[Microbiology] Re: Want to join this milis

N10 via microbio%40net.bio.net (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...
> Hello,
> my name is Tri, a student of  Food Science and Technology , Bogor 
> Agricultural University.
> Now
> I'm doing my final research at Surveillance institution (BPOM) about
> isolation and identification pathogens that can cause fodd disease.
> May
> 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)
> There
> 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 
> system.
> 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,

Hello Tri

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combined test systems have been replaced by strips which extend the range of 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 
epidemiological work.

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 
Salmonella culture.

Hope this helps

Mail me privately if you requirte further assistance

Bets N10

> 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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