Bordetella pertussis - MegaMicro

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Bordetella pertussis

Microbiology > Bacteriology > Gram-negative bacteria
a.       Structure
                          i.      Gram-negative bacteria
1.       Encapsulated
2.       Coccobacillus
3.       Oxidase positive
4.       Urease, nitrate reductase, & citrate negative
b.      Pathobiology:
                          i.      Physiology: aerobic, non-motile
                     ii.      Virulence Factors: Causes Whooping Cough
1.       Pertussis toxin (PTx)
a.       Protein based exotoxin
b.      Disrupts G-protein regulation of adenylate cyclase à leads to increased levels of cAMP
           i.      Inhibits early recruitment of macrophages & neutrophils
             ii.      Interferes with early chemokine production
           iii.      Inhibits neutrophil chemotaxis
c.       Causes a decreased entry of lymphocytes into lymph nodes à may lead to lymphocytosis
2.       Filamentous hemagglutinin adhesin (FHA)
a.       Binds to cilia of lung epithelial cells
3.       Fimbriae
a.       Attachment to host epithelium
4.       Pertactin (PRN)
a.       Outer membrane protein
b.      Promotes adhesion to tracheal epithelial cells
c.       Purified and used as component of acellular pertussis vaccine
5.       Tracheal cytotoxin
a.       Produced once anchored to lung epithelia
b.      Stops cilia from beating à host is unable to clear respiratory debris à coughing à expels bacteria capable of infecting other hosts
iii.      Tropic for lung epithelia
v.      Hosts: Human only

c.       Epidemiology
                          i.      Reservoir: human beings (only known)
d.      Laboratory diagnosis
                          i.      Nasopharyngeal or oropharynx swab is taken and tested in lab (in first 3 weeks)
1.       Gram stain à gram (-), coccobacilli, diplococci arrangement
2.       Cultured using Bordet-Gengou agar
                        ii.      "Cough Plate" - cough directly onto Bordet-Gengou
iii.      Nucleic acid techniqes (varied techniques and targets)
iv.      Serologic tests generally not helpful

e.      Disease manifestations: Pertussis (or Whooping Cough)
                         i.      Diagnostic methods:
1.       Diagnosing whooping cough in its early stages can be difficult because the signs and symptoms resemble those of other common respiratory illnesses, such as a cold, the flu or bronchitis.
2.       Diagnosis can be made with clinical symptoms and/or with laboratory test
                       ii.      Differential diagnosis:
1.       Upper Respiratory Infection
a.       Differentiation tests: CULTURE
                                                       i.      Negative is consistent with URI does not necessarily exclude Pertussis
                                                       ii.      Positive confirms Pertussis
2.       Respiratory syncytial viral infection
a.       Differential tests
                            i.      Viral isolation
                                                          ii.      Detection of viral antigens, viral RNA
                                                          iii.      Detect rise in serum antibodies

                     iii.      Therapy
1.       Macrolides: Erythromycin, clarithromycin, or azithromycin are typically the recommended treatment

                      iv.      Prevention and control
1.       Primary prevention is vaccine (acellular vaccine)
Related concepts

Key Words
whooping cough
Pertussis Toxin

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