Authors note: I have used Croxen et. al’s excellent 2013 review article from Clinical Microbiology Reviews, Recent Advances in Understanding Enteric Pathogenic Escherichia coli, throughout the text (multiple parts) though I do not always provide a citation when I quote or reference that paper. I have pasted in a link to the article itself (below) for anyone interested in checking the accuracy of my statements or simply learning more about the pathogenic E. coli.
Recent Advances in Understanding Enteric Pathogenic Escherichia coli
Although Escherichia coli can be an innocuous resident of the gastrointestinal tract, it also has the pathogenic…
I also have drawn on my own extensive knowledge of this organism and the pet food industry and their pathogen testing practices. I have included various slides I have presented on the topic at conferences or meetings as part of the background information. In addition I have spoken with other colleagues who are experts in the field for additional insights. Finally, my veterinarian provided some of the information discussed here and has been extremely helpful in providing cat and medication specific information as it relates to this issue. I do not name the brand of suspect contaminated pet food as I do not have direct evidence of that link, and unfortunately the chances of that are slim to none at this point. Like an idiot I threw away the bag from which I may have possibly been able to recover the suspected contaminant. As of the posting of this piece 01/26/19 Phoenix is still ill but slowly recovering and most importantly alive.
Full disclosure-I currently work for a company that has a business which is developing a set of diagnostic assays for the detection of pathogenic E. coli in foods. While I do consult for the development effort and may do some laboratory evaluations I am not currently directly involved in the R&D efforts. In the past, at a different company, I led an R&D team which developed a similar suite of assays. Those tests are still on the market and used today in a variety of food testing applications, including pet food.
Some of the largest clients of the third party food testing industry are pet food manufacturer’s. In general I have a very high opinion of their approach to food safety. Profit margins in the pet food industry are generally much higher then for makers of our own food, and thus they can afford to spend more money on things like additional testing. Partly driven by FDA pressure, but mostly because they are good people, the majority of pet food manufacturer’s (at least that I have met and worked with) our 100% committed to the safety of their product both for your pets (they are by and large animal lovers themselves), and of course the people that buy their products. All that said some are much better than others, and don’t even get me started on the food safety/microbiological nightmare that is “raw” pet food. In the case I will discuss the (suspect) food was dry kibble and produced by a large and well respected manufacturer. Obviously, gaps still exist and even among the best, there is always room for improvement.
This situation is the very definition of tragicirony. One of my beautiful cats, Phoenix, is very ill with what appears by all symptomology to be hemolytic uremic syndrome (HUS) caused by pathogenic E. coli, most likely acquired through consumption of contaminated pet food. This is the very same micro-organism with which I have worked in some capacity for the better part of my adult life. Several of my other cats were sickened but quickly recovered or have only mild lingering symptoms. The predominant bacteria isolated by the testing laboratory is morphologically and biochemically consistent with E. coli but has not yet been confirmed as a pathogenic strain. Testing by real time PCR and antibody latex agglutination has shown it to be negative for E. coli O157:H7, a frequently isolated strain in the United States, though mostly from meat and produce. Results are pending from tests for other pathogenic E. coli virulence markers and specific non O157:H7 serotypes. Antibiotic resistance profile testing was also performed on the strain, and showed it to be resistant to all of the penicillins and cephalosporins tested along with tetracycline.
Pet food is not typically considered a major source of E. coli infections in animals or people. People (mostly the very poor) do eat pet food and small children can become sickened by putting pet food into their mouths even if they do not swallow. A 2014 study found no toxigenic E. coli in a variety of pet foods tested over 2 years. However, out of the just over 1000 samples analyzed, 66 samples were positive for Listeria (32 of those were Listeria monocytogenes) and 15 samples were positive for Salmonella. These pathogens were isolated from raw foods and jerky-type treats, not the exotic animal dry feeds.
Over the course of the next few posts on this topic I intend to describe in detail what happened to Phoenix while at the same time (hopefully) educating the reader about the pathogenic E. coli and its role in foodborne disease in humans and animals. I will provide some minimal background on the biology of the organism, discuss current testing practices with a focus on highlighting weak points and gaps in the current system. I will also talk about the regulatory framework which guides testing decisions and its relevance to the pet food industry. The idea is to weave the story of Phoenix’s illness and (hopefully) full recovery throughout the text. I can’t promise success in this endeavor as this is only part 1 of the story, and has taken me the better part of a week to complete. I can promise serious effort and a rewarding read for those with the patience to stick with me. Let’s begin then with some background.
Background — The Pathogenic E. coli and shiga toxin producing Escherichia coli or (STEC)
Most E. coli are not pathogenic
First, a very important point. Most E. coli are not dangerous. If you have ever read an introductory microbiology textbook you are probably acquainted with that fact, and it is so oft repeated that it has become a truism among the microbiological cognescenti. Surprisingly, or perhaps not, direct evidence to back up this statement are hard to find, and may not actually exist. It is complicated by disagreements over how one defines “harmless” and “pathogenic” and the parsing of terms like “strain” and “serotype”. I asked a colleague, a well respected government researcher who specializes in pathogenic E. coli, for her take on this point and received the following reply (lightly edited for clarity).
“…..the final number of E. coli serotypes is very high, 50,000–100,000 or more” (Orskov and Orskov, 1992)…many “serotypes” have not been involved in illness. However, when it is stated that most E. coli are harmless, this may be referring to the particular strain, not specifically to a serotype. ..there are a large number of E. coli “cells” and strains in the GI tract, as opposed to the number of cells and strains of pathogenic E. coli in the environment. This may be what is meant when it is stated that most E. coli are harmless. However, I have never encountered in any publication where specific percentages are mentioned regarding harmless vs. non-harmful E. coli………………… Probably the answer is ….0.1–1%.” My own investigations into the literature brought me to a similar conclusion.
Pathogenic E. coli Nomenclature
The way pathogenic E. coli are named is particularly clumsy and difficult for the non expert to follow. Below I have included a few slides from a presentation I have given several times about STEC which attempts to describe the system favored by clinical microbiologists, doctors, and public health officials. The last slide I included contains some very generic background information specific to STEC.
If you made it through that long slog without falling asleep, congratulations, you did better than many who have attended one of my lectures on this topic. That is probably all the background information any sane person can take so I will end it there. In the next installment I will briefly discuss the regulation of pet foods in the United States and return the focus back to the Phoenix and his health situation. Stay tuned…
*With apologies to the classic X-Men series of the same name.