Carbapenem-resistant Gram-negative Bacteria Research Articles

Detection and molecular characterization of carbapenem-resistant gram-negative bacterial isolates.

Antimicrobial-resistant bacteria (ARB) are responsible for increased mortality and morbidity. Therefore, this study focuses on evaluating traditional and molecular diagnostic tools of carbapenem-resistant gram-negative bacteria (CRGNB). In order to achieve this, 94 samples, from different patients' specimens, and surrounding environment, were collected from intensive care units (ICUs) at Ain Shams University Specialized Hospital and the National Cancer Institute, Cairo, Egypt. The swabs were cultured on appropriate media, including Chromogenic medium (HiCrome KPC Agar Base "HIMEDI AM1831"), and MacConkey-10µg imipenem disc resulting in 136 isolates with different culture characteristics. Next, the selected isolates were subjected to VITEK 2 machine and 16SrRNA (16S ribosomal RNA) sequencing. The sensitivity of HiCROME KPC agar for CRGNB detection was 99.3% and 94.7%, in reference to the MacConkey-disc and VITEK-2 methods, respectively. The HiCrome KPC agar assumptions for bacterial identification were not as consistent as those of VITEK 2 (with only 47.4% agreement) and 16SrRNA gene sequencing analysis. The approaches discussed in this study facilitate providing rapid diagnosis and treatment of CRGNB, which helps increase survival rates. HiCrome KPC agar is considered a relatively accurate and easy method that can be used in any laboratory. In addition, the selected strains were deposited in the gene bank with the accession numbers OR553657, OR553658, and OR553659. It is noteworthy that Genus Acinetobacter is the major CRGNB isolated from the patients and environmental surfaces in the hospitals. This highlights the importance of proper environmental and terminal cleaning procedures in healthcare facilities and applying control measures to ensure infection prevention.

Carbapenem resistance in gram-negative pathogens in an Iranian hospital: high prevalence of OXA-type carbapenemase genes.

The widespread dissemination of carbapenem-resistant Gram-negative bacteria poses a significant threat to global public health. This study aimed to investigate the prevalence of carbapenem resistance in Gram-negative bacteria isolated from patients at the Children's Medical Center Hospital, Tehran, Iran, to understand the molecular mechanisms underlying this resistance. During the period spanning from June 2019 to June 2020, 777 Gram-negative bacterial strains were isolated. Antibiotic susceptibility testing was performed according to Clinical and Laboratory Standards Institute. Polymerase chain reaction was used to detect carbapenem resistance genes including bla OXA23, bla OXA24, bla OXA48, bla OXA51, bla OXA58, bla OXA143, bla KPC, bla IMP, bla VIM, and bla NDM. Among the total bacterial isolates, 141 (18.1%) exhibited carbapenem resistance. Escherichia coli was the most prevalent (57.4%), followed by Klebsiella pneumoniae (11.3%) and Acinetobacter baumannii (10.6%). Other notable contributors included Enterobacter spp. (5.7%), Salmonella spp. (3.5%), and Stenotrophomonas maltophilia (2.8%). Citrobacter spp., Proteus mirabilis, and Pseudomonas aeruginosa contributed to the distributions of two, one, and three isolates, respectively. Notably, bla OXA48 showed the highest prevalence (33%), followed by bla OXA143 and bla OXA58 (27% and 24%, respectively). In addition, bla OXA24 was present in 11% of the total isolates, bla OXA23 in 10%, and bla NDM in 10%, whereas bla KPC, bla VIM, and bla IMP were not detected. Our study highlights the prevalence of carbapenemase-producing Gram-negative isolates among pediatric patients. Notable resistance patterns, especially in K. pneumoniae and E. coli, underline the urgent need for proactive interventions, including appropriate antibiotic prescription practices and strengthening of antibiotic stewardship programs.

The oral cavity is a potential reservoir of gram-negative antimicrobial-resistant bacteria, which are correlated with ageing and the number of teeth

ObjectivesThe suppression of antimicrobial-resistant bacteria (ARB) is an important issue worldwide. In recent years, the presence of various ARB in the oral cavity has been reported, but the details remain unclear. Therefore, we aimed to isolate ARB from the oral cavity and investigate the factors affecting ARB colonization. MethodsThird-generation cephalosporin- or carbapenem-resistant gram-negative bacteria (GN-ARB) were isolated from the oral and nasal cavities of 514 participants who visited the dental clinic, and the whole-genome sequences of all the isolates were obtained. Additionally, the tongue microbiota was analysed by 16S rRNA sequencing. The correlations of GN-ARB isolation with clinical status and the tongue microbiota were subsequently investigated. ResultsAmong 514 participants, 131 and 13 GN-ARB strains were isolated from the oral cavities of 93 participants (18.1 %) and from the nasal cavities of 12 participants (2.3 %). The ARB were mainly affiliated with Acinetobacter spp. (39.7 %), Pseudomonas spp. (14.5 %) and Stenotrophomonas maltophilia (18.3 %). We found a correlation between the isolation of oral GN-ARB and ageing/the number of teeth. There were no significant correlations between the presence of GN-ARB and tongue microbiota composition. ConclusionsOur results suggest that the oral cavity is an important potential reservoir of GN-ARB and that ageing and tooth loss are risk factors for the presence of GN-ARB in the oral cavity.

Aeromonas and mcr–3: A Critical Juncture for Transferable Polymyxin Resistance in Gram-Negative Bacteria

Polymyxin antibiotics B and colistin are considered drugs of last resort for the treatment of multi-drug and carbapenem-resistant Gram-negative bacteria. With the emergence and dissemination of multi-drug resistance, monitoring the use and resistance to polymyxins imparted by mobilised colistin resistance genes (mcr) is becoming increasingly important. The Aeromonas genus is widely disseminated throughout the environment and serves as a reservoir of mcr–3, posing a significant risk for the spread of resistance to polymyxins. Recent phylogenetic studies and the identification of insertion elements associated with mcr–3 support the notion that Aeromonas spp. may be the evolutionary origin of the resistance gene. Furthermore, mcr–3-related genes have been shown to impart resistance in naïve E. coli and can increase the polymyxin MIC by up to 64-fold (with an MIC of 64 mg/L) in members of Aeromonas spp. This review will describe the genetic background of the mcr gene, the epidemiology of mcr-positive isolates, and the relationship between intrinsic and transferable mcr resistance genes, focusing on mcr–3 and mcr–3-related genes.

Hydrogel-based fluorescence assay kit for simultaneous determination of ceftazidime and avibactam

Monitoring the concentration of antibiotics rapidly and cost-effectively is crucial for accurate clinical medication and timely identification of drug-induced illnesses. Here, we constructed a novel fluorescent assay kit to monitor Zavicefta, an effective antibiotic composed of avibactam (AVI) and ceftazidime (CFZ) to treat carbapenem-resistant gram-negative bacteria infections. AVI can emit fluorescence, but CFZ cannot. To enable simultaneous measurement of both in one kit, we designed molecularly imprinted polymer (MIP) modified quantum dots (QDs) for CFZ determination. MIPs have received significant attention as an artificial antibody due to their exceptional specificity for various targets, particularly drugs with small molecular weight. Under the excitation wavelength of 350 nm, the detection process involves a decrease in QDs’ fluorescence signal at 600 nm owing to the “gate effect” between MIP and CFZ and the internal filtration effect between CFZ and QDs. Simultaneously, a fluorescence emission characteristic peak at 420 nm for AVI emerges. In addition, to simplify the operation procedure and improve determination throughput, the detection agents were incorporated into a hydrogel and placed in a 96-well plate, enabling concurrent quantification of AVI and CFZ within the respective range of 80–1000 μM and 1–1000 μM. The developed assay kit successfully determined AVI and CFZ in human serums and therapeutic drug monitoring in a live rabbit model. Recoveries of AVI and CFZ were 92.7–114%, with relative standard deviations below 6.0%. Moreover, a smartphone was employed to read the fluorescence signals, which was beneficial for cost reduction and out-of-lab analysis. This study will deliver a pragmatic resolution to developing high-throughput assay kits for drug determination.Graphical

Advances in the clinical treatment of multidrug-resistant pathogens using polymyxins.

Polymyxins are a vital class of antibiotics used to combat multidrug-resistant Gram-negative bacteria. However, their use is limited due to potential nephrotoxicity and the availability of alternative antibiotics. This review aims to examine the properties of polymyxins and the clinical advances in their use for treating infections caused by carbapenem-resistant Gram-negative bacteria (CR-GNB). This review analyses literature on polymyxin properties and various clinical approaches, including intravenous drip infusion, nebulized or dry powder inhalation, and ointment application. Treatment efficacy in terms of bacterial eradication, cure rate and mortality rate are reviewed and evaluated. Polymyxins have been reintroduced to treat critical infections due to the increasing prevalence of CR-GNB. Clinical trials and studies have confirmed that polymyxins can effectively treat CR-GNB infections when the formulation and administration are appropriate, with acceptable levels of nephrotoxicity. In the future, the development of polymyxin formulations will aim to improve their clinical effectiveness while reducing toxicity and side effects and preventing the emergence of polymyxin-resistant strains. Enhanced efficacy and minimized potential side effects can be achieved by developing new polymyxin-delivery systems that provide a smart and controlled release or customized patient administration.

IDENTIFICATION OF ANTIBACTERIAL AGENTS AGAINST KLEBSIELLA PNEUMONIAE TARGETING THE CTX-M-15 PROTEIN USING INTEGRATED STRUCTURE MODEL-BASED VIRTUAL SCREENING METHODS

The spread of carbapenem-resistant Gram-negative bacteria, particularly those having the bla CTX-M-15 gene, has stimulated a global challenge for β-lactam antimicrobial effectiveness. This study aims to identify commercially available compounds that demonstrate strong antibacterial properties with high efficacy and low toxicity to combat the increasing problem of antibiotic resistance. Virtual screening and molecular docking techniques were employed to generate a pharmacophore model based on the molecular structure. Eleven potential compounds were selected based on their IC50 values. Subsequently, a molecular docking approach was employed to select the best three small molecules for further comprehensive investigation. Moreover, absorption, distribution, metabolism, and excretion (ADME) and toxicity analysis ensured that it can be used as a drug without the effect of health. Finally, molecular dynamic (MD) simulations and generalized Born model and solvent accessibility (MMGB/SA) were carried out to evaluate the stability of these compounds against the receptor. Three selected compounds, specifically ZINCCID (ZINC94211493, ZINC20528448, and ZINC04331046), have exhibited strong binding affinities of -8.4, -8.1, and -7.7 kcal/mol, respectively. This has been predicted as a potential competitive inhibitor targeting CTX-M-15. However, further assessment through experimental lab studies is required to evaluate the efficacy of these compounds. Initially, a structure-based model was constructed, and subsequently, molecular docking, MD simulation, ADMET analysis, and MMGB/SA were performed. Through the A-to-Z virtual screening process, the top three natural compounds were identified as potential lead molecules in the development of novel drugs targeting CTX-M-15 for combating Klebsiella infections. Keywords: Klebsiella; Structure-based; Molecular docking; Pharmacophore modeling; CTX-M-15 protein; ADMET; MMGB/SA, MD simulation.

Persistent carbapenem resistance in mechanically ventilated ICU patients: A before-and-after analysis of the COVID-19 surge

ObjectiveHow did the antimicrobial resistance profile of critically ill patients evolve before, during, and after COVID-19 surge periods? MethodsWe retrospectively analysed all critically ill mechanically ventilated adult patients admitted to eight Brazilian hospitals from January 1st, 2018, to April 30th, 2023. We stratified the patients into three periods based on their admission date: pre-surge (Jan 01/2018-Mar 01/2020), surge (Mar 01/2020 - Oct 01/2021), and post-surge (after Oct 01/2021). We compared the proportion of positive cultures, prevalence of pathogens, and resistance rates across periods using the rate ratios (RR) and their 95% confidence intervals (95% CI). ResultsWe analysed 9,780 ICU patients: 3,718 were in the pre-surge, 3,815 in the surge, and 2,247 in the post-surge period. Patients in the surge period were younger (median: 70 vs. 74 pre-surge vs. 75 post-surge) and presented a higher duration of invasive mechanical ventilation (median 7 vs. 5 days). The utilisation of blood and respiratory cultures increased throughout periods (56.9 pre-surge vs. 69.4 surge vs. 70.4 patients/1,000 patient days post-surge). The isolation of carbapenem-resistant gram-negative bacteria increased during the surge (RR [95% CI]: 1.8 [1.5-2.2], compared to pre-surge), decreased in post-surge (RR [95% CI]: 0.72 [0.6-0.9], and remained higher than pre-surge (RR [95% CI]: 1.3 [1.0-1.6]). Resistance rates for Pseudomonas aeruginosa reduced from 32% in pre- to 23% post-surge, whereas Klebsiella pneumoniae doubled during the surge, 26% to 52%, and remained higher than pre-surge. ConclusionCarbapenem resistance increased during the surge period. Although it decreased post-surge, it remained higher than the rates observed before the pandemic.

Design, synthesis, and bioactivity investigation of novel cyclic lipopeptide antibiotics targeting top-priority multidrug-resistant gram-negative bacteria

ObjectivesPolymyxins are the last-line therapy for top-priority multidrug-resistant (MDR) gram-negative bacteria. However, polymyxin nephrotoxicity impedes its clinical application. This study aimed to design, synthesize, and identify a novel and promising polymyxin derivative with high efficacy and low toxicity. MethodsTo design polymyxin derivatives, we reduced the hydrophobicity of the two hydrophobic domains (fatty acyl chain and D-Phe6-L-Leu7) and modified the positive charged L-2,4-diaminobutyric acid (Dab) residues. Twenty-five derivatives were synthesized, and their antibacterial activities in vitro and renal cytotoxicities were determined. The nephrotoxicity and pharmacokinetic parameters of compound 12 were examined in rats. Antibacterial efficacy in vivo was evaluated using a mouse systemic infection model. Surface plasmon resonance analysis, compound 12-rifampicin combination therapy, and scanning electron microscopy were used to study the mechanism of action of compound 12. ResultsThis research found a new compound, identified as compound 12, which showed similar or increased antibacterial activity against all tested sensitive and carbapenem-resistant gram-negative bacteria. It exhibited reduced renal cytotoxicity and nephrotoxicity, a favorable pharmacokinetic profile, and maintained or improved antibacterial efficacy in vivo. Importantly, its anti-Pseudomonas aeruginosa activity significantly improved. Compound 12, when combined with rifampicin, enhanced the activity of rifampin against gram-negative bacteria. Compound 12 also showed a high affinity for lipopolysaccharide and disrupted cell membrane integrity. ConclusionReducing the hydrophobicity of the two domains reduced renal cytotoxicity and nephrotoxicity. Shortening the side chain of Dab3 by one carbon maintained or increased its antibacterial activity both in vitro and in vivo. Furthermore, only the length of the side chain of Dab9 could be shortened by one carbon among the Dab1,5 and Dab8,9 residues. The bactericidal effects of compound 12 were related to the disruption of cell membrane integrity. Compound 12 may be a promising candidate for combating sensitive and carbapenem-resistant gram-negative bacterial infections, especially Pseudomonas aeruginosa.

Prevalence and Molecular Epidemiology of Intestinal Colonization by Multidrug-Resistant Bacteria among Hematopoietic Stem-Cell Transplantation Recipients: A Bulgarian Single-Center Study.

Background/Objectives: Intestinal colonization by multidrug-resistant (MDR) bacteria is considered one of the main risk factors for invasive infections in the hematopoietic stem-cell transplant (HSCT) setting, associated with hard-to-eradicate microorganisms. The aim of this study was to assess the rate of intestinal colonization by MDR bacteria and their microbial spectrum in a group of post-HSCT patients to study the genetic determinants of beta-lactam and glycopeptide resistance in the recovered isolates, as well as to determine the epidemiological relation between them. Methods: The intestinal colonization status of 74 patients admitted to the transplantation center of University Hospital "St. Marina"-Varna in the period January 2019 to December 2021 was investigated. Stool samples/rectal swabs were screened for third-generation cephalosporin and/or carbapenem-resistant Gram-negative bacteria, methicillin-resistant Staphylococcus aureus (MRSA), vancomycin-resistant enterococci (VRE), and Stenotrophomonas maltophilia. Identification and antimicrobial susceptibility testing were performed by Phoenix (BD, Sparks, MD, USA) and MALDI Biotyper sirius (Bruker, Bremen, Germany). Molecular genetic methods (PCR, DNA sequencing) were used to study the mechanisms of beta-lactam and glycopeptide resistance in the collected isolates, as well as the epidemiological relationship between them. Results: A total of 28 patients (37.8%) were detected with intestinal colonization by MDR bacteria. Forty-eight non-duplicate MDR bacteria were isolated from their stool samples. Amongst them, the Gram-negative bacteria prevailed (68.8%), dominated by ESBL-producing Escherichia coli (30.3%), and followed by carbapenem-resistant Pseudomonas sp. (24.2%). The Gram-positive bacteria were represented exclusively by Enterococcus faecium (31.2%). The main beta-lactam resistance mechanisms were associated with CTX-M and VIM production. VanA was detected in all vancomycin-resistant enterococci. A clonal relationship was observed among Enterobacter cloacae complex and among E. faecium isolates. Conclusions: To the best of our knowledge, this is the first Bulgarian study that presents detailed information about the prevalence, resistance genetic determinants, and molecular epidemiology of MDR gut-colonizing bacteria in HSCT patients.

Antibiotics-free compounds for managing carbapenem-resistant bacteria; a narrative review.

Carbapenem-resistant (CR) Gram-negative bacteria have become a significant public health problem in the last decade. In recent years, the prevalence of CR bacteria has increased. The resistance to carbapenems could result from different mechanisms such as loss of porin, penicillin-binding protein alteration, carbapenemase, efflux pump, and biofilm community. Additionally, genetic variations like insertion, deletion, mutation, and post-transcriptional modification of corresponding coding genes could decrease the susceptibility of bacteria to carbapenems. In this regard, scientists are looking for new approaches to inhibit CR bacteria. Using bacteriophages, natural products, nanoparticles, disulfiram, N-acetylcysteine, and antimicrobial peptides showed promising inhibitory effects against CR bacteria. Additionally, the mentioned compounds could destroy the biofilm community of CR bacteria. Using them in combination with conventional antibiotics increases the efficacy of antibiotics, decreases their dosage and toxicity, and resensitizes CR bacteria to antibiotics. Therefore, in the present review article, we have discussed different aspects of non-antibiotic approaches for managing and inhibiting the CR bacteria and various methods and procedures used as an alternative for carbapenems against these bacteria.

Evaluation of phenotypic carbapenem inactivation methods among carbapenem resistant gram-negative bacteria isolated from blood culture specimens and their synergy testing

Evaluation of phenotypic carbapenem inactivation methods among carbapenem resistant gram-negative bacteria isolated from blood culture specimens and their synergy testing

Polymyxin B adjuvants against polymyxin B- and carbapenem-resistant Gram-negative bacteria.

Aim: Polymyxin B (PMB) is one of the few therapeutic options for treating infections caused by carbapenem-resistant Gram-negative bacteria (CR-GNB). However, the emergence of PMB-resistant CR-GNB strains has prompted the exploration of antibiotic adjuvants as potential therapeutic avenues. Thus, this study evaluates the potential of 3,5-dinitrobenzoic acid derivatives (DNH01, DNH11, DNH13 and DNH20) and isoniazid-N-acylhydrazones (INZ1-7, INZ9 and INZ11) as adjuvants to enhance PMB efficacy against CR-GNB.Materials & methods: MIC, MBC and drug combination assays were conducted using multidrug-resistant clinical isolates of Enterobacterales and Acinetobacter baumannii. In addition, the effects of PMB and PMB+DNH derivatives were assessed through flow cytometry and scanning electron microscopy (SEM).Results: DNH01, DNH11 and DNH20, unlike the INH-acylhydrazones, significantly restored PMB activity (MIC≤2μg/ml) in 80% of the tested isolates. Flow cytometry and SEM assays confirmed that DNH derivatives rescued the activity of PMB, yielding results comparable to those expected for PMB alone but at 256-fold lower concentrations.Conclusion: These findings suggest DNH derivatives hold substantial promise as PMB adjuvants to combat PMB-resistant CR-GNB infections.

Cefiderocol: a first and novel class of siderophore cephalosporin for Carbapenem-resistant Gram-negative infection

Antimicrobial resistance is currently recognized as an urgent concern against public health in worldwide. Carbapenem-resistant (CR) Gram-negative bacteria, such as Enterobacterales, Pseudomonas aeruginosa and Acinetobacter baumannii are listed as critical pathogens which are widely spread and can cause severe and often deadly infections in WHO guidance. Cefiderocol (Fetroja®), a novel and first siderophore cephalosporin, was approved for the infections caused by these problematic CR Gram-negative bacteria in Japan on November 30, 2023. Cefiderocol has unique mechanisms to be incorporated into bacterial cells using bacterial iron transportation system and to be highly stable against most β-lactamases, which lead to promising antibacterial activity against these Gram-negative bacteria including CR strains in vitro. In CREDIBLE-CR Ph3 trial, cefiderocol showed the good efficacy and safety for patients with CR Gram-negative bacteria. In APEKS-cUTI and APEKS-NP trials, cefiderocol showed non-inferiority and suggested superiority to imipenem/cilastatin in complicated urinary tract infection (cUTI) patients, and non-inferiority to high dose of meropemen in pneumonia patients, respectively. Cefiderocol is expected to be an optimal treatment for CR Gram-negative infections with limited treatment options and would be an important drug to combat the threat of CR bacteria.

Use of Cefiderocol in Adult Patients: Descriptive Analysis from a Prospective, Multicenter, Cohort Study.

Cefiderocol is a siderophore cephalosporin showing activity against various carbapenem-resistant Gram-negative bacteria (CR-GNB). No data currently exist about real-world use of cefiderocol in terms of types of therapy (e.g., empirical or targeted, monotherapy or combined regimens), indications, and patient characteristics. In this multicenter, prospective study, we aimed at describing the use of cefiderocol in terms of types of therapy, indications, and patient characteristics. Cefiderocol was administered as empirical and targeted therapy in 27.5% (55/200) and 72.5% (145/200) of cases, respectively. Overall, it was administered as monotherapy in 101/200 cases (50.5%) and as part of a combined regimen for CR-GNB infections in the remaining 99/200 cases (49.5%). In multivariable analysis, previous isolation of carbapenem-resistant Acinetobacter baumannii odds ratio (OR) 2.56, with 95% confidence interval (95% CI) 1.01-6.46, p=0.047] and previous hematopoietic stem cell transplantation (OR 8.73, 95% CI 1.05-72.54, p=0.045) were associated with administration of cefiderocol as part of a combined regimen, whereas chronic kidney disease was associated with cefiderocol monotherapy (OR 0.38 for combined regimen, 95% CI 0.16-0.91, p=0.029). Cumulative 30-day mortality was 19.8%, 45.0%, 20.7%, and 22.7% in patients receiving targeted cefiderocol for infections by Enterobacterales, A. baumannii, Pseudomonas aeruginosa, and any metallo-β-lactamase producers, respectively. Cefiderocol is mainly used for targeted treatment, although empirical therapies account for more than 25% of prescriptions, thus requiring dedicated standardization and guidance. The almost equal distribution of cefiderocol monotherapy and cefiderocol-based combination therapies underlines the need for further study to ascertain possible differences in efficacy between the two approaches.

Characterisation of carbapenemase-producing Gram-negative bacilli among clinical isolates in a tertiary care centre in Kerala, South India

Background: Infections caused by carbapenem-resistant Gram-negative bacteria are a cause for concern due to the limited choice of antibiotics available for their treatment. Aims, Settings and Design: This study screened multidrug-resistant (MDR) Gram-negative bacilli isolated from clinical samples over a period of one year, for carbapenem resistance and characterised them using phenotypic methods such as combined disc diffusion test (CDDT), modified Hodge test (MHT), E-test for metallo-beta-lactamase (MBL) and molecular method, PCR. Materials and Methods: Two hundred and ten MDR Gram-negative bacilli were screened for carbapenem resistance using Imipenem and Meropenem disc diffusion. These were further checked for carbapenemase production by CDDT, MHT and E-test for MBL. Those positive by E-test were subjected to PCR. Uniplex PCR for New Delhi metallo-beta-lactamase-1 was used for Escherichia coli and Klebsiella pneumoniae , and multiplex PCR for Imipenemase and Verona imipenemase was used for Pseudomonas aeruginosa and Acinetobacter baumannii isolates. Results: Twenty-three (11%) isolates were found to be carbapenem-resistant and included E. coli (six) K. pneumoniae (three), P. aeruginosa (five) and A. baumannii (nine). Seventeen (74%) isolates were positive by phenotypic methods and were subjected to PCR. Out of eight Enterobacteriaceae isolates subjected to PCR, all were positive for bla NDM gene. All were negative for bla KPC gene. All five A. baumannii isolates subjected to PCR were found to contain bla VIM gene. Two out of four P. aeruginosa isolates were positive for bla IMP , one was positive for bla VIM gene. One P. aeruginosa isolate was positive for both bla IMP and bla VIM gene. Conclusions: In view of the increasing resistance of Gram-negative bacilli to carbapenems, rational use of antibiotics needs to be emphasised.

Therapeutic drug monitoring of polymyxin B cerebrospinal fluid concentrations in patients with carbapenem-resistant Gram-negative bacteria-induced central nervous system infection.

Central nervous system (CNS) infections caused by carbapenem-resistant Gram-negative bacteria (CR-GNB) present a major health and economic burden worldwide. This multicentre prospective study aimed to assess the feasibility and usefulness of CSF therapeutic drug monitoring (TDM) after intrathecal/intraventricular administration of polymyxin B in patients with CNS infections. Forty-two patients treated with intrathecal/intraventricular administration of polymyxin B against CR-GNB-induced CNS infections were enrolled. CSF trough level (Cmin) was collected beginning on Day 2 post-polymyxin B initiation and thereafter. The primary outcomes were clinical cure and 28-day all-cause mortality. All patients started with intrathecal/intraventricular administration of polymyxin B at a dose of 5 g/day, corresponding to a median CSF Cmin of 2.93 mg/L (range, 0.21-25.74 mg/L). Clinical cure was 71.4%, and the median CSF Cmin of this group was higher than that of clinical failure group [3.31 (IQR, 1.73-5.62) mg/L versus 2.25 (IQR, 1.09-4.12) mg/L; P = 0.011]. In addition, with MICs ≤ 0.5 mg/L, maintaining polymyxin B CSF Cmin above 2.0 mg/L showed a higher clinical cure rate (P = 0.041). The 28-day all-cause mortality rate was 31.0% and had no association with CSF Cmin. After intrathecal/intraventricular administration of polymyxin B, CSF concentrations fluctuated considerably inter- and intra-individual. Polymyxin B CSF Cmin above 2.0 mg/L was associated with clinical cure when MICs were ≤ 0.5 mg/L, and the feasibility of TDM warrants additional clinical studies.

New antibiotics in clinical pipeline for treating infections caused by metallo-β-lactamases producing Gram-negative bacteria.

To discuss novel antibiotics under clinical development, focusing on agents showing in-vitro activity against metallo-β-lactamases (MBL)-producing carbapenem-resistant Gram-negative bacteria (CR-GNB). Currently, only a few approved agents show activity, alone or in synergistic combinations, against MBL-producing CR-GNB. If approved by regulatory agencies in case of favorable results from ongoing (and, for some agents, already completed) phase-3 studies, some novel β-lactam/β-lactamase inhibitor (BL/BLI) combinations could become available in the next few years as additional important options for treating MBL-producing CR-GNB infections. Additional interesting agents that belong both to BL/BLI combinations and to antibiotic classes other than BL and BL/BLI combinations have also shown activity against MBL-producing CR-GNB, with most of them being in early phases of clinical development. Improving the use of these novel agents through virtuous antimicrobial stewardship frameworks able to guarantee both the efficacious treatment of infections requiring their use and the avoidance of their use whenever not necessary remains a challenge of utmost importance that should not be overlooked.

Assessment of carbapenem resistance and carbapenemase genes in wastewater from cattle slaughterhouses: Implications for environmental antibiotic resistance surveillance

The objectives of the study were to determine the prevalence of carbapenem-resistant Gram-negative bacteria and assess the potential risks associated with cattle slaughterhouse wastewater. A total of 270 wastewater samples were collected from 10 different cattle slaughterhouses for microbiological analysis. Conventional culture methods were employed, followed by disc diffusion, the Modified Carbapenem Inactivation Method (mCIM), and the Modified Hodge Test (MHT) to identify carbapenem resistance. The Vitek® 2 compact system was used for species identification and antibiotic susceptibility profiling. Conventional and quantitative PCR (qPCR) were performed to detect specific carbapenemase genes (blaKPC, blaNDM, and blaOXA-48). Among the collected 72 carbapenem-resistant isolates, one Pseudomonas fluorescens, one Aeromonas hydrophila, and two Aeromonas sobria exhibited resistance to meropenem. Additionally, six P. fluorescens and two A. hydrophila isolates demonstrated intermediate resistance to meropenem. Furthermore, five carbapenem-resistant isolates were identified as Stenotrophomonas maltophilia, known to be inherently resistant to most antibiotics. Ten different antibiotics were evaluated in the antibiotic resistance panel and all Aeromonas isolates were found to be resistant to cefazolin and one A. hydrophila was detected as multi-drug resistant. The revealed data indicates that slaughterhouse wastewater can serve as a reservoir for antibiotic-resistant opportunistic pathogens. However, it may not pose a substantial risk for the distribution of carbapenemases, thereby mitigating concerns related to potential public health and environmental hazards associated with this aspect of slaughterhouse operations. This study contributes to understanding of antibiotic resistance in livestock-related environments and underscores the importance of continued monitoring and surveillance.

Real-world data on the effects of colistin sulfate and polymyxin B sulfate in the treatment of pneumonia induced by CR-GNB.

The aim of this study was to compare the efficacy and safety of colistin sulfate (CS) with polymyxin B sulfate (PMB) in the treatment of pneumonia induced by carbapenem-resistant Gram-negative bacteria (CR-GNB). Patients diagnosed with pneumonia caused by CR-GNB and admitted to the intensive care unit (ICU) from January 2020 to September 2022 were enrolled in this study. The patients were divided into the CS group and the PMB group according to their medication regimens. Group-wise demographic data, clinical efficacy, prognosis, and adverse events were analyzed and compared. A total of 120 patients (68 in the CS group and 52 in the PMB group) with pneumonia were included in the study. The majority of the pathogens were CR-Acinetobacter baumannii, followed by CR-Klebsiella pneumoniae, and CR-Pseudomonas aeruginosa. The clinical response rates in the CS and PMB groups after treatment were 62.0% and 65.4%, bacterial clearances were 44.0% and 36.5%, 28-day mortality rates were 16.0% and 13.5%, respectively; no significant differences between the two treatments were found. Nevertheless, the adverse effects were significantly less common in the CS group than in the PMB group, especially when treatments were administered intravenously. CS, a novel polymyxin E formulation, is as effective as PMB in treating pneumonia induced by CR-GNB while causing less side effects.