Micro Biology Lab Quiz 3 Ames Test - Epidemiology
psychrotrophic
20'C to 30'C
mesophilic
25'C to 40'C
thermophilic
45'C to 65'C
Dis-diffusion method
A petri plate containing nutrient agar is inoculated uniformly. Paper disks impregnated with various antimicrobial are placed on the agar surface. The antimicrobial agents diffuse from the disks from an area of HIGH concentration to an area of LOWER concentration.
Disinfectants
Chemical agents used on inanimate objects to lower the level of microbes on their surfaces
biological transmission
a diseases transmitted by an insect bite ex: malaria by mosquitoes
mutagens
a physical or chemical agent that alters the nucleotide base sequence of DNA
Ames spot test
a screening technique to identify high-risk compounds that must be tested for carcinogenic potential. Use impregnated disks with mutagens and can test multiple suspected mutagens.
During the Ames Test
a small sample of the test chemical (a suspected mutagen) is placed on the surface of glucose - minimal salts agar (GMSA) seeded with the lawn of the Salmonella auxotroph. (a small amount of hisitidine allows all the cells to go through a few divisions). If certain mutations occur, the bacteria may revert to a wild type, a prototroph, and grow to form a colony. Only bacteria that have mutated (reverted) to his+ (able to synthesize histidine) will grow into colonies.
Antibiotics
a substance that is antibiosis, against life, and is produced by a microorganism that inhibits other microorganisms.
droplet infection
a type of direct contact, in which microorganisms carried on liquid drops from cough or sneeze
psychrophilic
about 0'C to 20'C
hyperthermophilic
about 80'C or higher and by the presence of heat-resistant endospores
antimicrobial drugs
antimicrobial chemicals that are used internally, whether natural (antibiotics) or synthetic
carcinogens
any agents that is directly involved in causing cancer
communicable diseases
can be spread either directly or indirectly from one host to another
genotoxic
can cause mutations, which can result in cancer
noncommunicable diseases
cannot be transmitted from one host to another
bacteriostatic agents
causing temporary inhibition of growth
Antiseptics
chemical agents used on living tissue to decrease the number of microbes
Antimicrobial agents
chemicals that control the growth of microbes.
epidemiologist
compiles data on the incidence of a disease and its method of transmission and tries to locate the source of infection to decrease the incidence
Moist Heat
denatures enzymes more efficiently due to transfer of heat energy from moisture. Methods of moist heat: Pasteurization—temperature is maintained at 63°C for 30 minutes or 72°C for 15 seconds. Boiling—temperature is maintained at 100°C for 10 minutes to kill vegetative bacterial cells but does NOT inactivate endospores. Autoclaving—uses steam under pressure for sterilization, usually kills endospores. Standard conditions are 15 psi at 121°C for 15 minutes.
Dry Heat
denatures enzymes, dehydrates microbes, and kills by oxidation effects. Methods of dry heat: Hot-air ovens Incineration (i.e. flaming loops) a standard application of dry heat in a hot air oven is 170'C for 2 hours
Minimum inhibitory concentration (MIC)
determined by testing for bacterial growth in diffusion and can be correlated with zones of inhibition and compared to Table 1. on pg. 141
Pathogen
disease causing agent clinicians must isolate the pathogen and determine its sensitivity to antimicrobial agents practitioners must follow the dosage treatment to be aware of resistant forms of the organism that may occur
fomites
disease transmission by contact with contaminated inanimate objects ex: drinking glasses, bedding, and towels
rfa mutation
eliminates a portion of the lipopolysaccharode that coats the bacterial surface. This mutation increases the cell wall permeability; consequently, more mutagens enter the cell
optimal growth ranges
heat sensitivity is genetically determined and reflected in this..
carrier
humans who harbor pathogens but do not exhibit signs of the disease
secondary cases
infected family members
cold temperatures
inhibit microbial growth
vectors
insects and other anthropods that carry pathogens and transmit diseases from one host to another
mechanical transmission
insects carry a pathogen on their feet and transfer the pathogen to a person's food ex: houseflies and typhoid
mutagens or carcinogens
many chemicals are not these but are converted to mutagens in Vivo by liver enzymes
direct contact
means between hosts
Use-dilution Test steps
metal rings are dipped in bacterial cultures, metal rings placed into the disinfectant solution at the recommended concentrate, and rigs are then transferred to nutrient medium for the growth of surviving bacteria
heat kills
microbes
uvrB mutation
minimizes repair of mutations; as a result, the bacteria are much more sensitive to mutations
Ames test
most chemicals that have been shown to cause cancer in animals have proven mutagenic in this test
case definition
one of the first steps in analyzing a disease outbreak, it should include the typical symptoms of patients included as cases in an outbreak investigation
Sporadic
refers to a disease that occurs infrequently and irregularly
Pandemic
refers to an epidemic that has spread over several countries or continents, usually affecting a large number of people.
Epidemic
refers to an increase, often sudden, in the number of cases of a disease above what is normally expected in that population in that area when many people in a given area acquire the disease in a relatively short period of time
Endemic
refers to the constant presence and/or usual prevalence of a disease in a population within a geographic area a disease with presence in a population at relatively constant levels
bactericidal agents
result in bacterial death
Kirby-Bauer test
standardized methods for agar diffusion
Salmonella enterica Typhimurium
the ames test uses autotrophic strains of...
Zones of inhibition
the clear area surrounding an impregnated disk as means of measuring sensitivity. Zone size is affected by diffusion rate of the antimicrobial agent and the growth rate of the organism.
reservoir
the continual source of an infection
morbidity
the diseases and illness, injuries and disabilities in a population
index case
the first reported patient in a disease ooutbreak
Thermal death time (TDT)
the length of time required to kill all bacteria in a liquid culture at a given temperature.
mortality
the number of deaths within a specified period among people have a particular disease
epidemiolgy
the science that deals with when and where diseases occur and how they are transmitted in the human population
American official analytical chemist's use-dilution test
the standard method for measuring the effectiveness of a chemical agent
Thermal death point (TDP)
the temperature required to kill all bacteria in a liquid culture in 10 minutes.
Decimal reduction time (DRT)
the time, in minutes, in which 90% of a population of bacteria at a given temperature is killed.
container size, cell density, moisture content, pH, and medium composition
these can all affect heat sensitivity of organisms
Salmonella enterica Choleraesuis, Staphylococcus aureus, and Pseudomonas aeruginosa
these three strains of bacteria are used in the use-dilution test
epidemic curve
visual representation of outbreaks magnitude and time trend
information from a epidemic curve
where are you in the course of the epidemic and project its future course understand the incubation time and estimate the time of exposure (locate the index case)
extreme temperature
widely used to control the growth of microbes
an effective antimicrobial agent
will inhibit growth