Absence of 1-propanol does not universally exclude microbial ethanol formation. Boumba and colleagues documented ethanol production without reported 1-propanol in certain controlled bacterial and fungal blood cultures. The result supports caution with a negative single-marker rule, while leaving the size and origin of ethanol in an individual autopsy specimen unresolved.
A culture experiment, not a universal diagnostic sensitivity study
The 2024 study compared several bacterial species and Candida albicans in conventional broths and heat-denatured human blood. It also evaluated mathematical models in 122 selected autopsy samples, but the culture observations and the autopsy-model exercise were different parts of the investigation.
For the blood experiments, pooled human blood with initial glucose of 0.9–1.3 g/L was heated at 50°C for approximately two hours. Two-milliliter portions were inoculated to about 10⁶ colony-forming units/mL. Each culture condition used 16 tubes, with two removed on each day from day 0 through day 7. Cultures were maintained at 25°C under strictly anaerobic conditions or with an initial aerobic phase followed by an oil overlay on day 4.
Those manipulated specimens were surrogates for postmortem blood. Sixteen tubes are not 16 independent decedents, and these experiments do not reproduce the full microbial community, preservation or temperature history of a corpse.
Ethanol and 1-propanol did not always appear together
In Table 3, Enterococcus faecalis in the mixed-aeration blood condition produced ethanol ranging from 1 to 5 mg/dL, while 1-propanol was reported as zero. In the anaerobic condition, ethanol ranged from 1 to 7 mg/dL and 1-propanol from 0 to 0.01 mg/dL.
For C. albicans without added glucose, acidic blood cultures had ethanol of 1–8 mg/dL and neutral cultures 1–7 mg/dL; 1-propanol was reported as zero in both. Methyl-butanols were nevertheless present at 0.01–0.02 mg/dL. Thus, absence of one congener was not absence of all microbial products.
These ethanol ranges were modest: 1–8 mg/dL corresponds to 0.01–0.08 g/L. They should not be generalized into proof that any much higher concentration can develop without 1-propanol under the same conditions.
Medium and organism changed the pattern
The same organisms did produce 1-propanol in other culture settings. The findings therefore do not identify an organism that can never make it. Added glucose, culture composition and aeration affected the pattern, and only Staphylococcus aureus produced all the measured higher alcohols in the tested denatured-blood conditions.
The study also reported no 1-butanol in its fungal blood cultures. A panel interpreted as though every microbial species must produce the same set of congeners would disregard this experimental variation.
A reported zero remains method-dependent
Alcohols were measured by headspace GC–FID, and the two methyl-butanol isomers were reported as their sum. The 2024 paper refers to earlier analytical procedures rather than restating a complete numerical detection-limit validation. A table entry of zero should therefore be read as the reported analytical finding, not proof that no molecule was present.
The experiment establishes neither a clinical false-negative rate for 1-propanol nor a universal alternative cutoff. The selected 122-case autopsy group required ethanol above 0.10 g/L and at least one detectable higher alcohol, so it cannot estimate how often a completely congener-negative autopsy sample contains newly formed ethanol.
What follows for interpretation?
Evaluate the full volatile profile, specimen conditions and other evidence of exposure or microbial activity. A negative 1-propanol finding alone cannot settle ethanol origin, just as a positive finding alone does not quantify the amount produced after death. Our discussion of discordant EtG and EtS results addresses a different marker-based inference.
These culture findings do not establish drinking, impairment, antemortem ethanol concentration or cause of death in an individual.
Primary source
Boumba VA, Velivasi G, Kourkoumelis N. Ethanol and Higher Alcohols’ Production in Fungal and Bacterial Laboratory Cultures and Significance for Forensic Samples. Microorganisms. 2024;12:462. doi:10.3390/microorganisms12030462.
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