Skin infection and infestationSkin infection and infestation

Philip G. Murphy

Consultant Microbiologist, AMNCH, Tallaght

Clinical Professor, TCD

Tel ext : 3919

email : philip.murphy@amnch.ie

Lecture objectivesLecture objectives

• Skin microbiology

• Common skin infections

• Emergency skin infections

• Less common infections

• Non-bacterial infections

Normal skin floraNormal 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 - 10-30 % outside hospital

20-60 % in hospital staff

Resident colonisation

Pathogens 1Pathogens 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 ulcersSkin 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 ErysipelasCellulitis 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 childrenGroup 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

Microbiological emergencyCaused by exotoxin-producing Clostridium perfringensusually after direct inoculation of contaminated, ischaemic wound

Gas Gangrene

Myonecrosis, gas production, sepsis Rapid onset and toxaemia / shock

Crepitus, brawny oedemaFoul-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 cellulitisGangenous 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 DiseaseRitter’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 SyndromeToxic 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.

PyodermaPyoderma

• 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 DiseaseBorrellia burgdorferi

Erythema chronicum margans

Rx amoxycillin, 3rd gen cephalosporins

AbscessesAbscesses

• Subcutaneous: axillae, groin, perineum

postpartum breast• If foreign body - must remove• usually Staph. aureus, less commonly Strep.

pyogenes• Also anaerobes, TB,• Rx: Drainage +/- antibiotic

ParonychiaParonychia

• 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 bitesAnimal bites

• Pasturella multocida Rx: penicillins

+/- anaerobes

• Others: Tetanus

Rabies

Cat scratch fever

(Bartonella hensellae)

OthersOthers• 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 marginsin Lyme Disease

Other viralOther 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)

FungalFungal

• 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 toesDermatophyte infection:Trychophyton rubra, T. mentagrophytes, T. floccusum

InfestationsInfestations• 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

Nappy rashCandida albicansnot amoniacal

Candida nail infection

Roseola infantumviral, incubation 10-15 dfollows sore throat and fever - mistaken for pen allergy

Leishmania tropicadog, sandfly hosts

Kawaski disease? Infectiousplatelates raised, desquamationcoronary artery aneurysms

Herpes Zoster (shingles)

“ampicillin rash” seen in 2/3 rd’s of patients with infectious mononucleosison ampicillin for “sore throat”

Scalp ringwormTrichophyton 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 UlcerSelf inducedYoung adultsHCW or associated withNo distressEasy reach of dominant handPersonality: infantile,dependent,manipulativeFilm “The Secretary”

Anthrax

Erysipelothrix rhusiopathiae

Sarcoptes scabei

Orf / Molluscum contagiosum

Leprosy

Bedbug (cimex leticularis)

Chancroid : Haemophilus ducreyiiLymphogranuloma venereum: Chlamydia