Correlation between resistance mechanisms in Staphylococcus aureus and cell wall and septum thickening
Authors García AB, Viñuela-Prieto JM, López-González L, Candel FJ
Received 19 July 2017
Accepted for publication 28 August 2017
Published 17 October 2017 Volume 2017:10 Pages 353—356
Checked for plagiarism Yes
Review by Single-blind
Peer reviewers approved by Dr Amy Norman
Peer reviewer comments 2
Editor who approved publication: Professor Suresh Antony
Ana Belén García,1 José Manuel Viñuela-Prieto,1 Laura López-González,1 Francisco Javier Candel1,2
1Department of Clinical Microbiology, Hospital Clínico San Carlos, Complutense University, Madrid, Spain; 2Health Research Institute, Hospital Universitario San Carlos, Madrid, Spain
Purpose: The aim of the present study is to examine cell wall and septum thickening of methicillin-sensitive Staphylococcus aureus (MSSA), methicillin-resistant S. aureus (MRSA), and methicillin- and linezolid-resistant S. aureus (MLRSA) isolates by transmission electron microscopy to correlate the association of resistance mechanisms with major changes in the morphology of membrane or septum.
Materials and methods: MSSA, MRSA, and MLRSA strains obtained from clinical samples of an outbreak that occurred in 2010 at the Intensive Care Unit of our Hospital were thawed and sown at 37°C in blood agar overnight. After that, they were washed, pelleted, and treated with a fixer solution. Pellets were dehydrated and finally embedded in resin. Transmission electron microscopy was used to characterize cell wall and septum thickening in all isolates. The comparison between the measurements obtained for each group was performed by a Kruskal–Wallis test and a post hoc Dunn–Bonferroni’s pairwise comparison method.
Results: Differences in cell wall and septum thickness were statistically significant (P<0.001 and P<0.001, respectively) between the three groups. Moreover, significant differences were detected in wall and septum thickness between the MSSA and MRSA strains (P<0.001 and P<0.001, respectively) and between the MSSA and MLRSA strains (P<0.001 and P<0.001, respectively) but not between the MRSA and MLRSA strains (P=0.386 and P=0.117).
Conclusion: In this analysis, we correlate the resistance mediated by alterations in the cell membrane of S. aureus (methicillin-resistant, for example) with a greater thickness of the wall or septum. The resistance added to linezolid did not determine significant changes in the characteristics of the wall or septum with respect to those strains resistant only to methicillin.
Keywords: linezolid-resistant S. aureus, vancomycin intermediate S. aureus, VISA, protein synthesis inhibitor antibiotics, TEM
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