Microbiology Lab

• Ideal vaccine


  • Contains enough antigenic determinants
  • Contains antigenic determinants from all the strains of the pathogen that cause that disease
  • Has few (preferably no) side effects
  • Does not cause disease in the vaccinated person
• Vaccines children should receive between birth and entry into school

  • Hepatitis B (Hep B) Vaccine
  • Diphtheria toxoid-tetanus, toxoid-acellular pertussis (DTaP) vaccine
  • Haemophilus influenzae type B (HIB) vaccine
  • Measles-mumps-rubella (MMR) vaccine
  • Varicella (chickenpox) vaccine
  • Pneumococcal conjugate vaccine (PCV)
  • Influenza vaccine
  • Hepatitis A vaccine
• Types of vaccine


  • Attenuated Vaccines
  • Inactivated Vaccines
  • Subunit Vaccines
  • Conjugate Vaccines
  • Toxoid Vaccines
  • DNA Vaccines
  • Autogenous Vaccines
• Attenuated bacterial vaccines


  • BCG
  • cholera
  • tularemia
  • typhoid fever (oral vaccine)
• Inactivated viruses or viral antigens

  • hepatitis A
  • influenza
  • Japanese encephalitis
  • other encephalitis vaccines
  • polio (subcutaneous salk vaccine)
  • rabies
• Inactivated bacterial vaccine


  • anthrax
  • typhoid fever (subcutaneous vaccine)
  • Q fever
• Subunit vaccines


  Uses antigenic (antibody-stimulating) portions of a pathogen, rather than using the whole pathogen
• Conjugate vaccines


  Made by conjugating bacterial capsular antigens to molecules that stimulate immune system response
• Conjugate vaccines


  • Hib
  • Meningococcal vaccine
  • Pneumococcal vaccine
• Toxoid vaccines


  • Diphtheria
  • Tetanus
  • Commercial antisera containing antitoxins are used to treat diseases such as tetanus and botulism
• DNA vaccines


  Laboratory animals have very successfully protected using this technique, and reports of the induction of cellular immune responses in humans to a malaria parasite antigen, using DNA vaccines, have been published
• Autogenous vaccines


  One that has been prepared from bacteria isolated from a localized infection, such as a staphylococcal boil. The pathogens are killed and then injected into the same person to induce production of more antibodies
• Practical considerations in the use of vaccines

  • Aseptic Technique
  • Proper temperature storage
  • Expiration date should always be checked prior usage
  • Lot numbers should be kept in case of undesirable reactions to the vaccine given
• Hazards of immunization


  • Hypersensitivity
  • Reversion
  • Hepatitis B risk
  • Contamination
• Immediate-type hypersensitivity reactions


  Occur from within a few minutes to 24 hours after contact with a particular antigen
• Types of immediate-type hypersensitivity reactions

  • Type I Hypersensitivity Reactions - anaphylactic reactions/allergic reactions
  • Type II Hypersensitivity Reactions - cytotoxic reactions (involve damage to or death of body cells)
  • Type III Hypersensitivity Reactions - immune complex reactions (damage to tissues and organs is initiated by antigen-antibody complexes)
• Delayed-type hypersensitivity (DTH) reactions

  Usually take 24 - 48 hours or even longer to manifest themselves
• Type IV hypersensitivity reactions

  Also known as cell-mediated reactions; antibodies play only a minor role, if any; an example is a positive TB skin test
• Non-Specific Host Resistance


  • First Line of Defense
  • Second Line of Defense
• Specific Host Resistance


  • Third Line of Defense
• Two Major Arms of the Immune System

  • Cell Mediated Immune Response
  • Humoral (Antibody-Mediated) Immune Response
• Non-Specific Host Defense


  • General and serve to protect the body against many harmful substances
  • Includes the innate or inborn resistance observed among species of animals and some persons who have a natural resistance to certain diseases
• Skin and Mucous Membranes

  • Physical/mechanical barriers
  • Includes intact and unbroken skin
  • Sticky mucus serve as to entrap invaders
• Cellular and Chemical Factors Accounting for the Skin's Ability to Resist Pathogens

  • Dryness of most areas of the skin
  • Acidity and the temperature
  • Oily sebum
  • Perspiration
  • Sloughing of dead skin cells
• Cellular and Chemical Factors Accounting for the Mucous Membranes' Ability to Resist Pathogens

  • Lysozyme production
  • Lactoferrin
  • Lactoperoxidase – production of superoxide radicals
  • Rapid cell division
  • Mucociliary Coverings
• Protection of the Digestive System

  • Digestive Enzymes
  • Acidity of the stomach
  • Alkalinity of the intestines
  • Bile
  • Peristalsis & defecation
• Protection of the Genitourinary Tract

  • Urination
  • Expulsion of mucus secretions
  • Acidity of the vagina
• Microbial Antagonism


  • Happens when resident microbes fight the invasion of new microorganisms in a particular anatomical site
  • The inhibitory capability of the indigenous microflora has been attributed to competition for colonization sites, competition for nutrients, and production of substances that kill other bacteria - bacteriocins
• Cellular and Chemical Factors

  • Transferrin
  • Fever
  • Interferons
  • Complement System
  • Acute-Phase Proteins
  • Cytokines
  • Inflammation
  • Phagocytosis
• Transferrin


  • A glycoprotein with a high affinity to iron
  • Normal function is to store and deliver iron to host cells
• Fever


  • Body temperature greater than 37.8˚C
  • Fever augments the host's defense by stimulating leukocytes, reducing available free plasma iron, and inducing the production of IL-1
• How Fever Develops During an Infectious Disease

  1. Patient has septicemia caused by gram (-) bacteria

  2. Bacteria releases endotoxin into the patient's bloodstream

  3. Phagocytes ingest the endotoxin

  4. Ingested endotoxin stimulates the phagocytes to produce IL-1

  5. IL-1 stimulates the hypothalamus to produce prostaglandins

  6. Prostaglandins cause the hypothalamic thermostat to be set at a higher level

  7. Increased body heat continues until the temperature of the blood supplying the hypothalamus matches the elevated thermostat reading
• Detrimental Effects of Fever

  • Increased heart rate
  • Increased metabolic rate
  • Increased caloric demand
  • Mild to severe dehydration
• Interferons


  • Small, antiviral proteins produced by virus-infected cells
  • Not virus-specific; but, species-specific
  • Three types: Alpha, Beta, and Gamma
• Complement System


  • A group of approximately 30 different proteins found in normal blood plasma
  • The proteins interact with each other in a stepwise manner known as the "complement cascade"
  • Major consequences: Initiation and amplification of inflammation, attraction of phagocytes, activation of leukocytes, lysis of bacteria and other foreign cells, increased phagocytosis
• Acute-Phase Proteins


  • Enhances resistance to infection and promoting repair of damaged tissue
  • Includes C-Reactive Proteins, Serum Amyloid A Protein, Protease Inhibitors, Coagulation Proteins
• Cytokines


  • Chemical mediators that enable cells to communicate with each other
  • Some are chemoattractants, recruiting phagocytes to location, and direct role in host defense
• Inflammation


  • Normal response to any local injury, irritation, microbial invasion, or bacterial toxin
  • Three major events: Vasodilation, increased capillary permeability, egress of leukocytes
  • Purposes: Localize an infection, prevent the spread of microbial invaders, neutralize any toxins, aid in the repair of damaged tissue
• Inflammatory Exudate


  • Accumulation of fluid, cells, and cellular debris
  • Purulent Exudate or pus is thick and greenish yellow
• Pyogenic Microorganisms


  Staphylococci and streptococci