A Comprehensive Review on Potential Therapeutic Inhibitors of Nosocomial Acinetobacter baumannii Superbugs

A systematic review on the anti-microbial activities and structure-activity relationship (SAR) of quinoxaline derivatives

Anti-microbial resistance has become a serious global health issue affecting millions of people worldwide. Despite extensive drug discovery efforts aimed at identifying potent molecules for effective anti-microbial treatments, the emergence of superbugs remains a significant challenge. Thus, developing novel therapeutic agents is required to combat these evolving threats. The quinoxaline scaffold emerges as a promising heterocyclic framework for developing novel anti-microbial agents. It's simple, flexible structure, coupled with its bioisosteric relationship to extensively explored quinoline and naphthalene scaffolds, offers a potential avenue for circumventing bacterial resistance developed against these established classes. Hence it has sparked interest in researchers to develop novel antibiotics based on the quinoxaline core. This review focuses on the recent advances of quinoxaline derivatives as anti-microbial agents and their structure-activity relationship studies based on the literature published from 2015 to 2024. The systematic presentation of this information will assist researchers in identifying key substitution patterns around the quinoxaline nucleus, facilitating the development of structure-activity relationship (SAR), and guiding the design of novel anti-microbial drugs to combat the growing threat of anti-microbial resistance.

The Mortality of Colistin Monotherapy vs. Colistin-Sulbactam for Carbapenem-Resistant Acinetobacter baumannii Pneumonia: A Propensity Score Analysis

BACKGROUND

This study compared the mortality rates within 30 days of 2 different doses of sulbactam (6 g and 9-12 g daily) when used in colistin (COL)-based treatment regimens and COL monotherapy for carbapenem-resistant Acinetobacter baumannii (CRAB).

MATERIALS AND METHODS

This retrospective cohort study included 234 participants diagnosed with severe pneumonia due to CRAB infection at Phramongkutklao Hospital, Thailand, from July 1, 2011, to April 30, 2023. Participants were categorized into three groups: COL monotherapy, COL with 6 g of sulbactam daily (COL+S6g), and COL with 9-12 g of sulbactam daily (COL+SHD). Following the exclusion of patients with renal impairment (serum creatinine ≥1.5 mg/dl), a 1:2 propensity score (PS) matching was used to ensure comparable groups, with the COL group designated as the control. The matching variables included age, APACHE II scores, serum creatinine, intensive care units admission, and bacteremia. The number of participants in each group was as follows: 19 in COL, 32 in COL+S6g, and 38 in COL+SHD. The primary outcomes assessed were all-cause mortality rates at 7, 14, and 30 days. Kaplan-Meier survival curves and the Log-rank test were used to evaluate differences between groups, while multivariate Cox regression models were applied to determine the impact of treatment regimens.

RESULTS

The unmatching PS analysis indicated that the COL+SHD regimen significantly reduces mortality compared to the COL regimen; hazard ratios (HR) were 0.18 (95% confidence interval [CI], 0.06-0.55) for 7-day mortality and 0.53 (95% CI,-0.29-0.97) for 30-day mortality. In addition, the COL+SHD regimen also lowered mortality more than the COL+S6g regimen within 7 days (HR, 0.29; 95% CI, 0.11-0.75). After PS matching, the COL+SHD regimen significantly reduced 7-day mortality compared to the COL regimen (adjusted HR, 0.24; 95% CI, -0.07-0.82). However, COL+S6g did not differ in mortality from either COL+SHD or COL for 7-day mortality. At 14 days and 30 days, there were no significant regimens to reduce mortality.

CONCLUSION

Combining COL+SHD effectively reduced death in 7 days from severe pneumonia in CRAB infection treatment.

The Clinical Impression of NDM-producing Acinetobacter baumannii in Intensive Care Units of the University Referral Hospital in North India

Aims and background

Carbapenem-resistant Acinetobacter baumannii (CRAb), a major public health threat, causes severe infections in Intensive Care Unit (ICU) patients. It resists β-lactam antibiotics through mechanisms like New Delhi metallo-beta-lactamase (NDM).

Materials and methods

In ICU patients, 69 Acinetobacter species were isolated from 86 non-fermenting Gram-negative bacilli. Isolates were identified using biochemical methods and Matrix-assisted laser desorption ionization-time of flight (MALDI-TOF) mass spectrometry (MS), and carbapenem resistance detection was done by both phenotypic (mCIM and eCIM) and molecular methods.

Results

Out of 66 A. baumannii, 61 were carbapenem-resistant, with 20 confirmed as NDM producers. NDM-positive isolates exhibited higher resistance and were associated with significant mortality (75%).

Conclusion

NDM-positive Acinetobacter isolates are significant ICU pathogens with poor outcomes. Key risk factors include prolonged ICU stays, prior antimicrobial use, and inadequate therapy. Early detection and infection control are crucial.

Clinical significance

NDM-positive Acinetobacter infections in ICU patients are linked to poor outcomes, highlighting the need for early detection and control measures.

How to cite this article

Singh S, Verma A, Venkatesh V, Verma S, Reddy DH, Agrawal A. The Clinical Impression of NDM-producing Acinetobacter baumannii in Intensive Care Units of the University Referral Hospital in North India. Indian J Crit Care Med 2024;28(11):1044-1049.

Synthetic and Semisynthetic Compounds as Antibacterials Targeting Virulence Traits in Resistant Strains: A Narrative Updated Review

This narrative review paper provides an up-to-date overview of the potential of novel synthetic and semisynthetic compounds as antibacterials that target virulence traits in resistant strains. The review focused on research conducted in the last five years and investigated a range of compounds including azoles, indoles, thiophenes, glycopeptides, pleuromutilin derivatives, lactone derivatives, and chalcones. The emergence and spread of antibiotic-resistant bacterial strains is a growing public health concern, and new approaches are urgently needed to combat this threat. One promising approach is to target virulence factors, which are essential for bacterial survival and pathogenesis, but not for bacterial growth. By targeting virulence factors, it may be possible to reduce the severity of bacterial infections without promoting the development of resistance. We discuss the mechanisms of action of the various compounds investigated and their potential as antibacterials. The review highlights the potential of targeting virulence factors as a promising strategy to combat antibiotic resistance and suggests that further research is needed to identify new compounds and optimize their efficacy. The findings of this review suggest that novel synthetic and semisynthetic compounds that target virulence factors have great potential as antibacterials in the fight against antibiotic resistance.

Silver Nanoparticle-Based Therapy: Can It Be Useful to Combat Multi-Drug Resistant Bacteria?

The present review focuses on the potential use of silver nanoparticles in the therapy of diseases caused by antibiotic-resistant bacteria. Such bacteria are known as “superbugs”, and the most concerning species are Acinetobacter baumannii, Pseudomonas aeruginosa, Staphylococcus aureus (methicillin and vancomycin-resistant), and some Enterobacteriaceae. According to the World Health Organization (WHO), there is an urgent need for new treatments against these “superbugs”. One of the possible approaches in the treatment of these species is the use of antibacterial nanoparticles. After a short overview of nanoparticle usage, mechanisms of action, and methods of synthesis of nanoparticles, emphasis has been placed on the use of silver nanoparticles (AgNPs) to combat the most relevant emerging resistant bacteria. The toxicological aspects of the AgNPs, both in vitro using cell cultures and in vivo have been reviewed. It was found that toxic activity of AgNPs is dependent on dose, size, shape, and electrical charge. The mechanism of action of AgNPs involves interactions at various levels such as plasma membrane, DNA replication, inactivation of protein/enzymes necessary, and formation of reactive oxygen species (ROS) leading to cell death. Researchers do not always agree in their conclusions on the topic and more work is needed in this field before AgNPs can be effectively applied in clinical therapy to combat multi-drug resistant bacteria.