Diphtheria Flashcards
Diphtheria is caused by what bacteria?
Corynebacterium diphtheriae
Diphtheriods are what?
nondiphtherial corynebacteria
Diphtheroids are associated with what diseases?
respiratory tract infections
meningitis
septic arthritis
bacteraemia associated with venous catheters
heart valves
neurosurgical shunts and catheters.
Shape of Corynebacterium
- With irregular swelling at one end giving the club shaped appearance
- Metachromatic granules often located near the poles give beaded appearance on staining
Reservoir for the disease ?
Humans are the only known reservoirs
Primary mode of dissemination ?
Airborne
Respiratory droplets
Direct contact with infected skin lesions
Asymptomatic respiratory carrier states - important in endemic and epidemic disease
Mortality rates for Diphtheria ?
Highest at the extremes of age and Insufficiently immunized persons
Epidemiology of Diphtheria?
- 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).
Strains of C diphtheriae?
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.
Describe the membrane seen in Diphtheria
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.
How does the Toxin cause cell death?
- 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.
Clinical features site of manifestation ?
Respiratory
Cardiac
Neurological
Cutaneous manifestations
Clinical manifestations
- 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
Clinical picture of cutaneous manifestation ?
- 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.
Treatment of Diphtheria (vaccine)
- 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.
Treatment of diptheria (antibiotics)?
- Penicillin or erythromycin is the treatment of choice and is usually given for 14 days.
- Antibiotic treatment kills the organism and terminate toxin production.
Other antibiotics and supportive care that can be used ?
clindamycin
rifampin
tetracycline
Supportive care include
- rest
- analgesics
- airway management
- observation for development of secondary lung infections
- management of cardiac and neurologic complications.
Prevention (vaccination schedule)
- 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.
Are Boosters necessary after taking DPT vaccine ?
- 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.
Protection against Listeria is mediated via ?
Lymphokine activation of T cells on macrophages and by interleukin-18.
Listeria monocytogenes (listeriosis) usually affects what group of people ?
an important pathogen in pregnant patients, neonates, elderly individuals, and other immunocompromised individuals.
Transmission of Listeria monocytogenes is through?
Most infections are due to food-borne transmission.
- Transmission can also occur transplacentally or
- via an infected birth canal
- cross-infection in neonatal nurseries.
Listeriosis in pregnancy
- 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.
Neonatal listeriosis
- (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.
