Skin Infections (1) Fungal infections: # Tinea infections, including: 1.Tinea pedis (feet) 2.Tinea cruris (groin) 3.Tinea corporis (body) 4. Tinea capitis (head) # Candidiasis of skin, nail or feet # Pityriasis versicolor, caused by Malassezia furfur, and characterized by non-itchy hypo-or hyperpigmented macules.

Pityriasis versicolor

(2) Pediculosis pubis, caused by crab lice; and affects the head, body, pubic area. (3) Scabies, caused by the insect Sarcoptes scabiei, and characterized by: * Affects finger clefts, forearms and genitalia * Acquired by sexual close contact. (4) Viral skin infection, caused by herpes virus, enteroviruses, Measles virus, & Rubella virus (5) Commensal skin bacteria cause acne vulgaris

Acne vulgaris

Tinea infections Scaly lesions with raised Commonly seen during Infect skin, nails and Acquired from domestic or farm animals Caused by three fungal genera: * Trichophyton, * Microsporum * Epidermophyton

Trichophyton Epidermophyton Microsporum

Features of tinea Tinea pedis (feet): Infects interdigital spaces and causes itching, and blisters. * It is caused by Trichophyton rubrum and Trichophyton Tinea cruris (groin): Causes genitourinary Tinea corporis (body): Known as 'ringworm’. * It infects the arms, trunk and legs. * It caused by Trichophyton Tinea capitis: Infects scalp and hair. Causes scaling of scalp, dandruff, broken hair

Tinea pedis Tinea capitis

Lab. Diagnosis of tinea Presence of scales is diagnostic. Wood’s ultraviolet lamp shows Microsporum (only) as green Specimens collected are: Skin scales, nail clippings, and hair. Skin scales are obtained from edge of the lesion. Swabs are Microscopy: Using potassium Culture: Selective Sabouraud agar containing cycloheximide. Incubation at room temp. up to 3 weeks.

Acquired from animal (cats, dogs, rodents, cattle)Microsporum canis Acquired from soil Microsporum gypseum Acquired from school mates and colleagues Trichophyton rubrum Epidermophyton floccosum Sources of Tinea infections

Infections of Wounds, Abscesses, Burns Possible Pathogens: # Pseudomonas aeruginosa, Proteus, E. coli, Bacteroides, Klebsiella, Pasteurella. # Staph. aureus, Strep. pyogenes, Enterococci, Ana. streptococci, Cl. tetani, Mycobacteria, Cl. perfringens, Actinomycetes # Mycetoma, Histoplasma, Blastomyces, Candida albicans, Cryptococcus neoformans.

C. albicans

Association with Pyogenic S. aureus causes abscesses & skin P. aeruginosa is associated with burns and hospital cross E. coli, Proteus, Pseudomonas, & Bacteroides are isolated from abdominal Cl. perfringens causes deep wounds infections and gas Cl. tetani causes umbilical neonatal Myco. tuberculosis causes cold abscesses.

TB cold abscess

Lab. Diagnosis of of Wounds, Abscesses, and Burns infections Collection and Collect pus. If pus is absent, use a swab and transport in Amies transport If mycetoma is suspected, collect from If tuberculosis is suspected, aspirate pus. Report pus colour: red, brown, grey, Examine granules: colour, shape, size, and consistency.

Colour of pus

Examine Gram smear for: Staphylococci, streptococci, enterococci, Proteus, E. coli, Pseudomonas, Bacteroides, Cl. Examine for ZN stain for acid fast Examine KOH smear for: # Budding (Candida and Cryptococcus) # Branching (Nocardia) # Mycetoma granules (black, red, yellow, etc) # Actinomyces yellow granules.

Mycetoma

Inoculate blood agar and Mc Conkey agar plates and incubate aerobically Inoculate a neomycin plate & another blood agar plate and incubate anaerobically for 48 Inoculate a cooked meat medium and incubate up to 72 Decontaminate TB specimens by adding 4% sodium hydroxide for 10 min., and inoculate an LJ slope and incubate for 8 For fungi, inoculate a Sabouraud agar

Examination of LJ slope: M. TB with raised, dry, creamy Blood, neomycin, Mac Conkey agar: Look for colonies of aerobic and anaerobic Cooked meat medium, Look for: # Turbidity, reddening of meat, and gas bubbles (Cl. Perfringens) # Decomposition and blackening of the meat Subculture the cooked meat medium if the anaerobic plates were sterile.