Synergistic combinations of various antimicrobial agents are considered ideal strategies in combating clinical and multidrug resistant (MDR) infections. In this study, antibacterial potential of Jatropha curcas crude seed extracts, seed oil, commercially available antibiotics, and their combinations were investigated for their synergistic effect against clinical, MDR and ATCC bacterial strains by agar well diffusion assay. Methanolic extracts remained more active against Staphylococcus aureus (ATCC), with zone of inhibition (ZOI) of 21 mm, than clinical and methicillin-resistant S. aureus (MRSA) strains (ZOI range ~ 15.0–17.0 mm). Molecular docking demonstrated that beta-monolaurin from methanolic extract exhibited greater affinity conformation for UDP- N -acetylmuramoyl-tripeptide– d -alanyl- d -alanine (MurF) ligase’s active pocket with binding energy of -7.3 kcal/mol. Moxifloxacin exhibited greater activity against Escherichia coli (ATCC) (ZOI ~ 50.0 mm), followed by ofloxacin against Pseudomonas chlororaphis (47.3 mm), moxifloxacin against P. monteilii (47 mm) , P. aeruginosa (46.3 mm) and MRSA2 (46 mm) and ofloxacin against S. aureus (ATCC) strains (45.7 mm). Methanolic extract in combination with rifampicin showed the highest synergism against MRSA strains, A. baumannii , E. coli, E. faecalis, S. aureus, and P. aeruginosa , A. baumannii (MDR strain), P. chlororaphis , E. coli ATCC25922 and S. aureus ATCC25923. In combinations, moxifloxacin exhibited the highest antagonism. The methanolic, n -hexane, aqueous extracts and seed oil in various combinations with antibiotics showed 44.71, 32.94, 9.41 and 25.88% synergism, respectively. The current study showed that potency of antibiotics was improved when screened in combination with J. curcas seed’s components, supporting the drug combination strategy to combat antibacterial resistance. Electronic supplementary material The online version of this article (10.1186/s13568-019-0793-6) contains supplementary material, which is available to authorized users.

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S U M M A R YErwinia amylovora is the first member of the Enterobacteriaceae found to possess a thiamine pyrophosphate-dependent pyruvate decarboxylase yielding acetaldehyde and CO,. In conjunction with an NAD-dependent ethanol dehydrogenase this represents the route of ethanol formation and explains the high ethanol yields previously reported. The organism also possesses an a-acetolactate decarboxylase and is thus able to produce acetoin by both the recognized microbial pathways. Fermentation balances for pyruvate with bacterial suspensions and extracts at pH 6.0 are recorded. NADH oxidase and lactate dehydrogenase are present but NADH-NADP transhydrogenase, coenzyme A-dependent acetaldehyde dehydrogenase, formate dehydrogenase or formate hydrogenlyase could not be detected. The findings are discussed in relation to the classification of Erwinia and the comparative biochemistry of the Enterobacteriaceae. I N T R O D U C T I O NEnzymic and isotopic studies have established the operation of the Embden-Meyerhof glycolytic and hexose monophosphate oxidative pathways of glucose metabolism in the plant pathogen Erwinia amylovora (Katznelson, 1958 ;Sutton & Starr, 1960) ; the EntnerDoudoroff pathway is absent (De Ley, 1962). Sutton & Starr (1959) reported a yield of 1-55 moles of ethanol per mole of glucose fermented, which suggested to us the possibility of a yeast-type pyruvate decarboxylase yielding CO, and acetaldehyde, which could then be reduced to ethanol by ethanol dehydrogenase. Pyruvate decarboxylase has, however, only a very limited distribution in bacteria and has not previously been found in the Enterobacteriaceae, in which family the genus Erwinia is placed. As the characteristic fermentation patterns of the Enterobacteriaceae reflect the pathways for the further metabolism of pyruvate, we have investigated the metabolism of this compound by E. amylovora in relation to the mechanism of ethanol formation and the comparative biochemistry of the Enterobacteriaceae. M E T H O D SOrganism. The organism used throughout this work was Erwinia amylovora EA I 37 s which was kindly supplied by Professor M. P. Starr (University of California, Davis, U.S.A.) who had taken the strain from a parent culture EA 137, originally isolated from fire-blight of apple by Ark (1937). Both EA 137 and EA 137s were plant pathogenic when tested by Ark during the studies of Sutton & Starr (1959) and were typical of E. amyZovora in their biochemical reactions. For comparative studies of formate metabolism we have also used

Antimicrobial activities of deoiled seed kernel (mechanically pressed), fruit coat and seed coat of Jatropha curcas Linn. collected from two regions (Bannu and Peshawar) of Pakistan were investigated. The antimicrobial activities were carried out against Klebsiella pneumoniae (ATCC 43816), Escherichia coli (ATCC 10536), Staphylococcus aureus (ATCC 6538), Bacillus subtilis (ATCC 6633) and two clinical fungal isolates Aspergillus fumigatus and Candida albicans using agar well diffusion method. The antibacterial activities of Peshawar sample were found to be higher than Bannu, against selected strains. While antifungal activities of both samples were similar. Highest zone of inhibition 31.5 ± 0.7 mm was exhibited by n-hexane extract of deoiled seed kernel of Peshawar sample against Bacillus subtilis (ATCC 6633). The minimum inhibitory concentration of ethanolic extracts of deoiled seed kernel and seed coat of Peshawar sample was 31.25 - 25 mg/ml. Whereas, minimum inhibitory concentration of ethanolic and n-hexane extracts of Bannu sample was 62.5 - 125 mg/ml. The results suggested that antimicrobial potential of J. curcas Linn. varied with geographical distribution. The investigation of different varieties of medicinal plants belonging to the same species will greatly enhance the chances of best pharmaceuticals discovery. Bangladesh J. Bot. 50(2): 219-226, 2021 (June)