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Serpentine Cord: Introdction, Clinical Significance, and Keynotes

Serpentine cord or Cord factor or Trehalose dimycolate,TDM of Mycobacterium tuberculosis complex (MTBC) in Ziehl-Neelsen Staining of modified Middlebrook 7H9 Broth at a magnification of 1600X

Introduction

Fig. Serpentine cord or Cord factor or Trehalose dimycolate, TDM of Mycobacterium tuberculosis complex (MTBC) in Ziehl-Neelsen Staining of modified Middlebrook 7H9 Broth at a magnification of 1600X
Fig. Serpentine cord or Cord factor or Trehalose dimycolate (TDM) of Mycobacterium tuberculosis (MTB) in Ziehl-Neelsen Staining of modified Middlebrook 7H9 Broth at a magnification of 400X
  • The serpentine cord is a characteristic growth pattern of Mycobacterium tuberculosis (MTB) in liquid culture, especially in Middlebrook media or Lowenstein–Jensen (LJ) slants.
Fig. Serpentine cord or Cord factor or Trehalose dimycolate (TDM) of Mycobacterium tuberculosis complex (MTBC) in Auramine- Rhodamine staining of modified Middlebrook 7H9 Broth at a magnification of 400X-
  • It appears as long, intertwined, rope-like bacterial aggregates, resembling a snake or cord, under microscopic or macroscopic observation.
Fig. Cord factor or Trehalose dimycolate (TDM) of Mycobacterium tuberculosis complex (MTBC) in Auramine- Rhodamine staining of modified Middlebrook 7H9 Broth at a magnification of 400X
  • This cord formation is mediated by cell wall components, mainly cord factor (trehalose dimycolate, TDM), which promotes bacterial aggregation.
Fig. Serpentine cord or Cord factor or Trehalose dimycolate (TDM) of Mycobacterium tuberculosis complex (MTBC) in Auramine- Rhodamine staining of modified Middlebrook 7H9 Broth at a magnification of 400X

Clinical Significance

  • Diagnostic Value: The presence of serpentine cords can help differentiate virulent MTB strains from avirulent mycobacteria, as virulent strains form cords, whereas non-tuberculous mycobacteria often do not.
Fig. Serpentine cord or Cord factor or Trehalose dimycolate (TDM) of Mycobacterium tuberculosis complex (MTBC) in Auramine- Rhodamine staining of modified Middlebrook 7H9 Broth at a magnification of 1600X
  • Indicator of Virulence: Cord factor (TDM) is directly linked to virulence, stimulating host immune response, granuloma formation, and tissue necrosis.
Fig. Serpentine cord or Cord factor or Trehalose dimycolate (TDM) of Mycobacterium tuberculosis complex (MTBC) in Auramine-Rhodamine Fluorochrome stained smear microscopy of modified Middlebrook 7H9 Broth
  • Research and Pathophysiology: Studied in vitro to understand MTB aggregation, survival, and resistance to host defenses.
Fig. Cord factor or Trehalose dimycolate, TDM of Mycobacterium tuberculosis complex (MTBC) in Auramine-Rhodamine stained smear microscopy of liquid culture (Middlebrook medium)
  • Laboratory Observation: Useful in rapid presumptive identification of MTB during culture before molecular confirmation.
TDM of Mycobacterium tuberculosis complex (MTBC) inAuramine-Rhodamine Fluorochrome Stained smear microscopy of modified Middlebrook 7H9 Broth

Keynotes

  • Appearance: Rope-like, intertwined cord formation of MTB in liquid culture.
  • Mediated by: Cord factor (trehalose dimycolate).
  • Significance: Indicates virulent MTB strains.
  • Clinical Relevance: Helps differentiate MTB from non-tuberculous mycobacteria.
  • Laboratory Tip: Observe under a stereomicroscope or at the macroscopic level in LJ slants or Middlebrook media.
  • Associated with: Granuloma formation, host immune activation, and pathogenicity.
Fig. Cord factor or Trehalose dimycolate, TDM of Mycobacterium tuberculosis complex (MTBC) in Auramine-Rhodamine Fluorochrome stained smear microscopy of modified Middlebrook 7H9 Broth
Fig.Trehalose dimycolate, TDM of Mycobacterium tuberculosis (MTB) in Auramine-Rhodamine stained smear microscopy of liquid culture (Middlebrook medium)
Fig. Serpentine cord or cord factor of Mycobacterium tuberculosis (MTB) in liquid culture (Middlebrook medium)
Fig. Serpentine cord of Mycobacterium tuberculosis complex (MTBC) in liquid culture (Middlebrook medium)
Fig. Serpentine cord or cord factor of Mycobacterium tuberculosis (MTB) in liquid culture (Middlebrook medium)
Fig. Serpentine cord of Mycobacterium tuberculosis (MTB) in liquid culture (Middlebrook medium)

Further Readings

  1. https://pmc.ncbi.nlm.nih.gov/articles/PMC105205
  2. https://pmc.ncbi.nlm.nih.gov/articles/PMC7259532
  3. https://www.sciencedirect.com/science/article/abs/pii/S0732889325002500
  4. https://www.researchgate.net/publication/275837524_Cord_formation_in_BACTECTM_medium_aids_rapid_identification_of_Mycobacterium_tuberculosis_complex
  5. https://pubmed.ncbi.nlm.nih.gov/9705435
  6. https://www.researchgate.net/figure/Serpentine-cord-formation-in-M-tb-culture_fig2_288479628
  7. https://en.wikipedia.org/wiki/Cord_factor
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