Micobactérias

Mycobacterium abscessus

Rapidly growing acid-fast bacilli

Identification & Growth

Identification

Growth in under 7 days, non-chromogenic; subspecies abscessus, massiliense and bolletii
Grows even on ordinary blood agar — may be mistaken for a diphtheroid

Growth Conditions

Blood agar, Middlebrook or Löwenstein-Jensen, 30–35 °C, 3–7 days

Clinical Significance

Surgical site infection after video-assisted and cosmetic procedures
Pulmonary disease in cystic fibrosis and bronchiectasis

Intrinsic Resistance

Intrinsic resistance to common beta-lactams, antituberculosis drugs and most aminoglycosides
The erm(41) gene confers inducible macrolide resistance (except in M. massiliense)

Bench Alerts

Clarithromycin reading must be extended to 14 days to detect inducible resistance (CLSI M24)
Post-surgical outbreaks require investigation of instruments and disinfection solutions

Clinical Notes

Clinical presentations

Chronic progressive pulmonary disease, mainly in patients with bronchiectasis, cystic fibrosis or COPD, with radiologic pattern similar to other nontuberculous mycobacteria (NTM).
Skin, soft-tissue and surgical-site infections associated with cosmetic procedures, surgery, tattoos or contaminated penetrating trauma.
Disseminated infection in severely immunocompromised hosts, including catheter-related bacteremia and infections in transplant recipients.

Specimens and collection

Serial sputum samples (at least two to three specimens) for smear and culture, following ATS/IDSA diagnostic criteria for NTM pulmonary disease.
Tissue biopsy and wound material in mycobacteria-appropriate transport media, avoiding formalin when culture is required.
Catheter tip and blood culture using mycobacteria-specific systems (lysis-centrifugation or dedicated bottles) when device-associated bacteremia is suspected.

Epidemiology and at-risk populations

Rapidly growing mycobacterium, ubiquitous in water and soil, associated with outbreaks linked to contaminated tap water, ice, solutions and equipment in healthcare settings.
Subspecies M. abscessus subsp. abscessus, bolletii and massiliense differ in functional erm(41) status and macrolide response.
Patients with cystic fibrosis represent an important at-risk population for chronic colonization and pulmonary infection.

Resistance and therapeutic implications

CLSI M24 defines breakpoints for amikacin, cefoxitin, clarithromycin, imipenem, linezolid, tigecycline and other agents tested by broth microdilution.
Functional erm(41) confers inducible macrolide resistance; clarithromycin should be re-read at 14 days to detect this phenotype, except in the massiliense subgroup (nonfunctional erm(41)).
Prolonged multidrug therapy is required given intrinsic resistance to multiple classes; ATS/IDSA/ERS/ESCMID guidelines recommend combination regimens guided by susceptibility results.

Bench and reporting notes

Rapidly growing acid-fast bacillus (visible in 3–7 days on solid media), distinguishing it from slow-growing NTM.
Species and subspecies identification by sequencing (rpoB, hsp65) or validated mass spectrometry, since the subspecies informs the likelihood of macrolide response.
Always report the extended-read (day 14) clarithromycin result alongside the initial reading, flagging possible inducible resistance.

Sources

Educational decision-support content. It does not replace laboratory validation, current guidelines or review by the responsible professional.

FAQ: Frequently Asked Questions

How to identify Mycobacterium abscessus in the lab?

Mycobacterium abscessus is identified through growth in under 7 days, non-chromogenic; subspecies abscessus, massiliense and bolletii, grows even on ordinary blood agar — may be mistaken for a diphtheroid.

What are the intrinsic resistances of Mycobacterium abscessus?

This organism is naturally resistant to intrinsic resistance to common beta-lactams, antituberculosis drugs and most aminoglycosides, the erm(41) gene confers inducible macrolide resistance (except in m. massiliense). These drugs should not be reported as susceptible.

Where is Mycobacterium abscessus commonly found?

It is typically associated with surgical site infection after video-assisted and cosmetic procedures, pulmonary disease in cystic fibrosis and bronchiectasis.

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