Methods for Salmonella confirmation
Just wondering what methods people are using to carry out salmonella confirmation tests after getting a positive on BGA and/or XLD?
Just wondering what methods people are using to carry out salmonella confirmation tests after getting a positive on BGA and/or XLD?
Dear kehlan,
Most (rich) people use kits, the rest use “standard” procedures such as based on the (up-to-date) methodology given in regulatory texts like online - BAM or similar non-regulatory texts like (not so up-to-date) ICMSF.
Many people add an extra 1 or 2 shortcut methods which they have found useful from experience.
Rgds / Charles.C
PS - I didn't realise people were still using BGA. :smile:
Repeat streaking salmonella positive colonies on Hektoen enteric agar ans bismuth sulphite agar.pick salmonella positive colonies and stab in butt and streak the slant of lysine iron agar tube and triple sugar iron agar tube. Go for serological testing of salmonella for 'O' antigen and 'H" antigens (Agglutination test) and streak salmonella colony on nutrient agar for purity and do biochemical test on VITEK automated system or any available system like 3m petrifilm.
If confirmed sent the pure culture to outside accreditated lab for final confirmation.
What we do varies depending on budget and time available, but typically we take 5 colonies from the XLD/BGA plates and streak to nutrient agar & incubate overnight. Then we streak onto Urea agar and Salmonella Chromogenic agar and incubate. Remaining suspects are tested for 'O' antigen and 'H" antigens and any positives confirmed by PCR. Remaining positives at that stage are sent out to a reference lab for tserotyping, phage typing etc.
Sometimes we will use TSI slants, but generally find the results of these to be difficult to interpret. If available we sometimes use API20E kits from Biomerieux before proceding to PCR.
Dear All,
I might add that AFAIK from the Salmonella literature, and it has certainly been true IMEX, the use of multiple growth/pre-enrichment media is likely to generate detection of more individual Salmonella species than use of a single system.
And similarly for selective agars post enrichment.
One sometimes feels that Salmonella detection is more of an art than a science, with or w/o kits. Although O/H sera are truly indispensable.
Rgds / Charles.C
One sometimes feels that Salmonella detection is more of an art than a science, with or w/o kits. Although O/H sera are truly indispensable.
Totally agree, it is an art!
O and H sera tie in with my memories of doing this a few years ago. Just one question, which ones? I have been looking in catalogues and there are a bewildering array of different O and H sera available? so which ones do I buy?
I remember (and it was a long time ago so my memory is a bit vague) that we used a poly O and poly H for general ID and also a monovalent one to ensure it wasnt contamination from our positive control. but typically, as I wasnt responsible for it, I never took much notice of the numbers on the vials we used.
Oh and Ive seen a salmonella latex test kit on the market, anyone ever used it and have any thoughts about it?
O and H sera tie in with my memories of doing this a few years ago. Just one question, which ones? I have been looking in catalogues and there are a bewildering array of different O and H sera available? so which ones do I buy?
I remember (and it was a long time ago so my memory is a bit vague) that we used a poly O and poly H for general ID and also a monovalent one to ensure it wasnt contamination from our positive control. but typically, as I wasnt responsible for it, I never took much notice of the numbers on the vials we used.
Oh and Ive seen a salmonella latex test kit on the market, anyone ever used it and have any thoughts about it?
Dear kehlan,
It may well depend on what procedures / applications / objectives (eg species level) you are intending to use them for, for example, can see this well-thumbed article -
http://www.fda.gov/F...s/ucm070149.htm
(eg items 51-54, Section C)
And cost of course. :smile:
Rgds / Charles.C