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SUSCEPTIBILITY TESTING FOR RAPIDLY GROWING MYCOBACTERIA

Synonym(s):

​Mycobacterium, Rapid Grower, Susceptibility Test

Lab Section Category

Description

Indications

Specimen Required

​For mycobacteria isolated in CTBL or in other laboratories

Storage and Transport

​Isolates identified in referring labs must specify the organism’s identification and clinical source on the lab request form. For further instructions on packing, refer under IDENTIFICATION OF MYCOBACTERIA.

Method

​Microbroth dilution

Test Results

​Susceptible, Intermediate, Resistant, according to CLSI interpretive criteria

Reference Interval / Value

Turnaround Time

​1 - 2 weeks

Day(s) Test Set up

​Once a week

Remarks

​Drugs tested: Amikacin, cefoxitin, ciprofloxacin, clarithromycin*, doxycycline, imipenem**, linezolid, tobramycin***, trimethoprim-sulfamethoxazole and moxifloxacin. Tigecycline MICs are provided only upon request as there are no interpretative guidelines.

*Class representative for newer macrolides e.g. azithromycin. For the detection of the erm gene which causes inducible resistance to macrolides, a preliminary result is issued if the isolate is susceptible after Day 5 of incubation, followed by a final result after Day 14.
 
** Tentative CLSI breakpoints. Not predictive of results for meropenem or ertapenem as the activity against rapidly growing mycobacteria is greater for imipenem than for meropenem or ertapenem.

***M. chelonae from eye cultures only.

Change History Notes

  • 29 Apr 2016 06:25 PM

    Re-organized the wordings for the Remarks section.

  • 15 Jan 2018 06:25 PM

    Added in "To detect the erm gene which causes inducible resistance to macrolides" under remarks.

  • 22 May 2018 06:25 PM

    Amend "To detect" into "For the detection of" - in Remarks section.

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