RESPIRATORY TRACT



RESPIRATORY TRACTnose to alveoli continuous operation is essential constantly exposed to air & microbes divided into 2 regions : upper & lowerGeneralizationsMany cause local infections, some may spread systemicallyProfessional invaders - normal healthy host, specific attachment mechanisms, specific evasion tacticsSecondary invaders - impaired hostMost common infections seen by doctorsHigh morbidity ? absenteeismUpper - usually mild & self-limitingLower - can be severe & life-threateningin children bacterial in adultsUpper Respiratory Tract Infectionsitis = inflammation - surface infections1. Rhinitis = cold100% viral (see Table 18.4)Rhinovirus and Coronaviruses - 50%115 different Rhinoviruses all w/ different surface antigensOther viruses (Parainfluenza, Enterovirus, RSV, etc)transmission via aerosol and by contaminated handsbind to and infect ciliated epithelial cells of noseincubation is 1-3 daysdamage to epithelial cells ? mild inflammation, release of inflammatory mediators abundant mucusdiagnosed by clinical signs & symptoms (burning sensation in nose/throat, followed by sneezing, runny nose, fatigue, malaise. Sore throat and cough generally due to post nasal drip. No or low fever)treatment is symptomaticcontrol – interferon, sIgA, and IgG - immunity is short-lived2. Pharyngitis (= sore throat) and tonsilitisinfected mucosa or inflammation of lymphoid tissue70% viral – symptoms often include rhinorrhea, conjunctivitis, malaise or fatigue, hoarseness, and low-grade feverRhinovirus, Coronavirus, Adenovirus, etc, see Table 18.5CMV -clinically silent in URT esp. in infant/child – can spread from blood to placenta and infect fetus; second only to Down’s as a cause of mental retardationEBV -2 peaks 1-6 years and 14-20 years (infectious mononucleosis – fever, sore throat, petechiae on hard palate, lymphadenopathy and splenomegaly, with anorexia and lethargy. Symptoms due to release of cytokines. Plyclonal activation of B cells; WBC dif shows at least 10% atypical lymphocytes) EBV infections can re-activate, see Fig. 18.6.30% bacterial – usually no rhinorrhea, cough, or conjunctivitisS. pyogenes (age 5-15), onset is abrupt, acute - chills, headache, severe sore throat, lymph nodes swell, tonsils tender w/ white, pus-filled lesions, high fever, no cough, no nasal dischargeN. gonorrhoeae – in sexually activeC. diphtheria – rare in U.S.3. Otitis media and sinusitis = ear and sinusear infections are second most common infection of childhood (after colds) and most common cause of visits to pediatricians50% viralrespiratory syncytial virus (RSV), influenza, parainfluenza, rhinovirus, adenovirus50% bacteria - secondary invadersS. pneumoniae, Haemophilus influenzae, Moraxella4. EpiglottitisH. influenzae type B (vaccination = Hib)Severe inflammation with edema life-threatening respiratory obstructionLower Respiratory Tract Infections1. Laryngitis and tracheitisViruses (symptoms – hoarseness, burning retrosternal pain)Parainfluenza virus – croup (dry cough and inspiratory stridor)RSV, Influenza virus, AdenovirusBacteriaGAS, H. influenzae, S. aureusC. diphtheria - life threatening, rare in U.S. due to vaccination (DaPT)2. Whooping coughOrg - Bordetella pertussis (GNR, ox +, obligate aerobe)Humans are sole reservoirHighly contagiousTransmission - person - person airborne dropletsColonization - attach to ciliated mucosa in trachea using fimbriae & hemagglutinin also spreads to bronchiSeveral toxic factors -affect inflammation or damage ciliated epithelium1. pertussis toxin - A-B structure exotoxin; A unit is an ADP-ribosylase, disrupts signal transduction in affected cell - prod massive amts mucoid secretions2. Adenylate cyclase toxin - enters neutrophils & causes them to incr. cAMP - inhibits chemotaxis, phagocytosis, & killing3. Tracheal cytotoxin - kills tracheal epithelial cells4. EndotoxinIncubation - 1-3 weeksPathology - ciliated epithelium of trachea becomes covered w/ massive purulent exudatePresentationearly - runny nose, sneezing, fever, mild dry coughweek later - mucus & bact fill lower trachea, cough becomes paroxysmal - violent coughing fits, 5-20X w/ no breath in btwn - as air rushes back in - whoopalso vomiting, epistaxis, periorbital edema, conjunctival hemorrhageComplications - CNS anoxia, secondary pneumoniaImmunization - DaPTRate of infection in unvaccinated exposed - 90-95%; Mortality - up to 14%3. Acute bronchitis - Inflammation of the tracheal/bronchial tree assoc w/ infectionOrgsProfessional pathogens; Viruses (rhino-, corona-, adeno-, influenzae,) and Mycoplasma pneumoniaeSecondary invaders - S. pneumoniae, H. influenzae Presentation - cough - treatment is symptomatic - antibiotics? usually recommended4. Influenza = the FluOrg - Influenzavirus types A, B, C; A - segmented RNA, 3 major HA types, 2 major NA types; antigenic epitopes change from yr-yr (antigenic drift & shift)Transmission - person - person small airborne dropletsColonization - attaches via HA to sialic acid receptors on ciliated epithelium of trachea/bronchi, RME Incubation - 1-3 daysPathology - impair mucociliary clearance, tracheobronchitis, bronchospasms; cytokines released from damaged cells & WBC may symptomsPresentation - fever 102-104, chills, severe headache w/ retro-orbital pain, muscular aches (esp backache), dry cough, weakness (prostration).Most cases resolve 1-2 wksComplications - 1? influenza pneumonia (1% of cases but 30% fatality, pregnant women ↑ risk), 2? bacterial pneumonia (H. influenzae, S. pneumonia, S. aureus, S. pyogenes)Epidemics are indicated by the number of unexpected deaths due to influenza, when # exceeds 10,000-50,000 = epidemic5. Bronchiolitischildren less than 2swollen by inflammation, passage of air is restrictednecrosis of epithelial cells lining the bronchiolesOrgs75% RSVRespiratory Syncytial Virus - paramyxovirus (RNA), envelopedMost common cause of fatal bronchiolitis & pneumonia in infants (1/100 hospital) - humans only reservoirTransmission - resp. droplets to handsColonization - nasopharynx - surface spikes are fusion proteins that fuse host cells to cause "syncytia", then virus invades LRT by surface spread in secretionsIncubation 4-5 daysImmunopathology - maternal Ab in infant react w/ virus Ag, liberate histamine & other inflammatory mediatorsPresentation - cough, rapid respiration, cyanosis25% other viruses6. Pneumonia4,000,000 people/yr. Most common cause of infection related death in the US. 6th leading cause of deathwide range of microbes Transmission - inhalation or aspiration Colonization - attach to resp epitheliumPathology - respiratory distress from the interference of gas exchange in lungs, systemic effectsOrgschildren - viral or bacteria secondary to virusesadults - bacterial, kind depends on risk factors, age, other diseases - in hospitals GNBacterial - acute onset, high feverTypical - classic bacteria of acute, community-acquired - S. pneumoniae (25-60%), H. influenzae (5-15%), others - S. aureus, Klebsiella, E. coli, PseudomonasAtypical - M. pneumoniae, Chlamydia pneumoniae, Legionella pneumophila, Coxiella burnetiiChest examrales (abnormal crackles)evidence of consolidationchest x-rayViralTransmission - inhaled or from bloodColonization - attach specificallyOrgsRSV - childrenParainfluenza virus types 1 & 2 – children; hemagglutinin & neuraminidase & fusion proteinsAdenovirus - 41 types; 5% of acute resp. illnessInfluenzavirus7. Chronic Infections of the lungsTuberculosis - reviewFungiAspergillus fumigatus – aspergillosis - Predisposing condition - asthma, pre-existing lung cavities, chronic pulmonary disorders - fungal ball aspergilloma doesn’t invade but in immunosuppressed - invade lungs to produce disseminated diseaseHistoplasma capsulatum - histoplasmosisCoccidiodes immitis - San Joaquin Valley FeverBlastomyces dermititidis - blastomycosisPneumocystis jiroveci (formerally P. carinii) - pneumocystis pneumonia8. Cystic fibrosisvery viscous bronchiol secretions leads to fluid stasis in the lungs & infections w/ P. aeruginosa (S. aureus, H. influenzae, B. cepacia) ................
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