Pathogenic Prokaryotes

Pathogenic Prokaryotes Overview

Most bacteria are non-pathogenic, and pathogens are exceptions rather than the rule. No known pathogenic archaea exist. Over half of the top infectious diseases causing global deaths are bacterial.

Top Infectious Diseases

Key diseases include respiratory infections (number one killer, can be viral), AIDS (caused by HIV), diarrheal diseases, tuberculosis, and others. Malaria is caused by protists, while measles is viral.

Modes of Transmission

Two main modes of transmission: host-to-host and via agents (vectors or fomites). Vectors include organisms like ticks and mosquitoes that spread pathogens, while fomites are inanimate objects that harbor diseases, such as surfaces and money.

Virulence Factors

Pathogens require specific virulence factors to succeed in causing disease, which include:

  1. Entry (breaking through barriers like skin)

  2. Persistence (surviving within the host)

  3. Harmful outcomes (producing harmful substances like toxins).

Toxins: Exotoxins vs. Endotoxins

  • Exotoxins: Secreted by bacteria, such as the cholera toxin from Vibrio cholerae, causing diarrhea due to disrupted electrolyte balance, leading to dangerous dehydration.

  • Endotoxins: Part of gram-negative bacteria's cell walls, released upon cell death (e.g., Salmonella). Less harmful than exotoxins but can lead to illness from contaminated food.

Conclusion

Understanding the balance of bacteria is crucial; many are essential for health, while pathogens can exploit host vulnerabilities to cause disease. Efficient immune responses usually prevent illness despite the presence of many pathogens in our environment.

Here is a list of vocabulary terms and their definitions from the provided notes:

  • Pathogenic Prokaryotes: Prokaryotes (specifically bacteria, as no known pathogenic archaea exist) that are capable of causing disease.

  • Pathogens: Microorganisms capable of causing disease.

  • Host-to-host transmission: A direct mode of disease transmission from one infected organism to another.

  • Transmission via agents: A mode of disease transmission that involves an intermediary, such as vectors or fomites.

  • Vectors: Living organisms, like ticks and mosquitoes, that transmit pathogens from one host to another.

  • Fomites: Inanimate objects, such as surfaces and money, that can harbor and transmit infectious agents.

  • Virulence Factors: Specific traits or substances produced by pathogens that enable them to cause disease, including mechanisms for entry into the host, persistence within the host, and causing harmful outcomes.

  • Toxins: Harmful substances produced by pathogens that can cause damage to host tissues or interfere with normal physiological processes.

  • Exotoxins: Toxins secreted by living bacteria (e.g., cholera toxin from Vibrio cholerae) that can cause specific disease symptoms by disrupting cellular functions or electrolyte balance.

  • Endotoxins: Components of the outer membrane of gram-negative bacteria's cell walls (e.g., Salmonella) that are released when the bacterial cell dies, capable of causing illness.

  • Vibrio cholerae: A bacterium known for producing cholera toxin, an exotoxin that causes severe diarrheal diseases.

  • Salmonella: A type of gram-negative bacterium that releases endotoxins upon cell death, often associated with foodborne illnesses.