Treatment failure due to emergence of resistance to imipenem during therapy for Shewanellaalgae bacteraemia
Abstract number: 1134_02_282
Kim D.M., Oh M.-D.
We describe here a case of bacteraemia caused by S. algae, which was initially susceptible to imipenem, but the bacteria later became resistant during the treatment. In addition, we investigated the propensity of S. algae to develop resistance to imipenem by using a serial passage technique.
In vitro test for resistance induction
1. Bacterial strains
Resistant variants selection
(a) single step resistant variants were obtained from clinical Isolate on Mueller-Hinton agar containing increasing amounts of imipenem (1xMIC, 2xMIC, 4xMIC, 8xMIC),
(b) serial passage experiment
S. algae strain and P. aeruginosa ATCC 27853 were grown overnight in MuellerHinton agar and then grown overnight in MuellerHinton agar and then swabbed onto MuellerHinton agar plates containing one-half the MIC of imipenem. The surface growth at 24 h was swabbed to MuellerHinton agar containing twice the prior concentration of imipenem.
Single step resistant variants were selected from Isolate 1 at up to 4 times the MIC, whereas the resistant variant from P. aeruginosa ATCC 27853 could be selected at up to 2 times the MIC. All the resistant variants of S. algae selected either by a single step or by a sequential stepwise passage exhibited at up to 816 mg/ml of MIC, whereas those of P. aeruginosa ATCC 27853 showed up to 16 mg/ml of MIC
We documented that S. algae, which was initially susceptible to imipenem, subsequently became resistant to imipenem during the treatment. We also demonstrated in vitro that the initial isolate of S. algae could easily develop resistance to imipenem when the organism was exposed to imipenem, suggesting that S. algae organisms have a propensity toward resistance to imipenem.
|Session name:||XXIst ISTH Congress|
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