Bacterial infection of the skin and soft tissue joints and bone II

Question 1

streptococcus type

Answer 1

catalase neg, gram pos cocci in chains

aerobic and facultative anaerobe

Question 2

how are streptococcus organisms distinguished

Answer 2

hemolytic props (hemolytic props)
serologic (lancefield) groupings (antigens)

Question 3

what are lancefield antigen groupings? most common?

Answer 3

-looks for presence of certain antigens to differentiate beta hemolytic strep
-group in groups a-u
-A and B are the most common
D commonly found in enterococcus

Question 4

what group is s. pyogenes? and what does it cause?

Answer 4

• A

- causes strep throat, skin and soft tissue infections, rheumatic fever and glomerulonephritis

Question 5

what is s. pyogenes (group A) sensitive to whereas other beta hemolytic strep groups are not?

Answer 5

bacitracin

Question 6

what does s. pyogenes have in its capsule

Answer 6

hyaluronic acid -found in the ecm of our tissues so it looks like self material and thus we do not recognize it as a foreign substance and we dont phagocytose it

Question 7

what does s. pyogenes have that allow it to adhere to its host?

Answer 7

• pili
• lipoteichoic acid- adheres to fibronectin
• protein F and M protein = invasion of the epithelial cell

Question 8

M protein

Answer 8

• adhesion protein in s. pyogenes and are associated with invasion of epithelium
• has many varying N termini so they are categorized that way
• antiphagocytic
  -inhibits complement
  = IMPORTANT ADHESIN

Question 9

what are some toxins used by s. pyogenes?

Answer 9

• streptolysin O and Streptolysin S

- PORE FORMING TOXINS (like alpha toxin in s. aureus)

Question 10

what are some super antigens used in s. pyogenes?

Answer 10

• Spe- streptococcal pyrogenic exotoxins speA-C
• increase proinflammatory cytokine production causing strep toxic shock syndrome, scarlet fever and necrotizing fasciitis

Question 11

what is C5a peptidase?

Answer 11

peptidase made my s. pyogenes that degrades chemotactic C5a
C5a is an important in bringing neutrophils to the site of infection so if the Spe blocks its activity , you get no neutrophils to fight it off

Question 12

pathogenesis of s. pyogenes

Answer 12

• s. pyogenes binds via M protein
• releases streptolysin O that creates a hole in the epithelial cell allowing s. pyo to enter
• more streptolysin O is made in the cell leading to cell death
• M protein and capsid prevent phagocytosis
• C5a peptidase also allows for stoppage of chemtaxis by C5a

Question 13

impetigo
caused by?
when?
what occurs?
what can it be confused with?

Answer 13

• formation of bullous lesions on the face-mostly around the mouth that is mostly in neonates. -HONEYCOMB like
  caused by s. pyogenes and s. aureus
  -usually during the warmer months
  -confused with chicken pox or herpes

Question 14

how is bullous impetigo distinguished between the two bacterias?

Answer 14

s. aureaus- causes more extensive, bullous lesions that break down and leave thin paper-like crusts instead of thick amber crusts like in s. pyogenes
*** AMBER = PYOGENES
MROE EXTENSIVE, PAPERLIKE AND BROKEN DOWN= AUREUS

Question 15

how do you know a skin infection is erysipelas

Answer 15

• distinct border between diseased and not

Question 16

what’s necrotizing fasciitis and what is it also referred to as?
what mostly causes it?

Answer 16

• it is a gangrene or flesh eating bacteria

- caused mostly by group A strep

Question 17

what does necrotizing fasciitis usually present as?

Answer 17

• PAIN AND TENDERNESS SEVERE*** (looks grey) BUT LOOKS LIKE MINIMAL ERYTHYMA ON OVERLYING SKIN
• for milder causes at superficial levels, skin is more abnormal but the pain and tenderness is only mild or moderate
• as disease progresses over hrs, the pain worsens and get a change in skin look to more dusky or mottled erythema and edema

Question 18

how do you distinguish necrotizing fasciitis from cellulitis?

Answer 18

• necrotizing fasciitis is very painful and appears grey over time

Question 19

treatment of necrotizing fasciitis

Answer 19

• dead tissue block circulation to the wound and can easily colonized by the bacteria so you MUST debride the wound and create a clean margin
• do so via skin graft
• USE ANTIBIOTICS-BROADSPECTRUM

Question 20

what symptoms are known to be associated with s. pyogenes as pharyngitis

Answer 20

• yellow white exudate
• but also get SCARLET FEVER as a complication- which is release of exotoxin SpeA being released systemically and causing red spots on chest- strawberry tongue

endocarditis- M protein thought to mimic heart antigen to cause endocarditis of valves- react with heart sarcolemma membrane and myosin and synovium- occurs usually 3 weeks post strep pyogenes A infects for pharyngitis
=REMEMBER BOTH ARE FROM PHARANGITIS INFECTION

Question 21

*what can s. pyogenes infection of the skin cause?

Answer 21

-glomerulonephritis
-it can also be caused by a pharyngitis infection
-

Question 22

pathogenesis of glomerulonephritis

Answer 22

-type 3 sensitivity-
M antigen/streptokinase mimics self-antigen in the kidney and causes antigen- antibody complex that activates complement to attack it and attack the kidney cells causing inflammation
- occurs 1-4 weeks post pharyngitis and 3-6 wks post cutaneous infection

Question 23

acute poststreptococcal glomerulonephritis symptoms?

Answer 23

• hematuria, oliguria (protein in blood), htn, edema
• recent strep infection- see in culture
• reduced serum complement

Question 24

streptococcal toxic shock syndrome

Answer 24

• wound that progresses to necrotizing fasciitis and then turns to shock and death
• initially pain and nonspecific flu-like symptoms
• exotoxins of SpeA and C

Question 25

what is one of the main differences that distinguishes strep infection with staph infection?

Answer 25

strepto patients are mostly bacteremic and may get necrotizing fasciitis

Question 26

when diagnosing your patient, what dinstinguishes group A s. pyogenes from the rest

Answer 26

bacitracin suseptibility

Question 27

what can you look for serologically, that would indicate recent exposure to s. pyo in a patient that's maybe coming in with glomerulitis

Answer 27

- presence of anti-antigen O antibodies in the blood

Question 28

how is the treatment for s. pyogenes different from that of s. aureus

Answer 28

s pyogenes is PCN | s. aureus is vanco or oxacillin due to their b-lactamases

Question 29

``` what kind of bacteria is pseudomonas aeruginosa? stain movement oxidase fermentation blood agar produces grows where? how transmitted ```

Answer 29

- gram neg rod - aerobic - motile - oxidase pos - non-fermenter - blood agar-hemolytic - produces PYOCANIN - minimalist that grows in many conditions-temps ad nutrition - nosocomial infection- pt with antibiotics - transmission be contact or food/water - opportunistic pathogen

Question 30

what are some virulence factors of p. aeruginosa?

Answer 30

- capsule - adhesins like pilli, flagella, LPS and alginate - secretes phospholipase C (hemolysin), pyocyanin (proinflammatory), pyoverdin (siderophore) collagenase, lipase - HAS EXOTOXIN A- AN AB TOXIN THAT HAS B BIND HOST CELL AND A INACTIVATES EF-2 VIA ADP RIBOSYLATION AND BLOCKS PROTEIN SYNTHESIS CAUSING CELL DEATH - has a type 3 secretion system- exoenzyme s and t into target cells leading to cell damage and spread

Question 31

where does the antibiotics resistance come from in p. aeruginosa

Answer 31

- mutation of the porin proteins

Question 32

*pathogenesis of p. aeruginosa

Answer 32

- p. aeruginosa binds the cell - releases exotoxin A (AB toxin) that binds and A enters cell to bind EF-2 -blockage of ribosylation and DNA synth release of exotoxin via type 3 secretion system of exoenzymes s and t -cell destruction

Question 33

where do you mostly see p. aeruginosa infection

Answer 33

- CF pt - immnocompromised pt - burn victims - swimmer's ear (otitis externa) - infection via contaminated contact lens - hot tub folliculitis - osteochondritis- inflammation of the bone or cartilage after cut in shoe with moisture

Question 34

what is a possible outcome of p aeruginosa on patients who are neutropenic, DM or have extensive burns?

Answer 34

- pt can become bacteremic and it can lead to infection of blood vessels resulting in necrotic lesions known as ecthyma gangrenosum

Question 35

what is typical to find on a burn patient with a p. aeruginosa infection

Answer 35

-greenish blue color due to pyocyanin right on the moist surface of the wound that can eventually become bacteremic

Question 36

ecthyma gangrenosum

Answer 36

- caused by p. aeruginosa septicemia | - starts with erythromatous or pupuric macule and then quickly develops into a hemorrhagic bulla that ruptures

Question 37

pseudomonas folliculitis

Answer 37

- red papules that can turn into pruritic erythramatous pustules - can get it via hottub - will resolve in 5 days - p. aeruginosa infection

Question 38

green nails

Answer 38

- pseudomonas infection of the nails - grows biofim on ventral or dorsal surface of skin - must have a pre-existing condition (candida paronychia-from s aureus) sets up moist environment for propagation of p. aeruginosa - can tell its aeruginosa cuz its green

Question 39

webspace intertrigo

Answer 39

-infection of s. aeruginosa between toes due to excessive moisture for it to grow

Question 40

how do you treat and prevent s. aeruginosa infections

Answer 40

- treat- antibiotic resistance so do susceptibility testing- combo therapy of B lactam + aminoglycosides are used - prevent- clean medical equipment, don't use unnecessary antibiotics, maintain dry conditions