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non-infected and infected controls


Some history on the research on mutans streptococci. 

The hamster illustrates an important caries research area in Malmö, in particular during the 1960's and 1970's. Animal studies clarified many details about transmission of cariogenic microorganisms, role of diet and in particular sucrose. 

Professor Bo Krasse, inspired by the early works of Keyes and Fitzgerald in the USA performed many such studies in the 60ies and Professor Göran Frostell in the 70ies.

a hamster

Streptococcus mutans colonies on an MSB agar plate.

The colonies seen were often described as having a "frosted glass" appearance. They are surrounded by extra-cellular polysaccharides, formed by the sucrose in the MSB-plate.

Streptococcus mutans colonies

The agar plate is selective for mutans streptococci. It was developed in Dr Harold Jordan's lab at Forsyth Dental Center, Boston, by Drs Gold, Jordan and van Houte in 1973. Before that, Dr Jordan had been a visiting scientist in Malmö. The MSB - Mitis Salivarius Bacitracin - plate became a very important tool for future research as it facilitated the identification of these bacteria tremendously.

The pictures show Dr Gold, Dr Jordan (top) and Dr van Houte

Dr Gold

Dr van Houte

One of the first "cariogenic" strains identified in a human mouth, by Professor Krasse, was strain ING-BRITT. This strain has been used in many research laboratories around the world.

A serological identification scheme for the mutans streptococci was presented (in Malmö) by D Bratthall 1970.
The scheme was based on Ouchterlony diffusion-in-gel methods which was adapted from Professor A-B Laurell in Lund and from Professor L-Å Hanson and Dr C Wadsworth in Göteborg. A further fundamental prerequisite was the unique collection of oral strains identified and classified by Dr Jan Carlsson in Malmö. Later on Dr Carlsson became professor at Umeå University.

Can we find mutans streptococci outside the mouth? Can we find them on, for example, spoons contaminated by saliva? The picture shows a spoon which has been in a mouth and then incubated in a selective broth. Some mutans colonies can be seen.

How many colonies can be found? It depends on the saliva. If the saliva contains huge amounts of mutans colonies, there will be large amounts on the spoon. If there are no mutans streptococci in saliva, there will be no colonies on the spoon.

a spoon incubated in a selective broth

The findings described above were actually the basis for the development of the "spatula method" or "tongue-blade method" by Köhler and Bratthall, 1979. A wooden spatula was turned around in the mouth to become contaminated by saliva. It was then pressed against an MSB agar plate. After incubation, the number of colonies could be counted.

Using this method, large groups of individuals could easily be sampled. The method was used in several of our international projects.

the "spatula method"


A further development was presented in 1989 by Jensen and Bratthall - the "Strip mutans" method. Based on the same principles, a specially designed plastic strip is contaminated by saliva and incubated in a selective broth. After 48 hours the number of colonies can be counted or compared to a chart. The method gives an idea of the mutans streptococcal "load" of a person.

For a more detailed information, Strip mutans test.

the "Strip mutans" method

The two pictures show mutans colonies attaching to the strip in high magnification (Electron microscopy photo by Dr Jörgen Jönsson, Malmö).

The ability to attach to a surface is a key pathogenic factor of the microorganisms. Dr Ronald Gibbons, with whom we had the chance to collaborate for several years, was the one who introduced this important line of research in the dental field.

mutans colonies attaching to the strip1

mutans colonies attaching to the strip2


Mutans streptococci and caries risk assessment

Senast uppdaterad av Magnus Jando