According to recent literature, 95.4% of the strains associated with human clinical cases correspond to four species: , , and However, other less prevalent species such as are also described from clinical samples. Based on its low incidence, the latter species can be regarded as rare and it is the only species susceptible to ampicillin. From the taxonomic point of view, is considered a synonym of the species The objective of this study is to present a new clinical case associated with in order to increase the knowledge about this species The strain was recovered from the feces of a 69-year-old patient with a diarrheal syndrome and peritoneal psammocarcinoma. The preliminary identification as sp. was obtained with the API 20E, but it was characterized as and also as with different scores with the matrix-assisted laser desorption ionization time of flight (MALDI-TOF). Based on the sequence of the gene, it was confirmed to be . The antimicrobial resistance pattern showed that the strain was susceptible to ampicillin, penicillins in combination with beta-lactamase inhibitors, quinolones, carbapenems, aminoglycosides and cephalosporins, except cephalothin. In conclusion, the recognition of an strain susceptible to ampicillin should alert the clinical microbiologist of the possible involvement of this rare species. Furthermore, the MALDI-TOF database should be updated indicating that the species , is a synonym of .