Bacterial Respiratory Tract Infections Flashcards
Two examples of lower respiratory tract infections
Pneumonia, COPD
Three examples of upper respiratory tract infections
Sinusitis, otitis media, pharyngitis
List the 6 nine pathogens commonly associated with RTIs
S. pneumoniae, H. influenzae, Moraxella catarrhalis, Mycoplasma pneumoniae, Legionella, Bordetella pertussis
Describe the symptoms and the 3 forms of pneumonia
Inflammation of the lung, primarily the alveoli. Symptoms include: fever, cough, chest pain, shortness of breath. Can be community (CAP), hospital (HAP) or ventilator (VAP) acquired
Describe the basic characteristics of Streptococcus pneumoniae (7)
Most common cause of RTIs, small gram positive diplococci, alpha haemolytic, bile soluble, optochin sensitive (other viridans group strep are optochin R), disease causing types are always encapsulated, need to take a lung specimen because some adults and lots of children have normal colonies in nasopharynx,
List and describe the 3 virulence factor of S. pneumoniae
1) Capsule: most important factor, helps escape phagocytes, adherence factor for colonization, no capsule = no disease
2) Pneumolysin: destroys ciliated epithelial cells, activates classical complement pathway, suppresses oxidative burst in phagocytes
3) Secretory IgA protease
Name the 5 classes of antibiotics that can be used to treat pneumococcal infections
Penicillins, cephalosporins, macrolides, fluoroquinolones, vancomycin
Describe the basic characteristics of Haemophilus influenzae (5)
Most common cause of AE-COPD, gram negative bacilli, requires X (haem) and V (NAD) factors for growth, grows on chocolate agar, majority of mucosal disease is caused by non-encapsulated strains
Describe the porphyrin test
Determines an isolates X factor requirement. H. influenzae don’t make convert amino-levulinic acid to porphyrins.
Procedure: heavy suspension of organism in amino-levunlinic acid, incubate 4 hours, examine under UV light. Red fluorescence indicates conversion of acid to porphyrins, X-factor independence. No fluorescence indicates X-factor dependence.
How is H. influenzae treated? What does it mean if they have altered PBPs?
Amoxicillin with clavulinic acid because 18% of strains produce beta lactamase. 1% have altered PBPs which means they will be resistant to beta lactams independent of a beta lactamase.
Describe the basic characteristics of Moraxella catarrhalis (4)
Gram negative cocco-baccili. Associated with otitis media and sinusitis. 90% of strains are resistant to ampicillin and amoxicillin. Predictably susceptible to oral antibiotics.
Describe the basic morphology, staining, pathogenic characteristics and growth requirements of Legionella pneumophila
gram negative bacilli, thinly staining and easy to miss on a gram stain, intracellular, motile, BCYE agar required to grow, require L-cysteine for growth
Describe the laboratory diagnostics/antibiotic profile of Legionella
Culture and urinary Ag are the most specific and sensitive lab diagnoses, predictably resistant to the fluoroquinolones, macrolides are an excellent alternative antibiotic
Describe Mycoplasma pneumoniae morphology and its association with RTIs
Smallest free living bacteria, strict aerobe (all other mycoplasma are facultative anaerobes), lacks a cell wall, causes 70-80% of tracheabronchitis infections and 20-30% of pneumonias
What antibiotics would be used to treat mycoplasma infections? What antibiotics wouldn’t be used?
Highly susceptible to doxycycline, macrolides, fluoroquinolones. Lack a cell wall and are therefore not susceptible to cell wall active agents
