Microbiology 2

Question 1

What are three features of skin that prevent against infection?

Answer 1

• Dryness: dries out the organism
• Sebum: inhibits bacterial growth
• Competitive flora

Question 2

What are some protective bacterial flora?

Answer 2

Staph. Epidermidis, Corynebacterium, Propionibacterium

Question 3

How do you investigate a skin lesion where the surface is broken but is relatively superficial?

Answer 3

Swabs

Question 4

How do you investigate a skin lesion where the surface is broken but is relatively deep?

Answer 4

Pus or tissue sample +/- blood cultures

Question 5

How will staph aureus show on blood agar?

Answer 5

Golden

Question 6

How will coagulase - staph show on blood agar?

Answer 6

White

Question 7

Which variants of Staph are coagulase +?

Answer 7

Staph aureus only

Question 8

Which variants of Staph are coagulase -?

Answer 8

All types except staph aureus, a good example is staph epidermidis

Question 9

What will staph and strep be on a gram stain?

Answer 9

Positive

Question 10

An organism is gram + cocci in clusters, what is this likely to be?

Answer 10

Staphylococcus

Question 11

An organism is gram + cocci in chains, what is this most likely to be?

Answer 11

Streptococcus

Question 12

Once you have decided an organism is staph, what test will decipher if it is staph aureus?

Answer 12

Coagulase test will be positive

Question 13

Once you have decided an organism is strep, what test will decipher if it is Group A strep?

Answer 13

Haemolysis- will be B (complete) haemolysis

Question 14

In what conditions will staph aureus grow?

Answer 14

Aerobic and facultatively anaerobic

Question 15

Does staph aureus produce enzymes?

Answer 15

Yes (coagulase is an enzyme)

Question 16

Where does staph aureus usually cause infections?

Answer 16

Bone, skin, joint and wounds

Question 17

What is the antibiotic of choice for staph aureus?

Answer 17

Flucloxacillin

Question 18

Can MRSA be treated with flucloxacillin?

Answer 18

No

Question 19

What are some antibiotic options for MRSA?

Answer 19

Doxycycline, co-trimoxazole, clindamycin, vancomycin

Question 20

What is the enterotoxin produced by staph aureus associated with?

Answer 20

Food poisoning

Question 21

What are some skin infections which staph aureus can cause?

Answer 21

Minor skin sepsis
Cellulitis
Infected eczema
Impetigo
Wound infections

Question 22

Where are most other staph organisms found?

Answer 22

As skin commensals, not usually pathogenic

Question 23

When do coagulase - staph cause infections?

Answer 23

In association with foreign devices

Question 24

What can staph saprophyticus cause?

Answer 24

UTIs in women of child bearing age

Question 25

What conditions does strep grow in?

Answer 25

Aerobic and facultatively anaerobic

Question 26

How is streptococci classified?

Answer 26

Haemolysis on blood agar

Question 27

What does beta haemolytic strep mean?

Answer 27

Complete haemolysis- always pathogenic

Question 28

What does alpha haemolytic strep mean? Give examples.

Answer 28

Partial haemolysis e.g. Strep pneumoniae, strep viridans

Question 29

Where is strep viridans usually found? What can it cause?

Answer 29

Commensal of the mouth, throat, vagina | May cause infective endocarditis

Question 30

In terms of skin infection, which type of strep is the most important?

Answer 30

Group A beta haemolytic strep

Question 31

How is beta haemolytic strep further classified?

Answer 31

Based on antigenic surface structure

Question 32

What can group A strep cause?

Answer 32

Throat and severe skin infections

Question 33

What does group B strep cause?

Answer 33

Meningitis in neonates

Question 34

What are some skin infections that group A beta haemolytic strep can cause?

Answer 34

Infected eczema Impetigo Cellulitis Necrotising fasciitis

Question 35

What is an example of a group A beta haemolytic strep which can cause impetigo, cellulitis and necrotising fasciitis?

Answer 35

Strep pyogenes

Question 36

Group A strep are further divided into M protein groups. What are M1 and M3?

Answer 36

The major serotypes

Question 37

Group A strep are further divided into M protein groups. What are M18 and M3?

Answer 37

Severe invasive disease

Question 38

Describe impetigo?

Answer 38

This is a skin infection under the surface in the stratum corneum. It usually affects the face and may be linked with the lymphatic system.

Question 39

Is impetigo infectious?

Answer 39

Highly contagious through contact with discharge from the face

Question 40

Describe cellulitis?

Answer 40

A deeper skin infection in the dermis, but not associated with necrosis

Question 41

Describe necrotising fasciitis?

Answer 41

Group A strep penetrates the mucus membranes and develops in lesions which rapidly destroys connective tissue

Question 42

Do all skin infections require antibiotics?

Answer 42

Minor ones may not

Question 43

What antibiotics target Group A strep?

Answer 43

Mainly penicillin, though flucloxacillin may also work

Question 44

What is the treatment for necrotising fasciitis?

Answer 44

Immediate surgical debridement or amputation and antibiotics

Question 45

How will necrotising fasciitis present?

Answer 45

Little to see on the skin but will cause severe pain

Question 46

What are group 1 and 2 types of necrotising fasciitis?

Answer 46

1- mixed coliforms and anaerobes (usually post-abdominal surgery) 2- group A strep

Question 47

When should you take swabs of leg ulcers?

Answer 47

If signs of infection/cellulitis are present

Question 48

What antibiotic treats anaerobes?

Answer 48

Metronidazole

Question 49

What is the main fungal infection of skin?

Answer 49

Tinea (ringworm)

Question 50

What are TINEA: a) capitus b) barbae c) corporis d) manuum e) unguium f) cruris g) pedis

Answer 50

a) head b) beard c) body d) hand e) nail f) groin g) foot

Question 51

What is the common name for tine pedis?

Answer 51

Athlete's foot

Question 52

Where do fungi enter the skin?

Answer 52

Abraded or soggy skin

Question 53

Where do fungi only infect?

Answer 53

Keratinised surfaces

Question 54

Which sex is more likely to be affected by tinea infections? Which age group are they most common in?

Answer 54

- Males | - Children

Question 55

Where do tinea infections come from?

Answer 55

Mainly from other humans, though can be from animals or soil

Question 56

How do the lesions of tinea appear?

Answer 56

The lesions grow outwards and heal in the middle, giving a ring appearance

Question 57

What are some diagnostic tests for tinea infection?

Answer 57

- Fluorescence (Wood's lamp) | - Skin scrapings for microscopy and culture

Question 58

How do you treat small tinea infected areas?

Answer 58

Clotrimazole cream or topical nail paint

Question 59

What do you treat tinea corporis with?

Answer 59

Terbinafine

Question 60

What is the most common organism causing tinea infections?

Answer 60

Trichophyton Rubrum

Question 61

Where does microsporum canis come from?

Answer 61

Cats and dogs (cause of tinea infection)

Question 62

Where do candida infections occur?

Answer 62

Skin folds where the area is warm and moist e.g. under breasts, groin areas, under abdominal skin folds

Question 63

How do you treat candida infections?

Answer 63

Clometrizole cream or oral fluconazole

Question 64

What is Norwegian scabies?

Answer 64

A chronic, crusted form of scabies which is highly infectious

Question 65

What will scabies present with?

Answer 65

Intensely itchy rash affecting finger webs, wrists and genital areas

Question 66

How do you treat scabies?

Answer 66

- Malathion lotion applied overnight and then washed off | - Benzyl benzoate

Question 67

Who should benzyl benzoate not be used in?

Answer 67

Children

Question 68

Who are some examples of infectious patients who would need in a separate room?

Answer 68

- MRSA - Group A strep - Scabies