Practice Exam 1A Flashcards
Epidemiology
The study of the occurrence, distribution, and control of diseases in populations.
Endemic
Always present in the population, low morbidity or death rate.
Epidemic
Infect high numbers in a localized area, technically greater than expected numbers.
Common source epidemic
Sudden increase in the number of cases (i.e. food poisoning).
Host to host epidemic
Slow rise as it presents from person to person
Host to host transmission
I catch it directly from you or the air (e.g. respiratory viruses, STD’s, skin pathogens)
Indirect host to host transmission
A vector is needed.
Pandemic
Spread to multiple continents.
Incidence
new cases over time, often per year.
Prevalence
Percent or proportion of population infected at one point in time.
Morbidity
Incidence of deaths in a population.
Mortality
of deaths in a population.
Comorbidity
Other diseases in the same patient.
Nosocomial infection
Hospital based infection.
What are the main causes for the re-emergence of disease?
New infections (e.g. new viruses), old infections (e.g. infections that have been around, but recently identified), re-emergent infections (e.g. TB is reemerging & is becoming drug resistant), travel, longer lifespans, immunosuppressants, public health breakdown (e.g. vaccine shortages), natural disasters/sanitation/stress.
What is the incubation period in the stages of an infectious disease?
It is the initial stage of infection when the host is asymptomatic.
What is the pandromal period in the stages of an infectious disease?
It is the period when the first signs and symptoms appear.
What is the acute period in the stages of an infectious disease?
It is the period of invasion or illness, symptoms are full force.
What is the decline period in the stages of an infectious disease?
It is the period when the illness is declining.
What is the convalescent period in the stages of an infectious disease?
It is the period when health is being returned.
Vector
Something that transmits disease.
Carrier
Person who is infected, yet has no symptoms.
Reservoir
Animate or inanimate sources of disease.
Fomite
Inanimate object that can transmit disease.
Opportunistic infections
Infections caused by normal flora in the wrong place at the wrong time.
Strict infections
Never part of flora. Presence is always bad. For example, Mycobacterium tuberculosis is never part of normal flora, it is always bad.
Antiseptics
Works against infection by destroying or inhibiting microbes on skin or mucus membranes.
Disinfectants
Kill most, but not all microbes. NOT for use on patients, except alcohol which may be used on skin. Does NOT kill spores.
What organism serves as a standard intermediate indicator of the effectiveness of a disinfectant?
Mycobacterium tuberculosis
What is the major way that antiseptics differ from disinfectants?
Antiseptics can be applied to living tissue.
Sterilants
Used to kill ALL microbial forms, even spores.
Describe the lag phase in bacterial growth.
When bacterial begin dividing.
Describe the log/exponential phase.
When bacteria grown and divide with a doubling characteristic. Bacteria increase to 2n, n = # of generations (doublings).
When can you calculate generation time in bacterial growth?
In the log/exponential phase.
Describe the stationary phase of bacterial growth.
Bacteria stop growing.
Describe the death phase of bacterial growth.
Bacteria die.
Bacteriostatic agents.
Stop division of bacteria. They do NOT directly kill bacteria, they just stop them from dividing.
Bactericidal agents.
Directly kill bacteria.
Bacteriolytic agents.
Directly kill bacterial via lysis or breakdown of microbes.
Physical sterilization.
Moist or dry heat (e.g. autoclave), filtration, UV or ionizing radiation
Gas sterilization.
Highly efficient for sterilizing heat sensitive materials. Ethylene oxide is a commonly used gas sterilant, but it has limited use, because it is flammable, explosive, and carcinogenic to lab animals.
Chemical sterilization.
Using chemicals for sterilization (e.g. 2% glutaraldehyde or chemiclave)
2% Glutaraldehyde
Often used for cold sterilization. Alkylate DNA and proteins.
Chemiclave
Uses a chemical solution of alcohol and formaldehyde. Requires little water. It is quicker than an autoclave and sterilization pouches stay dry.
What are the proper time, temperature, and pressure for autoclaving?
250°F (121°C) for 15-20 minutes at 15 psi.
What is the best way to verify heat sterilization?
Use a biological indicator, such as bacterial spores.
Do gram negative or gram positive bacteria produce spores?
Gram positive bacteria only.
What are the main genera of gram positive bacteria that produce spores?
Bacillus and Clostridium
Are spores produced for survival or reproduction?
Gram positive bacteria produce spores for survival only.
What types of bacteria are highly resistant to disinfections, heat, stress, and oxidation?
Gram positive bacterial spores (i.e. Bacillus and Clostridium). This makes spores a good biological indicator to verify heat sterilization. An inadequate autoclave cycle can be detected by using bacterial spores.
What is the mechanism of action for quaternary ammonium?
Quaternary ammonium is a cationic compound that functions as a low level disinfectant, which denature cell membranes. It is used as a skin antiseptic. Down falls to this disinfectant: many viruses survive, all spores survive, and Pseudomonas can grow in a solution of quaternary ammonium.
What is the mechanism of action for hydrogen peroxide?
Hydrogen peroxide is an oxidizer that forms hydroxyl radicals. It is used as a disinfectant (>3%) or a sterilant (>25%). At high concentrations hydroxyl radicals oxidize tissues → tissue damage.
What is the mechanism of action for phenols?
Phenols disrupt enzymes/denature proteins. They are rarely used. However, low concentrations are found in many mouthwashes.
What is the mechanism of action for formaldehyde?
Formaldehyde is an alkylating agent that alkylates proteins and nucleic acids. When dissolved in water for a final concentration of 37% solution is called formalin.
What is the mechanism of action for bleach?
Bleach is an oxidizing agent that serves as a high level disinfectant. It has corrosive properties that are damaging to stainless steel.
Is pasteurization a disinfectant or sterilant?
It is a disinfectant only.
Define virulence.
The ability of a microbe to cause disease.
Define pathogenicity.
The likelihood that an infected person will show clinical symptoms.
Define infectiousness.
The number of exposed patients who become ill.
Define LD50.
The number of cells needed kill half of the animals in a test group. Lethal Dose of 50% = LD50. This is a measure of virulence.
Define attenuation.
The weakening of an organism.
