Skip to content

Advanced Diagnostic Laboratories

Identification of Acid Fast Bacilli


Test Code

AFB4

Description

This test is used for identification of acid fast bacilli (AFB) or partially acid fast organisms. Identification is performed 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).  See below for the different platforms, assays, and techniques that may be employed. 

This test is ordered for pure isolates sent to the laboratory for identification (e.g. AFID). It does not need to be ordered separately for clinical samples that require organism identification since it is automatically included in those tests (e.g. AFB1 and AFB3).

Note that full identification is needed for complete drug marker analysis. For instance, erm(41) cannot be reported without subspeciating M. abscessus. This is because erm(41) testing is not performed in the case of M. abscessus subsp. massiliense which will have a detectable gene although it is nonfunctional; this organism should be considered susceptible by the erm mechanism. On the other hand, if erm(41) is detected in the other two subspecies, mutations can cause them to be either resistant or susceptible. To get these important results, we recommend ordering full identification so that the results for all applicable resistance genes can be reported.