Spectra obtained by MHA.

<p>A) The spectrum obtained for the pure meropenem (arrived with ice) showed the peaks corresponding to the intact drug (384 ±1 Da) and to its sodium salts (406 ±1 Da; 428 ±1 Da); the spectrum obtained for the carbapenemase-nonproducing reference strain (<i>K</i>. <i>pneumoniae</i> ATCC BAA-1706) showed the same peaks as the pure meropenem, while the 2 carbapenemase-producing reference strains (<i>K</i>. <i>pneumoniae</i> ATCC BAA-1705, <i>bla</i>_<i>KPC</i> positive, and <i>K</i>. <i>pneumoniae</i> ATCC BAA-2146, <i>bla</i>_<i>NDM</i> positive) gave the peaks corresponding to the meropenem degradation (358 ±1 Da, the decarboxylated product) and to its sodium salts (380 ±1 Da; 402 ±1 Da; 424 ±1 Da). B) Example of spectra obtained for clinical samples tested with pure meropenem arrived with ice: a carbapenemase-nonproducing strain and two carbapenemase-producing strains, one of which (<i>K</i>. <i>pneumoniae</i> No. 1135 strain) showing the peaks corresponding to both the pure meropenem and the degradation products of the drug.