Incidental finding of Clostridium perfringens on human corpses used for the anatomy course

Human post-mortem tissues provide a valuable resource for undergraduate and professional teaching. Commonly, these tissues are embalmed using different chemicals, primarily with the objective to maintain tissue quality and to avoid putrefaction (Hammer et al. 2015; Thiel 1992). A recent study has questioned the disinfecting effects of commonly used embalming solutions (Balta et al. 2019). So far, little research has been conducted on the microbiota that may survive the embalming process, or even may cause cross contamination of other corpses (Brenner 2014). Bacterial or fungal contamination of anatomical specimens with human pathogens may pose staff and students likewise at risk. In particular, sporulating bacteria may be relevant owing their ability to survive in hostile environments for longer durations (Horneck et al. 1994). Clostridium species such as Clostridium perfringens may lead to the development of gas gangrene, potentially with fatal outcome (Suerbaum et al. 2020). C. perfringens is known to be resistant even to 50% ethanol environments for more than one hour (Koransky et al. 1978). For reasons of hygiene and workplace safety, it is important to understand which microorganisms may find a suitable environment to grow on chemically embalmed specimens, and which ones may be a potential harm to living humans. We report on an incidental finding of C. perfringens species on ethanol–glycerin (Hammer et al. 2012) and Thiel (Thiel 1992, 2002) embalmed specimens and which measures were taken to minimize the risk for students and staff in anatomy.

Bacteria species were detected on five of the six corpses investigated. The resulting bacterial cultures yielded four cases of C. perfringens, two Propionibacterium species, and one case each of C. innocuum, Escherichia coli and C. tertium, respectively. Four of the five containers with the moistening solution were contaminated with the bacterial species detected: C. perfringens and C. paraputrificum, Enterococcus faecalis, Enterococcus faecium and Leuconostoc mesenteroides (Table 1). These observations were made irrespective of the type of moistening solution.

Prior to the anatomical dissection of human corpses, two main steps of embalming are commonly performed: chemical fixation and conservation. Anatomical fixation relates to the procedures to interfere tissue decay and to prevent from (further) contamination and autolysis. Chemicals used for anatomical conservation help to maintain the state of fixation (Hammer et al. 2012). For safety reasons it is vital to evaluate the risk of bacterial/fungal contamination for both infection containment and hygiene purposes to work safely with embalmed corpses. Compared to formaldehyde based embalming which showed high bactericidal effects over 8 months of investigation in previous studies (Balta et al. 2019), Thiel solution and ethanol–glycerin embalming methods could be considered mild embalming methods with low formaldehyde concentrations aiming at good preservation of tissue softness for surgical training (Brenner 2014). Therefore, ongoing microbiological testing for quality assurance is performed. From the list of bacteria observed here, C. perfringens seems of special interest. The germ is widely distributed in soil and is regularly found in the human gastrointestinal tract without causing symptoms (Ohtani and Shimizu 2016). As a human pathogen, it is one of the major causes for gas gangrene. Less frequently gas gangrene is caused by C. septicum, C. histolyticum and more recently C. sordellii (Buboltz and Murphy-Lavoie 2022). For C. tertium, C. paraputrificum and C. innocuum, as found in the samples reported in this study, only a few case reports, including abscess formation, bacteremia, diarrhea and only one case of gas gangrene were  published (Fujitani et al. 2007; Vijayvargiya et al. 2020; Chen et al. 2022).

Though infection following skin injury hardly ever happens in healthy individuals. The inoculation of C. perfringens may prove detrimental in the presence of immunosuppression (Leiblein et al. 2020). Hence, special care must be taken to minimize any risk of infection (Suerbaum et al. 2020). Though cases of Clostridium species infection seem low in general (incidence of 1.8 per 100.000 persons per year), 42% of Clostridium infections are caused by C. perfringens (Fukui et al. 2017). Previous studies have yielded that Clostridium species are capable of surviving ethanol concentrations of up to 50% for more than one hour of incubation (Koransky et al. 1978).

Based on the observation of the bacteria above, three potential explanations were found for the onset of Clostridium species: 1) ubiquitarian environmental contamination, 2) contamination from storage systems or applicants, or 3) cross contamination from corpses of body donors harboring C. perfringens in their gastrointestinal tract. The presence of C. perfringens on the corpses and moistening solutions led to the conclusion that cross contamination seems to be the most likely explanation. We here hypothesize that a contamination of one (or several corpses) was spread when soaking the cover linen by submersion in the same moistening solution.