Bacterial Infections in Dermatology: Overview and Management

Flora

Two Types

Resident Flora 

• It is always present.
• Acts as the first line of defence.
• Forms a protective barrier.
• Important resident flora that can cause problems are.
  • Propionibacterium acnes
  • Corynebacterium
  • Staphylococcus epidermidis
• Transient Flora
  • Comes and goes.
  • Pathogenic flora that can cause diseases.
  • Examples:
    • Staphylococcus aureus
    • Beta-hemolytic streptococci

Classification of Bacterial Infections

• Non-follicular Infections
  • Not centered around hair follicles.
  • Can be caused by both Streptococcus and Staphylococcus.
• Follicular Infections
  • Always caused by Staphylococcus aureus.
  • Types include:
    • Folliculitis
    • Furuncle
    • Carbuncle

Also read: Bedside Tests in Dermatology

Impetigo

Overview

• Most commonly seen in children on the face.
• A superficial infection with two types:

1. Non-bullous Impetigo
   • More common, also known as Impetigo contagiosum.
   • Caused by both Streptococcus and Staphylococcus, with:
     • Staphylococcus is more common in developed nations.
     • Streptococcus is more common in developing nations.
   • If both are options, mark Streptococcus.
   • Common complication: Poststreptococcal glomerulonephritis (PSGN).
   • Spreads easily, hence the name Impetigo contagiosa.
2. Bullous Impetigo
   • Usually seen in newborns, preschoolers, and toddlers.
   • Can lead to Staphylococcal scalded skin syndrome (SSSS).

Ecthyma

• A deep but localized infection, primarily caused by Streptococcus but can also be caused by Staphylococcus.
• Commonly found on buttocks, thighs, and legs.
• Characterized by ulcers covered by thick, necrotic crusts, which are painful.

Erysipelas and Cellulitis

• These are generalized kind of infection (not localized)
• Soft tissue infection 
• Present usually on the lower limb or upper limb with warm, tender plaques
• Associated with fever and constitutional symptoms

Also read: Viral Skin Infections

Erysipelas

• It is more superficial
• Affects superficial dermis and lymphatics
• Well defined margins 
• Ear involvement seen

Cellulitis

• Is deeper
• Involve the whole of the dermis and the subcutaneous tissue.
• ILL defined
• Ear involvement is not seen

Pyoderma: Follicular Infections

Types of Folliculitis

1. Superficial folliculitis: Localized infection of upper part of the hair follicle
2. Deep Folliculitis: A deep infection around the hair follicle is called deep folliculitis. 

Severe Infections

• Furuncle: severe infection, involves peri follicular area
• Carbuncle: infection involves contiguous hair follicles
  • In superficial folliculitis 
  • Superficial lesions 
  • Located around hair margin 
  • Pustular causes little discomfort, not very painful—or is also called Bockhart's Impetigo

Bockhart's Impetigo

• Bockhart's impetigo is a superficial folliculitis (not an impetigo)
• Also known as Staphylococcus aureus superficial folliculitis
• caused by Staphylococcus aureus
  • Seen mostly in children. 
  • Pustules are seen
  • Develop in crops over the scalp and hair margin
  • Also present in the extremities. 
  • They heal within a week. 

Also read: INI-CET High Yield Questions for Dermatology

Chemical and Pseudofolliculitis

• Chemical folliculitis: Folliculitis caused by irritation from chemicals
• Pseudofolliculitis: This happens after waxing if it is not done properly.
  • The hair gets damaged, and this leads to inflammation of the hair follicle.

Deep Folliculitis

• Folliculitis can be very deep and is called Sycosis barbae. 
• Misnomer: Sycosis means a fungus, but it is a bacterial infection usually seen in the beard area. 
• It is differentiated from Tinea barbae, which is usually itchy and has a KOH positivity. 
• They appear like a fig tree, with a fig-like appearance

Lupoid sycosis

Severely deep folliculitis leads to lupoid-like scarring or lupus-like scarring. 

Peri-folliculitis

Furuncle 

• Lot of inflammation around a hair follicle

Carbuncle 

• Multiple hair follicle being affected 
• It is usually seen in diabetics and in the back

Both are very painful conditions requiring oral antibiotics.

Also read : Morphea: Causes, Symptoms, Risk Factors, Diagnosis, Treatment and Complications

Bacterial Toxin-Mediated Dermatoses

• Staphylococcus causes Staphylococcal scalded skin syndrome.
• Streptococcus causes scarlet fever
• Both can cause toxic shock syndrome
• Staphylococcal scalded skin synBacterial Toxin-Mediated Dermatoses syndrome is also called Ritter's disease 

○ It is different from Reiter's disease, which is to be discussed in systemic disease in skin. 

Staphylococcal Scalded Skin Syndrome (SSSS)

• This is seen in newborn 
• The primary is in the form of Bullous impetigo, ear infection caused by Streptococcus, which releases toxin called exfoliative toxin 1, which binds to Desmoglein-1, causing intraepidermal split (sub corneal split) 

 Presentation: 

• Newborn with fever
• Constitutional symptoms and might have had a Bullous impetigo
• Ear infection
• Peeling of skin. 

Positive nikolsky sign is seen 

• Also present in pemphigus group of disorder
• Positive in Staphylococcal scalded skin syndrome
• Positive in a drug reaction called toxic epidermal necrolysis
• Pseudo Nikolsky sign because it is not happening because of antigen or antibody deposition but because of keratinocyte necrosis and deposition. 
• Infections caused by staphylococcus and streptococcus

Infections Caused by Staphylococcus and Streptococcus

Corynebacterium Infections

Resident flora

• Etiology:
  • Healthy adults
  • Hot and humid climates
  • Asymptomatic/pruritic

Site:

Most common: toe webs followed by the groin crease

• Three infections:
  • Erythrasma
  • Pitted keratolysis
  • Trichomycosis axillaris

Types of Infections

1. Erythrasma is caused by specific species of Corynebacterium minutissima in presence of asymptomatic or hyperpigmentation that may be present on the axilla, groin, or interweb space. 

• Wood's lamp test: To differentiate it with tinea  
• Treatment: Tropical therapies include fusidic acid, clindamycin, or erythromycin. Oral options: clarithromycin, erythromycin

2. Trichomycosis axillaris 

• It is misnomer and not caused by fungal infection
• Corynebacterium causes this.
  • Corynebacterium tenuis (yellowish/brown granules present in axillary hair)
  • Corynebacterium propinguum
  • Corynebacterium flavescens
  • Serratia marcescens

3. Pitted keratolysis 

• Micrococcus sedentarius (now renamed to Kytococcus sedentarius) leads to Pitts in feet.
  • These superficial pits are asymptomatic on feet.

• Dermatophilus congolensis or species of Corynebacterium, Actinomyces, or streptomyces. 
• Seen in individuals who have
  • Hyperhidrosis 
  • Swimmers
  • Wet work
• Feet will be macerated here. 

Also read : Myoclonus: Causes, Symptoms, Diagnosis and Treatment

Anthrax 

• Caused by:
  • Bacillus anthracis
  • Zoonotic
  • Livestock handlers
  • Malignant pustule—no puss or no pain
• Development of papules or nodules that increase in size with pus to leave behind bluish regions on the exposed part.

Pseudomonas Skin Infections

Overview

• Pseudomonas aeruginosa
• It can cause green nails Syndrome
• Pseudomonas produces a toxin (pyoverdine), which is green in color. 
• Sometimes, an interweb infection can happen. 

• To differentiate with other diseases:
  • Do Wood's test—greenish fluorescence.
• It also causes hot tub folliculitis.
  • History of taking baths in Jacuzzis or contaminated swimming pools. 
  • On trunk: patient develops multiple monomorphic erythematous papules on trunk.

Three types of Ecthyma

1. Ecthyma Contagiosum - Parapox 
2. Ecthyma Infectiosum - Streptococcus 
3. Ecthyma Gangrenosum - Pseudomonas

Hemorrhagic pustules that evolve into necrotic ulcers

Eschar: hemorrhagic pustules rupture and cause black heaped up crust known as Eschar. 

Some others: 

• Necrotising fasciitis
• Gangrenous cellulitis
• Ear infection
• Treatment antipseudomonal beta-lactam (penicillin or cephalosporin), aminoglycosides, carbapenems (imipenem, meropenem)

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Management of Bacterial Infections

General Management Strategies

• Local hygiene
• Elimination of immunocompromising factors such as
  • Malnutrition, steroid therapy, and other systemic conditions like diabetes
• Remove crust by using condy's compresses.
  • KMNO4 (potassium permanganate)
  • KMNO4 has very good antiseptic and astringent activities. 
  • In water, put 1 or 2 crystals and dilute them to the tune of 1:1000.
  • And then use compresses to remove the crust. 
  • This way, remove the crystal and crust. 

Topical Treatments

• It is a localized infection; topical antibacterial agents can be used:
  • Bacitracin
  • Polymyxin B 
  • Neomycin 
  • Sodium fusidate
  • 1% framycetin
  • Mupirocin
  • Retapamulin, a newer agent
  • Ozenoxacin, a newer agent

Deep infections, immunocompromised patients use:

Systemic treatment

• Beta-lactamase-resistant penicillin, e.g., methicillin, nafcillin, cloxacillin, dicloxacillin
• Amoxicillin
• Erythromycin, cotrimoxazole, and the cephalosporins.
• These are oral groups of drugs. 

Recurrent infections

• Increased bacterial carriage 
• Intranasal mupirocin (apply it inside the nose)
• To stop colonization of streptococcus
  • Stop recurrent infections. 
  • Clindamycin (if serious, orally): 150 gm of BD for 3 months
• Rifampicin 600 mg/day for 10 days