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									    Skin infection and infestation

               Philip G. Murphy
  Consultant Microbiologist, AMNCH, Tallaght
            Clinical Professor, TCD

Tel ext : 3919
email : philip.murphy@amnch.ie
           Lecture objectives
•   Skin microbiology
•   Common skin infections
•   Emergency skin infections
•   Less common infections
•   Non-bacterial infections
                      Normal skin flora

• Resident:
       Coag. Neg. Staph, micrococci, diphtheroids

       anaerobes eg propionibacteria

• Transient:
       environmental contamination
       Staph. aureus, gram negatives

  survive a few hours, reduced by washing and skin antibacterial
  Staph aureus carriage: nose -   10-30 % outside hospital
                                  20-60 % in hospital staff
Resident colonisation
                   Pathogens 1
•   Staphylococcus aureus
•   Streptococcus pyogenes (Group A Strep)
•   Other haemolytic Strep
•   Anaerobes: Clostridia, cocci
•   Other bacteria:
       Corynebacterium diphtheriae, C. minutissimum,
       Erysipelothrix rhusiopathiae, Mycobacteria,
       Pseudomonas, Treponema, B. burgdorferi
• Viruses:    HS, VZ, Molluscum, Papovavirus, Coxsackie
• Fungi:      C. albicans, Microsporum, Trichophyton,
              Epidermophyton floccosum
               Pathogens 2
• Protozoa:
          Leishmania in Africa, Asia S. America
• Helminths:
          Onchocerciasis, Loa Loa, Strongyloides
• Arthropod:
          Sarcoptes scabiei, Pediculosis (lice)
               Skin ulcers
• vascular ulcers: skin flora        No Rx
                   If pathogens      +/- Rx
• Pseudomonas aeruginosa - ecthyma gangrenosum
• Anaerobes - Meleneys & Fournier’s gangrene
• Treponema - chancre
• M.tuberculosis - lupus vulgaris
• M. ulcerans - Buruli ulcer
• Borrelia vincenti - tropical ulcer
Furuncles (Boils) and Carbuncles
• Boils (furuncles) Staph. aureus lesions in hair
  follicles or sebaceous glands
• Carbuncles are larger deeper involving >1 hair
  follicle eg back of neck
• If recurrent check blood glucose.

• Rx flucloxacillin +/- Fusidic acid etc.
  +/- drainage
            Cellulitis and Erysipelas

• Spreading erythema and swelling
  Erysipelas when intradermal
  and due to GpAStrep
• 90% Haemolytic Strep (Group A)
• 10% Staphylococcus aureus
• ? Anaerobe involvement
Rx: Penicillin + Flucloxacillin
     Clindamycin + Ciprofloxacin
• Infection of hair follicles
   – usually pustular folliculitis
• Clinical presentation
   – follicle-centred pustules
   – e.g. in scalp, groin, beard &
     moustache (sycosis barbae)
• Mostly (95%) due to
  Staphylococcus aureus
• Treatment: oral flucloxacillin

Crusted vesicles on face/arms in children
Group A Strep. (Strep. pyogenes)
• +/- Staphylococcus aureus 2o infection
• infectious
• Impetigo neonatorum = Bullous impetigo
  due to Staphylococcus aureus (Group II, PT 71)
Rx: isolation, skin disinfection, antibiotic if severe
 Gas Gangrene
Microbiological emergency           Myonecrosis, gas production, sepsis
Caused by exotoxin-producing        Rapid onset and toxaemia / shock
Clostridium perfringens                Crepitus, brawny oedema
usually after direct inoculation of    Foul-smelling discharge, brown
contaminated, ischaemic wound          skin discoloration, bullae,
                                       May advance 1“ per hour!
                                       Disproportionate pain.
                                       Mortality > 25%
             Necrotising Fasciitis
                     Fig 1 Young woman presenting with cellulitis of
                     her lower abdomen after a caesarean section five
                     days earlier. Small areas of skin necrosis are
                     clearly visible

                     Fig 2 Late signs of necrotising fasciitis with
                     extensive cellulitis, induration, skin necrosis, and
                     formation of haemorrhagic bullae
Rx Surgery + Penicillin & Clindamycin
           Gangenous cellulitis
• Necrotising fasciitis
    – Type I polymicrobial (GNB, AnO2)
    – Type II Gp A Strep
•   Gas gangrene, (Clostridium perfringens)
•   Progressive synergistic gangrene (post op)
•   Synergistic necrotising
•   Immune compromised (Pseudomonas)
                   Ritter’s Disease
      or Toxic epidermal necrolysis, or Lyell’s Syndrome
                  or scalded child syndrome

•   Toxaemia, fever,
•   erythematous, tender skin lesions
•   Staph aureus Group II PT71
•   toxin induced split epidermis

Rx: Isolation, Skin disinfection, flucloxacillin
        Toxic Shock Syndrome
• Fever, rash, hypotension, GIT signs,
  myalgia, confusion, desquamation
• genital or non genital
• TSST-1 or enterotoxin
• 30% recurrence with low TSST-1 Ab
• Flucloxacillin, Ig.

• Skin lesions due to Strep. pyogenes /Staph. aureus
• Scrum pox, scabies, eczema, herpes
• nephritogenic strains (M types 49, 55)
• Gangrene
• Rx: debridement
  + antibiotics
(necrotizing fasciitis
              Lyme Disease
                  Borrellia burgdorferi

 Erythema chronicum margans

Rx amoxycillin, 3rd gen cephalosporins
• Subcutaneous: axillae, groin, perineum
  postpartum breast
• If foreign body - must remove
• usually Staph. aureus, less commonly Strep.
• Also anaerobes, TB,
• Rx: Drainage +/- antibiotic
• Infection of subcutaneous tissue around nailbed
• Staph aureus, Strep pyogenes, Herpes simplex

• Chronic form with loss of cuticle due to wet hands
  due to gram negatives, or yeasts
              Animal bites
• Pasturella multocida Rx: penicillins
  +/- anaerobes
• Others: Tetanus
           Cat scratch fever
           (Bartonella hensellae)
• Erysipeloid: Erysipelothrix rhusiopathiae
  blue-red discolouration with a sharp edge Rx: pen
• Erythrasma: Corynebacterium minutissimun Rx: Ery
• Acne vulgaris: skin flora ?Rx: Tet
• Lyme Disease: Borellia burgdorferi Rx: amp/cefotax.
• Diphtheria, burns, Anthrax, Leprosy, Yaws, Pinta

        Erythema chronicum margins
        in Lyme Disease
     Other viral

•   Warts: Papovavirus                  Varicella zoster(chickenpox)
•   Molluscum contagiosum: Pox virus
•   Orf, Milker’s Nodule: Pox viruses
•   Fifth Disease: Parvovirus

      Erythyma infectiosum
      (Fifth Disease
      or slapped cheek syndrome)

                                         Molluscum contagiosum
• Tinea (ringworm): Trichophyton, Microsporum, Epidermophyton
         Tinea capitis (scalp ringworm) M. audouini, T. schoenleinii
         Tinea corporis (body ringworm) Trichophyton spp.
         Tinea pedis (athlete’s foot) T rubrum,T. mentagrophytes var.
         interdigitalis, E. floccosum
         Tinea barbae (beard ringworm) T. verrucosum
         Tinea cruris (groin ringworm) T. rubrum, E. floccusum
         Tinea unguium (Nail ringworm) T. rubrum
Rx: antigungals: eg. terbinafine, griseofulvin
• Pityriasis versicolor: Malassezia furfur
• Sporotrichosis: Sporotrichium schenckii
• Mycetoma: Actinomyces,Streptomyces, Nocardia               Tinea corporis
Tinea pedis - usually between toes
Dermatophyte infection:
Trychophyton rubra, T. mentagrophytes, T. floccusum
• Scabies:    Sarcoptes scabiei mite
              Norwegian crusted
• Fleas:      Pulex irritans (human flea)
              Xenpopsylla cheopsis (Rat flea : Plague)
• Lice:       Pediculosis
                     Pediculus capitis (head louse)
                     Pediculus corporis (body louse)
                     Pythirus pubis (pubic or crab louse)
       May transmit Typhus (Rickettsia prowazeki)
                     Relapsing fever (Borellia recurrentis)
Rx: 1/2% Malathion topically
Varicella Zoster
                   Candida nail infection
Nappy rash
Candida albicans
not amoniacal
Roseola infantum
viral, incubation 10-15 d
follows sore throat and fever - mistaken for pen allergy
Leishmania tropica
dog, sandfly hosts
Kawaski disease
? Infectious
platelates raised, desquamation
coronary artery aneurysms
Herpes Zoster (shingles)
“ampicillin rash” seen in 2/3 rd’s
of patients with infectious mononucleosis
on ampicillin for “sore throat”
Scalp ringworm
  Trichophyton tonsurans
Ecthyma: exudate or crust of a pyogenic infection involving the entire epidermis.
Usually the consequence of neglected impetigo caused by Staphylococcus aureus or
group A streptococcus.
Can evolve from localized skin abscesses (boils) or within sites of preexisting trauma.
The margin of the ecthyma ulcer can be indurated, raised, and violaceous.
Untreated ecthymatous lesions can enlarge over the course of weeks or months to a
diameter of 2 to 3 cm.
Staphylococcal and streptococcal ecthyma occur most commonly on the lower
extremities of children, the elderly, and people who have diabetes. Poor hygiene and
neglect are key elements in its pathogenesis.

Ecthyma gangrenosum: single or multiple, cutaneous or mucous membrane ulcers that
are most often associated with prolonged neutropenia, Pseudomonas aeruginosa
bacteremia, and other serious bacterial infections. It resembles ecthyma caused by
staphylococcal or streptococcal organisms. First presenting as a painless nodular lesion, it
quickly develops a central hemorrhagic area that subsequently breaks down to form a
large necrotic ulcer.
Factitious Ulcer
                   Self induced
                   Young adults
                   HCW or associated with
                   No distress
                   Easy reach of dominant hand
                   Film “The Secretary”
                       Erysipelothrix rhusiopathiae         Orf / Molluscum contagiosum


Sarcoptes scabei

                                                               Chancroid : Haemophilus ducreyii
                                Lymphogranuloma venereum:

Bedbug (cimex leticularis)

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