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RESPIRATORY TRACT INFECTIONS (RTI). 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. GOALS.

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Respiratory tract infections rti

RESPIRATORY TRACT INFECTIONS (RTI)

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
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



General principles
General Principles

  • 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
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
Systemic Diseases that Begin in the URT

  • Measles

  • Mumps

  • Influenza

  • Meningitis

  • Sinusitis

  • Middle Ear Infection

  • Pneumonia

Dr B V Navaneeth, Dept of Microbiology


Agents of lower respiratory tract infections
Agents of Lower Respiratory Tract Infections

Legionairre’s Disease; Legionella pneumophila

Tuberculosis: Mycobacterium tuberculosis

Pneumonia

  • Viruses

    • Influenza

    • Measles

    • Many others

  • Bacteria

    • Streptococcus pneumoniae

    • Mycoplasma pneumoniae

    • Staphylococcus aureus

    • Almost ANY other

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

Bronchial washing / aspirate

Bronchoscopy

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


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