Microbiology

Question 1

How do staph and strep bacteria tend to enter the body?

Answer 1

Staph - through sebaceous glands

Strep - through damage in skin

Question 2

What can toxins on staph aureus cause?

Answer 2

Toxic shock

Scalded skin syndrome

Question 3

What skin infections can staph aureus cause?

Answer 3

Rash
Folliculitis
Abscess
Carbuncle
Impetigo
Scalded skin syndrome

Question 4

Which staphylococcus is coagulase positive?

Answer 4

Staph aureus

Question 5

What are virulence factors?

Answer 5

The ways in which bacteria kill

Question 6

What are examples of staph aureus virulence factors?

Answer 6

Coagulase
Fibrinogen binding protein
Superantigens
Toxinoses (PVL (Panton-Valentine Leukotoxin), gamma and alpha toxin)
Protease
Capsule

Question 7

What are examples of staph aureus virulence factors?

Answer 7

Coagulase
Fibrinogen binding protein
Toxinoses
Adhesions
PVL (Panton-Valentine Leukotoxin)

Question 8

How does coagulase aid pathogenesis?

Answer 8

Physical protection that allows better adherence to a site

Question 9

What is TSST-1?

Answer 9

A toxin released by staph aureus that causes toxic shock syndrome
Gets into blood and causes rapidly progressing, life-threatening illness
Overstimulates immune response

Question 10

What are the clinical features of toxic shock syndrome?

Answer 10

Fever (39˚)
Diffuse malar rash and desquamation
Hypotension
>3 organ systems involved

Question 11

Why is toxic shock syndrome associated with menstrual toxic shock?

Answer 11

If a tampon is contaminated with staph aureus, TSST-1 gets into the blood stream via the vagina

Question 12

How do adhesions contribute to pathogenesis?

Answer 12

Increase ability to colonise a site

Bind to fibrinogen-binding, fibrontectin-binding and collagen-binding molecules

Question 13

What does PVL positive staph aureus cause?

Answer 13

Sepsis
Necrotising fasciitis
- very severe, life-threatening

Question 14

Who are at risk of staph epidermidis infection?

Answer 14

Immunocompromised

Question 15

Does staph epidermidis coagulate plasma?

Answer 15

No - coagulase negative

Question 16

What is MRSA?

Answer 16

Methylin resistant staph aureus associated with hospitals

Question 17

Describe streptococcus pyogenes?

Answer 17

Group A strep
Gram positive cocci in chains
Catalase negative
Beta haemolysis
Lancefield classification A

Question 18

What are examples of skin infections does strep pyogenes cause?

Answer 18

Impetigo
Cellulitis
Necrotising fasciitis

Question 19

What are examples of non skin conditions that strep pyogenes causes?

Answer 19

Pharyngitis, tonsillitis (sore throat)
Rheumatic fever
Glomerulonephritis

Question 20

What are the virulence factors of strep pyogenes?

Answer 20

Capsule
M-protein (lets it bind to several proteins)
Haemolysins
Superantigenic toxins
DNAases
Fibronectin-binding proteins

Question 21

What is impetigo?

Answer 21

Contagious infection of the superficial skin

Question 22

What is cellulitis?

Answer 22

Deeper skin infection with invasion oft he dermis and subcutaneous fat
Patients have fever, rights, nausea

Question 23

What is necrotising fasciitis?

Answer 23

Infection that penetrates deep, into muscles and other subcutaneous structures
Rapid destruction of connective tissue can lead to toxic shock, amputation

Question 24

What are the causative organisms for type 1 and 2 necrotising fasciitis?

Answer 24

1 - clostridia

2 - strep pyogenes, staph aureus

Question 25

What is streptomycin S (SLS)?

Answer 25

Pore-forming cytolysin - secretes substance that is toxic to cells

Question 26

How does a capsule contribute to pathogenesis?

Answer 26

Anti-phagocytic

Question 27

How does fibrinogen binding protein contribute to pathogenesis?

Answer 27

Adhesion

Question 28

How do haemolysins alpha, beta, delta and gamma contribute to pathogenesis?

Answer 28

Cytolytic

Question 29

How does coagulase contribute to pathogenesis?

Answer 29

Clots plasma

Question 30

How does fibrinolysin contribute to pathogenesis?

Answer 30

Digests fibrin

Question 31

How does leukocidin (PVL) contribute to pathogenesis?

Answer 31

Kills leukocytes

Question 32

How does protein A contribute to pathogenesis?

Answer 32

Anti-phagocytic

Question 33

What is the best antibiotic for staph aureus?

Answer 33

Flucloxacillin

Question 34

What antibiotics are effective against MRSA?

Answer 34

Doxycycline Co-trimoxazole Clindamycin Vancomycin (if more sick)

Question 35

Which antibiotic that is effective against MRSA should be avoided, and why?

Answer 35

Clindamycin - one of the 4Cs, carries risk of C. diff

Question 36

What is the key thing to know about staph epidermidis?

Answer 36

It is not as likely to be pathogenic as staph aureus - often just commensal

Question 37

What skin conditions can be caused by strep pyogenes (group A strep)?

Answer 37

``` Infected eczema Impetigo Cellulitis Necrotising fasciitis Erysipelas ```

Question 38

What is the treatment for strep pyogenes infection?

Answer 38

Penicillin | or flucloxacillin

Question 39

What is suspected if there is a little bit of redness in skin which looks like cellulitis but patient in much more pain than you would expect?

Answer 39

Necrotising fasciitis

Question 40

What is the treatment for necrotising fasciitis?

Answer 40

Immediate surgical debridement

Question 41

What are the most important fungal diseases?

Answer 41

Candidisais | Tinea

Question 42

What is the pathogenesis of fungal infections?

Answer 42

Fungus enters abraded or soggy skin Hyphae spread in stratum corner Infects keratinised tissues only Increased epidermal turnover causes scaling Inflammatory response provoked in the dermis Hair follicles and shafts involved Lesions grows outwards and heals in the centre, giving a 'ring' appearance

Question 43

What is the most common organism to cause fungal infections?

Answer 43

Trichophyton rubrum

Question 44

How are fungal infections diagnosed?

Answer 44

Clinical appearance Woods light Skin scrapings, nail clippings, hair

Question 45

Which part of a lesion should a sample be taken from?

Answer 45

The edge - as it grows outwards and heals in the centre, the outside is where the organisms are

Question 46

Why are fungal infections usually not cultured?

Answer 46

Can usually tell from appearance, takes ages and doesn't change treatment

Question 47

What is the treatment for a small fungal infection?

Answer 47

Clotrimazole cream | Topical amorolfine nail paint

Question 48

What is the treatment for an extensive fungal infection?

Answer 48

Oral terbinafine or itraconazole

Question 49

Which areas are candida infections common in?

Answer 49

Under breasts, groin, abdominal skin folds, nappy area in babies

Question 50

How is diagnosis of candida infection done?

Answer 50

Swab for culture

Question 51

What is the treatment for candida infection?

Answer 51

Clotrimazole cream | Oral fluconazole

Question 52

What are the most common examples of parasitic infections?

Answer 52

Lice | Scabies

Question 53

How does scabies present?

Answer 53

Intensely itchy rash affecting finger webs, wrists, genital area

Question 54

What is the treatment for parasitic infections?

Answer 54

``` malathion lotion Benzyl benzoate (not in children) ```

Question 55

What are examples of viral diseases that present in the skin?

Answer 55

HSV HPV Varicella-Zoster virus (chicken pox) Viral exanthems

Question 56

What are examples of viral exanthems?

Answer 56

``` Enterovirus Rubella EBV Adenovirus Dengue virus HIV ```

Question 57

What are the erythematous exanthems that tend to start on the face?

Answer 57

Measles (with bit of conjunctivitis) | Rubella

Question 58

What are the erythematous exanthems that tend to start on the trunk?

Answer 58

Scarlet fever

Question 59

What are the paulo-vesicular exanthems (raised bumps with fluid)?

Answer 59

Chickenpox

Question 60

What are exanthems of the extremities?

Answer 60

Hand foot and mouth disease