Chloramphenicol Binding Sites of Acinetobacter baumannii Chloramphenicol Acetyltransferase CatB8.

Acinetobacter baumannii is a multidrug-resistant pathogen that has become one of the most challenging pathogens in global healthcare. Several antibiotic-resistant genes, including catB8, have been identified in the A. baumannii genome. CatB8 protein, one of the chloramphenicol acetyltransferases (Cats), is encoded by the catB8 gene. Cats can convert chloramphenicol (chl) to 3-acetyl-chl, leading to bacterial resistance to chl. Here, we present the high-resolution cocrystal structure of CatB8 with chl. The structure that we resolved showed that each monomer of CatB8 binds to four chl molecules, while its homologous protein only binds to one chl molecule. One of the newly discovered chl binding site overlaps with the site of another substrate, acetyl-CoA. Through structure-based biochemical analyses, we identified key residues for chl recruiting and acetylation of chl in CatB8. Our work is of significant importance for understanding the drug resistance of A. baumannii and the effectiveness of antibiotic treatment.

Quantifying Dynamic Phenotypic Heterogeneity in Resistant Escherichia coli under Translation-Inhibiting Antibiotics.

Understanding the phenotypic heterogeneity of antibiotic-resistant bacteria following treatment and the transitions between different phenotypes is crucial for developing effective infection control strategies. The study expands upon previous work by explicating chloramphenicol-induced phenotypic heterogeneities in growth rate, gene expression, and morphology of resistant Escherichia coli using time-lapse microscopy. Correlating the bacterial growth rate and cspC expression, four interchangeable phenotypic subpopulations across varying antibiotic concentrations are identified, surpassing the previously described growth rate bistability. Notably, bacterial cells exhibiting either fast or slow growth rates can concurrently harbor subpopulations characterized by high and low gene expression levels, respectively. To elucidate the mechanisms behind this enhanced heterogeneity, a concise gene expression network model is proposed and the biological significance of the four phenotypes is further explored. Additionally, by employing Hidden Markov Model fitting and integrating the non-equilibrium landscape and flux theory, the real-time data encompassing diverse bacterial traits are analyzed. This approach reveals dynamic changes and switching kinetics in different cell fates, facilitating the quantification of observable behaviors and the non-equilibrium dynamics and thermodynamics at play. The results highlight the multi-dimensional heterogeneous behaviors of antibiotic-resistant bacteria under antibiotic stress, providing new insights into the compromised antibiotic efficacy, microbial response, and associated evolution processes.

Evaluation of the in vitro effects of concentrations of antibiotics on three Enterobacteriaceae isolates.

Due to the misuse and overuse of antibiotics, bacteria are now exposed to sub-minimum inhibitory concentrations (sub-MICs) of antibiotics in various environments. In recent years, exposure of bacteria to sub-MICs of antibiotics has led to the widespread emergence of antibiotic-resistant bacteria. In this study, three bacterial species from the Enterobacteriaceae family (Raoultella ornithinolytica, Pantoea agglomerans and Klebsiella quasivariicola) were isolated from water. The antibiotic susceptibility of these bacteria to 16 antibiotics was then investigated. The effects of sub-MICs of four selected antibiotics (kanamycin, chloramphenicol, meropenem, and ciprofloxacin) on the growth, biofilm formation, surface polysaccharide production, siderophore production, morphology, and expression of the translational/transcriptional regulatory transformer gene rfaH of these bacteria were analysed. The MICs of kanamycin, chloramphenicol, meropenem, and ciprofloxacin were determined to be 1, 2, 0.03 and 0.03 µg/mL for R. ornithinolytica; 0.6, 6, 0.03 and 0.05 µg/mL for P. agglomerans; and 2, 5, 0.04 and 0.2 µg/mL for K. quasivariicola. The growth kinetics and biofilm formation ability decreased for all three isolates at sub-MICs. The surface polysaccharides of R. ornithinolytica and P. agglomerans increased at sub-MICs. There was no significant change in the siderophore activities of the bacterial isolates, with the exception of MIC/2 meropenem in R. ornithinolytica and MIC/2 kanamycin in K. quasivariicola. It was observed that the sub-MICs of meropenem and ciprofloxacin caused significant changes in bacterial morphology. In addition, the expression of rfaH in R. ornithinolytica and K. quasivariicola increased with the sub-MICs of the selected antibiotics.

A review on the antibiotic florfenicol: Occurrence, environmental fate, effects, and health risks.

Florfenicol, as a replacement for chloramphenicol, can tightly bind to the A site of the 23S rRNA in the 50S subunit of the 70S ribosome, thereby inhibiting protein synthesis and bacterial proliferation. Due to the widespread use in aquaculture and veterinary medicine, florfenicol has been detected in the aquatic environment worldwide. Concerns over the effects and health risks of florfenicol on target and non-target organisms have been raised in recent years. Although the ecotoxicity of florfenicol has been widely reported in different species, no attempt has been made to review the current research progress of florfenicol toxicity, hormesis, and its health risks posed to biota. In this study, a comprehensive literature review was conducted to summarize the effects of florfenicol on various organisms including bacteria, algae, invertebrates, fishes, birds, and mammals. The generation of antibiotic resistant bacteria and spread antibiotic resistant genes, closely associated with hormesis, are pressing environmental health issues stemming from overuse or misuse of antibiotics including florfenicol. Exposure to florfenicol at µg/L-mg/L induced hormetic effects in several algal species, and chromoplasts might serve as a target for florfenicol-induced effects; however, the underlying molecular mechanisms are completely lacking. Exposure to high levels (mg/L) of florfenicol modified the xenobiotic metabolism, antioxidant systems, and energy metabolism, resulting in hepatotoxicity, renal toxicity, immunotoxicity, developmental toxicity, reproductive toxicity, obesogenic effects, and hormesis in different animal species. Mitochondria and the associated energy metabolism are suggested to be the primary targets for florfenicol toxicity in animals, albeit further in-depth investigations are warranted for revealing the long-term effects (e.g., whole-life-cycle impacts, multigenerational effects) of florfenicol, especially at environmental levels, and the underlying mechanisms. This will facilitate the evaluation of potential hormetic effects and construction of adverse outcome pathways for environmental risk assessment and regulation of florfenicol.

Development of membrane-targeting TPP+-chloramphenicol conjugates to combat methicillin-resistant staphylococcus aureus (MRSA) infections.

Infections caused by drug-resistant bacteria have become a new challenge in infection treatment, gravely endangering public health. Chloramphenicol (CL) is a well-known antibiotic which has lost its efficacy due to bacterial resistance. To address this issue, herein we report the design, synthesis and biological evaluations of novel triphenylphosphonium chloramphenicol conjugates (TPP+-CL). Study results indicated that compounds 39 and 42 possessed remarkable antibacterial effects against clinically isolated methicillin-resistant Staphylococcus aureus (MRSA) with MIC values ranging from 1 to 2 µg/mL, while CL was inactive to the tested MRSA strains. In addition, these conjugates exhibited rapid bactericidal properties and low toxicity, and did not readily induced bacterial resistance, obviously outperforming the parent drug CL. In a mouse model infected with a clinically isolated MRSA strain, compound 39 at a dose of 20 mg/kg exhibited a comparable or even better in vivo anti-MRSA efficacy than the golden standard drug vancomycin, while no toxicity was observed.

Effect of Chloramphenicol as Antibiotic on the Structure and Function of Pepsin and Its Mechanism of Action.

The interaction between chloramphenicol (CHL) and pepsin (PEP), as well as the impact of CHL on PEP conformation, were investigated using spectroscopic techniques and molecular docking simulations in this study. The experimental results demonstrate that CHL exhibits a static quenching effect on PEP. The thermodynamic parameters indicate that the reaction between CHL and PEP is spontaneous, primarily driven by hydrogen bonding and van der Waals forces. Moreover, the binding distance of r<7 nm suggests the occurrence of Förster's non-radiative energy transfer between these two molecules. In the synchronous fluorescence spectrum, the maximum fluorescence intensity of PEP produced a redshift phenomenon, indicating that CHL was bound to tryptophan residues of PEP. The addition of CHL induces changes in the secondary structure of PEP, as confirmed by the observed alterations in peak values in three-dimensional fluorescence spectra. The UV spectra reveal a redshift of 3 nm in the maximum absorption peak, indicating a conformational change in the secondary structure of PEP upon addition of CHL. Circular dichroism analysis demonstrates significant alterations in the α-helix, ß-sheet, ß-turn, and random coil contents of PEP before and after CHL incorporation, further confirming its ability to modulate the secondary structure of PEP.

Synergistic antibacterial effects of exopolysaccharides/nickel-nanoparticles composites against multidrug-resistant bacteria.

The need for an alternative treatment to fight infectious diseases caused by antibiotic-resistant bacteria is increasing. A possible way to overcome bacterial resistance to antibiotics is by reintroducing commonly used antibiotics with a sensitizer capable of enhancing their antimicrobial effect in resistant bacteria. Here, we use a composite composed of exopolysaccharide capped-NiO NPs, with antimicrobial effects against antibiotic-resistant Gram-positive and Gram-negative bacteria. It potentiated the antimicrobial effects of four different antibiotics (ampicillin, kanamycin, chloramphenicol, and ciprofloxacin) at lower concentrations than their minimal inhibitory concentrations. We observed that the Ni-composite synergistically enhanced, fourfold, the antibacterial effect of kanamycin and chloramphenicol against multidrug-resistant Staphylococcus aureus and Pseudomonas aeruginosa, as well as ampicillin against multidrug-resistant Staphylococcus aureus, and ciprofloxacin against multidrug-resistant Pseudomonas aeruginosa by eightfold. We also found that Ni-composite could not inhibit biofilm synthesis on the tested bacterial strains. Our results demonstrated the possibility of using metal nanoparticles, like NiO, as a sensitizer to overcome bacterial antibiotic resistance.

Blue Light Potentiates Antibiotics in Bacteria via Parallel Pathways of Hydroxyl Radical Production and Enhanced Antibiotic Uptake.

In the age of antimicrobial resistance, the urgency by which novel therapeutic approaches need to be introduced into the clinical pipeline has reached critical levels. Antimicrobial blue light (aBL), as an alternative approach, has demonstrated promise as a stand-alone therapeutic method, albeit with a limited window of antimicrobial activity. Work by others indicates that treatment with antibiotics increases the production of reactive oxygen species (ROS) which may, in part, contribute to the bactericidal effects of antibiotics. These findings suggest that there may be potential for synergistic interactions with aBL, that similarly generates ROS. Therefore, in this study, the mechanism of aBL is investigated, and the potential for aBL to synergistically promote antibiotic activity is similarly evaluated. Furthermore, the translatability of using aBL and chloramphenicol in combination within a mouse model of Acinetobacter baumanii burn infection is assessed. It is concluded that porphyrins and hydroxyl radicals driven by "free iron" are paramount to the effectiveness of aBL; and aBL is effective at promoting multiple antibiotics in different multidrug-resistant bacteria. Moreover, rROS up-regulation, and promoted antibiotic uptake are observed during aBL+antibiotic exposure. Lastly, aBL combined with chloramphenicol appears to be both effective and safe for the treatment of A. baumannii burn infection. In conclusion, aBL may be a useful adjunct therapy to antibiotics to potentiate their action.

Synergistic effect of two antimicrobial peptides, BP203 and MAP-0403 J-2 with conventional antibiotics against colistin-resistant Escherichia coli and Klebsiella pneumoniae clinical isolates.

Drug-resistant Enterobacterales infections are a great health concern due to the lack of effective treatments. Consequently, finding novel antimicrobials or combining therapies becomes a crucial approach in addressing this problem. BP203 and MAP-0403 J-2, novel antimicrobial peptides, have exhibited effectiveness against Gram-negative bacteria. In this study, we assessed the in vitro antibacterial activity of BP203 and MAP-0403 J-2, along with their synergistic interaction with conventional antibiotics including colistin, rifampicin, chloramphenicol, ceftazidime, meropenem, and ciprofloxacin against colistin-resistant Escherichia coli and Klebsiella pneumoniae clinical isolates. The minimal inhibitory concentrations (MIC) of BP203 and MAP-0403 J-2 against tested E. coli isolates were 2-16 and 8-32 µg/mL, respectively. However, for the majority of K. pneumoniae isolates, the MIC of BP203 and MAP-0403 J-2 were >128 µg/mL. Notably, our results demonstrated a synergistic effect when combining BP203 with rifampicin, meropenem, or chloramphenicol, primarily observed in most K. pneumoniae isolates. In contrast, no synergism was evident between BP203 and colistin, chloramphenicol, ceftazidime, rifampicin, or ciprofloxacin when tested against all E. coli isolates. Furthermore, synergistic effects between MAP-0403 J-2 and rifampicin, ceftazidime or colistin were observed against the majority of E. coli isolates. Similarly, the combined effect of MAP-0403 J-2 with rifampicin or chloramphenicol was synergistic in the majority of K. pneumoniae isolates. Importantly, these peptides displayed the stability at high temperatures, across a wide range of pH values, in specific serum concentrations and under physiological salt conditions. Both peptides also showed no significant hemolysis and cytotoxicity against mammalian cells. Our findings suggested that BP203 and MAP-0403 J-2 are promising candidates against colistin-resistant E. coli. Meanwhile, the synergism of these peptides and certain antibiotics could be of great therapeutic value as antimicrobial drugs against infections caused by colistin-resistant E. coli and K. pneumoniae.

Antimicrobial resistance profiles of salmonella spp. and escherichia coli isolated from fresh nile tilapia (oreochromis niloticus) fish marketed for human consumption.

BACKGROUND: Salmonella spp. and pathogenic strains of Escherichia coli are among the major foodborne zoonotic pathogens. These bacterial pathogens cause human illnesses characterized by hemorrhagic colitis, vomiting, nausea, and other agent-related symptoms. The increasing occurrence of antimicrobial resistance in these pathogens is also a serious public health concern globally. Regular surveillance of phenotypes and genotypes of Salmonella spp. and Escherichia coli from animal-derived foods is necessary for effective reduction and control of these foodborne pathogens. This study was conducted to assess the occurrence, antimicrobial resistance, virulence genes and genetic diversity of Salmonella spp. and E. coli isolates from fresh Nile tilapia obtained from retail markets in Nairobi, Kenya. METHODS: A total of 68 fresh Nile tilapia fish samples were collected from retail markets and used for isolation of Salmonella spp. and E. coli. Antimicrobial susceptibilities of the isolates weretested by Kirby-Bauer agar disc diffusion method. According to the antimicrobial resistance profiles, the multi-drug resistant isolates were identified by 16 S rRNA sequencing and phylogenetic analysis using the Bayesian inference method. The MDR Salmonella spp. and E. coli isolates were subjected to PCR-based screening for the detection virulence and antibiotic resistance genes. RESULTS: The prevalence of contamination of the fish samples with Salmonella spp. and E.coli was 26.47% and 35.29% respectively. Overall phenotypic resistance among the Salmonella spp. ranged from 5.5% for ceftazidime, chloramphenicol, meropenem, nitrofurantoin and streptomycin and 22.2% for penicillin-G. For E. coli phenotypic resistance ranged from 4.2% for ceftazidime and chloramphenicol and 25% for rifampicin. Multi-drug resistance was observed in three Salmonella spp. and two E. coli isolates. Results of 16 S rRNA sequences, sequence alignment and phylogenic trees confirmed the identified MDR isolates as S. typhymurium WES-09, S. typhymurium MAK-22, S. typhimurium EMB-32 and E. coli MAK-26 and E. coli LAN-35. The presence of antibiotic-resistance genes belonging to ß-lactamases, tetracycline, sulfonamide, trimethoprim and aminoglycosides-resistant genes were detected in all the identified MDR isolates. CONCLUSIONS: The findings from this study indicate that Nile tilapia (Oreochromis niloticus) sold in retail markets can acts as reservoirs of Salmonella spp. and E. coli pathogens linked to human disease, some of which were multidrug resistance to critically important antimicrobials. Both microorganisms are of zoonotic significance and represent a significant public health risk to the society.

Combined antimicrobial effect of phage-derived endolysin and depolymerase against biofilm-forming Salmonella Typhimurium.

This study was designed to evaluate the antimicrobial activity of phage-derived endolysin (LysPB32) and depolymerase (DpolP22) against planktonic and biofilm cells of Salmonella Typhimurium (STKCCM). Compared to the control, the numbers of STKCCM were reduced by 4.3 and 5.9 log, respectively, at LysPB32 and LysPB32 + DpolP22 in the presence of polymyxin B (PMB) after 48-h incubation at 37 °C. LysPB32 + DpolP22 decreased the relative fitness (0.8) and the cross-resistance of STKCCM to chloramphenicol (CHL), cephalothin (CEP), ciprofloxacin (CIP), and tetracycline (TET) in the presence of PMB. The MICtrt/MICcon ratios of CHL, CEP, CIP, PMB, and TET were between 0.25 and 0.50 for LysPB32 + DpolP22 in the presence of PMB. These results suggest that the application of phage-encoded enzymes with antibiotics can be a promising approach for controlling biofilm formation on medical and food-processing equipment. This is noteworthy in that the application of LysPB32 + DpolP22 could increase antibiotic susceptibility and decrease cross-resistance to other antibiotics.

Unveiling synergism of polymyxin B with chloramphenicol derivatives against multidrug-resistant (MDR) Klebsiella pneumoniae.

Polymyxins are last-line antibiotics against multidrug-resistant Klebsiella pneumoniae but using polymyxins alone may not be effective due to emerging resistance. A previous study found that combining polymyxin B with chloramphenicol effectively kills MDR K. pneumoniae, although the bone marrow toxicity of chloramphenicol is concerning. The aim of this study is to assess the antibacterial efficacy and cytotoxicity of polymyxin B when combined with chloramphenicol and its derivatives, namely thiamphenicol and florfenicol (reported to have lesser toxicity compared to chloramphenicol). The antibacterial activity was evaluated with antimicrobial susceptibility testing using broth microdilution and time-kill assays, while the cytotoxic effect on normal bone marrow cell line, HS-5 was evaluated using the MTT assay. All bacterial isolates tested were found to be susceptible to polymyxin B, but resistant to chloramphenicol, thiamphenicol, and florfenicol when used alone. The use of polymyxin B alone showed bacterial regrowth for all isolates at 24 h. The combination of polymyxin B and florfenicol demonstrated additive and synergistic effects against all isolates (≥ 2 log10 cfu ml-1 reduction) at 4 and 24 h, respectively, while the combination of polymyxin B and thiamphenicol resulted in synergistic killing at 24 h against ATCC BAA-2146. Furthermore, the combination of polymyxin B with florfenicol had the lowest cytotoxic effect on the HS-5 cells compared to polymyxin B combination with chloramphenicol and thiamphenicol. Overall, the combination of polymyxin B with florfenicol enhanced bacterial killing against MDR K. pneumoniae and exerted minimal cytotoxic effect on HS-5 cell line.

Development of pBACpAK entrapment vector derivatives to detect intracellular transfer of mobile genetic elements within chloramphenicol resistant bacterial isolates.

Antimicrobial resistance disseminates throughout bacterial populations via horizontal gene transfer, driven mainly by mobile genetic elements (MGEs). Entrapment vectors are key tools in determining MGE movement within a bacterial cell between different replicons or between sites within the same replicon. The pBACpAK entrapment vector has been previously used to study intracellular transfer in Gram-negative bacteria however since pBACpAK contains a chloramphenicol resistance gene, it cannot be used in bacterial isolates which are already resistant to chloramphenicol. Therefore, we developed new derivatives of the pBACpAK entrapment vector to determine intracellular transfer of MGEs in an Escherichia coli DH5α transconjugant containing the chloramphenicol resistance plasmid pD25466. The catA1 of pBACpAK was replaced by both mcr-1 in pBACpAK-COL and aph(3')-Ia in pBACpAK-KAN, allowing it to be used in chloramphenicol resistant strains. The plasmid constructs were verified and then used to transform the E. coli DH5α/pD25466 transconjugants in order to detect intracellular movement of the MGEs associated with the pD25466 plasmid. Here we report on the validation of the expanded suite of pBACpAK vectors which can be used to study the intracellular transfer of MGEs between, and within, replicons in bacteria with different antimicrobial resistance profiles.

A retrospective study on antibacterial treatments for koalas infected with Chlamydia pecorum.

Chlamydiosis remains the leading infectious disease and is one of the key factors responsible for the dramatic reduction of koala populations in South-East Queensland (SEQ) and New South Wales (NSW) regions of Australia. Possible infection outcomes include blindness, infertility, painful cystitis, and death if left untreated. Studies have reported the treatment efficacy of chloramphenicol and doxycycline, which are the two most commonly administered treatments in diseased koalas, in clinical settings. However, none have directly compared the treatment efficacy of these antibacterials on koala survival. A retrospective study was essential to identify any relationships between the demographical information, and the animals' responses to the current treatment regimens. Associations were explored between six explanatory (sex; maturity; location; clinical signs, treatment; treatment duration) and two outcome variables (survival; post-treatment PCR). Results showed that female koalas had a statistical trend of lower odds of surviving when compared to males (OR = 0.36, p = 0.05). Koalas treated with chloramphenicol for ≥ 28 days had greater odds of surviving than when treated for < 28 days (OR = 8.8, p = 0.02), and those koalas administered doxycycline had greater odds of testing PCR negative when compared to chloramphenicol treatments (OR = 5.45, p = 0.008). There was no difference between the antibacterial treatments (chloramphenicol, doxycycline, and mixed/other) and the survival of koalas. Female koalas had greater odds of exhibiting UGT signs only (OR = 4.86, p < 0.001), and also greater odds of having both ocular and UGT clinical signs (OR = 5.29, p < 0.001) when compared to males. Of the koalas, 28.5% initially had no clinical signs but were PCR positive for C. pecorum. This study enables further understanding of the complex nature between chlamydial infection and response to antibacterial treatment.

Antibiotic susceptibility and clonal distribution of Staphylococcus aureus from pediatric skin and soft tissue infections: 10-year trends in multicenter investigation in China.

Background: Skin and Soft Tissue Infections (SSTIs) Surveillance Network of S. aureus In Pediatrics in China was established in 2009 to routinely report epidemiological changes. We aimed to monitor the present antibiotic sensitivity and molecular characteristics of S. aureus and methicillin-resistant S. aureus (MRSA) from SSTIs in children nationwide and track the changes over the past decade. Methods: Patients diagnosed with SSTIs from the dermatology departments of 22 tertiary pediatric hospitals in seven geographical regions of China were recruited continuously from May 2019 to August 2021. S. aureus was isolated, and its sensitivity to 15 antimicrobials was evaluated using the broth microdilution method. The molecular characteristics of the MRSA isolates were determined through multilocus sequence typing (MLST) and staphylococcal cassette chromosome mec (SCCmec) typing. The presence of the Panton-Valentine leukocidin gene (pvl) was determined. Results: The detection rate of S. aureus was 62.57% (1379/2204), among which MRSA accounted for 14.79% (204/1379), significantly higher than the result in previous study in 2009-2011 (2.58%, 44/1075). Compared with previous study, the sensitivity to cephalosporins and fusidic acid decreased to varying degrees, while that to chloramphenicol, ciprofloxacin, clindamycin, erythromycin, gentamicin, penicillin, and tetracycline increased significantly. The sensitivity to mupirocin, trimethoprim/sulfamethoxazole (TRISUL), and rifampicin still maintained at a high level (97.90%, 99.35% and 96.66% respectively). The leading multidrug resistance pattern of MRSA and methicillin-sensitive S. aureus (MSSA) were erythromycin-clindamycin-tetracycline (55.84%; 43/77) and erythromycin-clindamycin-chloramphenicol (27.85%, 44/158) respectively. 12 high-level mupirocin-resistant strains were detected, and notable differences in geographical distribution and seasonal variation were observed. The main types of MRSA were ST121 (46.08%, 94/204), followed by ST59 (19.61%, 40/204). SCCmec V (65.69%, 134/204) and SCCmec IV (31.86%, 65/204) were dominant epidemic types. ST121-V, ST59-IV, and ST22-V were the most prevalent clones nationwide. The detection rate of pvl had increased markedly from 9.09% (4/44) in 2009-2011 to 22.55% (46/204) in 2019-2021 (P<0.05). Conclusion: The antibiotic sensitivity and molecular characteristics of S. aureus from pediatric SSTIs has changed significantly over the past decade. To standardize medical care, provide timely and reasonable clinical treatment, and effectively manage infection control, Chinese pediatric SSTIs guidelines are urgently needed.

Induction of glioblastoma cell ferroptosis using combined treatment with chloramphenicol and 2-deoxy-D-glucose.

Glioblastoma, a malignant tumor, has no curative treatment. Recently, mitochondria have been considered a potential target for treating glioblastoma. Previously, we reported that agents initiating mitochondrial dysfunction were effective under glucose-starved conditions. Therefore, this study aimed to develop a mitochondria-targeted treatment to achieve normal glucose conditions. This study used U87MG (U87), U373, and patient-derived stem-like cells as well as chloramphenicol (CAP) and 2-deoxy-D-glucose (2-DG). We investigated whether CAP and 2-DG inhibited the growth of cells under normal and high glucose concentrations. In U87 cells, 2-DG and long-term CAP administration were more effective under normal glucose than high-glucose conditions. In addition, combined CAP and 2-DG treatment was significantly effective under normal glucose concentration in both normal oxygen and hypoxic conditions; this was validated in U373 and patient-derived stem-like cells. 2-DG and CAP acted by influencing iron dynamics; however, deferoxamine inhibited the efficacy of these agents. Thus, ferroptosis could be the underlying mechanism through which 2-DG and CAP act. In conclusion, combined treatment of CAP and 2-DG drastically inhibits cell growth of glioblastoma cell lines even under normal glucose conditions; therefore, this treatment could be effective for glioblastoma patients.

Effectively facilitating the degradation of chloramphenicol by the synergism of Shewanella oneidensis MR-1 and the metal-organic framework.

Electroactive bacteria (EAB) and metal oxides are capable of synergistically removing chloramphenicol (CAP). However, the effects of redox-active metal-organic frameworks (MOFs) on CAP degradation with EAB are not yet known. This study investigated the synergism of iron-based MOFs (Fe-MIL-101) and Shewanella oneidensis MR-1 on CAP degradation. 0.5 g/L Fe-MIL-101 with more possible active sites led to a three-fold higher CAP removal rate in the synergistic system with MR-1 (initial bacterial concentration of 0.2 at OD600), and showed a superior catalytic effect than exogenously added Fe(III)/Fe(II) or magnetite. Mass spectrometry revealed that CAP was transformed into smaller molecular weight and less toxic metabolites in cultures. Transcriptomic analysis showed that Fe-MIL-101 enhanced the expression of genes related to nitro and chlorinated contaminants degradation. Additionally, genes encoding hydrogenases and c-type cytochromes associated with extracellular electron transfer were significantly upregulated, which may contribute to the simultaneous bioreduction of CAP both intracellularly and extracellularly. These results indicated that Fe-MIL-101 can be used as a catalyst to synergize with EAB to effectively facilitate CAP degradation, which might shed new light on the application in the in situ bioremediation of antibiotic-contaminated environments.

Removal of chloramphenicol and resistance gene changes in electric-integrated vertical flow constructed wetlands.

The performance of an electric-integrated vertical flow constructed wetland (E-VFCW) for chloramphenicol (CAP) removal, changes in microbial community structure, and the fate of antibiotic resistance genes (ARGs) were evaluated. CAP removal in the E-VFCW system was 92.73% ± 0.78% (planted) and 90.80% ± 0.61% (unplanted), both were higher than the control system which was 68.17% ± 1.27%. The contribution of anaerobic cathodic chambers in CAP removal was higher than the aerobic anodic chambers. Plant physiochemical indicators in the reactor revealed electrical stimulation increased oxidase activity. Electrical stimulation enhanced the enrichment of ARGs in the electrode layer of the E-VFCW system (except floR). Plant ARGs and intI1 levels were higher in the E-VFCW than in the control system, suggesting electrical stimulation induces plants to absorb ARGs, reducing ARGs in the wetland. The distribution of intI1 and sul1 genes in plants suggests that horizontal transfer may be the main mechanism dispersing ARGs in plants. High throughput sequencing analysis revealed electrical stimulation selectively enriched CAP degrading functional bacteria (Geobacter and Trichlorobacter). Quantitative correlation analysis between bacterial communities and ARGs confirmed the abundance of ARGs relates to the distribution of potential hosts and mobile genetic elements (intI1). E-VFCW is effective in treating antibiotic wastewater, however ARGs potentially accumulate.

Acacia senegal Budmunchiamines as a Potential Adjuvant for Rejuvenating Phenicol Activities towards Escherichia coli-Resistant Strains.

The continuous emergence of bacterial resistance alters the activities of different antibiotic families and requires appropriate strategies to solve therapeutic impasses. Medicinal plants are an attractive source for researching alternative and original therapeutic molecules. In this study, the fractionation of natural extracts from A. senegal and the determination of antibacterial activities are associated with molecular networking and tandem mass spectrometry (MS/MS) data used to characterize active molecule(s). The activities of the combinations, which included various fractions plus an antibiotic, were investigated using the "chessboard" test. Bio-guided fractionation allowed the authors to obtain individually active or synergistic fractions with chloramphenicol activity. An LC-MS/MS analysis of the fraction of interest and molecular array reorganization showed that most identified compounds are Budmunchiamines (macrocyclic alkaloids). This study describes an interesting source of bioactive secondary metabolites structurally related to Budmunchiamines that are able to rejuvenate a significant chloramphenicol activity in strains that produce an AcrB efflux pump. They will pave the way for researching new active molecules for restoring the activity of antibiotics that are substrates of efflux pumps in enterobacterial-resistant strains.

Nanoparticles coated by chloramphenicol in hydrogels as a useful tool to increase the antibiotic release and antibacterial activity in dermal drug delivery.

BACKGROUND: Nanocarriers for antibacterial drugs became hopeful tools against the increasing resistance of bacteria to antibiotics. This work focuses on a comprehensive study of the applicability and therapeutic suitability of dermal carbopol-based hydrogels containing chloramphenicol carried by various nanoparticles (AuNPs and SiNPs). METHODS: The different forms of carbopol-based drugs for dermal use were obtained. Five different concentrations of chloramphenicol and two types of nanoparticles (silica and gold) in carbopol-based ointments were tested. The influence of different carbopol formulations with nanocarriers on the rheological properties as well as the release profile of active substances and bacteriostatic activity on five reference strains were determined. RESULTS: The properties of the obtained hydrogels were compared to a commercial formulation, and finally it was possible to obtain a formulation that allowed improved antimicrobial activity over a commercially available detreomycin ointment while reducing the concentration of the antibiotic. CONCLUSION: The work indicates that it is possible to reduce the concentration of chloramphenicol by four times while maintaining its bacteriostatic activity, which can improve the patient's safety profile while increasing the effectiveness of the therapy.