Greetings MES,
There is no specific legislation regulating microbiological limits in sugar as it is considered a safe RTE food, same as honey or cocoa etc.
However, from literature, and some mentions in FDA guidelines for the assessment of microbiological limits in foodstuffs it is advised to do some testing periodically for yeasts - molds, E. coli and pathogens. Yeasts and molds if under the right conditions (temperature and possible moisture from mishandling) can overcome the high osmotic environment and grow. Also, E. coli, can consume glucose and produce gasses (that's a more unlikely possibility than Y-M, as the conditions have to be extremelly favorable) and lastly pathogens for the possibility of the existence of spore forms.
In that you could also test for thermopihilic bacteria.
An average on the paramter limits of what I mentioned above is:
Yeast - Molds < 20cfu/10g
E. coli < 10cfu/10g
Thermophilic bacteria < 150cfu/10g
and absence of pathogens in 25g (mainly Salmonella, Listeria is very unlikely).
That's just a suggestion though, just to be on the safe side, because if you read for example EU legislation there is a footnote for Salmonella, quoting "Regular testing against the criterion is not required in normal circumstances for the following ready-to-eat foods ........ -sugar, honey and confectionery, including cocoa and chocolate products". I am underlining the key words, on which I base my comments.
Hope this helps!
Regards!
