6. An 8 gram sample of cream cheese was homogenised in sterile
Ringer’s solution to give a total volume of 20 cm3. The homogenate was
then serially diluted and 0.2 cm3 aliquots of a number of dilutions were
spread plated on duplicate nutrient agar plates. After incubation, the
following colony counts were recorded:
Dilution Replicate 1 Replicate 2
10-3 356 314
10-4 31 38
10-5 3 2
Calculate the average number of colony forming units per cm3 in the
homogenate.
………………………………………………………………
……………………………………………………………
………………………………………………………………
……………………………………………………………
………………………………………………………………
……………………………………………………………
………………………………………………………………
……………………………………………………………
………………………………………………………………
……………………………………………………………
………………………………………………………………
……………………………………………………………
………………………………………………………………
……………………………………………………………
………………………………………………………………
……………………………………………………………
………………………………………………………………
……………………………………………………………
………………………………………………………………
……………………………………………………………
Calculate the average number of colony forming units per gram of cream
cheese.
………………………………………………………………
……………………………………………………………
………………………………………………………………
……………………………………………………………
………………………………………………………………
……………………………………………………………
………………………………………………………………
……………………………………………………………
………………………………………………………………
……………………………………………………………
………………………………………………………………
……………………………………………………………
………………………………………………………………
……………………………………………………………
………………………………………………………………
……………………………………………………………
………………………………………………………………
……………………………………………………………
………………………………………………………………
……………………………………………………………
The following details were recorded about the growth of one of the
isolates from the cream cheese:
Colony
characteristics On Nutrient agar On Blood agar
Size
0.5-1.0 mm 0.5-1.0 mm
Shape
Smooth Smooth
Pigmentation
Translucent Transparent with narrow zone of ( haemolysis
A number of additional tests were then carried out on this isolate and
the following observations made:
Test
Observation
Methylene blue stain
Rod-shaped cells
Gram stain
Purple cells
Colony colour in reflected light
Blue-green
Ability to grow at 4єC
Yes
Motility
Tumbling motion
Identify this cream cheese isolate, explaining your reasoning in full.
………………………………………………………………
……………………………………………………………
………………………………………………………………
……………………………………………………………
………………………………………………………………
……………………………………………………………
………………………………………………………………
……………………………………………………………
………………………………………………………………
……………………………………………………………
………………………………………………………………
……………………………………………………………
………………………………………………………………
……………………………………………………………
………………………………………………………………
……………………………………………………………
………………………………………………………………
……………………………………………………………
………………………………………………………………
……………………………………………………………
………………………………………………………………
……………………………………………………………
………………………………………………………………
……………………………………………………………
………………………………………………………………
……………………………………………………………
………………………………………………………………
……………………………………………………………
………………………………………………………………
……………………………………………………………
What are the possible consequences of ingesting food contaminated with
this microorganism?
………………………………………………………………
……………………………………………………………
………………………………………………………………
……………………………………………………………
………………………………………………………………
……………………………………………………………
………………………………………………………………
……………………………………………………………
………………………………………………………………
……………………………………………………………
………………………………………………………………
……………………………………………………………
………………………………………………………………
……………………………………………………………
………………………………………………………………
……………………………………………………………
………………………………………………………………
……………………………………………………………
………………………………………………………………
……………………………………………………………
7. A 22-year-old male student was brought to the emergency room after a
2-day history of headache and fever. On the day of admission, the
patient had failed to come to school or to phone friends to explain why.
When notified of this fact, the patient’s friends had gone to his
flat, where they found the patient in bed, confused and highly agitated.
The patient was comatose when he arrived in the emergency room. Purpuric
skin lesions were present on his trunk and arms. Gram stain of
cerebrospinal fluid showed many Gram-negative diplococci, and the same
organism was isolated from blood. The patient died despite prompt
initiation of therapy with penicillin.
What is the most likely microorganism responsible for this fulminating
disease? Explain your reasoning in full.
………………………………………………………………
……………………………………………………………
………………………………………………………………
……………………………………………………………
………………………………………………………………
……………………………………………………………
………………………………………………………………
……………………………………………………………
………………………………………………………………
……………………………………………………………
………………………………………………………………
……………………………………………………………
………………………………………………………………
……………………………………………………………
………………………………………………………………
……………………………………………………………
………………………………………………………………
……………………………………………………………
What is the most likely source of this organism?
………………………………………………………………
……………………………………………………………
………………………………………………………………
……………………………………………………………
………………………………………………………………
……………………………………………………………
………………………………………………………………
……………………………………………………………
………………………………………………………………
……………………………………………………………
………………………………………………………………
……………………………………………………………
………………………………………………………………
……………………………………………………………
………………………………………………………………
……………………………………………………………
What other diseases are caused by this microorganism?
………………………………………………………………
……………………………………………………………
………………………………………………………………
……………………………………………………………
………………………………………………………………
……………………………………………………………
………………………………………………………………
……………………………………………………………
………………………………………………………………
……………………………………………………………
………………………………………………………………
……………………………………………………………
………………………………………………………………
……………………………………………………………
………………………………………………………………
……………………………………………………………
8. Forty-two people in the same town reported to their GPs with fever
(40°C), jaundice, and tender abdomen. All 42 had eaten an ice-slush
beverage purchased from a local convenience store. Liver function tests
were abnormal. Over the next several months, the symptoms subsided and
liver function returned to normal. What is the disease? Explain your
reasoning in full.
………………………………………………………………
……………………………………………………………
………………………………………………………………
……………………………………………………………
………………………………………………………………
……………………………………………………………
………………………………………………………………
……………………………………………………………
………………………………………………………………
……………………………………………………………
………………………………………………………………
……………………………………………………………
………………………………………………………………
……………………………………………………………
………………………………………………………………
……………………………………………………………
………………………………………………………………
……………………………………………………………
………………………………………………………………
……………………………………………………………
What pathogen is causing it? Explain your reasoning in full.
………………………………………………………………
……………………………………………………………
………………………………………………………………
……………………………………………………………
………………………………………………………………
……………………………………………………………
………………………………………………………………
……………………………………………………………
………………………………………………………………
……………………………………………………………
………………………………………………………………
……………………………………………………………
………………………………………………………………
……………………………………………………………
………………………………………………………………
……………………………………………………………
………………………………………………………………
……………………………………………………………
………………………………………………………………
……………………………………………………………
9. Twenty-two percent of the patients in a large hospital acquired
Clostridium difficile diarrhoea and colitis during their hospital stay.
These patients required longer hospital stays than uninfected patients.
Epidemiological studies provided the following information.
Rate of infections for patients: Single room 7%
Double room 17%
Triple room 26%
Rate of environmental isolation of C. difficile: Bed rail 10%
Commode 1%
Floor 18%
Call button 6%
Toilet 3%
Hands of hospital personnel after contact with patients that were
culture-positive for C. difficile: Used gloves 0%
Did not use gloves 59%
Had C. difficile before patient contact 3%
Washed with non-disinfectant soap 40%
Washed with disinfectant soap 3%
Did not wash hands 20%
What is the most likely mode of transmission of this bacterium in
hospitals?
………………………………………………………………
……………………………………………………………
………………………………………………………………
……………………………………………………………
………………………………………………………………
……………………………………………………………
………………………………………………………………
……………………………………………………………
………………………………………………………………
……………………………………………………………
………………………………………………………………
……………………………………………………………
………………………………………………………………
……………………………………………………………
………………………………………………………………
……………………………………………………………
………………………………………………………………
……………………………………………………………
………………………………………………………………
……………………………………………………………
How can transmission be prevented?
………………………………………………………………
……………………………………………………………
………………………………………………………………
……………………………………………………………
………………………………………………………………
……………………………………………………………
………………………………………………………………
……………………………………………………………
………………………………………………………………
……………………………………………………………
………………………………………………………………
……………………………………………………………
………………………………………………………………
……………………………………………………………
………………………………………………………………
……………………………………………………………
………………………………………………………………
……………………………………………………………
………………………………………………………………
……………………………………………………………
Biology Homework Solutions
#151734
An 8 gram sample of cream cheese was homogenised in sterile Ringer’s solution to give a total volume of 20 cm3.
6. An 8 gram sample of cream cheese was homogenised in sterile Ringer’s solution to give a total volume of 20 cm3. The homogenate was then serially diluted and 0.2 cm3 aliquots of a number of dilutions were spread plated on duplicate nutrient agar plates. After incubation, the following colony counts were recorded:
Dilution Replicate 1 Replicate 2
10-3 356 314
10-4 31 38
10-5 3 2
Calculate the average number of colony forming units per cm3 in the homogenate.
Calculate the average number of colony forming units per gram of cream cheese.
The following details were recorded about the growth of one of the isolates from the cream cheese:
Colony
characteristics On Nutrient agar On Blood agar
Size
0.5-1.0 mm 0.5-1.0 mm
Shape
Smooth Smooth
Pigmentation
Translucent Transparent with narrow zone of haemolysis
A number of additional tests were then carried out on this isolate and the following observations made:
Test
Observation
Methylene blue stain
Rod-shaped cells
Gram stain
Purple cells
Colony colour in reflected light
Blue-green
Ability to grow at 4ºC
Yes
Motility
Tumbling motion
Identify this cream cheese isolate, explaining your reasoning in full.
What are the possible consequences of ingesting food contaminated with this microorganism?
7. A 22-year-old male student was brought to the emergency room after a 2-day history of headache and fever. On the day of admission, the patient had failed to come to school or to phone friends to explain why. When notified of this fact, the patient’s friends had gone to his flat, where they found the patient in bed, confused and highly agitated. The patient was comatose when he arrived in the emergency room. Purpuric skin lesions were present on his trunk and arms. Gram stain of cerebrospinal fluid showed many Gram-negative diplococci, and the same organism was isolated from blood. The patient died despite prompt initiation of therapy with penicillin.
What is the most likely microorganism responsible for this fulminating disease? Explain your reasoning in full.
What is the most likely source of this organism?
What other diseases are caused by this microorganism?
8. Forty-two people in the same town reported to their GPs with fever (40°C), jaundice, and tender abdomen. All 42 had eaten an ice-slush beverage purchased from a local convenience store. Liver function tests were abnormal. Over the next several months, the symptoms subsided and liver function returned to normal. What is the disease? Explain your reasoning in full.
What pathogen is causing it? Explain your reasoning in full.
9. Twenty-two percent of the patients in a large hospital acquired Clostridium difficile diarrhoea and colitis during their hospital stay. These patients required longer hospital stays than uninfected patients. Epidemiological studies provided the following information.
Rate of infections for patients: Single room 7%
Double room 17%
Triple room 26%
Rate of environmental isolation of C. difficile: Bed rail 10%
Commode 1%
Floor 18%
Call button 6%
Toilet 3%
Hands of hospital personnel after contact with patients that were culture-positive for C. difficile: Used gloves 0%
Did not use gloves 59%
Had C. difficile before patient contact 3%
Washed with non-disinfectant soap 40%
Washed with disinfectant soap 3%
Did not wash hands 20%
What is the most likely mode of transmission of this bacterium in hospitals?
How can transmission be prevented?
What is this?
By OTA - Overall OTA Rating
Parita Bhuva, MD - 4.9/5
Purchase Cost Now
$2.19 CAD (was ~$79.80)
Included in Download
- Plain text response
- Attached file(s):
- Revision+sheet2-1 answers.doc
Why you can trust BrainMass.com
- Your Information is Secure
- Best Online Academic Help Service
- Students find real academic Success
- Koch's Postulates and Molecular Genetics - I understand that Koch's postulates have limitations, but I don't understand how that plays a role in molecular genetics. Here is my question. Given the limitations of Koch's postulates, what r ...
- Understanding Koch's postulates. - Describe how Koch's postulates establish the etiology of many infectious diseases. Explain why Koch's postulates do not apply to all infectious diseases by giving supporting examples.
- questions - 1.What is the three main types of microbiological culture media? Why are Petri dishes inverted after they cool? 2.Which are of a streak plate will contain the greatest amount of growth? The least amo ...
- Help with micro questions - Can you please confirm my choices for the 8 questions listed below. I was unable to make any choice for one or two of the questions, any help will be appreciated. 1. All of the following charact ...
- Generation time; doubling time - If the generation time is 90 minutes and the initial population contains 10^3 cells, how many bacteria will there be after 3 hours of exponential growth?
