Microbiology 7s: RTIs Flashcards
What is pneumonia? Sx?
- inflammation of alveoli
- Sx:
- fever
- cough
- SOB
- pleuritic chest pain
- abnormal CXR
Classification of pneumonia?
- Community acquired
- typical
- atypical
- Hospital-acquired = >48hrs since admission / artificial ventilation
What are the main organisms associated with pneumonia?
CAP:
- ** Streptococcus pneumoniae
- ** Haemophilus influenzae
- Moraxella catarrhalis
HAP:
- ** Staphylococcus aureus
- Klebsiella pneumoniae
** = more common
Most common organisms causing CA pneumonia in 0-1 month
- Escherichia coli,
- Group B Streptococcus,
- Listeria monocytogenes
Most common organisms causing CA pneumonia in 1-6 months
- Chlamydia trachomatis,
- Staphylococcus aureus,
- RSV
Most common organisms causing CA pneumonia in 6months-5yrs
- Mycoplasma pneumoniae,
- Influenza
Most common organisms causing CA pneumonia in 16-30yrs
- Mycoplasma pneumoniae,
- Streptococcus pneumoniae
What are the causes of typical CAP?
- Streptococcus pneumoniae
- Haemophilus influenzae
Main causes of atypical CAP?
- Legionella pneumophilia
- Mycoplasma pneumoniae
- Coxiella burnetii (Q fever)
- Chlamydia psittaci (Psittacosis)
- Mycobacterium tuberculosis
All gram -tive, except TB
non-TB: none have cell wall →
Cell-wall active antibiotics (e.g. penicillins) do NOT work → so need agents that work on protein synthesis:
- Macrolides (clarithromycin/erythromycin)
- Tetracyclines (doxycycline)
Ix for ?pneumonia?
- Bloods: FBC, U&Es, CRP → blood culture
- Sputum MC&S
- ABG
- CXR
What is the CURB 65 score?
Most DDx for pneumonia in pre-existing lung disease?
Haemophilus influenzae
CXR: ground glass shadowing. DDx?
- bats wing = PCP
- general = COVID
CT shows ground glass opacities. DDx?
Haemophilus influenzae
neonate with pnuemonia + sepsis. DDX?
Group B Streptococcus
Listeria monocytogenes
Pneumonia + hypoNa, abnormal LFTs. DDx?
Legionella pneumophilia
Urinary antigens +tive. DDx?
Legionella pneumophilia
Pneumonia + transverse myelitis + Otitis media + Bullous myringitis.
DDx?
Mycoplasma pneumoniae
pneumonia + hepatitis. DDx?
Coxiella burnetii (Q fever) - farm animals
Pneumonia + haemolytic anaemia, splenomegaly, rash. DDx?
Chlamydia psittaci
CXR: upper lobe/apical consolidation. DDx?
Mycobacterium tuberculosis
- Red rods acid-fast bacilli
- Culture: Lowenstein-Jenson medium → Auramine stain (screening) + Ziehl-Neelsen stain (diagnosis)
- EBUS → histology – i.e. caseating granuloma
DDx?
Mycobacterium tuberculosis
CXR halo sign. DDx?
aspergillus (fungal)
Cough + SOBOE. DDx?
PCP
pneumonia + silver stain. DDx?
PCP
Tx of Streptococcus pneumoniae
PO Amoxicillin/IV benzylpenicillin
If penicillin allergy:
PO Clarithromycin/IV cefuroxime, cefotaxime, ceftriaxone
Tx Haemophilus influenzae
Non-beta-lactamase-producing: PO/IV Amoxicillin
Beta-lactamase-producing:
PO/IV Co-amoxiclav
If penicillin allergy: IV cefuroxime, cefotaxime, ceftriaxone
Tx Moraxella catarrhalis
PO Amoxicillin/IV benzylpenicillin
If penicillin allergy:
PO Clarithromycin/IV cefuroxime, cefotaxime, ceftriaxone
Tx Group B Streptococcus
Benzylpenicillin /ampicillin + gentamycin (10 days)
If penicillin allergy: Vancomycin / clarithromycin
Tx. Legionella pneumophilia
Ciproflaxin/Clarithromycin
Tx Mycoplasma pneumoniae
azithromycin
Tx
Coxiella burnetii (Q fever)
PO Doxycycline/IV Clarithromycin
Tx Chlamydia psittaci
PO Doxycycline/IV Clarithromycin
Tx Mycobacterium tuberculosis
RIPE
- Rifampicin 6m
- Isoniazid 6m
- Pyrazinamide 2m
- Ethambutol 2m
tx Staphylococcus aureus
Non-MRSA: IV Flucloxacillin
MRSA: IV Vancomycin
tx Pseudomonas auroginosa
IV Ceftazidime/Ciprofloxacin + IV gentamycin
Tx Klebsiella pneumoniae
IV Ceftazidime/Ciprofloxacin
Tx aspergillosis
Amphotericin B
Tx influenza?
oseltamivir
Tx COVID
dexamethasone
Tx PCP?
co-trimoxazole
Summarise Streptococcus pneumoniae
- 50% of CAP
- RFs: young & old more at risk of invasive
- Gram +tive cocci
-
Ix:
-
MC&S:
- 5% CO2,
- blood agar
-
CXR:
- Lobar/apical consolidations
- Double heart border (‘Sail’ sign)
-
MC&S:
PO Amoxicillin/IV benzylpenicillin
If penicillin allergy:
PO Clarithromycin/IV cefuroxime, cefotaxime, ceftriaxone
Summarise Haemophilus influenzae
- 40% of CAP
- RFs: more common in pre-existing lung disease e.g., COPD
- Gram -tive coccobacilli
- Ix:
- MC&S: chocolate agar
- CXR:
- Cavitating lesions
- ~CT:
- ground glass opacities
Non-beta-lactamase-producing:
PO/IV Amoxicillin
Beta-lactamase-producing:
PO/IV Co-amoxiclav
If penicillin allergy:
IV cefuroxime, cefotaxime, ceftriaxone
Summarise Moraxella catarrhalis
- Small cause of CAP
- RFs: Older age, immunocompromised
- Gram -tive diplococcus
-
Ix:
- MC&S:
- blood agar → honey puck sign
- CXR:
- Lobar consolidations rare
- MC&S:
Mx: Same as strep pneumoniae
Summarise Group B Streptococcus
- Small cause of CAP
- RFs: Neonates, (<1month), older age, DM immunocompromised, lines, catheter
- Gram +tive, beta-haemolytic, cocci
- Sx:
- Normal pneumonia Sx
- ~ meningitis
- ~ sepsis
- ~ septic arthritis
- Ix:
- MC&S:
- blood agar
- CXR;
- lobar consolidation
- neonates: diffuse infiltrates
- MC&S:
Benzylpenicillin /ampicillin + gentamycin (10 days)
If penicillin allergy: Vancomycin / clarithromycin
Summarise Legionella pneumophilia
Summarise Mycoplasma pneumoniae
Summarise Q fever
Summarise Chlamydia psittaci
Summarise Mycobacterium tuberculosis
Summarise E coli
- 30% of HAP
- RFs: younger age (0-1 months)
- Gram -tive bacilli
- CXR: Lower lobe consolidation
- Tx:
Summarise Staphylococcus aureus
- More common in 1-6months
- Gram +tive
- CXR: Cavitating lesions
Non-MRSA: IV Flucloxacillin
MRSA: IV Vancomycin
tx for Pseudomonas auroginosa
IV Ceftazidime/Ciprofloxacin + IV gentamycin
Summarise Klebsiella pneumonia
- More common alcoholics/DM
- Gram -tive
- CXR: Cavitating lesions
IV Ceftazidime/Ciprofloxacin
Summarise aspergillus
- Fungal
- RFs: immmunocompromised
- special Sx:
- haemopytsis
- ‘asthma’
- CXR: halo sign
- Tx: amphotericin B
Summarise influenza
- viral
- RFs: extremes of ages, unvaccinated
- special Sx: myalgia
- Tx: oseltamivir
Summarise COVID
- viral
- RFs: unvaccinated
- Special Sx: anosmia
- CXR: ground glass shadowing
- Tx: dexamethasone
Summarise PCP
CXR: ground glass shadowing
Main difference between bronchitis & pneumonia
Bronchitis:
- Mainly smokers
- CXR normal
Main causes of bronchitis?
- Viruses
- Streptococcus pneumoniae
- Haemophilus influenzae
- Moraxella catarrhalis
tx of bronchitis?
§ Bronchodilation
§ Physiotherapy
§ Antibiotics
74yo woman
SOB, fever (38.5C), right-sided pleuritic chest pain, reduced percussion note & decreased air entry right base
PMHx IHD, CABG, AF; DHx warfarin Otherwise well
Admitted → commended on cefuroxime and doxycycline → continued to spike fevers
CXR → homogenous shadowing with meniscus level of right side
NEXT STEP? DIAGNOSIS?
- CT
- empyema
These are difficult to treat because they have a wall around them and the pus itself is very acidotic which
→ inactivates the antibiotics →hence why she continued to spike fevers even on ABx