Since the original description of Sarcina
organisms in humans by Goodsir in 1842 (9
), many observers speculated upon their significance; some have implicated the organism as pathogenic, while others have suggested the stomach as their natural habitat and their existence as a curiosity.(8
) Even though there appears to be considerable interest in the organism during this time period, to the best of our knowledge, a definitive series of human cases has not been published. This is the first series to confirm the identity of Sarcina
by DNA sequencing from formalin-fixed paraffin-embedded tissue, and to describe and correlate the clinical and pathologic findings in the upper gastrointestinal tract.
The scarcity of published literature on this organism raises the question of whether there was a decline in human cases since the original descriptions, followed by a recent resurgence. Our retrospective review of archived institutional pathology material over the past decade did not identify any additional cases of Sarcina organisms, supporting that the organism had not gone unrecognized or ignored in the recent past; however, we did identify a cluster of five cases over the relatively short course of 12 months in 2009–2010. In addition, the authors are aware of at least three additional cases that have been identified through consultation, following the completion of this study. This adds to the support of a recent reappearance of Sarcina in humans, especially among endoscopic biopsies.
The important clinical consideration is whether Sarcina is a contributory factor in the associated ulceration and mass formation, and therefore requires medical intervention, or whether it is simply a bystander in an underlying disease process. Given that two of the 6 biopsies showed no pathologic changes in the gastric mucosa, despite the presence of Sarcina, it is unlikely that Sarcina is the cause of ulceration or mass formation. However, it is also unlikely that the presence of Sarcina is merely an incidental finding and without consequence. All five patients in our series demonstrated retained food in the stomach at the time of endoscopy, either as a result of gastric outlet obstruction (due to mass or stricture) or gastroparesis. While it is unlikely that Sarcina is a cause of these functional disorders, the presence of these organisms may be considered a marker of delayed gastric emptying and a search for an underlying reason should be considered. For example, one patient was subsequently found to have an adenocarcinoma of the pylorus.
None of our patients showed the severity of disease that had been seen in earlier case reports of emphysematous gastritis and peritonitis. These three previously reported cases all showed underlying gastric outlet obstruction and ulcer formation.(13
) Two cases had prior medical intervention (bowel reduction secondary to malrotation, and a history of gunshot wound to the anterior chest) which might explain the gastric outlet obstruction. One patient developed gastric perforation and peritonitis, while the other two patients developed emphysematous gastritis. These two cases of emphysematous gastritis are the most provoking evidence that Sarcina
can cause significant disease in humans, as the organisms are gas-forming fermenters and cause lethal gastric bloating-like syndrome in animals. However, given our data, it seems more likely that a pre-existing mucosal defect (such as an ulcer) provided the nidus for emphysematous gastritis to develop, rather than direct invasion of Sarcina
into the gastric wall.
organisms’ characteristic tetrad packeting is the result of cell division in at least two planes of growth.(4
) The organism is a gram-positive, non-motile, chemoorganotrophic anaerobe, having exclusively fermentative metabolism and being relatively aerotolerant.(10
) The characteristic cell wall is refractile under light microscopy and was the feature that caused the earliest observers to believe these organisms were vegetable matter. The main differential diagnosis on light microscopy is with Micrococcus
shows a number of similar features, being a gram positive cocci that also occurs in tetrads or packets.(12
) These organisms also have a substantial cell wall, and can resemble Sarcina
on first glance. However, a number of features are helpful in differentiating the two organisms. For example, at 0.5 microns, Micrococcus
is considerably smaller than Sarcina
. In addition, Micrococcus
species tend to form clusters (), a feature not described among Sarcina
The authors are not aware of other microorganisms with similar morphology, size and clustering; we believe the histologic features of Sarcina are singular enough that a diagnosis can be made on routine hematoxylin and eosin stain. The molecular confirmation of Sarcina in nearly all of our histologically suspected cases provides support for a straightforward histologic diagnosis. Of note, the organisms in all cases were quite sparse, and the disappearance of Sarcina from the block upon recut was experienced with at least one case. Additional special stains, such as Browns and Hopps may help to highlight the unique tetrad morphology, but is not necessary for diagnosis.