What is the most common bacteria causing folliculitis?

Most Common Bacteria Causing Folliculitis

Staphylococcus aureus is the most common bacteria causing folliculitis, which is a superficial inflammation of the hair follicles. 1

Understanding Folliculitis

Folliculitis is characterized by inflammation that is superficial and limited to the epidermis, with pus present in the epidermis. This distinguishes it from deeper infections like furuncles, where suppuration extends through the dermis into the subcutaneous tissue. 1

Key characteristics of folliculitis include:

• Superficial inflammation of hair follicles 2
• Can affect individuals of any age or race 2
• Presents as inflammatory papules and pustules around hair follicles 1, 3

Causative Organisms

While several pathogens can cause folliculitis, bacterial causes predominate:

• Staphylococcus aureus: The predominant causative organism 1, 4, 3
• Other potential causative agents include:
  • Various Gram-negative bacteria 2
  • Fungal pathogens 2
  • Parasitic agents 2
  • Viral pathogens 2

Progression and Related Conditions

Folliculitis may progress to more severe forms of infection if left untreated:

• Furuncles (boils): When infection extends deeper through the dermis into subcutaneous tissue, forming a small abscess 1, 4
• Carbuncles: When infection extends to involve several adjacent follicles, producing a coalescent inflammatory mass with pus draining from multiple follicular orifices 1, 4

Antibiotic Resistance Patterns

The emergence of antibiotic-resistant strains is a growing concern:

• Methicillin-resistant S. aureus (MRSA) is increasingly identified in community-acquired skin infections 1, 5
• In a French study, approximately 5.8% of S. aureus strains causing skin infections were MRSA 5
• Resistance rates to other antibiotics included: penicillin (86%), erythromycin (32%), and ciprofloxacin (9.3%) 5

Diagnosis

Diagnosis is typically based on clinical presentation, but additional testing may be helpful:

• Cytology: A simple, rapid, and inexpensive diagnostic method that can reveal various bacterial, fungal, viral, and parasitic pathogens 2
• Culture: Recommended for recurrent or treatment-resistant cases 1
• Gram stain: May help identify the causative organism 1

Treatment Approach

Treatment depends on the severity and extent of the infection:

• For mild, localized folliculitis:

  • Topical antibiotics may be sufficient 4
  • Warm compresses can help promote drainage 1

• For more extensive or severe folliculitis:

  • Systemic antibiotics active against S. aureus are recommended 4, 3
  • Options include penicillinase-resistant penicillins (cloxacillin), cephalosporins, macrolides, or fluoroquinolones 4, 3

• For recurrent folliculitis:

  • Consider nasal decolonization with mupirocin if S. aureus carriage is identified 1
  • Daily chlorhexidine washes 1
  • Decontamination of personal items such as towels, sheets, and clothes 1

Special Considerations

• Patients with diabetes or immunodeficiencies may be more susceptible to gram-negative infections and may require broader-spectrum antibiotics 3
• Recurrent folliculitis may indicate underlying staphylococcal carriage, particularly in the anterior nares 1
• The prevalence of nasal staphylococcal colonization in the general population is 20-40% 1