MLS 4116: Clinical Bacteriology Exam
1 Study Guide Exam and All Actual
Answers.
What genus is the diphtheroid? - Answer Corynebacterium
C. diphtheriae clinical manifestations - Answer -respiratory: pharyngitis or tonsillitis; pseudo
membrane forms over tonsils and may extend down to the larynx and into trachea; can cause
respiratory obstruction
-cutaneous: pustule, nonhealing ulcer, most common in tropical and hot regions
Composition of C. diphtheriae pseudo membrane - Answer fibrin, leukocytes, cellular debris,
and bacteria
C. diphtheriae complications - Answer -respiratory obstruction or systemic effects of
diphtheria toxin absorbed at infection site
-mechanical obstruction of airway by the pseudo membrane, edema, and hemorrhage
-diphtheritic myocarditis characterized by cardiac enlargement and weakness
-paralysis caused by involvement of cranial and peripheral nerves (not serious until diaphragm is
involved)
C. diphtheriae natural habitat - Answer -humans are only natural host
-normal flora of skin and mm of oral cavity
-maintained in the population by asymptomatic carriers
C. diphtheriae routes of transmission - Answer -0-5 cases/year
-droplet aerosols of respiratory secretions
-hand to mouth contact
C. diphtheriae prevention and control - Answer -vaccine using diphtheria toxoid
-Schick test used to determine immunity in population (pos=susceptible=edema, necrosis,
desquamation; neg=immune=toxin neutralized by Abs & no reaction)
C. diphtheriae specimen sites - Answer respiratory: nasopharyngeal and throat swab
cutaneous: exudate from skin lesions
,C. diphtheriae microscopic morphology - Answer -gram positive (uneven staining due to
metachromatic/Babes-Ernst granules - don't take up CV as regularly)
-pleomorphic: appears as V and L formations; "chinese letter formation"; palisades
-club-shaped
-non-spore forming
-non-motile
C. diphtheriae media - Answer -Loeffler's coagulated serum: stimulates growth and
metachromatic granules
-Cyssteine-tellurite blood agar (CTBA)
-Tinsdale medium
-Blood agar
C. diphtheriae colony morphology on blood agar - Answer -looks like "dirty staph"
-may have small zone of beta-hemolysis
C. diphtheriae colony morphology on Tinsdale - Answer -brown to black halo
-also produced by C. ulcerans and C. pseudotuberculosis
C. diphtheriae colony morphoogy on Cysteine-tellurite - Answer -gray to black colonies
-organisms reduce tellurite to tellurium which is gray to black
C. diphtheriae virulence factors - Answer -diphtheria toxin
-dermonecrotic toxin
-hemolysin
Diphtheria toxin - Answer -produced by C. diphtheriae, C. ulcerans, and C.
pseudotuberculosis
-only produced by strains infected by bacteriophage carrying the tox gene
-toxin blocks protein synthesis
-non-toxic until exposed to trypsin: trypsinization results in two polypeptide fragments (A&B)
that are necessary for cytotoxicity
Dermonecrotic Toxin - Answer -sphingomyelinase that increases vascular permeability
-produced by straines of C. ulcerans and C. pseudotuberculosis
, Hemolysin - Answer hemolyzes RBCs
C. diphtheriae toxin detection - Answer -ELISA
-PCR to detect tox gene
-ELEK test
ELEK test - Answer -controls and unknown organisms are streaked on media with low iron
concentration
-each organism is streaked in a single straight line parallel to each other and 10mm apart
-a piece of filter paper strip impregnated with diphtheria antitoxin is laid along the center of the
plate at right angles to the streaks
-lines of precipitation will form if toxin is produced
-curved line of identity between identical organisms
C. diphtheriae treatment - Answer -antitoxin/antiserum: Abs from horses (can cause serum
sickness), human IgG, must be given early
-antibiotics: susceptible to penicillin and erythromycin for diphtheria and vancomycin for JK
group
-supportive therapy: removal of obstructions, minimize CHF, and regulate respiration
C. ulcerans - Answer -animal pathogen: human infections acquired through animal contact
-similar to c. diphtheriae but milder
-lower levels of toxin produciton
-mild pharyngitis
C. jeikeium - Answer -normal skin flora
-nosocomial infections in immunocompromised
-bacteremia associated with prosthetics, catheters, and heart valves
-strict aerobe
-highly resistant to antibiotics except vancomycin
C. urealyticum - Answer -one of most frequently isolated corynebacteria
-primarily a urine pathogen
-slow growing: cultures must be incubated at least 48 hrs
-strict aerobe
-catalase positive
1 Study Guide Exam and All Actual
Answers.
What genus is the diphtheroid? - Answer Corynebacterium
C. diphtheriae clinical manifestations - Answer -respiratory: pharyngitis or tonsillitis; pseudo
membrane forms over tonsils and may extend down to the larynx and into trachea; can cause
respiratory obstruction
-cutaneous: pustule, nonhealing ulcer, most common in tropical and hot regions
Composition of C. diphtheriae pseudo membrane - Answer fibrin, leukocytes, cellular debris,
and bacteria
C. diphtheriae complications - Answer -respiratory obstruction or systemic effects of
diphtheria toxin absorbed at infection site
-mechanical obstruction of airway by the pseudo membrane, edema, and hemorrhage
-diphtheritic myocarditis characterized by cardiac enlargement and weakness
-paralysis caused by involvement of cranial and peripheral nerves (not serious until diaphragm is
involved)
C. diphtheriae natural habitat - Answer -humans are only natural host
-normal flora of skin and mm of oral cavity
-maintained in the population by asymptomatic carriers
C. diphtheriae routes of transmission - Answer -0-5 cases/year
-droplet aerosols of respiratory secretions
-hand to mouth contact
C. diphtheriae prevention and control - Answer -vaccine using diphtheria toxoid
-Schick test used to determine immunity in population (pos=susceptible=edema, necrosis,
desquamation; neg=immune=toxin neutralized by Abs & no reaction)
C. diphtheriae specimen sites - Answer respiratory: nasopharyngeal and throat swab
cutaneous: exudate from skin lesions
,C. diphtheriae microscopic morphology - Answer -gram positive (uneven staining due to
metachromatic/Babes-Ernst granules - don't take up CV as regularly)
-pleomorphic: appears as V and L formations; "chinese letter formation"; palisades
-club-shaped
-non-spore forming
-non-motile
C. diphtheriae media - Answer -Loeffler's coagulated serum: stimulates growth and
metachromatic granules
-Cyssteine-tellurite blood agar (CTBA)
-Tinsdale medium
-Blood agar
C. diphtheriae colony morphology on blood agar - Answer -looks like "dirty staph"
-may have small zone of beta-hemolysis
C. diphtheriae colony morphology on Tinsdale - Answer -brown to black halo
-also produced by C. ulcerans and C. pseudotuberculosis
C. diphtheriae colony morphoogy on Cysteine-tellurite - Answer -gray to black colonies
-organisms reduce tellurite to tellurium which is gray to black
C. diphtheriae virulence factors - Answer -diphtheria toxin
-dermonecrotic toxin
-hemolysin
Diphtheria toxin - Answer -produced by C. diphtheriae, C. ulcerans, and C.
pseudotuberculosis
-only produced by strains infected by bacteriophage carrying the tox gene
-toxin blocks protein synthesis
-non-toxic until exposed to trypsin: trypsinization results in two polypeptide fragments (A&B)
that are necessary for cytotoxicity
Dermonecrotic Toxin - Answer -sphingomyelinase that increases vascular permeability
-produced by straines of C. ulcerans and C. pseudotuberculosis
, Hemolysin - Answer hemolyzes RBCs
C. diphtheriae toxin detection - Answer -ELISA
-PCR to detect tox gene
-ELEK test
ELEK test - Answer -controls and unknown organisms are streaked on media with low iron
concentration
-each organism is streaked in a single straight line parallel to each other and 10mm apart
-a piece of filter paper strip impregnated with diphtheria antitoxin is laid along the center of the
plate at right angles to the streaks
-lines of precipitation will form if toxin is produced
-curved line of identity between identical organisms
C. diphtheriae treatment - Answer -antitoxin/antiserum: Abs from horses (can cause serum
sickness), human IgG, must be given early
-antibiotics: susceptible to penicillin and erythromycin for diphtheria and vancomycin for JK
group
-supportive therapy: removal of obstructions, minimize CHF, and regulate respiration
C. ulcerans - Answer -animal pathogen: human infections acquired through animal contact
-similar to c. diphtheriae but milder
-lower levels of toxin produciton
-mild pharyngitis
C. jeikeium - Answer -normal skin flora
-nosocomial infections in immunocompromised
-bacteremia associated with prosthetics, catheters, and heart valves
-strict aerobe
-highly resistant to antibiotics except vancomycin
C. urealyticum - Answer -one of most frequently isolated corynebacteria
-primarily a urine pathogen
-slow growing: cultures must be incubated at least 48 hrs
-strict aerobe
-catalase positive
