For Patients

Skin Related Articles

Bactarial Infections of the Skin << back to index

Figure 1

Figure 1: This is a turn of the century advertisement for an antiseptic agent.

Most bacterial infections of the skin can be accounted for by three pathogens, Staphylococcus aureus, Streptococcus, and pseudomonas.


Definition: Inflammation (itis) of the follicle, the housing of the hair apparatus, particularly the upper portion. [Leider] Infection of the follicle, especially as in pustular folliculitis.

Most pustular folliculitis (95%) is due to staphylococcus aureus. The major sites of involvement include scalp, buttocks, chest and back, extremities. The clinical presentation is of follicle-centered pustules. The diagnosis is confirmed by gram stain and culture and sensitivity of pustule contents.

Figure 2

Figure 3
Figure 2: Folliculits of the moustache region, so-called sycosis barbae. This pustular folliculits was due to infection with Staphylococcus aureus.

Figure 3: Folliculits of the public region. Notice that within some of the pustules, one can see hair follicles.

Definition: derives from furunculus, diminutive of fur, a Latin word for thief. Thus it means petty thief. This term was used by Pliny and Celsus, and commonly today, to refer to a boil. [Leider]. Deep folliculitis.


Definition: Derives from Latin carbunculus, which means small (-unculus) piece of coal (carb-). [Leider] The word is applied now to the process in which multiple abscesses are in close apposition and have interconnecting sinuses.

acute paronychia

Definition: Acute: from the Latin acutus, acuere, to sharpen. Sudden, brief and severe. Paronychia: from Greek elements meaning condition (ia) near or next to (par-) a nail (-onych-). [Leider]

Figure 4
Figure 4: Acute (bacterial) paronychia. This painful inflammation began a few days earlier, and was quickly relieved by the use of oral antibiotics.


Definition: From Latin attack (im-) against (-peti-) (-go is a noun ending). Superficial infection (staph or strep) characterized by friable, "stuck-on" crusts.

Figure 5
Figure 5: This person has impetigo, manifest by the golden crust over erythematous skin.

Definition: From the Greek word elements meaning the result of (-ma) a breaking (-thy) out (ec-). Superficial pyoderma with firm crusts composed of necrotic tissue and inspissated pus seated upon shallow ulcers. [Leider]


Definition: Inflammation (-itis) of the little cells. A term used to denote diffuse inflammation of parenchyma without necrosis or sharp localization of pus.

Figure 6

Figure 7
Figure 6: This ankle wound became secondarily infected, leading to cellulitis, manifest by the erythematous halo around the wound and extending proximally on the leg.
Figure 7: The central crusted area on the nose represents a small area of echthyma, and is surrounded by erythematous skin of cellulitis.

Definition: From the Greek elements that mean red (erysi-) skin (-pelas). An acute streptococcal infection with well demarcated cellulitis attended by fever, malaise, weakness, and anorexia, etc. [Leider]

Erysipelas is a streptococcal infection, important for occasional association with glomerulonephritis, endocarditis, and lymphedema. Diagnosis of this condition is usually made by gram stain, and culture and sensitivity of tissue fluids. Bacteremia is common.

perianal bacterial dermatitis

Definition: Cellulitis of the skin adjacent to the anus.

Figure 8
Figure 8: The erythema of the perianal region in this patient is due to streptococcal cellulits. The patient complained of pain and pruritus for several days.
This condition is usually due to infection by streptococcus or staphylococcus. It is a common problem characterized by erythema and induration of the perianal skin, and patient complaints of associated pain and pruritus. The diagnosis confirmed by culture. The differential diagnosis includes infection by Candida albicans. Affected individuals may also have involvement of the pharynx and tonsils.