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Dermatology > Skin microbiology > Flashcards

Skin microbiology Flashcards

(50 cards)

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1
Q

How can staph. aureus be distinguished from other staphylococcal types and why?

A

Staph. aureus is coagulase positive - will coagulate at the bottom of a test tube

Also shows up golden on an agar plate

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2
Q

What property is unique to staph. aureus (compared to other staphylococcus)?

A

Produces enzymes including coagulase, an enzyme that causes clots to form

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3
Q

What are examples of toxins produced by staph. aureus?

A

Enterotoxin (food poisoning)

Staph. scalded skin syndrome toxin

Panton Valentine Leukocidin (MRSA)

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4
Q

Which bacteria is likely to stick to prosthetic materials in the body and why?

A

Staph. epidermidis

Produces a ‘slime’ that allows it to stick to these materials

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5
Q

Which species of staphylococcus causes UTIs in women of child-bearing age?

A

Staph. saprophyticus

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6
Q

What are the characteristics of beta-haemolytic streptococci?

A

Pathogenic

Produce toxins including haemolysin

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7
Q

What kind of infections are caused by group A beta-haemolytic bateria?

A

Throat infections

Severe skin infections

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8
Q

What kind of infections are caused by group B beta-haemolytic streptococci?

A

Meningitis in neonates

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9
Q

What are the characteristics of non-haemolytic streptococci?

A

Enterococcus species (E. faecalis, E. faecium)

Commensals of bowel

Common cause of urinary tract infection

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10
Q

What skin infections does staph. aureus cause?

A

Boils and Carbuncles

Other minor skin sepsis (infected cuts etc.)

Cellulitis

Infected eczema

Impetigo

Wound infection

Staphylococcal scalded skin syndrome

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11
Q

What skin infections does strep. pyogenes cause?

A

Infected eczema

Impetigo

Cellulitis

Erysipelas

Necrotising fasciitis – (N.B. may also be caused by mixed bacterial infection)

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12
Q

What does tinea mean?

A

Ringworm

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13
Q

How does tinea infection occur?

A

Fungus infection enters soggy/abraded skin

Hyphae spread in stratum corneum

Increased epidermal turnover causes scaling

Inflammatory response provoked (dermis)

Hair follicles and shafts invaded

Lesion grows outward and heals in centre, giving a “ring” appearance

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14
Q

Where does tinea infection occur?

A

Only occurs on keratinised surfaces e.g. nails, hair, body

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15
Q

Are males or females more commonly affected by ringworm?

A

Males

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16
Q

Which patients does scalp ringworm mainly affect?

A

Children

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17
Q

Which patients does foot and groin ringworm tend to affect?

A

Male patients

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18
Q

Which is the most common causal organism of dermatophytes?

A

Trichophyton rubrum

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19
Q

How is fungal infection of the skin diagnosed?

A

Clinical appearance

Woods light (fluorescence)

Skin scrapings, nail clippings, hair

Send to laboratory in a “Dermapak” for microscopy and culture (N.B. culture takes 2 weeks)

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20
Q

How should small areas of fungally infected skin/nails be treated?

A

Clotrimazole (Canestan) cream or similar

Topical nail paint (amorolfine)

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21
Q

How should extensive fungal skin nfection or scalp infection be treated?

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A

Terbinafine orally

Itraconazole orally

22
Q

Which areas of the body are usually affected by scabies?

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A

Finger webs

Wrists

Groin

23
Q

What is the treatment for scabies?

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A

Malathion lotion, applied overnight to whole body and washed off next day

Benzyl benzoate (avoid in children)

24
Q

What is the treatment for lice?

25
What are some of the complications of chickenpox?
Secondary bacterial Pneumonitis Haemorrhagic Scarring Encephalitis
26
Which skin diseases are due to varicella zoster virus?
Chickenpox Shingles
27
A 26-year-old man presented with a 5-day history of cough, fever, and mild dyspnea He had an exanthematous vesicular rash that had started 3 days before the respiratory symptoms began He smoked cigarettes (30 per day for the previous 14 years) His daughter had recently had chickenpox; he had not been vaccinated against the disease nor did he have a history of it A skin examination revealed a polymorphic rash with vesicles, pustules, and crusty lesions On Xray: multiple small nodules in both lungs On CT: no liver or CNS involvement What is the diagnosis?
Varicella pneumonia/chickenpox This diagnosis was made on the basis of the rash, pulmonary symptoms, and contact with a child with chickenpox
28
How is development of chickenpox in the neonate prevented?
Prevention with Varicella Zoster Immune Globulin in susceptible women in contact
29
How does shingles present?
Dermatomal distribution Tingling pain Erythema Vesicles Crust
30
In which patients is the incidence of shingles highest?
Elderly Immunocompromised
31
What is the diagnosis here and the management?
Opthalmic shingles/zoster (see involvement of tip of nose) Requires urgent referral to opthalmology
32
Which nerve is involved in opthalmic zoster?
Opthalmic division of trigeminal nerve
33
What are the features of Ramsay-Hunt syndrome?
Facial nerve palsy Vestibulocochlear nerve irritation - deafness, vertigo, tinnitus Vesicles and pain in auditory canal and throat
34
What is Ramsay-Hunt syndrome?
Geniculate or otic herpes zoster
35
What is the diagnosis here?
Primary gingivostomatisis - herpes simplex infection
36
Which patients are affected by primary gingivostomatitis and how long does it last?
Pre-school children Ulceration lasts around a week
37
What are the characteristics of type 1 herpes simplex virus?
Main cause of oral lesions Causes half of genital herpes Causes encephalitis
38
What are the characteristics of type 2 herpes simplex virus?
Rare cause of oral lesions Causes half of genital lesions Encephalitis / disseminated infection (particularly in neonates)
39
What is the treatment for herpes simplex virus and varicella zoster virus?
Aciclovir
40
Does aciclovir affect latent viruses?
No
41
How does aciclovir work?
It is selectively incorporated into viral DNA, inhibiting replication
42
What are the nodules in molluscum contagiosum like?
Fleshy, firm, umbilicated, pearlescent nodules 1 to 2 mm diameter
43
How can molluscum contagiosum be treated?
Usually self-limiting but can take months to disappear Local application of liquid nitrogen
44
What is herpangina?
A blistering rash of the back of the mouth
45
What organism causes herpangina?
Enterovirus: Coxsackie virus Echovirus
46
What is slapped cheek disease and what causes it?
Erythema infectiosum Caused by parovirus B19
47
What does slapped cheek disease look like?
Erythematous rash on the cheeks As the rash on the face fades a lacy macular rash on the body appears In adults rash may be absent and an acute polyarthritis of the small joints eg of the hands may be more prominent
48
How is parovirus confirmed in the lab?
Parvovirus B19 IgM test
49
. A 23-year-old woman presented to the emergency department after 1 day of fever, sore throat, arthralgia, and rash Diffuse erythema (Panel A) that blanched on pressure was noted over the face, neck, trunk, and arms, along with posterior cervical lymphadenopathy The next day, the fever and rash subsided, but she reported pain in the oral cavity Examination revealed petechial hemorrhages on the soft palate (Panel B) that disappeared spontaneously in 2 days She had no history of rubella vaccination What is the diagnosis and what would show up on lab tests?
Testing for rubella IgG antibody was negative, and testing for rubella IgM antibody was positive, which confirmed the clinical diagnosis of rubella
50
What is the causal organism in syphilis?
Treponema pallidum

Dermatology (8 decks)

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