Bacterial, Viral, Fungal Infections I

Question 1

initiation of infection: those that enter through bites/scratches

Answer 1

Streptococci., Mixed aerobic/anaerobic

bacteria, Pasteurella, many more species

Question 2

initiation of infection: those that enter through trauma

Answer 2

Cellulitis, fasciitis, myonecrosis, bone inf.

Question 3

causes of pasteurella multocida

Answer 3

deep skin infection, bacteriemia, endocarditis, osteomyelitis, septic arthritis

Question 4

what is pasteurella multocida

Answer 4

primarily zoonotic and part of normal flora of upper RT

Question 5

how does one get pasteurella multocida

Answer 5

via a cat or dog by bite or scratches, licking of broken skin,

Question 6

infections in keratinized epithelium and epidermis

Answer 6

keratinized epithelium: dermatophytic fungi

epidermis: warts (HPV), impetigo (staph `aureus and group A strep), cold sores (HHV-1)

Question 7

infections in dermis and hair follicles

Answer 7

dermis: cellulitis and erysipelas

hair follicles: folliculitis and abscesses

Question 8

infection in sebaceous glands

Answer 8

acne (propionibacterium acne)

Question 9

bacteria seen in hot tub folliculitis

Answer 9

pseudomonas

Question 10

where is streptococci normal seens

Answer 10

as part of normal flora in oral cavity, GI, and genital tract

Question 11

features of strep

Answer 11

gram positive cocci in chains, classified based on hemolysis on blood agar

Question 12

features of strep pyogenes

Answer 12

gram positive, beta hemolytic, strep that form pus and can occasionally cause purulent infections, infections can be in upper skin layer or it can go deep

Question 13

toxin of strep pyogenes

Answer 13

pyrogenic exotoxin (SPE) once called erythrogenic toxin
minority of strain carry this toxin which is carried on a phage

Question 14

what does the pyrogenic exotoxin do

Answer 14

stimulates cytokine release causing multiple effects like: red rash on skin –> scarlet fever

Question 15

how is pharyngitis spread

Answer 15

direct contact or aerosol

Question 16

carrier rate of untreated pharyngitis and where it is located

Answer 16

1-4 weeks or more after infection as organisms in in throat and sometimes anus

Question 17

type of infection is scarlet fever

Answer 17

group A beta strep infection

Question 18

symptoms of scarlet fever

Answer 18

strep throat with a characteristic rash
deep red color cheeks, temples, buccal mucosa
strawberry tongue
punctuate hemorrhages on palate
sandpaper rash on trunks, arms, and legs

Question 19

the exotoxin released from strep pyogenes can be attributed to what symptom in scarlet fever

Answer 19

sandpaper rash on trunks, arms, and legs

Question 20

what is staph aureus

Answer 20

gram positive cocci found in clusters and in thick cell walls
often found intracellularly in granulocytes

Question 21

cultural characteristics of staph aureus

Answer 21

grows on blood agar with aerobic conditions
white colony but can become yellow with age
usually beta hemolytic

Question 22

positive for staph aureus in about 30% of population

Answer 22

anterior nares

Question 23

virulence factors of staph aureus

Answer 23

coagulase, exotoxin, hemolysins, leukocidins

Question 24

diseases caused by staph infections

Answer 24

scalded skin syndrome, S. aureus exfoliatins, toxic shock syndrome,

Question 25

how does one get scalded skin syndrome

Answer 25

toxin is absorbed into the blood stream with erythema and intraepidermal desquamation occurring at remote sites

Question 26

can staph aureus be isolated from desquamation sites of scalded skin syndrome

Answer 26

no

Question 27

what is occurring staph aureus exfoliatins

Answer 27

exfoliatins are leading to intercellular splitting of the epidermis -- between the stratum spinosum and stratum granulosum by disruption of the intercellular junctions

Question 28

in s. aureus exfolatins, if toxin is produced at the site of infection what happens

Answer 28

epithelial desquamation at the remote sites of the body --> staph scalded skin syndrome

Question 29

what is toxic shock syndrome characterized by

Answer 29

high fever, vomiting, diarrhea, sore throat, muscle pain, shock within 48 hours with renal and hepatic damage also skin rash, strawberry tongue

Question 30

describe what happens after skin rash in toxic shock syndrome

Answer 30

desquamation at a deeper level than scalded skin syndrome

Question 31

what is the toxin in toxic shock syndrome

Answer 31

pyrogenic toxin called toxic shock syndrome toxin-1 (TSST-1)

Question 32

what does TSST-1 do

Answer 32

stimulates release of cytokines and direct toxic effects on endothelial cells Stimulates enhanced T-lymphocyte responses by direct interaction with surface receptors on T cell.

Question 33

situation where TSS is usually seen

Answer 33

when woman is menstruating and wears tampon for long periods of time -- provides environment for products of toxin which is absorbed from the local site (1 in 5 women have staph aureus as part of normal flora of vagina) non menstrual TSS does occur

Question 34

cause of impetigo and causative agent

Answer 34

insect bite or minor abrasion | staph aureus or group A strep

Question 35

what is impetigo characterized by

Answer 35

–Small vesicles with erythema | –Become pustular and later crusted

Question 36

complication of impetigo

Answer 36

post strep glomerulonephritis 2-4 weeks after skin infection but only if caused by strep pygogenes aka group A strep

Question 37

what can occur after beta strep infections

Answer 37

acute rheumatic fever

Question 38

what are characteristics of acute rheumatic fever

Answer 38

– Inflammatory disease • Fever, carditis, subcutaneous nodules, migratory polyarthritis – Heart valve damage • Murmurs, cardiac enlargement. • Repeat infections lead to progressive damage CCSEA and P-FACE chorea, carditis, subcutaneous nodules, erythematous marginatum, arthritis, pr elongation, fever, arthralgia, increased CRP and ESR

Question 39

pathogenesis of acute glomerulonephritis

Answer 39

antigen-antibody complexes in the kidney (type III hypersensitivity)

Question 40

what population acute glomerulonephritis after strep infection usually seen in

Answer 40

children

Question 41

other than straph aureus what other organism can cause TSS

Answer 41

strep pyogenes

Question 42

can staph aureus be found together strep pyogenes in impetigo

Answer 42

yeah in about 30% of cases

Question 43

coagulase and catalase positive

Answer 43

staph aureus

Question 44

is coagulase a toxin

Answer 44

no but it plays a role in its pathogenesis

Question 45

coagulase -- what does staph coated with fibrin prevent

Answer 45

phagocytosis (helps localize the lesion)

Question 46

other biological substances that staph aureus produces

Answer 46

Hemolysins, hyaluronidase, nuclease, lipase, protease

Question 47

major cytotoxin of staph aureus

Answer 47

staph aureus alpha toxin

Question 48

characteristic of alpha toxin

Answer 48

-- chromosomally encoded, low molecular weight protein – Causes necrosis or death in experimental animals -- Causes certain mammalian cell membranes to leak through pores formed by toxin – Causes RBC’s to lyse.

Question 49

what is panton valentine leukocidin (PVL)

Answer 49

it is a cytotoxin that lyses neutrophils and releases enzymes that damages host cells

Question 50

what is PVL associated with

Answer 50

- severe pneumonia - severe skin infections - common in community acquired methicillin resistant strains