Introduction to Microorganisms

• Microbes are virtually everywhere and are considered ubiquitous.

Acellular Microorganisms

• Viroids, prions, and viruses are acellular microorganisms.

Prokaryotic Microorganisms

• Archaea, bacteria, and cyanobacteria are prokaryotic microorganisms.

Eukaryotic Microorganisms

• Algae, Fungi, and Protozoa are eukaryotic microorganisms.

Germs and Pathogens

• Germs are microbes that cause disease.
• Pathogens are disease-causing microorganisms, also known as infectious agents.

Human Microbiome

• The human microbiome is also known as indigenous microbiota or human bioneme.

Opportunistic Pathogens

• Microbes that colonize our bodies and can cause disease under certain conditions are opportunistic pathogens.

Categories of Diseases Caused by Microbes

• Infectious Disease and Microbial Intoxication are the two categories of disease caused by microbes.

Pathogen Colonization

• When a pathogen colonizes a person's body it establishes itself and multiplies within the host.

Microbial Intoxication

• Microbial intoxication occurs when a pathogen produces a toxin in vitro.

Bacteria

• Bacteria are single-cell and unicellular organisms.
• Bacteria are considered prokaryotic because their genetic material is not enclosed in a nuclear membrane.

Archaea

• Archaea cell walls uniquely lack peptidoglycan.

Fungi

• Eukaryotic cells in fungi are defined by having a distinct nucleus with DNA, surrounded by a nuclear membrane.
• Fungi can be unicellular or multicellular.
• The cell wall of fungi is composed of chitin.
• Fungi can reproduce sexually or asexually.
• Slime molds share characteristics of both fungi and amoeba.
• Long filaments (hyphae) that branch and intertwine form visible masses called mycelia in fungi.
• Oval and larger than bacteria, yeast microorganisms cause bread to rise and produces alcohol from sugar.
• Candida albicans is the yeast that causes most yeast infections in women.

Protozoa

• Protozoa are unicellular, eukaryotic microbes.
• Protozoa absorb or ingest organic chemicals.
• Protozoa can reproduce sexually or asexually.

Algae

• Algae are photosynthetic eukaryotes with sexual and asexual reproductive forms.
• Algae can be unicellular or multicellular.

Viruses

• Most viruses possess either DNA or RNA, but not both.
• Viruses replicate using viral nucleic acid in a host cell.
• Viruses lack the genes and enzymes necessary for energy production.
• Viruses depend on ribosomes, enzymes, and metabolites of the host cell for protein and nucleic acid production.
• Bacteriophages are viruses that infect bacteria.

Viroids and Prions

• Viroids are composed of nucleic acid without protein coating.
• Prions are infectious proteinaceous particles without nucleic acid, linked to neurological diseases.
• Bovine spongiform encephalopathy and scrapie, including other neurologic diseases in humans are associated with prions.

Robert Hooke

• Robert Hooke reported "little boxes" or "cells" as life's smallest structural units.
• Robert Hooke introduced the beginning of Cell Theory.

Anton van Leeuwenhoek

• Anton van Leeuwenhoek is referred to as the Father of Microbiology.
• Anton van Leeuwenhoek was probably the first to observe live microorganisms through magnifying lenses.
• Anton van Leeuwenhoek invented the single-lens microscope.
• Anton van Leeuwenhoek described animalcules, including bacteria, algae, protozoa, and fungi observed through his simple-lens microscope in his series of papers.

Spontaneous Generation

• Francisco Redi opposed the theory of Spontaneous Generation.
• John Needham strengthened the theory of Spontaneous Generation.
• Lazzaro Spallanzani opposed Spontaneous Generation along with Francisco Redi.
• Rudolf Virchow challenged Spontaneous Generation.
• Rudolf Virchow introduced the Theory of Biogenesis.

Louis Pasteur

• Louis Pasteur is known as the Father of Immunology.
• Louis Pasteur disproved Spontaneous Generation with the Swan-neck Flask experiment.
• Louis Pasteur discovered the connection between microorganisms and food spoilage.
• Pasteurization is the process of heating a substance to 60°C for 30 minutes, which does not kill endospores.
• Louis Pasteur discovered vaccines for anthrax and rabies.
• Louis Pasteur started the Golden Age of Microbiology.

Germ Theory of Disease

• The Germ Theory of Disease says diseases are caused by microorganisms invading the body.

Ignaz Semmelweis

• Ignaz Semmelweis introduced the importance of handwashing.
• Ignaz Semmelweis introduced Chlorinated lime.

Joseph Lister

• Joseph Lister is known as the Father of Antiseptic technique.
• The purpose of aseptic technique is to prevent contamination.
• Joseph Lister introduced the utilization of carbolic acid as a wound disinfectant.

Robert Koch

• Robert Koch developed Pure Culture Technique.
• Robert Koch discovered Bacillus anthracis as the causative agent of anthrax.
• Robert Koch discovered Myobacterium tuberculosis that causes tuberculosis.
• Robert Koch discovered Vibrio cholera that cause cholera.
• Koch's Postulate is an experimental procedure to prove a microbe causes a specific infectious disease.

Edward Jenner

• Edward Jenner discovered the first vaccine.
• The first vaccine was for Smallpox.
• Edward Jenner discovered the technique of vaccination.

Paul Ehrlich

• Paul Ehrlich is known as the Father of Chemotherapy.
• Salvarsan/Arsphenamine/Compound 66 was the first chemotherapeutic agent against syphilis discovered by Paul Ehrlich.
• Paul Ehrlich introduced the term "Magic Bullet."

Antibiotics Discoveries

• Alexander Fleming discovered Penicillin from Penicillium notatum mold.
• Selman Waksman discovered Streptomycin from Streptomyces.

Immunity and Public Health

• Emil von Behring developed the method of producing immunity using antitoxin against diphtheria.
• John Snow studied cholera and identified its source and spread.

Lab Techniques

• Richard Petri, assisted by Robert Koch, discovered the petri dish for culturing media.
• Hans Christian Gram discovered the Gram staining technique.

HIV Discovery

• Francoise Barre-Sinoussi discovered the human immunodeficiency virus in a patient with swollen lymph nodes.

Cytology

• Cytology studies the structure and functions of cells.
• "Eu" means "True" in the context of eukaryotes.
• "Karyo" means "Nut or nucleus" in the context of eukaryotes.

Escherichia coli (E. coli)

• Enterotoxin and Endotoxin are toxins produced by Escherichia coli.
• Escherichia coli is normally found in the GI tract.
• E. coli causes UTI, Neonatal meningitis, Sepsis, Gastroenteritis, Common cause of HAP.
• Cotrimoxazole, Quinolones are treatments for Escherichia coli infections.
• EPEC is associated with diarrhea in infants and children.
• EPEC attaches to the mucosa of the upper small intestine, disrupting brush border microvilli.
• Enterotoxigenic E. coli (ETEC) causes Traveller's diarrhea (Montezuma's revenge), commonly contracted in developing countries.
• Enteroinvasive E. coli (EIEC) infection is similar to Shigellosis.
• Enteroinvasive E. coli (EIEC) infection is characterized by bloody diarrhea with pus and fever.
• Enterohemorrhagic E. coli (EHEC) infection is characterized by bloody diarrhea with no pus and fever.
• O157:H7 is the most common serotype of EHEC, which produces a powerful toxin called VEROTOXIN.
• EHEC can cause HUS (Hemolytic Uremic Syndrome).
• EAEC means Enteroaggresive E. coli.

Klebsiella pneumoniae

• Klebsiella pneumoniae is also known as Friedlander's bacillus mucous capsulatus.
• Klebsiella pneumoniae is the second most common cause of Gram-negative sepsis.

ESKAPE

• ESKAPE stands for Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumanii, Psedomonas aeruginosa, Enterobacter spp. in hospital-acquired infections.

Salmonella typhi

• Salmonella typhi causes Typhoid fever.
• Rotten egg diarrhea is a symptom associated with Salmonella typhi infection.
• Rose spots on the belly is a symptom of Salmonella typhi infection.
• The Widal Test is used for diagnostic test for salmonella.
• Chloramphenicol, Ciprofloxacin, Ceftriaxone are the drugs of choice for typhoid fever.
• Salmonella choleraesius causes Sepsis or septicemia.
• Salmonella enteritidis causes diarrhea or gastroenteritis.

Shigella dysenteriae

• Cotrimoxazole and Quinolones is the treatment for Shigella dysenteriae.

Proteus mirabilis

• Proteus mirabilis is a common cause of UTI.

Serratia marcescens

• Serratia marcescens produces a blood red pigment (red colonies).
• Serratia marcescens causes Endocarditis.

Infectious Disease Terms

• A causative agent is a substance causing disease, e.g., bacteria, parasites, fungi, and viruses.
• A reservoir in infectious disease is the habitat where an infectious agent lives, grows, and multiplies.
• A vector in infectious disease transmission is a living organism that transmits an infectious agent between hosts.
• Spores are cells produced by fungi, plants, and bacteria for defense against environmental stress.
• A positive result for lactose fermenting microorganisms is indicated by pink color of agar plates.
• A pink color on agar plates indicates a positive result for lactose fermentation.
• A yellow agar plate indicates a non-lactose fermenting microorganism.
• Virulence refers to the severity or harmfulness of a disease.
• Facultative refers to the ability to live under more than one specific environmental condition.
• Obligate means restricted to a particular characteristic or necessity, opposite of facultative.

Vibrio cholerae

• Exotoxin (cholera toxin) is the virulence factor of Vibrio cholerae.
• Tetracycline and ORS are the treatments for Vibrio cholerae infection.