Question

There is some evidence that it might have become foodborne, and you need to isolate it. Using the skills, you outlined fecal-oral transmission happening in swimming areas. That's unusual in this country--but this bacterium is so virulent that even small amounts were affecting people, you track it down to unpasteurized fruit juice. Create a plan to enumerate the bacteria present in different samples of fruit juice.

Answer 1

To enumerate bacteria present in the fruit juices 'spread plate' technique is the best one.Spread plate culture technique is one among the most widely used culture technique for isolating the bacteria.This method is used to isolate and to count liquid sample containing bacterias.The main microbial contaminants in fruit juices are Staphylococcus aureus and E. coli, also the species of Kebsiella, Vibrio cholera, Streptococcal spp.Other common bacterial contaminants of fruit juices are Pseudomonas aerogenosa, Proteus spp. and Salmonella typhi.

Un-pasteurized fruit juice samples can be collected and analyzed for total viable counts (TVC), total staphylococcal counts (TSC), total coliform counts (TCC) and Salmonella-Shigella spp etc for assessing the quality or the contamination rate of the juices.


Procedure:

◇. Serially dilute the fruit juice samples(by transferring 1 mL of each of fruit juice sample into 9 mL of sterile phosphate buffered saline tubes separately. )

◇. Pipette out 0.1 ml from desired dilution series onto the center of the surface of an agar plate.

◇. Dip the L-shaped glass rod spreader into alcohol and then flame it over bunsen burner as part of sterilisation.

◇. Spread the sample evenly over the surface of selective media including nutrient agar for total viable counts , Staph 110 agar for staphylococcal counts and MacConkey agar for coliform counts etc. Carefully rotating the Petri dish underneath at the same time.

◇. Incubate the plate at 37°C for 24 hours.

◇. Continue the same procedure for all fruit juice samples

◇. Calculate the CFU (colony forming unit) value of the sample. Once you count the colonies, multiply by the appropriate dilution factor to determine the number of CFU/ml in the original sample.


Total Viable counts:TVC more than 4 log10 CFU/ml indicates highly contaminated fruit juices.

Staphylococcal counts (SC):Presence of staphylococci more than 3 log10 CFU/ml is a health hazard as they cause spoilage of fruit juices and food borne diseases

Coliform counts (CC): Coliforms are considered as indicators of quality. Presence of coliforms in high numbers (CC ˃2 log10 CFU/ml) is health hazard causing spoilage of fruit juices and food borne diseases.

The presence bacteria in the selective media for other bacterias such as salmonenn spp, shigella spp etc also shows heavy contamination