Bordetella and Brucella

Bordetella: Basics & Pathogenesis - Whoop Toxin Terror

• Gram-negative coccobacilli, strictly aerobic.
• B. pertussis causes whooping cough (pertussis).
• Pathogenesis Stages:
  • Attachment: Mediated by adhesins (Filamentous hemagglutinin (FHA), pertactin, fimbriae) to ciliated respiratory epithelium.
  • Evasion & Damage:
    • Pertussis Toxin (PTx): ADP-ribosylates Gi protein → ↑cAMP → lymphocytosis, hypoglycemia, histamine sensitization. (📌 Pertussis Toxin = Permanently Turned on AC)
    • Adenylate Cyclase/Hemolysin Toxin: ↑cAMP locally.
    • Tracheal Cytotoxin: Damages ciliated cells, impairs clearance.
    • Dermonecrotic Toxin: Vasoconstriction.

⭐ Pertussis Toxin (PTx) is the major virulence factor, responsible for the characteristic paroxysmal cough and systemic manifestations like profound lymphocytosis (WBC often > 20,000/μL, mostly lymphocytes).

Bordetella: Clinical & Management - Cough Cure Quest

• Clinical Presentation (Whooping Cough):
  • Catarrhal Stage (1-2 wks): Rhinorrhea, malaise, mild cough; highly contagious.
  • Paroxysmal Stage (2-8 wks): Intense coughing fits, inspiratory "whoop", post-tussive vomiting, lymphocytosis.
  • Convalescent Stage (wks-months): Gradual recovery, lingering cough.
• Diagnosis:
  • Nasopharyngeal swab/aspirate: PCR (gold standard, esp. first 3 wks), Culture (Regan-Lowe/Bordet-Gengou agar; charcoal blood agar).
  • Serology: Useful later in illness.
• Management:
  • Macrolides: Azithromycin, Erythromycin, Clarithromycin (effective in catarrhal stage to ↓ severity & spread).
  • Supportive care: Oxygen, hydration.
  • Prophylaxis for close contacts.
• Complications: Pneumonia, otitis media, seizures, encephalopathy.

⭐ Marked lymphocytosis is a characteristic finding in the paroxysmal stage of pertussis.

Brucella: Basics & Pathogenesis - Fever Agent Antics

• Gram-negative coccobacilli; aerobic, non-motile, non-sporing.
• Biochemical markers: Catalase (+), Oxidase (+), rapid Urease (+). (📌 Urease helps differentiate)
• Zoonotic disease: Causes Undulant fever (Malta fever, Bang's disease).
  • Transmission: Unpasteurized dairy, animal contact, aerosols.
• Pathogenesis: Facultative intracellular parasite (macrophages of RES).
  • Evades killing: Inhibits phagolysosome fusion for intracellular survival.
  • Virulence: Type IV secretion system (VirB) is essential.
  • Pathology: Forms non-caseating granulomas.
  • Clinical: Undulant fever, drenching sweats, arthralgia, hepatosplenomegaly.

⭐ Brucella's hallmark is undulant fever, a relapsing febrile illness reflecting its persistence within the reticuloendothelial system, often acquired from unpasteurized milk.

Brucella: Clinical & Management - Brucella Battle Plan

• Clinical: Insidious onset.
  • Systemic: Undulant fever (cyclical), drenching sweats (mouldy odor), malaise, arthralgia.
  • Focal (common): Hepatosplenomegaly. Osteoarticular (sacroiliitis, spondylitis - most frequent, ~30-70%). Genitourinary (epididymo-orchitis). Neurobrucellosis (<5%). Endocarditis (rare, high mortality).
• Diagnosis:
  • Culture: Blood/BM (Gold Std; Castaneda’s medium, prolonged incubation 4-6w).
  • Serology: SAT ≥1:160 (non-endemic) or ≥1:320 (endemic)/4-fold rise. 2-ME (IgG, active). Coombs (non-agglutinating Abs). ELISA.
  • PCR: Rapid.
• Management: Combination therapy vital.

![Brucellosis symptoms, signs, and lab findings](https://ylbwdadhbcjolwylidja.supabase.co/storage/v1/object/public/notes/L1/Microbiology_Bacteriology_Bordetella_and_Brucella/e8e02c86-7fd6-4c05-81b6-5d5dc83773b4.png)
> ⭐ Relapse occurs in **5-15%** of cases, often due to poor adherence or sequestered infection.

High‑Yield Points - ⚡ Biggest Takeaways

• Bordetella pertussis causes whooping cough; its Pertussis toxin ADP-ribosylates Gi, increasing cAMP.
• Culture B. pertussis on Bordet-Gengou or Regan-Lowe media.
• Brucella species cause brucellosis (undulant fever), transmitted by unpasteurized dairy or animal contact.
• Brucella is a facultative intracellular pathogen, leading to granulomas.
• Diagnose brucellosis via blood/bone marrow culture and serology (Rose Bengal, SAT).
• Treat brucellosis with Doxycycline + Rifampicin.