Correction: Freischem et al. Interaction Mode of the Novel Monobactam AIC499 Targeting Penicillin Binding Protein 3 of Gram-Negative Bacteria. Biomolecules 2021, 11, 1057

In the original article [...]

β-lactam Resistance in Pseudomonas aeruginosa: Current Status, Future Prospects

Pseudomonas aeruginosa is a major opportunistic pathogen, causing a wide range of acute and chronic infections. β-lactam antibiotics including penicillins, carbapenems, monobactams, and cephalosporins play a key role in the treatment of P. aeruginosa infections. However, a significant number of isolates of these bacteria are resistant to β-lactams, complicating treatment of infections and leading to worse outcomes for patients. In this review, we summarize studies demonstrating the health and economic impacts associated with β-lactam-resistant P. aeruginosa. We then describe how β-lactams bind to and inhibit P. aeruginosa penicillin-binding proteins that are required for synthesis and remodelling of peptidoglycan. Resistance to β-lactams is multifactorial and can involve changes to a key target protein, penicillin-binding protein 3, that is essential for cell division; reduced uptake or increased efflux of β-lactams; degradation of β-lactam antibiotics by increased expression or altered substrate specificity of an AmpC β-lactamase, or by the acquisition of β-lactamases through horizontal gene transfer; and changes to biofilm formation and metabolism. The current understanding of these mechanisms is discussed. Lastly, important knowledge gaps are identified, and possible strategies for enhancing the effectiveness of β-lactam antibiotics in treating P. aeruginosa infections are considered.

Essential oils of Uvaria boniana – chemical composition, in vitro bioactivity, docking, and in silico ADMET profiling of selective major compounds

Phytochemical investigation applying GC (gas chromatography)-MS (mass spectrometry)/GC-FID (flame ionization detection) on the hydro-distilled essential oils of the Vietnamese medicinal plant Uvaria boniana leaf and twig lead to the detection of 35 constituents (97.36%) in the leaf oil and 52 constituents (98.75%) in the twig oil. Monoterpenes, monoterpenoids, sesquiterpenes, and sesquiterpenoids were characteristic of U. boniana essential oils. The leaf oil was represented by major components (E)-caryophyllene (16.90%), bicyclogermacrene (15.95%), α-humulene (14.96%), and linalool (12.40%), whereas four compounds α-cadinol (16.16%), epi-α-muurolol (10.19%), α-pinene (11.01%), and β-pinene (8.08%) were the main ones in the twig oil. As compared with the leaf oil, the twig oil was better in antimicrobial activity. With the same MIC value of 40 mg/mL, the twig oil successfully controlled the growth of Gram (+) bacterium Bacillus subtilis, Gram (−) bacterium Escherichia coli, fungus Aspergillus niger, and yeast Saccharomyces cerevisiae. In addition, both two oil samples have induced antiinflammatory activity with the IC50 values of 223.7–240.6 mg/mL in NO productive inhibition when BV2 cells had been stimulated by LPS. Docking simulations of four major compounds of U. boniana twig oil on eight relevant antibacterial targets revealed that epi-α-muurolol and α-cadinol are moderate inhibitors of E. coli DNA gyrase subunit B, penicillin binding protein 2X and penicillin binding protein 3 of Pseudomonas aeruginosa with similar free binding energies of −30.1, −29.3, and −29.3 kJ/mol, respectively. Furthermore, in silico ADMET studies indicated that all four docked compounds have acceptable oral absorption, low metabolism, and appropriated toxicological profile to be considered further as drug candidates.

Multidrug-resistant Neisseria gonorrhoeae infection in heterosexual men with reduced susceptibility to ceftriaxone, first report in Thailand

The global rapid emergence of azithromycin/ceftriaxone resistant Neisseria gonorrhoeae threatens current recommend azithromycin/ceftriaxone dual therapy for gonorrhea to ensure effective treatment. Here, we identified the first two N. gonorrhoeae isolates with decreased ceftriaxone susceptibility in Thailand. Among 134 N. gonorrhoeae isolates collected from Thai Red Cross Anonymous Clinic, Bangkok, two isolates (NG-083 and NG-091) from urethral swab in male heterosexual patients had reduced susceptibility to ceftriaxone (MICs of 0.125 mg/L). Both were multidrug resistant and strong biofilm producers with ceftriaxone tolerance (MBEC > 128 mg/L). NG-083 and NG-091 remained susceptible to azithromycin (MIC of 1 mg/L and 0.5 mg/L, respectively). Reduced susceptibility to ceftriaxone was associated with alterations in PBP2, PBP1, PorB, MtrR, and mtrR promoter region. NG-083 belonged to sequence type (ST) 7235 and NG-091 has new allele number of tbpB with new ST. Molecular docking revealed ceftriaxone weakly occupied the active site of mosaic XXXIV penicillin-binding protein 2 variant in both isolates. Molecular epidemiology results revealed that both isolates display similarities with isolates from UK, USA, and The Netherlands. These first two genetically related gonococcal isolates with decreased ceftriaxone susceptibility heralds the threat of treatment failure in Thailand, and importance of careful surveillance.

1253. Antimicrobial Activity of Cefepime in Combination with Taniborbactam Against Clinical Isolates of Enterobacterales from 2018-2020 Global Surveillance

Background Taniborbactam (formerly VNRX-5133) is a novel cyclic boronate-based broad-spectrum β-lactamase inhibitor with potent and selective direct inhibitory activity against both serine- and metallo-β-lactamases (Ambler Classes A, B, C and D). Taniborbactam restores the activity of cefepime against many difficult to treat organisms, including cephalosporin- and carbapenem-resistant Enterobacterales and Pseudomonas aeruginosa. The activity of the investigational combination cefepime-taniborbactam (FTB) and comparator agents was evaluated against clinical isolates of Enterobacterales from a 2018-2020 global surveillance study. Methods MICs of cefepime with taniborbactam fixed at 4 µg/mL and comparators were determined following CLSI M07-A11 guidelines against 10,543 Enterobacterales. Isolates were from community and hospital infections collected from 259 sites in 56 countries in 2018-2020. Resistant phenotypes were based on 2021 CLSI breakpoints. A set of 827 isolates with meropenem MIC ≥4 µg/mL (n=421) or with cefepime and/or ceftazidime MIC ≥2 µg/mL (n=406) was evaluated for the presence of MBLs, KPC, ESBLs, and OXA-48 group genes via PCR and sequencing. Forty-eight isolates with FTB MIC values of 16 µg/mL or greater were interrogated by WGS. Results Overall, 23.0% and 15.9% of isolates were nonsusceptible (NS) to cefepime and piperacillin-tazobactam (TZP), respectively (Table). FTB had potent activity against all Enterobacterales, with MIC50/90 values of 0.06/0.25 µg/mL and 99.5% inhibited at ≤8 µg/mL. FTB maintained activity against MBL-, KPC-, OXA-48 group, and ESBL-positive isolates (MIC90 range, 1 to >16 µg/mL; 80.5% to 100% inhibited at ≤8 µg/mL). Isolates with elevated FTB MICs had IMP-type enzymes, variation in the cefepime target (penicillin binding protein 3), permeability defects in combination with acquired β-lactamases, and/or possible up-regulated efflux. Results Table Conclusion Taniborbactam significantly restored the in vitro activity of cefepime against Enterobacterales, including isolates nonsusceptible to recently-approved BL/BLI combinations and expressing serine and metallo-β-lactamases. This support the continued development of FTB as a potential new treatment option for challenging infections due to resistant Gram-negative pathogens. Disclosures Meredith Hackel, PhD MPH, IHMA (Employee)Pfizer, Inc. (Independent Contractor) Mark G G. Wise, PhD, IHMA (Employee)Pfizer, Inc. (Independent Contractor) Daniel F. Sahm, PhD, IHMA (Employee)Pfizer, Inc. (Independent Contractor)

Isolation of Group A Streptococci with Reduced In Vitro β-Lactam Susceptibility Harboring Amino Acid Substitutions in Penicillin-Binding Proteins in Japan

Streptococcus pyogenes (group A Streptococcus , GAS) has long been regarded as being susceptible to β-lactams. However, amino acid substitutions in penicillin-binding protein (PBP)2X conferring reduced in vitro β-lactam susceptibility have been indicated since 2019 in the United States and Iceland. Here, we report the first isolation of Streptococcus pyogenes possessing the PBP2X substitution conferring reduced in vitro β-lactam susceptibility in Asia; however, the MICs were below the “susceptible” breakpoint of the CLSI.

Dinoxin B Withanolide from Datura inoxia Mill as an Effective Phytocompound Against Urinary Tract Infection causing Staphylococcus aureus

Background: Dinoxin B Withanolide was isolated from Datura inoxia and identified with its cytotoxic activity. But its antibacterial properties are not yet evaluated. We have previously reported the broad-spectrum antibacterial property of Dinoxin B Withanolide extracted from D.inoxia on standard strains. Objective: This research has focused to evaluate the efficacy of Dinoxin B Withanolide against infectious Staphylococcus aureus, including resistant strains. Methods: Electrospray Ionization-Mass Spectrometry is used to depict the presence of Dinoxin B withanolide from the chromatographic ethanolic leaf fraction. Antibacterial activity of different concentrations of Dinoxin B(12500-100000 μg/ml) was assessed using the agar diffusion, macro broth dilution, and time-kill assay methods. Docking studies and Drug likeness properties were analyzed. Result: Electrospray Ionization-Mass Spectrometry depicted the presence of Dinoxin B. All the isolates were susceptible to Dinoxin B within the range of 15±0.5mm to 24±0.5mm, and the bacteria were susceptible at a concentration rate of ≤12.5mg/ml. Time-kill assay showed that 25mg/ml of Dinoxin B displayed the highest inhibitory activity after four hours. The MBC values were compatible with the cidal concentration as seen in the time-kill study's growth curve. Computer-aided techniques resulted in a good Docking score towards Quorum-signaling Sar A protein (-7.82)and Penicillin Binding Protein(-6.9). Conclusion: Dinoxin B with its bactericidal properties and significant affinity towards Quorum-signaling Sar A protein and Penicillin Binding Protein can be considered as an effective bioactive compound against Methicillin Resistance Staphylococcus aureus.

Streptococcus pneumoniae serotypes that frequently colonise the human nasopharynx are common recipients of penicillin-binding protein gene fragments from Streptococcus mitis

Streptococcus pneumoniae is an important global pathogen that causes bacterial pneumonia, sepsis and meningitis. Beta-lactam antibiotics are the first-line treatment for pneumococcal disease, however, their effectiveness is hampered by beta-lactam resistance facilitated by horizontal genetic transfer (HGT) with closely related species. Although interspecies HGT is known to occur among the species of the genus Streptococcus , the rates and effects of HGT between Streptococcus pneumoniae and its close relatives involving the penicillin binding protein (pbp) genes remain poorly understood. Here we applied the fastGEAR tool to investigate interspecies HGT in pbp genes using a global collection of whole-genome sequences of Streptococcus mitis , Streptococcus oralis and S. pneumoniae . With these data, we established that pneumococcal serotypes 6A, 13, 14, 16F, 19A, 19F, 23F and 35B were the highest-ranking serotypes with acquired pbp fragments. S. mitis was a more frequent pneumococcal donor of pbp fragments and a source of higher pbp nucleotide diversity when compared with S. oralis . Pneumococci that acquired pbp fragments were associated with a higher minimum inhibitory concentration (MIC) for penicillin compared with pneumococci without acquired fragments. Together these data indicate that S. mitis contributes to reduced β-lactam susceptibility among commonly carried pneumococcal serotypes that are associated with long carriage duration and high recombination frequencies. As pneumococcal vaccine programmes mature, placing increasing pressure on the pneumococcal population structure, it will be important to monitor the influence of antimicrobial resistance HGT from commensal streptococci such as S. mitis .

Unipolar Peptidoglycan Synthesis in the Rhizobiales Requires an Essential Class A Penicillin-Binding Protein

While the structure and function of the bacterial cell wall are well conserved, the mechanisms responsible for cell wall biosynthesis during elongation are variable. It is increasingly clear that rod-shaped bacteria use a diverse array of growth strategies with distinct spatial zones of cell wall biosynthesis, including lateral elongation, unipolar growth, bipolar elongation, and medial elongation.

Rapid MRSA detection via tandem mass spectrometry of the intact 80 kDa PBP2a resistance protein

Treatment of antibiotic-resistant infections is dependent on the detection of specific bacterial genes or proteins in clinical assays. Identification of methicillin-resistant Staphylococcus aureus (MRSA) is often accomplished through the detection of penicillin-binding protein 2a (PBP2a). With greater dependence on mass spectrometry (MS)-based bacterial identification, complementary efforts to detect resistance have been hindered by the complexity of those proteins responsible. Initial characterization of PBP2a indicates the presence of glycan modifications. To simplify detection, we demonstrate a proof-of-concept tandem MS approach involving the generation of N-terminal PBP2a peptide-like fragments and detection of unique product ions during top-down proteomic sample analyses. This approach was implemented for two PBP2a variants, PBP2amecA and PBP2amecC, and was accurate across a representative panel of MRSA strains with different genetic backgrounds. Additionally, PBP2amecA was successfully detected from clinical isolates using a five-minute liquid chromatographic separation and implementation of this MS detection strategy. Our results highlight the capability of direct MS-based resistance marker detection and potential advantages for implementing these approaches in clinical diagnostics.