GRAM POSITIVE (+) AEROBIC BACILLI Flashcards
memroization
Aerobic gram-positive, spore-forming rods; catalase positive;’ most (but not all) are motile
Bacillus
The only truly pathogenic Bacillus
B. anthracis
The main host of B. anthracis:
Domesticated animals (e.g cows)
What disease is caused by B. anthracis
Anthrax
Enumerate types of anthrax:
- Cutaneous anthrax
- Gastrointestinal anthrax
- Inhalation anthrax
Most common anthrax type; characteristic central black painless eschar (ulcer) at the site of inoculation with surrounding edema; can lead to sepsis
Cutaneous anthrax
Most lethal and deadly anthrax type:
Inhalation anthrax
Other name of inhalation anthrax
“woolsorter’s disease”
The capsule of B. anthracis is made up of:
Poly-D-glutamic acid
Action of poly-D-glutamic acid in the capsule of B. anthracis
Antiphagocytic
Three proteins that makes up the anthrax toxin
- Protective Antigen (PA)
- Edema Factor (EF)
- Lethal Factor (LF)
EF + PA; responsible for cell and tissue edema:
Edema toxin
LF + PA; cause of death in infected animals and humans:
Lethal toxin
Bacillus anthracis on sheep blood agar at 24 hours:
Non-motile and Non-hemolytic
Tip: Read Bacillus anthracis as “Bacillus NONthracis”
Colony appearance of B. anthracis on blood agar:
“Medusa head” appearance of colonies
Microscopic appearance of B. anthracis:
Bamboo pole arrangement
“Boxcar” appearance (Centrally located spore)
Bacillus species that can cause food poisoning:
Bacillus cereus
2 distinct form of food poisoning caused by B. cereus:
- Emetic type
- Diarrheal type
Associated with fried rice, milk and pasta; caused by ingestion of preformed emetic toxin
Emetic type
Associated with meat dishes and sauces; ingested spores develop into vegetative cells that secrete enterotoxins
Diarrheal type
Difference between B. anthracis and B. cereus
B. anthracis:
- Non-hemolytic
- Non-motile
B. cereus:
- Beta-hemolytic
- Swarming motility (similar to proteus)
Other name of Corynebacterium diptheriae
Diphtheria bacillus/ Kleb Loeffler’s bacillus
An acute contagious disease characterized by the production of a systematic toxin and a false membrane lining on the throat (pseudomembranous)
Diphtheria
Appearance of C. diphtheriae on Loeffler’s serum agar:
(+) Poached egg colonies
Skin test for C. diptheriae susceptibility
Schick’s test
In vitro virulence test for C. diphtheriae:
ELECK METHOD
positive result for Elec method:
precipitin lines (+)
Nonlipophilic coryneform bacteria; Also known as Hoffman’s bacillus:
C. pseudodiphtheriticum
- Normal flora of human nasopharynx
Lipophilic coryneform bacteria:
- C. jeikeium
- C. urealyticum
Gram positive or gram variable coccobacillus (resembling Haemophilus), or diphtheroid-like rods
Listeria monocytogenes
Motility of L. monocytogenes:
Tumbling motility
CAMP (+) pattern of L. monocytogenes:
“shovel” pattern CAMP (+)
In motility medium, L. monocytogenes is positive with a characteristic “_______” shaped pattern:
“umbrella” shaped pattern in motility medium
Virulence test; culture instilled in rabbit eye causes purulent conjunctivitis; stimulates monocytes in rabbits:
Anton test
Differentiate L. monocytogenes and Corynebacteria:
L. monocytogenes
- Tumbling motility (+)/motile
- Salicin (+)
Corynebacteria
- Non-motile
- Salicin (-)
Diseases caused by L. monocytogenes:
- Gastroenteritis
- Meningitis
- Infection in pregnancy
- Granulomatosis Infantiseptica
Bacteria that causes Erysipeloid, aka “seal finger” and “whale finger”
Erysipelothrix rhusiopathie
Test that differentiates E. rhusiopathie from L. monocytogenes:
H2S
E. rhusiopathie - H2S (+)
L. monocytogenes (-)
Erysupelothrix rhusiopathie in motility medium is described as having:
“test tube brush” shape
Culture media incubation requirements for isolation of Mycobacterium:
Incubate in 5-10% CO2 (Capnophilic)
Culture media for isolation of Mycobacterium:
- Lowenstein-Jensen (L-J)
- Middlebrook 7H10 or 7H11 agar
Culture media for Mycobacterium that contains egg glycerol; more species grow, less drying out, good for niacin test; Difficult to prepare.
Lowenstein-Jensen (L-J)
Culture media for Mycobacterium that has clear agar and fewer contaminants; it’s clear agar can allow to see the colonies early through the microscope.
Middlebrook 7h10 or 7h11 agar
Stains for Mycobacterium:
- Acid-Fast stain
- Auramine-rhodamine fluorescent stain (Truant)
Best/preferred test for the identification of mycobacteria:
Niacin test
In Nitrate reduction test, which Mycobacterium is positive and which is negative:
Nitrate reduction test for Mycobacterium:
M. tuberculosis (+)
M. bovis (-)
Described as rough, wrinkled, dry, elevated, buff-colored (“cauliflower-like) at 35-37C
M. tuberculosis
The primary spread of the organism 9M. tuberculosis) is via ___________.
via aerosol droplets from coughing
True or false
The immunologic response to this infection (M. tuberculosis) is humoral rather than cellular.
False
The immunologic response to M. tuberculosis is cellular (rather than humoral)
Most common presentation of TB is as a ____________.
Chronic pulmonary disease
M. tuberculosis infection - In those with intact cell-mediated immunity, T cells and macrophages limit the multiplication and dissemination of the organism by forming _________.
Granulomas
Other tests for Mycobacterium tuberculosis:
- Mantoux Tuberculin skin test (TST)
- Interferon-gamma release assays (IGRAS)
Test used to determine whether an individual has been exposed to Mycobacterium tuberculosis; uses Purified protein derivative (PPD), which is a heat-killed, filtered, ammonium sulfate-precipitated organism; injected intradermally into the forearm.
Mantoux Tuberculin Skin test (TST)
Whole blood tests to detect tiuberculosis infection; including both latent TB infection (LTBI) and tuberculosis (TB) disease.
Interferon-gamma release assays (IGRAS)
two (2) approved IGRAS test:
- QuantiFERON-TB Gold In-Tube test (QFT-GIT)
- T-SPOT TB test (T-Spot)
Most common non-Tb mycobacterial infection (second to tuberculosis); Causes disseminated disease in HIV/AIDS with low CD4 count (<50)/Systemic disease
Mycobacterium avium complex
mycobacterium avium complex includes:
- M. avium
- M. intercellulare
Obligate intracellular organism’ reservoir is armadillos; causes HANSEN’S Disease (leprosy)
Mycobacterium leprae (Hansen’s Bacillus)
These are macrophages containing acid-fast bacilli described as “smears of tissue juice”:
Lepra cells
Milder disease; strong cell-mediated TH1 response contains infection; patches of hypopigmented skin with loss of sensation over affected area; (+) granuloma
Tuberculoid leprosy
Severe disease; depressed cell-mediated immunity; diffuse skin lesions with often deformed, thickened skin (Leonine facies); (-) granuloma
Lepromatous leprosy
Skin test for leprosy using a sterile extract from lepromatous nodules:
Lepronin test
Two (2) types of reaction of lepronin test:
- Early Fernandez reaction (24 to 48 hours)
- Late or Mitsuda reaction (3 to 4 weeks )
Diagnosis of Mycobacterium leprae:
Acid-fast organisms on skin biopsy
Causes Buruli ulcers in Africa
Mycobacterium ulcerans
Thin, branching and beaded modified acid fast-positive rods
Nocardia
Disease caused by Nocardia:
Nocardiosis
Causative organisms are soil-inhabiting (exogenous) Nocardia:
- N. asteroides
- N. brasiliensis