Cornyebacterium

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109 Terms

1

Corynebacteria

Non-spore-forming,non-branching, catalase positive bacilli

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2

Cornyeform or Diptheroid

They are slightly curved , gram-positive rods that may occur in singly or in palisades, with irregular swelling at the ends “club shaped” this termed as _______ or ______, diphtheria like bacteria.

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3

Skin and mucous membranes

Normal Flora

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Lipophilic and Nonlipophilic

2 classifications

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  • Corynebacterium urealyticum

  • Corynebacterium jeikeium

Lipophilic Spp.

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  • fastidious and slow growers

  • Require > 48 hours to grow

Characteristics of Lipophilic spp.

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Addition of lipids :

  • Tween 80

  • Serum

These enhances the growth of your bacteria in the culture media

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  • Corynebacterium ulcerans

  • Corynebacterium pseudotuberculosis

  • Corynebacterium striatum

  • Corynebacterium xerosis

  • Corynebacterium pseudodipheriticum

Nonlipophilic spp

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9
  • often dismissed as commensals

  • Can be considered opportunistic pathogens when they are isolated in various body sites

Characteristics of nonlipophilic spp.

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Corynebacterium diptheriae

Most significant pathogen of the group

  • “chinese letters” or “picket fence appearance”

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11

Kleb-Loeffler’s Bacilli

Corynebacterium diptheriae is also known as ?

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12

Chinese letters or picket fence appearance

Microscopic morphology

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13

Bacilli, Club-shaped

Shape

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14

Gram positive

Gram-staining reaction

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15

Non-branching

Structure

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16

Non-spore forming

Composition

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Non-motile

Motility

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18

Catalase positive bacilli

Catalase reaction

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19

Aerobic

Oxygen tolerance

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20

Pleomorphic

The ability to alter their shape in response to environmental conditions

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21

Penicillin

Drug of choice

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22

Erythromycin

Drug of choice for individuals resistant to penicillin

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23

Prompt administration of Antitoxin

Treatment

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24

Vaccination

Most patients don’t develop immunity after infection with this bacteria, _________ should be administered after a patient recovers.

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25
  • Formalin treated

  • part of a trivalent DTP (Diptheria, Tetanus, Pertussis) vaccine

Effective toxoid vaccine

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26

DTP (Diptheria, Tetanus, Pertussis)

Produces antibodies against the Diptheria toxin Only the disease not the Infection.

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27

Diptheria Toxin

This is the Major virulence factor of the bacteria

It is an exotoxin produced by strains of the C. dipgeriae that are infected with a lysogenic beta-phage that carries the tox gene.

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Lysogenic beta-phage

Virus infecting the C. diptheriae

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29
  • Oxygen

  • Alkaline pH

  • Iron concentration in medium

Environmental Conditions needed for this bacteria to grow outside the body (Toxin production : In vitro)

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7.8 - 8.0 pH

Alkaline pH

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Iron concentration in medium

The amount of iron needed for optimal toxin production is less than the amount needed for optimal growth.

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Fragment A and Fragment B

Diptheria toxin is a protein made up of two polypeptide chains namely ______ and ______.

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33

Fragment A

  • Enzymatically active site

  • Responsible for cytotoxicity

  • This disrupts protein synthesis

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Fragment B

  • Receptor binding site

  • Mediates (assists) the entry of fragment A into the cell cytoplasm

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35
  • Respiratory Diptheria

  • Cutaneous Diptheria

Clinical Infection

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36

Respiratory Diptheria

Is the most common clinical infection and it occurs in the non-immunized populations , carried/ infects the upper respiratory tract.

  • tonsils & pharynx

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Inhalation of droplets containing the bacteria or via hand-to-mouth contact

Infection of Respiratory Diptheria

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38

2-5 days

Incubation period of Respiratory Diptheria

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Low grade fever, Malaise, Mild sore throat

Symptoms of Respiratory Diptheria

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40

The organisms infects epithelial surface —> Bacteria multiply and produce toxins —> cause cell necrosis and inflammation —> formation of greyish-white pseudomembrane —>

If membrane spreads —> suffocation

Toxins observed —→ systematic effects:

  • Kidney (damage)

  • Heart (death)

  • Nervous system (Demyelinating peripheral nephritis )

Pathogenisis of Respiratory Diptheria

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41

Cutaneous diptheria

Uncommon, prevalent in the tropics and may have toxigenic and nontoxigenic strains

  • usually occurs in patients with poor hygiene

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42

Wounds/skin of infected persons

Where is Cutaneous diptheria found?

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They have non-healing ulcers with a grey membrane

Appearance of Cutaneous diptheria

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44

Babes Ernst granules,

Methylene blue

In Microscopy, this Contains metchromatic granules called _________that have a rod beaded appearance especially when stained with _________.

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45

Letter V or Letter L

Very pleomorphic so they have varying shapes that may appear in palisades or in sharp angles to one another in the ________ or _______ formation.

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46

Babes-Ernst Granules

Represent the accumulation of polymerized polyphosphates

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47
  • Sheep’s Blood Agar

  • Loeffler’s Medium

  • Cystine-tellurite blood agar

  • Tinsdale agar

Culture medium

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48

37 degrees celsius,

Can also grow at 150-40 degrees celsius

In culture, it optimally grows at what temperature?

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49

From a Dacron swab

  • nose or throat

  • Cutaneous diptheria on suspected lesions

Specimen used in culture

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50
  • Small grey granular colonies

  • Irregular edges

  • May have very small zones of beta-hemolysis

C. dipheriae in Sheep’s blood agar

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51

Loeffler’s Medium

  • Contains Serum + Egg

  • Poached-egg colonies

  • Small, smooth, slightly raised greyish colonies within entire margin

  • No longer recommended due to the overgrowth of normal flora

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Enhances the formation of Metachromatic granules

Purpose of serum and egg in Loeffler’s medium

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53

CBTA ( Crystine-tellurite blood agar)

  • Best medium for Corynebacterium

  • Produces black or brown colonies only C. diptheriae

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54

Due to the reduction of Potassium Tellurite

Why do CBTA ( Crystine-tellurite blood agar) produce black or brown colonies ?

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55

C. ulcerans and C. Pseudotuberculosis

These corynebacteria produce brown or black colonies with a brown halo due to cystinase activity

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56

C. diptheriae

Lacks urease production unlike C. ulceran and C. pseudotuberculosis

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Tinsdale agar

Produce grey/black colonies surrounded by a dark brown halo (forming hydrogen sulfide)

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urease Negative

Urease test result for C. diptheriae

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  • Magenta or pink

  • > 8.4 pH

Positive urea test

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60

Urease test

Tests for the presence of the urease enzyme

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Phenol Red

pH indicator for urease test

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Christensen’s Urea broth

Broth used for Urease Test

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Catalase test

test to determine if the bacteria produces catalase enzyme by breaking down Hydrogen Peroxide into water and gas

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Gas bubbles or effervescence

Positive result for Catalase test

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Sugar Fermentation Test

C. diptheriae ferments glucose and maltose without gas

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66

Remains red

Negative result for Sugar fermentation test

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67

Change to yellow

Positive result for Sugar fermentation test

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68

Nitrate Reduction

C. diptheriae reduces nitrate into nitrite

  • test for the bacteria’s ability to use nitrate as an electron acceptor at the electron transport chain

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Change from yellow to red

Positive result for Nitrate reduction test

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70
  • gravis

  • Intermedius

  • Mitis

Orer Corynebacterium diptheriae biotypes

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71

Gravis

Short rods, few granules, some degree of pleomorphism

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Intermedius

Long forms, poor granulation, pleomorphism

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mitis

Long curved, prominent granules, pleomorphism

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74

Guinea Pig Lethality Test

Tests for Toxigenicity, In Vivo

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  • ELISA

  • Immunochromatographic strip assay

  • PCR

  • ELEK TEST

Tests for Toxigenicity, In Vitro

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Guinea Pig Lethality Test

Test is (+) if the unprotected guinea pig dies within 24-96 hours and the control guinea pig lives ( a guinea pig is injected with a culture)

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ELISA

Fast and convenient method to detect serum anti toxin

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Immunochromatographic strip assay

Detects diptheria toxin in a matter of hours

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Polymerase Chain Reaction

Detects diptheria toxin gene and can be used directly on specimen

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80

ELEK Test

Performed for definitive ID of diptheria as a pathogen

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81

Trypticase soy Agar with Low iron content

Culture medium used for ELEK test

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82

Shick Test

  • Test for Immunity

  • A deactivated form of the antitoxin is injected intradermally

  • Positive (+) lack of antibodies = redness or swelling

  • No swelling = patient is still immune

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83
  • C. amycolatum

  • C. urealyticum

  • C. minutissimum

  • C. pseudotuberculosis

  • C. ulcerans

  • C. jeikeium

  • C. Pseudodiptheriticum

  • C. striatum

  • C. xerosis

Other Corynebacterium species

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84

C. amycolatum

  • One of the most frequently recovered from human specimens

  • Often misidentified as C. striatum, C. xerosis and C. minutissimum

  • Part of normal skin microbiota

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Prosthetic joint infections, blood stream infections, endocarditis

C. amycolatum associated infections

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Flat, dry, waxy , Nonlipophilic

C. amycolatum colony morphology

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Resistant to B-lactams, fluoroquinolones, macrolides, clindamycin, Aminoglycosides

C. amycolatum Antibiotic resistance

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Immunocompromised patients

C. amycolatum is common in?

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89

Corynebacterium urealyticum

One of the most frequent isolated clinically significant corynebacteria

  • primarily described as a urinary pathogen

  • Causes UTI, bacteremia, endocarditis and wound infections

  • Lipophilic and is a strict aerobe

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C. urealyticum

Nitrate negative , catalase positive, rapidly urease positive within minutes following inoculation to Christensen urea broth/slant

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Vancomycin

Drug of choice for C. urealyticum

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92

C. minutissimum

Etiologic agent of Erythrasma

  • superficial infection of the axillary and pubic skin

  • Patches of erythrasma are initially pink but quickly depress to be brown and scaly as skin starts to shed

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erythromycin or azithromycin

C. minutissimum Drug of choice

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94

C. pseudotuberculosis

  • rarely causes disease in humans

  • A veterinary pathogen

  • Causes Granulomatous lymphadenitis

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Brown halo

C. Pseudotuberculosis in CBTA

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small, yellowish-white colonies

C. Pseudotuberculosis In SBA

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C. pseudotuberculosis

Urease positive , negative gekatin hydrolysis test

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Penicillin, and erythromycin

Drug of choice for C. pseudotuberculosis

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99

C. ulcerans

Infects cattle and other animals; causes mastitis in cattle and other domestic and wild animals

  • produce less amount of diptheria toxin

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Ingestion of unpasteurized dairy products and contact with infected animals

How do humans acquire C. ulcerans?

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