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CFU Threshold for Hand Swab on Unwashed Hands

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changyang1230

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Posted 24 June 2018 - 02:28 PM

Hi all, 

 

I am a Malaysian doctor who currently lives in Australia. 

 

Recently it's become a hot discussion topic in Malaysia regarding the hygiene standard of migrant food handlers (mostly from poorer countries e.g. Bangladesh, India, Nepal etc) - anecdotally many of these migrant food handlers are noted to have poor food preparation standard and personal hygiene habits. 

 

A news report then cited a research study done by a Malaysian researcher (I have included the actual PDF below). Essentially the methodology is as below: 

- migrant food handlers are investigated

- a few restaurants in major Malaysian town are visited during peak hour, where these migrant food handlers have hand swabs taken on UNWASHED hands, on both hands. 

- these are analysed for APC, E. coli / coliform, and Staph aureus. 

- Sneed's standard is used for "acceptable level" - (less than 1.3 log10CFU for APC, less than 1.0 log10CFU for Enterobacteriaceae counts, and less than 1.0 log10CFU for S aureus counts). - PDF included. 

- they reported some shocking finding: 99.5% exceeded APC limit, 20.8% exceeded total coliform/Escherichia coli limit, 63.4% exceeded Staphylococcus aureus limit. 

 

Some of my concerns about its methodology: 

- local food handlers are not included so no point of reference. 

- Sneed's standard is for food handling surfaces e.g. cutting board. I haven't seen any validation study saying that these are usable for human hand swabs. 

- Is it legitimate to use unwashed hands? I thought surface swabs and hand swabs are supposed to be taken after they are WASHED. 

- Sneed's standard... it's a bit vague, but I am of the impression it should have "per cm^2" on them.  

- The only standard I have read is the Indian EIC guideline, where it is 100CFU/cm^2 for APC, and absent for both coliform and S aureus. 

- If my back of envelope calculation is correct, then for a standard adult hand size, two palmar surfaces (seem to be what they have swabbed from) would be approximately 400cm^2, which makes the acceptable standard 40000CFU if converted from the EIC standard, or equivalent to 4.6log10CFU in logarithmic unit. 

 

I found you guys through my online research in this area and I hope to receive feedback on my interpretation in this issue so far. This news report has been used as a fodder against foreign food handlers in Malaysia (with a huge undertone of xenophobia and racism), and from what I have found so far the whole study is pretty illegitimate going by the information I have found on this forum!

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Charles.C

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Posted 25 June 2018 - 09:57 AM

Hi changyang,

 

I liked the descriptive material in yr attached first file but found it difficult to interpret the data. Particularly due lack of info with respect to the sampling /foodhandler's hygiene procedures.

 

I presume no gloved hands (or equivalents) were involved in this study. For RTE activities I think "gloves" are a typical requirement in the US Food Code (albeit having an efficacy which is disputed elsewhere on this Forum).

 

As you commented, since the sampling was done pre-cleaning/sanitising hands, the latters microbial condition will presumably reflect whatever activity was  being undertaken prior to sampling which is unstated/unknown. (The consequence to micro. limits might then be as illustrated in the UK sheet of the excel file in ifsqn link below).

 

In addition to demonstrating non-compliant scenarios via random sampling, I would have thought it useful to establish a baseline relevant to the results obtained when properly implementing a standard handwashing/sanitizing SOP.

 

With respect to a CFU threshold for APC this afaik is subjective in that there is no internationally accepted standard. I compiled/summarised  a lot of published food contact surface micro data up to ca 2012 here -

 

http://www.ifsqn.com...ces/#entry60958

 

A similar limitation to the above interpreting of the APC data  seems to relate to the Coliform/E.coli results also IMO.

 

I noticed, inter alia, these other relatively recent studies -

 

Attached File  ms1 - micro contam. hands of food handlers,S.Africa,2014.pdf   835.38KB   106 downloads

Attached File  ms2 - hands micro status regarding sanitizer,2011.pdf   234.76KB   97 downloads

Attached File  ms3 - surface-hand micro data in retail establisments,2017,Serbia.pdf   332.98KB   84 downloads

 

This thread may also interest you -

 

http://www.ifsqn.com...other-surfaces/

 


Kind Regards,

 

Charles.C


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changyang1230

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Posted 25 June 2018 - 11:02 AM

Hi changyang,

 

I liked the descriptive material in yr attached first file but found it difficult to interpret the data. Particularly due lack of info with respect to the sampling /foodhandler's hygiene procedures.

 

I presume no gloved hands (or equivalents) were involved in this study. For RTE activities I think "gloves" are a typical requirement in the US Food Code (albeit having an efficacy which is disputed elsewhere on this Forum).

 

In Malaysia restaurant setting most RTE activities are done without any glove. 

 

As you commented, since the sampling was done pre-cleaning/sanitising hands, the latters microbial condition will presumably reflect whatever activity was  being undertaken prior to sampling which is unstated/unknown. (The consequence to micro. limits might then be as illustrated in the UK sheet of the excel file in ifsqn link below).

 

Are you referring to the 2006 (pub 2009) Little table? Should I be using the swabs for "recently cleaned surfaces that are in use"? So it would be 1000/cm^2 for ACC (I presume it is the same thing as APC / TPC)?

> First one needs to know what the handwashing procdure is.

 

In addition to demonstrating non-compliant scenarios via random sampling, I would have thought it useful to establish a baseline relevant to the results obtained when properly implementing a standard handwashing/sanitizing SOP.

 

With respect to a CFU threshold for APC this afaik is subjective in that there is no internationally accepted standard. I compiled/summarised  a lot of published food contact surface micro data up to ca 2012 here -

 

http://www.ifsqn.com...ces/#entry60958

 

Thanks - I have referred to this excel file prior to writing my original post and that's how I found the EIC standard.

 

A similar limitation to the above interpreting of the APC data  seems to relate to the Coliform/E.coli results also IMO.

 

 

I noticed, inter alia, these other relatively recent studies -

 

attachicon.gif ms1 - micro contam. hands of food handlers,S.Africa,2014.pdf

attachicon.gif ms2 - hands micro status regarding sanitizer,2011.pdf

attachicon.gif ms3 - surface-hand micro data in retail establisments,2017,Serbia.pdf

 

This thread may also interest you -

 

http://www.ifsqn.com...other-surfaces/

 

At the end of the day, the study looked at swabs of bare hands which are in active process of food preparation. The vast majority of these guidelines refer to food contact surfaces (cutting board etc) and only the Indian EIC guideline gave a figure for human hand swab - and even in this case they didn't specify clearly whether it's for a recently cleaned hand or an unwashed hand. 

 

Given the purpose of the study (to evaluate how clean the hands being used to prepare RTE foods are), are there any pre-existing guidelines out there that could have guided the interpretation of the results, or is this simply not how this is normally done? 

 

Again I thank you guys for being exceedingly helpful. 



Charles.C

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Posted 25 June 2018 - 11:05 AM

Hi changyang,

 

Try reading the first attachment regarding support for borrowing from work surface to hands.

 

It is unclear what the unit for cfu as (log) quoted actually is. Ideally it would be referenced to an area, eg cm2.

 

The primary objective is to validate (or invalidate) the hand's cleaning/sanitising procedure. But first you need a documented handwashing/implementation SOP, second realistic micro.criteria, third a validated measurement procedure.


Kind Regards,

 

Charles.C


Scampi

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Posted 25 June 2018 - 02:34 PM

It would appear that the high numbers would have come from only a couple of places

 

1) employees are not following proper handwashing procedures (if any training was done to follow)

 

2) lack of overall sanitaiton in the kitchens

 

So generally, no this is not a study that has a lot of merit. At the very least, hands should have been swabbed pre and post handwashing as a means of determining that process' success rate

 

We do not know how long the people had been working, whether or not they were handling things like raw poultry or ground beef etc etc etc

 

I don't think ANY decisive conclusions can or should be drawn from this "study"


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