causes of osteomyelitis?

Answer 29

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

Question 30

what is cellulitis? what causes it?

Answer 30

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

Question 31

what are abscesses?

Answer 31

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

Question 32

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

Answer 32

skin abscesses 1. furuncle = boil; infectin of hair follicle 2. carbuncle = multiple boils clistered together\ tonsillar abscesses - s. aureus lives in the nose! duhh

Question 33

what is the mainstay of treatment for an abscess?

Answer 33

incision and drainage

Question 34

what antibiotics are most strains of staph resistant to?

Answer 34

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

Question 35

what drug classes are used to treat staph?

Answer 35

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

Question 36

what is MRSA? why is it dangerous? how is it acquired?

Answer 36

methicillin-resistant-staph-aureus resistant to all β-lactams bc they express altered penicillin binding proteins (PBPs) hospital-acquired

Question 37

what drugs are used to treat MRSA?

Answer 37

vancomycin & daptomycin are the DOC can also use linezolid

Question 38

what are the characteristics of staph epidermidis? what are the 2 clinical scenarios it can cause? what is the treatment?

Answer 38

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

Question 40

how does staph epidermidis infect prosthetic materials in blood? what is the treatment?

Answer 40

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

Question 41

what are likely places staph epidermidis can infect a prosthetic?

Answer 41

catheter in blood stream for CTX packemakers \*\*\*prosthetic heart vaves prosthetic joints

Question 42

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

Answer 42

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

Question 43

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

Answer 43

UTIs

Question 44

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

Answer 44

E. Coli proteus, klebsiella, S. saprophyticus very rare - enterococcus

Question 45

key features of what bacteria? sexual activity young female - honeymooners cystitis nitrite negative on urine dipstick

Answer 45

staph saprophyticus UTI \*\*E.Coli is nitrite positive

Question 46

how is staph saprophyticus treated?

Answer 46

UTI antibiotics: 1. fluoroquinolones 2. SMX-TMP 3. Nitrofurantoin

Question 47

what antibiotics contain a β-lactam ring?

Answer 47

penicillins carbapenems aztreonam cephalosporins

Question 48

what part of the penicillins structure is unique?

Answer 48

thiazolidine ring

Question 49

what are the layers of the skin?

Answer 49