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There is an urgent global need for new strategies and drugs to control and treat multidrug-resistant bacterial infections. In 2017, the World Health Organization (WHO) released a list of 12 antibiotic-resistant priority pathogens and began to critically analyze the antibacterial clinical pipeline. This review analyzes "traditional" and "nontraditional" antibacterial agents and modulators in clinical development current on 30 June 2021 with activity against the WHO priority pathogens mycobacteria and Clostridioides difficile. Since 2017, 12 new antibacterial drugs have been approved globally, but only vaborbactam belongs to a new antibacterial class. Also innovative is the cephalosporin derivative cefiderocol, which incorporates an iron-chelating siderophore that facilitates Gram-negative bacteria cell entry. Overall, there were 76 antibacterial agents in clinical development (45 traditional and 31 nontraditional), with 28 in phase 1, 32 in phase 2, 12 in phase 3, and 4 under regulatory evaluation. Forty-one out of 76 (54%) targeted WHO priority pathogens, 16 (21%) were against mycobacteria, 15 (20%) were against C. difficile, and 4 (5%) were nontraditional agents with broad-spectrum effects. Nineteen of the 76 antibacterial agents have new pharmacophores, and 4 of these have new modes of actions not previously exploited by marketed antibacterial drugs. Despite there being 76 antibacterial clinical candidates, this analysis indicated that there were still relatively few clinically differentiated antibacterial agents in late-stage clinical development, especially against critical-priority pathogens. We believe that future antibacterial research and development (R&D) should focus on the development of innovative and clinically differentiated candidates that have clear and feasible progression pathways to the market.Conjugative plasmids are the principal mediator in the emergence and spread of antibiotic resistance genes in Enterobacterales. Plasmid entry exclusion (EEX) systems can restrict their transfer into the recipient bacteria carrying closely related plasmids. In this study, we identified and characterized a novel plasmid entry exclusion system in a carbapenem resistance plasmid pKPC_UVA01, which is responsible for widespread dissemination of the blaKPC carbapenemase gene among Enterobacterales in the United States. The identified eex gene in the recipient strain of different Enterobacterales species inhibited the conjugation transfer of pKPC_UVA01 plasmids at a range of 200- to 400-fold, and this inhibition was found to be a dose-dependent function of the EEX protein in recipient cells. The C terminus truncated version of eex or eex with an early termination codon at the C terminus region alleviated the inhibition of conjugative transfer. Unlike the strict specificity of plasmid exclusion by the known EEX protein, the newly identified EEX in the recipient strain could inhibit the transfer of IncP and IncN plasmids. The eex gene from the plasmid pKPC_UVA01 was not required for conjugative transfer but was essential in the donor bacteria for entry exclusion of this plasmid. This was a novel function of a single protein that is essential in both donor and recipient bacteria for the entry exclusion of a plasmid. This eex gene is found to be distributed in multidrug resistance plasmids similar to pKPC_UVA01 in different Enterobacterales species and may contribute to the stability of this plasmid type by controlling its transfer.New strategies to treat diseases in which biofilms contribute significantly to pathogenesis are needed, as biofilm-resident bacteria are highly recalcitrant to antibiotics due to physical biofilm architecture and a canonically quiescent metabolism, among many additional attributes. We, and others, have shown that when biofilms are dispersed or disrupted, bacteria released from biofilm residence are in a distinct physiologic state that, in part, renders these bacteria highly sensitive to killing by specific antibiotics. We sought to demonstrate the breadth of the ability of a recently humanized monoclonal antibody against an essential biofilm structural element (DNABII protein) to disrupt biofilms formed by respiratory tract pathogens and potentiate antibiotic-mediated killing of bacteria released from biofilm residence. Biofilms formed by six respiratory tract pathogens were significantly disrupted by the humanized monoclonal antibody in a dose- and time-dependent manner, as corroborated by confocal laser scanning microscopy (CLSM) imaging. Bacteria newly released from the biofilms of 3 of 6 species were significantly more sensitive than their planktonic counterparts to killing by 2 of 3 antibiotics currently used clinically and were now also equally as sensitive to killing by the 3rd antibiotic. The remaining 3 pathogens were significantly more susceptible to killing by all 3 antibiotics. A humanized monoclonal antibody directed against protective epitopes of a DNABII protein effectively released six diverse respiratory tract pathogens from biofilm residence in a phenotypic state that was now as, or significantly more, sensitive to killing by three antibiotics currently indicated for use clinically. These data support this targeted, combinatorial, species-agnostic therapy to mitigate chronic bacterial diseases.Polymyxins are considered as the last resort antibiotics to treat infections caused by multidrug-resistant Gram-negative pathogens. Pseudomonas aeruginosa is an opportunistic pathogen that causes various infections in humans. Proteins involved in lipopolysaccharide modification and maintaining inner and outer membrane integrities have been found to contribute to the bacterial resistance to polymyxins. Oligoribonuclease (Orn) is an exonuclease that regulates the homeostasis of intracellular (3'-5')-cyclic dimeric GMP (c-di-GMP), thereby regulating the production of extracellular polysaccharide in P. aeruginosa. Previously, we demonstrated that Orn affects the bacterial resistance to fluoroquinolone, β-lactam and aminoglycoside antibiotics. In this study, we found that mutation of orn increased the bacterial survival following polymyxin B treatment in a wild-type P. aeruginosa strain PA14. Overexpression of c-di-GMP degradation enzymes in the orn mutant reduced the bacterial survival. By using a fluorescence labeled polymyxin B, we found that mutation of orn increased the bacterial surface bound polymyxin B. Deletion of the Pel synthesis genes or treatment with a Pel hydrolase reduced the surface bound polymyxin B and bacterial survival. We further demonstrated that Pel binds to extracellular DNA (eDNA), which traps polymyxin B and thus protects the bacterial cells. Collectively, our results revealed a novel defense mechanism against polymyxin in P. aeruginosa.Trimethoprim/sulfamethoxazole (TMP/SMZ) is considered the treatment of choice for infections caused by Stenotrophomonas maltophilia, but limited pharmacodynamic data are available to support current susceptibility breakpoints or guide optimal dosing. Time-kill studies using a TMP/SMZ concentration of 4/40 μg/mL were conducted to compare 4 S. maltophilia with 4 Escherichia coli isolates having the same MICs (0.25/4.75 to 4/76 μg/mL) in cation-adjusted Mueller-Hinton broth (CAMHB) and ISO-Sensitest broth (ISO broth). With the exception of the resistant isolates (4/76 μg/mL), which resulted in regrowth approaching the growth of the control, TMP/SMZ displayed significantly greater killing for E. coli than for S. maltophilia at each MIC. Against E. coli, the mean changes at 24 h were -4.49, -1.73, -1.59, and +1.83 log10 CFU for isolates with MICs of 0.25/4.75, 1/19, 2/39, and 4/74 μg/mL, respectively. The area under the concentration-time curve for the free, unbound fraction of the drug (fAUC)/MIC ratio required for stasis and 1-log10 and 2-log10 CFU reductions were 40.7, 59.5, and 86.3, respectively. In contrast, TMP/SMZ displayed no stasis or CFU reductions against any S. maltophilia isolate regardless of the MIC, and no pharmacodynamic thresholds were quantifiable. Observations were consistent in both CAMHB and ISO broth. These data add increasing evidence that current TMP/SMZ susceptibility breakpoints against S. maltophilia should be reassessed.The objectives were to analyze treatment, clinical outcomes, and predictors of mortality in hospitalized patients with Acinetobacter baumannii infection. This was a retrospective cohort study of inpatients with A. baumannii cultures and treatment from 2010 to 2019. Patients who died during admission were compared to those who survived, to identify predictors of inpatient mortality, using multivariable unconditional logistic regression models. We identified 4,599 inpatients with A. baumannii infection; 13.6% died during admission. Fluoroquinolones (26.8%), piperacillin-tazobactam (24%), and carbapenems (15.6%) were used for treatment. Tigecycline (3%) and polymyxins (3.7%) were not used often. Predictors of inpatient mortality included current acute respiratory failure (adjusted odds ratio [aOR] 3.94), shock (aOR 3.05), and acute renal failure (aOR 2.01); blood (aOR 1.94) and respiratory (aOR 1.64) infectious source; multidrug-resistant A. baumannii (MDRAB) infection (aOR 1.66); liver disease (aOR 2.15); and inadequate initial treatment (aOR 1.30). Inpatient mortality was higher in those with MDRAB versus non-MDRAB (aOR 1.61) and in those with CRAB versus non-CRAB infection (aOR 1.68). Length of stay >10 days was higher among those with MDRAB versus non-MDRAB (aOR 1.25) and in those with CRAB versus non-CRAB infection (aOR 1.31). In our national cohort of inpatients with A. baumannii infection, clinical outcomes were worse among those with MDRAB and/or CRAB infection. Predictors of inpatient mortality included several current conditions associated with severity, infectious source, underlying illness, and inappropriate treatment. Our study may assist health care providers in the early identification of admitted patients with A. baumannii infection who are at higher risk of death.Klebsiella oxytoca complex comprises nine closely related species causing human infections. We curated genomes labeled Klebsiella (n = 14,256) in GenBank and identified 588 belonging to the complex, which were examined for precise species, sequence types, K- and O-antigen types, and virulence and antimicrobial resistance genes. The complex and Klebsiella pneumoniae share many K- and O-antigen types. Of the complex, K. oxytoca and Klebsiella michiganensis appear to carry more virulence genes and be more commonly associated with human infections.Azoles, the most commonly used antifungal drugs, specifically inhibit the fungal lanosterol α-14 demethylase enzyme, which is referred to as Erg11. Inhibition of Erg11 ultimately leads to a reduction in ergosterol production, an essential fungal membrane sterol. Many Candida species, such as Candida albicans, develop mutations in this enzyme which reduces the azole binding affinity and results in increased resistance. Candida glabrata is also a pathogenic yeast that has low intrinsic susceptibility to azole drugs and easily develops elevated resistance. In C. glabrata, these azole resistant mutations typically cause hyperactivity of the Pdr1 transcription factor and rarely lie within the ERG11 gene. Here, we generated C. glabrata ERG11 mutations that were analogous to azole resistance alleles from C. albicans ERG11. Three different Erg11 forms (Y141H, S410F, and the corresponding double mutant (DM)) conferred azole resistance in C. Crenigacestat glabrata with the DM Erg11 form causing the strongest phenotype. The DM Erg11 also induced cross-resistance to amphotericin B and caspofungin.
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