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Ultrastructural cell wall characteristics of clinical gentamycin-resistant Staphylococcus aureus isolates

Kenji Fukutsuji1, Sakuo Yamada, Tamotsu Harada

  • 1Department of Otolaryngology, Kawasaki Medical School, 577 Matsusima, Kurasiki, Okayama, Japan. fuku29fukusuke@yahoo.co.jp

Medical Molecular Morphology
|January 23, 2013
PubMed

Insights

Gentamycin resistance in Staphylococcus aureus is increasing. Resistant strains show significantly thicker cell walls, suggesting this is a common characteristic of gentamycin-resistant bacteria.

Area of Science:

  • Microbiology
  • Bacterial Ultrastructure
  • Antimicrobial Resistance

Background:

  • Frequent use of gentamycin (GM) ointment has led to increased gentamycin-resistant Staphylococcus aureus clinical isolates.
  • Understanding the characteristics of resistant strains is crucial for developing effective treatments.

Purpose of the Study:

  • To investigate the ultrastructural differences between gentamycin-resistant and gentamycin-sensitive Staphylococcus aureus clinical strains.
  • To explore potential genetic links to cell wall thickening in resistant strains.

Main Methods:

  • Transmission electron microscopy was used to examine the cell wall thickness of 14 clinical S. aureus isolates (7 resistant, 7 sensitive).
  • Polymerase chain reaction (PCR) was employed to detect genes encoding aminoglycoside-modifying enzymes (aac(6')-aph(2''), aph(3')-III, ant(4')-I).
  • A gentamycin-resistant mutant was generated in vitro from a sensitive parent strain for comparative analysis.

Main Results:

  • GM-resistant S. aureus strains exhibited significantly thicker cell walls (32.24 ± 5.99 nm) compared to GM-sensitive strains (19.02 ± 2.72 nm).
  • All tested GM-resistant strains carried the aac(6')-aph(2'') gene; however, a direct gene-to-cell wall thickening link was not definitively established.
  • An in vitro-derived GM-resistant mutant also displayed a thickened cell wall.

Conclusions:

  • A thickened cell wall is a common ultrastructural feature of gentamycin-resistant Staphylococcus aureus clinical isolates.
  • This finding may contribute to understanding the mechanisms of gentamycin resistance in S. aureus.

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