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Microbiology > Corynebacterium and Other Gram Positive Rods > Flashcards

Corynebacterium and Other Gram Positive Rods Flashcards

1
Q

Genus Corynebacteria characteristics

A
  • found in nature (soil, water plants) and mucosa and skin flora of humans and animals
  • catalase positive
  • pleomorphism results in palisades, picket fences, or Chinese letters
  • non acid fast
  • non branching gram positive rods
  • non spore forming
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2
Q

Cornyeform (diphtheroids) bacteria

A

An opportunistic pathogen that affects immunocompromised patients (Rhodoccus equi)

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3
Q

Metachromatic granules (characteristic of Corynebacterium)

A

Contain polymerized inorganic phosphate, an energy rich compound that acts as a reserve store of energy and phosphate

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4
Q

MALDI-TOF MS

A

Reliably identifies toxigenic strains of Cornyebacterium. But it is still limited right now

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5
Q

Media for Corynebacterium Diphtheria

A

Cystine tellurite:
- Cystine: selective, enhances growth of fastidious organisms
- potassium tellurite:
-selective:
Inhibits gram positive and gram neg bacteria
- differential:
Reduction of potassium tellurite, colonies are gray-black

-Modified tinsdale agar: organisms are differentiated based on the conversion of the tellurite to tellurium
- results in black colonies

  • Loeffler medium: contains serum and egg and stimulates growth of organism and production of metachromatic granules in the cells.
  • gray, white translucent colonies

-Pai agar

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6
Q

4 diphtheriae bio types differentiated by colony morphology

A
  1. Intermedius
  2. Mitis
  3. Gravis
  4. Belfanti
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7
Q

Vaccines for Diptheriae

A

Dtap and Tdap are the vaccines

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8
Q

ID of Diptheria toxin

A

Elek test: immunodiffusion test, definitive ID by detection of diptheriae toxin

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9
Q

Corynebacterium diptheriae significance

A

-releases an exotoxin that causes damage to heart and neural cells and can be lethal
- causes respiratory and cutaneous diphtheria
- causes pharyngitis and forms a pseudo membrane made up of cellular debris

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10
Q

Toxin production for Diptheriae

A

Exotoxin released into bloodstream and has 2 subunits
- A subunit: blocks protein synthesis by inactivating elongation factor
- B subunit: binds to heart and neural tissue

This is for Respiratory Diptheriae

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11
Q

Presumptive Diagnosis of Diptheriae

A
  • Determined by cystine-tellurite blood agar and modified tinsdale agar
  • growth on sheep blood agar (observation of hemolytic reactions)
  • loeffler and pai media: serum and egg and stimulate production of monochromatic granules
  • Loeffler methylene blue stain: detects monochromatic granules
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12
Q

Definitive idenitification for Diptheriae

A
  • Gueinea pig lethality test- lethal effect is neutralized by Diptheria antitoxi
  • immunodiffusion test: Elek plate, Diptheria antitoxin filter paper strip
  • tissue culture cell test: cytopathic effect is neutralized by Diptheria antitoxin
  • EIA
  • PCR
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13
Q

Corynebacterium jeikeium (JK)

A
  • opportunistic infections of blood, wounds, dialysis exit site, bone marrow transplant
  • causes meningitis, bacteremia, endocarditis, septicemia, pneumonia
  • opportunistic pathogen (immunocompromised)
  • normal skin flora
  • rule out if found in blood culture or in pure culture from normally sterile site
  • gram + coccobacilli that resemble strep
  • urease -, no nitrate reduction, ferments glucose
  • non-hemolytic, enhanced growth on Tween 80
  • identified by MALDI Tof
  • susceptible to vancomycin
    -multi drug resistant
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14
Q

C. Urealyticum

A
  • normal skin flora
  • causes UTIs, kidney stones, alkaline encrusted cystitis and pyelitis
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15
Q

C. Ulcerans

A

-normal skin flora
- causes diphtheria like infections, zoonotic and cutaneous infections

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16
Q

C. pseudo-tuberculosis

A
  • normal flora of sheep, goat, and horse
  • lymphadenitis
17
Q

Listeria Monocytogenes characteristics

A
  • found in soil and water
  • food borne outbreaks (fully cooked chicken linked to Tyson), so ingestion
  • transmitted transplacentally or through infected north canal
  • causes still birth, neonatal death, meningitis, bacteremia, encephalitis, endocarditis, conjunctivitis, skin infections, and lymphadenitis
    -end over end motility, when incubated in nutrient broth at RT for 1hour at 25 deg C
  • Umbrella shaped pattern when incubated overnight in semisolid agar
    At RT
  • grows well at 4 deg Celsius
  • gram positive coccobaccili in pairs and short chains
  • catalase positive (use catalase test to tell the difference between this and group B strep
    -prevention: wash vegetables, thoroughly cook meat, pregnant women should avoid soft cheeses
  • listeriolysin O is the major virulence factor
  • small, white, translucent, narrow zone of beta hemolysis, resembling strep
18
Q

Lactobacillus Characteristics

A
  • identified at the bench with alpha hemolytic, grey colonies on blood agar
  • catalase negative
  • non acid fast
  • does not hydrolyze esculin
  • H2S negative
  • gram stain: chaining coccobaccilli, spirals, palisading, picket fence, Cheerios, Chinese letters
  • non motile
  • maintains proper pH in in vagina
  • treat with penicillin
  • dental infection, bacteremia, and endocarditis
19
Q

Erysipelothrix Rhusiopathiae characteristics

A

-found in pigs, birds, fish, sheep, rabbits
-Infectious state: by direct contact or ingestion of contaminated water or meat (
-Cause skin lesions, bacteremia, and cellulitis
-On 5% sheep blood agar: they can be
-1. Large and rough colonies; slender filamentous, gram positive rods, can appear gram negative
-2. Small, smooth, and translucent colonies: small, slender rods or coccobacilli
-Produces H2S in TSI agar (black in TSI)
-Catalase negative and non motile

20
Q

Arcanobacterium

A

-differentiate from strep by doing the streptex test. It tests negative
-Non branching gram positive rods that are delicate and curved with pointed ends
-Exhibit beta hemolysis
-Pharyngitis in 10-30 year olds, abscess infections
-Catalase negative and non acid fast

21
Q

Rhodococcus

A

-aerobic actinomycete
-Non-hemolytic
-Growth on 5% sheep blood agar
-Shorter, branching gram positive rods (coccobacillary). Fragment into rods and cocci
-Identified at the bench, then sent to labcorp
-Mucoid salmon pink colonies
-Partially acid fast
-Found in fresh water, salt water, soil and farm animals
-Transmitted via respiratory inhalation (from feces) causes UTIs, bacteremia, wound infection, opportunistic pathogens

22
Q

Nocardia

A

-Partially acid fast
-Aerobic actinomycete
-Found in soil and water, saphroyte, lab contaminant, skin flora and upper respiratory tract
-Transmits through traumatic inoculation or inhalation, primary pulmonary infections that disseminate to brain
-Gram positive, beaded, branching, delicate filamentous with fragmentation
-Beta hemolytic on sheep blood agar, wrinkled, dry, adherent, crumbly, chalky white to orange-tan, smells like dirt
-BYCE, Martin Lewis, modified Thayer Martin, and solid medium with paraffin as carbon source
-Grow very SLOWLY
-Mycetoma (chronic), Lymphocutaneous, skin abscesses or cellulitis
-Identified by MALDI-Tof, susceptibility tests sent to labcorp

23
Q

Gardnerella Vaginalis

A

-thin peptidoglycan layer like gram negative
-Gram positive but stains as gram variable coccobaccilli (small pleomorphic)
-Detected by Affirm Vaginalis panel
-Clue cells: SQE with numerous attached small rods, seen in wet prep from vaginal swab
-Normal flora in female genital tract and get into the male urethra
-Media of choice: blood agar (non hemolytic), HBT Agar, CNS agar with added amphotericin
-SPS: free media or supplemented with gelatin
-Catalase negative, non acid fast
-Wet prep used for specimen

Microbiology (4 decks)

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