MT 1 (oct. 2019, etc.) Flashcards
There are 44 colonies on the agar. The dilution is 10^4 , what is the number of microbes? (ABCD options)
4.4 x 10^5 or 440,000
MPN sheet (+++, ++, - ), the first dilution was 10^-1 , what is the number of viable microbes? Key number = 320 Hoskins table = 320 = 9.3
MPN = 9.3 x 10^1 /g(ml)
What is the use of the LAL test?
Limulus Amebocyte Lysate (LAL).
- A reagent made from the blood of the horseshoe crab.
- In the presence of bacterial endotoxins, the lysate reacts to form a clot or cause a colour change depending on the technique.
- Detection of Gram- bacteria
What is the use of the ATP test?
ATP is the energy source in all living cells.
Examination of surfaces
What is true for E.coli?
Indole? Methyl red test? Voges-Proskauer test?
Citrate utilization test?
Indole test +
Methyl red test +
Voges-Proskauer test -
Citrate utilization test -
What is true for Enterococcus?
Aerob/anaerob? Usage? Catalase test? Slanetz-Bartley agar?
Aerotolerant anaerobic
Indicator for faecal contamination and insufficient heat treatment procedures
Catalase test –
Slanetz-Bartley agar +
5 samples with one that is Salmonella positive, what do you do?
Unsatisfactory, remove all products. (Ban it)
What is true for Listeria monocytogenes?
Catalase test? Haemolysis? CAMP test? Rhamnose?
Catalase test +
Beta-haemolysis
CAMP test + (w/Staph.aureus)
Rhamnose +
Redox potential
Instrumental culturing examination
During bacterial growth the redox potential of the medium decreases.
In which pH is sorbic acid most effective.
Options: 4, 5, 6, 7
4 (degree of dissociation is better at low pH = more effective)
What is true for Staphylococcus aureus?
Enzyme? Toxin produced at what temp.? Fermentation?
Has a thermostable deoxyribnuclease (DNase) enzyme
Toxin produced in between 20-45 0C
Ferments Lactose, sucrose and maltose
What is TDT?
Thermal Death Time at 121.10C
Botulinum toxin?
Neurotoxin = muscle spasm/flaccid paralysis
Nausea, vomiting, diarrhea
Which is psychrophilic?
Listeria monocytogenes Clostridium botulinum Yersinia enterocolitica Some strains of: Bacillus cereus / E.coli (Staph. A. is not)
Where does the toxin of Clostridium perfringens generate?
Can generate in intestine or found in food
Algae toxin, does it accumulate in fish or clams?
Shellfish and fish (supposedly)
What is the z-value?
The temperature increase that is necessary for the reduction of decimal reduction time (D) by 1 magnitude.
T/F: Food hygiene is the basic system of requirements and tools of guaranteeing food safety
TRUE
T/F: Food hygiene is the basic system of requirements and tools of guaranteeing food quality
FALSE
T/F: primary production means the manufacture of foodstuffs in processing plants
FALSE
T/F: Food hygiene requirements also refer to the primary production
TRUE?
T/F: Food toxicosis is caused by toxins produced by microorganism in the GI tract of consumers
FALSE
T/F: Toxico-infection is caused by toxins produced by microorganisms in GI tract of consumers
TRUE
T/F: Listeria monocytogenes is a mesophilic bacterium
FALSE –> psychrophilic
T/F: The disease caused by Listeria monocytogenes is characterised mainly by extraintestinal symptoms
TRUE
T/F: In case of foodborne infections caused by Listeria monocytogenes, the lethality is low.
20-30% (is this low?)
T/F: Staphylococcus aureus is a psychrophilic (cold loving) bacterium
FALSE –> mesophilic
T/F: Strains of Staphylococcus aureus pathogenic to animals typically do not cause disease in humans
TRUE
T/F: Food safety significance of S. aureus is associated with the enterotoxin production of a certain proportion of the strains
TRUE
