BI of the Skin

• a flat lesions characterized by change in color of the affected skin

  macules
• raised lesions, solid in consistency of less than 5 mm. in diameter

  papules
• flat with elevated surface (plateu-like) with more than 5 mm. in diameter

  plaques
• rounded raised lesions more than 5 mm. in diameter

  nodules
• (wheals or hives) ring-like papules or plaques with pinkish color

  urticaria
• fluid-filled lesions less than 5 mm. in diameter

  vesicles
• exudate-filled lesions

  pustules
• skin lesions due to bleeding into the skin

  purpura
• type of purpura that is less than 3 mm in diameter

  petechiae
• type of purpura lesion that is greater than3 mm in diameter

  ecchymosis
• crater-like lesions that involve deeper layers of the epidermis and dermis

  ulcers
• necrotic ulcer covered with blackened scab

  eschar
• Pathogenic bacteria possess characteristics that enable them to circumvent the body's defenses and exploit its resources, resulting in infection
• Staphylococci:

  1. Staphylococcus aureus

  ◦ gram-positive cocci

  ◦ usually arranged in pairs, short chains, or in grape-like clusters

  • Found in the skin and the nasopharynx

  • Produces enzymes and toxins

  • virulence

  • responsible for its invasiveness and pathogenicity
• Staphylococcus aureus Clinical Findings 1. Folliculitis

  – a pyogenic (pus-producing) infection involving the hair follicle

  - localized painful inflammation

  - heals rapidly after draining the pus

  2. Furuncle

  – an extension of folliculitis (Boil)

  - larger and painful nodules with underlying collection of dead and necrotic tissue

  3. Carbuncle

  – a coalescence of furuncles - extends into the subcutaneous tissue - with multiple sinus tracts.
• Staphylococcus aureus

  Clinical Findings :

  4. Sty or hordeolum – folliculitis occurring at the base of the eyelids

  5. Impetigo

  – common in young children and involves the face and the limbs

  -flattened red spot (macule) which later becomes pus-filled vesicle that ruptures and form crusts

  -caused by S. aureus and S. pyogenes
• Staphylococcus aureus 6. Staphylococcal Scalded Skin Syndrome (Ritter’s Disease)

  – found in newborns and young children with

  - sudden onset of perioral erythema that covers the whole body within two days.

  • Nikolsky sign

  – displacement of the skin when slight pressure is applied over the skin

  • Exfoliative toxin – is the toxin responsible for the manifestation • 7-10 days – antibodies against exfoliative toxin are produced and enabling the skin to become intact again and only the outer layer of the epidermis is affected hence there will be no scarring
• Staphylococci 2. Staphylococcus epidermidis • Gram-positive bacteria and it is a part of the skin’s normal flora

  • frequently linked to

  •"stitch abscess,"

  • UTI and endocarditis.

  • it causes infections in people who utilize prosthetic equipment
• 3. Streptococcus pyogenes

  • Gram-positive cocci, belong to group A betahemolytic = cause complete hemolysis of blood

  • M protein

  = major virulence factor

  = anti-phagocytic

  = produces enzymes and toxins

  à responsible for pathogenesis

  of infection caused by the organisms
• Streptococcus Pyogenes

  Clinical Manifestations: 1. Pyoderma (Impetigo) - a purulent skin infection that is localized and commonly involves the face and the upper and lower extremities.

  2. Erysipelas (St. Anthony’s Fire) – localized raised areas - associated with

  = pain

  = erythema

  = warmth accompanied

  = lymphadenopathy

  = systemic manifestation

  3. Cellulitis

  – involves the skin and subcutaneous tissue

  – involves the skin and subcutaneous tissue

  - associated with;

  = local inflammation

  = systemic signs
• Streptococcus Pyogenes

  Clinical Findings :

  4. Necrotizing Fasciitis – involves deep subcutaneous tissue - ‘flesh eating” or streptococcal

  gangrene

  • Starts as cellulitis à bullous à gangrenous à spread to the fascia, muscle and fat.

  • It become systemic à multi-organ failure à death

  Complications: • Acute glomerulonephritis - non- supporative, immunemediated complications and skin infections • Rheumatic fever

  - usually associated with S.

  pyogenes throat infection
• 4. Pseudomonas aeruginosa • Gram negative bacillus; arranged in pairs; encapsulated • an opportunist pathogen

  • common cause of Nosocomial infections

  • Resistant to most antibiotics and capable of producing water- soluble pigments like pyocyanin

  • Virulence – adhesins (Flagella, pili, LPS) and toxins – (exotoxin)

  enzymes
• Pseudomonas Aeruginosa

  Clinical Findings:

  1. Colonization of burn wounds characterized by blue-green pus that exudes a sweet grapelike odor.

  2. Folliculitis

  3. Secondary infection to acne and nail infection

  4. Osteochondritis - inflammation of the bone and cartilage of the foot
• Pseudomonas Aeruginosa

  Clinical Findings :

  5. Ocular keratitis in contact lens wearers, endocarditis and osteomyelitis in IV drug users

  6. External otitis (swimmer's ear) in healthy people, and severe external otitis in diabetics.

  7. Persons with cystic fibrosis die of respiratory failure caused by P.

  aeruginosa infection.

  8. P. aeruginosa frequent infects extensive skin burns

  = which can lead to sepsis
• 5. Clostridium perfringens

  • Gram-positive rod-shaped bacilli that are anaerobic and rarely produce endospores • produces toxins alpha, beta, iota, epsilon

  • alpha toxin – is the most lethal because it causes massive hemolysis and bleeding tissue destruction

  • associated with soil and water contaminated with feces
• 5. Clostridium Perfringens

  Clinical Findings:

  1. Soft tissue infections = Cellulitis, suppurative myositis, myonecrosis or gas gangrene

  ◦ Gas gangrene (Clostridial Myonecrosis)

  = is a life-threatening infection

  following a physical trauma or surgery

  = characterized by massive tissue

  necrosis with gas formation

  2. Shock, renal failure and death within two days of onset