Coliforms

Coliforms are normally present on raw produce, and their presence does not necessarily signify that pathogens are present nor that the produce has come in contact with feces.

The coliform group includes species from the genera Citrobacter, Klebsiella, Enterobacter, and E.coli. Other than E. coli, no foodborne outbreaks have been associated with coliforms.

Coliforms were historically used as "indicator microorganisms" to serve as a measure of fecal contamination, and thus potentially of the presence of enteric pathogens. Although some coliforms are found in the intestinal tract of man, most are found throughout the environment and have little sanitary significance.

In an effort to indicate 'quality' or 'safety' of such things as dairy products, drinking water, composted manure, and treated sewage, microbiologists developed the positive association of groups of bacteria to fecal contamination and dubbed this group of bacteria ''fecal coliform" . The term "thermotolerant coliforms" has recently been used to describe these organisms and is more appropriate.  These general terms for a large and diverse class of bacteria are useful and remain relevant in specific food, wastewater management, and water quality applications. However, they have limited or no useful meaning in describing quality or safety attributes of sprouts or other produce.

Coliform counts are inadequate to differentiate between fecal and non-fecal contamination.  E. coli is considered to be more closely associated with fecal contamination from warm-blooded vertebrates than are other members of the coliforms.  Generic E. coli in water or on fresh produce are poor indicators of fecal contamination and worse predictors of pathogen presence, but it is the best we have for now.  

 

Escherichia coli

E. coli is the abbreviated name of the bacterium in the Family Enterobacteriaceae named Escherichia (Genus) coli (Species).

 

Approximately 0.1% of the total bacteria within an adult's intestines (on a Western diet) are represented by E. coli. In a newborn infant's intestines E. coli, along with lactobacilli and enterococci, represent the most abundant bacterial flora. This is why organisms that inhabit the intestinal tract as normal flora are named enteric bacteria.

 

The presence of E. coli and other kinds of bacteria within our intestines is necessary for us to develop and operate properly, and for us to remain healthy.  E.coli, along with other species of bacteria synthesize vitamins for us to absorb. We pretty much depend upon E. coli in our intestines for our source of Vitamin K and B-complex vitamins.

  

The helpful bacteria like these are normally located only in regions of our body directly exposed to the internal environment, e.g., our intestines, upper and lower respiratory tract, etc, and never within our bloodstream or the tissues inside our body.

  

Unfortunately, there are some strains of E.coli, that you don't want anywhere in your body, including your intestinal tract.  These are the major subgroups of enterovirulent E. coli strains (collectively referred to as the EEC group) that cause gastroenteritis in humans:

  • Enterohemorrhagic E. coli (EHEC)--hemorrhagic colitis

  • Enterotoxigenic E. coli (ETEC)--gastroenteritis, traveler's diarrhea

  • Enteropathogenic E. coli (EPEC)--infant diarrhea

  • Enteroinvasive E. coli (EIEC)--bacillary dysentery

  • Enteroadherent E. coli (EAEC)--newly added category

      

EHEC have two unique characteristics in that they can produce toxins and are capable of colonizing the intestinal tract of susceptible humans. 

 

The organism causes hemorrhagic colitis, which has characteristic symptoms of bloody diarrhea and abdominal cramps; however, it may progress into hemolytic uremic syndrome, a more severe complication that can result in kidney failure and death.

 

In 1982, scientists identified the first dangerous strain in the United States. The type of harmful E. coli most commonly found in this country is named O157:H7, which refers to chemical compounds found on the bacterium's surface. This type produces one or more related, powerful toxins which can severely damage the lining of the intestines.

E. coli serotype O157:H7 has been most frequently implicated in foodborne diseases. Serotype O157:H7 is a rare variety of E. coli that produces large quantities of one or more related, potent toxins that cause severe damage to the lining of the intestine. These toxins are closely related or identical to the toxin produced by Shigella dysenteriae.

Cattle are the main sources of E. coli O157:H7, but other domestic and wild mammals also can harbor these bacteria. 

 

Most outbreaks of O157:H7 infections are caused by the consumption of contaminated ground beef; however, raw milk, and other foods, including sprouts, have also been implicated.  Most of the fatalities attributed to eating contaminated sprouts have involved E. coli O157:H7.

 

The most likely source of contamination in sprouts is by sprouting seed that is contaminated.  To date, all E. coli O157:H7 related outbreaks in sprouts have been attributed to contaminated seed.

Sprout growers need to be particularly concerned about purchasing seed that has been contaminated in the field, and introducing the pathogen into their sprouting process.  One of the outbreaks involving O157:H7 was traced back to seed that was transported to the seed processor in a dirty cattle truck. 

International Specialty Supply can pretest sprout growers seed for E. Coli O157:H7 before it is purchased.  This tested seed is called ISS Screened Sprouting Seed.  The seed cannot be guaranteed to be free of pathogens, but the testing procedure is an important  step in a sprout safety program to help reduce the risk of pathogens in sprouted products.

One should be concerned about organic seed as well because of the possible use of un-composted manure, although there has to date been no evidence that organic seed is more dangerous than other seed.

Other types, including O26:H11 and O111:H8, also have been found in this country and can cause human disease. 

Neither of these have been found in sprout to date.