L-6 Impetigo: Causes, Symptoms, and Risk Factors

Impetigo

• Staphylococcus aureus causes 80% of Non-bullous impetigo
• Streptococcus pyogenes causes 10%
• Methicillin-resistant Staphyloccocus aureus (MRSA) is also a cause
• Common in children aged 2-5 years, especially bullous impetigo (90%)
• Susceptibility increases in hot, humid climates with poor sanitation and overcrowding
• Susceptibility increases in Daycare centers and prisons
• Susceptibility increases with malnutrition, immunosuppression, diabetes mellitus, and scratching, transmitted via direct skin contact
• A bacterial infection of the superficial layers of the epidermis that is highly contagious
• Can be bullous or non-bullous, typically affecting the face and other body parts
• Often develops in traumatized skin like abrasions, lacerations, insect bites, or burns
• Skin barrier disturbance allows access to fibronectin receptors by S. pyogenes and S. aureus, which need fibronectin for colonization
• S. aureus produces Exfoliative toxin A, leading to loss of cell adhesion in the superficial epidermis, self-inoculation to other sites is common

Non-bullous and bullous Impetigo

• Non-bullous impetigo starts as a vesicle or pustule
• Multiple vesicles often merge and then rupture, forming a honey-colored crust with an erythematous base
• Bullous impetigo presents as small vesicles turning into flaccid bullae with clear or yellow fluid, which can become purulent or dark
• Surrounding erythema and edema are typical

Clinical Manifestations

• Erythematous vesicles or bullae with a yellow crust are present, and can be bullous or non-bullous
• It is typically pruritic and/or painful
• It is highly contagious and spreads easily, and may involve mild regional lymphadenopathy
• Fever is rare in non-bullous cases

Diagnosis and Management

• Diagnosis is clinical (H&P) for bullous or nonbullous types
• Serology (ASO titer) is not useful unless Acute post-streptococcal glomerulonephritis (APSGN) is suspected
• Treat with Topical or Oral antibiotics
• Antibiotics like cephalosporins, amoxicillin-clavulanate, or dicloxacillin decrease illness duration and complication chances in kidneys, joints, bones, lungs, and reduce the risk of acute rheumatic fever

Systemic Implications and Prevention

• Prescribe Systemic antibiotics for bullous impetigo and non-bullous cases with more than five lesions
• Systemic antibiotics are needed when there is deep tissue involvement, systemic infection signs, lymphadenopathy or lesions in the oral cavity
• Treat MRSA carriers in the nose with Mupirocin (Bactroban Nasal) applied in the nostrils (clindamycin or doxycycline)
• A complication is Acute post-streptococcal glomerulonephritis (APSGN), typically occurring 1-2 weeks post streptococcal infection
• Practicing good skin hygiene is effective as a preventative measure

Cellulitis

• Streptococcus pyogenes (Group A streptococcus) is the most common cause
• Followed by Staphylococcus aureus
• Atypical bacteria like Pasteurella multocida from dog/cat bites.
• Atypical bacteria like Vibrio vulnificus from oyster shell cuts
• Atypical bacteria like Pseudomonas aeruginosa in diabetic foot ulcers can cause cellulitis
• Risk factors include being immunocompromised, having MRSA, animal bites, diabetes mellitus, or being elderly
• An acute bacterial infection causing inflammation of the deep dermis and surrounding subcutaneous tissue, without an abscess or purulent discharge

Development and Causes

• Breakdown in the skin barrier from skin trauma or surgical incisions
• Breakdown in the skin barrier from intravenous site punctures or fissures between toes allow normal skin flora and other bacteria to infect the skin
• MRSA can cause cellulitis

Manifestations and Clinical Presentation

• The clinical presentation is a warm, erythematous area of skin with associated edema, and tenderness to palpation
• Fever, malaise, fatigue, and absence of abscess or purulent drainage are present

Evaluation and Treatment

• Two of the four criteria (warmth, erythema, edema, or tenderness) are needed to diagnose cellulitis
• Blood cultures are needed for immunocompromised patients, immersion injury, animal bites, and systemic infection or at risk of sepsis
• Cephalexin is the recommended antibiotic treatment, Clindamycin is a suitable choice if a patient is allergic to beta-lactamase inhibitors
• Trimethoprim-sulfamethoxazole + cephalexin is needed if cellulitis has risk factors for MRSA

Recovery and Complications

• Cellulitis should start resolving within 24 to 48 hours after initiating antibiotics
• Hospitalization and IV antibiotics are needed if immunocompromised patients exhibit systemic symptoms, or are refractory to po antibiotics
• Good prognosis overall, complications arise if along with Sepsis
• Complications arise if there are two or more Systemic Inflammatory Response Syndrome (SIRS) criteria (fever over 100.4 degrees F, tachypnea, tachycardia, or abnormal white cell count, Endocarditis, and Osteomyelitis

Erysipelas

• Streptococcus pyogenes (GABHS) is the cause
• Immunocompromised and elderly are at risk
• A superficial infection affecting the upper dermis and superficial lymphatic system arising from skin breaks
• Portals of entry involve surgical incisions, insect bites, and stasis ulcers

Locations

• Facial Erysipelas may be caused by a current infection in the nasopharynx
• Often diffuse erythematous, raised, well-demarcated, and commonly affects the lower extremities, with the face as the second most common site
• Known as "St. Anthony's Fire" because of its intense fiery rash

Comparison

• Erysipelas involves the upper dermis and superficial tissue
• Cellulitis involves the deep dermis and subcutaneous tissue

Presentation

• The clinical presentation is a bright red erythematous elevation of the affected skin with well-demarcated borders
• It may also have streaking when superficial lymphatics are involved
• It often affects the lower extremities, including interdigital toe spaces or the face

Assessment and Management

• Diagnosis is Clinical (H&P), with no lab workup unless at risk of complications
• Amoxicillin or Cephalexin are treatments, sepsis and Necrotizing infection
• Good skin hygiene and avoiding trauma is the way to reduce frequency

Folliculitis

• Staphylococcus aureus is the cause
• Pseudomonas aeruginosa is associated with hot tub folliculitis
• Ubiquitous and Benign, with no predilection for race, age, or sex. Mostly Self-limited.

Causation

• Damage to hair follicles through shaving, waxing, and wearing tight clothes or hair styling practices
• Contaminated hot tubs/pools/ tight plastic clothing, can spread from person-to-person (close contact)

Development

• A skin condition where the hair follicle is infected with bacteria, inflamed, and forms a pustule or erythematous papule
• Hair follicles are damaged or blocked, infection increased by perspiration, trauma, friction, and occlusion of the skin. Shaving is a common cause

Manifestations and Treatment

• Appears as small inflamed papules around hair follicles, pustules that break and crust.
• Pruritic and painful, mainly over areas of hair growth
• Clinical diagnosis, a treatment is topical Mupirocin, topical clindamycin, and benzoyl peroxide 5% wash.
• Recurrent/spreading infection is one complication

How to reduce frequency

• Good skin hygiene and cautious application of or exposure to skin irritants

Furunculosis

• FYI on "boils" caused by Staphylococcus aureus
• Commonly referred to as “boils”
• Red, swollen, and tender nodules, on hair-bearing parts of the body, and often pustular vesicles
• Moderate to severe furuncles are treated with incision and drainage and/or antibiotics

Carbunculosis

• FYI on a cluster of several skin boils/abscesses, usually caused by Staphylococcus aureus
• The infected mass is full of fluid, pus, and dead tissue, which appears like a lump
• Risk factors include elderly, obesity, poor hygiene, and overall health

Erythrasma

• FYI on the infection through Corynebacterium minutissimum
• Pink, red, or brown patches with scales that affect the upper epidermis
• Commonly appears in folds of the skin and is often pruritic with a musty odor
• Predispositions are obesity, hyperhidrosis, and a warm climate.
• Can be common in healthy and immunocompromised individuals

Ecthyma-FYI

• A "deep tissue form of impetigo" that's ulcerative.
• The lesion has violaceous margins and a honey crusted appearance
• Affects the dermis + epidermis and is caused by Staphylococcus aureus or Streptococcus pyogenes

Necrotizing Fasciitis

• FYI - Rare bacterial infection that spreads quickly in the body and may cause death
• Most common cause Streptococcus pyogenes (GAS), but other causes are Staphylococcus aureus, Vibrio vulnificus, and Clostridium perfringens
• Affects fascia + peri-fascial planes to cause Nacrotizing fascitis
• Needs prompt and accurate diagnosis, rapid antibiotic treatment, and prompt surgery
• May occur post-surgery or any invasive procedure, or even a minor procedure like phlebotomy