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Microbiology- Unit Three
Upper Respiratory Infections (T Pierce)
42
Medical
Professional
12/02/2009

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Term
common cold: etiology
Definition
  • five families of virus
    • parainfluenza
    • respiratory syncytial virus
    • rhinovirus (MAJOR)
    • coronavirus (second most)
    • enterovirus
      • influenza, adenovirus associated with more severe illness

Most etiologies are undiscovered though

Term
common cold: epidemiology
Definition
  • seasonal incidence- annual epidemics occur in colder months
    • rhinovirus: ealry fall, mid spring
    • coronavirus: winter
  • attack rates
    • highest in young children in nursery school
    • adults average 2-4 colds/yr
    • children average 6-8 colds/yr
Term
common cold: transmission
Definition
  • main reservoir: young children when they acquire new viral strands from school mates
  • secondary attack rates of family members vary
    • related risk factors: age, immunity
  • means of transmission
    • direct contact with infectious secretion
    • airborne droplets
Term
common cold: pathogenesis
Definition
  • characteristic changes in sloughed of epithelial lining
    • progressive nuclear pyknosis
    • formation of inclusion bodies
  • destructive effect on mucus membrane
  • chemical mediators (PG's, histamines, IL 1,6,8) and neurological reflexes such as parasympathetic pathway play a role
Term
common cold: clinical features
Definition
  • incubation period: 12-72 hrs (can be rapid)
  • nasal discharge and obstruction, sneezing, sore throat, cough, fever, loss of sense of smell/taste
  • median duration is 1 week
  • in young children, parainfluenza and RSV can cause viral pneumonia, croup, and bronchiolitis
Term
common cold: dx
Definition
  • clinical symptoms
  • marked pharyngeal injection or exudate warrants rapid Ag detection or throat culture for group A beta hemolytic strep
  • serological dx- 4 fold rise in Ab titers from acute and convelescent sera
  • rapid fluorescent Ab tests RSV, influenza, parainfluenza, adenoviruses
Term
common cold: tx
Definition
  • vasoconstrictors
  • antihistamines
  • antipyretics
Term
pharyngitis: etiology
Definition
  • viral
    • rhinovirus
    • adenovirus
    • influenza
    • parainfluenza
    • coxackievirus A
    • HSV
    • EBV
    • CMV
  • bacterial
    • group A and C beta hemolytic strep
    • N. gonorrhea
    • Corynebacterium diptheriae
    • Mycoplasma
    • anaerobic bacteria
Term
pharyngitis: pathogenesis
Definition
  • rhinovirus- stimulate pain nerve endings through release of inflammatory mediators
  • adenovirus, coxackievirus A- direct invasion of mucosa
  • group A strep- release of erythrogenic toxin, hemolysins
  • Corynebacterium diptheriae- fibrosis pseudomembrane
Term
pharyngitis: clinical presentation
Definition
  • group A strep symptoms may be mild
    • when severe: pharyngeal pain, odynophagia, fever, pharynx is often erythematous with an exudate, cervical adenopathy, leukocytosis may occur
  • viral pharyngitis
    • usual mild symptoms, except influenza
    • EBV and adenoviruses- cause exudative pharyngitis
    • coxsakie virus and HSV- may be distinguished with presence of vesicles
Term
pharyngitis: dx
Definition
  • main objective to distinguish viral from strept
  • rapid Ag detection tests for strep using a throat swab
    • 90% specific
    • 60-95% sensitive
  • negative test should be followed by throat culture
Term
pharyngitis: tx
Definition
  • strept pharyngitis- 10 day course of penicillin
  • viral pharyngitis- supportive
Term
epiglottis: definition and etiology
Definition
  • definition- rapid progressive cellulitis of epiglottis that can potentially occlude airway
  • etiology
    • H. influenza type B is isolated from blood or epiglottis of most pediatic and a good amount of adult patients
    • Other causes: strept, pneumo, staph
Term
epiglottis: clinical features, epidemiology
Definition
  • epidemiology- mainly in children
  • clinical features
    • fever, irritability, dysphonia, dysphagia, sore throat
    • on exam, pt sitting up, drooling
    • respiratory distress and inspiratory stridor may be present
    • may have a very rapid course
Term
epiglottis: dx
Definition
  • direct visualization under anesthesia- edematous red epiglottis
  • lab findings- leukocytosis, positive cultures of blood and epiglottis
  • sometimes evidence of pneumonia
  • radiograph of lateral neck- enlarged epiglottis
Term
epiglottis: tx
Definition
  • maintain adequate airway
  • in children, insert endotracheal or nasotracheal tube is recommended
  • antimicrobial therapy direct against H. influenza
    • ex: ampicillin-sulbactam, cephalosporins
  • us px in household contacts who are less than 4 yrs old
Term
croup (acute laryngotracheobronchitis): definition and etiology
Definition
  • definition
    • age specific viral infection, producing subglottic area inflammation, resulting in dsypnea and characteristic inspiratory stridulous sound
  • etiology
    • most common: parainfluenza type 1,3
    • others
      • parainfluenza 2
      • influenza
      • RSV
      • rhinovirus
      • enteroviruses
      • Mycoplasma pneumonia
Term
croup: pathophys
Definition
  • viral infection produce inflammation of nasopharynx
  • infection spreads to larynx and trachea, and then to lower tract
  • obstruction is greatest at subglottic area, the least distensible part of airway
  • impeded flow of air results in characteristic sound
Term
croup: clinical manifestation, epidemiology
Definition
  • epidemiology- children 3-36 months
  • clinical manifestation
    • URI symptoms usually precede
    • begin with hoarseness and cougph, proceeds to tachypnea, stridor
    • hypoxemia and hypercapnea may occur
    • some children have repeated episodes aka spasmodic croup (not that they have parainfluenza, but they react to infections the same way)
Term
croup: dx
Definition
  • characteristic clinical picture
  • lateral neck radiographs reveal subglottic swelling steeple sign
  • serologic dx is retrospective
  • viral isolation from throat, tracheal, nasal wash specimens
  • hear a seal barking sound
Term
croup: tx
Definition
  • supportive: follow pulse oximetry, in severely ill patients, follow PCO2
  • supplemental oxygen
  • nebulized epinepherin to reduce subglottic inflammation
  • systemic corticosteroids
  • children may require intubation
Term
otitis externa: definition, etiology
Definition
  • canal is narrow, trapping fluid and foreign objects
  • this causes maceration of superficial tissues
  • causative organisms
    • staph
    • strep
    • rare- pseudomonas
Term
acute localized otitis externa: clinical features and therapy
Definition
  • clinical features
    • usually occur as result of pustle or furnucle due to Staph
    • group A strep can cause erysipelas of canal
  • tx- systemic antibiotics and drainage may be necessary
Term
acute diffuse otitis externa (swimmers ear): clinical features, epidemiology, tx
Definition
  • epidemiology- hot, humid summers
  • clinical features
    • canal become edematous and red
    • gram negative rods (esp. Pseudomonas can play a significant role)
  • tx- with ear drops of topical antibiotics and steroids
Term
invasive (malignant) otitis externa: clinical features and tx
Definition
  • clinical features
    • severe necrotizing infection that spreads from squamous epithelium to adjacent soft tissue, bv's, cartilage, bone
    • usually affects elderly, diabetics
    • usually caused by Pseudomonas aeruginosa
  • tx- requires long course of systemic antibiotics
Term
otitis media: epidemiology
Definition
  • highest incidence 6-24 mnths of age
  • vast majority of kids affected have no anatomic defect
  • there is likely genetic susceptibility
  • age at first episode strongest predictor of recurrent infections
Term
otitis media: etiology
Definition
  • S. pneumonia (most common)
  • H influenza
  • Moraxella catarrhalis
  • Mycoplasma pneumoniae- hemorrhagic bullous myringitis
  • viruses
    • rhinovirus
    • RSV
    • influenza
    • enterovirus
Term
otitis media: pathogenesis
Definition
  • dysfunction of physiologic functions of eustachian tube plays a critical role
    • inadequate drainage into the nasopharynx of middle ear secretions
    • inadequate equilibrium of air pressure with that of external ear canal
Term
otitis media: dx, clinical manifestations
Definition
  • ear pain, drainage, hearing loss, fever, lethargy
  • tympanic membrane erythema and fluid in middle ear by pneumatic otoscopy
  • fluids may persist for prolonged peroid
Term
otitis media: tx
Definition
  • direct antibiotics against likely pathogen (ex: amoxicillin-clavulanate, macrolides)
  • surgical management, prevention
    • myringotomy
    • adenoidectomy
    • placmenet of tympanostomy tubes
Term
sinusitis: etiology
Definition
  • may be viral
  • half of causes due to Strept pneumo and H. influenza
  • anaerobic bacteria usually assoc. with dental disease
  • nosocomial sinusitis: Staph and gram negatives
  • immunocompromised host- gram negatives and fungi
Term
sinusits: pathogenesis
Definition
  • thought to be bacterial complication of viral colds
  • colds can cause reversible abnormalities of sinus cavities
  • sinus mucosal lining becomes inflammed and swollen
  • exudate develops containing bacteria and leukocytes
Term
sinusitis: clinical manifestations
Definition
  • purulent nasal and postnasal discharge, pressure over sinus areas of face, headache, nasal obstruction, fever
  • infection can extend to bone or intracranially
    • proptosis
    • limited EOM
    • meningitis
    • brain abscess
  • exam pts may have tenderness overlying the sinuses, abnormal sinus transillumination
Term
sinusitis: dx
Definition
  • clinical history and exam
  • sinus CT scans
  • sinus radiographs
  • sinus puncture with cultures of exudate ffor severely ill patients not responding to antibiotics
Term
sinusitis: tx
Definition
  • empiric antibiotics directed against suspected pathogens (S. pneumo, H influ)
    • amoxicillin-clavulanate
    • cephalosporins
    • extended spectrum fluoroquinones
  • immunocompromised host or hospital acquired sinusitis, consider tx Pseudomonas
Term
acute bronchitis: definition, etiology
Definition
  • definition- inflammatory condition of tracheobronchial tree associated with a respiratory infection
  • etiology
    • common cold viruses
    • influenza
    • adenovirus
    • rarely nonviral cause
      • M. pneumoniea
      • C. pneumoniae
      • B. pertusis
Term
acute bronchitis: clinical manifestations
Definition
  • cough, preceded by nasal and pharyngeal complaints, fever may be present
  • sputum production reported half the time, can be purulent in later stages, cough is prolonged in smokers
  • with tracheal involvement, there may be substernal chest pain
Term
acute bronchitis: dx, tx
Definition
  • dx- clinical history and exam
    • if cough persists, consider CXR
  • tx- symptomatic
    • cough suppressants
Term
chronic bronchitis: definition, etiology/epidemiology
Definition
  • definition- productive cough on most days during at least 3 consecutive months for more than 2 consecutive yrs
  • etiology/epi
    • important contributing factors
      • smoking
      • infection
      • inhalation of irritants
      • diseases that impair host defenses
        • ex: CF, IgA or IgM sublcass deficiencies
Term
chronic bronchitis: pathophysiology
Definition
  • significant increase in number of goblet cells lining the surface epithelium of major and minor bronchi
  • mucous glands in walls of larger bronchi hypertrophy
  • irritated airways respond by producing extra secretions, aggravating cough and promoting bronchospasm
Term
chronic bronchitis: clinical presentations
Definition
  • epidemiology- mainly older adult males over 40 who smoke and often have COPD
  • clinical presentation
    • incessant, productive cough, worse in morning
    • infection can induce acute exacerbation with increased, purulent sputum production
Term
chronic bronchitis: dx and tx
Definition
  • dx- clinical history
  • tx
    • smoking cessation
    • consider sputum analysis, if eosinophils present, investigate allergic component
    • pulm. function test to assess need for bronchodilators
    • pts with concomitant COPD- corticsteroids
    • antibiotics for acute exacerbations directed against H. flu and Strep pneumoa
      • Amoxicillin-clavulanate
      • cephalosporins
      • macrolides
      • expanded spectrum quinolones
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