[Microbiology] Re: Want to join this milis
(by limbic_lesion from hotmail.com)
Thu Apr 30 13:27:51 EST 2009
"Tri O.A. Samosir" <trioct_angelia from yahoo.com> wrote in message
news:mailman.1057.1240850824.13724.microbio from net.bio.net...
> my name is Tri, a student of Food Science and Technology , Bogor
> Agricultural University.
> I'm doing my final research at Surveillance institution (BPOM) about
> isolation and identification pathogens that can cause fodd disease.
> I know which forum discussion could I join to share about some research
> in microbiology?Cause in my country is too hard to get the literature
> (thanks before)
> was some question, that I couldn't find the answer when I have been
> asked to experiment with the reagents. Maybe you can help me, please...
> Why serotyping of Salmonella enterica O and H antigen is needed? what is
> the overplus result doing this stage if we used identification by API 20E
> As we know API 20E described the subspecies too, doesn't it? So by API
> we knew the serovar without serotyping stage. But why in WHO GSS
> protocol still use serotyping after identification by API. Is it to
> proof something?
> Thank you for the explanation
> Warmest regards,
Most robust protocols such as ISO standard require both Serological and
Biochemical identification of Salmonella cultures isolated from foods.
As you probabely know there several Thousands of differing Salmonella
species , not to mention sub species.
Classic biochemical tests inbclude Fermentation reactions ( also H2S
production ) and LDC ( decraboxylation reactions) as produced with Lysine
Iron agar and Triple sugar Iron agar slopes and butts. In many labs these
combined test systems have been replaced by strips which extend the range of
The problem is that by only biochemical using test it is imposibile to
actually speciate a Salmonella isolate. An Api strip will not speciate say
Salmonella agona or Salmonella seftenberg. Such strips apply broad well
established probabilites to reaction profiles which is an indication of
Genus rather than a specific confirmation or any other taxinomic status (
such as species). Many Enterobacteriaceae cross react on Biohemical
pannels either beacuse of their intrinsic genetic make up of by posseion of
plassmids. So for example AP 20 E strips can give low differentiation
between numerous Citrobacter species and Salmonella thus illustration the
weakness of relying purely on bichemical identification.
IT is imoprtant to be as certain as possible that one has isolated
Salmonella from a food product as obviously there is probable impact on
human health. Additonally in some countries Sero Group A Salmonella may
be isolated. This group includes Typhoid and it is imperative the correct
identification to species level is achieved. For epidemiological studies one
also needs eaxct typing of Salmonella isolates which cannot ever be
attained simply by biochemical profiling. SOme biochemical reactions such as
variation in the ability to ferment lactose can be usefull in
Serological identification allows typing to many sthousands of Salmonella
species and serovars . By conducting a few agglutionation reacts it is
possible to fisrtly confirm the isolate as Salmonella ( PLoy O Poly H
reactions) and then wdifferentiate any particular isolate to SERO GROUP
level ( commonly A-S although there are more). Most labs can support the
purchase of Poly H/O antisera and Group specific antisera. To actually
speciate an isolate requires species specific agglutination factors;of
which there are dozens. Most food labs would not stock ALL species specific
anti sera but would rely on a regional center of expertice for eaxt
specication of an isolate.
The message is API 20 E is other forms biochemically panneling cannot be
soley relied on to obtain a confident postive identification of a
Hope this helps
Mail me privately if you requirte further assistance
> Tri Octora Angelia
> Department of Food Science and Technology
> Bogor Agricultural University
> Ph. +62 856 2244 554
> trioct_angelia from yahoo.com
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