Bacterial skin infections

Bacteria such as some Staphylococcus species, Corynebacterium spp., Brevibacterium spp and Acinetobacter live on normal skin and cause no harm. Propionibacteria live in the hair follicles of adult skin and contribute to acne.

Some bacteria invade normal skin or wounds (causing wound infection). Bacteria, like viruses, may also sometimes result in exanthems (rashes). The most common bacteria to cause skin infections are:

• Staphylococcus aureus
  • Folliculitis
  • Furunculosis (boils)
  • Impetigo (school sores)
  • Methicillin (meticillin) resistant Staph. aureus
  • Staphylococcal scalded skin syndrome
  • Toxic shock syndrome
• Streptococcus pyogenes
  • Cellulitis
  • Erysipelas
  • Impetigo
  • Necrotising fasciitis
  • Scarlet fever
• Overgrowth of Corynebacterium spp. (erythrasma, pitted keratolysis & trichomycosis axillaris)

Other less common bacterial infections that cause skin signs include:

• Gonorrhoea
• Meningococcal disease
• Erysipelothrix insidiosa, cause of erysipeloid (usually an animal infection)
• Haemophilus ducreyi, cause of chancroid
• Haemophilus, cause of cellulitis in young children
• Klebsiella rhinoscleromatis, cause of rhinoscleroma
• Pseudomonas aeruginosa causes wound infections, athlete's foot, gram negative folliculitis, chronic paronychia, spa pool folliculitis and ecthyma gangrenosum
• Calymmatobacterium granulomatis, cause of granuloma inguinale
• Bacillus anthracis, cause of anthrax
• Clostridium perfringens and other species cause gas gangrene
• Treponema species cause syphilis, yaws and pinta
• Borrelia species cause Lyme disease
• Bartonella species cause cat scratch fever, bacillary angiomatosis and bartonellosis
• Mycobacterium species cause tuberculosis, leprosy and atypical mycobacterial infections
• Serratia marcescens is a facultative anaerobic gram-negative bacillus that may rarely cause skin infections such as cellulitis, abscesses and ulcers. These are more likely to arise in patients with immunodeficiency.

Other conditions sometimes caused by bacterial infection include:

• Kawasaki disease (mucocutaneous lymph node syndrome)
• Pseudofolliculitis barbae (shaving bumps)
• Sarcoidosis
• Scalp folliculitis
• Osler nodes and Janeway lesions (bacterial endocarditis)

Bacterial vaginosis is one cause of vaginal discharge, in which lactobacilli are replaced by gram positive cocci.