Advanced Diagnostic Laboratories | National Jewish Health | Clinical Laboratory | ISO 15189

Environmental Culture and Identification for Acid Fast Bacilli

Test Code

ENVCX

Description

This test includes culture for acid fast bacilli (AFB) and organism identification from clinically-relevant environmental water samples. The AFB culture is the inoculation of a clinical specimen onto multiple media types followed by monitoring for six weeks. Growth of any AFB (i.e. mycobacteria) or partially acid fast organisms (e.g. aerobic actinomycetes) is identified. Identification will occur to the greatest extent possible, which is usually to the species level but can be to the subspecies level for some organisms (e.g. Mycobacterium abscessus subsp. abscessus).

This test is used for identifying possible sources of clinical infection, it is not intended for sterility testing. Note that a smear from an environmental sample is not performed.

Collect

Two unique identifiers are required on the sample and on the test requisition.
Environmental water sample should be collected in a large, sterile, leak-proof container.
- Collect a minimum of 1,000 mL (1.0 L) of the environmental water to be tested.
- Samples should be shipped refrigerated.
Other environmental samples
- Use a sterile flocked swab with 1ml of Amies liquid media (e.g. ESwab)
- Swab the relevant surface, rolling it to ensure that the entire swab is used. Break off into the liquid media tube and transport.
- List the location the sample was taken from (e.g. water heater filter) , as well as the collection date.

Unacceptable Conditions

Environmental samples without two unique identifiers will be rejected.
Environmental samples received after 14 days will be rejected.

Stability

Environmental samples should be received in the lab within 4 days of collection.
Environmental samples received between 5 - 14 days’ post-collection will be processed with a disclaimer.
Environmental samples received after 14 days of collection will be rejected.

Notes

AFB smear is not performed.

Performed

Typically all days

Methodology

Water samples are treated with a detergent then filtered through a bacteriological membrane.

All samples are cultured on three solid media then incubated for 6 weeks. Mycobacteria or partially acid fast organisms are identified to the full extent possible, such as to the species or subspecies level (see AFB4 for further details).

Turnaround Time

The final report for the AFB culture is issued at 6 weeks. Cultures are read at 1, 3 and 6 weeks. Positive cultures are reported at the time of positivity and negative cultures reported at 1, 3, and 6 weeks.
Identification is reported within 3 days to 2 weeks, depending on the method(s) used.

Department

Infectious Disease Laboratory, Mycobacteriology

Synonyms

Environmental, Water sample

Reference Interval

Negative for acid fast bacilli.

Interpretation

Test	Interpretations
AFB Culture	Negative cultures are reported as negative for growth. Positive cultures are reported as organisms recovered with a colony count where possible (CFU/mL).
AFB Identification	Organisms are identified to the species or subspecies level, where possible.

CPT Code

This is a test algorithm. When it is ordered, sample processing is performed. If an organism is recovered, a reflex identification test will be ordered. The identification method used will depend on the organism.

	Method	CPT code	Billing codes	When is this applied?
AFB Culture	Specimen processing	87015	CXAFB2	All samples
AFB Identification	PCR/MALDI-TOF mass Spectrometry	87798 x 9	MASID (1st organism), MASI2 (2nd organism), MASI3 (3rd organism)	If appropriate organisms are recovered
AFB Identification	Line probe assay	87798 x 7	NTMID (1st organism), NTMD2 (2nd organism), NTMD3 (3rd organism)	If appropriate organisms are recovered
rpoB identification	Sequencing	87556	RPOB	If the appropriate organism is recovered.
16S identification	Sequencing	87153	16S	If the appropriate organism is recovered.