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Flashcards in toxigenic bacteria Deck (34):
1

compare Corynebacterium diphtheriae and Bordetella pertussis

In both cases, the primary site of infection is the upper respiratory tract, but the major manifestations of the infections are the result of the production of potent exotoxins that have similar enzymatic mechanisms of action at the molecular level. These toxins are components of extremely important vaccines.

2

Lab Diagnosis of C. diphtheria

Requires demonstration of toxin production by the isolate. Immunoprecipitation and PCR detection of tox gene. Cultures are obtained from the throat and/or any skin lesions in the case of cutaneous diphtheria. Can take at least 5 days

3

Corynebacterium structure

pleomorphic (occurring in various distinct forms), gram-positive bacilli. often appear as rods clubbed at one or both ends.

4

Clinical diagnosis of C. diphtheria

diagnosis is usually made on clinical grounds. Treatment (antitoxin and antibiotics) is administered before a final laboratory diagnosis is made bcause antibodies cannot reverse the effects of the toxin once it is bound to the eukaryotic cell receptor of the toxin, so the sooner the unbound toxin is neutralized the less likely it is to cause damage.

5

which form of diphtheria is more contagious

cutaneous form

6

B. pertussis structure

Gram-negative coccobacillus grows very slowly (small colonies in 3-5 days)

7

B. pertussis diagnosis

A nasopharyngeal (NP) aspirate (saline flush) or a nasopharyngeal swab is collected. The organism is most frequently recovered in the catarrhal or very early paroxysmal stages. The organism is extremely difficult to recover past the catarrhal stage. Culture is the Gold standard (100% specificity)- tkes 3-4 days. NO testing for toxin. Presently, a PCR based test is increasingly being used for diagnosis

8

During what time is pertussis best diagnosed

PCR should be tested from NP specimens taken at 0-3 weeks following cough onset, but may provide accurate results for up to 4 weeks of cough in infants or unvaccinated persons. After the fourth week of cough, the amount of bacterial DNA rapidly diminishes, which increases the risk of obtaining false-negative results.

9

Diphtheria toxin MOA

Cleaved by trypsin-like enzymes > releases active fragment A > Fragment B and hydrophobic domain help deliver fragment A to epidermal growth factor precursor then cytoplasm > Fragment A ADP-ribosylates Elongation factor-2 (EF-2) >EF-2 cant function in chain elongation so protein synthesis stops. Targt cells die (cardiac), kidney and peripheral nerves are damaged, heart stops

10

Pertussis toxin MOA

The A toxin ADP-ribosylates the inhibitory subunit of adenylyl cyclase of eukaryotic cell > adenylyl cyclase is turned on > increased cAMP. Pertussis toxin does NOT kill cell like diphtheria, but the full MOA is unknown

11

virulence factors for diphtheria

diphtheria toxin is only virulence factor

12

virulence factors for pertussis

1. pertussis toxin. 2. tracheal cytotoxin- part of the peptidoglycan, destroys ciliated epithelial cells in upper respiratory tract. 3. Adenylyl cylase toxin- affects macrophage trafficking. 4. Filametous hemagglutinin (FHA)- attachment to ciliated respiratory epithelial cells

13

regulation of diphteria toxin

regulated by iron. , increased amounts of iron in the environment (>10µM) will shut off toxin synthesis while <1µM will lead to increased expression. a dead eukaryotic cell gives up its iron more readily than a live cell, which is required for bacterial growth. Also requires tox gene from bacteriophage

14

regulation of pertussis toxin

VIR gene regulates most of the pertussis virulence factors.

15

Diphtheria manifestations

membranous nasopharyngitis and/or obstructive laryngotracheitis plus low-grade fever and gradual onset of manifestation during 1 to 2 days. Bull neck. Cutaneous diphtheria common in temperate climates. Toxin production affects heart, peripheral nerves and kidneys.

16

Organisms that cuase Cutaneous Diphtheria and Diphtheria-like infections

toxigenic Corynebacterium ulcerans carried by domestic and wild animals. Some of these strains carry a bacteriophage, which has the gene encoding diphtheria toxin. Treated like diphtheria

17

Who gets whooping cough

Mainly affects infants but adults can be asymptomatic carriers or, they may have mild disease that is unrecognized as Whooping Cough.You are NOT immune for life if you received the pertussis vaccine, but the disease is generally milder in persons who were immunized during their childhood

18

stages of whooping cough

(i) Catarrhal stage - inflammation of mucous membrane with a free discharge - resembles minor respiratory illness, highly communicable, dry cough. (ii) Paroxysmal stage - 1-6 weeks - sudden recurrence or intensification of symptoms, spasms or seizures & whoop. NOTE: in infants (less than 6 mo) adolescents and adults, the whoop or cough paroxysm will likely be considerably diminished or absent. (iii) Convalescent stage - 7-10 days, or up to several months. decreasing symptoms (cough) but, they may last for months.

19

Pertussis secondary complications

secondary viral and bacterial infections occur. Possible complications also include seizures and neurological damage from hypoxia that occurs during coughing seizures. cerebral hemorrhage. Also, in contrast to C. diphtheriae, Bordetella pertussis is known to produce invasive infection, particularly in the lung. Many infants with pertussis ultimately die of pneumonia.

20

Where does pertussis infect

has a predilection for ciliated epithelial cells. Tracheal epithelial cells are heavily colonized.

21

Which age range is the largest growing group for pertussis infections

adolescents and adults

22

pertussis immunity

Natural immunity wanes after 15 years. Immunity after immunization also wanes

23

Diphtheria treatment

Equine antitoxin for all, and used immediately ( do not wait for labs). Erythromycin is added to prevent spread (not a substitute for antitoxin). Penicillin can also be used. Close contacts should be vaccinated (toxoid) and given antibiotics.

24

how do you get diphtheria antitoxin

Call State Department of Health & CDC

25

Pertussis treatment

NO antitoxin therapy available. Antimicrobials (erythromycin) given early in the catarrhal stage may mitigate the symptoms of this disease. After paroxysms are established, antimicrobials have no effect on the course of illness and are given to limit spread of the organisms to others. This fact illustrates the toxin-mediated nature of the disease.

26

Why are antibiotics used for diphtheria and pertussis

while these agents have no direct effect on the toxins, Antibiotics: (i) can eliminate carriage and subsequent transmission of these organism (ii) reduce the bacterial load that is producing the toxins, thereby they may reduce the severity of the disease and (iii) are critical to prophylactic treatment of persons who have been in contact with someone who has the disease.

27

List the antigens for diphtheria and pertussis that elicit immune responses

Diphtheria: the toxin. Pertussis: toxin plus other antigens like adenylyl cyclase, FHA,

28

describe the DPT vaccine

The vaccine formerly used to protect against Diphtheria, Whooping Cough and tetanus. Trivalent: Diphtheria toxoid (non-toxic derivative of toxin), tetanus toxoid, and Merthiolate, heat, or formalin-killed cells from fully virulent (phase I) B. pertussis

29

Describe the tetramune vaccine

DPaT plus H. flu type B

30

efficacy/safety of DPT vaccine

The diphtheria toxoid and the tetanus toxoid portion part of the vaccine are perfect. The pertussis component was not. it was made of Merthiolate (which contains mercury) killed virulent B. pertussis (whole cell). This method worked, but side effects are observed. A new acellular pertussis vaccine was created with less adverse events, containing purified antigenic pertussis.

31

describe the DTaP vaccines

contain Diphtheria toxoid (non-toxic derivative of toxin), tetanus toxoid, and accelular pertussis. ACEL-IMUNE® and Tripedia® ---have now been licensed for the past 8-10 years for children 6 weeks- 6 years. Tripedia is licensed for the initial 4 doses and ACEL-IMUNE® for all 5 doses. Infanrix is also licensed for first four doses.

32

Tdap vaccination during pregnancy

The CDC now strongly recommends that pregnant women be vaccinated with Tdap during their third trimester even if they have been previously vaccinated. Also, cocooning (vaccinating those around the new infant) is recommended

33

List the available vaccines with pertussis component

• DTaP: Diphtheria-Tetanus-acellular Pertussis vaccine (commercial name Daptacel®)
• DTaP in combination with Haemophilus influenzae type b (Hib) vaccine
• DTaP in combination with hepatitis B and inactivated polio vaccines
• Tdap: Diphtheria-Tetanus-acellular Pertussis vaccine (commercial name Adacel®)

34

Who should receive vaccination with DTaP

1. Most infants and children younger than 6 years of age should receive DTaP beginning at two months of age. 2. 11-18 year olds should receive a single dose of Tdap instead of a Td booster if they have completed the recommended childhood DTP/DTaP immunization series and have not received Td or Tdap. 3. Adults 19-65 years of age should receive a single dose of Tdap (Adacel®) to every 10 years. Tdap may be given at an interval shorter than 10 years in order to protect against pertussis.