Dm. Livermore et al., In vitro activities of ertapenem (MK-0826) against recent clinical bacteria collected in Europe and Australia, ANTIM AG CH, 45(6), 2001, pp. 1860-1867
Ertapenem (MK-0826, L-749,345) is a l-beta -methyl carbapenem with a long s
erum half-life. Its in vitro activity was determined by broth microdilution
against 3,478 bacteria from 12 centers in Europe and Australia, with imipe
nem, cefepime, ceftriaxone, and piperacillin-tazobactam used as comparators
. Ertapenem was the most active agent tested against members of the family
Enterobacteriaceae, with MICs at which 90% of isolates are inhibited (MIC(9
0)s) of less than or equal to1 mug/ml for all species. Ertapenem also was m
ore active than imipenem against fastidious gram-negative bacteria and Mora
xella spp.; on the other hand, ertapenem was slightly less active than imip
enem against streptococci, methicillin-susceptible staphylococci, and anaer
obes, but its MIC(90)s for these groups remained less than or equal to0.5 m
ug/ml. Acinetobacter spp. and Pseudomonas aeruginosa. were also much less s
usceptible to ertapenem than imipenem, and most Enterococcus faecalis strai
ns were resistant. Ertapenem resistance, based an a provisional NCCLS MIC b
reakpoint of greater than or equal to 16 mug/ml, was seen in only 3 of 1,61
1 strains of the family Enterobacteriaceae tested, all of them Enterobacter
aerogenes. Resistance was also seen in 2 of 135 anaerobes, comprising I Ba
cteroides fragilis strain and 1 Clostridium difficile strain. Ertapenem bre
akpoints for streptococci have not been established, but an unofficial susc
eptibility breakpoint of less than or equal to2 mug/ml was adopted for clin
ical trials to generate corresponding clinical response data for isolates f
or which MICs were as high as 2 mug/ml, Of 234 Streptococcus pneumoniae str
ains tested, 2 required ertapenem MICs of 2 mug/ml and one required an MIC
of 4 mug/ml, among 67 non-Streptococcus pyogenes, non-Streptococcus pneumon
iae streptococci, single isolates required ertapenem MICs of 2 and 16 mug/m
l. These streptococci also had diminished susceptibilities to other p-lacta
ms, including imipenem as well as ertapenem. The Etest and disk diffusion g
ave susceptibility test results in good agreement with those of the broth m
icrodilution method for ertapenem.