The object of the study is to investigate whether all included patients receive treatment that is effective against all bacteria that are defined as sensitive to meropenem with the current treatment regimen. Will the investigators findings motivate routine monitoring of plasma concentrations in children receiving meropenem? Up to 50 patients will be included in the study, and all participants are children.

Inclusion Criteria:

• Children aged from 3 months to 18 years that receive treatment with meropenem. Inclusion is independent of how long the patient has been receiving treatment. Children receiving other treatment (except hemodialysis)/other medications can be included.

Exclusion Criteria:

• Children less than three months of age. Patients receiving hemodialysis. Lack of consent.

Patients at the Pediatric medical ward.