Slow-Growing Fungi in the Lab

By Dr. Zubair Khalid, DVM, MS, PhD · 2026-08-27

Quick Answer

• Slow-growing fungi require prolonged incubation, specialized media, and a structured weekly examination schedule to prevent missed or delayed identification.
• Select Sabouraud dextrose agar with antibiotics or inhibitory mold agar, incubate at 25 to 30 degrees Celsius, and hold cultures for up to four weeks before reporting negative results.
• A key limitation is that some dimorphic fungi pose aerosol hazards, so all manipulations must follow biosafety level practices appropriate to the organism.

At a Glance

Laboratory Design and Workflow for Slow-Growing Fungi

Physical Layout and Containment

The laboratory space for fungal culture work requires separation from bacterial processing areas. A dedicated mycology bench or room prevents cross-contamination from rapidly growing bacteria and molds. The Biosafety in Microbiological and Biomedical Laboratories guidance from the CDC and NIH describes the primary containment practices that apply to fungal culture work. These practices include performing manipulations inside a biological safety cabinet, using personal protective equipment, and decontaminating work surfaces before and after each session.

The biological safety cabinet is the central containment device for fungal culture work. All subculturing, slide preparation, and colony examination must occur inside this cabinet. The cabinet protects the worker from inhalation exposure to spores and protects the culture from airborne contamination. The cabinet should be certified annually and after any move or repair.

Workflow Design for Prolonged Incubation

A dedicated workflow for slow-growing fungi requires planning around the extended incubation period. The workflow begins with specimen receipt and inoculation, moves through periodic examination, and ends with identification or referral. Each step requires documentation so that the laboratory can track culture age and examination history.

The examination schedule should be posted near the incubator and recorded in a culture log. The log should include the specimen identifier, collection date, inoculation date, media used, incubation temperature, and the date of each examination. This record supports the decision to report a culture as negative after the full incubation period.

Media Selection and Preparation

Sabouraud Dextrose Agar

Sabouraud dextrose agar is the standard medium for primary isolation of fungi. The acidic pH of approximately 5.6 inhibits many bacteria and supports the growth of most pathogenic fungi. The medium is available in several formulations, including the addition of chloramphenicol to suppress bacterial growth and cycloheximide to suppress saprophytic molds.

The decision to use cycloheximide-containing media depends on the specimen source. For skin, hair, and nail specimens, cycloheximide is useful because it suppresses environmental molds that would otherwise overgrow the culture. For respiratory specimens, cycloheximide may inhibit some dimorphic fungi and should be used with caution. The laboratory should maintain both media types to accommodate different specimen sources.

Inhibitory Mold Agar

Inhibitory mold agar is an alternative primary medium that contains chloramphenicol and gentamicin to suppress bacteria. It does not contain cycloheximide, so it supports the growth of a wider range of fungi. This medium is useful for specimens where the suspected organism may be inhibited by cycloheximide.

The choice between Sabouraud dextrose agar and inhibitory mold agar is a management decision based on the specimen source and the suspected organism. For specimens from nonsterile sites, the inhibitory mold agar provides a broader recovery. For specimens from sterile sites, the Sabouraud dextrose agar with antibiotics is often sufficient.

Media Quality Control

Each new lot of media must be tested before use in clinical work. The American Type Culture Collection provides authenticated strains that can be used for quality control testing. The quality control strain should be inoculated onto the new medium and observed for expected growth characteristics. The results should be recorded in the quality control log.

The quality control test should include a positive control organism that is expected to grow on the medium and a negative control that is expected to be inhibited. For example, a dermatophyte strain should grow on Sabouraud dextrose agar with cycloheximide, while a saprophytic mold should be inhibited. The quality control record should include the strain identifier, the date of testing, the expected result, and the observed result.

Incubation Parameters and Temperature Control

Temperature Selection

The incubation temperature for slow-growing fungi is typically 25 to 30 degrees Celsius. This temperature range supports the growth of dermatophytes and environmental molds. Some dimorphic fungi require a different temperature for the yeast phase, which is discussed in the section on dimorphic fungi.

The incubator should be monitored daily and the temperature recorded. A thermometer inside the incubator should be checked against a certified reference thermometer on a regular schedule. The temperature record should be kept in the laboratory log.

Incubation Duration

The incubation period for slow-growing fungi is longer than for bacteria. The minimum incubation period is four weeks for dermatophytes and other slow-growing fungi. Some dimorphic fungi require up to six weeks of incubation before a culture can be reported as negative.

The laboratory must resist the pressure to report a negative culture before the full incubation period has elapsed. A culture that appears negative at two weeks may show growth at four weeks. The examination schedule should be followed strictly.

Incubation Environment

The incubator should be kept clean and free of contamination. The interior surfaces should be wiped with a disinfectant on a regular schedule. The incubator should not be used for other purposes, such as storing reagents or media.

The humidity inside the incubator should be controlled to prevent the media from drying out. Some laboratories use a pan of water inside the incubator to maintain humidity. The water should be changed regularly to prevent the growth of bacteria and fungi in the water.

Examination Schedule and Colony Assessment

Weekly Examination Protocol

The examination schedule for slow-growing fungi should be documented and followed consistently. The schedule should include a daily check of the incubator temperature and a weekly examination of each culture plate. The weekly examination should be performed inside the biological safety cabinet.

The examination should include a visual inspection of the colony morphology, a check for contamination, and a record of the colony size and color. The colony morphology should be described in the culture log. The description should include the colony texture, the surface color, the reverse color, and the presence of any exudate.

Colony Morphology Assessment

The colony morphology of a fungus is a key observation for identification. The texture can be described as cottony, woolly, granular, or powdery. The surface color can be white, cream, yellow, green, brown, or black. The reverse color can be the same as the surface or different.

The colony morphology should be recorded at each examination. The changes in morphology over time are also useful. A colony that starts white and becomes green over time is characteristic of some species of Aspergillus. A colony that remains white and becomes powdery is characteristic of some dermatophytes.

Slide Culture Preparation

The slide culture technique is used to observe the microscopic morphology of the fungus. The technique involves inoculating a small block of agar on a glass slide and covering it with a coverslip. The fungus grows on the agar and the coverslip, and the slide can be examined directly under the microscope.

The slide culture should be prepared when the colony is large enough to provide a sample. The sample should be taken from the edge of the colony, where the growth is most active. The slide culture should be incubated for 24 to 48 hours and then examined under the microscope.

The microscopic morphology includes the presence of hyphae, the type of hyphae, the presence of spores, and the arrangement of spores. The microscopic morphology is used to identify the fungus to the genus level and sometimes to the species level.

Identification of Dermatophytes

Key Features of Dermatophytes

Dermatophytes are a group of fungi that infect the skin, hair, and nails. They are the most common cause of fungal infections in humans and animals. The laboratory identification of dermatophytes is based on the colony morphology and the microscopic morphology.

The colony morphology of a dermatophyte is typically slow-growing and may be white, cream, or brown. The texture is often powdery or granular. The reverse color is often brown or red.

The microscopic morphology of a dermatophyte includes the presence of macroconidia and microconidia. The macroconidia are large, multicellular spores that are characteristic of the genus. The microconidia are small, single-celled spores that are also characteristic of the genus.

Species Identification

The species identification of a dermatophyte requires the observation of the macroconidia and microconidia. The shape, size, and arrangement of the macroconidia are used to distinguish the species. For example, the macroconidia of Trichophyton rubrum are pencil-shaped and have a smooth wall. The macroconidia of Microsporum canis are spindle-shaped and have a rough wall.

The species identification is important for the clinical management of the patient. The treatment of a dermatophyte infection depends on the species. The laboratory should report the species identification when it is possible.

Limitations of Morphological Identification

The morphological identification of dermatophytes is limited by the variability of the colony and microscopic morphology. The morphology can vary with the media, the incubation temperature, and the age of the culture. The morphology can also vary between the strains of the same species.

The laboratory should use a reference laboratory for the identification of unusual or difficult species. The reference laboratory can use molecular methods to confirm the species identification.

Identification of Dimorphic Fungi

The Dimorphic Life Cycle

The dimorphic fungi are a group of fungi that exist in two forms. At 25 to 30 degrees Celsius, they grow as a mold. At 35 to 37 degrees Celsius, they grow as a yeast or as a spherule. The dimorphic fungi include the agents of histoplasmosis, blastomycosis, coccidioidomycosis, and paracoccidioidomycosis.

The dimorphic fungi are a biosafety concern. The mold form produces spores that can be inhaled and cause infection. The Biosafety in Microbiological and Biomedical Laboratories guidance describes the containment requirements for the dimorphic fungi. The mold form should be handled in a biological safety cabinet, and the culture should be sealed when it is not being examined.

Conversion to the Yeast Phase

The conversion of the mold form to the yeast form is used to confirm the identification of a dimorphic fungus. The conversion is performed by subculturing the mold form to a rich medium and incubating at 35 to 37 degrees Celsius. The yeast form is observed after several days of incubation.

The conversion is not always successful. The failure of the conversion can be due to the strain, the media, or the incubation conditions. The laboratory should use a reference laboratory for the confirmation of the dimorphic fungi.

Biosafety Considerations

The dimorphic fungi are a biosafety concern because of the risk of inhalation of the spores. The Biosafety in Microbiological and Biomedical Laboratories guidance describes the containment requirements for the dimorphic fungi. The mold form requires a biological safety cabinet for all manipulations. The culture should be sealed with tape to prevent the release of spores.

The laboratory should have a written protocol for the handling of the dimorphic fungi. The protocol should include the use of the biological safety cabinet, the personal protective equipment, and the decontamination of the work area. The protocol should be reviewed and updated on a regular schedule.

Quality Control and Quality Assurance

Quality Control of Media and Reagents

The quality control of the media and reagents is a critical part of the fungal culture workflow. The American Type Culture Collection provides authenticated strains that can be used for the quality control of the media. The quality control test should be performed on each new batch of media and on a regular schedule for the media in use.

The quality control test should include a positive control and a negative control. The positive control should be a strain that is expected to grow on the medium. The negative control should be a strain that is expected to be inhibited by the medium. The results of the quality control test should be recorded in the quality control log.

Quality Control of the Incubator

The incubator should be monitored daily for the temperature. The temperature should be recorded in the incubator log. The thermometer should be checked against a reference thermometer on a regular schedule. The incubator should be cleaned on a regular schedule to prevent contamination.

Quality Control of the Examination

The examination of the culture should be performed by a trained person. The person should be able to recognize the colony morphology and the microscopic morphology of the common fungi. The person should also be able to recognize the signs of contamination.

The examination should be documented in the culture log. The log should include the date of the examination, the observation, and the initials of the person who performed the examination. The log should be reviewed by the supervisor on a regular schedule.

Common Failure Patterns and Troubleshooting

Failure Pattern 1: No Growth After the Incubation Period

The most common failure pattern is the absence of growth after the incubation period. The cause of the failure can be the media, the incubation temperature, or the specimen. The laboratory should review the quality control records for the media and the incubator. The laboratory should also review the specimen collection and transport records.

The decision to report a negative culture should be based on the full incubation period. The laboratory should not report a negative culture before the full incubation period has elapsed. The laboratory should also consider the possibility of a false negative due to the specimen quality.

Failure Pattern 2: Overgrowth by Contaminants

The overgrowth by contaminants is a common failure pattern in fungal culture. The contaminants can be bacteria, yeast, or environmental molds. The cause of the contamination can be the specimen, the media, or the laboratory environment.

The laboratory should use the media with antibiotics to suppress the bacterial growth. The laboratory should also use the media with cycloheximide to suppress the environmental molds. The laboratory should also maintain a clean environment and use the biological safety cabinet for all manipulations.

Failure Pattern 3: Slow Growth or No Growth of the Suspected Pathogen

The slow growth or no growth of the suspected pathogen is a failure pattern that can be due to the media, the incubation temperature, or the specimen. The laboratory should review the media selection and the incubation temperature. The laboratory should also consider the possibility that the suspected pathogen is not the cause of the infection.

The laboratory should consider the use of a different medium or a different incubation temperature. The laboratory should also consider the use of a molecular method for the detection of the pathogen.

Documentation and Record Keeping

Culture Log

The culture log is the primary record of the fungal culture work. The log should include the specimen identifier, the collection date, the specimen date, the media used, the incubation temperature, and the date of each examination. The log should also include the observation of the colony morphology and the microscopic morphology.

The culture log should be kept in a secure location and should be available for review. The log should be reviewed by the supervisor on a regular schedule. The log should be retained for the period required by the laboratory policy.

Quality Control Log

The quality control log is the record of the quality control tests. The log should include the date of the test, the media or reagent tested, the strain used, the expected result, and the observed result. The log should be reviewed by the supervisor on a regular schedule.

Incubator Log

The incubator log is the record of the incubator temperature. The log should include the date, the time, and the temperature. The log should be reviewed by the supervisor on a regular schedule.

Biosafety and Risk Assessment

Risk Assessment for Fungal Culture

The risk assessment for the fungal culture work should be performed before the work is started. The risk assessment should consider the specimen source, the suspected organism, and the laboratory procedures. The risk assessment should be documented and reviewed on a regular schedule.

The Biosafety in Microbiological and Biomedical Laboratories guidance describes the risk assessment process and the containment requirements for the different risk groups. The laboratory should follow the guidance for the risk group of the suspected organism.

Personal Protective Equipment

The personal protective equipment for the fungal culture work includes a laboratory coat, gloves, and eye protection. The gloves should be worn for all manipulations. The gloves should be changed between the specimens. The lab coat should be worn in the laboratory and removed before leaving the laboratory.

Decontamination

The decontamination of the work area and the equipment is a critical part of the fungal culture work. The work surfaces should be decontaminated before and after each use. The equipment should be decontaminated on a regular schedule. The decontamination should be performed with a disinfectant that is effective against the fungi.

The Biosafety in Microbiological and Biomedical Laboratories guidance describes the decontamination methods for the laboratory. The laboratory should follow the guidance for the decontamination of the work area and the equipment.

Antimicrobial Resistance and Public Health Context

The Role of the Laboratory in Antimicrobial Resistance

The laboratory plays a role in the detection of antimicrobial resistance. The World Health Organization describes the global problem of antimicrobial resistance and the need for surveillance. The laboratory should participate in the surveillance of antimicrobial resistance by performing the susceptibility testing and reporting the results.

The susceptibility testing of the fungi is performed by the Clinical and Laboratory Standards Institute methods. The laboratory should follow the standards for the susceptibility testing of the fungi. The results of the susceptibility testing should be reported to the clinician and to the public health authorities.

The Laboratory and the Public Health

The laboratory is a part of the public health system. The laboratory should report the results of the fungal culture to the public health authorities when the organism is a reportable disease. The laboratory should also report the results of the antimicrobial susceptibility testing to the public health authorities.

The American Society for Microbiology provides the professional context for the laboratory workforce. The laboratory should follow the professional standards for the practice of the microbiology.

Professional Escalation Criteria

When to Refer to a Reference Laboratory

The laboratory should refer to a reference laboratory when the identification of the fungus is uncertain. The reference laboratory can use the molecular methods to confirm the identification. The reference laboratory can also perform the susceptibility testing for the antifungal drugs.

The laboratory should also refer to a reference laboratory when the dimorphic fungus is suspected. The dimorphic fungus requires the biosafety level 3 containment. The laboratory should not attempt to identify the dimorphic fungus without the appropriate containment.

When to Consult a Clinician

The laboratory should consult a clinician when the culture result is unexpected or when the culture result does not match the clinical picture. The clinician can provide the clinical context for the culture result. The clinician can also provide the information about the patient's travel history and the exposure history.

The laboratory should also consult a clinician when the culture result is a rare or unusual species. The clinician can provide the information about the clinical significance of the species.

Documentation and Reporting

The Culture Report

The culture report should include the specimen identifier, the collection date, the specimen date, the media used, the incubation temperature, and the result of the culture. The result should include the identification of the organism and the susceptibility testing results, if performed.

The culture report should be reviewed by the supervisor before it is released. The report should be released to the clinician and the public health authorities, as required.

The Negative Culture Report

The negative culture report should be released after the full incubation period. The report should state that the culture was negative for the fungi after the full incubation period. The report should also state the incubation period and the media used.

The negative culture report should be reviewed by the supervisor before it is released. The report should be released to the clinician and the public health authorities, as required.

Limitations and Interpretation

The Limitations of the Culture

The culture is a useful method for the detection of the fungi, but it has limitations. The culture can be negative when the fungus is present in the specimen. The culture can also be positive when the fungus is a contaminant and not the cause of the infection.

The laboratory should interpret the culture result in the context of the clinical picture. The laboratory should also interpret the culture result in the context of the specimen quality. The laboratory should report the limitations of the culture to the clinician.

The Interpretation of the Culture Result

The interpretation of the culture result should be based on the clinical picture and the laboratory findings. The laboratory should report the culture result with the interpretation. The interpretation should include the clinical significance of the organism and the recommendation for the treatment.

The laboratory should also report the culture result with the limitations. The limitations should include the possibility of a false-negative and the possibility of a false-positive. The laboratory should report the limitations to the clinician.

A Practical Decision Framework for Culture Workup and Referral

The Core Decision Points in Slow-Growing Fungal Culture

The laboratory faces a series of decisions from the moment a specimen arrives until the final report is released. Each decision affects the time to identification and the risk of a missed pathogen. A structured decision framework reduces the variability that comes from individual judgment and ensures that the same specimen type is handled the same way every time. The framework below is built around five decision points that occur in every fungal culture workflow.

The first decision point is the specimen source and the suspected organism. This decision determines the media selection, the incubation temperature, and the biosafety level. The second decision point is the examination finding at each scheduled check. This decision determines whether the culture is progressing normally, whether it needs a subculture, or whether it should be referred. The third decision point is the appearance of a contaminant. This decision determines whether the culture can be salvaged or must be repeated. The fourth decision point is the failure of the suspected pathogen to grow. This decision determines whether the culture is truly negative or whether the conditions were wrong. The fifth decision point is the identification result. This decision determines whether the laboratory can report the species or must refer to a reference laboratory.

Decision Point 1: Specimen Source and Suspected Organism

The specimen source is the first and most important piece of information in the decision framework. The source determines the media selection and the incubation conditions. The Bacteriological Analytical Manual from the FDA describes the principle that the specimen source and the suspected organism drive the method selection. The same principle applies to fungal culture.

For skin, hair, and nail specimens, the suspected organism is a dermatophyte. The primary media should include Sabouraud dextrose agar with chloramphenicol and cycloheximide. The cycloheximide suppresses the environmental molds that are common contaminants of skin and nail specimens. The incubation temperature should be 25 to 30 degrees Celsius. The culture should be held for four weeks before a negative result is reported.

For respiratory specimens, the suspected organism may be a dimorphic fungus. The media should include inhibitory mold agar without cycloheximide. The cycloheximide can inhibit some dimorphic fungi, including the agent of histoplasmosis. The incubation temperature should be 25 to 30 degrees Celsius for the mycelial phase. The culture should be held for up to six weeks before a negative result is reported.

For sterile site specimens, the suspected organism may be a yeast or a mold. The media should include both Sabouraud dextrose agar and inhibitory mold agar. The incubation temperature should be 25 to 30 degrees Celsius. The culture should be held for four weeks before a negative result is reported.

The decision framework should be written down and posted in the laboratory. The framework should include the specimen source, the media, the incubation temperature, and the incubation period. The framework should be reviewed by the supervisor on a regular schedule.

Decision Point 2: Examination Findings at Scheduled Checks

The examination schedule is the second decision point in the framework. The schedule should be written down and followed consistently. The schedule should include a daily check of the incubator temperature and a weekly examination of each culture plate. The weekly examination should be performed inside the biological safety cabinet.

At each examination, the laboratory worker should record the colony morphology, the colony size, and the presence of any contamination. The worker should also record the color of the colony and the texture. The record should be made in the culture log.

The decision at each examination is whether to continue the culture, to subculture the colony, or to refer the culture. The decision is based on the observed morphology and the age of the culture. A colony that is growing and has a characteristic morphology should be continued. A colony that is large enough to provide a sample should be subcultured for identification. A colony that is unusual or difficult to identify should be referred to a reference laboratory.

The decision framework should include the criteria for each action. The criteria should be written down and applied consistently. The criteria should include the colony size, the colony morphology, and the age of the culture.

Decision Point 3: Contamination and Recovery

The appearance of a contaminant is the third decision point. The contaminant can be a bacterium, a yeast, or an environmental mold. The contaminant can overgrow the culture and prevent the growth of the suspected pathogen. The decision is whether the culture can be recovered or must be repeated.

The first step in the decision is to identify the contaminant. The contaminant can be identified by the colony morphology and the microscopic morphology. The contaminant can also be identified by the growth rate. A fast-growing mold that appears within the first few days is likely a contaminant. A slow-growing mold that appears after two weeks is more likely to be the suspected pathogen.

The second step in the decision is to determine whether the suspected pathogen is present in the culture. The culture should be examined for the presence of the suspected pathogen. If the pathogen is present, the culture should be subcultured to a fresh medium. The subculture should be taken from the edge of the colony, where the growth is most active. The subculture should be incubated under the same conditions as the original culture.

If the pathogen is not present, the culture should be repeated with a new specimen. The laboratory should contact the clinician to request a new specimen. The laboratory should also review the specimen collection and transport procedures to identify the source of the contamination.

The decision framework should include the criteria for the recovery of a contaminated culture. The criteria should include the presence of the suspected pathogen, the ability to subculture, and the age of the culture.

Decision Point 4: No Growth of the Suspected Pathogen

The failure of the suspected pathogen to grow is the fourth decision point. The failure can be due to the media, the incubation temperature, the specimen quality, or the absence of the pathogen. The decision is whether to report a negative culture or to investigate the cause of the failure.

The first step in the decision is to review the quality control records. The quality control records should show that the media supported the growth of the positive control organism. The records should also show that the incubator temperature was within the acceptable range. The American Type Culture Collection provides authenticated strains that can be used for the quality control of the media. The quality control records should be reviewed before the culture is reported as negative.

The second step in the decision is to review the specimen quality. The specimen should have been collected from the site of the infection. The specimen should have been transported to the laboratory in a timely manner. The specimen should have been processed in a timely manner. The laboratory should review the specimen collection and transport records to identify any problems.

The third step in the decision is to consider the possibility of a false negative. The culture can be negative when the fungus is present in the specimen but does not grow on the media. The fungus may require a different medium or a different incubation temperature. The fungus may also be present in a low number that is below the limit of detection of the culture method.

The decision to report a negative culture should be based on the full incubation period. The culture should not be reported as negative before the full incubation period has elapsed. The laboratory should also consider the use of a molecular method for the detection of the pathogen. The molecular method can detect the pathogen when the culture is negative.

Decision Point 5: Identification and Referral

The identification result is the fifth decision point. The decision is whether the laboratory can report the species identification or must refer to a reference laboratory. The decision is based on the confidence of the identification and the biosafety level of the organism.

The laboratory should be able to identify the common dermatophytes and the common environmental molds. The laboratory should be able to identify the species of Trichophyton, Microsporum, and Epidermophyton. The laboratory should also be able to identify the common species of Aspergillus and Penicillium.

The laboratory should refer to a reference laboratory when the identification is uncertain. The reference laboratory can use the molecular methods to confirm the identification. The reference laboratory can also perform the susceptibility testing for the antifungal drugs.

The laboratory should also refer to a reference laboratory when the dimorphic fungus is suspected. The dimorphic fungus requires the biosafety level 3 containment. The Biosafety in Microbiological and Biomedical Laboratories guidance describes the containment requirements for the dimorphic fungi. The laboratory should not attempt to identify the dimorphic fungus without the appropriate containment.

The decision framework should include the criteria for the referral. The criteria should include the uncertainty of the identification, the biosafety level of the organism, and the need for the susceptibility testing.

Implementing the Decision Framework in the Laboratory

The decision framework should be written down and posted in the laboratory. The framework should be reviewed by the supervisor on a regular schedule. The framework should be updated when the laboratory procedures change or when the new evidence becomes available.

The implementation of the framework requires the training of the laboratory staff. The staff should be trained on the decision points and the criteria for each action. The staff should also be trained on the documentation of the decisions. The training should be documented in the training records.

The implementation of the framework also requires the review of the outcomes. The laboratory should review the outcomes of the cultures on a regular schedule. The review should include the number of the positive cultures, the number of the negative cultures, the number of the contaminated cultures, and the number of the referred cultures. The review should identify the problems and the opportunities for the improvement.

The American Society for Microbiology provides the professional context for the laboratory workforce. The laboratory should follow the professional standards for the practice of the microbiology. The professional standards include the use of the decision framework and the review of the outcomes.

The Record System for the Decision Framework

The record system for the decision framework is the culture log. The culture log should include the specimen identifier, the collection date, the media used, the incubation temperature, and the date of each examination. The log should also include the decision at each examination and the reason for the decision.

The culture log should be kept in a secure location and should be available for review. The log should be reviewed by the supervisor on a regular schedule. The log should be retained for the period required by the laboratory policy.

The record system should also include the quality control log and the incubator log. The quality control log should include the date of the test, the media or reagent tested, the strain used, the expected result, and the observed result. The incubator log should include the date, the time, and the temperature.

The record system should be designed to support the decision framework. The records should provide the evidence for the decisions that were made. The records should also provide the evidence for the review of the outcomes.

Common Failure Patterns in the Decision Framework

The decision framework can fail in several ways. The most common failure is the failure to follow the framework. The laboratory worker may skip a decision point or make a decision without the evidence. The failure to follow the framework can lead to the missed identification or the delayed report.

The second common failure is the failure to document the decision. The laboratory worker may make a decision but not record it in the culture log. The failure to document the decision can lead to the confusion and the errors in the review.

The third common failure is the failure to review the outcomes. The laboratory may not review the culture results on a regular schedule. The failure to review the outcomes can lead to the repeated errors and the missed opportunities for the improvement.

The laboratory should have a written protocol for the review of the decision framework. The protocol should include the schedule for the review, the person responsible for the review, and the documentation of the review. The protocol should be reviewed and updated on a regular schedule.

The Role of the Decision Framework in the Public Health Context

The decision framework has a role in the public health context. The laboratory is a part of the public health system. The laboratory should report the results of the fungal culture to the public health authorities when the organism is a reportable disease. The laboratory should also report the results of the antimicrobial susceptibility testing to the public health authorities.

The World Health Organization describes the global problem of the antimicrobial resistance and the need for the surveillance. The laboratory should participate in the surveillance of the antimicrobial resistance by performing the susceptibility testing and reporting the results. The decision framework should support the surveillance by ensuring that the cultures are processed consistently and the results are reported accurately.

The Clinical and Laboratory Standards Institute provides the standards for the antimicrobial susceptibility testing. The laboratory should follow the standards for the susceptibility testing of the fungi. The results of the susceptibility testing should be reported to the clinician and to the public health authorities.

The Decision Framework as a Training Tool

The decision framework can be used as a training tool for the new laboratory staff. The framework provides a structured approach to the fungal culture work. The new staff can learn the decision points and the criteria for each action. The new staff can also learn the documentation requirements and the review process.

The training should include the hands-on practice with the culture work. The new staff should practice the inoculation, the examination, and the subculture. The new staff should also practice the documentation of the decisions. The training should be documented in the training log.

The training should also include the review of the common failure patterns. The new staff should learn the common failure patterns and the troubleshooting methods. The new staff should also learn the escalation criteria and the referral process.

The American Society for Microbiology provides the professional context for the laboratory workforce. The laboratory should follow the professional standards for the practice of the microbiology. The professional standards include the use of the decision framework and the review of the outcomes.

Frequently Asked Questions

How long should a fungal culture be incubated before reporting a negative result?

The incubation period for a fungal culture is typically four weeks for dermatophytes and other slow-growing fungi. Some dimorphic fungi require up to six weeks of incubation. The culture should not be reported as negative before the full incubation period has elapsed.

What is the difference between Sabouraud dextrose agar and inhibitory mold agar?

Sabouraud dextrose agar has a low pH and is selective for fungi. Inhibitory mold agar contains chloramphenicol and gentamicin to suppress bacteria. The choice between the two media depends on the specimen source and the suspected organism.

Why is cycloheximide added to some fungal culture media?

Cycloheximide is added to suppress the growth of environmental molds and saprophytic fungi. It is useful for specimens from skin, hair, and nails. It may inhibit some pathogenic fungi, so it should be used with caution for respiratory specimens.

What is the biosafety level for handling dimorphic fungi?

The mold form of the dimorphic fungi requires biosafety level 3 containment. The yeast form requires biosafety level 2 containment. The laboratory should follow the Biosafety in Microbiological and Biomedical Laboratories guidance for the containment of the dimorphic fungi.

How do I distinguish a dermatophyte from a contaminant mold?

The dermatophyte is identified by the colony morphology and the microscopic morphology. The colony is slow-growing and has a characteristic texture and color. The microscopic morphology includes the macroconidia and the microconidia. The contaminant mold is often fast-growing and has a different morphology.

What should I do if the culture is overgrown by a contaminant?

The culture should be examined for the presence of the suspected pathogen. If the pathogen is present, the culture should be subcultured to a fresh medium. If the pathogen is not present, the culture should be repeated with a new specimen.

When should I refer a culture to a reference laboratory?

The culture should be referred to a reference laboratory when the identification is uncertain or when the dimorphic fungus is suspected. The reference laboratory can use the molecular methods to confirm the identification and the susceptibility testing for the antifungal drugs.

What is the role of the laboratory in the antimicrobial resistance surveillance?

The laboratory is responsible for the detection of the antimicrobial resistance. The laboratory should perform the susceptibility testing and report the results to the clinician and the public health authorities. The World Health Organization describes the global problem of the antimicrobial resistance.

Using the Evidence

Related Diagnostic Guides

• Cell Culture Media: A Guide to Selection and Optimization
• Cell Culture Contamination: Sources, Detection, and Prevention
• Vero Cell Culture Techniques for Viral Diagnostics
• Viral Isolation and Embryonated Egg Culture Methods

References and Further Reading

• Biosafety in Microbiological and Biomedical Laboratories. CDC and NIH.
• Microbiology Resources. American Society for Microbiology.
• Antimicrobial Resistance. World Health Organization.
• Bacteriological Analytical Manual. U.S. Food and Drug Administration.
• Antimicrobial Susceptibility Testing. Clinical and Laboratory Standards Institute.
• Culture Collections. American Type Culture Collection.
• Laboratory Biosafety Manual. World Health Organization.
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This article is educational and does not replace validated laboratory procedures, institutional biosafety review, manufacturer instructions, or professional interpretation.