Antimicrobial Agents and Chemotherapy最新文献

β-Lactams present several desirable pharmacodynamic features leading to the rapid eradication of many bacterial pathogens. Imipenem (IPM) and cefoxitin (FOX) are injectable β-lactams recommended during the intensive treatment phase of pulmonary infections caused by Mycobacterium abscessus (Mab). However, their potency against Mab is many-fold lower than against Gram-positive and Gram-negative pathogens for which they were optimized, putting into question their clinical utility. Here, we show that adding the recently approved durlobactam-sulbactam (DUR-SUL) pair to either IPM or FOX achieves growth inhibition, bactericidal, and cytolytic activity at concentrations that are within those achieved in patients and below the clinical breakpoints established for each agent. Synergies between DUR-SUL and IPM or FOX were confirmed across a large panel of clinical isolates. Through in vitro resistant mutant selection, we also show that adding DUR-SUL abrogates acquired resistance to IPM and FOX. Since the use of β-lactam injectables is firmly grounded in clinical practice during the intensive treatment phase of Mab pulmonary disease, their potentiation by FDA-approved DUR-SUL to bring minimum inhibitory concentration distributions within achievable concentration ranges could offer significant short-term benefits to patients, while novel β-lactam combinations are optimized specifically against Mab pulmonary infections, for which no reliable cure exists.

Pathogen genomic surveillance in healthcare has the potential to enhance patient safety by detecting outbreaks earlier, thereby reducing morbidity and mortality. Despite benefits, there are barriers to adoption, including cost, expertise, and lack of standardized methodologies and incentives. This commentary advocates for 1) investment from healthcare payors, public health, and regulatory bodies and 2) additional research on genomic surveillance for improving patient outcomes and reducing infections. Effective implementation will require strategic investment and cross-sector collaboration.

Quinolone-induced antibiotic resistance (QIAR) refers to the phenomenon by which bacteria exposed to sublethal levels of quinolones acquire resistance to non-quinolone antibiotics. We have explored this in Escherichia coli MG1655 using a variety of compounds and bacteria carrying a quinolone-resistance mutation in gyrase, mutations affecting the SOS response, and mutations in error-prone polymerases. The nature of the antibiotic-resistance mutations was determined by whole-genome sequencing. Exposure to low levels of most quinolones tested led to mutations conferring resistance to chloramphenicol, ampicillin, kanamycin, and tetracycline. The mutations included point mutations and deletions and could mostly be correlated with the resistance phenotype. QIAR depended upon DNA gyrase and involved the SOS response but was not dependent on error-prone polymerases. Only moxifloxacin, among the quinolones tested, did not display a significant QIAR effect. We speculate that the lack of QIAR with moxifloxacin may be attributable to it acting via a different mechanism. In addition to the concerns about antimicrobial resistance to quinolones and other compounds, QIAR presents an additional challenge in relation to the usage of quinolone antibacterials.

Mycoplasma genitalium, a sexually transmitted bacterium, is a significant cause of urethritis in men and various reproductive tract infections in women, including cervicitis, pelvic inflammatory disease, endometritis, and potentially infertility. Treatment has become increasingly challenging due to the emergence of resistance to both first-line (azithromycin) and second-line (moxifloxacin) antibiotics. The need for new treatment options is critical. This study evaluates the in vitro efficacy of the novel antibiotic lefamulin against 54 M. genitalium isolates, including highly resistant variants. Additionally, the potential synergistic effects of combining lefamulin with doxycycline were assessed in eight selected isolates. Lefamulin exhibited strong antibacterial activity across all tested isolates, with minimal inhibitory concentrations (MICs) ranging from 0.0005 to 0.064 µg/mL. Minimal bactericidal concentrations ranged from 0.001 to 0.128 µg/mL and were equal to the MIC in 40 of 54 isolates and within two- and fourfold MIC in the rest of the isolates. Notably, lefamulin's MIC values were significantly lower than those of azithromycin, doxycycline, and moxifloxacin, underscoring its potent efficacy. Checkerboard assays revealed no antagonistic interaction between lefamulin and doxycycline, with some additive effects observed in certain isolates. These findings highlight lefamulin's potential as a highly effective treatment for M. genitalium infections, particularly those involving multi-drug-resistant strains. Given the increasing rates of resistance and the limitations of current therapies, lefamulin may represent a promising new option for managing this challenging pathogen. Further clinical studies are warranted to confirm these in vitro results and explore the therapeutic potential of lefamulin in combination with doxycycline.

The antimalarial quinolines pyronaridine and chloroquine both inhibit hemozoin crystallization, predominately produced by Plasmodium falciparum intra-erythrocytic trophozoite stage parasites. Pyronaridine extends activity to ring-stage chloroquine-sensitive parasites, in contrast to chloroquine. Here, we investigated chloroquine and pyronaridine hemozoin inhibition type correlated to stage-specific activity on chloroquine-resistant ring-stage artemisinin sensitive and resistant P. falciparum CamWT and CamWT-C580Y parasites. Pyronaridine (2.8 μM) is tenfold more potent at beta-hematin nucleation than chloroquine (40 μM). Both pyronaridine and chloroquine (0.2 and 0.7 μM, respectively) had similar sub-μM inhibition of beta-hematin extension. P. falciparum CamWT-C580Y parasites produce smaller width hemozoin crystals which extend less than isogenic CamWT hemozoin. Stage-specific pulse dose pyronaridine and chloroquine on CamWT-C580Y or CamWT isogenic parasites observed 3- to 4-fold higher pyronaridine IC₅₀s compared to 10- to 15-fold higher chloroquine on most CamWT-C580Y to CamWT stages. These findings collectively show that hemozoin nucleation inhibition widens stage-specific pyronaridine activity on P. falciparum drug-resistant parasites.

Carbapenemase-producing carbapenem-resistant Enterobacterales (CP-CRE) represent a significant global threat. The emergence of dual CP-CRE is particularly alarming, as they can potentially compromise the efficacy of newer antibiotics, further decreasing therapeutic alternatives. Herein, we report the emergence of multiple species of CP-CRE recovered from invasive infections in Chile that simultaneously harbor bla_KPC and bla_NDM and provide an in-depth genomic characterization of these worrisome pathogens. We collected carbapenem-resistant Enterobacterales (CRE) isolates from invasive infections over a 4-year period, across 11 healthcare centers in Chile. Bacterial species and the presence of carbapenemase genes were confirmed using MALDI-TOF and PCR assays, respectively. Antimicrobial susceptibility testing was conducted through disk diffusion and broth microdilution methods. Dual CP-CRE isolates were subjected to short- and long-read whole genome sequencing to perform a detailed genomic characterization of the isolates and of the mobile genetic elements harboring the enzymes. From a total of 1,335 CRE isolates, we observed an increase in the prevalence of CP-CRE, from 11% in 2019 to 38% in 2022. A total of 11 dual CP-CRE isolates were recovered, all of them harboring bla_KPC and bla_NDM. Species corresponded to Escherichia coli (n = 6), Klebsiella pneumoniae (n = 2), Klebsiella oxytoca (n = 2), and Citrobacter freundii (n = 1). Dual CP-CRE isolates exhibited resistance to all tested β-lactams except for cefiderocol. The bla_KPC and bla_NDM encoding genes were located on independent plasmids. Platforms harboring bla_KPC were diverse and included IncN, IncF, and IncFIB plasmids. In contrast, bla_NDM-7 was only found on fairly conserved IncX3 plasmids. We report that a rapid increase of CP-CRE in Chile, alongside with the emergence of multiple bacterial species of CP-CRE co-harboring bla_KPC-2/3 and bla_NDM-7, underscores a critical public health challenge. Our data suggest that the dissemination of bla_NDM-7 was predominantly facilitated by IncX3 plasmids, whereas the spread of bla_KPC involved multiple plasmid backbones. Active surveillance and genomic monitoring are critical to inform public policy and curtail the spread of these highly resistant pathogens.

We previously reported N-hydroxypyridinedione (HPD) compounds with mid-nanomolar efficacy and selectivity indexes around 300 against hepatitis B virus (HBV) replication. However, they lack pharmacological evaluation. Here, we report in vitro anti-HBV efficacy, cytotoxicity, and pharmacological characterization of 29 novel HPDs within seven subgroups. The best two compounds had EC₅₀s of 61 and 190 nM and selectivity indexes of 526 and 1,071. Compounds with one halogen on the major R group were most effective and compounds with large ether R groups were most cytotoxic. Compounds were not cytotoxic in primary human hepatocytes. All compounds were freely soluble in pHs reflecting plasma (7.4) and the gastrointestinal tract (5 and 6.5). Almost all highly soluble compounds were passively permeable at pH 5.0 and 7.4. Only 2 of 11 compounds tested were likely to be effluxed by p-glycoprotein. The most potent HPDs inhibited HBV replication over human ribonuclease H1 activity by 10-fold. Four of 19 compounds inhibited CYP2D6 >50%, but their CYP2D6 IC₅₀s were >8× higher than their anti-HBV EC₅₀. No compound substantially inhibited CYP3A4. Thirteen of 15 compounds had human microsomal half-lives >30 min with medium to low rates of intrinsic clearance. Eleven of 12 compounds bound plasma proteins by ≥80%; however, effects against HBV replication for only one would likely be physiologically relevant. These results identify two lead candidate HPDs with pharmacological characteristics resembling commercially available drugs that are suitable for in vivo pharmacological and efficacy studies.

Secondary peritonitis with intra-abdominal abscesses (IAA) is difficult to treat because of the supposed low rate of penetration of antimicrobial drugs at the site of infection. However, clinical data about the actual bioavailability of antimicrobial drugs in IAA are scarce. This prospective observational study aimed at assessing the drug penetration in IAA of the antibiotics (piperacillin-tazobactam, carbapenems) and antifungals (fluconazole, echinocandins) that are usually recommended for the treatment of intra-abdominal infections. Patients with IAA who underwent a radiological or surgical drainage procedure were included. Antimicrobial drug concentrations were measured in IAA (C_IAA) and in a simultaneous plasma sample (C_plasma) to assess the C_IAA/C_plasma ratio. The pharmacodynamic target was defined as a C_IAA equal or superior to the clinical breakpoints of susceptibility of the most relevant intra-abdominal pathogens. Clinical outcomes were assessed at hospital discharge. A total of 54 antimicrobial drug measurements were performed in 39 IAA samples originating from 36 patients. Despite important inter-individual variability, piperacillin-tazobactam exhibited the highest C_IAA/C_plasma ratios (median 2). The rates of target achievement were 75%-80% for piperacillin-tazobactam and meropenem but 0% for imipenem and ertapenem. These results tended to correlate with clinical outcomes (96% success rate versus 73%, respectively, P = 0.07). Among antifungals, fluconazole exhibited higher C_IAA/C_plasma ratios and rates of target achievement compared to echinocandins. However, no differences in clinical outcomes were observed. These results provide unique information about antimicrobial drug penetration in IAA in real clinical conditions and suggest that piperacillin-tazobactam and meropenem may have better efficacy compared to imipenem or ertapenem.

LPC-233 (a.k.a. VB-233) is a potent antibiotic targeting the essential enzyme LpxC in Gram-negative bacteria. We present herein the pharmacokinetics and pharmacodynamics data of LPC-233 for treating murine infections caused by Burkholderia pseudomallei, a potential biodefense pathogen. A range of doses was evaluated in a post-aerosol exposure model of B. pseudomallei-infected mice. After the aerosol challenge with the B. pseudomallei strain K96243, treatment was initiated with 10, 30, or 90 mg/kg of LPC-233 orally every 12 h (q12h) or 90 mg/kg intraperitoneally q12h for 14 days. A vehicle-control arm and a positive-control arm consisting of one of the recommended standards of care, ceftazidime (150 mg/kg, q6h) injected subcutaneously, were included. LPC-233 significantly and dose-dependently rescued mice from B. pseudomallei infection in comparison with the vehicle (P < 0.0001). At dose levels of 30 mg/kg or higher, the survival rate with LPC-233 was significantly higher than that from the ceftazidime arm (P range: 0.001-0.05). LPC-233 reversed the murine body weight loss caused by the B. pseudomallei infection more rapidly than ceftazidime did, suggesting that it is a faster-acting antibiotic in this dosing regimen. Despite the outstanding survival advantage of LPC-233 over ceftazidime, no significant differences in tissue burdens (liver, lung, spleen, and blood) were observed among any of the treatment groups surviving to the termination of the experiment, suggesting that similar to commercial antibiotics, LPC-233 treatment for lethal B. pseudomallei infection may likely require both an acute phase of intensive treatment and an eradication phase of prolonged treatment.

Bacterial efflux pumps play important roles in the antibiotic resistance and excretion of virulence factors. We previously characterized that TolCV1, a component of efflux pumps, plays critical roles in resistance to antibiotics and bile and also RtxA1 toxin secretion of Vibrio vulnificus. In this context, we speculated that TolCV1 blockers would have a dual effect of enhancing susceptibility to antibiotics and suppressing virulence of V. vulnificus. Here, we show that the chloride channel blocker 5-nitro-2-(3-phenylpropylamino) benzoic acid (NPPB) increases susceptibility to antibiotics and suppresses cytotoxicity of V. vulnificus through inhibition of TolCV1. NPPB significantly decreased TolCV1 in V. vulnificus cells by liberating the protein from the cell body. Checkerboard assay showed that NPPB enhanced the antimicrobial activities of antibiotics such as kanamycin, tetracycline, erythromycin, and ampicillin against V. vulnificus. Moreover, NPPB inhibited the secretion of RtxA1 toxin and protected host cells from V. vulnificus-induced cytotoxicity. In addition, NPPB markedly suppressed V. vulnificus growth in the presence of bile salts and enhanced the therapeutic effect of tetracycline in V. vulnificus-infected mice. The safety and efficacy of NPPB were confirmed at the cellular and animal levels. Collectively, TolCV1 inhibition by NPPB renders V. vulnificus less virulent and more susceptible to antibiotics.