Bacterial load

After counting all the appropriate plates, you proceed to calculate the concentration of viable bacteria in the original sample using the formula:

 

Number of Colonies × Dilution Factor = Colony Forming Units (CFUs)/mL. The results are shown below. 

 

#

Sample

Dilution series

Dilution Factor

Number of colonies

CFUs

A

Patient sample

10-1, 10-2, 10-3, 10-4

103

206

2.06 x 105

B

Meat storage area

10-2, 10-4, 10-6, 10-8

106

293

2.93 x 108

C

Cutting board

10-1, 10-2, 10-3, 10-4

102

180

1.80 x 104

D

Food preparation surface

10-2, 10-4, 10-6, 10-8

104

300

3.00 x 106

E

Sink 

10-1, 10-2, 10-3, 10-4

101

1

1.00

 

Dr. Spencer explains that the bacterial load is very high for the meat storage area, cutting board and food preparation surface and that the sink seems to be unaffected. 

 

[Specific thresholds are often defined by local or national health departments and organizations, such as the Food and Drug Administration in the United States or the European Food Safety Authority in the European Union. It is important for restaurants to adhere to these regulatory guidelines to ensure food safety compliance. A common guideline of acceptable levels is between ≤10 CFUs/m2 to ≤100 CFUs/m2. For precise numbers and guidance, specific regulations and recommendations of the relevant health authorities in specific areas will need to be followed.]

 

The patient sample results also support the notion that the patient got food poisoning. Dr. Spencer goes on to explain that these results will help the epidemiologist and sanitarian to properly disinfect the affected areas. At the same time, Dr. Spencer explains that there is still work to be done to identify the causative agen. This will be helpful not only for disinfection but also for choosing the most appropriate treatment for the patients. 


  • Streak plate method and pure cultures

Map: CS11 - MICROBIAL CULTURE AND GROWTH _RO (1053)
Node: 19860
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