Global challenge of multidrug-resistant Acinetobacter baumannii

Novel tetrahydronaphthalen-1-yl-phenethyl ureas: synthesis and dual antibacterial-anticancer activities

Cancer and antibiotic-resistant bacterial infections are significant global health challenges. The resistance developed in cancer treatments intensifies therapeutic difficulties. In addressing these challenges, this study synthesised a series of N,N'-dialkyl urea derivatives containing methoxy substituents on phenethylamines. Using isocyanate for the efficient synthesis yielded target products 14-18 in 73-76% returns. Subsequently, their antibacterial and anticancer potentials were assessed. Cytotoxicity tests on cancer cell lines, bacterial strains, and a healthy fibroblast line revealed promising outcomes. All derivatives demonstrated robust antibacterial activity, with MIC values ranging from 0.97 to 15.82 µM. Notably, compounds 14 and 16 were particularly effective against the HeLa cell line, while compounds 14, 15, and 17 showed significant activity against the SH-SY5Y cell line. Importantly, these compounds had reduced toxicity to healthy fibroblast cells than to cancer cells, suggesting their potential as dual-functioning agents targeting both cancer and bacterial infections.

Antibiotic resistome in landfill leachate and impact on groundwater

Landfill leachate is a hotspot in antibiotic resistance development. However, little is known about antibiotic resistome and host pathogens in leachate and their effects on surrounding groundwater. Here, metagenomic sequencing was used to explore profiles, host bacteria, environmental risks and influencing factors of antibiotic resistome in raw and treated leachate and surrounding groundwater of three landfills. Results showed detection of a total of 324 antibiotic resistance genes (ARGs). The ARGs conferring resistance to multidrug (8.8 %-25.7 %), aminoglycoside (13.1 %-39.2 %), sulfonamide (10.0 %-20.9 %), tetracycline (5.7 %-34.4 %) and macrolide-lincosamide-streptogramin (MLS, 5.3 %-29.5 %) were dominant in raw leachate, while multidrug resistance genes were the major ARGs in treated leachate (64.1 %-83.0 %) and groundwater (28.7 %-76.6 %). Source tracking analysis suggests non-negligible influence of leachate on the ARGs in groundwater. The pathogens including Acinetobacter pittii, Pseudomonas stutzeri and P. alcaligenes were the major ARG-carrying hosts. Variance partitioning analysis indicates that the microbial community, abiotic variables and their interaction contributed most to the antibiotic resistance development. Our results shed light on the dissemination and driving mechanisms of ARGs from leachate to the groundwater, indicating that a comprehensive risk assessment and efficient treatment approaches are needed to deal with ARGs in landfill leachate and nearby groundwater. ENVIRONMENTAL IMPLICATIONS: Antibiotic resistance genes are found abundant in the landfill sites, and these genes could be disseminated into groundwater via leaching of wastewater and infiltration of leachate. This results in deterioration of groundwater quality and human health risks posed by these ARGs and related pathogens. Thus measures should be taken to minimize potential negative impacts of landfills on the surrounding environment.

Bactericidal effect of bacteria isolated from the marine sponges Hymeniacidon perlevis and Halichondria panicea against carbapenem-resistant Acinetobacter baumannii

In this study, we evaluated the antimicrobial activity of bacteria isolated from the marine sponges Hymeniacidon perlevis and Halichondria panicea against seven Acinetobacter baumannii strains, the majority of which were clinically relevant carbapenem-resistant A. baumannii strains. We observed the inhibitory activity of 18 (out of 114) sponge-isolated bacterial strains against all A. baumanii strains using medium-throughput solid agar overlay assays. These inhibitory strains belonged to the genera Lactococcus, Pseudomonas, and Vagococcus. In addition, this antimicrobial activity was validated through a liquid co-cultivation challenge using an inhibitory strain of each genus and a green fluorescent protein-tagged A. baumanii strain. Fluorescence measurements indicated that the growth of A. baumanii was inhibited by the sponge isolates. In addition, the inability of A. baumanii to grow after spreading the co-cultures on solid medium allowed us to characterize the activity of the sponge isolates as bactericidal. In conclusion, this study demonstrates that marine sponges are a reservoir of bacteria that deserves to be tapped for antibiotic discovery against A. baumanii.

Antibiotic susceptibility patterns at the Médecins Sans Frontières (MSF) Acute Trauma Hospital in Aden, Yemen: a retrospective study from January 2018 to June 2021

Background

Antimicrobial resistance (AMR) is an urgent global health concern, especially in countries facing instability or conflicts, with compromised healthcare systems. Médecins Sans Frontières (MSF) established an acute trauma hospital in Aden, Yemen, treating mainly war-wounded civilians, and implemented an antimicrobial stewardship (AMS) programme. This study aimed to describe clinical characteristics and identify antibiotic susceptibility patterns representative of patients treated with antibiotics.

Methods

Retrospective cross-sectional study using routinely collected data from all patients treated with antibiotics in the MSF-Aden Acute Trauma hospital between January 2018 and June 2021. Routine clinical data from patients' files was entered into an AMS electronic database and microbiological data were entered into WHONET. Both databases were imported and merged in REDCap and analysed using RStudio.

Results

Three hundred and sixty-three of 481 (75%) included patients were injured by violence-related trauma. Most were men aged 19-45 years (n = 331; 68.8%). In total, 598 infections were diagnosed and treated. MDR organisms were identified in 362 (60.5%) infections in 311 (65%) patients. Skin and soft-tissue infections (SSTIs) (n = 143; 24%) were the most common, followed by osteomyelitis (n = 125; 21%) and intra-abdominal-infections (IAIs) (n = 116; 19%), and 111 (19%) secondary bloodstream infections were identified. Escherichia coli was the most frequently identified pathogen, causing IAI (n = 87; 28%) and SSTI (n = 43; 16%), while Staphylococcus aureus caused mainly osteomyelitis (n = 84; 19%). Most Gram-negatives were ESBL producers, including E. coli (n = 193; 81.4%), Klebsiella pneumoniae (n = 72; 77.4%) and Enterobacter cloacae (n = 39; 50%) while most S. aureus were methicillin resistant (n = 93; 72.6%).

Conclusions

High rates of MDR were found. This information will facilitate a comprehensive review of the empirical antibiotic treatment guidelines.

Stability study in selected conditions and biofilm-reducing activity of phages active against drug-resistant Acinetobacter baumannii

Acinetobacter baumannii is currently a serious threat to human health, especially to people with immunodeficiency as well as patients with prolonged hospital stays and those undergoing invasive medical procedures. The ever-increasing percentage of strains characterized by multidrug resistance to widely used antibiotics and their ability to form biofilms make it difficult to fight infections with traditional antibiotic therapy. In view of the above, phage therapy seems to be extremely attractive. Therefore, phages with good storage stability are recommended for therapeutic purposes. In this work, we present the results of studies on the stability of 12 phages specific for A. baumannii under different conditions (including temperature, different pH values, commercially available disinfectants, essential oils, and surfactants) and in the urine of patients with urinary tract infections (UTIs). Based on our long-term stability studies, the most optimal storage method for the A. baumannii phage turned out to be - 70 °C. In contrast, 60 °C caused a significant decrease in phage activity after 1 h of incubation. The tested phages were the most stable at a pH from 7.0 to 9.0, with the most inactivating pH being strongly acidic. Interestingly, ethanol-based disinfectants caused a significant decrease in phage titers even after 30 s of incubation. Moreover, copper and silver nanoparticle solutions also caused a decrease in phage titers (which was statistically significant, except for the Acba_3 phage incubated in silver solution), but to a much lesser extent than disinfectants. However, bacteriophages incubated for 24 h in essential oils (cinnamon and eucalyptus) can be considered stable.

Occurrence and characterization of β-lactamase-producing bacteria in biomedical wastewater and in silico enhancement of antibiotic efficacy

Wastewater discharged from hospitals is a recognized contributor to the dissemination of antibiotic-resistant bacteria and their associated genetic traits into the environment. This study focused on the analysis of β-lactamase-producing pathogenic bacteria within untreated biomedical wastewater originating from various hospitals in Dhaka City, Bangladesh, as well as in silico evaluation and structural activity relationship mentioned antibiotics were evaluated. In silico drug design techniques were applied to identify the relationship with how the functional group impacts the binding energy. Out of the 184 isolates obtained from well-established hospital sewage discharge points in Dhaka, 89 were identified as β-lactamase positive. These bacteria were subjected to antimicrobial susceptibility testing using the VITEK-2 assay, and their profiles of extended-spectrum beta-lactamase (ESBL) production were determined through molecular methodologies. Among the β-lactamase-positive isolates, considerable resistance was observed, particularly against ampicillin, Ceftriaxone, Cefuroxime, and Meropenem. The predominant resistant species included Escherichia coli, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter cloacae. The study identified the prevalence of ESBL-producing genes, with blaNDM-1 being the most prevalent, followed by blaOXA-1, blaSHV, blaCTX-M, and blaKPC. None of the isolates carried the blaTEM gene. In addition to characterizing these bacteria, the research explored ways to enhance the binding energy of four existing antibiotics as new inhibitors through computational studies. The findings revealed significant improvements in binding energy. Specifically, Meropenem initially exhibited a binding energy of -7.5 kcal/mol, notably increasing to -8.3 kcal/mol after modification. With an initial binding energy was only -7.9 kcal/mol, Ampicillin experienced an enhancement, reaching -8.0 kcal/mol post-modification. Similarly, Ceftriaxone, with an initial binding energy of -8.2 kcal/mol, increased to -8.5 kcal/mol following structural adjustments. Finally, Cefuroxime, initially registering a binding energy of -7.1 kcal/mol, substantially increased to -8.9 kcal/mol after modification. This finding establishes a foundation for future investigations in the development of modified antibiotics to address the issue of antibiotic resistance. It presents prospective remedies for the persistent problem of antibiotic-resistant bacteria in healthcare and the environment.

Detection of Aminoglycoside Modifying Enzyme (AME) genes in Acinetobacter baumannii isolates and the inhibitory effect of efflux pump activity on drug susceptibility pattern

INTRODUCTION

The development of aminoglycoside modifying enzymes (AMEs) and increased efflux activity are considered important aminoglycosides resistance mechanisms.

AIM

This study is focused on the detection of the AMEs gene and assessing the effect of efflux pump inhibitor on the reversal of A. baumannii drug susceptibility.

METHODOLOGY

Bacterial DNA was amplified using AMEs gene-specific primers. Isolates were also investigated for efflux pump activity using efflux pump inhibitor (EPI) i.e. Carbonyl cyanide m-chlorophenyl hydrazone (CCCP) and the impact of both mechanisms was analyzed.

RESULTS

Among A. baumannii isolates, 55% isolates (n ​= ​22/40) were identified to have aminoglycoside modifying enzymes genes; ant(3')-I gene (50%, 11/22), aac(6')-Ib gene (45.4%, 10/22), aph(3')-I gene (18.1%, 4/22) and aac(3)-I (9.1%, 2/22). Total 70% isolates have shown MIC alteration in different classes of drugs in response to EPI-CCCP. Such alteration was found in 100% amikacin sensitive and 58.6% amikacin resistant, 93.7% and 57.1% gentamicin sensitive and resistant isolates respectively.

CONCLUSION

The presence of aminoglycosides modifying enzymes was frequent among aminoglycosides resistant A. baumannii isolates and the coexistence of efflux pumps activity also plays an important role to increase drug resistance.

REPOSITORIES

Genbank and their accession numbers are MT903331[aac(3)-I], MT903332 MT903333 [ant(3')-I], MT903334, MT903335 [aph(3')-I)] and MT903336, MT940242 [ aac(6')-Ib].

The VBNC state: a fundamental survival strategy of Acinetobacter baumannii

IMPORTANCE

Currently, the viable but non-culturable (VBNC) state is an underappreciated niche for pathogenic bacteria which provides a continuous source for recurrent infections and transmission. We propose the VBNC state to be a global persistence mechanism used by various A. baumannii strains to cope with many stresses it is confronted with in the clinical environment and in the host. This requires a novel strategy to detect viable cells of this pathogen that is not only based on plating assays.

Antibiotic Resistance Pattern in Intensive Care Units in a Large Referral Hospital in Iran

Background & Objective

Antibiotic resistance, especially in the form of multidrug-resistant (MDR), is a big problem, especially in intensive care units (ICUs). This study aimed to evaluate antibiotic resistance and MDR patterns among patients hospitalized in the ICUs in one of the large referral centers in Iran.

Methods

The present study was conducted at Imam Khomeini Hospital in Tehran (a great referral hospital), which admits critically ill patients requiring ICU services. To determine the rate of positive cultures for resistant strains, the patient's blood specimens were sent to the laboratory of the hospital for inoculation on proper culture media within 2 hours of extraction. Antimicrobial susceptibility tests were done using the Bauer-Kirby disk diffusion method.

Results

A total of 1,755 samples were collected from the patients to assess microbial strains and antibiotic resistance. The most common microbial strains detected in the cultures extracted from peripheral blood samples were Klebsiella pneumonia (22.1%), Staphylococcus epidermidis (7.9%) and another coagulase-negative Staphylococcus (15.0%). The antibiogram test showed antibiotic resistance in 1,509 cases, leading to a resistance prevalence rate of 85.9%. The most common antimicrobial resistance observed was against cotrimoxazole (61.7%), ciprofloxacin (51.3%), imipenem (50.0%), and ampicillin (49.6%). The rate of MDR was found to be 96.3%.

Conclusion

In Iran's ICUs, a significantly high level of antibiotic resistance may be seen especially the MDR pattern, which indicates the need to change the pattern of prescribing and managing these drugs in ICU centers.

Global genomic epidemiology of chromosomally mediated non-enzymatic carbapenem resistance in Acinetobacter baumannii: on the way to predict and modify resistance

Introduction

Although carbapenemases are frequently reported in resistant A. baumannii clinical isolates, other chromosomally mediated elements of resistance that are considered essential are frequently underestimated. Having a wide substrate range, multidrug efflux pumps frequently underlie antibiotic treatment failure. Recognizing and exploiting variations in multidrug efflux pumps and penicillin-binding proteins (PBPs) is an essential approach in new antibiotic drug discovery and engineering to meet the growing challenge of multidrug-resistant Gram-negative bacteria.

Methods

A total of 980 whole genome sequences of A. baumannii were analyzed. Nucleotide sequences for the genes studied were queried against a custom database of FASTA sequences using the Bacterial and Viral Bioinformatics Resource Center (BV-BRC) system. The correlation between different variants and carbapenem Minimum Inhibitory Concentrations (MICs) was studied. PROVEAN and I-Mutant predictor suites were used to predict the effect of the studied amino acid substitutions on protein function and protein stability. Both PsiPred and FUpred were used for domain and secondary structure prediction. Phylogenetic reconstruction was performed using SANS serif and then visualized using iTOL and Phandango.

Results

Exhibiting the highest detection rate, AdeB codes for an important efflux-pump structural protein. T48V, T584I, and P660Q were important variants identified in the AdeB-predicted multidrug efflux transporter pore domains. These can act as probable targets for designing new efflux-pump inhibitors. Each of AdeC Q239L and AdeS D167N can also act as probable targets for restoring carbapenem susceptibility. Membrane proteins appear to have lower predictive potential than efflux pump-related changes. OprB and OprD changes show a greater effect than OmpA, OmpW, Omp33, and CarO changes on carbapenem susceptibility. Functional and statistical evidence make the variants T636A and S382N at PBP1a good markers for imipenem susceptibility and potential important drug targets that can modify imipenem resistance. In addition, PBP3_370, PBP1a_T636A, and PBP1a_S382N may act as potential drug targets that can be exploited to counteract imipenem resistance.

Conclusion

The study presents a comprehensive epidemiologic and statistical analysis of potential membrane proteins and efflux-pump variants related to carbapenem susceptibility in A. baumannii, shedding light on their clinical utility as diagnostic markers and treatment modification targets for more focused studies of candidate elements.

Active Surveillance of Antimicrobial Resistance and Carbapenemase-Encoding Genes According to Sites of Care and Age Groups in Mexico: Results from the INVIFAR Network

We analyzed the antimicrobial resistance (AMR) data of 6519 clinical isolates of Escherichia coli (n = 3985), Klebsiella pneumoniae (n = 775), Acinetobacter baumannii (n = 163), Pseudomonas aeruginosa (n = 781), Enterococcus faecium (n = 124), and Staphylococcus aureus (n = 691) from 43 centers in Mexico. AMR assays were performed using commercial microdilution systems (37/43) and the disk diffusion susceptibility method (6/43). The presence of carbapenemase-encoding genes was assessed using PCR. Data from centers regarding site of care, patient age, and clinical specimen were collected. According to the site of care, the highest AMR was observed in E. coli, K. pneumoniae, and P. aeruginosa isolates from ICU patients. In contrast, in A. baumannii, higher AMR was observed in isolates from hospitalized non-ICU patients. According to age group, the highest AMR was observed in the ≥60 years age group for E. coli, E. faecium, and S. aureus, and in the 19-59 years age group for A. baumannii and P. aeruginosa. According to clinical specimen type, a higher AMR was observed in E. coli, K. pneumoniae, and P. aeruginosa isolates from blood specimens. The most frequently detected carbapenemase-encoding gene in E. coli was blaNDM (84%).

Prevalence of Carbapenem Resistance Genes among Acinetobacter baumannii Isolated from a Teaching Hospital in Taiwan

The problem of antibiotic-resistant strains has become a global public issue; antibiotic resistance not only limits the choice of treatments but also increases morbidity, mortality and treatment costs. The multi-drug resistant Acinetobacter baumannii is occurring simultaneously in hospitals and has become a major public health issue worldwide. Although many medical units have begun to control the use of antibiotics and paid attention to the issue of drug resistance, understanding the transmission pathways of clinical drug-resistant bacteria and drug-resistant mechanisms can be effective in real-time control and prevent the outbreak of antibiotic-resistant pathogens. In this study, a total of 154 isolates of Acinetobacter baumannii obtained from Chia-Yi Christian Hospital in Taiwan were collected for specific resistance genotyping analysis. Ten genes related to drug resistance, including blaOXA-51-like, blaOXA-23-like, blaOXA-58-like, blaOXA-24-like, blaOXA-143-like, tnpA, ISAba1, blaPER-1, blaNDM and blaADC, and the repetitive element (ERIC2) were selected for genotyping analysis. The results revealed that 135 A. baumannii isolates (87.6%) carried the blaOXA-51-like gene, 4.5% of the isolates harbored the blaOXA-23-like gene, and 3.2% of the isolates carried the blaOXA-58-like gene. However, neither the blaOXA-24-like nor blaOXA-143-like genes were detected in the isolates. Analysis of ESBL-producing strains revealed that blaNDM was not found in the test strains, but 38.3% of the test isolates carried blaPER-1. In addition, blaADC, tnpA and ISAba1genes were found in 64.9%, 74% and 93% of the isolates, respectively. Among the carbapenem-resistant strains of A. baumannii, 68% of the isolates presenting a higher antibiotic resistance carried both tnpA and ISAba1 genes. Analysis of the relationship between their phenotypes (antibiotic resistant and biofilm formation) and genotypes (antibiotic-resistant genes and biofilm-related genes) studied indicated that the bap, ompA, ISAba1and blaOXA-51 genes influenced biofilm formation and antibiotic resistance patterns based on the statistical results of a hierarchical clustering dendrogram. The analysis of the antibiotic-resistant mechanism provides valuable information for the screening, identification, diagnosis, treatment and control of clinical antibiotic-resistant pathogens, and is an important reference pointer to prevent strains from producing resistance.

Photodynamic Therapy and Its Synergism with Melittin Against Drug-Resistant Acinetobacter baumannii Isolates with High Biofilm Formation Ability

Drug-resistant biofilm producer A. baumannii isolates are a global concern that warns researchers about the development of new treatments. This study was designed to analyze the effect of photodynamic therapy (PDT) as monotherapy and associated with melittin on multidrug-resistant A. baumannii isolates. Sub-lethal doses of photosensitizer, LED, and PDT were determined. The PDT effect on the biofilm and expression of biofilm-associated genes was evaluated by scanning electron microscopy and quantitative real-time PCR (qRT-PCR) methods, respectively. The synergistic effect of PDT and melittin on the survival of MDR/XDR strong biofilm producer isolates was evaluated by checkerboard assay. Survival rates were significantly decreased at the lowest concentration of 12.5-50 μg/ml in 4 min at an energy density of 93.75 J/cm2 (P < 0.05). The optimized PDT method had a bactericidal effect against all tested groups, and the mean expression levels of csu, abaI, bap, and ompA genes in the strong biofilm producers were decreased significantly compared to the control group. The combined effect of LED and melittin successfully reduced the MDR/XDR A. baumannii strong biofilm producers' growth from 3.1 logs. MB-mediated aPDT and combined treatment of PDT with melittin, which has been investigated for the first time in this study, can be an efficient strategy against MDR/XDR A. baumannii isolates with strong biofilm production capacity.

The Potential of Bacteriophage-Antibiotic Combination Therapy in Treating Infections with Multidrug-Resistant Bacteria

The growing threat of antibiotic resistance is a significant global health challenge that has intensified in recent years. The burden of antibiotic resistance on public health is augmented due to its multifaceted nature, as well as the slow-paced and limited development of new antibiotics. The threat posed by resistance is now existential in phage therapy, which had long been touted as a promising replacement for antibiotics. Consequently, it is imperative to explore the potential of combination therapies involving antibiotics and phages as a feasible alternative for treating infections with multidrug-resistant bacteria. Although either bacteriophage or antibiotics can potentially treat bacterial infections, they are each fraught with resistance. Combination therapies, however, yielded positive outcomes in most cases; nonetheless, a few combinations did not show any benefit. Combination therapies comprising the synergistic activity of phages and antibiotics and combinations of phages with other treatments such as probiotics hold promise in the treatment of drug-resistant bacterial infections.

Conjugates of monocyclic β-lactams and siderophore mimetics: a patent evaluation (WO2023023393)

INTRODUCTION

β-Lactams, which include monobactams, remain the most important class of antibiotics worldwide. Aztreonam, the only monobactam in clinical use, has remarkable activity against many Gram-negative bacteria, but limited activity against some of the most problematic multidrug-resistant (MDR) pathogens, such as MDR Pseudomonas aeruginosa and Acinetobacter baumannii co-expressing extended-spectrum- and metallo-β-lactamases, which can inactivate aztreonam by hydrolysis.

AREAS COVERED

Structurally novel siderophore-conjugated aztreonam derivatives with improved antibacterial properties against several high-priority pathogens are claimed. This invention reports that sidechain extension of aztreonam is tolerated; the coupling of its aminothiazoloxime carboxylic acid part with a siderophore mimetic significantly improved the antibacterial activity against several problematic strains, including MDR A. baumannii isolates with carbapenemase/cephalosporinase activity.

EXPERT OPINION

Finding new strategies to tackle bacterial resistance to β-lactam antibiotics is critical. Considering that β lactams are validated and safe drugs, this research may stimulate the field to develop new ideas in the arena of antimicrobial drug discovery, particularly with respect to siderophore mimetics.

Metabolomics revealed mechanism for the synergistic effect of sulbactam, polymyxin-B and amikacin combination against Acinetobacter baumannii

Introduction

The emergence of multidrug-resistant (MDR) Acinetobacter baumannii prompts clinicians to consider treating these infections with polymyxin combination.

Methods

Metabolomic analysis was applied to investigate the synergistic effects of polymyxin-B, amikacin and sulbactam combination therapy against MDR A. baumannii harboring OXA-23 and other drug resistant genes. The drug concentrations tested were based on their clinical breakpoints: polymyxin-B (2 mg/L), amikacin (16 mg/L), polymyxin-B/amikacin (2/16 mg/L), and polymyxin-B/amikacin/sulbactam (2/16/4 mg/L).

Results

The triple antibiotic combination significantly disrupted levels of metabolites involved in cell outer membrane structure including fatty acids, glycerophospholipids, nucleotides, amino acids and peptides as early as 15 min after administration. Amikacin and polymyxin-B alone perturbed a large number of metabolites at 15 min and 1 h, respectively, but the changes in metabolites were short-lived lasting for less than 4 h. In contrast, the combination treatment disrupted a large amount of metabolites beyond 4 h. Compared to the double-combination, the addition of sulbactam to polymyxin-B/amikacin combination produce a greater disorder in A. baumannii metabolome that further confer susceptibility of bacteria to the antibiotics.

Conclusion

The metabolomic analysis identified mechanisms responsible for the synergistic activities of polymyxin-B/amikacin/sulbactam against MDR A. baumannii.

A Bacteriophage Microgel Effectively Treats the Multidrug-Resistant Acinetobacter baumannii Bacterial Infections in Burn Wounds

Multidrug-resistant (MDR) Acinetobacter baumannii (A. baumannii) is one of the major pathogens present in burn wound infections. Biofilm formation makes it further challenging to treat with clinically available antibiotics. In the current work, we isolated the A. baumannii-specific bacteriophages (BPABΦ1), loaded into the chitosan microparticles followed by dispersion in gel, and evaluated therapeutic efficacy against MDR A. baumannii clinical strains. Isolated BPABΦ1 were found to belong to the Corticoviridae family, with burst size 102.12 ± 2.65 PFUs per infected host cell. The BPABΦ1 loaded chitosan microparticles were evaluated for quality attributes viz. size, PDI, surface morphology, in vitro release, etc. The developed formulation exhibited excellent antibiofilm eradication potential in vitro and effective wound healing after topical application.

CRISPR-Based Gene Editing in Acinetobacter baumannii to Combat Antimicrobial Resistance

Antimicrobial resistance (AMR) poses a significant threat to the health, social, environment, and economic sectors on a global scale and requires serious attention to addressing this issue. Acinetobacter baumannii was given top priority among infectious bacteria because of its extensive resistance to nearly all antibiotic classes and treatment options. Carbapenem-resistant A. baumannii is classified as one of the critical-priority pathogens on the World Health Organization (WHO) priority list of antibiotic-resistant bacteria for effective drug development. Although available genetic manipulation approaches are successful in A. baumannii laboratory strains, they are limited when employed on newly acquired clinical strains since such strains have higher levels of AMR than those used to select them for genetic manipulation. Recently, the CRISPR-Cas (Clustered regularly interspaced short palindromic repeats/CRISPR-associated protein) system has emerged as one of the most effective, efficient, and precise methods of genome editing and offers target-specific gene editing of AMR genes in a specific bacterial strain. CRISPR-based genome editing has been successfully applied in various bacterial strains to combat AMR; however, this strategy has not yet been extensively explored in A. baumannii. This review provides detailed insight into the progress, current scenario, and future potential of CRISPR-Cas usage for AMR-related gene manipulation in A. baumannii.

Acinetobacter baumannii in the critically ill: complex infections get complicated

Acinetobacter baumannii is increasingly associated with various epidemics, representing a serious concern due to the broad level of antimicrobial resistance and clinical manifestations. During the last decades, A. baumannii has emerged as a major pathogen in vulnerable and critically ill patients. Bacteremia, pneumonia, urinary tract, and skin and soft tissue infections are the most common presentations of A. baumannii, with attributable mortality rates approaching 35%. Carbapenems have been considered the first choice to treat A. baumannii infections. However, due to the widespread prevalence of carbapenem-resistant A. baumannii (CRAB), colistin represents the main therapeutic option, while the role of the new siderophore cephalosporin cefiderocol still needs to be ascertained. Furthermore, high clinical failure rates have been reported for colistin monotherapy when used to treat CRAB infections. Thus, the most effective antibiotic combination remains disputed. In addition to its ability to develop antibiotic resistance, A. baumannii is also known to form biofilm on medical devices, including central venous catheters or endotracheal tubes. Thus, the worrisome spread of biofilm-producing strains in multidrug-resistant populations of A. baumannii poses a significant treatment challenge. This review provides an updated account of antimicrobial resistance patterns and biofilm-mediated tolerance in A. baumannii infections with a special focus on fragile and critically ill patients.

Infection of Endothelial Cells with Acinetobacter baumannii Reveals Remodelling of Mitochondrial Protein Complexes

Acinetobacter baumannii is an antibiotic-resistant, Gram-negative pathogen that causes a multitude of nosocomial infections. However, pathogenicity mechanisms and the host cell response during infection remain unclear. In this study, we determined virulence traits of A. baumannii clinical isolates belonging to the most widely disseminated international clonal lineage, international cluster 2 (IC2), in vitro and in vivo. Complexome profiling of primary human endothelial cells with A. baumannii revealed that mitochondria, and in particular complexes of the electron transport chain, are important host cell targets. Infection with highly virulent A. baumannii remodelled assembly of mitochondrial protein complexes and led to metabolic adaptation. These were characterized by reduced mitochondrial respiration and glycolysis in contrast to those observed in infection with low-pathogenicity A. baumannii. Perturbation of oxidative phosphorylation, destabilization of mitochondrial ribosomes, and interference with mitochondrial metabolic pathways were identified as important pathogenicity mechanisms. Understanding the interaction of human host cells with the current global A. baumannii clone is the basis to identify novel therapeutic targets. IMPORTANCE Virulence traits of Acinetobacter baumannii isolates of the worldwide most prevalent international clonal lineage, IC2, remain largely unknown. In our study, multidrug-resistant IC2 clinical isolates differed substantially in their virulence potential despite their close genetic relatedness. Our data suggest that, at least for some isolates, mitochondria are important target organelles during infection of primary human endothelial cells. Complexes of the respiratory chain were extensively remodelled after infection with a highly virulent A. baumannii strain, leading to metabolic adaptation characterized by severely reduced respiration and glycolysis. Perturbations of both mitochondrial morphology and mitoribosomes were identified as important pathogenicity mechanisms. Our data might help to further decipher the molecular mechanisms of A. baumannii and host mitochondrial interaction during infection.

Risk factors for colonization with multidrug-resistant Gram-negative bacteria and Clostridioides difficile in Long Term Care Facilities (LTCFs) residents: the evidence from 27 facilities in a high endemic setting

Introduction

Residency in LTCFs increases the likelihood of colonization with multidrug resistant Gram-negative bacteria (MDR-GNB). We assessed the prevalence and risk factors for enteric colonization by III-generation cephalosporins-resistant and carbapenem-resistant (CR) GNB in a large group of LTCFs in a high endemic setting. We also assessed the prevalence and risk factors for C. difficile colonization.

Methods

A point prevalence survey with rectal screening (RS) was conducted in 27 LTCFs in north Italy. Epidemiological and clinical variables on the survey day, history of hospitalization and surgery within one year, and antibiotics within three months, were collected. The presence of III-generation cephalosporin resistant and CR GNB was assessed using a selective culture on chromogenic medium and PCR for carbapenemase detection. The presence of C. difficile was assessed using ELISA for GDH and RT-PCR to identify toxigenic strains. Multi-variable analyses were performed using two-level logistic regression models.

Results

In the study period 1947 RSs were performed. The prevalence of colonization by at least one GNB resistant to III-generation cephalosporin was 51% (E. coli 65%, K. pneumoniae 14% of isolates). The prevalence of colonization by CR GNB was 6%. 6% of all isolates (1150 strains) resulted in a carbapenem-resistant K. pneumoniae, and 3% in a carbapenem-resistant E. coli. KPC was the most frequent carbapenemase (73%) identified by PCR, followed by VIM (23%). The prevalence of colonization by C. difficile was 11.7%. The presence of a medical device (OR 2.67) and previous antibiotic use (OR 1.48) were significantly associated with III-generation cephalosporin resistant GNB colonization. The presence of a medical device (OR 2.67) and previous hospitalization (OR 1.80) were significantly associated with CR GNB. The presence of a medical device (OR 2.30) was significantly associated with C. difficile colonization. Main previously used antibiotic classes were fluoroquinolones (32% of previously treated subjects), III-generation cephalosporins (21%), and penicillins (19%).

Conclusion

Antimicrobial stewardship in LTCFs is a critical issue, being previous antibiotic treatment a risk factor for colonization by MDR-GNB. The prevalence of colonization by III-generation cephalosporin and CR GNB among LTCF residents also underlines the importance to adhere to hand hygiene indications, infection prevention and control measures, and environmental hygiene protocols, more achievable than rigorous contact precautions in this type of social setting.

Generation of Synthetic Acinetobacter baumannii-Specific Nanobodies

The bacterial pathogen Acinetobacter baumannii is a leading cause of drug-resistant infections. Here, we investigated the potential of developing nanobodies that can recognize A. baumannii over other Gram-negative bacteria. Through generation and panning of a synthetic nanobody library, we identified several potential lead candidates. We demonstrate how incorporation of next-generation sequencing analysis can aid in the selection of lead candidate nanobodies. Using monoclonal phage display, we validated the binding of lead nanobodies to A. baumannii. Subsequent purification and biochemical characterization revealed one particularly robust nanobody that specifically bound select A. baumannii strains compared to other common drug-resistant pathogens. These findings support the potential for nanobodies to selectively target A. baumannii and the identification of lead candidates for future investigation.

Navigating Available Treatment Options for Carbapenem-Resistant Acinetobacter baumannii-calcoaceticus Complex Infections

Carbapenem-resistant Acinetobacter baumannii-calcoaceticus complex (CRAB) is one of the top-priority pathogens for new antibiotic development. Unlike other antibiotic-resistant threats, none of the available therapies have been shown to consistently reduce mortality or improve patient outcomes in clinical trials. Antibiotic combination therapy is routinely used in clinical practice; however, the preferred combination has not been defined. This narrative review focuses on evidence-based solutions for the treatment of invasive CRAB infections. We dissect the promise and perils of traditional agents used in combination, such as colistin, sulbactam, and the tetracyclines, and offer clinical pearls based on our interpretation of the available data. Next, we investigate the merits of newly developed β-lactam agents like cefiderocol and sulbactam-durlobactam, which have demonstrated contrasting results in recent randomized clinical trials. The review concludes with the authors' perspective on the evolving treatment landscape for CRAB infections, which is complicated by limited clinical data, imperfect treatment options, and a need for future clinical trials. We propose that effective treatment for CRAB infections requires a personalized approach that incorporates host factors, the site of infection, pharmacokinetic-pharmacodynamic principles, local molecular epidemiology of CRAB isolates, and careful interpretation of antibiotic susceptibility testing results. In most clinical scenarios, a dose-optimized, sulbactam-based regimen is recommended with the addition of at least one other in vitro active agent. Should sulbactam-durlobactam receive regulatory approval, recommendations will need to be re-evaluated with the most recent evidence.

Population Pharmacokinetics and AUC-Guided Dosing of Tobramycin in the Treatment of Infections Caused by Glucose-Nonfermenting Gram-Negative Bacteria

PURPOSE

Tobramycin (TOB) exhibits variable pharmacokinetic properties due to the clinical condition of patients. This study aimed to investigate the AUC-guided dosing of TOB based on population pharmacokinetic analysis in the treatment of infections caused by Pseudomonas aeruginosa, Acinetobacter baumannii, and Stenotrophomonas maltophilia.

METHODS

This retrospective study was conducted between January 2010 and December 2020 after obtaining approval from our institutional review board. For 53 patients who received therapeutic drug monitoring of TOB, a population pharmacokinetic model was developed with covariates of estimated glomerular filtration rate using serum creatinine (eGFRcre) on clearance (CL) and weight on both CL and V_d in exponential error modeling (CL = 2.84 × [weight/70] × eGFRcre^0.568, interindividual variability [IIV] = 31.1%; V_d = 26.3 × [weight/70], IIV = 20.2%; residual variability = 28.8%).

FINDINGS

The final regression model for predicting 30-day mortality was developed with risk factors of AUC during a 24-hour period after the first dose to MIC ratio (odds ratio [OR] = 0.996; 95% CI, 0.968-1.003) and serum albumin (OR = 0.137; 95% CI, 0.022-0.632). The final regression model for predicting acute kidney injury was developed with the risk factors of C-reactive protein (OR = 1.136; 95% CI, 1.040-1.266) and AUC during a 72-hour period after the first dose (OR = 1.004; 95% CI, 1.000-1.001). A dose of 8 or 15 mg/kg was beneficial for achievement of AUC during a 24-hour period after the first dose/MIC >80 and trough concentration <1 µg/mL in patients with preserved kidney function and TOB CL >4.47 L/h/70 kg in the events of MIC of 1 or 2 µg/mL, respectively. We propose that the first dose of 15, 11, 10, 8, and 7 mg/kg for eGFRcre >90, 60 to 89, 45 to 59, 30 to 44, and 15 to 29 mL/min/1.73 m² be followed by therapeutic drug monitoring at peak and 24 hours after the first dose.

IMPLICATIONS

This study suggests that TOB use encourages the replacement of trough- and peak-targeted dosing with AUC-guided dosing.

Revealing the single-channel characteristics of OprD (OccAB1) porins from hospital strains of Acinetobacter baumannii

Nowadays, reports of antimicrobial resistance (AMR) against many antibiotics are increasing because of their misapplication. With this rise, there is a serious decrease in the discovery and development of new types of antibiotics amid an increase in multi-drug resistance. Unfermented Acinetobacter baumannii from gram-negative bacteria, which is one of the main causes of nosocomial infections and multi-drug resistance, has 4 main kinds of antibiotic resistance mechanism: inactivating antibiotics by enzymes, reduced numbers of porins and changing of their target or cellular functions due to mutations, and efflux pumps. In this study, characterization of the possible mutations in OprD (OccAB1) porins from hospital strains of A. baumannii were investigated using single channel electrophysiology and compared with the standard OprD isolated from wild type ATCC 19,606. For this aim, 5 A. baumannii bacteria samples were obtained from patients infected with A. baumannii, after which OprD porins were isolated from these A. baumannii strains. OprD porins were then inserted in an artificial lipid bilayer and the current-voltage curves were obtained using electrical recordings through a pair of Ag/AgCl electrodes. We observed that each porin has a characteristic conductance and single channel recording, which then leads to differences in channel diameter. Finally, the single channel data have been compared with the gene sequences of each porin. It was interesting to find out that each porin isolated has a unique porin diameter and decreased anion selectivity compared to the wild type.

Addressing antibiotic resistance: computational answers to a biological problem?

The increasing prevalence of infections caused by antibiotic-resistant bacteria is a global healthcare crisis. Understanding the spread of resistance is predicated on the surveillance of antibiotic resistance genes within an environment. Bioinformatics and artificial intelligence (AI) methods applied to metagenomic sequencing data offer the capacity to detect known and infer yet-unknown resistance mechanisms, and predict future outbreaks of antibiotic-resistant infections. Machine learning methods, in particular, could revive the waning antibiotic discovery pipeline by helping to predict the molecular structure and function of antibiotic resistance compounds, and optimising their interactions with target proteins. Consequently, AI has the capacity to play a central role in guiding antibiotic stewardship and future clinical decision-making around antibiotic resistance.

Antimicrobial resistance and molecular characterization of Escherichia coli isolated from bovine mastitis samples in Nghe An province, Vietnam

Background and Aim

Vietnam's dairy sector is in its early phase of large-scale farming development. Therefore, mastitis in cows is always a concern to farm owners. This study aimed to determine the antimicrobial susceptibility, resistance, and virulence-related genes of Escherichia coli isolated from bovine mastitis in Nghe An province of Vietnam.

Materials and Methods

Fifty E. coli strains were isolated from the clinical cases and subjected to this study. All isolates were tested for antimicrobial susceptibility by the disk-diffusion method, as described by the Clinical and Laboratory Standards Institute. Antimicrobial and virulence genes were confirmed by polymerase chain reaction with specific primers.

Results

All isolates were resistant to lincomycin and sulfamethoxazole and sensitive to gentamicin, while other antimicrobials showed resistance from 2% to 90%. Multidrug resistance was confirmed in 46% of isolates, and none of them were identified as extended-spectrum beta-lactamase producers. From fifty strains tested for antimicrobial and virulence genes, six isolates harbored tetA, 6 tetB, 13 sul1, 15 sul2, 2 Intimin (eae), 1 iutA, and 3 stx2.

Conclusion

Antimicrobial and multidrug resistances are the main virulence factors of E. coli isolated from bovine mastitis in Vietnam. The virulence genes encoding adhesion, siderophore, Shiga-toxin-producing, and antimicrobials resistant were first reported in Vietnam with low prevalence and contributed to the pathogenesis.

A two-year retrospective study of multidrug-resistant Acinetobacter baumannii respiratory infections in critically Ill patients: Clinical and microbiological findings

BACKGROUND

Acinetobacter baumannii infection is a serious public health problem because it is highly resistant to antimicrobial therapy and causes a high fatality rate in critically ill patients. The aim of the study is to examine the demographics, microbiological findings, clinical presentation, and outcomes of multi-drug-resistant Acinetobacter baumannii respiratory infections in adult ICU intubated patients during COVID-19 pandemic.

METHODS

This study included 115 mechanically ventilated adult ICU patients who had multi-drug-resistant Acinetobacter baumannii retrieved from respiratory samples during the COVID-19 pandemic in Albaha, Saudi Arabia. The information was obtained from medical and laboratory files. Univariate analysis was used to compare gender, COVID-19 infection, and outcomes.

RESULTS

The rate of Acinetobacter baumanni respiratory infections among adult ICU patients was 6.2 %. Almost 93 % developed ventilator-associated pneumonia, and five of them developed bacteremia. The isolates had significant antibiotic resistance patterns, of which 3 % were pandrug-resistant bacteria. The death rate was 74 %, with major risk factors including sepsis, septic shock, VAP, liver diseases, and the use of inappropriate antibiotic therapy that lacked both colistin and tigecycline. Patients with COVID-19 coinfection had worse outcomes compared to non-COVID-19 patients.

CONCLUSIONS

The identification of MDR-AB as a threat highlights the importance of surveillance studies in this region.

Clinical efficacy and safety of cefiderocol for resistant Gram-negative infections: a real-life, single-centre experience

OBJECTIVES

Cefiderocol is a 'siderophore' cephalosporin active against Gram-negative bacteria, including carbapenem-resistant strains. Data on the use of cefiderocol in real life are limited. We evaluated the efficacy and safety of cefiderocol in the context of our hospital clinical practice.

METHODS

This was a single-centre, observational, retrospective clinical study. We collected data for all patients who received cefiderocol therapy in our hospital, with a focus on clinical outcomes and adverse events.

RESULTS

The study cohort included 28 patients, with a median age of 73 years (25-83 years) and a high burden of co-morbidities. Up to 45 Gram-negative isolates were cultured from the study patients, the most common pathogen being Acinetobacter baumannii (31.1%). Cefiderocol was mostly prescribed for pneumonia (37.8% of cases), bloodstream infection (24.4%), urinary tract infection (22.2%) and intra-abdominal infection (20%), and largely as salvage therapy (92.8%). Of the 18 patients for whom follow-up cultures were available, 14 (77.8%) achieved eradication of the causative micro-organism. Therapeutic success (improvement/resolution of infection) occurred in 64.3% of cases at 7 days and 50% at 14 days from treatment start. Treatment failed in 9 cases (32.1%). No effects on kidney, liver or bone marrow function were observed.

CONCLUSIONS

Cefiderocol showed fair efficacy and excellent tolerability in highly co-morbid patients with a range of multiresistant infections. It may be an option for infections due to colistin-resistant pathogens, when other regimens fail or in cases at risk of kidney dysfunction.

The effectiveness of colistin/levofloxacin compared to colistin/meropenem in the treatment of ventilator-associated pneumonia (VAP) caused by carbapenem-resistant Acinetobacter baumannii: a randomized controlled clinical trial

Background and purpose

The treatment of ventilator-associated pneumonia (VAP) caused by carbapenem-resistant Acinetobacter baumannii (CRAB) is still a great challenge. This study evaluated the effectiveness of the colistin/levofloxacin regimen compared to the usual colistin/meropenem regimen in the treatment of patients with VAP caused by CRAB.

Experimental approach

The patients with VAP were randomly assigned to experimental (n = 26) and control (n = 29) groups. The first group received IV colistin 4.5 MIU every 12 h + levofloxacin 750 mg IV daily, and the second group received IV colistin with the same dose + meropenem 1 g IV every 8 h for 10 days. The clinical (complete response, partial response, or treatment failure) and microbiological responses at the end of the intervention were recorded and compared between the two groups.

Findings/Results

The complete response rate was higher (n = 7; 35%) and the failure rate was lower (n = 4; 20%) in the experimental group than in the control group (n = 2; 8%, and n = 11; 44%, respectively), but the differences were not statistically significant. Even though the microbiological response rate was higher in the experimental group (n = 14; 70%) than in the control group (n = 12; 48%), the difference was not statistically significant. The mortality rate was 6 (23.10%) and 4 patients (13.8%) in the experimental and control groups, respectively (P = 0.490).

Conclusion and implication

The levofloxacin/colistin combination can be considered an alternative regimen to meropenem/colistin in the treatment of VAP caused by CRAB.

Molecular Characterization of Carbapenem-Resistant Acinetobacter baumannii with Special Reference to Carbapenemases: A Systematic Review

Carbapenemases are β-lactamase enzymes that hydrolyze a variety of β-lactams including carbapenem and belong to different Ambler classes (A, B, D). These enzymes can be encoded by plasmid or chromosomal-mediated genes. The major issues associated with carbapenemases-producing organisms are compromising the activity and increasing the resistance to carbapenems which are the last resort antibiotics used in treating serious infections. The global increase of pathogen, carbapenem-resistant A. baumannii has significantly threatened public health. Thus, there is a pressing need for a better understanding of this pathogen, to know the various carbapenem resistance encoding genes and dissemination of resistance genes from A. baumannii which help in developing strategies to overcome this problem. The horizontal transfer of resistant determinants through mobile genetic elements increases the incidence of multidrug, extensive drug, and Pan-drug resistant A. baumannii. Therefore, the current review aims to know the various mechanisms of carbapenem resistance, categorize and discuss carbapenemases encoding genes and various mobile genetic elements, and the prevalence of carbapenemase genes in recent years in A. baumannii from various geographical regions.

Anti-adhesion and antibiofilm activities of Lavandula mairei humbert essential oil against Acinetobacter baumannii isolated from hospital intensive care units

This study aimed to assess, for the first time, the anti-adhesion and antibiofilm effects of Lavandula mairei Humbert essential oil against multidrug resistant Acinetobacter baumannii. Scanning electron microscope was used for visualizing its antibiofilm activity and the effect of this oil on surface physicochemical parameters was examined as a possible anti-adhesive target. Chemical analysis of Lavandulaa mairei essential oil showed a high content of carvacrol composition (79.12%). The oil tested exhibited antibacterial efficacy with inhibition diameters of 33 to 37.33 mm and minimum inhibitory and bactericidal concentrations of 1.56 µl ml^-1. The oil inhibited adhesion by 83.66%, detach 73.30% of adherent cells and eliminated 64.02% of the biofilm compared to the untreated control. Lavandula mairei essential oil has proven its possible application as a preventive strategy by intervening in the initial adhesion of Acinetobacter baumannii to polystyrene.

Preferential Selection of Low-Frequency, Lipopolysaccharide-Modified, Colistin-Resistant Mutants with a Combination of Antimicrobials in Acinetobacter baumannii

Colistin, which targets lipopolysaccharide (LPS), is used as a last-resort drug against severe infections caused by drug-resistant Acinetobacter baumannii. However, A. baumannii possesses two colistin-resistance mechanisms. LPS modification caused by mutations in pmrAB genes is often observed in clinical isolates of multidrug-resistant Gram-negative pathogens. In addition to LPS modification, A. baumannii has a unique colistin resistance mechanism, a complete loss of LPS due to mutations in the lpxACD genes, which are involved in LPS biosynthesis. This study aimed to elucidate the detailed mechanism of the emergence of colistin-resistant A. baumannii using strains with the same genetic background. Various colistin-resistant strains were generated experimentally using colistin alone and in combination with other antimicrobials, such as meropenem and ciprofloxacin, and the mutation spectrum was analyzed. In vitro selection of A. baumannii in the presence of colistin led to the emergence of strains harboring mutations in lpxACD genes, resulting in LPS-deficient colistin-resistant strains. However, combination of colistin with other antimicrobials led to the selection of pmrAB mutant strains, resulting in strains with modified LPS (LPS-modified strains). Further, the LPS-deficient strains showed decreased fitness and increased susceptibility to many antibiotics and disinfectants. As LPS-deficient strains have a higher biological cost than LPS-modified strains, our findings suggested that pmrAB mutants are more likely to be isolated in clinical settings. We provide novel insights into the mechanisms of resistance to colistin and provide substantial solutions along with precautions for facilitating current research and treatment of colistin-resistant A. baumannii infections. IMPORTANCE Acinetobacter baumannii has developed resistance to various antimicrobial drugs, and its drug-resistant strains cause nosocomial infections. Controlling these infections has become a global clinical challenge. Carbapenem antibiotics are the frontline treatment drugs for infectious diseases caused by A. baumannii. For patients with infections caused by carbapenem-resistant A. baumannii, colistin-based therapy is often the only treatment option. However, A. baumannii readily acquires resistance to colistin. Many patients infected with colistin-resistant A. baumannii undergo colistin treatment before isolation of the colistin-resistant strain, and it is hypothesized that colistin resistance predominantly emerges under selective pressure during colistin therapy. Although the concomitant use of colistin and carbapenems has been reported to have a synergistic effect in vitro against carbapenem-resistant A. baumannii strains, our observations strongly suggest the need for attention to the emergence of strains with a modified lipopolysaccharide during treatment.

Development and evaluation of a rapid and sensitive multienzyme isothermal rapid amplification with a lateral flow dipstick assay for detection of Acinetobacter baumannii in spiked blood specimens

Purpose

This study aimed to establish the multienzyme isothermal rapid amplification with a lateral flow dipstick (MIRA-LFD) assay and evaluate its performance in detection of A. baumannii in spiked blood specimens.

Methods

The study was divided into two stages: a pilot study to establish the methodology and a clinical validation study to evaluate its performance. In the first step, we designed primers specific to detect A. baumannii, optimized the MIRA-LFD assay and analyzed its performance regarding limits of detection, reproducibility, specificity, and efficiency of detection using real-time PCR method. In the second step, we obtained 50 spiked blood isolates and detected these pathogens by MIRA-LFD assay. The MIRA-LFD time was 15 min from DNA sample amplification to complete pathogen detection.

Results

The developed MIRA-LFD assay displayed a detection limit of 6 CFU/mL for detecting A. baumannii, which was significantly better than that of real-time PCR method, and no cross-reactivity was observed in other non-A. baumannii studied. The results obtained with 50 spiked blood isolates suggested that the developed MIRA-LFD assay had high specificity and sensitivity for identifying A. baumannii.

Conclusions

This study demonstrates that the established MIRA-LFD assay is time-saving, more effective and sensitive, which may become a powerful tool for rapid and reliable diagnosis of bloodstream infection caused by A. baumannii in primary hospitals.

Incidence, characteristics and risk factors of hypofibrinogenemia associated with tigecycline: A multicenter retrospective study in China

Background: Tigecycline was recently found to cause coagulation disorders, especially hypofibrinogenemia, which may interfere with the administration of antimicrobial therapy. This study aimed to investigate the incidence and clinical characteristics of and risk factors for tigecycline-associated hypofibrinogenemia.

Methods: In this multicenter retrospective study, patients receiving tigecycline or imipenem–cilastatin to treat Gram-negative bacterial infections in nine Chinese tertiary hospitals between January 2020 and December 2020 were enrolled. Baseline data and coagulation variables were compared using cohort and case–control studies.

Results: Totals of 485 patients treated with tigecycline and 490 patients treated with imipenem–cilastatin were included in this study. Compared with imipenem–cilastatin, tigecycline was associated with reduced fibrinogen and prolonged activated partial thromboplastin time and prothrombin time (all p < 0.001), with the most remarkable change in fibrinogen (down by 48.0%). The incidence of hypofibrinogenemia in patients treated with tigecycline was >50%, with propensity score-matched analysis or not. The relative risk of hypofibrinogenemia with tigecycline versus imipenem–cilastatin was 2.947 (95% CI: 2.151–4.039) at baseline balance. Tigecycline-associated hypofibrinogenemia led to a higher incidence (12.1%) of bleeding events. However, none of supplemental therapies after withdrawal had an effect on the normalization of fibrinogen levels. The risk factors for tigecycline-associated hypofibrinogenemia were treatment duration ≥6 days (odds ratio [OR] 5.214, 95% confidence interval [CI] 2.957–9.191, p < 0.001), baseline fibrinogen <4 g/L (OR 4.625, 95% CI 2.911–7.346, p < 0.001), cumulative dose ≥1,000 mg (OR 2.637, 95% CI 1.439–4.832, p = 0.002), receiving CRRT (OR 2.436, 95% CI 1.179–5.031, p = 0.016), baseline PT > 14 s (OR 2.110, 95% CI 1.317–3.380, p = 0.002) and baseline total bilirubin >21 μmol/L (OR 1.867, 95% CI 1.107–3.147, p = 0.019), while the protective factor was skin and soft tissue infection (OR 0.110, 95% CI 0.026–0.473, p = 0.003).

Conclusion: The clinical characteristics of and risk factors for tigecycline-associated hypofibrinogenemia identified in this study can offer practical reference for the clinical management of patients.

Lipocalin-2 is an essential component of the innate immune response to Acinetobacter baumannii infection

Acinetobacter baumannii is an opportunistic pathogen and an emerging global health threat. Within healthcare settings, major presentations of A. baumannii include bloodstream infections and ventilator-associated pneumonia. The increased prevalence of ventilated patients during the COVID-19 pandemic has led to a rise in secondary bacterial pneumonia caused by multidrug resistant (MDR) A. baumannii. Additionally, due to its MDR status and the lack of antimicrobial drugs in the development pipeline, the World Health Organization has designated carbapenem-resistant A. baumannii to be its priority critical pathogen for the development of novel therapeutics. To better inform the design of new treatment options, a comprehensive understanding of how the host contains A. baumannii infection is required. Here, we investigate the innate immune response to A. baumannii by assessing the impact of infection on host gene expression using NanoString technology. The transcriptional profile observed in the A. baumannii infected host is characteristic of Gram-negative bacteremia and reveals expression patterns consistent with the induction of nutritional immunity, a process by which the host exploits the availability of essential nutrient metals to curtail bacterial proliferation. The gene encoding for lipocalin-2 (Lcn2), a siderophore sequestering protein, was the most highly upregulated during A. baumannii bacteremia, of the targets assessed, and corresponds to robust LCN2 expression in tissues. Lcn2^-/- mice exhibited distinct organ-specific gene expression changes including increased transcription of genes involved in metal sequestration, such as S100A8 and S100A9, suggesting a potential compensatory mechanism to perturbed metal homeostasis. In vitro, LCN2 inhibits the iron-dependent growth of A. baumannii and induces iron-regulated gene expression. To elucidate the role of LCN2 in infection, WT and Lcn2^-/- mice were infected with A. baumannii using both bacteremia and pneumonia models. LCN2 was not required to control bacterial growth during bacteremia but was protective against mortality. In contrast, during pneumonia Lcn2^-/- mice had increased bacterial burdens in all organs evaluated, suggesting that LCN2 plays an important role in inhibiting the survival and dissemination of A. baumannii. The control of A. baumannii infection by LCN2 is likely multifactorial, and our results suggest that impairment of iron acquisition by the pathogen is a contributing factor. Modulation of LCN2 expression or modifying the structure of LCN2 to expand upon its ability to sequester siderophores may thus represent feasible avenues for therapeutic development against this pathogen.

A lack of therapeutic options has prompted the World Health Organization to designate multidrug-resistant Acinetobacter baumannii as its priority critical pathogen for research into new treatment strategies. The mechanisms employed by A. baumannii to cause disease and the host tactics exercised to constrain infection are not fully understood. Here, we further characterize the innate immune response to A. baumannii infection. We identify nutritional immunity, a process where the availability of nutrient metals is exploited to restrain bacterial growth, as being induced during infection. The gene encoding for lipocalin-2 (Lcn2), a protein that can impede iron uptake by bacteria, is highly upregulated in infected mice, and corresponds to robust LCN2 detection in the tissues. We find that LCN2 is crucial to reducing mortality from A. baumannii bacteremia and inhibits dissemination of the pathogen during pneumonia. In wild-type and Lcn2-deficient mice, broader transcriptional profiling reveals expression patterns consistent with the known response to Gram-negative bacteremia. Although the role of LCN2 in infection is likely multifactorial, we find its antimicrobial effects are at least partly exerted by impairing iron acquisition by A. baumannii. Facets of nutritional immunity, such as LCN2, may be exploited as novel therapeutics in combating A. baumannii infection.

Drug Resistance among Major Non-fermenting Gram-negative Pathogens Isolated from Respiratory Tract Infections in a Tertiary Care Hospital of South Karnataka

Non-fermenting gram-negative bacteria (NFGNB) frequently exhibit drug resistance. The purpose of this study was to determine the drug resistance pattern among the NFGNB isolates causing respiratory tract infections (RTIs). A retrospective analysis of the antimicrobial susceptibility pattern of non-fermenters causing RTIs over four years (2016- 2019) was done and the change in drug resistance pattern was studied. A total of 653 cases were obtained that included 191 (29.2%) Moraxella catarrhalis, 283 (43.3%) Pseudomonas aeruginosa, and 132 (20.2%) Acinetobacter baumannii, 47 (7.2%) Stenotrophomonas maltophilia isolates. A higher resistance (82.6%) was observed for piperacillin-tazobactam and cefpirome, followed by imipenem (79.5%) and ciprofloxacin (76.5 %) for A. baumannii isolates. A sharp decline in resistance pattern for piperacillin, cefpirome, Imipenem and cefoperazone-sulbactam in 2019 and an increasing resistance to gentamycin and ciprofloxacin were noted. Among P. aeruginosa isolates, 94% aztreonam and 83.4% cefoperazone-sulbactam resistance were detected. There was an increased resistance for cefpirome and piperacillin and a decreased resistance for Imipenem was recorded in 2019. In cases of M. catarrhalis, 22.51% of isolates were resistant to ciprofloxacin, followed by erythromycin (18.32%) and tetracycline (17.80 %). S. maltophilia showed a 100% sensitivity for co-trimoxazole and 2.1% resistance for ciprofloxacin. A constantly changing antibiotic-resistant pattern of non-fermenters compels for a continuous update of drug-resistant trends through a longitudinal surveillance program in different geographical areas.

Human serum albumin (HSA) regulates the expression of histone-like nucleoid structure protein (H-NS) in Acinetobacter baumannii

According to the Centers for Disease Control and Prevention, Acinetobacter baumannii is listed among the most threatening pathogens. A. baumannii is mainly a nosocomial pathogen with a distinctive ability to survive in multiple environments. These characteristics together with this bacterium's ability to acquire antibiotic resistance determinants make it a notorious pathogen. The presence of human serum albumin (HSA) is associated with modification of expression levels in numerous genes. The presence of HSA in the culture medium is also correlated with a reduction in levels of the global suppressor histone-like nucleoid structure protein, H-NS. Comparative transcriptome analysis of the wild type and isogenic Δhns strains cultured in lysogeny broth (LB) in the presence or absence of HSA revealed that the expression of a subset of eleven genes are modified in the Δhns cultured in LB and the wild-type strain in the presence of HSA, pointing out these genes as candidates to be regulated by the presence of HSA through H-NS. Six and five of these genes were up- or down-regulated, respectively. Three of these genes have functions in quorum sensing (acdA, kar and fadD), one in quorum quenching (aidA), two in stress response (katE, ywrO), three in metabolism (phaC, yedL1, and yedL2), one in biofilm formation (csuAB), and one in β-oxidation of fatty acids (fadA). The regulation of these genes was assessed by: (i) transcriptional analysis and qPCR at the transcriptional level; and (ii) by determining the phenotypic characteristics of each function. The results of these studies support the hypothesis that HSA-mediated reduction of H-NS levels may be one very important regulatory circuit utilized by A. baumannii to adapt to selected environments, such as those where HSA-containing human fluids are abundant.

Apolipoprotein E mimetic peptide COG1410 combats pandrug-resistant Acinetobacter baumannii

The emergence of pandrug-resistant bacteria breaks through the last line of defense and raises fear among people of incurable infections. In the post-antibiotic era, the pharmaceutical field turns to seek non-conventional anti-infective agents. Antimicrobial peptides are considered a prospective solution to the crisis of antimicrobial resistance. In this study, we evaluated the antimicrobial efficiency of an ApoE mimetic peptide, COG1410, which has been confirmed to exhibit strong neural protective activity and immunomodulatory function. COG1410 showed potent antimicrobial activity against pandrug-resistant Acinetobacter baumannii, even eliminating large inocula (108 CFU/ml) within 30 min. LC99.9 in PBS and 50% pooled human plasma was 2 μg/ml (1.4 μM) and 8 μg/ml (5.6 μM), respectively. Moreover, COG1410 exhibited biofilm inhibition and eradication activity, excellent stability in human plasma, and a low propensity to induce resistance. Although COG1410 easily entered bacterial cytoplasm and bound to DNA nonspecifically, the major mechanism of COG1410 killing was to disrupt the integrity of cell membrane and lead to leakage of cytoplasmic contents, without causing obvious pores on the cell surface or cell lysis. Additionally, transcriptome analysis showed that treatment with COG1410-enriched genes involved a series of oxidation–reduction processes. DCFH-DA probe detected an increased ROS level in the presence of COG1410, indicating ROS was another hit of this AMP. Furthermore, the action of COG1410 did not depend on the electronic interaction with the LPS layer, in contrast to polymyxin B. The strong synergistic interaction between COG1410 and polymyxin B dramatically reduced the working concentration of COG1410, expanding the safety window of the application. C. elegans infection model showed that combined therapy of COG1410 and polymyxin B was capable of significantly rescuing the infected nematodes. Taken together, our study demonstrates that COG1410 is a promising drug candidate in the battle against pandrug-resistant A. baumannii.

A Randomized Controlled Trial of Colistin Combined with Sulbactam: 9 g per Day versus 12 g per Day in the Treatment of Extensively Drug-Resistant Acinetobacter baumannii Pneumonia: An Interim Analysis

Extensively drug-resistant A. baumannii (XDRAB) pneumonia has a high mortality rate in hospitalized patients. One of the recommended treatments is colistin combined with sulbactam; however, the optimal dosage of sulbactam is unclear. In an open-label, superiority, randomized controlled trial, patients diagnosed with XDRAB pneumonia were randomly assigned (1:1) to receive colistin in combination with sulbactam at either 9 g/day or 12 g/day. The primary outcome was the 28-day mortality rate in the intention-to-treat population. A total of 88 patients received colistin in combination with sulbactam at a dosage of either 12 g/day (n = 45) or 9 g/day (n = 43). Trends toward a lower mortality rate were observed in the 12 g/day group at 7 days (11.1% vs. 23.3%), 14 days (33.3% vs. 41.9%), and 28 days (46.7% vs. 58.1%). The microbiological cure rate at day 7 was significantly higher in the 12 g/day group (90.5% vs. 58.1%; p = 0.02). Factors associated with mortality at 28 days were asthma, cirrhosis, APACHEII score ≥ 28, and a dosage of sulbactam of 9 g/day for mortality at any timepoint. Treatment with colistin combined with sulbactam at 12 g/day was not superior to the combination treatment with sulbactam at 9 g/day. However, due to being an interim analysis, this trial was underpowered to detect mortality differences.

Rapid Detection of Beta-Lactamases Genes among Enterobacterales in Urine Samples by Using Real-Time PCR

The objective of this study was to develop and evaluate newly improved, rapid, and reliable strategies based on real-time PCR to detect the most frequent beta-lactamase genes recorded in clinical Enterobacterales strains, particularly in Tunisia (bla_SHV12, bla_TEM, bla_CTX-M-15, bla_CTX-M-9, bla_CMY-2, bla_OXA-48, bla_NDM-1, and bla_IMP) directly from the urine. Following the design of primers for a specific gene pool and their validation, a series of real-time PCR reactions were performed to detect these genes in 78 urine samples showing high antibiotic resistance after culture and susceptibility testing. Assays were applied to DNA extracted from cultured bacteria and collected urine. qPCR results were compared for phenotypic sensitivity. qPCR results were similar regardless of whether cultures or urine were collected, with 100% sensitivity and specificity. Out of 78 multiresistant uropathogenic, strains of Enterobacterales (44 E. coli and 34 K. pneumoniae strains) show the presence of the genes of the bla group. In all, 44% E. coli and 36 of K. pneumoniae clinical strains harbored the bla group genes with 36.4%, 52.3%, 70.5%, 68.2%, 18.2%, and 4.5% of E. coli having bla_SHV-12, bla_TEM, bla_{CTX-M 15}, bla_CTX-M-9, bla_CMY-2, and bla_OXA-48 group genes, respectively, whereas 52.9%, 67.6%, 76.5%, 35.5%, 61.8, 14.7, and 1.28% of K. pneumoniae had bla_SHV-12, bla_TEM, bla_{CTX-M 15}, bla_CTX-M-9, bla_CMY-2, bla_OXA-48, and bla_NDM-1 group genes, respectively. The time required to have a result was 3 hours by real-time PCR and 2 to 3 days by the conventional method. Resistance genes of Gram-negative bacteria in urine, as well as cultured bacteria, were rapidly detected using qPCR techniques. These techniques will be used as rapid and cost-effective methods in the laboratory. Therefore, this test could be a good candidate to create real-time PCR kits for the detection of resistance genes directly from urine in clinical or epidemiological settings.

Osteomyelitis and Gentamicin-PMMA Chains

ABSTRACT

In chronic osteomyelitis, effective local antibiotic therapy after surgical debridement can be achieved by implantation of gentamicin-PMMA chains. The gentamicin concentrations at the site of infection are higher than that after systemic application of the same antibiotic. The appearance of this treatment is a particular aspect from a radiological point of view. Even if this is rare, these images deserve to be known when looking for osteomyelitis. We report a case of a 21-year-old man from Russia who had a bone scan in the context of chronic osteomyelitis persisting since a shin splints operation in a context of bilateral trauma in his country with antibiotic beads application.

Synergistic effects of dietary oxolinic acid combined with oxytetracycline on nonspecific immune responses and resistance against Vibrio parahaemolyticus infection of white shrimp (Penaeus vannamei)

This study investigated the synergistic effects of oxolinic acid (OA) combined with oxytetracycline (OTC) on white shrimp (Penaeus vannamei). Disk diffusion susceptibility testing was performed to analyze the sensitivity of Vibrio alginolyticus and Vibrio parahaemolyticus to different concentrations of OA and OTC. The results revealed that 50 mg OA/L combined with 50 mg OTC/L exhibited stronger antibacterial effects on V. alginolyticus and V. parahaemolyticus. The results of in vitro tests indicated that cotreatment with OA and OTC significantly reduced superoxide anion production and phenoloxidase activity, but not phagocytic activity. Subsequently, feeding trials were performed to investigate the immunomodulatory effects and bioaccumulation of dietary OA combined with OTC on shrimp. The healthy shrimp (15.13 ± 1.02 g) were divided into four groups: control, 100 mg OA/kg combined with 50 mg OTC/kg, 50 mg OA/kg combined with 100 mg OTC/kg, and 50 mg OA/kg combined with 50 mg OTC/kg. The shrimp were sampled to determine innate immunity parameters and residual OA and OTC levels in the muscle during a 28-day feeding regimen; the shrimp were fed the experimental diet from day 1 to day 5 and a commercial diet from day 6 to day 28. Residual OA levels were considerably higher in the group fed 100 mg OA/kg combined with 50 mg OTC/kg compared with the other groups and peaked on day 4. The residual OA levels of all the groups were below the detection limit after without providing OA. The residual OTC levels of the group fed 50 mg OA/kg combined with 100 mg OTC/kg were considerably higher from day 1 to day 4. The residual OTC levels in all the groups decreased rapidly and could not be detected on day 28. The administration of 50 mg OA/kg combined with 100 mg OTC/kg exerted the least effect on the white shrimp. Moreover, the survival rates of the treatment groups after the V. parahaemolyticus challenge were higher than those of the control group, especially the group fed 50 mg OA/kg combined with 100 mg OTC/kg. This result indicated that the synergistic effects of dietary OA and OTC are safe and effective. Combination therapy is a new method of antibiotic use in aquaculture.

Sequence-Specific Electrochemical Genosensor for Rapid Detection of blaOXA-51-like Gene in Acinetobacter baumannii

Acinetobacter baumannii (A. baumannii) are phenotypically indistinguishable from the Acinetobacter calcoaceticus−A. baumannii (ACB) complex members using routine laboratory methods. Early diagnosis plays an important role in controlling A. baumannii infections and this could be assisted by the development of a rapid, yet sensitive diagnostic test. In this study, we developed an enzyme-based electrochemical genosensor for asymmetric PCR (aPCR) amplicon detection of the blaOXA-51-like gene in A. baumannii. A. baumanniiblaOXA-51-like gene PCR primers were designed, having the reverse primer modified at the 5′ end with FAM. A blaOXA-51-like gene sequence-specific biotin labelled capture probe was designed and immobilized using a synthetic oligomer (FAM-labelled) deposited on the working electrode of a streptavidin-modified, screen-printed carbon electrode (SPCE). The zot gene was used as an internal control with biotin and FAM labelled as forward and reverse primers, respectively. The blaOXA-51-like gene was amplified using asymmetric PCR (aPCR) to generate single-stranded amplicons that were detected using the designed SPCE. The amperometric current response was detected with a peroxidase-conjugated, anti-fluorescein antibody. The assay was tested using reference and clinical A. baumannii strains and other nosocomial bacteria. The analytical sensitivity of the assay at the genomic level and bacterial cell level was 0.5 pg/mL (1.443 µA) and 103 CFU/mL, respectively. The assay was 100% specific and sensitive for A. baumannii. Based on accelerated stability performance, the developed genosensor was stable for 1.6 years when stored at 4 °C and up to 28 days at >25 °C. The developed electrochemical genosensor is specific and sensitive and could be useful for rapid, accurate diagnosis of A. baumannii infections even in temperate regions.

The type VI secretion system in Acinetobacter baumannii clinical isolates and its roles in antimicrobial resistance acquisition

Acinetobacter baumannii is a successful pathogen that can acquire various antibiotic resistance in a short time. However, little is known about how it can evolve from an antibiotic sensitive to a resistant phenotype. In this study, we investigated the roles of the type VI secretion system (T6SS) in the acquisition of antibiotic resistance of A. baumannii. T6SS gene cluster was found to be present in 51 of 77 A. baumannii clinical isolates, of which, it was found in 62% (8/13) of the multiple drug resistant (MDR) isolates, 90% (36/40) of the extensively drug-resistant (XDR) isolates and 26% (6/23) of the antibiotic sensitive isolates. There is a close relationship between the antimicrobial resistance and the presence of T6SS. Besides, T6SS + isolates showed lower biofilm formation activity and higher survival ability in the presence of normal human serum than T6SS- isolates. A. baumannii A152 with complete T6SS can outcompete E.coli effectively and can acquire the antibiotic resistance plasmids released by E.coli. In contrast, the T6SS core gene mutant A152Δhcp showed significantly decreased ability to acquire antimicrobial resistance plasmids from the prey bacteria. These results suggest that T6SS mediated bacterial competition plays important roles in the antimicrobial resistance of A. baumannii, which points out a new direction for us to study the antimicrobial resistance of A. baumannii.

Preclinical confirmation of UVC efficacy in treating infectious keratitis

PURPOSE

Preclinical evaluation of the therapeutic potential of antimicrobial 265 nm UVC for infectious keratitis.

METHODS

Four experiments explored UVC: 1) impact on bacterial and fungal lawns on agar, in individual or mixed culture, 2) bacterial inactivation dose in an in vitro deep corneal infection model, 3) dose validation in an ex vivo porcine keratitis model and 4) efficacy in a masked, randomised, controlled murine keratitis trial using bioluminescent Pseudomonas aeruginosa.

RESULTS

Minimum effective UVC exposures ranged between 2 s and 5 s for lawn bacteria and fungi in individual or mixed culture. Significant P. aeruginosa growth inhibition in the in vitro infection model was achieved with 15 s UVC, that resulted in a >3.5 log10 reduction of bacteria in a subsequent ex vivo keratitis model (p < 0.05). Bioluminescence fell below baseline levels in all treated animals, within 8 h of treatment (p < 0.05), in the in vivo study. Re-epithelialisation with corneal clarity occurred within 24 h in 75% of UVC-treated cases, with no relapse at 48 h. On plating, bacteria were recovered only from untreated controls.

CONCLUSIONS

UVC inhibited all tested bacteria and fungi, including mixed culture and strains linked to antibiotic resistance, in vitro, with exposures of ≤ 5 s. In vitro and ex vivo testing confirmed therapeutic potential of 15 s UVC. In vivo, 15 s UVC administered in two doses, 4 h apart, proved effective in treating murine bacterial keratitis.

Clinical data from studies involving novel antibiotics to treat multidrug-resistant Gram-negative bacterial infections

Multidrug-resistant (MDR) Gram-negative bacteria (GNB) are a critical threat to healthcare worldwide, worsening outcomes and increasing mortality among infected patients. Carbapenemase- and extended-spectrum β-lactamase-producing Enterobacterales, as well as carbapenemase-producing Pseudomonas and Acinetobacter spp., are common MDR pathogens. To address this threat, new antibiotics and combinations have been developed. Clinical trial findings support several combinations, notably ceftazidime-avibactam (CZA, a cephalosporin-β-lactamase inhibitor combination) which is effective in treating complicated urinary tract infections (cUTI), complicated intra-abdominal infections and hospital-acquired and ventilator-associated pneumonia caused by GNBs. Other clinically effective combinations include meropenem-vaborbactam (MVB), ceftolozane-tazobactam (C/T) and imipenem- relebactam (I-R). Cefiderocol is a recent siderophore β-lactam antibiotic that is useful against cUTIs caused by carbapenem-resistant Enterobacterales (CRE) and is stable against many β-lactamases. CRE are a genetically heterogeneous group that vary in different world regions and are a substantial cause of infections, among which Klebsiella pneumoniae are the most common. Susceptible CRE infections can be treated with fluoroquinolones, aminoglycosides or fosfomycin, but alternatives include CZA, MVB, I-R, cefiderocol, tigecycline and eravacycline. MDR Acinetobacter baumannii and Pseudomonas aeruginosa are increasingly common pathogens producing a range of different carbapenemases, and infections are challenging to treat, often requiring novel antibiotics or combinations. Currently, no single agent can treat all MDR-GNB infections, but new β-lactam-β-lactamase inhibitor combinations are often effective for different infection sites, and, when used appropriately, have the potential to improve outcomes. This article reviews clinical studies investigating novel β-lactam approaches for treatment of MDR-GNB infections.