Chapter 19 Gram-Positive Bacilli of Medical Importance · Mycobacterium leprae • Hansen's...

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–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

–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


• 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• 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

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


• toxin production - diffusion -toxemia – toxin

• two polypeptide fragments - B fragment heart and nervous cells A blocks protein synthesis


–local inflammatory response

–low-grade fever

–sore throat,nausea, vomiting enlarged

lymph nodes, severe swelling in neck


–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


• 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


• 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

tubercles


• 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


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


• 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


King Uziahas painted byRembrandt.

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)

Chapter 19 Gram-Positive Bacilli of Medical Importance · Mycobacterium leprae • Hansen's...

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