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Sst is and ssis

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Sst is and ssis

  1. 1. Skin and Soft Tissue Infections SSTIs Dr Kamran Afzal Asst Prof Microbiology
  2. 2. Skin - Structure and Function <ul><li>Large, complex organ that protects the body </li></ul><ul><li>Surface area of 1.9 m 2 </li></ul><ul><li>Consists of </li></ul><ul><ul><li>epidermis </li></ul></ul><ul><ul><li>dermis </li></ul></ul><ul><ul><li>appendages (hair follicles, sweat glands) </li></ul></ul><ul><li>Acts as a physical barrier </li></ul><ul><li>against microorganisms </li></ul>
  3. 3. Skin – Normal Flora <ul><li>Mostly gram-positive bacteria </li></ul><ul><ul><li>staphylococci </li></ul></ul><ul><ul><li>micrococci </li></ul></ul><ul><ul><li>corynebacteria (diphtheroids) </li></ul></ul><ul><ul><li>Propionibacterium acnes </li></ul></ul><ul><li>Vigorous washing reduces but does not completely eliminate NF </li></ul><ul><li>Sweat glands and hair follicles help </li></ul><ul><li>to re-establish bacterial flora </li></ul>
  4. 4. Staphylococcus species <ul><li>S. aureus </li></ul><ul><li>Coagulase negative staphylococci </li></ul><ul><ul><li>S. epidermidis </li></ul></ul><ul><ul><li>S. saprophyticus </li></ul></ul><ul><ul><li>Others </li></ul></ul><ul><li>Staph : grape-like clusters coccus : spherical </li></ul><ul><li>Gram-positive bacteria 0.5-1.5  m in diameter </li></ul><ul><li>Golden-yellow colonies on blood agar </li></ul><ul><li>All are catalase positive </li></ul><ul><li>All pathogenic S. aureus are coagulase positive </li></ul>
  5. 5. Staphylococcus Virulence Factors <ul><li>Coagulase </li></ul><ul><li>Toxins </li></ul><ul><ul><li>hemolysins </li></ul></ul><ul><ul><li>enterotoxins </li></ul></ul><ul><ul><li>pyrogenic toxins: A, B, C </li></ul></ul><ul><li>Exfoliatin </li></ul><ul><li>Leukocidin </li></ul><ul><li>Protein A </li></ul>
  6. 6. Streptococcus species <ul><li>Strepto : chain-like coccus : spherical </li></ul><ul><li>Gram-positive bacteria 0.5-1.5  m in diameter </li></ul><ul><li>White to grey colonies of various sizes on blood agar </li></ul><ul><li>Classified by ability to produce hemolysins </li></ul><ul><ul><li> -hemolytic: partial hemolysis of RBCs </li></ul></ul><ul><ul><ul><li>viridans streptococci, Streptococcus pneumoniae </li></ul></ul></ul><ul><ul><li> -hemolytic: complete hemolysis of RBCs </li></ul></ul><ul><ul><ul><li>Streptococcus pyogenes , Streptococcus agalactiae </li></ul></ul></ul><ul><ul><li> -hemolytic: no hemolysis of RBCs </li></ul></ul><ul><ul><ul><li>some Streptococcus milleri </li></ul></ul></ul>
  7. 7. Streptococcus pyogenes <ul><li>Group-A streptococci (GAS) from the Lancefield classification </li></ul><ul><li>Gram-positive bacteria in short chains, 0.5-1.0  m in diameter </li></ul><ul><li>Expresses  -hemolysis </li></ul><ul><li>Does not produce catalase or coagulase </li></ul><ul><li>M proteins </li></ul><ul><ul><li>Prevent phagocytosis </li></ul></ul><ul><ul><li>Induce vascular leak </li></ul></ul><ul><li>SPE </li></ul><ul><ul><li>Induce inflammatory cytokines </li></ul></ul><ul><ul><li>Release of IL-1, IL-2, INF- γ and TNF </li></ul></ul>
  8. 8. Anaerobes <ul><li>Commonly found as normal flora of the bowel and mouth </li></ul><ul><li>Can infect necrotic tissues including skin </li></ul><ul><li>Gram-positive </li></ul><ul><ul><li>Cocci </li></ul></ul><ul><ul><ul><li>Peptostreptococcus spp. </li></ul></ul></ul><ul><ul><li>Bacilli (rods) </li></ul></ul><ul><ul><ul><li>Propionibacterium acnes, Cl. perfringens , Cl. tetani, C. difficile </li></ul></ul></ul><ul><ul><ul><li>Actinomyces spp. </li></ul></ul></ul><ul><li>Gram-negative </li></ul><ul><ul><li>Cocci </li></ul></ul><ul><ul><ul><li>Veillonella spp. </li></ul></ul></ul><ul><ul><li>Bacilli </li></ul></ul><ul><ul><ul><li>Bacteroides fragilis </li></ul></ul></ul><ul><ul><ul><li>Fusobacterium spp. </li></ul></ul></ul>
  9. 9. Polymicrobial Infections <ul><ul><li>GAS </li></ul></ul><ul><ul><ul><li>12% spread </li></ul></ul></ul><ul><ul><li>GAS and S. aureus </li></ul></ul><ul><ul><ul><li>50% spread </li></ul></ul></ul><ul><ul><li>GAS with  -lysin and S. aureus </li></ul></ul><ul><ul><ul><li>75% spread </li></ul></ul></ul>
  10. 10. Skin Lesions <ul><li>Vesicles </li></ul><ul><ul><li>small, fluid-filled lesions in the epidermis </li></ul></ul><ul><ul><li>e.g. chicken pox </li></ul></ul><ul><li>Bullae </li></ul><ul><ul><li>larger, fluid-filled lesions in the epidermis </li></ul></ul><ul><li>Macules </li></ul><ul><ul><li>flat, reddish lesions from inflammatory infiltrate </li></ul></ul><ul><li>Papules </li></ul><ul><ul><li>raised lesions which, when contain pus, are called pustules </li></ul></ul>
  11. 11. Bacterial Infections of the Skin <ul><li>Folliculitis </li></ul><ul><ul><li>infection of hair follicle ( S. aureus ) </li></ul></ul><ul><li>Impetigo </li></ul><ul><ul><li>vesicular, later crushed, superficial infection of the skin ( S. pyogenes, S. aureus ) </li></ul></ul><ul><li>Cellulitis </li></ul><ul><ul><li>acute spreading infection of the skin extending to involve the subcutaneous tissues ( S. aureus, S. pyogenes, anaerobes) </li></ul></ul><ul><li>Erysipelas </li></ul><ul><ul><li>distinctive type of superficial cellulitis of the skin with prominent lymphatic involvement ( S. pyogenes ) </li></ul></ul>
  12. 12. Bacterial Infections of the Skin <ul><li>Furuncle </li></ul><ul><ul><li>deep inflammatory nodule usually developing from folliculitis ( S. aureus ) </li></ul></ul><ul><li>Carbuncle </li></ul><ul><ul><li>more extensive than a furuncle with involvement of the subcutaneous fat ( S. aureus ) </li></ul></ul><ul><li>Staphylococcal Toxic Shock Syndrome </li></ul><ul><ul><li>acute febrile illness with a generalized scarlitiniform eruption ( S. aureus ) </li></ul></ul><ul><li>Scalded Skin Syndrome </li></ul><ul><ul><li>widespread bullae and exfoliation from S. aureus strains producing an exfoliative exotoxin </li></ul></ul>
  13. 13. Soft Tissue Infections <ul><li>Necrotizing fasciitis </li></ul><ul><ul><li>“ flesh-eating disease” </li></ul></ul><ul><ul><li>severe infection involving the subcutaneous soft tissue, particularly the superficial and deep fascia </li></ul></ul><ul><li>Myositis </li></ul><ul><ul><li>infection of skeletal muscle (rare) </li></ul></ul><ul><ul><li>S. aureus, S. pyogenes (rare), mixed organisms </li></ul></ul><ul><li>Gas gangrene </li></ul><ul><ul><li>rapidly progressive, life-threatening, toxemic infection of skeletal muscle due to clostridia </li></ul></ul>
  14. 14. Cellulitis
  15. 15. Cellulitis Features Red Swollen Warm to touch No areas of pus Painful Tender Cellulitis
  16. 16. Treatment <ul><li>Local care </li></ul><ul><ul><li>immobilization </li></ul></ul><ul><ul><li>elevation to reduce swelling </li></ul></ul><ul><li>2 weeks of antibiotic therapy </li></ul><ul><li>Current antibiotics of choice are cloxacillin, clindamycin, doxycycline, or co-amoxiclav </li></ul><ul><li>Severe cellulitis should be treated initially with IV antibiotics </li></ul>
  17. 17. Abscess <ul><li>The collection of pus under the surface of the skin, in the area of cellulitis is termed an “abscess” </li></ul><ul><li>The pus in the abscess consists of dead, liquified tissue, billions of white blood cells and the responsible bacteria </li></ul><ul><li>The most common bacterium in the abscess is Staphylococcus aureus </li></ul><ul><li>There are many other bacteria that can cause abscesses </li></ul>
  18. 18. Abscess Features Cellulitis present Swollen Soft center, feels like fluid underneath Painful Tender Cellulitis Abscess
  19. 19. Abscess Large abscess about to be incised and drained of pus This is too large to drain in the ooutdoor
  20. 20. Treatment <ul><li>Abscesses should be drained </li></ul><ul><li>Clean the skin off with alcohol or iodine before opening the abscess </li></ul><ul><li>An antibiotic is needed to cover the common pathogens like Staphylococci and Streptococci </li></ul>
  21. 21. Necrotizing Fasciitis <ul><li>Necrotizing means turning living flesh to dead flesh </li></ul><ul><li>Fasciitis means the infection is spreading along the space between the fat and the muscle underneath </li></ul><ul><li>The infection cuts off the blood supply to the tissue above it and the tissue dies </li></ul><ul><li>The bacteria also enter the bloodstream and cause sepsis </li></ul>
  22. 22. Pathogenesis <ul><li>A polymicrobial infection, commonly caused by a mixture of anaerobic and aerobic bacteria </li></ul><ul><ul><li>clostridium species, enterobacteriaceae ( E. coli , Enterobacter , Klebsiella , and Proteus species), and “flesh-eating” streptococci </li></ul></ul><ul><ul><li>predisposing conditions: diabetes, abdominal surgery, perineal infection, trauma </li></ul></ul><ul><li>Usually starts at the site of non-penetrating trauma (a bruise) </li></ul>
  23. 23. Clinical signs <ul><li>If the area of redness is spreading rapidly this may be “nec fasc” </li></ul><ul><li>If the area is extremely painful </li></ul><ul><li>If the person shows signs of bacteraemia (fever, change in mental function such as delirium, profound weakness) </li></ul><ul><li>Draw a line around the red area with a pen, then watch for spreading beyond the line </li></ul><ul><li>If spreading ½ inch or more per hour </li></ul>If rapid spreading beyond this line occurs, this may be necrotizing fasciitis, and requires surgery
  24. 24. Management <ul><li>Immediate surgical debridement is critical and life saving </li></ul><ul><li>Skin grafting once infection controlled </li></ul><ul><li>Empiric antibiotics to cover anaerobes, gram negative bacilli, streptococci, and Staph aureus </li></ul><ul><ul><li>cloxacillin+metronidazole+ceftriaxone </li></ul></ul><ul><ul><li>vancomycin+ceftriaxone </li></ul></ul><ul><li>Antibiotics for a minimum of 3 wks </li></ul>
  25. 25. Myonecrosis (Gas Gangrene) <ul><li>A pure Clostridium perfringens infection </li></ul><ul><li>Gas in a gangrenous muscle group </li></ul><ul><li>Incubation period of hours to days </li></ul><ul><li>Local edema and pain accompanied by fever and tachycardia </li></ul><ul><li>Discharge is sero-sanguinous, dirty, and foul smelling </li></ul><ul><li>Pen G (3-4 million U q4h) or chloramphenicol </li></ul><ul><li>Surgical removal of infected muscle </li></ul>
  26. 26. Pyomyositis (Tropical Myositis) <ul><li>Infection of the muscles by Staphylococcus aureus presenting as atypical cellulitis </li></ul><ul><li>50% with co-morbidity (diabetes, alcoholic liver disease, concurrent corticosteroid therapy, immunosuppression) </li></ul><ul><li>Endemic in the tropics secondary to bacteraemia </li></ul><ul><li>Area is indurated with a “woody” consistency; erythema and tenderness is minimal initially </li></ul><ul><li>Fever and marked muscle tenderness may develop in 1-3 weeks </li></ul>
  27. 27. Pyomyositis (Tropical Myositis) <ul><li>Rhabdomyolysis - along with myoglobinuria and acute renal failure - may develop </li></ul><ul><li>MRI or CT may show muscle enlargement </li></ul><ul><li>Surgical drainage is essential </li></ul><ul><li>Staph aureus may be isolated from pus or blood culture </li></ul><ul><li>Empiric antibiotics directed against Staph </li></ul><ul><ul><li>cloxacillin 2 g iv q4h </li></ul></ul><ul><ul><li>vancomycin 1 g iv q12h or cefazolin 1g iv q8h </li></ul></ul>
  28. 28. Diabetic Foot Infection <ul><li>Cellulitis>Deep soft tissue infection>Osteomyelitis </li></ul><ul><li>Risk factors </li></ul><ul><ul><li>vascular disease </li></ul></ul><ul><ul><li>(macro and micro) </li></ul></ul><ul><ul><li>peripheral neuropathy </li></ul></ul><ul><ul><li>poor foot care </li></ul></ul>
  29. 29. Diabetic Foot Infection <ul><li>Organisms </li></ul><ul><ul><li>Skin flora </li></ul></ul><ul><ul><li>S. aureus ,  -hemolytic strep, diphtheroids </li></ul></ul><ul><ul><li>Gram-negative bacilli </li></ul></ul><ul><ul><li>E. coli, K. pneumoniae, Pseudomonas spp. </li></ul></ul><ul><ul><li>Anaerobes </li></ul></ul>
  30. 30. Management <ul><li>Glycaemic control </li></ul><ul><li>Deep tissue cultures </li></ul><ul><li>Antibiotics </li></ul><ul><ul><li>Non limb threatening </li></ul></ul><ul><ul><li>Cephalexin, Clindamycin, Cloxacillin </li></ul></ul><ul><ul><li>Limb threatening </li></ul></ul><ul><ul><li>Fluoroquinolone+Clindamycin, Pip-Tazo </li></ul></ul><ul><li>Surgical intervention </li></ul>
  31. 31. Surgical Site Infections SSIs
  32. 32. SSIs <ul><li>3 rd most common nosocomial infection (14-16%) </li></ul><ul><li>Most common nosocomial infection on surgical services </li></ul><ul><li>Increase cost and length of stay </li></ul>
  33. 33. Classification <ul><li>77% of deaths with nosocomial infections present due to infection </li></ul><ul><li>93% of these infections involved organs or spaces accessed during surgery </li></ul>
  34. 34. Pathogenesis <ul><li>Host factors </li></ul><ul><li>Inoculum size </li></ul><ul><li>Length of operation </li></ul>
  35. 35. Surgical Wound Classification
  36. 36. Carbuncle
  37. 37. Cellulitis
  38. 38. Cellulitis with bullae
  39. 39. Necrotizing fasciitis
  40. 40. Necrotizing fasciitis after debridement

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