Infectious Diseases Society of America 2022 Guidance on the Treatment of Extended-Spectrum β-lactamase Producing Enterobacterales (ESBL-E), Carbapenem-Resistant Enterobacterales (CRE), and Pseudomonas aeruginosa with Difficult-to-Treat Resistance (DTR-P. aeruginosa)

Identification of host genetic factors modulating β-lactam resistance in Escherichia coli harbouring plasmid-borne β-lactamase through transposon-sequencing

Since β-lactam antibiotics are widely used, emergence of bacteria with resistance to them poses a significant threat to society. In particular, acquisition of genes encoding β-lactamase, an enzyme that degrades β-lactam antibiotics, has been a major contributing factor in the emergence of bacteria that are resistant to β-lactam antibiotics. However, relatively few genetic targets for killing these resistant bacteria have been identified to date. Here, we used a systematic approach called transposon-sequencing (Tn-Seq), to screen the Escherichia coli genome for host genetic factors that, when mutated, affect resistance to ampicillin, one of the β-lactam antibiotics, in a strain carrying a plasmid that encodes β-lactamase. This approach enabled not just the isolation of genes previously known to affect β-lactam resistance, but the additional loci skp, gshA, phoPQ and ypfN. Individual mutations in these genes modestly but consistently affected antibiotic resistance. We have identified that these genes are not only implicated in β-lactam resistance by itself but also play a crucial role in conditions associated with the expression of β-lactamase. GshA and phoPQ appear to contribute to β-lactam resistance by regulating membrane integrity. Notably, the overexpression of the uncharacterized membrane-associated protein, ypfN, has been shown to significantly enhance β-lactam resistance. We applied the genes identified from the screening into Salmonella Typhimurium and Pseudomonas aeruginosa strains, both critical human pathogens with antibiotic resistance, and observed their significant impact on β-lactam resistance. Therefore, these genes can potentially be utilized as therapeutic targets to control the survival of β-lactamase-producing bacteria.

In vitro activity of ceftolozane/tazobactam, ceftazidime/avibactam and cefiderocol against clinical isolates of non-aeruginosa Pseudomonas

BACKGROUND

Although less virulent than Pseudomonas aeruginosa, non-aeruginosa Pseudomonas (NAP) are opportunistic pathogens that cause invasive infections, mainly in immunosuppressed or intensive care patients. MDR strains of NAP are increasingly isolated, especially MBL-producing isolates.

OBJECTIVES

We evaluated the activity of cefiderocol, ceftazidime/avibactam and ceftolozane/tazobactam against a collection of clinical isolates of NAP, which was voluntarily enriched with resistant strains.

METHODS

We retrospectively determined the MICs of cefiderocol, ceftazidime/avibactam and ceftolozane/tazobactam in 71 NAP clinical isolates. Most isolates of our collection were not susceptible to meropenem (75%) or ceftazidime (45%).

RESULTS

Among the first-line β-lactam-resistant isolates, the strains for which no carbapenemase was detected were susceptible to ceftolozane/tazobactam or ceftazidime/avibactam, except for one isolate. These latter associations were more active against P. fluorescens isolates than against other NAP. Most isolates (94%) of our collection were susceptible to cefiderocol, with a median MIC of 0.25 mg/L. In particular, the 19 carbapenemase-producing strains, including 15 VIM-producing strains, were susceptible to cefiderocol. Cefiderocol MICs were higher for P. fluorescens complex isolates (MIC50 = 2 mg/L) than for P. putida complex isolates (MIC50 = 0.25 mg/L). Resistance to cefiderocol was detected in only four isolates, of which three P. fluorescens complex isolates remained susceptible to ceftolozane/tazobactam and ceftazidime/avibactam.

CONCLUSIONS

Ceftolozane/tazobactam and ceftazidime/avibactam may be of interest as second-line β-lactams against non-carbapenemase-producing strains. Cefiderocol was highly active against NAP of our collection, especially MBL-producing isolates. Further studies are needed to correlate in vitro susceptibility of NAP to cefiderocol and clinical responses.

Antipseudomonal cephalosporins versus piperacillin/tazobactam or carbapenems for the definitive antibiotic treatment of Pseudomonas aeruginosa bacteraemia: new kids on the ICU block?

BACKGROUND

Pseudomonas aeruginosa bloodstream infections (Pa-BSIs) are still a major cause of mortality in ICUs, posing many treatment uncertainties.

METHODS

This multicentre, retrospective study analysed data from 14 Italian hospitals, including all consecutive adults developing Pa-BSI in ICU during 2021-22 and treated with antibiotics for at least 48 h. The primary aim was to identify predictors of 30 day mortality using Cox regression. Results were adjusted with inverse probability of treatment weighting (IPTW) and for immortal time bias.

RESULTS

Overall, 170 patients were included. High-risk BSI (source: lung, intra-abdominal, CNS) occurred in 118 (69%) patients, and 54 (32%) had septic shock. In 37 (22%), 73 (43%), 12 (7%) and 48 (28%) the definitive backbone therapy was piperacillin/tazobactam, carbapenems, colistin or new antipseudomonal cephalosporins (ceftolozane/tazobactam, n = 20; ceftazidime/avibactam, n = 22; cefiderocol, n = 6), respectively. Moreover, 58 (34%) received a second drug as combination therapy. The incidence of 30 day all-cause mortality was 27.6% (47 patients). By Cox regression, Charlson comorbidity index, neutropenia, septic shock and high-risk BSI were independent predictors of 30 day mortality, while previous colonization by P. aeruginosa, use of antipseudomonal cephalosporins as definitive treatment, and combination therapy were shown to be protective. However, after IPTW adjustment, only the protective effect of antipseudomonal cephalosporins was confirmed (adjusted HR = 0.27, 95% CI = 0.10-0.69), but not for combination therapy. Hence, the treatment effect was calculated: antipseudomonal cephalosporins significantly reduced mortality risk [-17% (95% CI = -4% to -30%)], while combination therapy was beneficial only in the case of septic shock [-66% (95% CI = -44% to -88%].

CONCLUSIONS

In ICU, antipseudomonal cephalosporins may be the preferred target therapy for the treatment of Pa-BSI; in addition, initial combination therapy may be protective in the case of septic shock.

Newly developed antibiotics against multidrug-resistant and carbapenem-resistant Gram-negative bacteria: action and resistance mechanisms

Antimicrobial resistance stands as one of the most urgent global health concerns in the twenty-first century, with projections suggesting that deaths related to drug-resistant infections could escalate to 10 million by 2050 if proactive measures are not implemented. In intensive care settings, managing infections caused by multidrug-resistant (MDR) Gram-negative bacteria is particularly challenging, posing a significant threat to public health and contributing substantially to both morbidity and mortality. There are numerous studies on the antibiotics responsible for resistance in Gram-negative bacteria, but comprehensive research on resistance mechanisms against new antibiotics is rare. Considering the possibility that antibiotics may no longer be effective in combating diseases, it is crucial to comprehend the problem of emerging resistance to newly developed antibiotics and to implement preventive measures to curb the spread of resistance. Mutations in porins and efflux pumps play a crucial role in antibiotic resistance by altering drug permeability and active efflux. Porin modifications reduce the influx of antibiotics, whereas overexpression of efflux pumps, particularly those in the resistance-nodulation-cell division (RND) family, actively expels antibiotics from bacterial cells, significantly lowering intracellular drug concentrations and leading to treatment failure.This review examines the mechanisms of action, resistance profiles, and pharmacokinetic/pharmacodynamic characteristics of newly developed antibiotics designed to combat infections caused by MDR and carbapenem-resistant Gram-negative pathogens. The antibiotics discussed include ceftazidime-avibactam, imipenem-relebactam, ceftolozane-tazobactam, meropenem-vaborbactam, aztreonam-avibactam, delafloxacin, temocillin, plazomicin, cefiderocol, and eravacycline.

[Epidemiology, diagnosis and treatment of adult patients with nosocomial pneumonia]

BACKGROUND

 Nosocomial pneumonia, encompassing hospital-acquired (HAP) and ventilator-associated pneumonia (VAP), remains a major cause of morbidity and mortality in hospitalized adults. In response to evolving pathogen profiles and emerging resistance patterns, this updated S3 guideline (AWMF Register No. 020-013) provides an evidence-based framework to enhance the diagnosis, risk stratification, and treatment of nosocomial pneumonia.

METHODS

 The guideline update was developed by a multidisciplinary panel representing key German professional societies. A systematic literature review was conducted with subsequent critical appraisal using the GRADE methodology. Structured consensus conferences and external reviews ensured that the recommendations were clinically relevant, methodologically sound, and aligned with current antimicrobial stewardship principles.

RESULTS

 For the management of nosocomial pneumonia patients should be divided in those with and without risk factors for multidrug-resistant pathogens and/or Pseudomonas aeruginosa. Bacterial multiplex-polymerase chain reaction (PCR) should not be used routinely. Bronchoscopic diagnosis is not considered superior to non-bronchoscopic sampling in terms of main outcomes. Combination antibiotic therapy is now reserved for patients in septic shock and high risk for multidrug-resistant pathogens, while select patients may be managed with monotherapy (e. g., meropenem). In clinically stabilized patients, antibiotic therapy should be de-escalated and focused, as well as duration shortened to 7-8 days. In critically ill patients, prolonged application of suitable beta-lactam antibiotics should be preferred. Patients on the intensive care unit (ICU) are at risk for invasive pulmonary aspergillosis (IPA). Diagnostics for Aspergillus should be performed with an antigen test from bronchial lavage fluid.

CONCLUSION

 This updated S3 guideline offers a comprehensive, multidisciplinary approach to the management of nosocomial pneumonia in adults. By integrating novel diagnostic modalities and refined therapeutic strategies, it aims to standardize care, improve patient outcomes, and enhance antimicrobial stewardship to curb the emergence of resistant pathogens.

Optimizing Antibiotic Treatment Duration for ESBL-Producing Enterobacteriaceae Bacteremia in ICU: A Multicentric Retrospective Cohort Study

BACKGROUND

The optimal duration of antibiotic treatment for extended-spectrum β-lactamase-producing Enterobacteriaceae (ESBL-E) bloodstream infections (BSI) in intensive care unit (ICU) is not established. We aim to evaluate the frequency and clinical outcomesof a short appropriate antibiotic treatment (≤7 days) (SAT) for ESBL-E BSI acquired in the ICU. We specifically assessed the rate of ESBL-E BSI relapse, and in-ICU mortality.

METHOD

All patients who acquired ESBL-E BSI in three ICU in Northern France between January 2011 and June 2022 were included in a multicenter retrospective cohort study. The factors associated with prescribing short (SAT, ≤7 days) versus long (LAT, >7 days) antibiotic treatment were analyzed. To evaluate the impact of SAT on mortality in the ICU, an estimation was applied using a Cox model with a time-dependent co-variable adjusted by inverse weighting of the propensity score.

RESULTS

In total, 379 patients were included. The proportion of patients receiving a SAT was 40% in the entire cohort and 25% in survivors beyond 7 days. In bivariate analysis, the factors associated with prescribing a SAT in survivors were shorter pre-bacteremia ICU stay (p = 0.005), lower proportion of chronic renal failure history (p = 0.034), cancer (p = 0.042), or transplantation (p = 0.025), less frequent exposure to carbapenem within 3 months (p = 0.015). There was a higher proportion of septic shock (p = 0.017) or bacteremia secondary to pneumonia (p = 0.003) in the group of survivors receiving a LAT. After adjustment, no difference in survival was found between the two groups (HR: 1.65, 95%CI: 0.91-3.00, p = 0.10).

CONCLUSION

In our cohort, one quarter of patients with ESBL-E bacteremia acquired in the ICU surviving beyond 7 days were treated with a SAT. SAT did not appear to affect survival. Patients who could benefit from a SAT need to be better identified.

Antimicrobial resistance among imipenem-non-susceptible Escherichia coli and Klebsiella pneumoniae isolates, with an emphasis on novel β-lactam/β-lactamase inhibitor combinations and tetracycline derivatives: The Taiwan surveillance of antimicrobial resistance program, 2020-2022

BACKGROUND

To determine susceptibility of imipenem-non-susceptible Escherichia coli (INS-EC) and Klebsiella pneumoniae (INS-KP) isolates collected during 2020-2022 through a national surveillance program in Taiwan to novel antibiotics, and to compare the results with those obtained during 2012-2018.

METHODS

Minimum inhibitory concentrations were determined by broth microdilution methods. Genes encoding carbapenemases including blaKPC, metallo-β-lactamase (MBL) genes, and blaOXA-48 were detected via multiplex PCR. Data retrieved from our 2012-2018 study were used for comparison.

RESULTS

Of 3260 E. coli and 1457 K. pneumoniae isolates collected during 2020-2022, 0.9 % and 9.5 %, were INS-EC and INS-KP, respectively. Cefepime-zidebactam, ceftazidime-avibactam, imipenem-relebactam, and meropenem-vaborbactam were active against 100 %, 75.9 %, 65.5 %, and 79.3 % of 29 INS-EC isolates respectively; and against 100 %, 90.6 %, 64.5 %, and 67.4 % of 138 INS- KP isolates, respectively. Susceptibility was contingent upon carbapenemase types. Susceptibility rates of cefepime-zidebactam and ceftazidime-avibactam remained constant from 2012 to 2018 through 2020-2022 but those of imipenem-relebactam and meropenem-vaborbactam decreased significantly, which may be partially attributable to the increasing prevalence of blaOXA-48. Eighteen MBL-gene-positive isolates and two blaKPC-positive isolates were resistant to ceftazidime-avibactam, whereas all were susceptible to cefepime-zidebactam. Tigecycline had a higher susceptibility rate than eravacycline and omadacycline for K. pneumoniae isolates. Lascufloxacin and delafloxacin were effective against fewer than 10 % of INS isolates. Susceptibilities to novel tetracyclines and fluoroquinolones remained similar from 2012 to 2018 through 2020-2022.

CONCLUSIONS

This study highlights significant resistance patterns of INS-EC and INS-KP isolates in Taiwan. The declining susceptibility rates and the rising prevalence of genetic resistance determinants highlight the importance of ongoing surveillance and antimicrobial stewardship.

Molecular epidemiology and β-lactam resistance mechanisms of Enterobacter cloacae complex isolates obtained from bloodstream infections, Kyoto, Japan

The Enterobacter cloacae complex (ECC) comprises multiple species that require genomic analysis for precise identification. They produce inducible AmpC β-lactamase and may carry acquired β-lactamases, which are responsible for cefotaxime and cefepime resistance. To determine the molecular epidemiology, antimicrobial resistance, and β-lactam resistance mechanisms of the ECC, we conducted whole-genome sequencing analysis, antimicrobial susceptibility testing, and mutation analysis on bloodstream ECC isolates from patients in Kyoto, Japan. In 194 ECC isolates, 13 species and six unnamed taxa were identified, with Enterobacter xiangfangensis (36%) being the most common. A total of 38% of the isolates were nonsusceptible to cefotaxime and presented relatively high nonsusceptibility rates to all antimicrobial agents tested. Among the different species, Enterobacter hoffmannii presented the highest nonsusceptibility rates to both β-lactams and non-β-lactams. Among the cefotaxime-nonsusceptible isolates, 16% harbored genes encoding extended-spectrum β-lactamases (ESBLs), carbapenemase, and/or plasmid-mediated AmpC, and ampC derepression was the predominant resistance mechanism in the remaining isolates. The prevalent sequence types (STs) in cefotaxime-susceptible and cefotaxime-nonsusceptible isolates were different, although some STs were shared by both groups. Cefepime nonsusceptibility was detected in 7% of the isolates and was associated with E. hoffmannii ST78 and E. xiangfangensis ST93, which carry ESBLs. Sixty-four mutants, experimentally obtained from eight cefotaxime-susceptible isolates, had various ampD mutations, and 42% and 99% of the mutants were nonsusceptible to cefepime and piperacillin/tazobactam, respectively, indicating the risks associated with the use of these antimicrobials. Continuous surveillance via genomic and phenotypic analyses is needed to combat antimicrobial resistance in the ECC.IMPORTANCEThe Enterobacter cloacae complex (ECC) is a group of pathogenic bacteria that cause nosocomial infections. The ECC produces chromosomal inducible AmpC β-lactamases, which is associated with treatment failure despite initial susceptibility to third-generation cephalosporins in selected ampC-derepressed mutants. The complex antimicrobial resistance mechanisms of the ECC and challenges in species identification have complicated our understanding of the ECC and the selection of appropriate treatment. In this study, we performed phenotypic, whole-genome sequencing, and mutation analyses among ECC isolates from patients with bloodstream infections to determine the precise molecular-based epidemiology, resistance mechanisms to third-/fourth-generation cephalosporins, specific species and clones that contribute to antimicrobial resistance, and acquisition rates of fourth-generation cephalosporin resistance in ampC-derepressed mutants. These data will help elucidate the local epidemiology and complex β-lactam resistance mechanisms in the ECC and guide appropriate antimicrobial therapy and infection control strategies for ECC-related infections.

A real-world investigation into prescribing patterns and effectiveness of ceftolozane/tazobactam among critically ill patients from SPECTRA

BACKGROUND

Ceftolozane/tazobactam (C/T) real-world use was examined in a global population of critical care patients treated in intensive care unit settings.

METHODS

The Study of Prescribing patterns and Effectiveness of Ceftolozane/Tazobactam Real-world Analysis (SPECTRA) is a multinational, retrospective observational study of 617 adults treated with C/T conducted between 2016 and 2020. Population-associated clinical, treatment-related, and microbiologic characteristics, resource utilization, and clinical outcomes were assessed in critical care patients.

RESULTS

In this SPECTRA critical care cohort (n=298), 81.5% had ≥1 comorbidity. Common infection sites were respiratory (50.0%), skin/wound/tissue (21.1%), blood (13.7%), and urine (10.3%); common pathogens were Pseudomonas aeruginosa (89.7%; 66.7% multidrug resistant), Klebsiella spp. (6.9%), and Escherichia coli (6.4%); 51.7% received C/T as third-line/salvage therapy. Thirty-day readmission rates were 3.4% (all cause) and 1.7% (infection related). Overall clinical success was 53.4% (95% confidence interval: 47.5% to 59.1%) and was greater with first-line C/T (62.2%) versus third line (45.5%). All-cause in-hospital mortality was 35.6%; infection-related mortality was 13.8%.

CONCLUSIONS

In this multinational, high-risk cohort, most patients had beneficial outcomes despite their clinical complexity and late intervention with C/T. These results support C/T use against a wide range of Gram-negative pathogens in critical care settings.

TRIAL REGISTRATION

Not applicable due to retrospective design.

Effects of different mechanisms on antimicrobial resistance in Pseudomonas aeruginosa: a strategic system for evaluating antibiotics against gram-negative bacteria

Our previous studies constructed a strategic system for testing antibiotics against specific resistance mechanisms using Klebsiella pneumoniae and Acinetobacter baumannii. However, it lacked resistance mechanisms specifically expressed only in Pseudomonas species. In this study, we constructed this system using Pseudomonas aeruginosa. In-frame deletion, site-directed mutagenesis, and plasmid transformation were used to generate genetically engineered strains with various resistance mechanisms from two fully susceptible P. aeruginosa strains. Antimicrobial susceptibility testing was used to test the efficacy of antibiotics against these strains in vitro. A total of 31 engineered strains with various antimicrobial resistance mechanisms from P. aeruginosa KPA888 and ATCC 27853 were constructed, and the same antibiotic resistance mechanism showed a similar effect on the MICs of the two strains. Compared to the parental strains, the engineered strains lacking porin OprD or lacking the regulator genes of efflux pumps all showed a ≥4-fold increase on the MICs of some of the 19 antibiotics tested. Mechanisms due to GyrA/ParC mutations and β-lactamases also contributed to their corresponding resistance as previously published. The strains constructed in this study possess well-defined resistance mechanisms and can be used to screen and evaluate the effectiveness of antibiotics against specific resistance mechanisms in P. aeruginosa. Building upon our previous studies on K. pneumoniae and A. baumannii, this strategic system, including a P. aeruginosa panel, has been expanded to cover almost all the important antibiotic resistance mechanisms of gram-negative bacteria that are in urgent need of new antibiotics.IMPORTANCEIn this study, an antibiotic assessment system for P. aeruginosa was developed, and the system can be expanded to include other key pathogens and resistance mechanisms. This system offers several benefits: (i) compound design: aid in the development of compounds that can bypass or counteract resistance mechanisms, leading to more effective treatments against specific resistant strains; (ii) combination therapies: facilitate the exploration of combination therapies, where multiple antibiotics may work synergistically to overcome resistance and enhance treatment efficacy; and (iii) targeted treatments: enable healthcare providers to prescribe more targeted treatments, reducing unnecessary antibiotic use and helping to slow the spread of antibiotic resistance. In summary, this system could streamline the development process, reduce costs, increase the success rate of new antibiotics, and help prevent and control antimicrobial resistance.

The efficacy and safety of ceftazidime/avibactam or polymyxin B based regimens for carbapenem-resistant Pseudomonas aeruginosa infection: a multicenter real-world and propensity score-matched study

Introduction

Carbapenem-resistant Pseudomonas aeruginosa (CRPA) infections pose a critical clinical challenge. Although ceftazidime/avibactam (CAZ/AVI) and polymyxin B (PMB) are frontline therapies, their comparative effectiveness in terms of 30-day survival, renal safety profiles, and clinical success rates remains poorly characterized. To address this knowledge gap, a multicenter real-world study was conducted.

Methods

CRPA-infected patients treated with PMB or CAZ/AVI-based regimens were enrolled from five hospitals between January 1, 2021, to July 31, 2023. Propensity score matching (PSM) and binary logistic regression analysis were performed to evaluate efficacy and acute renal injury (AKI) occurrence, and a multivariable COX proportional hazards regression of the 30-day all-cause mortality was performed.

Results

170 CRPA-infected patients were enrolled, among whom 124 (72.9%) had difficult-to-treat resistant P. aeruginosa (DTR-PA) infections and 77 (45.3%) received CAZ/AVI-based regimens. After 1:1 PSM, the results demonstrated that the CRPA clearance rate was significantly higher in the CAZ/AVI group compared to the PMB group (61.0% vs. 24.4%, p = 0.001); however, no significant differences were observed in clinical success rates (55.6% vs. 44.4%), incidence of AKI (26.8% vs. 39.0%), or 30-day all-cause mortality (7.3% vs. 12.2%) between the two groups (all p > 0.05). Compared with the PMB-based regimens, CAZ/AVI-based regimens were significantly associated with CRPA clearance success (OR 0.185, 95%CI 0.061-0.564, p < 0.001); additionally, multi-site infection (OR 0.295, 95%CI 0.097-0.899, p = 0.032) and the number of combined anti-PA antibiotics (OR 0.435, 95%CI 0.213-0.888, p = 0.022) were associated with enhanced CRPA clearance. The occurrence of AKI in patients with CRPA infection was associated with underlying diseases, including sepsis/septic shock (OR 3.405, 95%CI 1.007-11.520, p = 0.049), and diabetes mellitus (OR 3.600, 95%CI 1.018-12.733, p = 0.047). In addition, other CREs infection (HR 40.849, 95%CI 3.323-502.170, p = 0.004), APACHE II score (HR 1.072, 95%CI 1.032-1.114, p < 0.001) were found to be independent predictors of 30-day all-cause mortality.

Conclusion

In conclusion, CAZ/AVI-based regimens demonstrated superior efficacy in clearing CRPA compared to PMB-based regimens. Furthermore, several factors associated with AKI and mortality in CRPA-infected patients were identified, highlighting the need for further research to optimize treatment strategies.

Antimicrobial activity of cephamycins and β-lactam/β-lactamase inhibitors against ESBL-producing Escherichia coli and Klebsiella pneumoniae under standard and high bacterial inocula

This study investigated the in vitro antimicrobial activity of cephamycins and novel β-lactam/β-lactamase inhibitor combinations, against extended-spectrum beta-lactamase (ESBL)-producing Escherichia coli and Klebsiella pneumoniae isolates. ESBL-producing blood isolates were obtained between January and May 2023. The antibiotic susceptibility of the isolates was determined by broth microdilution method using standard (105 CFU/mL) and high (107 CFU/mL) inoculum sizes. Two randomly selected ESBL-producing isolates were subjected to time-kill assays for cephamycin. More than 80% of the isolates exhibited susceptibility to cefoxitin, cefmetazole, flomoxef, ceftazidime/avibactam, cefepime/enmetazobactam and imipenem/relebactam. Ceftolozane/tazobactam demonstrated in vitro efficacy against 62.1% of the ESBL-producing isolates. At the higher inoculum size, cefoxitin, cefmetazole, flomoxef, ceftolozane/tazobactam, ceftazidime/avibactam, cefepime/enmetazobactam, and imipenem/relebactam demonstrated in vitro efficacy against 48.3%, 75.9%, 70.0%, 0%, 82.8%, 100%, 89.7% of the ESBL-producing isolates. The frequencies of the inoculum effect with cefoxitin (3.7%), cefmetazole (14.8%), flomoxef (88.9%), ceftolozane/tazobactam (96.0%), ceftazidime/avibactam (34.5%), cefepime/enmetazobactam (10.3%), and imipenem/relebactam (10.3%) were identified. With standard inoculum, cephamycins reduced bacterial growth within 2-24 h. However, high inoculum resulted in regrowth after 12 h of cephamycin exposure. Cephamycins demonstrated high in vitro activity against ESBL-producing isolates at standard inoculum sizes. However, the in vitro time-kill experiments revealed that the efficacy of cephamycins is not fully maintained at high inoculum sizes.

Antimicrobial Resistance and Mortality in Carbapenem-Resistant Pseudomonas aeruginosa Infections in Southern Thailand

Background/Objectives: Carbapenem-resistant Pseudomonas aeruginosa (CRPA) is an important pathogen associated with high mortality and treatment failure rates. We aimed to assess the susceptibility of CRPA to antipseudomonal agents, identify its resistance mechanisms, and evaluate clinical outcomes in a sample of CRPA isolates. Methods: This was an in vitro study of a clinical isolate of CRPA from hospitalized patients with CRPA infection and a retrospective observational study of these patients, who were diagnosed between 14 February 2021 and 10 August 2023 at Songklanagarind Hospital in Songkhla, Thailand. In vitro experiments were conducted to determine the minimum inhibitory concentrations (MICs) of the antipseudomonal agents using the broth microdilution method. Resistance mechanisms were assessed using the modified carbapenem inactivation method, combined disk tests, and quantitative real-time reverse transcription polymerase chain reaction. Results: A total of 140 CRPA isolates were analyzed. Both traditional and novel β-lactams had high MICs. The most common resistance mechanism was the upregulation of the MexAB-OprM efflux pump (81.3%), followed by the downregulation of the OprD porin (48.9%) and metallo-β-lactamase (MBL) production (45.0%), and the overexpression of blaAmpC (41.0%). The 30-day all-cause mortality rate was 30.5%. The risk factors associated with 30-day mortality included a Charlson Comorbidity Index of ≥5 (OR: 3.43; 95% CI: 1.07-10.99; p = 0.03), sepsis (OR: 10.62; 95% CI: 1.26-89.44; p = 0.03), and septic shock (OR: 4.39; 95% CI: 1.67-11.55; p < 0.01). In contrast, receiving active documented therapy was significantly associated with reduced mortality (OR: 0.17; 95% CI: 0.04-0.74; p = 0.01). Conclusions: This study revealed higher MIC values of all β-lactams for CRPA, while colistin and amikacin remained effective. The resistance mechanisms included MexAB-OprM overexpression, OprD downregulation, MBL production, and blaAmpC overexpression, with a higher prevalence of MBL than in other regions of Thailand. High 30-day mortality was associated with comorbidities, sepsis, and septic shock, but active therapy reduced mortality.

Post-market safety profile of cefiderocol: a real-world pharmacovigilance exploratory analysis based on U.S. FDA adverse event reporting system (FAERS)

BACKGROUND

Cefiderocol is a new drug class, which is approved to treat Gram-negative bacteria infection. Its approval for marketing has provided clinicians with additional options for treating antimicrobial resistant gram-negative infections. The aim of our study was to assess the safety profiles of cefiderocol in real-world through data mining of the United States Food and Drug Administration Adverse Event Reporting System (FAERS).

METHODS

We included adverse event (AE) reports regarding cefiderocol submitted to the FAERS from 2019 quarter 4 (2019Q4) to 2024 quarter 3 (2024Q3). Disproportionality analyses, including reporting odds ratio (ROR), proportional reporting ratio (PRR), Bayesian Confidence Propagation Neural Network (BCPNN) and Multi-item Gamma Poisson Shrinker (MGPS) techniques were performed to identify the signals of disproportionate reporting of AEs in patients receiving cefiderocol. A signal of disproportionate reporting was detected if the lower limit of the 95% confidence interval (CI) of ROR > 1, the PRR was ≥ 2(while the Chi-Square of PRR was ≥ 4), the lower limit of 95% CI of the information component (IC025) was > 0, the lower limit of 95% CI of the Empirical Bayes Geometric Mean (EBGM05) was > 2 and at least 3 AEs were reported.

RESULTS

A total of 29 significant preferred terms (PTs) were identified among the 592 cefiderocol-associated adverse events (AEs) reports collected from the FAERS database. Cefiderocol-induced adverse events involved 24 System Organ Class (SOC). 29 positive signals of disproportionate reporting are also presented, such as Pathogen resistance (n = 16, ROR 189.35, PRR 184.26, IC 7.52, EBGM 183.89), Systemic candida (n = 3, ROR 138.79, PRR 138.19, IC7.11, EBGM 137.88), Drug resistance (n = 30, ROR 131.96, PRR 125.33, IC6.97, EBGM 125.16), and Drug effect less than expected (n = 6, ROR 68.42, PRR 67.74, IC6.08, EBGM 67.69). The most frequently observed were Death, Drug resistance and Treatment failure.

CONCLUSIONS

Our findings offer significant evidence regarding the safety profile of cefiderocol in real-world settings. This information may assist clinicians and pharmacists in enhancing their vigilance and improving the overall safety of cefiderocol in clinical practice.

Antimicrobial susceptibility of gram-negative bacteria: Analysis from patients in a laboratory network in Brazil

OBJECTIVES

This study aimed to describe the epidemiology and antimicrobial susceptibility patterns of gram-negative pathogens in Brazil from 2018 to 2020, addressing the gap in national data on healthcare-associated infections, using information from a private laboratory network.

METHODS

A cross-sectional study was conducted using a database from Fleury hospital network, a private laboratory in Brazil. The analysis included blood, urine, and lower respiratory tract samples collected from January 2018 to June 2020. The study included consecutive non-duplicated isolates of Enterobacterales or P. aeruginosa from inpatients aged ≥18 years old. Bacterial identification was performed using mass spectrometry, and antimicrobial susceptibility was determined following EUCAST/BrCAST guidelines.

RESULTS

A total of 25,180 isolates were included in the analysis. Most of the sample consisted of female patients (57.9%), with a mean age of 70 years (SD 18.1). Enterobacterales were the most prevalent pathogens found (76.2%), while P. aeruginosa was present in the remaining 23.8%. In terms of antimicrobial susceptibility, Enterobacterales exhibited a higher susceptibility rate to ceftazidime/avibactam (97.1%) and amikacin (95.6%), while P. aeruginosa showed a higher susceptibility rate to polymyxin B (97.1%) and ceftolozane/tazobactam (86.6%). Among carbapenem-resistant P. aeruginosa isolates, 75% were susceptible to ceftolozane/tazobactam. Additionally, 24.2% of K. pneumoniae complex samples were identified.

CONCLUSION

Enterobacterales was the most frequently encountered group in Brazil. Ceftazidime/avibactam and amikacin demonstrated the highest efficacy against this group, while ceftolozane/tazobactam and polymyxin had the highest efficacy against P. aeruginosa. This highlights the importance of new β-lactam-β-lactamase inhibitor combinations for the treatment of gram-negative infections.

Shortening antibiotic therapy duration for hospital-acquired bloodstream infections in critically ill patients: a causal inference model from the international EUROBACT-2 database

INTRODUCTION

Hospital-acquired bloodstream infections (HA-BSIs) are severe and require antibiotic therapy. In non-complicated BSIs, shortened therapy reduces side effects without compromising efficacy. The impact of shortened antibiotic therapy in HA-BSI critically ill patients without indication of prolonged therapy requires further evaluation.

METHODS

Using the international prospective EUROBACT-2 cohort, we compared shortened (7-10 days) versus long (14-21 days) treatment durations in ICU patients eligible for shortened therapy. Patients without antibiotic therapy within 3 days after HA-BSI occurrence or requiring prolonged therapy (due to infection source, microorganism, or clinical deterioration) were excluded. Treatment failure, defined as death, persistent infection, or subsequent infectious complications by Day 28, was assessed using an inverse-probability of treatment weighted (IPTW) logistic regression.

RESULTS

Among 2600 patients, 550 were eligible for shortened treatment, 213 received short, and 337 received long treatment. The most common infection source was intravascular catheters (33%), most common microorganisms were Enterobacterales (39%). Patients with long treatment were more frequently infected with Staphylococcus aureus (11% vs. 5.6%, p = 0.025) or difficult-to-treat microorganisms (23% vs. 7%, p < 0.001), and received more commonly combination therapy (46% vs. 30%, p < 0.001). Short treatment was associated with reduced 28-day treatment failure (OR 0.64, 95% CI 0.44-0.93, p = 0.019), mainly due to reduction in subsequent infectious complications (OR 0.58, 95% CI 0.37-0.91, p = 0.018). Mortality (OR 0.92 [95% CI 0.59, 1.43], p = 0.7) and persistent infection rates (OR 0.47 [95% CI 0.17, 1.14], p = 0.12) were similar.

CONCLUSIONS

In selected ICU patients with HA-BSI, shortened antibiotic treatment might be considered. Eurobact2 was a prospective international cohort study, registered in ClinicalTrials.org (NCT03937245).

Switch to amoxicillin-clavulanate oral therapy in urinary tract infection caused by extended-spectrum beta-lactamase-producing Escherichia coli: Assessment by chronic phase technetium-99m dimercaptosuccinic acid renal scintigraphy images

The incidence of urinary tract infection (UTI) caused by extensive beta-lactamase-producing Escherichia coli (ESBL-EC) is increasing, including in children. However, the available oral antibiotic treatment options for ESBL-EC are limited. Herein, we report the cases of two children diagnosed with UTI caused by ESBL-EC (ESBL-UTI) who were switched from empirical intravenous antibiotics in UTI to amoxicillin-clavulanic acid (AMPC/CVA) (14:1) after the causative organism was found to be ESBL-EC. A 3-month-old infant and an 8-month-old infant were admitted to our hospital with the chief complaint of fever. In both cases, UTI was suspected based on urinalysis results, and intravenous cefotaxime was started as an empiric antibiotic. In both cases, ESBL-EC was detected in urine culture, and the diagnosis of ESBL-UTI was confirmed. Results of antimicrobial susceptibility testing showed resistance to cefotaxime, but fever resolution was obtained in both cases following administration of intravenous cefotaxime. Since fever resolution was achieved, the antimicrobial was switched to oral AMPC/CVA (14:1) monotherapy with reference to antimicrobial susceptibility testing, and the two patients were discharged on days 5-6 of hospitalization. Antimicrobials were administered intravenously and orally for a total of 2 weeks. Chronic-phase technetium-99m dimercaptosuccinic acid renal scintigraphy showed no renal scarring. ESBL-UTI may require 2 weeks of intravenous antibacterial therapy, but in this case, both patients could be treated without renal scarring after conversion to oral AMPC/CVA alone. Since this is important to shorten the length of hospital stay, we will study the effect of this treatment modality in more cases in the future.

Comparing ceftazidime/avibactam and polymyxin B for treating carbapenem-resistant organisms infections: A propensity score-matched retrospective cohort study

BACKGROUND AND AIM

There are limited comparative studies of ceftazidime/avibactam (CAZ/AVI) vs. polymyxin B (PMB) for carbapenem-resistant organisms (CRO) infections. The aim of this study was to compare the efficacy and safety of CAZ/AVI and PMB in treating CRO infections.

METHODS

This single-centre, retrospective cohort study with propensity score-matching (PSM) involved adult patients with CRO infections. Patients who received the CAZ/AVI-based regimen were included in the cohort group; those prescribed with the PMB-based regimen were included in the control group. The primary outcome was 28-day all-cause mortality.

RESULTS

Among 298 eligible patients, 96 patients in each group were included in the PSM cohort. The CAZ/AVI group showed no improvement in 28-day or 14-day all-cause mortality, nor in 14-day clinical response, compared to the PMB group. However, the CAZ/AVI-based regimen was associated with higher 14-day clinical response rates than the PMB-based regimen in subgroups with carbapenem-resistant Pseudomonas aeruginosa (CRPA) infections and monotherapy. The CAZ/AVI group achieved greater CRO eradication than the PMB group (crude odds ratio [OR], 1.658; 95% confidence interval [CI], 1.108-2.480; P = 0.014; adjusted OR, 1.718; 95% CI, 1.055-2.798; P = 0.030). This advantage in CRO eradication with CAZ/AVI was consistent in most subgroups, including septic shock, bloodstream infection and lower respiratory tract infection. The CAZ/AVI and PMB groups had comparable nephrotoxicity (crude OR, 0.577; 95% CI, 0.306-1.089; P = 0.090; adjusted OR, 0.741; 95% CI, 0.361-1.521; P = 0.414).

CONCLUSION

CAZ/AVI-based and PMB-based regimens demonstrated similar clinical efficacy and nephrotoxicity in treating CRO infections. However, CAZ/AVI was superior to PMB in CRO eradication and treating CRPA infections. CAZ/AVI monotherapy was more effective than PMB monotherapy for CRO infections.

TRIAL REGISTRATION

ChiCTR2300078790 prospectively registered on 19 Dec 2023 (https://www.chictr.org.cn).

Characterization of a novel KPC-2 variant, KPC-228, conferring resistance to ceftazidime-avibactam in an ST11-KL64 hypervirulent Klebsiella pneumoniae

BACKGROUND

With the widespread clinical use of ceftazidime-avibactam (CZA), reports of resistance have increased continuously, posing immense threats to public health worldwide. In this study, we explored the underlying mechanisms leading to the development of CZA resistance in an ST11-KL64 hypervirulent Klebsiella pneumoniae CRE146 that harbored the blaKPC-228 gene.

METHODS

Twelve carbapenem-resistant Klebsiella pneumoniae (CRKP) strains were isolated from the same patient, including K. pneumoniae CRE146. Whole-genome sequencing (WGS), phylogenetic analysis, blaKPC gene cloning and pACYC-KPC construction assays were conducted to further explore the molecular mechanisms of CZA resistance. Quantitative siderophore production assay, string test, capsule quantification and Galleria mellonella in vivo infection model were applied to verify the level of pathogenicity of K. pneumoniae CRE146.

RESULTS

This strain carried key virulence factors, iutA-iucABCD operon and rmpA gene. Compared to the wild-type KPC-2 carbapenemase, the novel KPC-228 enzyme exhibited a deletion of four amino acids in the Ω-loop (del_167-170_ELNS). In addition, the emergence of CZA resistance appeared to be associated with drug exposure, and we observed the in vivo evolution of wild-type KPC-2 to KPC-228 and then the reversion to its original wild-type KPC-2. The blaKPC-228 gene was located within the double IS26 flanking the ISKpn6-blaKPC-228-ISKpn27 core structure and carried on an IncFII/IncR-type plasmid. Notably, CRE146 exhibited high-level resistance to CZA (64/4 mg/L) but increased susceptibility to meropenem (1 mg/L) and imipenem (0.5 mg/L) respectively. PACYC-KPC plasmids were constructed and expressed in K. pneumoniae ATCC13883. Compared to K. pneumoniae ATCC13883 harboring blaKPC-2, K. pneumoniae ATCC13883 harboring blaKPC-228 exhibited a high-level resistance to CZA (32/4 mg/L) and increased susceptibility to meropenem (1 mg/L) and imipenem (0.5 mg/L). Interestingly, K. pneumoniae ATCC13883 harboring blaKPC-228 showed a significant decrease in their resistance to all β-lactamases tested except CZA and ceftazidime.

CONCLUSIONS

In conclusion, we reported a novel KPC variant, KPC-228, in a clinical ST11-KL64 hypervirulent K. pneumoniae strain, which conferred CZA resistance, possibly through enhancing ceftazidime affinity and reducing avibactam binding. The blaKPC-228 can mutate back to blaKPC-2 under carbapenem pressure, which was very detrimental to clinical treatment. This strain carried both resistance and virulence genes, posing a major challenge in clinical management.

Carbapenem-resistant Klebsiella pneumoniae infections after liver transplantation: Drug resistance, risk factors and impact on prognosis

BACKGROUND

Liver transplant (LT) recipients are susceptible to carbapenem-resistant Klebsiella pneumoniae (CRKP) infections. Comprehensive research addressing the incidence, timing, infection sites, resistance patterns, treatment options, and associated risk factors among LT recipients with CRKP is now lacking.

AIM

To assess the incidence, resistance, therapy, and risk factors of CRKP infections post-LT, and to evaluate the impact of them on prognosis.

METHODS

A retrospective study was conducted, including 430 consecutive patients who underwent LT between January 2015 and June 2023. This study aimed to investigate the risk factors for CRKP infections and their influence on outcomes using logistic regression analysis.

RESULTS

Among the 430 patients who underwent LT, 20 (4.7%) experienced at least one documented CRKP infection within 3 months post-transplantation. The median time from LT to the onset of CRKP infections was 6.5 days. The lungs and bloodstream were the most common sites of CRKP infections. CRKP isolates were relatively susceptible to ceftazidime/avibactam (93.7%), polymyxin B (90.6%), and tigecycline (75.0%) treatment. However, all isolates were resistant to piperacillin/tazobactam, ceftazidime, cefepime, aztreonam, meropenem, and levofloxacin treatment. Recipients with CRKP infections had a mortality rate of 35%, the rate was 12.5% for those receiving ceftazidime/avibactam therapy. Multivariate analysis identified female sex [odds ratio (OR) = 3.306; 95% confidence interval (CI): 1.239-8.822; P = 0.017], intraoperative bleeding ≥ 3000 mL (OR = 3.269; 95%CI: 1.018-10.490; P = 0.047), alanine aminotransferase on day 1 post-LT ≥ 1500 U/L (OR = 4.370; 95%CI: 1.686-11.326; P = 0.002), and post-LT mechanical ventilation (OR = 2.772; 95%CI: 1.077-7.135; P = 0.035) as significant variables associated with CRKP. CRKP infections were related to an intensive care unit length (ICU) of stay ≥ 7 days and 6-month all-cause mortality post-LT.

CONCLUSION

CRKP infections were frequent complications following LT, with poor associated outcomes. Risk factors for post-LT CRKP infections included female sex, significant intraoperative bleeding, elevated alanine aminotransferase levels, and the need for mechanical ventilation. CRKP infections negatively impacted survival and led to prolonged ICU stays.

Advantages and limitations of large language models for antibiotic prescribing and antimicrobial stewardship

Antibiotic prescribing requires balancing optimal treatment for patients with reducing antimicrobial resistance. There is a lack of standardization in research on using large language models (LLMs) for supporting antibiotic prescribing, necessitating more efforts to identify biases and misinformation in their outputs. Educating future medical professionals on these aspects is crucial for ensuring the proper use of LLMs for supporting antibiotic prescribing, providing a deeper understanding of their strengths and limitations.

Mutational alterations in the QRDR regions associated with fluoroquinolone resistance in Pseudomonas aeruginosa of clinical origin from Savar, Dhaka

Bacterial DNA gyrase and topoisomerase IV are the major targets of quinolone antibiotic, and mutational alterations in quinolone resistance determining regions (QRDR) serve as major mechanism of resistance in most bacterial species, including P. aeruginosa. The present investigation was aimed to study the molecular mechanism of fluoroquinolone resistance among clinical P. aeruginosa isolated from Dhaka, Bangladesh, including alterations in target sites of the antimicrobial action. Laboratory collection of 53 P. aeruginosa were subjected to conventional cultural and biochemical characterization, followed by molecular identification using 16S rDNA sequencing. Susceptibility to ciprofloxacin and levofloxacin was tested by disc diffusion method followed by MIC assay. Resistant isolates were analyzed for mutation in their QRDR regions of gyrA and parC, and subjected to PCR detection of plasmid mediated quinolone resistance (PMQR) genes qnrA, qnrS and qnrB. Among the isolates, 28% were found to be resistant to both fluoroquinolones tested. All of the fluoroquinolone resistant isolates carried a single mutation in gyrA (Thr-83-Ile), while 20% carried a single parC mutation (Ser-87-Leu). Higher level of MIC was observed in isolates carrying alterations at both sites. None of the isolates harbored any PMQR genes investigated, suggesting that chromosomal mutations in QRDR regions to be the major contributing factor for quinolone resistance in P. aeruginosa under investigation.

Novel technologies for the diagnosis of urinary tract infections

Urinary tract infections (UTIs) impose a substantial burden on patient quality of life and urine testing accounts for the majority of workload in many clinical microbiology laboratories. Traditional UTI diagnosis relies on symptoms, urinalysis, and culture which are interpreted based on historical guidelines. This approach, while foundational, presents limitations, particularly in complex cases. Low-level bacteriuria and the presence of fastidious organisms are often overlooked or entirely missed in standard urine culture, stressing the need for novel diagnostic methods and technologies. This mini-review summarizes the existing state of UTI diagnostics in 2024 and covers current and upcoming technologies including rapid molecular-based pathogen identification, next-generation sequencing, and advanced antimicrobial susceptibility testing. However, these methods represent unique challenges, and as they are implemented, they will require the field to adapt to new concepts to avoid misdiagnosis and overtreatment.

Evaluation of Ceftazidime-avibactam and Ceftolozane-tazobactam Prescriptions in a Tertiary Hospital for Children in France: An Observational Study, 2017-2022

BACKGROUND

Infections caused by drug-resistant Gram-negative bacteria, including carbapenem-resistant Enterobacterales and Pseudomonas aeruginosa, are emerging in pediatric hospitals. New ß-lactam/ ß-lactamase inhibitor combinations exhibit activity against these pathogens; however, there is limited data regarding their use in pediatric populations.

OBJECTIVES

The study aimed to describe the characteristics of ceftazidime-avibactam (CAZ/AVI) and ceftolozane-tazobactam (C/T) prescriptions in children and assess their appropriateness.

METHODS

We retrospectively analyzed all CAZ/AVI or C/T prescriptions in children hospitalized in a French tertiary hospital between 2017 and 2022. All clinical, biological, and pharmacological data were collected prospectively as part of the antibiotic monitoring program set up by our antimicrobial stewardship (AMS) team.

RESULTS

In total, 50 CAZ/AVI and 25 C/T prescriptions were recorded, which concerned 21 and 20 patients, respectively. All patients had an underlying chronic condition. Most prescriptions originated from Pediatric Intensive Care Units and the Department of Pediatric Pulmonology and were mainly initiated for respiratory tract infections (n = 41/50, 82% of the CAZ/AVI prescriptions and n = 14/25, 56% of the C/T prescriptions). P. aeruginosa was the primary pathogen in documented infections for both CAZ/AVI and C/T prescriptions (n = 26/48, 54% and n = 16/19, 84%, respectively). Almost all prescriptions of CAZ/AVI and C/T were considered appropriate (n = 47/50, 94% for CAZ/AVI and n = 23/25, 92% for C/T, respectively) by the AMS team. Both CAZ/AVI and C/T treatments were well tolerated and resulted in clinical success in 33 (66%) and 19 (76%) cases, respectively.

CONCLUSION

Our study suggests that CAZ/AVI and C/T are reasonable treatment options for children infected with Gram-negative pathogens resistant to carbapenems.

Population Pharmacokinetics-Based Evaluation of Ceftazidime-Avibactam Dosing Regimens in Critically and Non-Critically Ill Patients With Carbapenem-Resistant Klebsiella pneumoniae

Purpose

This study aimed to describe the population pharmacokinetics (PopPK) of ceftazidime-avibactam (CAZ-AVI) in adult patients, and to develop optimal dosing regimens for both non-critically ill and critically ill patients by combining different pharmacokinetic/pharmacodynamic (PK/PD) targets.

Patients and Methods

A prospective, single-center study involving patients who were infected with CRKP and received CAZ-AVI therapy was conducted. Nonlinear mixed-effect modeling was used to develop a PopPK model. The optimal dosing regimen was assessed using Monte Carlo simulation.

Results

The PopPK analysis of CAZ-AVI included 91 steady-state concentrations from 45 adult patients. The data were modeled using a one-compartment model. The typical population values of CAZ and AVI clearances were 2.96 L/h and 3.09 L/h, and the volumes of distribution were 17.76 L and 18.25 L, respectively. Our study showed that creatinine clearance (CrCL) calculated using the Cockcroft-Gault equation significantly affected the pharmacokinetics of CAZ-AVI. The Monte Carlo simulation optimized the dosing regimen for both non-critically ill and critically ill patients with varying renal functions, providing detailed supplements to the instructions.

Conclusion

Our study established a PopPK model for CAZ-AVI and proposed a reference for dosing regimen adjustment based on the severity of the disease and renal functional status.

Difficult-to-Treat Pseudomonas aeruginosa Infections in Critically Ill Patients: A Comprehensive Review and Treatment Proposal

The management of infections caused by difficult-to-treat Pseudomonas aeruginosa in critically ill patients poses a significant challenge. Optimal antibiotic therapy is crucial for patient prognosis, yet the numerous resistance mechanisms of P. aeruginosa, which may even combine, complicate the selection of an appropriate antibiotic. In this review, we examine the epidemiology, resistance mechanisms, risk factors, and available and future therapeutic options, as well as strategies for treatment optimization. Finally, we propose a treatment algorithm to facilitate decision making based on the resistance patterns specific to each Intensive Care Unit.

Risk factors for Carbapenem-resistant Enterobacterales infections: A case-control study

BACKGROUND

Over years, concerning Carbapenem-resistant Enterobacterales (CRE) have advanced globally, posing a major threat to global health. Prior studies highlight previous antibiotic use and prolonged hospital stays as paramount risk factors for CRE infections. However, there are limited reports available with a focus on identifying risk factors for CRE infections by comparing CRE cases with controls. The aim is to evaluate factors associated with CRE infections among individuals admitted to hospitals in Mthatha.

METHODS

A retrospective case-control study among patients who attended Nelson Mandela Academic Hospital (NMAH) and Mthatha Regional Hospital (MRH), Eastern Cape, South Africa. Demographic, medical history and current hospitalisation factors were captured on clinical research forms. GraphPad Prism version 8 software was used for statistical analysis.

RESULTS

Out of the 226 participants with CRE infection, CRE cases were more likely than controls to be adults (51.9%, odds ratio [OR]: 1.34, 95% confidence interval [CI]: 0.72-2.55) and of male sex (54.9%, OR: 1.48, 95% CI: 0,87-2,45). Significant risk factors for CRE infections included underlying illnesses (OR: 2.55, 95% CI: 1.41-4.60, p = 0.002), urine catheterisation (OR: 5.40, 95% CI: 1.45-18.33, p = 0.01), intravascular devices (OR: 2.48, 95% CI: 1.06-6.03, p = 0.05) and prolonged hospital stay (OR: 1.87, 95% CI: 1.01-3.39, p = 0.048). CRE cases compared to controls were almost twice as likely to demise or have an extended hospital stay of more than one month. Klebsiella pneumoniae (62.6%) and Enterobacter cloacae (60.6%) were prevalent Enterobacterales associated with CRE.

CONCLUSION

Significant risk factors for CRE infections are underlying illnesses, urine catheterisation, intravascular devices and prolonged hospitalisation.Contribution: The complicated nature of CRE infections highlights the importance of targeted interventions to mitigate their spread and impact on public health.

Clinical Characteristics and Optimization of Empirical Antimicrobial Therapy for Febrile Neutropenia in Patients With Hematologic Malignancies

Purpose

Since the publication of the 2011 Infectious Diseases Society of America (IDSA) guidelines for empirical treatment of febrile neutropenia (FN), there have been significant shifts in pathogen profiles and emerging challenges in treatment. These include increased prevalence of multidrug-resistant (MDR) bacteria and changes in the distribution of Gram-negative or Gram-positive bacteria (GPB). The study aims to update and optimize empirical treatment strategies for hematological malignancy (HM) patients, a population particularly vulnerable to these evolving threats.

Methods

A literature review was conducted on studies published between January 2010 and December 2023 regarding empirical treatment of FN in HM patients, focusing on pathogen characteristics, treatment regimens, and duration of therapy.

Results

Approximately one-third of HM patients with FN experience fever of unknown origin (FUO), while 40-50% have clinically documented infections (CDI), and 10-30% present with microbiologically documented infections (MDI), with a predominance of Gram-negative bacteria (GNB). Factors such as prolonged neutropenia, prior broad-spectrum antibiotic use, and previous infections with drug-resistant bacteria are associated with MDR infections. Cefepime, piperacillin/tazobactam (PTZ), and carbapenem are viable empirical treatments for high-risk HM patients, though cefepime monotherapy's advantage remains uncertain. In cases of pneumonia, shock, or suspected carbapenem-resistant infections, combination therapy, tigecycline, and newer antibiotics like ceftazidime/avibactam (CAZ/AVI) are often used. Empirical broad-spectrum antibiotics can be safely discontinued in FUO patients after 48 hours of clinical stability and apyrexia.

Conclusion

Proper selection of empirical antibiotics and determining optimal treatment duration are essential for reducing antibiotic resistance and improving outcomes in HM patients with FN. These findings underscore the need for updated clinical guidelines that address evolving pathogen profiles and the growing challenge of MDR infections.

Rates of Resistance to Ceftazidime-Avibactam and Ceftolozane-Tazobactam Among Patients Treated for Multidrug-Resistant Pseudomonas aeruginosa Bacteremia or Pneumonia

Among consecutive patients with multidrug-resistant Pseudomonas aeruginosa bacteremia or pneumonia we found those treated with ceftazidime-avibactam were more likely to develop resistance (defined as ≥4-fold increased MIC) than those treated with ceftolozane-tazobactam (40% vs 10%; P = .002). Ceftazidime-avibactam resistance was associated with new mutations in ampC and efflux regulatory pathways.

Patient characteristics and antimicrobial susceptibility profiles of Escherichia coli and Klebsiella pneumoniae infections in international travellers: a GeoSentinel analysis

BACKGROUND

Antimicrobial resistance (AMR) is a global health crisis, with Enterobacterales, including Escherichia coli and Klebsiella pneumoniae, playing significant roles. While international travel to low- and middle-income countries is linked to colonization with AMR Enterobacterales, the clinical implications, particularly the risk of subsequent infection, remain unclear due to limited data. We aimed to characterize E. coli and K. pneumoniae infections in travellers and the antimicrobial susceptibility profiles of their isolates.

METHODS

We analysed data on E. coli and K. pneumoniae infections in travellers collected at GeoSentinel sites between 2015 and 2022, focusing on epidemiological, clinical and microbiological characteristics. We defined multi-drug resistance (MDR) as non-susceptibility to agents from at least three drug classes.

RESULTS

Over the 8-year period, we included 655 patients (median age 41 years; 74% female) from 57 sites in 27 countries, with 584 E. coli and 72 K. pneumoniae infections. Common travel regions included sub-Saharan Africa, Southeast Asia and South-Central Asia. Urinary tract infections predominated. Almost half (45%) were hospitalized. Among infections with antimicrobial susceptibility data across three or more drug classes, 203/544 (37%) E. coli and 19/67 (28%) K. pneumoniae demonstrated MDR. Over one-third of E. coli and K. pneumoniae isolates were non-susceptible to third-generation cephalosporins and cotrimoxazole, with 38% and 28% non-susceptible to fluoroquinolones, respectively. Travellers to South-Central Asia most frequently had isolates non-susceptible to third-generation cephalosporins, fluoroquinolones and carbapenems. We observed increasing frequencies of phenotypic extended spectrum beta-lactamase and carbapenem resistance over time.

CONCLUSIONS

E. coli and K. pneumoniae infections in travellers, particularly those to Asia, may be challenging to empirically treat. Our analysis highlights the significant health risks these infections pose to travellers and emphasizes the escalating global threat of AMR. Enhanced, systematic AMR surveillance in travellers is needed, along with prospective data on infection risk post travel-related AMR organism acquisition.

Activity of cefiderocol in combination with tetracycline analogues against carbapenem-resistant Acinetobacter baumannii

Therapeutic options for carbapenem-resistant Acinetobacter baumannii (CA-AB) are quite limited. Cefiderocol, a novel siderophore cephalosporin, has shown potent in vitro activity against CR-AB, and new tetracycline analogues such as eravacycline and omadacycline have been available in recent years. However, the synergism of cefiderocol with tetracycline analogues against CR-AB has not been well investigated. In this study, we evaluated the in vitro synergistic activity of cefiderocol in combination with tetracycline analogues (minocycline, tigecycline, eravacycline and omadacycline) against 48 clinical isolates of CR-AB by checkerboard methods and time-kill assays. Then we further verified the in vitro results with neutropenic murine thigh-infection models. Among 48 tested isolates tested with checkerboard methods, 35.4%, 33.3%, 50.0% and 37.5% showed synergistic interactions (FICI ≤ 0.5) in cefiderocol-minocycline combination, cefiderocol-tigecycline combination, cefiderocol-eravacycline combination and cefiderocol-omadacycline combination, respectively. None of the combinations exhibited any antagonistic interactions. In the time-kill assays, cefiderocol combined with tetracycline analogues showed synergistic effects in most isolates. Animal models found that combination therapy could reduce cell counts by nearly 2 log10 CFU/thigh compared with the monotherapy in the AB-2 isolate who was susceptible to minocycline (MIC = 4 mg/l). But for the AB-26 who was resistant to minocycline, the decrease of bacterial cell counts was less than 1 log10 CFU/thigh compared with cefiderocol monotherapy in the cefiderocol-minocycline, cefiderocol-tigecycline and cefiderocol-omadacycline therapies; while the cefiderocol-eravacycline combination could still reduce the bacterial cell counts nearly 2 log10 CFU/thigh compared with the monotherapy. In summary, the cefiderocol-eravacycline combination seems to be a promising therapeutic strategy for treating CR-AB infections.

Ceftazidime-avibactam tolerance and persistence among difficult-to-treat KPC-producing Klebsiella pneumoniae clinical isolates from bloodstream infections

PURPOSE

Tolerance and persistence occur "silently" in bacteria categorized as susceptible by antimicrobial susceptibility testing in clinical microbiology laboratories. They are different from resistance phenomena, not well-studied, and often remain unnoticeable. We aimed to investigate and characterize ceftazidime-avibactam (CZA) tolerance/persistence in 80 Klebsiella pneumoniae isolates from bloodstream infections.

METHODS

We used the Tolerance Disk Test (TDtest) to detect CZA tolerance/persistence and investigate the avibactam (AVI) influence on them, and time-kill assays with minimal duration for killing (MDK) determination to characterize/differentiate CZA tolerance from persistence, for selected isolates. Whole genome sequencing was performed for 49/80 selected isolates to investigate genes related to beta-lactam tolerance/persistence and resistance as well as phylogeny studies.

RESULTS

Tolerance/persistence to CZA was detected in 48/80 (60%) isolates, all extensively drug-resistant (XDR) or multidrug-resistant, carbapenem-resistant K. pneumoniae (CRKp), KPC producers, and previously categorized as susceptible (not resistant) to CZA. No heteroresistance was detected. CZA tolerance/persistence occurred due to ceftazidime tolerance/persistence and was not related to AVI in the CZA combination. 5/11 isolates were characterized as CZA-tolerant and 5/11 as CZA-persistent. The single (1/11) XDR and CRKp non-KPC producer was truly susceptible. All the CZA-tolerant/persistent isolates (ST11, ST258, ST340, ST437, ST16, ST17, and ST307) harbored the carbapenemase-encoding gene blaKPC-2. Mutation in only two genes (rpoS and degQ) related to beta-lactam tolerance/persistence was found in only 7/49 CZA-tolerant/persistent isolates, suggesting the presence of yet unknown beta-lactam tolerance/persistence genes.

CONCLUSION

Among the K. pneumoniae bloodstream isolates studied, 60%, previously categorized as susceptible to CZA, were, actually, tolerant/persistent to this antibiotic, all these KPC producers.

In vitro activity of cefepime-enmetazobactam on carbapenem-resistant Gram negatives

OBJECTIVES

Cefepime-enmetazobactam is a new β-lactam/βlactamase inhibitor combination with broad-spectrum activity against multidrug-resistant Enterobacterales, including extended-spectrum β-lactamase producers. This study evaluated the in vitro activity of cefepime-enmetazobactam towards a collection of carbapenem-resistant Enterobacterales (CRE), Pseudomonas aeruginosa and Acinetobacter baumannii compared to the other β-lactam/β-lactamase inhibitor combinations.

METHODS

The MIC of cefepime, cefepime-enmetazobactam, ceftazidime, ceftazidime-avibactam, meropenem, meropenem-vaborbactam, imipenem, imipenem-relebactam, and ertapenem were determined by broth microdilution on 2212 CRE, including 2089 carbapenemase producers (1000 OXA-48-like, 49 KPC, 697 NDM, 180 VIM, 1 IMP, 9 IMI, and 158 multiple carbapenemases) and 123 CRE that do not produce carbapenemase received at the French National Reference Centre (from March 1, 2023 to August 31, 2023), 50 P. aeruginosa, and 30 A. baumannii. All strains were fully sequenced.

RESULTS

We confirmed the absence of inhibitory activity of enmetazobactam towards metallo-β-lactamases. Cefepime-enmetazobactam and ceftazidime-avibactam exhibited a similar susceptibility (96.7% vs. 99.5%, respectively) on OXA-48-producers. Cefepime-enmetazobactam exhibited 66.9% and 63.3% susceptibility for CRE non-EPC and KPC, whereas those rates rose to 96.7%/95.9%, 93.4%/95.9%, and 95.9%/98.0% for ceftazidime-avibactam, imipenem-relebactam, and meropenem-vaborbactam, respectively. Low MICs (≤0.25 mg/L) were obtained for ceftazidime-avibactam-resistant KPC variants. Cefepime-enmetazobactam did not display a significant added value when compared with cefepime alone on Pseudomonas aeruginosa and Acinetobacter baumannii.

DISCUSSION

OXA-48 producers displayed high susceptibility to cefepime-enmetazobactam, which is similar to ceftazidime-avibactam, including for OXA-48 producers that coproduce a ceftazidime hydrolyzing enzyme (extended-spectrum β-lactamases or AmpC). In vivo experiments have to be implemented to confirm if cefepime-enmetazobactam might be a relevant alternative to ceftazidime-avibactam for the treatment of infections caused by OXA-48 producers.

Emergence of cefiderocol resistance during therapy in NDM-5-producing Klebsiella pneumoniae isolates harboring siderophore receptors mutations

Cefiderocol, a siderophore-conjugated cephalosporine, is a promising drug used to treat infection with carbapenem-resistant gram-negative bacteria. Here, we report a case of pneumonia induced by multiple gram-negative pathogens, including a carbapenem-resistant Klebsiella pneumoniae developing cefiderocol resistance within 32 days of cefiderocol therapy. Whole genome sequencing of three consecutive K. pneumoniae isolates revealed that the bacteria were isogenic and were carrying several broad-spectrum β-lactamases (blaNDM5 and blaCTX-M-15). Two isolates with elevated minimum inhibitory concentration against cefiderocol harbored mutations in genes encoding siderophore: one in the cirA gene and one in both the cirA and the fiu genes. The combination of a metallo-β-lactamase background and mutations in siderophore receptors was associated with phenotypic resistance to cefiderocol.

Targeting bacterial efflux pump effectively enhances the efficacy of Ru-based antibacterial agents against Gram-negative pathogen

The rise of antibiotic resistance has posed a great threat to human's life, thus develop novel antibacterial agents is urgently needed. It worthies to noted that Ru-based antibacterial agents often showed robust potency against Gram-positive pathogens, disrupted bacterial membrane and avoided bacterial resistance, making they promising antibiotic candidates. However, they are generally less active when applied to negative pathogens. To address this problem, a Ru-based metalloantibiotic (RuN) modified with a nitrothiophene moiety, which can target bacterial efflux pump, was designed and evaluated in this work. A series of assays demonstrated that RuN not only fully retained the advantages of Ru-based agents, such as destroyed bacterial membrane and induced reactive oxygen species production, but also can targeted bacterial efflux pumps. Of course, these properties make it effective in killing both Gram-positive and negative pathogens, its MIC values against Staphylococcus aureus and Escherichia coli lies at 3.125 and 6.25 μg/mL, respectively. Importantly, RuN also showed low toxicity and has robust anti-infective potency in two animal infection models. Together, our results paved an alternative way to enhance the anti-infective efficacy of Ru-based agents against resistant negative bacteria.

High prevalence of polymyxin-heteroresistant carbapenem-resistant Klebsiella pneumoniae and its within-host evolution to resistance among critically ill scenarios

PURPOSE

We aimed to explore the prevalence and within-host evolution of resistance in polymyxin-heteroresistant carbapenem-resistant Klebsiella pneumoniae (PHR-CRKP) in critically ill patients.

METHODS

We performed an epidemiological analysis of consecutive patients with PHR-CRKP from clinical cases. Our study investigated the within-host resistance evolution and its clinical significance during polymyxin exposure. Furthermore, we explored the mechanisms underlying the dynamic evolution of polymyxin resistance at both subpopulation and genetic levels, involved population analysis profile test, time-killing assays, competition experiments, and sanger sequencing. Additionally, comparative genomic analysis was performed on 713 carbapenemase-producing K. pneumoniae strains.

RESULTS

We enrolled 109 consecutive patients, and PHR-CRKP was found in 69.7% of patients without previous polymyxin exposure. 38.1% of PHR-CRKP isolates exhibited polymyxin resistance and led to therapeutic failure in critically ill scenarios. An increased frequency of resistant subpopulations was detected during PHR-CRKP evolution, with rapid regrowth of resistant subpopulations under high polymyxin concentrations, and a fitness cost in an antibiotic-free environment. Mechanistic analysis revealed that diverse mgrB insertions and pmrB hypermutations contributed to the dynamic changes in polymyxin susceptibility in dominant resistant subpopulations during PHR evolution, which were validated by comparative genomic analysis. Several deleterious mutations (e.g. pmrBLeu82Arg, pmrBSer85Arg) were firstly detected during PHR-CRKP evolution. Indeed, specific sequence types of K. pneumoniae demonstrated unique deletions and deleterious mutations.

CONCLUSIONS

Our study emphasizes the high prevalence of pre-existing heteroresistance in CRKP, which can lead to polymyxin resistance and fatal outcomes. Hence, it is essential to continuously monitor and observe the treatment response to polymyxins in appropriate critically ill scenarios.

Benchmarking antimicrobial use to antimicrobial resistance: a comparative study of two hospitals using current National Healthcare Safety Network (NHSN) metrics

OBJECTIVE

We aimed to determine whether benchmarking antimicrobial use (AU) to antimicrobial resistance (AR) using select AU/AR ratios is more informative than AU metrics in isolation.

DESIGN

We retrospectively measured AU (antimicrobial therapy days per 1,000 days present) and AU/AR ratios (specific antimicrobial therapy days per corresponding AR event) in two hospitals during 2020 through 2022. We then had antimicrobial stewardship committee members evaluate each AU and corresponding AU/AR value and indicate whether they believed it represented potential overuse, appropriate use, or potential underuse of the antimicrobials, or whether they could not provide an assessment.

SETTING

Two acute-care hospitals.

PATIENTS

Hospitalized patients.

RESULTS

In semi-annual facility-wide analyses, echinocandins had a median AU/AR ratio of 658.5 therapy days per fluconazole-resistant Candida event in Hospital A, IV vancomycin had a median AU/AR ratio of 114.9 and 108.2 therapy days per methicillin-resistant Staphylococcus aureus event in Hospital A and B, respectively, and linezolid had a median AU/AR ratio of 33.8 and 88.0 therapy days per vancomycin-resistant Enterococcus event in Hospital A and B, respectively. When AU and AU/AR values were evaluated by stewardship committees, more respondents were able to assess antimicrobial use based on AU/AR values compared to AU values. Based on AU/AR ratios, most respondents identified potential overuse of echinocandins and IV vancomycin in Hospital A, and potential overuse of linezolid and IV vancomycin in Hospital B.

CONCLUSION

Select AU/AR ratios provided informative metrics to antimicrobial stewardship personnel, which can be used to motivate audits of antimicrobial administration to determine appropriateness.

Mortality-related risk factors of carbapenem-resistant Enterobacteriaceae infection with focus on antimicrobial regimens optimization: a real-world retrospective study in China

OBJECTIVES

To determine the mortality-related risk factors for carbapenem-resistant Enterobacteriaceae (CRE) infection in hospitalized patients and to compare the clinical efficacy of different antimicrobial regimen.

METHODS

Data were retrospectively collected from a 3,500-bed regional medical center between January 2021 and June 2022. Mortality-related risk factors were analyzed by the Cox proportional regression model for multivariate analysis.

RESULTS

120 patients were included and the all-cause mortality was 20.8% (25/120). Multivariate analysis showed that age (HR = 1.035, 95%CI: 1.002-1.070, P = 0.036), SOFA score (HR = 1.169,95%CI: 1.066-1.281, P = 0.001), central venous catheter (HR = 3.858, 95%CI: 1.411-10.547, P = 0.009), the length of hospital stay (HR = 0.868, 95% CI: 0.806-0.936, P = 0.000) and combination therapy (HR = 3.152, 95%CI: 1.205-8.245, P = 0.019) were independent mortality risk factors after CRE infection. All patients received definitive therapy and 65.0% (78/120) received sensitive drug treatment. Among those 65.4% (51/78) received combination therapy and 34.6% (27/78) received monotherapy. Subgroup analysis of the non-sepsis group showed significantly lower mortality in monotherapy than in combination therapy (0% versus 22.2%, P = 0.034). Patients who received carbapenem-containing therapy had significantly higher mortality than those who received carbapenem-sparing therapy (31.3% versus 13.9%, P = 0.022). CAZ-AVI-containing therapy presented a lower mortality (19.0%) and a higher 7-day microbiological clearance (47.6%) compared to other antimicrobial regimens, but there were no statistical significance (P>0.05).

CONCLUSIONS

Patients with older age, higher SOFA score, central venous catheter, shorter hospital stay after CRE infection may had poor outcomes. Since patients with non-sepsis have a lower mortality rate from monotherapy, combination antibiotic treatment should not be routinely recommended. Patients who received CAZ-AVI-containing therapy presented a lower mortality compared to other antimicrobial regimens without statistical significance, further larger sample size is needed for verification.

Prevalence, Characterization, and Proteomic Relatedness Among β-Lactam-Resistant Bacteria Throughout the Poultry Production Chain in Greece

Extended-spectrum-β-lactamase (ESBL) and carbapenemase-producing Escherichia coli, Klebsiella pneumoniae and Acinetobacter spp. are associated with hospital-acquired infections and are commonly isolated across the poultry food production chain. Comprehensive data regarding the prevalence, spatiotemporal variations, and characterization of β-lactam-resistant bacteria in poultry farms and slaughterhouses is scarce. This study examines the prevalence and characteristics of β-lactam-resistant E. coli, K. pneumoniae, and Acinetobacter spp. isolated from poultry farms, slaughterhouses, and associated personnel in Greece. Strains were selectively isolated and identified via MALDI-TOF MS, which was also employed to identify possible relatedness. E. coli isolates were further classified into phylogenetic groups. The prevalence of β-lactam-resistant strains in farm and slaughterhouse environments was 15.0% (n = 15 strains)/57.3% (n = 71 strains) for E. coli, 11.0% (n = 11 strains)/1.6% (n = 2 strains) for K. pneumoniae, and 1.0% (n = 1 strain)/25.8% (n = 38 strains) for Acinetobacter spp., respectively. The prevalence of Acinetobacter spp. and E. coli on farmers' skin was 16.7% (n = 2 strains) and 8.3% (n = 1 strain), correspondingly. Significantly higher E. coli isolation rates were observed in warmer seasons. All strains were multidrug-resistant and most carried ESBL/AmpC genes. Most E. coli isolates belonged to phylogroups A (41.4%, n = 36) and B1 (24.1%, n = 21). Proteomic analysis indicated relatedness among strains from different regions and seasons. Thus, poultry farms and slaughterhouses may serve as significant reservoirs of β-lactam-resistant strains of E. coli, K. pneumoniae, and Acinetobacter spp.

Antimicrobial peptide Hs02 with rapid bactericidal, anti-biofilm, and anti-inflammatory activity against carbapenem-resistant Klebsiella pneumoniae and Escherichia coli

Carbapenem-resistant Klebsiella pneumoniae (CRKP) and Escherichia coli (CREC) are frequently detected in clinical settings, restricting the use of carbapenems. Therefore, there is an urgent need for new antimicrobial strategies to address infections caused by CRKP and CREC. This study investigated the antibacterial, anti-biofilm, and anti-inflammatory effects of the cationic antimicrobial peptide Hs02, along with its potential antimicrobial mechanisms against CRKP and CREC. The results revealed that Hs02 had a low minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) against CRKP and CREC, effectively eliminating the bacteria within 30 min. Moreover, Hs02 significantly prevents biofilm formation and disrupts the established biofilms. Further mechanistic studies demonstrated that Hs02 specifically targeted and bound to bacterial outer membrane lipopolysaccharides (LPS), disrupted membrane permeability and integrity, which led to intracellular reactive oxygen species (ROS) accumulation. Furthermore, Hs02 neutralized LPS, thereby suppressing the production of pro-inflammatory cytokines TNF-α, IL-6, and IL-1β in murine macrophage RAW 264.7 cells. In vitro, hemolysis and cytotoxicity assays confirmed Hs02's safety at the tested concentrations and proved that Hs02 improved the survival rate of Galleria mellonella larvae. In conclusion, the findings suggest that Hs02's interaction with LPS and the resulting disruption of membrane integrity may be key factors driving its rapid bactericidal and anti-inflammatory effects.

IMPORTANCE

Eukaryotic antimicrobial peptides are typically amphipathic peptides consisting of approximately 50 amino acids. Many macromolecular proteins in our body contain polypeptide sequences that show characteristics similar to those of antimicrobial peptides. The present research highlights a gap in the current literature regarding the mechanisms by which the intragenic antimicrobial peptide Hs02, derived from human proteins, exerts its rapid bactericidal and anti-inflammatory effects. The findings demonstrate that lipopolysaccharide (LPS) is a key target of Hs02's antimicrobial activity and that its ability to neutralize LPS is crucial for its anti-inflammatory effects.

Genomic insights on cgMLST markers, drug resistance, and urease cluster of Proteus mirabilis strains

Proteus mirabilis, a significant pathogenic bacterium within the Enterobacteriaceae family, is widely distributed across various natural environments. This study conducted a genomic comparison analysis of 1,267 strains of P. mirabilis using extensive genome data from public databases. The objective was to elucidate the pan-genomic structure of P. mirabilis, revealing the composition and distribution of core and accessory gene families among different strains. Additionally, an attempt was made to construct a core genome multilocus sequence typing scheme specific to this species in order to enhance the precision of describing genetic diversity and evolutionary relationships. Furthermore, the study delved into the mechanisms of resistance of P. mirabilis to carbapenems and quinolones. Our findings underscore significant challenges posed by P. mirabilis in terms of antibiotic resistance, with widespread resistance observed particularly against beta-lactams and an increasing trend in resistance to carbapenems and quinolones. These results highlight the severity of P. mirabilis as a pathogen and underscore its rapid evolution and adaptability in developing resistance. This study aims to deepen our understanding of the antibiotic resistance of P. mirabilis, providing important insights for the development of future antimicrobial drugs, promoting effective treatment and control of this pathogen, and mitigating its threat to human health.

IMPORTANCE

The bacterium Proteus mirabilis is a common pathogenic bacterium that is known to cause a variety of human infections. The drug-resistant genes carried by P. mirabilis present a significant challenge to clinical treatment, particularly in regard to the organism's notable resistance to commonly used beta-lactam and quinolone drugs. Furthermore, the prevalence of the urease gene cluster of P. mirabilis at the urease gene level may be associated with the formation of kidney stones. The objective of the study is to analyze the bacterium's drug resistance, urease gene clusters, and gene distribution in genomes in order to facilitate the development of antimicrobial drugs and improve the treatment and control of P. mirabilis infections.

Identification of Potential Inhibitors of Three NDM Variants of Klebsiella Species from Natural Compounds: A Molecular Docking, Molecular Dynamics Simulation and MM-PBSA Study

BACKGROUND

Klebsiella species have emerged as well-known opportunistic pathogens causing nosocomial infections with β-lactamase-mediated resistance as a prevalent antibiotic resistance mechanism. The discovery and emergence of metallo-β-lactamases, mainly new- Delhi metallo-β-lactamases (NDMs), have increased the threat and challenges in healthcare facilities.

OBJECTIVES

A computational screening was conducted using 570 natural compounds from Dr. Duke's Phytochemical and Ethnobotanical data to discover promising inhibitors for NDM-6, NDM-9, and NDM-23 of the Klebsiella species.

METHODS

Using homology modeling on the Raptor-X web server, the structures of the three NDM variants were predicted. The structures were validated using various computational tools and MD simulation for 50 ns. Lipinski - Vebers' Filter and ADMET Screening were used to screen 570 compounds, followed by docking in Biovia Discovery Studio 2019 using the CDOCKER module. GROMACS was used to simulate the compounds with the highest scores with the proteins for 50 ns. Using the MM-PBSA method and g_mmpbsa tool, binding free energies were estimated and per-residue decomposition analysis was conducted.

RESULTS

The three structures predicted were found stable after the 50 ns MD Simulation run. The compounds Budmunchiamine-A and Rhamnocitrin were found to have the best binding energy towards NDM-6, NDM-9, and NDM-23, respectively. From the results of MD Simulation, MM-PBSA binding free energy calculations, and per-residue decomposition analysis, the Protein-ligand complex of NDM-6 with Budmunchiamine A and NDM-9 with Rhamnocitrin was relatively more stable than the complex of NDM-23 and Rhamnocitrin.

CONCLUSION

The study suggests that Budmunchiamine-A and Rhamnocitrin are potential inhibitors of NDM-6 and NDM-9, respectively, and may pave a path for in-vivo and in-vitro studies in the future.

Navigating antibiotic therapy in acute cholangitis: Best practices and new insights

Globally, antibiotic resistance is linked to increased morbidity, mortality, and healthcare costs, which necessitates further research on optimal antibiotic usage. Acute cholangitis (AC), a common cause of community-acquired bacteremia, often requires antimicrobial therapy. Therefore, studying the appropriate use of antibiotics for AC is considered crucial for suppressing the emergence of resistant bacteria and reducing adverse antibiotic-associated events. The Tokyo Guidelines 2018 (TG18) recommend 4-7 days of antibiotics post-biliary drainage. However, this lacks strong evidence and is based primarily on various evidence and expert opinions. Recent retrospective studies advocate for a shorter 1-3-day antibiotic course for AC, thereby prompting a need to reassess the treatment duration to balance therapeutic efficacy and minimize resistance and adverse effects. Choosing the appropriate duration and antibiotics based on susceptibility to pathogens causing cholangitis is important. Awareness of local resistance patterns and understanding patients' risks of resistant pathogens are prerequisite for effective treatment. We must explore the applicability of these guidelines in specific scenarios such as severe AC, positive blood cultures, fever, or hilar biliary obstructions due to malignancy. This comprehensive review considers both the duration and type of antibiotics and aims to enhance treatment outcomes while reducing the risk of resistant bacterial infections.

Risk factors and molecular epidemiology of colonizing carbapenem-resistant Enterobacterales in pediatric inpatient in Shenzhen, China

OBJECTIVES

The spread of CRE has been rapid on a global scale and represents a significant challenge in nosocomial infections worldwide. The aim is to evaluate the risk factors for CRE colonization and to describe the molecular and clinical characteristics of CRE colonization in pediatric inpatients in Shenzhen, China.

METHODS

We collected stool specimens from 2474 randomly selected pediatric inpatient hospitalized in 2 pediatric hospitals in Shenzhen between January 2023 and December 2023 for subsequent microbiological analysis, including microbial culture, species identification, antimicrobial sensitivity testing, genetic characterization and multilocus sequence typing (MLST). In addition, we conducted a case-control study to identify potential risk factors for gastrointestinal CRE colonization.

RESULTS

Of the 2474 non-replicating pediatric stool specimens collected, 3.6 % (n = 90) test positive for CRE. The most dominant CRE species were Escherichia coli (n = 67, 74.5 %), and Klebsiella pneumoniae (n = 17, 19.0 %). Multidrug resistance and carbapenemase production were observed in most CRE isolates. In CR E. coli and CR K. pneumoniae, the blaNDM was the predominant resistance gene, accounting for 95.5 % and 76.5 %, respectively. MLST showed considerable clonal diversity among the CR E. coli and CR K. pneumoniae isolates and the most common ST in CR E. coli was ST48 (n = 6, 9.0 %) and ST35 in CR K. pneumoniae (n = 4, 23.5 %).

CONCLUSIONS

This study once again shows that pediatric inpatients in South China were colonized by a diversity of CRE strains, increasing the likelihood of difficult-to-treat infections. Hospitals and competent authorities should take appropriate public health measures, to prevent the further spread of CRE.

Whole Genome Sequencing Insights on Extensive Drug Resistant Klebsiella pneumoniae and Pseudomonas aeruginosa Traumatic Infection

<b>Background and Objective:</b> It is well documented that Whole Genome Sequencing (WGS) has recently used to explore new resistance patterns and track the dissemination of extensive and pan drug-resistant microbes in healthcare settings. This article explores the link between traumatic infections caused by road traffic accidents (RTAs) leading to coma and the development of chest infections caused by extensively drug-resistant (XDR) <i>Klebsiella pneumoniae</i> and <i>Pseudomonas aeruginosa</i>. <b>Materials and Methods:</b> The study was carried out from March to December 2022 which included a 45-year-old male patient admitted to the ICU of Al Ramadi Teaching Hospitals following a severe RTA that resulted in a TBI and subsequent coma. Two study isolates were diagnosed bacteriologically using the VITEK^®-2 technique including resistant mechanisms like extended-spectrum beta-lactamases and carbapenemases. Whole genome sequencing was performed using a DNA nanoball sequencing platform from BGI-Tech. Genome assembly and annotation were done using the bacterial bioinformatics resource center. The report on Comprehensive Genome Analysis includes a phylogenetic analysis using the reference and representative genomes provided by PATRIC. <b>Results:</b> <i>Klebsiella pneumoniae</i> and <i>P. aeruginosa</i> isolates were XDR, producing ESBLs and carbapenemases. The WGS detection NDM-5 gene in the <i>K. pneumoniae</i> strain is not very common compared to the NDM-1 and blaOXA-181 g. At the same time, a file in <i>P. aeruginosa</i> isolate found genes GES-type ESBL (not reported in Iraq before), blaPAO and blaOXA-396 with NDM-1 all these genes are carbapenemases. In phylogenetic analysis, the <i>K. pneumoniae</i> isolate has an evolutionary relationship with strains originating from China while <i>P. aeruginosa</i> was globally unique. <b>Conclusion:</b> The XDR <i>K. pneumoniae</i> and <i>P. aeruginosa</i> pose a public health threat. The WGS revealed unique virulence and antibiotic-resistance genes associated with nosocomial outbreaks. The XDR isolates carrying NDM-5, blaOXA-181 and GES-type ESBL genes were detected.

Risk Factors and Outcomes of Multidrug-resistant Pseudomonas aeruginosa in Kelantan, Malaysia: A Multicenter Case-control Study

Background

Increasing trend and spread of multidrug-resistant Pseudomonas aeruginosa (MDR-PA) in clinical settings is a great challenge in managing patients with infections caused by this pathogen.

Objective

To determine the risk factors and outcomes of MDR-PA acquisition in the northeastern state of Malaysia. In addition, this study also reported on the susceptibility pattern and common resistant genes among MDR-PA.

Materials and Methods

MDR-PA isolates obtained between March 2021 and February 2022 from all four major hospitals in the state of Kelantan, Malaysia, were submitted for susceptibility and resistant genes identification. The clinical data of the patients with MDR-PA were retrospectively reviewed. The risk factors and outcomes of MDR-PA acquired patients were analyzed by comparing with patients who acquired susceptible-PA while admitted to the same hospital during the study time.

Results

A total of 100 MDR-PA and 100 susceptible-PA cases were included. Ceftolozane-tazobactam was susceptible in 41.3% of MDR-PA compared to only 4%-8% with other β-lactams. About half (46%) of the MDR-PA isolates harbored the bla -NDM-1 gene, but none had the bla -OXA-48 gene. Factors independently associated with MDR-PA acquisitions were age (OR: 1.02; P = 0.028), genitourinary disorder (OR: 6.89; P = 0.001), and central venous catheter (OR: 3.18; P = 0.001). In addition, MDR-PA acquisitions were found to be associated with antimicrobial treatment failure (41.1% vs. 25.0%; P = 0.001) and mortality (40.0% versus 6.0%; P <0.001).

Conclusion

Most of the MDR-PA strains in Kelantan tertiary hospitals harbored the bla -NDM-1 gene, which is easily transmissible and can lead to an outbreak. Nonetheless, a significant number of the MDR-PA isolates were still susceptible to ceftolozane-tazobactam.

Molecular characterization of ST15 carbapenem-resistant Klebsiella pneumoniae isolated in a single patient

BACKGROUND

The carbapenem-resistant Klebsiella pneumoniae (CRKP) poses a serious threat to antibiotic applicability and public health. During treatment, K. pneumoniae (KP) frequently exhibits shifts in drug-resistant phenotypes, complicating clinical treatment as it transitions from sensitivity to resistance. In this study, we analysed the clinical and molecular characteristics of drug resistance changes in KP strains isolated from a single patient, and the potential mechanisms underlying these resistance changes.

METHODS

Antimicrobial susceptibility test and string test were conducted to evaluate the resistant and virulent characterization of the strains. Pulsed-field gel electrophoresis (PFGE) was used to investigate the homology relationship between the strains. The whole genome sequencing and phylogenetic analysis of 9 representative isolates was also performed. The transfer ability of the drug-resistant plasmid was studied by plasmid conjugation experiment. The transconjugants were verified by polymerase chain reaction amplification of specific genes, antimicrobial susceptibility test and PFGE.

RESULTS

Our results revealed that 9 KP strains, isolated from the same patient, exhibited 'resistance-sensitivity-resistance-sensitivity' alternately to carbapenems. The differences in DNA fingerprint bands among the nine KP isolates were ≤3, which can be classified as the same PFGE type. Phylogenetic analysis showed that these 9 strains constituted a distinct branch within the phylogenetic tree. All nine KP strains belonged to the ST15-KL19 clone. Six of the strains were classified as CRKP, all of which carried 11 drug resistance genes: oqxB, oqxA, fosA6, aac(3)-lld, blaSHV-28, blaKPC-2, blaOXA-1, mph(A), tet(A), catB3 and aac(6')-lb-cr, mediating drug resistance to quinolones, fosfomycin, aminoglycosides, β-lactam, carbapenems, macrolides and chloramphenicol, belonging to multi-drug resistant bacteria. The carbapenem-resistant plasmid p2-KP3762-1 was found to transfer within species, from CRKP to hypervirulent KPRJF293HA, carbapenem-sensitive KP KP3657 and Escherichia coli C600 at a frequency of (1.19 ± 1.58) ×10-6, (1.09 ± 1.38) ×10-7 and (10.9 ± 9.53) ×10-6 respectively, resulting in the dissemination of carbapenem resistance genes.

CONCLUSIONS

In this study, KP strains isolated from a single patient exhibited an alternating phenotype of resistant-sensitive-resistant-sensitive to carbapenems. The 9 KP isolates share a high degree of genetic similarity. The plasmid p2-KP3762-1, harbouring the carbapenem resistance gene blaKPC-2, may undergo inter-strain and inter-clone transfer via conjugation in the patient during treatment. Furthermore, our findings suggest that the pathogens in this patient are likely to have a common ancestral origin.

Efficacy and Safety of Aerosol Inhalation of Colistin Sulfate for the Treatment of Carbapenem-Resistant Klebsiella pneumoniae Infection in the Peri-Operative Period of Liver Transplantation: A Single-Center Retrospective Study

Objective: This study intended to evaluate the clinical efficacy and safety of colistin sulfate aerosol inhalation in combination with ceftazidime-avibactam for the treatment of pulmonary carbapenem-resistant Klebsiella pneumoniae (CRKP) infection during the peri-operative period of liver transplantation. Materials and Methods: A retrospective analysis was designed to investigate 52 patients who developed pulmonary CRKP infection after liver transplantation between December 1, 2019, and November 30, 2022. On the basis of whether they received colistin sulfate aerosol inhalation, the patients were divided into the treatment group (n = 29) and the control group (n = 23). The baseline information, infection status, CRKP enzyme type, inflammatory markers, liver and kidney function, and prognosis were compared and analyzed. Results: There were no significant differences in patient characteristics, infection status, and drug resistance enzyme type between the treatment group (treated with colistin sulfate aerosol inhalation and ceftazidime and avibactam sodium for injection) and the control group (treated with ceftazidime and avibactam sodium for injection alone). Colistin sulfate aerosol inhalation treatment reduced concentrations of inflammatory markers, with post-treatment white blood cell count, procalcitonin, and C-reactive protein significantly lower than pre-treatment levels (p < 0.05). Except for C-reactive protein at 14 days (p = 0.032), the two groups had no significant differences in other indicators. There were no significant differences in alanine aminotransferase, aspartate aminotransferase, total bilirubin, and glomerular filtration rate after treatment, indicating no discernible alteration in liver and kidney function. In addition, the treatment group took a significantly shorter time to normalize body temperature compared with the control group (p = 0.025), but there were no significant differences in the cure with no colonization rate and all-cause mortality rate between the two groups. Conclusions: The combination of colistin sulfate aerosol inhalation and ceftazidime and avibactam sodium for injection is effective in treating pulmonary CRKP infection during the peri-operative period of liver transplantation. It does not impose an additional burden on liver and kidney function, providing a new treatment option for this type of infection.