welcome!

It has been a while since I did a post on sifin so this week we are returning to highlight their bacterial test reagents for Salmonella, Shigella, Yersinia & E. coli diagnostics, and their monoclonal antibodies.

If you remember my first article about sifin, that was the very first article I wrote for BioConnections since graduating university in 2023 (I think that's when it was) so let's see if I have improved in 7 months.

Who are sifin?... for the uninitiated

From their about section, sifin diagnostics emerged from the former 'Staatliches Institut für Immunpräparate und Nährmedien' of the GDR. In 1992, a German family of entrepreneurs' investments resulted in the survival of the diagnostic division (encompassing microbiology and blood group serology) following reunification.

Since 1992, sifin has remained family owned and has remained firmly embedded in the diagnostic industry. Thanks to the expertise and competence of their highly qualified staff & sifin's reliability and flexibility to meet customers' demands, sifin diagnostics has an excellent reputation in the international diagnostic market.

What products does sifin manufacture? 

sifin diagnostics offers a comprehensive line of specific test reagents for serotyping in clinical and veterinary diagnostics. These bacterial test reagents are based on monoclonal antibodies, leading to strong and specific agglutination without cross-reaction. All of their antibodies are developed, and manufactured, in-house, being available as ready-to-use reagents in dropper bottles, or as a bulk item. 

sifin diagnostics only deals in monoclonal antibodies, you won't find any of that polyclonal, cross-reacting, tosh. So (you may remember this bit) why do monoclonal antibodies trump polyclonal when you compare the two? 

✅Monoclonal antibodies are each made up of an absolutely uniform antibody population. The population is uniform in terms of the immunoglobulin class, specificity, avidity and heat stability. These very extensively investigated properties of the particular monoclonal antibody remain unchanged throughout all the manufacturing steps.

✅They can be standardised and adjusted to a precisely reproducible antibody concentration whereby a consistent quality across different batches is guaranteed.

✅Monoclonal antibodies lead to rapid and significant agglutination for all the serovars that have the homologous antigen, regardless of other antigens or partial antigens that may be present.

✅Monoclonal antibodies are free of additional antibodies.

✅The production of monoclonal antibodies is independent of immunoserum donors. They are produced using biotechnology by harvesting cell culture supernatants containing antibodies.

✅Antibody specificities that cannot be produced by polyclonal means e.g. O:3, O:13, H:1, H:e, H:l, H:n) can also be isolated as monoclonal antibodies.

There are 4 main categories that their bacterial test reagents fall into: 

• Salmonella diagnostics
• Shigella diagnostics
• Yersinia diagnostics
• Coli diagnostics 

Each category contains specific test reagents depending on what you need. Here's a list for your convenience. 

Salmonella diagnostics

• Test reagents for screening 
• O-Group Pool Test reagents 
• H-Phase Pool Test reagents
• Group specific test reagents Anti-Salmonella
• Monospecific test reagents Anti-Salmonella O
• Monospecific test reagents Anti-Salmonella Vi 
• Monospecific test reagents Anti-Salmonella H
• Control antigens for the Anti-Salmonella test reagents
• Control sera for the Salmonella O and OH test antigens
• Control sera for the Salmonella H test Antigen

Shigella Diagnostics

• Polyspecific test reagents Anti-Shigella
• Monospecific test reagents Anti-Shigella
• Control antigens for the Anti-Salmonella test reagents

Yersinia Diagnostics

• Monospecific test reagents Anti-Yersinia enterocolitica O

Coli Diagnostics

• Polyspecific test reagents Anti-Coli 
• Monospecific test reagents Anti-Coli 
• E. coli relevant to veterinary medicine 

THE CONTROL SECTION

Salmonella Control Antigens

These control antigens are designed for use in the quality control of the Anti-Salmonella test reagents to determine the O, H & Vi antigens listed using a slide agglutination test. 

Shigella Control Antigens 

These control antigens are designed for use in the quality control of the polyspecific test Anti-Shigella reagents when performing a slide agglutination test. 

To note, the control antigen for Shigella dysenteriae can also be used to test the monospecific test reagents Anti-Shigella dysenteriae type 1, and Anti-Shigella dysenteriae type 2. Furthermore, the control antigen for Shigella sonneii is also used to test the Anti-Shigella sonnet S-form & F-form (phases I & II) test reagents. 

Guidance on the procedure for serotyping both Salmonella serovars and pure cultures of Salmonella spp. 

Test Reagents for screening 

For the slide agglutination test using polyvalent, group and monospecific test reagents, start with a subculture of the suspect colony or colonies, preferably on non-selective culture medium such as Nutrient Agar, Blood Agar or Kligler Agar. Before starting the serotyping, it is necessary to confirm biochemically that the isolate belongs to the Salmonella genus. For this purpose, alternative procedures (e.g. MALDI mass spectroscopy: MALDI-TOF) can also be used, presuming that the suitability of the procedure has been verified.

O-Group Pool test reagents

First carry out the test with Anti-Salmonella OMA and Anti-Salmonella OMB: Approx. 98% of Salmonella can be assigned. If the strain does not agglutinate, it is recommended to test this strain with Anti-Salmonella Vi. If this reaction is also negative the strain must be agglutinated with Anti-Salmonella OMC, Anti-Salmonella OMD, Anti-Salmonella OME, Anti-Salmonella OMF and Anti-Salmonella OMG.

H-Phase Pool test reagents

The test, using Anti-Salmonella HMA, Anti-Salmonella HMB or Anti-Salmonella HMC, enables the identification of the most common H-antigens or H-antigen complexes of Salmonella strains. Furthermore the presence of the antigen complex H:1 should be tested by Anti-Salmonella H:1 (TR 1437, TR 5437).

Group specific test reagents Anti-Salmonella

Mixtures of monoclonal antibodies of the corresponding specificities in the form of cell culture supernatants. To determine the serogroup of Salmonella spp. that agglutinate with the omnivalent test reagent and/or the polyspecific test reagent Anti-Salmonella I. They agglutinate exclusively Salmonella spp. of the declared serogroup. According to the frequency of the reported serovars, the group-specific test reagents should be used in the following order:

1. Anti-Salmonella group D
2. Anti-Salmonella group B
3. Anti-Salmonella group C
4. Anti-Salmonella group E
5. Anti-Salmonella O:2 corresponds to Anti-Salmonella group A

Further information on Coli diagnostics

Polyspecific test reagents Anti-Coli 

For the serological detection of isolated E. coli strains from human test material or other origins, by slide agglutination methods. 

Monospecific test reagents Anti-Coli

Used for the serological detection and serovar determination of isolated E. coli strains from human test material, or other origin, by method of slide agglutination and Widal reaction (confirmatory test). 

E.coli relevant to veterinary medicine 

• Coli Diagnostics in young poultry: The polyspecific screening reagent Anti-Coli A is intended for use in the serological detection of O 1, O 2, O 18 & O 78 antigen of E.coli strains isolated from test material, using slide agglutination. An isolate with positive results requires testing with monospecific reagents for further characterisation, and to rule out unspecific agglutinations a confirmatory test such as the Gruber-Widal test must be performed. 
• Coli diagnostics in young pigs: The test sera are used to test for the presence of type-specific antigens with Escherichia coli isolates from pigs. They are used as evidence of antigens on the cell surface of the E. coli isolate (O antigen, K antigen and F antigen) using slide agglutination. First, carry out a screening agglutination with the polyspecific test serum Anti-coli P. If the reaction with the polyspecific test serum is positive, the isolate must then be typed with the monospecific test sera. 
• Coli diagnostics in young cattle: The test sera are used to test for the presence of type-specific antigens with Escherichia coli isolates from cattle. They are used as evidence of antigens on the cell surface of the E. coli isolate (O antigen, K antigen and F antigen) using slide agglutination. First carry out a screening agglutination with the polyspecific test serum Anti-Coli C. If the reaction with the polyspecific test serum is positive, the isolate must then be typed with the monospecific test sera. The F5 (K99) antigen is often not formed in sufficient quantities on standard culture media. It is therefore recommended to use Minca agar when culturing to promote the formation of the fimbrial antigen F5 (K99).