Vancomycin tolerant, methicillin-resistant Staphylococcus aureus reveals the effects of vancomycin on cell wall thickening

• Published in: PloS one Vol. 10; no. 3; p. e0118791
• Main Authors: Cázares-Domínguez, Vicenta, Cruz-Córdova, Ariadnna, Ochoa, Sara A, Escalona, Gerardo, Arellano-Galindo, José, Rodríguez-Leviz, Alejandra, Hernández-Castro, Rigoberto, López-Villegas, Edgar O, Xicohtencatl-Cortes, Juan
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 20.03.2015; Public Library of Science (PLoS)
• Subjects: Adaptation, Physiological - drug effects; Antibiotics; Antimicrobial agents; Cell Wall - drug effects; Cell walls; Child; Clinical isolates; Cross Infection - drug therapy; Cross Infection - microbiology; Drug resistance; Drug Resistance, Microbial - drug effects; Electron microscopy; Electrophoresis, Gel, Pulsed-Field; Genes; Genes, Bacterial; Genetic polymorphisms; Genotype; Gram-positive bacteria; Health aspects; Health care; Humans; Incidence; Infection; Infections; Laboratories; Mec gene; Medical records; Methicillin; Methicillin-Resistant Staphylococcus aureus - cytology; Methicillin-Resistant Staphylococcus aureus - drug effects; Methicillin-Resistant Staphylococcus aureus - genetics; Methicillin-Resistant Staphylococcus aureus - isolation & purification; Methods; Microbial drug resistance; Microbial Sensitivity Tests; Opportunist infection; Patients; Pediatrics; Penicillin; Phenotype; Phenotypes; Phylogeny; Polymorphism, Genetic; Staphylococcus aureus; Staphylococcus aureus infections; Staphylococcus infections; Thickening; Transmission electron microscopy; Vancomycin; Vancomycin - pharmacology; Wall thickness; United States > US
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0118791

Methicillin-resistant Staphylococcus aureus (MRSA) is an important opportunistic pathogen that causes both healthcare- and community-acquired infections. An increase in the incidence of these infections may lead to a substantial change in the rate of vancomycin usage. Incidence of reduced susceptibility to vancomycin has been increasing worldwide for the last few years, conferring different levels of resistance to vancomycin as well as producing changes in the cell wall structure. The aim of the present study was to determine the effect of vancomycin on cell wall thickening in clinical isolates of vancomycin-tolerant (VT) MRSA obtained from pediatric patients. From a collection of 100 MRSA clinical isolates from pediatric patients, 12% (12/100) were characterized as VT-MRSA, and from them, 41.66% (5/12) exhibited the heterogeneous vancomycin-intermediate S. aureus (hVISA) phenotype. Multiplex-PCR assays revealed 66.66% (8/12), 25% (3/12), and 8.33% (1/12) of the VT-MRSA isolates were associated with agr group II, I, and III polymorphisms, respectively; the II-mec gene was amplified from 83.3% (10/12) of the isolates, and the mecIVa gene was amplified from 16.66% (2/12) of the isolates. Pulsed field electrophoresis (PFGE) fingerprint analysis showed 62% similarity among the VT-MRSA isolates. Thin transverse sections analyzed by transmission electron microscopy (TEM) revealed an average increase of 24 nm (105.55%) in the cell wall thickness of VT-MRSA compared with untreated VT-MRSA isolates. In summary, these data revealed that the thickened cell walls of VT-MRSA clinical isolates with agr type II and SCCmec group II polymorphisms are associated with an adaptive resistance to vancomycin.