Bacterial & Fungal skin, Soft
Tissue & Muscle infections
For Second Year Medical
Students
Prof. Dr Asem Shehabi
Infections of Skin & Soft Tissues
 Infections depends upon the Layers of Skin & Soft
Tissues involved ( epidermis, dermis, subcutis,
muscle).. Infections may involve one or several skin
layers.
 Skin Infections are associated with: swelling
,tenderness, warm skin, blisters, ulceration, fever
headache.. Rarely systemic disease..septicemia.
 Few Normal Bacteria & Yeast species live in hair
follicles- Skin .. may cause inflammation of Hair
follicles .. folliculitis, Abscess formation ( Boils)..
Type of Skin Infection-1
 Skin infection increased by presence of minor skin
injuries, abrasions.. Increase production Androgenic
Hormones after Puberty.. Increase activities
Sebaceous ducts.. secretion Sebum (Fatty Acid+
Peptides) Increase keratin & skin desquamation .
 Acne vulgaris is the most common skin disorder that
affects more Jung male adults than females..Mostly
face.. less other body parts due to accumulation of oil
sebaceous glands & dead tissues.
 Causative Agent: Anaerobic Propionibacteria acnes ,
gram+ve small bacilli excrete Enzymes.. split sebum ..
cause mild to severe forms inflammation.
Pityrosporum folliculitis is a condition where
the yeast invades hair follicles and causes an
itchy, Acne-like eruption caused by P.acne
Common Normal Skin Flora & Pathogens
 Staphylococci, hemolytic Streptococci ( Group A)
Micrococci, Propionibacteria , Acinetobacter
 Pityrosporum and other Yeasts..Candida species.
 S. aureus : coagulase+ve.. Various Enterotoxins &
enzymes( Coagulase, DNAse, hyaluronidase), skin
infections is the most common & important cause of
human Skin diseases.
 About 15-40 per cent of healthy humans are healthy
carriers of S. aureus ..nose or skin..feces.
 S.epidermidis is also common in skin..less virulent..
No toxins ..opportunistic pathogen..
 Clinical features commonly staphylococci:
 Folliculitis / Furuncles .. Hair follicular-based papules
and pustules.. Erythematous lesions.. affect All ages.
Skin Infections
Staphylococci skin infections
 S. epidermidis.. normal inhabitants of the skin
surface.. but Less Pathogenic. Most its infections
occur in normal individuals.. Dry Skin.. Injury.. but
underlying illness increase the risk of infection..
Infants.. compromised patients.
 S.aureus is more associated with serious skin
infection due to release of 2 important toxins..not all
strains
1-Toxic Schlock Syndrome: TSST-1(Enterotoxin)
Super antigens activate T-lymphocytes..Cytokines,
caused by localized-systemic infection.. Rash & Skin
Desquamation may be associated with sepsis, high
fever, multi-organ failure.. kidney failure.. can be fatal.
2-Scalded Skin Syndrome: Epidermolytic/ Exfoliative
Toxins (A,B).. Minor skin lesion.. Destruction skin
intercellular connection.. Large blisters containing
Fluid .. Skin scaling.. Painful.. Common in small
children.. Develop specific antitoxins..general massive
inflammatory response.. rarely causes kidney failure
..Shock.. Death without antibiotic treatment .
 Staphylococci are becoming increasingly resistant to
many commonly used antibiotics including:
Penicillins-Cephalospoins.. Methicillin & flucloxacillin ,
Augmentin (amoxycillin + clavulonic acid) .. Blactamase-resistant penicillins.. Other antibiotics
 Worldwide Spread Methicillin resistance (MRSA)..
20-90% ..in Jordan about 60% clinical isolates (2004)
Diagnosis &Treatment of staphylococcal
infections
 Lab Diagnosis of staphylococcal infections should be
confirmed by: culture, gram-stain, positive cocci, +ve
catalase , coagulase test .
 Effective treatment For MRSA .. Vancomycin,
Teicoplanin, Imipenem, Fusidic acid
 Drainage of pus collections before treatment
 Surgical removal (debridement) of dead tissue
(necrosis)
 Removal of foreign bodies (stitches) that may be a
focus of persisting infection
 Treating underlying skin disease..Prevent repeat
infection..No Vaccine available
Streptococcal Skin Infections-1
 Streptococcus pyogenes / B-H-Group A) ..Major
virulence factors: M-Protein, Hemolysin O & S,
Streptokinase (Fibrinolysin-digest Fibrin & Proteins in
Plasma), Streptodornase (DNAse) Erythrogenicpyogenic exotoxins,Toxic Shock Syndrome toxin
 Cellulites/ Erysipelas : Acute Rapidly Spreading
Infection in skin & Subcutaneous tissues..Following..
Wounds, Burns.. Highly Communicable..Massive
Edema, Lymphatic's inflammation..Children.
Impetigo: Pyoderma Superficial Layers Skin..
Epidermis, Blisters, Children.. Highly
Communicable..followed Streptococcus Sore Throat
or rarely S. aureus wound infection.
2/
– Scarlet fever: Following Group A Strept. Sore throat
infection.. Erythematous skin rash due to release
Erythrogenic Toxin.. Strawberry tong.. small
children.. permanent immunity
- Necrotizing fasciitis : Few strains group A , Minor
trauma, Invasive infection, pyogenic exotoxins,
Subcutaneous tissues & Fascia, Rapid spread
necrosis..Sever tissue damage..Pain, Fever, Sever
systemic illness.. Fatal without Rapid Antibiotic
Treatment
- Streptococcal Toxic Shock Syndrome:
pyrogenic toxin /superantigens/TSS, Infected
Trauma, Bacteremia, Respiratory & Multi Organ
Failure.. 30% Death.
Skin rash - Scarlet Fever
B-H-Streptococci
Diagnosis & Treatment
 Culture on blood, B-Hemolytic reaction, Gram-+ve
cocci in chain, catalase-ve, Bacitracin-Susceptible
 Serotyping should used to confirm group of
streptococcal infection.. A, B, C etc. using antisera
against group-specific cell wall carbohydrate –
Antigens (Lancefield classification)
 Penicillin is the drug of choice.. All Group A
streptococci are very sensitive to penicillin.
 Patients with penicillin allergy may be given
Erythromycin.. Azithromycin..
Less Common Bacterial Skin Infections
 N.gonorrhoea..Salmonella typhi or paratyphi..
General Skin rash..Rosa spots
 Soft chancre /chancroid : Haemophilus
ducreyi..Gram-ve bacilli, STD.. Painful Skin Ulcer..
Extra Genitalia .. Common in Tropical Region.
 Syphilis: Treponema pallidum.. Genital ulcers..
 Meningococemia: N. meningitidis.. Sepsis, Skin rash
& hemorrhage..Thrombosis
 Rickettsia diseases: Small intracellular bacteria
human, R. prowazeki (Typhus), R. rickettsii (Spotted
fever).. Transmitted by body lice.. systemic diseases
 Pseudomonas aeruginosa : Wound infections, Burns
/2
 Bacillus anthracis.. Cutaneous Black Lesions..
 Clostridium perfingens and other sp. : Necrotizing
Fasciitis.. Myonecrosis, Cellulitis, tissues putrefaction,
gas production/ Gas gangrene.. Surgical/Traumatic
wound.. Skin- Subcutaneous (Mixed Infection)..
Specific Enzymes & Exotoxins
 Borrelia Burgdorferi : Lyme disease .. Transmitted
by Tick/ Insect bites.. Incub. 1-3 weeks.. Annular
Rash.. Chronic Skin Lesion.. Cardiac & Neurological
Abnormality.. Arthritis.. Endemic USA, China, Japan
 Bartonella species: G-ve bacilli Bartonellosis Cat
Scratch Fever..followed Cat scratch or bite..Skin
lesions.. Subacute regional lymphadenitis..Septicemia.
Tuberculosis-Leprosy-1
 Cutaneous Tuberculosis (TB).. Cutaneous TB is a
relatively uncommon form of extra-pulmonary TB..
 Rare M. tuberculosis.. Common M. marinumulcerans.. Low Temperature..Water.. Skin Lesions..
Chronic cutaneous ulcer.. Small granulomas Follow
skin injury..Trauma.
 Leprosy: Chronic bacterial infection caused by
M. leprae.. It primarily affects cold body sites skin,
mucous membranes.. peripheral nerves ..nose, ears,
eye lids and testes.
 characterized by multiple skin lesions accompanied
first by sensation loss/ anesthesia.. sensory loss in the
affected areas, toes, finger tips, tissue destructions.
Leprosy-2
Leprosy-3
3/
 Lebrosy can affect people of all races around the
world. However, it is most common in warm, wet
areas in the tropics and subtropics.
 In most cases, it is spread through long-term
contact with a person who has the disease but
has not been treated.
 Most people will never develop the disease
even if they are exposed to the bacteria.. have
a natural immunity to leprosy.
 Worldwide prevalence is reported to be around 5.5
million, with 80% of these cases found in 5 countries:
India, Indonesia, Myanmar, Brazil and Nigeria.
Clinical Leprosy-4
 Infection incubation period range from 6 months - 40
years or longer. usually begins in the extremities
 Leprosy forms depend on the person's immune
response to the infection.
 There are several forms of leprosy:
 Tuberculoid form.. Mild Form.. Few AF Bacilli,
Lepromin skin test +ve, Presence nerve sensation
 lepromatous type Severe form.. Numerous Acid-fast
bacilli, Loss nerve sensation.. Lepromin skin test -ve
Diagnosis & Treatment
 Lab Diagnosis: A skin biopsy may show
characteristic granulomas (mixed inflammatory cell
infiltrate in the deeper layers of the skin, the dermis)
with involvement of the nerves.
 Presence Acid fast bacilli.. number of bacilli visible
depending on the type of leprosy.. No Culture.. No
Protected Vaccine available.. BCG may help &
reduce the severity of disease
 Treatment: Dapsone, Rifampin, Clofazimine. Life-long
Treatment ..No Cure but Less Tissue Damage and
Spread of Infection.
Common Fungal Skin Infection-1
 Superficial & Cutaneous Mycosis: Invade only dead
tissues of the skin.. keratinized body tissues.. Skin,
Hair, Nails. causes skin peeling, redness, itching,
burning.. less blisters and sores.
 Malnourishment, poor hygiene, suppressed immunity
& warm moist climate may increase the incidence
fungal skin infection
 Dermatophytes: Trichopyhton, Microsporum,
Epidermatophyton spp., Yeast forms Piytrosporum,
Trichosporons ..present in hair follicles & skin folding.
 Transmission: Usually from person to person or
animal to person.. dust particles..common more with
chronic skin disorders.
Tinea Corporis
Tinea pedis -Tinea capitis kerion
Skin Fungal Infection-2
 Tinea capitis: Hair follicles, scalp circular patches..
Scaling, Hair Loss..Children..Rare adults
 Tinea corporis: Skin annular-erythematic lesions,
Vesicles, Scaling.. Itching.. Rash.. All Ages.. Mostly
caused by Dermatophytes ..rarely mixed with Yeast
 Tinea pedis : Red vesicles.. Interdigital spaces, web
lesions, Toes, Plantar surface.. Feet, Itching.. Chronic
lesions..Wearing tight shoes/socks, increased feet
sweating.. More in Adults than children.. Cased by all
Dermatophytes.
 Tinea cruris: Pelvic area.. Groin.. Erythematic
Lesions, Itching, Chronic.. more common in male
young adults..mostly Epidermophyton spp
Skin Fungal Infection-3
 Tina unguium (Onychomycosis): Mostly caused by
Trichophyton ,Microsporum.. less Candida..fingernails
& toenails. Nails become colorless/dark colored,
thicken, disfigure and brittle..Diabetes
 Psoriasis is a common skin disorder produces thick
red plaques covered with silvery scales..can affect the
nails, scalp, skin and joints..not caused by fungus and
not transmitted to others.
 Eczema develops due to multiple immunological &
other medical conditions.. Skin becomes inflamed or
irritated..No infectious agent involved.
 Aspergillus & Cryptococcus spp. Rare cause localised
skin or nail..
Onychomycosis-Psoriasis
Skin Fungal Infection-3
 Tinea Versicolor/Pityriasis: Malassezia furfur /
Piytrosporum folliculitis.. Lipophilic Yeast
..difficult to culture in Labs. Part skin flora..
Endogenous infection.. Skin Moist-Folded
Area.. Discoloration.. Red Spots.. Mostly FaceNeck Finger Trunk..Mild..rarely Chronic, Stress
conditions, UV-Light, Common in young adults.
 Head dundruff, Seborrheic dermatitis.
 White & Black Piedra..Trichosporon spp., Soft
to hard nodules. scalp hair & hair shaft , skin
face , any body part.
Yeat skin infection
 Candidasis: C. albicans, C. glabrata, C. tropicalis..
Other spp. Endogenous infection..moist folds of skin..
Lesions, finger nails, toenails, Finger webs.. Diabetes,
immuno-compromessed.. more common in Infant &
women.. Candida infections can look just like other
types of dermatitis /eczema or skin allergy. itching,
redness..infection
 Blasmycosis: Blastomyces dermatitidis &
Histoplasmosis : Histoplasma capsulatum..
Dimorphic Fungi.. Soil ..Spore Inhalation.. Respiratory
infection.. Systemic Infection.. Complications: Skin
ulcerations/lesions Granulomas..causes severe
damages..common USA, Canada
Tinea Pityrisis / versicolor
Seborrheic dermatitis
Lab diagnosis-4
 Direct microscopic examination of skin scales
dissolved in a 10 % solution potassium hydroxide
(KOH).. demonstrating the fungus as small Filaments /
Yeast like structures.
 Culture: Sabouraud Dextrose agar, Incubation at
room temperature & 37 C for 2-6 Weeks. . Slow
growth for Dermatophytes..Rapid growth Candida.
 ChromCandida agar.. used for rapid identification of
common Candida species.
 Treatment: Most skin infections respond very well to
topical antifungal drugs..Less systemic drug .. interact
with Ergosterol ..causing Fungal Cell membrane
disruption.. Imidazole drugs ..miconazole,
clotrimazole, econazole, ketoconazole, fluconazole