Severe Vaccine Preventable Bacterial Infections Of The Upper Respiratory Tract Flashcards
What causes Diphtheria?
A G+ Bacilli called Corynebacterium diphtheriae
Diphtheria is a toxin-mediated disease. What is the toxin encoded by?
Toxin actually encoded by bacteriophage = virus of bacteria
What do you call C. diphtheriae that doesn’t have bacteriophage?
C.diphtheriae that doesn’t have bacteriophage infecting itself (called Non-toxigenic C. diphtheriae) doesn’t
cause disease and can sometimes be part of normal flora of upper respiratory tract
Where else can C. diphtheria be found?
Occasionally C. diphtheriae can be found on skin so can also rarely get cutaneous diphtheria
Explain the pathogenesis of Diphtheria
Bacteria adhere to epithelium via pili
* Local superficial growth and replication of bacteria (doesn’t invade deeper into body)
* Toxin destroys cells forming an ulcer covered with necrotic cells- the necrotic layer is called a ‘false membrane’
* With extensive inflammation and swelling of surrounding tissues and lymph nodes
* Can cause obstruction of respiratory tract depending on location, especially narrow areas like larynx
* Toxin is also absorbed systemically and can cause damage to distant cells, particularly myocardium and nerve cells
How is diphtheria spread?
Spread from person to person by droplet spread from upper respiratory tract, or by direct contact
Who is at risk of diphtheria?
At risk: unvaccinated or incompletely vaccinated, including older adults with waning immunity
* In unvaccinated population affects mainly pre-school children
* In partially vaccinated population affects mainly older children, teenagers and even adults
The diphtheria vaccine is made of what?
Vaccine contains diphtheria toxoid
* Bacterial exotoxin that has been modified by chemical or other treatment so that it is no longer toxic
but retains immunogenic properties
* Generates antibodies to diphtheria toxin so don’t develop disease
Diphtheria Tx
Anti-toxin to neutralise unbound toxin
* Antibiotics to reduce infectivity and prevent spread
* Airway support
* Contacts who have been exposed to a case need to be tested, and given antibiotics and vaccine
What is whooping cough
Severe childhood respiratory infection
* Typically starts as mild upper respiratory tract infection (like common cold), but then some
days later get episodes of persistent coughing (paroxysms) followed by an inspiratory
‘whooping’ sound or sometimes by vomiting
How long does the paroxysmal cough last?
1-2 months or more
What microbe causes whooping cough?
Bordatella pertussis, a G- coccobacillus
Explain the pathogenesis of Bordatella Pertussis
Infects ciliated mucosal cells of upper airway, then produces a variety of toxic factors that
influence disease process
What are the 6 complications of pertussis?
Anoxia leading to central nervous system complications including seizures and brain
damage
* Exhaustion
* Malnutrition
* Trauma due to coughing- subconjunctival haemorrhage, pneumothorax, etc
* Secondary bacterial infection
* Long lasting lung damage;
Who is at risk of Pertussis?
Unimmunised people are at risk, especially young infants under 6 months of age. Older
children and adults may develop disease due to incomplete immunisation or waning
immunity. But disease may not be classical presentation- maybe just persistent cough
