Osteomyelitis - Staph and other Pathogens - Atchley Flashcards
1
Q
gram positive cocci
A
- staphylococci
- streptococci
- enterococci (once a type of strep)
2
Q
catalase
A
- splits hydrogen peroxide into water and O2
- bubbles if positive
- test to differentiate strep and staph
3
Q
staphylococci
A
- catalase positive and gram positive
- arranged in clusters
- coagulase + –> staph aureus (fibrin blood clots) –> ferments mannitol (yellow)
- coagulase - –> staph saprophyticus and epidermidis –> does not ferment mannitol (pink)
- mannitol salt agar (7.5% NaCl)
4
Q
streptococci
A
- catalase negative and gram positive
- arranged in chains
- alpha hemolysis –> strep viridans and pneumonia
- beta hemolysis –> strep pyogenes (GAS) and agalactiae (GBS)
- gamma hemolysis –> strep Bovis and faecalis
5
Q
what organism looks like staph aureus on mannitol agar?
A
enterococcus faecalis
6
Q
staph aureus
A
- gram +
- beta hemolytic (total hemolysis)
- coagulase +
- ferments mannitol
- colonized in nose
7
Q
staph aureus virulence factors
A
- protein A –> binds IgG Fc –> prevents opsonization/phagocytosis
- coagulase –> fibrin coat
- hemolysins and leukocidins –> lyse RBCs and WBCs
- Penicillinase –> degrades penicillin
- hyaluronidase –> digest connective tissue
- lipase –> degrade fat and oil
- protease –> destroy tissue proteins
- exfoliatin (exotoxin) –> scalded skin syndrome (skin slough)
- enterotoxin –> heat stable exotoxin
- TSST –> superantigen; release TNF-alpha and IL-1
- PVL –> kills WBCs and tissues by forming pores in leukocytes –> necrotizing skin/pneumoniae
8
Q
staph aureus toxin related diseases
A
- food poisoning (enterotoxins) –> meats and mayo; nausea and vomiting (common); diarrhea (rare)
- Toxic Shock Syndrome (TSST-1) –> fever, shock, red rash, diarrhea; peeling of palms/soles; tampons aka packing; organ system failure
- scalded skin syndrome (exfoliatin) –> skin sloughs off –> liquify stratum granulosum and detach keratinocytes (heals with no scar)
9
Q
staph aureus infectious/inflammatory diseases
A
- bullous impetigo (only staph aureus) –> superficial skin infection; children; skin blistering
- pneumonia –> lobar pneumonia (rare)
- acute endocarditis –> healthy tissue; no preexisting heart valve
- osteomyelitis –> children (leg long bones); adults (spine); hematogenous spread; tissue damage
- cellulitis (usually strep pyogenes) –> deep dermis and subq infection
- abscesses –> pockets of pus (folliculitis, furuncle, carbuncle)
10
Q
impetigo can be caused by what 2 organisms?
A
- staph aureus (common)
- strep pyogenes (rare)
11
Q
what causes subacute endocarditis?
A
- strep viridans
- slower onset of symptoms
- mouth flora, dental procedures
- history of valve abnormality
12
Q
organism of central lines and IV drug abusers?
A
staph aureus
-can lead to sepsis
13
Q
organisms that cause osteomyelitis
A
- staph aureus (main)
- strep pneumonia
- strep pyogenes
- salmonella in sickle cell patients
14
Q
puncture wound through a shoe?
A
pseudomonas
15
Q
2 organisms that can cause foliculitis?
A
staph (common) and strep (rare)
16
Q
MRSA - methicillin resistant staph aureus
A
- resistant to beta lactams
- alters PBP (blocks binding) due to mecA gene
- treatment: vancomycin, daptomycin, linezolid
17
Q
staph epidermidis
A
- nosocomial infections –> blood culture contaminant, prosthetic devices (forms biofilms)*
- always methicillin resistant
- coagulase neg, novobiocin sensitive*
18
Q
staph saprophyticus
A
- 2nd most common cause UTIs in active women
- nitrite neg
- E. coli is #1 cause UTIs (nitrite pos)
- honeymooner cystitis
- coagulase neg, novobiocin resistant*
19
Q
strep galloylyticus
A
- high chance of colon cancer
- do colonoscopy
20
Q
strep pyogens GAS
A
- strep throat
- beta hemolytic
- bacitracin sensitive*
21
Q
strep pyogenes virulence factors
A
- M protein –> autoantibodies against endocardium and synovial connective tissue –> mitral valve damage
- streptolysin O –> digests RBCs (hemolysins); ASO titer to look for antibodies of once infected strep
- streptococcal pyrogenic exotoxin –> scarlet fever and toxic shock like syndrome
- streptokinase –> activate plasminogen –> digest fibrin clot
- hyaluronidase –> break connective tissue
22
Q
strep pyogenes infections
A
- strep throat
2. skin infections (ex. impetigo, folliculitis, #1 cause of cellulitis)*
23
Q
strep pyogens toxin mediated disease
A
- scarlet fever –> strep throat, sunburn skin rash post fever, strawberry tongue; spare palms/soles; “sandpaper skin”
- necrotizing fasciitis –> infection of deep tissues; gangrene; pyogenic exotoxin; muscle fascia
24
Q
3 types of necrotizing fasciitis
A
- type 1: polymicrobial and anaerobes (bactericides, clostridium); vibrio vulnificus (saltwater)
- type 2: strep pyogenes flesh eating bacteria; sometimes staph aureus
- type 3: gas gangrene (clostridium)
25
Q
strep pyogenes autoimmune disease
A
- rheumatic fever –> type 2 hypersensitivity; M protein targets joints and heart valves
- post streptococcal glomerularnephritis –> hypersensitivity type 3; acute kidney failure (reversible)
26
Q
infectious diseases that have rashes of the palms and soles
A
- cocksackie virus: hand, foot, and mouth disease
- Rocky Mountain spotted fever
- syphilis
27
Q
stigma of acute endocarditis
A
- Janeway lesions –> hemorrhagic macules on hands/feet
- osler nodes –> lumps on fingers/toes
28
Q
strep agalactiae GBS
A
- produces CAMP factor (arrowhead) –> enhance beta hemolysis
- bacitracin resistant*
29
Q
strep agalactiae GBS diseases
A
- serious in babies –> meningitis, pneumonia, sepsis
- peaks in < 3 months in babies
- carried vaginally by 25% of women –> screen 36 weeks*
30
Q
strep pneumonia
A
- alpha hemolytic, gram + in pairs
- diplococci –> lancets
- polysaccharide capsule
- asplenic –> high risk for sepsis with encapsulated organisms
- IgA protease and pneumolysin –> green halo
- # 1 cause of meningitis and pneumonia in adults**
- # 1 cause of otitis media in children**
- lobar pneumonia
31
Q
strep viridans
A
- mouth flora –> dental carries (strep mutans)
- alpha hemolytic
- subacute endocarditis (strep sanguis) –> affect abnormal heart valves (mitral)
- adhere to platelets by producing dextran to bind fibrin
32
Q
enterococcus GDS
A
- normal gut flora
- grow in 6.5% NaCl and bile –> also grows staph
- nitrite negative…E. coli is nitrite +
- UTIs and endocarditis
- faecalis ferments mannitol salt
- resistant to vancomycin
33
Q
strep gallolyticus aka strep bovis
A
- normal gut flora
- colon cancer –> order colonoscopy
- grows in bile, not salt
34
Q
optochin
A
- strep viridans resistant
- strep strep pneumonia sensitive
35
Q
bacitracin
A
- GBS resistant
- GAS sensitive
36
Q
CAMP
A
- GBS positive
- GAS negative
