ICL 2.9: Staphylococci Flashcards

Question

what are superantigens?

Answer 1

they bind MHC II on macrophage to *force* interaction with T cell TCR macrophages release IL-1β (fever) + TNFα (hypotension, shock) T cells release IL-2, IFNγ, TNFβ (hypotension, shock)

Answer 2

α toxin = forms pores that allow loss of osmoregulation β toxin = cleaves lipids in membranes of RBC, fibroblasts, leukocytes, macrophages 𝛿 toxin = has detergent-like qualities that disrupt membranes of many cells γ and PV toxin = forms pores in leukocytes

Answer 3

it's an s. aureus toxin that's a superantigen* causes staphylococcal scaled skin syndrome (SSSS) = exfoliative dermatitis (literally pealing baby skin) exfoliative toxins are proteases that cleave desmoglein 1, which disrupts cell-to-cell adhesion in epidermis Ab can neutralize toxin! less than 5-10% of strains contain these toxins

Answer 4

A = food poisoning, usually ham* all are superantigens!! also all are heat stable and acid-resistant 30-50% of S. aureus strains carry enterotoxins

Answer 5

TSST-1 = toxic shock syndrome toxin-1 = toxin of s. aureus it's a superantigen --> stimulates cytokines leading to hypovolemia and shock damages many cells, including endothelial cells, leading to vascular leakage

Answer 6

1. person-to-person 2. fomites 30% chronically colonized, 50% intermittently colonized, 20% never colonized s. aureus can survive on dry surfaces because of PG and capsule

Answer 7

1. vaginal carriage of S. aureus occurs in 10% of women 2. hospital personnel have high rates of colonization (50% - 90%) 3. wounds or foreign body penetration (catheters, prosthetic valve/joints)

Answer 8

CA MRSA strain(s) carry the Panton-Valentine leukocidin (PVL) toxins* association of PVL toxin in CA-MRSA with skin and soft tissue infections and severe necrotizing pneumonia with sepsis

Answer 9

1. skin trauma 2. high BMI 3. cosmetic body shaving 4. prison residence 5. physical contact with a person who has a draining lesion or is a carrier of MRSA 6. sharing equipment that is not cleaned or laundered between users 7. tattoo recipient 8. military

Answer 10

1. adherence 2. immune evasion 3. penetration into tissue 4. inoculum size 5. host immune status

Answer 11

s. aureus can adhere to: 1. mucosal cells/nasal epithelial cells teichoic acids on bacterial cell wall bind fibronectin to allow adherence to mucosal cells coagulase allows bacterial clumping/aggregation 2. traumatized or broken skin coagulase degrades fibrinogen --> fibrin (clot) 3. endothelial surfaces teichoic acids bind fibronectin

Answer 12

1. Protein A binds antibodies to limit clearance 2. Polysaccharide capsule inhibits PMN phagocytosis 3. Catalase limits toxic effects of PMN H2O2 4. Cytolytic toxins lyse a variety of immune cells

Answer 13

1. toxin action 2. localized infection (pyogenic disease) 3. systemic infection (disseminated infection; bacteremia)

Answer 14

1. SSSS 2. staph food poisoning 3. toxic shock syndrome 4. cutaneous infections (pyogenic disease) 5. bacteremia/endocarditis 6. pneumonia 7. osteomyelitis 8. septic arthritis

Answer 15

SSSS = staph scalded skin syndrome primarily in newborns toxins act on the dermis --> staph secretes exfoliative toxins systemically abrupt perioral erythema --> 2 days later whole body --> skin detaches easily --> may form bullae --> usually self-resolving in 7-10 days but may administer anti-Staph antibiotics or local wound care antibodies neutralize toxins

Answer 16

ingestion of preformed enterotoxin (usually enterotoxin A or B; superantigen); food appears normal common with processed meats, especially ham* there's abrupt onset of nausea/vomiting, abdominal pain, diarrhea 2 - 6 h after ingestion; symptoms may last 24 h usually occurs in community outbreaks but it's self limiting! Abs develop and are cross-protective

Answer 17

TSS = toxic shock syndrome associated with staph strains producing TSST-1 (superantigen) abrupt onset of fever, hypotension, diffuse rash, vomiting, diarrhea, myalgia rash progresses to desquamation of palms and soles** (unique) CNS, GI, liver, blood, musculature, renal systems involved 2 scenarios: 1. non-menstrual = usually 48 hours after a surgical procedure; patient looks septic but wound looks good 2. menstrual = young women age 15-25 using tampons during menses

Answer 18

remove source of the Staph (removes toxin production): abscesses, fluid collections, tampons supportive measures, immunoglobulins, antibiotics

Answer 19

1. impetigo 2. folliculitis 3. furuncles 4. carbuncles 5. hidradenitis suppurativa 6. cellulitis 7. lymphagitis

Answer 20

superficial infection of the skin, face, and limbs young children begins as a vesicular lesion (macule; flat and red) --> pustule (pus-filled) --> crusty erosion 80% of impetigo are Staph; 20% Group A Strep

Answer 21

one of the possible disease outcomes of s. aureus Hematogenous spread to bone or area adjacent to trauma in children, affects long bones (rapid growth and highly vascularized) in adults, affects vertebral column Brodie abscess = foci of Staph

Answer 22

1. Pus contains few bacteria 2. Culture from base of abscess 3. Blood sample should be cultured, not stained 4. rapid test = staphaurex

Answer 23

rapid test; latex agglutination for s. aureus infection S. aureus bound coagulase binds fibrinogen that is bound to latex beads S. aureus Protein A binds Fc region on rabbit IgG that is bound to latex beads Latex beads and S. aureus clump together

Answer 24

remove foreign bodies or drain pus duration of therapy depends on the type of infection bone, foreign body, endocarditis require at least 4 weeks of antibiotics

Answer 25

MSSA = methicillin sensitive s. aureus good drug choices are β-lactams = nafcillin, oxacillin, cefazolin

Answer 26

most frequently due to altered penicillin binding proteins (PBP2a)- mecA gene Vancomycin best choice because it's resistant to more drugs than CA-MRSA

Answer 27

clindamycin, doxycycline, trim-sulfa (Bactrim), linezolid, vancomycin good initial choices if CA-MRSA suspected rifampin resistance occurs rapidly and combination therapy is useful

Answer 28

VRSA = MRSA that is Vancomycin intermediate-sensitive or resistant this is due to thickened PG or vanA gene from Enterococci (modified PG) consider linezolid or Synercid or daptomycin

Answer 29

1. s. epidermidis 2. s. lugdunensis 3. s. saphrophyticus 4. s. hemolyticus

Answer 30

they typically produce polysaccharide slime layer that aids in attachment to surfaces (e.g. catheters, shunts, prosthetic joints)

Answer 31

coagulase negative catalase positive γ hemolysis = white color on agar

Answer 32

normal resident bacteria on skin, mucous membranes antibiotic resistance encoded by plasmids; can easily transfer within or between genus/species nearly all infections are hospital acquired usually caused by infection after “hardware” is introduced into body or “line sepsis” specially artificial valves* common cause of artificial valve endocarditis (40% S. epi) requires aggressive treatment with Vancomycin + gent + rifampin and removal of the valve

Answer 33

native valve endocarditis

Answer 34

β hemolytic on blood agar coagulase negative PYR) positive [rapid test] --> most staph are negative!! requires aggressive treatment with vancomycin + gent + rifampin and removal of valve

Answer 35

UTIs infection occurs in healthy young women in an outpatient setting

Answer 36

catalase positive coagulase negative γ-hemolytic on blood agar novobiocin resistant

Answer 37

opportunistic infections it's a normal resident bacteria on skin, mucous membranes infections similar to S. epidermidis = line infections, endocarditis, septicemia, etc. 2nd most common cause of coag neg Staph infections

Answer 38

catalase positive coagulase negative non-hemolytic on blood agar

Answer 39

MICROBIOLOGY: Gram + cocci; clusters; β-hemolytic; catalase positive; coagulase (clumping factor) positive; carbohydrate capsule inhibits phagocytosis PATHOLOGY: PG immunostimulatory; teichoic acid binds fibronectin (adhesion); Protein A binds antibody; coagulase (clumping factor); catalase; hyaluronidase; fibrinolysin; nuclease; toxins (cytolytic, exfoliative, enterotoxins, TSS1; superantigens) EPIDEMIOLOGY: colonized at birth; fomites; person-to-person; vaginal colonization; wounds CLINICAL: Toxin-mediated (food poisoning, Scalded Skin Syndrome [SSSS], Toxic Shock Syndrome [TSS]); Cutaneous (impetigo, folliculitis, carbuncles, furuncles, sweat glands, wound infections); Bacteremia, endocarditis; Pneumonia; DIAGNOSIS: Culture from abscess, blood, nasopharynx (SSSS), vagina (TSS); rapid disease (food poisoning); Staphaurex; PCR or PFGE TREATMENT: Culture susceptibility; nafcillin, oxacillin, cefazolin; MRSA = vanc; CA-MRSA = clindamycin, doxy, bactrim, linezolid, vanc

Answer 40

Υ-hemolytic resident on skin hospital acquired infection; cath infections; artificial valve endocarditis >80% methicillin-res; >50% resistant to erythromycin, clindamycin, chloramphenicol, tetracyclines; treat with vanc, rifamin, or cipro

Answer 41

β hemolytic; PYR test positive native valve endocarditis treat with vanc + gent + rifampin

Answer 42

Υ-hemolytic novobiocin resistant UTIs treat with fluoroquinolones or bactrim (trimethoprim-sulfamethoxazole)

Answer 43

Υ-hemolytic; resident on skin line infections, septicemia less frequent UTI, wound infections, bone and joint infections

ICL 2.9: Staphylococci Flashcards

(67 cards)