In vitro functional analysis and in silico structural modelling of pathogen-secreted polyglycine hydrolases

Polyglycine hydrolases are fungal effectors composed of an N-domain with unique sequence and structure and a C-domain that resembles β-lactamases, with serine protease activity. These secreted fungal proteins cleave Gly-Gly bonds within a polyglycine sequence in corn ChitA chitinase. The polyglycine hydrolase N-domain (PND) function is unknown. In this manuscript we provide evidence that the PND does not directly participate in ChitA cleavage. In vitro analysis of site-directed mutants in conserved residues of the PND of polyglycine hydrolase Es-cmp did not specifically impair protease activity. Furthermore, in silico structural models of three ChitA-bound polyglycine hydrolases created by High Ambiguity Driven protein-protein DOCKing (HADDOCK) did not predict significant interactions between the PND and ChitA. Together these results suggest that the PND has another function. To determine what types of PND-containing proteins exist in nature we performed a computational analysis of Foldseek-identified PND-containing proteins. The analysis showed that proteins with PNDs are present throughout biology as either single domain proteins or fused to accessory domains that are diverse but are usually proteases or kinases.

Culture-free detection of β-lactamase-Producing bacteria in urinary tract infections using a paper sensor

Developing simple, inexpensive, fast, sensitive, and specific probes for antibiotic-resistant bacteria is crucial for the management of urinary tract infections (UTIs). We here propose a paper-based sensor for the rapid detection of β-lactamase-producing bacteria in the urine samples of UTI patients. By conjugating a strongly electronegative group -N+(CH3)3 with the core structures of cephalosporin and carbapenem antibiotics, two visual probes were achieved to respectively target the extended-spectrum/AmpC β-lactamases (ESBL/AmpC) and carbapenemase, the two most prevalent factors causing antibiotic resistance. By integrating these probes into a portable paper sensor, we confirmed 10 and 8 cases out of 30 clinical urine samples as ESBL/AmpC- and carbapenemase-positive, respectively, demonstrating 100% clinical sensitivity and specificity. This paper sensor can be easily conducted on-site, without resorting to bacterial culture, providing a solution to the challenge of rapid detection of β-lactamase-producing bacteria, particularly in resource-limited settings.

In vitro activity of cefiderocol against European Pseudomonas aeruginosa and Acinetobacter spp., including isolates resistant to meropenem and recent β-lactam/β-lactamase inhibitor combinations

Carbapenem-resistant Pseudomonas aeruginosa and Acinetobacter spp. represent major threats and have few approved therapeutic options. Non-‍fermenting Gram-negative isolates were collected from hospitalized inpatients from 49 sites in 6 European countries between 01 January 2020 and 31 December 2020 and underwent susceptibility testing against cefiderocol and β-lactam/β-lactamase inhibitor combinations. Meropenem-resistant (MIC >8 mg/L), cefiderocol-susceptible isolates were analyzed by PCR, and cefiderocol-resistant isolates were analyzed by whole-genome sequencing to identify resistance mechanisms. Overall, 1,451 (950 P. aeruginosa; 501 Acinetobacter spp.) isolates were collected, commonly from the respiratory tract (42.0% and 39.3%, respectively). Cefiderocol susceptibility was higher than ‍β‍-‍l‍a‍c‍t‍a‍m‍/‍β‍-‍l‍a‍c‍t‍a‍mase‍ inhibitor combinations against P. aeruginosa (98.9% vs 83.3%-91.4%), and P. ‍aeruginosa resistant to meropenem (n = 139; 97.8% vs 12.2%-59.7%), β-lactam/β-lactamase inhibitor combinations (93.6%-98.1% vs 10.7%-71.8%), and both meropenem and ceftazidime-avibactam (96.7% vs 5.0%-‍‍45.0%) or ‍ceftolozane-tazobactam (98.4% vs 8.1%-54.8%), respectively. Cefiderocol and sulbactam-durlobactam susceptibilities were high against Acinetobacter spp. (92.4% and 97.0%) and meropenem-resistant Acineto‍bacter ‍spp. (n = 227; 85.0% and 93.8%) but lower against sulbactam-durlobactam- (n ‍= 15; 13.3%) and cefiderocol- (n = 38; 65.8%) resistant isolates, respectively. Among meropenem-resistant P. aeruginosa and Acinetobacter spp., the most common β-‍‍lactamase genes were metallo-β-lactamases [30/139; blaVIM-2 (15/139)] and oxacillinases [215/227; blaOXA-23 (194/227)], respectively. Acquired β-lactamase genes were identified in 1/10 and 32/38 of cefiderocol-resistant P. aeruginosa and Acinetobacter spp., and pirA-like or piuA mutations in 10/10 and 37/38, respectively. Conclusion: cefiderocol susceptibility was high against P. aeruginosa and Acinetobacter spp., including meropenem-resistant isolates and those resistant to recent β-lactam/β-lactamase inhibitor combinations common in first-line treatment of European non-fermenters.

IMPORTANCE

This was the first study in which the in vitro activity of cefiderocol and non-licensed β-lactam/β-lactamase inhibitor combinations were directly compared against Pseudomonas aeruginosa and Acinetobacter spp., including meropenem- and β-lactam/β-lactamase inhibitor combination-resistant isolates. A notably large number of European isolates were collected. Meropenem resistance was defined according to the MIC breakpoint for high-dose meropenem, ensuring that data reflect antibiotic activity against isolates that would remain meropenem resistant in the clinic. Cefiderocol susceptibility was high against non-fermenters, and there was no apparent cross resistance between cefiderocol and β-lactam/β-lactamase inhibitor combinations, with the exception of sulbactam-durlobactam. These results provide insights into therapeutic options for infections due to resistant P. aeruginosa and Acinetobacter spp. and indicate how early susceptibility testing of cefiderocol in parallel with β-lactam/β-lactamase inhibitor combinations will allow clinicians to choose the effective treatment(s) from all available options. This is particularly important as current treatment options against non-fermenters are limited.

Activity of cefiderocol and innovative β-lactam/β-lactamase inhibitor combinations against isogenic strains of Escherichia coli expressing single and double β-lactamases under high and low permeability conditions

OBJECTIVES

To analyse the impact of the most clinically relevant β-lactamases and their interplay with low outer membrane permeability on the activity of cefiderocol, ceftazidime/avibactam, aztreonam/avibactam, cefepime/enmetazobactam, cefepime/taniborbactam, cefepime/zidebactam, imipenem/relebactam, meropenem/vaborbactam, meropenem/xeruborbactam and meropenem/nacubactam against recombinant Escherichia coli strains.

METHODS

We constructed 82 E. coli laboratory transformants expressing the main β-lactamases circulating in Enterobacterales (70 expressing single β-lactamase and 12 producing double carbapenemase) under high (E. coli TG1) and low (E. coli HB4) permeability conditions. Antimicrobial susceptibility testing was determined by reference broth microdilution.

RESULTS

Aztreonam/avibactam, cefepime/zidebactam, cefiderocol, meropenem/xeruborbactam and meropenem/nacubactam were active against all E. coli TG1 transformants. Imipenem/relebactam, meropenem/vaborbactam, cefepime/taniborbactam and cefepime/enmetazobactam were also highly active, but unstable against most of MBL-producing transformants. Combination of β-lactamases with porin deficiency (E. coli HB4) did not significantly affect the activity of aztreonam/avibactam, cefepime/zidebactam, cefiderocol or meropenem/nacubactam, but limited the effectiveness of the rest of carbapenem- and cefepime-based combinations. Double-carbapenemase production resulted in the loss of activity of most of the compounds tested, an effect particularly evident for those E. coli HB4 transformants in which MBLs were present.

CONCLUSIONS

Our findings highlight the promising activity that cefiderocol and new β-lactam/β-lactamase inhibitors have against recombinant E. coli strains expressing widespread β-lactamases, including when these are combined with low permeability or other enzymes. Aztreonam/avibactam, cefiderocol, cefepime/zidebactam and meropenem/nacubactam will help to mitigate to some extent the urgency of new compounds able to resist MBL action, although NDM enzymes represent a growing challenge against which drug development efforts are still needed.

Quantification of β-lactamase producing bacteria in German surface waters with subsequent MALDI-TOF MS-based identification and β-lactamase activity assay

Environmental oligotrophic bacteria are suspected to be highly relevant carriers of antimicrobial resistance (AMR). However, there is a lack of validated methods for monitoring in the aquatic environment. Since extended-spectrum β-lactamases (ESBLs) play a particularly important role in the clinical sector, a culturing method based on R2A-medium spiked with different combinations of β-lactams was applied to quantify β-lactamase-producing environmental bacteria from surface waters. In German surface water samples (n = 28), oligotrophic bacteria ranging from 4.0 × 103 to 1.7 × 104 CFU per 100 mL were detected on the nutrient-poor medium spiked with 3rd generation cephalosporins and carbapenems. These numbers were 3 log10 higher compared to ESBL-producing Enterobacteriales of clinical relevance from the same water samples. A MALDI-TOF MS identification of the isolates demonstrated, that the method leads to the isolation of environmentally relevant strains with Pseudomonas, Flavobacterium, and Janthinobacterium being predominant β-lactam resistant genera. Subsequent micro-dilution antibiotic susceptibility tests (Micronaut-S test) confirmed the expression of β-lactamases. The qPCR analysis of surface waters DNA extracts showed the presence of β-lactamase genes (blaTEM, blaCMY-2, blaOXA-48, blaVIM-2, blaSHV, and blaNDM-1) at concentrations of 3.7 (±1.2) to 1.0 (±1.9) log10 gene copies per 100 mL. Overall, the results demonstrate a widespread distribution of cephalosporinase and carbapenemase enzymes in oligotrophic environmental bacteria that have to be considered as a reservoir of ARGs and contribute to the spread of antibiotic resistance.

The Biofilm Lifestyle Shapes the Evolution of β-Lactamases

The evolutionary relationship between the biofilm lifestyle and antibiotic resistance enzymes remains a subject of limited understanding. Here, we investigate how β-lactamases affect biofilm formation in Vibrio cholerae and how selection for a biofilm lifestyle impacts the evolution of these enzymes. Genetically diverse β-lactamases expressed in V. cholerae displayed a strong inhibitory effect on biofilm production. To understand how natural evolution affects this antagonistic pleiotropy, we randomly mutagenized a β-lactamase and selected for elevated biofilm formation. Our results revealed that biofilm evolution selects for β-lactamase variants able to hydrolyze β-lactams without inhibiting biofilms. Mutational analysis of evolved variants demonstrated that restoration of biofilm development was achieved either independently of enzymatic function or by actively leveraging enzymatic activity. Taken together, the biofilm lifestyle can impose a profound selective pressure on antimicrobial resistance enzymes. Shedding light on such evolutionary interplays is of importance to understand the factors driving antimicrobial resistance.

Phylogenetic Characterization of Resistant Salmonella Strains in Typhoid Fever Patients in Nigeria

Salmonella species are Enterobacteriaceae associated with typhoid fever. In this study, the distribution of broad-spectrum β-lactamase regulatory genes and genetic relatedness of isolates was determined. Stool samples (400) were collected from patients with fever in Dalhatu Araf Specialist Hospital (DASH), Lafia, Nigeria, between March 2020 and April 2021. Salmonella species were isolated and extended-spectrum β-lactamase distribution was determined among resistant isolates using polymerase chain reaction (PCR). Genetic relatedness of Salmonella species resistant to the 10 first-line antibiotics administered was determined among S typhi isolated. Of the 60 isolates that were confirmed to belong to the genus Salmonella, 12 (20.0%) isolates with bla SHV genes were the most prevalent, blaOXA-1 and blaCTX-M-9 were present in 5 isolates each, while blaCTX-M-4 and blaTEM genes with a prevalence of 1.7% each were the least obtained in the isolates. Two isolates had a multidrug-resistant index (MDRI) of 1, and 2 others were positive with the S typhi staG gene. Sequencing to determine their diversity showed that isolates ST36 and ST138, respectively, had MDRI = 1 and are clustered in a group with a similarity coefficient of 0.00634. The 2 isolates had the highest genetic similarity, which indicates that the genetic diversity between the isolates is low, while Salmonella strain ST313L2 had a high level of genetic distance from the other isolates. The most resistant isolates are closely related which calls for concern.

A computational investigation of galactopyranoside esters as antimicrobial agents through antiviral, molecular docking, molecular dynamics, pharmacokinetics, and bioactivity prediction

One of the most common viral infections worldwide is the Human Papilloma Virus (HPV) which has been linked to cancer and other diseases in many countries. Monosaccharide esters are significant in the field of carbohydrate chemistry because they are efficient in the synthesis of pharmacologically active compounds. Therefore, the present study aimed to perform thermodynamic, molecular docking and molecular dynamics study of a series of previously designed monosaccharaides, methyl β-d-galactopyranoside (MGP, 1) esters (2-10) with along with their physicochemical and pharmacokinetic properties. We have optimized the MGP esters employing the DFT study at the B3LYP/6-311 + G (d,p) level of theory. The subsequent analysis also investigated the electronic energies, enthalpies, entropies, polarizability, and natural bond orbital (NBO) of these modified esters. Then, MGP esters were docked into CTX-M-15 extended-spectrum beta-lactamase from Escherichia coli (PDB: 4HBT) and E2 DNA-binding domain from human papillomavirus type 31 (PDB: 1A7G), and the results revealed that most of the esters can efficiently bind to the target. Desmond was used to doing molecular dynamics simulations at 200 ns in addition to molecular docking to look at the binding conformational stability of the protein-ligand complex. Based on RMSD and RMSF, it was determined that the stability of the protein-ligand combination was maintained during the whole 200 ns simulations for all compounds. Finally, a pharmacokinetic study suggests that modified esters of MGP exhibited better pharmacokinetic characteristics and were less hazardous than the parent drug. This work demonstrated that potential MGP esters can efficiently bind to 4HBT and 1A7G proteins and opened avenues for the development of newer antimicrobial agents that can target dangerous pathogens.Communicated by Ramaswamy H. Sarma.

Multiplex Microarrays in 96-Well Plates Photoactivated with 4-Azidotetrafluorobenzaldehyde for the Identification and Quantification of β-Lactamase Genes and Their RNA Transcripts

Antibiotic-resistant bacteria represent a global issue that calls for novel approaches to diagnosis and treatment. Given the variety of genetic factors that determine resistance, multiplex methods hold promise in this area. We developed a novel method to covalently attach oligonucleotide probes to the wells of polystyrene plates using photoactivation with 4-azidotetrafluorobenzaldehyde. Then, it was used to develop the technique of microarrays in the wells. It consists of the following steps: activating polystyrene, hybridizing the probes with biotinylated target DNA, and developing the result using a streptavidin-peroxidase conjugate with colorimetric detection. The first microarray was designed to identify 11 different gene types and 16 single-nucleotide polymorphisms (SNPs) of clinically relevant ESBLs and carbapenemases, which confer Gram-negative bacteria resistance to β-lactam antibiotics. The detection of bla genes in 65 clinical isolates of Enterobacteriaceae demonstrated the high sensitivity and reproducibility of the technique. The highly reproducible spot staining of colorimetric microarrays allowed us to design a second microarray that was intended to quantify four different types of bla mRNAs in order to ascertain their expressions. The combination of reliable performance, high throughput in standard 96-well plates, and inexpensive colorimetric detection makes the microarrays suitable for routine clinical application and for the study of multi-drug resistant bacteria.

The Dynamics of OXA-23 β-Lactamase from Acinetobacter baumannii

Antibiotic resistance is a pressing topic, which also affects β-lactam antibiotic molecules. Until a few years ago, it was considered no more than an interesting species from an academic point of view, Acinetobacter baumanii is today one of the most serious threats to public health, so much so that it has been declared one of the species for which the search for new antibiotics, or new ways to avoid its resistance, is an absolute priority according to WHO. Although there are several molecular mechanisms that are responsible for the extreme resistance of A. baumanii to antibiotics, a class D β-lactamase is the main cause for the clinical concern of this bacterial species. In this work, we analyzed the A. baumanii OXA-23 protein via molecular dynamics. The results obtained show that this protein is able to assume different conformations, especially in some regions around the active site. Part of the OXA-23 protein has considerable conformational motility, while the rest is less mobile. The importance of these observations for understanding the functioning mechanism of the enzyme as well as for designing new effective molecules for the treatment of A. baumanii is discussed.

Comprehensive screening of marine metabolites against class B1 metallo-β-lactamases of Klebsiella pneumoniae using two-pronged in silico approach

The emergence of antibiotic resistance is one of the major global threats in healthcare. Metallo-β-Lactamases (MBL) are a class of enzymes in bacteria that cleave β-lactam antibiotics and confer resistance. MBLs are further divided into subclasses B1, B2 and B3. Of these, subclasses B1-MBLs (including NDM-1, VIM-2 and IMP-1) constitute the clinically prevalent lactamases conferring resistance. To date, no effective drugs are available clinically against MBLs. In this work, we aim to identify potent inhibitors for the B1 subclass of MBL from available marine metabolites in Comprehensive Marine Natural Product database through integrated in silico approaches. We have used two methods, namely, the high-throughput strategy and the pharmacophore-based strategy to identify potential inhibitors from marine metabolites. High-throughput virtual screening identified N-methyl mycosporine-Ser, which had the highest binding affinity to NDM-1. The pharmacophore-based approach based on co-crystallized ligands identified makaluvic acid and didymellamide with higher binding affinity across B1-MBLs. Taking into account of the advantage of a pharmacophore model-based approach with higher binding affinity, we conclude that both makaluvic acid and didymellamide show potential broad-spectrum effects by binding to all three B1-MBL receptors. The study also indicates the need to take multiple in silico approaches to screen and identify novel inhibitors. Together, our study reveals promising inhibitors that can be identified from marine systems.Communicated by Ramaswamy H. Sarma.

Transmission of β-lactamases in the pork food chain: A public health concern

Antimicrobial resistance (AMR) is a risk for public health that requires management in a One Health perspective, including humans, animals, and the environment. The food production chain has been identified as a possible route of transmission of AMR bacteria to humans. The most critical issue regards resistance to the Critically Important Antimicrobials (CIAs), such as β-lactams antibiotics. Here, pigs were analysed along the entire food producing chain, including feces, carcasses and pork products (fresh meat, fermented and seasoned products) ensuring treaciability of all samples. Escherichia coli were isolated and their ability to produce ESBL and AmpC β-lactamases was evaluated both phenotypically and genotypically. Strains with the same AMR profile from feces, carcasses, and meat products were selected for phylogenetic and comparative genomic analyses to evaluate the possible "farm-to-fork" transmission of β-lactams resistant bacteria. Results showed that the percentage of ESBL strains in fecal E. coli was approximately 7% and increased slightly in the pork food chain: the 10% of ESBL E. coli isolated from carcasses and the 12.5% of isolates from fresh meat products. AmpC E. coli were found only in feces, carcasses, and fresh meat with a low prevalence. Results showed that of the 243 pigs followed along the entire food chain genetic similarities in E. coli isolated from farm-to-fork were found in only one pig (feces, carcasses and fresh meat). Frequent similarities were shown in resistant E. coli isolates from carcasses and fresh meat or fermented product (three pork food chain). Moreover, in one case, bacteria isolated from fresh meat and fermented product were genotypically similar. Concluding, direct transmission of β-lactams resistance from farm-to-fork is possible but not frequent. Further studies are needed to improve risk communication to consumers and access to clear and reliable information and health concerns on food.

The emergence of clonally diverse carbapenem-resistant Enterobacter cloacae complex in West Bengal, India: a dockyard of β-lactamases periling nosocomial infections

Carbapenem-resistant Enterobacter cloacae complex (CRECC) constitutes a global public health threat challenging clinical treatment and infection control, especially in low- and middle-income countries such as India. We analyzed the antimicrobial susceptibility, major β-lactamase genes, plasmid profiles, and genetic relatedness to understand the molecular epidemiology of CRECC clinical isolates (n = 44) in West Bengal, India, during 2021-2022. The majority (> 55%) of the isolates were resistant to fluoroquinolones, aminoglycosides, and co-trimoxazole, even > 20% for tigecycline and > 35% were extensively drug-resistant. Co-β-lactamase production was categorized into twenty-seven types, importantly NDM (84%), OXA-48 (40%), TEM (61%), CTX-M (46%), OXA-1 (55%), and MIR (27%). The NDM-1 and OXA-181 were major variants with the first observations of NDM-24 and -29 variants in India. Wide-range of plasmids (2 to > 212 kb) were harbored by the β-lactamase-producing isolates: small (91%), medium (27%), large (9%), and mega (71%). IncX3, ColE1, and HI2 were noted in about 30% of isolates, while IncF and R were carried by < 20% of isolates. The clonally diverse CRECC isolates were noted to cause cross-infections, especially at superficial site, bloodstream, and urinary-tract. This is the first molecular surveillance on CRECC in India. The study isolates serve as the dockyard of NDM, TEM, and CTX-M harboring a wide range of plasmids. The outcomes of the study may strengthen local and national policies for infection prevention and control practices, clarifying the genetic diversity among CRECC. Extensive genomic study may further intersect the relationships between these different plasmids, especially with their sizes, types, and antibiotic resistance markers.

DNA supercoiling and regulation of intrinsic β-lactamase in pathogenic Escherichia coli

This review addresses the involvement of DNA supercoiling in the development of virulence and antibiotic profiles for uropathogenic Escherichia coli and the emergence of new pathotypes such as strain ST131 (serotype O25:H4). The mechanism suggests a role for topoisomerase enzymes and associated mutations in altering the chromosomal supercoiling state and introducing the required DNA twists for expression of intrinsic β-lactamase by ampC and certain virulence factors. In Escherichia coli, constitutive hyperexpression of intrinsic ampC is associated with specific mutations in the promoter and attenuator regions. However, many reports have documented the involvement of slow growth interventions in the expression of intrinsic resistance determinants. There is evidence that a stationary phase transcriptional switch protein, "BolA," is involved in the expression of the intrinsic ampC gene under starvation conditions. The process involves changes in the activity of the enzyme "gyrase," which leads to a change in the chromosomal DNA topology. Consequently, the DNA is relaxed, and the expression of the bolA gene is upregulated. The evolution of the extraintestinal pathogenic E. coli strain ST131 has demonstrated successful adaptability to various stress conditions and conferred compensatory mutations that endowed the microbe with resistance to fluoroquinolones and β-lactams. The results of this study provided new insights into the evidence for the influence of DNA topology in the expression of virulence genes and various determinants of antibiotic resistance (e.g., the intrinsic ampC gene) in Escherichia coli pathotypes.

Examining the activity of cefepime-taniborbactam against Burkholderia cepacia complex and Burkholderia gladioli isolated from cystic fibrosis patients in the United States

The novel clinical-stage β-lactam-β-lactamase inhibitor combination, cefepime-taniborbactam, demonstrates promising activity toward many Gram-negative bacteria producing class A, B, C, and/or D β-lactamases. We tested this combination against a panel of 150 Burkholderia cepacia complex (Bcc) and Burkholderia gladioli strains. The addition of taniborbactam to cefepime shifted cefepime minimum inhibitory concentrations toward the provisionally susceptible range in 59% of the isolates tested. Therefore, cefepime-taniborbactam possessed similar activity as first-line agents, ceftazidime and trimethoprim-sulfamethoxazole, supporting further development.

Carbapenem resistance in Enterobacterales from agricultural, environmental and clinical origins: South Africa in a global context

Carbapenem agents are regarded as last-resort antibiotics, however, bacterial resistance towards carbapenems has been reported in both clinical and agricultural settings worldwide. Carbapenem resistance, defined as the resistance of a bacteria towards one or more carbapenem drugs, can be mediated in either of, or a combination of, three mechanisms-although, the mechanism mediated through the production of carbapenemases (β-lactamases that are able to enzymatically degrade carbapenems) is of most significance. Of particular concern is the occurrence of carbapenemase producing Enterobacterales (CPE), with literature describing a dramatic increase in resistance globally. In South Africa, increases of carbapenemase activity occurring in Enterobacter species, Klebsiella pneumoniae, Acinetobacter baumannii and Pseudomonas aeruginosa have recently been reported. CPE can also be found in agricultural environments, as global studies have documented numerous instances of CPE presence in various animals such as pigs, cattle, seafood, horses and dogs. However, most reports of CPE occurrence in agricultural settings come from Northern America, Europe and some parts of Asia, where more extensive research has been conducted to understand the CPE phenomenon. In comparison to clinical data, there are limited studies investigating the spread of CPE in agricultural settings in Africa, highlighting the importance of monitoring CPE in livestock environments and the food chain. Further research is necessary to uncover the true extent of CPE dissemination in South Africa. This review will discuss the phenomenon of bacterial antibiotic resistance (ABR), the applications of the carbapenem drug and the occurrence of carbapenem resistance globally.

In vitro activity of new combinations of β-lactam and β-lactamase inhibitors against the Mycobacterium tuberculosis complex

As meropenem-clavulanic acid is recommended for the treatment of drug-resistant tuberculosis, the repurposing of new carbapenem combinations may provide new treatment options, including oral alternatives. Therefore, we studied the in vitro activities of meropenem-vaborbactam, meropenem-clavulanic acid, and tebipenem-clavulanic acid. One hundred nine Mycobacterium tuberculosis complex (MTBC) clinical isolates were tested, of which 69 were pan-susceptible and the remaining pyrazinamide- or multidrug-resistant. Broth microdilution MICs were determined using the EUCAST reference method. Meropenem and tebipenem were tested individually and in combination with vaborbactam 8 mg/L and clavulanic-acid 2 and 4 mg/L, respectively. Whole-genome sequencing was performed to explore resistance mechanisms. Clavulanic acid lowered the modal tebipenem MIC approximately 16-fold (from 16 to 1 mg/L). The modal meropenem MIC was reduced twofold by vaborbactam compared with an approximately eightfold decrease by clavulanic acid. The only previously described high-confidence carbapenem resistance mutation, crfA T62A, was shared by a subgroup of lineage 4.3.4.1 isolates and did not correlate with elevated MICs. The presence of a β-lactamase inhibitor reduced the MTBC MICs of tebipenem and meropenem. The resulting MIC distribution was lowest for the orally available drugs tebipenem-clavulanic acid. Whether this in vitro activity translates to similar or greater clinical efficacy of tebipenem-clavulanic acid compared with the currently WHO-endorsed meropenem-clavulanic acid requires clinical studies. IMPORTANCE Repurposing of already approved antibiotics, such as β-lactams in combination with β-lactamase inhibitors, may provide new treatment alternatives for drug-resistant tuberculosis. Meropenem-clavulanic acid was more active in vitro compared to meropenem-vaborbactam. Notably, tebipenem-clavulanic acid showed even better activity, raising the potential of an all-oral treatment option. Clinical data are needed to investigate whether the better in vitro activity of tebipenem-clavulanic acid correlates with greater clinical efficacy compared with the currently WHO-endorsed meropenem-clavulanic acid.

The functional repertoire of AmpR in the AmpC β-lactamase high expression and decreasing β-lactam and aminoglycosides resistance in ESBL Citrobacter freundii

Citrobacter freundii is characterized by AmpC β-lactamases that develop resistance to β-lactam antibiotics. The production of extended-spectrum β-lactamase (ESBL) is substantially high in Escherichia coli, C. freundii, Enterobacter cloacae, and Serratia marcescens, but infrequently explored in C. freundii. The present investigation characterized the ESBL C. freundii and delineated the genes involved in decrease in antibiotics resistance. We used the VITEK-2 system and Analytical Profile Index (API) kit to characterize and identify the Citrobacter isolates. The mRNA level of AmpC and AmpR was determined by RT-qPCR, and gel-shift assay was performed to evaluate protein-DNA binding. Here, a total of 26 Citrobacter strains were isolated from COVID-19 patients that showed varying degrees of antibiotic resistance. We examined and characterized the multidrug resistant C. freundii that showed ESBL production. The RT-qPCR analysis revealed that the AmpC mRNA expression is significantly high followed by a high level of AmpR. We sequenced the AmpC and AmpR genes that revealed the AmpR has four novel mutations in comparison to the reference genome namely; Thr64Ile, Arg86Ser, Asp135Val, and Ile183Leu while AmpC remained intact. The ΔAmpR mutant analysis revealed that the AmpR positively regulates oxidative stress response and decreases β-lactam and aminoglycosides resistance. The AmpC and AmpR high expression was associated with resistance to tazobactam, ampicillin, gentamicin, nitrofurantoin, and cephalosporins whereas AmpR deletion reduced β-lactam and aminoglycosides resistance. We conclude that AmpR is a positive regulator of AmpC that stimulates β-lactamases which inactivate multiple antibiotics.

Increased Incidence and Risk Factors of Infections by Extended-Spectrum β-Lactamase-Producing Enterobacterales During the COVID-19 Pandemic: A Retrospective Case-Control Study

Purpose

To investigate changes in the incidence of infections by extended-spectrum β-lactamase-producing Enterobacterales (ESBL-E) and analyzed whether there was an association between endogenous changes in the organism due to COVID-19 infection and the infections by ESBL-E.

Patients and Methods

The study was a single-center retrospective case-control design. A total of 107 patients infected by ESBL-E during the COVID-19 pandemic were selected as the case group, while 214 uninfected patients selected by 1:2 propensity score matching (PSM) acted as the control group. Univariate analysis, LASSO logistic regression, and multivariate logistic regression were used to determine the risk factors for ESBL-E infection. An interrupted time series was used to analyze the changes in the incidence of ESBL-E infections in hospitalized patients during the COVID-19 pandemic.

Results

The incidence of infection with ESBL-E showed a significant increase during COVID-19 (3.42 vs 4.92 per 1000 patients, p = 0.003). The incidence of ESBL-E infections increased at an average rate of 0.45 per 1000 patients per week compared to the pre-pandemic period (p = 0.022). Multivariate logistic regression analysis showed that a length of hospitalization ≥ 15 days (OR: 2.98 (1.07-8.28), chronic kidney disease (OR: 4.25 (1.32-13.70), white blood cell (WBC) > 9.5×10^9/L (OR: 3.04 (1.54-6.01), use of hormonal drugs (OR: 2.38 (1.04-5.43), antibacterial drug use 1 type (OR: 5.38 (2.04-14.21), antibacterial drug use 2 types (OR: 23.05 (6.71-79.25) and antibacterial drug use ≥ 3 types (OR: 88.35 (8.55-912.63) were independent risk factors for infection with ESBL-E, while chronic obstructive pulmonary disease (COPD) was a protective factor (OR: 0.14 (0.03-0.66). COVID-19 was not an independent risk factor for infection by ESBL-E.

Conclusion

During the COVID-19 pandemic, the incidence of infections by ESBL-E increased significantly. Increased exposure to traditional risk factors were the main reasons, however, COVID-19 was not an independent risk factor for ESBL-E infection.

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.

Treatment of Piperacillin-Tazobactam-Nonsusceptible/Ceftriaxone-Susceptible Infections With Carbapenem Versus Carbapenem-Sparing Antimicrobials

Background

Escherichia coli and Klebsiella pneumoniae with a piperacillin-tazobactam-nonsusceptible/ceftriaxone-susceptible (TZP-NS/CRO-S) phenotype have been increasingly identified, with limited available literature evaluating treatment strategies.

Methods

This was a retrospective study of noncritically ill adults hospitalized between 2013 and 2021 and treated at least 48 hours for TZP-NS/CRO-S E coli or K pneumoniae infections. The primary composite endpoint included escalation to intensive care unit, infection- or treatment-related readmission, mortality, and infection recurrence. Outcomes were compared between groups who received carbapenem (CG) versus carbapenem-sparing agents (CSG) as targeted gram-negative therapy.

Results

Of 1062 patients screened, 200 were included (CG, n = 51; CSG, n = 149). Baseline characteristics, including Charlson Comorbidity Index (CCI; median [interquartile range], 6 [3-9] vs 6 [4-9]; P = .704), were similar between groups, except for more immunocompromised CG patients (29% vs 11%, P = .001). The most common infection sources were urinary (31% vs 57%, P = .002) and bloodstream (18% vs 17%, P = .887). Eighty-eight percent of the CG received meropenem, while 58% of the CSG received ceftriaxone as targeted therapy. There was no statistical difference in the primary endpoint between overall groups (27% vs 17%, P = .123), nor when stratified by infection source. More patients in the CSG switched to oral therapy (15 [29%] vs 100 [67%], P < .001). In multivariate analysis, CCI was an independent predictor of the primary outcome (odds ratio [OR], 1.199 [95% confidence interval, 1.074-1.340]; P = .001), while treatment with carbapenem-sparing therapy was not.

Conclusions

Our study did not find improved clinical outcomes with targeted carbapenem therapy for TZP-NS/CRO-S infections. Carbapenem-sparing agents may be considered to spare carbapenems in noncritically ill patients similar to those included in our cohort.

Sulfonamidoboronic Acids as "Cross-Class" Inhibitors of an Expanded-Spectrum Class C Cephalosporinase, ADC-33, and a Class D Carbapenemase, OXA-24/40: Strategic Compound Design to Combat Resistance in Acinetobacter baumannii

Acinetobacter baumannii is a Gram-negative organism listed as an urgent threat pathogen by the World Health Organization (WHO). Carbapenem-resistant A. baumannii (CRAB), especially, present therapeutic challenges due to complex mechanisms of resistance to β-lactams. One of the most important mechanisms is the production of β-lactamase enzymes capable of hydrolyzing β-lactam antibiotics. Co-expression of multiple classes of β-lactamases is present in CRAB; therefore, the design and synthesis of "cross-class" inhibitors is an important strategy to preserve the efficacy of currently available antibiotics. To identify new, nonclassical β-lactamase inhibitors, we previously identified a sulfonamidomethaneboronic acid CR167 active against Acinetobacter-derived class C β-lactamases (ADC-7). The compound demonstrated affinity for ADC-7 with a K_i = 160 nM and proved to be able to decrease MIC values of ceftazidime and cefotaxime in different bacterial strains. Herein, we describe the activity of CR167 against other β-lactamases in A. baumannii: the cefepime-hydrolysing class C extended-spectrum β-lactamase (ESAC) ADC-33 and the carbapenem-hydrolyzing OXA-24/40 (class D). These investigations demonstrate CR167 as a valuable cross-class (C and D) inhibitor, and the paper describes our attempts to further improve its activity. Five chiral analogues of CR167 were rationally designed and synthesized. The structures of OXA-24/40 and ADC-33 in complex with CR167 and select chiral analogues were obtained. The structure activity relationships (SARs) are highlighted, offering insights into the main determinants for cross-class C/D inhibitors and impetus for novel drug design.

Development of AMBER Parameters for Molecular Simulations of Selected Boron-Based Covalent Ligands

Boron containing compounds (BCCs) aroused increasing interest in the scientific community due to their wide application as drugs in various fields. In order to design new compounds hopefully endowed with pharmacological activity and also investigate their conformational behavior, the support of computational studies is crucial. Nevertheless, the suitable molecular mechanics parameterization and the force fields needed to perform these simulations are not completely available for this class of molecules. In this paper, Amber force field parameters for phenyl-, benzyl-, benzylamino-, and methylamino-boronates, a group of boron-containing compounds involved in different branches of the medicinal chemistry, were created. The robustness of the obtained data was confirmed through molecular dynamics simulations on ligand/β-lactamases covalent complexes. The ligand torsional angles, populated over the trajectory frames, were confirmed by values found in the ligand geometries, located through optimizations at the DFT/B3LYP/6-31g(d) level, using water as a solvent. In summary, this study successfully provided a library of parameters, opening the possibility to perform molecular dynamics simulations of this class of boron-containing compounds.

β-Lactam potentiators to re-sensitize resistant pathogens: Discovery, development, clinical use and the way forward

β-lactam antibiotics are one of the most widely used and diverse classes of antimicrobial agents for treating both Gram-negative and Gram-positive bacterial infections. The β-lactam antibiotics, which include penicillins, cephalosporins, monobactams and carbapenems, exert their antibacterial activity by inhibiting the bacterial cell wall synthesis and have a global positive impact in treating serious bacterial infections. Today, β-lactam antibiotics are the most frequently prescribed antimicrobial across the globe. However, due to the widespread use and misapplication of β-lactam antibiotics in fields such as human medicine and animal agriculture, resistance to this superlative drug class has emerged in the majority of clinically important bacterial pathogens. This heightened antibiotic resistance prompted researchers to explore novel strategies to restore the activity of β-lactam antibiotics, which led to the discovery of β-lactamase inhibitors (BLIs) and other β-lactam potentiators. Although there are several successful β-lactam-β-lactamase inhibitor combinations in use, the emergence of novel resistance mechanisms and variants of β-lactamases have put the quest of new β-lactam potentiators beyond precedence. This review summarizes the success stories of β-lactamase inhibitors in use, prospective β-lactam potentiators in various phases of clinical trials and the different strategies used to identify novel β-lactam potentiators. Furthermore, this review discusses the various challenges in taking these β-lactam potentiators from bench to bedside and expounds other mechanisms that could be investigated to reduce the global antimicrobial resistance (AMR) burden.

LY2183240 regioisomers act as competitive and selective inhibitors of class C β-lactamases

The regioisomers of the anandamide-acting drug LY2183240 exhibited specific potent and competitive inhibitory activities against class C β-lactamases. More explicitly, the 1,5- and 2,5-regioisomers inhibited AmpC from Enterobacter hormaechei (formerly Enterobacter cloacae) with K_i values of 1.8 µM and 2.45 µM, respectively. Structural molecular modelling studies revealed the interaction of the regioisomers with the relevant residues of the catalytic site of cephalosporinase from E. hormaechei P99, which included Tyr¹⁵⁰, Lys³¹⁵ and Thr³¹⁶.

Diversity and Distribution of β-Lactamase Genes Circulating in Indian Isolates of Multidrug-Resistant Klebsiella pneumoniae

Klebsiella pneumoniae (Kp) has gained prominence in the last two decades due to its global spread as a multidrug-resistant (MDR) pathogen. Further, carbapenem-resistant Kp are emerging at an alarming rate. The objective of this study was (1) to evaluate the prevalence of β-lactamases, especially carbapenemases, in Kp isolates from India, and (2) determine the most prevalent sequence type (ST) and plasmids, and their association with β-lactamases. Clinical samples of K. pneumoniae (n = 65) were collected from various pathology labs, and drug susceptibility and minimum inhibitory concentrations (MIC) were detected. Whole genome sequencing (WGS) was performed for n = 22 resistant isolates, including multidrug-resistant (MDR) (n = 4), extensively drug-resistant (XDR) (n = 15), and pandrug-resistant (PDR) (n = 3) categories, and genomic analysis was performed using various bioinformatics tools. Additional Indian MDRKp genomes (n = 187) were retrieved using the Pathosystems Resource Integration Center (PATRIC) database. Detection of β-lactamase genes, location (on chromosome or plasmid), plasmid replicons, and ST of genomes was carried out using CARD, mlplasmids, PlasmidFinder, and PubMLST, respectively. All data were analyzed and summarized using the iTOL tool. ST231 was highest, followed by ST147, ST2096, and ST14, among Indian isolates. bla_ampH was detected as the most prevalent gene, followed by bla_CTX-M-15 and bla_TEM-1. Among carbapenemase genes, bla_OXA-232 was prevalent and associated with ST231, ST2096, and ST14, which was followed by bla_NDM-5, which was observed to be prevalent in ST147, ST395, and ST437. ST231 genomes were most commonly found to carry Col440I and ColKP3 plasmids. ST16 carried mainly ColKP3, and Col(BS512) was abundantly present in ST147 genomes. One Kp isolate with a novel MLST profile was identified, which carried bla_CTX-M-15, bla_OXA-1, and bla_TEM-1. ST16 and ST14 are mostly dual-producers of carbapenem and ESBL genes and could be emerging high-risk clones in India.

Whole Genome-Based Characterization of Multidrug Resistant Enterobacter and Klebsiella aerogenes Isolates from Lebanon

Enterobacter spp. and Klebsiella aerogenes are rod-shaped Gram-negative opportunistic pathogens. This study aimed at the molecular and genomic characterization of multidrug resistant Enterobacter spp. and K. aerogenes isolates recovered from hospitalized patients in a tertiary care hospital in Lebanon. A total of 59 Enterobacter spp. clinical isolates consisting of 41 carbapenem-resistant and 18 susceptible by Etest were included in this study. Genotypic identification through whole-genome sequencing (WGS) was performed and confirmed in silico. Resistance and plasmid profiles were studied using ResFinder4.0 and Plasmid-Finder2.1. Multilocus sequence typing (MLST) was used to determine the isolates' clonality. Using the average nucleotide identity (ANI) we identified and confirmed that 47 (80%) isolates were E. hormaechei, 11 (18%) were Klebsiella aerogenes and 1 (2%) was an E. cloacae. Carbapenem-resistance was detected among 41 isolates all showing an MIC₉₀ of ≥ 32 μg/mL for ertapenem, imipenem, and meropenem. bla_NDM-1 (58.5%), bla_ACT-16 (54%), and bla_OXA-1 (54%) were the most common detected β-lactamases, while bla_CTX-M-15 (68%) was the main detected extended-spectrum β-lactamase (ESBL) encoding gene. Chromosomal ampC, carbapenemase encoding genes, and porin modifications were among the detected carbapenem resistance determinants. The carbapenemase encoding genes were linked to three well-defined plasmid Inc groups, IncFII/IncFIB, IncX3, and IncL. MLST typing revealed the diversity within the studied isolates, with ST114 being the most common among the studied E. hormaechei.: The spread of carbapenem-resistant isolates in clinical settings in Lebanon is a serious challenge. Screening and continuous monitoring through WGS analysis could effectively limit the dissemination of drug-resistant isolates in hospitalized patients. IMPORTANCE Drug resistance is an increasing global public health threat that involves most disease-causing organisms and antimicrobial drugs. Drug-resistant organisms spread in health care settings, and resistance to multiple drugs is common. Our study demonstrated the mechanisms leading to resistance against the last resort antimicrobial agents among members of the Enterobacteriaceae family. The spread of carbapenem-resistant bacteria in clinical settings is a serious challenge. Screening and continuous monitoring could effectively limit the dissemination of drug-resistant isolates in hospitalized patients.

Crystal structure of a polyglycine hydrolase determined using a RoseTTAFold model

Polyglycine hydrolases (PGHs) are secreted fungal proteases that cleave the polyglycine linker of Zea mays ChitA, a defensive chitinase, thus overcoming one mechanism of plant resistance to infection. Despite their importance in agriculture, there has been no previous structural characterization of this family of proteases. The objective of this research was to investigate the proteolytic mechanism and other characteristics by structural and biochemical means. Here, the first atomic structure of a polyglycine hydrolase was identified. It was solved by X-ray crystallography using a RoseTTAFold model, taking advantage of recent technical advances in structure prediction. PGHs are composed of two domains: the N- and C-domains. The N-domain is a novel tertiary fold with an as-yet unknown function that is found across all kingdoms of life. The C-domain shares structural similarities with class C β-lactamases, including a common catalytic nucleophilic serine. In addition to insights into the PGH family and its relationship to β-lactamases, the results demonstrate the power of complementing experimental structure determination with new computational techniques.

Multi-drug Resistance, β-Lactamases Production, and Coexistence of bla NDM-1 and mcr-1 in Escherichia coli Clinical Isolates From a Referral Hospital in Kathmandu, Nepal

The ability of pathogenic Escherichia coli to produce carbapenemase enzymes is a characteristic that allows them to resist various antibiotics, including last-resort antibiotics like colistin and carbapenem. Our objectives were to identify rapidly developing antibiotic resistance (AR), assess β-lactamases production, and detect mcr-1 and bla _NDM-1 genes in the isolates. A prospective cross-sectional study was carried out in a referral hospital located in Kathmandu from November 2019 to December 2020 using standard laboratory and molecular protocols. Among 77 total E. coli isolates, 64 (83.1%) of them were categorized as MDR. Phenotypically 13 (20.3%) colistin-resistant, 30 (46.9%) ESBL and 8 (12.5%) AmpC producers, and 5 (7.8%) ESBL/AmpC co-producers were distributed among MDR-E. coli. Minimum inhibitory concentrations (MIC) against the majority of MDR isolates were exhibited at 1 g/L. Of these 77 E. coli isolates, 24 (31.2%) were carbapenem-resistant. Among these carbapenem-resistant bacteria, 11 (45.9%) isolates were reported to be colistin-resistant, while 15 (62.5%) and 2 (8.3%) were MBL and KPC producers, respectively. Out of 15 MBL producers, 6 (40%) harbored bla _NDM-1, and 8 (61.5%) out of 13 colistin-resistant pathogens possessed mcr-1. The resistance by colistin- and carbapenem were statistically associated (P < .001). However, only 2 (18.2%) of the co-resistant bacteria were found to have both genes. Our study revealed the highly prevalent MDR and the carbapenem-resistant E. coli and emphasized that the pathogens possess a wide range of capabilities to synthesize β-lactamases. These findings could assist to expand the understanding of AR in terms of enzyme production.

Trends of β-Lactamase Occurrence Among Escherichia coli and Klebsiella pneumoniae in United States Hospitals During a 5-Year Period and Activity of Antimicrobial Agents Against Isolates Stratified by β-Lactamase Type

Background

The temporal and longitudinal trends of β-lactamases and their associated susceptibility patterns were analyzed for Escherichia coli and Klebsiella pneumoniae isolates consecutively collected in 56 United States hospitals during 2016-2020.

Methods

Isolates (n = 19 453) were susceptibility tested by reference broth microdilution methods. Isolates that displayed minimum inhibitory concentration (MIC) values ≥2 mg/L for at least 2 of the following compounds-ceftazidime, ceftriaxone, aztreonam, or cefepime-or resistance to the carbapenems were submitted to whole genome sequencing for identification of β-lactamases. Longitudinal and temporal trends were determined by slope coefficient. New CTX-M and OXA-1 variants were characterized.

Results

Extended-spectrum β-lactamases (ESBLs) were detected among 88.0% of the isolates that displayed elevated cephalosporin/aztreonam MICs without carbapenem resistance. bla _CTX-M-15 was detected among 55.5% of the ESBL producers. ESBL rates were stable over time, but significant increases were noted among bloodstream infection and K pneumoniae isolates, mainly driven by an increase in bla _CTX-M. Carbapenem resistance and carbapenemase genes were noted among 166 and 145 isolates, respectively, including 137 bla _KPC, 6 bla _SME, 3 bla _OXA-48-like, and 3 bla _NDM. Ceftazidime-avibactam and carbapenems were very active (>99% susceptibility) against ESBL producers without carbapenem resistance. Ceftazidime-avibactam inhibited 97.0% of the carbapenem-resistant isolates. This agent and meropenem-vaborbactam inhibited 96.4% and 85.0% of the 2020 isolates, respectively.

Conclusions

Overall, ESBL-producing isolates were stable, but an increase was noted for K pneumoniae isolates driven by CTX-M production. Carbapenem-resistant Enterobacterales rates decreased in the study period. The prevalence of metallo-β-lactamases and OXA-48-like remains low. Continuous surveillance of β-lactamase-producing isolates is prudent.

Boronic Acid Transition State Inhibitors as Potent Inactivators of KPC and CTX-M β-Lactamases: Biochemical and Structural Analyses

Design of novel β-lactamase inhibitors (BLIs) is one of the currently accepted strategies to combat the threat of cephalosporin and carbapenem resistance in Gram-negative bacteria. Boronic acid transition state inhibitors (BATSIs) are competitive, reversible BLIs that offer promise as novel therapeutic agents. In this study, the activities of two α-amido-β-triazolylethaneboronic acid transition state inhibitors (S02030 and MB_076) targeting representative KPC (KPC-2) and CTX-M (CTX-M-96, a CTX-M-15-type extended-spectrum β-lactamase [ESBL]) β-lactamases were evaluated. The 50% inhibitory concentrations (IC₅₀s) for both inhibitors were measured in the nanomolar range (2 to 135 nM). For S02030, the k₂/K for CTX-M-96 (24,000 M^-1 s^-1) was twice the reported value for KPC-2 (12,000 M^-1 s^-1); for MB_076, the k₂/K values ranged from 1,200 M^-1 s^-1 (KPC-2) to 3,900 M^-1 s^-1 (CTX-M-96). Crystal structures of KPC-2 with MB_076 (1.38-Å resolution) and S02030 and the in silico models of CTX-M-96 with these two BATSIs show that interaction in the CTX-M-96-S02030 and CTX-M-96-MB_076 complexes were overall equivalent to that observed for the crystallographic structure of KPC-2-S02030 and KPC-2-MB_076. The tetrahedral interaction surrounding the boron atom from S02030 and MB_076 creates a favorable hydrogen bonding network with S70, S130, N132, N170, and S237. However, the changes from W105 in KPC-2 to Y105 in CTX-M-96 and the missing residue R220 in CTX-M-96 alter the arrangement of the inhibitors in the active site of CTX-M-96, partially explaining the difference in kinetic parameters. The novel BATSI scaffolds studied here advance our understanding of structure-activity relationships (SARs) and illustrate the importance of new approaches to β-lactamase inhibitor design.

Biochemical exploration of β-lactamase inhibitors

The alarming rise of microbial resistance to antibiotics has severely limited the efficacy of current treatment options. The prevalence of β-lactamase enzymes is a significant contributor to the emergence of antibiotic resistance. There are four classes of β-lactamases: A, B, C, and D. Class B is the metallo-β-lactamase, while the rest are serine β-lactamases. The clinical use of β-lactamase inhibitors began as an attempt to combat β-lactamase-mediated resistance. Although β-lactamase inhibitors alone are ineffective against bacteria, research has shown that combining inhibitors with antibiotics is a safe and effective treatment that not only prevents β-lactamase formation but also broadens the range of activity. These inhibitors may cause either temporary or permanent inhibition. The development of new β-lactamase inhibitors will be a primary focus of future research. This study discusses recent advances in our knowledge of the biochemistry behind β-lactam breakdown, with special emphasis on the mechanism of inhibitors for β-lactam complexes with β-lactamase. The study also focuses on the pharmacokinetic and pharmacodynamic properties of all inhibitors and then applies them in clinical settings. Our analysis and discussion of the challenges that exist in designing inhibitors might help pharmaceutical researchers address root issues and develop more effective inhibitors.

Characterization of a Carbapenem-Resistant BKC-1-Producing Clinical Isolate Belonging to the Pseudomonas putida Group from Brazil

Since its first report, the class A Brazilian Klebsiella carbapenemase (BKC) has been detected only among Enterobacterales isolates from Brazilian hospitals. In this study, we characterized a multidrug-resistant Pseudomonas juntendi clinical isolate and identified a 43.3-kb plasmid carrying bla_BKC-1 and a class 1 integron (In1996) containing the arr-2, qnrVC1, dfrA21, and aac(6')-Ib' gene cassettes. Our results confirm the ability of Pseudomonas putida group isolates to acquire antimicrobial resistance determinants and further act as resistance reservoirs.

Genetic Relationship between Salmonella Isolates Recovered from Calves and Broilers Chickens in Kafr El-Sheikh City Using ERIC PCR

A prevalent bacterial intestinal infection with severe economic damage is salmonellosis. Our study was carried out to diagnose Salmonella from chickens and calves, to determine its resistance to antimicrobials' phenotypic and genotypic characterization of integrons and β lactamase genes in the multidrug resistance of different Salmonella serotypes, and to detect the genetic relationship between Salmonella isolates collected from different origins using an ERIC PCR. In total, 200 samples from diseased chicken and diarrheic calves were obtained from 50 various farms from Kafr El-sheikh, Egypt. Salmonella poultry isolates were characterized as S. Typhimurium (3/8), S. Enteritidis (3/8), and S. Kentucky (2/8), but Salmonella isolates from cattle were S. Enteritidis (1/2) and S. Kentucky (1/2). When antibiotic susceptibility testing was completed on all of the isolates, it showed that there was multidrug resistance present (MDR). A PCR was applied for identifying the accompanying class 1 integrons and ESBLs from MDR Salmonella isolates (two isolates of S. Kentucky were divided as one from calf and one from poultry). Our results detected blaTEM and class 1 integron, but were negative for bla IMP, bla VIM, and bla SHV. An ERIC PCR was conducted for understanding the clonal relation between various β-lactamase-producing MDR Salmonella isolates. The same four previously mentioned isolates were also tested. The two isolates of S. Enteritidis isolated from poultry and calves had 100% similarity despite indicating that there were interactions between broilers and calves living on the same farm that caused infection from the same Salmonella strains, while the other two isolates of S. Kentucky showed only 33% serovarities.

Bacterial Resistance to β-Lactam Antibiotics in Municipal Wastewater: Insights from a Full-Scale Treatment Plant in Poland

This study investigated enzymatic and genetic determinants of bacterial resistance to β-lactam antibiotics in the biocenosis involved in the process of biological treatment of wastewater by activated sludge. The frequency of bacteria resistant to selected antibiotics and the activity of enzymes responsible for resistance to β-lactam antibiotics were estimated. The phenomenon of selection and spread of a number of genes determining antibiotic resistance was traced using PCR and gene sequencing. An increase in the percentage of bacteria showing resistance to β-lactam antibiotics in the microflora of wastewater during the treatment process was found. The highest number of resistant microorganisms, including multi-resistant strains, was recorded in the aeration chamber. Significant amounts of these bacteria were also present in treated wastewater, where the percentage of penicillin-resistant bacteria exceeded 50%, while those resistant to the new generation β-lactam antibiotics meropenem and imipenem were found at 8.8% and 6.4%, respectively. Antibiotic resistance was repeatedly accompanied by the activity of enzymes such as carbapenemases, metallo-β-lactamases, cephalosporinases and β-lactamases with an extended substrate spectrum. The activity of carbapenemases was shown in up to 97% of the multi-resistant bacteria. Studies using molecular biology techniques showed a high frequency of genes determining resistance to β-lactam antibiotics, especially the blaTEM1 gene. The analysis of the nucleotide sequences of blaTEM1 gene variants present in bacteria at different stages of wastewater treatment showed 50-100% mutual similarity of.

CTX-M-Producing Bacteria Isolated from a Highly Polluted River System in Portugal

Enterobacteriaceae resistant to third-generation cephalosporins are a great concern for public health, as these are first-line drugs to treat infections. The production of carbapenemases and extended spectrum beta-lactamases (ESBLs) and/or the overexpression of AmpC β-lactamases are the main mechanisms of resistance to these antibiotics. Among the ESBLs, CTX-M β-lactamases are the most prevalent worldwide. Our aims were to determine the prevalence of cefotaxime-resistant Enterobacteriaceae along a heavily polluted river and characterize bla_CTX-M carriers. River water was collected in 11 sites along the main course and tributaries, in two sampling moments. Water quality was evaluated and a collection of cefotaxime-resistant isolates was obtained. bla_CTX-M carriers were characterized regarding phylogenetic affiliation, clonality, antibiotic susceptibility, gene diversity, and context. Water presented very low quality in all sites. From 147 cefotaxime-resistant isolates, 46% carried bla_CTX-M and were affiliated with Escherichia, Klebsiella, Enterobacter, and Citrobacter. Molecular typing revealed clonal isolates in different sites and over the two years, suggesting survival of the strains in the river or continuous pollution inputs from the same sources. Eight variants of bla_CTX-M were found, with bla_CTX-M-15 being the most prevalent (52.5%). Sites with a lower water quality showed the highest resistance rates and prevalence of bla_CTX-M, suggesting that river water may embody human health risks.

Molecular and Kinetic Characterization of MOX-9, a Plasmid-Mediated Enzyme Representative of a Novel Sublineage of MOX-Type Class C β-Lactamases

The MOX lineage of β-lactamases includes a group of molecular class C enzymes (AmpCs) encoded by genes mobilized from the chromosomes of Aeromonas spp. to plasmids. MOX-9, previously identified as a plasmid-encoded enzyme from a Citrobacter freundii isolate, belongs to a novel sublineage of MOX enzymes, derived from the resident Aeromonas media AmpC. The bla_MOX-9 gene was found to be carried on a transposon, named Tn7469, likely responsible for its mobilization to plasmidic context. MOX-9 was overexpressed in Escherichia coli, purified, and subjected to biochemical characterization. Kinetic analysis showed a relatively narrow-spectrum profile with strong preference for cephalosporin substrates, with some differences compared with MOX-1 and MOX-2. MOX-9 was not inhibited by clavulanate and sulbactam, while both tazobactam and avibactam acted as inhibitors in the micromolar range.

Broad-Spectrum Inhibitors against Class A, B, and C Type β-Lactamases to Block the Hydrolysis against Antibiotics: Kinetics and Structural Characterization

The emergence of antibiotic resistance has led to a global crisis for the physician to handle infection control issues. All antibiotics, including colistin, have lost efficiency against emerging drug-resistant bacterial strains due to the production of metallo-β-lactamases (MBLs) and serine-β-lactamases (SBLs). Therefore, it is of the utmost importance to design inhibitors against these enzymes to block the hydrolytic action against antibiotics being used. Although various novel β-lactamase inhibitors are being authorized or are under clinical studies, the coverage of their activity spectrum does not include MDR organisms expressing multiple classes of β-lactamases at a single time. This study reports three novel broad-spectrum inhibitors effective against both SBLs and MBLs. Virtual screening, molecular docking, molecular dynamics simulations, and an in silico pharmacokinetic study were performed to identify the lead molecules with broad-spectrum ability to inhibit the hydrolysis of β-lactam. The selected compounds were further assessed by in vitro cell assays (MIC, 50% inhibitory concentration [IC₅₀], kinetics, and fluorescence against class A, B, and C type β-lactamases) to confirm their efficacies. A 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay was performed to check the toxicity of screened lead molecules. All three selected inhibitors were found to reduce MIC and showed good affinity against all the SBLs and MBLs produced by class A, B, and C type β-lactamases. These nontoxic novel non-β-lactam broad-spectrum inhibitors bind to the active site residues of selected β-lactamases, which are crucial for β-lactam antibiotic hydrolysis. These inhibitors may be proposed as a future drug candidate in combination with antibiotics as a single formulation to control infection caused by resistant strains. Hence, this study plays a significant role in the cure of infections caused by antibiotic-resistant bacteria.

IMPORTANCE Several inhibitors for usage in conjunction with antibiotics have been developed. However, to date, there is no commercially available broad-spectrum β-lactamase inhibitor that targets both MBLs and SBLs. Here, we showed three novel broad-spectrum inhibitors with promising results through computational techniques and in vitro studies. These inhibitors are effective against both SBLs and MBLs and hence could be used as future drug candidates to treat infections caused by multidrug-resistant bacteria producing both types of enzymes (SBLs and MBLs).

Insights into the Bacterial Diversity and Detection of Opportunistic Pathogens in Mexican Chili Powder

Chili powder is the most frequently consumed spice in Mexican diets. Thus, the dissemination of microorganisms associated with chili powder derived from Capsicum annuum L. is significant during microbial quality analysis, with special attention on detection of potential pathogens. The results presented here describe the initial characterization of bacterial community structure in commercial chili powder samples. Our results demonstrate that, within the domain Bacteria, the most abundant family was Bacillaceae, with a relative abundance of 99% in 71.4% of chili powder samples, while 28.6% of samples showed an average relative abundance of 60% for the Enterobacteriaceae family. Bacterial load for aerobic mesophilic bacteria (AMB) ranged from 10⁴ to 10⁶ cfu/g, while for sporulated mesophilic bacteria (SMB), the count ranged from 10² to 10⁵ cfu/g. Bacillus cereus sensu lato (s.l.) was observed at ca. ˂600 cfu/g, while the count for Enterobacteriaceae ranged from 10³ to 10⁶ cfu/g, Escherichia coli and Salmonella were not detected. Fungal and yeast counts ranged from 10² to 10⁵ cfu/g. Further analysis of the opportunistic pathogens isolated, such as B. cereus s.l. and Kosakonia cowanii, using antibiotic-resistance profiles and toxinogenic characteristics, revealed the presence of extended-spectrum β-lactamases (ESBLs) and Metallo-β-lactamases (MBLs) in these organisms. These results extend our knowledge of bacterial diversity and the presence of opportunistic pathogens associated with Mexican chili powder and highlight the potential health risks posed by its use through the spread of antibiotic-resistance and the production of various toxins. Our findings may be useful in developing procedures for microbial control during chili powder production.

Rapid and Sensitive Electrochemical Assay of Cefditoren with MWCNT/Chitosan NCs/Fe2O3 as a Nanosensor

In this research, a glassy carbon electrode (GCE) modified by MWCNT/chitosan NCs/Fe₂O₃ was prepared for the determination of the cephalosporin antibiotic cefditoren (CFT) using adsorptive stripping differential pulse and cyclic voltammetry techniques. The effects of pH, the scan rate, the deposition potential, the accumulation time, and modification agents on the determination of CFT were analyzed. The results showed that the modified electrode significantly increased the oxidation peak current of CFT. Under optimized conditions, the MWCNT/chitosan NCs/Fe₂O₃/GCE nanosensor exhibited a linear response between 0.2 µM and 10 µM toward CFT. The limit of detection and quantification were determined to be 1.65 nM and 5.50 nM, respectively. Model drugs (cefdinir, cefpodoxime, cephalexin, and ceftazidime compounds) were used to enlighten the CFT oxidation mechanism. Moreover, the nanosensor was used to analyze CFT in a pharmaceutical dosage form and commercial deproteinated human serum samples. The accuracy of these methods was proven in the recovery studies, with values of 96.98 and 98.62% for the pharmaceutical dosage form and commercial deproteinated human serum sample, respectively.

Chemically synthesised flavone and coumarin based isoxazole derivatives as broad spectrum inhibitors of serine β-lactamases and metallo-β-lactamases: a computational, biophysical and biochemical study

The β-lactam antibiotics are the most effective medicines for treating bacterial infections. Resistance to them, particularly through the production of β-lactamases, which can hydrolyse all kinds of β-lactams, poses a threat to their continued use. The synthesised flavone and coumarin based isoxazole derivatives have the potential to be used as broad-spectrum inhibitors of the mechanistically different serine-(SBL) and metallo-β-lactamases (MBL). The synthesised compounds were discovered as potent β-lactamase inhibitors using molecular docking and in silico pharmacokinetic analysis. We studied the binding of chemically synthesised inhibitors to clinically significant β-lactamases of class A, B, and C using biophysical and biochemical approaches, and computational analyses. These molecules follow Lipinski's rule of five and have acceptable solubility, permeability, and oral bioavailability. These molecules were found to be non-toxic and non-carcinogenic. MIC results suggest that these molecules restore the antibiotic efficacy against class A, B, and C β-lactamases. Kinetics data showed that these molecules reduce the catalytic efficiency of clinically relevant class A, B, and C β-lactamases. Fluorescence study showed significant interaction between these flavone-/coumarin-based isoxazole derivatives and class A/B/ C β-lactamases. This study showed promising effect of these new generation compounds as broad spectrum β-lactamase inhibitors of both SBLs and MBLs.Communicated by Ramaswamy H. Sarma.

β-Lactamase-Responsive Hydrogel Drug Delivery Platform for Bacteria-Triggered Cargo Release

Antibiotic resistance is a growing public health threat that complicates the treatment of infections. β-Lactamase enzymes, which hydrolyze the β-lactam ring present in many common antibiotics, are a major cause of this resistance and are produced by a broad range of bacterial pathogens. Here, we developed hydrogels that degrade specifically in the presence of β-lactamases and β-lactamase-producing bacteria as a platform for bacteria-triggered drug delivery. A maleimide-functionalized β-lactamase-cleavable cephalosporin was used as a crosslinker in the fabrication of hydrogels through end-crosslinked polymerization with multiarm thiol-terminated poly(ethylene glycol) macromers via Michael-type addition. We demonstrated that only hydrogels containing the responsive crosslinker were degraded by β-lactamases and β-lactamase-producing bacteria in vitro and in an ex vivo porcine skin infection model. Fluorescent polystyrene nanoparticles, encapsulated in the hydrogels as model cargo, were released at rates that closely tracked hydrogel wet mass loss, confirming β-lactamase-triggered controlled cargo release. Nonresponsive hydrogels, lacking the β-lactam crosslinker, remained stable in the presence of β-lactamases and β-lactamase-producing bacteria and exhibited no change in mass or nanoparticle release. Furthermore, the responsive hydrogels remained stable in non-β-lactamase enzymes, including collagenases and lipases. These hydrogels have the potential to be used as a bacteria-triggered drug delivery system to control unnecessary exposure to encapsulated antimicrobials, which can provide effective infection treatment without exacerbating resistance.

Characterization of β-Lactamases and Multidrug Resistance Mechanisms in Enterobacterales from Hospital Effluents and Wastewater Treatment Plant

Antimicrobials in wastewater promote the emergence of antibiotic resistance, facilitated by selective pressure and transfer of resistant genes. Enteric bacteria belonging to Escherichia coli, Klebsiella pneumoniae, Klebsiella oxytoca, Enterobacter cloacae, and Citrobacter species (n = 126) from hospital effluents and proximate wastewater treatment plant were assayed for susceptibility to four antimicrobial classes. The β-lactamase encoding genes harbored in plasmids were genotyped and the plasmids were sequenced. A multidrug resistance phenotype was found in 72% (n = 58) of E. coli isolates, 70% (n = 43) of Klebsiella species isolates, and 40% (n = 25) of Enterobacter and Citrobacter species. Moreover, 86% (n = 50) of E. coli, 77% (n = 33) of Klebsiella species, and 25% (n = 4) of Citrobacter species isolates phenotypically expressed extended spectrum β-lactamase. Regarding ESBL genes, bla_CTX-M-27 and bla_TEM-1 were found in E. coli, while Klebsiella species harbored bla_CTX-M-15, bla_CTX-M-30, or bla_SHV-12. Genes coding for aminoglycoside modifying enzymes, adenylyltransferases (aadA1, aadA5), phosphotransferases (aph(6)-1d, aph(3″)-Ib), acetyltransferases (aac(3)-IIa), (aac(6)-Ib), sulfonamide/trimethoprim resistant dihydropteroate synthase (sul), dihydrofolate reductase (dfrA), and quinolone resistance protein (qnrB1) were also identified. Monitoring wastewater from human sources for acquired resistance in clinically important bacteria may provide a cheaper alternative in regions facing challenges that limit clinical surveillance.

Induction of AmpC-Mediated β-Lactam Resistance Requires a Single Lytic Transglycosylase in Agrobacterium tumefaciens

The remarkable ability of Agrobacterium tumefaciens to transfer DNA to plant cells has allowed the generation of important transgenic crops. One challenge of A. tumefaciens-mediated transformation is eliminating the bacteria after plant transformation to prevent detrimental effects to plants and the release of engineered bacteria to the environment. Here, we use a reverse-genetics approach to identify genes involved in ampicillin resistance, with the goal of utilizing these antibiotic-sensitive strains for plant transformations. We show that treating A. tumefaciens C58 with ampicillin led to increased β-lactamase production, a response dependent on the broad-spectrum β-lactamase AmpC and its transcription factor, AmpR. Loss of the putative ampD orthologue atu2113 led to constitutive production of AmpC-dependent β-lactamase activity and ampicillin resistance. Finally, one cell wall remodeling enzyme, MltB3, was necessary for the AmpC-dependent β-lactamase activity, and its loss elicited ampicillin and carbenicillin sensitivity in the A. tumefaciens C58 and GV3101 strains. Furthermore, GV3101 ΔmltB3 transforms plants with efficiency comparable to that of the wild type but can be cleared with sublethal concentrations of ampicillin. The functional characterization of the genes involved in the inducible ampicillin resistance pathway of A. tumefaciens constitutes a major step forward in efforts to reduce the intrinsic antibiotic resistance of this bacterium. IMPORTANCE Agrobacterium tumefaciens, a significant biotechnological tool for production of transgenic plant lines, is highly resistant to a wide variety of antibiotics, posing challenges for various applications. One challenge is the efficient elimination of A. tumefaciens from transformed plant tissue without using levels of antibiotics that are toxic to the plants. Here, we present the functional characterization of genes involved in β-lactam resistance in A. tumefaciens. Knowledge about proteins that promote or inhibit β-lactam resistance will enable the development of strains to improve the efficiency of Agrobacterium-mediated plant genetic transformations. Effective removal of Agrobacterium from transformed plant tissue has the potential to maximize crop yield and food production, improving the outlook for global food security.

ROCker Models for Reliable Detection and Typing of Short-Read Sequences Carrying β-Lactamase Genes

Identification of genes encoding β-lactamases (BLs) from short-read sequences remains challenging due to the high frequency of shared amino acid functional domains and motifs in proteins encoded by BL genes and related non-BL gene sequences. Divergent BL homologs can be frequently missed during similarity searches, which has important practical consequences for monitoring antibiotic resistance. To address this limitation, we built ROCker models that targeted broad classes (e.g., class A, B, C, and D) and individual families (e.g., TEM) of BLs and challenged them with mock 150-bp- and 250-bp-read data sets of known composition. ROCker identifies most-discriminant bit score thresholds in sliding windows along the sequence of the target protein sequence and hence can account for nondiscriminative domains shared by unrelated proteins. BL ROCker models showed a 0% false-positive rate (FPR), a 0% to 4% false-negative rate (FNR), and an up-to-50-fold-higher F1 score [2 × precision × recall/(precision + recall)] compared to alternative methods, such as similarity searches using BLASTx with various e-value thresholds and BL hidden Markov models, or tools like DeepARG, ShortBRED, and AMRFinder. The ROCker models and the underlying protein sequence reference data sets and phylogenetic trees for read placement are freely available through http://enve-omics.ce.gatech.edu/data/rocker-bla. Application of these BL ROCker models to metagenomics, metatranscriptomics, and high-throughput PCR gene amplicon data should facilitate the reliable detection and quantification of BL variants encoded by environmental or clinical isolates and microbiomes and more accurate assessment of the associated public health risk, compared to the current practice.

IMPORTANCE Resistance genes encoding β-lactamases (BLs) confer resistance to the widely prescribed antibiotic class β-lactams. Therefore, it is important to assess the prevalence of BL genes in clinical or environmental samples for monitoring the spreading of these genes into pathogens and estimating public health risk. However, detecting BLs in short-read sequence data is technically challenging. Our ROCker model-based bioinformatics approach showcases the reliable detection and typing of BLs in complex data sets and thus contributes toward solving an important problem in antibiotic resistance surveillance. The ROCker models developed substantially expand the toolbox for monitoring antibiotic resistance in clinical or environmental settings.

Penicillin-Binding Proteins, β-Lactamases, and β-Lactamase Inhibitors in β-Lactam-Producing Actinobacteria: Self-Resistance Mechanisms

The human society faces a serious problem due to the widespread resistance to antibiotics in clinical practice. Most antibiotic biosynthesis gene clusters in actinobacteria contain genes for intrinsic self-resistance to the produced antibiotics, and it has been proposed that the antibiotic resistance genes in pathogenic bacteria originated in antibiotic-producing microorganisms. The model actinobacteria Streptomyces clavuligerus produces the β-lactam antibiotic cephamycin C, a class A β-lactamase, and the β lactamases inhibitor clavulanic acid, all of which are encoded in a gene supercluster; in addition, it synthesizes the β-lactamase inhibitory protein BLIP. The secreted clavulanic acid has a synergistic effect with the cephamycin produced by the same strain in the fight against competing microorganisms in its natural habitat. High levels of resistance to cephamycin/cephalosporin in actinobacteria are due to the presence (in their β-lactam clusters) of genes encoding PBPs which bind penicillins but not cephalosporins. We have revised the previously reported cephamycin C and clavulanic acid gene clusters and, in addition, we have searched for novel β-lactam gene clusters in protein databases. Notably, in S. clavuligerus and Nocardia lactamdurans, the β-lactamases are retained in the cell wall and do not affect the intracellular formation of isopenicillin N/penicillin N. The activity of the β-lactamase in S. clavuligerus may be modulated by the β-lactamase inhibitory protein BLIP at the cell-wall level. Analysis of the β-lactam cluster in actinobacteria suggests that these clusters have been moved by horizontal gene transfer between different actinobacteria and have culminated in S. clavuligerus with the organization of an elaborated set of genes designed for fine tuning of antibiotic resistance and cell wall remodeling for the survival of this Streptomyces species. This article is focused specifically on the enigmatic connection between β-lactam biosynthesis and β-lactam resistance mechanisms in the producer actinobacteria.

Conjugation of a Hybrid Plasmid Encoding Hypervirulence and Carbapenem Resistance in Klebsiella pneumoniae of Sequence Type 592

Klebsiella pneumoniae simultaneously carrying genes encoding carbapenem resistance and hypervirulence causes fatal infections, representing a severe threat to human health. These carbapenem-resistant and hypervirulent K. pneumoniae (hvCRKP) strains are increasingly reported worldwide and have been found to belong to a variety of sequence types (STs). In this study, we report and characterized an hvCRKP strain of ST592, an uncommon ST, which caused a fatal infection in intensive care unit (ICU) in China and represents a novel type of hvCRKP. We demonstrated that this novel hvCRKP type emerged from the carbapenem-susceptible hypervirulent K. pneumoniae (hvKP) lineage of the K57 capsular type. K57 hvKP contains a pLVPK-like virulence plasmid and then acquired a conjugative bla_KPC–2-carrying plasmid to form hvCRKP. The pLVPK-like virulence plasmid contains no complete conjugation module but was able to be transferred by fusion with the conjugative bla_KPC–2-carrying plasmid during conjugation. This represents a new mechanism of simultaneous transfer genetic determinants of carbapenem resistance and virulence and highlights the undergoing expansion of hvCRKP, which requires rigorous monitoring and novel countermeasures to curb plasmid-mediated transmission.

Evaluation of Tebipenem Hydrolysis by β-Lactamases Prevalent in Complicated Urinary Tract Infections

Tebipenem pivoxil is the first orally available carbapenem antibiotic and has been approved in Japan for treating ear, nose, and throat and respiratory infections in pediatric patients. Its active moiety, tebipenem, has shown potent antimicrobial activity in vitro against clinical isolates of Enterobacterales species from patients with urinary tract infections (UTIs), including those producing extended-spectrum β-lactamases (ESBLs) and/or AmpC β-lactamase. In the present study, tebipenem was tested for stability to hydrolysis by a set of clinically relevant β-lactamases, including TEM-1, AmpC, CTX-M, OXA-48, KPC, and NDM-1 enzymes. In addition, hydrolysis rates of other carbapenems, including imipenem, meropenem, and ertapenem, were determined for comparison. It was found that, similar to other carbapenems, tebipenem was resistant to hydrolysis by TEM-1, CTX-M, and AmpC β-lactamases but was susceptible to hydrolysis by KPC, OXA-48, and NDM-1 enzymes with catalytic efficiency values (k_cat/K_m) ranging from 0.1 to 2 × 10⁶ M^-1s^-1. This supports the reported results of antimicrobial activity of tebipenem against ESBL- and AmpC-producing but not carbapenemase-producing Enterobacterales isolates. Considering that CTX-M and AmpC β-lactamases represent the primary determinants of multidrug-resistant complicated UTIs (cUTIs), the stability of tebipenem to hydrolysis by these enzymes supports the utility of its prodrug tebipenem, tebipenem pivoxil hydrobromide (TBP-PI-HBr), as an oral therapy for adult cUTIs.

Antimicrobial resistance in Escherichia coli isolated from on-farm and conventional hatching broiler farms in Ireland

Background

On-farm hatching (OH) systems are becoming more common in broiler production. Hatching conditions differ from conventional farms as OH chicks avoid exposure to handling, transport, post-hatch water and feed deprivation. In contrast, chicks in conventional hatching conditions (CH) are exposed to standard hatchery procedures and transported post hatching. The objectives of this pilot study were to investigate the prevalence and frequency of Escherichia coli resistant to antimicrobials, including presumptive ESBL/AmpC-producing E. coli, isolated from environmental and faecal samples from OH versus CH hatching systems, and to investigate the presence of ESBL/AmpC-producing encoding genes.

Results

Environmental samples were collected from one flock in 10 poultry farms (5 OH farms, 5 CH farms) on day 0 post disinfection of the facilities to assess hygiene standards. On D10 and D21 post egg/chick arrival onto the farm, samples of faeces, boot swabs and water drinker lines were collected.

E. coli were isolated on MacConkey agar (MC) and MacConkey supplemented with cefotaxime (MC+). Few E. coli were detected on D0. However, on D10 and D21 E. coli isolates were recovered from faeces and boot swabs. Water samples had minimal contamination. In this study, 100% of cefotaxime resistant E. coli isolates (n=33) detected on selective media and 44% of E. coli isolates (84/192) detected on nonselective media were multidrug resistant (MDR). The antimicrobial resistance (AMR) genotype for the 15 ESBL/AmpC producing isolates was determined using multiplex PCR. Six of these were selected for Sanger sequencing of which two were positive for bla_CMY-2, two for bla_TEM-1 and two were positive for both genes.

Conclusions

There was no difference in E. coli isolation rates or prevalence of AMR found between the OH versus CH systems, suggesting that the OH system may not be an additional risk of resistant E. coli dissemination to broilers compared to the CH systems. The frequency of β-lactam resistant E. coli in boot swab and faeces samples across both OH (24/33 (73%)) and CH (9/33 (27%)) systems may indicate that hatcheries could be a reservoir and major contributor to the transmission of AMR bacteria to flocks after entry to the rearing farms.

The Ins and Outs of Susceptibility Testing for New β-Lactam/β-Lactamase Inhibitor Combinations for Gram-Negative Organisms

Ceftazidime-avibactam, meropenem-vaborbactam, and imipenem-relebactam are among the newest β-lactam/β-lactamase inhibitors (BL/BLIs) introduced to the North American antibiotic market. All have broad Gram-negative activity, including against certain carbapenemases. Despite this, susceptibility testing is warranted due to variable activity against certain β-lactamases (e.g., oxacillinases) and the presence of acquired resistance mechanisms in some isolates. Here, we discuss what we know about these new antimicrobial agents and how to navigate implementation of susceptibility testing and reporting of these agents in clinical laboratories.