BACTE LECT AE

    Cards (70)

    • Aerobic Gram-Positive Bacilli
      • Sporeformer: Bacillus
      • Non-sporeformer: Corynebacteria
      • Listeria
      • Erysipelothrix
      • Arcanobacterium
      • Kurthia
      • Rothia
      • Paenibacillus
      • Nocardia
      • Rhodococcus
      • Gordonia
      • Tsukamurella
      • Streptomyces
      • Actinomadura
      • Tropheryma
    • Bacillus
      • Aerobic, sporeforming bacilli, gram(+) rods
      • Largest pathogenic bacteria so far
    • Bacillus morphology
      • Facultative, large, square-ended (boxcar-shaped), encapsulated, non-motile, gram(+) rods in an ellipsoidal to ovoid with centrally located endospore
      • They occur in chains giving a bamboo pole appearance
      • Most members are saprophytic, prevalent in soil, water, air, and vegetation
    • Significant Bacillus species
      • Bacillus anthracis (Anthrax bacillus)
      • Bacillus cereus (Fried rice bacillus)
      • Bacillus polymyxa (Source of polymyxin antibiotics)
      • Bacillus stearothermophilus (For autoclave efficiency checking)
      • Bacillus pumilus (Biological indicator for sterilization methods)
      • Bacillus thuringensis (Biological control for insect vectors)
      • Bacillus subtilis (Hay bacillus; source of bacitracin antibiotics)
    • Bacillus anthracis
      • Large, encapsulated, non-motile, gram(+) rods with square ends, arranged in long chains giving a disjointed bamboo-pole appearance
      • Sporulate aerobically
    • Bacillus anthracis capsule
      Made up of D-glutamic acid; considered as virulence factor which prevents phagocytosis
    • Bacillus anthracis anthrax toxin
      Causes vascular permeability and capillary thrombosis; has 3 components: Protective antigen, Edema factor, Lethal factor
    • Forms of anthrax
      • Cutaneous
      • Pulmonary
      • Gastrointestinal
      • Injection
    • Cutaneous anthrax
      Also called Malignant pustule; most common form; initiated by entrance of bacilli through abrasions of the skin; pustule appears on hands or forearms which develops into vesicles of filled with dark fluid; rupture of vesicles reveal BLACK ESCHAR (no pus) formation
    • Pulmonary anthrax
      Also called Inhalational Anthrax or Woolsorter's disease or Ragpicker's disease; most severe form initiated by inhalation of spores during shearing, sorting, and handling of animal hair
    • Gastrointestinal anthrax
      Also called violent enteritis; the rarest form; initiated by ingestion of bacilli or spore from infected meat resulting to invasion and ulceration of gastrointestinal mucosa
    • Injection anthrax
      This has been identified among drug users; associated with soft tissue infection
    • Specimens for laboratory identification
      • Swab of vesicles
      • Sputum
      • Stool
      • Blood
      • CSF
    • Microscopy
      1. G/S: boxcar-shaped Gram-positive bacilli with unstained central spore
      2. MacFadyean's method (spore stain): using polychrome methylene blue for capsule
    • Culture (GOLD STANDARD for B. anthracis)
      1. BAP – non-hemolytic, opaque in "Medusa or Lion-head" appearance due to masses of long, hair-like curls
      2. PEA – recommended for fecal specimen
      3. NA – colonies have "Cut-glass appearance" on transmitted light
      4. Egg Yolk agar (EYA) – to determine lecithinase production of B. anthracis
      5. Gelatin Medium – organisms liquify gelatin resembling an "Inverted Fir tree or Inverted Pine Tree" appearance
      6. PLET (Polymyxin Lysozyme EDTA Thallous acetate) – selective medium for the isolation of B. anthracis in contaminated specimen; this culture medium maybe added with bicarbonate agar to induce B. anthracis capsule formation
    • Laboratory tests
      • String of Pearl Test
      • Ascoli Precipitin Test
      • Mouse Virulence Test
    • String of Pearl Test
      Reflects the susceptibility of the strain to penicillin; organism is streaked on solid media with 10-unit penicillin disk placed over the streak and incubated for 3-6 hours at 37°C; the cells become large and spherical occurring in chains as seen on the surface of the agar, resembling a string of pearls (+)
    • Ascoli Precipitin Test
      Diagnostic precipitin test for Bacillus anthracis; the extract of infected tissue shows a ring of precipitate when layered over a serum
    • Mouse Virulence Test
      Inject 0.2 ml – 0.5 ml intraperitoneally of barely turbid saline suspension; (+) mouse will die 24-72 hours
    • Treatments for anthrax
      • Penicillin
      • Tetracycline
      • Erythromycin
      • Chloramphenicol
    • Bacillus cereus
      • Morphologically similar to Bacillus anthracis but usually motile
      • Resistant to penicillin and sensitive to vancomycin
      • Colonies are beta-hemolytic, small, shiny and compact or large, feathery and spreading
      • On BAP – large and feathery, beta-hemolytic with "frosted glass" appearance
      • Virulence factors include Enterotoxins, cerelysin, Phospholipase C, pyogenic toxin
    • Bacillus cereus food poisoning
      • Short incubation type (Emetic type) – associated with FRIED RICE due to heat-stable enterotoxin; patient vomits with no fever
      • Long incubation type (Diarrheal type) – associated with meat or vegetable dishes; associated with health-labile enterotoxin; watery stool without fever
    • Lecithinase test
      Bacillus cereus is one of the many species that produce the enzyme lecithinase, demonstrated by a zone of opacity (whitish color on the agar) extending away from the bacterial growth
    • Treatments for Bacillus cereus
      • Chloramphenicol
      • Aminoglycosides
      • Clindamycin
      • Erythromycin
      • Vancomycin
    • Bacillus anthracis
      Bacillus cereus
    • Bacillus subtilis
      • Hay bacillus
      • Very common laboratory contaminant
      • The source of BACITRACIN antibiotics
      • Can cause eye infections among prohibited drug users
      • On BAP - Beta-hemolytic; large, flat and dull; pink, yellow, orange or brown pigmentation; with a ground glass appearance
      • Morphologically similar to Bacillus cereus
      • Mannitol (+), Xylose (+), Arabinose (+)
    • Corynebacteria
      • Belong to the family Corynebacteriaceae
      • Gram-positive rods
      • Non-motile; non-sporeforming
      • With club-shaped ends and palisade arrangement
      • Highly pleomorphic which often occurs in XVYL formation or referred to as "Chinese letters"
      • Produce metachromatic granules (Babes Ernst granules), thus, in stained smear, they appear as beaded appearance
    • Classification of Corynebacteria
      • Lipophilic Corynebacteria (lipids enhances the growth): Corynebacterium jeikeium, Corynebacterium urealyticum
      • Non-lipophilic Corynebacteria (exhibits fermentative or oxidative metabolism): Corynebacterium amycolatum, Corynebacterium diphtheriae, Corynebacterium pseudotuberculosis, Corynebacterium pseudodiphthericum, Corynebacterium striatum, Corynebacterium ulcerans, Corynebacterium xerosis
      • Corynebacteria causing Human Infections: Corynebacterium diphtheriae, Corynebacterium jeikeium, Corynebacterium pseudotuberculosis, Corynebacterium pseudodiphthericum, Corynebacterium ulcerans, Corynebacterium urealyticum
      • Normal Flora (sometime opportunistic) - collectively called DIPHTHEROIDS: Corynebacterium xerosis, Corynebacterium pseudodiphthericum/ hofmanii, Propionibacterium acnes, Corynebacterium equi
    • Corynebacterium diphtheriae
      • Also Kleb Loeffler's Bacillus
      • Highly pleomorphic in X,V,Y and L formations
      • These Chinese character arrangements are caused by snapping during binary fission
      • 4 major biotypes: C. diphtheriae var gravis (produces serious disease), C. diphtheriae var intermedius (mild disease), C. diphtheriae var belfanti (mild disease), C. diphtheriae var mitis (cause very minimal disease)
    • Diphtheria pathogenesis
      • Caused by powerful exotoxin produced by the strains of C. diphtheriae infected with specific beta bacteriophage carrying the TOX gene responsible for toxin production (heat labile polypeptide) which destroys the epithelial cells lining the respiratory tract and numerous membrane by arresting CHON synthesis of the cells
      • The organism exhibits Lysogenicity
      • Pseudomembrane formation – the most pathognomonic sign of diphtheria; grayish white pseudo-membrane formation usually occurs in the upper respiratory tract; initial lesions usually occurs on tonsils and oropharynx which then spreads to the nasopharynx and trachea
      • Clinical manifestations: low grade fever, malaise, and mild sore throat; edematous and tender cervical lymph nodes (bull neck appearance); mechanical obstruction of the airway may ensue due to the membrane accompanying edema of the larynx and trachea; complications may involve the cardiovascular and nervous system; hemorrhaging of the nasal mucosa (endothelial damage)
    • Laboratory identification of Corynebacterium diphtheriae
      1. Specimen: NPS and Throat swab
      2. Stained smear – to demonstrate the characteristic morphology and use of special stains to demonstrate the metachromatic granules (LAMB, Neisser's, Ljubinsky and Gohar)
      3. Culture: BAP, Tinsdale Tellurite Medium, Pai's coagulated medium, CTA, LSS – enhances the pigmentation and granule production
    • Cultural characteristics of Corynebacterium diphtheriae

      • On blood agar, the C diphtheriae colonies are small, granular, and gray with irregular edges and may have small zones of hemolysis
      • On agar containing potassium tellurite, the colonies are brown to black with a brown
    • Schick's test
      Susceptibility test for diphtheria; procedure: right forearm inject ID, 0.1 ml of toxin (Test); left forearm inject ID, 0.1 ml of toxoid (Control)
    • Diphtheria symptoms
      • Hemorrhaging of the nasal mucosa (endothelial damage)
      • Pronounced cervical adenopathy and swelling creating a bull neck appearance
    • Specimen for laboratory identification
      • NPS and Throat swab
    • Examinations for laboratory identification
      1. Stained smear – to demonstrate the characteristic morphology and use of special stains to demonstrate the metachromatic granules (LAMB, Neisser's, Ljubinsky and Gohar)
      2. Culture: BAP, Tinsdale Tellurite Medium
      3. Pai's coagulated medium
      4. CTA
      5. LSS – enhances the pigmentation and granule production
    • Diphtheria colonies on blood agar
      • Small, granular, and gray with irregular edges and may have small zones of hemolysis
    • Diphtheria colonies on agar containing potassium tellurite
      • Brown to black with a brown
    • Schick's test

      Susceptibility test for diphtheria
    • Schick's test procedure
      1. Right forearm inject ID, 0.1 ml of toxin (Test arm)
      2. Left arm, inject 0.1 ml toxoid (control arm)
      3. Read after 24-48 hours up to 6 days
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