Bacterial Pathogens - Zahrt Flashcards
How is respiratory divided?
Upper airway and Lower airway
Where can bacteria be found in the respiratory system?
In the upper airway. The lower airway is sterile
What defenses does the body have to prevent lower respiratory infection?
Size selection
Mucus secretions
Mucociliary elevator
Immune cells and response
How do pathogens spread into the lower airway?
Direct inhalation (>10um) Aspiration from upper airway Spread along mucus membrane Direct implantation Hematogenous spread
From a throat culture, you find a gram negative coccobasillus. What bacteria is this?
Bordetella Pertussis
Describe the pathogenesis of bordetella pertussis.
Binds to cilia using pertactin, filamentous hemaglutinin and pili. Pertussis toxin alters adenylate cyclase (G-i alpha) and produces massive amounts of mucus and damages the cilia.
What are the three stages of infection for bordetella pertussis?
catarrhal- runny nose, mild coughing, flu-like symptoms
paroxysmal- “barking” coughing fits, vomitting
convalescence- decrease in coughing, no vomitting
From a throat culture, you find a gram negative basillus arranged in pallisades. What bacteria is this?
Corynebacterium diptheriae
Describe the pathogenesis of corynebacterium diptheriae
Uses pili to attach to upper respiratory tract cells; produces diptheria toxin which modifies EL-2 and prevents protein synthesis.
Forms a pseudo membrane.
From a throat culture, you find a gram negative diplococci. What bacteria is this?
Neisseria meningitidis
How is neisseria classified by oxidase and catalase tests?
Oxidase +
catalase +
What diseases can neisseria meningitidis cause?
Pharyngitis
Pneumonia
Meningitis
Describe the pathogenesis of neisseria meningitidis
type IV pili allow it to bind to the cells of nasopharynx. It’s polysaccharide capsule prevents it from being destroyed by either lysosomes or PMNs. It releases endotoxins and lipooligosaccharides as toxins.
Which four serotypes are included in the neisseria meningitidis vaccine?
A, C, Y, W135
From a throat culture, you find a gram positive cocci. It is catalase negative and beta-hemolytic. What bacteria is this?
streptococcus pyogenes
What diseases can streptococcus pyogenes cause?
scarlet fever
pharyngitis
Describe the pathogenesis of streptococcus pyogenes.
Capsule protects it from phagocytosis and complement.
Lipotechoic acid and T proteins mediate adhesion to the respiratory cells.
M proteins binds complement and immunoglobulins
Various DNAse, streptolysins, and peptidases chew up complement, blood cells, and pepetides.
pyogenic endotoxins produce sickness.
How is streptococcus pyogenes usually diagnosed?
Rapid antigen detection test; it is not usually cultured and tested.
From a throat culture, you find a gram positive cocci. It is catalase positive. What bacteria is this?
staphylococcus aureus
Describe the pathogenesis of staphylococcus aureus
Capsule protects it from phagocytosis
Expresses lipase, nuclease and hyaluronidase to chew up cells.
Lipotechoic acids and protein A promote cell binding
Coagulase activates fibrinogen into fibrin
various cytotoxins are released
From a throat culture, you find a gram positive cocci. It is catalase negative and alpha-hemolytic. What bacteria is this?
streptococcus pneumoniae
What diseases can streptococcus pneumoniae cause?
lobar pneumonia
sinusitis
otitis media
Describe the pathogenesis of streptococcus pneumoniae
pneumolysin
capsule
adehsion proteins
From a throat culture, you find a gram negative rod. It grows on chocolate agar. What bacteria is this?
Haemophilus influenzae
