Efficiency of handwash, alcohol gel & soap

[cat_n30]

I am a college student coming toward the end of my course. My final project I have compared the efficiency of handwash, soap and alcohol gels. Using nutrient agar plates to count the bacteria before, 5 minutes after and an hour after (using each of the products). I have my results, but wondered if anyone else has any useful information for me?

[ecoli]

I'm not sure 5 minutes or even an hour would be a useful timepoint. With most bacteria, you will not see a good visualization of growth unless you leave them overnight. If you don't have any bacterial growth, you can't see any bacterial non-growth to compare it to, and would have no idea if your experiment worked.

[John Cuthber]

I don't think that's what he meant.

I think he meant sampling their hands after 5 min or 1 hr after washing.

[CharonY]

You should be sure that the agar plates you use are able to capture a significant amount of skin colonizing bacteria. Either that or use a variety of media. If you did not, you should discuss what bacteria are able to grow within the time frame and under the condition you cultivated and whether this includes a significant bias or not.

[cat_n30]

I used 3 products, carex handwash (which I see my GP has by his sink) Cuticura Alcohol hand Gel (which claims to kill 99.9% of bacteria within 15 seconds) and a basic soap. I did a control, as suggested and just used water. A thumb/finger print was placed in the Agar dish (pre washing) then 5 mins after the application, and an hour after application.(fresh agar plates obviously!) The experiment was repeated only twice, I appreciate that repetion is best. The agar plates were labelled and sealed incubating for the same amount of time, at the same temperature, and monitored. The results (I am having to count the amount of 'dots') but some of the plates are a huge blob of bacteria, and I'm guessing that I will have to estimate by size. Any advice on better practice would be welcome? The overall 'WINNER' is looking like the Carex handwash. Something that surprised me. I did expect the Alcohol Gel to do much better. Any advice about writing up the experiment would be very welcome too. Thanks for the great responses Cat

[cellbioS]

The results (I am having to count the amount of 'dots') but some of the plates are a huge blob of bacteria, and I'm guessing that I will have to estimate by size. Any advice on better practice would be welcome? The overall 'WINNER' is looking like the Carex handwash. Something that surprised me. I did expect the Alcohol Gel to do much better. Any advice about writing up the experiment would be very welcome too. Thanks for the great responses Cat

 

Sorry this may be a little late for your report but are you sure that "blob" is bacteria and not a fungal contamination of the agar plate itself. It sometimes happens, esp if the plates haven't been stored/handled properly.

 

Don't forget to discuss any "negative" data if it exists.