Intro to Diagnostic Bacteriology

• Microbiology is the study of microorganisms, including certain nonliving entities and living organisms
• Microbes are ubiquitous, meaning they are virtually everywhere
• Microbes are subdivided into four groups:

  • Viruses: very simple microbes consisting of nucleic acid, a few proteins, and in some cases, a lipid envelope. They are completely dependent on the cells they infect for their survival and replication.
  • Bacteria: with RNA and DNA, metabolic machinery for self-replication, and a complex cell wall structure; can be prokaryotic and simple unicellular organisms
• Pathogens are disease-causing microorganisms such as bacteria, fungi, protozoans, and viruses
• Types of pathogens:

  • True Pathogen: causes disease in a healthy host
  • Opportunistic Pathogens: cause disease in an immunocompromised host
• Pathogenicity refers to the ability of an organism to cause disease in a host organism
• Virulence refers to the degree of pathogenicity, indicating the power by which a pathogen can cause severe disease
• Pathogenic determinants or virulence factors are genetic, biochemical, or structural features that enable a pathogen to cause disease in a host organism
• Infection refers to the entry, invasion, and multiplication of pathogens in or on the host body system, leading to subsequent tissue injury and progression to overt disease
• Types of infection: Based on Source of Pathogen

  • Endogenous Infection: arising from colonizing flora
  • Exogenous Infection: arising from invading pathogens from the external environment
• Types of Infection: Based on Etiologic /Causative Agent

  Nosocomial Infection is acquired during hospitalization, while Zoonotic Infection (Zoonosis) is an animal disease that can spread to humans; animal acquired infection
• Disease is an altered health state in an infected host, while an infectious disease is caused by a pathogen invading body tissues and causing damage
• Communicable Disease is an infectious disease capable of spreading from person to person
• Symptoms are subjective evidence of disease perceived by the patient, while signs are observable evidence of disease
• Normal flora refers to bacteria in or on different body sites that usually do not harm the host unless the host defense is compromised
• Earliest known infectious diseases include the Black Plague, smallpox, rabies, dysentery, and other diseases with historical accounts
• Pioneers in the science of microbiology:

  • Anton van Leeuwenhoek: first to see live bacteria and protozoa, known as the "Father of Microbiology"
  • Louis Pasteur: demonstrated different microbe fermentation products, introduced aerobes and anaerobes, developed vaccines
  • Robert Koch: made significant contributions to the germ theory of disease, discovered bacteria causing tuberculosis and cholera
• John Tyndall provided initial evidence of microbes' heat resistance, while Ferdinand Cohn clarified reasons for incomplete microorganism elimination by heat
• Dr. Oliver Wendell Holmes observed fewer infections in home births compared to hospital births, Dr. Ignaz Semmelweis linked infections to autopsy room exposure, and Joseph Lister introduced aseptic techniques to reduce microbes in medical settings
• Careers in microbiology include Bacteriologist, Phycologists, Protozoologists, Mycologist, Virologists, and Cell Biologists who may become genetic engineers
• Microbiology is the study of microorganisms, including certain nonliving entities and living organisms
• Microbes are ubiquitous, meaning they are found everywhere
• Microbes are subdivided into four groups:

  • Viruses: very simple microbes consisting of nucleic acid, a few proteins, and in some cases, a lipid envelope
  • Bacteria: with RNA and DNA, metabolic machinery for self-replication, and a complex cell wall structure (prokaryotic)
  • Fungi: subdivided into single-celled organisms (yeasts) or multi-celled organisms (molds), with some medically important members existing in both forms
  • Parasites: subdivided into single-celled organisms (protozoa) or multi-celled organisms (worms and bugs)
• Pathogens are disease-causing microorganisms such as bacteria, fungi, protozoans, and viruses
• Types of pathogens:

  • True Pathogen: causes disease in a healthy host
  • Opportunistic Pathogens: cause disease in an immunocompromised host
• Pathogenicity refers to the ability of an organism to cause disease in a host organism
• Virulence refers to the degree of pathogenicity, the power by which a pathogen can cause severe disease
• Pathogenic determinants/virulence factors are genetic, biochemical, or structural features that enable a pathogen to cause disease in a host organism
• Infection refers to the entry, invasion, and multiplication of pathogens in or on the host body system, resulting in subsequent tissue injury and progression to overt disease
• Types of infection:

  • Endogenous Infection: arising from colonizing flora
  • Exogenous Infection: arising from invading pathogens from the external environment
  • Acute Infection: rapid/sudden onset of severe symptoms
  • Chronic Infection: gradual onset of mild to moderate symptoms
• Nosocomial Infection is acquired during hospitalization

  • Zoonotic Infection (Zoonosis) is an animal disease that can spread to humans
• Disease is an altered health state in an infected host

  • Infectious Disease is caused by a pathogen invading body tissues and causing damage
  • Communicable Disease is capable of spreading from person to person
• Symptoms are subjective evidence of disease, while signs are observable evidence of disease
• Normal flora are bacteria in or on different sites of the body that usually do not harm the host unless the host defense is compromised
• Earliest known infectious diseases include the Black Plague, smallpox, rabies, dysentery, and syphilis
• Pioneers in the science of microbiology:

  • Anton van Leeuwenhoek: first to see live bacteria and protozoa
  • Louis Pasteur: demonstrated different microbes produce different fermentation products, introduced aerobes and anaerobes, developed vaccines
  • Robert Koch: significant contributions to the germ theory of disease, discovered bacteria causing tuberculosis and cholera
• John Tyndall provided initial evidence of microbes' heat resistance, Ferdinand Cohn clarified reasons for incomplete elimination of microorganisms, leading to the establishment of the term "sterile"
• Dr. Oliver Wendell Holmes observed fewer infections in home births compared to hospital births, Dr. Ignaz Semmelweis showed infections in maternity wards, Joseph Lister introduced aseptic techniques to reduce microbes in medical settings
• Careers in microbiology include Bacteriologist, Phycologists, Protozoologists, Mycologist, Virologists, and Cell Biologists
• Microbiology is a branch of biology which deals with the study of living organisms that are too small to be seen by the naked eye