PRELIM

• Microbiology is the study of the biology of microscopic organisms - viruses, bacteria, algae, fungi, molds, and protozoa, microorganisms that cannot be seen with the naked eye
• Why study microbiology


  Because of their ability to cause diseases
• Life on Earth would not survive without microorganisms
• Antonie Philips van Leeuwenhoek


  • Dutch microbiologist and microscopist in the Golden Age of Dutch science and technology, commonly known as "the Father of Microbiology", and one of the first microscopists and microbiologists
• Louis Pasteur


  • French chemist and microbiologist renowned for his discoveries of the principles of vaccination, microbial fermentation, and pasteurization
• Robert Hooke


  • English polymath active as a scientist, natural philosopher and architect, credited as one of the first two scientists to discover microorganisms using a compound microscope that he built himself
• Alexander Fleming


  • Scottish physician and microbiologist, best known for discovering the world's first broadly effective antibiotic substance, which he named penicillin
• Heinrich Hermann Robert Koch


  • German physician and microbiologist, regarded as one of the main founders of modern bacteriology as the discoverer of the specific causative agents of deadly infectious diseases including tuberculosis, cholera and anthrax
• Frederick Griffith


  • British bacteriologist whose focus was the epidemiology and pathology of bacterial pneumonia
• Alexandre Emile Jean Yersin


  • Swiss-French physician and bacteriologist, remembered as the co-discoverer of the bacillus responsible for the bubonic plague or pest, which was later named in his honour: Yersinia pestis
• Edward Jenner


  • English physician and scientist who pioneered the concept of vaccines and created the smallpox vaccine, the world's first vaccine
• Key developments in microbiology


  • 1665 - Publication of the first description of microbes by Robert Hooke
  • 1667 - Observation of "little animals" by Anton van Leeuwenhoek
  • 1796 - Smallpox Vaccination - first scientific validation by Edward Jenner
  • 1850 - Advocating Handwashing in the prevention of the spread of disease by Ignaz Semmelweis
  • 1861 - Spontaneous Generation disproved by Louis Pasteur
  • 1862 - Publication of the paper supporting the germ theory of disease by Louis Pasteur
  • 1867 - Practice of Antiseptic Surgery by Joseph Lister
  • 1876 - Discovery of Bacillus Anthracis which became the first proof of germ theory by Robert Koch
  • 1881 - Utilization of solid culture media for bacterial growth by Robert Koch
  • 1882 - Outlined Koch's Postulate by Robert Koch
  • 1882 - Development of Acid-fast stain by Paul Erlich
  • 1884 - Gram Stain developed by Hans Christian Gram
  • 1885 - First Rabies Vaccination by Louis Pasteur
  • 1887 - Invention of the Petri Dish by Richard J. Petri
  • 1892 - Discovery of Viruses by Dmitri Iosifovich Ivanovski
  • 1893 - Zoonosis - first described by T. Smith, F.I. Kilbourne
  • 1899 - Viral dependence on living host cells for reproduction recognized by Martinus Beijerinck
  • 1900 - Proof the mosquitoes carry the agent of yellow fever by Walter Reed
  • 1910 - Discovered the cure for syphilis by Paul Erlich
  • 1928 - Discovery of Penicillin by Alexander Fleming
  • 1953 - Proposed and built the DNA Model by J. Watson, F. Crick
  • 1977 - Development of the DNA sequencing method by W. Gilbert, F. Sanger
  • 1983 - Invention of the Polymerase Chain Reaction (PCR) by Kary Mulis
  • 1995 - Publication of the first microbial genomic sequence by The Institute for Genomic Research (TIGR)
• Branches of microbiology


  • Pure Microbiology
  • Applied Microbiology
• Sub-branches of pure microbiology

  • Bacteriology
  • Virology
  • Mycology
  • Parasitology
  • Phycology
  • Immunology
  • Protozoology
  • Nematology
• Sub-branches of applied microbiology

  • Environmental Microbiology
  • Medical Microbiology
  • Industrial Microbiology
  • Pharmaceutical Microbiology
  • Food & Dairy Microbiology
  • Agricultural Microbiology
  • Aquatic Microbiology
  • Aeromicrobiology
  • Microbial Genetics
• Definitions of key terms

  • Acute phase
  • Anaerobe
  • Antibody
  • Antigen
  • Antisepsis
  • Bacteremia
  • Bactericidal
  • Bacteriocin
  • Capnophile
  • Disinfection
  • Disinfectant
  • Etiologic agent
  • Fastidious
  • Genotype
  • Gram-positive bacteria
  • Gram-negative bacteria
  • Halophilic
  • Immunocompetent
  • Immunocompromised
  • Immunosuppression
  • Latent phase
  • Mesophile
  • Microaerophile
  • Microaerophilic
  • Microbial load
  • Obligate aerobe
  • Obligate anaerobe
  • Nosocomial infection
  • Opportunistic infection
  • Pathogenicity
  • Phenotype
  • Sepsis
  • Resistant strain
  • Susceptible
  • Intermediate
  • Zoonosis
  • Zoonotic
• Intermediate


  Implying that the agent might be effective for infections located at body sites where the drugs are physiologically concentrated, or when a high dosage of drug can be used
• Zoonosis


  Disease that humans acquire from exposure to infected animals or products made from infected animals
• Zoonotic


  Pertaining to diseases that can be transmitted from animals
• the bacterial strain tested may be appropriately treated with the dosage of antimicrobial agent recommended for that type of infection and infecting species
• Sterilization is the destruction of all forms of life including bacterial spores using chemical or physical methods
• Disinfection is the destruction of some forms of life except bacterial spores using chemical or physical methods
• Factors affecting degree of microbial killing

  • Types of organisms
  • Microbial load
  • Concentration of disinfecting agent
  • Presence of organic material
  • Nature of surface to be disinfected
  • Contact time
  • Temperature
  • pH
• Spores


  • Rich in proteins, lipids, and carbohydrates
  • Rich in dipicolinic acid and calcium
• Cell walls of mycobacteria

  • Rich in lipids
• Higher number of organisms require longer exposure to disinfecting agents
• Organic material affects killing activity by inactivating the disinfecting agent
• Bleach is easily inactivated by organic material
• Heat under steam autoclave at 121°C for 15 minutes sterilizes all microorganisms except prions
• Dry heat sterilization requires longer exposure times and higher temperatures compared to moist heat
• Boiling at 100°C for 10 minutes kills most microorganisms but does not sterilize
• Pasteurization at 63°C or 72°C eliminates food-borne pathogens and organisms responsible for food spoilage without affecting taste
• Filtration


  Using thin membrane filters with pore sizes of 0.45, 0.80 and 0.22 µm to remove bacteria, yeasts, molds and small viruses
• HEPA filters


  Remove microorganisms larger than 0.3 µm, used in laboratory hoods and air systems
• Ionizing radiation


  Gamma rays or electron beam with short wavelength and high energy, used for sterilization of disposable supplies
• Non-ionizing radiation


  UV rays with long wavelength and low energy, used for disinfection of surfaces
• Principles of chemical sterilization/disinfection

  • Reaction with components of the cytoplasmic membrane
  • Denaturation of cellular proteins
  • Reaction with the thiol (–SH) groups of enzymes
  • Damage of RNA and DNA
• Alcohols


  60-90% ethyl or isopropyl alcohol, inactivate microorganisms by denaturing protein
• Formaldehyde


  37% aqueous solution or formaldehyde gas, reacts with the thiol (–SH) groups of enzymes, carcinogenic agent
• Glutaraldehyde


  2% solution, inactivates DNA and RNA through alkylation, rapid killing action, remains active in presence of organic materials