What Is Invasive Candidiasis?

Overview

Invasive candidiasis is a serious fungal infection caused by a type of yeast (fungus) called Candida. The Candida fungus enters your bloodstream, where it can then spread to other parts of your body, such as your heart valves, brain and central nervous system, eyes, kidneys, bones, liver, spleen and others. It can lead to long hospital stays and can even be fatal. 

Candida is a fungus which usually lives on your skin, in your throat, mouth, and in the flora of the human gastrointestinal tract and vagina without causing any problems. Candidiasis is when this yeast grows out of control and usually causes minor infections such as thrush.

Several different factors may contribute to this, such as diabetes, chemotherapy, and stem cell and organ transplantation. Sometimes, it may lead to a more serious infection, such as candidemia. This is when the candida gets into your bloodstream. Candidemia was found to be the most common form of invasive candidiasis in 2020, with an overall rate of 3.5 cases per 100,000 people and a rate of 16.8 cases per 100,000 in those assigned male at birth (AMAB) and over 75 years of age. It is quite common in hospital patients, especially those in the intensive care unit (ICU).

Severe candidemia can lead to invasive candidemia and even death if left untreated. The other form of invasive candidiasis is non-candidaemic systemic candidiasis. This is when Candida invade a normally sterile site such as the abdominal cavity.¹ 

The mortality of patients with invasive candidiasis is as high as 40%, even with antifungal treatment.¹ Early diagnosis and treatment are crucial for a positive outcome. However, it can be difficult to diagnose early, as most patients suffering from invasive candidiasis are already suffering from other conditions or have recently undergone surgery, and symptoms are similar to those of other infections.

Antifungal medication is used to treat invasive candidiasis. It may also be given as a preventative measure to at-risk patients, such as those with bone marrow or organ transplants or those undergoing abdominal surgery. Previously, the most common species of Candida in hospitals was Candida albicans; however, recently, there has been a shift to non-albicans Candida species being the major cause of infection, and some of these are more resistant to antifungal medication.¹

Causes of invasive candidiasis

As mentioned previously, Candida normally lives on the skin and in the body of the majority (up to 60%) of healthy people without causing any problems.² However, sometimes the Candida can grow out of control, enter the bloodstream and spread to the internal organs. There are several different types of Candida species that can cause invasive infections, but the majority of invasive infections are caused by five different microorganisms:

• Candida albicans
• Candida glabrata
• Candida tropicalis
• Candida parapsilosis
• Candida krusei

Overall, Candida albicans is the most common pathogen in most hospital settings.² In some parts of the world, a usually rare pathogen called Candida auris has emerged as a major cause of invasive candidiasis. This has been a problem because Candida glabrata is resistant to first-choice antifungal drugs such as echinocandins and fluconazole.²

Certain people may be more at risk for developing invasive candidiasis, such as:

• People suffering from diabetes because disruption of the oral mucosa barrier puts them at higher risk of oral candidiasis.³
• Patients who have had an extended hospital stay, especially those in ICU.
• People with long-term vascular catheters because Candida is more easily able to enter your body when the catheter is being inserted into the skin.
• Patients who have had recent abdominal surgery, such as Candida, can enter the peritoneum when the bowel is opened or perforated.⁴
• Premature babies
• People with a weakened immune system, such as someone undergoing chemotherapy or someone who has recently had an organ transplant, have a greater risk of Candida entering their bloodstream.
• People who have received lots of broad-spectrum antibiotics in hospital, leading to a microbiome imbalance in the gut.⁵

As Candida is present on the skin, healthcare workers need to practise proper hand hygiene to prevent the spread of infections.

Signs and symptoms of invasive candidiasis

The symptoms of invasive candidiasis symptoms can be difficult to distinguish from other illnesses, especially bacterial infections, as most people who develop invasive candidiasis are already ill or recovering from surgery.

The most common symptoms are:

• Fever
• Chills

Some symptoms are specific depending on where the infection has spread to. For example, an invasive candidiasis infection in the brain can cause confusion, headaches and memory loss, whereas an infection in the eye can cause vision changes.

Management and treatment for invasive candidiasis

Invasive candidiasis is treated with an antifungal medication, usually given intravenously (using a needle via a vein in your arm). It usually involves a stay in the hospital. The type and specific dose of the antifungal medication given usually depends on several factors, such as your age, strength of the immune system, and the location and severity of the infection. For most patients, treatment is an echinocandin, given intravenously. Fluconazole and amphotericin B may also be used. Studies have shown that early treatment leads to a more positive outcome and increases the likelihood of survival of the patient.²

Antifungal resistance to echinocandins and fluconazole is emerging in hospital settings worldwide.²  Candida auris is often resistant to antifungal medication and also some disinfectants used in healthcare settings. This means that the infection may not respond to the medication given, and it will therefore, not be effective in treating it. Infection and symptoms may, therefore, persist for longer and require further treatment.

Treatment is normally continued for two weeks once symptoms have resolved and once blood cultures are negative for Candida. However, severe infections may need treatment for longer. 

Patients in the ICU who are at high risk of invasive candidiasis should be considered for antifungal prophylaxis (preventative treatment before an infection has occurred).⁴ However, care should be taken, as the overuse of antifungals in hospitals has led to a shift to drug-resistant Candida species in hospitals, which are more difficult to treat.⁴ 

Diagnosis

Invasive candidiasis is diagnosed by looking at a patient's medical history and symptoms, performing a physical examination, and using laboratory tests. Usually, a blood culture, or sample from the infected body site, is taken to see if Candida will grow and multiply. This can take a few days.

FAQs

How can I prevent invasive candidiasis?

Patients at risk of invasive candidiasis, such as abdominal surgery patients, may be treated with antifungal medication as prophylaxis (preventative treatment prior to an infection).⁴ Additionally, healthcare workers should always wash their hands before administering intravenous injections or catheters, and the skin should be cleaned beforehand. It is also a good idea to look out for the first signs of infection, such as redness or pain around the site of an IV or catheter, to ensure that treatment can be given promptly.

How common is invasive candidiasis?

Invasive candidiasis is the most common fungal disease among hospitalised patients.² In 2020, it occurred at an overall rate of 3.5 cases per 100,000 people and at a rate of 16.8 cases per 100,000 in those assigned males at birth (AMAB) and over 75 years of age. 

Who is at risk of invasive candidiasis?

People with other medical conditions are most at risk of invasive candidiasis. People who have had surgery, especially abdominal, are most at risk of developing invasive candidiasis. People with a weakened immune system, or cancer, are undergoing chemotherapy, and those who have undergone a transplant are most at risk. Also, people who have recently stayed in the hospital, especially those in the ICU or who have had a catheter, are most at risk of developing invasive candidiasis.

What can I expect if I have invasive candidiasis?

The most common symptoms of invasive candidiasis are fever and chills. This may initially be confused for a bacterial infection; however, if they don’t go away after treatment, it could indicate invasive candidiasis. Invasive candidiasis is a serious condition that needs prolonged treatment in a hospital and can be fatal. It can also cause serious long-term complications such as endocarditis and osteomyelitis.

When should I see a doctor?

Anyone at high risk of candida infections or anyone experiencing any symptoms should contact their healthcare provider. Also, anyone suffering from fever and chills, which do not go away after antibiotic treatment, should contact their doctor.

Summary

Invasive candidiasis is a major cause of illness and mortality in hospitals. In many developed countries, Candida species rank in the top three or four pathogens causing healthcare-related bloodstream infections.

Most infections occur in patients who have spent a prolonged time in the hospital, especially in intensive care units (ICU). The most common risk factors are a long-term central venous catheter, recent major surgery, especially abdominal, and patients with a weakened immune system. Patients who have recently spent time in the hospital or have any of the known risk factors for developing invasive candidiasis should, therefore, contact their healthcare provider if they experience any signs of infection.

Early treatment with antifungal medication such as echinocandins and fluconazole provides the best outcome, as mortality rates for invasive candidiasis can be as high as 40%. It may be helpful to give preventative antifungal medication to some high-risk patients, such as those about to undergo abdominal surgery. However, care should be taken as there has been an increase in species of Candida resistant to first-line antifungal drugs due to overuse of antifungal drugs in hospitals, and these resistant strains may be more difficult to treat.