180 infection Flashcards
A microorganism is: 3 things
• an organism too small to be seen without the aid of a microscope
Size smaller than 0.1 mm or 100 um
• relatively simple in structure and often unicellular (single celled); also called a “microbe
The four groups of microorganisms are:
(Protozoa, Fungi, Bacteria, Viruses)
protozoa, 2 key features
-Protozoa are unicellular creatures that are able to move either by flagella or amoeboid (pseudopods) motion
-Each cell has a nucleus and is enclosed by a plasma membrane.
-Protozoa live in water and soil and feed on bacteria and small particles.
-Some protozoa live in our bodies without causing any harm but a few are responsible for disease
2 types of protozoa
(Parasites, Amoebae)
parasites 2 examples and they move by what
Giardia lamblia, Trichomonas
flagella
Giardia lamblia
• Most common protozoa in Canada
• Found in lakes, streams and rivers
• Locomote by flagella and attach to intestinal wall by two sucking discs
• Infection results in giardiasis or “beaver fever”
Trichomonas vaginalis
Sexually transmitted parasite
• Found clinically in urine and vaginal swabs
• Locomote by flagella
• Amoebae example and movement
Entamoeba histolytica
Entamoeba histolytica
• Predominantly infects humans causing amoebiasis
• Only 10-20% of people will exhibit symptoms; symptoms can include bloody diarrhea and abdominal pain
• Found in water and contaminated foods
• Prevention through improved sanitation
Fungi, 3 key
• Can be single celled or complex multicellular organisms
• Nucleus and rigid cell wall
• Divided into yeasts and moulds
yeast: 3, type or repro
• unicellular
• asexual budding reproduction
• Infections include: oral thrush or vaginal yeast infections caused by Candida sp.
moulds key 3
• multicellular structures
• Asexual hyphae reproduction
• Infections include: Athlete’s foot and ringworm
bacteria 4 key, where often found /?
• Unicellular; rigid cell wall
• No organized nucleus
• Found everywhere there is moisture and nutrients
• Can cause infections
virus 2 key
• Requires a host for survival (obligate intracellular parasites)
• Contain only one type of nucleic acid (DNA or RNA)
• Very tiny
• Rely on host for ability to reproduce
• Viruses cannot multiply in the non-cellular environment and do not grow in foods, water, bacterial culture media, or medications.
virus composed of 3
of nucleic acid, protein coat and sometimes lipids/ envelope
envelope - virulence
• Lipid envelope ↓ virulence (easier to kill) with disinfectants
treatment for the 4 micor
• Protozoal infection = antiprotozoal drug
• Fungal infection = antifungal drug
• Bacterial infection = antibiotic
• Viral infection = antiviral
size of micor
protozoa 15-10
fungi 5-10 um
bacteria 0.3-5
virus 0.02-0.2
shape of bacteria is maintained by
rigid cell wall
3 shapes of bacteria
Cocci = round/spherical shaped
Bacilli (Rods) = rectangular shaped boxes
Spirilla = curved or spiral shaped
gram stain
• Developed in 1884 by Hans Christian Gram
• Allows bacteria to be easily viewed under a microscope
• Bacteria can be divided into two groups based on their ability to take dye in during staining process
• Gram Positive = Purple (or bluish-black)
• Gram Negative = Pink/ Red
3 reasons for gram stain
• First step in bacterial identification
• Aids doctor’s decision on course of antibiotics and appropriate disinfectant to use
Bacterial Endospores happen in which bacteria
gram positive rods
spores can 3 key
• Occur in a few types of gram positive rods
• Spores can live for months or years without nutrients or moisture
• Spores are resistant to heat, cold and disinfectants
vegetative vs endospore
• Vegetative Cell= actively growing and multiplying bacterial cells, do not contain endospores
• Endospore = dormant form of bacteria able to withstand environmental extremes
sporulation vs germination
• Sporulation=production of endospores, Sporulation takes place when certain nutrients are depleted. One copy of the genetic material and a tiny amount of cytoplasm is enclosed by a layer of insulating material and the whole structure is covered with several compact layers of spore coat
• When a favorable environment occurs the endospore can germinate and become active again
• Germination: A “viable” endospore is one able to germinate (grow) into a vegetative cell when moisture and nutrients are provided. One spore will germinate into one vegetative bacterium.
• Important virulence factor
• Two primary components of an endospore:
1) One copy of genetic material
2) Outer protective spore coat
endospore sterilization , 2 key
- Endospores are quite resistant to heat. Most vegetative bacteria are killed by exposure to moist heat at 60 – 80°C for 10 minutes but spores will survive these high temperatures. Some spores are killed by boiling but others require a temperature of 121°C for 12 - 15 minutes for destruction.
- Endospores are more resistant to disinfectants than vegetative bacteria. Low level disinfectants may not kill endospores and high-level disinfectants require extended exposure times
1.4 Binary Fission, what it is and steps
• Process of bacterial cell reproduction
-elongation, DNA replication, polar attraction, separation by a cell wall
generation time and slow vs fast
• Generation Time = time required for binary fission to occur and the population to double, affected by temperature and available nutrients, related to the rate at which bacteria cause disease.
Rapidly growing bacteria have a generation time of 15-30 minutes
Slow growing bacteria can have a generation time of 12-24 hours (or more!)
colony
The generation time also determines the amount of time required for bacteria to form visible growth on culture media. A “colony” is a visible mass of bacteria that develops on the surface of a solid culture medium after a period of time and represents all the descendants of a single bacterial cell.
Bacterial Growth Curve
lag, log, stationary, death, convalescnece for humans
lag
• Bacterial cells adapting to new environment
• Usually a few hours (2)
• LAG = no symptoms (incubation of organism)
log
• Maximum growth period where all cells are dividing at a constant rate (exponential growth)
• Symptoms = Acute stage of infection
• If left out of control patient would die during this phase
stationary
• Exhaust in supply of nutrients therefor halting growth
• Bacterial end products accumulate and prevent further growth
• Number of live bacteria stays constant
• Symptoms = no worse at this stage but no sign of recovery
death
• Death of bacteria, not host
• Bacteria start to die quickly
• Endospore formation occurs at this time, survive the longest
• Symptoms subside and recovery starts.
CONVALESCENCE STAGE
• Patient experiences complete recovery during this stage
• Can occur over a short period of time or a long period of time
virus replication lots steps 8:
• Virus locates matching host cell receptor on cell surface and attaches to cell
• For the Adenoviruses causing colds, the complementary sites are located on epithelial cells of the respiratory tract while the HIV virus which causes AIDS attaches to receptor sites of specific white blood cells called lymphocytes
• Once the virus attaches to the receptor, the host cell welcomes it inside (engulf/endocytosis)
• Cell realizes intruder presence and breaks down the protein coat of the virus, releasing free floating genetic material
• Viral DNA or RNA heads to host cell nucleus for replication
• Host cell enzymes and metabolic pathways hijacked for use by virus
• Viral proteins are produced in cytoplasm
• Viral DNA/RNA produced in the nucleus
2 effects of virus on cell host
• Cell death
-Viral replication until host cell bursts (lyses)
-Destruction of virus infected cell by body’s immune system (lymphocytes)
• Oncogenic tumor cell (oncogenic viruses, ex Hep B)
-Infect but do not kill the host cell
-Virus establishes long term/persistent infection
-Alters the cell’s genetic material to create a tumor cell
how to control viruses, 2 antiviral ex
• NOT ANTIBIOTICS: Antibiotics have no effect on viral replication. This is because antibiotics are directed against metabolic pathways of bacteria and since viruses have no metabolic activities of their own, antibiotics provide no antiviral activity
• Hard to find drugs to target viral replication that won’t kill the host cell
• Examples of antivirals:
Acyclovir – controls genital Herpes, Zidovudine (ZDV) – control HIV virus
generation time is affected by
temp and nutrients
lytic cycle vs lysogenic cycle
The lytic cycle involves the reproduction of viruses using a host cell to manufacture more viruses; the viruses then burst out of the cell. The lysogenic cycle involves the incorporation of the viral genome into the host cell genome, infecting it from within
What about its target makes HIV such a dangerous virus to humans
targets lymphocytes, immune cells
Normal Flora
• Established bacterial populations (skin/mucous membranes)
• Do not cause disease under normal circumstances
• Can cause disease if balance is interrupted
• Line of defense
• Help break down food/ digestion and evacuation
• most people basically have the same normal flora in the mouth. However, the normal flora composition varies depending on the site: normal flora of the mouth is different from normal flora of the intestine or the skin
area of the body having the greatest normal flora population
lrg intestine
normal flora in the upper resp do whar
occupy attachment sites on host cells and prevent pathogenic bacteria from invading respiratory tissue
flora and babies
• Placental barrier prevents microbial penetration
• Babies born with little-no normal flora
• Exposed to bacteria through:
birth, touch, milk, environment
where does normal flora establishes 4 key
• skin and mucous membranes lining the gastrointestinal, respiratory, and genital tracts.
