Kurtha zopfil

Other Names

Bacterium zopfiiKurthia zopfiiZopfius zopfii

Synopsis

Kurthia zopfii (Supplement Ingredient Spelling: Kurtha zopfil)

Overview and Nomenclature

Kurtha zopfil is a non-standard transliteration or typographical variant of the bacterium formally named Kurthia zopfii (Kurth 1883) Trevisan 1885. It appears on product labels — most notably those of the soil-based-organism (SBO) probiotic product Prescript-Assist — as a phonetically abbreviated form. The organism's scientific name is Kurthia zopfii (Kurth 1883) Trevisan 1885, and it carries NCBI Taxonomy ID 1650. It is important to note from the outset that the form "Kurtha zopfil" does not appear in any peer-reviewed taxonomic, microbiological, or clinical literature; the valid and accepted binomial is Kurthia zopfii, and all scientific data discussed in this article refers to that organism.

The genus name Kurthia honors the German microbiologist H. Kurth, who first described the organism. The organism was originally designated "Bacterium zopfii" when first isolated in 1883. In class Bacilli and order Bacillales, the family Planococcaceae includes the genus Kurthia, of which Kurthia zopfii is the type species; strain ATCC 33403 (= BARNES F64/100; DSM 20580; NCIB 9878; and NCTC 10597) is the type strain, which was first isolated in 1883.

Identity and Taxonomy

Full Taxonomic Classification

The accepted taxonomy of Kurthia zopfii is: Domain Bacteria, phylum Bacillota (Firmicutes), class Bacilli, order Bacillales, family Planococcaceae, genus Kurthia, species Kurthia zopfii.

Morphological and Physiological Characteristics

K. zopfii is a motile, saprophytic, Gram-positive firmicute consisting of regular, unbranched rods that fragment into a coccoid morphology in older cultures. Members of the Kurthia genus are Gram-positive aerobes that do not ferment glucose. The organism is catalase-positive, oxidase-negative, and exhibits a strictly aerobic, chemoorganotrophic metabolism with a strictly respiratory (non-fermentative) character. Kurthia species produce very weak acidity from glucose or carbohydrates in peptone media, and amino acids, alcohols, and fatty acids are used as carbon sources.

On growth media, Kurthia gibsonii and Kurthia zopfii display rhizoid colonies on yeast nutrient agar, with loops and whorls of chains of rods at the colony edge giving a characteristic "Medusa-head appearance," and growth on nutrient gelatin slants produces a "bird's feather" appearance.

Genome

The predicted genome size of the type strain ATCC 33403 is 2,878,279 base pairs, with 37.05% G+C content. A 2018 genome-sequencing project published in Microbiology Resource Announcements formally established the complete genome sequence of the type strain.

Species Diversity within the Genus

The genus Kurthia contains three recognized species: K. zopfii, K. gibsonii, and K. sibirica; additional species are mentioned in the literature but have not been validated. Numerical taxonomic analysis has divided Kurthia isolates into two main clusters, one containing the type strain of K. zopfii and a second representing K. gibsonii; the two species are distinguished from each other by nine phenotypic characters.

Natural Sources and Environmental Distribution

Nonpathogenic K. zopfii has been isolated from intestinal contents, fecal material, meats, meat products, milk, water, and air, including air at high altitudes. The type strain of K. zopfii was originally isolated from intestinal contents of poultry as "Bacterium zopfii," and many strains have since been found in meats, meat products, and milk, air from abattoirs, and also environments as diverse as wastewater and air samples collected above 3,000 m in altitude.

Kurthia species are widely distributed in the environment and are common in feces of farm animals, milk, soil, surface waters, and meat and meat products after cold storage. K. zopfii is frequently isolated from meats, especially comminuted meats; its proportion of the aerobic flora in such products at the point of production does not generally exceed 10%, and it is not known to cause spoilage of refrigerated meats, though there is some evidence to suggest that its presence in the flora may be indicative of high temperatures during production or distribution.

K. zopfii is recognized as a food spoilage organism, particularly associated with off-flavors and taints in cured and fresh meat stored at elevated temperatures. In studies of vacuum-packaged meat spoilage, Kurthia zopfii has been observed to appear among late-stage spoilage-associated microbiota.

Use as a Dietary Supplement Ingredient

The Prescript-Assist Multi-Strain Probiotic

Kurtha zopfil / Kurthia zopfii is not marketed as a standalone dietary supplement. Instead, it appears exclusively as one component of multi-organism, soil-based-organism (SBO) probiotic products. The best-documented such product is Prescript-Assist, a commercial probiotic-prebiotic complex that listed the organism on its ingredient label.

Each capsule of Prescript-Assist included a proprietary blend of Leonardite and the following organisms designated as Class I (beneficial microorganisms): Anthrobacter agilis, Anthrobacter citreus, Anthrobacter globiformis, Anthrobacter luteus, Anthrobacter simplex, Acinetobacter calcoaceticus, Azotobacter chroococcum, Azotobacter paspali, Azospirillum brasiliense, Azospirillum lipoferum, Bacillus brevis, Bacillus marcerans, Bacillus pumilis, Bacillus polymyxa, Bacillus subtilis, Bacteroides lipolyticum, Bacteroides succinogenes, Brevibacterium lipolyticum, Brevibacterium stationis, Kurtha zopfil, Myrothecium verrucaria, Pseudomonas calcis, Pseudomonas dentrificans, Pseudomonas fluorescens, Pseudomonas glathei, Phanerochaete chrysosporium, Streptomyces fradiae, Streptomyces cellulosus, and Streptomyces griseoflavus.

Prescript-Assist contains a spectrum of 29 microflora falling into eleven taxonomic categories, and prebiotic complexes promote the proliferation of these microflora, together with humic and fulvic acids extracted from ancient plant deposits. The product's prebiotic carrier material — Leonardite — is a naturally occurring mineral rich in humic substances.

Common Forms and Preparations

As a supplement ingredient, K. zopfii / "Kurtha zopfil" is found only in multi-organism probiotic blends, primarily in capsule form. These products typically combine the microbial strains with prebiotic compounds intended to support microbial proliferation. In the documented clinical study of Prescript-Assist, the dosage form was a 500-mg capsule of the proprietary blend. The organism is presented as a component of a "soil-based organism" formulation, reflecting its environmental origin. No standalone preparations, extracts, or isolates of K. zopfii have been identified in the peer-reviewed supplement literature.

Traditional and Historical Use

There is no documented tradition of deliberate therapeutic use of Kurthia zopfii in any historical, ethnobotanical, or folk medicine system. The organism was first identified scientifically in 1883 and has no pre-modern history of intentional use by any culture. Its appearance in dietary supplements is a modern, late-twentieth and early-twenty-first-century phenomenon tied to the commercial development of SBO-based probiotic products.

The theoretical rationale offered by manufacturers of SBO probiotics draws on the broader concept that soil-based probiotics are bacteria found in soil that have evolved in contact with humans, and until very recently, humans were exposed to soil and soil-based organisms daily through eating, farming, and hunting. This framing is a marketing and conceptual construct, not a documented historical tradition specific to K. zopfii.

Key Constituents and Microbiological Properties

Because K. zopfii is a bacterium and not a botanical, there are no "phytochemical constituents" in the conventional sense. Its biologically relevant characteristics as a supplement component relate to its cellular and metabolic properties.

Cell wall type: K. zopfii is a Gram-positive firmicute; characteristically, the phylum Firmicutes consists of Gram-positive bacteria with low G+C content.
Metabolic profile: Kurthia species are aerobic, chemoorganotrophic, with a strictly respiratory metabolism; they are not fermentative. They produce very weak acidity from glucose or carbohydrates in peptone media, and amino acids, alcohols, and fatty acids serve as carbon sources.
Genome content: The predicted genome size is 2,878,279 bp, with 37.05% G+C content, encoding 2,910 genes (2,810 protein-coding).
Growth characteristics: The organism is motile and saprophytic, meaning it derives nutrients from dead or decaying organic matter — a hallmark consistent with its soil and comminuted-meat habitats.

No specific bioactive compounds, secondary metabolites, or defined mechanisms of probiotic action have been characterized in peer-reviewed literature for K. zopfii used as a human dietary supplement. The mechanisms of action attributed to Prescript-Assist as a whole product (see below) cannot be attributed specifically to this single component organism.

Scientific Evidence by Area of Use

Important Preliminary Note on Attribution

All clinical research on products containing "Kurtha zopfil" / Kurthia zopfii examines the multi-organism Prescript-Assist blend as a whole. No clinical study has isolated the contribution of K. zopfii specifically from the other 28 co-administered organisms or the Leonardite prebiotic matrix. Therefore, any outcomes described below represent effects of the entire Prescript-Assist formulation and cannot be attributed to K. zopfii alone.

1. Irritable Bowel Syndrome (IBS)

The primary area of human clinical research on Prescript-Assist (the product listing "Kurtha zopfil") is irritable bowel syndrome (IBS). In terms of PubMed-indexed studies, two were conducted, both by the Battelle Seattle Research Center, Washington, USA: (1) Bittner AC, Croffut RM, Stranahan MC, "Prescript-Assist probiotic-prebiotic treatment for irritable bowel syndrome: a methodologically oriented, 2-week, randomized, placebo-controlled, double-blind clinical study," Clin Ther 2005 Jun;27(6):755–61.

Study 1 (2005 RCT): The symptomatic efficacy of Prescript-Assist had previously been evaluated clinically only in an open-label study; this study was conducted primarily to compare the effects of Prescript-Assist with placebo in patients with a diagnosis of IBS, with a secondary goal of determining the number and nature of symptom clusters ("subsyndromic factors") characterizing IBS. Patients were randomly assigned to receive either Prescript-Assist as one 500-mg capsule or placebo, in a 2-week double-blind design.

Study 2 (2007 Extension): The aim of the follow-up study was to extend a previous 2-week assessment of the probiotic-prebiotic complex in patients with IBS. In this open-label, partially controlled, 1-year (14 ± 2 months) extension study, data were collected from patients with IBS who continued treatment following the 2-week study; data were collected at 2 and approximately 60 weeks after the end of the original study. A total of 25 patients entered the 2-week extension and 22 completed the approximately 60-week follow-up study (20 women, 2 men; age range, 20–70 years; all white).

Treatment was associated with a continued reduction in general ill feelings/nausea at 4 weeks (P < 0.007), and at ≥52-week follow-up, the rate of remissions was 81.5% to 100% (P < 0.003). The authors concluded that treatment with the probiotic-prebiotic complex may be an option for short-term (2–4 weeks) and long-term (approximately 60-week) reductions in IBS symptoms.

Evidence quality assessment: These two studies represent the entirety of indexed human clinical evidence. Both studies have significant methodological limitations: the 2005 trial was short (2 weeks) and small; the 2007 extension was open-label and partially controlled, enrolled only 22 completers, and was conducted by the same research group (Battelle Seattle Research Center). There is a recognized lack of assessment and systematic reporting of adverse events in probiotic intervention studies, and interventions are often poorly documented, meaning the current literature is not well equipped to answer questions on the safety of probiotic interventions with confidence. No independent replication of these studies has been published in the peer-reviewed literature. The evidence for clinical benefit must therefore be characterized as preliminary and insufficient to draw firm conclusions.

2. Other Gastrointestinal Conditions

The Prescript-Assist combination has been discussed in the context of conditions such as Crohn's disease and chronic fatigue syndrome/fibromyalgia because IBS is frequently comorbid with these disorders, but both published studies dealt specifically with irritable bowel syndrome, which is often co-morbid with chronic fatigue syndrome. No independent controlled trials have evaluated Prescript-Assist (or any product containing K. zopfii) specifically for Crohn's disease, ulcerative colitis, or chronic fatigue syndrome. Any discussion of benefits in these areas remains speculative and unsupported by direct clinical trial evidence.

3. Food Safety and Meat Spoilage (Non-therapeutic context)

Outside the supplement context, K. zopfii has been studied as a component of meat-spoilage microbial communities. K. zopfii is listed among predominant bacteria associated with meat spoilage in food microbiology literature. This finding is relevant to understanding the organism's environmental niche but does not inform its use or safety as a supplement ingredient.

Body Systems and Health Areas

Based on the available literature, K. zopfii — as part of the Prescript-Assist multi-strain blend — has been investigated only in relation to the gastrointestinal system, specifically:

Intestinal symptomatology: IBS-associated symptoms including nausea, general ill feelings, and bowel irregularities, based on the two Bittner et al. studies described above.
Gut microbiota modulation: The theoretical rationale for SBO probiotic use includes modulation of intestinal microflora balance, though no mechanistic human studies specific to K. zopfii exist.

No peer-reviewed evidence supports claims relating to immune function, metabolic health, cardiovascular health, or any other organ system for K. zopfii specifically or for Prescript-Assist as a whole beyond the two IBS studies cited.

Dosage Forms and Reported Dosages

In the published 2005 clinical study, participants received Prescript-Assist as one 500-mg capsule of the proprietary blend. The contribution of K. zopfii specifically within each 500-mg capsule was not disclosed; it was part of a 29-organism proprietary formulation whose individual organism concentrations were not reported in the peer-reviewed literature.

No dosage information for K. zopfii as an isolated ingredient has been published in any peer-reviewed source, pharmacopeia, government monograph, or institutional health database. No established daily intake, effective dose, or dose-response relationship has been identified for this organism in any regulatory or scientific document.

Safety Considerations

Pathogenicity Profile of Kurthia zopfii

Although some members of the genus Kurthia are pathogens, no reports of pathogenicity have been made specifically for K. zopfii. This characterization is reflected across multiple peer-reviewed microbiological sources. Its bacteria are strictly aerobic, and so far there is no evidence of pathogenicity.

However, within the broader genus, pathogenic potential is documented for other species. Kurthia spp. are considered primarily as non-pathogenic bacteria, although there have been reports about their pathogenicity in humans, causing diarrhoea, endocarditis, pilonidal cysts, pneumonia, prostatitis, and septicaemia. These reports involve other Kurthia species, most notably K. gibsonii and the now-reclassified K. bessonii, rather than K. zopfii itself.

Kurthia species are primarily non-pathogenic. Although strains of bacteria identified as "Kurthia spp." have been isolated from various clinical materials, most commonly from the feces of patients suffering from diarrhea, there is no evidence of pathogenicity in authentic members of the genus.

They are not part of the normal human flora, and in the majority of cases, they have not normally been regarded as pathogenic. Kurthia infections rarely become systemic, though K. zopfii was isolated from the blood of an infant with septicaemia in at least one case report.

Regulatory Status

Kurthia zopfii does not appear on the FDA's Generally Recognized as Safe (GRAS) list as a standalone ingredient, nor has it received a Qualified Presumption of Safety (QPS) designation from the European Food Safety Authority (EFSA). It has no entry in the FDA's Dietary Supplement Ingredient Directory, no WHO monograph, no ESCOP or German Commission E monograph, and no USP or European Pharmacopoeia entry. Its presence in supplement products has not been accompanied by formal premarket safety review of the specific organism.

Immunocompromised Individuals

K. gibsonii and K. zopfii are frequently found in the environment, decomposing organic materials, swine carcasses, feces of farmyard animals, and spoiled food, and consequently they might cause gastroenteral infections. This environmental profile suggests that immunocompromised individuals may be at increased theoretical risk from exposure.

Safety Data Gaps

The safety evidence base for K. zopfii as a supplement ingredient is exceptionally thin. There is a recognized lack of assessment and systematic reporting of adverse events in probiotic intervention studies, and the current literature is not well equipped to answer questions on the safety of probiotic interventions with confidence. No dedicated toxicology studies, dose-finding safety trials, or pharmacokinetic assessments of K. zopfii as a supplement ingredient have been published in the peer-reviewed literature. The absence of adverse event reports specific to this organism in a supplement context cannot be taken as affirmative evidence of safety, given the very limited human research conducted with the multi-strain product in which it is found.

Product-Level Safety Considerations

Because K. zopfii appears only in multi-organism blends, its safety cannot be fully evaluated in isolation. The Prescript-Assist formulation also contains organisms such as Myrothecium verrucaria and various Pseudomonas species, some of which have separate safety considerations in other regulatory contexts. No regulatory authority has issued a specific safety communication addressing Prescript-Assist or its constituent K. zopfii component.

Absence from Authoritative Evidence Databases

Kurthia zopfii / "Kurtha zopfil" is not indexed in the NIH Office of Dietary Supplements fact sheets, the NCCIH herb and supplement database, Cochrane systematic reviews, the WHO monograph series, the European Pharmacopoeia, ESCOP monographs, or German Commission E monographs. No entry exists on Examine.com as a standalone supplement ingredient. This consistent absence from all major authoritative evidence resources reflects the near-total lack of evidence evaluating this organism independently as a health supplement.

Summary of Evidence Strength

Taxonomic and microbiological identity: Well-established in peer-reviewed literature since 1883; genome sequenced and deposited (ATCC 33403).
Supplement use: Documented as a labeled ingredient in multi-organism SBO probiotic products; no independent monograph or regulatory review exists.
Clinical efficacy (IBS): Two small, methodologically limited studies of the multi-strain Prescript-Assist blend — not of K. zopfii alone — suggest possible IBS symptom reduction; evidence is preliminary and not independently replicated.
Mechanisms of action: No published mechanistic data specific to K. zopfii as a supplement ingredient.
Safety: K. zopfii is classified as non-pathogenic in microbiological literature, but formal safety assessment as a human dietary supplement ingredient is absent. Isolated case reports exist of septicaemia involving K. zopfii.
Traditional use: None documented.

References

Health Conditions

Health conditions that Kurtha zopfil may help support.

No conditions available.

Body Systems

Body systems that Kurtha zopfil may help support.

No body systems available.