Microbiology of Infant Botulism and Tetanus

Botulism

• Caused by Clostridium botulinum
• Associated with honey consumption
• Can occur through wound botulism: growth of C. botulinum in wounds
• Treatment involves respiratory assistance and antitoxins
• Prevention: proper canning and use of nitrites in foods

Tetanus

• Caused by Clostridium tetani
• Gram-positive, endospore-forming, obligate anaerobe
• Grows in deep wounds with anaerobic conditions
• Releases tetanospasmin neurotoxin, which enters the CNS and causes death from spasms of respiratory muscles
• Prevented by vaccination with tetanus toxoid (DTaP)
• Booster required every 10 years
• Fewer than 10 cases per year, with a mortality rate of 25-50%
• Treatment involves tetanus immune globulin (TIG) and debridement of infected tissue

Listeriosis

• Caused by Listeria monocytogenes
• Gram-positive rod
• Usually foodborne and asymptomatic
• Can cause meningitis, especially in immunocompromised individuals
• Can invade the bloodstream, causing sepsis
• Reproduces in phagocytes, spreading from cell to cell
• Infects pregnant women, crossing the placenta and leading to stillbirth
• Uses actin polymerization for bacterial movement

Leprosy

• Also known as Hansen's disease
• Caused by Mycobacterium leprae
• Acid-fast rod that grows best at 30°C
• Generation time of 12 days
• Grows in peripheral nerves and skin cells
• Survives macrophages and invades the myelin sheath
• Transmission requires prolonged contact with an infected person or inhalation of secretions
• Two forms: tuberculoid (neural) and lepromatous (progressive)
• Diagnosed with skin biopsy or skin smear, blood test
• Treatment involves antibiotics (Dapsone, Rifampin, and Clofazimine) for 6-24 months

African Trypanosomiasis

• Caused by Trypanosoma brucei gambiense
• Humans are the only reservoir
• Transmitted from animals to humans by the tsetse fly
• Distributed in West and Central Africa
• Few early symptoms, followed by fever, headache, and CNS deterioration
• Parasite evades antibodies through antigenic variation
• Difficult to develop a vaccine
• Treated with eflornithine, which crosses the blood-brain barrier
• Prevention involves eliminating tsetse fly vectors

Amebic Meningoencephalitis

• Caused by Naegleria fowleri
• Causes primary amebic meningoencephalitis (PAM)
• Protozoan infects the nasal mucosa from swimming water, penetrates the brain, and feeds on brain tissues
• 100% fatal

Rabies

• Caused by the rabies virus
• Genus Lyssavirus, bullet-shaped, single-stranded RNA
• Easily develops mutants
• Usually transmitted by the saliva of an animal bite
• Can also cross mucous membranes
• Initial symptoms: muscle spasms of the mouth and pharynx, hydrophobia
• Virus multiplies in skeletal muscles, travels through the PNS to brain cells, causing encephalitis
• Average incubation of 30-50 days
• Forms Negri bodies in the brain stem
• Two forms: furious (classical) and paralytic (dumb or numb)

Nervous System Diseases Caused by Prions

• Prion: abnormally folded protein
• Causes normal proteins in the brain tissue to become abnormally folded
• Leads to spongiform degeneration, a chronic and fatal condition
• Transmissible spongiform encephalopathies (TSE)
• Examples: sheep scrapie

Microbial Diseases of the Cardiovascular and Lymphatic Systems

• Structure and function of the cardiovascular and lymphatic systems
• Cardiovascular system: circulates blood through the body's tissues
• Lymphatic system: transports interstitial fluid, picks up microorganisms and infectious agents
• Bacterial infections of the heart: endocarditis, pericarditis
• Sepsis and septic shock: acute illness due to the presence of pathogens or their toxins in the blood
• Lymphangitis: inflammation of the lymph vessels
• Gram-negative sepsis: caused by E. coli, Klebsiella spp., and Pseudomonas aeruginosa
• Gram-positive sepsis: caused by S. aureus, Enterococcus faecalis
• Puerperal sepsis: caused by S. pyogenes, transmitted to the mother during childbirth
• Rheumatic fever: autoimmune complication of S. pyogenes infection

Toxoplasmosis

• Caused by Toxoplasma gondii
• Undergoes its sexual phase in cat intestines
• Oocysts shed in cat feces
• Contact with cat feces introduces oocysts to the intestines
• Oocysts form trophozoites that invade cells, may become a chronic infection
• Primary danger is congenital infection, which can cause stillbirth, neurological damage, and blindness

Malaria

• Caused by Plasmodium parasites
• Transmitted by Anopheles mosquitoes
• Four species: P. vivax, P. falciparum, P. malariae, and P. ovale
• Mosquito bite transmits sporozoite into the bloodstream
• Enters liver cells, undergoes schizogony, and releases merozoites into the bloodstream
• Merozoites infect RBCs, undergo schizogony, and rupture infected RBCs, releasing toxic compounds
• Some merozoites develop into gametocytes, which are taken up by a mosquito, repeating the cycle