Understanding Pathogens: Types and Effects

Pathogens

• Microorganisms that cause illness and disease by infecting the body and overwhelming the immune system.

Medical Definition

• Disease-causing agents, including bacteria, viruses, fungi, helminths, protozoans, and prions.
• Cause illness unless the immune system effectively combats them.
• Originates from the Greek word 'pathos' (disease) and the French word 'genique' (producing), meaning disease-producing.

Types of Pathogens

• Six types: bacteria, viruses, fungi, protozoans, helminths, and prions.
• Infect the body through mucous membranes, open wounds, or the eyes, nose, and mouth.
• Replicate inside the body, localizing or becoming systemic.
• Cause disease by replicating and attacking cells, triggering an overactive immune response, or secreting toxins.

Bacteria

• Unicellular organisms found everywhere, including inside the human body.
• Most are helpful, aiding in creating antibiotics and supporting the immune system.
• Harmful bacteria often result from antibiotic overuse, leading to antibiotic-resistant strains.
• The CDC identifies six highly antibiotic-resistant bacteria, known by the acronym ESKAPE:
  • Enterococcus faecium
  • Staphylococcus aureus
  • Klebsiella pneumoniae
  • Acinetobacter baumannii
  • Pseudomonas aeruginosa
  • Enterobacter spp.
• Cause diseases such as sepsis, lung infections, and necrotizing fasciitis.
• Antibiotics either kill or halt the replication of non-resistant bacteria
  • Tetracycline is a broad-spectrum antibiotic
  • Penicillin is a narrow-spectrum antibiotic with primarily use to kill staphylococcus and streptococcus infections.

Viruses

• Microorganisms found ubiquitously in the environment and the human body, smaller than bacteria.
• Not cell-like; are fragments of DNA mixed with proteins.
• Their living status is debated due to their reliance on a living cell for replication.
• Replicate through either a lytic cycle (rapid) or a lysogenic cycle (dormant insertion into DNA).
• Examples:
  • Influenza virus (common flu): causes cough, body ache, and fever.
  • Norovirus: causes gastrointestinal infection with cramping, diarrhea, and vomiting.
  • Measles virus: transmitted through air droplets, causes skin rashes, cough, runny nose, and fever.
• Antibiotics cannot treat viruses; vaccines and other treatments can address infection symptoms.

Fungi

• Eukaryotic organisms (complex cells with membrane-bound nuclei).
• Ubiquitous in the environment and body.
• Infections can be exogenous (airborne transmission) or endogenous (stemming from within).
• Candidiasis: an overgrowth of Candida albicans, causing illnesses in the vagina, gut, or throat.
• Ringworm: a skin infection causing red, inflamed, itchy rings, common in warm climates and immunocompromised patients.
• Antifungals like nystatin and fluconazole can treat fungal infections.
• Treatments aim for low toxicity due to the drugs targeting eukaryotic cells, like those in the human body.

Protozoa

• Single-celled parasitic organisms.
• Replicate independently or within a human host.
• Spread via animal vectors (e.g., mosquitos) or the fecal-oral route.
• Replicate inside the body, causing localized or systemic diseases.
• Giardia: spread by contaminated water, causing gut illness that can be treated with antibiotics.
• Plasmodium: causes malaria, spread by mosquitos; symptoms include fever, chills, body aches, and flu-like symptoms; can be fatal if untreated.
• Diagnosed through stool, blood, and X-ray tests and treated with strong antibiotics like azithromycin.

Helminths

• Large, multicellular parasitic organisms.
• Most do not replicate inside the host.
• Three categories: flatworms, thorny-headed worms, and roundworms.
• Untreated infections can cause chronic inflammatory disease over many years.
• Filariform (hookworm): infects the intestine, causing abdominal cramping, diarrhea, and bloody stool in serious infections.
• Ascaris (roundworms): feed off blood and tissue in the gut, producing eggs passed through feces.
• Treated with anthelmintics (anti-worm medications) like albendazole and mebendazole.

Prions

• Non-living pathogens composed of protein groupings.
• Infect brain cells, causing normally-folded proteins to misfold.
• Mad Cow disease: caused by eating meat infected with prions.
• Gerstmann-Sträussler-Scheinker disease (GSS): extremely rare.
• Symptoms include confusion, hallucinations, rapidly developing dementia, difficulty speaking, and muscle stiffness.
• Infections are fatal; treatments focus on managing symptoms due to the lack of a cure.

Preventing Infection

• Frequent hand washing.
• Practicing safe sex.
• Vaccination.
• Avoiding sharing personal items or drinks.
• Protection against insect bites.
• Cleaning cooking surfaces.
• Maintaining clean bathrooms.
• Properly cooking food.

Explore pathogens, microorganisms causing disease by overwhelming the immune system. Learn about different pathogens like bacteria, viruses, fungi, protozoans, helminths and prions. Understand how they infect the body, replicate, and cause illness through various mechanisms.