Lecture 4 LRTI Flashcards
How may deaths on a global scale are caused by LRTI
Approx 4 million
What is the difference between acute and chronic LRTI considering symptom appearance after infection
Acute is sudden onset within days
Chronic can be a few weeks or months before symptoms
What percentage of population carry s pneumoniae transiently in URT -
Approx 10%
Name some acute LRTI
Pneumonia Bronchitis Bronchiolitis Legionnaires disease Whooping cough
Name some chronic LRTI
Tuberculosis
Aspergillosis
Cystic fibrosis
Which microorganism causes bronchitis (inflammation of trachea-bronchial tree)?
Almost always viral such as adenovirus
What age group does bronchiolitis occur in and what is the microorganism which predominantly causes the disease
Under 2 yrs as lungs underdeveloped
RSV
How can legionnaires be controlled
Decent chlorination of water - associated with water and ventilation systems.
Flush taps once weekly for 2 mins to flush out in dead legs.
What microorganism primarily causes legionnaires disease
L. Pneumophila (over 90% of cases)
L pneumophila is a GPR true or false
False. It is a GNR
Which type of patient will become infected with aspergillosis
Immunocompromised breathe in spores and get aspergilloma.
Which microorganisms primarily cause infections in cystic fibrosis patients
S aureus and P aeruginosa
Pneumonia can be caused by fungi, bacteria, viruses AND parasites. True or false
True!!
Parasites - ascaris lumbracoides
What are the two types of acquired pneumonia
Community acquired pneumonia (CAP)
Hospital acquired pneumonia (HAP)
How many people die in pneumonia in the uk per year (approx)
30,000
The symptoms of pneumonia often depend on what
What agent has caused the disease, e.g bacterial can have different symptoms to viral
Name some risk factors for CAP
Smoking, pet birds such as parrots, elderly/young, alcoholics/homeless, underlying illness e.g. CF
What is aspiration pneumonia
Aspiration = sedated patents e.g alcoholics, patient breathe in gastric juices and take mouth flora and this juice into lungs and cause pneumonia
What is recurrent pneumonia
Recurrent = 2 episodes of pneumonia a year for an adult with a clear x ray of chest between each case (children is 3 cases),
What is the definiton of CAP
Develop in patient that has had no hospital contact
What is the definiton of HAP
Pneumonia present in a patient 48-72hrs AFTER being admitted to hospital.
Prior to 48hrs suggest community acquired.
Every year what % of uk adults will have CAP
0.5%-1%
How many patients presenting to their GP with LRTI symptoms are diagnosed with CAP
5-12%
How many of the 5-12% of patients diagnosed by a GP with CAP are admitted to hospital
22-42% a
What are the signs (NOT SYMPTOMS) of typical pneumonia
Cough, cyanosis (blue fingertips), tachypnoea (rapid breathing), tachycardia
What are the symptoms (NOT SIGNS) of typical pneumonia
Fever, muscle aches, shakes/rigors, dyspnoea (shortness of breath), sputum production (consolidation material in lungs) which is RUST COLOURED
Why is sputum from typical pneumonia rust coloured
Due to blood - fresh blood and old lysed blood cells.
Which microorganism are associated with typical CAP
Most common: streptococcus pneumoniae
Less common: Haemophilus influenzae (live in URT)
S aureus (CF)
P aeruginosa (CF)
Which microorganism is one of the main. Causes of respiratory tract infections worldwide
S pneumoniae
Kill over 1 mil individuals every year
What are the signs (NOT SYMPTOMS) of ATYPICAL pneumonia
Rash Cyanosis Tachypnoea Tachycardia Dry cough
What are the SYMPTOMS (NOT SIGNS) of Atypical pneumonia
Headache Confusion Diarrhoea Incontinence NO SPUTUM - NON RESPIRATORY
Which microorganisms are most commonly associated with ATYPICAL CAP
Most common; mycoplasma pnuemoniae
Less common bacteria; legionella pneumophila
Chlamydophila psittaci (psittacosis)
Chlamydophila pneumoniae
Virus causing: Influenza A/B, Rhinovirus, RSV
How does the consolidation in lungs differ between typical and atypical pneumonia
Typical - widespread consolidation - lots of pathogens and inflammatory cells.
ATYPICAL - patchy consolidation - not much inflammatory material in lungs so dont produce sputum
Describe s pneumoniae morphology
Diplococcus (not normal chains) and lancet shape
Describe the morphology of mycoplasma pneumoniae
No cell wall so pleomorphic - can use beta lactams
Which risk groups for CAP will typically display ATYPICAL pneumonia ONLY. Name the microorganisms involved which each group.
Smokers/travel abroad - L. Pneumophila (legionnaires)
Contact with birds (Cl. Psittaci)
Which risk groups for CAP will typically display TYPICAL pneumonia ONLY. Name the microorganisms involved which each group.
Alcoholics/homeless - S. Pneumoniae
Underlying illness e.g. CF - P aeruginosa , S aureus
Which risk groups for CAP will typically display ATYPICAL pneumonia AND typical pneumonia. Name the microorganisms involved which each group.
Elderly/young - S. Pneumoniae for typical, M pneumoniae for ATYPICAL
Pneumonia is the 3rd most common HAI at 23%, T or F.
True
Typical/ Atypical symptoms are only present in CAP. T or F
False. It is for both HAP and CAP.
Name some risk factors for HAP
1- ventilatory support - patients may get endotracheal tube put in URT if have breathing difficulties. Can get contamination from poor hygiene e.g. Klebsiella pneumoniae and Pseudomonas aeruginosa.
2-immunosuppression : organ transplantation, aspergillus fumigatus
3- immobility and vomiting - aspiration pneumonia, oral bacteria e;.g anaerobic bacteria
Define VAP
Ventilation associated pneumonia (VAP) 48 hour after ventilation
What is the treatment regimen for uncomplicated CAP
Amoxicillin or erythromycin. Due to resistance now moxifloxacin (4th gen quinolone act on DNA gyrase). 1 tablet a day.
What is the treatment regimen for severe CAP of unknown aetiology (cause)
Cefuroxime (beta lactam) + erythromycin for mycoplasma
What is the treatment regimen for atypical pneumonia (CAP/HAP)
Erythromycin
What is the treatment regimen for HAP
Cefotaxime +/- Gentamicin
Cefotaxime is high gen cephalosporin, gentamicin toxic to humans so need to dose appropriately to kill microbe but not to damage kidneys and ears
Why is S pneumoniae capsule a major virulence factor
Anti-phaocytic - prevent c3b adhesion to cell wall
92 different capsular types (differnt serotypes) but 90% of pneumonias are caused by about 23 serotypes (PPSV23 vaccine)
Describe the cell wall of S pneumoniae
Gram positive cell wall, 6 layers of peptidoglycan with covalently bound teichoic acid and cell membrane anchored lipoteichoic acid (forssman antigen)
Why does s pneumoniae spread in crowded settings such as hospitals, prisons or day care centres
Respiratory droplets via person to person horizontal spread
What is the serotyping that can be performed using a homologous antibody for capsule of S pneumoniae
Quellung reaction
State a major adhesion mechanism of s pneumoniae
CbpA adhesin - functions as cell- surface adhesin interacting with carbohydrates on pulmonary epithelial surface in nasopharynx.
State the importance of CbpA as a virulence factor
functions as cell- surface adhesin interacting with carbohydrates on pulmonary epithelial surface in nasopharynx.
Also shown to be bound to secretory component of IgA and complement component C3.
What mechanisms does s pneumoniae use to evade the immune system
PspA (protective antigen) inhibits complement mediated opsonisation of pneumococci just like capsule.
IgA1 protease: cleaves IgA1 at the hinge region the principal immunoglobulin isotope for the respiratory tract. It also cleaves a neuraminidase that cleaves sialic acid from glycoconjugates which uncovers epitopes for pneumococcal adherence.
What toxin release mechanisms does s pneumoniae have
Autolysins LytA, LytB, LytC & Pneumolysin
What is the role of pneumolysin
Pneumolysin - toxin released during autolysis (cell lysis) by LytA (extra reading); inhibit neutrophil chemotaxis, phagocytosis, lymphocyte proliferation and immunoglobulin synthesis
Toxin is important in causing meningitis as it damages ependymal cilia that line the ventricles of the brain and induces brain cells to undergo apoptosis
What do the autolysins do
Autolysins LytA, LytB, LytC - break peptide cross linkingin cell wall peptidoglycan which releases cell wall components; massive inflammation and pneumolysin release
They have been suggested to have a role in bacterial uptake of DNA and daughter cell separation (extra reading)
H202 produced by pneumococcus is a potent __?
Fill in the blank
Haemolysin
When are LytA, LytB and LytC released by s pneumoniae
During the stationary phase of growth - peptidoglycan and capsular material released into blood stream and get inflammation.
Bacterial growth has logarithmic, stationary and decline phase of growth
What is the role of teichoic acid (extra)
Adhesin (binds fibronectin), immunomodulatory
Case study: a 65yr old patient coughing up blood sputum, widespread consolidation in both lungs with shortness of breath.
What is the likely diagnosis and microorganism to blame
Community associated pneumonia with typical presentation
Streptococcus pneumonia or possibly haemophilus influenzae
Case study: a 65yr old patient coughing up blood sputum, widespread consolidation in both lungs with shortness of breath.
What samples should be taken, when and why?
Sputum early morning before breakfast to prevent food contamination and to get build up of bacteria and inflammatory material overnight
Urine sample
Case study: a 65yr old patient coughing up blood sputum, widespread consolidation in both lungs with shortness of breath.
What tests would be performed on sputum sample
Gram stain and culture
Case study: a 65yr old patient coughing up blood sputum, widespread consolidation in both lungs with shortness of breath.
What test would be performed on Urine sample
Antigen detection (rapid pneumococcal antigen test) to detect the capsular antigen.
Case study: a 65yr old patient coughing up blood sputum, widespread consolidation in both lungs with shortness of breath.
What agar would be used to culture the sputum sample and what must be done to the sputum before plating
Sputum must be combined with sputolysin (N-acetylcysteine) which breaks down the sputum to a more watery form and release microorganisms stuck in mucus.
Blood agar + optochin disc
Chocolate agar
Case study: a 65yr old patient coughing up blood sputum, widespread consolidation in both lungs with shortness of breath.
Why is a optichin disc added to the agar plate for culture?
S pneumoniae is sensitive to it so get a clear zone if present
Case study: a 65yr old patient coughing up blood sputum, widespread consolidation in both lungs with shortness of breath.
What are the safety considerations to be made when culturing and handling the sample
S pneumoniae is cat 2 pathogen
Sputum sample is cat 3 laboratory with class I safety cabinet
What is important about Class I safety cabinet
Negative pressure, air flow away from worker.
0.74m^3/sec air flow rate
Hepa filter
Describe the basic and full identification process used for s pnuemoniae
Basic : colony appearance (alpha haemolytic) so get green colonies, 1mm in diameter. Capsular producing strains may look mucoidal on agarose especially if grownunder anaerobic conditions
Full ID: Optochin sensitivity - large zone approx 16mm of inhibition around disk, distinguish it from other oral streptococci
Case study: a 65yr old patient coughing up blood sputum, widespread consolidation in both lungs with shortness of breath.
What non culture techniques will be performed on the urine sample
Immunochromatographic assay/lateral flow assay
Rabbit anti strep pnuemoniae bound to nitrocellulose membrane, urine added to test well and read result in 15 mins (similar to pregnancy test, line in control and test = positive, line in control but not test is negative).
What does the poor sensitivity (86%) of the lateral flow assay mean when given a negative result
Doesn’t necessarily mean there is an infection as poor sensitivity.
What antibiotic treatment is recommended for s pnuemoniae infection
Moxifloxacin (flouroquinolones are active against bacteria)
What % of S pnuemoniae is resistant to penicillin?
50%
What % of s pnuemoniae is multidrug resistant (to macrolides, tetracycline, etc)
25%
What are the two vaccinations against z pnuemoniae
PPSV23 - for at risk patients, 23 valent pnuemococcal polysaccharide vaccine (not hugely effective)
PCV13 - for children under 2 yrs. Prevent other infections that s pnuemoniae may cause
