Clinical Isolates Of Acinetobacter Baumannii Research Articles

Efficacy of Cefiderocol, a Novel Siderophore Cephalosporin, against Multidrug Resistant Acinetobacter baumannii Clinical Isolates in Japan.

Multidrug-resistant Acinetobacter baumannii (MDRAB) is an important pathogen that causes nosocomial infections and is resistant to almost all antibiotics, including carbapenems. Cefiderocol is a novel siderophore cephalosporin active against a broad spectrum of gram-negative bacteria. However, the susceptibility of MDRAB to cefiderocol has not yet been reported in Japan. In this study, we measured the minimum inhibitory concentrations (MICs) of antibiotics including cefiderocol against MDRAB clinical isolates collected during a nosocomial outbreak between 2009 and 2010 at the Teikyo University Hospital in Japan. We found that all 10 MDRAB clinical isolates tested were susceptible to cefiderocol, with an MIC range of 0.12 to 1 μg/mL. All the isolates also exhibited resistance to ampicillin-sulbactam and an intermediate resistance to colistin, whereas nine of them were susceptible to tigecycline. DNA sequencing revealed that all strains harbored an OXA-51-like carbapenemase, a major cause of carbapenem resistance in A. baumannii in Japan. In conclusion, this study showed that the cefiderocol susceptibility of MDRAB clinical isolates in Japan was equivalent to that to colistin or tigecycline, and thus cefiderocol is a potential treatment option for MDRAB infections.

Antimicrobial susceptibility and genetic characteristics of multi-drug resistant Acinetobacter baumannii isolates in Northwest China.

In recent decades, widespread multi-drug resistant (MDR) bacteria have become a serious problem in healthcare facilities. To systematically summarize and investigate the prevalence and genomic features of clinical MDR Acinetobacter baumannii (A. baumannii) clinical isolates recovered from the first hospital of Lanzhou University, we collected 50 MDR A. baumannii isolates isolated in the first quarter of 2022 and using whole-genome sequencing investigate the genotypic characteristics. All of these isolates were generally resistant to the common β-lactamase antibiotics. Resistance to cefoperazone-sulbactam varies greatly between different clones. The proportion of CC208 isolates resistant and mediated to cefoperazone-sulbactam is as high as 84.6%. There were no isolates resistant to tigecycline and colistin. The presence of blaOXA - 23 (94.0%) and blaOXA - 66 (98.0%) were the most frequent determinants for carbapenem resistance. Two main endemic clones were identified, one (ST469oxf) was predominantly circulating in ICUs and carried the same resistance genes, virulence genes and transposons, and the other clone (CC208) carried more resistance genes and had more widely disseminated. Our study showed that clinical MDR A. baumannii isolates circulating in our hospital exhibited highly similar genetic features. We should take timely and effective measures to control the further epidemic of these isolates.

Antimicrobial combination effects against multidrug-resistant Acinetobacter baumannii and Pseudomonas aeruginosa strains: A cross-sectional study.

Emergence of multidrug resistance in non-fermenting Gram-negative bacilli is a threat to public health. Combination therapy is a strategy for the treatment of antibiotic-resistant infections. In this cross-sectional study, a total of 63 nonduplicate clinical isolates of Acinetobacter baumannii and Pseudomonas aeruginosawere collected from various specimens. Identification of bacterial isolates was performed by phenotypic and molecular tests. Antibiotic susceptibility patterns and detection of β-lactamase genes were determined using the broth microdilution and polymerase chain reaction (PCR) techniques, respectively. Then, the combined effects analysis was determined by the checkerboard method. Based on the status of resistance to carbapenems (imipenem and meropenem), 25 isolates of each genus were selected for further investigation. For A. baumannii, bla OXA-23, bla OXA-58, and bla OXA-48 genes were positive in 21 (84%), 17 (68%), and 11 (44%) of isolates, respectively. In P. aeruginosa isolates, bla VIM was the most common gene (44%) and other genes including bla IMP, bla NDM, and bla OXA-23 were found in nine (36%), six (24%), and three (12%) isolates, respectively. Meropenem (MER)-tigecycline (TIG) had a significant synergistic effect against 20 (80%) A. baumannii (pvalue < 0.001). This combination was also efficient against 5 (20%) P. aeruginosa isolates. Moreover, the other combination, tigecycline-amikacin (TIG-AMK) was effective against 10 (40%) A. baumannii isolates. The combination of colistin (COL) and MER showed a significant synergistic effect against 21 (84%) A. baumannii (pvalue < 0.001) and 17 (68%) P. aeruginosa isolates (pvalue < 0.001). The MER-TIG and COL-MER combinations are promising options against resistant bacteria. Our study could be helpful for the development of a new treatment recommendation.

Cerastecins inhibit membrane lipooligosaccharide transport in drug-resistant Acinetobacter baumannii.

Carbapenem-resistant Acinetobacter baumannii infections have limited treatment options. Synthesis, transport and placement of lipopolysaccharide or lipooligosaccharide (LOS) in the outer membrane of Gram-negative bacteria are important for bacterial virulence and survival. Here we describe the cerastecins, inhibitors of the A. baumannii transporter MsbA, an LOS flippase. These molecules are potent and bactericidal against A. baumannii, including clinical carbapenem-resistant Acinetobacter baumannii isolates. Using cryo-electron microscopy and biochemical analysis, we show that the cerastecins adopt a serpentine configuration in the central vault of the MsbA dimer, stalling the enzyme and uncoupling ATP hydrolysis from substrate flipping. A derivative with optimized potency and pharmacokinetic properties showed efficacy in murine models of bloodstream or pulmonary A. baumannii infection. While resistance development is inevitable, targeting a clinically unexploited mechanism avoids existing antibiotic resistance mechanisms. Although clinical validation of LOS transport remains undetermined, the cerastecins may open a path to narrow-spectrum treatment modalities for important nosocomial infections.

The effect of tigecycline-usnic acid combination on tigecycline-non-susceptible Acinetobacter baumannii clinical isolates and the role of usnic acid as an adjuvant efflux pump inhibitor

The effect of tigecycline-usnic acid combination on tigecycline-non-susceptible Acinetobacter baumannii clinical isolates and the role of usnic acid as an adjuvant efflux pump inhibitor

In vitro activity of apramycin (EBL-1003) in combination with colistin, meropenem, minocycline or sulbactam against XDR/PDR Acinetobacter baumannii isolates from Greece.

To evaluate the in vitro activity of the combination of apramycin with colistin, meropenem, minocycline or sulbactam, against some well-characterized XDR Acinetobacter baumannii clinical isolates from Greece, to understand how apramycin can be best incorporated into clinical practice and optimize effectiveness. In vitro interactions of apramycin (0.5×, 1× and 2× the MIC value) with colistin (2 mg/L), meropenem (30 mg/L), minocycline (3.5 mg/L) or sulbactam (24 mg/L) were tested using time-kill methodology. Twenty-one clinical A. baumannii isolates were chosen, exhibiting apramycin MICs of 4-16 mg/L, which were at or below the apramycin preliminary epidemiological cut-off value of 16 mg/L. These isolates were selected for a range of colistin (4-32 mg/L), meropenem (16-256 mg/L), minocycline (8-32 mg/L) and sulbactam (8-32 mg/L) MICs across the resistant range. Synergy was defined as a ≥2 log10 cfu/mL reduction compared with the most active agent. The combination of apramycin with colistin, meropenem, minocycline or sulbactam was synergistic, at least at one of the concentrations of apramycin (0.5×, 1× or 2× MIC), against 83.3%, 90.5%, 90.9% or 92.3% of the tested isolates, respectively. Apramycin alone was bactericidal at 24 h against 9.5% and 33.3% of the tested isolates at concentrations equal to 1× and 2× MIC, while the combination of apramycin at 2× MIC with colistin, meropenem or sulbactam was bactericidal against all isolates tested (100%). The apramycin 2× MIC/minocycline combination had bactericidal activity against 90.9% of the tested isolates. Apramycin combinations may have potential as a treatment option for XDR/pandrug-resistant (PDR) A. baumannii infections and warrant validation in the clinical setting, when this new aminoglycoside is available for clinical use.

Antimicrobial efficacy of eravacycline against emerging extensively drug-resistant (XDR) Acinetobacter baumannii isolates

PurposeDrug-resistant Acinetobacter baumannii is an emerging threat. This study has been conducted to observe the efficacy of eravacycline along with the RND-efflux pump system. MethodsA cross-sectional study was done collecting 48 clinical isolates of Acinetobacter baumannii. MICs of 15 antibiotics were detected along with BMD of tigecycline and eravacycline. PCR products of drug-resistant regulatory genes were sequenced and analyzed. ResultsOf the total 48 Isolates, 35 (72.91%) were XDR and 13 (27.08%) were MDR. Out of all, 60.41% of isolates were found to be susceptible to eravacycline by BMD according to both FDA and EUCAST guidelines. A 2-fold decline of MIC50/90 was observed with the use of eravacycline compared to tigecycline. RND-efflux genes like AdeC in 30 (62.5%) isolates and Regulatory gene AdeS in 29 (60.41%) isolates were detected, explaining the existing resistance mechanism. ConclusionsXDR Acinetobacter poses an escalating threat due to its resistance to multiple antibiotics, raising serious concerns in healthcare settings. Eravacycline is an encouraging new drug for empirical use in severe infection caused due to the same. Molecular investigation and strict antimicrobial stewardship should be followed to control the emergence, and a better understanding of mechanisms of resistance to prevent the spread of drug-resistant isolates.

The role of type VI secretion system genes in antibiotic resistance and virulence in Acinetobacter baumannii clinical isolates.

The type VI secretion system (T6SS) is a crucial virulence factor in the nosocomial pathogen Acinetobacter baumannii. However, its association with drug resistance is less well known. Notably, the roles that different T6SS components play in the process of antimicrobial resistance, as well as in virulence, have not been systematically revealed. The importance of three representative T6SS core genes involved in the drug resistance and virulence of A. baumannii, namely, tssB, tssD (hcp), and tssM was elucidated. A higher ratio of the three core genes was detected in drug-resistant strains than in susceptible strains among our 114 A. baumannii clinical isolates. Upon deletion of tssB in AB795639, increased antimicrobial resistance to cefuroxime and ceftriaxone was observed, alongside reduced resistance to gentamicin. The ΔtssD mutant showed decreased resistance to ciprofloxacin, norfloxacin, ofloxacin, tetracycline, and doxycycline, but increased resistance to tobramycin and streptomycin. The tssM-lacking mutant showed an increased sensitivity to ofloxacin, polymyxin B, and furazolidone. In addition, a significant reduction in biofilm formation was observed only with the ΔtssM mutant. Moreover, the ΔtssM strain, followed by the ΔtssD mutant, showed decreased survival in human serum, with attenuated competition with Escherichia coli and impaired lethality in Galleria mellonella. The above results suggest that T6SS plays an important role, participating in the antibiotic resistance of A. baumannii, especially in terms of intrinsic resistance. Meanwhile, tssM and tssD contribute to bacterial virulence to a greater degree, with tssM being associated with greater importance.

N-ASETİL SİSTEİNİN ACINETOBACTER BAUMANNII İZOLATLARINA KARŞI ANTİMİKROBİYAL ETKİSİ VE ANTİBİYOTİKLERLE ETKİLEŞİMİ

Objective: The objective of this study was to delve into the effect of N-acetylcysteine (NAC) molecule on the minimum inhibitory concentration (MIC) of meropenem, ciprofloxacin, and gentamicin in clinical isolates of Acinetobacter baumannii, aiming to find potential alternatives for the treatment of bacterial infections that are resistant to conventional antibiotics. Material and Method: The study included 25 A. baumannii isolates that were confirmed to be resistant to meropenem, ciprofloxacin, and gentamicin. The susceptibility of antibiotics was re-evaluated in the presence of NAC using the microdilution method. FIC indexes were calculated based on the checkerboard test results to determine the effect of the combination, defined as synergistic or additive. Result and Discussion: The study demonstrated that NAC molecule, when used alongside meropenem, ciprofloxacin, and gentamicin, effectively reduced the MIC values of these antibiotics against Acinetobacteria. Furthermore, NAC molecule exhibited a synergistic effect when combined with meropenem. Additive effects were observed in all isolates for the GEN-NAC and CIP-NAC combinations. In conclusion, the findings suggest that NAC molecule could serve as a new alternative for combined drug therapy, offering a promising approach to treatment.

Investigation of EpsA, OmpA, and Bap Genes among MDR and XDR Acinetobacter baumannii Isolatesin Khorramabad, Iran.

Acinetobacter baumannii is an opportunistic hospital pathogen with high antibiotic resistance, and the ability to produce biofilm. This study aimed to investigate epsA, ompA, and bap genes involved in biofilm formation in MDR and XDR clinical isolates of Acinetobacter baumannii in Khorramabad, Iran. In this study, 79 A.baumannii isolates were collected from various samples of the patients admitted to tertiary hospitals in Khorramabad city, Iran, between January and August 2019. After performing the semi-quantitative evaluation of biofilm production by microtiter plate assay, screening of isolates carrying epsA, ompA, and bap genes was done by PCR method. Finally, statistical analyses were conducted using SPSS 22. Among 79 A.baumannii isolates, 52% XDR, 40% MDR, and 16% non-XDRMDR isolates were found to be biofilm producers. All XDR and 94% MDR isolates had ompA and epsA genes, and bap genes were detected among > 80% of these isolates. Moreover, the presence of biofilm-related genes and biofilm production among non-XDRMDR isolates were less than among resistant isolates (p≤ 0.01). Based on the results, biofilm production and simultaneous presence of epsA, ompA, and bap genes among MDR, and XDR A. baumannii isolates have been found to be significantly more than non-XDR-MDR isolates.

In vitro activity of sulbactam-durlobactam against colistin-resistant and/or cefiderocol-non-susceptible, carbapenem-resistant Acinetobacter baumannii collected in U.S. hospitals.

The activity of a novel β-lactamase inhibitor combination, sulbactam-durlobactam (SUL-DUR), was tested against 87 colistin-resistant and/or cefiderocol-non-susceptible carbapenem-resistant Acinetobacter baumannii clinical isolates collected from U.S. hospitals between 2017 and 2019. Among them, 89% and 97% were susceptible to SUL-DUR and imipenem plus SUL-DUR, with MIC50/MIC90 values of 2 µg/mL/8 µg/mL and 1 µg/mL/4 µg/mL, respectively. The presence of amino acid substitutions in penicillin-binding protein 3, including previously reported A515V or T526S, was associated with SUL-DUR non-susceptibility.

Engineering of a decellularized bovine skin coated with antibiotics-loaded electrospun fibers with synergistic antibacterial activity for the treatment of infectious wounds.

An ideal antibacterial wound dressing with strong antibacterial behavior versus highly drug-resistant bacteria and great wound-healing capacity is still being developed. There is a clinical requirement to progress the current clinical cares that fail to fully restore the skin structure due to post-wound infections. Here, we aim to introduce a novel two-layer wound dressing using decellularized bovine skin (DBS) tissue and antibacterial nanofibers to design a bioactive scaffold with bio-mimicking the native extracellular matrix of both dermis and epidermis. For this purpose, polyvinyl alcohol (PVA)/chitosan (CS) solution was loaded with antibiotics (colistin and meropenem) and electrospun on the surface of the DBS scaffold to fabricate a two-layer antibacterial wound dressing (DBS-PVA/CS/Abs). In detail, the characterization of the fabricated scaffold was conducted using biomechanical, biological, and antibacterial assays. Based on the results, the fabricated scaffold revealed a homogenous three-dimensional microstructure with a connected pore network, a high porosity and swelling ratio, and favorable mechanical properties. In addition, according to the cell culture result, our fabricated two-layer scaffold surface had a good interaction with fibroblast cells and provided an excellent substrate for cell proliferation and attachment. The antibacterial assay revealed a strong antibacterial activity of DBS-PVA/CS/Abs against both standard strain and multidrug-resistant clinical isolates of Acinetobacter baumannii, Pseudomonas aeruginosa, and Escherichia coli. Our bilayer antibacterial wound dressing is strongly suggested as an admirable wound dressing for the management of infectious skin injuries and now promises to advance with preclinical and clinical research.

Comparison of 16S rRNA Sequencing and VITEK 2 Analysis for the Identification of Acinetobacter baumannii Clinical Isolates: A Study from Southwestern Province of Saudi Arabia

Comparison of 16S rRNA Sequencing and VITEK 2 Analysis for the Identification of Acinetobacter baumannii Clinical Isolates: A Study from Southwestern Province of Saudi Arabia

Identification of Multiple Drug-Resistance Genes in Clinical Isolates of Acinetobacter baumannii

Around the world, Acinetobacter baumannii is a nosocomial pathogen that accounts for 80% of hospitalized patient infections. This opportunistic bacterium can cause a wide range of infections, including skin and soft tissue infections, meningitis, pneumonia acquired on a ventilator, urinary tract infections, and bacteremia, all of which have a high death rate of almost 63.3%. Finding multidrug-resistant genes in the clinical isolates of A. baumannii was the goal of this study. Twenty-four (24) A. baumannii clinical isolates were obtained from the Federal Teaching Hospital in Gombe, Nigeria, and subcultured on MacConkey agar for eighteen to twenty-four hours at 37 ˚C. The isolates were identified using traditional biochemical testing, morphology, and cultural traits. The VITEK was then used to validate the identification. Twenty of the 24 isolates had been identified as A. baumannii. The Kirby Bauer method and CLSI recommendations were utilized to determine the antibiotic susceptibility of the A. baumannii isolates. Polymerase Chain Reaction was used to identify the genes that were resistant to many drugs. According to the data, fifteen (15) A. baummanii isolates, or 75% of the total, were likely multidrug resistant. The presence of the BlaNDM-1 gene in eight isolates, the BlaOXA23 gene in six isolates, and the BlaVIM gene in just four isolates was confirmed by molecular detection of the MDR genes from these isolates. These results show that a significant portion of the isolates of A. baumannii carried genes resistant to many drugs, which could be the root cause of any infection treatment failure caused by this organism.

Antimicrobial and anti-virulence activities of 4-shogaol from grains of paradise against gram-negative bacteria: Integration of experimental and computational methods

Ethnopharmacological relevanceBacterial resistance to antibiotics is a growing global concern, highlighting the urgent need for new antimicrobial candidates. Aframomum melegueta was traditionally used for combating urinary tract and soft tissue infections, which implies its potential as an antimicrobial agent. Aim of studyThis study was designed to explore the antibacterial and anti-virulence capabilities of 4-shogaol isolated from A. melegueta seeds versus gram-negative bacteria: Serratia marcescens, Klebsiella pneumoniae, Acinetobacter baumannii, and the clinically important pathogen Pseudomonas aeruginosa. Materials and methods4-Shogeol was isolated from A. melegueta seeds and its MICs were determined for Acinetobacter baumannii (ATCC-17978), Pseudomonas aeruginosa (ATCC-27853), Klebsiella pneumoniae (ATCC-700603), and Serratia marcescens clinical isolate. The anti-efflux activity and effect on the bacterial cell membrane for the compound were evaluated. Furthermore, the anti-virulence activities of the compound were evaluated. The effects of 4-shogeol at sub-MIC on bacterial motility, biofilm formation, and production of virulent enzymes and pigments were assessed. The anti-quorum sensing activities of 4-shogeol were evaluated virtually and by quantification its effect on the expression of quorum sensing encoding genes. The in vivo protection assay was conducted to evaluate the effect of 4-shogaol on the P. aeruginosa capacity to induce pathogenesis in mice. Finally, the effect of shogaol-antibiotics combination was assessed. ResultsThe research revealed that 4-shogaol's antibacterial action primarily involves disrupting the bacterial cell membrane and efflux pumps. It also exhibited significant anti-virulence effects by reducing biofilm development and repressing virulence factors production, effectively protecting mice against P. aeruginosa infection. Furthermore, when combined with antibiotics, 4-shogaol demonstrated synergistic effects, leading to reduced minimum inhibitory concentrations (MICs) against P. aeruginosa. Its anti-virulence properties were linked to its ability to disrupt bacterial quorum sensing (QS) mechanisms, as evidenced by its interaction with QS receptors and downregulation of QS-related genes. Notably, in silico analysis indicated that 4-shogaol exhibited strong binding affinity to different P. aeruginosa QS targets. ConclusionThese findings suggest that 4-shogaol holds promise as an effective anti-virulence agent that can be utilized in combination with antibiotics for treating severe infections caused by gram-positive bacteria.

Characterization of disinfectant susceptibility profiles among clinical isolates of Acinetobacter baumannii in Ardabil, Iran

AbstractAntimicrobial disinfectants have been extensively used to control hospital-acquired infections worldwide. Prolonged exposure to bacteria could promote resistance to antimicrobial disinfectants. This study evaluated the antimicrobial activity of four commonly used disinfectants; triclosan, chlorhexidine digluconate, benzalkonium chloride, and formaldehyde against Acinetobacter baumannii clinical isolates. This study also determined the prevalence and association of efflux pumps encoding genes qacE, qacED1, emrA, and aceI with tolerance to disinfectants. A total of 100 A. baumannii isolates were included in the current study. The antimicrobial disinfectants' minimum inhibitory concentration (MIC) was determined using an agar dilution method. Genes involved in resistance to disinfectants were investigated by PCR method. The benzalkonium chloride MICs ranged between 32 and 128 μg mL−1, chlorhexidine digluconate 8–64 μg mL−1, triclosan 1–32 μg mL−1, and formaldehyde 128 μg mL−1. Overall, the highest MIC90 value was identified for formaldehyde (128 μg mL−1), followed by benzalkonium chloride and chlorhexidine digluconate (64 μg mL−1, each one) and triclosan (4 μg mL−1). In the present study, the qacE, qacED1, emrA, and aceI genes were found in 91%, 55%, 100%, and 88% of isolates, respectively. The qacG gene was not identified in our A. baumannii isolates. The qacED1 gene was associated with higher MICs for all disinfectants tested (P &lt; 0.05), while the qacE and aceI genes were associated with higher MICs for benzalkonium chloride and chlorhexidine. This study indicated that triclosan is the most effective disinfectant against A. baumannii isolates.

Network meta-analysis of antibiotic resistance patterns in gram-negative bacterial infections: a comparative study of carbapenems, fluoroquinolones, and aminoglycosides

IntroductionAntimicrobial resistance poses a grave global threat, particularly with the emergence of multidrug-resistant gram-negative bacterial infections, which severely limit treatment options. The increasing global threat of antimicrobial resistance demands rigorous investigation, particularly concerning multidrug-resistant gram-negative bacterial infections that present limited therapeutic options. This study employed a network meta-analysis, a powerful tool for comparative effectiveness assessment of diverse antibiotics. The primary aim of this study was to comprehensively evaluate and compare resistance patterns among widely used antibiotic classes, namely carbapenems, fluoroquinolones, and aminoglycosides, for combating gram-negative pathogens.MethodsWe searched PubMed, Web of Sciences, Scopus, Scholarly, Medline, Embase, and Cochrane databases up to August 27, 2023. Studies showing antibiotic resistance in clinical isolates of Enterobacteriaceae, Pseudomonas aeruginosa, and Acinetobacter baumannii exposed to carbapenems, fluoroquinolones, and aminoglycosides were included. This study determined treatment-specific resistance percentages and ranked these treatments based on resistance using a random-effects network meta-analysis technique. To investigate the impact of the study and pathogen features, subgroup and meta-regression analyses were performed. Risk ratios and 95% confidence intervals (CIs) were calculated using a network meta-analysis (NMA) incorporating both direct and indirect evidence. Clinical improvement, cure, microbiological eradication, and death from any cause were the primary outcomes. Nephrotoxicity was a secondary result.ResultsThe analysis included 202 publications and 365,782 gram-negative isolates. The NMA included data from 20 studies and 4,835 patients. Carbapenems had the lowest resistance rates throughout the pathogen spectrum, with resistance percentages of 17.1, 22.4, and 33.5% for Enterobacteriaceae, P. aeruginosa, and A. baumannii, respectively. For the same infections, aminoglycosides showed resistance rates of 28.2, 39.1, and 50.2%, respectively. Fluoroquinolones had the highest resistance rates at 43.1, 57.3, and 65.7%, respectively. Unexpectedly, resistance to all three antibiotic classes has increased over time, with multidrug resistance being the most prevalent.ConclusionThis extensive network meta-analysis provides an overview of the patterns of resistance throughout the world and how they are changing. The most effective choice is still carbapenems, but the increasing resistance highlights the critical need for multimodal therapies to protect antibiotic effectiveness against these powerful gram-negative infections.

In vitro activity of cefiderocol and other newly approved antimicrobials against multi-drug resistant Gram-negative pathogens recovered in intensive care units in Spain and Portugal.

The antimicrobial resistance is a significant public health threat, particularly for healthcare-associated infections caused by carbapenem-resistant Gram-negative pathogens which are increasingly reported worldwide. The aim of this study was to provide data on the in vitro antimicrobial activity of cefiderocol and that of commercially available comparator antibiotics against a defined collection of recent clinical multi-drug resistant (MDR) microorganisms, including carbapenem resistant Gram-negative bacteria collected from different regions in Spain and Portugal. A total of 477 clinical isolates of Enterobacterales, Pseudomonas aeruginosa, Acinetobacter baumannii and Stenotrophomonas maltophilia were prospectively (n=265) and retrospectively (n=212) included (2016-2019). Susceptibility testing was performed using standard broad microdilution and results were interpreted using CLSI-2021 and EUCAST-2021 criteria. Overall, cefiderocol showed a good activity against Enterobacterales isolates, being 99.5% susceptible by CLSI and 94.5% by EUCAST criteria. It also demonstrated excellent activity against P. aeruginosa and S. maltophilia isolates, all being susceptible to this compound considering CLSI breakpoints. Regarding A. baumannii (n=64), only one isolate was resistant to cefiderocol. Our results are in agreement with other studies performed outside Spain and Portugal highlighting its excellent activity against MDR gram-negative bacteria. Cefiderocol is a therapeutic alternative to those available for the treatment of infections caused by these MDR bacteria.

Nonadditive functional interactions between ligand-binding sites of the multidrug efflux pump AdeB from Acinetobacter baumannii.

Multidrug efflux is one of the major mechanisms of antibiotic resistance identified in clinical isolates of the human pathogen Acinetobacter baumannii. The multiple antibiotic resistance in this species is often enabled by the overproduction of the tripartite efflux pump AdeABC. In this pump, AdeB is the inner membrane transporter from the resistance-nodulation-division (RND) superfamily of proteins, which is responsible for the recognition and efflux of multiple structurally unrelated compounds. Like other RND transporters, AdeB is a trimeric protein with ligand-binding sites located in the large periplasmic domains. Previous structural studies, however, highlighted the uniqueness of AdeB interactions with ligands. Up to three ligand molecules were bound to one protomer of AdeB, mapping its substrate translocation path. In this study, we introduced single and double substitutions in the identified ligand-binding sites of AdeB. Our results show that the mechanism of substrate translocation by AdeB is different from that of other characterized RND transporters and that the functional interactions between the sites are nonadditive. We identified AdeB mutants with both the loss and the gain of antibiotic susceptibility phenotypes, as well as AdeB mutations making A. baumannii cells overproducing such pump variants even more susceptible to multiple antibiotics than efflux-deficient cells. IMPORTANCE Multidrug efflux pumps of the resistance-nodulation-division superfamily of proteins are important contributors to various aspects of bacterial physiology and antibiotic resistance. Studies of the best-characterized model transporter AcrB from Escherichia coli suggested that these transporters operate by a functional rotation mechanism in which various substrates bind to at least two different binding sites. This study suggests that the mechanism of AdeB is distinct and that the binding sites in this transporter are functionally linked.

Comparison of loop-mediated isothermal amplification, multiplex PCR, and REP- PCR techniques for identification of carbapenem-resistant Acinetobacter baumannii clinical isolates

Background and Objectives: Acinetobacter baumannii, an opportunistic pathogen, is related to hospital-acquired infections and increased mortality. This study aimed to develop the loop-mediated isothermal amplification (LAMP) test for the fast-de- tecting of A. baumannii isolates as well as determining genetic relatedness for these isolates via the REP-PCR technique.&#x0D; Materials and Methods: LAMP primers and multiplex PCR primers were designed for recognizing A. baumannii isolates harboring the bla SHV-1 , bla PER-1 , bla , AMPC, qnr, and aac (6)-1 genes, were collected (October 2020 to February 2021) from Shahid Motahari Hospital, Tehran, Iran. Combination disc test (CDT) results were used to assess the phenotypic iden- tification of isolates from ESBL producers. The sensitivity of the LAMP method was evaluated using a range of serial dilu- tions of genomic DNA. Results were compared between the LAMP technique, and multiplex PCR. The genetic diversity of clinical isolates was determined by REP-PCR.&#x0D; Results: Among one hundred A. baumannii samples and based on the combined disc test, 56% of isolates were ESBL pro- ducers. The sensitivity of the LAMP technique for the identification of A. baumannii was 4.06 ng/μl whilst the multiplex PCR was (16.2 ng/μl). Regarding multiplex PCR, (68%) of the isolates were bla SHV-1 positive, (40%) bla , (85%) aac (6́)-1, AMPC (67%), bla TEM-1 (63%), and (15%) qnr respectively. While in LAMP, (69%) of isolates were bla positive, (86%) aac (6')-1, and (20%) qnr. The results of AMPC, bla TEM-1 , and bla PER-1 genes showed 100% compatibility between multiplex PCR and LAMP assays. The results of REP-PCR indicated there were 17 clones, clone A at 14% was the most prevalent of the isolates.&#x0D; Conclusion: Wherever equipment and financial constraints are crucial, the LAMP test offers a better and more potent detec- tion rate for the identification of A. baumannii isolates than multiplex PCR. Furthermore, the genetic diversity of A. bauman- nii in these clinical isolates showed frequent commonality of genotypes.