Skin Infections Chapter 23 Normal Microbiota of the Skin o large numbers of microorganisms live on in the skin o numbers depend upon location and moisture content o skin flora are opportunistic pathogens o most in 3 major groups diphtheroids staphylococci yeasts o Diphtheroids named for resemblance to Corynebacterium diphtheriae Gram positive bacteria with variable shape often club o Staphylococci low virulence no toxins responsible for body odor due to bacterial break down of sweat common skin diphtheroid Propionibacterium acnes in acne feed on trapped sebum in blocked hair follicles Gram positive salt tolerant Maintains balance among microbial skin flora principle species Staphylococcus epidermidis prevent colonization of pathogenic flora on skin eukaryotes tiny lipophilic feed on lipids yeast on normal skin from late childhood throughout life very common and generally harmless in some can cause skin conditions such as scaly rash dandruff or tinea versicolor o Fungi yeasts o Tinea versicolor Hair Follicle Infections o Folliculitis o Furuncles small red bump or pimple often hair can be pulled infection resolves if infection spreads from follicle to adjacent tissues a furuncle or boil localized redness swelling tenderness pus often drains from the lesion with a plug of inflammatory cells and dead tissue numerous furuncle lesions produce a carbuncle o Carbuncles large areas of redness swelling tenderness often fever etc numerous sites of draining pus usually develop in areas where skin is thick Ex back of the neck o Causative Agent most hair follicle infections caused by Staphylococcus aureus spreading to subcutaneous tissue larger abcess systemic spread can lead to infection of the heart bones and brain more virulent than more common staphylococci on the skin in nostrils a very significant pathogen responsible for numerous medical conditions Staphylococcus aureus two important virulence factors among many coagulase not an enzyme o coagulase prothrombin staphylothrombin converts fibrinogen fibrin o some coagulase on Staph aureus surface coated with fibrin protection blood clots from phagocytosis clumping factor o attaches Staph aureus to fibrinogen and fibrin in wounds o catheters etc become fibrinogen coated quickly after insertion aids Staph Scalded Skin Syndrome o Staphylococcal scalded skin syndrome SSSS aureus colonization there primarily in infants potentially fatal o Causative Agent Staphylococcus aureus Disease due to production of toxin exfoliatin toxin destroys integral layers of the outer epidermis tox genes either on plasmid or on the chromosome o Symptoms skin appears burned scalded first generalized redness other symptoms malaise irritability fever nose mouth and genitalia may be painful before other indicators become apparent within 48 hours skin becomes red wrinkled large fluid filled blisters form skin is tender to the touch may feel rough toxin released at even a small infection spreads to larger areas of skin toxin splits the epidermis just below dead keratinized outer layer outer layer of skin detaches marked body fluid loss susceptibility to secondary infection such as Candida Pseudomonas o Pathogenesis Mortality rates can reach 40 o Epidemiology depends on prompt diagnosis prompt treatment patient age and overall health 5 of S aureus strains produce exfoliatins SSSS in any age group mainly infants the elderly and immuno compromised Transmission person to person cases usually isolated small epidemics can occur in nurseries protective patient isolation limits spread of infection and exposure to potential secondary pathogens o Prevention o Treatment penicillinase resistant penicillin removal of dead skin to prevent secondary infection Lyme Disease o recognized in mid 1970 s in Lyme Connecticut o Symptoms First Stage erythema migrans skin rash swollen lymph nodes rash small red spot at the site of tick bite slowly enlarges other symptoms are influenza like malaise chills fever headache stiff neck joint and muscle pain and backache Second Stage 2 to 8 weeks post rash Involves heart and nervous system o electrical conduction in heart impaired dizziness fainting o paralysis of facial muscles o impaired concentration emotional upset Third Stage arthritis o usually large joints such as knee o develops in 60 of untreated o within 6 months after rash o slow disappearance over years chronic nervous system impairment may occur depression o Causative Agent Borrelia burgdorferi large 10 x 25 um microaerophilic spirochete Lyme s is a zoonosis introduced into skin through bite of infected tick humans are accidental hosts o in skin bacteria migrate outward in radial fashion o inflammation causes an expanding rash o Epidemiology widespread in USA disease is a zoonosis several tick species implicated as vectors most important is black legged tick Ixodes scapularis nymph stage seeking blood mealn is mainly responsible for transmitting disease check for ticks o Prevention o Treatment Viral Skin Disease Varicella Chicken Pox antibiotics relatively effective in early stage less effective in late disease probably because bacteria are not actively multiplying prolonged IV ampicillin popular name for varicella very common rash among children incidence declined due to vaccination produces a latent infection that becomes reactivated after recovery of initial illness reactivated disease shingles o Symptoms most cases mild recovery uncomplicated more severe symptoms in older children and adults 20 of adults develop pneumonia rash appears on back of head face mouth rash is diagnostic lesions progress red spots macules small bumps papuales small blisters vesicles pus filled blisters pustules lesions itch and appear at different times healing begins after pustules break and crust over major threat to newborn can lead to Congenital Varicella Syndrome if mother develops disease in few days before and after birth high mortality severe birth defects o Sequellae include Shingles herpes zoster reactivation of dormant virus most commonly rash around waist Reye s Syndrome vomiting and coma especially in children ages 5 15 liver and brain damage 30 mortality evidence suggests aspirin therapy increases risk o Epidemiology annual incidence once several millions but declined due to vaccine transmitted by respiratory secretions and skin lesions incidences increase in winter and spring due to close contact incubation 2 weeks but infective 1 2 days before rash and until blisters crust over persist in the