Otitis Media/Externa Pathogenesis, Epidemiology, and Treatment (PDF)

OTITIS MEDIA/EXTERNA PAT H O G E N E S I S , E P I D E M I O LO G Y A N D T R E AT M E N T Prepared by: BMS 150 Nick Inglis, Ph.D. Feb 12, 2023 OTITIS MEDIA (OM) ACUTE OTITIS MEDIA (AOM) ACUTE OTITIS MEDIA (AOM): COMPLICATIONS Suppurative complications of AOM - Acute ma...

OTITIS MEDIA/EXTERNA PAT H O G E N E S I S , E P I D E M I O LO G Y A N D T R E AT M E N T Prepared by: BMS 150 Nick Inglis, Ph.D. Feb 12, 2023 OTITIS MEDIA (OM) ACUTE OTITIS MEDIA (AOM) ACUTE OTITIS MEDIA (AOM): COMPLICATIONS Suppurative complications of AOM - Acute mastoiditis - Meningitis - Brain abscesses 21000 deaths from AOM per year 30 per 10,000 individuals: hearing loss Perforation of tympanic membrane OTITIS MEDIA WITH EFFUSION (OME) CHRONIC SUPPURATIVE OTITIS MEDIA (COM/CSOM) ACUTE OTITIS MEDIA (AOM) - EPIDEMIOLOGY OTITIS MEDIA WITH EFFUSION (OME) - EPIDEMIOLOGY Incidence and prevalence have been difficult to establish CHRONIC SUPPURATIVE OTITIS MEDIA - EPIDEMIOLOGY CAUSAL PAT H WAY S F O R OT I T I S M E D I A EUSTACHIAN TUBE ANATOMY THE COMMON OTOPATHOGENS Streptococcus pneumoniae (Pneumococcal conjugate vaccine?) Haemophilus influenzae Moraxella catarrhalis Pseudomonas aeruginosa HAEMOPHILUS INFLUENZA X Factor (Hemin) V Factor (NAD+) H. influenzae HAEMOPHILUS INFLUENZAE: VIRULENCE FACTORS Adhesins Polysaccharide capsule Lipid A chains/lipooligosaccharides Fimbriae IgA protease Biofilms MORAXELLA CATARRHALIS Gram –ve, diplococcus, aerobic bacteria Common for URT, middle ear, eye infections Commonly resistant to beta lactam drugs Part of normal microbiota of ~3% of people. (children more) Variable rates of colonizations in communities. MORAXELLA CATARRHALIS: VIRULENCE FACTORS Antiobiotic resistance (b-lactamase resistance) Outer Membrane Proteins - uspA1-A2, Pili Iron-Regulated Proteins - Transferrin-Binding proteins - Lactoferrin-binding proteins Lipid A chains/lipooligosaccharides STREPTOCOCCUS PNEUMONIAE: VIRULENCE FACTORS Polysaccharide capsule Fimbriae Surface proteins that inhibit activation of complement PSEUDOMONAS INFECTIONS Caused by Pseudomonas aeruginosa – an opportunistic pathogen that becomes an infectious agent following the burning away of skin; can also cause otitis externa PSEUDOMONAS AERUGINOSA: VIRULENCE FACTORS Fimbriae and adhesins to improve attachment Formation of biofilms Produce enzymes like elastase, which breaks down elastic fibres, degrades complement system, cleaves IgG and IgA antibodies Pyocyanin with triggers free radical accumulation (this is what causes tissue damage) PSEUDOMONAS AERUGINOSA: EPIDEMIOLOGY P. aeruginosa is found mostly in soil; not a component of regular microbiota Cannot penetrate epidermal layer independently – good news! Common nosocomial infection agent (10% of hospital infections) STAPHYLOCOCCUS AUREUS Salt tolerant, facultative anaerobe, resistant to dessication, UV radiation and heat Along with Staphylococcus epidermidis, make up ~90% of microbiota of skin. Common cause of otitis externa VIRULENCE FACTORS STAPHYLOCOCCUS AUREUS: 1. ENZYMES Coagulase, Hyaluronidase, Staphylokinase Hyaluronidase and collagenase Coagulase and kinase Bacterium Hyaluronidase Bacterium Coagulase Clot Clotting Kinase protein Epithelial cells Collagenase Collagen layer Invasive bacteria Bacteria produce Bacteria invade deeper Bacteria produce Clot forms. Bacteria later produce reach epithelial hyaluronidase and tissues. coagulase. kinase, dissolving clot surface. collagenase. and releasing bacteria. Extracellular enzymes VIRULENCE FACTORS STAPHYLOCOCCUS AUREUS: 1. ENZYMES Lipase, beta-lactamase Lactam ring b-lactamase (penicillinase) Penicillin breaks this bond Inactive penicillin VIRULENCE FACTORS STAPHYLOCOCCUS AUREUS: 2. STRUCTURAL DEFENSES Capsule/slime layer glycocalyx Phagocytosis blocked by capsule Incomplete phagocytosis Capsule around Capsule around Bacteria bacterium bacterium reproduce Phagocytic vesicle Phagocyte Lysosome Antiphagocytic factors VIRULENCE FACTORS STAPHYLOCOCCUS AUREUS: 2. STRUCTURAL DEFENSES Binding IgG antibody stem regions Pseudopod of phagocyte Fc receptor protein Prevention of Opsonization VIRULENCE FACTORS STAPHYLOCOCCUS AUREUS 3. TOXINS Cytolytic toxins to disrupt membranes of a large number of cell types Leukocydin – kills leukocytes (another means of avoiding phagocytosis) Epidermal Cell Differentiation Inhibitors – produces large holes in the lining of blood vessels Exfoliative toxins (Toxic Shock Syndrome Toxin) SOME OTHER DISEASES CAUSED BY STAPHYLOCOCCUS AUREUS Skin diseases Reproductive system diseases lecture Systemic infections/ cardiovascular Respiratory system diseases Gastrointesstinal system diseases THANKS! H AV E A G R E AT D AY ! ! ! KEY SOURCE : S CHIDLE R ET AL. (2016). OTITIS MEDIA N AT. R E V. D I S. P R I M 2 ( 1 ) ; H T T P S : / / W W W. N C B I. N L M. N I H. G O V / P M C / A R T I C L E S / P MC7097351/