@article{3084520,
    title = "Interlaboratory comparison of agar dilution and etest methods for
determining the MICs of antibiotics used in management of Neisseria
meningitidis infections",
    author = "Vazquez, JA and Arreaza, L and Block, C and Ehrhard, I and Gray, SJ and and Heuberger, S and Hoffmann, S and Kriz, P and Nicolas, P and Olcen, P and and Skoczynska, A and Spanjaard, L and Stefanelli, P and Taha, MK and and Tzanakaki, G",
    journal = "Antimicrobial Agents and Chemotherapy",
    year = "2003",
    volume = "47",
    number = "11",
    pages = "3430-3434",
    publisher = "AMER SOC MICROBIOLOGY",
    issn = "0066-4804, 1098-6596",
    doi = "10.1128/AAC.47.11.3430-3434.2003",
    abstract = "Previous studies have shown that there is considerable variation in the
methods and media used to determine the susceptibility of Neisseria
meningitidis to antimicrobial agents in different countries. In this
study, national and regional reference laboratories used a standardized
methodology to determine the MICs of antibiotics used in the management
of meningococcal infection. Fourteen laboratories participated in the
study, determining the susceptibility to penicillin G, rifampin,
cefotaxime, ceftriaxone, ciprofloxacin, and ofloxacin of a collection of
17 meningococci, of which 11 strains were previously defined as having
intermediate resistance to penicillin (Pen(I)) by sequencing and
restriction fragment length polymorphism analysis of the penA gene. The
MIC was determined by agar dilution and Etest with Mueller-Hinton agar
(MH), MH supplemented with sheep blood (MH+B), and MH supplemented with
heated (chocolated) blood. Several laboratories encountered problems
obtaining confluent growth with unsupplemented MH. MH+B was considered
to give the most congruent and reproducible results among the study
laboratories. The modal MIC for MH+B for each antibiotic and method was
calculated to define the MIC consensus, allowing assessment of each
individual laboratory’s data in relation to the others. The agreement in
each antibiotic/method/medium combination was defined as the percentage
of laboratories with a result within one dilution of the modal result.
For the whole study, an agreement of 90.6% was observed between agar
dilution and Etest methods. The agreement in each
laboratory/antibiotic/method combination ranged from 98.2% to 69.7%,
with six laboratories demonstrating agreement higher than 90% and 11
more than 80%. The ability of the laboratories to detect the Pen(I)
isolates ranged from 18.2% to 100%. The apparent difficulty in
interpreting susceptibility to rifampin, particularly with the Etest
method, is very interesting."
}