Broad-spectrum Β-lactams Research Articles

In-vitro activity of newly-developed β-lactamase inhibitors avibactam, relebactam and vaborbactam in combination with anti-pseudomonal β-lactam antibiotics against AmpC-overproducing clinical Pseudomonas aeruginosa isolates.

Overproduction of the intrinsic chromosomally-encoded AmpC β-lactamase is one of the main mechanisms responsible for broad-spectrum β-lactam resistance in Pseudomonas aeruginosa. Our study aimed to evaluate the in-vitro activity of anti-pseudomonal β-lactam molecules associated with the recently-developed and commercially-available β-lactamase inhibitors, namely avibactam, relebactam and vaborbactam, against P. aeruginosa isolates overproducing their AmpC. MIC values of ceftazidime, cefepime, meropenem, imipenem and ceftolozane with or without β-lactam inhibitor were determined for 50 AmpC-overproducing P. aeruginosa clinical isolates. MIC breakpoints for resistance were retained at 8mg/L for β-lactams and β-lactam/β-lactamase inhibitor combinations containing ceftazidime, cefepime and meropenem, while 4mg/L was used for those containing imipenem and ceftolozane. The concentration of all β-lactamases inhibitors was fixed at 4mg/L, except for vaborbactam (8mg/L). The rates of isolates not being resistant to ceftazidime, cefepime, meropenem, imipenem and ceftolozane were found at 12%, 22%, 34%, 8% and 74%, respectively. When combined with avibactam, those rates increased to 60%, 62%, 60%, 46%, and 80%, respectively. The highest rates were found with relebactam-based combinations, being 76%, 64%, 66%, 76% and 84%, respectively. By contrast, associations with vaborbactam did not lead to significantly increased "non-resistance" rates. Our results showed that all combinations including relebactam led to higher "non-resistance" rates against AmpC-overproducing P. aeruginosa clinical isolates. The best activity was achieved by combining ceftolozane and relebactam, that might therefore be considered as an excellent clinical alternative against AmpC overproducers.

Development of prediction models for carbapenem-resistant Klebsiella pneumoniae acquisition and prognosis in adult patients.

To explore the risk factors and clinical outcomes of carbapenem-resistant Klebsiella pneumoniae (CRKP) infection and establish nomograms to predict the probability of CRKP infection and mortality in adult patients. Patients infected with KP from August 2019 to April 2021 in a tertiary hospital in Shanghai were enrolled. Risk factors associated with CRKP and 30-day mortality were identified using multivariate logistic regression analysis and Cox regression analysis. Overall, 467 patients with KP infection were enrolled, wherein 210 (45.0%) patients were infected with CRKP and 257 (55.0%) patients with carbapenem-susceptible K. pneumoniae (CSKP). Five factors, namely Charlson's Comorbidity Index (CCI) ≥ 3, the use of central venous catheterization, prior hospitalization during the 3months before infection, and previous exposure to carbapenems and broad-spectrum β-lactams, were found to be independently associated with CRKP infection. Based on these parameters, the nomogram showed a better performance as indicated by C-index of 0.94 (95% confidence interval [CI]: 0.92-0.96) and well-fitted calibration curves. CRKP was independently associated with 30-day mortality. Multivariate Cox regression analysis revealed that age ≥65years, higher CCI scores, higher Sequential Organ Failure Assessment scores, the presence of respiratory failure, albumin levels ≤30g/L, and non-appropriate treatments in 3days, were associated with 30-day mortality. The predictive nomogram established in this study can facilitate the clinicians to make better clinical decisions when treating patients with KP infection.

Repurposing of Oxicam Derivatives to Inhibit NDM-1: Molecular Docking and Molecular Dynamic Simulation Studies

The New Delhi Metallo-β-lactamase-1 (NDM-1) causes hydrolysis of broad spectrum β-lactam antibiotics, such as carbapenems, resulting in the development of antimicrobial resistance. Still, there are not any approved NDM-1 inhibitors, globally. Therefore, repositioning approved medicines as NDM-1 inhibitors to combine with carbapenems may be a crucial strategy to combat resistant pathogens. This study repurposes. Oxicam derivatives as inhibitors of bacterial NDM-1. The two-dimensional structures were obtained from the PubChem database. Twenty derivatives of oxicam were assessed computationally to realize their NDM-1 inhibition capability. To identify potential inhibitors of the NDM-1 target protein, a molecular docking protocol was used. In addition, drug-likeness and pharmacokinetic properties were predicted for the designed molecules. Three compounds with the most negative ΔGbinding results were chosen for additional study using molecular dynamic (MD) simulations. The compounds M010, M013, and M016 possessed a significantly more negative binding free energy than the positive control and other designed molecules, had stable MD simulations (Root-mean-square deviation < 0.5 Å), passed Lipinski's rule of five, and possessed favourable physicochemical and pharmacokinetic properties. The findings can inform In vitro studies of the promising compounds.

Convergence of mcr-1 and broad-spectrum β-lactamase genes in Escherichia coli strains from the environmental sector

The mcr-type gene encodes the main plasmid-mediated mechanism of colistin resistance and has been reported in several bacterial species obtained from different sources. Anthropogenic activities in the environment favor the evolution of antimicrobial resistance. Indeed, mcr-1-positive Escherichia coli strains were susceptible to non-polymyxins antimicrobials, but now emerging as multidrug-resistant (MDR) lineages. In this regard, hundreds of surface water and agricultural soil samples were screened for the presence of E. coli carrying the mcr-type genes and mcr-1-positive strains were subjected to in-depth genomic analysis. Almost all colistin-resistant strains were classified as MDR, highlighting those obtained from soils that showed resistance to extended-spectrum cephalosporins and carbapenems. International and high-risk clones of E. coli were identified, with ST10 and ST1720 shared between water and soil samples. Resistome analysis showed a broad resistome (AMR, metal tolerance, and biocide resistance). The mcr-1.1 and mcr-1.26 allelic variants were detected on IncX4 and IncI2 plasmids. Curiously, mcr-1-positive E. coli strains from agricultural soils harbored plasmid-mediated blaCTX-M-1, blaCTX-M-8, or blaKPC-2 genes. Virulome analysis demonstrated traits of a high putative virulence potential, with the presence of extraintestinal pathogenic E. coli. Comparative analysis revealed the persistence and dissemination of plasmid-mediated antimicrobial resistance genes in genetically diversity E. coli strains at the human-animal-environmental interface. These findings demonstrate a possible emerging AMR trend with the convergence of resistance to colistin and broad-spectrum β-lactams in environmental-derived E. coli strains.

Triggered Release of Ampicillin from Metallic Implant Coatings for Combating Periprosthetic Infections.

Periprosthetic infections caused by Staphylococcus aureus (S. aureus) pose unique challenges in orthopedic surgeries, in part due to the bacterium's capacity to invade surrounding bone tissues besides forming recalcitrant biofilms on implant surfaces. We previously developed prophylactic implant coatings for the on-demand release of vancomycin, triggered by the cleavage of an oligonucleotide (Oligo) linker by micrococcal nuclease (MN) secreted by the Gram-positive bacterium, to eradicate S. aureus surrounding the implant in vitro and in vivo. Building upon this coating platform, here we explore the feasibility of extending the on-demand release to ampicillin, a broad-spectrum aminopenicillin β-lactam antibiotic that is more effective than vancomycin in killing Gram-negative bacteria that may accompany S. aureus infections. The amino group of ampicillin was successfully conjugated to the carboxyl end of an MN-sensitive Oligo covalently integrated in a polymethacrylate hydrogel coating applied to titanium alloy pins. The resultant Oligo-Ampicillin hydrogel coating released the β-lactam in the presence of S. aureus and successfully cleared nearby S. aureus in vitro. When the Oligo-Ampicillin-coated pin was delivered to a rat femoral canal inoculated with 1000 cfu S. aureus, it prevented periprosthetic infection with timely on-demand drug release. The clearance of the bacteria from the pin surface as well as surrounding tissue persisted over 3 months, with no local or systemic toxicity observed with the coating. The negatively charged Oligo fragment attached to ampicillin upon cleavage from the coating did diminish the antibiotic's potency against S. aureus and Escherichia coli (E. coli) to varying degrees, likely due to electrostatic repulsion by the anionic surfaces of the bacteria. Although the on-demand release of the β-lactam led to adequate killing of S. aureus but not E. coli in the presence of a mixture of the bacteria, strong inhibition of the colonization of the remaining E. coli on hydrogel coating was observed. These findings will inspire considerations of alternative broad-spectrum antibiotics, optimized drug conjugation, and Oligo linker engineering for more effective protection against polymicrobial periprosthetic infections.

The Spx stress regulator confers high-level β-lactam resistance and decreases susceptibility to last-line antibiotics in methicillin-resistant Staphylococcus aureus.

Infections caused by methicillin-resistant Staphylococcus aureus (MRSA) are a leading cause of mortality worldwide. MRSA has acquired resistance to next-generation β-lactam antibiotics through the horizontal acquisition of the mecA resistance gene. Development of high resistance is, however, often associated with additional mutations in a set of chromosomal core genes, known as potentiators, which, through poorly described mechanisms, enhance resistance. The yjbH gene was recently identified as a hot spot for adaptive mutations during severe infections. Here, we show that inactivation of yjbH increased β-lactam MICs up to 16-fold and transformed MRSA cells with low levels of resistance to being homogenously highly resistant to β-lactams. The yjbH gene encodes an adaptor protein that targets the transcriptional stress regulator Spx for degradation by the ClpXP protease. Using CRISPR interference (CRISPRi) to knock down spx transcription, we unambiguously linked hyper-resistance to the accumulation of Spx. Spx was previously proposed to be essential; however, our data suggest that Spx is dispensable for growth at 37°C but becomes essential in the presence of antibiotics with various targets. On the other hand, high Spx levels bypassed the role of PBP4 in β-lactam resistance and broadly decreased MRSA susceptibility to compounds targeting the cell wall or the cell membrane, including vancomycin, daptomycin, and nisin. Strikingly, Spx potentiated resistance independently of its redox-sensing switch. Collectively, our study identifies a general stress pathway that, in addition to promoting the development of high-level, broad-spectrum β-lactam resistance, also decreases MRSA susceptibility to critical antibiotics of last resort.

Altered PBP4 and GdpP functions synergistically mediate MRSA-like high-level, broad-spectrum β-lactam resistance in Staphylococcus aureus.

In Staphylococcus aureus, high-level, broad-spectrum resistance to β-lactams such as methicillin, also referred to as methicillin resistance, is largely attributed to mecA. This study demonstrates that S. aureus strains that lack mecA but contain mutations that functionally alter PBP4 and GdpP can also mediate high-level, broad-spectrum resistance to β-lactams. Resistance brought about by the synergistic action of functionally altered PBP4 and GdpP was phenotypically comparable to that displayed by mecA, as seen by increased bacterial survival in the presence of β-lactams. An analysis of mutations detected in naturally isolated strains of S. aureus revealed that a significant proportion of them had similar pbp4 and GGDEF domain protein containing phosphodiesterase (gdpP) mutations, making this study clinically significant. This study not only identifies important players of non-classical mechanisms of β-lactam resistance but also indicates reconsideration of current clinical diagnosis and treatment protocols of S. aureus infections.

(p)ppGpp modifies RNAP function to confer β-lactam resistance in a peptidoglycan-independent manner.

(p)ppGpp is a nucleotide alarmone that controls bacterial response to nutrient deprivation. Since elevated (p)ppGpp levels confer mecillinam resistance and are essential for broad-spectrum β-lactam resistance as mediated by the β-lactam-insensitive transpeptidase YcbB (LdtD), we hypothesized that (p)ppGpp might affect cell wall peptidoglycan metabolism. Here we report that (p)ppGpp-dependent β-lactam resistance does not rely on any modification of peptidoglycan metabolism, as established by analysis of Escherichia coli peptidoglycan structure using high-resolution mass spectrometry. Amino acid substitutions in the β or β' RNA polymerase (RNAP) subunits, alone or in combination with the CRISPR interference-mediated downregulation of three of seven ribosomal RNA operons, were sufficient for resistance, although β-lactams have no known impact on the RNAP or ribosomes. This implies that modifications of RNAP and ribosome functions are critical to prevent downstream effects of the inactivation of peptidoglycan transpeptidases by β-lactams.

Stenotrophomonas maltophilia Belonging to Novel Sequence Types ST473 and ST474 in Wild Birds Inhabiting the Brazilian Amazonia.

Stenotrophomonas maltophilia is an opportunistic human pathogen associated with nosocomial and community-acquired infections. We have conducted a microbiological and genomic surveillance study of broad-spectrum cephalosporin- and carbapenem-resistant Gram-negative bacteria colonizing wild birds inhabiting the Brazilian Amazonia. Strikingly, two S. maltophilia strains (SM79 and SM115) were identified in Plain-throated antwren (Isleria hauxwelli) passerines affected by Amazonian fragmentation and degradation. Noteworthy, SM79 and SM115 strains belonged to new sequence types (STs) ST474 and ST473, respectively, displaying resistance to broad-spectrum β-lactams, aminoglycosides and/or fluoroquinolones. In this regard, resistome analysis confirmed efflux pumps (smeABC, smeDEF, emrAB-tolC and macB), blaL1 and blaL2, aph(3')-IIc and aac(6')-Iak, and Smqnr resistance genes. Comparative phylogenomic analysis with publicly available S. maltophilia genomes clustered ST473 and ST474 with human strains, whereas the ST474 was also grouped with S. maltophilia strains isolated from water and poultry samples. In summary, we report two novel sequence types of S. maltophilia colonizing wild Amazonian birds. The presence of opportunistic multidrug-resistant pathogens in wild birds, from remotes areas, could represent an ecological problem since these animals could easily promote long-distance dispersal of medically important antimicrobial-resistant bacteria. Therefore, while our results could provide a baseline for future epidemiological genomic studies, considering the limited information regarding S. maltophilia circulating among wild animals, additional studies are necessary to evaluate the clinical impact and degree of pathogenicity of this human opportunistic pathogen in wild birds.

Variation in antibiotic consumption in very preterm infants-a 10 year population-based study.

Wide variations in antibiotic use in very preterm infants have been reported across centres despite similar rates of infection. We describe 10 year trends in use of antibiotics and regional variations among very preterm infants in Norway. All live-born very preterm infants (<32 weeks gestation) admitted to any neonatal unit in Norway during 2009-18 were included. Main outcomes were antibiotic consumption expressed as days of antibiotic therapy (DOT) per 1000 patient days (PD), regional variations in use across four health regions, rates of sepsis and sepsis-attributable mortality and trends of antibiotic use during the study period. We included 5296 infants: 3646 (69%) were born at 28-31 weeks and 1650 (31%) were born before 28 weeks gestation with similar background characteristics across the four health regions. Overall, 80% of the very preterm infants received antibiotic therapy. The most commonly prescribed antibiotics were the combination of narrow-spectrum β-lactams and aminoglycosides, but between 2009 and 2018 we observed a marked reduction in their use from 100 to 40 DOT per 1000 PD (P < 0.001). In contrast, consumption of broad-spectrum β-lactams remained unchanged (P = 0.308). There were large variations in consumption of vancomycin, broad-spectrum β-lactams and first-generation cephalosporins, but no differences in sepsis-attributable mortality across regions. The overall antibiotic consumption was reduced during the study period. Marked regional variations remained in consumption of broad-spectrum β-lactams and vancomycin, without association to sepsis-attributable mortality. Our results highlight the need for antibiotic stewardship strategies to reduce consumption of antibiotics that may enhance antibiotic resistance development.

Emergence of KPC-113 and KPC-114 variants in ceftazidime-avibactam-resistant Klebsiella pneumoniae belonging to high-risk clones ST11 and ST16 in South America.

Two novel variants of Klebsiella pneumoniae carbapenemase (KPC) associated with resistance to ceftazidime-avibactam (CZA) and designated as KPC-113 and KPC-114 by NCBI were identified in 2020, in clinical isolates of Klebsiella pneumoniae in Brazil. While K. pneumoniae of ST16 harbored the blaKPC-113 variant on an IncFII-IncFIB plasmid, K. pneumoniae of ST11 carried the blaKPC-114 variant on an IncN plasmid. Both isolates displayed resistance to broad-spectrum cephalosporins, β-lactam inhibitors, and ertapenem and doripenem, whereas K. pneumoniae producing KPC-114 showed susceptibility to imipenem and meropenem. Whole-genome sequencing and in silico analysis revealed that KPC-113 presented a Gly insertion between Ambler positions 264 and 265 (R264_A265insG), whereas KPC-114 displayed two amino acid insertions (Ser-Ser) between Ambler positions 181 and 182 (S181_P182insSS) in KPC-2, responsible for CZA resistance profiles. Our results confirm the emergence of novel KPC variants associated with resistance to CZA in international clones of K. pneumoniae circulating in South America. IMPORTANCE KPC-2 carbapenemases are endemic in Latin America. In this regard, in 2018, ceftazidime-avibactam (CZA) was authorized for clinical use in Brazil due to its significant activity against KPC-2 producers. In recent years, reports of resistance to CZA have increased in this country, limiting its clinical application. In this study, we report the emergence of two novel KPC-2 variants, named KPC-113 and KPC-114, associated with CZA resistance in Klebsiella pneumoniae strains belonging to high-risk clones ST11 and ST16. Our finding suggests that novel mutations in KPC-2 are increasing in South America, which is a critical issue deserving active surveillance.

Antibiotic Consumption During the Coronavirus Disease 2019 Pandemic and Emergence of Carbapenemase-Producing Klebsiella pneumoniae Lineages Among Inpatients in a Chilean Hospital: A Time-Series Study and Phylogenomic Analysis.

The impact of coronavirus disease 2019 (COVID-19) on antimicrobial use (AU) and resistance has not been well evaluated in South America. These data are critical to inform national policies and clinical care. At a tertiary hospital in Santiago, Chile, between 2018 and 2022, subdivided into pre- (3/2018-2/2020) and post-COVID-19 onset (3/2020-2/2022), we evaluated intravenous AU and frequency of carbapenem-resistant Enterobacterales (CRE). We grouped monthly AU (defined daily doses [DDD]/1000 patient-days) into broad-spectrum β-lactams, carbapenems, and colistin and used interrupted time-series analysis to compare AU during pre- and post-pandemic onset. We studied the frequency of carbapenemase-producing (CP) CRE and performed whole-genome sequencing analyses of all carbapenem-resistant (CR) Klebsiella pneumoniae (CRKpn) isolates collected during the study period. Compared with pre-pandemic, AU (DDD/1000 patient-days) significantly increased after the pandemic onset, from 78.1 to 142.5 (P < .001), 50.9 to 110.1 (P < .001), and 4.1 to 13.3 (P < .001) for broad-spectrum β-lactams, carbapenems, and colistin, respectively. The frequency of CP-CRE increased from 12.8% pre-COVID-19 to 51.9% after pandemic onset (P < .001). The most frequent CRE species in both periods was CRKpn (79.5% and 76.5%, respectively). The expansion of CP-CRE harboring blaNDM was particularly noticeable, increasing from 40% (n = 4/10) before to 73.6% (n = 39/53) after pandemic onset (P < .001). Our phylogenomic analyses revealed the emergence of two distinct genomic lineages of CP-CRKpn: ST45, harboring blaNDM, and ST1161, which carried blaKPC. AU and the frequency of CP-CRE increased after COVID-19 onset. The increase in CP-CRKpn was driven by the emergence of novel genomic lineages. Our observations highlight the need to strengthen infection prevention and control and antimicrobial stewardship efforts.

Cyanobacteria as a critical reservoir of the environmental antimicrobial resistome.

Antimicrobial resistance (AMR) is predicted to cause a worldwide annual toll of 10 million deaths by 2050. This looming public health threat has been linked to antibiotic overuse and pollution, which places selective pressures on AMR maintenance and transfer in and between microbial populations. We examined the distribution, diversity and potential mobility of AMR genes in cyanobacteria. While cyanobacteria are not pathogenic, we hypothesised that they could be a major environmental reservoir for AMR genes. Genes encoding AMR to seven antimicrobial drug classes were found in 10% of cyanobacterial genomes. AMR genes were found in 13% of freshwater, 19% of terrestrial, 34% of symbiotic, 2% of thermal spring, and 3% of marine genomes. AMR genes were found in five cyanobacterial orders with 23% of Nostocales and 8% of Oscillatoriales strains containing AMR genes. The most frequently observed alleles were ansamycin resistance genes, which were present in 7% of strains. AMR genes responsible for resistance to broad-spectrum β-lactams, chloramphenicols, tetracyclines, macrolides, and aminoglycosides were associated with mobile genetic elements or plasmid replicons or both. These results suggest that cyanobacteria are an extensive reservoir, and potential vector, for AMR genes in diverse terrestrial and aquatic habitats.

A computational odyssey: uncovering classical β-lactamase inhibitors in dry fruits

In the antibacterial arsenal, β-lactams have held a prominent position, but increasing resistance due to unauthorized use and genetic factors requires new strategies. Combining β-lactamase inhibitors with broad-spectrum β-lactams proves effective in combating this resistance. ESBL producers demand new inhibitors, leading to the exploration of plant-derived secondary metabolites for potent β-lactam antibiotics or alternative inhibitors. Using virtual screening, molecular docking, ADMET analysis, and molecular dynamic simulation, this study actively analyzed the inhibitory activity of figs, cashews, walnuts, and peanuts against SHV-1, NDM-1, KPC-2, and OXA-48 β-lactamases. Using AutoDock Vina, the docking affinities of various compounds for target enzymes were initially screened, revealing 12 bioactive compounds with higher affinities for the target enzymes compared to Avibactam and Tazobactam. Top-scoring metabolites, including Oleanolic acid, Protocatechuic acid, and Tannin, were subjected to MD simulation studies to further analyze the stability of the docked complexes using WebGro. The simulation coordinates, in terms of RMSD, RMSF, SASA, Rg, and hydrogen bonds formed, showed that these phytocompounds are stable enough to retain in the active sites at various orientations. The PCA and FEL analysis also showed the stability of the dynamic motion of Cα residues of phytochemical-bound enzymes. The pharmacokinetic analysis of the top phytochemicals was performed to analyze their bioavailability and toxicity. This study provides new insights into the therapeutic potential of phytochemicals of selected dry fruits and contributes to future experimental studies to identify βL inhibitors from plants. Communicated by Ramaswamy H. Sarma

Description of Antimicrobial-Resistant Escherichia coli and Their Dissemination Mechanisms on Dairy Farms.

Despite its importance in veterinary medicine, there is little information about antimicrobial resistance (AMR) and its transmission in dairy cattle. The aim of this work is to compare AMR phenotypes and genotypes in resistant Escherichia coli and to determine how the resistance genes spread among the E. coli population on dairy farms in Québec, Canada. From an existing culture collection of E. coli isolated from dairy manure, a convenient selection of the most resistant isolates (a high level of multidrug resistance or resistance to broad-spectrum β-lactams or fluoroquinolones) was analyzed (n = 118). An AMR phenotype profile was obtained for each isolate. Whole genome sequencing was used to determine the presence of resistance genes, point mutations, and mobile genetic elements. In addition, a subset of isolates from 86 farms was taken to investigate the phylogenetic relationship and geographic distribution of the isolates. The average agreement between AMR phenotypes and genotypes was 95%. A third-generation cephalosporin resistance gene (blaCTX-M-15), a resistance gene conferring reduced susceptibility to fluoroquinolones (qnrS1), and an insertion sequence (ISKpn19) were detected in the vicinity of each other on the genome. These genes were harbored in one triplet of clonal isolates from three farms located >100 km apart. Our study reveals the dissemination of resistant E. coli clones between dairy farms. Furthermore, these clones are resistant to broad-spectrum β-lactam and fluoroquinolone antimicrobials.

1714. In Vitro Activity of Tebipenem Against Clinically Significant Gram-Positive Bacteria Isolated from Patients with Cancer

Abstract Background Carbapenems represent the most potent and broad-spectrum β-lactams and are minimally affected by most β-lactamase enzymes. however, all carbapenems currently in use including meropenem and ertapenem, are parenterally administered. Tebipenem pivoxil (TBPM-PI-HBr) is a new broad-spectrum orally-administered antibiotic, from the carbapenem subgroup of β-lactam antibiotics. It is the only oral carbapenem and could be an alternative to intravenous injection carbapenem antibiotic therapy. This study aimed to evaluate the in vitro activity of tebipenem, a novel oral carbapenem, against recent gram-positive clinical isolates from cancer patients. Methods We tested 300 gram-positive isolates are recently isolated (2019-2021) from our cancer patients, collected from blood cultures against tebipenem and comparators. Clinical and laboratory Standards Instituted (CLSI) approved broth microdilution method was used with appropriate ATCC controls. MIC50, MIC90, MIC ranges and percent of susceptibility calculations were made using FDA breakpoints when available. There is no tebipenem susceptibility breakpoint for gram-positive isolates currently. MIC90 and MICs range of tebipenem and comparators against 300 gram-positive isolates from cancer patients Results MIC90 and range of tebipenem and comparators are shown in table(1). Tebipenem gave the lowest MIC90 and MIC ranges against most gram-positive isolates including Bacillus species, Corynebacterium species, Enterococcus faecalis, Micrococcus species, MSSA S.aureus, Staphylococcus lugdunensis. β-hemolytic Streptococcus, Streptococcus pneumonie, Viridans group streptococci, and Rothia species. The comparative potency of tebipenem vs meropenem as a carbapenem in this study showed that, tebipenem MIC values were generally lower at least 2-4 fold. Conclusion Our data demonstrate that oral tebipenem has promising activity against clinically significant bacterial pathogens isolated from cancer patients and it has compatible activity to that of meropenem as a carbapenem in this study. Further clinical evolution for oral carbapenem treatment of bacterial infections is warranted. Disclosures All Authors: No reported disclosures.

When and How to Use MIC in Clinical Practice?

Bacterial resistance to antibiotics continues to be a global public health problem. The choice of the most effective antibiotic and the use of an adapted dose in the initial phase of the infection are essential to limit the emergence of resistance. This will depend on (i) the isolated bacteria and its resistance profile, (ii) the pharmacodynamic (PD) profile of the antibiotic used and its level of toxicity, (iii) the site of infection, and (iv) the pharmacokinetic (PK) profile of the patient. In order to take account of both parameters to optimize the administered treatment, a minimal inhibitory concentration (MIC) determination associated with therapeutic drug monitoring (TDM) and their combined interpretation are required. The objective of this narrative review is thus to suggest microbiological, pharmacological, and/or clinical situations for which this approach could be useful. Regarding the microbiological aspect, such as the detection of antibiotic resistance and its level, the preservation of broad-spectrum β-lactams is particularly discussed. PK-PD profiles are relevant for difficult-to-reach infections and specific populations such as intensive care patients, cystic fibrosis patients, obese, or elderly patients. Finally, MIC and TDM are tools available to clinicians, who should not hesitate to use them to manage their patients.

Computational modelling of potential Zn-sensitive non-β-lactam inhibitors of imipenemase-1 (IMP-1)

Antibiotic resistance (AR) remains one of the leading global health challenges, mostly implicated in disease-related deaths. The Enterobacteriaceae-producing metallo-β-lactamases (MBLs) are critically involved in AR pathogenesis through Zn-dependent catalytic destruction of β-lactam antibiotics, yet with limited successful clinical inhibitors. The efficacy of relevant broad-spectrum β-lactams including imipenem and meropenem are seriously challenged by their susceptibility to the Zn-dependent carbapenemase hydrolysis, as such, searching for alternatives remains imperative. In this study, computational molecular modelling and virtual screening methods were extensively applied to identify new putative Zn-sensitive broad-spectrum inhibitors of MBLs, specifically imipenemase-1 (IMP-1) from the IBScreen database. Three ligands, STOCK3S-30154, STOCK3S-30418 and STOCK3S-30514 selectively displayed stronger binding interactions with the enzymes compared to reference inhibitors, imipenem and meropenem. For instance, the ligands showed molecular docking scores of −9.450, −8.005 and −10.159 kcal/mol, and MM-GBSA values of −40.404, −31.902 and −33.680 kcal/mol respectively against the IMP-1. Whereas, imipenem and meropenem showed docking scores of −9.038 and −10.875 kcal/mol, and MM-GBSA of −31.184 and −32.330 kcal/mol respectively against the enzyme. The ligands demonstrated good thermodynamic stability and compactness in complexes with IMP-1 throughout the 100 ns molecular dynamics (MD) trajectories. Interestingly, their binding affinities and stabilities were significantly affected in contacts with the remodelled Zn-deficient IMP-1, indicating sensitivity to the carbapenemase active Zn site, however, with non-β-lactam scaffolds, tenable to resist catalytic hydrolysis. They displayed ideal drug-like ADMET properties, thus, representing putative Zn-sensitive non-β-lactam inhibitors of IMP-1 amenable for further experimental studies.

Impact of Antibiotic Use for Febrile Neutropenia on Gut Microbiome Phyla in Children with Leukemia and Lymphoma

Introduction: Approximately 40% of children with leukemia/lymphoma experience one or more episodes of febrile neutropenia. These episodes are treated with empiric intravenous antibiotics that include broad spectrum β-lactams and vancomycin. Although studies suggest antibiotics change the gut microbiome, the effect is unclear. This study reports the impact of repeated courses and duration of antibiotic use on microbiome. Methods: We examined 39 pediatric patients diagnosed and treated at the IWK Health Centre, Nova Scotia Canada for acute lymphoblastic leukemia (28), acute myeloid leukemia (5), non-Hodgkin lymphoma (4) or Hodgkin lymphoma (2) after informed consent. DNA was extracted from 127 stool samples from timepoints before and during treatment were used for whole shotgun sequencing (Nextera XT). Sequences were cleaned of low quality, and human, and PhiX174 contaminate sequences (kneaddata pipeline). MetaPhlAn3 was used to profile the taxonomic composition of the microbial community. Samples were grouped by number of courses, none, 1-2, or ≥3, and by duration of courses, none, short (≤10 days), long/mixed (>10 days or mix of long and short) of β-lactams, vancomycin, or general antibiotic use. The abundance of phyla within these groups were compared using the Kruskal Wallis test (α<0.05) and post hoc Dunn test for pairwise comparison, corrected for multiple tests. This study was approved by the IWK ethics board. Results: The 39 patients include 22 males and 17 females, with 29 patients over the age of 3 and 10 patients under 3. Bacteroidetes phylum abundant in the gut were decreased when exposed to repeated courses of all antibiotic groups with none vs ≥3 courses (β-lactam p=0.0012; vancomycin p=0.0018; multiple antibiotic p=0.0021) and 1-2 courses vs ≥3 courses (β-lactam p=3.1E-6; vancomycin p=0.024; multiple antibiotic p=1.6E-8). We also noted an increase in Firmicutes in the children who received 1-2 courses vs ≥3 courses of β-lactam antibiotics (p=0.034). The phylum Proteobacteria was increased across those children who received 1-2 courses vs ≥3 courses (β-lactam p=8.1E-6; vancomycin p=0.0018; multiple antibiotic p=1.6E-5) and also increased in none vs ≥3 courses for vancomycin (p=3.8E-4). We noted differences in abundance based on duration of antibiotic treatment. For Bacteroidetes the abundance is higher in children who receive short course antibiotics vs those that receive longer course (>10 days) for β-lactam and multiple antibiotic (p=1.3E-6 and p=4.4E-7 respectively) and lower in children who receive short course vancomycin vs longer course (p=0.024). The Proteobacteria in the samples of children treated with β-lactam and multiple antibiotics showed higher abundance in those who received longer duration antibiotics (p=2.7E-5 and p=8.7E-6 respectively) whereas the children who received short courses of vancomycin showed higher counts (p=0.0018). No difference in Firmicute abundance was detected. Discussion: Concordant with the spectrum of β-lactam antibiotics, we saw a decrease in abundance of Bacteroidetes a predominately gram-negative gut bacterium. In contrast the Proteobacteria, a gram-negative phylum, was increased in children exposed to repeated courses of antibiotics. When we consider duration of antibiotic treatment, we see that the Bacteroidetes have higher prevalence in children who do not receive antibiotics or receive shorter course antibiotics indicating that this phylum is controlled by antibiotic treatment. In contrast, the Proteobacteria are more prevalent in children who receive longer duration of β-lactam. One limitation of this study was non-uniformity of stool sample collection due to logistical reasons in pediatric population. Conclusion: Repeated courses of antibiotics administered empirically to pediatric cancer patients with leukemia/lymphoma increases the relative abundance of certain gram-negative bacteria in the microbiome. Longer courses of the β-lactams and multi-antibiotic samples result in higher relative abundance of Proteobacteria potentially increasing infections in immunocompromised children. Further studies to determine optimum antibiotic duration and therapy are needed.

Enhancing antimicrobial activity of β-lactam antibiotic via functionalized mesoporous carbon-based delivery platforms

Bacterial immunity to antibiotics is currently increasing as a result of inadequate drug use and the generation of antimicrobial resistance. Developing new antibiotics is challenging, hence suitable carriers are sought to enhance activity of already known drugs. The ordered mesoporous carbons modified with urea, thiourea, and cetyltrimethylammonium bromide (CTAB), presented in this study, show great potential as carrier platforms for tebipenem pivoxil - a broad-spectrum orally-administered β-lactam antibiotic. The functional groups generated on the surface of carbon materials contributed to the reduction of their negative surface charge, which turned into positive under low pH conditions. At the same time, they led to a decrease in the hexagonal structure ordering of the carbon samples and a deterioration of the textural parameters. The effect of the amount of modifier used on the ability of carbon materials to release the selected antibiotic was investigated. The drug release process was carried out in two different environments (neutral and strongly acidic). It has been shown that the presence of functional groups on the surface of carbon carriers determines the amount of antibiotic liberated, especially at pH 7.0. The antimicrobial activity of the tebipenem pivoxil-loaded into the carbon carriers was assessed on a group of gram-positive and gram-negative bacteria. The highest decrease in the minimal inhibitory concentration value for the CTAB-modified systems was demonstrated, indicating a better antimicrobial efficiency against pathogenic strains coupled with an improvement in tebipenem pivoxil solubility. Small and negatively charged worm-like particles of the surfactant-functionalized carbon carrier are characterized by better dispersion in the receptor fluid resulting in faster and more effective diffusion of the antibiotic molecules from their outer surface. Ordered mesoporous carbons in addition to increased antibiotic dissolution rate, have no impact on drug permeability in the gastrointestinal tract in the in vitro model.