5 Targets to Test for in Your Production Environment: #2 Faecal Indicator Organisms

#2 Faecal Indicator Organisms

What are they?

Testing for indicator organisms is an indispensable component for any microbiological testing program. Though they themselves are not always pathogenic, they may serve to indicate the presence of pathogenic microorganisms that have made their way into food via improper sanitation or a process failure. Thus, they indirectly provide valuable information about the safety and quality of foods. Faecal contamination of the process environment can include pathogenic organisms such as Salmonella or pathogenic E. coli., among others.

There are three microorganism groups that are commonly identified as faecal indicators: Coliforms, Enterobacteriaceae and E. coli.

  • Coliforms: Genera that fit this classification are Escherichia, Enterobacter, Klebsiella, and Citrobacter. Coliforms are known to be naturally present in the environment and are not exclusively indicators of faecal pollution.
  • Enterobacteriaceae: This family includes 20 genera such as E. coli and all other members of the coliform group, as well as foodborne pathogens like Salmonella, Shigella, Yersinia and other related genera. Enterobacteriaceae are useful in monitoring sanitation in food manufacturing plants, although they are more widely used as indicators in Europe than in the United States.
  • E. coli.: These are present at high concentrations in all mammalian feces. Though they do not multiply in water, they can survive and grow in certain foods, meaning they do not necessarily indicate recent faecal contamination.

Although these three groups cannot definitively identify the presence of faecal contamination, testing for them is still a useful monitoring tool.

Where do faecal indicator organisms come from?

While there are multiple sources of potential faecal product contamination, it most often occurs during the slaughtering process. Inadequate personal hygiene on the part of staff can also introduce bacteria into the production environment and product. For fresh produce, the most common cause of faecal contamination is inadequate handling before and during harvesting. If fields are fertilized with cattle manure, the risk of introducing pathogenic E. coli is high, while Salmonella is more an issue in pig and poultry manure. Process water can also harbor faecal organisms.

What type of process controls are utilized?

To minimize the risk of product contaminations, a well-established cleaning and sanitizing regime must be in effect during production. Proper slaughtering practices can help to avoid contamination from the carcass itself, as can good hygiene practices during the entire production process in general. Between shifts, food-contact surfaces (FCS’s) as well as non-food-contact surfaces (NFCS’s) should be cleaned and sanitized. To validate these checks, samples should be taken from FCS’s on a daily basis, and from NFCS’s on a regular basis before, during and after the production run.

What methods do processors use to test?

Quantitative, agar-based cultural methods are the most common methods used for monitoring the processing environment. Generally, there are two ways to conduct agar media-based methods: direct or indirect. With direct methods, plates or dip-slides are placed on the surface to be sampled. These systems are advantageous in terms of handling compared to indirect methods since there is no additional equipment needed and the sampling procedure is very fast. However, the sampling area in this method is limited. Indirect sampling is carried out with swabs, tissues or sponges that are then diluted in a buffer solution before being pipetted into petri dishes and streaked out. The tested surface area can be much broader; tight spaces and gaps can also be tested, but more handling steps and additional supplies are needed. Liquid media-based methods can expand the sampling area even further, but do not allow for quantifiable testing results. 

There’s more to come! The series continues with a look at Salmonella.

This article was originally published in International Food and Meat Topics, vol. 29, no. 4 (August 2018).