NORMAL MICROBIAL FLORA AND
IMMUNITY OF RESPIRATORY TRACT
DR NAZIA KHAN
OBJECTIVES
• DESCRIBE INNATE IMMUNE DEFENSE MECHANISMS OF RESPIRATORY TRACT.
• IDENTIFY NORMAL MICROBIAL FLORA OF UPPER RESPIRATORY TRACT.
• DISCUSS BENEFICIAL ROLE & DISEASE CAUSING ABILITY OF NORMAL FLORA OF RESPIRATORY
TRACT.
• RESPIRATORY TRACT IS DIVIDED INTO UPPER
AND LOWER RESPIRATORY TRACT:
• IT IS ONE OF THE MOST IMPORTANT PORTAL
OF ENTRY FOR MICROBES
IMMUNITY
BODY’S ABILITY TO RESIST OR ELIMINATE POTENTIALLY
HARMFUL FOREIGN MATERIALS OR ABNORMAL CELLS.
Functions of immune system
1.
2.
3.
4.
Defending against invading pathogens.
Removing worn out cells & damaged tissues, paving the way for wound healing
& repair.
Identifying & destroying abnormal/mutant cells (Immune surveillance)---defense against cancer
Mounting inappropriate immune responses which lead either to allergies or
autoimmune diseases.
INNATE IMMUNE DEFENSE MECHANISMS OF
RESPIRATORY TRACT
CHARACTERISTICS OF INNATE IMMUNITY
• RESISTANCE THAT EXISTS PRIOR TO EXPOSURE
• READILY AVAILABLE
• NON SPECIFIC
• DOES NOT IMPROVE ON REPEATED EXPOSURES
• THERE IS NO IMMUNOLOGIC MEMORY
A.
ANATOMICAL BARRIERS:
. ARCHITECTURE OF THE NOSE:
 NASAL HAIR: FILTER OUT DUST & OTHER LARGE AIRBORNE PARTICLES
 NASAL MEATUS
 STICKY MUCUS: ACTS AS TRAPPING MECHANISM
 CILIARY MOTION -DISLODGE PATHOGENS
B. PHYSIOLOGICAL BARRIERS:
 COUGH REFLEX: AIDS IN EXPECTORATING SPUTUM
 SNEEZE REFLEX: HELPS EXPELS IRRITANT OUT FROM URT
 MUCOCILIARY ESCALATOR:
•
CONSTANT MOVEMENT OF MUCUS FROM LRT TOWARDS PHARYNX
•
EXTREMELY IMPORTANT MECHANISM
•
DAMAGE TO THIS CAUSES MANY INFECTIVE DISEASES OF LRT
C. BIOCHEMICAL & CELLULAR COMPONENTS
 UPPER RESP TRACT
• NASAL FLUID CONTAINS
• LYSOZYME
• LACTOFERRIN
• IGA ANTIBODIES
 LOWER RESP TRACT
• NO CILIA
• ALVEOLAR FLUID
• LYSOZYME
• IGG ANTIBODIES
• ALVEOLAR MACROPHAGES
(PHAGOCYTOSIS)
• NEUTROPHILS
• INFLAMMATORY RESPONSE
D. MICROBIOLOGICAL
• ALPHA HEMOLYTIC STREPTOCOCCI: APPEAR WITHIN 12
HOURS AFTER BIRTH ,BECOME DOMINANT ORGANISMS
OF THE OROPHARYNX
• MICROCOCCI, COLIFORMS, PROTEUS, LACTOBACILLI
• PREDOMINANT ORGANISMS IN THE UPPER RESPIRATORY
TRACT : NONHEMOLYTIC AND ALPHA HEMOLYTIC
STREPTOCOCCI, NEISSERIA
• OTHERS: STAPHYLOCOCCI, DIPHTHEROIDS, HAEMOPHILI,
PNEUMOCOCCI, MYCOPLASMAS, PREVOTELLA
BENEFICIAL ROLE OF NORMAL FLORA
 INHIBITS ATTACHMENT OF PATHOGENS
 COVERS THE RECEPTOR SITES
 PHYSICAL COMPETITION FOR NUTRIENTS
 CREATE ADVERSE ENVIRONMENT FOR PATHOGEN
BY
•
MUTUAL INHIBITION BY METABOLIC OR TOXIC
PRODUCTS
•
MUTUAL INHIBITION BY ANTIBIOTIC MATERIALS
OR BACTERIOCINS
•
OTHER MECHANISMS
Respiratory epithelium
HARMFUL EFFECTS OF RESPIRATORY FLORA
ENDOGENOUS INFECTIONS
• URT INFECTIONS BY VIRUSES, SMOKING ETC.-CILIARY DAMAGE
• ACUTE BACTERIAL MENINGITIS (NS. MENINGITIDIS)
• ACUTE LOBAR PNEUMONIA (STREPTOCOCCUS PNEUMONIAE)
• EXTENSION OF RESP FLORA TO SINUSES –ACUTE SINUSITIS
• NASAL PACKING IN EPISTAXIS-INFECTIVE ENDOCARDITIS
(VIRIDANS STREPTOCOCCI)
• USE OF ANTIMICROBIALS
• THRUSH (CANDIDA)
• IMMUNE SUPPRESSION RESULTS IN OVERGROWTH OF FLORA
• ACUTE ESOPHAGITIS (CANDIDA ) IN HIV
HARMFUL EFFECTS OF RESPIRATORY FLORA
EXOGENOUS INFECTION/
NOSOCOMIAL INFECTIONS
SURG SITE INFECTION IN HOSP BY STAPH
AUREUS
Thrush
USUALLY SOURCE IS HEALTHCARE
PROVIDER
MRSA OUTBREAKS IN ITCS/ WARDS FROM
POOR HAND HYGIENE
HIV Esophagitis
• THANK YOU