1. Skin, and Soft Tissue Infections

2. RAJAN S Cleveland Clinic Journal of Medicine 2012;79:57-66

3. Impetigo
Impetigo is a common skin infection caused by streptococcus group A or staphylococcus bacteria
MRSA is becoming a common cause.
Most common in children, particularly those in unhealthy living conditions.
In adults, it may follow other skin or upper respiratory infection.

4. Symptoms
A single or multiple blisters filled with pus with a reddish raw base (in infants).
Itchy or painful blister: yellow or honey colored fluid oozes and the lesion become crusty.
It may spread to other areas and other persons.
Affected sites: face, arms, or legs. It may cause local lymphadenopathy.

6. Diagnosis
Based mainly on the appearance of the skin lesion.
A culture of the skin or lesion usually grows the bacteria Streptococcus pyogenes or Staphylococcus spp.
The culture can help determine if MRSA is the cause.

7. Prognosis & Complications
The sores of impetigo heal slowly and seldom scar.
Complications:
post-streptococcal glomerulonephritis.
condition often recur in young children
Spread to other parts of the body (common)
Permanent skin damage and scarring (very rare).

8. Bullous impetigo Mainly seen in children younger than 2 years.
Involves painless, fluid-filled blisters
mostly on the arms, legs, and trunk.
surrounded by red and itchy (but no sores) skin.
The blisters may be large or small.
After they break they form yellow scabs.
Caused by S. aureus toxins that separate the dermis from epidermis.

10. Ecthyma
Ecthyma is a skin infection similar to impetigo but more sever because it invade deeper "deep impetigo”.
Most often caused by Streptococcus sp.
The infection start in skin that has been injured due to a scratch or insect bite.
It often develops on the legs.
Small blister or pustule with a red border which later erodes and form an ulcers.
Diagnosis: clinically or analysis of aspirated fluid or biopsy in the laboratory.

12. Acne vulgaris Acne vulgaris or cystic acne or simply acne.
Acne affects mostly skin with a greater number sebaceous follicles: the face, the upper part of the chest, and the back.
A common human skin disease
Symptoms: scaly red skin, blackheads and whiteheads, seborrhea (increased sebum secretion), papules, pustules, nodules (large papules), and possibly scarring.

13. Causes:
Hormonal: androgens (testosterone,)
Genetic.
Psychological.
Diet.
Infectious Agent
Propionibacterium acnes.
Staphylococcus epidermidis.

14. Pathogenesis:
Acne develops as a result of blockages in the follicles by hyper keratinization Enlargement of sebaceous glands and increase sebum production In these conditions, the commensal bacterium Propionibacterium acnes can cause infection, leading to inflammatory lesions (papules, pustules, or nodules) in the dermis, which results in redness and may result in scarring or hyperpigmentation.

16. Boils and carbuncles
Boils and carbuncles are painful, pus-filled bumps (microabscesses around the hair follicles).
Boils (furuncles) usually start as red, tender lumps full of pus which grow larger and more painful until they rupture and drain.
A carbuncle is a cluster of boils.
Common sites: face, neck, armpits*, buttocks or thighs (hair-bearing areas are more likely to sweat).
The causative organism is S. aureus.
Armpits: axilla

17. Staphylococci enter through a cut or scratch into skin then neutrophils rush to the site.
A painful, red bump appear with red, swollen skin around it. The bump increase in the size over a few days as it fills with pus (cloud reach the size of a golf ball) with yellow-white tip that eventually ruptures and allows the pus to drain out.
Once the boil drains, the pain usually subsides.
Small boils usually heal without scarring but a large boil may leave a scar.

18. A carbuncle is a cluster of boils that often occurs on the back of the neck, shoulders or thighs.
Carbuncles are deeper and more severe and more likely to leave a scar.
Risk factors: Although anyone can develop boils or carbuncles but the following factors can increase the risk.
Close contact with staph infection patients.
Diabetes.
Other skin conditions.
Compromised immunity.

19. Complications of boils and carbuncles:
Blood poisoning,
MRSA.
Skin abscess.
Diagnosis:
Culture in these situations:
recurring infections.
No response to standard treatment.
weakened immune system.

20. draining the boil with an incision Antibiotics in certain situations.
Treatment: For larger boils and carbuncles
draining the boil with an incision
Antibiotics in certain situations.
Boils & carbuncles should never be squeezed; risk of blood dissemination.
Treatment must be initiated if the lesions became extremely painful or high fever developed.

21. Skin abscess A skin abscess is collection of pus in the skin.
Pus: dead neutrophils + dead bacteria+ dead tissues.
It is a defensive reaction of the tissue to prevent the spread of infectious.
Skin abscesses may occur after:
A bacterial infection (often staphylococcus; boils and folliculitis)
A minor wound or injury.
Foreign material.
It may occur anywhere on the body and affects people of all ages.

22. Symptoms may include:
Fever & chills.
Local swelling, redness, tenderness & warmth.
Hard tissue (induration)
Open or closed sore, or domed nodule. fluid drainage.
Complications:
Usually cure with proper treatment.
Infections caused by MRSA are do not respond to regular antibiotics and need special medicines.
Spread to the blood and throughout the body.
Tissue death (gangrene).

24. Cellulitis Cellulitis is inflammation of the subcutaneous tissues.
Caused by S. pyogenes and S. aureus .
Cellulitis appears as a swollen red area of skin, feels hot and tender, and it may spread rapidly.
Skin on lower legs is most commonly affected.
Cellulitis may affect only skin's surface or can spread to lymph nodes and bloodstream.
The spreading infection may rapidly turn life-threatening, if left untreated

25. Symptoms and Signs:
Redness, swelling, tenderness, pain, warmth, fever. The borders are indistinct.
Risk factors include:
Lymphedema.
History of cellulitis.
Intravenous drug use.
Obesity.
Weakened immune system.
Skin conditions.

26. Complications:
The bacteria can spread rapidly throughout the lymph nodes and bloodstream.
Recurrent episodes of cellulitis:
may damage the lymphatic drainage system leading to chronic swelling of the affected extremity
In rare cases
infection spread to the fascia (necrotizing fasciitis)

27. Cellulitis is usually a superficial infection of the skin
Cellulitis is usually a superficial infection of the skin. But if severe or if left untreated, it can spread into lymph nodes and bloodstream. Pictured here is mild cellulitis (left) and severe cellulitis (right).

28. Necrotizing fasciitis
A rapidly progressive inflammatory infection of the fascia, with secondary necrosis of the subcutaneous tissues.
Risk factors:
diabetes mellitus, vascular insufficiencies and cancer.
Group A beta-hemolytic Streptococcus a major cause. However, other pathogens may be present, including:
Clostridium, Enterobacteriaceae (e.g. Escherichia coli), Pseudomonas and Klebsiella

29. Signs and symptoms
Rapid progression of severe pain with fever.
Swelling , redness, hotness, blister, gangrene and necrosis. Gas crepitus under the skin.
Mortality as high as 73 % if untreated
Survivors may have a shorter life span owing to infectious causes such as pneumonia, cholecystitis, urinary tract infections, and sepsis.
Complications:
Scarring with cosmetic deformity & limb loss.
Septic shock with cardiovascular collapse (Toxic shock syndrome)
Organ failure including renal failure.

30. Diagnosis:
WBC , differential , ESR, blood urea.
Microbiology
Culture &Gram's stain (blood, tissue)
Susceptibility tests
Treatment:
Intravenous antibiotic therapy. combination of penicillin G, aminoglycoside and clindamycin.
Surgery to remove dead tissue and amputations of affected limbs, in some cases.
Hyperbaric oxygen to preserve healthy tissue.