Reading...
Play button
Play button
Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
35 Cards in this Set
- Front
- Back
|
What's the most important species in the Staphylococcus species?
|
S aureus - frequenct cause of human disease.
Not mobile, no flagella. No spores. -facultative anaerobes -can grow in high salt concentrations (10% NaCl) - can grown in temps from 18-40C |
|
|
What is the morphology of staphylococci?
|
You can cluster formation; no plane of division that is constrained.
|
|
|
Describe the cell wall structure of Staphylococcus.
|
Capsule and polysacch. slime
peptidoglycan teichoic acid catalse-positive |
|
|
1) what does staphylococcus dervie from (name)
2) aureus |
1) staphylo: bunch of grapes, coccus- grain or berry
2) golden |
|
|
Where would you find S aureus?
|
Find it on anterior nare perineum.
2. Often found as a transient colonizer in the anterior nares, sometimes on the skin, and in the vagina of ~5% of women. 3. Is often transmitted from the skin and nose by direct contact or via fomites (survives well on dry surfaces). 4. Major problem as a hospital-acquired infection. Proper hand washing and universal precautions are important in preventing transmission. 5. Risk factors for carriage and disease include presence of foreign bodies (like catheters or prostheses), frequent needle injections, diabetes, reduced humoral immunity, surgical procedures, close personal contact (wrestlers, football players). |
|
|
What's MRSA?
|
MRSA (Methicillin-Resistant Staphylococcus aureus) now the most common cause of community-acquired skin/soft tissue infection
|
|
|
Color of Gram +?
Gram -? |
Gram + = purple
Gram - = pink Most common way to identify S. aureus |
|
|
Catalase test?
|
This test checks to see if bacteria can break down hydrogen peroxide to hydrogen and oxygen.
If its -, have streptococci If its +, do oxidase test |
|
|
Oxidase test?
|
cytochrome C test activity.
- = staphylococcus + = micrococcus - obligate aerobe if you have staphylococcus, do coagulase test |
|
|
Coagulase assay gives you? What does adding novobicin help you differentiate?
|
Test it on staphylococcus
+ = S. Aureus - = test on coagular negative staphylococci. add novobiocin, to eather get S. epidermis or S. saprophyticus |
|
|
Describe the hemolysis and colony appearance for S. aureus S. epidermis, and S. saprophyticus
|
S. aureus = b-hemolytic, “golden” colonies on blood agar plates
S. epidermidis = non-hemolytic, white colonies on blood agar plates S. saprophyticus = non-hemolytic, white colonies on blood agar plates |
|
|
What is mannitol salt agar for?
|
Mannitol-salt agar = useful for recovery of S. aureus from contaminated samples
|
|
|
What are some nucleic acid based test?
|
PCR, pulse-field gel electrophoresis, FISH (fluorescent in situ hybridization)
|
|
|
What are some virulence factors in staphylococcus
|
capsule, peptidoglycan, protein A, teichoic acid, and cytoplasmic membrane.
|
|
|
Capsular polysaccharide
|
- 11 serotypes (5 and 7 are most important)
- PMN activity - Role in attachment to indwelling devices - Most strains also possess a slime layer – aids in attachment to tissues and foreign bodies |
|
|
What activity does peptidoglycan possess?
|
- Possesses endotoxin-like activity
(stimulates cytokines such as IL-1 from monocytes) - Elicits PMN (neutrophil) recruitment abscess formation |
|
|
Protein A?
|
- most S. aureus, but not coagulase-negative staphylococci
- covalently linked to peptidoglycan - affinity for Fc portion of IgG1, IgG2, IgG4 (significantly reducing antibody-mediated clearance) - secreted protein A can also bind antibody and these immune complexes can activate and consume C’ - Useful Ag for diagnostic test |
|
|
Teichoic acids?
|
- species-specific antigens
contain phosphate and are linked covalently to N-acetyl-muramic acid in peptidoglycan or to cytoplasmic membrane - mediate binding of Staph to host mucosal surfaces via fibronectin poorly immunogenic |
|
|
What's the purpose of the cytoplasmic barrier?
|
- complex structure
- osmotic barrier - focal point of cell biosynthesis and respiration |
|
|
Describe staphylococcus adhesion
|
1) its a key strategy used by baceteria localized to specific envi ( for pathogens, to host tissues)
2) teichoic acid + surface proteins MSCARMMs covalently boudn to peptidoglycan are called Staph adhesions 3) bind to fibronectin, elastin, collagen |
|
|
What are 4 groupings of staphyloocci toxins?
|
cytotoxins, exfoliative toxins, enterotoxins, toxic shock syndrome txoin-1.
last 3 are superantigens: APC, MHC II interacts w/ T cell but bind outside the cleft without the need of a second signal. Without the need of a specific signal. All T cells will be activated, not just specific ones. |
|
|
Describe cytotoxic alpha toxin
|
- chormosomal or plasmic encoded
-33KDa polypept - most S Aureus possess this toxin -Disrupts smooth muscle (blood vessels), toxic for hepatocytes, leukocytes, RBCs, platelets -- Lipophilic; forms 1 – 2 mm pores in membranes (K+, Na+, Ca+ flux and osmotic instability) |
|
|
Beta (b)-Toxin or sphingomyelinase C
|
Heat labile 35,000 Da polypeptide
- Specificity for host sphingomyelin and lysophosphatidylcholine - Toxic to RBCs, fibroblasts, leukocytes, macrophages - Hydrolyzes membrane phospholipids (directly related to membrane concentration of surface sphingomyelin) |
|
|
Delta (d)-Toxin
|
- 3,000 Da polypeptide
- Most S. aureus strains possess this toxin (and other staphylococci) - Cytotoxic to many cells by affecting cell membrane Possesses surfactant “detergent-like” activity believed to be mode of action in membrane disruption and cell toxicity |
|
|
Gamma (g)-Toxin and Panton-Valentine Leukocidin
|
- these are bi-component toxins (two polypeptide chains)
- S component (3 types; HlgA, HlgC, LukS-PV) - F component (2 types; HlgB, LukF-PV) - Affect cell integrity and osmotic stability by forming pores (some combinations more leukotoxic, some more hemolytic) γ-toxins made by most S. aureus strains, <5% of nosocomial MRSA strains make P-V leukocidin, while nearly all community |
|
|
Exfoliative toxin (SSSS)
|
exfoliative dermatitis
- serine proteases 2 types ETA (heat stable, chromosomally encoded) ETB (heat labile, plasmid encoded) - cleaves desmoglein-1 in epidermal cell desmosomes (bridges between cells) in the stratum granulosum epidermis - Host produces neutralizing antibodies that clear toxin - More significant in children than adults - Prevalence varies geographically usually <5 and < 10%, respectively |
|
|
Enterotoxins
|
8 serologically distinct types (A-E, G-I)
with 3 subtypes of serotype C enterotoxin - Heat stable (100°C for > 30 min) - Resistant to gastric and jejunal secretions - Cause of food poisoning (type A), milk product contamination (types C and D), and staphylococcal pseudomembranous enterocholitis (type B) - 30-50% of S. aureus strains possess enterotoxin |
|
|
Toxic Shock syndrome toxin 1
|
(TSST-1; previously enterotoxin F)
- 22,000 Da and chromosomally encoded - Heat and protease resistant - Requires O2 and neutral pH for production (may contribute to low incidence despite high incidence of S. aureus wound infections) - stimulates T-cell proliferation and potent host cytokine response - responsible for systemic effects observed during TSS |
|
|
Staphylooccoal enzymes
1) coagulase 2) catalase 3) hyaluronidase 4) fibrinolysin 5) lipases 6) nuclease 7) penicilinase |
Coagulase: 2 forms: Bound and Free
Directly converts fibrinogen to fibrin This causes clumping of bacteria and elicits the fibrin coat observed around abscesses Localizes infection and possibly protects from phagocytosis Catalase: converts H2O2 to water and O2 gas (phagocytosis and metabolism are sources of H2O2) Hyaluronidase: hydrolyzes hyaluronic acid (polysaccharides present in the intercellular connective tissue) Fibrinolysin: (also known as streptokinase) degrades fibrin clots Lipases: hydrolyze lipids to invade cutaneous and subcutaneous tissue (role in boil development) Nuclease: degrades nucleic acids (function is unknown) Penicillinase: β-lactamase (degrades β-lactam ring of penicillins) |
|
|
What is bullous impetigo?
|
Localized form of SSSS
Toxin-mediated (S. aureus) Blisters (culture positive) Common for young children Highly communicable |
|
|
Impetigo
|
Begins as small macule (red spot)
Becomes pus-filled (pustule) may have erythematous base Pustule ruptures crusty Usually caused by S. aureus sometimes Group A strep |
|
|
What are some infections caused by staphylococcus epidermidis and coagulase - Staph
|
UTIs (S. saprophyticus; nosocomial UTIs S. epidermidis)
Osteomyelitis (direct = sternal wounds; via hematogenous route) Endocarditis Bacteremia (immunosuppressed patients) Endophthalmitis Infections of indwelling devices: IV catheters Hemodialysis shunts Prosthetic cardiac valves Cerebrospinal fluid shunts Pacemaker wires Breast implants Prosthetic joints |
|
|
What does S. aureus most commonly cause?
What is it resistnat to? |
absessces, so you need surgical drainage
resisitant to Beta lactams due to plasmid encoded pencilinase |
|
|
What would be the antibiotic of choice if MRSA was suspected?
|
resistance is appearing but intermediate. Vancomycin is dru of choice. Must drain the abscess.
|
|
|
What is S. epidermis and S. saprophyticus?
|
S. epidermis: part of normal flora nd is opportunisitic pathogen that can cause endocarditis and prosthetic joint infections.
S. saphrophytcus - common cause of UTIs |
