title: Antibiotic Susceptibility of Biofilm Cells and Molecular Characterisation of Staphylococcus hominis Isolates from Blood.
abstract: OBJECTIVE
  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.
authors.affiliation: Servicio de Gastroenterología, Hospital Universitario Dr. José Eleuterio González, Universidad Autónoma de Nuevo León, Monterrey, Nuevo León, México.
authors.forename: Soraya
authors.initials: S
authors.lastname: Mendoza-Olazarán
authors.affiliation: Hospital Civil de Guadalajara, Fray Antonio Alcalde, and Instituto de Patología Infecciosa y Experimental, Centro Universitario de Ciencias de la Salud, Universidad de Guadalajara, Guadalajara, Jalisco, México.
authors.forename: Rayo
authors.initials: R
authors.lastname: Morfín-Otero
authors.affiliation: Departamento de Microbiología e Inmunología, Facultad de Ciencias Biológicas, Universidad Autónoma de Nuevo León, Monterrey, Nuevo León, México.
authors.forename: Licet
authors.initials: L
authors.lastname: Villarreal-Treviño
authors.affiliation: Hospital Civil de Guadalajara, Fray Antonio Alcalde, and Instituto de Patología Infecciosa y Experimental, Centro Universitario de Ciencias de la Salud, Universidad de Guadalajara, Guadalajara, Jalisco, México.
authors.forename: Eduardo
authors.initials: E
authors.lastname: Rodríguez-Noriega
authors.affiliation: Departamento de Patología Clínica, Hospital Universitario Dr. José Eleuterio González, Universidad Autónoma de Nuevo León, Monterrey, Nuevo León, México.
authors.forename: Jorge
authors.initials: J
authors.lastname: Llaca-Díaz
authors.affiliation: Servicio de Infectología, Hospital Universitario Dr. José Eleuterio González, Universidad Autónoma de Nuevo León, Monterrey, Nuevo León, México.
authors.forename: Adrián
authors.initials: A
authors.lastname: Camacho-Ortiz
authors.affiliation: Departamento de Microbiología, Facultad de Medicina, Universidad Autónoma de Nuevo León, Monterrey, Nuevo León, México.
authors.forename: Gloria M
authors.initials: GM
authors.lastname: González
authors.affiliation: Servicio de Gastroenterología, Hospital Universitario Dr. José Eleuterio González, Universidad Autónoma de Nuevo León, Monterrey, Nuevo León, México.
authors.forename: Néstor
authors.initials: N
authors.lastname: Casillas-Vega
authors.affiliation: Servicio de Gastroenterología, Hospital Universitario Dr. José Eleuterio González, Universidad Autónoma de Nuevo León, Monterrey, Nuevo León, México.|Departamento de Patología Clínica, Hospital Universitario Dr. José Eleuterio González, Universidad Autónoma de Nuevo León, Monterrey, Nuevo León, México.
authors.forename: Elvira
authors.initials: E
authors.lastname: Garza-González
mesh_terms: D000581:Amidohydrolases / Q000235:genetics / Q000378:metabolism; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D016470:Bacteremia / Q000188:drug therapy / Q000382:microbiology; D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D018441:Biofilms / Q000187:drug effects* / Q000254:growth & development; D002440:Cefoxitin / Q000494:pharmacology; D002876:Chromosomes, Bacterial / Q000737:chemistry / Q000378:metabolism; D002939:Ciprofloxacin / Q000494:pharmacology; D024881:Drug Resistance, Bacterial / Q000235:genetics*; D015964:Gene Expression Regulation, Bacterial; D006801:Humans; D008712:Methicillin / Q000494:pharmacology; D008826:Microbial Sensitivity Tests; D009876:Operon; D010068:Oxacillin / Q000494:pharmacology; D046915:Penicillin-Binding Proteins / Q000235:genetics / Q000378:metabolism; D010802:Phylogeny; D010933:Plankton / Q000187:drug effects / Q000254:growth & development; D013203:Staphylococcal Infections / Q000188:drug therapy / Q000382:microbiology; D041181:Staphylococcus hominis / Q000145:classification / Q000187:drug effects / Q000235:genetics* / Q000302:isolation & purification; D014640:Vancomycin / Q000494:pharmacology
chemical_list: D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D046915:Penicillin-Binding Proteins; D002939:Ciprofloxacin; D002440:Cefoxitin; D014640:Vancomycin; D000581:Amidohydrolases; D008712:Methicillin; D010068:Oxacillin