Osteomyelitis - Staph and other Pathogens - Atchley

Question 1

gram positive cocci

Answer 1

1. staphylococci
2. streptococci
3. enterococci (once a type of strep)

Question 2

catalase

Answer 2

• splits hydrogen peroxide into water and O2
• bubbles if positive
• test to differentiate strep and staph

Question 3

staphylococci

Answer 3

• 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)

Question 4

streptococci

Answer 4

• 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

Question 5

what organism looks like staph aureus on mannitol agar?

Answer 5

enterococcus faecalis

Question 6

staph aureus

Answer 6

• gram +
• beta hemolytic (total hemolysis)
• coagulase +
• ferments mannitol
• colonized in nose

Question 7

staph aureus virulence factors

Answer 7

1. protein A –> binds IgG Fc –> prevents opsonization/phagocytosis
2. coagulase –> fibrin coat
3. hemolysins and leukocidins –> lyse RBCs and WBCs
4. Penicillinase –> degrades penicillin
5. hyaluronidase –> digest connective tissue
6. lipase –> degrade fat and oil
7. protease –> destroy tissue proteins
8. exfoliatin (exotoxin) –> scalded skin syndrome (skin slough)
9. enterotoxin –> heat stable exotoxin
10. TSST –> superantigen; release TNF-alpha and IL-1
11. PVL –> kills WBCs and tissues by forming pores in leukocytes –> necrotizing skin/pneumoniae

Question 8

staph aureus toxin related diseases

Answer 8

1. food poisoning (enterotoxins) –> meats and mayo; nausea and vomiting (common); diarrhea (rare)
2. Toxic Shock Syndrome (TSST-1) –> fever, shock, red rash, diarrhea; peeling of palms/soles; tampons aka packing; organ system failure
3. scalded skin syndrome (exfoliatin) –> skin sloughs off –> liquify stratum granulosum and detach keratinocytes (heals with no scar)

Question 9

staph aureus infectious/inflammatory diseases

Answer 9

1. bullous impetigo (only staph aureus) –> superficial skin infection; children; skin blistering
2. pneumonia –> lobar pneumonia (rare)
3. acute endocarditis –> healthy tissue; no preexisting heart valve
4. osteomyelitis –> children (leg long bones); adults (spine); hematogenous spread; tissue damage
5. cellulitis (usually strep pyogenes) –> deep dermis and subq infection
6. abscesses –> pockets of pus (folliculitis, furuncle, carbuncle)

Question 10

impetigo can be caused by what 2 organisms?

Answer 10

• staph aureus (common)

- strep pyogenes (rare)

Question 11

what causes subacute endocarditis?

Answer 11

• strep viridans
• slower onset of symptoms
• mouth flora, dental procedures
• history of valve abnormality

Question 12

organism of central lines and IV drug abusers?

Answer 12

staph aureus

-can lead to sepsis

Question 13

organisms that cause osteomyelitis

Answer 13

1. staph aureus (main)
2. strep pneumonia
3. strep pyogenes
4. salmonella in sickle cell patients

Question 14

puncture wound through a shoe?

Answer 14

pseudomonas

Question 15

2 organisms that can cause foliculitis?

Answer 15

staph (common) and strep (rare)

Question 16

MRSA - methicillin resistant staph aureus

Answer 16

• resistant to beta lactams
• alters PBP (blocks binding) due to mecA gene
• treatment: vancomycin, daptomycin, linezolid

Question 17

staph epidermidis

Answer 17

• nosocomial infections –> blood culture contaminant, prosthetic devices (forms biofilms)*
• always methicillin resistant
• coagulase neg, novobiocin sensitive*

Question 18

staph saprophyticus

Answer 18

• 2nd most common cause UTIs in active women
• nitrite neg
• E. coli is #1 cause UTIs (nitrite pos)
• honeymooner cystitis
• coagulase neg, novobiocin resistant*

Question 19

strep galloylyticus

Answer 19

• high chance of colon cancer

- do colonoscopy

Question 20

strep pyogens GAS

Answer 20

• strep throat
• beta hemolytic
• bacitracin sensitive*

Question 21

strep pyogenes virulence factors

Answer 21

1. M protein –> autoantibodies against endocardium and synovial connective tissue –> mitral valve damage
2. streptolysin O –> digests RBCs (hemolysins); ASO titer to look for antibodies of once infected strep
3. streptococcal pyrogenic exotoxin –> scarlet fever and toxic shock like syndrome
4. streptokinase –> activate plasminogen –> digest fibrin clot
5. hyaluronidase –> break connective tissue

Question 22

strep pyogenes infections

Answer 22

1. strep throat

2. skin infections (ex. impetigo, folliculitis, #1 cause of cellulitis)*

Question 23

strep pyogens toxin mediated disease

Answer 23

1. scarlet fever –> strep throat, sunburn skin rash post fever, strawberry tongue; spare palms/soles; “sandpaper skin”
2. necrotizing fasciitis –> infection of deep tissues; gangrene; pyogenic exotoxin; muscle fascia

Question 24

3 types of necrotizing fasciitis

Answer 24

1. type 1: polymicrobial and anaerobes (bactericides, clostridium); vibrio vulnificus (saltwater)
2. type 2: strep pyogenes flesh eating bacteria; sometimes staph aureus
3. type 3: gas gangrene (clostridium)

Question 25

strep pyogenes autoimmune disease

Answer 25

1. rheumatic fever --> type 2 hypersensitivity; M protein targets joints and heart valves 2. post streptococcal glomerularnephritis --> hypersensitivity type 3; acute kidney failure (reversible)

Question 26

infectious diseases that have rashes of the palms and soles

Answer 26

- cocksackie virus: hand, foot, and mouth disease - Rocky Mountain spotted fever - syphilis

Question 27

stigma of acute endocarditis

Answer 27

- Janeway lesions --> hemorrhagic macules on hands/feet | - osler nodes --> lumps on fingers/toes

Question 28

strep agalactiae GBS

Answer 28

- produces CAMP factor (arrowhead) --> enhance beta hemolysis - bacitracin resistant*

Question 29

strep agalactiae GBS diseases

Answer 29

- serious in babies --> meningitis, pneumonia, sepsis - peaks in < 3 months in babies - carried vaginally by 25% of women --> screen 36 weeks*

Question 30

strep pneumonia

Answer 30

- 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

Question 31

strep viridans

Answer 31

- 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

Question 32

enterococcus GDS

Answer 32

- 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

Question 33

strep gallolyticus aka strep bovis

Answer 33

- normal gut flora - colon cancer --> order colonoscopy - grows in bile, not salt

Question 34

optochin

Answer 34

- strep viridans resistant | - strep strep pneumonia sensitive

Question 35

bacitracin

Answer 35

- GBS resistant | - GAS sensitive

Question 36

CAMP

Answer 36

- GBS positive | - GAS negative