What Is Candida glabrata? Symptoms, Causes, and Treatment

Candida glabrata is a yeast that lives harmlessly in the gut, mouth, and genital tract of most healthy people but can turn dangerous when the immune system weakens or the body’s microbial balance shifts. It is the second most common cause of candidemia (a Candida bloodstream infection) in North America and Northern Europe, and it stands out from other Candida species for a troubling reason: it is often resistant to the most widely prescribed antifungal drugs. Understanding what sets this organism apart, who it threatens, and how doctors manage it matters because its prevalence has been rising in hospitals worldwide for more than two decades.

Not the Candida You Think

The name “Candida glabrata” is a bit misleading. Despite sharing a genus name with the better-known Candida albicans, the two species are only distantly related. C. glabrata is actually a closer genetic relative of baker’s yeast, Saccharomyces cerevisiae, the organism used to brew beer and leaven bread.¹ Both species descended from an ancestor that underwent an ancient whole-genome duplication event, placing them in the same branch of the yeast family tree.² This means C. glabrata and C. albicans evolved the ability to infect humans independently, through entirely different biological strategies.¹ Researchers have proposed reclassifying C. glabrata under a new genus name, Nakaseomyces glabratus, and some recent clinical literature uses that term. For now, most doctors and lab reports still use “Candida glabrata.”

One of the most visible differences between the two is shape. C. albicans can switch between a round yeast form and elongated filaments called hyphae, and that shapeshifting is one of its primary tools for invading tissue. C. glabrata cannot do this. It grows only as small, round yeast cells.³ Instead of drilling into tissue with filaments, it relies on a different playbook: sticking tenaciously to surfaces and quietly dodging the immune system.

How It Causes Trouble

C. glabrata compensates for its lack of hyphae with an unusually large arsenal of adhesin proteins on its surface. These proteins let it grip tightly to human cells, medical devices, and mucosal surfaces, establishing a foothold that the body struggles to dislodge. Genome comparisons show a correlation between the number of adhesin genes a yeast species carries and its ability to cause disease, and C. glabrata sits at the high end of that scale.³

Once attached, C. glabrata has a remarkable talent for surviving inside the very immune cells meant to kill it. Macrophages, the white blood cells that swallow and destroy pathogens, engulf C. glabrata as expected. But instead of dying, the yeast can survive and even multiply inside those cells while triggering surprisingly little alarm. It modifies the internal environment of the compartment that traps it, adapts to the harsh antimicrobial chemicals there, and scavenges scarce nutrients, particularly iron.⁴⁵ This stealth strategy lets it persist in the body for long periods without provoking the strong inflammatory response that would normally alert the host and recruit more immune defenders.

C. glabrata also forms biofilms, structured communities of cells encased in a protective matrix. These biofilms coat catheters, dentures, and other implanted medical devices, and they are extremely difficult to treat because the matrix shields the cells from antifungal drugs.⁶ In hospital settings, C. glabrata can even form mixed biofilms with bacteria like Klebsiella pneumoniae on venous catheters, complicating treatment further.⁷

Who Gets Infected

In a healthy person, C. glabrata sits quietly as part of the normal microbial community. Infections happen when something tips the balance. The risk factors overlap with those for other Candida infections but lean in some specific directions.

Diabetes: People with diabetes, especially those with poorly controlled blood sugar, face elevated risk. One study found that patients with C. glabrata bloodstream infections were roughly two and a half times more likely to have diabetes than patients with C. albicans infections.⁸ The metabolic disruption of diabetes suppresses immune defenses in ways that favor fungal overgrowth.⁹
Prolonged hospital stays and ICU care: Extended time in an intensive care unit, broad-spectrum antibiotic use, central venous catheters, and mechanical ventilation all increase risk. In one study of ICU patients with C. glabrata candidemia, all had received broad-spectrum antibiotics and had a central line.¹⁰
Prior antifungal exposure: Patients who have already been treated with antifungal drugs, particularly azoles like fluconazole, are at higher risk of developing a resistant C. glabrata infection.¹¹
Advanced age and serious illness: Cancer, cardiovascular disease, organ transplantation, and other conditions that weaken immunity or require invasive procedures open the door.¹²

The abdominal cavity deserves specific mention. C. glabrata bloodstream infections were over four times more likely to originate from an abdominal source than C. albicans infections, making patients who have had abdominal surgery or peritonitis particularly vulnerable.⁸

Symptoms and Where Infections Show Up

C. glabrata does not cause a unique set of symptoms that you could distinguish from other Candida infections by how you feel. Instead, the symptoms depend entirely on where the infection takes hold.

In the bloodstream (candidemia), the most common and most dangerous presentation, symptoms resemble sepsis: fever that does not respond to antibiotics, chills, low blood pressure, and a general rapid decline. Septic shock developed in a majority of patients in one series, and acute kidney failure was common.¹² Clinicians typically suspect candidemia when a hospitalized patient on broad-spectrum antibiotics spikes a persistent fever without an obvious bacterial explanation.

In the urinary tract, C. glabrata can colonize bladder catheters and cause urinary tract infections, and the urinary tract was the most common identified source of C. glabrata candidemia in one ICU study.¹⁰

In the vaginal tract, C. glabrata is a well-recognized cause of vulvovaginal candidiasis, often presenting as itching, burning, and discharge that fails to clear with the standard over-the-counter fluconazole treatment. In fact, recurrent yeast infections that keep coming back despite treatment should raise suspicion for C. glabrata rather than C. albicans, since the two require different management approaches.

In the mouth and esophagus, immunocompromised patients (those receiving chemotherapy, transplant recipients, people living with HIV) can develop oral thrush or esophageal candidiasis caused by C. glabrata, though C. albicans is more commonly responsible in those locations.

Why Antifungal Resistance Is the Central Problem

The defining clinical challenge of C. glabrata is drug resistance, particularly to azoles, the class of antifungals that includes fluconazole. This is not a minor laboratory curiosity. Fluconazole resistance in C. glabrata bloodstream infections was independently associated with nearly a fourfold increase in the risk of death within 30 days.¹³

The main resistance mechanism involves molecular pumps that sit in the cell membrane and physically push azole drugs back out of the cell before they can do their work. A transcription factor called Pdr1 controls the genes for these pumps. When Pdr1 mutates into a hyperactive form, the pumps ramp up and the cell becomes resistant to fluconazole and often to other azoles too.¹⁴ A global surveillance study of azole-resistant C. glabrata isolates confirmed that the vast majority showed overexpression of these efflux pump genes, with about two-thirds overexpressing one pump gene and over three-quarters overexpressing another.¹⁵

Resistance to echinocandins, the drug class doctors typically turn to when azoles fail, is a growing concern. Echinocandin resistance in C. glabrata arises primarily from mutations in two genes called FKS1 and FKS2, which encode the drug’s target enzyme. In a large screening of over 1,000 C. glabrata isolates, 51 carried mutations in these hotspot regions, and nearly all of those were resistant to at least one echinocandin.¹⁶ Recent research has uncovered an even more worrying mechanism: gene conversion events where pieces of FKS1 and FKS2 swap segments, creating novel chimeric genes that can carry resistance mutations from one gene into the other.¹⁷

Dual resistance to both azoles and echinocandins leaves very few treatment options and is associated with the worst outcomes. Case reports have documented C. glabrata isolates from a single patient developing sequential resistance to itraconazole, fluconazole, amphotericin B, and voriconazole over just 18 months.¹⁸

How C. glabrata Is Diagnosed

Identifying which Candida species is causing an infection is critical because treatment choices differ sharply between species. The traditional method involves growing the organism from a blood culture or tissue sample and then using biochemical or growth-based tests to determine the species, a process that can take days.

Newer technology has sped this up considerably. A technique called MALDI-TOF mass spectrometry can identify Candida species from a culture plate with essentially perfect accuracy and produce results in about 30 minutes.¹⁹²⁰ This speed matters because every hour of delay in appropriate antifungal therapy worsens outcomes in candidemia. Direct identification from positive blood culture bottles (skipping the step of growing colonies on a plate first) works well for C. albicans, though it can occasionally be less reliable for non-albicans species including C. glabrata, where growing on a plate first still gives the most dependable results.²¹

Once the species is identified, antifungal susceptibility testing tells clinicians which drugs the particular isolate is likely to respond to. Given C. glabrata’s propensity for resistance, many infectious disease specialists consider susceptibility testing essentially mandatory for this species rather than optional.

Treatment Approaches

Because of the high rates of azole resistance, echinocandins (caspofungin, micafungin, or anidulafungin) are the standard first-line treatment for invasive C. glabrata infections.²² If susceptibility testing later confirms that the isolate is sensitive to fluconazole, clinicians sometimes transition the patient from intravenous echinocandin to oral fluconazole to complete the treatment course at home.

There is an important nuance for critically ill patients, however. Research in animal models of neutropenic (low white blood cell count) hosts found that standard echinocandin dosing may only hold C. glabrata at bay without actually killing it, and that higher doses would be needed to achieve a truly fungicidal effect.²³ This finding has fueled ongoing clinical discussion about whether current echinocandin doses are adequate for the sickest patients.

For vaginal C. glabrata infections, the treatment picture looks different. Fluconazole, which is the standard go-to for vaginal yeast infections, often fails against C. glabrata. Boric acid vaginal suppositories have shown markedly better results: in a trial of patients with diabetes and C. glabrata vaginitis, boric acid achieved a mycological cure rate more than double that of oral fluconazole.²⁴ Boric acid has also been used successfully against azole-resistant C. glabrata vaginitis when standard antifungals fail entirely.²⁵

How Deadly Is a C. glabrata Bloodstream Infection

The mortality numbers for C. glabrata candidemia are sobering. A large European observational study found that the death rate directly attributable to the infection itself was about 24% for C. glabrata, compared with roughly 8% for C. albicans.²⁶ A single-center study found an all-cause 30-day mortality of about 31% for C. glabrata versus roughly 15% for C. albicans.²⁷ In ICU settings, overall 30-day mortality has been reported at over 50%, with renal failure being a strong predictor of death.¹⁰

Multiple factors feed into this high mortality. C. glabrata infections tend to strike patients who are already critically ill. The organism’s intrinsic tolerance to azoles means that initial empiric therapy sometimes misses it. And the immunoevasion strategies described earlier let the infection smolder, sometimes delaying recognition. Among patients with C. glabrata bloodstream infection, both the severity of the underlying illness (measured by clinical scoring systems) and the presence of neutropenia were independently associated with 30-day mortality.¹³

Geographic Patterns

C. glabrata does not show up at the same rates everywhere. Northern Europe and the United States report some of the highest proportions of C. glabrata among candidemia cases, while countries in Southern Europe and Latin America see relatively more infections caused by C. parapsilosis instead.²⁸ The reasons are not entirely clear but likely involve regional differences in antifungal prescribing practices, patient demographics, and healthcare-system factors. Globally, C. albicans remains the most common cause of candidemia, but its share has been declining, while C. glabrata has held steady or risen as a proportion of infections in many surveillance studies.

New Drugs on the Horizon

The fear of running out of effective treatments has driven significant investment in new antifungals. One of the most promising is ibrexafungerp, a first-in-class drug that attacks the same target enzyme as echinocandins (beta-1,3-glucan synthase) but does so from a different binding site, which means it can work even against many echinocandin-resistant strains. Laboratory testing has shown potent activity against C. glabrata isolates that resist both azoles and echinocandins, though some FKS mutations can reduce its effectiveness too.²⁹ Importantly, ibrexafungerp can be taken by mouth, which would give doctors an oral option for patients who currently need intravenous echinocandins.

Researchers are also investigating entirely new drug targets. One recent study identified key metabolic enzymes in C. glabrata as potential therapeutic targets and tested novel chemical compounds against them in the lab, with one candidate showing promising antifungal activity.³⁰ Work using large-scale genetic screening is also mapping out every gene that contributes to drug resistance across all five glucan-synthase-targeting antifungals, aiming to identify which drug sequences and combinations minimize the chance of cross-resistance developing.³¹ These efforts are still early-stage, but they reflect a growing recognition that fighting C. glabrata will require a deeper toolkit than what is currently available.

C. glabrata and the Gut Microbiome

As a common colonizer of the human intestinal tract, C. glabrata does not exist in isolation. It interacts with the surrounding bacterial community in ways that can matter for health beyond the fungus itself. In mouse models, a decline in protective anaerobic gut bacteria, particularly Lactobacillus species, was associated with C. glabrata overgrowth. The presence of C. glabrata in turn deepened the loss of Lactobacillus, creating a feedback loop that worsened intestinal inflammation.³²

There is also evidence that pre-existing gut colonization with C. glabrata can worsen subsequent bacterial infections. In a mouse model, animals already colonized with C. glabrata developed more severe Clostridioides difficile infections than animals without the fungus on board.³³ This kind of fungal-bacterial interplay is only beginning to be understood, but it suggests that C. glabrata’s role in hospital-acquired infections may extend beyond the direct damage it causes on its own. Disrupting the gut microbiome with broad-spectrum antibiotics does not just create a vacancy that C. glabrata can fill; the fungal overgrowth itself may make the gut more vulnerable to the next pathogen that comes along.