Microbiology of Respiratory Tract Infections II Flashcards
What is present in the nasopharynx to protect agains RTIs?
Nasal hairs
Ciliated epithelia
IgA
What is present in the oropharynx to protect against RTIs?
Saliva
sloughing
Cough
What type of gram positive bacteria colonise the nasopharynx and oropharynx?
Alpha haemolytic streptococcus and beta-haemolytic strep
Staph aureus
What type of gram negative bacteria colonise the nasopharynx and oropharynx?
Haemophilus influenza
Moraxella catharalis
Other
What is epiglottis?
Inflammation of the pipiglottis and superior larynx
What bacteria causes acute epiglottitis?
Haemophilus influenza type B
What clinical presentation does acute epiglottitis have in children?
Sore trhorat
Drooling
Severe stridor
Hight termperature
What are the risk factors for eppiglottitis?
Immunocompromised/suppressed
Transmission of capsulated strain to unvaccinated host
How is acute epiglottitis treated?
Admit to ICU
Ceftriaxone
What does a gram stain of haemophilia influenza show?
Pus cells and gram negative coccobacillus
What are the upper respiratory tract defences?
Nasopharynx
Oropharynx
What are the conducting airways’ defences?
Trachea and bronchi
What normally colonises the conducting airways?
Not usually colonised
How do the conducting airways resist infection?
Mucociliary escalator
Cough
AMPs
Cellular and humoral immunity
When are acute exacerbation of COPD typical?
Following a viral infection
Winter (temp decrease / humidity increase)
What bacteria cause an acute exacerbation of COPD?
Haemophilus Influenza
Moraxella Catarrhalis
Strep pneumonia
What is cystic fibrosis?
Congenital disorder that causes abnormally viscous mucous and blockage of many tubular structures including the conducting airways and lungs
What are the bacteria that are involved in CF infections due to inefficient clearance and mucous build-up?
Staph aureus Haemophilus influenza Strep pneumoniae Pseudomonas aeruginosa Burkholderia capacia many others
What causes acute bronchitis?
90% viral (others including whooping cough=
Preceeded by URT infection
What is pertussis?
Acute tracheobronchitis
“Whooping cough”
How is pertussis diagnosed?
Pernasal swab - culture in charcoal blood agar / PCR / serology
What are the common causes of community-acquired pneumonia?
Strep pneumoniae
H. influenza
M. carrhalis
What are atypical causes of CAP?
Mycoplasma pneumoniae
Legionella pneumophilia
Chlamydophila pneumoniae
Chlamydophila psitacci
What are other lung infections besides CAP?
Hospital accrued pneumonia
Immune defects and anatomical abnormalities
TB
What is the pathogenesis of legionella Pneumonia?
Invade alveolar macrophages and replicated
How is legionella pneumonia transmitted?
Inhalation of contaminated water droplets
No person-person transmission
How is legionella pneumonia diagnosed?
Legionella urinary antigen - detect hero group
Culture
Paired serology - rise in titres
PCR from sputum
What are risk factors for HAP?
Invasive ventilation
Issues with mucociliary escalator (from drugs?)
Sedation
Immunosuppression
What bacteria cause HAP?
60% gram negative: E. coli / Kleb. spp. / Pseudomonas spp
CAP organisms: S. aureus / anaerobes
In which patients is pneumocystis pneumonia (PCP) very common?
AIDS patients / immunosuppressed
What are the clinical symptoms of PCPß
Fever Dry cough Dyspnoea Fatigue Higher fever if non-HIV
How is PCP diagnosed?
BAL > Sputum > PCR
How is PCP treated?
Co-trimoxazole
How is legionella pneumonia treated?
Clarithromycin
Erythromycin
Quinolone (e.g. levofloxacin)
Which antibiotic would be used to treat an acute exacerbation of COPD?
Amoxicillin (1st line)
Doxycycline (2nd line)
How is pertussis / whopping cough treated?
Antibiotics
What is Aspergillus?
Fungal chest infection
What usually causes Aspergillus?
Aspergillus fumigatus
What does aspergillus cause in immunocompromised/suppressed patients?
Severe pneumonia
Pre-existing chest condition
Invasive disease
What does aspergillus cause in immunocompetent patients?
Localised pulmonary infection
Aspergilloma in pre-existing chest cavities
What is an Aspergilloma?
Fungal ball
How is aspergillus transmitted?
Inhalation of fungal spores
How is Aspergillus diagnosed?
BAL (Broncho-alveolar lavage) - fungal culture / PCR
Tissue histopathology
How is Aspergillus treated?
Amphotericin B
Voriconazole
Surgery
What bacterium causes TB?
Mycobacterium tuberculosis (thick waxy coat)
What is the pathogenesis of TB?
Engulfed by alveolar macrophages in alveoli - resist killing & multiply
Most TB is latent but can be reactivated (10% immediate)
What is TB infection associated with?
Travel to high-prevalence areas
Immunocompromised/suppressed
How does the Ziehl-neelson stain work?
Red dye added to smear - heated (to allow dye to penetrate waxy coat) - acid/alcohol added - waxy coat retain dye - counter-stain added - mycobacterium appear reed
What are the three diagnostic tools for TB?
ZN
PCR
Culture
What are the 3 main routes of transmission?
Contact
Airborne
Droplet
