Respiratory Pathogens Flashcards
P mechanism of spread
Aerosols are important for person-to-person transmission of
many infectious diseases.
Most pathogens survive poorly in air; thus, they are
effectively transmitted only over short distances
Respiratory tract environments
Different pathogens characteristically colonize the respiratory
tract at different levels.
The upper and lower respiratory tracts offer different
environments (temperature, air flow, pH, etc.) and favor
different microbes.
GAS
group A streptococci
commonly found in low numbers in the
upper respiratory tract of healthy individuals
GAS diseases
Pharyngitis
Scarlet fever
Septicaemia
Toxic shock syndrome
Rheumatic fever
Rarely: Cellulitis and fasclitis
pharyngitis
Streptococcus pyogenes (Group A Streptococcus; GAS) is a Gram-positive host-adapted bacterial pathogen.
It most often causes mild human infections such as pharyngitis or impetigo
Scarlet fever
A Strep A infection (usually beginning with the throat) where erythrogenic
toxins such as SpeA, produced by the bacterium when it is infected by a bacteriophage (T12) causes a high fever, rash and ‘strawberry tongue’ that used to cause significant mortality in
children.
Septicaemia
‘blood poisoning’ an infection of the bloodstream that can lead to septic shock
and death (50% mortality rate).
Rheumatic fever
An inflammatory disease that affects the heart, joints, skin, and brain
Rheumatic heart disease
Type of rheumatic fever
-An autoimmune response following a poorly treated Strep A infection
-The disease typically develops two to four weeks after a streptococcal throat infection. -The exact mechanisms that lead to
the disease are not clear, but it is understood that molecular mimicry of the bacterium results in the immune system targeting the heart valves, which results in valve scarring and damage.
cellulitis + fasciitis
Streptococcus pyogenes under rare circumstances can occasionally cause
sudden and severe tissue infections such as: cellulitis, a subcutaneous skin
infection or erysipelas.
-fasciitis = (flesh eating disease)
Diphtheria
A severe upper respiratory disease that typically infects children and caused by Corynebacterium diphtheriae, a Grampositive bacterium that forms irregular rods during growth
Corynebacterium diphtheriae mechanism of spread
-Spreads by airborne droplets and enters the body via the respiratory route.
-Pathogenic strains lysogenized by bacteriophage β produce a powerful exotoxin that causes a pseudomembrane in the patient’s throat.
-Death due to a combination of partial suffocation by the pseudomembrane and tissue destruction in various organs due to dissemination of the toxin
Resistance against Corney bacterium
Previous infection or immunization provides resistance.
symptoms of diptheria
A swollen neck is a common symptom of
diphtheria.
-The pseudomembrane in
an active case of diphtheria restricts airflow and swallowing and is associated with a severe sore throat
diptheria treatment
-Prevention of diphtheria is achieved by the DTP3/DTaP (diphtheria toxoid, tetanus toxoid, and acellular pertussis) vaccine.
-Antibiotics can be used for active infections/Diphtheria antitoxin is available for acute cases because antibiotics
take time that patients fighting off an exotoxin may not have
Pertussis
-Also known as whopping cough
-Caused by Bordetella perussis
-Pertussis is an acute, highly infectious respiratory disease that frequently occurs in children but also in adolescents and adults.
Pertusis symptoms
-It is characterized by a recurrent, violent cough that may lead to fatal complications such as pneumonia, pulmonary hypertension and encephalopathy.
-Usually the disease starts with mild, cold-like symptoms but this is followed by a prolonged
violent cough that can last for up to 10 weeks. -Small children may struggle to breathe.
-Inadequate vaccination has led to consistent upward trend of infections in recent years.
Trend of pertusis infections
rises from 20% in 1981 to a local maximum at about 70% in 1990, then remains steady till 2001; then it rises to a
maximum at 85% in 2016 and remains steady till 2018
Pertusis mechanism of infection
-Surface proteins of B. pertussis, including filamentous hemaglutinin and pertactin act as
adhesins and allow attachment to the epithelium in the upper respiratory tract.
-In infants, the bacteria form lower respiratory tract infections.
Petusis mechanism of disease
-Toxins such as tracheal cytotoxin (TCT), a fragment of peptidoglycan, kills ciliated epithelial cells preventing mucus and debris from being removed from the upper respiratory tract.
-It is thought that pertussis toxins also cause elevated numbers of white blood cells in the
lung arteries causing a blockage of these vessels, known as pulmonary hypertension.
In infants this results in hypoxia (lack of oxygen) and brain damage/death via
encephalopathy, cerebral hemorrhage and cortical atrophy
Treatment of pertusis
Antibiotics
Tuberculosis
A respiratory disease, primarily of the lungs although it can also manifest in the brain, spine, kidneys. In fact, any part of the body
Causative agent of TB
The causative agent is Mycobacterium tuberculosis, which was established
by Robert Koch in 1882. At that time TB killed 1 out of every seven people in
Europe. It still kills millions of people each year (1.5 million in 2020). South
Africa has one of the highest burdens of TB in the world.
Mycobacterium descirption
Mycobacteria are aerobic rod-shaped bacteria that are unusual in that they have unconventional cell walls
which are rich in lipids called mycolic acids.
