What is endotoxin?  I heard that exposure to it can cause illness symptoms that are somewhat similar to those caused by mold.  Is it present in homes too?  Anon.

 

            Endotoxin is a large molecule (a lipopolysaccharide) that is found in the cell walls of certain bacteria classified as Gram-negative because they do not take up this type of stain when their cells are exposed to it.

            A large number of bacterial species are Gram negative including many enteric types (such as E. coli) that are found in the human gut as well as in other animals.  Because of this, Gram-negative bacteria are very common in both indoor and outdoor environments (including our homes, daycare centers, schools, etc).

            When Gram-negative bacteria die, the cells lyse (breakdown) and release endotoxin molecules into the environment.  Numerous scientific studies have shown that endotoxin can cause significant inflammatory responses in test cells in culture as well as on exposure in humans.

            Endotoxin is commonly found in the floor dust of our homes and other buildings.  It can become airborne and result in human exposure that causes a variety of flu-like symptoms.  In European buildings Gram-negative bacteria reportedly grow in cool mist humidifiers used in office buildings.  Endotoxins in those humidifiers are can become aerosolized with office workers developing symptoms of what is called “humidifier fever”.

            Humidifier fever has not been reported in this country since we do not humidify our office/institutional buildings and if we do, we use steam.  However, “humidifier fever”-type symptoms are very common among factory workers who do “machining” kind of work.  Their exposure results from the use of metal-working fluids which become heavily contaminated with Gram-negative bacteria despite the fact that biocides are regularly added to control bacterial growth.

            As is common with most pest control agents, these biocides do not achieve total control.  Indeed they push bacterial populations in the direction of Gram-negative types.  Their inability to take up the Gram stain reflects the composition of the cell wall which apparently makes them more resistant to biocides.

            The amount of endotoxin in floor dust of buildings depends on a variety of factors.  These include the presence of children, the numbers of occupants, the presence of pets, livestock nearby, building dampness, etc.

            As one would expect, endotoxin levels are higher in buildings where small children are present/play.  This is especially true in many daycare centers.   Indeed the presence of higher floor dust endotoxin levels has been hypothesized as contributing to increased illness rates among daycare children with paradoxically lower overall respiratory illness rates later in life (this early-in-life exposure apparently causes the development of some type of resistance to later-in-life respiratory illnesses.

            To be continued.

November 11, 2004