Microbiology

Question 1

define virulence

Answer 1

the capacity of a microbe to cause damage to the host

Question 2

list 5 virulence factors

Answer 2

adhesion- enables binding of the organism to host tissue

invasin - enables the organism to invade a host cell/ tissue

impedin - enables the organism to avoid host defense mechanism

aggressin - causes damage to the host directly

modulin - induces damage to the host cell indirectly

Question 3

list 6 virulence factors of staph aureus

Answer 3

fibrinogen binding protein

leukocidin (PVL)

TSST-1 (toxin)

adhesion

kills leukocytes

shock, rash, desquamation

Question 4

why is there many different presentation/ conditions and syndromes caused by staph aureus infection

Answer 4

lots of different strains and sub strains with different virulence factors

Question 5

what do toxins do

Answer 5

cause direct damage to immune system or systemic damage to host

Question 6

name 2 toxinoses caused by s. aureus

Answer 6

toxic shock, scaled skin syndrome

Question 7

name 6 skin staph aureus infections

Answer 7

rash, folliculitis, abscess, carbuncle, impetigo, scaled skin syndrome

Question 8

name symptoms of TSS

Answer 8

rapid progression (48hrs), high fever, vomiting, diarrhea, sore throat, muscle pain, diffuse macular rash and desquamation, hypotension

Question 9

what toxin causes scaled skin syndrome and what do they target

Answer 9

exfoliatin toxins

desmoglein-1 (DG-1)

Question 10

who gets SSS and where do they get it

Answer 10

neonates; face, axialla and groin

Question 11

what do superantigens do

Answer 11

overstimulate immmune system (activate 1 in 5 t cells when normal is 1 in 10000) causing massive release of cytokines and inappropriate immune response

Question 12

how does staph aureus cause TSS

Answer 12

on tampon diffuse through wall of vagina into bloodstream then superantigens overstimulate immune response

Question 13

name components invloved in adhesion

Answer 13

extra cellular matrix, fibrinogen binding, collagen binding

Question 14

name components of host defence evasion

Answer 14

superantigens, alpha toxin and PVL, coagulase

Question 15

what is PVL and what skin infections is it associated with

Answer 15

panton valentine leukocidin

reccurent furunculosis
sepsis
necrotising fascitis (PVL and alpha toxin linked with CA-MRSA responsible for NF)

Question 16

give features of nectorising pneumonia

Answer 16

precedes influenza like illness, rapid progression, acute resp distress, deterioration in pulmonary function

Question 17

strep pyogens is beta haemolytic- why is this important

Answer 17

as haemolysis breakdown of red blood cells- has power to do this in host and cause damage to tissues

Question 18

what skin infections can be cause by s. pyogenes

Answer 18

impetigo, cellulitis, NF

Question 19

where does s. pyogenes adhere to

Answer 19

oropharynx and nasopharynx on non ciliated cells covered in mucus

Question 20

name two components of s. pyogenes adhesion

Answer 20

hyaluronic acid, CD44 +ve keratinocytes

Question 21

how does s. pyogenes evade host defense

Answer 21

CAPSULEs

Question 22

give features of impetigo

Answer 22

highly contagious through contact with discharge on the face (usually face)

Question 23

name 6 GAS diseases

Answer 23

impetigo, cellulitis, erysipelas, NF, TSS, pyrogenic exotoxin

Question 24

what is GAS

Answer 24

group A streptocoocal

Question 25

what are features of erysipelas

Answer 25

localised, fever, rigours and nausea

Question 26

where in skin is a cellulitis infection

Answer 26

dermis

Question 27

name two components of GAS tissue/ cell destruction

Answer 27

hemolysins, stretolysin

Question 28

does s aureus or s pyrogenes cause TSS- why

Answer 28

both- as produce similar exo proteins, virulence factors and diseas mechanisms

Question 29

where is s pyogenes normally found

Answer 29

pharynx

Question 30

how does sebum protect from infection

Answer 30

fatty acids inhibit bacterial growth

Question 31

what does a skin swap showing staph epi mean

Answer 31

most likely a commensal

Question 32

MRSA is transient, what does this mean

Answer 32

colonies in skin come and go

Question 33

how can skin commensals protect from infection

Answer 33

competition with pathogens

Question 34

name three common skin commensals

Answer 34

staphylococcus epidermis corynebacterium sp. (diptheroids) propionobacterium so.

Question 35

when can skin commensals cause infection

Answer 35

if they enter the blood stream could cause infection

Question 36

cocci in bunches=

Answer 36

staph

Question 37

cocci in chains=

Answer 37

strep

Question 38

when do you take blood cultures to diagnose an infection

Answer 38

if patient is showing systemic symptoms

Question 39

ONLY 1 staph is coagulase positive, which one is it

Answer 39

s. aureus

Question 40

which is the most common type of beta haemolytic strep

Answer 40

group A

Question 41

how do you classify streptococci

Answer 41

haemolysis

Question 42

what are the 3 subdivisions of streptococci

Answer 42

alpha (partial) haemolysis beta (complete) haemolysis gamma (non) haemolytic

Question 43

name 2 alpha haemolytic strep and what they cause

Answer 43

strep. pneumonia (pneumonia) strep viridans (commensals, endocarditis)

Question 44

name 2 beta haemolytic strep and what they cause

Answer 44

group A strep (throat, skin infection) group B strep (neonatal meningitis) groups C, G ect

Question 45

name a non haemolytic strep and what it causes

Answer 45

enterococcus sp. (gut commensal, UTI)

Question 46

how do you distinguish staphylococci

Answer 46

coagulase testing

Question 47

name the coagulase positive staphylcocci and what it causes

Answer 47

staph aureus, wound, bone, joint and skin infections

Question 48

what type of environment does staphylococcus grow in best

Answer 48

is aerobic (best in air) and facultatively anaerobic (can grow without air)

Question 49

why does staph aureus test coagulase positive

Answer 49

as produces the enzyme coagulase

Question 50

what antibiotics are used to treat s aureus infections

Answer 50

FLUCLOXACILLIN

Question 51

what is MRSA

Answer 51

methicillin resistant staph aureus

Question 52

name 3 toxins produces by strains of s aureus and what they cause

Answer 52

enterotoxin- food poisening SSSST- staphylococcal scaled skin syndrome toxin PVL- panton valentine leucocidin

Question 53

why is flucloxacillin used to treat s aureus

Answer 53

as other antibiotics have much higher mortality rates

Question 54

name 7 skin infections caused by staph aureus

Answer 54

``` boils and carbuncles, minor skin sepsis', cellulitis, infected eczema, impetigo, wound infection, Staph scaled skin syndrome ```

Question 55

can antibiotics penetrate pus

Answer 55

no

Question 56

what are the treatment options for MRSA causing skin and soft tissue infections

Answer 56

NOT FLUCLOXACILLIN - doxycycline (oral) - co-trimoxazole - clindamycin - linezolid

Question 57

what are the treatment options for MRSA causing bloodstream infections

Answer 57

NOT FLUCLOXACILLIN - vancomycin - daptomycin

Question 58

are coagulase negative staph usually skin commensals or pathogens

Answer 58

commensals

Question 59

when can coagulase negative staph cause infections

Answer 59

in association with implanted material- produces slime that enables it to stick to prosthetic material

Question 60

in who can staph saprophyticus cause UTIs

Answer 60

in women of child bearing age

Question 61

are staph and strep cocci gram positive or negative

Answer 61

positive

Question 62

what environment to streptococci grow best in

Answer 62

aerobic and facultatively anaerobic

Question 63

are beta haemolytic steptococci pathogenic or commensal organisms

Answer 63

pathogenic

Question 64

name a toxin produced by beta haemolytic strep that causes damage to tissues

Answer 64

haemolysin

Question 65

what classifies beta haemolytic strep in groups (a, b, c...)

Answer 65

antigenic structure on surface (serological grouping)

Question 66

what infections does group A strep. pyogenes cause

Answer 66

infected eczema, impetigo, cellulitis, erysipelas, NF

Question 67

where is strep viridans a commensal of

Answer 67

mouth, throat, vagina

Question 68

what antibiotics for strep. pyogenes (group A strep)

Answer 68

penicillin, also flucloxacillin

Question 69

what is the treatment for NF

Answer 69

surgical debridement and antibiotics

Question 70

what are helpful diagnostic signs of NF

Answer 70

pain much worse than presentation, crepitous sound when you press it, air on xray, CT and MRI if very severe

Question 71

what is NF

Answer 71

necrotising facitis- bacterial infection spreading along fascial planes below skin surface causing rapid tissue destruction

Question 72

what are the two types of NF

Answer 72

type 1- mixed anaerobes and coliforms (post abdo surgery) | type 2- group A strep infection

Question 73

what antibiotic for NF

Answer 73

depends on microorganisms found on tissue taken from surgery

Question 74

what is the underlying problem of leg ulcers

Answer 74

vascular

Question 75

when should you take a swap from a leg ulcer

Answer 75

if signs of cellulitis or infection are present

Question 76

what organisms are worth treating if found on leg ulcers

Answer 76

strep pyogenes (group A), staph aureus, beta haemolytic strep, anaerobes (especially in diabetic patients)

Question 77

when is an ulcer likely to be associated with osteomyelitis

Answer 77

if there for over 2 months and bigger than 2 cm

Question 78

what is tinea

Answer 78

ringworm

Question 79

``` name the places affected by tinae form the name tinea capitis tinea barbae tinea corporis tinea manuum tinea unguium tinea cruris tinea pedis ```

Answer 79

``` captitis- head barbae- beard corporis- body manuum- hand unguium- nails cruris- groin pedis- foot (athletes foot) ```

Question 80

describe the pathogenesis of ring worm

Answer 80

fungus enters through abraded or soggy skin hyphae spread in stratum corneum infects keratonised tissues only (skin, hair, nails) increased epidermal turnover causes scaling inflammatory response provoked (dermis) hair follicles and shafts invaded lesion grows outward and heals in centre giving a ring appearance

Question 81

who does ringworm generally and scalp ringworm gernerally affect

Answer 81

generally men scalp children

Question 82

what are the sources of dermatophyte infections (fungal)

Answer 82

other humans (most common) animals soil

Question 83

name another fungal organism spread by human to human transmission

Answer 83

trichophyton rubrum

Question 84

how do you diagnose fungal (dermatophyte) infections

Answer 84

clinical appearance woods light (fluorescence) skin scrapings, nail clippings, hair

Question 85

where should skin scrapings be taken from

Answer 85

the edge of the scaly lesion

Question 86

how do you treat small areas of fungally infected skin or nails

Answer 86

clotrimazole (canestan) cream/ similar | topical nail paint (amorolfine)

Question 87

how do you treat fungal scalp infections

Answer 87

terbinafine orally | itraconazole orally

Question 88

where is candida intertrigo seen and why

Answer 88

intertrigo (in skin folds)- under breasts, groin areas, abdo folds, nappy areas

Question 89

how do you treat candida intertrigo

Answer 89

clotrimazole cream, oral fluconazole

Question 90

what bug causes scabies

Answer 90

sarcoptes scabiei

Question 91

what is norwegian scabies

Answer 91

chronic crusted form of scabies

Question 92

where does scabies affect

Answer 92

finger webs, wrists, genital area

Question 93

how do you treat scabies

Answer 93

malathion lotion applied overnight to whole body and washed off next day benzyl benzoate

Question 94

what are pediculosis

Answer 94

lice capitis- head corporis- body

Question 95

what is phthirus pubis

Answer 95

pubic louse

Question 96

what is the treatment for lice

Answer 96

malathion

Question 97

why are gram positive organisms a worry for infection control

Answer 97

can survive in environment because of cell wall structure

Question 98

what skin conditions require single room isolation for infection control

Answer 98

group a strep infection MRSA infection scabies (long sleeve gown for norwegian)

Question 99

what organisms causes athletes foot

Answer 99

trichophyton rubrum

Question 100

what is the treatment for tineae pedis

Answer 100

``` oral terinafine (if nails involved) topical clotrimazole (if just skin) ```

Question 101

what two organisms cause impetigo

Answer 101

staph aureus and strep pyrogenes

Question 102

how do you treat strep pyogenes impetigo

Answer 102

oral penicillin

Question 103

what extra infection control precautions for a child with impetigo

Answer 103

droplet and contact precautions

Question 104

what bacterial can cause infection from cat and dog bites

Answer 104

pasturella multocida- gram negative bacilli

Question 105

what are the presenting features of rabies

Answer 105

viral encephalitis- fever, altered mental state

Question 106

what is the treatment for rabies

Answer 106

post exposure vaccination, hyperimmune globulin

Question 107

how can you get rabies in UK

Answer 107

bite from UK bat

Question 108

is rabies a virus or bacteria

Answer 108

virus

Question 109

dermatophyte infections can be treated with which two drugs when small areas or skin and nails are implicated

Answer 109

clotrimazole (cream) | amorolfine (nail paint)

Question 110

how can candida intertrigo be treated (3)

Answer 110

clotrimazole cream nystatin (oral/topical) oral fluconazole

Question 111

in a diabetic patient with a severe leg ulcer, what antibiotic could be given for anaerobic cover

Answer 111

metronidazole

Question 112

what class of haemolytic strep is S. pneumoniae

Answer 112

alpha

Question 113

what class of haemolytic strep is S. agalactiae

Answer 113

alpha

Question 114

what class of haemolytic strep is S. pyogenes

Answer 114

beta

Question 115

what class of haemolytic strep is S. viridans

Answer 115

alpha

Question 116

what class of haemolytic strep are bowel commensals

Answer 116

trick question= non- haemolytic

Question 117

what bacteria commonly causes UTIs in women of child bearing age

Answer 117

atpah, saprophyticus (young sexually active girls)

Question 118

what are the two types of NF

Answer 118

type 1- caused by aerobic/ anaerobic bac (usually after surgery) type 2- associated with group A strep arises spontaneously in healthy individuals

Question 119

what is nokilskys sign

Answer 119

when slight rubbing causes exfoliation of the outermost layer (seen in staph scaled skin syndrome)

Question 120

what is the most common causative organism of tinea fungal infections

Answer 120

trichophytom rubrum

Question 121

what organisms causes golden crusting on infections

Answer 121

S, aureus

Question 122

which antibiotics can be used to treat step. pyogenes

Answer 122

flucloxicillin or penicllin

Question 123

what bacteria sauses SSSS

Answer 123

staph aureus

Question 124

what class of beta haemolytic strep is associated with neonatal menigitis

Answer 124

B

Question 125

would a patient with group A strep infection need isolation

Answer 125

no

Question 126

what investigations are best for dermatophyte infections

Answer 126

woods light (fluorescence), skin scrapings, nail clippings or hair sampling fro culturing

Question 127

how would an infection with scabies be treated

Answer 127

benzyl benzoate

Question 128

what bacteria causes acne of the upper arm and armpit

Answer 128

propionobacterium

Question 129

is staph epidermis coagulase positive or negative

Answer 129

negative

Question 130

what bacteria causes sphillis

Answer 130

treponema pallidum