2. INTYODRUCTION
Skin is largest organ of body Maintains homeostasis, protects
underlying tissues and organs, protects body from mechanical
injury, microbial , damaging substances, and ultraviolet rays of sun.
2
3. • In immunocompetent patients, streptococci and staphylococci
cause the majority of skin infections, producing a spectrum of
skin lesions ranging from common to rare .
3
4. NORMAL HUMAN SKIN
• Colonized soon after birth by a large number of bacteria that
live as commensals on the epidermis and epidermal
appendages.
4
5. Normal skin flora
classification organisms location
Aerobic cocci Staphylococcus aureus**
S. saprophyticus
S. epidermidis
Micrococcus luteus
All body sites, especially
intertriginous areas
Coryneform aerobes Corynebacterium minutissimum
C. lipophilicus
C. xerois
Brevibacterium epidermidis
intertriginous areas
(axillae, inguinal, toe web)
Anaerobic
corynebacterium
Propionibacterium acnes
P. granulosum
P. avidum
Sebaceous glands,
follicles
Gram negative bacteria Acinebacter spp. Axilla, inguinal, arm pits
Yeasts Malassezia furfur Sebaceous glands- rich
areas (scalp)
5
6. The role of the normal flora
• PREVENT SKIN INFECTIONS
–by providing ecological competition for pathogenic
microorganisms .
–by hydrolyzing lipids of sebum to produce free fatty acids,
which are toxic to many bacteria.
6
7. COMMON PYODERMAS
• FOLLICULITIS is inflammation of hair follicles from Infection.
• A furuncle develops when the entire follicle and surrounding
tissue are involved.
• A carbuncle develops When cluster of follicles involved.
7
9. Etiologies
• S.aureus -is the most common infectious cause of Bacterial
folliculitis,Furuncle & curbuncle.
9
10. .
PATHOGENESIS
• One of the main virulence factors of S. aureus is the production of
adhesins that facilitate binding to host epithelial cell surfaces.
• Like as teichoic acid, lipoteichoic acid, fibronectin-binding
proteins.
10
11. Host related factors
- Pre-existing tissue injury or inflammation (surgical wound, burn,
trauma)
- Maceration, shaving, chronic wounds, excoriation of pruritic
insect bites, and disruption of the epidermal barrier by other
pathogens.
- Immunosuppression,
-Glucocorticoid therapy, and atopy
11
effective in the majority of bacterial skin infections, an increase in
the prevalence of community acquired methicillin-resistant
Staphylococcus aureus (CA-MRSA)is a growing concern
*Whether or not S. aureus is a true resident or contaminant of the skin is a matter of controversy.
However, it is commonly found in the anterior nares (3S% of population), perineum (20%), and
axillae and toe webs (5-10%).
IS. epidermidis is the most common coccus on human skin.
The acidic milieu which results inhibits the growth of other organisms such as Streptococcus pyogenes.
Various surface components of S. aureus, such as teichoic acid,
lipoteichoic acid, fi bronectin-binding proteins, and type 5 and
type 8 capsular polysaccharides, have all been implicated as
substances responsible for, or contributing to, binding of the
organism in the nose