Chapter 19 Gram-Positive Bacilli of Medical Importance
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Chapter 19
Gram-Positive Bacilliof Medical Importance
Spore-formersnon-spore-formers
acid fast
Important Bacilli
Bacillis anthracisBacillus cereus
Clostridium perfringensClostridium tetani
Clostridium botulinumCorynebacterium diphtheriaeMycobacterium tuberculosis
Mycobacterium leprae
Gram positive bacilli
• spore-forming bacilli, motile;
• Spore - survival structureresists heat, drying,
radiation, chemicals
Bacillus spore
Gram Positive Bacilli
• Aerobes: –Bacillus - Aerobic, catalase +, degrades complex macromolecules
– exoenzymes - antiboitics– Endospore - widespread dispersal -
dust, water, plants, animals fur
Bacillus anthracis
• BIG - square 3-5 X 1-1.2 microns, central spores– Polypeptide capsule, Exotoxins
produce necrosis and swelling– Easily grows, sporulates in soil -
grazing animals– Common in cattle - vaccines,
destroy herds - US cases - fur trimmed souveniers BIOTERRORISMBIOTERRORISM
Bacillus anthracis
Bacillus anthracis
Bacillus anthracis–Cutaneous Anthrax - spores enter skin
through small cuts, abrasions–Lesion lump (papule) -black, enlarging,
eschar–Pulmonary Anthrax (woolsorter's disease) -
handling wool spores in dust– Spores in lungs - germinates exotoxins -
septicemia - death in a few hours - capillary clots, shock
–Gastrointestinal Anthrax - eating rare contaminated meat
Cutaneous Anthrax
Bacillus anthracis
Bacillus anthracis–Treatment: penicillin, tetracycline -
toxemia not affected by treatment
–Prevention: vaccines of live attenuated spores and toxoid used on livestock
–Purified toxoid used in at risk humans (vets, now military)
–Contaminated animals disinfected, carcasses burned, not buried. Fur, hides, etc gas sterilized
Bacillus cereus
– Spores land on food, rice, potatoes, meat
– Spores survive cooking, reheating
– Enterotoxins: N/V/D abdominal cramps -
usually self-limiting in about 24 hours
Bacillus cereus
Bacilluscereus
Anaerobic Gram Positive Bacilli
Clostridium perfringensClostridium difficileClostridium tetani
Clostridium botulinum
Clostridium sp.gram-positive, (terminal, swollen) spore-
forming rods, anaerobic, catalase -–Ubiquitous in environment - infectious
diseases not communicable -– spores enter skin, through wounds - grow
release exotoxins,– spores enter foods, grow and release
toxins
Clostridium sp.
• C. perfringens = gangrene• C. difficile = colitis• C. tetani = tetanus• C. botulinum = botulism
Clostridium perfringensGas gangrene -–1. anaerobic cellulitis - only in damage
tissue, toxin and gas, does not spread
–2. myonecrosis quickly progressive, toxins diffuse to healthy tissue
– Surgical, compound fractures, sores, septic abortions, puncture gunshot wounds, crushing injuries with dirt.
– Not very invasive, need dead tissue, anaerobic conditions
Clostridium perfringens
Clostridium perfringens
Clostridium perfringens
–Exotoxin - alpha toxin = Lecithinase, rupture RBCs, swelling, tissue destruction
– Collagenase, hyalurminidase, DNase– Ferments carbohydrates in muscle- gas
–Treatment: debridment - surgical removal of damaged, infected tissues
– Cephalosporin (cefoxitin) or penicillin– Hyperbaric oxygen
Clostridium difficileAntibiotic-associated colitis -
• normal flora of GI tract - after treatment with ampicillin, clindamycin, cephalosporins, patient develops diarrhea since C.d. able to grow.
• Diarrhea, cramps, fever, WBC'selevated - inflammation, epithelium sloughs off with fibrin attached.
Clostridium difficile
Clostridium difficile
• Stop antibiotics, restored electrolytes• Oral vancomycin - several weeks,
intestinal flora restore (yoghurt)• Cecal perforation fatal• Spores in stools, prevent spread to
others
Clostridium tetani
Tetanus /lockjaw–Spores enter through wound, burns,
umbilical stumps, surgical procedures
–Spores grow
–Exotoxins - tetanospasmin - neurotoxin -local nerves to spinal neurons block release of neurotransmitter that inhibits "inappropriate contraction" so muscles contract without control
Clostridium tetani
Clostridium tetani
Tetanus /lockjaw
– Jaw muscles one of first to be affected,
then back, death due to respiratory
collapse
–Treatment:Antitoxin (human tetanus
immune globulin) - binds and inactivates
toxin
Tetanus
Clostridium botulinum• rare but more serious - intoxication -
Spores found in soil, water, intestinal tract of animals – “limber neck”
• Poorly preserved foods, low acid -vegetables, meat, fish, dairy.
• Spores - improperly processed -anaerobic conditions - store at room temp
• No effect on taste or smell
Clostridium botulinum
Clostridium botulinum
• Swallowed toxin absorbed into small intestine, circulatory tract and lymphatics
• Affect neuromuscular junction of muscles, block release of acetylcholine (signal for contraction)
• 12-72 hours - constipation, vision (double), difficulty swallowing, dizziness, respiratory complications
Clostridium botulinum
Clostridium botulinum• Infant Botulism -
– 2 weeks and 6 months old, spores ingested - honey implicated
– poor sucking, limp-baby
• Wound botulism - flaccid paralysis (IDU)
• Treatment: antitoxin, ID foods; penicillin
• Prevention: home-canning improved, boiled for 10 min
Clostridium botulinum
Gram Positive Regular Non-Spore-forming Rods• Regular - stain uniformly, • rod-shaped--• Lactobacillus, Listeria, Erysipelothrix,
Kurthia, Caryophanon, Bronchothrix, Renibacterium
Listeria monocytogenes
• Ubiquitous, motile, short to long filaments in palisades, beta-hemolytic, resists cold, heat, salt, pH extremes and bile.
• Contaminated dairy, poultry, meat, especially raw milk cheeses - Listeriagrows during aging process
Listeria monocytogenes
Listeria monocytogenes• Adults: mild, fever, sore throat,
diarrhea• Transmitted to fetus/ neonate
intrauterine - premature abortion, neonates -meningitis
• Treatment: penicillin, ampicillin, erythormycin
• Prevention: cook foods, pasteurize dairy products
Erysipelothrix rhusiopathiae– Animals and environment (tonsils of pigs-
swine erysipelas ), water, sewage– Handlers, slaughterhouse workers, butchers,
vets– Via scratch or abrasion - lesion: swollen,
dark red, burning itching –Endocarditis and septicemia–Treatment: penicillin or erythromycin–Vaccine for pigs, not effective in humans
Gram-positive Irregular Non-spore-forming Rods
• Pleomorphic, stain unevenly, catalase +, mycolic acid (waxy) peptidoglycan
• Corynebacterium, Mycobacterium, Nocardia
Corynebacteriumdiphtheriae
• Respiratory tract infection, Cutaneous form
• Prevented with successful vaccine, seen in unvaccinated 1-10 yo, healthy carriers
Corynebacteriumdiphtheriae
Corynebacteriumdiphtheriae -
• Aerosole transmission• Fomites• milk
– local infection - tonsils,pharynx, larynx, trachea
Corynebacteriumdiphtheriae -
• toxin production - diffusion -toxemia – toxin
• two polypeptide fragments - B fragment heart and nervous cells A blocks protein synthesis
Corynebacteriumdiphtheriae -
–local inflammatory response
–low-grade fever
–sore throat,nausea, vomiting enlarged
lymph nodes, severe swelling in neck
Corynebacteriumdiphtheriae -
–pseudomembrane - greenish-gray solidified fibrous exudate cells and fluid develop in pharynx stuck on pull off-bleeding
–Toxemia - heart = inflamed nerves/cranium - weakness and paralysis
Corynebacteriumdiphtheriae -
Corynebacteriumdiphtheriae -
• Untreated - asphyxiation, respiratory collapse, heart damage
• ID quickly, gram stain or alkaline methylene blue
• Treatment: diphtheria antitoxin (horses) Pencillin, erythromycin
• Prevented: vaccine DPT
Additional species
• Proprionibacterium -
• Aerotolerant anaerobe, no toxins
• Proprionibacterium acnes– oil glands - acne vulgaris
MycobacteriumAcid-Fast
• Mycolic acids in layers - waxy coat - resists drying, chemicals, acids,
• Long slender straight or curved, filamentous or branching, granules, no spores aerobic
Mycobacterium tuberculosis
Mycobacterium tuberculosis
• TB very prevalent up to about 50 years ago - antibiotic therapy
• Predisposing conditions: poverty, inadequate nutrition, unsanitary living conditions, underlying debilitation of immune system, lung damage, genetics.
• No toxins or enzymes, waxes help prevent destruction even when phagocytised
Mycobacterium tuberculosis
tubercles
Mycobacterium tuberculosis
• Infants infected, stays dormant, reactivated in 20's 15 mil in US 1/3 of world carry TB
• ONLY 5% of those infected may manifest the disease
Mycobacterium tuberculosis–Primary TB - tiniest aerosols, inhaled into
alveoli About 10 cells to start infection -phagocytized by macrophages, multiply intracellularly, mild fever
–3-4 weeks - cell mediated response -monocytes migrate - tubercules
–Tubercle = TB, then macrophages, then fibroblasts and lymphocytes and neutrophils
–Necrosis of tubercle = calcification
–Tuberculin reaction
Mycobacterium tuberculosis
Caseation, lesions
Mycobacterium tuberculosis– Secondary TB - tubercles expand and drain into
bronchioles - coughing, greenish or bloody sputum, fever, anorexia, weight loss, extreme fatigue, night sweats, chest pain wasting of body = consumption
– Extrapulmonary - lymph nodes, kidneys, long bones, genital tract, brain, meninges
– Detection: • 1 tuberculin test
• 2. X ray
• 3. ID acid-fast
Mycobacterium tuberculosis–Tuberculin testing - purified protein
derivative – cell- mediated hypersensitivity
–Treatment: sufficient to kill bacillus 6-24 months
–Two drugs - Isoniazide, rifampin, ethambutol, streptomycin, pyrazinamide, thioactazone, para-aminosalicylic acid
–Prevention: vaccine BCG (bacille Calmet-Guerin strain of M.bovis - 20-80% protective for several years
Mycobacterium leprae
• Hansen's bacillus– Strict parasite (armadillo), slow grower
– Leprosy - chronic progressive disease skin and nerves - severe disfigurement
– Not readily communicated - no even sure of transmission
– 15 leper colonies in Asia, Africa, Central and South American and Pacific Islands, Siberia, Korea, China, Hawaii, Texas, California, Louisiana 2-3K
Mycobacterium leprae
Mycobacterium leprae
King Uziahas painted byRembrandt.
Mycobacterium leprae
Mycobacterium leprae–T cell response factor determines
progressiveness
–Tuberculoid - shallow skin lesions
–Leproid - nose, eyes, eyebrows, chin, testes - thickening –lepromas
–Treatment dapsone
–Rifampin and dapsone for tuberculoid
–Rifampin, dapsone and clofazimine (2-10 years)
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