Multidrug-resistant Bacteria Research Articles

Molecular Detection of Carbapenemases in Acinetobacter baumannii Strains of Portugal and Association With Sequence Types, Capsular Types, and Virulence

Carbapenem-resistant Acinetobacter baumannii (CRAB) is an important nosocomial pathogen. The capsular type (K-type) is considered a major virulence factor, contributing to the evasion of host defenses. The global spread and dissemination dynamics between K-types, sequence types (ST), antibiotic resistance genes, and virulence factors remain largely unknown in Portugal. A collection of 96 CRAB clinical samples collected between 2005 and 2019 in the northern region of Portugal were tested for antimicrobial susceptibility profile and screened by polymerase chain reaction for resistance genetic determinants. A subset of 26 representative isolates was subjected to whole-genome sequencing to assess K types, ST types, and genomic relatedness. The pathogenicity of distinct K-types was also tested using Galleria mellonella model. For the 96 CRAB isolates analyzed, high antimicrobial resistance (>90%) was observed to the carbapenems, fluoroquinolones, and miscellaneous agents. Greater antimicrobial susceptibility (∼30%-57%) was observed for aminoglycosides, particularly tobramycin, and amikacin. Genotypically, 75 strains (78.5%) carried blaOXA-23-like, 18 strains (18.8%) carried blaIMP-like, and 11 strains (14.9%) carried blaOXA-40-like carbapenem resistance genes, respectively. Associations between OXA and ST/capsular locus (KL) types were observed over the years (eg, OXA-40-like/ST46Past/KL120 and OXA-23-like/ST2Past/KL2). ST2Past of clonal complex II was present in most strains, a dominant drug-resistant lineage in the United States and Europe. KL7 was also the most prevalent KL-type (38.5%), followed by KL2 (34.6%), KL120 (23.1%), and KL9 (3.8%). Virulence assessment for different K-types in a Galleria mellonella model revealed a significantly increased virulence for KL120 when compared with KL7, KL9, and KL2. There are specific CRAB serotypes circulating in Portugal, accounting by the low diversity of acquired carbapenemase genes (OXA-23-like and OXA-40-like), ST types (ST2 and ST46) and KL types (KL2, KL7, KL9, and KL120) identified. The high prevalent of ST2, especially when associated with KL2 and blaOXA-23-like, suggest that antibiotic resistance has been driven by clonal expansion of clonal complex II. Such findings provide useful information on the diversity of multidrug-resistant bacterium that might be relevant for antibacterial interventions.

Prevalence of antibiotic resistance genes in bacteria from Gomti and Ganga rivers: implications for water quality and public health.

Rivers serve as a significant habitat and water sources for diverse organisms, including humans. An important environmental and public health concern is the increase in antibiotic-resistant bacteria (ARBs) and genes (ARGs) in aquatic ecosystems brought about by excessive pollutant flow. The research highlighted that river water, which is receiving discharge from wastewater treatment plants, is harbouring multidrug-resistant bacteria. River water samples were collected in January, April, July and October 2022 from three separate locations of each Gomti and Ganga river. A total of 114 bacteria were isolated from Gomti as well as the Ganga River. All the isolates were tested for their resistance to various antibiotics by disc diffusion method. The isolated bacteria were tested for the antibiotic resistance genes using PCR and were identified by 16s rRNA sequencing. The ARBs percentages for each antibiotic were as follows: ampicillin (100%); cefotaxime (96.4, 63.1%); erythromycin (52.6, 57.8%); amikacin (68.4, 50.8%); tetracycline (47.3, 54.3%); nalidixic acid (47.3, 45.6%); streptomycin (68.4, 49.1%); gentamycin (43.8, 35%); chloramphenicol (26.3, 33.3%); neomycin (49.1, 29.8%) and ciprofloxacin (24.5, 7.01%). Further, antibiotic resistance genes in Gomti and Ganga water samples disclose distinctive patterns, including resistance to ermB (25, 40%); tetM (25, 33.3%); ampC (44.4, 40%) and cmlA1 (16.6%). Notably cmlA1 resistant genes were absent in all bacterial strains of the Gomti River. Additionally, gyrA gene was not found in both the river water samples. The presence of ARGs in the bacteria from river water shows threat of transferring these genes to native environmental bacteria. To protect the environment and public health, constant research is necessary to fully understand the extent and consequences of antibiotic resistance in these aquatic habitats.

Applications of Nanotechnology in Treating Infections Caused by Multidrug Resistance Bacteria

Applications of Nanotechnology in Treating Infections Caused by Multidrug Resistance Bacteria

Challenges and opportunities of phage therapy for Klebsiella pneumoniae infections.

Traditional antibiotics have been effective in many cases. However, the rise in multidrug-resistant bacteria has diminished their therapeutic efficacy, signaling the dawn of an era beyond antibiotics. The challenge of multidrug resistance in Klebsiella pneumoniae is particularly critical, with increasing global mortality and resistance rates. Therefore, the development of alternative therapies to antibiotics is urgently needed. Phages, which are natural predators of bacteria, have inherent advantages. However, comprehensive information on K. pneumoniae phages is lacking in current literature. This review aims to analyze and summarize relevant studies, focusing on the present state of phage therapy for K. pneumoniae infections. This includes an examination of treatment methodologies, associated challenges, strategies, new phage technologies, clinical trial safety and efficacy, regulatory issues, and future directions for phage therapy development. Enhancing phage technology is crucial for addressing the evolving threat of multidrug-resistant K. pneumoniae.

Phage therapy: A novel approach against multidrug-resistant pathogens.

The rapid rise of multidrug-resistant (MDR) organisms has created a critical need for alternative treatment options. Phage therapy is gaining attention as an effective way to fight bacterial infections by using lytic bacteriophages to specifically target and kill harmful bacteria. This review discusses several phage therapeutic options and emphasizes new developments in phage biology. Phage treatment has proven to be successful against MDR bacteria, as evidenced by multiple human clinical trials that indicate favorable results in treating a range of diseases caused by these pathogens. Despite these promising results, challenges such as phage resistance, regulatory hurdles, and the need for standardized treatment protocols remain. To effectively combat MDR bacterial infections, future research must focus on enhancing phage effectiveness, guaranteeing safety for human usage and incorporating phage therapy into clinical practice.

Effect of X-ray radiation on Multi-drug Resistant (MDR) Enterobacteriaceae & P.aeruginosa isolated from burn unit patient. The phenotypic and molecular study, Biofilm formation

Background: Multi-drug-resistant (MDR) bacteria are a significant global health concern due to their elevated rates of morbidity and mortality in burn patients. In This study investigated the presence of multidrug-resistant pathogenic bacteria in individuals with burn injuries, the formation of biofilms, and the impact of X-ray radiation. Method: For this study Clinical swabs about120 burn patients were obtained between December 2023 and June 2024 from burn units at Ramadi and Falluja Teaching Hospitals. Both conventional and Vitek2(bioMérieux) methods were used to identify the bacterial isolates. The isolates were then divided into three multi-drug resistance groups. The Colorimetric method (MTP) detected biofilms. To detect blaOXA-23,blaOXA-48, Omp, and blaTEM resistance genes, multiplex PCR was used. This research used two lumbosacral spine X-ray levels. Two levels of radiation were used 40 (80KV) mAs and 51.2 (85KV). Result: Results of burn isolation revealed 30(27%) P.aeruginosa, 18(16%) k.pneumoniae, 7(6%) E.coli, 7(6%) P.mirabilis. Of the all isolates, 100% produced biofilm. The Multiplex-PCR analysis revealed that the blaTEM genes were the predominant ones, constituting 30% of the samples. Subsequently, blaOXA-23 constituted 24.5% of the cases, whereas Omp accounted for 22.7% and blaOXA-48 for 13.6%. The radiation impact of X-rays produced by two dosages, 40(80KV)mAs for 125msec and 51,2(85KV) mAs for 160msec, demonstrates that there is no effect or alteration in the resistance capacity of all the bacterial isolates tested. Conclusion: This study showed that burn unit isolates produce ESBLs, which is a major concern in the intensive care unit due to its high morbidity and potential mortality. These data match antibiotic phenotypic test results showing substantial cefepime resistance. All isolates forming biofilms, this may association with high pathogenicity. This demands quick intervention to manage nosocomial outbreaks. No X-ray effect was seen on susceptibility a burn unit bacterial isolate.

Molecular characterization of blaTEM and blaCTX-M ESBLs genes producing Escherichia coli isolates from urinary tract infections (UTIs) in Al-Basrah province, Iraq

Urinary tract infections (UTIs) are primarily caused by Gram-negative Enterobacteriaceae bacteria, accounting for 80–90% of uropathogenic Escherichia coli infections. Multidrug-resistant (MDR) bacteria, such as extended-spectrum β-lactamases (ESBLS), pose a significant threat to global healthcare systems. The current study relied on 200 urine samples collected from patients suffering urinary tract infections (UTIs) in Al Sadr Teaching Hospital in Al-Basrah Province,Iraq from the 5th January to 22nd February. A result of cultivated 200 samples collected from urinary tract infection patients showed 71 (35.5%) positive samples on MacConkey agar, eosin methylene blue (EMB), and HiChromeTM E.coli agar, and bacterial growth was distributed to 47 (66.2%) Escherichia coli and 24 (33.8%) of Gram-negative species. The diagnostic gene 16S rDNA by PCR method showed that all 47 E. coli isolates had a molecular weight of around 585 bp at 100%. Furthermore, positive results were shown in 44 (93.6%) of the E.coli isolates in the current study that produced ESBLs by using the double-disc approximation method (DAM). While 3 (6.4%) isolates revealed negative results for ESBLs, whereas the13(27.7%) of the E.coli isolates gave positive results for ESBL. While 34(72.3%) E.coli isolates showed negative results for produced ESBLs by using the double-disc synergy test (DDST), there were significant differences (P<0.01) between positive and negative isolates in both methods used to detect ESBL-producing isolates. Extended-spectrum β-lactamses (ESBLs) genes were detected by using PCR to amplify the blaTEM and blaCTX-M genes in E.coli isolates. The amplified genes' bands were characterised approximately at (800 bp) for blaTEM and (754 bp) for blaCTX-M , the products were compared to the standard molecular DNA ladder at (2000 bp). According to the results, 47(100%) E.coli isolates gave positive results for the blaTEM gene. While blaCTX-M gene was shown, only 23(48.9%) E.coli isolates had positive results for the blaCTX-M gene.

Synthesis of metal(II) acetate complexes with a heterocyclic azo dye ligand: Characterization, geometrical molecular structures, antioxidant, biological activities, DNA binding and molecular docking studies

A series of Cu(II), Co(II), Ni(II), Mn(II), and UO2(II) complexes have been prepared from the ligand 4-(2’,4’-dihydroxybenzaldehyde phenylazo)antipyrine (H2L). FT-IR spectra demonstrated that the ligand under investigation behaves as a bi-and tridentate centre ligand through the phenolic oxygen of aldehydic, azo nitrogen atoms and carbonyl oxygen of antipyrine and forms a stable five- and six-membered chelating ring. From the X-ray crystallographic analysis (XRD) patterns of the ligand and complexes showed the polycrystalline phases are indicated by the multiple diffraction peaks in the 1igand and its complex (5). The HOMO‒LUMO energy gaps (∆E) were used to create theoretical models for the structure and confirmation barriers in molecular systems for the ligand (H2L) and metal complexes. It was found that the Cu(II), Co(II), Ni(II), and Mn(II) complexes have lower values for HOMO‒LUMO energy gaps (∆E), indicating that they are more stable than the 1igand. The biological activities of ligand (H2L) and its metal complexes showed that ligand was stronger antimicrobial and antioxidant agent than its metal complexes. 50 µg/ml H2L caused inhibition zones ranged from 13 to 20 mm against the tested bacteria and 13 to 16 against fungi. In addition, the present study tested metal (II) acetate complexes with a heterocyclic azodye ligand for their application in the textile industry as antimicrobial dyed fabrics. All obtained results confirmed the possibility of using the prepared compounds in different industrial applications. The 1igand (H2L) and its metal complexes showed moderate to strong antimicrobial activities in agar well diffusion, MIC, and antioxidant tests. Ligand and its metal complexes revealed inhibition zones against all tested microbes ranged between 6 to 24 mm. The MIC values of ligand and its metal complexes were recorded at 20 to 30 μg/ml and 30 to 145 μg/ml, respectively. 50 µg/ml of 1igand and its metal complexes was enough to complete inhibit Gram negative E. coli moreover they could inhibit the multidrug resistant bacteria K. pneumoniae and Pseudomonas sp. By molecular docking study, it was found that the complex (1) showed the highest and better binding affinity (-8.38874 and -7.74442 kcal/mol) than other 1igand (H2L) and complexes (2–5) for the breast cancer (3HB5) protein central activity and the colon cancer (2HQ6) protein central activity.

Combination of medicinal plants with antibiotics against Klebsiella pneumoniae and Acinetobacter baumannii

Background and aims: One essential plant-based strategy to deal with infections is antimicrobial synergism, which can make antimicrobials more efficient. The aim of this study was to investigate the interaction between these extracts and two widely used antibiotics, meropenem and gentamicin, on two multidrug-resistant (MDR) bacteria, K. pneumoniae and A. baumannii, in vitro. Methods: Different concentrations of Rosa damascena Mill., Malva sylvestris L., and Zataria multiflora Boiss. hydroalcoholic extracts (2-fold serial dilution from 131072 to 256 μg/mL) were administered against two MDR bacteria, and their combination with gentamicin and meropenem (serial dilution from 32 to 0.015 μg/mL) was investigated by the resazurin-based microdilution and the checkerboard method. The phytochemical properties of the extracts were also examined, and the total phenolic content (TPC), total flavonoid content (TFC), anthocyanin content, and antioxidant capacity of the extracts were determined. Results: Z. multiflora and R. damascena showed high antibacterial activity, and their minimal inhibitory concentrations on Acinetobacter baumannii were 1024 and 2048 μg/mL, respectively. Z. multiflora also had high TFC, TPC, and antioxidant activity and demonstrated additive interaction with meropenem and gentamicin with fractional inhibitory concentrations of 1 and 0.75, respectively. Conclusion: We suggest the potency of Z. multiflora-antibiotic combinations in treating MDR A. baumannii after future clinical studies.

Design, synthesis, and bioactivity investigation of novel cyclic lipopeptide antibiotics targeting top-priority multidrug-resistant gram-negative bacteria

ObjectivesPolymyxins are the last-line therapy for top-priority multidrug-resistant (MDR) gram-negative bacteria. However, polymyxin nephrotoxicity impedes its clinical application. This study aimed to design, synthesize, and identify a novel and promising polymyxin derivative with high efficacy and low toxicity. MethodsTo design polymyxin derivatives, we reduced the hydrophobicity of the two hydrophobic domains (fatty acyl chain and D-Phe6-L-Leu7) and modified the positive charged L-2,4-diaminobutyric acid (Dab) residues. Twenty-five derivatives were synthesized, and their antibacterial activities in vitro and renal cytotoxicities were determined. The nephrotoxicity and pharmacokinetic parameters of compound 12 were examined in rats. Antibacterial efficacy in vivo was evaluated using a mouse systemic infection model. Surface plasmon resonance analysis, compound 12-rifampicin combination therapy, and scanning electron microscopy were used to study the mechanism of action of compound 12. ResultsThis research found a new compound, identified as compound 12, which showed similar or increased antibacterial activity against all tested sensitive and carbapenem-resistant gram-negative bacteria. It exhibited reduced renal cytotoxicity and nephrotoxicity, a favorable pharmacokinetic profile, and maintained or improved antibacterial efficacy in vivo. Importantly, its anti-Pseudomonas aeruginosa activity significantly improved. Compound 12, when combined with rifampicin, enhanced the activity of rifampin against gram-negative bacteria. Compound 12 also showed a high affinity for lipopolysaccharide and disrupted cell membrane integrity. ConclusionReducing the hydrophobicity of the two domains reduced renal cytotoxicity and nephrotoxicity. Shortening the side chain of Dab3 by one carbon maintained or increased its antibacterial activity both in vitro and in vivo. Furthermore, only the length of the side chain of Dab9 could be shortened by one carbon among the Dab1,5 and Dab8,9 residues. The bactericidal effects of compound 12 were related to the disruption of cell membrane integrity. Compound 12 may be a promising candidate for combating sensitive and carbapenem-resistant gram-negative bacterial infections, especially Pseudomonas aeruginosa.

Strain-level multidrug-resistant pathogenic bacteria in urban wastewater treatment plants: Transmission, source tracking and evolution

Wastewater treatment plants (WWTPs) serve as reservoirs for various pathogens and play a pivotal role in safeguarding environmental safety and public health by mitigating pathogen release. Pathogenic bacteria, known for their potential to cause fatal infections, present a significant and emerging threat to global health and remain poorly understood regarding their origins and transmission in the environment. Using metagenomic approaches, we identified a total of 299 pathogens from three full-scale WWTPs. We comprehensively elucidated the occurrence, dissemination, and source tracking of the pathogens across the WWTPs, addressing deficiencies in traditional detection strategies. While indicator pathogens in current wastewater treatment systems such as Escherichia coli are effectively removed, specific drug-resistant pathogens, including Pseudomonas aeruginosa, Pseudomonas putida, and Aeromonas caviae, persist throughout the treatment process, challenging complete eradication efforts. The anoxic section plays a predominant role in controlling abundance but significantly contributes to downstream pathogen diversity. Additionally, evolution throughout the treatment process enhances pathogen diversity, except for upstream transmission, such as A. caviae str. WP8-S18-ESBL-04 and P. aeruginosa PAO1. Our findings highlight the necessity of expanding current biomonitoring indicators for wastewater treatment to optimize treatment strategies and mitigate the potential health risks posed by emerging pathogens. By addressing these research priorities, we can effectively mitigate risks and safeguard environmental safety and public health.

Trends in Antimicrobial Resistance of Uropathogens Isolated from Urinary Tract Infections in a Tertiary Care Hospital in Dhaka, Bangladesh.

Background/Objectives: Urinary tract infection (UTI) is a prevalent microbial infection in medical practise, leading to significant patient morbidity and increased treatment costs, particularly in developing countries. This retrospective study, conducted at a tertiary care hospital in Dhaka, Bangladesh, aims to examine the antimicrobial resistance (AMR) patterns of uropathogens and evaluate whether these patterns are influenced by demographic factors such as gender, age, or patient status. Methods: Standard microbiological techniques were used to identify uropathogens, and AMR patterns were determined using the Kirby-Bauer disc diffusion method. Results: Out of 6549 urine samples, 1001 cultures were positive. The infection was more prevalent in females compared to males. The incidence of UTIs in children aged 0-10 years accounted for 12.59% of the total cases, with this age group also exhibiting the highest rate of polymicrobial infections. Among the bacterial uropathogens, 71.19% of isolates were multidrug resistant (MDR) and 84.27% were resistant to at least one antibiotic. Escherichia coli (n = 544, 73.90% MDR) and Klebsiella species (n = 143, 48.95% MDR) were the most common Gram-negative uropathogens, while Enterococcus species (n = 78, 94.87% MDR) was the predominant Gram-positive isolate in this study. Our results indicate that most uropathogens showed resistance against ceftazidime, followed by cefuroxime, trimethoprim-sulfamethoxazole, amoxicillin-clavulanate, and netilmicin. Moderate levels of resistance were observed against ciprofloxacin, levofloxacin, aztreonam, and cefpodoxime. Conclusions: Amikacin was observed to be effective against Gram-negative uropathogens, whereas cefixime was more active against Gram-positive microorganisms, such as Enterococcus species. Moreover, a principal coordinate analysis (PCoA) depicted no significant influence of gender, patient status, or age on AMR patterns. For the continued usefulness of most antibiotics, periodic analysis of the AMR patterns of uropathogens can help assess the rise of MDR bacteria, and therefore guide the selection of appropriate antibiotic treatment strategies.

Enhanced Antibacterial Activity of Levofloxacin with Cucurbit[7]uril-Functionalized Gold Nanoparticles.

Bacterial infection is one of the major concerns of the growing society, and over the years, different permutations and combinations of various drugs and adjuvants have been attempted, which led to considerable improvements in the efficacy of the antibacterial drugs. In this regard, macrocyclic receptors such as cyclodextrin, cucurbiturils, calixarene, etc., have played a major role by modulating the drug properties that supplement the antibacterial efficacy. In this study, we have developed cucurbit[7]uril (CB7)-functionalized Au nanoparticles (CB7AuNPs) to modulate the activity of an antibiotic, levofloxacin (LOFL). From the spectroscopic and thermodynamic changes in the LOFL, it has been established that two of the prototropic forms, LOFLH and LOFLH2+, form strong 1:1 host/guest complexes with CB7/CB7AuNP. Both these interactions led to significant upward shifts in the pKa values as well as photostability of LOFL, thereby enhancing the availability of the active form for the antibacterial activity, at the physiological pH. Further, the LOFL uptake has also been established on CB7AuNP, which retained the CB7-LOFL activity at very low concentration of the CB7 host, functionalized on AuNP. Detailed antibacterial studies of LOFL, both as complexed with CB7 and CB7AuNP, were carried out using four food-borne pathogens (Escherichia coli, S. Typhimurium, Bacillus cereus, and Staphylococcus aureus), which revealed a creditable enhancement in the antibacterial property, irrespective of the bacterium strain. These results are quite promising at this stage for the development of drugs customized for multidrug-resistant bacteria.

Prevalence and Molecular Epidemiology of Intestinal Colonization by Multidrug-Resistant Bacteria among Hematopoietic Stem-Cell Transplantation Recipients: A Bulgarian Single-Center Study.

Background/Objectives: Intestinal colonization by multidrug-resistant (MDR) bacteria is considered one of the main risk factors for invasive infections in the hematopoietic stem-cell transplant (HSCT) setting, associated with hard-to-eradicate microorganisms. The aim of this study was to assess the rate of intestinal colonization by MDR bacteria and their microbial spectrum in a group of post-HSCT patients to study the genetic determinants of beta-lactam and glycopeptide resistance in the recovered isolates, as well as to determine the epidemiological relation between them. Methods: The intestinal colonization status of 74 patients admitted to the transplantation center of University Hospital "St. Marina"-Varna in the period January 2019 to December 2021 was investigated. Stool samples/rectal swabs were screened for third-generation cephalosporin and/or carbapenem-resistant Gram-negative bacteria, methicillin-resistant Staphylococcus aureus (MRSA), vancomycin-resistant enterococci (VRE), and Stenotrophomonas maltophilia. Identification and antimicrobial susceptibility testing were performed by Phoenix (BD, Sparks, MD, USA) and MALDI Biotyper sirius (Bruker, Bremen, Germany). Molecular genetic methods (PCR, DNA sequencing) were used to study the mechanisms of beta-lactam and glycopeptide resistance in the collected isolates, as well as the epidemiological relationship between them. Results: A total of 28 patients (37.8%) were detected with intestinal colonization by MDR bacteria. Forty-eight non-duplicate MDR bacteria were isolated from their stool samples. Amongst them, the Gram-negative bacteria prevailed (68.8%), dominated by ESBL-producing Escherichia coli (30.3%), and followed by carbapenem-resistant Pseudomonas sp. (24.2%). The Gram-positive bacteria were represented exclusively by Enterococcus faecium (31.2%). The main beta-lactam resistance mechanisms were associated with CTX-M and VIM production. VanA was detected in all vancomycin-resistant enterococci. A clonal relationship was observed among Enterobacter cloacae complex and among E. faecium isolates. Conclusions: To the best of our knowledge, this is the first Bulgarian study that presents detailed information about the prevalence, resistance genetic determinants, and molecular epidemiology of MDR gut-colonizing bacteria in HSCT patients.

Chemical composition and antimicrobial activity of Plinia rivularis essential oil against multidrug-resistant bacteria

IntroductionThe increasingly common occurrences of multidrug-resistant bacteria represent a global health threat and the discovery of new alternative remedies is necessary. The use of essential oils (EOs) in the treatment of many pathogenic bacteria is promising and several examples have already been highlighted regarding their inhibitory action. Among the botanical families, Myrtaceae stands out for presenting important species that supply bioactive products. MethodsIn this work we investigate the chemical composition of Plinia rivularis (Myrtaceae) leaf EO and its antibacterial activity against resistant and non-resistant bacteria. The EO was obtained by two methods, hydrodistillation and steam distillation. Gas chromatography-flame ionization detector (GC-FID), gas chromatograph-mass spectrometry (GC-MS), nuclear magnetic resonance spectroscopy (NMR) and Fourier transform infrared spectroscopy (FTIR) were the techniques used in the EO chemical characterization. ResultsThe EOs were obtained with yields of 0.37 and 0.16% by hydrodistillation and steam distillation methods, respectively. The analyzes revealed the EOs chemical profile showing the compounds 2H-benzocyclohepten-2-one,3,4,4a,5,6,7,8,9-octahydro-4a-methyl (synonym: 4a-methyl-3,4,4a,5,6,7,8,9-octahydro-2H-benzo[7]annulen-2-one), rosifoliol, β-eudesmol and the diterpene kaurene as main constituents. Through preparative thin-layer chromatography (PTLC), it was possible to obtain the diterpene kaurene with a content of 91%, which was also characterized by NMR. The minimum inhibitory concentrations of EO against bacteria ranged from 0.56 to 2.25 mg.ml−1 and 2.25–36 mg.ml−1 for sensitive and resistant bacteria, respectively. Also, EO showed synergistic activity with amikacin and cefotaxime against carbapenem-resistant Pseudomonas aeruginosa (KPC). ConclusionsThis is the first report on the chemical composition of P. rivularis EO. Comparison of extraction methods showed variation in yields and small changes in component content. The EO demonstrated activity against resistant and non-resistant bacteria. In addition, the synergistic effect of EO against resistant bacteria may be explored in future studies.

Population pharmacokinetic analysis and dosing optimization of colistin sulphate in lung transplant recipients with pneumonia: A prospective study

ObjectiveCurrently, there is a lack of information on the clinical pharmacokinetics (PK), effectiveness, and safety of colistin sulphate (CS) in lung transplant recipients. This study aims to improve CS dosing regimens and evaluate its population PK in lung transplant recipients. MethodsThis study evaluated the clinical efficacy, microbiological efficacy, and adverse events of CS in lung transplant recipients. The NONMEM program was employed to construct the population PK model, and Monte Carlo simulations were executed to establish dosing regimens according to the probability of target attainment (PTA). ResultsThe study included 146 CS concentrations, spanning from 0.05 to 4.18 mg/L from 39 lung transplant recipients with multidrug-resistant Gram-negative bacteria. 26 (66.67%) patients successfully eradicated bacteria, and 30 (76.92%) patients had clinical cure or improvement. Additionally, only 2 (5.13%) patients developed CS-related nephrotoxicity. The PK profile was effectively represented by a one-compartmental model with linear elimination. Creatinine clearance and concomitant furosemide use were recognized as covariates influencing the clearance of CS. Based on the PTA results, a daily dosage of 1.5 million IU, divided into 2–3 administrations, could attain a PTA exceeding 90% for MIC ≤ 1 µg/mL at creatinine clearance of about 110 mL/min. However, this regimen would lead to insufficient exposure for MIC ≥ 2 µg/mL. ConclusionsThe clearance of CS is significantly influenced by concomitant furosemide use and renal function. The currently recommended dosing regimens by label sheet may result in subtherapeutic exposure for MIC exceeding 1 mg/L in lung transplant recipients.

Esculetin Combats Multidrug-Resistant Salmonella Infection and Ameliorates Intestinal Dysfunction via the Nrf2 Pathway.

The increasing incidence of multidrug-resistant (MDR) Salmonella enterica serovar Typhimurium (S. Tm), known for causing invasive enteric infections, presents a significant public health challenge. Given the diminishing efficacy of existing antibiotics, it is imperative to explore novel alternatives for the treatment of MDR S. Tm infections. Here, we identified esculetin (EST), a natural coumarin abundant in dietary foods and herbs, as a compound exhibiting broad-spectrum antibacterial properties against a range of MDR bacteria. Our findings demonstrate that EST effectively inhibited the proliferation and expansion of MDR S. Tm in both in vitro experiments and animal models. Specifically, EST significantly downregulated the type 3 secretion system-1 (T3SS-1) virulence expression of MDR S. Tm, thereby preventing its invasion into intestinal epithelial cells. In S. Tm-infected mice, we observed cecal injury characterized by the upregulation of inflammatory cytokines, a reduction in goblet cell numbers, a decreased expression of tight junction proteins, and microbial dysbiosis. Conversely, EST treatment ameliorated these pathological changes induced by S. Tm infection and reduced oxidative stress by activating the nuclear factor erythroid 2-related factor 2 (Nrf2) signaling pathway, thereby improving intestinal barrier function. These results suggest that dietary coumarins or a targeted plant-based diet may offer a promising strategy to counteract MDR bacteria-induced enteric diseases.

Synergistic antimicrobial activity of alpha-linolenic acid in combination with tetracycline or florfenicol against multidrug-resistant Salmonella typhimurium

Salmonella is a major foodborne pathogen that can be transmitted from livestock and poultry to humans through the food chain. Due to the widespread use of antibiotics, antibiotic resistance Salmonella has become an important factor threatening food safety. Combining antibiotic and non-antibiotic agents is a promising approach to address the widespread emergence of antibiotic-resistant pathogens.In this study, we investigated the antibiotic resistance profile and molecular characterization of different serotypes of Salmonella isolated from large-scale egg farms using drug susceptibility testing and whole genome sequencing. The synergistic effect of alpha-linolenic acid (ALA) with antibiotics was evaluated using the checkerboard test and time-kill curve. The molecular mechanism of α-linolenic acid synergism was explored using biochemical assays, pull-down assays, and molecular docking. In vivo efficacy of ALA in combination with florfenicol (FFC) or tetracycline (TET) against multidrug-resistant (MDR) Salmonella enterica subsp. enterica serovar typhimurium was also investigated using a mouse model.We found that ALA reduced the minimum inhibitory concentration (MIC) of tetracycline and florfenicol in all strains tested. When ALA (512 mg/L) was combined with florfenicol (32 mg/L) or tetracycline (16 mg/L), we observed disruption of cell membrane integrity, increased outer membrane permeability, lowered cell membrane potential, and inhibition of proton-drive-dependent efflux pumps. The synergistic treatment also inhibited biofilm production and promoted oxidative damage. These changes together led to an increase in bacterial antibiotic susceptibility. The improved efficacy of ALA combination treatment with antibiotics was validated in the mouse model. Molecular docking results indicate that ALA can bind to membrane proteins via hydrogen bonding. Our findings demonstrated that combined treatment using ALA and antibiotics is effective in preventing infections involving MDR bacteria. Our results are of great significance for the scientific and effective prevention and control of antibiotic resistance Salmonella, as well as ensuring food safety.

Thymus algeriensis essential oil: Phytochemical investigation, bactericidal activity, synergistic effect with colistin, molecular docking, and dynamics analysis against Gram-negative bacteria resistant to colistin

Due to the increasing resistance prevalence to the last line of antibiotics, such as colistin, and the rising threat of multi-drug resistant bacteria, it is crucial to find alternative therapeutic options. The current study focuses on evaluating antibacterial activities alone and in combination with colistin of Thymus algeriensis essential oil (TA-EO) against colistin-resistant Klebsiella pneumoniae, Pseudomonas aeruginosa, and Escherichia coli co-harboring mcr-1 gene. GC/MS was used to determine the chemical composition of TA-EO. Disc diffusion and microdilution techniques were used to evaluate the antimicrobial activities of TA-EO. Synergism between colistin and TA-EO was evaluated by checkerboard assay. The major compounds of TA-EO were docked with known enzymes involved in resistance to colistin, as well as the biosynthesis of peptidoglycan and amino acids. GC/MS revealed that TA-EO was of carvacrol chemotype (67.94 %). The TA-EO showed remarkable antibacterial activities against all Gram-negative bacterial strains, with the diameter of inhibition zones varied between 30 and 50 mm and a ratio MBC/MIC equal to 1 for the vast majority of bacterial isolates. Interestingly, the checkerboard showed synergism between TA-EO and colistin against colistin-resistant Escherichia coli co-harboring mcr-1 gene (FICI˂1) and reduced the MIC of colistin by 16- to 512-fold and those of TA-EO by 4- to 16-fold. The docking study demonstrated that carvacrol had high binding free energies against MCR-1, a phosphoethanolamine transferase extracellular domain, and its catalytic domain implicated in resistance to colistin, and undecaprenyl pyrophosphate synthase in complex with magnesium which is involved in bacterial peptidoglycan biosynthesis. The molecular dynamics study for 100-ns also revealed the stability of the MCR-1/carvacrol complex with a constant surface area over the simulation. These results support using carvacrol or TA-EO as a bactericidal agent, either alone or in combination with colistin, to treat infections caused by colistin-resistant Gram-negative bacteria.

Medical residents' knowledge, attitudes and practices regarding antibiotics, antimicrobial stewardship and multidrug-resistant bacteria: a cross-sectional study in a major university in Iran.

Antimicrobial resistance (AMR) is one of the biggest threats to global public health systems. This study aimed to assess the knowledge, attitudes and practice about AMR, antimicrobial stewardship programs (ASPs) and multidrug-resistant (MDR) bacteria. A web-based questionnaire survey was conducted among the residents of Isfahan University of Medical Sciences from May to November 2023. Data analysis was done using SPSS version 24.0 software. Overall, 400 out of 450 medical residents responded to the questionnaire, giving a response rate of 88.9%. The participants' ages ranged from 26 to 54 years, and the majority were female (227/400 56.8%). Average scores for knowledge, attitudes, and practices were 53.70 ± 15.88, 36.97 ± 5.89 and 24.69 ± 4.24, respectively. In terms of knowledge, only 26.8% had heard the term "ASPs" and knew what it was. Most incorrect answers appeared to the treatment of infection caused by MDR bacteria including ESBL-producing Escherichia coli (27.8%) and carbapenem-resistant Klebsiella pneumoniae (30.8%), as well as the atypical bacteria (45.5%). Approximately, 50 and 71.7% said they had received no specific training in the fields of microbiological sampling methods and the appropriate time to prescribe antibiotics, respectively. Surprisingly, regarding practice, 81.8% of the respondents stated that antibiotics are used to treat flu or the common cold. Residents considered their training on important issues including ASPs, MDR bacteria and the spectrum of antibiotics insufficient. This result highlights the need for targeted training interventions about antibiotic prescription in the curriculum at the university with more emphasis on ASPs to limit the development of resistance.