Week 7: Respiratory system (upper and lower) Flashcards
Streptococcal pharyngitis bacteria
S. pyogenes
Streptococcal pharyngitis symptoms (4)
Fever, headache, tonsillitis, otitis media
Scarlet fever bacteria
S. pyogenes
Scarlet fever host (1)
Humans only
Scarlet fever rash cause
Erythrogenic toxin of s.pyogenes
Corynebacterium diptheriae location
Throat of asymptomatic carrier
Corynebacterium diptheriae transmission
Airborne
Does Corynebacterium diptheriae form spores?
Nope
Corynebacterium diptheriae shape
Club
C. diptheria disease symptoms (4)
Sore throat, neck swelling, leather formation in throat, skin infection (cutaneous diptheria)
In diptheria, describe the term ‘leather’
Formation of grey membrane in throat from fibrin, bacterial cells and dead tissue cells
What causes damage in diphtheria
Exotoxin which circulates in blood and damages heart and kidneys
Diphtheria treatment and prevention
Penicillin and erythromycin in conjunction with antitoxin, immunisation with diphtheria toxoid
Otitis media
Infection of middle ear
Inflammation -> Pus increases pressure against eardrum -> pain
Otitis media causes (highest to lowest- 6)
S. pneumoniae (35%)
Non-encapsulated H. influenzae (20-30%)
Moraxella catarrhalis (10-15%)
S. pyogenes (8-10%)
Others (bacteria/non-bacterial cause) (3-5%)
S. aureus (1-2%)
Viral causes of common cold (2)
Rhinoviruses and coronaviruses
Which antibody contributes to immunity against viral colds?
IgA
In influenza, what component of the virus contributes to its pathogenicity? What are the names of these components (2)
Spike proteins (neuraminidase and haemagglutinin)
Define antigenic shift in relation to viruses
Spike proteins change so that antibodies against the spike proteins become ineffective
Gram status, oxygen use and shape of Bordella pertussis
Gram negative, obligate aerobe, cocco-bacillus
How does Bordetella pertussis capsule contribute to its pathogenicity
Capsule allows it to attach to ciliated cells in trachea, impeding their action and destroying them
Causative agent of pertussis (whooping cough)
Bordetella pertussis
Does bordetella pertussis produce toxins?
Yes
Pertussis treatment
Erythromycin and airway protection (postural drainage, keep head and face down, high humidity)
Name and describe the three stages of pertussis
Catarrhal stage: resembles common cold (2-3 weeks incubation)
Paroxysmal stage: prolonged sieges of coughing (mucous accumulation) (physiological damage)
Convalescence stage: lasts few months, recovery
Describe the gram status of mycobacterium tuberculosis
Neither gram positive nor gram negative due to lipid cell wall, acid fast
How does M. tuberculosis cause disease
Bacteria are inhaled and reach alveolar macrophages, phagocytosed but survive. As they multiply, more macrophages are attracted forming a tubercle. Macrophages die, releasing bacteria and forming a caseous centre in the tubercle. The tubercle ruptures, spilling bacteria into the rest of the body.
Tuberculosis treatment
Streptomycin
Multiple therapy: isoniazid, rifampin, pyrazinamide
Drug resistant cases: ethambutol or streptomycin
Explain the mechanism of the tuberculin skin test
Proteins from tuberculosis are injected into the skin. If the person has been previously infected, memory T cells react with the antigen leading to hardening and reddening of the area.
Diagnosis of tuberculosis
Isolation, acid fast staining, cultivation on loweinstein agar, production of CO2 in broth containing palmitic acid, DNA probes, PCR and rRNA
Tuberculosis vaccine
Live attenuated strain of avirulent strain M. bovis (BCG vaccine)
What is a potential issue of the tuberculin skin test?
VAccinated individuals will have a positive reaction
What is a potential issue of the BCG vaccine for tuberculosis?
Live strain so may be dangerous in the immunocompromised
Bacterial pneumonia causes (2)
Strep pneumoniae (typical), other microorganisms (atypical)
S. pneumoniae characteristics (gram, shape, capsule?)
Positive, ovoid, diplococcus, has capsule
S. pneumoniae treatment + prevention
Penicillin, vaccine of purified capsular material
Diagnosis of S. pneumoniae (lab)
alpha haemolytic
susceptible to optichin
H. influenza (atypical pneumonia) gram status
Gram negative
H. influenza (atypical pneumonia) treatment
Beta lactamase resistant second generation cephalosporins
Mycoplasma pneumonia (atypical pneumonia) characteristics
Lacks cell wall
Forms small fried egg like colonies in medium with horse serum and yeast extract
M. pneumoniae pneumonia diagnosis (3)
Serology
PCR
Complement fixation to detect IgM and IgG
Legionnaire’s is a type of what disease caused by which bacteria?
Pneumonia, Legionella pneumoniae
Legionella pneumoniae (atypical pneumonia) characteristics
Gram negative, aerobic rod
Chlamydia psittaci and Chlamydia pneumoniae characteristics
Gram negative, obligate intracellular
From bird droppings vs person to person contact
Q fever (atypical pneumonia) cause
Coxiella burnetti
Meliodosis (atypical pneumonia) cause
Burkholderia pseudomallei
Viral diseases of lower RT (4)
Severe acute respiratory syndrome (SARS)
Viral pneumonia
Respiratory syncytial virus
Influenza
Fungal diseases of lower respiratory tract (3)
Histoplasmosis casued by Histoplasma capsulatum: airborne spores from soil -> human
Pneumocystis pneumonia (P. jiroveci formerly P. carini)
Coccidioidomycosis caused by Coccidioides imitis
How do fungal diseases of the LRT occur?
Production of spores in immunocompromised patients
Describe the disease cycle of coccidiodomycosis (6)
Soil
1. Arthrospore germinates into tubular hypha
2. Hypha segmant into arthrospores and separate from hypha. Some become airborne and some return to the soil.
3. Airborne arthrospore is inhaled
Human
4. Inhaled arthrospore enlarges and begins to develop into spherule
5. Endospores develop in spherule
6. Spherule releases endospores which spread in tissue and develop into new spherules
Coccidioidomycosis is an example of a _ disease of the lower RT
Fungal
