Intro to microbiology Flashcards
What are the 3 domains of life?
Archaea, Bacteria, and Eukarya
What are the differences between prokaryotes and eukaryotes?
- presence of nucleus
- structure of ribosomes
- enzymes involved in DNA replication/RNA synthesis
What eukaryotes cause disease?
Fungi, protazoa, parasitic worms (helminths), ectoparasitic arthopods
What are the two classifications that make up the scientific name of an organism? Which one is capitalized?
genus and species
genus is capitalized
What is the name of microbes living in and on our bodies? Where on our bodies do they live? What is the name of their collective genome?
microbiota
skin, nares, oral cavity, intestines, and genitourinary tract
microbiome
What are the possible shapes of bacteria and what are their names (singular and plural)?
- spheres [cocci (pl.) coccus (sing.)]
- rods [bacilli (pl.) bacillus (sing.)]
- spirals [spirilla (pl.) spirillum (sing)]
- slightly curved rods (vibrios)
- flexible spirals [spirochaetes]
- short rods [coccobacilli]
What is the name for bacteria that adopt multiple shapes?
pleomorphic
What are the typical bacterial arrangements and their names?
diplococcus or diplobacillus (two cells), streptococcus or streptobacillus (chains), and staphylococcus (clusters)
What is the typical size range of bacteria? What instrument are they visible with?
0.2-0.5 micrometers
light microscope
What are plasmids? What do they frequently carry?
Extrachromosomal genetic material often required for virulence 1. genes for antibiotic resistance 2. genes for adherence to host cells 3. toxin genes
Name the difference in bacterial and eukaryotic organelles
Bacteria–> no ER, Golgi, or lysosomes
bacterial ribosomes = 70S
eukaryotic ribosomes= 80S
Name of bacterial cell asexual reproduction
Binary Fission
Gram Staining Characteristics:
color after staining, membrane components
Why is this an important identification?
Gram positive:
- purple after staining
- cell wall peptidoglycan (thicker)
- teichoic acids
Gram negative:
- pink after staining
- cell wall peptidoglycan (thinner)
- outer membrane–> (outer half) lipopolysaccharide (LPS) (inner half) phospholipids
Important to know when determining treatment plan.
Accumulation of this protein can cause septic shock during an infection by a gram negative bacteria. Why does this happen?
LPS
excessive inflammatory response
What is the name of proteins on the outside layer of gram negative bacteria that for pores or channels? What is their function?
porins
small molecules can diffuse passively
What is the procedure used to identify organisms resistant to Gram staining. Name an example of an organism that would require this type of identification.
Acid-fast
use to identify bacteria with waxy cell wall
Mycoplasmas– lack a cell wall
Mycobacterium tuberculosis (causal agent TB)
Describe a bacterial capsule. What is its purpose?
gelatinous layer that surrounds bacterium composed of mainly polysaccharides
inhibits phagocytosis
What are protein fibers that rotate and allow bacterial cell to move through fluids?
flagella
What are proteinaceous rod-like structure on surface of bacteria that allow adherence to various surfaces? Why are they important?
Pili (sing. pilus)
Important for colonization and initiation of infection
In what conditions would bacteria produce spores/endospores?
Describe the structure of spores and to what they are resistant.
What are medically relevant bacteria that form spores?
When nutrients such as C or N are scarce and allows the bacteria to remain dormant for years
Spores have thick multilayer coat, highly dehydrated, contain bacterial DNA with small amounts cytoplasm. They are resistant to heat, chemicals, and desiccation.
When favorable conditions return, the bacteria reconvert to metabolically active cells.
Example: Clostridium (tetanus and botulism) and Bacillus (anthrax)
What is a biofilm? Where do they grow?
communities of bacteria embedded in a polysaccharide matrix that adhere to a surface
mucosal surfaces, teeth, implanted devices, catheters
What is the name for bacterial that only replicate inside the host cell? What is an example of this type of bacterai?
obligate intracellular parasites
Example: Chlamydia
What is the name of bacteria that have complex nutritional requirements?
nutritionally fastidious
What does it mean for a bacteria to be a:
- strict anerobe
- strict/obligate anaerobe
- facultative anaerobes
- microaerophile
- oxygen must be present for the organism to grow (divide)
- cannot grow in the presence of oxygen
- can grow whether or not oxygen is present
- grow best at low oxygen concentration
What is a unique ability of strict anaerobes and facultative anaerobes?
the ability to ferment sugars, producing acids as a by-product
What conditions are important for bacterial growth? What are mesophiles?
temperature and pH
bacterial that can grow between 25-40 degrees celciius
What is the typical pH conditions that medically relevant bacteria are able to grow? What is an example of a bacteria that is an exception to this rule?
pH 7.2-7.4 Helicobacter pylori (causal agent or gastric ulcers) grows in the stomach (low pH)
Why is it important to know environment and nutrient requirements of an organism?
so that clinical specimens are cultured under the appropriate conditions
What is a selective component in bacteria cultures? What is an example?
have components that inhibit the growth of some organisms but not other
bile salts inhibit the growth of gram positive organisms but not gram negative
What is the name of visible bacterial masses found on solid media cultures?
colonies
What are differential media cultures? What is an example?
contain an indicator
a dye the changes color due to metabolic activity,
What are the criteria through which most medically important bacteria are identified?
morphology, staining properties, cultural requirements, and biochemical properties
What is the study of fungi called? Fungal infections?
mycology and mycosis
What are the qualities of media cultures intended to promote fungal growth?
inhibit bacterial growth
– acidic pH or addition antibiotics
What are the three components of fungal cell membrane?
Name the major identifiable difference between mammalian and fungal cell membranes.
lipids, glycoproteins, and sterols
fungal sterol: ergosterol
mammalian: cholesterol
What are the components of fungal cell walls?
carbohydrates (chitin, mannan, glucan)
What is the name for fungal asexual reproductive spores? Do fungi always reproduce asexually?
conidia
no, they also reproduce sexually
Name the major differences between yeasts and molds:
Yeast: *unicellular *spherical/ovoid form *2-5 micrometers *divide forming buds (daughter cells) *identified through fermentation and assimilation of carbohydrates
Molds
- multicellular–> colony = mycelium
- part of mycelium grows into medium to provide nutrients to aerial hypae forming a “fuzzy” outgrowth
- identified through color and texture of colonies as well as the specialized reproductive structures
What group of people are most susceptible to fungal infections and where are the two places from which those infections usually arise?
immunosuppressed people
fungi of the microbiota or after exposure to environmental fungi
What are the four divisions of mycosis?
- superficial and cutaneous: fungus grown on body surfaces
- subcutaneous: involve subcutaneous tissue and rarely disseminate
- opportunistic: infections caused by fungi present in the environment or the microbiota that normally do not affect healthy people
- systemic or endemic mycosis: include fungi capable of infecting healthy individuals
What is the general size of protazoa? Are they multicellular or single-cellular organisms?
2-100 micrometers
single-celled
How to protozoa move?
simple cytoplasmic extrusions (pseudopods) OR
more complex structures (cilia and flagella0
What types of cells do intracellular protozoa infect?
Where are non-intracellular protozoa found?
Red blood cells, macrophages, epithelial, brain, muscle
blood, intestine and genitourinary system
Describe a protozoa cyst
produced during harsh environmental conditions
the cyst is surrounded by thick cell wall that provides protection and facilitates transmission via fecal-oral route
What are the 3 modes of transmission for protozoa?
ingestion, sexual contact, insect vector
What form of reproduction is utilized by potozoa?
Asexual inside humans
may engage in sexual reproduction inside insect vectors
What are examples of disease causing protozoa?
malaria, dysentery, chagas disease and leishmaniasis
What is the general size of helminths? What size are the larvae? Are the multi-cellular or uni-cellular?
multicellular (primitive nervous and excretory system– no circulatory system) and are millimeters to meters
larvae are 100-200micrometers
Where are helminths and protozoa most commonly fond?
tropical and subtropical regions
What are the common modes of helminth transmission?
- fecal-oral (swallowing eggs/ larva)
- ingestion larva present in tissue of another host (beef, pork, or fish)
- penetration fo skin by larva
- injection by blood-sucking insects
How do helminths attach? Where are these structures located?
hooks, suckers or teeth usually located anteriorly
How do helminth’s reproduce?
majority do not replicate within host, but release eggs in fecal material as a result of sexual reproduction
What are the two classifications of helminths? What are their characteristics?
Nematoda (round worms):
- intestinal parasites or infect blood, lymphatics or subcutaneous tissue
- hookworms have teeth (buccal plaques) to attache to intestinal wall and feed on blood
Cestoda (tapeworms)
- anterior part or scolex with hooks/suckers to attache to intestine
- segmented body
Trematodes (fluke/flatworms):
- non-segmented body
- oral and ventral suckers- attachment and migration
- schistosomes (blood flukes)= most important in terms of prevalence and severity of disease
What are the three characteristics in determining severity of helminthic infection?
size, movement and longevity
- blockage of internal organ, pressure exerted by growing parasite
- migration larval forms through body damages tissue
- host inflammatory response is often damaging
What is the exoskeleton of arthropods composed of?
chitin
What is the name for organisms the live in on or on the host’s skin from which they take their nourishment?
ectoparasite
What are the two divisions of arthropods and their characteristics? Provide examples of organisms from each classification.
Arachnids *8 legs *Example: spiders, ticks, and mites Insects *6 legs *Example: mosquitoes, flies (tsetse, sandflies), lice, fleas, deduviid bugs, and bedbugs
What is an example of an arthropod acting as a carrier?
depositing infectious agent in the environment
Example: house flies or cockroaches carrying bacterium Shigella
What is an example of an arthropod causing direct damage to the host?
human itch mite (Sarcoptes scabiei var. hominis) causes scabies
What is the name of the viral characteristic that they are only able to multiply inside living cells due to a lack fo organelles and metabolic activity?
obligate intracellular parasites
What is the size of viruses? Through which devise are they visible?
10-100 nanometers
observed through electron microscopy
What are they types of genome found in viruses?
What are the possible configurations?
DNA, ssRNA, dsRNA, ssDNA and dsDNA
linear or circular and can consist of one or more fragments
What is the name of the protein shell surrounding viral nucleic acid?
What additional outer structure is present in some viruses?
capsid
lipid outer envelope –> acquired from host cell nucleocapsid/ It contains specific viral proteins
Name and describe the three type of nucleocapsids:
Icosahedral symmetry: protein molecules are arranged in the shape of an icosahedron (polyhedron with 20 faces)
Helical symmetry: the capsid surrounds the nucleic acid int eh form of a helix or spiral to form a tubular nucleocapsid
Complex symmetry: exhibited by few families, for example, the human immunodeficiency virus (HIV)shows a pyramid-shaped central core
What are the classification criteria for viruses?
symmetry, presence/absence envelope and nucleic acid characteristics
What are infective glycoproteins devoid of nucleic acid?
prions
What is the name of the chronic diseases caused by prions?
What are their characteristics?
transmissible spongiform encephalopathies
chronic, long incubation (up to 20 yrs), fatal
What is the native and diseased identification of prion proteins? What is the cause of this change?
PrP^c (native)
Prp^Sc (diseased)
change in conformation from alpha-helical to insoluble beta-sheet structure
How does Prp^Sc replicate?
Prp^Sc replicates upon interaction with native Prp^c, changes it to the misfolded conformation, which accumulate in vacuoles in neural tissues
Prp^Sc is highly resistant to degradation and inactivation by:
heat or chemicals
What are the three ways human prion diseases are acquired?
- inheritance of mutations in the PrP gene
- spontaneous occurrence (sporadic Creutzfeldt-Jacob disease)
- acquisition through environmental exposure (medical procedures, food contaminated with bovine spongiform encephalopathy prions)
The use of physical procedures or chemical agents to destroy ALL microbial forms, including bacterial endospores
Sterilization
use of chemical agents on the skin or other living tissue to inhibit or eliminate microbes; no sporadical action is implied
Antisepsis
use of physical procedures or chemical agents to destroy most microbial forms on a material or object (bacterial spores and other relatively resistant organisms may remain viable)
Disinfection
mild heating to reduce the microbial load commonly used in the dairy and other food processing industries
Pasteurization
Sterilization method:
moist heat sterilization
autoclave
How does an autoclave work?
load is placed in double wall or jacketed chamber
stem circulates at temperature beyond boiling point of water
High temp is maintained for defined amount of time, then restored to atmospheric pressure
Sterilization method:
oven, requires prolonged exposure times and higher temperatures
describe when this would be used
Dry heat
used for glassware, some powders and oils
Sterilization method:
use with media or biologics that are sensitive to heat
describe when this would be used
Filtration
Viral-retentive filters, solutions for intravenous use (eliminate endotoxins present in cell wall gram negative bacteria)
Sterilization method:
causes DNA damage
describe when this would be used
Radiation
medical or dental products, food preservation
Sterilization method:
toxic alkylating agent of hydroxyl, carboxyl, amino and sulfhydryl groups
describe when this would be used
Ethylene oxide gas
sterilizing heat-sensitive materials, gas must dissipate after sterilization (mutagenic and explosive)
used under defined temperature and humidity
Sterilization method:
include aldehydes, hydrogen peroxide and peracetic acid
liquid chemicals
What are standard precautions taken when interacting with patients?
- hand hygiene
- respiratory hygiene/cough etiquette
- safe injection practices
- proper disposal of needles and scalpels
- Personal Protective Equipment
These supplement the standard precautions and are used when the patient is infected or suspected to be infected with a highly transmissible organism
transmission-based precautions
