Different Conformations Revealed by NMR Underlie Resistance to Ceftazidime/Avibactam and Susceptibility to Meropenem and Imipenem among D179Y Variants of KPC ß-Lactamase.

ß-Lactamase-mediated resistance to ceftazidime-avibactam (CZA) is a serious limitation in the treatment of Gram-negative bacteria harboring Klebsiella pneumoniae carbapenemase (KPC). Herein, the basis of susceptibility to carbapenems and resistance to ceftazidime (CAZ) and CZA of the D179Y variant of KPC-2 and -3 was explored. First, we determined that resistance to CZA in a laboratory strain of Escherichia coli DH10B was not due to increased expression levels of the variant enzymes, as demonstrated by reverse transcription PCR (RT-PCR). Using timed mass spectrometry, the D179Y variant formed prolonged acyl-enzyme complexes with imipenem (IMI) and meropenem (MEM) in KPC-2 and KPC-3, which could be detected up to 24 h, suggesting that IMI and MEM act as covalent ß-lactamase inhibitors more than as substrates for D179Y KPC-2 and -3. This prolonged acyl-enzyme complex of IMI and MEM by D179Y variants was not observed with wild-type (WT) KPCs. CAZ was studied and the D179Y variants also formed acyl-enzyme complexes (1 to 2 h). Thermal denaturation and differential scanning fluorimetry showed that the tyrosine substitution at position 179 destabilized the KPC ß-lactamases (KPC-2/3 melting temperature [Tm] of 54 to 55°C versus D179Y Tm of 47.5 to 51°C), and the D179Y protein was 3% disordered compared to KPC-2 at 318 K. Heteronuclear 1H/15N-heteronuclear single quantum coherence (HSQC) nuclear magnetic resonance (NMR) spectroscopy also revealed that the D179Y variant, compared to KPC-2, is partially disordered. Based upon these observations, we discuss the impact of disordering of the Ω loop as a consequence of the D179Y substitution. These conformational changes and disorder in the overall structure as a result of D179Y contribute to this unanticipated phenotype.

Pulmonary haemorrhage in neonates: Systematic review of management.

AIM: Pulmonary haemorrhage (PH) is an acute catastrophic event with low incidence yet high mortality among neonates. We aimed to systematically review the management of PH. METHODS: A search was carried out of the PubMed, EMBASE and Cochrane databases according to the PRISMA guidelines. Data were extracted on study design and size, patient demographics, primary and adjunctive treatment methods, and treatment outcomes. RESULTS: Sixteen studies with 385 newborn infants were included and were significantly heterogeneous regarding treatment methods. Primary treatments included surfactant, high-frequency oscillatory ventilation (HFOV), epinephrine, coagulopathy management, intermittent positive pressure ventilation, cocaine and tolazoline. Adjunctive treatment methods included blood products, HFOV, increased positive end-expiratory pressure, vitamin K, surfactant, adrenaline, vasopressors and inotropes. All five studies using surfactant as primary treatment were effective in improving oxygenation index measures and preventing recurrence of PH, and three studies found no association between surfactant and death or long-term disability. Ventilatory support, epinephrine, management of coagulopathy and tolazoline were all found to be effective primary treatments for PH. CONCLUSION: There are several effective methods of managing PH in neonates. Further understanding of the aetiology of PH and ongoing research will allow future prevention and improvements in management of PH.

Early childhood educators' psychological distress and wellbeing during the COVID-19 pandemic.

There is growing awareness of the impacts of COVID-19 on children, families, and more recently, early childhood educators. This study aimed to add to this research and explore Australian early childhood educators' psychological distress and wellbeing in relation to COVID-19. Accordingly, 205 educators (117 early childhood educators, 86 leaders and 2 others) completed the Impact of Event Scale-Revised, measuring levels of post-traumatic distress, and an open-ended question on wellbeing, both in relation to COVID-19. Educators' responses to the open-ended question were matched to those who scored high, medium, and low on the Impact of Events Scale-Revised. Results demonstrated 66.8% of educators scored in the low range for post-traumatic distress, 11.7% scored in the moderate range, and 21.5% scored in the high range for post-traumatic distress on the Impact of Events Scale-Revised. Participants scoring in the low range on the Impact of Events Scale-Revised provided fewer comments regarding the emotional impacts of COVID-19. There were no differences between the groups in terms of fear of COVID-19 infection, challenges related to increased workload during the pandemic, and frustration with the Australian government response to COVID-19. Educators and early childhood leaders reported comparable wellbeing challenges during the pandemic. This research has implications for the types of support provided to educators during future pandemics.

Insights into the l,d-Transpeptidases and d,d-Carboxypeptidase of Mycobacterium abscessus: Ceftaroline, Imipenem, and Novel Diazabicyclooctane Inhibitors.

Mycobacterium abscessus is a highly drug-resistant nontuberculous mycobacterium (NTM). Efforts to discover new treatments for M. abscessus infections are accelerating, with a focus on cell wall synthesis proteins (M. abscessus l,d-transpeptidases 1 to 5 [LdtMab1 to LdtMab5] and d,d-carboxypeptidase) that are targeted by ß-lactam antibiotics. A challenge to this approach is the presence of chromosomally encoded ß-lactamase (BlaMab). Using a mechanism-based approach, we found that a novel ceftaroline-imipenem combination effectively lowered the MICs of M. abscessus isolates (MIC50 ≤ 0.25 µg/ml; MIC90 ≤ 0.5 µg/ml). Combining ceftaroline and imipenem with a ß-lactamase inhibitor, i.e., relebactam or avibactam, demonstrated only a modest effect on susceptibility compared to each of the ß-lactams alone. In steady-state kinetic assays, BlaMab exhibited a lower Ki app (0.30 ± 0.03 µM for avibactam and 136 ± 14 µM for relebactam) and a higher acylation rate for avibactam (k2/K = 3.4 × 105 ± 0.4 × 105 M-1 s-1 for avibactam and 6 × 102 ± 0.6 × 102 M-1 s-1 for relebactam). The kcat/Km was nearly 10-fold lower for ceftaroline fosamil (0.007 ± 0.001 µM-1 s-1) than for imipenem (0.056 ± 0.006 µM-1 s-1). Timed mass spectrometry captured complexes of avibactam and BlaMab, LdtMab1, LdtMab2, LdtMab4, and d,d-carboxypeptidase, whereas relebactam bound only BlaMab, LdtMab1, and LdtMab2 Interestingly, LdtMab1, LdtMab2, LdtMab4, LdtMab5, and d,d-carboxypeptidase bound only to imipenem when incubated with imipenem and ceftaroline fosamil. We next determined the binding constants of imipenem and ceftaroline fosamil for LdtMab1, LdtMab2, LdtMab4, and LdtMab5 and showed that imipenem bound >100-fold more avidly than ceftaroline fosamil to LdtMab1 and LdtMab2 (e.g., Ki app or Km of LdtMab1 = 0.01 ± 0.01 µM for imipenem versus 0.73 ± 0.08 µM for ceftaroline fosamil). Molecular modeling indicates that LdtMab2 readily accommodates imipenem, but the active site must widen to ≥8 Å for ceftaroline to enter. Our analysis demonstrates that ceftaroline and imipenem binding to multiple targets (l,d-transpeptidases and d,d-carboxypeptidase) and provides a mechanistic rationale for the effectiveness of this dual ß-lactam combination in M. abscessus infections.

A Standard Numbering Scheme for Class C ß-Lactamases.

Unlike for classes A and B, a standardized amino acid numbering scheme has not been proposed for the class C (AmpC) ß-lactamases, which complicates communication in the field. Here, we propose a scheme developed through a collaborative approach that considers both sequence and structure, preserves traditional numbering of catalytically important residues (Ser64, Lys67, Tyr150, and Lys315), is adaptable to new variants or enzymes yet to be discovered and includes a variation for genetic and epidemiological applications.

Structural Insights into the Inhibition of the Extended-Spectrum ß-Lactamase PER-2 by Avibactam.

The diazabicyclooctane (DBO) avibactam (AVI) reversibly inactivates most serine-ß-lactamases. Previous investigations showed that inhibition constants of AVI toward class A PER-2 are reminiscent of values observed for class C and D ß-lactamases (i.e., k2/K of ≈103 M-1 s-1) but lower than other class A ß-lactamases (i.e., k2/K = 104 to 105 M-1 s-1). Herein, biochemical and structural studies were conducted with PER-2 and AVI to explore these differences. Furthermore, biochemical studies on Arg220 and Thr237 variants with AVI were conducted to gain deeper insight into the mechanism of PER-2 inactivation. The main biochemical and structural observations revealed the following: (i) both amino-acid substitutions in Arg220 and the rich hydrophobic content in the active site hinder the binding of catalytic waters and acylation, impairing AVI inhibition; (ii) movement of Ser130 upon binding of AVI favors the formation of a hydrogen bond with the sulfate group of AVI; and (iii) the Thr237Ala substitution alters the AVI inhibition constants. The acylation constant (k2/K) of PER-2 by AVI is primarily influenced by stabilizing hydrogen bonds involving AVI and important residues such as Thr237 and Arg220. (Variants in Arg220 demonstrate a dramatic reduction in k2/K) We also observed that displacement of Ser130 side chain impairs AVI acylation, an observation not made in other extended-spectrum ß-lactamases (ESBLs). Comparatively, relebactam combined with a ß-lactam is more potent against Escherichia coli producing PER-2 variants than ß-lactam-AVI combinations. Our findings provide a rationale for evaluating the utility of the currently available DBO inhibitors against unique ESBLs like PER-2 and anticipate the effectiveness of these inhibitors toward variants that may eventually be selected upon AVI usage.

Resurrecting Old ß-Lactams: Potent Inhibitory Activity of Temocillin against Multidrug-Resistant Burkholderia Species Isolates from the United States.

Burkholderia spp. are opportunistic human pathogens that infect persons with cystic fibrosis and the immunocompromised. Burkholderia spp. express class A and C ß-lactamases, which are transcriptionally regulated by PenRA through linkage to cell wall metabolism and ß-lactam exposure. The potency of temocillin, a 6-methoxy-ß-lactam, was tested against a panel of multidrug-resistant (MDR) Burkholderia spp. In addition, the mechanistic basis of temocillin activity was assessed and compared to that of ticarcillin. Susceptibility testing with temocillin and ticarcillin was conducted, as was biochemical analysis of the PenA1 class A ß-lactamase and AmpC1 class C ß-lactamase. Molecular dynamics simulations (MDS) were performed using PenA1 with temocillin and ticarcillin. The majority (86.7%) of 150 MDR Burkholderia strains were susceptible to temocillin, while only 4% of the strains were susceptible to ticarcillin. Neither temocillin nor ticarcillin induced bla expression. Ticarcillin was hydrolyzed by PenA1 (kcat/Km = 1.7 ± 0.2 µM-1 s-1), while temocillin was slow to form a favorable complex (apparent Ki [Ki app] = ∼2 mM). Ticarcillin and temocillin were both potent inhibitors of AmpC1, with Ki app values of 4.9 ± 1.0 µM and 4.3 ± 0.4 µM, respectively. MDS of PenA revealed that ticarcillin is in an advantageous position for acylation and deacylation. Conversely, with temocillin, active-site residues K73 and S130 are rotated and the catalytic water molecule is displaced, thereby slowing acylation and allowing the 6-methoxy of temocillin to block deacylation. Temocillin is a ß-lactam with potent activity against Burkholderia spp., as it does not induce bla expression and is poorly hydrolyzed by endogenous ß-lactamases.

Nacubactam Enhances Meropenem Activity against Carbapenem-Resistant Klebsiella pneumoniae Producing KPC.

Carbapenem-resistant Enterobacteriaceae (CRE) are resistant to most antibiotics, making CRE infections extremely difficult to treat with available agents. Klebsiella pneumoniae carbapenemases (KPC-2 and KPC-3) are predominant carbapenemases in CRE in the United States. Nacubactam is a bridged diazabicyclooctane (DBO) ß-lactamase inhibitor that inactivates class A and C ß-lactamases and exhibits intrinsic antibiotic and ß-lactam "enhancer" activity against Enterobacteriaceae In this study, we examined a collection of meropenem-resistant K. pneumoniae isolates carrying blaKPC-2 or blaKPC-3; meropenem-nacubactam restored susceptibility. Upon testing isogenic Escherichia coli strains producing KPC-2 variants with single-residue substitutions at important Ambler class A positions (K73, S130, R164, E166, N170, D179, K234, E276, etc.), the K234R variant increased the meropenem-nacubactam MIC compared to that for the strain producing KPC-2, without increasing the meropenem MIC. Correspondingly, nacubactam inhibited KPC-2 (apparent Ki [Ki app] = 31 ± 3 µM) more efficiently than the K234R variant (Ki app = 270 ± 27 µM) and displayed a faster acylation rate (k2/K), which was 5,815 ± 582 M-1 s-1 for KPC-2 versus 247 ± 25 M-1 s-1 for the K234R variant. Unlike avibactam, timed mass spectrometry revealed an intact sulfate on nacubactam and a novel peak (+337 Da) with the K234R variant. Molecular modeling of the K234R variant showed significant catalytic residue (i.e., S70, K73, and S130) rearrangements that likely interfere with nacubactam binding and acylation. Nacubactam's aminoethoxy tail formed unproductive interactions with the K234R variant's active site. Molecular modeling and docking observations were consistent with the results of biochemical analyses. Overall, the meropenem-nacubactam combination is effective against carbapenem-resistant K. pneumoniae Moreover, our data suggest that ß-lactamase inhibition by nacubactam proceeds through an alternative mechanism compared to that for avibactam.

Beyond Piperacillin-Tazobactam: Cefepime and AAI101 as a Potent ß-Lactam-ß-Lactamase Inhibitor Combination.

Impeding, as well as reducing, the burden of antimicrobial resistance in Gram-negative pathogens is an urgent public health endeavor. Our current antibiotic armamentarium is dwindling, while major resistance determinants (e.g., extended-spectrum ß-lactamases [ESBLs]) continue to evolve and disseminate around the world. One approach to attack this problem is to develop novel therapies that will protect our current agents. AAI101 is a novel penicillanic acid sulfone ß-lactamase inhibitor similar in structure to tazobactam, with one important difference. AAI101 possesses a strategically placed methyl group that gives the inhibitor a net neutral charge, enhancing bacterial cell penetration. AAI101 paired with cefepime, also a zwitterion, is in phase III of clinical development for the treatment of serious Gram-negative infections. Here, AAI101 was found to restore the activity of cefepime against class A ESBLs (e.g., CTX-M-15) and demonstrated increased potency compared to that of piperacillin-tazobactam when tested against an established isogenic panel. The enzymological properties of AAI101 further revealed that AAI101 possessed a unique mechanism of ß-lactamase inhibition compared to that of tazobactam. Additionally, upon reaction with AAI101, CTX-M-15 was modified to an inactive state. Notably, the in vivo efficacy of cefepime-AAI101 was demonstrated using a mouse septicemia model, indicating the ability of AAI101 to bolster significantly the therapeutic efficacy of cefepime in vivo The combination of AAI101 with cefepime represents a potential carbapenem-sparing treatment regimen for infections suspected to be caused by Enterobacteriaceae expressing ESBLs.

"Switching Partners": Piperacillin-Avibactam Is a Highly Potent Combination against Multidrug-Resistant Burkholderia cepacia Complex and Burkholderia gladioli Cystic Fibrosis Isolates.

In persons with cystic fibrosis (CF), airway infection with Burkholderia cepacia complex (Bcc) species or Burkholderia gladioli presents a significant challenge due to inherent resistance to multiple antibiotics. Two chromosomally encoded inducible ß-lactamases, a Pen-like class A and AmpC are produced in Bcc and B. gladioli Previously, ceftazidime-avibactam demonstrated significant potency against Bcc and B. gladioli isolated from the sputum of individuals with CF; however, 10% of the isolates tested resistant to ceftazidime-avibactam. Here, we describe an alternative antibiotic combination to overcome ceftazidime-avibactam resistance. Antimicrobial susceptibility testing was performed on Bcc and B. gladioli clinical and control isolates. Biochemical analysis was conducted on purified PenA1 and AmpC1 ß-lactamases from Burkholderia multivorans ATCC 17616. Analytic isoelectric focusing and immunoblotting were conducted on cellular extracts of B. multivorans induced by various ß-lactams or ß-lactam-ß-lactamase inhibitor combinations. Combinations of piperacillin-avibactam, as well as piperacillin-tazobactam plus ceftazidime-avibactam (the clinically available counterpart), were tested against a panel of ceftazidime-avibactam nonsusceptible Bcc and B. gladioli The piperacillin-avibactam and piperacillin-tazobactam-ceftazidime-avibactam combinations restored susceptibility to 99% of the isolates tested. Avibactam is a potent inhibitor of PenA1 (apparent inhibitory constant [Kiapp] = 0.5 µM), while piperacillin was found to inhibit AmpC1 (Kiapp = 2.6 µM). Moreover, piperacillin, tazobactam, ceftazidime, and avibactam, as well as combinations thereof, did not induce expression of blapenA1 and blaampC1 in the B. multivorans ATCC 17616 background. When ceftazidime-avibactam is combined with piperacillin-tazobactam, the susceptibility of Bcc and B. gladioli to ceftazidime and piperacillin is restored in vitro Both the lack of blapenA1 induction and potent inactivation of PenA1 by avibactam likely provide the major contributions toward susceptibility. With in vivo validation, piperacillin-tazobactam-ceftazidime-avibactam may represent salvage therapy for individuals with CF and highly drug-resistant Bcc and B. gladioli infections.

Probing the Mechanism of Inactivation of the FOX-4 Cephamycinase by Avibactam.

Ceftazidime-avibactam is a "second-generation" ß-lactam-ß-lactamase inhibitor combination that is effective against Enterobacteriaceae expressing class A extended-spectrum ß-lactamases, class A carbapenemases, and/or class C cephalosporinases. Knowledge of the interactions of avibactam, a diazabicyclooctane with different ß-lactamases, is required to anticipate future resistance threats. FOX family ß-lactamases possess unique hydrolytic properties with a broadened substrate profile to include cephamycins, partly as a result of an isoleucine at position 346, instead of the conserved asparagine found in most AmpCs. Interestingly, a single amino acid substitution at N346 in the Citrobacter AmpC is implicated in resistance to the aztreonam-avibactam combination. In order to understand how diverse active-site topologies affect avibactam inhibition, we tested a panel of clinical Enterobacteriaceae isolates producing blaFOX using ceftazidime-avibactam, determined the biochemical parameters for inhibition using the FOX-4 variant, and probed the atomic structure of avibactam with FOX-4. Avibactam restored susceptibility to ceftazidime for most isolates producing blaFOX; two isolates, one expressing blaFOX-4 and the other producing blaFOX-5, displayed an MIC of 16 µg/ml for the combination. FOX-4 possessed a k2/K value of 1,800 ± 100 M-1 · s-1 and an off rate (koff) of 0.0013 ± 0.0003 s-1 Mass spectrometry showed that the FOX-4-avibactam complex did not undergo chemical modification for 24 h. Analysis of the crystal structure of FOX-4 with avibactam at a 1.5-Å resolution revealed a unique characteristic of this AmpC ß-lactamase. Unlike in the Pseudomonas-derived cephalosporinase 1 (PDC-1)-avibactam crystal structure, interactions (e.g., hydrogen bonding) between avibactam and position I346 in FOX-4 are not evident. Furthermore, another residue is not observed to be close enough to compensate for the loss of these critical hydrogen-bonding interactions. This observation supports findings from the inhibition analysis of FOX-4; FOX-4 possessed the highest Kd (dissociation constant) value (1,600 nM) for avibactam compared to other AmpCs (7 to 660 nM). Medicinal chemists must consider the properties of extended-spectrum AmpCs, such as the FOX ß-lactamases, for the design of future diazabicyclooctanes.

Inactivation of the Pseudomonas-Derived Cephalosporinase-3 (PDC-3) by Relebactam.

Pseudomonas aeruginosa is a prevalent and life-threatening Gram-negative pathogen. Pseudomonas-derived cephlosporinase (PDC) is the major inducible cephalosporinase in P. aeruginosa In this investigation, we show that relebactam, a diazabicyclooctane ß-lactamase inhibitor, potently inactivates PDC-3, with a k2/K of 41,400 M-1 s-1 and a koff of 0.00095 s-1 Relebactam restored susceptibility to imipenem in 62% of multidrug-resistant P. aeruginosa clinical isolates, while only 21% of isolates were susceptible to imipenem-cilastatin alone. Relebactam promises to increase the efficacy of imipenem-cilastatin against P. aeruginosa.

Characterization of the AmpC ß-Lactamase from Burkholderia multivorans.

Burkholderia multivorans is a member of the Burkholderia cepacia complex, a group of >20 related species of nosocomial pathogens that commonly infect individuals suffering from cystic fibrosis. ß-Lactam antibiotics are recommended as therapy for infections due to Bmultivorans, which possesses two ß-lactamase genes, blapenA and blaAmpC PenA is a carbapenemase with a substrate profile similar to that of the Klebsiella pneumoniae carbapenemase (KPC); in addition, expression of PenA is inducible by ß-lactams in Bmultivorans Here, we characterize AmpC from Bmultivorans ATCC 17616. AmpC possesses only 38 to 46% protein identity with non-Burkholderia AmpC proteins (e.g., PDC-1 and CMY-2). Among 49 clinical isolates of Bmultivorans, we identified 27 different AmpC variants. Some variants possessed single amino acid substitutions within critical active-site motifs (Ω loop and R2 loop). Purified AmpC1 demonstrated minimal measurable catalytic activity toward ß-lactams (i.e., nitrocefin and cephalothin). Moreover, avibactam was a poor inhibitor of AmpC1 (Kiapp > 600 µM), and acyl-enzyme complex formation with AmpC1 was slow, likely due to lack of productive interactions with active-site residues. Interestingly, immunoblotting using a polyclonal anti-AmpC antibody revealed that protein expression of AmpC1 was inducible in Bmultivorans ATCC 17616 after growth in subinhibitory concentrations of imipenem (1 µg/ml). AmpC is a unique inducible class C cephalosporinase that may play an ancillary role in Bmultivorans compared to PenA, which is the dominant ß-lactamase in Bmultivorans ATCC 17616.

Relebactam Is a Potent Inhibitor of the KPC-2 ß-Lactamase and Restores Imipenem Susceptibility in KPC-Producing Enterobacteriaceae.

The imipenem-relebactam combination is in development as a potential treatment regimen for infections caused by Enterobacteriaceae possessing complex ß-lactamase backgrounds. Relebactam is a ß-lactamase inhibitor that possesses the diazabicyclooctane core, as in avibactam; however, the R1 side chain of relebactam also includes a piperidine ring, whereas that of avibactam is a carboxyamide. Here, we investigated the inactivation of the Klebsiella pneumoniae carbapenemase KPC-2, the most widespread class A carbapenemase, by relebactam and performed susceptibility testing with imipenem-relebactam using KPC-producing clinical isolates of Enterobacteriaceae MIC measurements using agar dilution methods revealed that all 101 clinical isolates of KPC-producing Enterobacteriaceae (K. pneumoniae, Klebsiella oxytoca, Enterobacter cloacae, Enterobacter aerogenes, Citrobacter freundii, Citrobacter koseri, and Escherichia coli) were highly susceptible to imipenem-relebactam (MICs ≤ 2 mg/liter). Relebactam inhibited KPC-2 with a second-order onset of acylation rate constant (k2/K) value of 24,750 M-1 s-1 and demonstrated a slow off-rate constant (koff) of 0.0002 s-1 Biochemical analysis using time-based mass spectrometry to map intermediates revealed that the KPC-2-relebactam acyl-enzyme complex was stable for up to 24 h. Importantly, desulfation of relebactam was not observed using mass spectrometry. Desulfation and subsequent deacylation have been observed during the reaction of KPC-2 with avibactam. Upon molecular dynamics simulations of relebactam in the KPC-2 active site, we found that the positioning of active-site water molecules is less favorable for desulfation in the KPC-2 active site than it is in the KPC-2-avibactam complex. In the acyl complexes, the water molecules are within 2.5 to 3 Å of the avibactam sulfate; however, they are more than 5 to 6 Å from the relebactam sulfate. As a result, we propose that the KPC-2-relebactam acyl complex is more stable than the KPC-2-avibactam complex. The clinical implications of this difference are not currently known.

Avibactam Restores the Susceptibility of Clinical Isolates of Stenotrophomonas maltophilia to Aztreonam.

Stenotrophomonas maltophilia is an emerging opportunistic pathogen, classified by the World Health Organization as one of the leading multidrug-resistant organisms in hospital settings. The need to discover novel compounds and/or combination therapies for S. maltophilia is urgent. We demonstrate the in vitro efficacy of aztreonam-avibactam (ATM-AVI) against S. maltophilia and kinetically characterize the inhibition of the L2 ß-lactamase by avibactam. ATM-AVI overcomes aztreonam resistance in selected clinical strains of S. maltophilia, addressing an unmet medical need.

Military Sexual Trauma As a Risk Factor for Treatment Non-Response from an Online, Self-Management Posttraumatic Stress Disorder Treatment for Women Veterans.

Women veterans are exposed to high rates of trauma, including military sexual trauma (MST), and face unique barriers to posttraumatic stress disorder (PTSD) treatment. Telehealth interventions that are tailored to women veterans' unique lived experiences may improve treatment engagement and outcomes. It is important to ascertain how beneficial new telehealth interventions are in the context of different patient characteristics and trauma types, particularly for lower-intensity telehealth interventions (e.g., web-based programs or apps). This secondary analysis of a randomized clinical trial conducted in a sample of 102 women veterans examines predictors of treatment response to a self-management, telehealth intervention for PTSD: Delivery of Self Training and Education for Stressful Situations-Women Veterans (DESTRESS-WV). In the trial, women veterans with PTSD received either an online cognitive behavioral intervention with phone coaching, or phone monitoring alone. We examined associations between baseline patient characteristics (demographics, trauma types, and clinical symptoms) and treatment outcome at post-treatment, 3 months, and 6 months, focusing on the association between treatment outcome and MST. Our primary outcomes were changes in PTSD (PTSD Symptom Checklist, Version 5, PCL-5) and depression (8-item Patient Health Questionnaire, PHQ-8) in the full sample, adjusting for treatment condition. Women veterans who identified MST as the primary trauma for which they were seeking PTSD treatment experienced a nearly nine-point lesser improvement on the PCL-5 than those seeking PTSD treatment for other trauma types (e.g., childhood abuse, combat trauma; p = .0073). Similar patterns were found for depression symptoms. To our knowledge, this is the first study to examine the association between trauma type and treatment outcomes within the context of a self-management, telehealth treatment for PTSD. While the study was not powered to examine differential treatment response for patient subgroups, our exploratory findings suggest that gaps remain in providing effective PTSD care for women veterans who experienced MST.Trial registration: The trial and analysis plan were preregistered in ClinicalTrials.gov (Identifier: NCT02917447).

The Effectiveness of Imipenem-Relebactam against Ceftazidime-Avibactam Resistant Variants of the KPC-2 ß-Lactamase.

BACKGROUND: Ceftazidime-avibactam was approved by the FDA to treat infections caused by Enterobacterales carrying blaKPC-2. However, variants of KPC-2 with amino acid substitutions at position 179 have emerged and confer resistance to ceftazidime-avibactam. METHODS: The activity of imipenem-relebactam was assessed against a panel of 19 KPC-2 D179 variants. KPC-2 and the D179N and D179Y variants were purified for biochemical analyses. Molecular models were constructed with imipenem to assess differences in kinetic profiles. RESULTS: All strains were susceptible to imipenem-relebactam, but resistant to ceftazidime (19/19) and ceftazidime-avibactam (18/19). KPC-2 and the D179N variant hydrolyzed imipenem, but the D179N variant's rate was much slower. The D179Y variant was unable to turnover imipenem. All three ß-lactamases hydrolyzed ceftazidime at varying rates. The acylation rate of relebactam for the D179N variant was ~2.5× lower than KPC-2. Poor catalytic turnover by the D179Y variant precluded the determination of inhibitory kinetic parameters. Acyl-complexes with imipenem and ceftazidime were less prevalent with the D179N variant compared to the D179Y variant, supporting the kinetic observations that the D179Y variant was not as active as the D179N variant. Relebactam was slower to form an acyl-complex with the D179Y variant compared to avibactam. The D179Y model with imipenem revealed that the catalytic water molecule was shifted, and the carbonyl of imipenem was not within the oxyanion hole. Conversely in the D179N model, imipenem was oriented favorably for deacylation. CONCLUSIONS: Imipenem-relebactam overcame the resistance of the D179 variants, suggesting that this combination will be active against clinical isolates harboring these derivatives of KPC-2.

Body composition is associated with operative and oncologic outcomes in the management of retroperitoneal and trunk soft tissue sarcoma.

BACKGROUND: Sarcopenia, myosteatosis and obesity in cancer may confer negative clinical outcomes, but their prevalence and impact among patients with retroperitoneal and trunk soft tissue sarcoma have not been systematically studied. The aim of this study was to determine body composition among patients with retroperitoneal and trunk sarcoma, and assess impact on operative and oncologic outcomes. METHODS: Consecutive patients undergoing treatment with curative intent from 2009 to 2019 were studied. Subcutaneous fat area and visceral fat areas, intramuscular adipose, lean body mass and fat mass were determined at diagnosis by CT at L3. Univariable and multivariable linear, logistic and Cox proportional hazards regression were performed. RESULTS: 95 patients (43.2% retroperitoneal, 48.4% trunk, 46.3% multivisceral resection) were studied. Visceral obesity was evident in 47.4%. Postoperative morbidity occurred in 25.9%, with preoperative radiotherapy (OR10.53 [95% CI 1.08-102.39], P = 0.042) and fat mass (OR1.41 [1.12-1.79], P = 0.004) independently predictive on multivariable analysis, while intramuscular adipose independently predicted inpatient LOS (P < 0.001), wound infection (P = 0.024, OR1.20 [1.02-1.40]) and major postoperative morbidity (P = 0.027, OR1.15 [1.02-1.31]). Increasing fat mass, subcutaneous fat area and intramuscular adipose were associated with greater tumor size (all P < 0.01), while intramuscular adipose predicted disease progression during neoadjuvant therapy (P = 0.024), and independently predicted disease specific survival (DSS) (P = 0.005, HR1.11 [1.03-1.20]) and overall survival (OS) on multivariable analysis (P < 0.001, HR1.19 [1.08-1.31]). CONCLUSION: Visceral obesity is common in retroperitoneal and trunk sarcoma, and measures of adiposity are associated with adverse operative, but not oncologic outcomes. Myosteatosis is independently associated with postoperative morbidity and adverse oncologic outcomes. Body composition may represent a marker of risk among patients with retroperitoneal and trunk sarcoma.