Gram-negative Bacterial Infections Research Articles

Prediction of carbapenem-resistant gram-negative bacterial bloodstream infection in intensive care unit based on machine learning

BackgroundPredicting whether Carbapenem-Resistant Gram-Negative Bacterial (CRGNB) cause bloodstream infection when giving advice may guide the use of antibiotics because it takes 2–5 days conventionally to return the results from doctor's order.MethodsIt is a regional multi-center retrospective study in which patients with suspected bloodstream infections were divided into a positive and negative culture group. According to the positive results, patients were divided into the CRGNB group and other groups. We used the machine learning algorithm to predict whether the blood culture was positive and whether the pathogen was CRGNB once giving the order of blood culture.ResultsThere were 952 patients with positive blood cultures, 418 patients in the CRGNB group, 534 in the non-CRGNB group, and 1422 with negative blood cultures. Mechanical ventilation, invasive catheterization, and carbapenem use history were the main high-risk factors for CRGNB bloodstream infection. The random forest model has the best prediction ability, with AUROC being 0.86, followed by the XGBoost prediction model in bloodstream infection prediction. In the CRGNB prediction model analysis, the SVM and random forest model have higher area under the receiver operating characteristic curves, which are 0.88 and 0.87, respectively.ConclusionsThe machine learning algorithm can accurately predict the occurrence of ICU-acquired bloodstream infection and identify whether CRGNB causes it once giving the order of blood culture.

Membrane Permeability Dominates over Electrostatic Interactions in Dictating Drug Transport in Osmotically Shocked Escherichia coli.

To combat surging multidrug-resistant Gram-negative bacterial infections, better strategies to improve the efficacy of existing drugs are critical. Because the dual membrane cell envelope is the first line of defense for these bacteria, it is crucial to understand the permeation properties of the drugs through it. Our recent study shows that isosmotic conditions prevent drug permeation inside Gram-negative bacteria, Escherichia coli, while hypoosmotic stress enhances the process. Here, we unravel the reason behind such differential drug penetration. Specifically, we dissect the roles of electrostatic screening and low membrane permeability in the penetration failure of drugs under osmotically balanced conditions. We compare the transport of a quaternary ammonium compound malachite green in the presence of an electrolyte (NaCl) and a wide variety of commonly used organic osmolytes, e.g., sucrose, proline, glycerol, sorbitol, and urea. These osmolytes of different membrane permeability (i.e., nonpermeable sucrose and NaCl, freely permeable urea and glycerol, and partially permeable proline and sorbitol) clarify the role of osmotic stress in cell envelope permeability. The results showcase that under balanced osmotic conditions, drug molecules fail to penetrate inside E. coli cells because of low membrane permeabilities and not because of electrostatic screening imposed by the osmolytes. Contribution of the electrostatic interactions, however, cannot be completely overruled as at osmotically imbalanced conditions, drug transport across the bacterial subcellular compartments is found to be dependent on the osmolytes used.

Genetic Screening Revealed the Negative Regulation of miR-310~313 Cluster Members on Imd Pathway during Gram-Negative Bacterial Infection in Drosophila

Innate immune response is the first line of host defense against pathogenic microorganisms, and its excessive or insufficient activation is detrimental to the organism. Many individual microRNAs (miRNAs) have emerged as crucial post-transcriptional regulators of immune homeostasis in Drosophila melanogaster. However, the synergistical regulation of miRNAs located within a cluster on the Imd-immune pathway remains obscured. In our study, a genetic screening with 52 transgenic UAS-miRNAs was performed to identify ten miRNAs or miRNA clusters, including the miR310~313 cluster, which may function on Imd-dependent immune responses. The miRNA RT-qPCR analysis showed that the expression of miR-310~313 cluster members exhibited an increase at 6–12 h post E. Coli infection. Furthermore, the overexpression of the miR-310~313 cluster impaired the Drosophila survival. And the overexpression of miR-310/311/312 reduced Dpt expression, an indication of Imd pathway induced by Gram-negative bacteria. Conversely, the knockdown of miR-310/311/312 led to increases in Dpt expression. The Luciferase reporter expression assays and RT-qPCR analysis confirmed that miR-310~313 cluster members directly co-targeted and inhibited Imd transcription. These findings reveal that the members of the miR-310~313 cluster synergistically inhibit Imd-dependent immune responses by co-targeting the Imd gene in Drosophila.

In vitro and in vivo activities of KSP-1007, a broad-spectrum inhibitor of serine- and metallo-β-lactamases, in combination with meropenem against carbapenem-resistant Gram-negative bacteria.

KSP-1007 is a novel bicyclic boronate-based broad-spectrum β-lactamase inhibitor and is being developed in combination with meropenem (MEM) for the treatment of infections caused by carbapenem-resistant Gram-negative bacteria, a global health concern, and here, we describe its characteristics. KSP-1007 exhibited low apparent inhibition constant (Ki app) values against all classes of β-lactamase, including imipenemase types and oxacillinase types from Acinetobacter baumannii. Against 207 Enterobacterales and 55 A. baumannii, including carbapenemase producers, KSP-1007 at fixed concentrations of 4, 8, and 16 µg/mL dose-dependently potentiated the in vitro activity of MEM in broth microdilution MIC testing. The MIC90 of MEM/KSP-1007 at 8 µg/mL against Enterobacterales was lower than those of MEM/vaborbactam, ceftazidime/avibactam, imipenem/relebactam, and colistin and similar to those of aztreonam/avibactam, cefiderocol, and tigecycline. The in vitro activity of MEM/KSP-1007 at ≥4 µg/mL against Enterobacterales harboring metallo-β-lactamase was superior to that of cefepime/taniborbactam. MEM/KSP-1007 showed excellent activity against Escherichia coli with PBP3 mutations and New Delhi metallo-β-lactamase compared to aztreonam/avibactam, cefepime/taniborbactam, and cefiderocol. MEM/KSP-1007 at 8 µg/mL showed greater efficacy against A. baumannii than these comparators except for cefiderocol, tigecycline, and colistin. A 2-fold reduction in MEM MIC against 96 Pseudomonas aeruginosa was observed in combination with KSP-1007. MEM/KSP-1007 demonstrated bactericidal activity against carbapenemase-producing Enterobacterales, A. baumannii, and P. aeruginosa based on minimum bactericidal concentration/MIC ratios of ≤4. KSP-1007 enhanced the in vivo activity of MEM against carbapenemase-producing Enterobacterales, A. baumannii, and P. aeruginosa in murine systemic, complicated urinary tract, and thigh infection models. Collectively, MEM/KSP-1007 has a good profile for treating carbapenem-resistant Gram-negative bacterial infections.

A pharmacovigilance study of adverse events associated with polymyxins based on the U.S. Food and Drug Administration Adverse Event Reporting System (FAERS) database

ABSTRACT Background Polymyxins have been regarded as last-line treatment for multidrug-resistant gram-negative bacterial infections. Nonetheless, concerns regarding toxicity persist. This study aimed to explore and compare potential adverse events (AEs) between colistin and polymyxin B (PMB). Methods Outpatient antibiotic use associated with acute upper respiratory infections in China: a nationwide cross-sectional study Polymyxins-related AEs were retrieved from the U.S. Food and Drug Administration Adverse Event Reporting System between 2004 and 2022. Potential signals were estimated by the reporting odds ratio (ROR), and subgroup analyses were preformed to adjust for potential factors in AEs with significant disproportionality. Results Analysis of 3,915 records involving 718 patients revealed a higher disproportionality of renal and urinary disorders (ROR 1.62, 95% CI 1.01–2.59) and acute kidney injury (ROR 1.75, 95% CI 1.07–2.87) with colistin treatment. Conversely, colistin exhibited a lower risk for neurotoxicity (ROR 0.47, 95% CI 0.30–0.73). Seven cases of skin hyperpigmentation were reported with PMB, whereas none were reported with colistin. Over 80% of cases involving polymyxin-related AEs occurred during the first two weeks of therapies, with a median onset time of 4.5 days. Conclusions Outpatient antibiotic use associated with acute upper respiratory infections in China: a nationwide cross-sectional study Patients received colistin displayed a higher potential risk of nephrotoxicity but a lower risk of neurotoxicity. Clinicians should be vigilant in monitoring the AEs of hyperpigmentation disorders induced by PMB.

Development of rabbit models of ventilator-associated bacterial pneumonia produced by carbapenem-resistant Pseudomonas aeruginosa.

Ventilator-associated bacterial pneumonia (VABP) is among the most intractable of carbapenem-resistant Gram-negative bacterial infections. New antimicrobial agents are critically needed for the treatment of VABP. However, current conventionally used animal model systems are inadequate to meet this challenge. We, therefore, developed rabbit models of VABP caused by carbapenem-resistant Pseudomonas aeruginosa. Persistently neutropenic New Zealand White rabbits were used throughout the study. The early-phase intubated model (0-24 h) received mechanical ventilation, while the late-phase intubated model (72-96 h) was ambulatory. The following outcome parameters were studied: survival, residual tissue bacterial burden (CFU/g), residual BAL bacterial burden (CFU/mL), lung weights, pulmonary lesion score, histology, O2 saturation, radiographic imaging, and histology. Each anesthetized rabbit received a predetermined endotracheal bacterial inoculum, and ventilators were set to FiO2 = 40% and PEEP = 8 mmHg. Within the first 12 h post-inoculation, mean bacterial burdens in lung tissue and BAL fluid, respectively, were established at approximately 107 CFU/g and 106 CFU/mL, persisted through 24 h in the early-phase model and increased in the late-phase model to approximately 108 CFU/g and 107 CFU/mL. Mean max SpO2 was ≥98 mmHg, and mean nadir SpO2 was ≥68 mmHg. Serial thoracic radiographs demonstrated progressive multilobar pneumonic infiltrates. Lung histology revealed progressive focal bronchopneumonia, coagulative necrosis, intra-alveolar hemorrhage, alveolar epithelial cell necrosis, and bacterial microcolonies. The new rabbit model of VABP produced by carbapenem-resistant Pseudomonas aeruginosa recapitulates the pathophysiological, microbiological, diagnostic imaging, and histological patterns of human disease by which to assess critically needed new antimicrobial agents against this lethal infection.

Infection-related mortality and infection control practices in childhood acute myeloid leukemia in a limited resource setting: Experience with the Indonesian national protocol.

In resource-limited settings, addressing infections remains a substantial challenge in the management of children with Acute Myeloid Leukemia (AML). In Indonesia, infection-related mortality (IRM) is thought to be high compared to high-income countries. However, there has been no previous study of infection profile and IRM in Indonesian patients with AML. This study aimed to describe infections and IRM in children with AML treated according to the Indonesian National AML protocol and to describe the implementation of infection control practices in resource-limited settings. This retrospective observational study used secondary data from the medical records of pediatric patients with AML treated with the National Protocol at Dr. Sardjito Hospital, Yogyakarta, Indonesia, from April 2012 to September 2018. Essential patient characteristics, time of IRM, and cause of death were recorded, and infection control practices were observed. Data were analyzed using descriptive statistics. 113 patients with AML were treated with the National protocol, and 83 met the inclusion criteria. Infections occurred in 69 (83%) patients with a total of 123 episodes (mean 1.8/patient). Death was seen in 48 (58%) patients, with 19 (23%) IRM. The majority of infections were in the gastrointestinal tract (n = 51, 30.5%), sepsis (n = 29, 17%), and respiratory tract (n = 28, 17%). Infections mostly occurred during the first induction (41%). There were 90 (73%) episodes of clinically documented infection and 33 (27%) episodes of microbiologically documented infection. The positivity rate of blood cultures was only 27%. The majority of bacteria detected were gram-negative (n = 25, 69%), and among them were Klebsiella pneumonia (19%) and Escherichia coli (19%). Candida albicans was detected in 1 (2%) culture. Suboptimal infection prevention and control were found in the clinical practice. Infections and infection-related mortality in children with AML treated using the National protocol were frequent, mainly occurring during the first induction phase. Compliance with infection prevention and control measures needs improvement. Urgent attention is required for better supportive care, including isolation rooms, antibiotics, and antifungals. The predominance of Gram-negative bacterial infections highlights the necessity for further research into effective prophylaxis. Enhanced healthcare and nursing professional vigilance and tailored antibiotic strategies are vital. Improving compliance and ensuring adequate supportive care resources are essential, emphasizing nursing's pivotal role. Further research is crucial to drive advancements in infection control strategies.

Decoding the Structure-Function Relationship of the Muramidase Domain in E. coli O157.H7 Bacteriophage Endolysin: A Potential Building Block for Chimeric Enzybiotics.

Bacteriophage endolysins are potential alternatives to conventional antibiotics for treating multidrug-resistant gram-negative bacterial infections. However, their structure-function relationships are poorly understood, hindering their optimization and application. In this study, we focused on the individual functionality of the C-terminal muramidase domain of Gp127, a modular endolysin from E. coli O157:H7 bacteriophage PhaxI. This domain is responsible for the enzymatic activity, whereas the N-terminal domain binds to the bacterial cell wall. Through protein modeling, docking experiments, and molecular dynamics simulations, we investigated the activity, stability, and interactions of the isolated C-terminal domain with its ligand. We also assessed its expression, solubility, toxicity, and lytic activity using the experimental data. Our results revealed that the C-terminal domain exhibits high activity and toxicity when tested individually, and its expression is regulated in different hosts to prevent self-destruction. Furthermore, we validated the muralytic activity of the purified refolded protein by zymography and standardized assays. These findings challenge the need for the N-terminal binding domain to arrange the active site and adjust the gap between crucial residues for peptidoglycan cleavage. Our study shed light on the three-dimensional structure and functionality of muramidase endolysins, thereby enriching the existing knowledge pool and laying a foundation for accurate in silico modeling and the informed design of next-generation enzybiotic treatments.

A systematic evaluation of population pharmacokinetic models for polymyxin B in patients with liver and/or kidney dysfunction.

Polymyxin B (PMB) is considered a last-line treatment for multidrug-resistant (MDR) gram-negative bacterial infections. Model-informed precision dosing with population pharmacokinetics (PopPK) models could help to individualize PMB dosing regimens and improve therapy. However, the external prediction ability of the established PopPK models has not been fully elaborated. This study aimed to systemically evaluate eleven PMB PopPK models from ten published literature based on a new independent population, which was divided into four different populations, patients with liver dysfunction, kidney dysfunction, liver and kidney dysfunction, and normal liver and kidney function. The whole data set consisted of 146 patients with 391 PMB concentrations. The prediction- and simulation-based diagnostics and Bayesian forecasting were conducted to evaluate model predictability. In the overall evaluation process, none of the models exhibited satisfactory predictive ability in both prediction- and simulation-based diagnostic simultaneously. However, the evaluation of the models in the subgroup of patients with normal liver and kidney function revealed improved predictive performance compared to those with liver and/or kidney dysfunction. Bayesian forecasting demonstrated enhanced predictability with the incorporation of two to three prior observations. The external evaluation highlighted a lack of consistency between the prediction results of published models and the external validation dataset. Nonetheless, Bayesian forecasting holds promise in improving the predictive performance of the models, and feedback from therapeutic drug monitoring is crucial in optimizing individual dosing regimens.

Efficacy of Random Forest Models in Predicting Multidrug-Resistant Gram-Negative Bacterial Nosocomial Infections Compared to Traditional Logistic Regression Models.

This study evaluates whether random forest (RF) models are as effective as traditional Logistic Regression (LR) models in predicting multidrug-resistant Gram-negative bacterial nosocomial infections. Data were collected from 541 patients with hospital-acquired Gram-negative bacterial infections at two tertiary-level hospitals in Urumqi, Xinjiang, China, from August 2022 to November 2023. Relevant literature informed the selection of significant predictors based on patients' pre-infection clinical information and medication history. The data were split into a training set of 379 cases and a validation set of 162 cases, adhering to a 7:3 ratio. Both RF and LR models were developed using the training set and subsequently evaluated on the validation set. The LR model achieved an accuracy of 84.57%, sensitivity of 82.89%, specificity of 80.10%, positive predictive value of 84%, negative predictive value of 85.06%, and a Yoden index of 0.69. In contrast, the RF model demonstrated superior performance with an accuracy of 89.51%, sensitivity of 90.79%, specificity of 88.37%, positive predictive value of 87.34%, negative predictive value of 91.57%, and a Yoden index of 0.79. Receiver operating characteristic curve analysis revealed an area under the curve of 0.91 for the LR model and 0.94 for the RF model. These findings indicate that the RF model surpasses the LR model in specificity, sensitivity, and accuracy in predicting hospital-acquired multidrug-resistant Gram-negative infections, showcasing its greater potential for clinical application.

Antibiotic susceptibility profile of Pseudomonas species isolated from clinical specimens to access, watch and reserve drugs across various hospital settings at a tertiary care hospital of central India

Background and Objectives: Over the last decade, hospital-acquired infections, particularly in the critical care setting, have become more common, with Gram-negative bacterial infections having the highest prevalence. This study aims to determine the prevalence and antibiotic susceptibility pattern of Pseudomonas species to WHO’s, aware class of antibiotics, which are commonly prescribed across various ICU’s, medical and surgical wards of our tertiary care teaching hospital.
 Materials and Methods: This prospective study conducted from January 2021 to June 2022 at a tertiary care centre of cen- tral India identified Pseudomonas species from clinical samples using standard procedures and antimicrobial susceptibility testing performed as per Clinical Laboratory Standards Institute (CLSI) guidelines (M100; 32th Edition).
 Results: A total of 1490 non duplicate Pseudomonas species isolates were grown from 21,019 culture positive clinical sam- ples, of which 1247 were Pseudomonas aeruginosa. Out of these 1247 Pseudomonas aeruginosa 384 were MDR (30.7%). Pseudomonas aeruginosa were most commonly isolated from the pus samples (85%). ICU isolates were significantly more resistant to antibiotics than those from other units. P. aeruginosa strains from ICUs showed the highest rates of resistance to ceftazidime (93.9%). Reserve drug colistin showed good susceptibility (98.2%). All the 18 colistin resistant strains were found to be negative for plasmid mediated mcr-1,2,3 genes.
 Conclusion: The study shall help to generate and disseminate the data so that proper antibiotic policy can be made for judi- cious use of Access, Watch and Reserve antibiotics and antibiotic de-escalation plan can be put forth.

Effect of nicotinamide mononucleotide on osteogenesis in MC3T3-E1 cells against inflammation-induced by lipopolysaccharide.

Nicotinamide mononucleotide (NMN) is extensively utilized as an anti-aging agent and possesses anti-inflammatory properties. Lipopolysaccharide (LPS) activates Toll-like receptor 4, a process modulated by intracellular signaling pathways such as the Wnt/β-catenin pathway. This study investigated the impact of NMN on osteogenesis in the presence of LPS. To elucidate the role of NMN in osteogenesis in the context of Gram-negative bacterial infection after LPS treatment, we cultured a mouse pre-osteoblast cell line (MC3T3-E1) and subsequently incubated it with NMN and/or LPS. We then evaluated osteogenic activity by measuring alkaline phosphatase activity, assessing gene expression and protein levels, and performing Alizarin Red S staining and immunocytochemistry. MC3T3-E1 cells underwent successful differentiation into osteoblasts following treatment with osteogenic induction medium. LPS diminished features related to osteogenic differentiation, which were subsequently partially reversed by treatment with NMN. The restorative effects of NMN on LPS-exposed MC3T3-E1 cells were further substantiated by elucidating the role of Wnt/β-catenin signaling, as confirmed through immunocytochemistry. This study showed that infection with Gram-negative bacteria disrupted the osteogenic differentiation of MC3T3-E1 cells. This adverse effect was partially reversed by administering a high-dose of NMN. Drawing on these results, we propose that NMN could serve as a viable therapeutic strategy to preserve bone homeostasis in elderly and immunocompromised patients.

Population pharmacokinetic/pharmacodynamic target attainment analysis of IV fosfomycin for the treatment of MDR Gram-negative bacterial infections.

IV fosfomycin is used against MDR Gram-negative bacilli (GNB) but has dose-limiting side effects, especially in patients with impaired kidney function. To determine the optimal dosage of IV fosfomycin for patients with varying degrees of kidney function. Adult patients receiving IV fosfomycin for treatment of GNB were eligible. Five serial blood samples were collected after at least three doses of fosfomycin; plasma was assayed by LC-MS/MS and modelled by population pharmacokinetic analysis. The PTA for AUC24/MIC of 98.9 for Escherichia coli and Klebsiella pneumoniae, and 40.8 for Pseudomonas aeruginosa were computed by Monte Carlo simulations. Cumulative fractions of response (CFR) were analysed for each pathogen using EUCAST MIC distributions. A total of 24 patients were included. Creatinine clearance (CLCR) and gender significantly influenced fosfomycin clearance. The kidney function-adjusted dosing regimens are proposed by using the lowest dose that can achieve ≥90% PTA for AUC24/MIC of 98.9 at an MIC of ≤32 mg/L (EUCAST v.13 susceptibility breakpoint for Enterobacterales). For patients with normal kidney function (CLCR 91-120 mL/min), a dosage of 15 g/day is suggested. This regimen achieved 97.1% CFR against E. coli, whereas CFR was 72.9% for K. pneumoniae and 76.7% for P. aeruginosa. A fosfomycin dosage of 15 g/day with adjustment according to kidney function provided high PTA and CFR when treating E. coli. This dosage is lower than that used in current practice and may improve tolerability. Higher dosages may be needed for P. aeruginosa; however, safety data are limited.

Pyrrole-based inhibitors of RND-type efflux pumps reverse antibiotic resistance and display anti-virulence potential.

Efflux pumps of the resistance-nodulation-cell division (RND) superfamily, particularly the AcrAB-TolC, and MexAB-OprM, besides mediating intrinsic and acquired resistance, also intervene in bacterial pathogenicity. Inhibitors of such pumps could restore the activities of antibiotics and curb bacterial virulence. Here, we identify pyrrole-based compounds that boost antibiotic activity in Escherichia coli and Pseudomonas aeruginosa by inhibiting their archetype RND transporters. Molecular docking and biophysical studies revealed that the EPIs bind to AcrB. The identified efflux pump inhibitors (EPIs) inhibit the efflux of fluorescent probes, attenuate persister formation, extend post-antibiotic effect, and diminish resistant mutant development. The bacterial membranes remained intact upon exposure to the EPIs. EPIs also possess an anti-pathogenic potential and attenuate P. aeruginosa virulence in vivo. The intracellular invasion of E. coli and P. aeruginosa inside the macrophages was hampered upon treatment with the lead EPI. The excellent efficacy of the EPI-antibiotic combination was evidenced in animal lung infection and sepsis protection models. These findings indicate that EPIs discovered herein with negligible toxicity are potential antibiotic adjuvants to address life-threatening Gram-negative bacterial infections.

Calcium channel inhibitor and extracellular calcium improve aminoglycoside-induced hair cell loss in zebrafish.

Aminoglycosides are commonly used antibiotics for treatment of gram-negative bacterial infections, however, they might act on inner ear, leading to hair-cell death and hearing loss. Currently, there is no targeted therapy for aminoglycoside ototoxicity, since the underlying mechanisms of aminoglycoside-induced hearing impairments are not fully defined. This study aimed to investigate whether the calcium channel blocker verapamil and changes in intracellular & extracellular calcium could ameliorateaminoglycoside-induced ototoxicity in zebrafish. The present findings showed that a significant decreased number of neuromasts in the lateral lines of zebrafish larvae at 5days' post fertilization after neomycin (20μM) and gentamicin (20mg/mL) exposure, which was prevented by verapamil. Moreover, verapamil (10-100μM) attenuated aminoglycoside-induced toxic response in different external calcium concentrations (33-3300μM). The increasing extracellular calcium reduced hair cell loss from aminoglycoside exposure, while lower calcium facilitated hair cell death. In contrast, calcium channel activator Bay K8644 (20μM) enhanced aminoglycoside-induced ototoxicity and reversed the protective action of higher external calcium on hair cell loss. However, neomycin-elicited hair cell death was not altered by caffeine, ryanodine receptor (RyR) agonist, and RyR antagonists, including thapsigargin, ryanodine, and ruthenium red. The uptake ofneomycininto hair cells was attenuated by verapamil and under high external calcium concentration. Consistently, the production of reactive oxygen species (ROS) in neuromasts exposed to neomycin was also reduced by verapamil and high external calcium. Significantly, zebrafish larvae when exposed to neomycin exhibited decreased swimming distances in reaction to droplet stimulus when compared to the control group. Verapamil and elevated external calcium effectively protected the impaired swimming ability of zebrafish larvae induced by neomycin. These data imply that prevention of hair cell damage correlated with swimming behavior against aminoglycoside ototoxicity by verapamil and higher external calcium might be associated with inhibition of excessive ROS production andaminoglycoside uptake through cation channels. These findings indicate that calcium channel blocker and higher external calcium could be applied to protect aminoglycoside-induced listening impairments.

Characterizing Antibiotic Regimen Modification Behavior, Patient Characteristics, and Outcomes for Patients with Gram-Negative Bacterial Infections, A Retrospective Single-Center Study.

Few studies describe the frequency of antibiotic regimen modification behaviors in the acute care setting. We sought to ascertain patient and treatment characteristics, details of regimen modification, and clinical outcomes with antibiotic modifications. This retrospective study included patients admitted to Hoag Memorial Hospital from 1 January 2019-31 March 2021 with a complicated infection caused by a Gram-negative organism resistant to extended-spectrum cephalosporins or with the potential for resistance (AmpC producers). A total of 400 patients were included. The predominant sources were bloodstream (33%), urine (26%), and respiratory (24%), including patients with multiple sources. The most isolated organisms were Pseudomonas spp. and ESBL-producing organisms, 38% and 34%, respectively. A total of 72% of patients had antibiotic regimen modifications to their inpatient antibiotic regimens. In patients where modifications occurred, the number ranged from one to six modifications. The most common reasons for modifications included a lack of patient response (14%), additional history reviewed (9%), and decompensation (7%). No difference in clinical outcomes was observed based on antibiotic modifications. The numerous changes in therapy observed may reflect the limitations in identifying patients with resistant organisms early on in admission. This highlights the need for more novel antibiotics and the importance of identifying patients at risk for resistant organisms.

Signaling through the Salmonella PbgA-LapB regulatory complex activates LpxC proteolysis and limits lipopolysaccharide biogenesis during stationary-phase growth.

Salmonella enterica serovar Typhimurium (S. Typhimurium) controls lipopolysaccharide (LPS) biosynthesis by regulating proteolysis of LpxC, the rate-limiting enzyme and target of preclinical antibiotics. PbgA/YejM/LapC regulates LpxC levels and controls outer membrane (OM) LPS composition at the log-to-stationary phase transition. Suppressor substitutions in LPS assembly protein B (LapB/YciM) rescue the LPS and OM integrity defects of pbgA-mutant S. Typhimurium. We hypothesized that PbgA regulates LpxC proteolysis by controlling LapB's ability to bind LpxC as a function of the growth phase. According to existing models, when nutrients are abundant, PbgA binds and restricts LapB from interacting with LpxC and FtsH, which limits LpxC proteolysis. However, when nutrients are limited, there is debate whether LapB dissociates from PbgA to bind LpxC and FtsH to enhance degradation. We sought to examine these models and investigate how the structure of LapB enables salmonellae to control LpxC proteolysis and LPS biosynthesis. Salmonellae increase LapB levels during the stationary phase to promote LpxC degradation, which limits lipid A-core production and increases their survival. The deletion of lapB, resulting in unregulated lipid A-core production and LpxC overabundance, leads to bacterial growth retardation. Tetratricopeptide repeats near the cytosol-inner membrane interface are sufficient for LapB to bind LpxC, and remarkably, LapB and PbgA interact in both growth phases, yet LpxC only associates with LapB in the stationary phase. Our findings support that PbgA-LapB exists as a constitutive complex in S. Typhimurium, which differentially binds LpxC to control LpxC proteolysis and limit lipid A-core biosynthesis in response to changes in the environment.IMPORTANCEAntimicrobial resistance has been a costly setback for human health and agriculture. Continued pursuit of new antibiotics and targets is imperative, and an improved understanding of existing ones is necessary. LpxC is an essential target of preclinical trial antibiotics that can eliminate multidrug-resistant Gram-negative bacterial infections. LapB is a natural LpxC inhibitor that targets LpxC for degradation and limits lipopolysaccharide production in Enterobacteriaceae. Contrary to some studies, findings herein support that LapB remains in complex instead of dissociating from its presumed negative regulator, PbgA/YejM/LapC, under conditions where LpxC proteolysis is enhanced. Advanced comprehension of this critical protein-lipid signaling network will lead to future development and refinement of small molecules that can specifically interfere.

Leveraging Large Data, Statistics, and Machine Learning to Predict the Emergence of Resistant E. coli Infections.

Drug-resistant Gram-negative bacterial infections, on average, increase the length of stay (LOS) in U.S. hospitals by 5 days, translating to approximately $15,000 per patient. We used statistical and machine-learning models to explore the relationship between antibiotic usage and antibiotic resistance over time and to predict the clinical and financial costs associated with resistant E. coli infections. We acquired data on antibiotic utilization and the resistance/sensitivity of 4776 microbial cultures at a Kaiser Permanente facility from April 2013 to December 2019. The ARIMA (autoregressive integrated moving average), neural networks, and random forest time series algorithms were employed to model antibiotic resistance trends. The models' performance was evaluated using mean absolute error (MAE) and root mean squared error (RMSE). The best performing model was then used to predict antibiotic resistance rates for the year 2020. The ARIMA model with cefazolin, followed by the one with cephalexin, provided the lowest RMSE and MAE values without signs of overfitting across training and test datasets. The study showed that reducing cefazolin usage could decrease the rate of resistant E. coli infections. Although piperacillin/tazobactam did not perform as well as cefazolin in our time series models, it performed reasonably well and, due to its broad spectrum, might be a practical target for interventions in antimicrobial stewardship programs (ASPs), at least for this particular facility. While a more generalized model could be developed with data from multiple facilities, this study acts as a framework for ASP clinicians to adopt statistical and machine-learning approaches, using region-specific data to make effective interventions.

Antimicrobial and Diagnostic Stewardship of the Novel β-Lactam/β-Lactamase Inhibitors for Infections Due to Carbapenem-Resistant Enterobacterales Species and Pseudomonas aeruginosa.

Carbapenem-resistant Gram-negative bacterial infections are a major public health threat due to the limited therapeutic options available. The introduction of the new β-lactam/β-lactamase inhibitors (BL/BLIs) has, however, altered the treatment options for such pathogens. Thus, four new BL/BLI combinations-namely, ceftazidime/avibactam, meropenem/vaborbactam, imipenem/relebactam, and ceftolozane/tazobactam-have been approved for infections attributed to carbapenem-resistant Enterobacterales species and Pseudomonas aeruginosa. Nevertheless, although these antimicrobials are increasingly being used in place of other drugs such as polymyxins, their optimal clinical use is still challenging. Furthermore, there is evidence that resistance to these agents might be increasing, so urgent measures should be taken to ensure their continued effectiveness. Therefore, clinical laboratories play an important role in the judicious use of these new antimicrobial combinations by detecting and characterizing carbapenem resistance, resolving the presence and type of carbapenemase production, and accurately determining the minimum inhibitor concentrations (MICs) for BL/BLIs. These three targets must be met to ensure optimal BL/BLIs use and prevent unnecessary exposure that could lead to the development of resistance. At the same time, laboratories must ensure that results are interpreted in a timely manner to avoid delays in appropriate treatment that might be detrimental to patient safety. Thus, we herein present an overview of the indications and current applications of the new antimicrobial combinations and explore the diagnostic limitations regarding both carbapenem resistance detection and the interpretation of MIC results. Moreover, we suggest the use of alternative narrower-spectrum antibiotics based on susceptibility testing and present data regarding the effect of synergies between BL/BLIs and other antimicrobials. Finally, in order to address the absence of a standardized approach to using the novel BL/BLIs, we propose a diagnostic and therapeutic algorithm, which can be modified based on local epidemiological criteria. This framework could also be expanded to incorporate other new antimicrobials, such as cefiderocol, or currently unavailable BL/BLIs such as aztreonam/avibactam and cefepime/taniborbactam.

In vitro activity of cefepime/taniborbactam and comparator agents against Gram-negative bacterial bloodstream pathogens recovered from patients with cancer.

Taniborbactam is a β-lactamase inhibitor that, when combined with cefepime, may offer a potential treatment option for patients with serious and resistant Gram-negative bacterial (GNB) pathogens. This study evaluated in vitro activity of cefepime/taniborbactam and comparator agents against GNB pathogens isolated from patients with cancer at our institution. A total of 270 GNB pathogens (2019-23) isolated from patients with cancer were tested against cefepime/taniborbactam and comparator agents commonly used for these patients. CLSI-approved broth microdilution methods were used. MIC50, MIC90, MIC range and percentage of susceptibility calculations were made using FDA breakpoints when available. Cefepime/taniborbactam showed highly potent activity against tested Enterobacterales, including isolates producing ESBLs and carbapenem-resistant Enterobacterales. At a provisional breakpoint of ≤16/4 mg/L, cefepime/taniborbactam inhibited most tested species of GNB pathogens, with overall 98.9% susceptibility, which was significantly (P < 0.0001) higher than the susceptibility of the GNB isolates to all other tested comparator agents, ranging from 39.6% for cefepime to 86.3% for ceftazidime/avibactam. Our results showed that taniborbactam in combination with cefepime improved in vitro activity against GNB pathogens isolated from patients with cancer, including MDR Pseudomonas aeruginosa, carbapenem-resistant Enterobacterales, ESBL-producing Enterobacterales and Stenotrophomonas maltophilia isolates, with highest activity compared with all tested comparator agents, including other β-lactam/β-lactamase inhibitor combinations. Further studies are warranted to explore the efficacy of cefepime/taniborbactam for empirical initial treatment of GNB infections in cancer patients with high rates of febrile neutropenia requiring hospitalization.