Acinetobacter Strains Research Articles

Isolation and identification of a novel aerobic denitrifying bacterium with quorum quenching activity and the effect of environmental factors on its performance

A novel aerobic denitrifying bacterium capable of quorum quenching (QQ), Acinetobacter strain WZL728, was first isolated. WZL728 showed excellent aerobic denitrification performance and QQ activity. Besides, its optimal aerobic denitrification condition was pH 7.1, temperature 32.0 °C, C/N ratio 7.4 and shaking speed 108.0 rpm. However, its optimal QQ condition was pH 7.2, temperature 32.4 °C, C/N ratio 7.1 and shaking speed 96.1 rpm. The QQ activity of WZL728 was more tolerant to environmental changes than its aerobic denitrification performance because of the different response of its denitrification and QQ function genes expression. Moreover, it was revealed that the strain degraded N-acyl-homoserine lactones (AHLs) with long acyl chains by secreting extracellular QQ acylase. Due to the high QQ activity of the aerobic denitrifying bacterium, it may have great potential for controlling membrane biofouling in the field of wastewater treatment. • A novel aerobic denitrifier with QQ activity (WZL728) was isolated and identified. • WZL728 efficiently removed nitrate and degraded AHLs under aerobic conditions. • The QQ of WZL728 was more tolerant to environmental changes than denitrification. • WZL728 hydrolyzed AHLs with long acyl chains by secreting exogenous acylase.

The Antibiotic Resistance Rates in Multidrug Resistant Acinetobacter Isolates from Microbiological Culture Samples of Adult Patients in Turkey: A Retrospective Study

Objective: Acinetobacter species lead to extremely serious infections, particularly in hospitalized patients, and in patients with impaired host defense. The high rates of resistance against several antibiotics detected in recent years have created serious issues in treatments of different diseases. We aimed to examine antibiotic resistance profiles of Acinetobacter species isolated from patients who are treated as outpatients in polyclinics or hospitalized in services or intensive care units (ICU), against various antimicrobial therapies. Materials and Methods: Antibiotic resistance of Acinetobacter strains isolated from 533 clinical samples collected between 2017-2021 years in Bandırma State Hospital Clinical Microbiology Laboratory were evaluated retrospectively. The identification of isolates and antibiotic susceptibility tests were performed by BD Phoenix (Becton Dickinson, USA) automated system. Results: Most of Acinetobacter strains were isolated from respiratory secretions (32.5%) and from urine (24.4%). Of species, 63.8% were Acinetobacter baumannii, 34.9% Acinetobacter baumannii complex, 1.1% other Acinetobacter spp., 0.2% Acinetobacter lwoffii. Resistance rates to antibiotics were found as following: ciprofloxacin 91.1%, meropenem 91.3%, imipenem 89.2%, gentamicin 82.5%, trimethoprim-sulfamethaxasol 78.6%, amikacin 66.3% (highest in 2020), aztreonam 99.0% (significantly decreased in 2020), ceftriaxone 100%, ampicillin 100%, amoxicillin-clavulanate 100%, ertapenemicin 100%, cefuroxime 100%, netilmicin 62.5%, nitrofurantion 100%, colistin 4.7% and levofloxacin 87.1%. The samples collected from patients hospitalized in service and ICU were found more resistant against Ciprofloxacin, Levofloxacin, Meropenem, Imipenem, Trimethoprim/Sulfamethoxazole, Gentamicin and Amikacin (P<0.0001). Conclusion: Colistin resistance against Acinetobacter infections was observed to be low, hence colistin could be utilized in treatments. Infection control measures have to be taken in services and ICU, and rational antibiotic use policies should be applied so as to prevent the spread of infection

The Antibiotics Susceptibility Profile of Acinetobacter spp Isolated from Clinical Specimens in University Teaching Hospital

The genus Acinetobacter currently contains 34 species, the vast majority of which are not regularly implicated in causing infection. However, Carbapenems have long been thought of as the agents of choice for serious Acinetobacter baumannii infections. The objective of this study is to determine the Antibiotics susceptibility profile of Acinetobacter spp Isolated from clinical specimen University of Ilorin Teaching Hospital, Ilorin. The descriptive cross-sectional study is conducted in UITH located in North Central Nigeria. 10 strains of Acinetobacter spp. were isolated from clinical samples between February to July 2018. The isolated strains were identified using standard microbiological methods, API20NE. Antimicrobial susceptibility was performed using the Modified Kirby Bauer method with the organism tested against Amoxicillin, Amoxicillin-Clavulanate, Ceftriaxone, Cefixime, Cefuroxime, Streptomycin, Perfloxacin, Gentamicin, Imipenem, Nitrofurantoin. Most of the antibiotics used in this study are mostly multi-drug resistant. Amoxicillin (100%), Cefixime, Amoxicillin Clavulanate (100%), Cefuroxime (100%), Gentamicin (100%), Nitrofurantoin (100%), Ceftriaxone (100%) but 80% are susceptible to Imipenem. Carbapenems are the best antibiotic treatment option for infections arising from these organisms although a coordinated rational usage is desired along with a functional antibiotic prescription policy to avoid treatment failures. Continuous monitoring of resistance patterns is necessary to strengthen infection control policies.

Phytohormones producing rhizobacteria alleviate heavy metals stress in soybean through multilayered response

Aimof the current research was to use plant growth promoting rhizobacteria for sequestration and biotransformation of the toxic form of Cr and As into non-toxic form. Remediating these contaminants using microbes is a common technique and rhizo-microbiota not only relieves metal stress but also acts as biofertilizers. Role of plant growth-promoting rhizobacterial (PGPR) strains Acinetobacter beijerinckii (C5) and Raoultella planticola (C9) in counteracting chromium and arsenic stress in soybean seedlings was assessed. The isolated rhizobacteria were able to tolerate excessive quantities (up to 1200 ppm) of chromate and arsenate in liquid media. Beside their growth in heavy metal containing media, the strains were able to bio-transform chromate and arsenate to their least toxic form. They released significant quantities of stress related metabolites including phenols, flavonoids, proline, sugars and protein even in the presence of 1200 ppm of the heavy metals. They also released several plant hormones together with indole-3-acetic acid (IAA), salicylic acid (SA) and gibberellins. Another important feature of the isolates was their ability to solubilize phosphate and release siderophores and exposure to different levels of the selected heavy metals enhanced phosphate solubilization potential of both the isolates by up to 2-fold. Release of siderophore in A. beijerinckii C5 was enhanced by increasing heavy metals concentration in the media but in case of R. planticola C9 a decline was noted. When inoculated on soybean seedlings, the isolates modulated several metabolites of the hos plant enabling them to combat heavy metal toxicity at different levels. The PGPR strains boosted host’s antioxidants production which minimized the oxidative damage by scavenging excessive ROS produced under stress. Control plants showed upregulation of stress response metabolites compared to PGPR application, whereas, IAA and SA were significantly higher in PGPR associated seedlings. In conclusion, PGPR alters the physiological and metabolic responses of soybean enabling it to cope better with chromate and arsenic toxicity and grow well under the stress.

Investigation of Potential In Vitro Anticancer and Antimicrobial Activities of Balanites aegyptiaca (L.) Delile Fruit Extract and Its Phytochemical Components.

The therapeutic importance of Balanites aegyptiaca in folk medicine for the treatment of several common human diseases has led researchers to conduct phytochemical and pharmacological studies on extracts from various parts of the plant. In the current study, the phytochemical composition of the B. aegyptiaca methanolic fruit extract was characterized, and its antimicrobial activity was evaluated together with the cytotoxic activity against MCF-7, PC-3, and Caco-2, compared with normal Vero cells. Further, its effects on cell cycle arrest, apoptosis induction and expression of apoptosis-related genes were assessed. The phytochemical screening revealed the presence of fatty acids and their esters in addition to phytosterols, steroid derivatives, and bioflavonoid glycosides with oleic and palmitic acids being the prevalent components (24.12 and 21.56%, respectively). The results showed considerable cytotoxic activity of the extract against the three cancer cell lines (MCF-7, PC-3, and Caco-2) with a selectivity index ranging from 5.07 to 6.52. This effect was further confirmed with the accompanied increased total apoptosis of treated PC-3 cells (19.22% of the total number of cells) compared to the control cells (0.64% of the total number of cells) with cell cycle arrest at G1 phase and the increased transcription of pro-apoptotic genes including P53 (3.69) and BAX (3.33) expressed as fold change (2^ ΔΔCT). The calculated minimum inhibitory concentration (MIC) was similar (62.5 µg/mL) against the three tested bacterial strains (Acinetobacter johnsonii, Serratia marcescens and Agrobacterium tumefaciens), while it was higher than 1000 µg/mL for the fungal species (Rhizoctonia solani, Penicillium italicum, and Fusarium oxysporium). Our findings suggest a promising anticancer activity for B. aegyptiaca, which paves the way for more detailed future studies.

PHENOTYPIC DETECTION OF METALLO BETA LACTAMASE IN CARBAPENEM RESISTANT ACINETOBACTER SPECIES IN INTENSIVE CARE UNIT IN A TERTIARY CARE HOSPITAL

Introduction: Acinetobacter causes a wide range of illness in debilitated and hospitalized patients. Carbapenem resistance in Acinetobacter species is an emerging problem and is a cause of concern as many nosocomial infections with Acinetobacter species are resistant to most other antibiotics. The present study was aimed to study metallo-β-lactamase (MBL) production in Acinetobacter species. Data Material and Methods: was collected retrospectively from October 2021 to March 2022. Out of all the clinical samples obtained (respiratory secretions, pus, blood & urine), all Carbapenem resistant isolates of Acinetobacter species were included. Antimicrobial susceptibility testing was done by standard Kirby Bauer disk diffusion method. MBL detection was done by imipenem-EDTA combined disk method and Modied Hodge test. Out of total Results: 325 Acinobacter isolates isolated from intensive care unit (ICU), 228 were found to be carbapenem (Imipenem & Meropenem) resistant and these were further processed for MBL production. Out of 228 Carbapenem resistant Acinetobacter isolates 198 (86.84%) and 170 (74.56%) were found MBL producer by Combined Disc test and Modied Hodge Test respectively. This Conclusion: study demonstrated that multidrug resistant strains of Acinetobacter are common in ICU of tertiary care hospitals. Unwarranted and unrestricted usage of antibiotics and production of MBL is associated with emergence of resistance in nosocomial pathogens. Regular monitoring and documentation of carbapenem resistant is crucial in developing strategies to control infection due to these bacteria.

Molecular Characterization of Gene-Mediated Resistance and Susceptibility of ESKAPE Clinical Isolates to Cistus monspeliensis L. and Cistus salviifolius L. Extracts.

Background Multidrug resistance (MDR) and extensively drug-resistant (XDR) are now the biggest threats to human beings. Alternative antimicrobial regimens to conventional antibiotic paradigms are extensively searched. Although Cistus extracts have long been used for infections in traditional folk medicines around the world, their efficacy against resistant bacteria still needs to be elucidated. We aim to investigate the antibiotic susceptibility profiles of clinical strains Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter cloacae (acronym “ESKAPE”), and their resistance mechanisms by PCR, as well as their sensitivity to C. monspeliensis (CM) and C. salviifolius (CS) methanol extracts and their fractions. Methods Antibiotic susceptibility profile and resistance mechanism were done by antibiogram and PCR. Fractions of CM and CS were obtained using maceration and Soxhlet; their antibacterial activities were evaluated by determining inhibition zone diameter (IZD), minimum inhibitory concentration (MIC), and minimum bactericidal concentration (MBC). Results Results revealed that all strains were XDR except S. aureus, which was MDR. The PCR indicates the presence of gene-mediated resistance (blaCTX-M, blaSHV, blaOXA-48, blaNDM, blaOXA-51, blaOXA-58, blaIMP, blaVIM, and blamecA). Also, maceration was slightly better for bioactivity preservation. Overall, the extracts of CM (IZD = 20 mm, MIC = 0.01 mg/mL) were more active than those of CS. All extracts inhibited MRSA (methicillin-resistant Staphylococcus aureus) and ERV (Enterococcus faecium Vancomycin-Resistant) with interesting MICs. The ethyl acetate fraction manifested great efficacy against all strains. Monoterpene hydrocarbons and sesquiterpenes oxygenated were the chemical classes of compounds dominating the analyzed fractions. Viridiflorol was the major compound in ethyl acetate fractions of 59.84% and 70.77% for CM and CS, respectively. Conclusions The superior activity of extracts to conventional antibiotics was seen for the first time in the pathogens group, and their bactericidal effect could be a promising alternative for developing clinical antibacterial agents against MDR and XDR ESKAPE bacteria.

Plasmids as Key Players in Acinetobacter Adaptation.

This review briefly summarizes the data on the mechanisms of development of the adaptability of Acinetobacters to various living conditions in the environment and in the clinic. A comparative analysis of the genomes of free-living and clinical strains of A. lwoffii, as well as the genomes of A. lwoffii and A. baumannii, has been carried out. It has been shown that plasmids, both large and small, play a key role in the formation of the adaptability of Acinetobacter to their living conditions. In particular, it has been demonstrated that the plasmids of various strains of Acinetobacter differ from each other in their structure and gene composition depending on the lifestyle of their host bacteria. Plasmids of modern strains are enriched with antibiotic-resistant genes, while the content of genes involved in resistance to heavy metals and arsenic is comparable to plasmids from modern and ancient strains. It is concluded that Acinetobacter plasmids may ensure the survival of host bacteria under conditions of various types of environmental and clinical stresses. A brief overview of the main mechanisms of horizontal gene transfer on plasmids inherent in Acinetobacter strains is also given.

Virulence Characteristics and Emerging Therapies for Biofilm-Forming Acinetobacter baumannii: A Review.

Simple SummaryAcinetobacter baumannii (A. baumannii) is one of the ESKAPE organisms and has the competency to build biofilms. These biofilms account for the most nosocomial infections all over the world. This review reflects on the various physicochemical and environmental factors such as adhesion, pili expression, growth surfaces, drug-resistant genes, and virulence factors that profoundly affect its resistant forte. Emerging drug-resistant issues and limitations to newer drugs are other factors affecting the hospital environment. Here, we discuss newer and alternative methods that can significantly enhance the susceptibility to Acinetobacter spp. Many new antibiotics are under trials, such as GSK-3342830, The Cefiderocol (S-649266), Fimsbactin, and similar. On the other hand, we can also see the impact of traditional medicine and the secondary metabolites of these natural products’ application in searching for new treatments. The field of nanoparticles has demonstrated effective antimicrobial actions and has exhibited encouraging results in the field of nanomedicine. The use of various phages such as vWUPSU and phage ISTD as an alternative treatment for its specificity and effectiveness is being investigated. Cathelicidins obtained synthetically or from natural sources can effectively produce antimicrobial activity in the micromolar range. Radioimmunotherapy and photodynamic therapy have boundless prospects if explored as a therapeutic antimicrobial strategy.Acinetobacter species is one of the most prevailing nosocomial pathogens with a potent ability to develop antimicrobial resistance. It commonly causes infections where there is a prolonged utilization of medical devices such as CSF shunts, catheters, endotracheal tubes, and similar. There are several strains of Acinetobacter (A) species (spp), among which the majority are pathogenic to humans, but A. baumannii are entirely resistant to several clinically available antibiotics. The crucial mechanism that renders them a multidrug-resistant strain is their potent ability to synthesize biofilms. Biofilms provide ample opportunity for the microorganisms to withstand the harsh environment and further cause chronic infections. Several studies have enumerated multiple physiological and virulence factors responsible for the production and maintenance of biofilms. To further enhance our understanding of this pathogen, in this review, we discuss its taxonomy, pathogenesis, current treatment options, global resistance rates, mechanisms of its resistance against various groups of antimicrobials, and future therapeutics.

Acinetobacter baylyi Strain BD413 Can Acquire an Antibiotic Resistance Gene by Natural Transformation on Lettuce Phylloplane and Enter the Endosphere.

Antibiotic resistance spread must be considered in a holistic framework which comprises the agri-food ecosystems, where plants can be considered a bridge connecting water and soil habitats with the human microbiome. However, the study of horizontal gene transfer events within the plant microbiome is still overlooked. Here, the environmental strain Acinetobacter baylyi BD413 was used to study the acquisition of extracellular DNA (exDNA) carrying an antibiotic resistance gene (ARG) on lettuce phylloplane, performing experiments at conditions (i.e., plasmid quantities) mimicking those that can be found in a water reuse scenario. Moreover, we assessed how the presence of a surfactant, a co-formulant widely used in agriculture, affected exDNA entry in bacteria and plant tissues, besides the penetration and survival of bacteria into the leaf endosphere. Natural transformation frequency in planta was comparable to that occurring under optimal conditions (i.e., temperature, nutrient provision, and absence of microbial competitors), representing an entrance pathway of ARGs into an epiphytic bacterium able to penetrate the endosphere of a leafy vegetable. The presence of the surfactant determined a higher presence of culturable transformant cells in the leaf tissues but did not significantly increase exDNA entry in A. baylyi BD413 cells and lettuce leaves. More research on HGT (Horizontal Gene Transfer) mechanisms in planta should be performed to obtain experimental data on produce safety in terms of antibiotic resistance.

Biodegradation of Dibutyl Phthalate by the New Strain Acinetobacter baumannii DP-2.

Optimizing the culture conditions of DBP degradation by bacteria and investigating its biodegradation pathways have a great importance to develop effective PAEs pollution control strategies. In this study, we investigated the cultivation condition optimization, degradation kinetics, and degradation pathways of a newly isolated dibutyl phthalate (DBP) degradation strain, which was isolated from activated sludge and identified as Acinetobacter baumannii DP-2 via morphological observation, biochemical identification, and 16S rDNA sequence analysis. The degradation conditions were optimized based on the results of single-factor experiments and response surface optimization experiments. The DBP degradation rate of Acinetobacter baumannii DP-2 reached up to 85.86% when the inoculation amount was 17.14%, the DBP concentration was 9.81 mg·L−1 and the NaCl concentration was 5 g·L−1. The GC-MS analysis results indicated that the intermediate metabolites of Acinetobacter baumannii DP-2 mainly consisted of DMP, MBP, PA, and benzoic acid derivatives, which confirmed the degradation pathway from DBP to PA under aerobic pathway and then to BA under anaerobic pathway. In summary, Acinetobacter baumannii DP-2 shows great potential for the degradation of DBP in contaminated soils.

Prevalence incidence and clinical outcome of Klebsiella and Acinetobacter ventilator-associated pneumonia

Introduction: Antimicrobial resistance identification for each hospital has benefits in management of nosocomial infections. Objectives: The aim of this study was to determine antimicrobial susceptibility of meropenem against Acinetobacter and Klebsiella strains in samples obtained from hospitalized patients with ventilator-associated pneumonia (VAP). Patients and Methods: In this cross-sectional study, 100 patients with VAP were selected from the intensive care unit (ICU) of Amin hospital in Isfahan. Lung secretions were collected and tested for bacterial infections. In samples with the positive bacterial infection, E-test and agar diffusion test were used to determine and compare the susceptibility of Acinetobacter and Klebsiella strains to meropenem. Results: The two susceptibility testing methods – E-test and agar diffusion test – showed similar results in 87 cases (87%) therefore, 84 cases were resistant and three cases were susceptible to meropenem. However, in 13 cases, the result of the agar diffusion test was resistant and the result of E-test was sensitive. According to the Kappa test, the agreement between the two tests was 0.87 and statistically significant (P <0.001). Conclusion: Due to the high resistance of Klebsiella and Acinetobacter strains to meropenem, it should not be used as an experimental treatment in patients diagnosed with VAP caused by these strains. We recommend using meropenem for Acinetobacter and Klebsiella after susceptibility testing by E-test confirmed its efficacy.

Organic and inorganic nitrogen removals by an ureolytic heterotrophic nitrification and aerobic denitrification strain Acinetobacter sp. Z1: Elucidating its physiological characteristics and metabolic mechanisms

Although heterotrophic nitrification-aerobic denitrification (HN-AD) is promising in nitrogen removal, it remains unclear for most HN-AD strains in physiological characteristics and metabolic mechanisms. In this study, a newly isolated strain Acinetobacter sp. Z1 converted not only inorganic nitrogen, but also organic nitrogen to N2. Among them, urea was the preferential nitrogen substrate. Single-factor experiments showed that efficient HN-AD process occurred with acetate as carbon source, C/N ratios of 12 for NH4+-N and 15 for NO3–-N, pH 8, 30 °C, DO of ∼5.8 mg/L and salinity less than 1.5 %. Subsequently, response surface analysis was applied to predict the optimal growth conditions. Its complete genome annotation in combination with enzymatic activity assay and nitrogen balance calculation showed that at least four pathways involved in nitrogen metabolism. This work indicates that ureolytic strain Z1 could be prepared as bacterial agents with other HN-AD strains to treat urea-containing wastewater like urine from urban community.

Comparison of fast Fourier transform infrared spectroscopy biotyping with whole genome sequencing-based genotyping in common nosocomial pathogens

Early detection of bacterial transmission and outbreaks in hospitals is important because nosocomial infections can result in health complications and longer hospitalization. Current practice to detect outbreaks uses genotyping methods amplified fragment length polymorphism (AFLP) and whole genome sequencing (WGS), which are not suitable methods for real-time transmission screening of both susceptible and resistant bacteria. The aim was to assess the typing technique Fourier transform infrared (FTIR) spectroscopy as real-time screening method to discriminate large amounts of susceptible and resistant bacteria at strain level when there is no evident outbreak in comparison with the WGS reference. Isolates of past hospital outbreak strains of Acinetobacter baumannii/calcoaceticus complex (n = 25), Escherichia coli (n = 31), Enterococcus faecium (n = 22), Staphylococcus aureus (n = 37) and Pseudomonas aeruginosa (n = 30) were used for validation of FTIR. Subsequently, Enterococcus faecalis (n = 106) and Enterococcus faecium (n = 104) isolates from weekly routine screening samples when no potential outbreak was present were analysed. FTIR showed reproducibility and congruence of cluster composition with WGS for A. baumannii/calcoaceticus complex and E. faecium outbreak isolates. The FTIR results of E. faecalis and E. faecium isolates from routine samples showed reproducibility, but the congruence of cluster composition with WGS was low. For A. baumannii/calcoaceticus complex and E. faecium outbreak isolates, FTIR appears to be a discriminatory typing tool. However, our study shows the discriminatory power is too low to screen real-time for transmission of E. faecium and E. faecalis at patient wards based on isolates acquired in routine surveillance cultures when there is no clear suspicion of an ongoing outbreak.

Metagenomic views on taxonomic and functional profiles of the Himalayan Tsomgo cold lake and unveiling its deterzome potential.

Cold habitat is considered a potential source for detergent industry enzymes. This study aims at the metagenomic investigation of Tsomgo lake for taxonomic and functional annotation, unveiling the deterzome potential of the residing microbiota at this site. The present investigation revealed molecular profiling of microbial community structure and functional potential of the high-altitude Tsomgo lake samples of two different temperatures, harvested during March and August. Bacteria were found to be the most dominant phyla, with traces of genomic pieces of evidence belonging to archaea, viruses, and eukaryotes. Proteobacteria and Actinobacteria were noted to be the most abundant bacterial phyla in the cold lake. In-depth metagenomic investigation of the cold aquatic habitat revealed novel genes encoding detergent enzymes, amylase, protease, and lipase. Further, metagenome-assembled genomes (MAGs) belonging to the psychrophilic bacterium, Arthrobacter alpinus, were constructed from the metagenomic data. The annotation depicted the presence of detergent enzymes and genes for low-temperature adaptation in Arthrobacter alpinus. Psychrophilic microbial isolates were screened for lipase, protease, and amylase activities to further strengthen the metagenomic findings. A novel strain of Acinetobacter sp. was identified with the dual enzymatic activity of protease and amylase. The bacterial isolates exhibited hydrolyzing activity at low temperatures. This metagenomic study divulged novel genomic resources for detergent industry enzymes, and the bacterial isolates secreting cold-active amylase, lipase, and protease enzymes. The findings manifest that Tsomgo lake is a potential bioresource of cold-active enzymes, vital for various industrial applications.

Isolation, identification and biodegradation characterization of a novel monensin-degrading bacterial strain

Biodegradation of antibiotic pollutants by microorganisms has received widespread attention, to which the identification of microorganisms capable of efficiently degrading antibiotics is a key. In this study, a strain DM-1 with high degradation capability was successfully isolated from monensin-contaminated chicken manure by using monensin as the sole carbon source. The strain was further identified basing on morphological, physiological and biochemical characteristics and 16S rRNA gene sequence-based phylogenetic analysis. The degradation efficiency of DM-1 for monensin was determined by HPLC post-column derivatization, and then the degradation conditions of DM-1 were optimized. DM-1 was identified as a strain of Acinetobacter and named as Acinetobacter baumannii DM-1. The optimal conditions for monensin degradation by strain DM-1 were pH 7.0, 30 ℃, and initial monensin concentration of 50 mg/L. The strain DM-1 degraded more than 87.51% of monensin at an initial concentration of 10 mg/L in 28 days, while only a slight decrease in monensin concentration was observed in the control without monensin-degrading strain. This study indicates that the strain DM-1 has a promising application prospect in the bioremediation of monensin-contaminated environment.

Profiling Antibiotic Resistance in Acinetobacter calcoaceticus.

Background: Acinetobacter spp. have emerged as troublesome pathogens due to their multi-drug resistance. The majority of the work to date has focused on the antibiotic resistance profile of Acinetobacter baumannii. Although A. calcoaceticus strains are isolated in the hospital setting, limited information is available on these closely related species. Methods & Results: The computational analysis of antibiotic resistance genes in 1441 Acinetobacter genomes revealed that A. calcoaceticus harbored a similar repertoire of multi-drug efflux pump and beta-lactam resistance genes as A. baumannii, leading us to speculate that A. calcoaceticus would have a similar antibiotic resistance profile to A. baumannii. To profile the resistance patterns of A. calcoaceticus, strains were examined by Kirby–Bauer disk diffusion and phenotypic microarrays. We found that Acinetobacter strains were moderately to highly resistant to certain antibiotics within fluoroquinolones, aminoglycosides, tetracyclines, and other antibiotic classes. These data indicate that A. calcoaceticus has a similar antibiotic resistance profile as A. baumannii ATCC 19606. We also identified that all Acinetobacter species were sensitive to 5-fluoroorotic acid, novobiocin, and benzethonium chloride. Conclusion: Collectively, these data provide new insights into the antibiotic resistance in A. calcoaceticus and identify several antibiotics that could be beneficial in treating Acinetobacter infections.

Enhancing fluoroglucocorticoid defluorination using defluorinated functional strain Acinetobacter. pittii C3 via humic acid-mediated biotransformation

Defluorination is a key factor in reducing biologically accumulated carcinogenic and teratogenic toxicity of fluoroglucocorticoids (FGCs). To enhance defluorination efficiency, a highly efficient defluorination-degrading strain Acinetobacter. pittii C3 was isolated, and the promotion mechanism through humic acid (HA)-mediated biotransformation was investigated. Optimal biodegradation conditions for Acinetobacter sp. pittii C3 were pH of 7.0, temperature of 25 ℃, and HA content of 5.5 mg/L, according to response surface methodology analysis. The attenuation rate constant and maximum defluorination percentage of triamcinolone acetonide (TA) in HA-mediated biotransformation system (HA-C3) were 3.99 × 10−2 and 96%, respectively, which were 2.22 and 1.24 times higher than those in the unitary C3 biodegradation system (U-C3), respectively. The major defluorination pathways included elimination, hydrolysis, and hydrogenation, with contributions of 24.5%, 32.4%, and 43.1%, respectively. The bio-reductive hydrodefluorination rate was enhanced by 1.89 times that of HA-mediated, while the other two defluorination pathways exhibited insignificant changes. HA, as the congeries of negatively charged microbes and hydrophobic TA, accelerates the electron transfer rate between Acinetobacter. pittii C3 and TA through the quinone groups. Furthermore, the mutual conversion between the functional groups of hydroxyl oxidation and ketone reduction of HA provided electron donors for TA reductive defluorination and hydrogenation and electron acceptors for TA oxidation. This study provides an effective strategy for FGC-enhanced detoxification using natural HA.

Efficient enzymatic depolymerization of polycaprolactone into 6-hydroxyhexanoic acid by optimizing reaction conditions and microbial conversion of 6-hydroxyhexanoic acid into adipic acid for eco-friendly upcycling of polycaprolactone

Polycaprolactone (PCL) is one of the most widely used biodegradable plastics. An enzymatic method that utilizes Candida antarctica lipase B (CalB) was used to successfully depolymerize PCL into 6-hydroxyhexanoic acid (6-HHA) and confirmed by high-performance liquid chromatography analysis. To improve the 6-HHA production titer, we optimized various depolymerization conditions, such as pH, reaction temperature, enzyme addition timing, and enzyme quantities. The optimized reaction conditions included a calcium carbonate-controlled pH, a reaction temperature of 50 °C, and the addition of 0.69 U CalB once every 24 h for 2 days. These variables produced a titer of 114.9 g/L of 6-HHA and productivity of 2.87 g/L/h from 100 g/L PCL. We also attempted to produce adipic acid (AA) using 6-HHA prepared from PCL depolymerization. Using a recombinant Escherichia coli strain with the 6-HHA dehydrogenase and 6-oxohexanoic acid dehydrogenase genes from Acinetobacter strain SE19, 6-HHA was successfully converted into AA. To best our knowledge, ours is the first report regarding an optimization study to improve the PCL depolymerization efficiency via an enzymatic reaction method and the microbial upcycling of 6-HHA into AA. Thus, this study sets the groundwork for the eco-friendly recycling of waste PCL into a value-added chemical using a biocatalytic method.

The role of Acinetobacter baumannii CarO outer membrane protein in carbapenems influx

The gram-negative strain Acinetobacter baumannii is a cocobacillus, non-motile and aerobic organism that is often found in nosocomial infections. Many institutions worldwide such as WHO are grappling with antibiotic resistance A. baumannii. Therefore, in recent years, there have been many studies in the literature about antibiotic resistance mechanisms. We studied the specificity of carbapenems for CarO, an outer membrane protein associated with imipenem-resistance that was strongly related to a decrease in CarO expression level or changes in protein structure. The specificity of five different carbapenems, imipenem, biapenem, ertapenem, faropenem, and meropenem, against the A. baumannii ATCC-17978 CarO protein, as well as the specificity of imipenem for five different types Type-1, Type-2, Type-3, Type-4, and ATCC-17978 CarO protein, were investigated using computational methods. In this study, homology modeling, molecular docking, membrane–protein complex building, and 800 ns long MD simulation methods were followed. The interactions of imipenem with the extracellular region of five different forms of CarO protein were investigated in this study, as well as five different antibiotic binding profiles to the model organism ATCC-17978 CarO protein. The mechanism of CarO influx has been revealed with this study at the molecular level and this data is intended to be used in future research, mutagenesis, and clinical trials.