Metallo-beta-lactamase Research Articles

Integrating Siderophore Substructures in Thiol-Based Metallo-β-Lactamase Inhibitors

Metallo beta lactamases (MBLs) are among the most problematic resistance mechanisms of multidrug-resistant Gram-negative pathogens due to their broad substrate spectrum and lack of approved inhibitors. In this study, we propose the integration of catechol substructures into the design of thiol-based MBL inhibitors, aiming at mimicking bacterial siderophores for the active uptake by the iron acquisition system of bacteria. We synthesised two catechol-containing MBL inhibitors, as well as their dimethoxy counterparts, and tested them for in vitro inhibitory activity against NDM-1, VIM-1, and IMP-7. We demonstrated that the most potent catechol-containing MBL inhibitor is able to bind Fe3+ ions. Finally, we could show that this compound restores the antibiotic activity of imipenem in NDM-1-expressing K. pneumoniae, while leaving HUVEC cells completely unaffected. Thus, siderophore-containing MBL inhibitors might be a valuable strategy to overcome bacterial MBL-mediated resistance to beta lactam antibiotics.

BACTERIOLOGICAL PROFILE AND ITS SUSCEPTIBILITY PATTERN IN PATIENTS OF VENTILATIOR ASSOCIATED PNEUMONIAADMITTED IN MEDICAL INTENSIVE CARE UNIT(MICU), PMCH, PATNA

INTRODUCTION Ventilator associated pneumonia (VAP) is dened as pneumonia that occurs more than 48hrs following endotracheal intubation and initiation of mechanical ventilation. VAP remains a major cause of mortality and morbidity among ICU's patients. MATERIAL AND METHOD A total of 100 samples were collected from patients admitted in medical ICU in PMCH, Patna. Patients should have sign and symptoms suggestive of VAP. Culture, identication, and antibiotic sensitivity of organism was done. OBSERVATION AND RESULT The microbiological results revealed that gram negative bacilli were the most common bacterial agents responsible for VAP and accounted for 88% of all the causative agents. The most common isolated organisms were Acinetobacter baumannii (36%) followed by pseudomonas aeruginosa (24%), Klebsiella pneumoniae (18%), klebsiella oxytoca (8%), E. coli (4%). Staph. aureus (10%). 70% of the isolated VAP pathogen were multidrug resistant. CONCLUSIONS VAP is increasingly associated with MDR pathogens. Production of ESBL, AmpC beta lactamases and metallo beta lactamases were responsible for the multidrug resistance of these pathogens. Increasing prevalence of MDR pathogens in patients with late onset VAPindicate that appropriate broad-spectrum antibiotics should be used to treat them. It is useful in implementing simple and effective preventive measures including precaution during emergency intubation, minimizing the occurrence of reintubation, and judicious use of antibiotics.

Beta-Lactamase-Producing Gram-Negative Bacterial Isolates Among the Patients Attending a Tertiary Care Hospital, Kathmandu, Nepal.

Over the times, carbapenems have been the choice of drug for treating multidrug-resistant (MDR) and extended spectrum beta-lactamase (ESBL)-producing organisms. The current study aimed at determining the occurrence of metallo beta-lactamase (MBL) and AmpC beta-lactamase (ABL) in gram negative bacteria isolated from clinical samples. A cross-sectional study was conducted amongst the patients visiting Manmohan Memorial Medical College and Teaching Hospital (MMTH), Kathmandu, Nepal from August 2017 to January 2018. A total of 4351 samples including urine, pus, wound swab, endotracheal tip, catheter tip, and blood were collected from the patients and processed by standard conventional microbiological methods. Antibiotic susceptibility testing (AST) of the isolates was performed by Kirby-Bauer disk diffusion method. Double disc synergy test was performed on carbapenem resistant organisms to detect production of MBL and inhibitor-based test was used for the detection of ABL production. Of the 4351 samples, 421 bacterial isolates belonging to 16 different genera were recovered, of which 303 (71.97%) were Gram negative bacilli (GNB). E. coli (189/303) and S. aureus (80/118) were the most prevalent among gram negatives and gram positives, respectively. Bacterial incidence was found significantly associated with gender, specimen type, and the department where the patients were enrolled. Colistin-sulfate and polymycin-B were the most effective drug against GNB, whereas imipenem against gram positives. Prevalence of MDR and methicillin-resistant S. aureus (MRSA) was 35.15% and 60%, respectively. The prevalence of MBL and ABL-producing isolate was 11(3.6%) and 13(4.3%), respectively. Pseudomonas aeruginosa (5/11) and E. coli (9/13) were the major MBL and ABL producers, respectively. MBL and ABL production was found to be significantly associated with the age of the patient and the specimen type. A regular antibiotic surveillance activity with screening for MBL and ABL-producing bacterial isolates in the hospital settings to curb the incidence and transmission of such difficult-to-treat pathogens.

Phenotypical Detection of β-Lactamases in a Multidrug-Resistant and Extensively Drug-Resistant Chryseobacterium indologens: A Rare Human Pathogen With Special References to Risk Factor.

Chryseobacterium indologenes is gram-negative bacteria that cause infection in humans. It is less frequently isolated in the laboratory. The development of drug-resistant and its intrinsic ability to resist a wide range of antimicrobials enables them to cause mortality in an immunocompromised patient with a longer hospital stay. Our study objectives are to investigate antimicrobial-resistant patterns, drug-resistant enzymes, and the risk factor analysis associated with multidrug-resistant (MDR), extensively drug-resistant (XDR), and Pan-drug resistant (PDR) within 2 years. Altogether 53 strains of Chryseobacterium indologens were obtained from 5000 specimens that were processed for routine bacterial culture. The bacterial identification was done using conventional techniques (colony morphology, gram staining, flexirubin test, and biochemical tests) as well as the VITEK-2 System to further confirm. The bacterial isolate were processed to observe antimicrobial susceptibility test (AST) using disk diffusion method. MDR XDR and PDR were classified following European Centre for Disease Prevention and Control guidelines. C. indologens strains with beta-lactamases such as extended-spectrum beta-lactamases (ESBL), metallo beta-lactamases (MBL), and Amp-C beta-lactamases (Amp-C) were detected phenotypically. The highest isolation of C. indologens was observed in a sputum sample. In vitro antimicrobial susceptibility test revealed susceptibility to tigecycline followed by levofloxacin, cotrimoxazole, and piperacillin-tazobactam. From 53 isolates of C. indologens, MDR accounts for 56.60% and 22.64% for XDR. Combined antimicrobial therapy and longer hospital stay were found to be the leading risk factor. All 53 C. indologenes strains were detected as MBL. Total ESBL was detected in 16.98% of MBL producer strains and Amp-C was observed in 13.20% of MBL-producing strains. All 3 enzyme co-oproducers were seen in only 5.66% of C. indologens. Although it is rarely encountered in the laboratory, it showed a remarkable effect in patients with underlying predisposing factors and prolonged hospital stays. The presence of betalactamases determined the drug-resistant activity on a wide spectrum of tested antibiotics.

Microbiological Profile of Osteomyelitis and Antibiotic Resistance Pattern of Bacterial Isolates with Special Reference to MDR Strains at a Tertiary Care Hospital, Kanpur, Uttar Pradesh, India

Introduction: Osteomyelitis is an inflammatory process that affects bone due to the contiguous infection, direct inoculation, or haematogenous spread of microorganisms. It is an infectious disease that is difficult to diagnose and treatment is complex because of its heterogeneity, pathophysiology, clinical presentation and management. Aim: To determine microbiological profile osteomyelitis and antibiotic resistance pattern of bacterial isolates with special reference to Multidrug Resistance (MDR) strains. Materials and Methods: A cross-sectional study was conducted in the Department of Microbiology and Department of Orthopedics Rama Medical College Hospital and Research Centre Kanpur, Uttar Pradesh, India. A total of 100 samples from osteomyelitis cases were aerobically cultured and isolates from culture positives were identified by standard procedures. Antimicrobial Susceptibility Testing (AST) was done following Clinical and Laboratory Standards Institute (CLSI) guidelines. Staphylococcal isolates were screened for methicillin resistance and Gram negative bacilli were screened for MDR production. Results: Out of 100 samples, 76% were culture positive and 24% were culture negative. Males were more affected than females. Staphylococcal spp. (47.3%) was predominant, E. coli (14.4%) and Klebsiella spp. (11.8%), Pseudomonas spp. (9.2%), Proteus spp. (5.2%), Coagulase-Negative Staphylococci (CoNS) (3.9%). Among the MDR strains, Methicillin Resistant Staphylococcus aureus (MRSA) was 44.4%. All the MDR Staphylococcal isolates were 100% sensitive for linezolid. Among the MDR Gram negative bacilli were Extended Spectrum Beta Lactamases (ESBL) (50%), AmpC (17.6%) and Metallo Beta Lactamase (MBL) (14.7%) and they were 100% sensitive for polymixin B and colistin. Conclusion: The microbiological profile of osteomyelitis in the present study showed high prevalence of MRSA44% as the commonest agent, sensitive only to linezolid. E. coli ESBL (50%) and MBL-14.7% were sensitive only to colistin and polymixin B, therefore proper infection control practices and antibiotic policy has to be followed to reduce the incidence of MDR strains.

Detection of Carbapenemase Production by Modified Carbapenem Inactivation Method among Carbapenem Resistant Gram- negative Bacilli at a Tertiary Care Centre in Coimbatore, Tamil Nadu, India

Introduction: In the era of increasing antimicrobial resistance, knowing the mechanism of carbapenem resistance can aid in choosing an apt drug for treatment of patients. There are only few studies estimating the burden of carbapenem resistance and determining the mechanism of resistance among the isolates in our locale. Aim: To determine the prevalence of carbapenemase production by modified Carbapenem Inactivation Method (mCIM) among the Carbapenem Resistant Gram-Negative Bacteria (CRGNB)- Enterobacteriaceae and Pseudomonas aeruginosa isolated in our hospital. Materials and Methods: This was a prospective observational study conducted in Department of Microbiology, KMCH, Coimbatore, Tamil Nadu, India during the period of June 2021 to August 2021. A total of 165 isolates of Enterobacteriaceae family and P. aeruginosa which were resistant to one of the carbapenems (imipenem, meropenem or ertapenem) by Vitek MIC testing were included in the study. All were subjected to mCIM and EDTA-modified CIM (eCIM) test and interpreted as per the CLSI M100 S31 guidelines. Results: Among the 165 isolates, 130 (78.8%) were K. pneumoniae, 27 (16.4%) were other Enterobacteriaceae and eight (4.8%) were P. aeruginosa. Prevalence of mCIM positivity was 51.5% (85 isolates). Approximately, 98% of the mCIM positives (Carbapenemase Producing Gram-Negative Bacteria [CPGNB]) were eCIM positive indicating Metallo-Beta- Lactamase (MBL) production. Conclusion: Performing mCIM in CRGNB is important in routine practice to identify CPGNBs. Due to very high prevalence of MBL among carbapenemase producers, it is advisable to choose ceftazidime avibactam plus aztreonam as the treatment option for CPGNB in our locale.

An Innovative Laboratory Technique Showcasing the Synergy among CeftazidimeAvibactam and Aztreonam in Combating Infections caused by Enterobacterales producing Metallo-beta-lactamases: A Prospective Study

ntroduction: Combination therapy with CeftazidimeAvibactam (CAZ-AVI) and Aztreonam (ATM) has been studied in the context of infections caused by Enterobacterales that produce Metallo-Beta-Lactamases (MBL). The development of combination therapy is a crucial factor in combating MBLproducing Enterobacterales. As most isolates from Intensive Care Unit (ICU) patients produce a variety of beta-lactamases, offering resistance to a broad range of antibiotics, they need to be treated with the CAZ-AVI and ATM combination. This study addresses a pressing public health issue-the rise of multidrugresistant bacteria, particularly MBL-producing Enterobacterales. By investigating the synergy between CAZ-AVI and ATM, the study aims to provide valuable insights to guide clinical practice, improve patient outcomes, and contribute to the global effort to combat antibiotic resistance. Aim: To demonstrate the synergy between CAZ-AVI and ATM in patients with infections caused by MBL-producing Enterobacterales. Materials and Methods: A prospective study was conducted in the Department of Microbiology at Symbiosis Medical College for Women (SMCW) and Symbiosis University Hospital and Research Centre (SUHRC), Symbiosis International (Deemed University), Lavale, Pune, Maharashtra, India. The study duration was six months, from January 2023 to June 2023. All isolates meeting the inclusion criteria were processed to demonstrate synergy between CAZ-AVI and ATM. Isolates from the Enterobacteriaceae family with resistant breakpoints for carbapenemase, ceftazidimeavibactam, and aztreonem, as determined by the Phoenix automated system, were included in the study. Restoration of the ATM breakpoint was observed following the addition of CAZ/AVI to ATM. Breakpoints provided by the BD Phoenix system were compared to the results obtained from CAZ/AVI and ATM disc diffusion/stacking, E-strip/disc methods, in terms of susceptibility and resistance. Results were simultaneously compared with the broth disc elution test, considered the gold standard. Results: Sensitivity, specificity, Positive Predictive Value (PPV), and Negative Predictive Value (NPV) were calculated for the E-test/disc and disc stacking methods. The disc stacking synergy test demonstrated a PPV of 96.88% and an NPV of 62.5%. By using the E-test/disc, the ATM/CAZ-AV synergy test revealed a PPV of 97.22% and an NPV of 83.33% when CAZ/ AVI was added to ATM. Comparatively, disc stacking was less sensitive than the broth disc elution. Conclusion: In the majority of MBL-producing Enterobacterales that are ATM-resistant, the CAZ/AVI+ATM combination showed strong synergy. In the microbiology laboratory, the E-test/disc and disc stacking approaches are rapid, repeatable, and reliable methods for checking clinically significant synergy.

Detection of β-lactamases among Multi-drug Resistant Enterobacteriaceae Colonising Gut of Normal Adults and Patient Population

Background and aims Antibiotic resistance is a growing threat in the medical field and the Enterobacteriaceae leading commensals in the gut are more likely to develop resistance. In this study we aimed to compare the anti-microbial resistance pattern with a special reference to beta-lactamase producers in Escherichia coli and Klebsiella pneumoniae as normal flora and pathogens.Methods A total of 120 bacterial strains of E. coli and Klebsiella were tested for antibiotic sensitivity by Kirby Bauer Disk diffusion method. Multi-drug resistant MDR bacteria were identified and phenotypically classified based on beta lactamase production into ESBL Extended Spectrum beta Lactamase AmpC beta Lactamase and MBL Metallo beta Lactamase respectively.Results Ampicillin resistance was the highest in both categories showing rates of 34 56 and 50 83.3 in normal and pathogenic strains respectively. Cefotaxime was a close second with resistance rates of 25 41.6 and 37 61.6. Imipenem showed the lowest resistance rates of 7 11.6 and 4 6.60 in normal and pathogenic strains. Pathogenic and normal strains showed an MDR rate of 51.6 and 40.5 respectively. ESBL production was observed in 1.6 P 41.6 N AmpC was 31.6 P 20 N and MBL was detected in 25 P 16.6 N.Conclusion The study revealed an alarming rate of beta lactamase-producing MDR commensals in the region. The narrow gap between the hospitalized and healthy individuals in resistance rates was a proof of rapid transmission of resistance genes signifying the need for screening even the normal population for antibiotic resistance patterns.

Klebsiella infections in a pediatric intensive care unit: incidence, antimicrobial susceptibility, and resistance genes

BackgroundInfections with multidrug-resistant K. pneumoniae is associated with high morbidity and mortality especially among critically ill patients. This was the main principle to conduct a detailed study about this organism, its resistance pattern, and type of its resistance genesSubjects and methodsA cross-sectional study was carried out in a pediatric intensive care unit on patients with age range from 1 month to 12 years over a period of 1 year with positive K. pneumoniae using standard microbiological culture and antibiogram sensitivity testing. All collected samples were processed using multiplex PCR technique to identify the most relevant resistant genes.ResultsForty-four patients had 54 positive cultures for K. pneumoniae, out of which 17 patients (38.6%) passed away. The most prevalent-resistant gene was New Delhi metallo-beta lactamase (NDM) gene (65.4%) followed by cefotaximase (CTX-M) gene (57.7%). Extensively drug-resistant K. pneumoniae was detected in (15.9%) of the results and was proved to be independent risk factor increasing mortality odds 139 folds.ConclusionThe evolution of resistance of Klebsiella pneumoniae was proved to be associated with a high mortality rate. Continuous widespread surveillance of Klebsiella pathogen focusing on identification of resistance genes and antibiotic resistance pattern is highly recommended.

Prevalence of Extended Spectrum Betalactamase and Metallobetalactamase Producing Acinetobacter baumannii Isolated from Different Infections in Baghdad City of Iraq

Introduction: Acinetobacter baumannii is an important pathogen related to hospital-acquired infections worldwide. This study was designed to isolate A. baumannii from different clinical specimens, investigate the presence of antibiotic resistants’ and detect the prevalence of extended spectrum betalactamase (ESBL) and metallobetalactamase (MBL) production among A. baumannii isolates. Methods: Over a 6-months period, 500 different clinical samples were collected from four hospitals in Baghdad. Identification of bacterial isolates and antibiotic sensitivity test were performed using Vitek 2 system. A. baumannii isolates were screened for MBL and ESBL production. Results: Among the collected clinical samples, (424) were bacterial isolates. Of these, 69 samples (16.27%) were identified as A. baumannii. A largest number of A. baumannii isolates were isolated from sputum (at a percentage of (50.72%) followed by blood (30.43%), urine (13.04%), cerebrospinal fluid (CSF) (2.89%) and wound (2.89%). Antimicrobial susceptibility test showed that A. baumannii isolates displayed different resistance rates to the applied antibiotics. It was resistant to β-lactam antibiotics: ceftazidime, piperacillin/tazobactam, cefepime and imipenem at a percentage of (90, 87, 85.5 and 74%), respectively. It was resistant to aminoglycosides (gentamycin and amikacin) at 80 and 81%, respectively. The resistance rate to trimethoprim/sulfamethoxazole was 87, and 80% to Ciprofloxacin. In the present study, all imipenemresistant A. baumannii isolates 51 (74%) were positive for MBL production. 57 (82.6%) β-lactam resistant isolates were ESBL producers.

229. Molecular and Clinical Epidemiology of Carbapenemase-Producing E. coli Isolates from Different Global Regions (CRACKLE-2)

Abstract Background Carbapenemase-producing (CP) Escherichia coli (CPEc) are a global public health threat. We describe the epidemiology and outcomes of patients with CPEc isolates obtained in CRACKLE 2, a prospective cohort study of hospitalized patients with positive cultures for CP Enterobacteriaceae. Methods In CRACKLE-2, patients with CPEc were enrolled from 26 hospitals in 6 countries (ClinicalTrials.gov NCT03646227). Clinical data were collected, and bacterial isolates underwent whole genome sequencing (WGS). Here, we included unique patients with CPEc by WGS (n=114). The primary outcome was desirability of outcome ranking (DOOR) at 30 days after index culture. Chi squared tests with alpha = 0.05 were used to evaluate differences in culture source and outcomes between metallo-beta-lactamase (MBL) and non-MBL isolates. Results Of 114 CPEc isolates, 57 (50%) represented infection (Table 1). Isolates primarily arose from urine (34%) and blood (21%). Compared to non-MBL isolates, isolates containing MBL were more often from urine (41% vs 29%) and less frequently from blood (6% vs 32%); p=0.02. We observed strong regional variations in CP (Figure 1) and MBL (p < 0.0001). Sequence type (ST) 167 was more common among MBL than non-MBL isolates (31% vs 2%, p< 0.0001); non-MBL isolates were more often ST410 and ST131 (17% and 20%). Extended-spectrum beta-lactamases (ESBL) were present in 52% of isolates; most commonly, CTX-M-15 in both MBL (33%) and non-MBL isolates (34%). Phylogenetic analysis of the isolates and corresponding region, bacterial characteristics, and DOOR outcomes are in Figure 1. Death at 30 days occurred in 18 (16%) of patients, more commonly among non-MBL than MBL CPEc (23% vs 6%; p=0.01). The probability of a better DOOR outcome for a randomly selected MBL was 58% [95% CI: 48.2, 67.4], indicating no significant difference between the groups. Figure 1:Phylogenetic population structures of Carbapenemase-producing Escherichia coli (CPEc) isolates Legend: Infection = categorization as infection or colonization. ST = sequence type. BlaCarb = Carbapenemase gene. BlaESBL = acquired ESBL enzymes. DOOR = desirability of outcome ranking. DOOR rankings: 1 = Alive without events; DOOR 2 = Alive with 1 event; DOOR 3 = Alive with 2 or 3 events; DOOR 4 = dead. Conclusion Emergence of carbapenem resistance with important geographic variations was observed in E coli including among high-risk clones such as ST131. Mortality was higher among non-MBL isolates, which were more frequently from blood, but these findings may be confounded by region. Disclosures Vance G. Fowler, Jr, MD, MHS, Affinergy: Grant/Research Support|Affinergy: Honoraria|Affinium: Honoraria|Amphliphi Biosciences: Honoraria|ArcBio: Stocks/Bonds|Basilea: Grant/Research Support|Basilea: Honoraria|Bayer: Honoraria|C3J: Honoraria|Cerexa/Forest/Actavis/Allergan: Grant/Research Support|Contrafect: Grant/Research Support|Contrafect: Honoraria|Cubist/Merck: Grant/Research Support|Debiopharm: Grant/Research Support|Deep Blue: Grant/Research Support|Destiny: Honoraria|Genentech: Grant/Research Support|Genentech: Honoraria|Integrated Biotherapeutics: Honoraria|Janssen: Grant/Research Support|Janssen: Honoraria|Karius: Grant/Research Support|Medicines Co.: Honoraria|MedImmune: Grant/Research Support|MedImmune: Honoraria|NIH: Grant/Research Support|Novartis: Grant/Research Support|Novartis: Honoraria|Pfizer: Grant/Research Support|Regeneron: Grant/Research Support|Regeneron: Honoraria|Sepsis diagnostics: Sepsis diagnostics patent pending|UpToDate: Royalties|Valanbio: Stocks/Bonds Cesar A. Arias, MD, PhD, Entasis Phramceuticals: Grant/Research Support|MeMed Diagnostics: Grant/Research Support|Merck: Grant/Research Support David Paterson, MBBS, Accelerate: Honoraria|bioMerieux: Honoraria|Entasis: Advisor/Consultant|Janssen-Cilag: Grant/Research Support|MSD: Advisor/Consultant|MSD: Grant/Research Support|MSD: Honoraria|Pfizer: Grant/Research Support|Pfizer: Honoraria|PPD: Grant/Research Support|Shionogi: Grant/Research Support|VenatoRx: Advisor/Consultant Karen M. Ordonez, MD, AstraZeneca: Expert Testimony|Biomerieux: Expert Testimony|Farma de Colombia: Expert Testimony|MSD: Expert Testimony|Pfizer: Expert Testimony Souha S. Kanj, Pr, MSD, Pfizer, Gilead, Menarini, Astellas: Advisor/Consultant|MSD, Pfizer, Gilead, Menarini, Astellas: Honoraria Robert Bonomo, MD, Cystic Fibrosis Foundation: Grant/Research Support|Merck: Grant/Research Support|NIH: Grant/Research Support|VA: Grant/Research Support|VenatoRx: Grant/Research Support|Wockhardt: Grant/Research Support David van Duin, MD, PhD, Achaogen: Advisor/Consultant|Allergan: Advisor/Consultant|Astellas: Advisor/Consultant|MedImmune: Advisor/Consultant|Melinta: Advisor/Consultant|Merck: Advisor/Consultant|Merck: Grant/Research Support|NeuMedicine: Advisor/Consultant|Pfizer: Advisor/Consultant|Qpex: Advisor/Consultant|Roche: Advisor/Consultant|Sanofi-Pasteur: Advisor/Consultant|Shionogi: Advisor/Consultant|Shionogi: Grant/Research Support|T2 Biosystems: Advisor/Consultant|Tetraphase: Advisor/Consultant.

The in vitro and in vivo potential of metal-chelating agents as metallo-beta-lactamase inhibitors against carbapenem-resistant Enterobacterales.

The recent surge in beta-lactamase resistance has created superbugs, which pose a current and significant threat to public healthcare. This has created an urgent need to keep pace with the discovery of inhibitors that can inactivate these beta-lactamase producers. In this study, the in vitro and in vivo activity of 1,4,7-triazacyclononane-1,4,7 triacetic acid (NOTA)-a potential metallo-beta-lactamase (MBL) inhibitor was evaluated in combination with meropenem against MBL producing bacteria. Time-kill studies showed that NOTA restored the efficacy of meropenem against all bacterial strains tested. A murine infection model was then used to study the in vivo pharmacokinetics and efficacy of this metal chelator. The coadministration of NOTA and meropenem (100mg/kg.bw each) resulted in a significant decrease in the colony-forming units of Klebsiella pneumoniae NDM-1 over an 8-h treatment period (>3 log10 units). The findings suggest that chelators, such as NOTA, hold strong potential for use as a MBL inhibitor in treating carbapenem-resistant Enterobacterale infections.

1692. Ceftibuten-Xeruborbactam: In vitro Potency against Enterobacterales in Comparison with Other Oral Beta-lactams (BL) and Beta-lactamase Inhibitor (BLI) Combinations

Abstract Background The broad spectrum BLI xeruborbactam (XER, formerly, QPX7728) can be delivered IV or orally as the isobutyryloxymethyl prodrug. The prodrug form is in clinical development in combination with ceftibuten (BUT) for oral treatment of resistant gram-negative infections. The objective of this study was to compare the in vitro potency of BUT-XER to that of other investigational oral BL/BLI combinations and tebipenem (TBP) in blinded head-to-head testing against extended beta-lactamase (ESBL) producing and carbapenem-resistant Enterobacterales (CRE). Methods A total of 980 Enterobacterales including 515 ESBL and 460 CRE, including 195 KPC-, 97 OXA-48-like- and 168 metallo beta-lactamase (MBL) producers, were susceptibility tested by reference broth microdilution against BUT-XER (at fixed 4 mg/L) and comparator BLs or BL/BLI combinations (tested at their recommended BLI concentrations). MIC testing was conducted blinded to drug identity using CLSI reference microdilution methods and controlled using approved quality control bacterial strains and ranges. Results BLI inhibitor combinations and TBP had excellent potency against ESBL isolates with MIC90 in the ≤ 0.03-0.06 mg/L range for BUT-avibactam (AVI) and BUT-XER and in 0.125-0.25 mg/L range for TBP, BUT-VNTX-6236 (VNRX) and cefpodoxime (CPD)-ETX1317 (ETX) (Table). Against KPC and OXA-48-producers, BUT-XER and BUT-AVI (MIC90 0.25-0.5 mg/L) were 4-fold more potent than BUT-VNRX and CPD-ETX (MIC90 of 1-2 mg/L); TBP was not active against these strains. BUT-XER and CPD-ETX were the most potent agents against MBL-producing strains; however, anti-MBL activity of CPD-ETX was due to intrinsic antibacterial activity of ETX. TPB, BUT-AVI and BUT-VNTX did not have any relevant activity against MBL-producing strains. Conclusion BUT-XER had the broadest antimicrobial profile, with activity against ESBL and all carbapenemase producing isolates. Its potency against ESBL-producing isolates was comparable to the carbapenem TBP. Its in vitro potency and spectrum combined with the potential of once-daily administration based on PK studies warrants further clinical development. Disclosures Mariana Castanheira, PhD, AbbVie: Grant/Research Support|Cidara: Grant/Research Support|GSK: Grant/Research Support|Melinta: Grant/Research Support|Pfizer: Grant/Research Support|Shionogi: Grant/Research Support Jill Lindley, BS, AbbVie: Grant/Research Support.

1693. Meropenem-Xeruborbactam: In Vitro Potency against Gram-Negative Bacteria in Comparison with Marketed and Investigational Beta-lactam (BL)/Beta-lactamase Inhibitor (BLI) Combinations

Abstract Background Several BLI combinations have entered into clinical testing or been approved for use but there are few comparative studies of their in vitro activity. Xeruborbactam (XER, formerly QPX7728) is a cyclic boronate BLI with potent inhibitory activity against serine and metallo-beta-lactamases (MBL). It is in clinical development in combination with meropenem (MEM). The objective of this study was to compare in vitro potency of MEM-XER to that of other investigational and approved BL/BLI combinations in head-to-head testing against recent isolates of carbapenem-resistant Enterobacterales (CRE) and Acinetobacter baumannii (CRAB) as well as Pseudomonas aeruginosa (PA). Methods The test panel of recent worldwide isolates consisted of 507 CRE including 168 MBL producers (157 NDM, 11 VIM, 1 IMP), 506 CRAB, and 506 PA that were representative of current isolates and included 65 MDR (resistant to ≥ 3 antimicrobial classes) strains. MEM-XER was tested with XER at a fixed 8 mg/L conc. and other BL/BLI combinations at their recommended BLI concentrations. MIC testing was conducted blinded to drug identity using CLSI reference methods and controlled using approved quality control bacterial strains and ranges. Results The MIC50 and MIC90 for MEM-XER vs CRE ranged from ≤ 0.03 mg/L to 0.06 mg/L and 0.06 mg/L to 1 mg/L, respectively. MEM-XER and cefepime-taniborbactam (FEP-TANI) were the only BL/BLIs with activity against MBL-producers; based on MIC90, MEM-XER (MIC90 of 1 mg/L) was 16-fold more potent than FEP-TANI (MIC90 of 16 mg/L). MEM-XER and sulbactam-durlobactam (SUL-DUR) were the only agents with high potency against CRAB, with MIC50/MIC90 of 0.5/4 mg/L and 1/2 mg/L. For the representative panel of PA, the potency of MEM-XER, FEP-TAN, ceftolozane-tazobactam (TOL-TAZ), imipenem-relebactam (IMP-REL), and CAZ-AVI was similar with MIC90s ranging between 2-8 mg/L; for the MDR panel, MIC90‘s were > 8 mg/L for all combinations, with MER-XER, IMP-REL, TOL-TAZ, and CAZ-AVI having MIC50’s of 2-4 mg/L. Conclusion Compared to the marketed or investigational BL/BLIs, MEM-XERU had the broadest coverage of carbapenem-resistant gram-negative bacteria, with the most differentiating property being activity against multiple strains of MBL-producing CRE and CRAB. Disclosures Mariana Castanheira, PhD, AbbVie: Grant/Research Support|Cidara: Grant/Research Support|GSK: Grant/Research Support|Melinta: Grant/Research Support|Pfizer: Grant/Research Support|Shionogi: Grant/Research Support Jill Lindley, BS, AbbVie: Grant/Research Support.

650. Cefiderocol use in burn patients admitted to an intensive care unit

Abstract Background Cefiderocol is a novel cephalosporin that binds to ferric acid and is moved across the outer membrane of Gram-negative bacilli via iron transport. Once through the outer membrane, cefiderocol is able to exert typical cephalosporin activity. Because of its ‘Trojan horse’-like mechanism of action, cefiderocol is able to elude typical bacterial resistance mechanisms and has activity against multidrug-resistant organisms (MDROs), including Acinetobacter spp. and Pseudomonas spp. While cefiderocol is considered to be relatively safe, it does have the potential to predispose to secondary infection with Clostridioides difficile. We present a case series where cefiderocol was used to treat infections caused by MDROs in burn patients admitted to our burn intensive care unit (BICU). Methods A clinical review of patients admitted to the BICU who received cefiderocol between September 2019 and April 2022 was performed. Results Five patients received 6 courses of cefiderocol. Three patients (60%) had flame burns, one patient (20%) had a scald burn, and one patient (20%) had blast injury. The median burn size was 47% TBSA (IQR 31, 60 days). The median time from injury to cefiderocol initiation was 73.5 days (IQR 49.5, 108). The median duration of cefiderocol therapy was 7 days (IQR 7, 16). The most common indications for cefiderocol treatment were pneumonia (33.3%) and bacteremia (33.3%), followed by wound infection (16.7%), and discitis/osteomyelitis (16.7%). Organisms isolated included Escherichia coli (n=2), Enterobacter cloacae (n=1), Acinetobacter baumannii (n=1), and Pseudomonas aeruginosa (n=2). All isolates were carbapenem resistant, and only one isolate was susceptible to amikacin (Acinetobacter baumannii). The 2 E. coli isolates carried a New Delhi metallo-beta lactamase. Two thirds of patients (n=4) achieved a clinical cure with cefiderocol treatment. Three of the 5 patients (60%) died during their hospital stay. All patients received appropriate doses of cefiderocol based on the current prescribing recommendations. No patients developed infection with C. difficile as a result of cefiderocol treatment. Conclusion Cefiderocol is a cephalosporin with novel mechanism of action that can be used to treat MDROs in burn patients, with no secondary C. difficile infections observed. Disclosures All Authors: No reported disclosures.

Rapid Evolution of a Fragment-like Molecule to Pan-Metallo-Beta-Lactamase Inhibitors: Initial Leads toward Clinical Candidates.

With the emergence and rapid spreading of NDM-1 and existence of clinically relevant VIM-1 and IMP-1, discovery of pan inhibitors targeting metallo-beta-lactamases (MBLs) became critical in our battle against bacterial infection. Concurrent with our fragment and high-throughput screenings, we performed a knowledge-based search of known metallo-beta-lactamase inhibitors (MBLIs) to identify starting points for early engagement of medicinal chemistry. A class of compounds exemplified by 11, discovered earlier as B. fragilis metallo-beta-lactamase inhibitors, was selected for in silico virtual screening. From these efforts, compound 12 was identified with activity against NDM-1 only. Initial exploration on metal binding design followed by structure-guided optimization led to the discovery of a series of compounds represented by 23 with a pan MBL inhibition profile. In in vivo studies, compound 23 in combination with imipenem (IPM) robustly lowered the bacterial burden in a murine infection model and became the lead for the invention of MBLI clinical candidates.

Phenotypic and genotypic detection of resistance mechanisms in carbapenem-resistant gram-negative bacteria isolated from Egyptian ICU patients with first emergence of NDM-1 producing Klebsiella oxytoca.

Carbapenems are considered the last resort to treat several infections, particularly in intensive care units (ICUs). However, increasing carbapenem resistance is problematic because it leads to high morbidity and mortality rates. This study aimed to determine the rate of carbapenem resistance among Gram-negative bacteria collected from patients in ICUs and to identify their resistance mechanisms using phenotypic and genotypic methods. Antimicrobial susceptibility testing was carried out using the disc diffusion method among 180 Gram-negative bacterial isolates. Productions of carbapenemases, metallo-beta-lactamases (MBLs) and the harboring of carbapenemase-encoding genes, were detected in 40 selected carbapenem-resistant Gram-negative bacteria (CR-GNB). Of 40 selected CR-GNB isolates, 28 (70%), and 20 (50%) isolates were phenotypically positive for carbapenemase, and MBL production, respectively. Furthermore, 22 (55%) showed amplification of one or more of the carbapenemase-encoding genes, including bla NDM-1, bla VIM-2, and bla OXA-48. This study described the first emergence of NDM-1 producing Klebsiella oxytoca in Egyptian ICUs. High incidence of CR-GNB detected in the ICUs in our study area may be attributed to the overuse of antibiotics, including carbapenems, and improper application of infection control measures. These findings confirm the need for the application of a strict antibiotic stewardship program.

Fosfomycin susceptibility among Escherichia coli causing urinary tract infection in a tertiary care centre in Western Maharashtra

Background and objective: Urinary tract infection(UTI) is one of the most common bacterial infections encountered in clinical practice. UTIs caused by extended-spectrum beta-lactamase (ESBL) AmpC and metallo-beta-lactamase (MBL) producing Escherichia coli (E. coli) are difficult to treat. Fosfomycin is an old antibiotic that has excellent bactericidal activity against a wide range of bacteria. This study aimed to determine the fosfomycin susceptibility of E. coli causing UTI in a tertiary care hospital in Western Maharashtra, India. Material and methods: The study was conducted at a tertiary care center in Pune, a city of Western Maharashtra, India. Urine samples from UTI cases yielding significant (> 1x 105 cfu/ml) growth of E. coli were included in study. E. coli isolates were tested for susceptibility to fosfomycin and a panel of antimicrobial agents by Kirby Bauer disc diffusion method. All the isolates were tested for production of ESBL, AmpC and MBL. Result: A total of 88 E. coli were isolated of which, 47 (53.40%) and 41 (46.59%) were from male and female patients respectively. Of the total E. coli isolates, 58 (65.9%) were from in-patient cases. Multi-drug resistance was found in 69 (78.40%) isolates and remaining 19 (21.6%) were resistant to different antimicrobials tested. All (100%) the MDR and non-MDR isolates were sensitive to fosfomycin. Highest resistance was present against nalidixic acid (93.8%) while resistance was least against nitrofurantoin (15.91%), piperacillin/tazobactam (17.1%) and meropenem (18.18%). Of the total, 35 (50.72%) isolates were both AmpC and ESBL producers while 11 (15.94%) and 8 (11.59%) were only AmpC and ESBL producers respectively. MBL was positive in 15 (21.73%) of E. coli isolates. All those isolates tested sensitive to fosfomycin. Conclusion: The study revealed that fosfomycin had excellent activity against MDR E. coli causing UTI in our area. IMC J Med Sci. 2023; 17(1): 008. DOI: https://doi.org/10.55010/imcjms.17.008 *Correspondence: Dr. Sameena Khan, Department of Microbiology, Dr. D. Y. Patil Medical College, Hospital and Research Centre, Dr. D. Y. Patil Vidyapeeth, Pimpri, Pune, Maharashtra, India. E-mail: sameenak27@gmail.com

Prevalence of metallo beta-lactamase and Amp C beta-lactamase producing pathogens causing surgical site infection in a tertiary care teaching centre in Southern India

Abstract Background: Surgical site infection (SSI) is the most common type of hospital-acquired infection-causing public health problems. The study was undertaken to know the aerobic bacteriology of SSI with special reference to the detection of metallo-beta-lactamase (MBL) and AmpC beta-lactamases among Gram-negative bacilli. Methods: The present cross-sectional study was conducted in 140 patients clinically suspected to have SSIs. Samples were collected from patients after considering inclusion and exclusion criteria. Results: Out of 85 Gram-negative bacilli, 9 isolates (10.6%) were Amp C producers. Out of a total of 85 Gram-negative bacilli, 3 isolates (3.5%) were MBL producers. Two isolates of Pseudomonas aeruginosa and 1 isolate of Acinetobacter spp. were positive for MBL production. In the present study, MBL production was seen in 3.5%, of Gram-negative bacilli. Conclusions: Early identification of such resistant strains is important to plan the appropriate antibiotic therapy. Strict infection control practices and judicious use of available antibiotics are essential to prevent the emergence of multidrug-resistant strains.

In-vitro Activity of Ceftazidime-Avibactam Against Carbapenem-Resistant K. pneumoniae in a Tertiary-Care Center in Al-Ahsa, KSA

Abstract Introduction/Objective Carbapenem-resistant Enterobacteriaceae (CRE) represents an urgent global threat. Klebsiella pneumoniae is a common cause of various clinical infections showing increased rates of resistance. Carbapenem-resistant Klebsiella pneumoniae (CR-KP) is often multi-drug resistant and sometimes becomes pan-drug resistant causing serious infections with substantial morbidity, mortality and cost. Ceftazidime-avibactam (CZA) is considered to be a good alternative to standard CRE therapy. In our region, CRE is mostly due to OXA-type carbapenemases which are inhibited by CZA, however, metallo-beta-lactamases (MBLs) are being increasingly reported and against which CZA is inactive. The aim of this study is to determine the activity of CZA against CRE-KP isolated in our hospital. Methods/Case Report Single-center, prospective study on consecutive non-duplicate CRE-KP isolates recovered from various clinical specimens in 2020 and 2021. BD Phoenix® system was used for initial Identification and susceptibility testing. E-test was done to confirm susceptibility and determine the minimum inhibitory concentration (MIC) for CZA. The standards of the Clinical and Laboratory Standards Institute were followed. Results (if a Case Study enter NA) 95 CRE-KP isolates were collected. CRE-KP was mostly isolated from: Respiratory samples: 36% (n=34), bedsores: 28% (n=27), urine: 23% (n=22) and 11% (10 isolates) were retrieved from blood cultures. 65% of patients were admitted to the intensive care unit (ICU), 13% were in long-term care wards and 13% were admitted for management of infected bedsores. 88 isolates were susceptible to CZA (93%) with MIC50= 1.5 μg/mL and MIC90= 4.0 μg/mL. 26 isolates (27%) were sensitive only to CZA. Susceptibility to tigecycline was 54%, amikacin 18% and gentamicin 17%. Other antimicrocbials including ceftolozane-tazobactam were basically ineffective. Conclusion Ceftazidime-avibactam shows excellent in-vitro activity against CR-KP isolates tested in this study. Further clinical studies on treatment efficacy and emergence of resistance are needed. Moreover, with the recent increase in reported MBLs-mediated resistance in our region, infection control measures, resistance-surveillance programs, and molecular testing may prove essential in the fight against carbapenem-resistant Enterobacteriaceae.