Skin infection and infestation Philip G. Murphy Consultant Microbiologist, AMNCH, Tallaght Clinical Professor, TCD Tel ext :

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 substances Staph aureus carriage: nose % outside hospital % 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

Folliculitis 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

Impetigo Crusted vesicles on face/arms in children Group A Strep. (Strep. pyogenes) +/- Staphylococcus aureus 2 o infection infectious Impetigo neonatorum = Bullous impetigo due to Staphylococcus aureus (Group II, PT 71) Rx: isolation, skin disinfection, antibiotic if severe

Microbiological emergency Caused by exotoxin-producing Clostridium perfringens usually after direct inoculation of contaminated, ischaemic wound Gas Gangrene Myonecrosis, gas production, sepsis Rapid onset and toxaemia / shock Crepitus, brawny oedema Foul-smelling discharge, brown 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 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.

Pyoderma 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 Fournier/Meleneys)

Lyme Disease Borrellia burgdorferi Erythema chronicum margans Rx amoxycillin, 3rd gen cephalosporins

Abscesses Subcutaneous: axillae, groin, perineum postpartum breast If foreign body - must remove usually Staph. aureus, less commonly Strep. pyogenes Also anaerobes, TB, Rx: Drainage +/- antibiotic

Paronychia 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 Rabies Cat scratch fever ( Bartonella hensellae)

Others 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 Molluscum contagiosum: Pox virus Orf, Milker’s Nodule: Pox viruses Fifth Disease: Parvovirus Molluscum contagiosum Varicella zoster(chickenpox) Measles Erythyma infectiosum (Fifth Disease or slapped cheek syndrome)

Fungal 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

Infestations 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 transmitTyphus (Rickettsia prowazeki) Relapsing fever (Borellia recurrentis) Rx: 1/2% Malathion topically

Varicella Zoster

Nappy rash Candida albicans not amoniacal Candida nail infection

Roseola infantum viral, incubation 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 Personality: infantile,dependent,manipulative Film “The Secretary”

Anthrax Erysipelothrix rhusiopathiae Sarcoptes scabei Orf / Molluscum contagiosum Leprosy Bedbug (cimex leticularis) Chancroid : Haemophilus ducreyii Lymphogranuloma venereum: Chlamydia