Antibiotic Susceptibility of Biofilm Cells and Molecular Characterisation of Staphylococcus hominis Isolates from Blood

Soraya Mendoza-Olazarán, Rayo Morfín-Otero, Licet Villarreal-Treviño, Eduardo Rodríguez-Noriega, Jorge Llaca-Díaz, Adrián Camacho-Ortiz, Gloria M González, Néstor Casillas-Vega, Elvira Garza-González

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24 Citations (Scopus)


OBJECTIVES: We aimed to characterise the staphylococcal cassette chromosome mec (SCCmec) type, genetic relatedness, biofilm formation and composition, icaADBC genes detection, icaD expression, and antibiotic susceptibility of planktonic and biofilm cells of Staphylococcus hominis isolates from blood.

METHODS: The study included 67 S. hominis blood isolates. Methicillin resistance was evaluated with the cefoxitin disk test. mecA gene and SCCmec were detected by multiplex PCR. Genetic relatedness was determined by pulsed-field gel electrophoresis. Biofilm formation and composition were evaluated by staining with crystal violet and by detachment assay, respectively; and the biofilm index (BI) was determined. Detection and expression of icaADBC genes were performed by multiplex PCR and real-time PCR, respectively. Antibiotic susceptibilities of planktonic cells (minimum inhibitory concentration, MIC) and biofilm cells (minimum biofilm eradication concentration, MBEC) were determined by the broth dilution method.

RESULTS: Eighty-five percent (57/67) of isolates were methicillin resistant and mecA positive. Of the mecA-positive isolates, 66.7% (38/57) carried a new putative SCCmec type. Four clones were detected, with two to five isolates each. Among all isolates, 91% (61/67) were categorised as strong biofilm producers. Biofilm biomass composition was heterogeneous (polysaccharides, proteins and DNA). All isolates presented the icaD gene, and 6.66% (1/15) isolates expressed icaD. This isolate presented the five genes of ica operon. Higher BI and MBEC values than the MIC values were observed for amikacin, vancomycin, linezolid, oxacillin, ciprofloxacin, and chloramphenicol.

CONCLUSIONS: S. hominis isolates were highly resistant to methicillin and other antimicrobials. Most of the detected SCCmec types were different than those described for S. aureus. Isolates indicated low clonality. The results indicate that S. hominis is a strong biofilm producer with an extracellular matrix with similar composition of proteins, DNA and N-acetylglucosamine; and presents high frequency and low expression of icaD gene. Biofilm production is associated with increased antibiotic resistance.

Original languageEnglish
Article numbere0144684
Pages (from-to)e0144684
JournalPLoS One
Issue number12
Publication statusPublished - 1 Dec 2015
Externally publishedYes

Bibliographical note

Publisher Copyright:
© 2015 Mendoza-Olazaran et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Copyright 2018 Elsevier B.V., All rights reserved.

All Science Journal Classification (ASJC) codes

  • General Biochemistry,Genetics and Molecular Biology
  • General Agricultural and Biological Sciences
  • General


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