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Chapter 14: Principles of Disease and Epidemiology

Terms in this set (55)

normal vs. transient flora
- normal: microbiota that permanently colonize the host
- transient: microbiota that colonize the host for a short duration
what is microbial antagonism?
- competition between microbes
- germ-free animal gets infected by 10 rods of E. coli while normal animal gets infected by 1,000,00
why is Clostridium difficile a problem in nosocomial settings?
many patients in the hospital are on antibiotics, making their normal flora # go down making them more susceptible to diseases
how is FMT used to treat C. diff?
FMT is used to treat infection by giving the patient new fecal material from a healthier biome in order to enhance their own
define and provide an example of commensalism
- symbiotic relationship where one organism benefits
- Staphylococcus epidermitis bacteria on the skin
define and provide an example of mutualism
- symbiotic relationship where both organisms benefit
- E. coli creates vitamin K and B while we house it
define and provide an example of parasitism
- symbiotic relationship where one organism benefits at the expense of the other
- influenza virus
what are opportunistic pathogens?
- pathogens that cause disease when in a specific environment
- Canidia albicans: yeast infections of the vagina
What is Koch's postulates?
used to prove cause of infectious disease

1. same pathogen must be present in every case
2. pathogen must be isolated and grown in a pure culture
3. pathogen must cause disease in healthy organism
4. pathogen must be isolated in healthy animal and shown to be in the original organism
exceptions to Koch's postulates
- some pathogens can cause several disease conditions
- some pathogens can only cause disease in humans
- some are hard to grow in pure cultures
- multiple organisms can cause the same disease
difference between signs and symptoms
- signs: an objective change in the body that can be measured or observed as a result of disease (swelling, fever, vital signs)

- symptoms: a subjective change in body function that is felt by the patient as a result of the disease (pain, fatigue)
define and provide an example of a communicable disease
- a disease that is spread from one host to another
- colds, flu, whooping cough
define and provide an example of a contagious disease
- a disease that is easily spread from one host to another
- measles, chickenpox
define and provide an example of a non-communicable disease
- a disease not transmitted from one host to another
- tetanus, botulism
sporadic disease
disease that occurs occasionally in a population
endemic disease
disease that is constantly present in a population
epidemic disease
disease acquired by many hosts in a given area in a short time
pandemic disease
a worldwide epidemic
acute vs. chronic disease
- acute: symptoms develop rapidly, easier to treat
- chronic: develops slowly, harder to treat
subacute disease
diseases that cause both acute and chronic symptoms in a host
latent disease
a disease that cause periods of symptoms and periods of no symptoms
herd immunity
- immunity in most of a population
- develops from people overcoming the disease and vaxx
differentiate between local, systemic, and focal infections
- local: pathogens are limited to a small area in the body
- systemic: pathogens cause infection throughout the whole body
- focal: systemic infection that began as a local infection
bacteremia vs. septicemia
- bacteremia: the presence of small numbers of bacteria in the blood
- septicemia: the growth of bacteria in the blood
primary vs. secondary infections
- primary: acute infection that causes initial illness
- secondary: opportunistic infection after primary infection compromises host (pneuomnia in elderly after flu)
predisposing factors for acquiring an infection
- predisposing factors make the body more susceptible to disease
- short urethras in female could cause more UTI contractions
- sickle-cell gene more susceptible to pneumonia, blood infection, etc.
- chemotherapy
What are probiotics? give examples
- live microbes applied to the body intended to exert a beneficial effect
- Lactobacillus, E. coli
list and define stages of disease development
- incubation period: first stage of infection with no signs or symptoms
- prodromal period: mild signs and symtpoms
- period of illness: peak of infection, most severe signs and symptoms
- period of decline: still showing signs and symptoms, but not as severe
- period of convalescence: lowest level of signs and symptoms, no more
At what stage are individuals infectious to others?
any stage, depends on infection
reservoir of infection
continual sources of infection
human reservoir
AIDs, gonorrhea
animal reservoir
rabies, lyme
nonliving reservoir
botulism, tetanus, cholera, typhoid
contact transmission
- direct: close association between infected and susceptible hosts, handshakes, influenza, rabies
- droplet: transmission via airborne droplets (< 1 m), coughing or sneezing, pneumonia
- indirect: spread fomite (inanimate objects), on surfaces, MRSA
vehicle transmission
- inanimate reservoirs: food, water, soil, blood, shigellosis, salmonella
- airborne: transmitted via droplets farther than 1 m, staphylococci and streptococci
Vector transmission
- animals that carry pathogens from one host to another
- mechanical: arthropod carries pathogen passively on feet
- biological: pathogen reproduces in vector
what are nosocomial infection?
infection acquired as a result of a hospital stay
"perfect storm" for nosocomial infections
- microorganisms in the air from sick patients
- compromised host
- chain of transmission via healthcare workers
nosocomial infection and opportunistic microorganism
patients in the hospitals are already compromised and many are on antibiotics which lower their normal flora numbers making them more susceptible to infection; opportunistic pathogens take this as a chance to infect
How can nosocomial infections be prevented?
- washing hands before seeing patients
- washing hands overall
- improvements with single-use sterile equipment
- improved disinfection criteria
- decrease the use of immunosuppressive drugs
- have infection control committee at the hospital
identify the frequency of different types of nosocomial infections
- UTIs: 32%
- surgical site infections: 22%
- other, skin infections: 17%
- lower respiratory infections: 15 %
- bacteremia caused by IV catheterizations: 14%
what organism is responsible for nearly half of all nosocomial diarrhea
Clostridium
Gram (+) organisms associated with nosocomial infections
Coagulase (-) Staphlococci, S. aureus, Enterococcus
Gram (-) organisms associated with nosocomial infections
E. coli, Pseudomonas aeruginosa
MRSA vs. VRSA
- MRSA: Methicillin Resistant Staphylococcus aureus
- VRSA: Vancomycin Resistant Staphylococcus aureus
what is the first organism that infants encounter as they pass through the vagina?
lactobacillus
what are emerging infectious diseases?
diseases that are increasing in incidence or showing a potential to increase in the near future
reasons for emerging infectious diseases
- evolution of new strains
- inappropriate use of antibiotics and pesticides
- changes in weather
- modern transportation
- ecological disaster
- public health failure
descriptive epidemiology
collection and analysis of data regarding occurrence of disease
analytical epidemiology
comparison of a disease group and a healthy group
experimental epidemiology
study of a disease using controlled experiments
case reporting
healthcare workers report specified disease to local, state, and national offices
morbidity vs. mortality
- morbidity: incidence of a specific notifiable disease
- mortality: deaths from notifiable diseases
examples of notifiable diseases
- plague
- measles
- malaria
- influenzae
- lyme disease
what is the main source for epidemiological information in the US?
Centers for Disease Control and Prevention (CDC)
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