Staph + related gram pos. organisms

Question 1

Is staph gram positive or negative?

Answer 1

Gram positive

Question 2

What does staph appear like in culture?

Answer 2

Grape like clusters

Question 3

Is staph catalase positive or negative?

Answer 3

Catalase positive

Question 4

List 4 important species of staphylococci.

Answer 4

S. aureus
S. epidermidis
S. lugdunensis
S. saprophyticus

Question 5

Name as many conditions as you can that can be caused by a serious staph infection.

Answer 5

• Pyoderma
• Faruncle/carbuncle
• Toxin-mediated infections

Question 6

What are the 3 toxin-mediated infections a/w staph?

Answer 6

• Scalded skin syndrome
• Toxic-shock syndrome
• Food poisoning

Question 7

What age range is most susceptible to scalded skin syndrome?

Answer 7

Neonates and children under age of four

similar to bad sunburn, separates skin layers

Question 8

Name as many virulence factors as you can a/w staph (8+)

Answer 8

1. Capsules (blocks PMNs)
2. Protein A (binds Fc)
3. PVL (leukocidin)
4. Coagulase (coats bacteria w/fibrin, easing opsonization)
5. Hemolysins (alpha, beta, gamma, delta)
6. Toxins (exfoliatins, epidermolytic, enterotoxins)
7. Enzymes (fibrinolysin, hyaluronidase, PLC)
8. Superantigens (TSST-1, SPE)

Question 9

What staph virulence factor is responsible for staphylococcal scalded skin syndrome?

Answer 9

Exfoliatins or epidermolytic toxins

Question 10

What virulence factor is responsible for staphylococcal food poisoning?

Answer 10

Enterotoxin

Question 11

How does fibrinolysin act as a virulence factor for staph?

Answer 11

Break down fibrin clots and facilitate spread

Question 12

How does hyaluronidase act as a virulence factor for staph?

Answer 12

Hydrolyzes ICM in tissue to spread

Question 13

How does PLC act as a virulence factor for staph?

Answer 13

Tissues affected by this enzyme become more susceptible to damage/destruction by complement components/products

Question 14

What are the consequences of superantigens a/w staph, such as TSST-1 (toxic shock syndrome toxin 1) and SPE (streptococcal pyogenic exotoxin)? (3)

Answer 14

• Pyrogenicity – cause extreme fever
• Superantigenicity – cause immune system to overreact
• Enhance lethal effects of minute amounts of endotoxin

Question 15

Is S. aureus coagulase-neg or pos?

Answer 15

Coagulase positive

Question 16

Is S. epidermidis coagulase-neg or pos?

Answer 16

Coagulase negative

Question 17

S. epidermidis infections are a/w _____________.

Answer 17

Indwelling devices

Question 18

Is S. saprophyticus coagulase-neg or pos?

Answer 18

Coagulase negative

Question 19

Besides being coagulase negative, what other test is used to differentiate S. saprophyticus from other types of staph?

Answer 19

*Novobiocin resistance

this abx is now only used in lab

Question 20

What demographic is S. saprophyticus most commonly seen in?

What condition do they usually present with?

Answer 20

• Young women

- UTI

Question 21

Is S. lugdunesis coagulase-neg or pos?

Answer 21

Coagulase negative

Question 22

What tests would indicate that one is positive for S. lugdunesis, rather than another type of staph?

Answer 22

They are PYR and orthnithine positive

Question 23

The diseases caused by S. lugdunesis are similar to those caused by __________.

Answer 23

S. aureus

Question 24

List 6 settings that have been associated with community-acquired (CA-) MRSA outbreaks.

Answer 24

1. Men who play sports w/men - MPSM
2. Prisons, jails
3. Military recruits
4. Daycare + other institutional centers
5. Newborn nurseries + other healthcare settings
6. Men who have sex with men - MSM

Question 25

List 5 severe disease syndromes in which MRSA should be considered in the differential diagnosis.

Answer 25

1. Sepsis 2. Osteomyelitis 3. Necrotizing PNA 4. Septic arthritis 5. Necrotizing fasciitis

Question 26

In hospitals, the most important reservoirs of MRSA are ________________.

Answer 26

Colonized or infected pts | Both infected and colonized patients contaminate hospital environment with same relative frequency

Question 27

What is the name of the gene a/w MRSA? What does it encode? How did it evolve?

Answer 27

mecA - Encodes PBP2a - Nlly PCN binds PBP, thus inhibiting bacterial cell wall expansion and growth. MecA evolved to encode for a new protein that does the same thing (PBP2a)

Question 28

MecA is carried on a mobile genetic element called:

Answer 28

staphylococcal cassette chromosome mec (SCCmec)

Question 29

What sx are usually first noticed w/MRSA? (3)

Answer 29

- Abscesses, pustular lesions, “boils” - “Spider bites” - Cellulitis

Question 30

Describe effective infection prevention measures to control MRSA infections in the hospital. (objective, but it's obvious)

Answer 30

- Compulsive hand hygiene for all pt interactions (behavioral change) - Contact/Droplet precautions: gowns, gloves, masks - Effective cleaning of the pt care environment: clean shared/dedicated equipment, stethoscopes, BP cuffs, thermometer, TV remotes - Appropriate use of abx

Question 31

True or false: Installing hand cleanser dispensers inside and outside all patients’ rooms failed to produce a statistically significant decrease in MRSA bacteremia.

Answer 31

False. (didn't get drop until we started testing everyone via real-time PCR and then isolating them in hospital)

Question 32

Running tests in the excessive presence of these 3 substances can generate errors or invalid results in PCR testing of MRSA:

Answer 32

1. Whole blood 2. Mucus 3. Nasal Spray

Question 33

Describe the typical habitat of staph. | What’s the most common body site that it’s found in that can easily be cultured?

Answer 33

``` Found in external environment Found on skin and mucous membranes - *Anterior nares - 20-40% of adults have it there - Intertriginous skin folds - Perineum - Axillae - Vagina ``` Significant opportunistic pathogen under appropriate conditions

Question 34

What are some factors that can pre-dispose to staph infection?

Answer 34

1. Defects in leukocyte chemotaxis 2. Opsinization/AB defects 3. Defects in intracellular killing (membrane bound oxidase system) 4. Skin injuries (e.g. burns) 5. Foreign bodies (e.g. prosthetics) 6. Viral infections 7. Underlying dz's 8. Abx use which staph isn't susceptible to

Question 35

What are the "usual" sites of staph infection? (3, but they're combined)

Answer 35

1. Skin 2. Nose + throat 3. GI tract, urethra, vagina

Question 36

Define pyoderma. | - What are 2 possible causes

Answer 36

Any skin disease that is pyogenic (pus). - Infectious (e.g. staph) - Autoimmune (e.g. pyoderma gangrenosa)

Question 37

# Define furuncle. How does it differ from carbuncle? (next slide)

Answer 37

- Furuncle (or boil) skin dz caused by infection of hair follicles, resulting in localized pus accumulation + dead tissue - A carbuncle is an abscess larger than a boil, usually with 1+ openings draining pus (most common at nape of neck)