L1

• Microbiology is simply defined as the study of microbes, or living organisms of microscopic size.
• French chemist, Louis Pasteur, whose demonstration that fermentation was caused by the growth of bacteria and yeast (1857-60) provided a main impetus for the development of the science.
• Parasitology is simply a branch of zoology that deals with a specialized group of animals (called parasites)
• physiologically dependent on other organisms

  (called hosts) for their survival.
• relationship between them, called PARASITISM, is

  intimate and almost always obligatory since the parasite dies if it is eventually separated

  from its host, which is its source of food, shelter and/or the appropriate environment for

  survival, growth and reproduction.
• Commensals are organisms that routinely colonize body surfaces without doing harm.
• Pathogens are organisms that damage the human host either by direct invasion and injury or by the production of harmful toxic products.
• Medical Microbiology is the study of interactions between humans and the microorganisms with which they coexist.
• Medical Parasitology is important for you to understand:

  (a) the infection process (the mechanism by which parasites establish themselves in the human host),

  (b) pathogenesis (the mechanism by which parasites harm man), and

  (c) epidemiology (the factors affecting their transmission within the population).
• Sedillot who first used the term microbe in 1878, but is now commonly replaced by that of microorganisms.
• Vectors an indefinite host; contribute or facilitate transmission of a parasite from one host to another susceptible host. They usually transmit arthropod-borne

  pathogens.
• Phylum Arthropoda – Class Insecta
• Parasitic animals

  • Phylum Platyhelminthes (flat worms)
  • Phylum Aschelminthes (round worms)
• Fungi Kingdom - Mycology, the study of this kingdom, includes both multicellular fungi and unicellular fungi (classified as higher protists).
• Kingdom Protista – single-celled/ unicellular, and also classified as higher protist
• According to Engelkirk, et.al. organisms classified as protists can reproduce asexually.
• Protozoa are animal-like microorganisms capable of causing infections among humans and other animals.
• Kingdom Monera - unicellular, prokaryotic organisms. Monerans are also categorized as the Kingdom of prokaryotes/ Lower protists.
• Kingdom Monera - They are commonly called bacteria,

  and have a wide variety including pathogens and commensals.
• Bacteria with rigid and thick cell wall

  Free-living (extracellular) – the cocci and the rods

  Obligate intracellular parasites - Chlamydiae, and Rickettsiae
• Bacteria with flexible thin cell walls - the Spirochetes
• Bacteria without cell wall – Mycoplasma
• Viruses – acellular infectious agents, which are obligate intracellular parasites. Though they are not considered as living entities, they are microscopic in size, and

  are generally classified as microbes.
• Fever is perhaps the cardinal clue to the presence of infection; however, it is important to emphasize that not all infections cause fever and not all fevers result from infection.
• Non-infectious causes of fever include:

  a. Neoplasms

  b. CNS disease

  c. Rheumatic diseases

  d. Hypersensitivity reactions

  e. Metabolic derangements
• Pain may be a reflection of inflammation and tissue destruction or may occur as a result of the pressure on sensitive structures caused by an enlarging infected mass.
• Weight loss may occur in the setting of a chronic infection.
• Progressive debility is a vague but important symptom. It maybe the reflection of the catabolic effects of infection, or it may be traced to more specific problems such as malabsorption, CNS disease and cardiovascular impairment.
• Change in physiologic function of a particular organ system (e.g. progressive shortness of breath as a result of pneumonia, alteration in mental status due to meningitis, and diarrhea caused by enteritis) may reflect infection.
• Abnormal laboratory test results may suggest the presence of infection even in the asymptomatic patient. Common examples include abnormal chest x-rays, elevated circulating leukocyte counts, and the presence of WBC in normally acellular body fluids (e.g. in the urine, CSF, joint fluid, and peritoneal fluid).
• Our current concept of nomenclature (naming) is based on the 18th century work of a British botanist, Carl Von Linne, and is called a binomial system.
• Genus - First word of the name Capitalized and italicized (or

  underlined)
• Species - Second word of the name Nor capitalized but italicized (or underlined)
• GENUS AND SPECIES Common Name

  Neisseria gonorrheae Gonococcus

  Neisseria meningitidis Meningocoocus

  Salmonella typhi Typhoid bacillus
• Common examples include abnormal chest x-rays, elevated circulating leukocyte counts, and the presence of WBC in normally acellular body fluids (e.g. in the urine, CSF, joint fluid, and peritoneal fluid).
• Synonyms for commensals include normal flora, normal microflora, normal microbiota, indigenous flora, indigenous microflora, and indigenous microbiota.