Skin Infections Flashcards

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1
Q

What is the structure of skin?

A

The human skin can be generally divided into
three sections:

❖ Epidermis,
❖ Outermost layer,
❖ Dermis in the middle,
❖ Hypodermis (or subcutaneous tissue)

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2
Q

Functions of skin

Epidermis

A

Immune defences:
o Filters out UV damage
o Produces pigmentation
o Defence against
pathogens
o Moderates temperature

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3
Q

Functions of skin

Dermis

A

o Pliability
o Tensile strength
o Elasticity

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4
Q

Functions of skin

Hypodermis

A

Insulation
o Calorie reserve
o Cushioning and shock
absorption

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5
Q

What is normal skin flora?

A

Normal flora, mostly commensal microorganisms:
❖ Staphylococcus aureus
❖ Staphylococcus epidermidis
❖ Propionibacterium
❖ Streptococci spp.
❖ Candida albicans (yeast)
➢ Can become pathogenic if skin barrier is broken by injury, burn, insect bite or surgery,
or if the immune system becomes suppressed

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6
Q

Normal skin defence?

A

Colonisation is limited by:
❖ Limited moisture availability.
❖ Acid pH.
❖ Surface temperature.
❖ Salty sweat.
❖ Excreted chemicals – sebum/fatty acids.
❖ Competition

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7
Q

What is the pathogenesis of skin infections?

A

Skin infections can be caused by viruses, bacteria, fungi, or parasites.

▪ Bacteria cause cellulitis, impetigo.
▪ Viruses cause herpes simplex.
▪ Fungi cause athlete’s foot and yeast infections.
▪ Parasites cause body lice, head lice.

 Infections may arise from pathogens that gain entry through damaged skin or via haematogenous spread (meningococcal skin rash).

 Bacterial toxins produced by infections at other sites may also result in skin changes

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8
Q

What are Enzymatic Bacterial Defences?

A

Hyaluronidase
Staphylokinase
➢ Lipase
Β-Lactamase (penicillinase)

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9
Q

What are Hyaluronidase?

A

breaks down hyaluronic acid, major component of
extracellular matrix, enables bacteria to spread between cells in the body

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10
Q

What are Staphylokinase

A

digests blood clots once nutrients and space become
limiting to spread to new areas of the body, only produced by S. aureus.

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11
Q

What are Lipase

A

digests lipids, allows growth on skin surface and cutaneous oil glands

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12
Q

What are Β-Lactamase (penicillinase)

A

breaks down beta-lactam antimicrobial drugs,
such as penicillin and cephalosporin. Present in over 90% of S. aureus strains.

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13
Q

What is cellulitis?

A

Spreading skin infection of the subcutaneous layer.

❖ Results in swelling (oedema), redness (erythema),
tenderness & pain.
❖ Common causes are S. aureus (50%) and S.
pyogenes.
❖ Originate from skin lesions such as boils and ulcers.
❖ Can infect the bloodstream in extreme cases.
❖ Initial treatment should therefore be focused on
treating S. aureus and S. pyogenes.

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14
Q

What are the risk factors for cellulitis?

A

 Immunocompromised patients
 Oedema caused by venous insufficiency
 Lymphoedema: Lymphatic obstruction resulting in chronic swelling of the arms or legs
 History of cellulitis: Having had cellulitis before increases the risk of getting it again
 Diabetes and obesity

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15
Q

How is cellulitis diagnosed?

A

 Medical History:
▪ Symptoms experienced, including duration and severity
▪ Recent trauma to the skin. For example, a bite, burn, or laceration
▪ Underlying comorbidities

 physical exam
 Blood sample: levels of creatinine, bicarbonate, creatine phosphokinase, and C-reactive
protein (CRP).
 Skin swab/aspirate for bacterial culture
 If cellulitis is diagnosed, categorise the severity using the Eron classification system (1-4)

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16
Q

Treatment of cellulitis?

A

Oral Antibiotics: 10 to 21 days
 Painkillers
 IV Antibiotics
 Surgery
 When choosing antibiotics: take account of the severity of symptoms, the site of infection,
the risk of uncommon pathogens and any microbiological results and MRSA status if known
 Managing underlying conditions such as diabetes, venous insufficiency, eczema and
oedema

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17
Q

What is impetigo?

A

Infection of the epidermis.

 Mainly affects children.
 Transmitted via skin contact.
 Secondary spread as a result of scratching.
 Main cause is S. pyogenes but also S. aureus.
 Mostly no treatment required but antibiotic creams administered to help prevent spread of infection.

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18
Q

What is folliculitis?

A

inflammation of hair follicle

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19
Q

What is boil/furuncle?

A

If pimples spread and abscess is visible on
the outside of skin, then it is a
boil/furuncle

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20
Q

What is furnuncle?

A

If furuncle spreads deeper, then it
becomes a carbuncle

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21
Q

Features of folliculitis, furuncles and carbuncles

A

Commonly caused by Staphylococcus aureus

Perianal lesions are often caused by a mixture of faecal microorganisms (including
Escherichia coli , Pseudomonas aeruginosa , anaerobes and the Streptococcus
anginosus group)

Pain and tenderness increase with pressure

Most will mature and emerge into a lesion that discharges yellowish pus

May produce fever and elevation of WBC count

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22
Q

Diagnosis and Treatment of folliculitis et al.

A

Diagnosis is made after a medical history and physical exam

Culture of the drainage of the wound (aspirated pus)

Treatment: Surgical drainage combined with the administration of
antibiotics (e.g. flucloxacillin for S. aureus ; metronidazole for

Whenever methicillin resistant S. aureus (MRSA) is suspected, antibiotics
such as vancomycin might be required

Warm compress is applied to promote circulation

23
Q

What is acne vulgaris?

A

Inflammatory disease of the hair follicle and the
sebaceous glands

Sex hormones may contribute

Occurs within sebaceous follicles with keratin plugs
blocking the sebaceous canal, resulting in


Acne vulgaris is triggered by Propionibacterium.

Certain factors may trigger or worsen acne such as
Hormonal changes and Certain medications

Psychological impact

24
Q

Diagnosis of Acne

A

There are no special tests performed for the
diagnosis of acne

Medical history/ physical examination

Depending on the severity of the condition;
certain tests can be prescribed. For example,
hormonal imbalance

25
Q

Treatment - Systemic Antibiotics Acne

A

Systemic antibiotics are used in combination with non antibiotic topical agents to prevent
resistance and enhance effectiveness

Tetracyclines, macrolides, trimethoprim/sulfamethoxazole, penicillin, and cephalosporins have
been used effectively in the treatment of inflammatory acne

26
Q

Treatment - Acne - Topical Antibiotics

A

Topical Antibiotics including clindamycin 1% and erythromycin 2%, are commonly used for the
treatment of mild to moderate acne in combination with benzoyl peroxide.

Topical antibiotics possess anti inflammatory, bacteriostatic and/or bactericidal properties.

Erythromycin and clindamycin are available in combination with benzoyl peroxide: Use of
combination agents is recommended to reduce the risk of resistance

27
Q

What is toxic shock syndrome?

A


TSS is an acute, multi system, toxin mediated illness

28
Q

How is TSS caused?

A

Caused by toxin producing strains of Staphylococcus aureus and Streptococcus pyogenes
(group A streptococcus

Involves multiple organ systems

TSS results from the ability of bacterial toxins to act as superantigens, stimulating immune cell
expansion and increase cytokine expressionW

29
Q

What does TSS do to the body?

A

A repetitive cycle of cell stimulation and cytokine release causes tissue damage

Characterised by fever, hypotension, diffuse macular erythematous rash and desquamation of
the skin.

30
Q

Diagnosis of TSS

A

There’s no one particular test for toxic shock syndrome

Blood cultures: Test the presence of a staph or strep
infection.

Blood tests: to measure blood clotting and bleeding
times, cell counts, electrolytes, and liver function,
among others.

Urine tests.

Lumbar puncture. To collect CSF (cerebrospinal fluid)
for culture

31
Q

What is the treatment for TSS?

A

I ntravenous antibiotics pending culture results include the use of a β lactam agent and a
lincosamide

In cases the causative organism is unknown, the antibiotic regimen should cover both S. aureus
(including MRSA if indicated) and S. pyogenes

Treat dehydration, shock, and organ damage

Regulate blood pressure, Blood transfusion

Dialysis if there is evidence of kidney failure

Oxygen to help with breathing

In case of severe TSS surgery may be needed to remove dead tissue and to clean the area

32
Q

What is Paronychia?

A

Paronychia inflammation / infection of the surrounding tissue of fingernail or toenail

33
Q

What is onychia?

A

Onychia infection of the nail matrix , followed by shedding of the nail

34
Q

What is paronychia and onychia caused by?

A

Caused by Staphylococcus aureus or Streptococcus pyogenes and or one of several species of
the fungus Onychomyces

35
Q

How is Onycholysis characterised?

A

Onychomycosis affects the nail bed. It is accompanied by pus formation and can be extremely
painful if left untreated

Onycholysis is when your nail separates from its nail bed

36
Q

Symptoms of Paronychia?

A


Symptoms of Paronychia include swollen or tender areas on the nail that are red and warm,
with sometimes bleeding involved

37
Q

Diagnosis of Nail conditions

A

Diagnosis
is made by identifying the bacteria or fungi causing the infection Analysing the nail
clipping or taking a swab of the infected area

38
Q

Treatment of the nail conditions

A

Oral antifungal Itraconazole Lamisil (Terbinafine), lotrimazole or ketoconazole

Oral antibiotic, such as dicloxacillin or clindamycin.

Medicated nail polish solutions include Eucerin, Acrada and Ciclopirox can be used to treat
onychomycosis if the underlying cause is a fungal infection. Treatment can take six to nine
months. The treatment has both anti inflammatory and antibacterial properties.

At home treatment: Soak finger or toe in hot solution of Epsom salt 3 times daily

39
Q

Fungal Skin Infections - What are they?

A

Mycoses are diseases caused by fungi

Dermatophytes are keratinophilic “keratin loving” organisms. Keratin is a major protein found in nails,
hair, and skin

All dermatophytes, except for few, produce proteolytic and keratolytic enzymes that enable them to
use keratin as source of nutrition

Dermatophytes produce spores which are highly resistant, surviving in the dry environment. High
temperatures(100 o C)

The infection caused by this fungus is called by the Romans “tinea”( which means small insect larvae)

40
Q

What different types of skin infections can you get?

A

Tinea capitis infection of the head, scalp, eyebrows, eyelashes

Tinea favosa infection of the scalp (crusty hair)

Tinea corporis infection of the body (smooth skin)

Tinea cruris infection of the groin (jock itch)

Tinea unguium infection of the nails

Tinea barbae infection of the beard

Tinea manuum infection of the hand

Tinea pedis infection of the foot (athlete’s foot)

41
Q

What infection is

Tinea corporis

A

Trunk
Pruritus; circular erythematous lesion, scaling,
clearing from centre

42
Q

What infection is

Tinea Crurls

A

Epidermophyton floccosum
Trichophyton rubrum
Groin
lesions similar to tinea corporis

43
Q

What infection is

Tinea pedis

A

Epidermophyton floccosum
Trichophyton spp
Feet
Pruritus; cracking and scaling between toes

44
Q

What infection is

Tinea unguium

A

Nails
Trichophyton spp
Thick, yellowish nails with surrounding
Erythema

45
Q

What infection is?

Tinea Capitis

A

Hair
Trichophyton tonsurans
Erythematous patches on scalp with scaling;
hairs break, leaving bald patches

46
Q

What different types of fungal skin infections are there?

A

Tinea sp.

Microsporum sp.

Trichophyton sp.

Epidermophyton sp.

47
Q

How are fungal skin infections generally visualised?

A

Most fluoresce under UV light

48
Q

What treatment is used for fungal skin infection?

A

Oral antifungals:

Terbinafine.

Itraconazole.
Topical treatments

49
Q

What is a type of viral skin infection?

A

Herpes simplex virus

50
Q

How is HSV characterised?

A

Double stranded DNA virus.

Transmitted via saliva and cold sores of
infected individuals.

Virus replicates in oral mucosal cells.

Febrile illness with mouth ulcerations.

Infect eye conjunctivitis.

Finger herpetic whitlow.

51
Q

What is Varicella Zoster virus infection?

A

Chicken pox

52
Q

How is Varicella Zoster iNFECTION CHARACTERISED?

A

Double stranded DNA virus.

Transmission via respiratory droplets or direct contact with skin lesions.

Over 90% children in western countries infected.

Illness is usually mild.

53
Q

What complications does Varicella Zoster virus caused?

A

Interstitial pneumonia.

Lymphocytic meningitis.

Encephalomyelitis.

54
Q
A