RESPIRATORY TRACT
INFECTIONS (RTI)
Dr B V Navaneeth, Dept of Microbiology
Dr B V Navaneeth, Dept of Microbiology
OVERVIEW
URTIs common most often
seen in GP
LRTIs < common but > likely
cause serious illness & death
Diagnosis & therapy presents
challenge to both clinician & lab staff
Preventive strategies available for
several RIs
Dr B V Navaneeth, Dept of Microbiology
GOALS
General Principles of Pathogenesis of RTI
Host Defenses in the URT, LRT
Agents of Infection in URT, LRT
Prevention and Treatment
Dr B V Navaneeth, Dept of Microbiology
Dr B V Navaneeth, Dept of Microbiology
General Principles
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Encounter
Entry
Spread
Multiplication
Evasion of Host
Defenses
Damage
Transmission
Dr B V Navaneeth, Dept of Microbiology
Pathogenesis – inhalation, aspiration,
haemotogenous
Nasal hairs & its mucus coverings
- filters
Epiglottis & cough reflexes
Trachea & Bronchi – mucus lining &
mucociliary escalator
Antimicrobial factors in secretions –
lysozyme, lactoferrin & secretary
IgA, alveolar macrophages
Dr B V Navaneeth, Dept of Microbiology
Respiratory Pathogens
Influenza virus
Adhere to mucosal epithelial cells by
specific surface antigens
Under go genetic reassortment –
expression of novel adhesins
S pneumoniae & H influenzae
Capsule – resist phagocytosis
IgA protease – disabling mucosal IgA
Mycobacterium – resist phagocytosis
Dr B V Navaneeth, Dept of Microbiology
Agents of Upper Respiratory Tract
Infections
Common cold (rhinitis)
Many viruses; rhino, corona, adeno, influenza
Pharyngitis and laryngotracheitis
Streptococcus pyogenes
Corynebacteria diphtheriae
Many viruses
Epiglottitis
Haemophilus influenzae
Bronchitis
Bordetella pertussis
Many viruses
Dr B V Navaneeth, Dept of Microbiology
Systemic Diseases that Begin in the URT
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Measles
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Mumps
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Influenza
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Meningitis
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Sinusitis
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Middle Ear Infection
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Pneumonia
Dr B V Navaneeth, Dept of Microbiology
Agents of Lower Respiratory Tract
Infections
Legionairre’s Disease; Legionella pneumophila
Tuberculosis: Mycobacterium tuberculosis
Pneumonia
Bacteria
Streptococcus pneumoniae
Mycoplasma pneumoniae
Staphylococcus aureus
Almost ANY other
Viruses
Influenza
Measles
Many
others
Fungi & Parasites
Dr B V Navaneeth, Dept of Microbiology
Lab Diagnosis of LRTI
Responsible pathogen not determined in as many as 50% of cases
Sputum
Expectorated
Gastric aspirate (children)
Induced
Postural drainage / thoracic
percussion/ aerosal induced
Endotracheal / tracheostomy suction
Bronchoscopy
Bronchial washing / aspirate
Bronchio-alveolar lavage (BAL)
Protected bronchial brush samples
Open lung biopsy
Dr B V Navaneeth, Dept of Microbiology
Over view
Obtaining a protected
catheter bronchial
brush during a
bronchoscopy
examination
Dr B V Navaneeth, Dept of Microbiology
Lab Diagnosis of LRTI
Direct exam
Sputum / saliva
Microscopy
Gram stain / AFB
Gomori methenamine-PCP
DFA - Legionella
Direct antigen test for viruses
Culture
BA / CA / MAC / LJ
Identification tests
AST
Report & Interpretations
Dr B V Navaneeth, Dept of Microbiology