Salmonella is one of the most common foodborne illnesses in the world, causing approximately 1.35 million infections, 26,500 hospitalizations, and 420 deaths in the United States alone every year, according to estimates by the Center for Disease Control and Prevention (CDC).
This being so, one often wonders how one little type of bacteria can cause wide-spread destruction. This is because “salmonella” does not refer to a single type of bacteria. In reality, there are hundreds, even thousands, of salmonella serotypes.
Serotypes, according to the CDC, are groups within a single “species” of microorganisms, such as bacteria or viruses, which share distinctive surface structures. This is why, under a microscope, the surface of all Salmonella bacteria look the same. But upon closer inspection, each serotype actually has a unique pattern. This distinct pattern is determined by two distinctive structures on the bacteria’s surface.
The first important surface structure is the O antigen, which is the outermost portion of the bacteria’s surface covering. The other is called the H antigen, a “slender threadlike structure”, which is also a part of the flagella. According to the CDC, while the O antigens are distinguished by their different chemical makeups, the H antigens are distinguished by the protein content of the flagella. With both of these structures, it is made possible for scientists to then determine the distinct serotype.
While yes, there are many different types of serotypes, generally most Salmonella outbreaks, in humans, are caused by several, more common serotypes. It is in the studies of these more common serotypes that scientists are able to both understand the “natural history of all Salmonella strains” and the illness itself better.
Heidelberg, Newport, Oranienburg, etc… About two Dozen Salmonella Serotypes are Responsible for Most Human Illnesses
Serotyping, the “subtyping test based on differences of microbial (e.g. bacteria or virus) surfaces”, has been the tried-and-true method for the CDC in solving Salmonella outbreaks since the 1960s. Health officials serotype an infected patient, and when they subsequently discover just one more person who has become ill with the same serotype, an outbreak is assumed, and an investigation immediately opens.
Serotyping has therefore naturally become the “core of public health monitoring” of Salmonella, according to the CDC, for over 50 years. With scientists’ more advanced DNA technology, particular serotypes can be separated even further into different subtypes, enabling scientists to detect outbreaks even more efficiently than before.
So yes, serotyping Salmonella is incredibly important, and has undoubtedly prevented the spread of some pretty nasty outbreaks. Future further technological advances in DNA sequencing will only make this process even quicker, soon eliminating large outbreaks all together.
