We explore the intramolecular distortions present in divalent metal ion-carboxylate ion pairs using vibrational spectroscopy of the cryogenically cooled, mass-selected species isolated in the gas phase. The spectral signatures of the C-O stretching modes are identified using the perdeutero isotopologues of the acetate and propionate anions to avoid congestion arising from the CH fundamentals. Both Ca and Mg are observed to bind in a symmetrical, so-called "bidentate" arrangement to the -CO¯ group. The very strong deformations of the head groups displayed by the binary complexes dramatically relax when either neutral water molecules or counterions are attached to the MgRCO¯ cation. These results emphasize the critical role that local coordination plays when using the RCO¯ bands to deduce the metal ion complexation motif in condensed media.

Dissemination of carbapenem-resistant Acinetobacter baumannii is currently one of the priority themes discussed around the world, including in Brazil, where this pathogen is considered endemic. A total of 107 carbapenem-resistant A. baumannii (CRAB) isolates were collected from patients with bacteraemia attended at a teaching hospital in Brazil from 2008 to 2014. From these samples, 104 (97.2%) carried blaOXA−23−like, all of them associated with ISAba1 The blaOXA−231 (1.9%) and blaOXA−72 (0.9%) genes were also detected in low frequencies. All isolates were susceptible to minocycline, and 38.3% of isolates presented intermediate susceptibility to tigecycline (MIC = 4 μg/ml). Molecular typing assessed by multi-locus sequence typing demonstrated that the strains were mainly associated with clonal complexes CC79 (47.4%), followed by CC1 (16.9%), and CC317 (18.6%), belonging to different pulsotypes and in different prevalences over the years. Changes in the clones' prevalence reinforce the need of identifying and controlling CRAB in hospital settings to preserve the already scarce therapeutic options available.

Acinetobacter baumannii is a leading cause of complicated infections in the hospital environment, particularly among severely ill patients [1]. The crude mortality attributed to Acinetobacter species causing bloodstream infections is higher than 50 % [2]. Carbapenems have been one of the main antimicrobial classes used against A. baumannii infections [3], but the emergence and dissemination of carbapenemases have diminished the utility of this class of drugs from an already limited list of existing treatment options [4]. In Brazil, it is known that carbapenem-resistant A. baumannii is considered endemic [5], and the main lineages circulating in that country are those belonging to the clonal complexes (CCs) CC1, CC15 and CC79 [6,7]. Among the alternatives for the treatment of infections due to carbapenem-resistant A. baumannii, polymyxins and other non-blactam agents, such as tetracyclines, may be valuable options [3]. Given the increasing rates of multidrug-(MDR) and extensively drug-resistant (XDR) A. baumannii [8], determination of the antimicrobial susceptibility of alternative agents is needed to assess the availability of potential therapeutic options. Thus, the aim of this study was to assess the in vitro activity of antimicrobial agents against carbapenemresistant A. baumannii isolates recovered from clinical specimens of patients from several hospitals in the state of São Paulo, Brazil.A total of 71 A. baumannii isolates recovered from clinical specimens of non-duplicate patients attending 64 different health institutions located in 23 different cities across the state of São Paulo, Brazil, referred to the Instituto Adolfo Lutz from 2008 to 2013 were evaluated. The Instituto Adolfo Lutz, a public health laboratory of São Paulo State, Brazil, receives MDR pathogens, as a reference laboratory, from hospitals across the state of São Paulo on an ongoing and voluntary basis for identification and antimicrobial susceptibility testing. Isolates were mostly recovered from blood or vascular catheter (47.9 %), cerebrospinal fluid (21.9 %), tracheal secretion (13.7 %) and urine (12.3 %); remaining sources were bronchoalveolar lavage, peritoneal fluid and unidentified source (1.4 %, each). Species identification was confirmed by sequencing analysis of the 16S-23S rRNA gene spacer region (internal transcribed spacer) [9]. Antimicrobial susceptibility was determined by disc diffusion methodology [10] for amikacin, gentamicin, tobramycin, ciprofloxacin, levofloxacin, piperacillin-tazobactam, ticarcillin-clavulanate, cefotaxime, cefepime, ceftazidime and trimethoprim-sulfamethoxazole. The MIC values were determined for imipenem, meropenem, ampicillin-sulbactam and minocycline (Sigma-Aldrich) using the broth microdilution technique [11]. Polymyxin B and colistin susceptibilities were determined by agar dilution [11]; tigecycline susceptibility was assessed by Etest (bioM erieux) in freshly prepared Mueller-Hinton agar (Oxoid). MIC values that inhibited 50 % (MIC 50 ) and 90 % (MIC 90 ) of the population were calculated, ...