MBIO Ch. 24 and up

• Rumen


  Large anaerobic fermentation chambers in herbivores
• Fermentation in the rumen

  1. Cellulolytic microbes hydrolyze cellulose to free glucose

  2. Glucose is then fermented, producing volatile fatty acids (e.g., acetic, propionic, butyric)

  3. Fatty acids pass through the rumen wall into the bloodstream and are utilized by the animal as its main energy source

  
• Abrupt changes in an animal's diet


  Can result in changes in the rumen flora
• Rumen acidification (acidosis)


  One consequence of such a change, can lead to inflammation of the rumen and potential acidification of the blood (which is potentially lethal for the cow)
• Denitrification is a(n) anaerobic respiration process resulting in the reduction of nitrate or nitrite into nitrogen gas
• In nature, nitrogen fixing bacteria must form symbiotic relationship with plant roots
• There are approximately 10^13 microbes in human (about the same as human cells)
• Microbiome


  Microbes living in complex communities
• Fiber (cellulose) is considered indigestible for humans but facilitates bowel movement
• Cellulose degrading bacteria (e.g., Ruminococcus) are lost from the human gut microbiome in industrial societies but present among rural human societies
• Cellulose degrading bacteria turn fiber into digestible carbohydrates that feed other microbes
• Hypersensitivity Classification


  • Type 1 (Immediate)
  • Type 2 (Cytotoxic)
  • Type 3 (Immune complex)
  • Type 4 (Delayed type)
• Type 1 Hypersensitivity


  Ig E sensitization of mast cells, reaction in minutes, examples: bee venom, hay fever
• Type 2 Hypersensitivity


  IgG interaction with cell surface antigen, reaction in hours, examples: drug reactions (penicillin)
• Type 3 Hypersensitivity


  IgG interaction with soluble or circulating antigen, reaction in hours, example: systemic lupus erythematosus (SLE)
• Type 4 Hypersensitivity


  Th1 inflammatory cell activation of macrophages, reaction in days (24-48 h), examples: poison ivy, tuberculin test
• Autoimmune diseases may be caused by type II, type III, or type IV reactions
• Immediate Hypersensitivity


  • Allergy, can be mild to life-threatening (e.g., anaphylaxis)
• Type IV Delayed-type hypersensitivity


  • Cell-mediated hypersensitivity characterized by tissue damage (hives, blisters) due to inflammatory responses produced by Th1 inflammatory cells, examples: poison ivy blisters, contact dermatitis
• Superantigens


  Proteins capable of eliciting a strong response by interacting with T cell receptors (TCRs), may produce systemic inflammatory reactions
• Autoimmune diseases


  • Systemic lupus erythematosus (SLE)
  • Type 1 diabetes mellitus
  • Rheumatoid arthritis
• Autoimmunity


  Occurs when T and B cells are activated to produce immune reactions against self proteins, resulting in host tissue damage
• Immunodeficiency


  • Severe combined immune deficiency syndrome (SCID) is a serious, congenital deficiency of both B and T cells, patients live a restricted life, limiting their exposure to pathogens ("Boy in the Bubble" syndrome)
  • Acquired Immunodeficiency syndrome (AIDS) is caused by HIV infection that progresses and kills CD4+ T cells, patients are prone to opportunistic infections and cancer, since they are deficient in T cell help
• Immunizations against bacteria


  • Haemophilus influenzae type B (Hib)
  • Meningococcal (Neisseria meningitidis)
  • Pneumococcal (Streptococcus pneumoniae)
  • Tetanus, diphtheria, pertussis (DTaP, Tdap)
• Immunizations against viruses


  • Hepatitis A virus
  • Hepatitis B virus
  • Human papillomavirus (HPV)
  • Influenza virus
  • Inactivated poliovirus (IPV)
  • Measles, mumps, rubella (MMR)
  • Rotavirus
  • Varicella virus (chicken pox)
• Immunotherapy


  Harness cells and other components of the immune system to fight or prevent diseases, including anticancer vaccines
• Mechanisms of Action of Major Antibacterial Agents

  • Efficacy, toxicity, spectrum, cost effectiveness, route of administration
• Antimicrobial Drugs That Target Nonbacterial Pathogens

  • Antiviral drugs (host or viral targets, interferons)
  • Drugs that target eukaryotic pathogens
• Epidemiology


  The study of the occurrence, distribution, and determinants of health and disease in a population
• Disease incidence


  The number of new cases of the disease in a given period of time
• Disease prevalence


  The total number of new and existing cases in a population in a given time
• Types of disease


  • Endemic
  • Epidemic
  • Pandemic
• Mortality


  The incidence of death in a population
• Morbidity


  The incidence of disease, including fatal and nonfatal diseases
• Disability-Adjusted Life Year (DALY)


  Quantitatively measures disease burden in terms of lost years due to the disease, disability due to disease, and premature death
• Herd immunity


  Transmission of infection is reduced when a large proportion of a population becomes immune to a disease
• Modes of disease transmission

  • Direct host-to-host
  • Indirect host-to-host (via living agents called vectors or nonliving agents called fomites)
• Disease carriers and reservoirs

  Reservoirs are sites in which infectious agents remain viable and from which individuals can become infected, carriers are pathogen-infected individuals showing no signs of clinical disease
• Zoonosis


  Any disease that primarily infects animals but is occasionally transmitted to humans
• The introduction of a measles vaccine eliminated measles as a common childhood infection in the United States, pathogen eradication removes all of a pathogen from any reservoir