Staphylococci and Related Gram + cocci Flashcards Preview

Pathophysiology > Staphylococci and Related Gram + cocci > Flashcards

Flashcards in Staphylococci and Related Gram + cocci Deck (45)
Loading flashcards...
1

What are the two major groups in the family microccaceae?

1) micrococcus
2) rothia

2

What are the 5 KEY characteristics of staph?

1) Gram + (clusters)
2) non-motile
3) non-spore-forming
4) catalase positive
5) facultative anaerobes

3

What is the main way to determine staph from strep?

CATALASE testing

+ = staph
- = strep

4

What are the 4 main types of staph to know?

1) aureus
2) epidermidis
3) lugdunensis
4) saprophyticus

5

Where is staph aureus normally found?

perineum, axillae, vagina

6

What are 5 factors that predispose one to staph aureus infection?

1) defects in leukocyte chemotaxis
2) defects in opsonization by antibodies
3) defects in intracellular killing of bacteria following phagocytosis
4) skin injuries
5) presence of foreign bodies

7

True or false: the usual site of infection is that where the organism is part of the normal flora

TRUE

(skin, nose + throat, GI tract, urethra, vagina)

8

Define pyoderma

any skin disease that is pyogenic (pus forming)

9

What is a furuncle?

skin disease caused by infection of hair follicles resulting in localized accumulation of pus and dead tissue

10

What is a carbuncle?

abscesses larger than boils (with one or more openings)

11

What are 3 toxin-mediated infections from staph aureus?

1) scalded skin syndrome
2) toxic shock syndrome
3) food poisoning

12

What are 4 components that interfere with phagocytosis? (AKA VIRULENCE FACTORS)

1) capsules
2) protein A
3) panton-valentine leukocidin (PVL)
4) coagulase

13

How do capsules interfere with phagocytosis?

prevent ingestion of organisms by PMNs

14

How does Protein A act as a virulence factor?

binds to Fc region of IgG interfering with opsonization and ingestion of organism by PMNs

15

What is PVL and what does it do?

enzyme that alters cation permeability of rabbit and human leukocytes resulting in white cell destruction

16

How does Coagulase work?

binds to prothrombin catalyzing fibronogen to fibrin which then coats cells (with fibrin) rendering them resistant to opsonization and phagocytosis

17

Which type of staph aureus is more infectious, PVL+ or PVL-?

PVL+

18

What are the 4 hemolysins in staph aureus?

alpha, beta, gamma, delta

19

What are the hallmarks of alpha hemolysin?

lyses RBCs, dermonecrotic on SubQ injection, leukocyte toxicity

20

What are the hallmarks of beta hemolysin?

shingomyelinase
produces hot-cold lysis

21

What are hallmarks of delta hemolysin?

acts as surfactant to disrupt cell membrane (forms channels that result in leakage of cellular contents)
can cause enterocolitis in neonates

22

What are the hallmarks of gamma hemolysin?

can cause lysis in a variety of cells

23

What toxins are responsible for staphylococcal scalded skin syndrome?

exfoliatins (aka epidermolytic toxins)

works by dissolving mucopolysaccharide matrix of epidermis causing separation of skin layers

24

What are enterotoxins?

heat-stable molecules responsible for clinical features of staphylococcal food poisoning, probably most common cause of food poisoning in U.S.

25

What 3 enzymes are produced by staph aureus?

1) Fibrinolysins - break down fibrin clots and facilitate spread of infection
2) Hyaluronidase - hydrolyze intercellular matrix of acid mucopolysacch to spread organisms to adjacent tissues
3) Phospholipase C - makes tissues more susceptible to damage by complement

26

What are examples of some superantigens associated with staph aureus?

toxic shock (TSST-1)
streptococcal pyrogenic exotoxins (SPE)

27

What 3 biological characteristics are shared by staph aureus supertoxins?

pyrogenicity
superantigenicity
enhance lethal effects

all induce polyclonal T-cell proliferation

28

What virulence factor is used to identify staph aureus?

coagulase

if it clots it is staph aureus

29

What is the alternative coagulase test?

latex agglutination

agglutination = positive

30

What is the most common coagulase NEGATIVE staph?

staphylococcus epidermidis