Scientists Found Promising Probiotics Inside Asian Elephant Poop

Captive Asian elephants face a quiet digestive crisis as they age. Tooth wear makes it harder to process the fibrous plants they depend on, and disruptions to the gut's microbial community can cascade into malnutrition, weakened immunity, and dangerous infections. A new study published in Veterinary World suggests that the solution may already be living inside the elephants themselves.

Researchers at institutions in Thailand collected fresh fecal samples from 25 clinically healthy captive Asian elephants, aged 30 to 50 years, in Krabi Province. From those samples, they isolated, screened, and molecularly identified lactic acid bacteria (LAB) strains with the goal of finding candidates suitable for use as host-specific probiotics. The results are preliminary, but three strains in particular stood out.

L. plantarum Strains from Elephant Feces Show Broad Antimicrobial Power

The team recovered 195 LAB isolates in total. Of those, 52 inhibited all five tested pathogens: Escherichia coli, Salmonella enterica serovar Typhimurium, Pseudomonas aeruginosa, Staphylococcus aureus, and Klebsiella pneumoniae. Inhibition zone diameters of 11 to 13 mm placed the antimicrobial activity in the "strong" category. Eleven isolates cleared a higher bar, showing inhibition zones of 12 to 15 mm alongside survival rates of 74.67% to 91.67% at pH 3.0 and 75.17% to 98.15% in 1% bile salt, conditions chosen to mimic the physiological stress bacteria face in the elephant gut.

Three isolates, labeled I9, I56, and I145, consistently performed best across every metric. Cell surface hydrophobicity, a measure of a bacterium's ability to adhere to intestinal walls, ranged from 74.03% to 92.24% in the top-performing group, while autoaggregation capacity reached 70.60% to 85.74%, signaling strong cell-to-cell bonding that helps form stable colonies in the gut. Molecular analysis using 16S rRNA gene sequencing confirmed that these three standout isolates are Lactiplantibacillus plantarum, a species with a growing track record across animal species. Research on L. plantarum in livestock gut health documents its ability to produce antimicrobial compounds like plantaricin that suppress pathogens including Salmonella and E. coli, a profile consistent with what the Thai team observed in vitro.

Why Host-Specific Probiotics Matter for Captive Elephant Health

Asian elephants are monogastric hindgut fermenters, meaning they rely on microbial communities in their large intestine to break down fibrous plant material into usable energy. When that microbial balance shifts, the consequences are serious: reduced energy availability, impaired nitrogen metabolism, and a weakened defense against opportunistic pathogens. Aging animals are especially vulnerable because dental wear limits their ability to process roughage in the first place.

The principle driving this line of research is that probiotic effects are strain- and host-specific. A bacterium that works well in poultry or swine may not colonize or function effectively in an elephant's very different digestive environment. Research on gut microbiome interventions for captive elephants has highlighted the importance of identifying the dominant lactic acid bacteria in Asian elephants specifically before selecting appropriate probiotic candidates. Sourcing strains directly from healthy elephant feces is one way to prioritize strains already adapted to that environment. Notably, L. plantarum has also been found in the gastrointestinal tracts of other megaherbivores, including rhinoceros, hippopotamus, and giraffes, suggesting it may be a recurring and ecologically relevant colonizer in this class of animals.

16S rRNA Sequencing Anchors the Molecular Identification

Earlier work on elephant gut microbiota often relied on phenotypic characterization alone, categorizing bacteria by shape, growth patterns, and biochemical reactions rather than genetic identity. This study moved beyond that by performing 16S rRNA gene sequencing and phylogenetic analysis on the 11 top-performing isolates. The approach is well established for resolving species-level identity in LAB, where morphological similarities between genera can otherwise create ambiguity. Broader reviews of molecular identification techniques for L. plantarum note that 16S rRNA sequencing, while powerful, captures genus-level diversity most reliably, with whole-genome sequencing offering finer strain-level resolution for future work.

The sequencing revealed that four of the 11 superior isolates were L. plantarum and seven were Enterococcus faecalis. The researchers flagged the E. faecalis identification as a concern: while common in gut environments, the species carries potential virulence factors and opportunistic pathogenic traits that make it a weaker candidate for deliberate probiotic use. That distinction made the L. plantarum isolates the clear focus of the study's conclusions.

Safety Looks Solid in the Lab, but In Vivo Tests Are Still Needed

All 11 selected isolates tested non-hemolytic, showing gamma-hemolysis rather than the cell-lysing activity that would signal a pathogenic risk. All were susceptible to five clinically relevant antibiotics: ampicillin, chloramphenicol, streptomycin, tetracycline, and enrofloxacin. That antibiotic susceptibility matters because some probiotic strains can carry transferable resistance genes; research on antibiotic resistance risks in probiotic bacteria has highlighted this as a legitimate concern for both animal and human health. The clean susceptibility profile here suggests these particular strains pose a low transfer risk, though the authors are careful to frame this as in vitro evidence only.

The study's core limitation is that everything described so far was conducted in a petri dish or test tube. The researchers did not assess bile salt hydrolase activity, epithelial adhesion under dynamic gut conditions, or short-chain fatty acid production directly. There was no certified reference probiotic strain used as a positive control, a methodological gap the authors acknowledge. Broader reviews of challenges in applying probiotics to livestock underscore the distance between promising in vitro data and confirmed efficacy in a living animal, noting that optimal dosage, formulation stability, and delivery strategy all require separate investigation.

The Path from Lab Dish to Elephant Barn

The authors describe this as the first study to combine molecularly validated identification with a comprehensive in vitro probiotic evaluation for elephant-origin LAB strains. The published research calls for in vivo trials in Asian elephants as the immediate next step, alongside studies of strain-specific dosage and formulation stability. Comparative work between captive and wild elephant populations is also proposed, which could clarify whether these strains reflect a natural symbiosis or an artifact of the captive diet.

For now, isolates I9, I56, and I145 represent a biologically plausible starting point: bacteria that already live in healthy elephant guts, can survive the conditions of that gut, and can suppress five pathogens without showing obvious safety red flags. Whether they will perform as well inside a living elephant as they do in a laboratory remains an open question, but it is one researchers are now positioned to ask.

Evidence rating

INVESTIGATIONAL — 67/100

Caveats:

• All findings are from in vitro laboratory tests only — no animal or clinical trials have been conducted to confirm these effects in living elephants.
• No certified reference probiotic strain was used as a positive control, limiting methodological benchmarking.
• Funding source was not disclosed by the authors.

In vitro isolation and characterization study using fecal samples from 25 captive Asian elephants. All findings are laboratory-based with no in vivo validation; results show functional probiotic properties under simulated conditions but cannot establish efficacy or safety in living animals. Not yet replicated in any independent population.