Microbiology & Parasitology

• Carolus Linnaeus is known as the Father of Taxonomy
• Binomial nomenclature classifies organisms according to their genus and species name
• Genus name is capitalized and species name is the specific epithet, both are italicized
• Bacteria are simple, single-celled (unicellular) prokaryotes with most having cell walls containing peptidoglycan
• Bacteria are often described based on their general shape and reproduce through binary fission and conjugation
• Types of bacteria shapes include:

  • Coccus (spherical)
  • Bacillus (rod-shaped)
  • Spirillum, spirochete, vibrio (curved)
• Genus and specific epithet sources for some microorganisms:

  • Salmonella enterica: Honors public health microbiologist Daniel Salmon, found in the intestines
  • Streptococcus pyogenes: Appearance of cells in a chain, forms pus
  • Saccharomyces cerevisiae: Fungus that uses sugar, makes beer
  • Penicillium chrysogenum: Tuftlike appearance microscopically, produces a yellow pigment
  • Trypanosoma cruzi: Corkscrew appearance, honors epidemiologist Oswaldo Cruz
• Archaea are unicellular prokaryotes with cell walls lacking peptidoglycan, including methanogens, extreme halophiles, and extreme thermophiles
• Protists are a group of Eukaryotes that are not plants, animals, or fungi, including algae and protozoa
• Algae can be unicellular or multicellular, have cell walls made of cellulose, and are photosynthetic organisms
• Protozoa make up the backbone of many food webs, may have cilia/flagella and pseudopods, and some are pathogens like Giardia lamblia
• Fungi are eukaryotes including mushrooms, yeasts, and molds that form visible masses called mycelia
• Viruses are acellular, contain a core made of DNA or RNA surrounded by a protein coat, and reproduce using the cellular machinery of other organisms
• Helminths are multicellular parasitic worms, divided into flatworms and roundworms
• • Large Intestine: Contains the largest numbers of microbiota, with antimicrobial chemicals produced by the mucosa
• Representatives of normal microbiota by body region:

  • Skin: Microbes in direct contact are not residents, with resistant barriers like keratin and low pH inhibiting many microbes
  • Eyes: Tears and blinking eliminate or inhibit microbes, including Staphylococcus and Propionibacterium
  • Nose and Throat: Some normal microbiota are potential pathogens, nasal secretions kill or inhibit many microbes
  • Mouth: Ideal environment for diverse microbial populations, with dislodging mechanisms like biting and salivary flow
• Origin of microbiota in newborns:

  • Vaginal birth: Mother's reproductive tract
  • Caesarean Section: Maternal skin biota
  • Early diet influences the infant's microbiome
• Basic infectious disease epidemiology terms:

  • Endemic: Diseases constantly present in a population within a particular region
  • Epidemic: Occur in a short time within a geographic region, often caused by environmental or population changes
  • Pandemic: Worldwide scale
• Chain of infection components:

  • Reservoir: Where germs can live and multiply
  • Portal of exit: Means for germs to escape from the reservoir
  • Mode of transmission: Direct (contact, droplet spread) and Indirect (airborne, vectors)
  • Portal of entry: Manner in which a pathogen enters a susceptible host
  • Susceptible host: Depends on the immunity of a person
• Stages of diseases:

  • Incubation Period: Initial entry of the pathogen into the host, factors involved in pathogen multiplication
  • Prodromal Period: Pathogens continue to multiply, host starts experiencing general signs and symptoms
  • Period of Illness: Signs and symptoms are more severe
  • Period of Decline: Pathogen numbers decrease, signs and symptoms decline
  • Period of Convalescence: Patient returns to normal functions, some diseases may result in permanent damage
• Microbes and human welfare:

  • Recycling vital elements by microbial ecology, converting atmospheric nitrogen to nitrates
  • Sewage treatment: Removal of large waste, conversion of organic materials by bacteria
  • Bioremediation using bacterial enzymes like Bacillus and Alcanivorax
  • Insect pest control using Bacillus thuringiensis
  • Biotechnology and recombinant DNA technology for gene therapy and modified bacteria for agricultural purposes
• Microbiome, also known as microbiota, consists of microorganisms living stably in and on the human body, helping prevent the growth of disease-causing agents
• References:

  • Bernardino, Gilbert. College of Nursing, University of the Cordilleras
  • Parker, et.al (2021) "Microbiology" openstax.org