Respiratory Tract Infections Flashcards
What examples are there of compromise to respiratory defences?
Poor swallow- cva, muscle weakness, alcohol. Aspirating of salivary secretions
Abnormal ciliary function- smoking, viral infection, kartageners
Abnormal mucus- cf
Dilated airways- bronchiectasis
Defects in host immunity- HIV, asplenic, complement deficient
What is pneumococcus known as?
Old mans friend but actually one of the commonest caused of CAP.
Bacteraemic
Green alpha haemolysis
Bile soluble optochin sensitivity
What is s pneumonia?
Gram positive diplococci
30-50% of cap
Acute onset, severe pneumonia, fever, rigours, lobar consolidation
Almost always penicillin sensitive, know travel history
Resistance in Europe
What is pneumonia?
Inflammation of lung alveoli
Patients are sick, mortality of 5-10%
Fever, cough, pleuritic chest pain, shortness of breath
Often localising signs and abnormal cxr or normal in atypical
How is pneumonia classified?
Community acquired
Hospital acquired- ventilator associated
Pre existing lung disease, immunocompromised, geography, season, epidemics, travel, exposure to animals and contacts
What are the main organisms in cap?
S pneumonia H influenzae Moraxella catarrhalis- follows viral infection S aureus Klebsiella pneumoniae
What ages are various pathogens likely to infect people?
0-1 months- E. coli, gbs, listeria
1-6 months- chlamydia trachomatis, s aureus, Rsv
6 months-5 years- mycoplasma, influenza
16-30 years- m pneumoniae, s pneumoniae
What are the causes of cap?
Typical- s pneumonia, h influenzae
Atypical- legionella
mycoplasma (barking cough)
coxiella burnetti. (Q fever) , farm animals, hepatitis
Chlamydia psittaci- birds, splenomegaly, rash, haemolytic anaemia
What would you expect to find in examination of cap?
Pyrexia Tachycardia, tachypnoea Cyanosis, dullness to percussion, tactile vocal fremitus Bronchial breathing Crackles
What investigation would you ask for cap?
Fbc, u&e, crp
Bc, sputum and mc&S
Abg- useful in PCP, desaturate on exertion
Cxr
How do you manage cap?
CURB 65 score- confusion, urea more than 7, rr more than 30, bp less than 90 systolic, less than 60 diastolic, more than 65 years
Score 2- maybe admit
Score 2-5 manage as severe
What is bronchitis?
Inflammation of medium sized airways
Mainly in smokers
Cough, fever, increased sputum production, increased sob
Cxr is normal
Organisms- virus, s pneumonia, h influenza, m catarrhalis
Bronchodilation, physiotherapy, humidified oxygen
Which organisms can give cavitating pneumonia?
S aureus
Klebsiella
H influenza gram neg bacilli
What is h influenzae?
Gram neg coccobacillus
15-35% of cap
More common with pre existing lung disease
May produce b lactamase- augmentin plus or minus clarithromycin
What clincal signs point to legionella?
Confused Smoker Hyponatriaemic Infected water droplets Multi organ failure Special culture- buffered charcoal yeast extract Asymptomatic- Pontiac fever
What are atypical pneumonia caused by?
Organisms without a cell wall- mycoplasma, legionella, chlamydia, coxiella
Cell wall active abx eg pencillin don’t work
Need agents that work on protein synthesis- clari, erithromycin, tetracycline like doxycycline
Extrapulmonary feature- hepatitis, low sodium, flu like
What is the respiratory tract split into?
Upper- sinusitis, tonsillitis
Lower- bronchitis, pneumonia, empyema, bronchiectasis, lung abscess
How is legionella spread?
Aerosol spread
Environmental breakouts
Associated with confusion, abdo pain and diarrhoea
Lymphopenia, hyponatraeima
Diagnosis by antigen in urine/serum serotype 1
Sensitive to macrolides
How are coxiella burnetti and chlarmyida psittaci spread?
Common in domestic farm animals Transmitted by aerosol or milk Dx by serology Sensitive to macrolides Psittaci- spreads by birds by inhalation Dx by serology Sensitive to macrolides
What should be done if empyema is found?
Send sample for microbiology, cytology, check ldh, low ph
Needs removal
What are the differentials for failing to improve on treatment?
Empyema Proximal obstruction Resistant organism Not receiving/ absorbing abx Immunosuppression Other diagnosis- lung cancer, cryptogenjc organising pneumonia
How can s aureus lead to necrotising pneumonia?
Production of pvl, recurrent boils, cabuncles, young person
Want to know if colonised
Contacts
What is a hospital acquired pneumonia?
More than 48 hours in hospital
Often previous abx, plus or minus ventilator
Infectious vs non infectious causes of abnormal Cxr/lung function
Bronchial lavage- desirable to differentiate upper respiratory from lower flora
What pathogens would cause hospital acquired pneumonia?
Enterobacteriaciae S aureus Pseudomonas Other H influenza Acinetibacter baumanii
What is PCP?
Pneumocystis carinii, Protozoa Ubiquitous in environment Insidious onset Dry cough, weight loss, SOB, malaise Cxr bat wings Immunofluroscence on BAL Treat with co amox and prophylaxis too Apple green
What diseases can aspergillus fumigatus cause?
Allergic bronchopulmonary aspergillosis- chronic wheeze, eosinophilia, bronchiectasis
Aspergilloma- fungal ball often in pre existing cavity, may cause haemoptysis
Invasive aspergillosis- immunocompromised, treat with amphotericin B
What lower tract infections can be associated with immunosupression?
HIV- PCP, TB, atypical mycobacteria
Neutropenia- fungi, aspergillus
Bone marrow transplant- CMV
Splenectomy- encapsulated organisms, s pneumonia, h influenza, malaria
What can be done in the microbiology lab for diagnosis of lrti?
Sputum Blood cultures BAL Pleural fluid Antigen tests Antibody tests Immunofluroscence PCR
What are antibody tests useful for?
Useful in paired serum samples
Usually collected on presentation and 10-14 days later
Look for rise in antibody level over time
Useful for organisms that are difficult to culture- chlaymida, legionella
What is empric therapy for cap?
Amoxicillin or erythromycin/clarithromycin
Admision- augmentin and clari
Allergic- cefuroxime and clari
What is the therapy for hospital acquired?
1st line- ciprofloxacin plus minus vanco/ tazocin
2ndline/ITU- piptazobactam and vanco
Specific therapy- mrsa- vanco
Pseudo- piptazobactam or ciprofloxacin plus minus gentamicin
