Invasive candidiasis: Candida bloodstream infection and deep Candida infections

Candida are yeasts that live harmlessly on the skin and in the gut and mouth of many people. They are best known for causing oral thrush and vaginal thrush, which are common, usually mild and treated with topical or oral antifungal medicines. Invasive candidiasis is different. The Fungal Infection Trust explains that Candida may enter the bloodstream and lead to disseminated disease, known as invasive candidiasis, and that this is a very serious infection.

It can show up as a bloodstream infection (candidaemia), or it can settle in deeper sites. The Trust describes deep infections including Candida of the oesophagus in people with HIV or other severe illness, and Candida peritonitis, an infection inside the abdomen that can follow bowel surgery and is often a mixed bacterial and Candida infection. Some people have silent spread to places such as a heart valve, bone or the inside of the eye.

No NHS patient-information page on invasive candidiasis was found when this page was written, so it relies on a UK specialist charity and NHS sepsis guidance. If you or someone close to you has been given this diagnosis, your infection or microbiology team is the best source of detail for the specific case.

Most cases happen in hospital. The Trust names critically ill patients in intensive care, particularly people with diabetes or kidney failure, and says the risk is linked to the number of antibiotics a person has had and to immune suppression. People who have had gastrointestinal, pancreatic, transplant or thoracic surgery, and those receiving nutrition intravenously, are also at higher risk.

Extremely premature babies are at high risk, but otherwise the Trust says rates of Candida bloodstream infection rise with age. The NHS adds more generally that the risk of sepsis is higher in people whose immune system is weakened, for example by HIV or sickle cell disease, chemotherapy, corticosteroids or immunosuppressants, and in people with a catheter.

The Trust says the commonest clinical features are fever, increased shortness of breath or oxygen requirement, and rising inflammatory markers in the blood. A rash is unusual unless caused by one species, Candida tropicalis. About 35% of people with Candida bloodstream infection are extremely unwell with septic shock.

These features closely resemble bacterial sepsis, which is why antibiotics are often started without antifungals. That is not necessarily a failure of care: in a very sick person the first priority is to treat the most likely causes quickly, and a fungal cause may only be recognised later, for example when blood cultures grow yeast. If you are at home and concerned about sepsis, the NHS lists what to look for in adults, including confusion or slurred speech, uncontrollable shivering, muscle pain, difficulty breathing, blue, pale or blotchy skin, and a high or low temperature, and says to call 999 or go to A&E if sepsis is suspected.

Accurate diagnosis of fungal disease is usually not straightforward, according to the Trust. For a Candida bloodstream infection the key test is a blood culture, which grows the yeast in the laboratory and allows it to be identified. The Trust says blood cultures are positive in about 40% of patients with invasive candidiasis, so a negative culture does not rule it out, and other tests may be used, including DNA detection, antigen tests and scans where there are signs of deep infection.

Identifying the species matters because different Candida species respond differently to antifungal drugs. About half of these infections are caused by Candida albicans, with others including Candida glabrata, Candida parapsilosis, Candida tropicalis and, more recently, Candida auris. Culture also shows whether the yeast is resistant to a particular antifungal.

Treatment is with antifungal medicines, mostly given into a vein in hospital. The Trust says the current best therapy for most people with Candida bloodstream infection is one of the echinocandins: caspofungin, anidulafungin or micafungin. Amphotericin B and fluconazole are the main alternatives, and amphotericin B is also available in safer lipid formulations. Flucytosine is occasionally used for resistant species or where there is eye or urine infection, because it gets to those sites.

Different drugs suit different species. The Trust notes that fluconazole is active against most Candida species but not Candida krusei or Candida auris, and that echinocandins are available only intravenously. The choice of medicine and how long it is given are decisions for the infection specialists, working with the team treating any underlying condition.

Candida auris is described by the Trust as an emerging pathogen, first reported in 2009 from an ear canal infection in Japan, which is associated with life-threatening invasive disease such as bloodstream and wound infections. It can colonise the skin, particularly the groin and armpit, and invade to cause disease of varying severity. Because fluconazole is not active against it, careful identification of the species matters. See the separate page on Candida auris for more.

Invasive candidiasis is serious. The Trust estimates that globally about 626,000 people each year have Candida in their bloodstream and that this leads to about 254,000 deaths. Outcomes depend on the person's underlying illness and how quickly effective treatment starts. Many people who recover from the infection are recovering from a critical illness at the same time, so rehabilitation and follow-up as described in intensive care recovery pages apply.

Invasive candidiasis is treated as an inpatient condition in NHS or private acute hospitals under the care of microbiology or infectious diseases specialists alongside the main treating team. It is not something managed by self-referral. If you are worried about an infection in a relative in hospital, ask the ward team who the infection specialist is and what the plan is.