Pertussis & Legionnaires Disease (Ditki Notes)

• Pertussis, Legionnaires' disease, and related viruses are discussed
• These are related to immunology and microbiology

Gram-Negative Rods

• This category includes Pertussis, Legionnaires', and related viruses.

Bartonella

• Transmitted to humans through insect vectors
• Bartonella bacilliformis causes Carrión disease, mainly in the Andes mountains.
• Oroya fever is the first phase of infection, presenting as acute hemolytic bacteremia with fever and anemia and can be fatal
• The second phase is chronic verruga peruana, characterized by blood-filled cutaneous nodules
• Treatment involves chloramphenicol or ciprofloxacin
• Bartonella quintana is transmitted in louse feces, causing trench fever, also known as "5-day fever."
• Recurring fever symptoms include headache, weakness, and pain, especially in the tibia
• Immunocompromised individuals with bacteremia may experience myalgia, malaise, weight loss, fever, and headache, possibly leading to subacute endocarditis or bacillary angiomatosis
• Bacillary angiomatosis involves neovascular proliferation and blood-filled nodules in the skin, subcutaneous tissues, and bones
• Bartonella henselae is transmitted by cats and their fleas, causing Cat-scratch disease, typically presenting as lymphadenopathy
• Infection can spread, leading to bacillary angiomatosis in the skin, lymph nodes, spleen, and liver
• Subacute endocarditis may occur.

Bordetella

• Causes pertussis, also known as whooping cough.
• The DTaP vaccine (Diphtheria, Tetanus, and Pertussis) and booster vaccines help prevent pertussis
• Bordetella pertussis and Bordetella parapertussis exist; Bordetella pertussis causes a more severe illness
• Pertussis is most dangerous in infants, as it can cause respiratory failure
• Adolescent and adult pertussis cases are rising, with these populations acting as reservoirs for the bacteria

Stages of Pertussis

• Incubation: 7-10 days
• Catarrhal: 1-2 weeks, common cold symptoms
• Paroxysmal: 1-10 weeks, forceful coughing fits followed by "whooping" sound. Post-tussive vomiting is common
• Convalescence: Coughing is reduced, but serious complications such as pneumonia, seizures, apnea, and encephalopathy can occur.

Virulence Factors of Bordetella pertussis

• These factors facilitate invasion and destruction of the respiratory tract
• Adhesins, including filamentous hemagglutinin and fimbriae, are involved
• Adenylate cyclase toxin blocks phagocytosis and prevents T-cell activation
• Dermonecrotic toxin forms necrotic lesions in tissues
• Tracheal cytotoxin destroys ciliated cells of the respiratory tract
• Pertussis toxin: Increases cyclic AMP, promotes leukocytosis, and suppresses the host immune response through Type IV secretion systems

Brucella

• Number one cause of bacterial zoonotic infections; associated with livestock.
• Epidemics lead to economic devastation in farm animals
• Brucella melitensis is associated with most human infections
• Brucella are intracellular pathogens that cause chronic infections with granuloma formation, especially in the reticuloendothelial system
• Treatment includes doxycycline and streptomycin or rifampin; relapse is common
• Brucellosis mimics other infectious diseases, delaying diagnosis
• Early infection: Undulant fever with chills, sweating, coughing, vomiting, and weakness
• Advanced infection: Systemic with multi-organ effects and increased risk of abortion

Francisella tularensis

• Associated with rabbits, ticks, and flies and is an intracellular pathogen
• Tularensis: Ulceroglandular tularemia is the most common presentation, characterized by localized ulcers and glandular swellings
• Glandular tularemia: glandular swellings occur
• Oculoglandular tularemia also exists
• Oropharyngeal infections, and pneumonic tularemia can be fatal
• Treatment is gentamicin

Legionella Pneumonia

• Found in water, including natural bodies, spas, air conditioners, and water misters
• Legionnaires' disease: Severe pneumonia with consolidation and multi-organ damage and is treated with macrolides
• Pontaic fever: Less severe, with flu-like symptoms like fever, chills, myalgia, malaise, and headache
• Antibiotic treatment is unnecessary due to illness being self-limiting