Introduction

According to the teaching of the Catholic Church on the Sacrament of the Eucharist dogmatically defined during the 13th session of the Council of Trent (1551) (The Catechism of the Council of Trent 2009), the substance of the bread and wine changes into the body and blood of Christ during sacramental celebration of the Holy Mass. The Church refers to this total conversion as ‘transubstantiation’. The Church considers God’s presence in the Eucharist as a mystery being beyond human senses and beyond the possibility of scientific verification but experienced by spiritual insight and Christian faith. Only this phenomenon can be called a Eucharistic miracle in the strict sense, beyond the possibility of verification by scientific research (Kopeć 1989).

However, in the Catholic Church’s history, there have been more than 150 individual cases of ‘Eucharistic miracles’—the events where the authorities proclaimed that the transcendental truth has been confirmed and become perceptible to human senses and reason (Virgolini et al. 2023). The most common manifestation of those events is the bloody colouring of the Host and the transformation of the substance into a structure unlike bread but resembling human tissue. The Church is careful to investigate reports of unusual signs concerning the Eucharist with caution, lest credence is given to something that proves to be unfounded, but still, only a few such events have ever been investigated scientifically. In recent years, the Catholic Church has generally attempted to find a standardised investigative process, which is not always easy because the investigations should be multidisciplinary and coordinated, and the Church has no internal experts who can conduct such investigations.

In line with her doctrine, the Church used to make painstaking efforts to safeguard the liturgical rites to avoid contamination and profanation of the Holy Sacrament. According to the specific liturgical requirements, this bread must be unleavened and made purely of wheat. The ‘chain of custody’ should always be under control, meaning that the bread and wine prepared for liturgy are stored in a safe place before the liturgy and the remaining Eucharist Hosts after the liturgy are always guarded in the closed tabernacles, with access restricted only for the persons called to perform liturgical services. The integrity of the Eucharistic Host is maintained, and special attention is given during the distribution of communion to the faithful. Rarely, when the Host falls to the ground, it is transferred to a special container filled with pure water, called vasculum (Aquinas 1920). Typically, the Host resolves in the water. However, in the last few decades, some instances of substances resembling blood or tissues appeared on (or derived from) consecrated hosts. For those cases, the Church, far from hastily announcing ‘miracles’, ordered thorough scientific examinations to elucidate the character of the events. Unfortunately, except for isolated instances (Virgolini et al. 2023; Linoli 1971), the results of those efforts were never communicated to the general scientific community in the form of peer-reviewed papers. Instead, some of the conclusions were disseminated in a popular rather than scientific form, causing ambiguity and confusion (Chłopkowska 2017; Serafini 2021). On the other hand, in the popular media, such phenomena are often met with arrogant comments such as ‘There are no miracles, there are Serratia marcescens’. While it is essentially plausible that the substance resembling blood on consecrated hosts is actually prodigiosin, a red pigment produced by Serratia marcescens; such general statements, unsupported by evidence, can also be regarded as a kind of unproven belief.

This study, for the first time, presents a comprehensive forensic analysis of 25 actual cases of the changes appearing on the consecrated hosts. To elucidate the nature and origin of these changes, we used a variety of well-established laboratory techniques dedicated to the identification of biological traces in forensics. Finally, based on our own experience, we suggest a complete procedure suitable for reliable examination of similar cases in the future.

Materials and methods

The specimens

The study included a total of 25 cases of colour or structure changing of Eucharistic Host (in the form of white bread) after the consecration. They come from churches and other places in Poland, Germany, the USA, and South Africa, where Communion was distributed. All examinations were ordered by the Church’s officials. In most cases, the hosts fell to the ground shortly after the consecration, mostly during distribution of the Holy Sacrament. They were then picked up and placed in the water-filled containers (vascula) to dissolve, a procedure according to the ‘Liturgica instaurationes’ (Kozłowski 2018). However, after several days of storage and observation, some of the hosts did not dissolve. Instead, they exhibited the signs of red and purple colour stains (Fig. 1a–h), with corresponding liquid turning red, rusty, yellowish, or dark brown (Fig. 1a, e–h). The stains were usually either jelly-like (Fig. 1a, e–h) or dried (Fig. 1b–d), sometimes with corresponding signs resembling the mould colonies (Fig. 1a, c), while the liquids (if present) were mostly opaque.

Fig. 1
Fig. 1
Full size image

Examples of the materials found on the liturgical hosts: a case no.13; b case no.14; c case no. 2; d case no.10; e case no. 20; f case no. 16; g case no. 17; h case no. 15

In one instance, the material came from the hosts stored in a chalice and stolen from a chapel, which was then found in a forest area nearby. Each case was assigned a sequential number (Tables 1 and 2). The cases were analysed in the laboratories of the Collegium Medicum in Bydgoszcz, or in the laboratories of the Medical University of Wrocław and the University of Warsaw. Documentation of cases 1–15 is deposited in the Pontifical Faculty of Theology in Wrocław, whereas the documentation of cases 16–25 is deposited at the Department of Forensic Medicine, Ludwik Rydygier Collegium Medicum of the Nicolaus Copernicus University, Bydgoszcz, Poland.

Table 1 The overview of the results of initial forensic and genetic examination of 25 cases including materials from the consecrated hosts. ( +), positive result; ( −), negative result; (?), inconclusive result; NP, not performed; HPH, HemoPhan (non-specific blood test); HCh, HemCheck (specific human blood test); HBB EA, human haemoglobin TaqMan™ Gene Expression Assay (specific human blood test); QFDuo, Quantifiler® Duo DNA Quantification Kit (specific test for human and male DNA); PPlex ESI Pro, PowerPlex ESI 17 Pro System (multiplex amplification system for human autosomal DNA microsatellites); NGM SE, AmpFℓSTR® NGM Select™ PCR Amplification Kit (multiplex amplification system for human autosomal DNA microsatellites); YFiler, AmpFLSTR ™ Yfiler ™ Amplification Kit (multiplex amplification system for Y-chromosomal microsatellites)
Full size table
Table 2 The overview of the results of histological, mycological, and microbiological investigation of 25 cases including materials from the consecrated hosts. ( +), positive result; ( −), negative result; (?), inconclusive result; NP, not performed
Full size table

The overview of the analysed specimens is given in Tables 1 and 2. In most cases, both the isolated fragments of stains (typically, of a 1-cm diameter) and 5–10 uL of liquid substance were assigned to different laboratories (genetic, microbiological, mycological, histological) and subjected to further analysis. The scheme of the procedure undertaken is presented in Fig. 2.

Fig. 2
Fig. 2
Full size image

The procedural framework adopted for this study. The sample undergoes division to facilitate microbiological and mycological surveys, alongside forensic examination. Notably, both forensic and microbiological analyses encompass genetic assessments

In the following subchapters, the methods used during investigations are introduced.

Mycological and microbiological examination

The samples 1–15 were analysed in Wrocław or Warsaw, whereas the samples 16–25, in Bydgoszcz. All samples were inoculated on the microbiological media to stimulate fungal and bacterial growth.

In Bydgoszcz, the samples were inoculated on BD Columbia Agar with 5% sheep blood, BD MacConeky Agar, BD Pseudosel Agar (Cetrimide Agar), BD Enterococcosel Agar for a 5-day incubation at 37 °C in air atmosphere, and on BD Sabouraud agar with gentamicin and chloramphenicol (Becton Dickinson) for a 10-day incubation at 30 °C in air atmosphere. Samples were also incubated in brain–heart broth. The identification of isolated strains was performed with MALDI Biotyper (Bruker) according to the manufacturer’s instructions. The application of the MALDI Biotyper identified the isolates to species with an identification score of 2.000 and category A—a reliable identification at the species level.

The samples 2–15 analysed in mycological laboratories at the University of Warsaw were inoculated to Maltose Agar and/or Potato Glucose Agar and/or Sabouraud Glucose Agar to stimulate fungal growth from the inoculum. The incubation for fungal growth was performed at the temperature of 18 °C. The samples were observed and documented using the dissecting and optical microscopes (Nikon SMZ 800, Nikon Eclipse E200 and Nikon Eclipse E600 using Nikon DX-1200 or Nikon DS—Ri 2 cameras) with NIS Elements software. Slides were stained using lactophenol blue or material was suspended in lactic acid.

Mycelium fragments with a thin layer of the medium (0.9–1.0 μm thick) were prepared for LM and FM. For general observation, they were immersed in a lactic acid. They were observed with white light, and 300 nm UVB light. They were examined using a Nikon Eclipse 90i microscope. A UV2B filter (Nikon) was used to check both hyphae autofluorescence and fluorescence with Calcofluor White. Micrometry and photomicrography were accomplished by means of a Nikon Eclipse 90i (NIS-Elements AR software).

The DNA isolation was performed from the original sample (if homogenous), or from 7 days culture (if heterogenous). The DNA isolation was performed using ExtractMe Genomic DNA Kit (Blirt S.A, Gdańsk, Poland) following the manufacturer’s instructions. The PCR with the primers ITS1 and ITS4f (White et al. 1990) was performed. ITS region was used as the universal fungal barcode (Schoch et al. 2012). The amplification was performed using the ‘TaqNova-RED’ PCR mix, containing Taq DNA polymerase. The PCR reaction was conducted using the BioRad T100TM Thermal Cycler, with the programme described in Okrasińska et al. (2021). Products were visualised by electrophoresis in 1% agarose gel with Midori Green DNA stain (Nippon Genetics). PCR products were purified with the ExtractMe DNA Clean-Up & Gel-Out kit (Blirt S.A.). Sequencing was outsourced to an external company, Genomed S.A. (Warsaw, Poland). The sequences, forward and reverse, if both were obtained, were assembled using the Chromas (https://technelysium.com.au/wp/chromas/) or DNA Subway software (Williams et al. 2014) and compared against NCBI nucleotide databases using the BlastN search (Altschul et al. 1990). The nucleotide sequences have been deposited in the GenBank under accession numbers PQ470030, PQ475905, PQ481993, PQ481994, PQ482317, and PQ489325. To check the presence of Serratia marcescens the CHROMagar™ Serratia (distribution Biomaxima) were used.

Histological examination

Specimens prepared for histopathology examinations taken form solid material were fixed with formalin, paraffin-embedded, and then stained with haematoxylin and eosin (H&E) staining, and additionally, the Grocott’s method was used for the visualisation of fungi. The results were interpreted by a specialised pathologist.

Forensic investigations

Initial examination

Initially, the samples from cases no. 16–25 (Table 1) were examined for the presence of blood and specifically, for human blood (haemoglobin), using HemoPhan (Erba Lachema) or Bluestar OBTI (Bluestar Forensic) and HemCheck (Hydrex) tests, respectively. In one instance of an inconclusive result in HemCheck test (case no. 23), the sample was subjected to alternative RNA analysis with the use of High-Capacity cDNA Reverse Transcription Kit and human haemoglobin (HBB) TaqMan™ Gene Expression Assay (Thermo Fisher Scientific). The samples from cases no. 1–15 (Table 1) were not subjected to initial biochemical tests for the presence of blood and human blood; instead, they were directly examined for the presence of human and male DNA, on demand of the officials ordering the research.

Genetic analysis

Both stains and liquids were subjected to DNA extraction using GeneMATRIX Bio-Trace DNA Purification Kit (EurX). In one instance (case no. 23. Table 1), RNA was extracted with the use of organic method employing TRIzol™ Reagent (Invitrogen). Total amounts of human DNA and human male DNA in the samples were quantified using the Quantifiler® Duo DNA Quantification Kit (Thermo Fisher Scientific) and ViiA 7 Real-Time PCR System (Applied Biosystems). The latter was also used for performing HBB TaqMan™ Gene Expression Assay (case no. 23, Table 1).

Depending on a result of DNA quantitation, microsatellite markers were tested using the PowerPlex ESI Pro System (Promega), or AmpFℓSTR® NGM Select™ PCR Amplification Kit (Life Technologies), including 16 STRs (D3S1358, D19S433, D2S1338, D22S1045, D16S569, D18S51, D1S1656, D10S1248, D2S441, TH01, vWA, D21S11, D12S391, D8S1179, FGA, ACTB2), and amelogenin (X,Y) locus. In one instance, the AmpFLSTR ™ Yfiler ™ Amplification Kit (Thermo Fisher Scientific) was used to analyse 17 Y-STRs (DYS385, DYS19, DYS389I/II, DYS390, DYS391, DYS392, DYS393, DYS437, DYS438, DYS439, DYS448, DYS456, DYS458, DYS635, and Y GATA H4). PCR reactions were performed in the GeneAmp PCR System 9700 thermal cycler (Applied Biosystems), while the products were analysed on the ABI PRISM® 3130xl Genetic Analyzer and the GeneMapper® ID v. 3.2 software (Applied Biosystems). For autosomal STR probability estimates with corresponding values of likelihood ratio (LRs), both STR frequency database from Polish population and global STRidER (STRs for Identity ENFSI Reference Database, available online at https://strider.online) were used. Y-STR haplotype frequency was estimated with the use of YHRD database (Willuweit and Roewer 2015) for both minimal (DYS385, DYS19, DYS389I/II, DYS390, DYS391, DYS392, DYS393 loci) and complete haplotype. The Y-chromosome haplogroup prediction based on Y-STR haplotype was performed using the Y-DNA Haplogroup Predictor NEVGEN available online at http://nevgen.org.

Results

Tables 1 and 2 summarise the obtained results. In two cases, the investigation did not resolve the colour and structural changes. In one of those cases, a detailed identification of fungi was not performed. Fungal cultures were confirmed for more than 50% of cases.

Genetic investigations

In 6 out of 9 cases, the initial non-specific biochemical tests for the presence of blood showed positive results (Table 1). However, in 9 out of 10 cases, the specific HemCheck test for the presence of human haemoglobin proved negative. The only exception was a liquid from the case no. 23 (Table 1) which appeared inconclusive in the HemCheck test but was then verified as negative using both Bluestar and much more sensitive HBB TaqMan™ Gene Expression Assay.

Irrespective of the results of initial biochemical tests, the specimens from all analysed cases but one (24/25, Table 1) showed no human and male DNA. Only in the solid material from case no. 21, low amounts of both human and male DNA (20–200 pg/microL) were found using the Quantifiler® Duo DNA Quantitation kit, which allowed receiving both complete autosomal STR profile and Y-STR haplotype from that sample (Table 3). The frequency of autosomal genotype in the Polish population was (LR = 1/4,032,298,980,460,700,000,000), while the complete Y-STR haplotype was not found in the YHRD database, neither in complete dataset (n = 289,405 haplotypes) nor in the Eurasian metapopulation (n = 9750 haplotypes). However, for the Y-STR minimal haplotype obtained from the case no. 21, 37 matches were found in 349,750 haplotypes, which equals Kappa value of approximately 1 match in 10,457 haplotypes. For the Eurasian metapopulation, the respective values are 5 matches in 18,163 haplotypes and Kappa = 1 match in 3735 haplotypes. Finally, the minimal case’s no. 21 Y-STR haplotype was observed twice in the Polish subset of the YHRD (8,247 haplotypes) which equals Kappa of approximately 1 match in 3 575 haplotypes. The Y-haplogroup prediction based on Y-STR haplotype pointed to the northern European-specific clade I1. Additionally, we have searched the YHRD database for neighbouring haplotypes, i.e. haplotypes differing from the searched one by one repeat in one locus out of all searched. We have found no neighbouring haplotypes in the Y17 part of the YHRD (consisting of 17-loci haplotypes concordant with Yfiler® system). However, the search for neighbouring haplotypes in the Y12 part of the YHRD database (concordant with PowerPlex Y® system) detected 139 neighbouring haplotypes. Based on these similarities, the YHRD algorithm classified the obtained haplotype as Western European.

Table 3 Autosomal- and Y-STR profile of the solid material from case no. 21
Full size table

Mycological and microbiological investigation

Expectedly, for some of the specimens, a variety of contaminating bacteria were found in microbiological analysis (Table 2), including those giving orange and pink pigmentation (Brevundimonas intermedia, case no. 21, Serratia marcescens, cases no.4 and 7). Similarly, at least two species of fungi were revealed by a cultivation which, when cultured at suitable conditions, produce reddish-pink or orange-reddish pigments (Epicoccum spp., eight cases; Fusarium spp., cases no.4, 24, Table 2).

Histological examination

In most cases, dominant, very abundant and numerous structures were revealed, corresponding to fungi and microorganisms, most likely typical of the process of putrefaction and decomposition, confirmed by histochemical examination for the presence of fungi (positive Grocott staining). Scattered single exfoliated epidermal cells are also present, confirmed by positive immunohistochemical staining with an antibody against keratins (PanCK, CKAE1/AE3). Moreover, histopathological material contained less numerous, but very distinct, scattered shreds, streaks, strands, and fibre-like conglomerates of strongly eosinophilic structures with a structure similar to filaments, the morphology and structure of which most closely resembles exfoliated keratin masses, but this epidermal origin could not be confirmed in immunohistochemical methods.

The microscopic features of Fusarium culmorum and Epicocum nigrum found as host contaminants under visible and UVB light are summarised in Fig. 4. In one case, in the histopathological image, bundles of fibres were observed, appearing reddish-brown with visible striations and nuclei, resembling cardiac muscle fibres. Grocott’s staining did not reveal the presence of fungi (case no. 1, Table 2). In the second case, the histopathological image was similar to the previous one, but nuclei were not visible. The immunohistochemical examination (IHC) did not reveal the presence of muscle tissue (case no. 2, Table 2). In both cases, the results yielded conflicting outcomes; therefore, we leave these cases for further investigation.

Discussion

The present study for the first time provides a comprehensive forensic analysis of 25 actual cases including unusual (‘miraculously looking’) materials found on the consecrated hosts. While the analysed specimens came from a routine forensic casework of three academic institutes only, the phenomenon of modern-day ‘Eucharistic miracles’ seems to be on the rise, being reflected by a growing number of forensic examinations ordered by the Catholic Church’s officials. Unfortunately, very few of the results of that research were published in scientific papers (Virgolini et al. 2023; Linoli 1971) and thus subjected to critical analysis of reviewers and other interested parties. Instead, partial results are being disseminated in the popular media, resulting in understandable public interest, but also in unnecessary oversimplification and confusion (Chłopkowska 2017; Serafini 2021; and references herein).

As follows from this study, none of the presented cases revealed the actual proof of existence of human blood, human material other than single epidermal cells and erythrocytes (probably very low-level human contamination), and human and male DNA, irrespective of the unusual appearance of the analysed specimens. However, it is noteworthy that in some cases (no. 1 and 2), we could not find scientific explanation for unusual structures resembling cardiac muscle. Suspecting partially autolysed mycelial cords, in the case of no. 2, we conducted staining with Calcofluor, a fluorescent blue dye, which stains fungal and plant structures binding to cellulose and chitin, and we obtained no effect, despite typical staining the additional Cadophora malorum hyphae present in the sample (positive control).

The positive results of non-specific biochemical tests for the presence of blood (HemoPhan) obtained for several specimens can be easily explained by the contamination of vascula with bacterial and fungal material. Specifically, the HemoPhan test is based on the peroxidase activity of haemoglobin which catalyses the oxidation of the indicator due to the presence of the organic hydroperoxide present on the diagnostic pad, while microbial and fungal peroxidases may certainly give false positive results (PHAN and Erba Lachema n.d.). In this respect, it is worth noting that vascula, the containers used for rinsing the priest’s fingers with water after the distribution of Communion, are rarely cleaned and probably never specifically decontaminated. It is also apparent that most of the cases analysed in this study included the hosts that had fallen to the ground, which certainly favoured contamination. Moreover, the presence of bacteria (Brevundimonas intermedia, Serratia spp.,) and fungi (Epicoccum nigrum, Fusarium spp. Penicillium rubrum, Penicillium purpurogenum), producing spectacular-looking pigments were proved in several specimens analysed in this study by a cultivation (Méndez et al. 2011; Thomas and Tirumale 2022; Tuttobello et al. 1969). All above mentioned fungi are common both in buildings and outdoor (Gutarowska et al. 2023; Rizzi-Longo et al. 2009). It is also worth noting that some of those fungi, including Epicoccum nigrum (found in 32% cases, Table 2) may resemble human tissues in microscopic analysis under certain staining conditions, due to the commonly produced mycelial cords called synnema. Epicoccum synnema could be composed by several red coloured hyphae, with frequent cross-walls (Fig. 3). Interestingly, the red pigment is produced by Epicoccum growing with autolysed yeast and glucose (Tuttobello et al. 1969). Yeast was usually present in the fluid in the vessels and glucose, along with maltose, is usually a product of starch degradation.

Fig. 3
Fig. 3
Full size image

Synnema of Epicoccum nigrum (Collection of Botanic Garden, University of Warsaw, M. Wrzosek)

The microscopic features of Fusarium culmorum and Epicocum nigrum found as host contaminants under visible and UVB light are shown in Fig. 4. Under white light, both fungi have intense red filaments and secrete dye into the substrate. Under UVB light, Fusarium hyphae show no autofluorescence while Epicoccum hyphae glow intensely orange. It is particularly interesting to compare the luminescence of the two mushrooms after the addition of the dye Calcofluor white, which binds to the chitinous wall. While the filaments, chlamydospores, and spore of Fusarium react very clearly with Calcofluor, only the young filaments of Epicoccum react similarly to the dye. In the intensely glowing older filaments and medium, the effect of Calcofluor is imperceptible.

Fig. 4
Fig. 4Fig. 4
Full size image

The microscopic features of Fusarium culmorum and Epicocum nigrum found as host contaminants under visible and UVB light

Finally, the presence of human and male DNA in the solid specimen from case no. 21 can be easily explained by the existence of DNA transferred from a person to a host via contact with the host itself, the phenomenon referred to as ‘touch DNA’, ‘contact DNA’, or ‘trace DNA’ and discussed thoroughly in forensic DNA community (van Oorschot et al. 2019). Such interpretation is further supported by the lack of any human tissue material on that specimen (Table 2). The Y-STR profile obtained from that sample suggests European biogeographic ancestry (haplogroup I1), while the autosomal STR profile would certainly allow individual identification if the appropriate reference material was available. In a broader perspective, the existence of contact DNA is certainly expected on the hosts touched by the priest and sometimes also by the faithful (in the case of quite common Communion in the hand). Based on the cases described in this study, we suggest following the procedure routinely employed in forensic DNA laboratories in the analysis of similar cases in the future. The first steps would certainly include searching for human blood or other human tissues, with the use of a variety of approaches, from simple biochemical non-specific tests to tissue-specific RNA analyses (Sijen and Harbison 2021). In the second step, the presence of human and male DNA should be verified, followed by DNA profiling of autosomal and haploid (Y-chromosomal) markers and prediction of biogeographic ancestry, if necessary. In the interpretation of the DNA typing results, the phenomenon of ‘trace DNA’ must be considered. Finally, the nature of unusually looking materials should be elucidated by microbiological, histopathological, and mycological analysis.

There are several methods which should be suggested for such analysis. The first one is a direct microscopic analysis of the sample. If there are fungal spores in the material indicating the presence of Fusarium spp. or Epicoccum spp., the molecular identification could be skipped. Both genera produce characteristic spores, which have a discriminative value. It should be underlined that Fusarium reaches 440 spp., and Epicoccum is known as one of the commonest fungi isolated from indoor environments, outdoor air samples and is often noted in the decaying plant material (Gutarowska et al. 2023; Rizzi-Longo et al. 2009; Oliveira et al. 2010; Braga et al. 2018).

However, Epicoccum spp., and Fusarium spp. often grow as ‘mycelia sterilia’, without any reproductive structures. Where the direct microscopic identification is impossible, we suggest obtaining the sequence of the most universal molecular marker ITS. Both fungi in the genus level are easily identified by those markers, and the amplification is usually seamless. We suggest using the young, 7 days culture, rather than the original sample to avoid the contamination by associated fungi, especially yeasts.

The confusing colour and structure of the host can be caused by the development of many microorganisms in consortium. Filamentous fungi can overgrow the medium; yeasts and bacteria evoke the impression of meatiness and some of them can stain the sample in red (e.g. Serratia marcescens). Such structures were observed during examination of case no. 4 (Fig. 5).

Fig. 5
Fig. 5
Full size image

Case no. 4. The mix-culture of Serratia marcescens and fungal hyphae (Fusarium sp.)

The use of the chromogenic Serratia marcescens Lab-Agar (BioMaxima), or molecular, biochemical, immunochemical methods of Serratia marcescens identifications is strongly suggested (Bussalleu and Althouse 2018; Roig et al. 1983). The presence of Serratia marcescens is detected by-blue-green to metallic blue dye of colonies growing on the chromogar. The proposed primer set for the selective amplification of S. marcescens, was suggested by Bussalleu and Althouse (2018).

However, it is worth noting that S. marcescens was found exclusively in two cases, casting doubt on its significance in alleged miraculous occurrences associated with the appearance of bloody spots.

The use of DNA metabarcoding of samples is another good option for microorganism identification. This method makes it possible to bypass the step of obtaining axenic cultures. The sample as submitted serves as a source for DNA isolation. The ITS1 or ITS2 marker is standard for fungi, and the 16S rDNA gene for bacteria, mainly, the V3–V4 region (Giampaoli et al. 2021; Tran et al. 2017; Zhang et al. 2023). It is worth noting, however, that this method has limited resolution of species and strains, so the combining of different methods gives the best assignment to the taxon.

Surprisingly enough, the evaluation of partial results revealed to the general public in the cases of putative ‘Eucharistic miracles’ in Poland and other countries (Chłopkowska 2017; Serafini 2021) unequivocally showed that some of the above procedures were either omitted or their results were ignored. That led to premature and confusing decisions, possible to avoid if the standards of scientific rigour had been applied.

In summary, scientific investigations are always necessary when the Church decides to proclaim a supernatural occurrence. The scientific panel must unanimously conclude that the chain of storage was correct and that there is no explanation for what happened to the host.

Once the results are known, and the scientific procedures do not come close to solving the problem of substance change, the bishop of the place can conclude that something very unusual has happened, or decide not to give the incident any publicity. It happens that certain circumstances of an incident are not clear. Then, the Church generally shows restraint and does not proclaim the miracle despite inexplicable changes of substance.

Finally, we would like to emphasise that the research we are conducting is not aimed at ascertaining the miraculous nature of a phenomenon, since we have neither the authority nor the competence to do so, but trying to explain it on the basis of natural phenomena. If we do not succeed in doing so, then we leave the decision as to the possibility of a special Eucharistic sign in the hands of the ecclesiastical authorities.