title: Is gentamicin necessary in the antimicrobial treatment for group B streptococcal infections in the elderly? An in vitro study with human blood products.
abstract: BACKGROUND
  According to expert opinions, gentamicin should be administered as an adjunct to penicillin against severe group B streptococcal (GBS) infections. Whether the adjunct is important is of particular interest for elderly patients. Not only is the risk of aminoglycoside nephrotoxicity higher in elderly persons, but their immune defence to bacterial infections may also be impaired.
  
  
  METHODS
  Time-kill assays with human blood products, such as serum, neutrophilic granulocytes (opsonophagocytic assays) and whole blood from healthy, elderly volunteers were performed to evaluate the effect of gentamicin in combination with penicillin.
  
  
  RESULTS
  In time-kill assays with human serum and in opsonophagocytic assays, we saw a trend for faster killing with the penicillin-gentamicin combination therapy. This effect was seen 4 and 6 h after antibiotic exposure but not at time points evaluated at ≥8 h. In whole blood killing assays, no difference in killing rates was observed with adjunctive gentamicin therapy.
  
  
  CONCLUSIONS
  The criteria for synergism were not fulfilled when the effect of penicillin-gentamicin combinations was compared with that of penicillin monotherapy. Rapid killing of GBS within the first few hours was observed in time-kill assays with human blood products. Considering that elderly people are prone to gentamicin nephrotoxicity and that in severe GBS infection a high penicillin dose is administered every 4-6 h, the prolonged use of adjunctive aminoglycosides in these infections requires caution.
authors: a Institute for Infectious Diseases, University of Bern , Bern , Switzerland.|b Graduate School for Cellular and Biomedical Sciences, University of Bern , Bern , Switzerland.
authors: Corinne
authors: C
authors: Ruppen
authors: c Division and Laboratory of Clinical Pharmacology, Service of Biomedicine, Department of Laboratories , Lausanne University Hospital (Centre Hospitalier Universitaire Vaudois, CHUV) , Lausanne , Switzerland.
authors: Laurent
authors: L
authors: Decosterd
authors: a Institute for Infectious Diseases, University of Bern , Bern , Switzerland.|d Department of Infectious Diseases , Bern University Hospital and University of Bern , Bern , Switzerland.
authors: Parham
authors: P
authors: Sendi
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000900:Anti-Bacterial Agents / Q000494:pharmacology* / Q000627:therapeutic use; D004347:Drug Interactions; D005839:Gentamicins / Q000494:pharmacology* / Q000627:therapeutic use; D006801:Humans; D050296:Microbial Viability / Q000187:drug effects*; D010406:Penicillins / Q000494:pharmacology* / Q000627:therapeutic use; D013290:Streptococcal Infections / Q000188:drug therapy / Q000382:microbiology*; D013292:Streptococcus agalactiae / Q000187:drug effects* / Q000302:isolation & purification
chemical_list: D000900:Anti-Bacterial Agents; D005839:Gentamicins; D010406:Penicillins
keywords: Group B Streptococcus; Streptococcus agalactiae; aminoglycosides; gentamicin; synergism