1. Bacterial skin infections

2. The skin provides a remarkably good barrier against bacterial infections. Although many bacteria come in contact with or reside on the skin, they are normally unable to establish an infection. When bacterial skin infections do occur, they can range in size from a tiny spot to the entire body surface. Many types of bacteria can infect the skin. The most common are Staphylococcus and Streptococcus. Skin infections caused by less common bacteria may develop in people while hospitalized or living in a nursing home.

3. Some people are at particular risk of developing skin infections. For example, people with diabetes are likely to have poor blood flow, especially to the hands and feet, and the high levels of sugar (glucose) in their blood decrease the ability of white blood cells to fight infections. Prevention involves keeping the skin undamaged and clean. When the skin is cut or scraped, the injury should be washed with soap and water and covered with a sterile bandage.

4. Most common bacterial skin infections Folliculitis: Folliculitis is an infection of a hair follicle. It looks like a tiny red or white pimple at the base of a hair. There may be only one infected follicle or many. Each infected follicle is itchy or slightly painful, but the person otherwise does not feel sick. Its usually caused by staphy or strept.. but can be caused also by gram negative rods like pseudomonas. Treatment by topical antibiotics like tetracycline, gentamycin or fucidic acid.

5. Skin abscesses: Skin abscesses are warm, painful, pus-filled pockets of infection below the skin surface that may occur on any body surface. Abscesses may be one to several inches in diameter. By staph,strept and gram negative rods. Treatment needs surgical drainage along with systemic and topical antibiotics.

6. Furuncles (boils) are tender, smaller, more superficial abscesses that by definition involve a hair follicle and the surrounding tissue. Furuncles are common on the neck, breasts, face, and buttocks. They are uncomfortable and may be painful when closely attached to underlying structures (for example, on the nose, ear, or fingers). Usually by staph or strept.

7. Carbuncles are multiple furuncles that are connected to one another below the skin surface. If not treated, abscesses often come to a head and rupture, discharging a creamy white or pink fluid. Bacteria may spread from the abscess to infect the surrounding tissue and lymph nodes. The person may have a fever and feel generally sick. The conditions usually caused by staph and commomly around the neck. more common in diabetic and debilitated patients. Treatment require surgical debridment and heavy systemic antibiotic therapy

8. Cellulitis is a spreading bacterial infection of the skin and the tissues immediately beneath the skin. Cellulitis may be caused by many different bacteria. The most common are those of the Streptococcusand Staphylococcus species. Streptococci spread rapidly in the skin because they produce enzymes that hinder the ability of the tissue to confine the infection. Cellulitis that is caused by Staphylococcusbacteria usually occurs in open wounds and pus-filled pockets (abscesses). Many other bacteria can cause cellulitis. Bacteria usually enter through small breaks in the skin that result from scrapes, punctures, surgery, burns, fungal infections (such as athlete's foot), and skin disorders. Areas of the skin that become swollen with fluid (edema) are especially vulnerable. However, cellulitis can also occur in skin that is not obviously injured.

9. Symptoms Cellulitis most commonly develops on the legs but may occur anywhere. Cellulitis usually only affects one side, such as one hand or one leg. The first symptoms are redness, pain, and tenderness over an area of skin. These symptoms are caused both by the bacteria themselves and by the body's attempts to fight the infection. The infected skin becomes hot and swollen and may look slightly pitted, like an orange peel. Fluid-filled blisters, which may be small (vesicles) or large (bullae), sometimes appear on the infected skin. The borders of the affected area are not distinct.

10. Most people with cellulitis feel only mildly ill, but some may have a fever, chills, rapid heart rate, headache, low blood pressure, and confusion. As the infection spreads, nearby lymph nodes may become enlarged and tender (lymphadenitis) and the lymphatic vessels may become inflamed (lymphangitis)

11. Prognosis Most cellulitis resolves quickly with antibiotic therapy. Occasionally, people develop abscesses. Serious but rare complications include severe skin infections that rapidly destroy tissue (called necrotizing skin infections) and spread of bacteria through the blood (bacteremia). When cellulitis affects the same site repeatedly, especially the leg, lymphatic vessels may be damaged, causing permanent swelling of the affected tissue

12. Treatment Prompt treatment with antibiotics can prevent the infection from spreading rapidly and reaching the blood and internal organs. Antibiotics that are effective against both streptococci and staphylococci (such as dic loxacillin or cephalexin If doctors suspect methicillin- resistant Staphylococcus aureus infection, treatment may include antibiotics such as trimethoprim or doxycycline ) Also, the affected part of the body is kept immobile and elevated to help reduce swelling. Cool, wet dressings applied to the infected area may relieve discomfort. Disorders that increase risk of developing cellulitis in the future (for example, athlete's foot) are treated. Symptoms of cellulitis usually disappear after a few days of antibiotic therapy. Abscesses are cut open and drained.

13. Erysipelas is a superficial form of cellulitis typically caused by streptococci. Erysipelas causes a shiny, painful, red, raised patch on the skin. The edges have distinct borders and do not blend into the nearby normal skin. The patch feels warm and firm to the touch. It occurs most frequently on the legs and face. People often have a high fever, chills, and a general feeling of illness (malaise). Antibiotics given by mouth, such as penicillin, can cure the infection. For a severe infection, intravenous penicillin is needed. Cold packs and drugs for pain may relieve discomfort. Fungal foot infections may be an entry site for infection and may require treatment with antifungal drugs to prevent recurrence.

14. Impetigo is a skin infection, caused by Staphylococcus aureus, Streptococcus pyogenes, or both, that leads to the formation of scabby, yellow-crusted sores and, sometimes, small blisters filled with yellow fluid. Impetigo is common. It affects mostly children. Impetigo can occur anywhere on the body but most commonly occurs on the face, arms, and legs. The blisters that may form (bullous impetigo) vary in size and can last for days to weeks. Impetigo often affects normal skin but may follow an injury or a condition that causes a break in the skin, such as a fungal infection, sunburn, or an insect bite.

15. Impetigo is itchy and slightly painful. The itching often leads to extensive scratching, particularly in children, which serves to spread the infection. Impetigo is very contagious—both to other areas of the person's own skin and to other people. Impetigo typically causes clusters of tiny blisters that rupture and develop a honey- colored crust over the sores. Bullous impetigo is similar except that the sores typically enlarge rapidly to form larger blisters. The blisters burst and expose larger bases, which become covered with honey-colored varnish or crust.

16. Lymphangitis is infection of one or more lymphatic vessels, usually caused by streptococci. Streptococci bacteria usually enter the lymphatic vessels from a scrape or wound in an arm or a leg. Often, a streptococcal infection in the skin and the tissues just beneath the skin (cellulitis) spreads to the lymph vessels. Occasionally, staphylococci or other bacteria are the cause. Red, irregular, warm, tender streaks develop on the skin in the affected arm or leg. The streaks usually stretch from the infected area toward a group of lymph nodes, such as those in the groin or armpit. The lymph nodes become enlarged and feel tender.

17. Common symptoms include a fever, shaking chills, a rapid heart rate, and a headache. Sometimes these symptoms occur before the red streaks appear. The diagnosis of lymphangitis is based on its typical appearance. A blood test usually shows that the number of white blood cells has increased to fight the infection. Most people recover quickly with antibiotics that kill staphylococci and streptococci, such asdicloxacillin oxacillin

18. Staphylococcal scalded skin syndrome is a reaction to a staphylococcal skin infection in which the skin blisters and peels off as though burned. Certain types of staphylococci bacteria secrete toxic substances that cause the top layer of the epidermis to split from the rest of the skin. Because the toxin spreads throughout the body, staphylococcal infection of a small area of skin may result in peeling over the entire body. Staphylococcal scalded skin syndrome occurs almost exclusively in infants and children under the age of 6.

19. Symptoms begin with an isolated, crusted sore that may look like impetigo. In newborns, the infection may appear in the diaper area or around the stump of the umbilical cord. In older children, the face is the typical site of infection. Diagnosis A diagnosis is made by the appearance of skin peeling after an apparent staphylococcal infection. If no signs of staphylococcal infection are observed, doctors often do a biopsy, in which a small piece of skin is removed and sent to the laboratory to be tested.

20. prognosis and Treatment With prompt diagnosis and treatment, staphylococcal scalded skin syndrome rarely causes death. The topmost layer of the skin is quickly replaced, and healing usually occurs within 5 to 7 days after start of treatment. Treatment is with antibiotics given by vein and later by mouth. Doctors give people who have a widespread infection and oozing sores the same treatment they give to people who have been burned. Skin moisturizers (emollients) may be used to help protect the skin after it has healed.

21. Erythrasma is infection of the top layers of the skin caused by the bacterium Corynebacterium minutissimum. Erythrasma affects mostly adults, especially those with diabetes and those living in the tropics. Erythrasma is most common in the foot, where it causes scaling, cracking, and breakdown of the skin between the 4th and 5th toes. This infection is also common in the groin, where it causes irregularly shaped pink or brown patches and fine scaling especially where the thighs touch the scrotum (in men). The armpits, skinfolds under the breasts or on the abdomen, and the area between the vaginal opening and the anus (perineum) are prone to this infection, particularly among people with diabetes and among obese middle-aged women An antibiotic given by mouth, such as erythromycin or tetracycline can eliminate the infection. Antibacterial soaps, such as chlorhexidine, may also help. Drugs applied directly to the affected area (topically), such as erythromycin.

22. Mycobacterial skin infections Cutaneous tuberculosis Cutaneous tuberculosis (TB) is essentially an invasion of the skin by Mycobacterium tuberculosis, the same bacteria that cause TB of the lungs (pulmonary TB). Cutaneous TB is a relatively uncommon form of extrapulmonary TB (TB infection of other organs and tissues).

23. Types of cutaneous TB TB verrucosa cutis Occurs after direct inoculation of TB into the skin in someone who previously infected with mycobacteria Presents as a purplish or brownish-red warty growth Lesions most often occur on the knees, elbows, hands, feet and buttocks Lesions may persist for years but can clear up even without treatment

24. Lupus vulgaris Persistent and progressive form of cutaneous TB Small sharply defined reddish-brown lesions with a gelatinous consistency (called apple-jelly nodules) Lesions persist for years, leading to disfigurement and sometimes skin cancer

25. Scrofuloderma Skin lesions result from direct extension of underlying TB infection of lymph nodes, bone or joints Often associated with TB of the lungs Firm, painless lesions that eventually ulcerate with a granular base May heal even without treatment but this takes years and leaves unsightly

26. Miliary TB Chronic TB infection that has spread from the primary infection (usually in the lungs) to other organs and tissues via the bloodstream Skin lesions are small (millet-sized) red spots that develop into ulcers and abscesses More likely in immunocompromised patients, eg HIV, AIDS, cancer The patient is generally sick Prognosis is poor (many patients die even if diagnosed and treated)

27. Tuberculid Generalised exanthem in patients with moderate or high degree of immunity to TB because of previous infectionexanthem Usually in good health with no identifiable focus of active TB in skin or elsewhere Erythema induratum (Bazin disease) presents as recurring nodules or lumps on the back of the legs (mostly women) that may ulcerate and scar. It is a type of nodular vasculitis.nodular vasculitis Papulonecrotic tuberculid results in crops of recurrent crusted skin papules on knees, elbows, buttocks or lower trunk that heal with scarring after about 6 weeks.

28. The diagnosis is usually made or confirmed by characteristic histopathological features on skin biopsy. Typical tubercles are epithelioid granulomas with or without caseation.characteristic histopathological featuresskin biopsy Treatment Patients with pulmonary or extrapulmonary TB disease need to be treated with antitubercular drugs. This usually involves a combination of antibiotics (isoniazid,rifampicin, pyrazinamide and ethambutol) given over a period of several months and sometimes years.rifampicin Occasionally surgical excision of localised cutaneous TB is recommended.