WorksheetsNatural Host-Microbe Interactions & Counting Microbes
Total questions: 28
Worksheet time: 30mins
Exposure to bacterial pathogens may lead to disease in the host. What is the correct order of the occurrences?
disease, infection, contact
contact, disease, infection
contact, infection, disease
infection, disease, contact
The ID50 of a pathogen is the number of microorganisms required to:
infect 50% of the hosts
benefit 50% of the hosts
cause disease in 50% of the hosts
immunise 50% of the hosts
kill 50% of the hosts
Organisms that cause disease when the body's defences are lowered are called?
parasites
commensals
transient flora
opportunists
colonisers
Which of the following factors influences the ability of a microorganism to cause disease?
the virulence of the organism
the nutritional state of the host
method of transmission of the pathogen
the immune status of the host
all of the above
Which of the following site/s should be sterile in healthy individuals?
the eyes
the stomach
the lower respiratory tract
the upper respiratory tract
You are studying the growth of E. coli by inoculating a small amount of culture into a new type of growth medium. You take measurements of turbidity at 20 hours and 24 hours. You observed that turbidity levels are exactly the same. Which phase during the bacterial growth curve do you think the data are best described by?
the lag phase
the log phase
the stationary phase
the death phase
not enough information to conclude results
Which factor prevents the stomach from being colonised by most microbes?
peristalsis
digestive enzymes
secretory immunoglobulins
bile
acids
Which of the following is an indirect bacterial counting method?
counting cells under the microscope
counting colonies from a drop plate
counting colonies from a spread plate
comparing turbidity of cultures against McFarland Standards
none of the above is indirect because all are direct methods
You are growing E. coli in the lab from an inoculum consisting of 1 bacterial cell. How many cells will you have at the end of 5 generations of bacterial divisions?
5 cells
10 cells
8 cells
16 cells
32 cells
What gram-positive bacteria predominantly live on the skin?
corynebacteria
propionibacteria
straphylococci
malssezia
flavobacteriales
What is the microflora of the skin influenced by?
weather
age
hygiene
low moisture
sugar
What bacteria colonise the upper respiratory tract?
staphylococci
streptococci
haemophilus
diphtheroid
pseudomonas
What bacteria colonises the lower respiratory tract?
staphylococci
streptococci
haemophilus
diphtheroid
none of these answers
What genus of bacteria is present in the large intestine?
Clostridium
Bacteroides
Streptococcus
Planomerista
Which organs are sterile?
bladder
kidneys
urethra
reproductive organs
What are the main bacteria that are colonised in the reproductive organs?
Lactobacillus
E. coli
Candida spp.
Proteus spp.
T or F. The NRF prevents colonisation of potential pathogens
true
false
T or F. Some antibiotics prescribed for an infection will also inhibit pathogen growth on the NRF
true
false
What are the steps of an infection?
exposure, adherence, invasion, infection
adherence, invasion, exposure, infection
exposure, infection, invasion, adherence
infection, invasion, adherence, exposure
What is an endogenous infection?
source from host itself - cause infection when displaced to susceptible site
from external environment - many pathogens passed from person to person
passed from mother to child
What is a congenital infection?
passed from mother to child
source from host itself
from external environment
T or F. Opportunistics are microorganisms that would not normally cause infection resulting in disease
true
false
T or F. Parasites are when one organism benefits and the host benefits
true
false
T or F. Enterococcus faecium is a gram-positive bacteria that is drug-resistant to vancomycin & penicillin and is also considered a superbug
true
false
Define virulence
measurement of pathogenicity
when organism is lost/decreased
ability to cause disease
damage to the host
Define attenuation
when virulence of organism is lost/decreased
ability of microorganisms to cause disease
influence of host and environmental conditions
degree of damage to host cell
T or F. A decrease in ID50 leads to less pathogenic microorganisms
true
false
What are the host risk factors?
age
stress
diet
compromised host
lack of sleep
