Exogenous NADH promotes the bactericidal effect of aminoglycoside antibiotics against Edwardsiella tarda

The global surge in multidrug-resistant bacteria owing to antibiotic misuse and overuse poses considerable risks to human and animal health. With existing antibiotics losing their effectiveness and the protracted process of developing new antibiotics, urgent alternatives are imperative to curb disease spread. Notably, improving the bactericidal effect of antibiotics by using non-antibiotic substances has emerged as a viable strategy. Although reduced nicotinamide adenine dinucleotide (NADH) may play a crucial role in regulating bacterial resistance, studies examining how the change of metabolic profile and bacterial resistance following by exogenous administration are scarce. Therefore, this study aimed to elucidate the metabolic changes that occur in Edwardsiella tarda (E. tarda), which exhibits resistance to various antibiotics, following the exogenous addition of NADH using metabolomics. The effects of these alterations on the bactericidal activity of neomycin were investigated. NADH enhanced the effectiveness of aminoglycoside antibiotics against E. tarda ATCC15947, achieving bacterial eradication at low doses. Metabolomic analysis revealed that NADH reprogrammed the ATCC15947 metabolic profile by promoting purine metabolism and energy metabolism, yielding increased adenosine triphosphate (ATP) levels. Increased ATP levels played a crucial role in enhancing the bactericidal effects of neomycin. Moreover, exogenous NADH promoted the bactericidal efficacy of tetracyclines and chloramphenicols. NADH in combination with neomycin was effective against other clinically resistant bacteria, including Aeromonas hydrophila, Vibrio parahaemolyticus, methicillin-resistant Staphylococcus aureus, and Listeria monocytogenes. These results may facilitate the development of effective approaches for preventing and managing E. tarda-induced infections and multidrug resistance in aquaculture and clinical settings.

Seven-day antibiotic therapy for Enterobacterales bacteremia in high-risk neutropenic patients: toward a new paradigm

PURPOSE

Data on short courses of antibiotic therapy for Enterobacterales bacteremia in high-risk neutropenic patients are limited. The aim of the study was to describe and compare the frequency of bacteremia relapse, 30-day overall and infection-related mortality, Clostridiodes difficile infection and length of hospital stay since bacteremia among those who received antibiotic therapy for 7 or 14 days.

METHODS

This is a multicenter, prospective, observational cohort study in adult high-risk neutropenic patients with hematologic malignancies or hematopoietic stem cell transplant and monomicrobial Enterobacterales bacteremia. They received appropriate empirical antibiotic therapy, had a clinical response within 7 days, and infection source control. Clinical, epidemiological and outcomes variables were compared based on 7 or 14 days of AT.

RESULTS

Two hundred patients were included (100, 7-day antibiotic therapy; 100, 14-day antibiotic therapy). Escherichia coli was the pathogen most frequently isolated (47.5%), followed by Klebsiella sp. (40.5%). Among those patients that received 7-day vs. 14-day antibiotic course, a clinical source of bacteremia was found in 54% vs. 57% (p = 0.66), multidrug-resistant Enterobacterales isolates in 28% vs. 30% (p = 0.75), and 40% vs. 47% (p = 0.31) received combined empirical antibiotic therapy. Overall mortality was 3% vs. 1% (p = 0.62), in no case related to infection; bacteremia relapse was 7% vs. 2% (p = 0.17), and length of hospital stay since bacteremia had a median of 9 days (IQR: 7-15) vs. 14 days (IQR: 13-22) (p =  < 0.001).

CONCLUSIONS

These data suggest that seven-day antibiotic therapy might be adequate for patients with high-risk neutropenia and Enterobacterales bacteremia, who receive appropriate empirical therapy, with clinical response and infection source control.

Effect of incremental tazobactam concentrations on the bactericidal activity of piperacillin against ESBL-producing enterobacterales clinical isolates causing bacteraemia

We evaluated the activity of piperacillin in relation to INCREASING TAZOBACTAM CONCENTRATION against ESBL-producing Enterobacterales collected from patients with bacteraemia. Increasing tazobactam concentration (4, 12 or 24 mg/L) exerted a reduction of piperacillin MICs under the clinical breakpoint in a concentration-dependent manner (0%, 60% and 90% of clinical isolates). Also, activity of piperacillin/tazobactam based at higher achievable serum concentrations (123/14 mg/L) is needed to reduce the bacterial growth in 92% of ESBL-producers. CHANGES IN THE PIPERACILLIN MIC IN RELATION TO INCREASING TAZOBACTAM SUGGEST THAT REALTIME TDM COULD BE USED FOR DRIVEN ANTIMICROBIAL THERAPY WITH PIPERACILLIN/TAZOBACTAM IN BSI DUE TO ESBL STRAINS.

Emergence and expansion of carbapenem resistant enterobacterales in the Western Cape Province, South Africa

BACKGROUND

Carbapenem resistant Enterobacterales (CRE) have become established as leading pathogens in South African healthcare facilities. The aim of this study is to describe the epidemiology of CRE carriage and clinical infection episodes at healthcare facilities in the Western Cape Province of South Africa (2016-2020), and identify factors associated with mortality in CRE infected patients.

METHODOLOGY

We used routine data from the Provincial Health Data Centre to track the emergence of CRE in healthcare facilities in the Western Cape Province of South Africa. We included all CRE episodes (clinical and carriage) at Western Cape hospitals (including day and inpatients) from 2016 to 2020 to determine the distribution of CRE, patient demographics and antibiotic resistance phenotypes. Logistic regression was performed to identify factors associated with mortality from clinical CRE episodes.

RESULTS

2242 CRE episodes (1580 [70.5%] clinical and 662 [29.5%] carriage) were identified. From these, 2281 CRE isolates were identified, with Klebsiella species predominating (1644, 72.1%). Affected patients had a median age of 31 (IQR 0-52) years, and 1167 (52.0%) were male. Most CRE episodes were recorded in central hospitals (70.0%, p < 0.001). Where outcome data was available, crude in-hospital mortality rates were 26.9% (371/1379) for CRE clinical episodes versus 6.4% (41/640) for CRE carriage episodes (p < 0.001). Factors that showed a statistically significant association with in-hospital mortality were female sex [adjusted odd ratio (aOR) 1.40 (95% confidence interval (CI) 1.09-1.560)], adult patients [aOR 1.76 (95% CI 1.20-2.57)], CRE isolation from a sterile specimen [aOR 0.41 (95% CI 0.32-0.53)], and >3 days between hospital admission and specimen collection [aOR 1.56 (95% CI 1.11-2.18)].

CONCLUSIONS

CRE episodes at Western Cape healthcare facilities are concentrated at tertiary hospitals, with high case fatality rates in patients with clinical CRE episodes. Infection control interventions must be strengthened to reduce transmission of CRE, and to reduce infection risks.

Amoxicillin-Clavulanate Breakpoints Against Enterobacterales: Rationale for Revision by the Clinical and Laboratory Standards Institute

Amoxicillin-clavulanate (AMC) is among the most frequently prescribed antibiotics globally. It has broad antibacterial activity against gram-positive, gram-negative, and anaerobic bacteria and has been used to treat infections caused by a broad range of pathogens. AMC breakpoints against Enterobacterales were initially set in the 1980s. However, since that time, increases in antibiotic resistance, advances in pharmacokinetic/pharmacodynamic analyses, and publication of additional clinical data prompted a reassessment by the Clinical and Laboratory Standards Institute (CLSI) Subcommittee on Antimicrobial Susceptibility Testing. Based on this contemporary reappraisal, the CLSI retained the Enterobacterales breakpoints but revised comments regarding dosing associated with use of the AMC breakpoints in the 2022 supplement of M100. This viewpoint provides insight into the CLSI breakpoint reevaluation process and summarizes the data and rationale used to support these revisions to the AMC Enterobacterales breakpoint.

Recovery of Vandammella animalimorsus from an immunocompetent female patient following cat bite to the lower leg

We report a case of Vandammella animalimorsus in an adult female patient following a cat scratch/bite. Animal bite/scratches may lead to zoonotic transmission of bacteria that subsequently lead to infection. Wound management and antimicrobial therapy is often necessary. The organism was initially misidentified as Neisseria animaloris/zoodegmatis and highlights the difficulty of correctly identifying some bacteria in clinical microbiology laboratories.

Outcomes of inadequate empiric therapy and timing of newer antibacterial therapy in hospitalized adults with culture-positive Enterobacterales and Pseudomonas aeruginosa: a multicenter analysis

BACKGROUND

Infections caused by multi-drug resistant Gram-negative pathogens are associated with worse clinical outcomes in critically ill patients. We evaluated hospital outcomes based on adequacy of overall and newer antibacterial therapy for Enterobacterales (ENT) and Pseudomonas aeruginosa (PsA) in US patients.

METHODS

Hospitalized adults ≥ 18 years old with facility-reported antibiotic susceptibility from 2018-2022 across 161 facilities in the BD Insights Research Database were identified as ENT- or PsA-positive. Generalized linear mixed models were used to evaluate the impact of inadequate empiric therapy (IET) and time to initiate newer antibacterials (ceftazidime-avibactam; ceftolozane-tazobactam; cefiderocol; meropenem-vaborbactam; eravacycline; and imipenem-cilcastatin-relebactam) on hospital mortality and post-culture length of stay (LOS).

RESULTS

Among 229,320 ENT and 36,027 PsA susceptibility results, 1.7% and 16.8% were carbapenem non-susceptible (carb-NS), respectively. Median time to first susceptibility result was longer for carb-NS vs. carb susceptible in ENT (64 h vs. 48 h) and PsA (67 h vs. 60 h). For ENT, IET was associated with significantly higher mortality (odds ratio [OR],1.29 [95% CI, 1.16-1.43, P < 0.0001]) and longer hospital LOS (14.8 vs. 13.3, P < 0.0001). Delayed start to newer antibacterial therapy was associated with significantly greater hospital mortality for ENT (P = 0.0182) and PsA (P = 0.0249) and significantly longer post-culture LOS for ENT (P < 0.0001) and PsA (P < 0.0001).

CONCLUSIONS

Overall, IET and delayed use of newer antibacterials are associated with significantly worse hospital outcomes. More rapid identification of high-risk patients can facilitate adequate therapy and timely use of newer antibacterials developed for resistant Gram-negative pathogens.

Carbapenem-resistant Enterobacterales sepsis following endoscopic retrograde cholangiopancreatography: risk factors for 30-day all-cause mortality and the development of a nomogram based on a retrospective cohort

BACKGROUND

Endoscopic retrograde cholangiopancreatography (ERCP) has become a routine endoscopic procedure that is essential for diagnosing and managing various conditions, including gallstone extraction and the treatment of bile duct and pancreatic tumors. Despite its efficacy, post-ERCP infections - particularly those caused by carbapenem-resistant Enterobacterales (CRE) - present significant risks. These risks highlight the need for accurate predictive models to enhance postprocedural care, reduce the mortality risk associated with post-ERCP CRE sepsis, and improve patient outcomes in the context of increasing antibiotic resistance.

OBJECTIVE

This study aimed to examine the risk factors for 30-day mortality in patients with CRE sepsis following ERCP and to develop a nomogram for accurately predicting 30-day mortality risk.

METHODS

Data from 195 patients who experienced post-ERCP CRE sepsis between January 2010 and December 2022 were analyzed. Variable selection was optimized via the least absolute shrinkage and selection operator (LASSO) regression model. Multivariate logistic regression analysis was then employed to develop a predictive model, which was evaluated in terms of discrimination, calibration, and clinical utility. Internal validation was achieved through bootstrapping.

RESULTS

The nomogram included the following predictors: age > 80 years (hazard ratio [HR] 2.61), intensive care unit (ICU) admission within 90 days prior to ERCP (HR 2.64), hypoproteinemia (HR 4.55), quick Pitt bacteremia score ≥ 2 (HR 2.61), post-ERCP pancreatitis (HR 2.52), inappropriate empirical therapy (HR 3.48), delayed definitive therapy (HR 2.64), and short treatment duration (< 10 days) (HR 5.03). The model demonstrated strong discrimination and calibration.

CONCLUSIONS

This study identified significant risk factors associated with 30-day mortality in patients with post-ERCP CRE sepsis and developed a nomogram to accurately predict this risk. This tool enables healthcare practitioners to provide personalized risk assessments and promptly administer appropriate therapies against CRE, thereby reducing mortality rates.

Hospital mortality and length of stay associated with Enterobacterales positive blood cultures: a multicenter analysis

Delayed time to antimicrobial susceptibility results can impact patients' outcomes. Our study evaluated the impact of susceptibility turnaround time (TAT) and inadequate empiric antibacterial therapy (IET) in patients with bloodstream infections (BSI) caused by Enterobacterales (ENT) species on in-hospital mortality and length of stay (LOS). This retrospective, multicenter investigation which included 29,570 blood ENT-positive admissions across 161 US healthcare facilities evaluated the association between antimicrobial susceptibility testing (AST) TAT, carbapenem susceptibility, and empiric therapy on post-BSI in-hospital mortality and LOS following an ENT BSI event in adult patients. After adjusting for outcomes covariates, post-BSI in-hospital mortality was significantly higher for patients in the IET vs adequate empiric therapy (AET) group [odds ratio (OR): 1.61 (95% CI: 1.32, 1.98); P < 0.0001], and when AST TAT was >63 h [OR:1.48 (95% CI: 1.16, 1.90); P = 0.0017]. Patients with carbapenem non-susceptible (carb-NS) ENT BSI had significantly higher LOS (16.6 days, 95% CI: 15.6, 17.8) compared to carbapenem susceptible (carb-S, 12.2 days, 95% CI: 11.8, 12.6), (P < 0.0001). Extended AST TAT was significantly associated with longer LOS for TAT of 57-65 h and >65 h (P = 0.005 and P< 0.0001, respectively) compared to TAT ≤42 h (reference). Inadequate empiric therapy (IET), carb-NS, and delayed AST TAT are significantly associated with adverse hospital outcomes in ENT BSI. Workflows that accelerate AST TAT for ENT BSIs and facilitate timely and adequate therapy may reduce post-BSI in-hospital mortality rate and LOS.IMPORTANCEFor patients diagnosed with bloodstream infections (BSI) caused by Enterobacterales (ENT), delayed time to antimicrobial susceptibility (AST) results can significantly impact in-hospital mortality and hospital length of stay. However, this relationship between time elapsed from blood culture collection to AST results has only been assessed, to date, in a limited number of publications. Our study focuses on this important gap using retrospective data from 29,570 blood ENT-positive admissions across 161 healthcare facilities in the US as we believe that a thorough understanding of the dynamic between AST turnaround time, adequacy of empiric therapy, post-BSI event mortality, and hospital length of stay will help guide effective clinical management and optimize outcomes of patients with ENT infections.

Estimation of latamoxef (moxalactam) dosage regimens against β-lactamase-producing Enterobacterales in dogs: a pharmacokinetic and pharmacodynamic analysis using Monte Carlo simulation

One of the most significant research areas in veterinary medicine is the search for carbapenem substitutes for the treatment of extended-spectrum β-lactamase (ESBL)-producing Enterobacterales (ESBL-E). This study applied a pharmacokinetic/pharmacodynamic (PK/PD) strategy in validating optimal latamoxef (LMX) therapeutic regimens against canine ESBL-E infections. Five dogs were administered a bolus dose of 40 mg/kg LMX intravenously to measure serum drug concentrations and determine PK indices using the noncompartmental model. The highest minimum inhibitory concentration (MIC) with a probability of target attainment ≥90% was used to compute the PK/PD cutoff values for bacteriostatic (time for which the unbound drug concentration was above the MIC [fTAM] ≥ 40%) and bactericidal (fTAM ≥ 70%) effects when administered at 20, 30, 50, and 60 mg/kg, in addition to 40 mg/kg. The cumulative fraction of response (CFR) was determined using the MIC distribution of wild-type ESBL-E in companion animals. The PK/PD cutoff values can be increased by reducing the dosing interval rather than increasing the dose per time. Based on the calculated CFRs for ESBL-producing Escherichia coli and Klebsiella pneumoniae, all LMX regimens in this study and those administered at 30-60 mg/kg every 8 and 6 hr were found to be optimal (CFR ≥ 90%) for exerting bacteriostatic and bactericidal effects, respectively. However, the regimens of 50 and 60 mg/kg every 6 hr may merely exert bacteriostatic effects on ESBL-producing Enterobacter cloacae. Further clinical trials are required to confirm the clinical efficacy of LMX.

Clinical outcomes in patients infected with ertapenem-only-resistant Enterobacterales versus multi-carbapenem-resistant Enterobacterales

BACKGROUND

Use of anti-carbapenem-resistant Enterobacterales (anti-CRE) agents such as ceftazidime/avibactam has been associated with improved clinical outcome in cohorts that primarily include patients infected with CRE that are resistant to meropenem (MCRE).

OBJECTIVES

To clarify whether patients with CRE resistant to ertapenem but susceptible to meropenem (ertapenem-only-resistant Enterobacterales; EORE) benefit from therapy with anti-CRE agents.

METHODS

Patients treated for CRE infection in hospitals in the USA between 2016 and 2019 and enrolled in the CRACKLE-2 study were included. The primary outcome was the desirability of outcome ranking (DOOR) assessed at 30 days after index cultures.

RESULTS

The EORE group included 213 patients and the MCRE group included 643. The demographics were similar between the groups except for the patients' race and origin before admission. The MCRE group received anti-CRE agents for definitive therapy significantly more frequently compared with the EORE group (30% versus 5% for ceftazidime/avibactam). We did not observe a significant difference between the groups in the adjusted DOOR probability of a more desirable outcome for a randomly selected patient in the EORE group compared with the MCRE group (52.5%; 95% CI, 48.3%-56.7%). The MCRE group had a similar proportion of patients who died at 30 days (26% versus 21%) and who were discharged to home (29% versus 40%), compared with the EORE group.

CONCLUSIONS

Patients with clinical EORE infection rarely received anti-CRE agents, but attained similar outcomes compared with patients with MCRE infection. The findings support current IDSA treatment guidance for meropenem- or imipenem-based therapy for treatment of EORE infections.

MultiRapid ATB NP test for detecting concomitant susceptibility and resistance of last-resort novel antibiotics available to treat multidrug-resistant Enterobacterales infections

BACKGROUND

Recently developed therapeutics against Gram-negative bacteria include the β-lactam-β-lactamase inhibitor combinations ceftazidime-avibactam (CZA), meropenem-vaborbactam (MEV), and imipenem-relebatam (IPR), and the siderophore cephalosporin cefiderocol (FDC). The aim of this study was to develop a test for rapid identification of susceptibility/resistance to CZA, MEV, IPR, and FDC for Enterobacterales in a single test for rapid clinical decision making.

METHODS

The MultiRapid ATB NP test is based on the detection of glucose metabolism occurring after bacterial growth in the presence of defined concentrations of CZA, MEV, IPR, and FDC, followed by visual detection of colour change of the pH indicator red phenol (red to yellow) generated by the acidification of the medium upon bacterial growth. This test is performed in 96-well microplates. The MultiRapid ATB NP test was evaluated using 78 Enterobacterales isolates and compared to the reference method broth microdilution.

RESULTS

The MultiRapid ATB NP test displayed 97.0% (confidence interval [CI] 92.6-98.8) sensitivity, 97.7% (CI 94.3-99.1) specificity, and 97.4% (CI 95.0-98.7) accuracy. The results were obtained after 3 h of incubation at 35 °C ± 2 °C, representing at least a 15-h gain-of-time compared with currently used antimicrobial susceptibility testing methods.

CONCLUSION

The MultiRapid ATB NP test provided accurate results for the concomitant detection of susceptibility/resistance to CZA, MEV, IPR, and FDC in Enterobacterales, independent of the resistance mechanism. This test may be suitable for implementation in any microbiology routine laboratory.

Candida auris inpatient screening in collaboration with the public health department

Candida auris is a multidrug-resistant fungal pathogen that is associated with nosocomial outbreaks in patients with extensive health care exposure and treatment outside the United States. The Ohio Department of Health recommends C auris screening in high-risk patients. However, this can be operationally difficult for many health care facilities. This report describes a C auris and carbapenem-resistant Enterobacterales inpatient screening program done in collaboration with state public health.

Carbapenem use in extended-spectrum cephalosporin-resistant Enterobacterales infections in US hospitals and influence of IDSA guidance: a retrospective cohort study

BACKGROUND

Disparate and rapidly changing practice recommendations from major professional infectious diseases societies for managing non-severe infections caused by extended-spectrum β-lactamase-producing Enterobacterales might hamper carbapenem stewardship. We aimed to understand the real-world management of extended-spectrum cephalosporin-resistant (ECR) Enterobacterales infections in US hospitals and factors influencing preference for carbapenems over alternative treatments.

METHODS

This retrospective cohort study included adults (aged ≥18 years) admitted to hospital with ECR Enterobacterales infections in the PINC AI database. Antibiotic regimens were assessed during empirical and targeted treatment periods and by infection severity and site. Likelihood of receiving targeted carbapenems over time and before or after initial release of the Infectious Diseases Society of America (IDSA) guidance on Sept 8, 2020, was established with generalised estimating equations controlling for patient, hospital, and temporal confounders.

FINDINGS

Between Jan 1, 2018, and Dec 31, 2021, 30 041 inpatient encounters with ECR Enterobacterales infections were identified at 168 US hospitals, of which 16 006 (53·3%) encounters were in women and 14 035 (46·7%) were in men, with a mean age of 67·3 years (SD 15·1). Although few patients received carbapenems empirically (5324 [17·7%] of 30 041), many did so as targeted treatment (17 518 [58·3%] of 30 041), including subgroups of patients without septic shock (3031 [45·6%] of 6651) and patients with urinary tract infections without septic shock (1845 [46·8%] of 3943) in whom specific narrower-spectrum alternatives were active. Transitions from non-carbapenem to carbapenem antibiotics occurred most often on the day that the ECR phenotype was reported, regardless of illness severity. Carbapenems were the predominant choice to treat ECR Enterobacterales infections over time (adjusted odds ratio 1·00 [95% CI 1·00-1·00]), with no additional immediate change (1·07 [0·95-1·20]) or sustained change (0·99 [0·98-1·00]) after IDSA guidance release.

INTERPRETATION

High carbapenem use in targeting non-severe ECR Enterobacterales infections in US hospitals predates 2020 IDSA guidance and has persisted thereafter. Efforts to increase awareness and implementation of recommendations among clinicians to use carbapenem-sparing alternatives in ECR Enterobacterales infections might decrease global carbapenem selective pressure.

FUNDING

US National Institutes of Health Intramural Research Program, National Institute of Allergy and Infectious Diseases, and US Food and Drug Administration.

Horizontal Gene Transfer of blaNDM-5 Among Three Different Enterobacteriaceae Species Isolated from a Single Patient

BACKGROUND

In this study, Escherichia coli, Klebsiella oxytoca, and Citrobacter amalonaticus carrying blaNDM-5 were isolated from a single patient.

METHODS

The antibiotic susceptibility of the isolates was evaluated by using E-test and agar dilution methods, and blaNDM-5 was identified in genomic and plasmid DNA by using polymerase chain reaction and sequencing. Whole genome sequencing and de novo assembly were used for species characterization, resistance gene identification, and plasmid analysis.

RESULTS

All three species had identical plasmids, which were similar to pEC463-NDM5, a plasmid harboring blaNDM-5. Transconjugation experiments confirmed the horizontal gene transfer of blaNDM-5, highlighting the need for a close monitoring of Enterobacteriaceae species harboring this gene.

CONCLUSIONS

This study conclusively demonstrates the propensity for horizontal gene transfer of blaNDM-5 among Enterobacteriaceae species, underlining the importance of vigilant monitoring to combat antibiotic resistance.

Cefoperazone targets D-alanyl-D-alanine carboxypeptidase (DAC) to control Morganella morganii-mediated infection: a subtractive genomic and molecular dynamics approach

Morganella morganii is a Gram-negative bacterial pathogen that causes bacteremia, urinary tract infections, intra-abdominal infections, chorioamnionitis, neonatal sepsis, and newborn meningitis. To control this bacterial pathogen a total of 3565 putative proteins targets in Morganella morganii were screened using comparative subtractive analysis of biochemical pathways annotated by the KEGG that did not share any similarities with human proteins. One of the targets, D-alanyl-D-alanine carboxypeptidase DacB [Morganella] was observed to be implicated in the majority of cell wall synthesis pathways, leading to its selection as a novel pharmacological target. The drug that interacted optimally with the identified target was observed to be Cefoperazone (DB01329) with the estimated free energy of binding -8.9 Kcal/mol. During molecular dynamics simulations; it was observed that DB01328-2exb and DB01329-2exb complexes showed similar values as the control FMX-2exb complex near 0.2 nm with better stability. Furthermore, MMPBSA total free energy calculation showed better binding energy than the control complex for DB01329-2exb interaction i.e. -31.50 (±0.93) kcal/mol. Our presented research suggested that D-alanyl-D-alanine carboxypeptidase DacB could be a therapeutic target and cefoperazone could be a promising ligand to inhibit the D-alanyl-D-alanine carboxypeptidase DacB protein of Morganella morganii. To identify prospective therapeutic and vaccine targets in Morganella morganii, this is the first computational and subtractive genomics investigation of various metabolic pathways exploring other therapeutic targets of Morganella morganii. In vitro/in vivo experimental validation of the identified target D-alanyl-D-alanine carboxypeptidase and the design of its inhibitors is suggested to figure out the best dose, the drug's effectiveness, and its toxicity.Communicated by Ramaswamy H. Sarma.

Antimicrobial Susceptibility and Genetic Epidemiology of Extended-Spectrum β-Lactamase-Positive Enterobacterales Clinical Isolates in Central Poland

The extended-spectrum β-lactamases (ESβLs) are bacterial enzymes capable of hydrolyzing penicillins, cephalosporins, and aztreonam. The prevalence of ESβL is increasing among clinically significant microorganisms worldwide, drastically reducing the therapeutic management of infectious diseases. The study aimed to determine the drug susceptibility of ESβL-positive clinical isolates acquired from patients hospitalized in Lodz, central Poland, and analyze the prevalence of specific genes, determining acquired resistance in these bacteria. The samples of ESβL-positive clinical isolates were gathered in 2022 from medical microbiological laboratories in the city of Lodz, central Poland. The strains were subjected to biochemical identification and antimicrobial susceptibility testing following EUCAST guidelines. The presence of studied genes (blaCTX-M, blaSHV, blaTEM, blaPER, blaVEB) was confirmed by PCR. Over 50% of studied isolates were resistant to gentamicin, cefepime, ceftazidime and ciprofloxacin. The most common ESβL gene was blaCTX-M. In most isolates, the resistance genes occurred simultaneously. The blaPER was not detected in any of the tested strains. ESβL-producing strains are largely susceptible to the currently available antibiotics. The observation of the coexistence of different genes in most clinical isolates is alarming.

Mutation Rate of AmpC β-Lactamase-Producing Enterobacterales and Treatment in Clinical Practice: A Word of Caution

In a retrospective multicenter study of 575 patients with bloodstream infections or pneumonia due to wild-type AmpC β-lactamase-producing Enterobacterales, species with low in vitro mutation rates for AmpC derepression were associated with fewer treatment failures due to AmpC overproduction (adjusted hazard ratio, 0.5 [95% CI, .2-.9]). However, compared to cefepime/carbapenems, using third-generation cephalosporins as definitive therapy remained associated with this adverse outcome (15% vs 1%).

Carbapenem-resistant Enterobacteriaceae in the livestock, humans and environmental samples around the globe: a systematic review and meta-analysis

Carbapenem-resistant Enterobacteriaceae (CRE) have diminished treatment options causing serious morbidities and mortalities. This systematic review and meta-analysis assessed the prevalence and associated factors of Enterobacteriaceae infections in clinical, livestock and environmental settings globally. The population intervention comparison and outcome strategy was used to enroll studies using the preferred reporting system for systematic review and meta-analysis to include only cross-sectional studies. Search engines used to retrieve articles included journal author name estimator, PubMed, Google Scholar and African Journals Online (AJOL). The Newcastle-Ottawa scale was used to assess the quality of studies. Sixteen articles from 2013 to 2023 in Africa, Asia, Europe and South America were studied. The pooled prevalence of CRE was 43.06% (95% CI 21.57-66.03). Klebsiella pneumoniae (49.40%), Escherichia coli (26.42%), and Enterobacter cloacae (14.24%) were predominant. Klebsiella pneumoniae had the highest resistance with the blaKPC-2 in addition to blaNDM, blaOXA-48, blaIMP and blaVIM. The blaKPC-2 genes occurrence was associated with environmental (P-value < 0.0001) and South American studies (P-value < 0.0001), but there was no difference in the trends over time (P-value = 0.745). This study highlights the high rates of CRE infections, particularly within blaKPC production. Monitoring and surveillance programs, research and infection control measures should be strengthened. Additionally, further studies are needed to explore the mechanisms driving the predominance of specific bacterial species and the distribution of resistance genes within this bacterial family.

Edwardsiella tarda Attenuates Virulence upon Oxytetracycline Resistance

The relationship between antibiotic resistance and bacterial virulence has not yet been fully explored. Here, we use Edwardsiella tarda as the research model to investigate the proteomic change upon oxytetracycline resistance (LTB4-ROTC). Compared to oxytetracycline-sensitive E. tarda (LTB4-S), LTB4-ROTC has 234 differentially expressed proteins, of which the abundance of 84 proteins is downregulated and 15 proteins are enriched to the Type III secretion system, Type VI secretion system, and flagellum pathways. Functional analysis confirms virulent phenotypes, including autoaggregation, biofilm formation, hemolysis, swimming, and swarming, are impaired in LTB4-ROTC. Furthermore, the in vivo bacterial challenge in both tilapia and zebrafish infection models suggests that the virulence of LTB4-ROTC is attenuated. Analysis of immune gene expression shows that LTB4-ROTC induces a stronger immune response in the spleen but a weaker response in the head kidney than that induced by LTB4-S, suggesting it's a potential vaccine candidate. Zebrafish and tilapia were challenged with a sublethal dose of LTB4-ROTC as a live vaccine followed by LTB4-S challenge. The relative percentage of survival of zebrafish is 60% and that of tilapia is 75% after vaccination. Thus, our study suggests that bacteria that acquire antibiotic resistance may attenuate virulence, which can be explored as a potential live vaccine to tackle bacterial infection in aquaculture.

Using the CLSI rAST breakpoints of Enterobacterales in positive blood cultures

OBJECTIVES

The objective of this study was to provide the clinic with rapid and accurate results of antimicrobial susceptibility testing for the treatment of patients with bloodstream infections. To achieve this, we applied the Clinical and Laboratory Standards Institute (CLSI) blood culture direct rapid antimicrobial susceptibility test (rAST) to assess the susceptibility of the most common Enterobacterales found in blood cultures.

METHODS

In this study, we utilized the CLSI blood culture direct rapid antimicrobial susceptibility test to assess the susceptibility (rAST) of the most common Enterobacterales present in blood cultures. We chose this method for its simplicity in analysis, and our aim was to predict minimum inhibitory concentrations (MICs) using the rAST. As a benchmark, we assumed that Broth Macrodilution method (BMD) results were 100% accurate. For data evaluation, we employed the terms categorical agreement (CA), very major errors (VME), and major errors (ME).

RESULTS

Our findings demonstrate that the CLSI rAST method is reliable for rapidly determining the in vitro susceptibility of Enterobacterales to common antimicrobial drugs in bloodstream infections. We achieved a concordance rate of 90% in classification within a 10-hour timeframe. We identified a total of 112 carbapenem-resistant Enterobacterales (CRE) strains, and there was no significant difference in the detection rate of CRE at 6, 10, and 16 hours. This suggests that CRE can be identified as early as 6 hours.

CONCLUSION

The CLSI rAST is a valuable tool that can be utilized in clinical practice to quickly determine the susceptibility of Enterobacterales to antimicrobial drugs within 10 hours. This capability can greatly assist in the clinical management of patients with bloodstream infections.

In vitro and in vivo activity of ceftazidime/avibactam and aztreonam alone or in combination against mcr-9, serine- and metallo-β-lactamases-co-producing carbapenem-resistant Enterobacter cloacae complex

PURPOSE

Enterobacteriaceae carrying mcr-9, in particularly those also co-containing metallo-β-lactamase (MBL) and TEM type β-lactamase, present potential transmission risks and lack adequate clinical response methods, thereby posing a major threat to global public health. The aim of this study was to assess the antimicrobial efficacy of a combined ceftazidime/avibactam (CZA) and aztreonam (ATM) regimen against carbapenem-resistant Enterobacter cloacae complex (CRECC) co-producing mcr-9, MBL and TEM.

METHODS

The in vitro antibacterial activity of CZA plus ATM was evaluated using a time-kill curve assay. Furthermore, the in vivo interaction between CZA plus ATM was confirmed using a Galleria mellonella (G. mellonella) infection model.

RESULTS

All eight clinical strains of CRECC, co-carrying mcr-9, MBL and TEM, exhibited high resistance to CZA and ATM. In vitro time-kill curve analysis demonstrated that the combination therapy of CZA + ATM exerted significant bactericidal activity against mcr-9, MBL and TEM-co-producing Enterobacter cloacae complex (ECC) isolates with a 100% synergy rate observed in our study. Furthermore, in vivo survival assay using Galleria mellonella larvae infected with CRECC strains co-harboring mcr-9, MBL and TEM revealed that the CZA + ATM combination significantly improved the survival rate compared to the drug-treatment alone and untreated control groups.

CONCLUSION

To our knowledge, this study represents the first report on the in vitro and in vivo antibacterial activity of CZA plus ATM against CRECC isolates co-harboring mcr-9, MBL and TEM. Our findings suggest that the combination regimen of CZA + ATM provides a valuable reference for clinicians to address the increasingly complex antibiotic resistance situation observed in clinical microorganisms.

Ertapenem Versus Meropenem for the Treatment of Extended Spectrum Beta-Lactamase-Producing Enterobacterales Bacteremia in Critically Ill Patients

BACKGROUND

The preferred carbapenem for treatment of infections caused by extended spectrum beta-lactamase-producing Enterobacterales (ESBL-E) in critically ill patients is debated.

OBJECTIVE

The purpose of this study was to evaluate the difference in clinical failure between ertapenem and meropenem for treatment of ESBL-E bacteremia in critically ill patients. Of concern is ertapenem use in hypoalbuminemia given the potential for higher drug clearance.

METHODS

This retrospective, matched cohort study compared critically ill patients treated with ertapenem or meropenem for ESBL-E bacteremia between October 2016 and August 2022. Patients were matched on age, sex, lowest albumin, and in a 1:2 ratio of ertapenem to meropenem. The primary outcome, clinical failure, was a composite of 30-day mortality, antibiotic escalation, and microbiological failure. Secondary outcomes included all-cause readmission and development of superinfection.

RESULTS

Of 54 patients, 18 received ertapenem and 36 meropenem. Most had a urinary infection source (55.6% vs 41.7%, P = 0.393). There was no difference in clinical failure (50.0% vs 38.9%, P = 0.436). Ertapenem patients had antibiotic escalation more often (33.3% vs 2.8%, P = 0.002). There was no difference in 30-day mortality (11.1% vs 27.8%, P = 0.298), microbiological failure (27.8% vs 11.1%, P = 0.142), all-cause readmission (22.2% vs 13.9%, P = 0.461), or development of superinfection (11.1% vs 13.9%, P = 1.000).

CONCLUSION AND RELEVANCE

There was no difference in clinical failure in a small, retrospective cohort of critically ill patients receiving ertapenem or meropenem for ESBL-E bacteremia. Ertapenem may be appropriate in some critically ill and hypoalbuminemic patients, though additional data are needed.