title: MIC versus MBEC to determine the antibiotic sensitivity of Staphylococcus aureus in peritoneal dialysis peritonitis.
abstract: BACKGROUND
  Peritoneal dialysis (PD)-related peritonitis is a common and morbid complication of PD. Bacteria are able to create a biofilm on the PD catheter, which can be a source of recurrent infection. Biofilms undergo a phenotypic change resulting in increased antibiotic resistance. ♢
  
  
  METHODS
  21 clinical isolates of different patients with PD peritonitis secondary to Staphylococcus aureus were collected. They were analyzed for their antibiotic susceptibility in the planktonic form using the standard minimum inhibitory concentration (MIC) and in a biofilm using minimum biofilm eradication concentration (MBEC). Chi-square was used to compare the sensitivity results. ♢
  
  
  RESULTS
  The isolates were susceptible to all the antibiotics tested using MIC. Every antibiotic except gentamicin lost its efficacy when the bacteria were grown in a biofilm (p > 0.05). The change in susceptibility was statistically significant to a level of p < 0.001 for all antibiotics tested. ♢
  
  
  CONCLUSIONS
  In PD peritonitis that is long standing, recurrent, or not responsive to therapy, MBEC testing should be considered as a biofilm may be present. Gentamicin should be strongly considered over other agents for empiric gram-negative coverage as it may be providing synergy in the setting of Staphylococcus aureus. Also, the newer anti-staphylococcal drugs should be tested for their performance in a biofilm using the MBEC method.
authors.affiliation: Division of Nephrology, Department of Medicine, University of Calgary, Calgary, Alberta, Canada. lgirard@ucalgary.ca
authors.forename: Louis P
authors.initials: LP
authors.lastname: Girard
authors.forename: Howard
authors.initials: H
authors.lastname: Ceri
authors.forename: Allan P
authors.initials: AP
authors.lastname: Gibb
authors.forename: Merle
authors.initials: M
authors.lastname: Olson
authors.forename: Farshad
authors.initials: F
authors.lastname: Sepandj
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D018441:Biofilms / Q000187:drug effects*; D002437:Cefazolin / Q000494:pharmacology; D002939:Ciprofloxacin / Q000494:pharmacology; D002981:Clindamycin / Q000494:pharmacology; D004338:Drug Combinations; D024881:Drug Resistance, Bacterial / Q000187:drug effects*; D005839:Gentamicins / Q000494:pharmacology; D006801:Humans; D008826:Microbial Sensitivity Tests; D010068:Oxacillin / Q000494:pharmacology; D010530:Peritoneal Dialysis / Q000009:adverse effects*; D010538:Peritonitis / Q000382:microbiology*; D016459:Prosthesis-Related Infections / Q000382:microbiology; D012293:Rifampin / Q000494:pharmacology; D013203:Staphylococcal Infections / Q000382:microbiology*; D013211:Staphylococcus aureus / Q000187:drug effects*; D014640:Vancomycin / Q000494:pharmacology
chemical_list: D000900:Anti-Bacterial Agents; D004338:Drug Combinations; D005839:Gentamicins; D002981:Clindamycin; D002939:Ciprofloxacin; D014640:Vancomycin; D002437:Cefazolin; D010068:Oxacillin; D012293:Rifampin