Revision of standards for adjusting the cation content of Mueller-Hinton broth for testing susceptibility of Pseudomonas aeruginosa to aminoglycosides.
A multilaboratory study was undertaken to reassess the amount of calcium and magnesium that should be added to Mueller-Hinton broth when testing Pseudomonas aeruginosa against amikacin, gentamicin, isepamicin, netilmicin, and tobramycin. To achieve parity with agar dilution tests, cation-adjusted broth should contain 20 to 25 mg of calcium and 10 to 12.5 mg of magnesium per liter rather than the 50- and 25-mg/liter supplements recommended previously. For quality control of tests with contemporary media, MIC control limits should be adjusted by lowering the current MIC limits by at least 1 doubling-dilution interval.
Barry
A L
AL
Clinical Microbiology Institute, Tualatin, Oregon 97062.
Reller
L B
LB
Miller
G H
GH
Washington
J A
JA
Schoenknect
F D
FD
Peterson
L R
LR
Hare
R S
RS
Knapp
C
C
D000617:Aminoglycosides; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D002412:Cations; D003470:Culture Media / Q000592:standards*; D006801:Humans; D008274:Magnesium; D008826:Microbial Sensitivity Tests / Q000379:methods / Q000592:standards*; D011550:Pseudomonas aeruginosa / Q000187:drug effects* / Q000302:isolation & purification
D000617:Aminoglycosides; D000900:Anti-Bacterial Agents; D002412:Cations; D003470:Culture Media; D008274:Magnesium