Microbiology of bacterial, fungal and parasite infections

Question 1

What are staphylococcus bacteria?

Answer 1

Gram POSITIVE (purple) cocci in clusters
Aerobes and faculative anaerobes.

Question 2

What are the 2 important types of staphylococcus?

Answer 2

1) Staph aureus which is coagulase positive and shows up golden on agar
2) coagulase negative staphs e.g. epidermidis

Question 3

What does coagulase positive mean?

Answer 3

Clots plasma

Question 4

What is SSSST?

Answer 4

Staph. scalded skin syndrome toxin

Question 5

What is PVL?

Answer 5

A toxin called Panton Valentine Leukocidin

Question 6

What kind of infections do coag. negative staphs (e.g. S. epidermidis) cause?

Answer 6

Infection in artificial materials e.g. valves, catheters, joints.

Question 7

What kind of infections do Staph. saprophyticus cause?

Answer 7

UTIs in women of child bearing age

Question 8

Describe streptococcus bacteria

Answer 8

Gram positive cocci in chains.

Aerobic and faculative anaerobes

Question 9

How are streptococci classified?

Answer 9

Beta haemolytic - complete
Alpha haemolytic - partial
Gamma haemolytic- none

Question 10

What are examples of beta haemolytic streps (dangerous!) ?

Answer 10

Group A strep causes throat and skin infections

Group B causes neonatal meningitis

Question 11

Give two examples of alpha haemolytic strep

Answer 11

Strep pneumoniae which causes pneumonia

Strep viridans which cause endocarditis

Question 12

What kind of gamma strep are commensals of bowels and cause UTIs?

Answer 12

Enterococcus faecalis

Question 13

What kind of infections can strep. pyogenes (A) cause?

Answer 13

Infected eczema
Impetigo
Cellulitis
Erysipelas
necrotising fasciitis

Question 14

How are infections diagnosed?

Answer 14

A swab of the lesion is taken if the surface is broken.
If it is a deeper lesion then pus or tissue can be taken.
Blood cultures if systemic

Question 15

What is the treatment for staph aureus and strep. pyogenes infections?

Answer 15

Flucloxacillin

Question 16

What is necrotising fasciitis?

Answer 16

Infection spreading along fascial planes below skin surface leading to rapid tissue destruction.
little to see on skin surface

Question 17

How is necrotising fasciitis treated?

Answer 17

Medical emergency.

Immediate surgical debridement required as well as abx tx

Question 18

What is the protocol for treating leg ulcers?

Answer 18

Only take swabs if signs of cellulitis or infection.
Treat if strep. pyognes, staph. aureus or other beta haemolytics.
Also treat if ? anaerobes espec in diabetic patients.

Question 19

What is tinea?

Answer 19

Ringworm

Question 20

Where does tinea capitis affect?

Answer 20

scalp

More common in children

Question 21

Where does tinea unguiun affect?

Answer 21

nails

Question 22

Where does tinea cruris affect?

Answer 22

Groin

Question 23

What is tinea pedis also known as?

Answer 23

Athlete’s foot

Question 24

What is the pathogenesis of fungal infections?

Answer 24

Fungus enters soggy skin
Hyphae is spread in stratum corneum and infects keratinised tissues only.
An increased epidermal turnover causes scaling.
Hair follicles are invaded.

Question 25

Why do dermatophytes have a ringed appearance?

Answer 25

The lesion grows outwards and heals in the centre

Question 26

How is a fungal infection diagnosed?

Answer 26

By clinical appearance Woods light by fluorescence Skin scrapings (scaly edge of lesion) or nail clippings are sent to lab in a dermapak. Culture takes 2wks +

Question 27

What is the treatment for small areas of fungal infected skin and nails?

Answer 27

Clotrimazole (Canestan cream)

Question 28

What is the treatment for candida?

Answer 28

Clotrimazole cream with oral fluconazole

Question 29

What organisms cause scabies?

Answer 29

Sarcoptes scabiei

Question 30

What is the common presentation for scabies?

Answer 30

Intensely itchy rash affecting fingers, webs, wrists and genital areas

Question 31

How are scabies transmitted?

Answer 31

Close skin to skin contact e.g.. sex and also sharing towels

Question 32

What is the treatment for scabies?

Answer 32

Malathion lotion applied overnight to whole body and washed off the next day. Benzyl benzoate can also be given but not in children!

Question 33

How are lice (pediculus capitis) treated?

Answer 33

Malathion

Question 34

What are the infection control issues with dermatology?

Answer 34

Patients who shed large amounts of skin give off bacteria into the environment.

Question 35

Which patients need single room isolation and contact precaution?

Answer 35

``` Group A strep infections (Infected eczema Impetigo Cellulitis Erysipelas necrotising fasciitis) MRSA infected Scabies infected ```