Week 3 Notes
Week 3 Notes HTH 245
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This 3 page Class Notes was uploaded by Katlyn Palka on Friday September 16, 2016. The Class Notes belongs to HTH 245 at James Madison University taught by in Fall 2016. Since its upload, it has received 5 views. For similar materials see Foundations of Infectious Disease in Health Sciences at James Madison University.
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Date Created: 09/16/16
Review quiz ● The common cold is endemic meaning it is always around it is not an emerging or reemerging disease Chapter 4: Bacteria ● Some bacteria can undergo binary fission (multiply) in as little as 20 minutes ● Atypical bacteria: ○ Mycoplasmas ○ Chlamydiae ○ Rickettsiae ● Cell shapes and Patterns ○ The majority of bacterial cells are either: ■ Bacilli (rod shaped) ■ Cocci (spherical) ■ Spirilla (spiral) ● Naming bacteria ○ Microbes are named following the binomial system ■ The names are italicized ■ Each organelle carries two names (binomial) ● First is the genus ○ The first letter of the genus is capitalized ● Second is the species ○ Example: humans, Homo (genus) sapiens (species) ■ Some microbes are named after the scientist that discovered or first described them ● Anatomy of a bacterial cell ○ The envelope is the most exterior part of the cell consisting of: ■ Capsule ● Function: it promotes virulence (the capacity to produce disease) in some cases ● The capsule is not integral for the life of the cell ● Presence of the capsule interferes with phagocytosis (antiphagocytic) ○ Phagocytosis: a mechanism in the cell in which bacteria are engulfed and killed by the cell ● The immune system has a hard time dealing with bacterial cells that have capsules ■ Cell wall ● All bacteria have cell walls with the exception of mycoplasmas ● The cell wall provides resistance of inward diffusion of water ○ If this didn’t happen the membrane would swell and eventually burst (lyse) ○ Penicillin weakens the cell wall of bacterial cells and then it will rupture the cell wall, which kills the bacterial infection ■ Human cells don’t have cell walls that is why they do not rupture ● Bacteria are divided into 2 groups based on the type of cell wall they have ○ Gram negative (thin) ○ Gram positive (thick) ■ They both stain a purplebluish color after application of crystal violet. Then after iodine and alcohol are added the gram positive remains purple and the gram negative turns colorless ■ Broad spectrum antibiotics: work against both gram positive and gram negative ■ Narrow spectrum antibiotics: work against either gram positive or gram negative ■ Cell (outer) membrane/plasma membrane ● Only present in gram negative cells ● Controls the passage of molecules between the external environment and the bacterial cell ● It is selectively permeable ○ Allows certain molecules to pass freely in and out of the cell ● The cell membrane is double layered ● Cytoplasm ○ It is enclosed within the cell membrane ○ Nucleoid: ■ Contains the chromosomal DNA ■ Responsible for the bacteria growing and multiplying (binary fission) ■ There is no nuclear membrane around the nucleus in bacterial cells. ○ Spores: ■ An encapsulated piece of DNA and acts like a time capsule (stays dormant and they are viable for long periods) ■ When the bacteria dies the spore stay in that state of dormancy (they have little or no metabolism) ● Is resistant to heat, boiling, drying, radiation, and various chemical compounds including alcohol ○ Plasmids: ■ Small circular molecules of nonchromosomal DNA ■ They aren’t essential to the cell ■ Some plasmids carry genes that confer virulence ■ Some have genes that are resistant to antibiotic which are called R (resistance) factors ● Appendages ○ Flagella ■ They are composed of a protein called flagellin and are used for motility ● Motility allows for some diseaseproducing bacteria to spread through the tissues of the body ○ Pili ■ They are present in most gram negative bacterial cells ■ Function: adhesions that anchor the bacteria to the mucus membranes ● Allows for colonization which helps establish the disease ■ They form a bridge that allows for DNA to pass from cell to cell ● Bacterial growth ○ For unicellular organisms the terms growth and multiplication can be used interchangeably ○ For multicellular organisms growth refers to an increase in the size of the individual as a unit. Whereas multiplication refers to the increase in total number of cells in an individual, but not the number of individuals ○ Growth phases: ■ Lag phase: ● When the body is first infected and the bacteria is trying to establish itself ● Represents the adaptation of the new environment for the cells. ● In this phase the immune system kills off the weak cells ○ This allows for bacteria to attack the strong cells ● The bacterial cells use their appendages to stick to the cells of the body and start to infect ● There are no symptoms at this stage ■ Exponential (logarithmic) phase: ● There is an explosion of growth ● This is where you start to see the first symptoms ■ Stationary phase: ● The growth rate slows because there is not enough nutrients for the bacterial cells so the bacterial cells slowly start to die off ● When the immune system or antibiotics start to take action ○ If the immune system or antibiotics don’t work the body will start to become overwhelmed and you stay in the stationary phase and eventually die ■ Death phase: ● The bacterial cells die at a faster rate than they are growing ● Occurs if the immune system or antibiotics kill off the bacterial cells ● Culturing bacteria: diagnostics ○ When a clinical specimen is obtained through a swab, urine or blood culture. ○ After it is obtained, it is streaked across the agar plate to aid in identification ■ Agar is a jelly like substance that comes from seaweed and allows for the production of colonies of the bacteria which make it recognizable for diagnosis ○ You can’t diagnose all bacterial infections through a culture because some take too long to grow ■ Other tests that can be done are blood tests ● Atypical bacteria ○ Mycoplasmas: ■ They are bacterial without a cell wall ■ They are the smallest type of bacteria ■ Ex: walking pneumonia ○ Chlamydiae: ■ They are obligate intracellular parasites ● They need a host to grow. They can only grow inside a cell ■ They are transmitted from person to person ○ Rickettsiae: ■ They are rodshaped bacteria ■ They are also obligate intracellular parasites ■ They are transmitted through arthropods (ticks, fleas, lice, mosquitoes, etc.) ■ Ex: typhus fever