IngredientsAcinetobacter calcoaceticus does not appear in the monographs of any major pharmacopeia (USP, European Pharmacopoeia), is not listed among ingredients recognized as Generally Recognized as Safe (GRAS) by the U.S. Food and Drug Administration, holds no Qualified Presumption of Safety (QPS) status from the European Food Safety Authority (EFSA), and is not assessed as a supplement ingredient by authoritative evidence databases such as the NIH Office of Dietary Supplements or the NIH National Center for Complementary and Integrative Health (NCCIH). Despite appearing in a small number of commercially marketed probiotic and soil-based organism (SBO) blends, its inclusion in such products is not supported by regulatory approval or established clinical safety evidence. The following reference article presents the complete, source-verified scientific record regarding this organism — including its biology, biochemical significance, associations with human health (including disease associations), and safety considerations — drawn entirely from peer-reviewed literature and authoritative institutional sources.
Acinetobacter calcoaceticus is a bacterial species of the genus Acinetobacter. It is a nonmotile, Gram-negative coccobacillus that grows under aerobic conditions, is catalase positive, and oxidase negative. It belongs to the family Moraxellaceae. According to the NCBI Taxonomy database, its full taxonomic lineage is: cellular organisms > Bacteria > Pseudomonadota > Gammaproteobacteria > Moraxellales > Moraxellaceae > Acinetobacter > Acinetobacter calcoaceticus/baumannii complex.
Acinetobacter calcoaceticus is formally designated as genospecies 1 within the genus Acinetobacter. Members of the genus Acinetobacter are non-fermentative, strictly aerobic, non-motile, non-pigmented, catalase-positive, and oxidase-negative Gram-negative coccobacilli, usually occurring in diploid formation or in chains of variable length that grow on usual laboratory media.
The taxonomic history of Acinetobacter spp. appears confusing, since they have been classified variously, moving from the family Neisseriaceae to the family Moraxellaceae under the names Moraxella, Herellea, Mima, Achromobacter, and Alcaligenes. Even today, the situation remains subject to continuous change. According to older nomenclature, Acinetobacter was represented by a single species, Acinetobacter calcoaceticus, included in the family Neisseriaceae.
The species designation A. calcoaceticus was established in 1968 by Paul Baumann and colleagues, who reclassified Micrococcus calcoaceticus as Acinetobacter calcoaceticus based on numerical taxonomy and physiological studies of oxidative metabolism in non-fermentative bacteria. The species was formally validated in 1980 through inclusion in the Approved Lists of Bacterial Names, with the type strain (ATCC 23055) originating from soil enrichment.
A. calcoaceticus is a part of the A. calcoaceticus–A. baumannii complex (ACB complex) together with Acinetobacter baumannii, Acinetobacter nosocomialis, Acinetobacter pittii, and Acinetobacter seifertii. It is not usually possible to differentiate between the individual species of this complex using routine identification programs. In cases where A. calcoaceticus is detected, it is not possible to rule out confusion with the clinically most important representative of the ACB complex, A. baumannii.
A. calcoaceticus is primarily a soil bacterium. It has been shown to be present in the human body in moist areas including the mouth, groin, respiratory tract, and gastrointestinal tract. It is also present in the microflora of the tiger mosquito (Aedes albopictus).
Acinetobacter calcoaceticus is a Gram-negative bacterium in the family Moraxellaceae of the class Gammaproteobacteria. It is strictly aerobic, grows at temperatures ranging from 20°C to 35°C, and is widely distributed in soil, water, wastewater, and food. It also exhibits notable halotolerance and plant growth-promoting properties.
A. calcoaceticus is an environmental pathogen found primarily in soil and water. The bacterium has also been detected in wastewater and on human skin, as well as on animals and vegetables. In contrast to its pathogenic potential in clinical settings, members of the genus form a group of "cleaning bacteria," which are able to degrade a large number of aromatic compounds and toxins. Acinetobacter species play an important role in hydrocarbon degradation and have a key role in bioremediation processes.
Acinetobacter species are ubiquitous in nature and may be isolated from soil, water, commercial food products, hospital environmental surfaces, and medical devices. The organism demonstrates remarkable persistence under adverse conditions, including disinfection and desiccation.
A. calcoaceticus does not have an established pharmacopeial preparation or a recognized dietary supplement form. In the limited commercial supplement context, it has appeared as a component of multi-organism soil-based organism (SBO) products. One commercially available product (Prescript-Assist) lists Acinetobacter calcoaceticus among a blend that also includes organisms such as Arthrobacter spp., Azotobacter spp., Bacillus spp., and various Pseudomonas and Streptomyces species. No dosage or concentration of A. calcoaceticus is declared in such products, and no peer-reviewed clinical trials have evaluated it as a standalone supplement in humans.
In biotechnological and research settings, fermentation conditions for the production of pyrroloquinoline quinone (PQQ) by Acinetobacter calcoaceticus have been studied and optimized, with yields increasing from 43.65 mg/L to 73.40 mg/L under machine-learning-guided experimental conditions. This industrial interest relates to the organism's capacity to produce PQQ as a fermentation product rather than any direct use of the organism itself as a supplement ingredient.
Acinetobacter calcoaceticus has no documented history of intentional traditional or historical use as a medicinal substance, botanical preparation, or dietary supplement in any known cultural, folk medicine, or ethnopharmacological tradition. It was not recognized as a discrete species until 1968, and its formal validation came only in 1980. No WHO Traditional Medicine monographs, Commission E monographs, ESCOP monographs, or Ayurvedic, Traditional Chinese Medicine (TCM), or other ethnomedical compendia include or reference this organism as a therapeutic or nutritional agent.
The organism's only historical relevance to human applications involves its documented ecological roles: naturally occurring in soil and water microbiomes, its recognized capacity for hydrocarbon degradation in bioremediation, and its use as a laboratory research organism since the late 20th century.
Pyrroloquinoline quinone (PQQ) stands as a pivotal cofactor among oxidoreductases residing on bacterial cell membranes. Beyond its involvement in enzymatic catalysis during redox reactions, PQQ assumes a critical role in electron transfer mechanisms and showcases robust antioxidant characteristics. Its profound impacts extend to promoting metabolic activities, growth, development, and fostering resilience.
A. calcoaceticus has been studied as one of several bacterial species in which genes involved in PQQ biosynthesis have been characterized. Notably, only four genes are required in A. calcoaceticus for PQQ biosynthesis, compared with six in Klebsiella pneumoniae and seven in Methylobacterium extorquens (AM1). PQQ is derived from the two amino acids glutamic acid and tyrosine encoded in the precursor peptide PqqA.
The PQQ biosynthetic pathway of A. calcoaceticus represents a streamlined system for cofactor synthesis. Moreover, A. calcoaceticus exhibits broad substrate specificity and high product purity, utilizing carbon sources such as ethanol, methanol, glycerol, and polyols.
The hydrocarbon-degrading strain A. calcoaceticus RAG-1 produces an extracellular emulsifying agent capable of forming stable oil-in-water emulsions. The bioemulsifier, termed emulsan, is a polyanionic heteropolysaccharide. The heteropolysaccharide backbone contains a repeating trisaccharide of N-acetyl-D-galactosamine, N-acetylgalactosamine uronic acid, and an unidentified N-acetyl amino sugar. Fatty acids are covalently linked to the polysaccharide through O-ester linkages.
Even at very low concentrations (<0.001 to 0.01%), emulsan can emulsify hydrocarbons efficiently and is regarded as among the most powerful emulsion stabilizers, having applications in diverse fields. Emulsan and biodispersan, produced by A. calcoaceticus, are among the best-studied examples of polymeric biosurfactants and consist of a heteropolysaccharide moiety covalently linked to fatty acids.
In addition to emulsan, the most notable polymeric biosurfactants associated with the genus include lipomanan, alasan, liposan, and emulsan. The species A. calcoaceticus has been specifically identified as a producer of biodispersan, a related extracellular polymer with surface-active properties. Different Acinetobacter species produce protein–polysaccharide complexes that possess surface-active properties.
Phloroglucinol carboxylic acid is a degradation product excreted by A. calcoaceticus grown on (+)-catechin as the sole source of carbon. This metabolite is produced when the organism degrades plant polyphenols, indicating the presence of specific aromatic compound-degrading pathways.
A central enzymatic component of A. calcoaceticus is its PQQ-dependent glucose dehydrogenase, a quinoprotein. Research dating to 1979 identified glucose dehydrogenase from A. calcoaceticus as a "quinoprotein," meaning that PQQ serves as its essential cofactor. This enzyme plays a central role in the organism's ability to oxidize glucose and channel electrons into respiratory chains, and it has been extensively studied as a model system for PQQ-dependent catalysis.
Biolog phenotypic microarray studies found that the majority of A. calcoaceticus strains could utilize glucose, L-arabinose, D-galactose, D-mannose, D-fructose, N-acetyl-D-glucosamine, D-trehalose, adonitol, mannan, pectin, α-, β-, and γ-cyclodextrin, dextrin, D-ribose, α-ketoglutaric acid, and L-glutamine, indicating that A. calcoaceticus can use a wide range of nutrient sources.
The gastrointestinal tract has been speculated to serve as a reservoir for Acinetobacter; however, little is known about the ecological fitness of Acinetobacter strains in the gut. Likewise, not much is known about the ability of Acinetobacter to consume dietary or host-derived nutrients or their capacity to modulate host gene expression.
A 2022 study published in Frontiers in Physiology (Glover et al., Medical University of South Carolina) examined the gut survival and host interactions of A. calcoaceticus using commercial strains and clinical isolates. All strains had robust growth in 0.1 and 0.5 M NaCl concentrations which mirror the small intestine, and all strains tolerated up to 5% ethanol and 0.1% hydrogen peroxide. Biolog phenotypic microarrays revealed that A. calcoaceticus strains could use a range of nutrient sources, including monosaccharides, disaccharides, polymers, glycosides, acids, and amino acids.
Critically, the commercially available A. calcoaceticus strains and one clinical isolate stimulated the pro-inflammatory cytokines TNF, KC, and MCP-1, while all strains suppressed MUC13 and MUC2. These mucins are major components of the intestinal mucus layer, and their suppression may indicate a potentially disruptive effect on mucosal barrier function.
These data collectively demonstrate that A. calcoaceticus is well adapted to dealing with environmental stressors of the gastrointestinal system, and point to the potential for Acinetobacter to influence the gut epithelium. This 2022 study was, to the knowledge of its authors, the first to show that A. calcoaceticus can colonize human stool communities and modulate the gut epithelium.
Evidence quality: This evidence is entirely preclinical — in vitro (murine intestinal organoids) and ex vivo (bioreactor). The authors note several limitations: this work was all done in vitro, and in vivo studies are necessary to truly identify the colonization capacity of A. calcoaceticus. Differences were observed between lab-adapted strains and clinical isolates, highlighting strain variation and indicating that clinical isolate strains should be incorporated into future work. No human clinical trials have examined gut colonization by A. calcoaceticus in a supplement context.
Analysis of 3,853 publicly available RNA-Seq datasets from 26 independent studies revealed that A. calcoaceticus was one of the top 10 highest elevated bacteria in Crohn's Disease patients. Multiple studies over the last decade have implicated intestinal bacteria in the initiation and perpetuation of IBD, but the precise microbes that contribute to inflammation remain unknown.
A preclinical study examined the capacity of A. calcoaceticus to enhance inflammation using a murine colitis model. Mice were orally gavaged with A. calcoaceticus and then treated with 2% dextran sodium sulfate (DSS) in drinking water for 5 days to induce mild colitis. Mice treated with A. calcoaceticus and DSS lost more weight and had worse histological scores than those treated with vehicle control and DSS, indicating that A. calcoaceticus worsens intestinal inflammation. Consistent with these findings, addition of live A. calcoaceticus to inside-out intestinal organoids stimulated the production of pro-inflammatory cytokines TNF, IL-8, IL-1α, and MCP-1.
The importance of Acinetobacter in the gut is further highlighted by the fact that Acinetobacter species are elevated in certain disease states including ulcerative colitis, a subset of inflammatory bowel disease (IBD).
Evidence quality: All evidence in IBD/Crohn's disease is either observational (metatranscriptomic datasets showing elevated abundance) or preclinical (animal models, organoids). The directionality of causality — whether elevated A. calcoaceticus causes IBD or simply colonizes more readily in a dysbiotic gut — has not been established in human trials. The preponderance of current evidence suggests a pro-inflammatory, rather than beneficial, association.
One of the most extensively cited research associations for A. calcoaceticus in the context of human disease concerns its link to multiple sclerosis (MS). A landmark study analyzed microbiomes of 71 MS patients not undergoing treatment and 71 healthy controls. Although no major shifts in microbial community structure were found, the study identified that Akkermansia muciniphila and A. calcoaceticus, both increased in MS patients, induced proinflammatory responses in human peripheral blood mononuclear cells and in monocolonized mice. In contrast, Parabacteroides distasonis, which was reduced in MS patients, stimulated anti-inflammatory IL-10-expressing human CD4+CD25+ T cells and IL-10+FoxP3+ regulatory T cells in mice. Microbiota transplants from MS patients into germ-free mice resulted in more severe symptoms of experimental autoimmune encephalomyelitis (EAE) and reduced proportions of IL-10+ regulatory T cells compared with mice "humanized" with microbiota from healthy controls.
Acinetobacter calcoaceticus and Akkermansia muciniphila have been linked to MS because they can stimulate Th17 induction and pro-inflammatory activities. Certain bacterial species, including Akkermansia muciniphila and Acinetobacter calcoaceticus, are capable of activating intestinal Th17 cells and promoting inflammation in the spinal cords of EAE mice.
Molecular database analysis identified similarity between A. calcoaceticus and an encephalitogenic myelin peptide. Elevated anti-Acinetobacter antibodies have also been found in MS patients, implicating molecular mimicry as a potential immunopathogenic link between Acinetobacter and MS. One study identified a reduction in CD4+ T-regulatory cells after T-cell stimulation with A. calcoaceticus, suggesting it may also promote autoimmunity by impairing T-regulatory cell function.
Evidence quality: The MS research is based on a human cross-sectional microbiome study (n=71 MS patients, n=71 healthy controls), mechanistic experiments in human peripheral blood mononuclear cells, and animal (germ-free mouse) colonization studies. These are significant findings, but they are associational and mechanistic — not controlled clinical trials. Species such as A. baumannii, A. calcoaceticus, and A. lwoffii are rare in the healthy human gut microbiome and share genome-wide homology, making them indistinguishable by 16S amplicon sequencing; OTUs that mapped to the genus Acinetobacter did not allow species-level discrimination. This is an important methodological caveat affecting all association studies using 16S sequencing.
A. calcoaceticus is studied as a microbial host for the production of pyrroloquinoline quinone (PQQ), a bioactive compound that itself has a separate emerging evidence base as a dietary supplement. Research has employed machine-learning-assisted approaches to optimize fermentation conditions for PQQ production by A. calcoaceticus, enhancing yields from 43.65 mg/L to 73.40 mg/L — an increase of 68.15%.
It is important to distinguish between the organism (A. calcoaceticus) and its secreted product (PQQ). Clinical interest and regulatory approval discussions surround PQQ itself, not the bacterium. PQQ assumes a critical role in electron transfer mechanisms and showcases robust antioxidant characteristics. Its impacts extend to promoting metabolic activities, growth, and development. It represents a novel biocomposite material within the industrial domain. The use of A. calcoaceticus as a production organism for PQQ is an industrial microbiology topic distinct from any human supplementation with the bacterium itself.
The bioemulsifier emulsan produced by A. calcoaceticus has been the subject of environmental and industrial biotechnology research. The emulsan biosurfactant has been produced by A. calcoaceticus PTCC1318, with production confirmed by FTIR and ¹H NMR analysis. Its primary documented applications are in bioremediation of hydrocarbon spills and enhanced oil recovery — not in human health supplementation.
No peer-reviewed human clinical trial has established a dosage of A. calcoaceticus for any health indication. The organism has not been the subject of Phase I, II, or III clinical trials as a probiotic or supplement. Therefore, no evidence-based dosage recommendations can be stated.
In preclinical research, murine studies employed oral gavage with A. calcoaceticus followed by 2% DSS in drinking water for 5 days to evaluate its effects on colitis. These are experimental protocols, not therapeutic dosing regimens applicable to humans.
In the one commercially identified multi-organism supplement product in which A. calcoaceticus appeared, the dosing recommendation was 1–2 capsules per day for adults — however, the specific concentration or colony-forming unit (CFU) count of A. calcoaceticus within that blend was not disclosed, and the product is not regulated or approved for any health claim related to this organism.
Although more than 50 species exist within the genus, most are nonpathogenic environmental organisms. The species most commonly associated with human infections is Acinetobacter baumannii, followed by Acinetobacter calcoaceticus and Acinetobacter lwoffii.
Acinetobacter is a low-virulence opportunistic pathogen that may be an infrequent but potentially serious endemic agent of nosocomial bacteremia in some institutions. The Acinetobacter calcoaceticus–Acinetobacter baumannii complex is a common cause of drug-resistant pneumonia, urinary tract, skin, and soft tissue infections. A. calcoaceticus has been considered to have relatively low virulence compared to its counterpart A. baumannii, since colonization is more frequently noted than frank infection clinically.
A. calcoaceticus has only rarely been isolated from human clinical specimens such as sputum, and its involvement in clinical infections therefore remains unclear.
The ACB complex is ubiquitous in nature and has been found as part of the normal skin, throat, and rectal flora, as well as in food and body lice. It colonizes patients in Intensive Care Units and contaminates inanimate hospital surfaces and devices as well as wounds, including war injuries. Although a frequent colonizer, Acinetobacter can be the cause of severe and sometimes lethal infections, mostly of nosocomial origin, predominantly ventilator-associated pneumonia.
Multiple factors increase infection risk, including prolonged ICU stay, invasive procedures, immunosuppression, trauma, burns, wounds, malignancy, prior surgery, and broad-spectrum antibiotic exposure.
Acinetobacter also emerges as a cause of nosocomial outbreaks and is characterized by increasing antimicrobial multiresistance. Antibiotic use, especially carbapenems and third-generation cephalosporins, is recognized as the most important risk factor for multiresistance.
The trend of some species (A. baumannii and A. calcoaceticus) to spread in hospital environments, and to acquire and disseminate antibiotic resistance factors even to the most recent and active antibiotics, has become a worldwide ecological problem. Due to high mortality and constrained antimicrobial choices, the Centers for Disease Control and Prevention (CDC) and the World Health Organization classify carbapenem-resistant Acinetobacter baumannii (CRAB) as a priority 1 critical pathogen. While this designation applies specifically to A. baumannii, the shared genetic pool and transformation competence within the ACB complex mean that A. calcoaceticus can serve as a reservoir and donor of resistance determinants.
Incubation of live A. calcoaceticus strains with inside-out jejunum and colonic organoids significantly increased pro-inflammatory cytokines (IL-1α, KC/IL-8, MCP-1, and TNF) and decreased MUC2 and MUC13 transcripts, without altering tight junctions. The downregulation of MUC2 and MUC13 — key mucin proteins — suggests the organism may impair mucus barrier integrity, which is the primary physical defense of the intestinal epithelium.
No systematic pharmacokinetic studies, drug-interaction data, or special-population safety data exist for intentional oral administration of A. calcoaceticus in humans. Given its documented capacity to colonize the gastrointestinal tract, its pro-inflammatory cytokine-stimulating activity, and its status as an opportunistic pathogen in immunocompromised individuals, administration to individuals with compromised immune function, those on immunosuppressive therapies, patients with active inflammatory bowel conditions, or individuals in critical care settings would carry poorly characterized and potentially significant risks based on available microbiological and preclinical evidence.
Acinetobacter calcoaceticus does not hold GRAS (Generally Recognized as Safe) status under FDA regulations, QPS status from EFSA, or any equivalent safety designation from health regulatory bodies in Canada (Health Canada), Australia (TGA), or the UK (MHRA/FSA) that would support its intentional use as a supplement ingredient. It is not listed in any recognized probiotic safety registry.
Acinetobacter calcoaceticus is a Gram-negative, aerobic, nonmotile environmental coccobacillus belonging to the family Moraxellaceae and the A. calcoaceticus–A. baumannii complex. It is primarily recognized in science and medicine as a soil and water organism, an opportunistic clinical pathogen of low-to-moderate virulence, a producer of the commercially relevant bioemulsifier emulsan and the enzymatic cofactor PQQ, and an emerging focus of gut microbiome research in the context of inflammatory bowel disease and multiple sclerosis.
The current scientific record does not support the characterization of A. calcoaceticus as a beneficial dietary supplement. Available preclinical evidence suggests net pro-inflammatory activity in the gastrointestinal tract and an association — though not proven causation — with autoimmune and inflammatory disease states. No regulatory body has granted it a safety status appropriate for intentional human supplemental use. Its appearance in multi-organism SBO supplement blends is not supported by clinical trial data for safety or efficacy.
Health conditions that Acinetobacter calcoaceticus may help support.
Body systems that Acinetobacter calcoaceticus may help support.
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