Skin Bacteria Flashcards
Actinomyces Israelii
- Gram+, filamentous (fungiesk), anaerobe, non acid fast, forms sulfur granules, yellow/orange, molar tooth appearance.
Normal flora, oral cavity, gut, female genital tract. engogenous-opportunistic (dental work (prophylaxis, IUD)
Chronic granulomatous lesions that form abcesses in CT and suppurate.
Cervicofacial actinomycosis: lumpy jaw nodules. hard woody feel granulomatous forms draining abcess. spread to other tissue - thighs, bone, CNS, pelvic PID
TX. drainage/debridement, penicillin G for months (granulomas)
Bacteriodes Fragilis
- Gram-, rod, pleomorphic, obligate anaerobe, 20% bile salt enhaces growth(esculin and gentamycin - BBE agar), catalase and superoxidase+ (resistant to killing)
Human colon, vagina, feces. endogenous-acute appendicitis, any surgery (prophylaxis)
- LPS without lipid A (no endotoxic)
- adhesion capsue and pili
- succinic acid production during anaerobic growth (gas chromatography for fatty acid identification)
- capsule toxin induce absess (strong PAMP)
intra-abdominal abcess, peritonitis, genital infections, PID females, necrotizing fasciitis, bacterimia - polymicrobial infections.
TX. metronidazole (produces betalactamases), wound dranage and hyperbaric chamber
Clostridium Perfringens
- Gram+, rod, spore former (not in vivo), anaerobic, (alpha toxin in egg yolk agar)
Soil, human colon. Spores introdced to wounds.
RISK: trauma, septic abortions, diabetic/poor circulation
- alpha toxin (lecithinase phospholipase). hemolytic/necrotic
- collagenase, fibrinolysis etc…!
Myonecrosis (Gas Gangrene), crepitant tissue, foul smell, GI infection, diarrhea, necrotisn enteritis (pigbel)
TX. surgical, high dose penicillin (abcess), hyperbaric oxygen, debridement of wound. (GI gastroenteritis is self limiting)
Enterococcus Faecalis
- Streptococci, Grm+. cocci, chains/pairs,. catalase neg. lactobacillale (facultative anaerobe)
- Group D lancefiel Ag, growth in 6.5% NaCl, bile sesistance, PYR+, bactricin and optochin resistant, hydrolyze esculin agar.
Human colon, urethra, female genital tract. Autoinoculation, nosocomil, endogenous perferation of bowel.
RISK: hospitalizatin, catheder, broad spectrum antibiotics (esp vancomycin)
- Biofilm
- antibiotic resistant (inherent and plasmid gene acquired)
soft tissue infections, cystitis, pyelonephritis, bacteremia, endocarditis
TX. aminoglycosides and cell wall active antibiotics. (antibiotics!!!! resistance)
Mycobacterium Chelonae
tap water etc (tatoo)
soft tissue infection in cosmatic/medical procedures.
non-healing wound, subcutaneueou nodule or abcess. may cause lung disease, joint infection, eye etc
Mycobacterium Leprae
- acid fast, rod, cannot be grown in culture (mice)
Human only (armadillo have similar disease). Person-person with up to 20 year incubation period, exact transmission unk.
RISK: children in close contact with infected peroson (armadillo)
- caspule to resist phago
- mycobacterial cell wall (survive inside cell) - histiocytes and schwann cells
- preference to lwo termpurature (extremeties including testicles)
Hansen’s-leprosy. progressive, disfiguring, two types of response
- Tuberculoid_:_ strong Tcell response (weak humoral). cutaneous macualr rash, pigment loss, fine sensory loss, lepromin skin test positive. regional. granulomas with macrophage giant cell. NOT infectious
- Lepromatous: weak Tcell mediated immunity (good humoral). wide spread nodular lesions involving mucosal surface, ocular involvemtn iris and keratitis. Tcell anergy. B Cell responsive. symetrical. foamy histiocytes full of intracellular bacteria. highly infectious.
TX. dapsone w/wo rifampin for tuberculoid. clofazimine for lepromatous.
Mycobacterium Marinum
cold.warm fresh.salted water.
fishtank granuloma. localized granuloma which may spread ascending to lymphatics. (resembles sporotricholsis - nocardia).
Mycobacterium Ulcerans
slow flowing rivers, ponds, swamps. tropical, sub ptropical
Buruli Ulcer. nodule in a week then in a month ulcerated spread rapidly skin surface (fast growing)
Norcardia Asteriodes
- gram+ and weak acid fast, beaded fillament, branchd, with surface projections, rehalose dimycolate (cord factor), waxy slow grower with areal hyphea.
Environment/soil rich with organic mater. exogenous, airpborne or trauma (weak immune system)
- catalase and oxidase+
- cord factor prevents phago-lyso fusion
bronchitis, pneumonia, lung abcess cavity, Cutaneous nocardiosis. mycetoma resembles actinomycosis (no face involvement), lymphocutaneous infections, cellulitis, chronic ulcerative abcess. CNS abcess and chronic meningitis.
TX. trimethoprim-sulfamethoxazole (~12 months granuloma)
Propionibacterium Acnes
Gram+, short small rods, nonspore, anaerobic, produce propionic acid from sugars.
Human skin, conjunctiva, external ear, oropharynx and female genital. endogenous - opportunistic
Acne vulgaris: matebolic byproducts induce inflammatory response in sebaceous glands / wounds
Staphylococcus Aureus
- gram+. cocci. cluster grape. catalase+, growth at 7.5%NaCl
- Coagulase+, beta hemolytic, mannitol fermentor, golden yellow/white,
Human nose, skin, lower colon, vagina. Shedding, droplets, aerosol, formites.
RISK: broken skin, foreign body (tampon), diabetes, post influenza pneumonia, neutropenia, chronic granulomatous disease
- protein A: antiphagocytic binds Fc region of IgG preventing C3b and phago binding.
- capsule: antiphagocytic
- cytolytic membrane damaging toxins: staphylolysin, leukotoxin and leukocidin (P-V leukocidin)
- staphylokinase/fibrinolysin: degrades fibrin clots assits bacterial escape from clots
- coagulase: forms fibrin clots secreted and surface membrane
- hyaluronidase: dissolves intra-cellular cement allowing bacterial spread
- lipotechoic acid, peptodoglucan have endotoxin activity-activation of macrophages and release inflammatory cytokines inducing septic shock
- Pyeogenic infection: impetigo (pyoderma), folliculitis (stye), furuncles (boils), carbuncles. cellulites, abcess, severe necrotizin fasciitis (panton valentine P-V-leukocidin - CA-MRSA. kills phago cells releasign their contents)
- Toxin mediated disease: Scalded skin syndrome/Ritter’s syndrom (exfoliating toxin serine protease in nose toxin to systemic skin), toxic shock syndroms (TSST - hypotensive, diarrhea, rash, renal/hepatic), food poisoning.
- diarrhea: acute explosive exudation (dysentry: bloody, purulent WBC>RBC, persists on fasting) within 1-6 hours.
- Septicemia:
- osteomyelitis and septic arthritis (most common cause osteomyeolitis)
- pneumonia and empyema
- bacteremia and acute endocarditis
TX. penicillin G resistant, produce beta-lactamase,
Staphylococcus Epidermidis
- gram pos. cocci. cluster grape. catalase pos.
- gamma hemolytic, white, novobiocin sensitive
Normal skin flora
surface slime layer and biofilm formation (implants) hides from immune response
Nosocomial infection, endocarditis, catheter and prosthetic joint infection.
Vibrio Vulnificus
- Gram-, curved rod, motile, facultative anaerobic, oxidase+, halophilic
- blood agar MacConkey, TBCS (thiosulfate Citrate Bile Salts sucroce), blue/green colonies
warm estuarine or marine water, (gulf coast). direct contact contaminated salt water or ingestion shellfish
capsule, cytolysin, extracellular enzymes
Bullae, necrotizing fasciitis (24-48 hrs after exposure), septecemia.
TX. doxycycline and 3rd Gen cephalosporin
