Candida albicans : Infectious Substances Pathogen Safety Data Sheet

Section I – Infectious agent

Name

Candida albicans

Agent type

Fungus

Taxonomy

Family

Debaryomycetaceae

Genus

Candida

Species

albicans

Synonym or cross-reference

Candidiasis, thrush, Candida claussenii, Candida langeronii

Characteristics

Brief description

Candida albicans (C. albicans) is a diploid and encapsulated single-celled fungus^{Footnote 1}. As a polymorphic fungus it can occur as ovoid-shaped budding yeast, pseudohyphal forms with ellipsoid cells and constrictions at the septa or as parallel-walled true hyphae depending on temperature, pH, and nutrients^{Footnote 2}. Asexual reproduction occurs by budding with formation of blastoconidia^{Footnote 3}. Smooth, white, 2 to 4 mm colonies appear within 48-72 hours when cultured on fungal media such as Sabouraud glucose agar at 37oC. The genome of C. albicans is 16 Mb and contains 6114 open reading frames, 774 of which are species specific^{Footnote 1}.

Properties

There are a number of factors that contribute to the ability of C. albicans to be a pathogen. During infection, C. albicans produces molecules that allow for adhesion (adhesins) to, and invasion (invasins) of host cells which allow C. albicans to enter host cells by endocytosis^{Footnote 4Footnote 5}. Contact with the host cells can also trigger the yeast-to-hypha transition and directed growth through thigmotropism allowing for tissue invasion. C. albicans also produces hydrolases which are thought to aid in infection involving active penetration of host cells^{Footnote 4}. The production of biofilms on both biotic and abiotic (catheters, dentures and central lines) surfaces makes the infection more resistant to antimicrobials and host immune responses as well as aiding in the dissemination of yeast cells to other areas^{Footnote 4}. Finally the genomic plasticity if C. albicans is associated with increased acquiring if anti-fungal resistance^{Footnote 6}.

Section II – Hazard identification

Pathogenicity and toxicity

C. albicans is a commensal microorganism as it is a member of the gastrointestinal, oropharyngeal and female genital flora of healthy individuals^{Footnote 3}. However, it is also an opportunistic pathogen in humans under certain conditions, such as: immunodeficiency (chemotherapy and HIV infection), lack of competing flora (antibiotic treatment) or when given access to the blood stream (wounds and indwelling catheters)^{Footnote 5}. There are two subtypes of C. albicans infection: mucosal and systemic.

Among mucosal infections the most frequent clinical form is thrush/oral candidiasis, where infection can be observed on the tongue, palate or other mucosal surfaces, and is characterized by single or multiple, ragged white patches^{Footnote 7}. Gum infection is also a common complication of oral surgical procedures. Infection of the vagina, vulvovaginal candidiasis, occurs at least once in a lifetime for 75% of women and is characterized by thick, curd like discharge (leucorrhea), eruption and itching of the vulva^{Footnote 8}. Risk factors include pregnancy, use of intrauterine devices, use of oral contraceptives, douching and use of antibiotics. Esophageal candidiasis is manifested by inflammatory patches that develop on the esophagus, causing painful swallowing and substernal chest pain^{Footnote 3}. In immunocompromised patients (such as those with HIV infection), similar lesions can also occur on the small intestine and stomach. Chronic mucocutaneous candidiasis is a rare genetic disease, which occurs in individuals with defects in immune response against Candida. It involves chronic infections of the skin, hair, face, scalp and hands, and can further disseminate to deeper tissues and major body organs such as kidneys, heart and brain which may lead to septicimea (candidemia – Candida in blood) and death^{Footnote 3Footnote 9}. Infections of the nail (paronychial and onychomycotic candidosis), superficial invasion of mucous membranes, cutaneous infections of the macerated skin (in crural folds, diaper area in infants), eye infections such as endophthalmitis are examples of other infections caused by C. albicans^{Footnote 3Footnote 10}.

Invasive candidiasis refers to infections of the bloodstream, intra-abdominal compartment, peritonitis or osteomyelitis with mortality estimates for these infections from 10-20%^{Footnote 5}. Cases of invasive candidiasis are commonly associated with ICU stays and are usually a result of increased or abnormal colonization and a somewhat compromised host. Clinical manifestations of invasive candidiasis are generally non-specific.

Epidemiology

C. albicans is of worldwide prevalence. It has been isolated from soil, animals, hospitals, inanimate objects and food^{Footnote 11Footnote 12Footnote 13}. Both mucosal and systemic infections caused by C. albicans can occur in immunocompetent and immunosuppressed individuals^{Footnote 11}. C. albicans is the most common fungal pathogen responsible for nosocomial systemic infections, and also the most commonly isolated pathogen from clinical samples obtained from mucous membranes such as oral cavity, gastrointestinal tract and vagina^{Footnote 11}.

Risk factors associated with the development of candidiasis include: antibiotic therapy; administration of steroids, immunosuppressants, or chemotherapy; prior surgery; solid organ or hematopoietic stem cell transplants; diseases such as AIDS, leukemia, diabetes, lymphoma and COVID-19; as well as trauma and burn patients^{Footnote 3Footnote 4Footnote 11Footnote 14}. There has been a decrease in the incidence of oral candidiasis in HIV infected patients, since the introduction of the highly active antiretroviral therapy (HAART)^{Footnote 11}.

Host range

Natural host(s)

Humans.

Other host(s)

Experimentally infected animals include porcine, mice, rats and quail^{Footnote 15Footnote 16Footnote 17Footnote 18}.

Infectious dose

Unknown.

Incubation period

Unknown.

Communicability

Although rare, person-to-person transmission can occur between family members or between patients^{Footnote 19Footnote 20}.

Section III – Dissemination

Reservoir

Humans^{Footnote 3}.

Zoonosis

None.

Vectors

None.

Section IV – Stability and viability

Drug susceptibility/resistance

Susceptibility has been shown for amphotericin B, nystatin, flucytosine, the azoles, echinocandins, and combination drug therapies ^{Footnote 21}. Topical and oral azoles such as butoconazole, clotrimazole, triazole, and econazole lipogel as well as ibrexafungerp can be used against vaginal candidiasis. Antifungals such as fluconazole or itraconazole are used to treat mucocutaneous candida infections. Voriconazole, and echinocandins can be effective against cutaneous candidiasis although an azole is preferred. For systemic invasive candidiasis caused by C. albicans infection, the preferred initial therapy is echinocandin, while an alternative and step down treatment would be fluconazole^{Footnote 5}.

Resistance of C. albicans to fluconazole has been associated with repeated use of this drug, particularly in immunosuppressed patients who are taking this drug chronically for prophylaxisis^{Footnote 9}. Resistance to echinocandins has also been reported. Multiple drug resistance within the genus Candida, and specifically in C. albicans is increasing and is exacerbated by the low number of anti-fungals available^{Footnote 6Footnote 22}.

Susceptibility to disinfectants

Candida albicans strains can be killed effectively with sodium hyphochlorite (5% and 0.5%), iodine (2%) and potassium iodide (4%) within 30 seconds^{Footnote 23}. Chlorhexidine acetate (0.5%) is able to completely kill C. albicans strains within 5 minutes. C. albicans strains are resistant to calcium hydroxide. C. albicans isolates are also susceptible to 70% ethanol, 0.5% ecodiol and a combination of 1.2% sodium hyphochlorite and 0.5% ecodiol^{Footnote 24}. The commercial anti-septics Betadine (10% Iodine polyvinylpyrrolidone), Dermacide (2% Sodium laurylsulfate) and Dosisepsine (0.05% Chlorhexidine digluconate), as well as Chitosan (a low molecular biodegradable derivative of chitin) have also been shown to be effective^{Footnote 25}.

Physical inactivation

UV light has been shown to reduce fungal load, but is ineffective in killing the yeast completely^{Footnote 24}. Most microorganisms are also inactivated by moist heat (121°C for 15-30 minutes)^{Footnote 26}.

Survival outside host

C. albicans can survive on inanimate surfaces for 24 hours – 120 days, and on palms for about 45 minutes^{Footnote 20}. C. albicans has been isolated from bed-sheets, cots, and wash-basins of nurseries, and it has also been found to be able to survive and grow in distilled water at room temperature^{Footnote 27}. The fungus can survive on drying in darkness for 5 hours, and 1 hour if also exposed to light. Under experimental conditions, cell viability was found to be 10% after 150 days in seawater, 180 days in rain water and 210 days in tap water^{Footnote 28}.

Section V – First aid/medical

Surveillance

Monitor for symptoms. Direct examination of the fungus or the fungus in culture in the clinical specimen can confirm the presence of infection if key characteristics (size and shape of yeast, presence of pseudophypahe, blastoconidia, chlamydospores, and absence of arthroconidia and capsule) are observed^{Footnote 3}. Other methods include biochemical tests, serological methods such as ELISA, and molecular biology methods such as restriction enzyme analysis (REA), PCR, and pulse-field gel electrophoresis (PFGE)^{Footnote 3Footnote 5}. Tests for beta-D-glucan can indicate invasive fungal infection through a positive test, but as this is not specific for C. albicans, it is useful primarily as a negative predictor of infection^{Footnote 29}.

Note: The specific recommendations for surveillance in the laboratory should come from the medical surveillance program, which is based on a local risk assessment of the pathogens and activities being undertaken, as well as an overarching risk assessment of the biosafety program as a whole. More information on medical surveillance is available in the Canadian Biosafety Handbook (CBH).

First aid/treatment

Administer proper drug therapy. Eliminating predisposing factors such as administration of antibiotics, steroids, and immunosuppressants; humidity, local maceration, vaginal pH, and removal of infected catheter, can help in resolving infections^{Footnote 3}.

Note: The specific recommendations for first aid/treatment in the laboratory should come from the post-exposure response plan, which is developed as part of the medical surveillance program. More information on the post-exposure response plan can be found in the CBH.

Immunization

None.

Note: More information on the medical surveillance program can be found in the CBH, and by consulting the Canadian Immunization Guide.

Prophylaxis

Although fluconazole has been used for prophylaxis of C. albicans infections in HIV infected patients, its prolonged exposure has been associated with emergence of fluconazole resistant strains^{Footnote 11}.

Note: More information on prophylaxis as part of the medical surveillance program, can be found in the CBH.

Section VI – Laboratory hazard

Laboratory-acquired infections

Low risk of infection to laboratory worker^{Footnote 30}. A medical student has been reported to develop rash and folliculitis 2 days after she spilled a heavy suspension of C. albicans on her leg while conducting a laboratory experiment.

Note: Please consult the Canadian Biosafety Standard (CBS) and CBH for additional details on requirements for reporting exposure incidents. A Canadian biosafety guideline describing notification and reporting procedures is also available.

Sources/specimens

Epithelial scrapings or exudates from lesions; sputum; bronchoalveolar lavage; blood^{Footnote 3}.

Primary hazards

Accidental parenteral inoculation, direct exposure of the skin to the pathogen.

Special hazards

None.

Section VII – Exposure controls/personal protection

Risk group classification

Candida albicans is a Risk Group 2 Human Pathogen and Risk Group 2 Animal Pathogen^{Footnote 31Footnote 32}.

Containment requirements

Containment Level 2 facilities, equipment, and operational practices outlined in the CBS for work involving infectious or potentially infectious materials, animals, or cultures.

Protective clothing

The applicable Containment Level 2 requirements for personal protective equipment and clothing outlined in the CBS are to be followed. The personal protective equipment could include the use of a labcoat and dedicated footwear (e.g., boots, shoes) or additional protective footwear (e.g., boot or shoe covers) where floors may be contaminated (e.g., animal cubicles, PM rooms), gloves when direct skin contact with infected materials or animals is unavoidable, and eye protection where there is a known or potential risk of exposure to splashes.

Note: A local risk assessment will identify the appropriate hand, foot, head, body, eye/face, and respiratory protection, and the personal protective equipment requirements for the containment zone and work activities must be documented.

Other precautions

A biological safety cabinet (BSC) or other primary containment devices to be used for activities with open vessels, based on the risks associated with the inherent characteristics of the regulated material, the potential to produce infectious aerosols or aerosolized toxins, the handling of high concentrations of regulated materials, or the handling of large volumes of regulated materials.

Use of needles and syringes to be strictly limited. Bending, shearing, re-capping, or removing needles from syringes are to be avoided, and if necessary, performed only as specified in standard operating procedures (SOPs). Additional precautions are required with work involving animals or large-scale activities.

For diagnostic laboratories handling primary specimens that may contain Candida albicans
the following resources may be consulted:

• Human Diagnostic Activities Biosafety Guideline
• Local Risk Assessment Biosafety Guideline

Section VIII – Handling and storage

Spills

Allow aerosols to settle. Wearing personal protective equipment, gently cover the spill with absorbent paper towel and apply suitable disinfectant, starting at the perimeter and working towards the centre. Allow sufficient contact time with disinfectant before clean up (CBH).

Disposal

All materials/substances that have come in contact with the regulated materials to be completely decontaminated before they are removed from the containment zone or standard operating procedures (SOPs) to be in place to safely and securely move or transport waste out of the containment zone to a designated decontamination area / third party. This can be achieved by using decontamination technologies and processes that have been demonstrated to be effective against the regulated material, such as chemical disinfectants, autoclaving, irradiation, incineration, an effluent treatment system, or gaseous decontamination (CBH).

Storage

The applicable Containment Level 2 requirements for storage outlined in the CBS are to be followed. Primary containers of regulated materials removed from the containment zone to be labelled, leakproof, impact resistant, and kept either in locked storage equipment or within an area with limited access.

Section IX – Regulatory and other information

Canadian regulatory information

Controlled activities with Candida albicans require a Pathogen and Toxin licence issued by the Public Health Agency of Canada (PHAC). C. albicans is a terrestrial animal pathogen in Canada; therefore, importation of C. albicans requires an import permit under the authority of the Health of Animals Regulations (HAR). The PHAC issues a Pathogen and Toxin licence which includes a Human Pathogen and Toxin Licence and an HAR importation permit.

The following is a non-exhaustive list of applicable designations, regulations, or legislations:

• Human Pathogens and Toxins Act andHuman Pathogens and Toxins Regulations
• Health of Animals Actand Health of Animals Regulations
• Transportation of Dangerous Goods Act and Transportation of Dangerous Goods Regulations

Last file update

February, 2024

Prepared by

Centre for Biosecurity, Public Health Agency of Canada.

Disclaimer

The scientific information, opinions, and recommendations contained in this Pathogen Safety Data Sheet have been developed based on or compiled from trusted sources available at the time of publication. Newly discovered hazards are frequent and this information may not be completely up to date. The Government of Canada accepts no responsibility for the accuracy, sufficiency, or reliability or for any loss or injury resulting from the use of the information.

Persons in Canada are responsible for complying with the relevant laws, including regulations, guidelines and standards applicable to the import, transport, and use of pathogens in Canada set by relevant regulatory authorities, including the Public Health Agency of Canada, Health Canada, Canadian Food Inspection Agency, Environment and Climate Change Canada, and Transport Canada. The risk classification and related regulatory requirements referenced in this Pathogen Safety Data Sheet, such as those found in the Canadian Biosafety Standard, may be incomplete and are specific to the Canadian context. Other jurisdictions will have their own requirements.

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