Diphtheria

Question 1

Diphtheria is caused by what bacteria?

Answer 1

Corynebacterium diphtheriae

Question 2

Diphtheriods are what?

Answer 2

nondiphtherial corynebacteria

Question 3

Diphtheroids are associated with what diseases?

Answer 3

respiratory tract infections
meningitis
septic arthritis
bacteraemia associated with venous catheters
heart valves
neurosurgical shunts and catheters.

Question 4

Shape of Corynebacterium

Answer 4

• With irregular swelling at one end giving the club shaped appearance
• Metachromatic granules often located near the poles give beaded appearance on staining

Question 5

Reservoir for the disease ?

Answer 5

Humans are the only known reservoirs

Question 6

Primary mode of dissemination ?

Answer 6

Airborne
Respiratory droplets
Direct contact with infected skin lesions
Asymptomatic respiratory carrier states - important in endemic and epidemic disease

Question 7

Mortality rates for Diphtheria ?

Answer 7

Highest at the extremes of age and Insufficiently immunized persons

Question 8

Epidemiology of Diphtheria?

Answer 8

• C diphtheriae infection in children who are not immunized is 70 times higher than in children who have received primary immunization.
• Death usually occurs within the first week, either from asphyxia or heart disease.
• Diphtheroids infections tend to occur in children and elderly and in individuals who are neutropenic, or immunocompromised or those with prosthetic devices (eg heart valves, dialysis catheters, neurologic shunts).

Question 9

Strains of C diphtheriae?

Answer 9

C.gravis
C.intermedius
C.mitis
C. belfanti in decreasing order of virulence
.
C. gravis grows faster and produces toxin earlier and in greater amount than others.

Question 10

Describe the membrane seen in Diphtheria

Answer 10

Layers of death cells result in characteristic membrane of diphtheria which is
- thick and leathery, composed of bacteria, necrotic epithelium, macrophages and fibrin.
- The membrane firmly adheres to underlying mucosa and forceful removal causes bleeding.
- Membrane can spread down the bronchial tree, causing airway obstruction and dyspnea.

Question 11

How does the Toxin cause cell death?

Answer 11

• Active domain then causes inactivation of elongation factor 2 [EF2] thereby inhibiting cellular protein synthesis.
  Protein synthesis inhibition causes cell death.
• toxin-induced damage may also involve the heart, kidneys, and peripheral nerves.

Question 12

Clinical features site of manifestation ?

Answer 12

Respiratory
Cardiac
Neurological
Cutaneous manifestations

Question 13

Clinical manifestations

Answer 13

• Respiratory features usually follows an incubation period of 2-4 days as
• nasal discharge
• sore throat involving the posterior pharynx and tonsils.
• Onset is sudden, with low-grade fevers, malaise
• membrane development on one or both tonsils, with extension to other parts of the respiratory system.

Membrane obstruction of airway results in dyspnoea and may be complicated by suffocation

Question 14

Clinical picture of cutaneous manifestation ?

Answer 14

• Cutaneous infections can present as non-healing ulcers
• starting with a vesicle or pustule progressing to punched-out lesions, with curved elevated margins.
• The lesions are initially painful and may be covered with eschar.
• After a few weeks, the lesions become painless and often have a serosanguineous exudate.

Question 15

Treatment of Diphtheria (vaccine)

Answer 15

• Single dose intravenous Diphtheria antitoxin (DAT) given as 20,000-100,000 units
• usually after a test dose
  -The antiserum works only to neutralize the toxin before it enters the cell.

Question 16

Treatment of diptheria (antibiotics)?

Answer 16

• Penicillin or erythromycin is the treatment of choice and is usually given for 14 days.
• Antibiotic treatment kills the organism and terminate toxin production.

Question 17

Other antibiotics and supportive care that can be used ?

Answer 17

clindamycin
rifampin
tetracycline

Supportive care include
- rest
- analgesics
- airway management
- observation for development of secondary lung infections
- management of cardiac and neurologic complications.

Question 18

Prevention (vaccination schedule)

Answer 18

• Routine immunization is incorporated into National Programme on Immunization(NPI) for all children in Nigeria in the first year of life.
• This is usually included in DPT (Diphtheria, pertusis and tetanus) vaccines on the 6th, 10th and 14th weeks of life.
• Immunization reduces the likelihood of carrier status.
• Even partial immunization confers a reduced risk of severe disease.

Question 19

Are Boosters necessary after taking DPT vaccine ?

Answer 19

• Immunity to diphtheria wanes 4 years after toxoid injections in the absence of natural infection or booster dose.
• Hence, booster doses are needed every 10 years by people travelling from non endemic to endemic region.

Question 20

Protection against Listeria is mediated via ?

Answer 20

Lymphokine activation of T cells on macrophages and by interleukin-18.

Question 21

Listeria monocytogenes (listeriosis) usually affects what group of people ?

Answer 21

an important pathogen in pregnant patients, neonates, elderly individuals, and other immunocompromised individuals.

Question 22

Transmission of Listeria monocytogenes is through?

Answer 22

Most infections are due to food-borne transmission.
- Transmission can also occur transplacentally or
- via an infected birth canal
- cross-infection in neonatal nurseries.

Question 23

Listeriosis in pregnancy

Answer 23

• Listeria may proliferate in the placenta and cause infection due to impaired cell-mediated immunity during pregnancy
• especially during the third trimester when cell-mediated immunity is at its lowest.

Consequences
- Preterm labor and/or delivery is common.
- Abortion, stillbirth
- Intrauterine infection are possible.

Question 24

Neonatal listeriosis

Answer 24

• (granulomatosis infantisepticum)
• Listeria acquired in utero via transplacental transmission results
  in Early-onset sepsis, with premature birth.
• Late-onset meningitis is acquired through vaginal transmission, although it also has been reported with cesarean deliveries.

Question 25

Investigation of listeriosis

Answer 25

Blood culture
- Blood culture results are positive in 60-75% of CNS infections.

CSF wet mount
Listeria demonstrates “tumbling motility”

CSF gram stain
- Results are positive in less than 50% of patients.

CSF analysis
- reveals pleocytosis
- CSF protein levels are moderately elevated
- CSF glucose levels may be low, and if so, are associated with a poor prognosis.

CSF culture
- findings are positive in nearly 100% of patients.

Question 26

Laboratory results showing diphtheroids should heightened awareness of the possibility of?

Answer 26

Listeria infection.

Note;
- Serologic testing is not reliable.
- Synovial fluid and/or prosthetic joint material should be cultured in cases of septic arthritis.
- Stool cultures are neither sensitive nor specific.

Question 27

Treatment of listeriosis

Answer 27

• Intravenous antibiotics must be started immediately when the diagnosis is suspected or confirmed.
• Diagnosis is established by culture of the organism from blood, CSF, or other sterile body fluid.
• Person-to-person transmission does not occur; therefore, isolation precautions are not necessary.

Question 28

Prevention of listeriosis

Answer 28

• Cook all raw food thoroughly.
• Wash raw vegetables.
• Avoid consumption of raw (unpasteurized) milk or milk products.
• Wash hands, knives, and cutting boards after handling uncooked foods.
  Cook food to a safe internal temperature.