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