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Minimal inhibitory concentrations (MICs) of ticarcillin/clavulanic acid (TLc), ceftolozane/tazobactam (C/T), and aztreonam (AT) were determined for 6 SPM-1-producing Pseudomonas aeruginosa (PSA) using Etest® strips and the synergistic effect of such antimicrobials against was evaluated by gradient diffusion strip crossing (GDSC) test. The fraction inhibitory concentration indexes (FICI) were calculated and showed a synergistic (n = 3) and additive (n = 2) effects of TLc + AT against SPM-1 producers, while TLc + C/T combination caused no effect. Average MIC reduction of TLc and AT by GDSC was 3-fold and 2-fold dilutions, respectively. Thus, TLc + AT might be a candidate as a combination therapy to treat SPM-1-producing PSA infections., Competing Interests: Declaration of Competing Interest G.T.C. has recently received research funding and/or consultation fees from MSD, Eurofarma, Pfizer and Sanofi. A.C.G. has recently received research funding and/or consultation fees from Bayer, Cristália, InfectoPharm, Eurofarma, Pfizer, MSD, and Zambon. D.P.N. consultant, speaker bureau member or have received research funding from Allergan, Bayer, Cepheid, Merck, Melinta, Pfizer, Wockhardt, Shionogi, and Tetraphase. C.R.V.K. consultant, speaker bureau member or have received research funding from Pfizer, Eurofarma, Johnson & Johnson, Biotest AG and New Objective outside the submitted work; Other authors have nothing to declare. This study was not financially supported by any Diagnostic/Pharmaceutical company. This work was partially presented as a poster (P2800) during the 29th European Congress of Clinical Microbiology and Infectious Diseases (ECCMID) in Amsterdam, 2019., (Copyright © 2021 Elsevier Inc. All rights reserved.)

We evaluated the performance of five phenotypic tests [Modified Hodge Test (MHT); combined-disk test (CDT) using phenylboronic acid, EDTA, and cloxacillin; CarbaNP and CarbAcinetoNP; Blue-Carba, Carbapenembac™ and Carbapenembac Metallo™] for carbapenemase detection in Gram-negative bacilli (GNB). A total of 73 carbapenemase producers and 27 non-carbapenemase producers were tested. All GNB were subcultured onto Müeller-Hinton agar (MHA), MacConkey agar (MAC), and sheep blood agar (SBA). High sensitivity (100%) and specificity (100%) was observed for MHA using CarbaNP, Blue-Carba, and Carbapenembac™. The sensitivity and specificity of CarbaNP (98.6%/100%), Blue-Carba (97.1%/91.0%), and Carbapenembac™ (100%/96.5%) were slightly lower for SBA. In contrast, unacceptable sensitivity rates of CarbaNP (71.1%) and Blue-Carba (66.6%), but not Carbapenembac™ (97.3%), were observed for MAC. The colorimetric methods showed high sensitivity and specificity to detect carbapenemase production from isolates grown on MHA or SBA. However, colonies obtained from MAC must not be tested for carbapenemase detection by colorimetric methods., (Copyright © 2019 Elsevier Inc. All rights reserved.)

The intrinsic polymyxin resistance displayed by Serratia marcescens makes the acquisition of carbapenemase encoding genes a worrisome event. This study report a SME-4-producing S. marcescens isolate causing septic shock in Brazil. The insertion of novel resistance determinants and their consequent spread in our territory is noteworthy., (Copyright © 2017 Elsevier Inc. All rights reserved.)