Microbiology bacterial/fungal/parasitic

Question 1

Staphylococcus

• gram stain appearance
• 2 types?

Answer 1

-Gram + cocci in clusters

-coagulase + e.g. staph aureus (golden)
coagulase - e.g. staph epidermis

Question 2

Staphylococcus Aureus

• produces what enzyme?
• infects what?
• antibiotic of choice?
• toxins produced (some strains) (3)

Answer 2

• Coagulase, clots plasma
• wounds/skin/bone/joint infections
• Flucloxicillin

-Enterotoxin- food poisoning
PVL-Panton Vallentine leukocidin
SSSST-Staph scalded skin syndrome toxin

Question 3

Coagulase Neg staphs

• source?
• infects what?
• difficult to treat why?

Answer 3

• skin commensals
• implanted artificial material
• Biofilm develops over site of infection

Question 4

Streptococcus

• gram stain appearance
• classification and features

Answer 4

-Gram + cocci in chains

-by haemolysis:
Beta- haemolytic (complete)
produces haemolysin and tissue damage group A and group B

alpha-haemolytic (partial)
Strep pneumoniae (pneumonia)
Strep viridans (commensal)

Gamma-haemolytic (none)
enetrococcus, bowel commensal

Question 5

List the skin infections caused by Staph aureus (7)

Answer 5

Boils/carbuncles and minor skin sepsis
cellulitis
infected eczema
impetigo
wound infection
SSSS

Question 6

List infection caused by Group A strep (5)

Answer 6

Infectded eczema
Impetigo
cellulitis 
Erysipelas
necrotising fascitis

Question 7

Diagnosis of skin infection investigations?

Answer 7

Swab lesion if surface broken
pus/tissue collection if deeper in lesion
+ blood cultures if pyrexial

Question 8

antibiotic for Group A strep?

Answer 8

Penicillin

Question 9

Necrotising fascitis?

• causative?
• treatment

Answer 9

• Mixed anaerobes and coliforms after abdo surgery OR Group A strep
• immediate surgical debridement and antibiotic treatment

Question 10

Dermatophyte infection

• what is it
• presentation
• causative organism
• pathogenesis
• diagnosis
• treatment

Answer 10

• ringworm
• round lesions, red rings, itchy
• trichophyton rubrum

-fungus enters soggy/abraded skin
hyphenate spread in the stratum corneum
inc epidermal turnover causing scale
inflammatory response, hair follicles invaded
lesions grow outwards

-Clinical presentation
woods lamp
Skin scrapings + nail clippings

-small= clotrimazole cream, topical nail paint
large= terbinafine (oral) itraconazole (oral)

Question 11

treatment for candida

Answer 11

Clotrimazole (cream)

fluconazole (oral)

Question 12

Scabies

• causative organism?
• presentation?
• treatment?

Answer 12

• Sarcopstes Scabiei
• intensely itchy rash in webs fingers, genital area, wrists

-malathion lotion (also lice)
benzyl benzoate