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Staphylococci
Micro
| Question | Answer |
|---|---|
| What is the oxygen dependance of Staphylococci? | Facultative Anaerobes |
| A yellow, beta-hemolyticu colony on a blood agar is suggestive for what? | S. aureus |
| A White, non hemolytic colony on blood agar is suggestive for what? | S. epidermis |
| Gram positive cocci in cluster; Catalase positve; Coagulase Postive? | S. Aureus |
| Gram postivei cocci in clusters; Catalase Positive; Coagulase Negative; Acid from glucose positive? | S. epidermidis |
| Gram postive cocci in clusters; Catalase Positive; Coagulase Negative; Acid from glucose negative? | S. Saprophyticus |
| What gram positive cocci are easy to distinguish by a catalase test? | Staphylococcus (positive) and Streptococcus (negative) |
| What are the 5 skin infections caused by Staphylococcus Aureus? | Furnuncle,impetigo, carbuncle, mastitis, cellulits (folliculitis) |
| What are the 2 wound infections caused by staph aureus? | community aquired and surgical |
| What can infection of the apocrine sweat glands with staph aureus lead to? | Hidradentis suppurtiva |
| What is impetigo usually due to? | group A strep (30% are due to group A strep and S. Aureus) |
| What are some deep lesion (metastatic infections) that can be caused by S. Aureus? | osteomyelitis, septic arthritis, meningitis, pneumonia |
| What are some bacteremia related diseases caused by Staph Aureus? | endocarditis, meningitis, pneumonia, pyelonephritis, septicemia, and septic shock |
| What is septic shock caused by in S. aureus? | Peptidoglycan |
| What can diabetes mellitus predispose a person through s. aureus infections? | boils, furnuncles, carbuncles, and wound infections and bacteremia |
| What are the risk factors for endocarditis caused by S. aureus? | heroin addiction and prosthetic heart valve |
| What is the | 1 host defense against S. Aureus infections? |
| What three virulence factors of S. aureus protect it from phagocytes? | protein A, catalase, leukocidin |
| How does protein A protect S. aureus from phagocytosis? | it bonds the Fc region of Ig's |
| What does techoic acid do in S. aureus? | binds fibronectin and induces shock |
| What does coagulase in S. aureus do? | initiates conversion of fibrinogen to fibrin |
| What does the virulence factor hyaluronidase do for S. aureus? | acts on hyaluronic acids in CT and facilitates dissemination through subcutaneous tissues |
| What are the differnet cytotoxins that S. aureus produce? | Alpha hemolysin; Beta toxin (sphingomyelinase C - kills cells by hydrolysis of membrane phospholipids); Delta toxin; Gamma toxin and Panton-Valentine Leukocidin (lysis of neutrophils and macrophages) |
| What toxins are produced by S. aureus which cause clinical diseases? | Exfoliatin A, B; Toxic shock syndrome toxin (TSST-1); Staphylococcus enterotoxin |
| What are the 5 toxin mediated diseases caused by S. Aureus? | Bullous impetigo, Scalded Skin Syndrome; Staphylococcal scarlet fever; toxic shock syndrome; food poisoning |
| What diseases do the exfoliatin A and B toxins secreted by S. Aureus cause? | Bullous impetigo; scalded skin syndrome; staphylococcal scarlet fever |
| How do Exfoliatins cause scalded skin syndrome? | Serine proteases - cause splitting of desmosomes in the stratum granulosum epidermis |
| What is the superantigen that is produced by S. aureus? | TSST-1 (toxic shock syndrome toxin 1) |
| Who are at risk for developing toxic shock syndrome? | menstruating women; women with barrier contraceptive devices; persons who have undergone nasal surgery |
| What are the top three lab findings in toxic shock syndrome? | elevated serum creatinine; thrombocytopenia; hypocalcemia |
| What are the major clinical signs and symptoms of toxic shock syndrome? | diarrhea, myalgia, vomiting, fever |
| What do staphylococcus enterotoxin cause? | food poisoning |
| Is there fever due to S. aureus enterotoxin induced diarrhea? | NO |
| Where are S. aureus enterotoxins coded? | many are phage-encoded |
| This is a gram-positive facultative anaerobe which is spore forming capable of producing diarrheal disease, emetic disease, and other opportunistic infections? | Bacillus cereus |
| What bacillus cereus toxin causes diarrheal disease due to increased cAMP? | Heat labile enterotoxin |
| What bacillus Cereus toxin causes emetic disease? | Heat stabile enterotoxin |
| Which B. cereus disease has a longer incubation and a longer duration (diarrheal or emetic)? | Diarrheal (caused by heat labile toxin) |
| Which B. cereus disease is due to ingestion of PRE-FORMED toxin? | Emetic disease (found in RICE) |
| Which foods would cause the diarrheal disease due to B cereus? | meat, vegetables, sauces |
| What is the difference between food poisoning due to S. aurues and B. cerues? | S. aureus has vomiting AND diarrhea |
| What kind of diarrhea is caused by B. cereus (watery, inflammatory, bloody)? | Watery |
| Studies show that non-carriers are inherently resisten to colonization by S. aureus T/F? | TRUE; may be due to host or bacterial factors |
| What are some places highly susceptible to MRSA? | outpatient clinics, sports settigns, tattoo parlors (many others) |
| What is bacteriophage typing useful for ? | Useful in tracking antibiotic resistance, investigating outbreaks in food poisoning |
| Where is the Penicilinase gene encoded for in S. aureus? | plasmid |
| Where is the MecA gene (responsible for methicillin resistance) encoded within the MRSA? | in the chromosome (rare transfer) |
| What gram positive, coagulase positive will you suspect if a patient has an infected wound and history of a dog bite? | Staph intermedius |
| What are the two coagulase negative Staphylococcus capable of causing disease in humans? | S. epidermidis, and S. saprophyticus |
| What are the infections caused by Staph epidermidis? | UTI (hospital aquired); osteomyelitis; endocarditis; bacteremia (immunosuppresed); endophtalmitis (ocular surgery); indwelling foreign devices |
| What protects Staphylococcus epidermidis from antibiotics when found on indwelling medical devices? | Biofilms |
| What is the 2nd most common cause of community-aquired UTI? | Staphylococcus saprophyticus |
| What does staphylococcus saprophyticus make that can increase the pH of urine? | urease |
| What is the benefit of coagulase for S. aureus? | forms a fibrin formation around the bacteria protecting it from phagocytosis |
| Staphylokinase is secreted from S. aureus to do what? | lyses fibrin clots (used to penetrate) |
| A patient has comes in with severe hypotension, rash, hx of vomiting and diarrhea and her hands and soles appear to be sloughing off. She is currently menstruating? | Toxic Shock Syndrome |
| Sexy staff often make people excited directly? | septic arthritis; skin infections; osteomyelitis; meningtis; pneumonia; endocarditis; DIRECT ORGAN INVOLEMENT |
| What is impetigo? | A contagious disease often in the face; vesicles led to pustules which crust over to become honey-colored, wet and flaky |
| What is currently being used to treat MRSA although resitance to it is slowly occuring? | Vancomycin |
| What gives S. epidermidis the ability to stick to medical devices? | Polysaccharide capsule (extracellular polymers) |
Created by:
lamsonma
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