title: Reduced susceptibility to vancomycin and biofilm formation in methicillin-resistant Staphylococcus epidermidis isolated from blood cultures.
abstract: This study aimed to correlate the presence of ica genes, biofilm formation and antimicrobial resistance in 107 strains of Staphylococcus epidermidis isolated from blood cultures. The isolates were analysed to determine their methicillin resistance, staphylococcal cassette chromosome mec (SCCmec) type, ica genes and biofilm formation and the vancomycin minimum inhibitory concentration (MIC) was measured for isolates and subpopulations growing on vancomycin screen agar. The mecA gene was detected in 81.3% of the S. epidermidis isolated and 48.2% carried SCCmec type III. The complete icaADBC operon was observed in 38.3% of the isolates; of these, 58.5% produced a biofilm. Furthermore, 47.7% of the isolates grew on vancomycin screen agar, with an increase in the MIC in 75.9% of the isolates. Determination of the MIC of subpopulations revealed that 64.7% had an MIC ≥ 4 μg mL-1, including 15.7% with an MIC of 8 μg mL-1 and 2% with an MIC of 16 μg mL-1. The presence of the icaADBC operon, biofilm production and reduced susceptibility to vancomycin were associated with methicillin resistance. This study reveals a high level of methicillin resistance, biofilm formation and reduced susceptibility to vancomycin in subpopulations of S. epidermidis. These findings may explain the selection of multidrug-resistant isolates in hospital settings and the consequent failure of antimicrobial treatment.
authors.affiliation: Laboratório de Microbiologia, Departamento de Microbiologia e Imunologia, Instituto de Biociências de Botucatu, Universidade Estadual Paulista, Botucatu, SP, Brasil.
authors.forename: Luiza
authors.initials: L
authors.lastname: Pinheiro
authors.affiliation: Laboratório de Microbiologia, Departamento de Microbiologia e Imunologia, Instituto de Biociências de Botucatu, Universidade Estadual Paulista, Botucatu, SP, Brasil.
authors.forename: Carla Ivo
authors.initials: CI
authors.lastname: Brito
authors.affiliation: Laboratório de Microbiologia, Departamento de Microbiologia e Imunologia, Instituto de Biociências de Botucatu, Universidade Estadual Paulista, Botucatu, SP, Brasil.
authors.forename: Valéria Cataneli
authors.initials: VC
authors.lastname: Pereira
authors.affiliation: Laboratório de Microbiologia, Departamento de Microbiologia e Imunologia, Instituto de Biociências de Botucatu, Universidade Estadual Paulista, Botucatu, SP, Brasil.
authors.forename: Adilson de
authors.initials: Ad
authors.lastname: Oliveira
authors.affiliation: Laboratório de Microbiologia, Departamento de Microbiologia e Imunologia, Instituto de Biociências de Botucatu, Universidade Estadual Paulista, Botucatu, SP, Brasil.
authors.forename: Carlos Henrique
authors.initials: CH
authors.lastname: Camargo
authors.affiliation: Laboratório de Microbiologia, Departamento de Microbiologia e Imunologia, Instituto de Biociências de Botucatu, Universidade Estadual Paulista, Botucatu, SP, Brasil.
authors.forename: Maria de Lourdes Ribeiro de Souza da
authors.initials: Mde L
authors.lastname: Cunha
mesh_terms: D000328:Adult; D000362:Agar; D000368:Aged; D018441:Biofilms / Q000254:growth & development*; D003428:Cross Infection; D003470:Culture Media; D005260:Female; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D016106:Methicillin Resistance / Q000235:genetics*; D008826:Microbial Sensitivity Tests; D008875:Middle Aged; D009876:Operon / Q000235:genetics*; D016133:Polymerase Chain Reaction; D013203:Staphylococcal Infections / Q000097:blood*; D013212:Staphylococcus epidermidis / Q000145:classification / Q000302:isolation & purification / Q000502:physiology; D062606:Tertiary Care Centers; D014640:Vancomycin / Q000008:administration & dosage; D020713:Vancomycin Resistance / Q000235:genetics*
chemical_list: D003470:Culture Media; D014640:Vancomycin; D000362:Agar