The GI-MAP™ Opportunistic Bacteria Section: Full Species List

Search for the GI-MAP™ opportunistic bacteria species list and most of what comes back is a scanned copy of someone else’s report or a supplement funnel. Here is the actual list, organized the way the report itself organizes it, with a sentence or two of honest context for each organism — and an equally honest explanation of what this section of a stool test can and cannot tell you.

What “opportunistic bacteria” means on a stool test

Opportunists are organisms that live in many healthy guts without causing any trouble. They earn the name because they take opportunities: when protective commensal flora is depleted (after a course of antibiotics, for example), when digestion upstream falters, or when the gut’s immune defenses — secretory IgA in particular — run low, these organisms can expand into the vacated space. Because the GI-MAP™ is a quantitative PCR test, it does not just report that an opportunist is present; it reports how much of it was found, against a reference range set by the lab. (If the mechanics of qPCR are new to you, the stool PCR test explainer covers them.)

Two things this section is not. It is not a list of infections — these are not the acute pathogens, which have their own section of the report. And it is not a diagnosis: a number above a reference range is a data point for a practitioner, not a verdict. The interpretive guide walks the whole report section by section.

Dysbiotic and overgrowth bacteria: the species list

The first grouping covers organisms whose elevation practitioners read mainly as a sign of dysbiosis — an ecosystem out of balance — rather than as pointers to any specific condition.

• Bacillus spp. — common soil and food organisms that pass through everyone’s gut. Elevations are generally read as part of a broader overgrowth picture rather than as a specific problem.
• Enterococcus faecalis and Enterococcus faecium — normal residents in small numbers. Overgrowth is associated with disrupted flora, often after antibiotics; some strains carry resistance genes, one reason the report also screens for antibiotic-resistance genes.
• Morganella spp. — a histamine-producing member of the Enterobacteriaceae family. Practitioners consider elevations particularly in people with histamine-intolerance-type symptoms such as flushing and food reactions.
• Pseudomonas spp. and Pseudomonas aeruginosa — environmental bacteria found in water and soil. Elevations are associated with reduced colonization resistance. P. aeruginosa is a serious pathogen in hospital and immunocompromised settings, but detection in the stool of a generally healthy person is not equivalent to that.
• Staphylococcus spp. and Staphylococcus aureus — primarily skin and nasal residents that show up in stool in passing. Persistent elevation is read as a dysbiosis signal; S. aureus is better known for toxin-mediated food poisoning than for colonizing the gut.
• Streptococcus spp. — a large and mostly harmless genus. Practitioners often consider elevated stool Streptococcus alongside low stomach acid and upper-gut fermentation patterns, and it comes up frequently in SIBO discussions.
• Mycobacterium avium subsp. paratuberculosis (MAP) — the cause of Johne’s disease in cattle, included because researchers have long investigated a possible association with Crohn’s disease. That association remains debated, and detection does not diagnose anything.

Autoimmune-associated bacteria: the species list

The report groups the next set under a heading along the lines of “potential autoimmune triggers.” Be clear about what that label is: a reflection of research literature exploring associations — mostly molecular-mimicry hypotheses, where bacterial proteins resemble human ones — not established causation. Detecting any of these organisms does not mean you have, or will develop, an autoimmune condition.

• Citrobacter spp. and Citrobacter freundii — Enterobacteriaceae that practitioners consider in the context of gut inflammation and general dysbiosis when elevated.
• Klebsiella spp. and Klebsiella pneumoniae — studied for decades in relation to ankylosing spondylitis through molecular-mimicry hypotheses; also an ordinary low-level gut resident in many people.
• Proteus spp. and Proteus mirabilis — researched in relation to rheumatoid arthritis, and better known clinically as a urinary tract organism. On a stool panel, an elevation is read as overgrowth, nothing more specific.
• Prevotella copri — its expansion correlated with new-onset rheumatoid arthritis in a frequently cited 2013 study, yet it is also abundant in perfectly healthy people who eat fiber-rich diets. It is the clearest example on the panel of why an isolated elevation proves nothing by itself.
• Fusobacterium spp. — associated in research with inflammatory bowel conditions and studied in colorectal cancer contexts. On a stool panel it is a quantity for your practitioner to weigh, not a diagnosis to fear.

Methanogens and the other additional markers

• Desulfovibrio spp. — sulfate-reducing bacteria that produce hydrogen sulfide gas. Practitioners consider elevations in people reporting gas, bloating and sulfur-smelling flatulence, and the genus attracts research interest in inflammatory bowel disease.
• Methanobacteriaceae — technically archaea rather than bacteria. Methane production is associated with slowed intestinal transit, so practitioners weigh this marker in constipation-predominant pictures — the pattern behind what breath-test clinicians call intestinal methanogen overgrowth.

How to read an elevated result

Detected is not the same as diseased, and elevated is not the same as causal. When this section comes back with red flags, practitioners typically weigh four things together: how far above the reference range the result sits; whether one organism is elevated or several are at once (a pattern that suggests the ecosystem’s checks and balances are failing); what the rest of the report says — the commensal bacteria such as Akkermansia and Faecalibacterium, secretory IgA, calprotectin and the digestion markers; and whether any of it matches the symptoms you actually have. An impressive-looking bar on a chart with no symptoms behind it warrants far less excitement than the internet will offer you.

One thing an elevated opportunist never does is prescribe: a stool result alone is not an indication for antibiotics, antimicrobials or anything else. If you want qualified help with your numbers, that is exactly what the practitioner-written Interpretation Review ($245) is for, and our results page explains what to expect when your report arrives. The biomarker guides cover the neighboring sections of the report, and the gut infections hub — including Candida overgrowth — covers the organisms that live outside this one.

GI-MAP opportunistic bacteria: common questions

What are opportunistic bacteria on the GI-MAP?

They are organisms that live in many healthy guts without causing trouble but can contribute to symptoms when they overgrow or when the host’s defenses run low. The GI-MAP™ quantifies them by qPCR and flags results above the lab’s reference range. Detection alone is normal and expected — it is quantity and context that practitioners weigh.

Is there an official GI-MAP opportunistic bacteria species list PDF?

Diagnostic Solutions Laboratory publishes practitioner-facing documentation, and the panel it describes evolves over time. The most reliable species list is the one printed on your own report, because it reflects the exact panel version your sample was run against. The list on this page is an accurate general guide to what reports commonly show as of the date at the bottom of the page.

Do high opportunistic bacteria mean I need antibiotics?

No. A stool test result on its own is not an indication for antibiotics or any other treatment — no stool test can support that conclusion. Whether any intervention is appropriate is a clinical judgment for a qualified practitioner, made from your whole report, your history and your symptoms together.

Which GI-MAP bacteria are considered autoimmune-associated?

The report typically groups Citrobacter species including C. freundii, Klebsiella species including K. pneumoniae, Proteus species including P. mirabilis, Prevotella copri and Fusobacterium species under a potential-autoimmune-triggers heading. The grouping reflects research exploring associations, not established causation, and detecting one of these does not mean you have or will develop an autoimmune condition.

Why do healthy people have opportunistic bacteria?

Because opportunistic describes behavior, not mere presence. A normal gut ecosystem includes these organisms in small numbers, held in check by the commensal flora and the gut’s immune defenses. They only become relevant when that balance is lost — which is exactly why the GI-MAP™ quantifies them instead of just reporting detected or not detected.

Related: GI-MAP interpretive guide · Biomarker guides · Gut infections · Sample report · Cost · FAQ