This study material has been compiled from a copy-pasted text (likely a medical textbook chapter) and a lecture audio transcript on bacterial skin infections.

---

📚 Bacterial Skin Infections: A Comprehensive Study Guide

Introduction to Bacterial Skin Infections

The human skin is a complex ecosystem, home to hundreds of bacterial species that form its natural microbiota. These organisms are crucial in preventing infections by competing with harmful pathogens. However, when the skin barrier is compromised or this delicate balance is disrupted, bacterial infections can arise. These infections can be a primary issue (e.g., impetigo) or a complication of an existing skin condition (e.g., atopic dermatitis). In severe cases, they can lead to multisystem dysfunction, such as toxic shock syndrome. The naming of these diseases often indicates the infection's site and depth, from the superficial stratum corneum to the deeper subcutaneous tissue, and the causative organism.

1. Gram-Positive Cocci: Staphylococcal and Streptococcal Infections

These bacteria, primarily Staphylococcus aureus and Streptococcus pyogenes (Group A Streptococci, GAS), cause a wide range of skin conditions.

1.1. Impetigo

• 📚 Definition: A very common, highly contagious bacterial infection.
• ✅ Major Organisms: Staphylococcus aureus and Streptococcus pyogenes (GAS).
• 📍 Location: Most commonly on the face or extremities of children, especially around the nose and mouth.
• 🔬 Clinical Features:
  • Eroded skin with characteristic "honey-colored" crusts.
  • Bullous variant: Often seen in major body folds (e.g., axillae), caused by S. aureus due to local release of an exfoliative toxin that dissolves the upper epidermis (acantholysis).
• 📈 Risk Factors: Nasal carriage of S. aureus, breaks in the epidermal barrier (e.g., atopic dermatitis, arthropod bites, trauma, scabies).
• 🤔 Differential Diagnosis (DDx):
  • Eroded lesions: Insect bites, dermatitis (nummular, atopic), herpes simplex, prurigo simplex.
  • Bullae: Bullous insect bites, thermal burns, herpes simplex, acute contact dermatitis, autoimmune bullous dermatoses.
• 💊 Treatment (Rx):
  • Local wound care (soap, removal of crusts by soaking).
  • Mild cases: Topical mupirocin, retapamulin, ozenoxacin, or fusidic acid.
  • Moderate to severe: Oral antibiotics, chosen based on local prevalence of Methicillin-Resistant S. aureus (MRSA).

1.2. Ecthyma

• ✅ Major Organism: Most commonly Streptococcus pyogenes.
• 🔬 Clinical Features: Ulceration with a hemorrhagic crust that extends into the superficial dermis (deeper than impetigo). Can heal with scarring.
• 📍 Location: Often on the lower extremities.
• 📈 Risk Factors: Edematous limb, arthropod bites, pre-existing ulceration.
• ⚠️ Important Distinction: Not to be confused with ecthyma gangrenosum (due to septic emboli).
• 🤔 DDx: Ulcers secondary to vasculitis or other etiologies.
• 💊 Rx: Systemic antibiotics (refer to general treatment guidelines).

1.3. Bacterial Folliculitis

• 📚 Definition: Infection centered on hair follicles.
• ✅ Major Organisms: Most common is S. aureus, followed by Gram-negative bacteria (e.g., in acne vulgaris patients on long-term antibiotics).
• 🔬 Clinical Features:
  • Superficial: 1-4 mm pustules on an erythematous base, often with a central hair shaft.
  • Deep (Sycosis): Tender, erythematous papulonodules, often with a central pustule.
• 📍 Location: Beard area, upper trunk, buttocks, thighs. Shaving can be an exacerbating factor.
• 🤔 DDx: Culture-negative folliculitis, acne vulgaris, fungal/viral/Demodex folliculitis, rosacea, chloracne, pseudofolliculitis barbae.
• 💊 Rx:
  • Superficial: Antibacterial washes (benzoyl peroxide, chlorhexidine) or topical gels (clindamycin/benzoyl peroxide).
  • Widespread staphylococcal: Oral antibiotics.

1.4. Abscesses, Furuncles, and Carbuncles

• 📚 Definitions:
  • Abscess: Localized collection of pus.
  • Furuncle: Abscess involving a hair follicle.
  • Carbuncle: Involvement of multiple, adjacent hair follicles.
• ✅ Major Organism: S. aureus (most frequent presentation for community-acquired MRSA, CA-MRSA).
• 🔬 Clinical Features:
  • Furuncles: Firm, tender, red nodules.
  • Carbuncles: Begin similarly but become larger, with multiple draining sinus tracts. Heal with scarring.
• 📍 Location:
  • Furuncles: Face, neck, axillae, buttocks, perineum, thighs.
  • Carbuncles: Trunk and thighs.
• 🤔 DDx: Ruptured epidermoid cyst, hidradenitis suppurativa, cystic acne.
• 💊 Rx:
  • Fluctuant lesions: Incision and drainage (I&D).
  • Systemic antibiotics: Indicated for lesions around nose/ear, severe/extensive disease, surrounding cellulitis, systemic illness, non-responsive lesions, or immunocompromised patients.

1.5. Erysipelas

• ✅ Major Organism: Most commonly Streptococcus pyogenes.
• 📚 Definition: Infection of the superficial dermis with significant lymphatic involvement.
• 📍 Location: Often on the face and neck or the leg.
• 🔬 Clinical Features: Well-defined area of hot, indurated, bright erythema that is painful and tender. May have superimposed pustules, vesicles, bullae, or hemorrhagic necrosis.
• 📈 Affected Populations: Young, debilitated, elderly, and those with limb edema or lymphedema.
• 🤔 DDx: Cellulitis, irritant contact dermatitis, early necrotizing fasciitis, herpes zoster, erysipeloid breast cancer, Sweet syndrome.
• 💊 Rx: 10-14 day course of penicillin (route depends on severity).

1.6. Cellulitis

• 📚 Definition: Infection of the deep dermis and sometimes the subcutaneous fat.
• ✅ Major Organisms: Most commonly Streptococcus pyogenes or S. aureus. In diabetics/immunocompromised, Gram-negative bacilli. In children, Haemophilus influenzae (incidence decreased due to vaccine).
• 🔬 Clinical Features: Rubor (redness), calor (warmth), dolor (pain), tumor (swelling). Borders are more ill-defined than erysipelas. Can become bullous or necrotic. Systemic symptoms (fever, chills, malaise) are common.
• 📈 Risk Factors (Lower Extremity): Previous DVT, previous cellulitis with lymphangitis, chronic edema, tinea pedis.
• 🤔 DDx: Lipodermatosclerosis, stasis dermatitis, erysipelas, early necrotizing fasciitis, "pseudocellulitis" (e.g., arthropod bites, erythema migrans, Sweet syndrome, contact dermatitis).
• 💊 Rx: Systemic antibiotics (refer to general treatment guidelines).

1.7. Blistering Distal Dactylitis

• ✅ Major Organism: Secondary to GAS > S. aureus.
• 📚 Definition: Localized infection of the volar fat pad of a finger or toe.
• 📍 Location: Finger or toe (most common in children).
• 🔬 Clinical Features: Erythema and swelling, followed by one or more vesicles or bullae.
• 🤔 DDx: Herpetic whitlow, burn, acute paronychia, bullous impetigo, frictional bulla.
• 💊 Rx: Drainage of blisters and systemic antibiotics.

1.8. Botryomycosis

• ✅ Major Organisms: Most commonly S. aureus, followed by Pseudomonas spp.
• 🔬 Clinical Features: Cutaneous and subcutaneous nodules that may have pustules, purulent discharge, or become ulcerative/verrucous. Often in immunosuppressed hosts.
• 💡 Key Feature: "Grains" (macroscopic bacterial colonies) seen in biopsy specimens and pustular discharge.
• 📈 Risk Factors: Often develops at sites of trauma.
• 🤔 DDx: Ruptured epidermoid cyst, abscess, actinomycotic/eumycotic mycetoma, actinomycosis, atypical mycobacterial/dimorphic fungal infection.
• 💊 Rx: Surgical excision with debridement and/or antibiotic therapy based on organism.

1.9. Necrotizing Fasciitis

• 📚 Definition: Rapidly progressive necrosis of subcutaneous fat and fascia.
• ✅ Major Organisms: Usually polymicrobial (anaerobes and aerobes); ~10% secondary to GAS; also CA-MRSA.
• 🔬 Clinical Features: Leads to undermining and ulceration; may have a foul discharge and not bleed on incision.
  • Initially resembles cellulitis, but pain is often out of proportion to clinical findings and extends beyond apparent involvement.
  • Additional clues: tense edema, blisters, crepitus, mottled violaceous or pale gray color (impending necrosis).
  • Anogenital involvement is called Fournier gangrene.
  • Systemic symptoms: fever, chills, malaise, leukocytosis.
• 📈 Risk Factors: Older age, diabetes mellitus, alcoholism, peripheral vascular disease, immunosuppression.
• ⚠️ Diagnosis: Requires a high index of suspicion. Urgent surgical consultation is critical.
• 🤔 DDx: Cellulitis, trauma with hematoma, pyomyositis, clostridial myonecrosis, phlebitis.
• 💊 Rx: Surgical debridement is the mainstay; broad-spectrum IV antibiotics.

1.10. Pyomyositis

• 📚 Definition: Primary bacterial infection of skeletal muscle.
• ✅ Major Organism: Most commonly S. aureus.
• 📈 Associated with: Immunosuppression, including HIV infection.

1.11. Staphylococcal Scalded Skin Syndrome (SSSS)

• ✅ Major Organism: S. aureus, phage group II strains, producing exfoliative toxins that bind to desmoglein 1, leading to dissolution of the upper epidermis.
• 📈 Affected Populations: More common in infants and children; occasionally adults with chronic renal insufficiency.
• 🔬 Clinical Features:
  • Prodrome: Malaise, fever, irritability, sore throat; purulent rhinorrhea or conjunctivitis (initial infection often extracutaneous).
  • Tender erythema on face and intertriginous zones, generalizing over 1-2 days.
  • Skin becomes "wrinkled" and sloughs over 3-5 days, leading to denuded areas.
  • Radial fissures with scale-crust around mouth and eyes.
• 🤔 DDx: Sunburn, drug reaction, Kawasaki disease, Stevens-Johnson syndrome/toxic epidermal necrolysis (SJS/TEN).
• 💊 Rx: Hospitalization and IV anti-staphylococcal antibiotics.

1.12. Toxic Shock Syndrome (TSS)

• 📚 Definition: Severe, toxin-mediated systemic illness.

• Staphylococcal Toxic Shock Syndrome (TSS)

  • ✅ Major Organism: Staphylococcus aureus, producing exotoxin (toxic shock syndrome toxin-1).
  • 📈 Associations: Historically with menstruation/tampon use; nowadays with surgical packing, meshes, and cutaneous infections (e.g., abscesses).
  • 🔬 Clinical Features: Sudden onset of high fever, myalgias, vomiting, diarrhea, headache, pharyngitis. Hypotension is a key finding.
    • Scarlatiniform changes initially on trunk, spreading centrifugally.
    • Erythema and edema of palms and soles, followed by desquamation 1-3 weeks later.
    • Mucous membrane findings: erythema, "strawberry tongue," conjunctival hyperemia.
  • 🤔 DDx: Streptococcal TSS, drug reaction with sepsis, Kawasaki disease (in children), scarlet fever.
  • 💊 Rx: Hospitalization and IV antibiotics.

• Streptococcal Toxic Shock Syndrome (Streptococcal TSS)

  • ✅ Major Organism: GAS (especially M types 1 and 3), producing exotoxins A and/or B.
  • 📈 Associated Infection: Most common site is the skin (e.g., cellulitis, necrotizing fasciitis).
  • 💊 Rx: Hospitalization and IV antibiotics.

1.13. Scarlet Fever

• ✅ Major Organism: GAS, producing erythrogenic toxins (types A, B, C).
• 📈 Affected Population: Children (1-10 years), usually following streptococcal tonsillitis or pharyngitis.
• 🔬 Clinical Features:
  • Sore throat, headache, malaise, chills, anorexia, nausea, high fevers.
  • Erythema of neck, chest, axillae, generalizing over 4-6 hours.
  • Erythema blanches with pressure, studded with tiny papules ("sunburn with goose pimples").
  • Flushed cheeks with circumoral pallor.
  • Pastia lines: Linear petechial streaks in major body folds (axillary, inguinal, antecubital).
  • Desquamation of distal digits after 7-10 days.
• ⚠️ Post-infectious Sequelae: Acute glomerulonephritis, rheumatic fever.
• 🤔 DDx:
  • Palmoplantar desquamation: Kawasaki disease, TSS, any preceding infection with high fever.
  • Exanthem: Drug eruption, viral exanthem, early SSSS, scarlatiniform eruption in TSS and Kawasaki disease.
• 💊 Rx: 10-14 day course of penicillin or amoxicillin.

1.14. Bacteremia/Septicemia

• 🔬 Cutaneous Manifestations: Petechiae and purpura (may develop central pustules or hemorrhagic bullae), subcutaneous abscesses.
• Endocarditis: Can be acute (S. aureus) or subacute (Streptococcus spp.).
  • Cutaneous signs: Splinter hemorrhages, Osler nodes, Janeway lesions.

2. Diverse Bacterial Skin Infections: Gram-Positive Bacilli, Gram-Negative, Spirochetes, and Filamentous Bacteria

2.1. Gram-Positive Bacilli

2.1.1. Clostridial Skin Infections

• ✅ Major Organisms: Clostridia spp. (Gram-positive bacilli, live on dead organic matter).
• 🔬 Clinical Forms:
  • Anaerobic cellulitis: Generally due to Clostridium perfringens. Incubation >3 days. Minimal visible skin changes, crepitus, thin, dark gray-brown, foul-smelling ("dirty dishwater") exudate. Pain often absent or mild. No symptoms of toxemia.
  • Myonecrosis (Gas Gangrene): Shorter incubation, very rapid course. Overlying skin has dark yellow to bronze discoloration, sometimes with bullae or necrosis, and severe swelling. Toxemia (e.g., hypotension) generally present.
• 📈 Risk Factors: Trauma, diabetes mellitus, peripheral vascular disease, injection drug use.
• 💊 Rx: Early surgical debridement and empirical antibiotics (e.g., clindamycin plus a third-generation cephalosporin).

2.1.2. Corynebacterium (and Kytococcus) Skin Infections

• Erythrasma
  • ✅ Major Organism: Corynebacterium minutissimum.
  • 📚 Definition: Superficial, localized infection.
  • 🔬 Clinical Variants:
    • Interdigital: Most common, chronic maceration with fissuring or scaling.
    • Intertriginous: Thin red-brown plaques in axillae and groin/upper inner thigh.
    • "Disciform": Often on the trunk; diabetes mellitus is a risk factor.
  • 💡 Diagnostic Feature: Bright, coral-red fluorescence with Wood's lamp examination.
  • 💊 Rx: Topical clindamycin or erythromycin; prevent moisture with topical aluminum chloride.
• Pitted Keratolysis
  • ✅ Major Organisms: Kytococcus sedentarius and Corynebacterium spp.
  • 📈 Contributing Factors: Hyperhidrosis, prolonged occlusion, increased surface pH.
  • 🔬 Clinical Features: 1-3 mm crater-like depressions in the stratum corneum, primarily on soles. Often accompanied by a distinctive malodor.
  • 💊 Rx: Topical clindamycin or erythromycin; decrease sweat with topical aluminum chloride.
• Trichomycosis Axillaris
  • 📚 Definition: Common disorder, often subtle, accompanied by malodor.
  • 🔬 Clinical Features: Hair shafts ensheathed with adherent yellow > red or black concretions composed of organisms. Most common in axillae, can cause chromhidrosis.
  • 💊 Rx: Shaving of hair; topical antimicrobials (e.g., benzoyl peroxide, erythromycin) to prevent recurrence.

2.1.3. Other Gram-Positive Skin Infections

• Anthrax
  • ✅ Major Organism: Bacillus anthracis.
  • 📈 Epidemiology: Farmers, ranchers exposed to animals/hides; agent of biological terrorism.
  • 🔬 Cutaneous Clinical Features:
    • Incubation ~7 days.
    • Purpuric macule or papule (resembles insect bite, pruritic).
    • Within 48 hours, vesicle forms with surrounding non-pitting edema.
    • Central vesicle ulcerates, small vesicles may form around ulcer.
    • Lesion becomes hemorrhagic and depressed, forming a painless, black, necrotic eschar centrally, with increased surrounding erythema and edema.
    • Eschar dries, loosens, and sloughs over 1-2 weeks, no permanent scar.
  • 💊 Rx (Cutaneous): Fluoroquinolone (e.g., ciprofloxacin) for 7-10 days (or 60 days if risk of inhalational disease).
  • 🛡️ Prevention: Vaccine for high-risk populations.
• Erysipeloid
  • ✅ Major Organism: Erysipelothrix rhusiopathiae.
  • 🔬 Clinical Variants:
    • Localized cellulitis: Infection due to traumatic inoculation (e.g., fish/meat handlers). Hand is frequent site, characteristic red-violet color.
    • Generalized: Uncommon, multiple pink plaques, usually with immunosuppression, fever, arthralgias.
  • 💊 Rx (Localized): Penicillin.

2.2. Gram-Negative Cocci

2.2.1. Acute Meningococcemia

• ✅ Major Organism: Neisseria meningitides.
• 📈 Epidemiology: Young children (6 months-1 year) and young adults in close quarters (dormitories, barracks).
• 🔬 Clinical Features:
  • Skin lesions in 1/3 to 1/2 of patients due to septic emboli.
  • Initially subtle petechiae, evolving into irregularly shaped purpura with a central gunmetal gray necrosis.
  • Gram-negative cocci may be seen on Gram stain of lesional tissue.
  • Systemic manifestations: fever, chills, hypotension, meningoencephalitis, pneumonia, pericarditis, myocarditis.
• 💊 Rx: IV penicillin or ceftriaxone.
• 🛡️ Prevention: Vaccination.

2.2.2. Chronic Meningococcemia

• 📚 Definition: Indolent infection due to Neisseria meningitides.
• 🔬 Clinical Features: Recurrent episodes of fever, chills, night sweats, arthralgias. Polymorphous skin lesions (pink macules/papules, nodules, petechiae/purpura) representing small vessel vasculitis.
• 💊 Rx: As for acute meningococcemia; close contacts should also be treated.

2.2.3. Gonorrhea & Disseminated Gonococcal Infection

• (Refer to Chapter 69 for details).

2.3. Gram-Negative Bacilli

2.3.1. Pseudomonal Infections

• Gram-Negative Toe-Web Infection
  • ✅ Major Organisms: Pseudomonas aeruginosa (most common), E. coli, Proteus mirabilis.
  • 📈 Risk Factors: Pre-existing tinea pedis, occlusion (tight shoes).
  • 🔬 Clinical Features: Burning, pain. Malodorous exudate with a blue-green tinge, "grape-juice" odor, moth-eaten appearance of skin due to maceration and erosions. Can lead to cellulitis in severe cases.
• Otitis Externa ("Swimmer's Ear")
  • 🔬 Clinical Features: Swollen auditory ear canal with greenish purulent discharge. Extreme pain with manipulation of the pinna.
  • 💊 Rx: Antimicrobial drops (e.g., ofloxacin), oral analgesics.
• Pseudomonal Folliculitis (Hot Tub Folliculitis)
  • (Refer to Table 31.2 for details).
• Pseudomonas Hot-Foot Syndrome
  • 📈 Epidemiology: Develops acutely on soles of healthy children/adolescents after swimming in water with high P. aeruginosa concentrations.
  • 🔬 Clinical Features: Painful and tender, red-purple, 1-2 cm nodules on weight-bearing aspects of feet.
  • 💡 Note: Self-limiting.
• Cellulitis
  • 🔬 Clinical Features: Similar to S. aureus cellulitis. Can occur on lower extremity (with toe-web infection) or external ear (post-op).
• Ecthyma Gangrenosum
  • 📚 Definition: A sign of bacteremia or septicemia.
  • ✅ Major Organisms: Most commonly Gram-negative bacilli (Pseudomonas), but also opportunistic fungi.
  • 📈 Affected Population: Primarily immunocompromised hosts (especially with prolonged neutropenia).
  • 🔬 Clinical Features: Red-purple macule or patch that develops central necrosis (sometimes preceded by hemorrhagic bulla). Number varies. Most common location is the groin.
  • 💡 Diagnosis: Culture of tissue (sterile biopsy) combined with histopathology.
• Treatment of Pseudomonal Infections
  • Superficial: 5% acetic acid soaks, topical antibiotics (gentamicin, silver sulfadiazine). Oral fluoroquinolone if minimal improvement or severe.
  • Severe/Systemic: Piperacillin/tazobactam or doripenem (if penicillin-allergic); may combine with aminoglycoside.

2.3.2. Diseases Caused by Bartonella Species

• Cat-scratch disease: B. henselae. Vector: Cat flea. Epidemiology: Young people. Features: Lymphadenopathy, systemic symptoms.
• Bacillary angiomatosis: B. henselae (also B. quintana). Epidemiology: Immunocompromised. Features: Bright red papules (resemble pyogenic granulomas), lichenoid papules/plaques, subcutaneous nodules.
• Bartonellosis (Carrion disease, Oroya fever, verruga peruana): B. bacilliformis. Vector: Sand fly. Epidemiology: Peru, Ecuador, Colombia. Features: Oroya fever (fever, hemolytic anemia), Verruga peruana (erythematous patches with bright red papules/nodules).
• Trench fever/"urban" trench fever: B. quintana. Vector: Human body louse. Epidemiology: WWI troops, now associated with homelessness/poor hygiene. Features: Relapsing fever.

2.3.3. Other Gram-Negative Skin Infections with Fever and Skin Findings

• Vibrio vulnificus infection: Raw seafood/seawater exposure. Features: Hemorrhagic bullae with cellulitis.
• Tularemia: Infected rabbits, deerfly/tick vector. Features: Ulcers, lymphadenopathy (may show sporotrichoid pattern).
• Glanders: Burkholderia mallei. Direct contact with infected animals. Features: Sporotrichoid pattern (nodule, pustule, or vesicle with erythema).
• Plague: Yersinia pestis. Contaminated food/water, fleas. Features: Bubonic form (pustule/ulcer with painful lymphadenopathy), Septicemic form (emboli as vesicles, carbuncles, petechiae, purpura).
• Typhoid fever: Salmonella typhi. Features: "Rose spots" (2-8 mm pink, blanching papules on anterior trunk).

2.4. Spirochetes

2.4.1. Lyme Disease & Syphilis

• (Refer to Chapter 15 and Chapter 69 for details).

2.4.2. Other Treponemal Diseases

• Endemic Syphilis
  • ✅ Major Organism: Treponema pallidum endemicum.
  • 📈 Epidemiology: Africa, Arabian peninsula, Southeast Asia; children <15 years.
  • 🔬 Stages: Secondary (macerated patches on lips/tongue/pharynx, angular stomatitis, condyloma lata, lymphadenopathy); Tertiary (gummas, destruction of palate/nasal septum).
• Pinta
  • ✅ Major Organism: T. carateum.
  • 📈 Epidemiology: Central and South America.
  • 🔬 Stages: Primary (minute macules/papules with erythematous haloes -> infiltrated plaques); Secondary (smaller, variably pigmented scaly macules/papules); Tertiary (symmetric, depigmented, vitiligo-like lesions).
• Yaws
  • ✅ Major Organism: T. pallidum pertenue.
  • 📈 Epidemiology: Warm, humid, tropical climates; children <15 years.
  • 🔬 Stages: Primary (erythematous, infiltrated, painful papule -> ulcer); Secondary (smaller lesions adjacent to orifices or primary site); Tertiary (destructive skin lesions, palmoplantar thickening, chronic osteitis).

2.5. Filamentous Bacteria

2.5.1. Actinomycosis

• ✅ Major Organism: Most commonly Actinomyces israelii.
• 📍 Major Sites: Cervical, pulmonary, gastrointestinal.
• 🔬 Skin Involvement: Most common with cervical variant ("lumpy jaw") – irregular subcutaneous nodules that drain exudate containing "grains" (sulfur granules).
• 💊 Rx: Penicillin.

2.5.2. Actinomycotic Mycetoma

• ✅ Major Organisms: Most commonly Nocardia, also Actinomadura madurae, A. pelletieri, Streptomyces somaliensis.
• 📈 Source: Organisms found in soil and on plant material.
• 🔬 Clinical Features: Traumatic inoculation causes a painless nodule that enlarges, suppurates, and drains via sinus tracts. Purulent discharge contains grains. Foot is usual site. May involve underlying muscle and bone.
• 🤔 DDx: Eumycotic mycetoma (distinguished by culture or filament diameter).

2.5.3. Nocardiosis

• 📚 Definition: Infection caused by Nocardia species.
• 🔬 Four Major Clinical Forms:
  • Actinomycotic mycetoma: Half of all cases due to Nocardia. Painless nodule -> suppuration -> sinus tracts, grains. Foot is usual site.
  • Lymphocutaneous: Days to weeks after trauma. Persistent crusted pustule or abscess. Ascending lymphatic streaks (sporotrichoid pattern), tender lymph nodes.
  • Superficial cutaneous: Traumatic implantation of foreign objects.
  • Pulmonary/Systemic: Subcutaneous abscesses of chest wall, pustules, nodules, cutaneous fistulae. Almost universally fatal if untreated. Most commonly Nocardia asteroides.
• 💊 Rx: Sulfonamides are drugs of choice (minocycline alternative). Duration 6-12 weeks for localized disease. Surgical excision for deep abscesses.

---