Physical compatibility of sulbactam/durlobactam with select intravenous drugs during simulated Y-site administration.

PURPOSE: Sulbactam/durlobactam is a combination antibiotic designed to target Acinetobacter baumannii, including carbapenem-resistant and multidrug-resistant strains. The objective of this study was to determine the physical compatibility of sulbactam/durlobactam solution during simulated Y-site administration with 95 intravenous (IV) drugs. METHODS: Vials of sulbactam/durlobactam solution were diluted in 0.9% sodium chloride injection to a volume of 100 mL (the final concentration of both drugs was 15 mg/mL). All other IV drugs were reconstituted according to the manufacturer's recommendations and diluted with 0.9% sodium chloride injection to the upper range of concentrations used clinically or tested undiluted as intended for administration. Y-site conditions were simulated by mixing 5 mL of sulbactam/durlobactam with 5 mL of the tested drug solutions in a 1:1 ratio. Solutions were inspected for physical characteristics (clarity, color, and Tyndall effect), turbidity, and pH changes before admixture, immediately post admixture, and over 4 hours. Incompatibility was defined as any observed precipitation, significant color change, positive Tyndall test, or turbidity change of ≥0.5 nephelometric turbidity unit during the observation period. RESULTS: Sulbactam/durlobactam was physically compatible with 38 out of 42 antimicrobials tested (90.5%) and compatible overall with 86 of 95 drugs tested (90.5%). Incompatibility was observed with albumin, amiodarone hydrochloride, ceftaroline fosamil, ciprofloxacin, daptomycin, levofloxacin, phenytoin sodium, vecuronium, and propofol. CONCLUSION: The Y-site compatibility of sulbactam/durlobactam with 95 IV drugs was described. These compatibility data will assist pharmacists and nurses to safely coordinate administration of IV medications with sulbactam/durlobactam.

Optimizing antibiotic dosing regimens for nosocomial pneumonia: a window of opportunity for pharmacokinetic and pharmacodynamic modeling.

INTRODUCTION: Determining antibiotic exposure in the lung and the threshold(s) needed for effective antibacterial killing is paramount during development of new antibiotics for the treatment of nosocomial pneumonia, as these exposures directly affect clinical outcomes and resistance development. The use of pharmacokinetic and pharmacodynamic modeling is recommended by regulatory agencies to evaluate antibiotic pulmonary exposure and optimize dosage regimen selection. This process has been implemented in newer antibiotic development. AREAS COVERED: This review will discuss the basis for conducting pharmacokinetic and pharmacodynamic studies to support dosage regimen selection and optimization for the treatment of nosocomial pneumonia. Pharmacokinetic/pharmacodynamic data that supported recent hospital-acquired bacterial pneumonia/ventilator-associated bacterial pneumonia indications for ceftolozane/tazobactam, ceftazidime/avibactam, imipenem/cilastatin/relebactam, and cefiderocol will be reviewed. EXPERT OPINION: Optimal drug development requires the integration of preclinical pharmacodynamic studies, healthy volunteers and ideally patient bronchoalveolar lavage pharmacokinetic studies, Monte-Carlo simulation, and clinical trials. Currently, plasma exposure has been successfully used as a surrogate for lung exposure threshold. Future studies are needed to identify the value of lung pharmacodynamic thresholds in nosocomial pneumonia antibiotic dosage optimization.

Recent progress on MOF-based optical sensors for VOC sensing.

The raising apprehension of volatile organic compound (VOC) exposures urges the exploration of advanced monitoring platforms. Metal-organic frameworks (MOFs) provide many attractive features including tailorable porosity, high surface areas, good chemical/thermal stability, and various host-guest interactions, making them appealing candidates for VOC capture and sensing. To comprehensively exploit the potential of MOFs as sensing materials, great efforts have been dedicated to the shaping and patterning of MOFs for next-level device integration. Among different types of sensors (chemiresistive sensors, gravimetric sensors, optical sensors, etc.), MOFs coupled with optical sensors feature distinctive strength. This review summarized the latest advancements in MOF-based optical sensors with a particular focus on VOC sensing. The subject is discussed by different mechanisms: colorimetry, luminescence, and sensors based on optical index modulations. Critical analysis for each system highlighting practical aspects was also deliberated.

One-step synthesis of biofunctional carbon quantum dots for bacterial labeling.

In this study, we used a simple one-step dry heating method to synthesize mannose-modified fluorescent carbon quantum dots (Man-CQDs) from solid ammonium citrate and mannose, and successfully applied for labeling Escherichia coli. The highly soluble Man-CQDs had an average particle diameter of 3.1±1.2 nm and exhibited a quantum yield of 9.8% at excitation and emission wavelengths of 365 and 450 nm, respectively. The fluorescent Man-CQDs could selectively bind to the FimH lectin unit in the flagella of the wild-type 1 E. coli K12 strain. We optimized the labeling efficiency of the Man-CQDs by controlling the ratio of ammonium citrate to mannose during their synthesis. The specific binding of the mannose units to E. coli allowed quantitative detection of the bacteria at levels down to 450 colony forming units mL(-1) in lab samples, and facilitate the application of the Man-CQDs for bacterial analyses of real samples (tap water, apple juice, human urine). The synthesis of our Man-CQDs, their labeling, and their use in the detection of bacteria were all simple, inexpensive and efficient processes.

Detection of arsenic(III) through pulsed laser-induced desorption/ionization of gold nanoparticles on cellulose membranes.

We have developed an assay based on gold nanoparticle-modified mixed cellulose ester membrane (Au NPs-MCEM) coupled with laser-induced desorption/ionization mass spectrometry (LDI-MS)-for the detection of arsenic(III) ions (arsenite, AsO2(-)) in aqueous solution. When the Au NPs reacted with lead ions (Pb(2+)) in alkaline solution (5 mM glycine-NaOH, pH 12), Au-Pb complexes, PbO, and Pb(OH) were formed immediately on the Au NP surfaces. The Pb species reacted rapidly with subsequently added AsO2(-) to form PbOAs2O3, (PbO)2As2O3, and/or (PbO)3As2O3 shells (2-5 nm) on the Au NPs' surfaces. As a result, significant observable aggregation of the Au NPs occurred in the solution. This Pb(2+)/Au NP probe allowed the detection of AsO2(-) at concentrations as low as 0.6 µM with high selectivity (at least 100-fold over other anions and metal ions). To further improve the sensitivity, we prepared Au NPs-MCEM for the LDI-MS-based detection of AsO2(-) ions. The intensity of the signal for the [Pb](+) ions in the mass spectra increased when the Au NPs-MCEM reacted with AsO2(-); in contrast, the intensity of the signal for [Au](+) ions decreased. Accordingly, the [Pb](+)/[Au](+) peak ratio increased upon increasing the AsO2(-) concentration over the range from 10 nM to 10 µM. The limit of detection at a signal-to-noise ratio of 3 was 2.5 nM, far below the action level of As (133 nM, ca. 10 ppb) permitted by the US EPA for drinking water. Relative to other nanoparticle-based arsenic sensors, this approach is rapid, specific, and sensitive; in addition, it can be applied to the detection of AsO2(-) in natural water samples (in this case, streamwater, lake water, tap water, groundwater, and mineral water).

Membrane-based assay for iodide ions based on anti-leaching of gold nanoparticles.

We report a label-free colorimetric strategy for the highly selective and sensitive detection of iodide (I(-)) ions in human urine sample, seawater and edible salt. A poly(N-vinyl-2-pyrrolidone)-stabilized Au nanoparticle (34.2-nm) was prepared to detect I(-) ions using silver (Ag(+)) and cyanide (CN(-)) ions as leaching agents in a glycine-NaOH (pH 9.0) solution. For the visual detection of the I(-) ions by naked eye, and for long time stability of the probe, Au nanoparticles (NPs) decorated mixed cellulose ester membrane (MCEM) was prepared (Au NPs/MCEM). The Au NPs-based probe (CN(-)/Ag(+)-Au NPs/MCEM) operates on the principle that Ag(+) ions form a monolyar silver atoms/ions by aurophilic/argentophilic interactions on the Au NPs and it accelerates the leaching rate of Au atoms in presence of CN(-) ions. However, when I(-) is introduced into this system, it inhibits the leaching of Au atoms because of the strong interactions between Ag/Au ions and I(-) ions. Inductively coupled plasma mass spectrometry, surface-assisted laser desorption/ionization time-of-flight mass spectrometry were used to characterize the surface properties of the Au NPs in the presence of Ag(+) and I(-). Under optimal solution conditions, the CN(-)/Ag(+)-Au NPs/MCEM probe enabled the detection of I(-) by the naked eye at nanomolar concentrations with high selectivity (at least 1000-fold over other anions). In addition, this cost-effective probe allowed the determination of I(-) ions in complex samples, such as urine, seawater, and edible salt samples.

Bacterial genes involved in type I secretion and sulfation are required to elicit the rice Xa21-mediated innate immune response.

Innate immunity to microorganisms relies on the specific sensing of pathogen-associated molecules by host recognition receptors. Whereas studies in animals have largely focused on the recognition of extracellular pathogen-associated molecules by the TLR (toll-like receptor) superfamily, few studies have been carried out in plants, and it is not understood how these molecules are secreted or modified. The rice Xa21 gene encodes a receptor-like kinase that provides immunity against strains of the bacterial pathogen Xanthomonas oryzae pv. oryzae carrying AvrXa21 activity. We identified four X. oryzae pv. oryzae genes that are required for AvrXa21 activity. raxA, raxB, and raxC encode proteins with similarity to a membrane fusion protein, an ATP-binding cassette transporter, and an outer membrane protein, respectively, of bacterial type I secretion systems. The fourth gene, raxST, encodes a sulfotransferase-like protein. Sequence analysis of three naturally occurring X. oryzae pv. oryzae strains no longer recognized by Xa21 revealed alterations in the raxST and raxA genes. The raxC gene complemented an Escherichia coli tolC mutant for secretion of a double glycine-leader peptide confirming the function of raxC in type I secretion. These results indicate that bacterial type I secretion is necessary for Xa21-mediated recognition and immunity and further suggest that type I secretion and modification of pathogen-associated molecules play an important role in triggering the innate immune response in rice.

RaxH/RaxR: a two-component regulatory system in Xanthomonas oryzae pv. oryzae required for AvrXa21 activity.

Xanthomonas oryzae pv. oryzae is the causal agent of bacterial leaf blight, one of the most serious diseases in rice. X. oryzae pv. oryzae Philippine race 6 (PR6) strains are unable to establish infection in rice lines expressing the resistance gene Xa21. Although the pathogen-associated molecule that triggers the Xa21-mediated defense response (AvrXa21) is unknown, six rax (required for AvrXa21 activity) genes encoding proteins involved in sulfur metabolism and Type I secretion were recently identified. Here, we report on the identification of two additional rax genes, raxR and raxH, which encode a response regulator and a histidine protein kinase of two-component regulatory systems, respectively. Null mutants of PR6 strain PXO99 that are impaired in either raxR, raxH, or both cause lesions significantly longer and grow to significantly higher levels than does the wild-type strain in Xa21-rice leaves. Both raxR and raxH mutants are complemented to wild-type levels of AvrXa21 activity by introduction of expression vectors carrying raxR and raxH, respectively. These null mutants do not affect AvrXa7 and AvrXa10 activities, as observed in inoculation experiments with Xa7- and Xa10-rice lines. Western blot and raxR/gfp promoter-reporter analyses confirmed RaxR expression in X. oryzae pv. oryzae. The results of promoter-reporter studies also suggest that the previously identified raxSTAB operon is a target for RaxH/RaxR regulation. Characterization of the RaxH/RaxR system provides new opportunities for understanding the specificity of the X. oryzae pv. oryzae-Xa21 interaction and may contribute to the identification of AvrXa21.

Antagonistic Interactions Between Strains of Xanthomonas oryzae pv. oryzae.

ABSTRACT The ability of some phytopathogenic bacterial strains to inhibit the growth of others in mixed infections has been well documented. Here we report that such antagonistic interactions occur between several wild-type strains of the rice bacterial blight pathogen Xanthomonas oryzae pv. oryzae. In mixed inoculations, a wild-type Philippine strain was found to inhibit the growth of a wild-type Korean strain. Furthermore, a nonpathogenic mutant of the Philippine strain maintained these antagonistic properties. Growth curve analysis indicated that both the wild-type Philippine strain and its nonpathogenic mutant inhibited the growth of the Korean strain 2 days after infection and prior to the onset of disease symptoms. When mixed with the nonpathogenic mutant, 10 out of 18 diverse wild-type X. oryzae pv. oryzae strains did not cause disease. Conversely, three of the strains that were not affected by the nonpathogenic mutant were found to inhibit the growth of both the wild-type and mutant Philippine strains, indicating that antagonism is widespread and strain specific. The observed growth inhibition occurred only in planta and did not correlate with bacteriocin activity in vitro. Antagonistic interactions also were found to affect resistance (R) gene-mediated resistance. The R gene Xa21 was capable of protecting rice plants coinoculated with nonantagonistic virulent and avirulent strains; however, when avirulent strains were coinoculated with virulent antagonistic strains, disease ensued. Taken together, these results indicate that X. oryzae pv. oryzae has evolved strategies to compete with rival strains in a fashion that allows virulent strains to evade R gene-mediated protection even when avirulent strains are present in the inoculum.

Molecular determinants of disease and resistance in interactions of Xanthomonas oryzae pv. oryzae and rice.

Xanthomonas oryzae pv. oryzae is the causal agent of rice bacterial blight disease. Numerous genes critical for virulence have been identified. This article reviews current knowledge on the molecular mechanisms of X. oryzae pv. oryzae virulence.

The Xanthomonas oryzae pv. lozengeoryzae raxP and raxQ genes encode an ATP sulphurylase and adenosine-5'-phosphosulphate kinase that are required for AvrXa21 avirulence activity.

Xanthomonas oryzae pv. oryzae (Xoo) Philippine race 6 (PR6) is unable to cause bacterial blight disease on rice lines containing the rice resistance gene Xa21 but is virulent on non-Xa21 rice lines, indicating that PR6 carries avirulence (avrXa21) determinants required for recognition by XA21. Here we show that two Xoo genes, raxP and raxQ, are required for AvrXa21 activity. raxP and raxQ, which reside in a genomic cluster of sulphur assimilation genes, encode an ATP sulphurylase and APS (adenosine-5'-phosphosulphate) kinase. These enzymes function together to produce activated forms of sulphate, APS and PAPS (3'-phosphoadenosine-5'-phosphosulphate). Xoo PR6 strains carrying disruptions in either gene, PR6DeltaraxP or PR6DeltaraxQ, are unable to produce APS and PAPS and are virulent on Xa21-containing rice lines. RaxP and RaxQ are similar to the bacterial symbiont Sinorhizobium meliloti host specificity proteins, NodP and NodQ and the Escherichia coli cysteine synthesis proteins CysD, CysN and CysC. The APS and PAPS produced by RaxP and RaxQ are used for both cysteine synthesis and sulphation of other molecules. Mutation in Xoo xcysI, a homologue of Escherichia coli cysI that is required for cysteine synthesis, blocked APS- or PAPS-dependent cysteine synthesis but did not affect AvrXa21 activity, suggesting that AvrXa21 activity is related to sulphation rather than cysteine synthesis. Taken together, these results demonstrate that APS and PAPS production plays a critical role in determining avirulence of a phytopathogen and reveal a commonality between symbiotic and phytopathogenic bacteria.