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21 Cards in this Set
- Front
- Back
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Staphylococci Characteristics
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gram positive, non-motile, non spore forming, 0.5-1um diameter
isolates grow in clusters aerobes or facultative anaerobes grow best on blood enriched media and are beta-hemolytic grow at 18-40 C CAN grow in 10% NaCl ALL CATALASE + *S. aureus is COAGULASE +, others negative |
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3 main pathogens of Staph
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S. aureus = most virulent
*in nares, skin, vagina *golden colonies S. epidermidis = foreign body *normal flora of skin and mucus membranes S. saprophyticus = UTI *genitourinary skin |
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Staph Diseases
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S. aureus
1. skin/soft tissue infection *furuncle (boil) = follicultilis or sebaceous gland infection very painful, drain, antibiotics *carbuncle = deep seated infection of several hair follicles, spread into inelastic tissue of neck, results in- fever, bacteremia, leukocytosis, severe pain treat via systematic ab 2. bone/joint infection 3. bacteremia, endocarditis 4. toxin mediated disease, food poisoning, toxic shock 5. necrotizing pneumonia S. epidermidis 1. opportunistic infections of catheters, shunts, prosthetic devices, surgical wounds, bactermia, and endocarditis S. saprophyticus *community acquired UTI |
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Staph Cell Wall Virulence Determinants
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1. capsule- inhibits phagocytosis, chemotaxis, proliferation of mononuclear cells
2. peptidoglycan- 50% of cell wall weight, endotoxin like activity, activates complement and attracts neutrophils 3. protein A- inhibits Ab mediated clearance by binding Fc terminal of most IgG (anti-inflammatory) |
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Staph Cell Enzymes as Virulence Determinants
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1. catalase- neutralizes oxidative burst of phagocytes
2. coagulase- converts fibrinogen to fibrin by binding prothrombin *promotes clots w/aids in a place to hide from immune response 3. fibrinolysin 4. hyaluronidase 5. lipases/nucleases |
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Toxins as Virulence Determinants
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1. cytotoxins alpha, beta, gamma, and delta = toxic to leukocytes, RBCs, macrophages, platelets, and fibroblasts
2. ***exofoliative toxins- serine proteases act on stratum granulosum of epidermis 3. panton-valentine leukocidin - damages neutrophils via membrane pore formation |
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Toxins as Superantigens
(S. aureus and GAS have these) *antigen binds to MHC II, activate T cell and bind to invariant region- stimulate massive cytokine production by CD4+ cells |
1. enterotoxins B,C = release inflammatory mediators in gut = increased peristalsis and CNS effect contributes to puking
*food poisoning *staph toxic shock syndrome 2. TSST-1, generalized inflammatory mediator *staph toxic shock syndrome |
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Staphylococcal Scalded Skin Syndrome
(exfoliative toxin at work) |
infants w/sudden onset of skin tenderness and eruptions
NIKOLSKY'S SIGN = gentle lateral pressure displaces normal skin into bullae manage fluids/electrolytes treat via systemic ab |
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Toxic Shock Syndrome
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rapid, fever, hypotension, sunburn rash w/desquamates
1. menstrual TSS *s. aureus producing TSST-1 2. nonmenstrual TSS *wound associated (adult) or suppurative (child) *s. aureus, TSST-1 and toxin B and C *GAS - strep pyrogenic exotoxin |
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TSS treatment/prevention
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staph =bactermia, rash is less than strep
vanco + clindamycin to inhibit recurrences are seen w/menstrual cases- due to failure to produce ab to TSST-1 |
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Staphylococcal Food Poisoning
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vomiting onset 1-6 hrs
*custard, canned food, potato salad, ice cream pre-formed enterotoxin in food no antibiotics- fluid as necessary |
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Bone/Joint Infections
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S. aureus leading cause
empiric therapy must cover STAPH |
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Pelvic Syndrome
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Bone/Joint Infection
Septic Thrombophlebitis Septic emboli to lungs |
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Osteomyelitis
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kids- long bones
nasal/skin colonizations = transient bacteremia w/minor trauma acute onset of fever, pain, refusal to bear weight or other functional limitation dx: x-ray, bone scan, blood and bone cultures tx: empiric: IV than PO ab *ESR and CRP used as guide |
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Cystic Fibrosis
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most common CF infection : Pseudomonas aeruginosa
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MRSA
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pencillinase producing s. aureus has second alteration and becomes PBP2a-producing S. aureus
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CA-MRSA
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USA300 clone- 98% carry Panton-Valentine leukocidin
(direct toxin of neutrophils and epithelial cells) skin decolonization by weekly bleach or chlorhexidane baths to rid in community or nares decolonization by mupirocin (bactroban) or retapamulin (altebax) |
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S. saprophyticus
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CA-UTI in young women
*distant #2 behind E. coli greater adhererance to urinary epithelium no virulence factors shared with s. aureus- does express urease (degrades urea to NH4 for growth) |
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S. epidermidis
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adheres to foreign bodies
*associated w/indwelling catheters, prosthetic devices hard to eradicate antibiotic resistance...treat with vanco |
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Infective Endocarditis
(path: deposition of platelets, thrombin...vegetations) |
pre-existing valvular abnormality are targetted
freq of valves involved: MV > AV > MV + AV > TV >> PV |
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Endocarditis
(right sided w/ IVDU) (need 3 independent blood samples which are negative after seven days of incubation) |
causative mo:
GRAM + 1. S. aureus *prosthetic valve - early *acute - janeway lesion on skin and spots in eyes 2. Viridans streptococci *subacute (glomerulonephritis) 3. S. epidermidis *prosthetic valve - late 4. Enterococci *surgery for endocarditis 5. other streptococci Gram - 1. HACEK organisms Fungi |
