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SKIN AND SOFT TISSUE INFECTIONS: NECROTIZING FASCIITIS

Monday, May 2nd, 2011

Pathophysiology
In necrotizing fasciitis, fulminant bacterial infection of the subcutaneous tissue results in liquefactive necrosis of the superficial fascia, subcutaneous fat, and deep fascia. Historic and modern terms referring to the infection and its subtypes include hospital gangrene, phagedena, hemolytic streptococcal gangrene, progressive synergistic bacterial gangrene, and many others. Superficial skin initially remains intact as the necrosis extends along fascial planes in as little as a few hours. The exudate is thin and often described as “dishwater pus. Vascular thrombosis leads to necrosis of large areas of skin.
Necrotizing fasciitis can affect any area of the body, but abdominal wall, extremities, and perineum are the most common. The infection begins with the introduction of pathogens into the subcutaneous fascia. Possible routes include trauma, injections, cutaneous infections (including cellulitis, ulcers, abscesses, and varicella), insect bites, deep infections, or hematogenous spread from distant sites. Inciting trauma may be minor and even unnoticed; some cases are idiopathic.
Abdominal wall necrotizing fasciitis is usually a postoperative complication, particularly after fecal contamination of the abdominal cavity. Abdominal wall infections have also occurred after gut perforation, or secondary to other abdominal pathologies. Fournier’s gangrene typically refers to necrotizing fasciitis of the male genitalia and perineum, usually secondary to local infections (genitourinary, intra-abdominal, or perianal), trauma, or instrumentation. Vulvar involvement in women has been described and has similar causes. Head and neck cases are rare but particularly dangerous, given the possibility of spread along cervical fascial planes and involvement of major blood vessels and the mediastinum.
Microbiology
Culture of microorganisms from infection sites reveals two major types of necrotizing fasciitis. Type I is polymicrobial, involving a mix of anaerobic and facultative bacteria, often including Enterobacteriaceae and non-group A streptococci. Type II infections are caused by group A B-hemolytic streptococci (primarily Streptococcus pyogenes) alone or with staphylococci. Increased virulence of some group A streptococcal strains may be related to exotoxins, surface proteins, and variable levels of immunity among hosts.
Abdominal and perineal infections tend to be type I in nature and are typically caused by enteric pathogens. Common bacteria include gram-negative enteric bacilli, enterococci, and anaerobic species, such as Bacteroides and Clostridium species. Most studies have shown that necrotizing fasciitis of the extremities and idiopathic cases tend to be type II in etiology. However, many observational studies may not have used rigorous anaerobic bacteria isolation methods, and one large case series described mostly polymicrobial infections predominated by anaerobes in any site.
Marine Vibrio species, most notably Vibrio vulnificus, may cause necrotizing fasciitis following contact with seawater, fish, or shellfish. Other causes include group В streptococci, Pasturella multocida, and Candida species.
*120/348/5*

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TYPES OF INFECTION: HEMOLYTIC STREPTOCOCCUS INFECTIONS

Sunday, December 26th, 2010

The streptococcus is one of the most widely distributed and variable organisms that attacks mankind. Such conditions as sore throat, sinus infections, scarlet fever, erysipelas, puerperal fever, or lymphangitis may be caused by streptococci. Other conditions associated with such streptococci include acute rheumatic fever and acute inflammations of the kidney.
Such infections are found in all races, in both sexes, at all ages, and they come on at any time of the year. Scarlet fever is said to be rare in the tropics. Very small babies, under three months of age, seldom have streptococcal infections, because they get some immunity from their mothers at the time of birth. Tonsillitis, pharyngitis, and scarlet fever are more frequent up to ten years of age. Streptococcal infections can result from contaminated food, milk, water but most frequently pass from one person to another with coughing, sneezing, spitting and what are known as “hand-to-mouth” infections.
Tonsillitis and pharyngitis are usually streptococcal infections which begin with sore throats. When there is a rash, the rash is said to represent sensitivity of the skin to the products of the streptococcus; this condition is scarlet fever. Infections of the sinuses usually follow infection of the tonsils and throat. Ear infections occur in many cases and the streptococci are said to be responsible for ten per cent of ear infections. Specific methods of inoculation against streptococci are difficult because of the many different varieties of the germ. The Dick test will indicate whether or not a child is susceptible to the streptococcus of scarlet fever and there are methods of building resistance against these streptococci by inoculating small doses of the toxin.
Regardless of the portion of the body that is attacked by the streptococci, the control of the condition is now possible through the proper use of the sulfonamide and antibiotic drags. Streptococci are especially susceptible to attack by the sulfonamide drugs. The complications of infected throats are more important than the sore throat itself. Penicillin is the antibiotic drag most frequently used in treating throats infected with streptococci. Penicillin is especially beneficial in laryngitis, pharyngitis, tonsillitis and scarlet fever. The complications of scarlet fever have in the past done more harm than the disease itself. In severe cases of scarlet fever convalescent serum may be used, and good results have been reported from use of the antitoxin.
Saline gargles and irrigations of the throat help to wash out the byproducts of throat infection. One of the most significant advances is the use of sulfonamide drags to prevent streptococcal infections. When there are outbreaks in large homes, in barracks, in asylums, or places where great numbers of people assemble, the sulfonamide drugs may be taken as a means of preventing infection with the streptococci. All sorts of attempts have been made to cut down respiratory diseases by the use of ultraviolet light in the air, by the spraying of medicated vapors or aerosols and by other techniques for keeping the germs from floating in the air. These, in general, have not been successful.
*3/318/5*

TYPES OF INFECTION: HEMOLYTIC STREPTOCOCCUS INFECTIONSThe streptococcus is one of the most widely distributed and variable organisms that attacks mankind. Such conditions as sore throat, sinus infections, scarlet fever, erysipelas, puerperal fever, or lymphangitis may be caused by streptococci. Other conditions associated with such streptococci include acute rheumatic fever and acute inflammations of the kidney.Such infections are found in all races, in both sexes, at all ages, and they come on at any time of the year. Scarlet fever is said to be rare in the tropics. Very small babies, under three months of age, seldom have streptococcal infections, because they get some immunity from their mothers at the time of birth. Tonsillitis, pharyngitis, and scarlet fever are more frequent up to ten years of age. Streptococcal infections can result from contaminated food, milk, water but most frequently pass from one person to another with coughing, sneezing, spitting and what are known as “hand-to-mouth” infections.Tonsillitis and pharyngitis are usually streptococcal infections which begin with sore throats. When there is a rash, the rash is said to represent sensitivity of the skin to the products of the streptococcus; this condition is scarlet fever. Infections of the sinuses usually follow infection of the tonsils and throat. Ear infections occur in many cases and the streptococci are said to be responsible for ten per cent of ear infections. Specific methods of inoculation against streptococci are difficult because of the many different varieties of the germ. The Dick test will indicate whether or not a child is susceptible to the streptococcus of scarlet fever and there are methods of building resistance against these streptococci by inoculating small doses of the toxin.Regardless of the portion of the body that is attacked by the streptococci, the control of the condition is now possible through the proper use of the sulfonamide and antibiotic drags. Streptococci are especially susceptible to attack by the sulfonamide drugs. The complications of infected throats are more important than the sore throat itself. Penicillin is the antibiotic drag most frequently used in treating throats infected with streptococci. Penicillin is especially beneficial in laryngitis, pharyngitis, tonsillitis and scarlet fever. The complications of scarlet fever have in the past done more harm than the disease itself. In severe cases of scarlet fever convalescent serum may be used, and good results have been reported from use of the antitoxin.Saline gargles and irrigations of the throat help to wash out the byproducts of throat infection. One of the most significant advances is the use of sulfonamide drags to prevent streptococcal infections. When there are outbreaks in large homes, in barracks, in asylums, or places where great numbers of people assemble, the sulfonamide drugs may be taken as a means of preventing infection with the streptococci. All sorts of attempts have been made to cut down respiratory diseases by the use of ultraviolet light in the air, by the spraying of medicated vapors or aerosols and by other techniques for keeping the germs from floating in the air. These, in general, have not been successful.*3/318/5*

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