Who invented the culture plate method

A scientist called Robert Koch ran the laboratory and was looking for a reliable pure culture technique for growing lots of bacteria. A lot of the earlier methods for bacteria growth were opened to the air, which resulted in cross-contamination. Building on methods such as the bell jar on a glass plate technique, Petri invented a culture dish very similar to the one we are familiar with today.

He named the invention after himself and went on to write a word paper about how to use the dish. Identifying plague bacteria — During another outbreak of the plague in in Asia, a Swiss-French bacteriologist called Alexandre Yersin discovered that the Yersinia pestis bacterium was responsible for the condition. He also identified which culture media optimised the development of the bacillus, thereby allowing scientists to reproduce the same conditions in their laboratory and study the microorganism.

Discovery of Penicillin — Perhaps one of the most famous pharmaceutical discoveries that the Petri dish can be attributed to is that of Penicillin.

Staphylococcus is the bacteria responsible for the likes of boils, sore throats and abscesses. Fleming noticed something unusual about one of his Petri dishes as it was dotted with colonies apart from in one area where a blob of mould was growing. The ePetri was designed to do away with the need for bulky microscopes and significantly reduce human labour time, while improving the way in which the culture growth can be recorded.

A small camera in the dish can send data from the ePetri dish and transfer it to a computer outside the incubator by a cable connection. This is said to save time and reduce contamination risks. Although chemicals, such as dyes, had been known to have antimicrobial effects since , when Paul Ehrlich published work on the inhibitory effect of arsenic compounds on syphilis8 they were not incorporated into media formulations until the first selective media were developed in the s.

The level of conjugation in the bile salts determines its selectivity profile: conjugated bile salts are less inhibitory and allow the growth of staphylococci and enterococci; while more disassociated salts such as desoxycholate are much more selective, only allowing growth of Enterobacteriacae. The selectivity of tetrathionate depends on whether or not an organism possesses the enzyme tetrathionase. Salmonellae and Proteus species possess the enzyme, so can grow in the presence of tetrathionate.

The science of microbiology has certainly come a long way with the development of immunological and molecular methods but have culture media changed very much? Certainly many of the basic ingredients come from the same sources as those used by Koch, but the science behind the products has definitely moved on.

Peptones can be hydrolysed using either acid or enzymes, and control of the production processes allows Oxoid to develop new peptones which give optimal growth of specific organisms.

The quality of peptones is also tightly controlled with limits on peptone manufacture and quality control specifications for parameters such as the residual moisture, ash, amino and total nitrogen, phosphates, salt, pH, metal ion content, as well as microbiological tests. Oxoid have developed a range of Veggietones — vegetable based peptones made from raw materials such as pea and fungal proteins that are digested using bacterial and fungal enzymes — all of which are guaranteed to be completely animal free.

It is critical that media have constant gel strength as the effect on colony morphology can be dramatic. High gel strength media will grow small colonies because the flow of nutrients and removal of toxins is reduced. Low gel strength media will allow the growth of larger colonies, but can be difficult to streak. Blood — Fresh blood is defibrinated, to remove the clotting factors and variation between batches is minimised by adjusting the packed cell volume, sterility tests are also performed.

To ensure the best possible haemolytic reactions, Oxoid prepare their ready-to-use blood plates using an in-line blood addition process and batches of blood that have often been drawn less than 48 hours previously.

Not only has Oxoid defined the science behind many of the traditional ingredients, but they have also introduced many new formulations. In Levine and Schoenlein13 listed 2, published culture media formulations and, although many thousands have been published since, there are probably less than which are in regular day-to-day use.

These tend to be formulations that have been refined over time with the addition of more complex selective or diagnostic ingredients, for example, chromogens. Chromogenic media Chromogens are molecules designed to mimic metabolic substrates which are colourless until they are cleaved by the target enzyme.

Once cleaved the molecule becomes both insoluble and coloured, so builds up within the cell. This means that colonies of an organism which possess the enzyme can be easily differentiated from those that do not. By designing a selective base medium and adding chromogenic substrates media can be designed that allow differentiation and identification of groups of organisms.

A large number of chromogenic media are now available for organisms as wide ranging as E. Food Media Much of the early microbiology had a clinical focus — but the food industry face different challenges. Theirs is not so much a question of identification of an unknown organism, but one of developing specialised methods that can indicate the presence of pathogens even at a level of one organism in 25 g of food.

These methods must also detect stressed and injured cells which are sensitive to most selective agents. This requirement for recovery of low levels of stressed pathogens means that most methods are based on pre-enrichment and selective enrichment broths which are used to increase the numbers of target organisms before plating.

Emerging Pathogens New organisms, also present new challenges and require new isolation methods. Shepard identified Legionella pneumophilia as the pathogen which caused Legionnaires disease14— this required the development of new media both for clinical and water testing applications; in Barry Marshall demonstrated that isolates from gastric and duodenal ulcers all contained a Campylobacter-like organism later called Helicobacter pylori15; as recently as , the first Vancomycin Resistant Staphylococcus aureus was found in Michigan and in Oxoid launched one of the first chromogenic media to specifically detect the emerging pathogen Enterobacter sakazakii from infant formula milk.

In the past, media were developed through empirical experiments — now they can be designed using in-depth knowledge of both the biochemistry of the target organism and the raw materials. Oxoid control every step in the product chain, from the raw materials to the prepared medium which allows us to develop and produce the high quality media required by microbiology laboratories today.

References 1. Bizo, B. Sci ed. Koch, R. Some of the best inventions seem so obvious after the event. The Petri dish, a circular flat dish with a lid that is used for growing bacteria on a bed of nutrient jelly, is one such innovation.

It can be found in any immunology laboratory in the world and its basic design has not changed since it was first invented in by a German microbiologist called Julius Richard Petri. Petri worked in the laboratory of the bacteriologist Robert Koch, the titan of microbiology who was the first to prove the link between specific bacterial infections and certain diseases, namely cholera and tuberculosis.

Koch first demonstrated the technique in at the International Medical Congress in London.