Lecture 16- Bacterial Diseases Of The Respiratory System

Question 1

Common diseases of the upper respiratory system

Answer 1

*laryngitis- streptococcus pneumoniae

*tonsillitis- s.pneumoniae

*epiglottitis- haemophilia influenzae

*sinusitis- general bacteria

Question 2

Scarlet fever

Answer 2

Caused by streptococcus pyogenes

Erythrogenic; redness producing toxin produces symptoms
Childhood disease- 2+8 years
Easily treated with antibiotics

Fever, rash, sore throat, swollen tongue + flushed cheeks; peeling skin when rash fades
^sometimes confused with measles
Highly contagious + is spread by close contact
Incubation; 2-5 days

Question 3

Scarlet fever- complications

Answer 3

Can develop into a more serious infection if untreated

Can develop into; ear infection, throat abscess, pneumonia, inflammation of the sinuses, skin/soft tissue infection, joint inflammation, septicaemia, meningitis

Later complications; bone/joint problems, liver, kidney/heart damage

Question 4

Diphtheria

Answer 4

Highly dangerous disease
Corynebacterium diphtheriae; gram + rod

Characterised by pseudo-membranes at the back of the throat
Membrane of fibrin, dead tissue + bacteria

D toxin produced by= lysogenized C.diptheriae
Prevented by= vaccine
Cutaneous diphtheria- infected skin wound leads to slow healing ulcer

Question 5

Pertussis; whopping cough

Answer 5

Bordetella pertussis; gram- coccobaccilus
Capsule
Tracheal cytotoxin; damages walls of ciliated cells
Pertussis toxin; prevented by vaccine
Cell fragments
3 stages;
1. Catarrhal stage; like common cold
2. Paroxysmal stage; violent coughing sieges
3. Convalescence stage

Question 6

Complications in infants + young children

Answer 6

Usually most severely affected + likely to develop severe complications;
- pneumonia
- temporary pauses in breathing due to difficulty breathing
- weight loss due to excessive damage
- seizures/ brain damage
- encephalitis - acute inflammation of the brain

Question 7

Immunity against pertussis

Answer 7

Vaccination- does not give life long immunity
Individuals can become re-infected + spread infection
Risk for children too young to be vaccinated

Question 8

Tuberculosis

Answer 8

Caused by mycobacterium tuberculosis
Rod shaped bacilli
Acid fast; resistant to most conventional microbiological staining techniques
PCR diagnosis

Question 9

Mtb infection, membrane + targets

Answer 9

Spread like common cold
Tb occurs- bacteria inhaled by human host
Primary defence; tracheal + brachial epithelium

Mtb membrane;
-waxy impermeable barrier
-unusual complex membrane lipids; mycolic acids
-slow growing
-adaptive- can hide in body

Drugs + targets;
Front line drugs; isoniazid, rifampicin, pyrazinamide + ethambutol

Question 10

Decline in TB

Answer 10

Decline in TB – Key Reasons
Better housing and nutrition improved general health.
Identifying and screening people with TB (national programmes).
Treating infected individuals to reduce spread.
Contact tracing and examining close contacts.
Early treatment of latent TB to prevent disease development.
BCG vaccination used as part of prevention (stopped routine UK use in 2005).
🧬 HIV and TB Connection
HIV epidemic led to a rise in TB cases.
HIV weakens immunity, making TB infection progress faster to active disease.
Higher risk of TB disease in people co-infected with HIV.

Question 11

Pneumonia + pneumococcal pneumonia

Answer 11

Inflammation of the tissues in the lungs
Alveoli= become inflamed and fill with fluid
Symptoms= cough, difficulty with breathing; oxygen deficit

Fatal in some cases; babies, young children + elderly, smokers

PP;
Streptococcus pneumoniae; gram + encapsulated diplococci
Diagnosis- culturing bacteria
Penicillin = drug choice

Question 12

Haemophilus influenzae pneumonia

Answer 12

Gram - coccobacillus
Alcoholism, poor nutrition, cancer or diabetes= factors
Second gen cephalosporin

Question 13

Mycoplasmal pneumonia

Answer 13

Mycoplasma pneumoniae; pleomorphic, wall-less bacteria
Known as primary atypical pneumonia/ walking pneumonia
Common in= children/young adults
Diagnosis; PCR / igM antibodies

Question 14

Legionellosis

Answer 14

legionella pneumophila= gram - rod
- found in water
- transmitted by inhaling aerosols; not transmitted from human to human
Diagnosis= culturing bacteria
Treatment= erythromycin

Question 15

Infection

Answer 15

Begins with the inhalation of the legionella pneumophila bacterium
Not transmitted from human to human
Legionella reach alveoli + come into contact with alveolar macrophage
^ takes bacteria into food vacuole inside the cell
Bacteria divide within vesicle- becomes studded with ribosomes + eventually kill macrophage

Question 16

Lung damage

Answer 16

Caused by;
- attracting phagocytes and T cells to the infected area
^ lungs become damaged because these cells release cytokines + other toxic products which do not kill the bacteria but damage the lung
- legionella survives= releases enzymes
- legionella pneumophila = damage lung tissue is by producing extracellular proteases -> lesion formation in lung tissue

Question 17

Psittacosis; ornithosis

Answer 17

Chlamydophila psittaci; gram - intracellular bacterium
Transmitted to humans by elementary bodies from bird droppings
Reorganises into reticulate body after being phagocytized
Diagnosis= culturing bacteria in eggs/cell culture
Treatment= tetracycline

Question 18

Fungal pneumonias

Answer 18

Rare in UK healthy individuals; immune-compromised
Associated with travelling
Examples; histoplasmosis, pneumocystis, coccidiodomycosis + blastomycosis

Question 19

Opportunistic fungi involved in respiratory disease

Answer 19

Aspergillus
Rhizopus
Mucor