Thai ethnomedicinal plants as resistant modifying agents for combating Acinetobacter baumannii infections

ABSTRACTS: BACKGROUND: Acinetobacter baumannii is well-recognized as an important nosocomial pathogen, however, due to their intrinsic resistance to several antibiotics, treatment options are limited. Synergistic effects between antibiotics and medicinal plants, particularly their active components, have intensively been studied as alternative approaches. METHODS: Fifty-one ethanol extracts obtained from 44 different selected medicinal plant species were tested for resistance modifying agents (RMAs) of novobiocin against A. baumannii using growth inhibition assay. RESULTS: At 250 μg/ml, Holarrhena antidysenterica, Punica granatum, Quisqualis indica, Terminalia bellirica, Terminalia chebula, and Terminalia sp. that possessed low intrinsic antibacterial activity significantly enhanced the activity of novobiocin at 1 μg/ml (1/8xminimum inhibitory concentration) against this pathogen. Holarrhena antidysenterica at 7.8 μg/ml demonstrated remarkable resistant modifying ability against A. baumannii in combination with novobiocin. The phytochemical study revealed that constituents of this medicinal plant contain alkaloids, condensed tannins, and triterpenoids. CONCLUSION: The use of Holarrhena antidysenterica in combination with novobiocin provides an effective alternative treatment for multidrug resistant A. baumannii infections

Reversal of Tetracycline Resistance by Cepharanthine, Cinchonidine, Ellagic Acid and Propyl Gallate in a Multi-drug Resistant Escherichia coli

Bacterial resistance to antibiotics is an increasing threat to global healthcare systems. We therefore sought compounds with potential to reverse antibiotic resistance in a clinically relevant multi-drug resistant isolate of Escherichia coli (NCTC 13400). 200 natural compounds with a history of either safe oral use in man, or as a component of a traditional herb or medicine, were screened. Four compounds; ellagic acid, propyl gallate, cinchonidine and cepharanthine, lowered the minimum inhibitory concentrations (MICs) of tetracycline, chloramphenicol and tobramycin by up to fourfold, and when combined up to eightfold. These compounds had no impact on the MICs of ampicillin, erythromycin or trimethoprim. Mechanistic studies revealed that while cepharanthine potently suppressed efflux of the marker Nile red from bacterial cells, the other hit compounds slowed cellular accumulation of this marker, and/or slowed bacterial growth in the absence of antibiotic. Although cepharanthine showed some toxicity in a cultured HEK-293 mammalian cell-line model, the other hit compounds exhibited no toxicity at concentrations where they are active against E. coli NCTC 13400. The results suggest that phytochemicals with capacity to reverse antibiotic resistance may be more common in traditional medicines than previously appreciated, and may offer useful scaffolds for the development of antibiotic-sensitising drugs

Proteome Analyses of Cellular Proteins in Methicillin-Resistant Staphylococcus aureus Treated with Rhodomyrtone, a Novel Antibiotic Candidate

The ethanolic extract from Rhodomyrtus tomentosa leaf exhibited good antibacterial activities against both methicillin-resistant Staphylococcus aureus (MRSA) and S. aureus ATCC 29213. Its minimal inhibitory concentration (MIC) values ranged from 31.25–62.5 µg/ml, and the minimal bactericidal concentration (MBC) was 250 µg/ml. Rhodomyrtone, an acylphloroglucinol derivative, was 62.5–125 times more potent at inhibiting the bacteria than the ethanolic extract, the MIC and MBC values were 0.5 µg/ml and 2 µg/ml, respectively. To provide insights into antibacterial mechanisms involved, the effects of rhodomyrtone on cellular protein expression of MRSA have been investigated using proteomic approaches. Proteome analyses revealed that rhodomyrtone at subinhibitory concentration (0.174 µg/ml) affected the expression of several major functional classes of whole cell proteins in MRSA. The identified proteins involve in cell wall biosynthesis and cell division, protein degradation, stress response and oxidative stress, cell surface antigen and virulence factor, and various metabolic pathways such as amino acid, carbohydrate, energy, lipid, and nucleotide metabolism. Transmission electron micrographs confirmed the effects of rhodomyrtone on morphological and ultrastructural alterations in the treated bacterial cells. Biological processes in cell wall biosynthesis and cell division were interrupted. Prominent changes including alterations in cell wall, abnormal septum formation, cellular disintegration, and cell lysis were observed. Unusual size and shape of staphylococcal cells were obviously noted in the treated MRSA. These pioneer findings on proteomic profiling and phenotypic features of rhodomyrtone-treated MRSA may resolve its antimicrobial mechanisms which could lead to the development of a new effective regimen for the treatment of MRSA infections

High rate of subclinical chikungunya virus infection and association of neutralizing antibody with protection in a prospective cohort in the Philippines.

BACKGROUND: Chikungunya virus (CHIKV) is a globally re-emerging arbovirus for which previous studies have indicated the majority of infections result in symptomatic febrile illness. We sought to characterize the proportion of subclinical and symptomatic CHIKV infections in a prospective cohort study in a country with known CHIKV circulation. METHODS/FINDINGS: A prospective longitudinal cohort of subjects ≥6 months old underwent community-based active surveillance for acute febrile illness in Cebu City, Philippines from 2012-13. Subjects with fever history were clinically evaluated at acute, 2, 5, and 8 day visits, and at a 3-week convalescent visit. Blood was collected at the acute and 3-week convalescent visits. Symptomatic CHIKV infections were identified by positive CHIKV PCR in acute blood samples and/or CHIKV IgM/IgG ELISA seroconversion in paired acute/convalescent samples. Enrollment and 12-month blood samples underwent plaque reduction neutralization test (PRNT) using CHIKV attenuated strain 181/clone25. Subclinical CHIKV infections were identified by ≥8-fold rise from a baseline enrollment PRNT titer 50 years old. Baseline CHIKV PRNT titer ≥10 was associated with 100% (95%CI: 46.1, 100.0) protection from symptomatic CHIKV infection. Phylogenetic analysis demonstrated Asian genotype closely related to strains from Asia and the Caribbean. CONCLUSIONS: Subclinical infections accounted for a majority of total CHIKV infections. A positive baseline CHIKV PRNT titer was associated with protection from symptomatic CHIKV infection. These findings have implications for assessing disease burden, understanding virus transmission, and supporting vaccine development

Unfolded protein response is an early, non-critical event during hepatic stellate cell activation.

Hepatic stellate cells activate upon liver injury and help at restoring damaged tissue by producing extracellular matrix proteins. A drastic increase in matrix proteins results in liver fibrosis and we hypothesize that this sudden increase leads to accumulation of proteins in the endoplasmic reticulum and its compensatory mechanism, the unfolded protein response. We indeed observe a very early, but transient induction of unfolded protein response genes during activation of primary mouse hepatic stellate cells in vitro and in vivo, prior to induction of classical stellate cell activation genes. This unfolded protein response does not seem sufficient to drive stellate cell activation on its own, as chemical induction of endoplasmic reticulum stress with tunicamycin in 3D cultured, quiescent stellate cells is not able to induce stellate cell activation. Inhibition of Jnk is important for the transduction of the unfolded protein response. Stellate cells isolated from Jnk knockout mice do not activate as much as their wild-type counterparts and do not have an induced expression of unfolded protein response genes. A timely termination of the unfolded protein response is essential to prevent endoplasmic reticulum stress-related apoptosis. A pathway known to be involved in this termination is the non-sense-mediated decay pathway. Non-sense-mediated decay inhibitors influence the unfolded protein response at early time points during stellate cell activation. Our data suggest that UPR in HSCs is differentially regulated between acute and chronic stages of the activation process. In conclusion, our data demonstrates that the unfolded protein response is a JNK1-dependent early event during hepatic stellate cell activation, which is counteracted by non-sense-mediated decay and is not sufficient to drive the stellate cell activation process. Therapeutic strategies based on UPR or NMD modulation might interfere with fibrosis, but will remain challenging because of the feedback mechanisms between the stress pathways

Estimating the burden of antimicrobial resistance: a systematic literature review.

Background: Accurate estimates of the burden of antimicrobial resistance (AMR) are needed to establish the magnitude of this global threat in terms of both health and cost, and to paramaterise cost-effectiveness evaluations of interventions aiming to tackle the problem. This review aimed to establish the alternative methodologies used in estimating AMR burden in order to appraise the current evidence base. Methods: MEDLINE, EMBASE, Scopus, EconLit, PubMed and grey literature were searched. English language studies evaluating the impact of AMR (from any microbe) on patient, payer/provider and economic burden published between January 2013 and December 2015 were included. Independent screening of title/abstracts followed by full texts was performed using pre-specified criteria. A study quality score (from zero to one) was derived using Newcastle-Ottawa and Philips checklists. Extracted study data were used to compare study method and resulting burden estimate, according to perspective. Monetary costs were converted into 2013 USD. Results: Out of 5187 unique retrievals, 214 studies were included. One hundred eighty-seven studies estimated patient health, 75 studies estimated payer/provider and 11 studies estimated economic burden. 64% of included studies were single centre. The majority of studies estimating patient or provider/payer burden used regression techniques. 48% of studies estimating mortality burden found a significant impact from resistance, excess healthcare system costs ranged from non-significance to $1 billion per year, whilst economic burden ranged from$21,832 per case to over $3 trillion in GDP loss. Median quality scores (interquartile range) for patient, payer/provider and economic burden studies were 0.67 (0.56-0.67), 0.56 (0.46-0.67) and 0.53 (0.44-0.60) respectively. Conclusions: This study highlights what methodological assumptions and biases can occur dependent on chosen outcome and perspective. Currently, there is considerable variability in burden estimates, which can lead in-turn to inaccurate intervention evaluations and poor policy/investment decisions. Future research should utilise the recommendations presented in this review. Trial registration: This systematic review is registered with PROSPERO (PROSPERO CRD42016037510)

Synergistic antibacterial effects of colistin in combination with aminoglycoside, carbapenems, cephalosporins, fluoroquinolones, tetracyclines, fosfomycin, and piperacillin on multidrug resistant Klebsiella pneumoniae isolates.

Multidrug resistant Enterobacterales have become a serious global health problem, with extended hospital stay and increased mortality. Antibiotic monotherapy has been reported ineffective against most drug resistant bacteria including Klebsiella pneumoniae, thus encouraging the use of multidrug therapies as an alternative antibacterial strategy. The present works assessed the antibacterial activity of colistin against K. pneumoniae isolates. Resistant isolates were tested against 16 conventional antibiotics alone and in combination with colistin. The results revealed that all colistin resistant isolates demonstrated multidrug resistance against the tested antibiotics except amikacin. At sub-inhibitory concentrations, combinations of colistin with amikacin, or fosfomycin showed synergism against 72.72% (8 of 11 isolates). Colistin with either of gentamicin, meropenem, cefoperazone, cefotaxime, ceftazidime, moxifloxacin, minocycline, or piperacillin exhibited synergism against 81.82% (9 of 11 isolates). Combinations of colistin with either of tobramycin or ciprofloxacin showed synergism against 45.45% (5 in 11 isolates), while combinations of colistin with imipenem or ceftolozane and tazobactam displayed 36.36% (4 of 11 isolates) and 63.64% (7 of 11 isolates) synergism. In addition, combinations of colistin with levofloxacin was synergistic against 90.91% (10 of 11 isolates). The results revealed that combinations of colistin with other antibiotics could effectively inhibit colistin resistant isolates of K. pneumoniae, and thus could be further explore for the treatment of multidrug resistant pathogens

Prenylated Flavone from Roots of a Hybrid between Artocarpus heterophyllus

One new prenylated flavone, 2,8-dihydroxy-3,10-dimethoxy-6-(2-methyl-1-propen-1-yl)-6H,7H-[1]benzopyrano[4,3-b][1]-benzopyran-7-one, together with 24 known compounds were isolated from crude acetone extract from the roots of a hybrid between Artocarpus heterophyllus and Artocarpus integer. Their structures were determined by 1D and 2D nuclear magnetic resonance (NMR) spectroscopic data. The antioxidant and antibacterial activities of the isolated compounds were evaluated. The new compound showed potent antioxidant activity against DPPH• and superoxide with IC50 values of 0.033 and 0.125 mg mL-1, respectively. Significant antibacterial activity against Acinetobacter baumannii was observed with MIC value of 50 mg mL-1

Rifampicin Enhanced Carbapenem Activity with Improved Antibacterial Effects and Eradicates Established <i>Acinetobacter baumannii</i> Biofilms

Biofilm-mediated infections are critical to public health and a leading cause of resistance among pathogens, amounting to a prolonged hospital stay and increased mortality rate in the intensive care unit. In this study, the antibacterial and antibiofilm activities of rifampicin or carbapenem monotherapies were compared with rifampicin and carbapenem combination therapies against rifampicin-resistant and carbapenem-resistant Acinetobacter baumannii isolates. Among 29 CRAB isolates, 24/29 (83%) were resistant to rifampicin, with MIC values between 2–256 µg/mL. Checkerboard assays disclosed that combination therapies at FICIs between 1/8 and 1/4 improved the activity of carbapenems at subinhibitory concentrations. Time-kill kinetics indicated a 2- to 4-log reduction at 1/2 MIC rifampicin + 1/4 MIC carbapenem and 1/4 MIC rifampicin + 1/4 MIC carbapenem against the isolates, with the MIC values ranging from 2–8 µg/mL. The MTT assay revealed a dose-dependent decrease of the cell viability of established bacterial biofilm at 4 MIC rifampicin + 2 MIC carbapenems, with a percentage reduction of 44–75%, compared with monotherapies at 16 MIC. Scanning electron microscopy further confirmed bacterial cell membrane disruption, suggesting a synergism between carbapenem and rifampicin against a representative isolate. The findings demonstrated that the combination of rifampicin with carbapenems could improve antibacterial activities and eradicate established Acinetobacter baumannii biofilm