Bordetella Bacteria and Whooping Cough

Bordetella

• Small, Gram-negative, aerobic, encapsulated coccobacilli
• Most important species: Bordetella pertussis
• Virulence factors:
  • Attachment factors: Filamentous hemagglutinin (FHA), Pertussis toxin (PTx)
  • Factors mediating tissue damage: PTx, Adenylate cyclase toxin, Tracheal cytotoxin, Endotoxin
• Causes whooping cough
• Culture characteristics:
  • Enriched medium (blood)
  • Bordet-Gengou agar (blood agar + growth factor)
  • Charcoal blood agar
  • Slow grower (6-7 days at 37°C)
  • Colonies characterized by mercury droplets appearance

Whooping Cough

• Incubation period: 1-2 weeks
• Acute respiratory disease (mainly affects children)
• Transmitted via inhalation of droplets
• Non-invasive organism
• Stages:
  • Catarrhal stage (1-2 weeks): attachment and adhesion, virulence factors: FHA, PTx
  • Paroxysmal stage (3 weeks): tissue damage, virulence factors: PTx, Adenylate cyclase toxin, Tracheal cytotoxin, Endotoxin
  • Convalescent stage (3 weeks): slow recovery, no organism

Diagnosis

• Can be diagnosed clinically
• Specimens: Nasopharyngeal secretion swab, Aspiration of Nasopharyngeal secretion, Cough plate
• Direct detection: Direct Fluorescent Assay (DFA), Polymerase Chain Reaction (PCR)
• Culture: Bordet-Gengou agar, Charcoal agar
• Identification: Oxidase +ve, Catalase +ve, Morphology: mercury droplets appearance

Treatment and Prevention

• Treatment: Erythromycin
• Prevention: Whooping cough vaccine (killed whole cell vaccine, part of DPT vaccine), Acellular vaccine (genetically inactivated PTx) (DTaP)
• Chemoprophylaxis: Erythromycin

Brucella

• Named after David Bruce (1855-1931)
• Characteristics: Short, Gram-negative, aerobic, non-motile, non-capsulated, facultative intracellular pathogen
• Zoonotic disease: primary infection in animals
• Members of the genus: Brucella abortus, Brucella melitensis, Brucella suis

Brucellosis

• Undulant fever or malt fever
• Zoonotic
• Mode of transmission: ingestion of animal secretion, direct contact with infected animal, inhalation of animal secretion
• Pathogenesis: Endotoxin is the major virulence factor
• Clinical manifestation: Fever, chill, sweating, headache, malaise, weakness, undulant fever, body ache, enlarged lymph nodes, liver, spleen, osteomyelitis, meningitis
• Lab diagnosis:
  • Specimens: blood, bone marrow (invasive), other samples (according to site of infection)
  • Direct detection and cultivation (dangerous)
  • Serology: Standard tube agglutination test, ELISA, Brucellin Test

Treatment and Prevention

• Combination therapy for long time: Doxycycline & Rifampicin
• Prevention: Control of infected animal, Live attenuated vaccine for cattle, Pasteurization of milk