title: Laboratory evaluation of the serum dilution test in serious staphylococcal infection.
abstract: Four test media were studied to determine performance characteristics of serum dilution tests used to monitor antimicrobial therapy during serious Staphylococcus aureus infection being treated with highly protein-bound antibiotics. Serum inhibitory titers and serum bactericidal titers obtained with Mueller-Hinton broth supplemented with calcium and magnesium were 3- to 16-fold higher than titers obtained with whole human serum buffered with N-2-hydroxyethylpiperazine-N'-2-ethanesulfonic acid (HEPES). In cation-supplemented Mueller-Hinton containing 5% albumin or in cation-supplemented Mueller-Hinton combined with an equal volume of human serum, titers were 2- to 5-fold higher than in whole human serum buffered with HEPES. Clinical or animal studies are needed to establish whether the higher titers observed with patient serum containing highly protein-bound drugs diluted in low protein-content media would foster inadequate dosage regiments. In the meantime, both infectious disease clinicians and microbiologists should be aware of this potential pitfall.
mesh_terms: D000900:Anti-Bacterial Agents / Q000378:metabolism* / Q000627:therapeutic use; D001682:Biological Availability; D002437:Cefazolin / Q000378:metabolism; D002506:Cephalexin / Q000378:metabolism; D003470:Culture Media; D004009:Dicloxacillin / Q000378:metabolism; D005069:Evaluation Studies as Topic; D006801:Humans; D010068:Oxacillin / Q000378:metabolism; D010403:Penicillin Resistance; D011485:Protein Binding; D012698:Serologic Tests; D013203:Staphylococcal Infections / Q000097:blood* / Q000188:drug therapy; D013211:Staphylococcus aureus / Q000187:drug effects* / Q000235:genetics
chemical_list: D000900:Anti-Bacterial Agents; D003470:Culture Media; D004009:Dicloxacillin; D002437:Cefazolin; D002506:Cephalexin; D010068:Oxacillin