Bacterial and viral infections

Question 1

-nb commensal bacterial are the normal, non-harmful flora colonizing humans

staphylococcus aureus. not part of resident flora other than in a minority who carry it in nostrils, perineum, armpits

-skin conditions caused by staph aureus (5)

Answer 1

• impetigo can also be caused by strep
• cellulitis
• ecthyma
• furunculosis/boils
• scalded skin syndrome
• toxic shoke syndrome

Question 2

-ecthyma - type of lesion (1) forms where(1) complication

Answer 2

ecythyma

• an ulcer. forming under a crusted surface infection - eg insect bite, neglected minor trauma.
• heals with scarring - because the ulcer is full thickness of the epidermis. whereas impetigo is only the stratum corneum.

Question 3

furunculosis/boils

• infection of where. who is at increased risk (5). type of lesion (1) morphology (3) course (3). complications (4) rarer complications (2)
• sudden appearance of many furuncles may suggest what (1)
• investigations (4)
• treament. general (1) acute episode (1). anitbiotics when(3) . chronic (1)

Answer 3

• infection of a hair follicle
• teenage boys partularly susceptible, diabetes, systemic steroids, skin disease, minor trauma. some individuals may have chronic furunculosis. may carry staph in nose , groin
• nodule - red, with central supperating core. tender
• -*enlarges, may discharge, usually then clears.
• complications - fever, enlarged drainage nodes, scarring. rare ones - septicaemia, caverous sinus thrombosis
• sudden appearance of many may suggest virulent staph inc strains of MRS.

investigating

-Hx and skin examination - check for underlying skin diseases - eg scabies, eczema

-FBC. urine glucose - check for diabetes

-culture swabs - check organism is staph. ab sensitivity

treatment

-general - antiseptic soaps

-acute episode - incision and drainage, ab in eruptions, systemic sx or immunosupressed

-chronic - treat carrier sites nose or groin w topical antibiotics

Question 4

carbuncle

• infection of what (1) dcm (3). Sx (2)
• who is predisposed (1)
• Mx(2)

Answer 4

• deep inection of many hair follicles
• dcm - swelling, supperation, discharge from many points
• Sx - pain, systemic upset
• diabetic pts predisposed.
• Mx - topical and systemic. ab incision and drainage may speed up healing but is difficult

Question 5

scalded skin syndrome

• dmc (4)
• who is at risk (2) what is the cause (1)
• Mx(1)

Answer 5

• skin - resembles a scalp, tender, erythema, sloughing (=sheding) of patches of stratum corneum
• children, pts with renal failure are at risk. adults usually have antibody to the toxin. cause of a toxic produced by staph from infection elsewhere eg imetigo
• systemic antibiotics
• nb differential in adults is toxic epidermal necrolysis. this involves full thickness damage to epidermis - skin biopsy will distinguish*

Question 6

toxic shock syndrome

• dmc (3). Sx(1). complication (1) course (1)
• cause (1)
• Mx(2)

Answer 6

• wide spread eythematous rash. fever.
• complication is shock - i think septic?
• 1-2 wks later initial reaction is followed by desquamation most markedly fingers and hands
• case is staph toxic mainly due to overgrowth of staph in vagina of woman using tampon
• Mx systemic ab and irrigation of infected site

Question 7

streptococcus pyogenes. what infections can be caused by streptococcal bacteria(6)

Answer 7

• impetigo
• cellulitis
• erysipelas
• necrotizing fasciitis

Question 8

• erysipelas
• Sx(2). type of lesion(1) dmc(4)
• complications(3)
• Mx
• cause
• course

Answer 8

• first Sx malaise, fever
• after a few hours a plaque erupts - erythematous, spreading, well define edge, may blister
• complications - can be fatal if untreated. episodes can affect same area repeatedly. this can cause lymphoedema
• caused by strep entering through broken skin - between toes, behind ears
• Mx - systemic penicillin, sometimes given iv.
• also treat cause of original skin split eg tinea pedis*

Question 9

necrotizing fasciitis - this is rare and is caused by strep plus anaerobes

• at risk pts (2)
• at first resembles what(1) progresses to what (2)
• complication (1)
• Ix (3)
• Mx(2)
• prog(1)

Answer 9

• diabetics, post surgery
• at first resembles cellulitis. progresses to necrosis of skin and subcutaneous tissue
• complication - central anaesthetic area due to cutaneous nn damage
• Ix - incision biopsy. culture. MRI to assess spreading.
• Mx - surgical debridement, iv ab
• prognosis is poor

Question 10

impetigo

-caused by staph aureus or streptococcal bacteria or both together

>general rule what type is staph and what type is strep

• type of lesion (1) may become (1)
• d(2)
• course (3)
• Ix (2) and Mx (1)

Answer 10

• general rule the bullous type of staph and the ulcerated crusted type is strep
• blisters. may become pustule.
• lesions often multiple and around face. can also affect folicles.
• pustules may rupture leaving exudation and crusting. condition can spread through a family. tends to be self limiting.
• streptococcal impetigo can trigger acute glomerulonephritis.
• examination. swabs for culture. severe cases may need ab.

Question 11

cellulitis - can be caused by staph or strep or other bacteria

• inflammation deeper than erysipelas. often involving subcutaneous tissue
• dcm (2)
• cause
• mx

Answer 11

• affected area very swollen. border less well defined than in erysipelas
• cause - usually trauma
• -*Mx - systemic ab, sometimes iv. also rest and elevation.

Question 12

-HPV - viral warts

-some possible patterns (6)

Answer 12

• common warts
• plantar warts
• mosaic warts
• plane warts
• facial warts
• anogenital warts

Question 13

HPV - viral warts

-who is most at risk (2). course (1). Mx (1)

Answer 13

• school children, immosupressed
• spontaneous resolution as healthy immune response overcomes infection. ranges from months - years in different pts.
• -*Mx either leave warts or cyrotherapy

Question 14

• common warts - type of lesion (1). colour (1). surface (1) d(3) pain?(1)
• planar warts -d(1) pain?(1)
• mosaic warts - d(4)

Answer 14

• common warts - papule (or nodule depending on size). skin coloured. irregular surface. hands, face, genitals. usually pain free
• plantar warts - less elevated than common warts. occur on soles of feet. can be painful.

-mosaic warts - multiple small tightly packed individual warts. occur on soles, palms, around finger nails

Question 15

• plane warts. type of lesion (1) surface (1) d(3) colour (1) course (2) c (1) pain?(1)
• facial warts - d(1) pain?(1)
• anogenital warts - type of lesion (2) surface (1) d(1) pain?(1) risk factors (2)

Answer 15

• plane warts. papules, smooth, skin coloured. face, shaven legs, backs of hands. become inflammed and resolve spontaneously. not painful. may be arranged in a line.
• facial warts. most common in beard area of men. spread by shaving. not painful
• anogenital warts - papillomatous plaques. moist surface. anywhere in genital region. may be painful. risks - sexual abuse in children, or spreading from common warts elsewhere.

Question 16

chicken pox

• how is virus spread(1) what is incubation period(1)
• course (5)

Answer 16

• spread via respiratory route. incubation period of 14 days.
• slight malaise > skin reaction > clears after a few days > may leave scarring > second attacks rare

Question 17

chicken pox

• morphology (4 stages)
• distribution (2)
• Sx(1)

Answer 17

• papules > clear vesicles > pustules > crusting lesions
• often appear in crops. most profuse over trunk
• itchy

Question 18

Mx chicken pox

• for healthy pts self limiting
• for immunocomprimised (1)

Answer 18

-antivirals for immunocomprimised - aciclovir, famciclovir, valaciclovir

Question 19

herpex simplex

• two types - type 1 d (1) type 2 d(1)
• course (3)
• route of infection is through mucous mebranes or abraded skin

Answer 19

• type 1 is extragenital, usually mouth
• type 2 is genital
• this is not absolute*
• -*course - primary ep > virus can lie latent in nerve ganglia > recurrent episode

Question 20

-primary infection

• lasts how long (1)
• morphology (2 stages)
• Sx (6)
• some common distrubitions (3)

Answer 20

• lasts about 2 wks
• vesicles > ulcers
• gingivostomatitis, malaise, headache, fever, enlarged cervical lymph nodes, pain
• scattered over mouth (lips and mucous membranes), face, gentials

Question 21

herpes simplex - Recurrent infections

-d(1)

• precipitators (4)
• morphology (3)
• course - what occurs in first few hours (1) when does crusting occur (1) how long does whole episode usually last (1)

Answer 21

-same place as primary

• resp infections, stress, menustration, uv radiation
• erythema, vesicles, crusting
• first few hours > tingling, pain . crusting after 1-2 days. whole episode lasting about 12 days.

Question 22

• Mx
• prophylactic (1)
• what may prevent secondary bacterial infection (1)
• topical Mx (1)
• for more severe or withbsystemic Sx (1)

Answer 22

• prophylactic - sunblock
• topical antibacterial
• topical aciclovir applied 5-6 times / day
• for more severe or withbsystemic Sx oral aciclovir

Question 23

molluscum contagiousum caused by common pox viris

• -*spread how (1)
• incubation perdiod (1)
• morphology. shape (1) colour (2) surface characteristics (3)
• distribution depends on (1)

Answer 23

• spread via contact - direct, sexual, sharing towels, swimming pools
• 2-6 wks incubation
• hemispherical. white or pink. shiny, may have a mosaic appearance on close inspection, may have a central cheesy core giving characteristic umblinical appearnce
• distrubtion depends on mode of infection

Question 24

• molluscum contagiousum
• who is more at risk of extensive infections (2)
• course (untreated) (2)

Answer 24

• immunocomprimised individuals, atopic individuals due to spreading via scratching and use of topical preperations
• brief local inflammation, lesions clear 6-9 months

Question 25

Mx (2) for children (1)

Answer 25

-prevent spreading within family

-destructive methods - lead to inflammation and then resolution

• eg squeezing, piercing
• for children it is best to leave them to be self limiting as destruction can be painful. or use anaesthesia