October 24, 2021

Study Finds Kosher Chickens Have More Antibiotic-Resistant E. coli

A new study published in F1000Research and funded by Northern Arizona University has found that kosher chickens contain more antibiotic-E. coli bacteria. Scientists could not explain why kosher chickens had the highest level, which organic chicken had antibiotic-resistant bacterial levels just as high as conventionally raised chickens. Only chickens that were raised without antibiotics (RWA) had lower levels of antibiotic-resistant E. coli. But they still contained antibiotic-resistant bacteria.

Raw whole chickenScientists purchased 213 samples of raw chicken from 15 locations in New York City from April through June 2012. They screened generic E. coli isolates from each sample for resistance to 12 antibiotics and did not assess virulence for each sample. Kosher chicken had the highest frequently of antibiotic-resistant E. coli, almost twice that of conventional products, even though kosher is perceived as being cleaner. In fact, the study says “organic, RWA, and kosher food products supply a growing market niche. Consumers perceive that they offer health benefits and are willing to pay a premium for them. The actual health benefits of organic foods are largely anecdotal. Little is known about the frequency of antibiotic-resistant microorganisms on kosher products.”

The study authors believe that production methods may affect the amount of antibiotic-resistant E. coli on chickens. Kosher chickens are produced differently from conventional chicken, and those certifications are privately regulated so they could not be examined. Kosher preparation details how the animal is killed, how it is prepared, and its environment after slaughter.

The bacteria were most commonly resistant to cefazolin (41.3%), following by ampicillin (31.5%), tetracycline (30.4%), and ampicillin sulbactam (19.6%). Within the categories of chicken purchased, brands did not vary in the extent of resistance. Over half of all strains collected had resistance to one or more antibiotics: 55% from conventionally raised, 58% from RWA, 60% from organic, and 76% from kosher samples. Almost half of the kosher samples were resistant to four antibiotics, compared to about 15% of the conventional and organic chickens, and less than 5% of the RWA samples.

Shared facilities for slaughter could promote cross-contamination among the different types of poultry and account for these findings. Some corporations with both organic and conventional products use the same facilities for slaughter. The authors conclude by saying that more studies are needed to test whether these findings are consistent. They also say that more consistent surveillance or auditing would add consumer protection.


  1. Dear Linda,

    I have been producing chickens that are both Organic and Kosher for over 20 years.
    I’m not a rabbi, but i have inspected the process thousands of times.

    The kosher process starts from point of slaughter only, with very little input on what occurs before. It pre-dates factory-farming.
    Part of the post-slaughter process is that :-
    1) The chickens must be soaked in running water for 30 – 40 minutes and
    2) packed with salt, inside and out, for an hour, which is then rinsed off.
    The reason is that Jews are not allowed to eat blood (and so make strenuous efforts to rid the meat of blood).

    I suspected that the salting would kill a substantial amount (all?) of the bacteria. Perhaps a food microbiologist could advise ?

    Unless they are organic, all chickens, whether kosher, halal or neither, come from the same factory-farms, so the original provenance is the same.
    One has to assume that the sampled chickens were definitely kosher and not just labelled as such. The kosher food industry, is heavily regulated and inspected, so mislabelling is exceedingly unlikely.

    One thing that I insist on is that Organic Kosher chickens are scrupulously separated by time and space, and washed in separate water (at stage 1).
    This is because all the detritus from factory-farmed animals, that has not been removed by post-slaughter evisceration, might mix around.
    Factory-farmed chickens are given antibiotics daily, and are believed to be a major vector for transmission of antibiotic resistance to humans.

    This ‘communal washing’ might be a reason for the elevated levels of antibiotic resistant bacteria found in factory-farmed kosher chickens in this study, but only if the salting process does not kill a substantial amount of bacteria. Or, perhaps there are other reasons.

    I would be interested in having my Organic Kosher chickens tested.

    Best regards,

    Leon Pein

    • Linda Larsen says

      Thank you for your post; your information about kosher meat preparation is interesting. But salt will not kill bacteria in the flesh of the chicken; some on the surface may be destroyed. Only heat kills all bacteria. But if there are a lot of bacteria and they grow long enough to produce toxins that are not destroyed with heat, someone can still get sick even if the chicken is thoroughly cooked.

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