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Corynebacteria
Non-spore-forming,non-branching, catalase positive bacilli
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.
Skin and mucous membranes
Normal Flora
Lipophilic and Nonlipophilic
2 classifications
Corynebacterium urealyticum
Corynebacterium jeikeium
Lipophilic Spp.
fastidious and slow growers
Require > 48 hours to grow
Characteristics of Lipophilic spp.
Addition of lipids :
Tween 80
Serum
These enhances the growth of your bacteria in the culture media
Corynebacterium ulcerans
Corynebacterium pseudotuberculosis
Corynebacterium striatum
Corynebacterium xerosis
Corynebacterium pseudodipheriticum
Nonlipophilic spp
often dismissed as commensals
Can be considered opportunistic pathogens when they are isolated in various body sites
Characteristics of nonlipophilic spp.
Corynebacterium diptheriae
Most significant pathogen of the group
“chinese letters” or “picket fence appearance”
Kleb-Loeffler’s Bacilli
Corynebacterium diptheriae is also known as ?
Chinese letters or picket fence appearance
Microscopic morphology
Bacilli, Club-shaped
Shape
Gram positive
Gram-staining reaction
Non-branching
Structure
Non-spore forming
Composition
Non-motile
Motility
Catalase positive bacilli
Catalase reaction
Aerobic
Oxygen tolerance
Pleomorphic
The ability to alter their shape in response to environmental conditions
Penicillin
Drug of choice
Erythromycin
Drug of choice for individuals resistant to penicillin
Prompt administration of Antitoxin
Treatment
Vaccination
Most patients don’t develop immunity after infection with this bacteria, _________ should be administered after a patient recovers.
Formalin treated
part of a trivalent DTP (Diptheria, Tetanus, Pertussis) vaccine
Effective toxoid vaccine
DTP (Diptheria, Tetanus, Pertussis)
Produces antibodies against the Diptheria toxin Only the disease not the Infection.
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.
Lysogenic beta-phage
Virus infecting the C. diptheriae
Oxygen
Alkaline pH
Iron concentration in medium
Environmental Conditions needed for this bacteria to grow outside the body (Toxin production : In vitro)
7.8 - 8.0 pH
Alkaline pH
Iron concentration in medium
The amount of iron needed for optimal toxin production is less than the amount needed for optimal growth.
Fragment A and Fragment B
Diptheria toxin is a protein made up of two polypeptide chains namely ______ and ______.
Fragment A
Enzymatically active site
Responsible for cytotoxicity
This disrupts protein synthesis
Fragment B
Receptor binding site
Mediates (assists) the entry of fragment A into the cell cytoplasm
Respiratory Diptheria
Cutaneous Diptheria
Clinical Infection
Respiratory Diptheria
Is the most common clinical infection and it occurs in the non-immunized populations , carried/ infects the upper respiratory tract.
tonsils & pharynx
Inhalation of droplets containing the bacteria or via hand-to-mouth contact
Infection of Respiratory Diptheria
2-5 days
Incubation period of Respiratory Diptheria
Low grade fever, Malaise, Mild sore throat
Symptoms of Respiratory Diptheria
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
Cutaneous diptheria
Uncommon, prevalent in the tropics and may have toxigenic and nontoxigenic strains
usually occurs in patients with poor hygiene
Wounds/skin of infected persons
Where is Cutaneous diptheria found?
They have non-healing ulcers with a grey membrane
Appearance of Cutaneous diptheria
Babes Ernst granules,
Methylene blue
In Microscopy, this Contains metchromatic granules called _________that have a rod beaded appearance especially when stained with _________.
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.
Babes-Ernst Granules
Represent the accumulation of polymerized polyphosphates
Sheep’s Blood Agar
Loeffler’s Medium
Cystine-tellurite blood agar
Tinsdale agar
Culture medium
37 degrees celsius,
Can also grow at 150-40 degrees celsius
In culture, it optimally grows at what temperature?
From a Dacron swab
nose or throat
Cutaneous diptheria on suspected lesions
Specimen used in culture
Small grey granular colonies
Irregular edges
May have very small zones of beta-hemolysis
C. dipheriae in Sheep’s blood agar
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
Enhances the formation of Metachromatic granules
Purpose of serum and egg in Loeffler’s medium
CBTA ( Crystine-tellurite blood agar)
Best medium for Corynebacterium
Produces black or brown colonies only C. diptheriae
Due to the reduction of Potassium Tellurite
Why do CBTA ( Crystine-tellurite blood agar) produce black or brown colonies ?
C. ulcerans and C. Pseudotuberculosis
These corynebacteria produce brown or black colonies with a brown halo due to cystinase activity
C. diptheriae
Lacks urease production unlike C. ulceran and C. pseudotuberculosis
Tinsdale agar
Produce grey/black colonies surrounded by a dark brown halo (forming hydrogen sulfide)
urease Negative
Urease test result for C. diptheriae
Magenta or pink
> 8.4 pH
Positive urea test
Urease test
Tests for the presence of the urease enzyme
Phenol Red
pH indicator for urease test
Christensen’s Urea broth
Broth used for Urease Test
Catalase test
test to determine if the bacteria produces catalase enzyme by breaking down Hydrogen Peroxide into water and gas
Gas bubbles or effervescence
Positive result for Catalase test
Sugar Fermentation Test
C. diptheriae ferments glucose and maltose without gas
Remains red
Negative result for Sugar fermentation test
Change to yellow
Positive result for Sugar fermentation test
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
Change from yellow to red
Positive result for Nitrate reduction test
gravis
Intermedius
Mitis
Orer Corynebacterium diptheriae biotypes
Gravis
Short rods, few granules, some degree of pleomorphism
Intermedius
Long forms, poor granulation, pleomorphism
mitis
Long curved, prominent granules, pleomorphism
Guinea Pig Lethality Test
Tests for Toxigenicity, In Vivo
ELISA
Immunochromatographic strip assay
PCR
ELEK TEST
Tests for Toxigenicity, In Vitro
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)
ELISA
Fast and convenient method to detect serum anti toxin
Immunochromatographic strip assay
Detects diptheria toxin in a matter of hours
Polymerase Chain Reaction
Detects diptheria toxin gene and can be used directly on specimen
ELEK Test
Performed for definitive ID of diptheria as a pathogen
Trypticase soy Agar with Low iron content
Culture medium used for ELEK test
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
C. amycolatum
C. urealyticum
C. minutissimum
C. pseudotuberculosis
C. ulcerans
C. jeikeium
C. Pseudodiptheriticum
C. striatum
C. xerosis
Other Corynebacterium species
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
Prosthetic joint infections, blood stream infections, endocarditis
C. amycolatum associated infections
Flat, dry, waxy , Nonlipophilic
C. amycolatum colony morphology
Resistant to B-lactams, fluoroquinolones, macrolides, clindamycin, Aminoglycosides
C. amycolatum Antibiotic resistance
Immunocompromised patients
C. amycolatum is common in?
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
C. urealyticum
Nitrate negative , catalase positive, rapidly urease positive within minutes following inoculation to Christensen urea broth/slant
Vancomycin
Drug of choice for C. urealyticum
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
erythromycin or azithromycin
C. minutissimum Drug of choice
C. pseudotuberculosis
rarely causes disease in humans
A veterinary pathogen
Causes Granulomatous lymphadenitis
Brown halo
C. Pseudotuberculosis in CBTA
small, yellowish-white colonies
C. Pseudotuberculosis In SBA
C. pseudotuberculosis
Urease positive , negative gekatin hydrolysis test
Penicillin, and erythromycin
Drug of choice for C. pseudotuberculosis
C. ulcerans
Infects cattle and other animals; causes mastitis in cattle and other domestic and wild animals
produce less amount of diptheria toxin
Ingestion of unpasteurized dairy products and contact with infected animals
How do humans acquire C. ulcerans?