The British Journal of Nutrition has retracted a 2013 paper by a group of researchers from Taiwan after learning that the authors had studied the wrong strain of microbe.
The article was titled “Oral Lactobacillus reuteri GMN-32 treatment reduces blood glucose concentrations and promotes cardiac function in rats with streptozotocin-induced diabetes mellitus.”
According to the abstract:
Impaired regulation of blood glucose levels in diabetes mellitus (DM) patients and the associated elevation of blood glucose levels are known to increase the risk of diabetic cardiomyopathy (DC). In the present study, a probiotic bacterium, Lactobacillus reuteri GMN-32, was evaluated for its potential to reduce blood glucose levels and to provide protection against DC risks in streptozotocin (STZ)-induced DM rats. The blood glucose levels of the STZ-induced DM rats when treated with L. reuteri GMN-32 decreased from 4480 to 3620 mg/l (with 10⁷ colony-forming units (cfu)/d) and 3040 mg/l (with 10⁹ cfu/d). Probiotic treatment also reduced the changes in the heart caused by the effects of DM. Furthermore, the Fas/Fas-associated protein with death domain pathway-induced caspase 8-mediated apoptosis that was observed in the cardiomyocytes of the STZ-induced DM rats was also found to be controlled in the probiotic-treated rats. The results highlight that L. reuteri GMN-32 treatment reduces blood glucose levels, inhibits caspase 8-mediated apoptosis and promotes cardiac function in DM rats as observed from their ejection fraction and fractional shortening values. In conclusion, the administration of L. reuteri GMN-32 probiotics can regulate blood glucose levels, protect cardiomyocytes and prevent DC in DM rats.
Trouble is, the authors had used a different strain of Lactobacillus, as the retraction notice explains:
The article by Lin et al. ( 1 ) has been retracted at the request of the authors. The strain of bacteria reported in the article was Lactobacillus reuteri GMN-32. However, the authors have contacted the British Journal of Nutrition to state that in fact the strain of bacteria used was Lactobacillus paracasei-32. Because of the fundamental nature of this error, the findings cannot be interpreted in the manner stated in the original article, and therefore this paper has been retracted. The authors apologise for this error.
How does one go about detecting the wrong strain of bacterium AFTER a paper was published? Identification of the strain, I assume, is probably the golden rule in microbiology or any field of study involving organisms and living beings. It’s truly astonishing to read that this basic error still takes place. In this case, it’s not that the strain is different, the species is totally different. That’s like mixing oranges with lemons. How many times has this paper been cited?
The strain of bacterium was misidentified, but can it be said that their model still experienced decreased blood glucose levels and reduced apoptosis of cardiocytes? If that is the case and they can state the strain used was consistent the they should amend the paper and resubmit the findings, perhaps with a note regarding the initial misinterpretation.
The authors may submit a new manuscript at a later date. Or they might not feel confident that they know when or how the mistake happened. The strain used at various stages of the study might be indeterminate.