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Screening antimicrobial activity of various extracts of Urtica dioica

Modarresi-Chahardehi A, Ibrahim D, Fariza-Sulaiman S, Mousavi L

Rev. Biol. Trop., 2012 Dec;60(4):1567-76.
PMID: 23342511

Urtica dioica or stinging nettle is traditionally used as an herbal medicine in Western Asia. The current study represents the investigation of antimicrobial activity of U. dioica from nine crude extracts that were prepared using different organic solvents, obtained from two extraction methods: the Soxhlet extractor (Method I), which included the use of four solvents with ethyl acetate and hexane, or the sequential partitions (Method II) with a five solvent system (butanol). The antibacterial and antifungal activities of crude extracts were tested against 28 bacteria, three yeast strains and seven fungal isolates by the disc diffusion and broth dilution methods. Amoxicillin was used as positive control for bacteria strains, vancomycin for Streptococcus sp., miconazole nitrate (30 microg/mL) as positive control for fungi and yeast, and pure methanol (v/v) as negative control. The disc diffusion assay was used to determine the sensitivity of the samples, whilst the broth dilution method was used for the determination of the minimal inhibition concentration (MIC). The ethyl acetate and hexane extract from extraction method I (EA I and HE I) exhibited highest inhibition against some pathogenic bacteria such as Bacillus cereus, MRSA and Vibrio parahaemolyticus. A selection of extracts that showed some activity was further tested for the MIC and minimal bactericidal concentrations (MBC). MIC values of Bacillus subtilis and Methicillin-resistant Staphylococcus aureus (MRSA) using butanol extract of extraction method II (BE II) were 8.33 and 16.33mg/mL, respectively; while the MIC value using ethyl acetate extract of extraction method II (EAE II) for Vibrio parahaemolyticus was 0.13mg/mL. Our study showed that 47.06% of extracts inhibited Gram-negative (8 out of 17), and 63.63% of extracts also inhibited Gram-positive bacteria (7 out of 11); besides, statistically the frequency of antimicrobial activity was 13.45% (35 out of 342) which in this among 21.71% belongs to antimicrobial activity extracts from extraction method I (33 out of 152 of crude extracts) and 6.82% from extraction method II (13 out of 190 of crude extracts). However, crude extracts from method I exhibited better antimicrobial activity against the Gram-positive bacteria than the Gram-negative bacteria. The positive results on medicinal plants screening for antibacterial activity constitutes primary information for further phytochemical and pharmacological studies. Therefore, the extracts could be suitable as antimicrobial agents in pharmaceutical and food industry.

Matched MeSH terms: Gram-Negative Bacteria/classification; Gram-Negative Bacteria/drug effects*
Dynamic interaction of colistin and meropenem on a WT and a resistant strain of Pseudomonas aeruginosa as quantified in a PK/PD model

Mohamed AF, Kristoffersson AN, Karvanen M, Nielsen EI, Cars O, Friberg LE

J Antimicrob Chemother, 2016 May;71(5):1279-90.
PMID: 26850719 DOI: 10.1093/jac/dkv488

Combination therapy can be a strategy to ensure effective bacterial killing when treating Pseudomonas aeruginosa, a Gram-negative bacterium with high potential for developing resistance. The aim of this study was to develop a pharmacokinetic/pharmacodynamic (PK/PD) model that describes the in vitro bacterial time-kill curves of colistin and meropenem alone and in combination for one WT and one meropenem-resistant strain of P. aeruginosa.

Matched MeSH terms: Gram-Negative Bacteria
Design, synthesis, and biological evaluation of 1,8-naphthyridine glucosamine conjugates as antimicrobial agents

Mohammed AAM, Suaifan GARY, Shehadeh MB, Okechukwu PN

Drug Dev Res, 2019 02;80(1):179-186.
PMID: 30570767 DOI: 10.1002/ddr.21508

In the quest for discovering potent antimicrobial agents with lower toxicity, we envisioned the design and synthesis of nalidixic acid-D-(+)-glucosamine conjugates. The novel compounds were synthesized and evaluated for their in vitro antimicrobial activity against Gram positive bacteria, Gram negative bacteria and fungi. Cytotoxicity using MTT assay over L6 skeletal myoblast cell line, ATCC CRL-1458 was carried out. In vitro antimicrobial assay revealed that 1-ethyl-7-methyl-4-oxo-N-(1,3,4,6-tetra-O-acetyl-2-deoxy-D-glucopyranose-2-yl)-[1,8]-naphthyridine-3-carboxamide (5) and 1-ethyl-7-methyl-4-oxo-N-(2-deoxy-D-glucopyranose-2-yl)-[1,8]-naphthyridine-3-carboxamide(6) possess growth inhibitory activity against resistant Escherichia coli NCTC, 11954 (MIC 0.1589 mM) and Methicillin resistant Staphylococcus aureus ATCC, 33591 (MIC 0.1589 mM). Compound (5) was more active against Listeria monocytogenes ATCC 19115 (MIC 0.1113 mM) in comparison with the reference nalidixic acid (MIC 1.0765 mM). Interestingly, compound (6) had potential antifungal activity against Candida albicans ATCC 10231 (MIC <0.0099 mM). Remarkably, the tested compounds had low cytotoxic effect. This study indicated that glucosamine moiety inclusion into the chemical structure of the marketed nalidixic acid enhances antimicrobial activity and safety.

Matched MeSH terms: Gram-Negative Bacteria/drug effects; Gram-Negative Bacteria/physiology
Design, synthesis and antimicrobial evaluation of novel glycosylated-fluoroquinolones derivatives

Mohammed AAM, Suaifan GARY, Shehadeh MB, Okechukwu PN

Eur J Med Chem, 2020 Sep 15;202:112513.
PMID: 32623216 DOI: 10.1016/j.ejmech.2020.112513

Herein we report the design, synthesis and biological evaluation of structurally modified ciprofloxacin, norfloxacin and moxifloxacin standard drugs, featuring amide functional groups at C-3 of the fluoroquinolone scaffold. In vitro antimicrobial testing against various Gram-positive bacteria, Gram-negative bacteria and fungi revealed potential antibacterial and antifungal activity. Hybrid compounds 9 (MIC 0.2668 ± 0.0001 mM), 10 (MIC 0.1358 ± 00025 mM) and 13 (MIC 0.0898 ± 0.0014 mM) had potential antimicrobial activity against a fluoroquinolone-resistant Escherichia coli clinical isolate, compared to ciprofloxacin (MIC 0.5098 ± 0.0024 mM) and norfloxacin (MIC 0.2937 ± 0.0021 mM) standard drugs. Interestingly, compound 10 also exerted potential antifungal activity against Candida albicans (MIC 0.0056 ± 0.0014 mM) and Penicillium chrysogenum (MIC 0.0453 ± 0.0156 mM). Novel derivatives and standard fluoroquinolone drugs exhibited near-identical cytotoxicity levels against L6 muscle cell-line, when measured using the MTT assay.

Matched MeSH terms: Gram-Negative Bacteria/drug effects
Fulltext Medicinal properties screening of Mallotus paniculatus extract

NA Bahaman, Raha Ahmad Raus, Yusilawati Ahmad Nor, Al Mamun, Abdullah, Noor Suhana Adzahar, Dayang Fredalina Basri

IIUM Medical Journal Malaysia, 2020;19(1):5-12.
MyJurnal

Introduction: Traditionally, Mallotus paniculatus (Balik Angin) plant is used in the treatment of various
diseases in rural areas such as remedy after childbirth, wound healing and fever. In this present study, four
medicinal properties of the plant were investigated which included antibacterial, antifungal, anticancer and
antioxidant activities. Materials and Methods: Potential medicinal compounds were extracted from the plant
leaves by sonication with 3 different solvents namely ethanol, ethyl acetate and hexane respectively. The
antibacterial and antifungal properties were determined using disc diffusion agar and broth dilution assay,
the antioxidant activity by DPPH scavenging assay and the anticancer effect by MTT assay. Results: From the
screening of the medicinal properties, M. paniculatus leave extracts were shown to possess antibacterial,
antioxidant and anticancer properties but not antifungal properties. Ethanolic and ethyl acetate extracts of
the leave were active against gram positive bacteria (Staphylococcus aureus and Bacillus subtilis) but not
gram negative bacteria (Pseudomonas aeruginosa and Escherichia coli). The antioxidant activity of the
ethanolic crude extract was high; with IC50 of 30 μg/ml comparable with the positive controls; ascorbic acid
and butylated hydroxytoluene (BHT). Both ethanolic and ethyl acetate extracts were cytotoxic against breast
cancer (MCF7), colon cancer (HT-29), cervix cancer (Hela) cell lines. Conclusion: M. paniculatus leave
extract has many potential medicinal values for further studies.

Matched MeSH terms: Gram-Negative Bacteria
Synthesis, in vitro antimycobacterial evaluation and docking studies of some new 5,6,7,8-tetrahydropyrido[4',3':4,5]thieno[2,3-d]pyrimidin-4(3H)-one schiff bases

Narender M, Jaswanth S B, Umasankar K, Malathi J, Raghuram Reddy A, Umadevi KR, et al.

Bioorg Med Chem Lett, 2016 Feb 01;26(3):836-840.
PMID: 26755393 DOI: 10.1016/j.bmcl.2015.12.083

Development of multidrug resistant (MDR) and extensively drug resistant (XDR) tuberculosis (TB) has been considered as major health burden, globally. In order to develop novel, potential molecules against drug resistant TB, twenty two (22) new 3-substituted-7-benzyl-5,6,7,8-tetrahydropyrido[4',3':4,5]thieno[2,3-d]pyrimidin-4(3H)-one (6a-k) and 3-substituted-7-benzyl-2-methyl-5,6,7,8-tetrahydropyrido[4',3':4,5]thieno[2,3-d]pyrimidin-4(3H)-one (7a-k) derivatives were designed and synthesized by using appropriate synthetic protocols. Pantothenate synthetase (PS) was considered as the target for the molecular docking studies and evaluated the binding pattern at active site, as PS plays a significant role in the biosynthesis of pantothenate in Mycobacterium tuberculosis (MTB). The preliminary in vitro antibacterial screening of test compounds was carried out against two strains of Gram-positive (Bacillus subtilis and Staphylococcus aureus) and Gram-negative (Escherichia coli and Klebsiella pneumoniae) bacteria. The antimycobacterial screening was performed against MTB H37Rv and an isoniazid-resistant clinical isolate of MTB. The compounds 6b, 6c, 6d, 6k, 7b, 7c, 7d and 7k exhibited promising antibacterial activity MIC in the range of 15-73 μM against all bacterial strains used and compounds 6d and 7b showed antimycobacterial activity (IC50 <340 μM in LRP assay) and (MIC <9 μM in broth microdilution method).

Matched MeSH terms: Gram-Negative Bacteria/drug effects; Gram-Negative Bacteria/metabolism
Synthesis and characterization of gentamicin loaded ZSM-5 scaffold: Cytocompatibility and antibacterial activity

Nazemi N, Rajabi N, Aslani Z, Kharaziha M, Kasiri-Asgarani M, Bakhsheshi-Rad HR, et al.

J Biomater Appl, 2023 Jan;37(6):979-991.
PMID: 36454961 DOI: 10.1177/08853282221140672

Porous structure, biocompatibility and biodegradability, large surface area, and drug-loading ability are some remarkable properties of zeolite structure, making it a great possible option for bone tissue engineering. Herein, we evaluated the potential application of the ZSM-5 scaffold encapsulated GEN with high porosity structure and significant antibacterial properties. The space holder process has been employed as a new fabrication method with interconnected pores and suitable mechanical properties. In this study, for the first time, ZSM-5 scaffolds with GEN drug-loading were fabricated with the space holder method. The results showed excellent open porosity in the range of 70-78% for different GEN concentrations and appropriate mechanical properties. Apatite formation on the scaffold surface was determined with Simulation body fluid (SBF), and a new bone-like apatite layer shaping on all samples confirmed the in vitro bioactivity of ZSM-5-GEN scaffolds. Also, antibacterial properties were investigated against both gram-positive and gram-negative bacteria. The incorporation of various amounts of GEN increased the inhibition zone from 24 to 28 (for E. coli) and 26 to 37 (for S. aureus). In the culture with MG63 cells, great cell viability and high cell proliferation after 7 days of culture were determined.

Matched MeSH terms: Gram-Negative Bacteria
Fulltext Deacetylation of K481 and K484 on Penaeid Shrimp Hemocyanin Is Critical for Antibacterial Activity

Nie J, Aweya JJ, Yu Z, Zhou H, Wang F, Yao D, et al.

J Immunol, 2022 Aug 01;209(3):476-487.
PMID: 35851542 DOI: 10.4049/jimmunol.2200078

Although invertebrates' innate immunity relies on several immune-like molecules, the diversity of these molecules and their immune response mechanisms are not well understood. Here, we show that Penaeus vannamei hemocyanin (PvHMC) undergoes specific deacetylation under Vibrio parahaemolyticus and LPS challenge. In vitro deacetylation of PvHMC increases its binding capacity with LPS and antibacterial activity against Gram-negative bacteria. Lysine residues K481 and K484 on the Ig-like domain of PvHMC are the main acetylation sites modulated by the acetyltransferase TIP60 and deacetylase HDAC3. Deacetylation of PvHMC on K481 and K484 allows PvHMC to form a positively charged binding pocket that interacts directly with LPS, whereas acetylation abrogates the positive charge to decrease PvHMC-LPS attraction. Besides, V. parahaemolyticus and LPS challenge increases the expression of Pvhdac3 to induce PvHMC deacetylation. This work indicates that, during bacterial infections, deacetylation of hemocyanin is crucial for binding with LPS to clear Gram-negative bacteria in crustaceans.

Matched MeSH terms: Gram-Negative Bacteria
Anti-infective activities of 11 plants species used in traditional medicine in Malaysia

Nor Azman NS, Hossan MS, Nissapatorn V, Uthaipibull C, Prommana P, Jin KT, et al.

Exp Parasitol, 2018 Nov;194:67-78.
PMID: 30268422 DOI: 10.1016/j.exppara.2018.09.020

Treatment of drug resistant protozoa, bacteria, and viruses requires new drugs with alternative chemotypes. Such compounds could be found from Southeast Asian medicinal plants. The present study examines the cytotoxic, antileishmanial, and antiplasmodial effects of 11 ethnopharmacologically important plant species in Malaysia. Chloroform extracts were tested for their toxicity against MRC-5 cells and Leishmania donovani by MTT, and chloroquine-resistant Plasmodium falciparum K1 strain by Histidine-Rich Protein II ELISA assays. None of the extract tested was cytotoxic to MRC-5 cells. Extracts of Uvaria grandiflora, Chilocarpus costatus, Tabernaemontana peduncularis, and Leuconotis eugenifolius had good activities against L. donovani with IC50 

Matched MeSH terms: Gram-Negative Bacteria/drug effects
Fulltext Comparative Study of CDST & Multiplex PCR to Detect MBL Producing Gram-Negative Bacilli among VAP Patients Admitted in a Public Medical College Hospital of Bangladesh

Nusrat T, Akter N, Haque M, Rahman NAA, Dewanjee AK, Ahmed S, et al.

Pathogens, 2019 Sep 12;8(3).
PMID: 31547453 DOI: 10.3390/pathogens8030151

BACKGROUND: Ventilator-associated pneumonia (VAP) is the most common nosocomial infection in intensive care units (ICU), which accounts for 25% of all ICU infection. Documenting carbapenem-resistant gram-negative bacilli is very important as these strains may often cause outbreaks in the ICU setting and are responsible for the increased mortality and morbidity or limiting therapeutic options. The classical phenotypic method cannot provide an efficient means of diagnosis of the metallo-β-lactamases (MBLs) producer. Polymerase chain reaction (PCR) assays have lessened the importance of the phenotypic approach by detecting metallo-β-lactamase resistance genes such as New Delhi metallo-β-lactamase (NDM), Imipenemase (IMP), Verona integron-encoded metallo-β-lactamase (VIM), Sao Paulo metallo-β-lactamase (SPM), Germany Imipenemase (GIM).
OBJECTIVE: To compare the results of the Combined Disc Synergy Test (CDST) with that of the multiplex PCR to detect MBL-producing gram-negative bacilli.
MATERIALS AND METHOD: A total of 105 endotracheal aspirates (ETA) samples were collected from the ICU of a public school in Bangladesh. This cross-sectional study was carried out in the Department of Microbiology, Chittagong for quantitative culture, CDST test, and multiplex PCR for blaIMP, blaVIM, blaNDM genes of MBL producers.
RESULTS: Among the 105 clinically suspected VAP cases, the quantitative culture was positive in 95 (90%) and among 95 g-negative bacilli isolated from VAP patients, 46 (48.42%) were imipenem resistant, 30 (65.22%) were MBL producers by CDST, 21 (45.65%) were identified as MBL producers by multiplex PCR.
CONCLUSION: PCR was highly sensitive and specific for the detection of MBL producers.

Matched MeSH terms: Gram-Negative Bacteria
Antibiotic resistance and sensitivity pattern of Metallo-β-Lactamase Producing Gram-Negative Bacilli in ventilator-associated pneumonia in the intensive care unit of a public medical school hospital in Bangladesh

Nusrat T, Akter N, Rahman NAA, Godman B, D Rozario DT, Haque M

Hosp Pract (1995), 2020 Aug;48(3):128-136.
PMID: 32271642 DOI: 10.1080/21548331.2020.1754687

BACKGROUND: Ventilator-associated pneumonia (VAP) is the most common nosocomial infection in intensive care units (ICU), accounting for 25% of all ICU infections. Antimicrobial resistance is increasing and becoming a significant health problem worldwide, increasing hospital length of stay, mortality and costs. Identifying antibiotic resistance patterns in VAP is important as this can cause outbreaks in ICUs. To date, there have been limited studies assessing this in Bangladesh. Consequently, the primary objective of this research was to study the species of bacterial growth and to determine the antibiotic resistance patterns of Metallo-β-Lactamase (MBL) producing gram-negative bacilli among ICU patients with VAP in a public medical school hospital, Bangladesh. In addition, identify the factors associated with a positive culture to provide future guidance.
METHOD: Cross-sectional study performed in the Chattogram Medical College Hospital, Bangladesh. Mueller Hinton agar plates were used for antibiotic sensitivity testing by the Kirby-Buer disc diffusion test.
RESULTS: Among 105 clinically suspected VAP cases, qualitative cultures were positive in 95 (90%) of them. The most common bacteria identified were Acinetobacter spp. (43.2%), Klebsiella spp. (20%) and Pseudomonas spp. (18.9%). A positive culture was not associated with patients' age or gender. Among 41 isolated Acinetobacter spp., 38 (92.7%) were resistant to gentamicin followed by 36 (87.8%) to ceftriaxone. Among 24 isolated Klebsiella spp., 22 (83.3%) were resistant to ceftriaxone. Among 18 isolated Pseudomonas spp., 16 (88.8%) were resistant to ciprofloxacin, and 13 (72.2%) were resistant to ceftriaxone. Among nine isolated E.coli, all were resistant to ceftriaxone and ciprofloxacin. All four Proteus spp. (100%) isolated were resistant to ciprofloxacin. Additionally, phenotype MBL producing was 65.22% and genotype was 45.65% among imipenem resistant pathogens. Imipenem resistant pathogens were sensitive to amoxyclav, amikacin¸ azithromycin, ceftazidime, ceftriaxone, colistin and gentamycin.
CONCLUSION: A positive culture was detected in 90% of VAP patients, but it was not associated with the patients' age and gender. The most common bacteria identified were Acinetobacter spp., Klebsiella spp. and Pseudomonas spp., where the majority of these were resistant to ceftriaxone. The results are being used to provide future guidance on the empiric management of VAP in this hospital.

Matched MeSH terms: Gram-Negative Bacteria/isolation & purification*
Fulltext A pentaplex PCR assay for the detection and differentiation of Shigella species

Ojha SC, Yean Yean C, Ismail A, Singh KK

Biomed Res Int, 2013;2013:412370.
PMID: 23509722 DOI: 10.1155/2013/412370

The magnitude of shigellosis in developing countries is largely unknown because an affordable detection method is not available. Current laboratory diagnosis of Shigella spp. is laborious and time consuming and has low sensitivity. Hence, in the present study, a molecular-based diagnostic assay which amplifies simultaneously four specific genes to identify invC for Shigella genus, rfc for S. flexneri, wbgZ for S. sonnei, and rfpB for S. dysenteriae, as well as one internal control (ompA) gene, was developed in a single reaction to detect and differentiate Shigella spp. Validation with 120 Shigella strains and 37 non-Shigella strains yielded 100% specificity. The sensitivity of the PCR was 100 pg of genomic DNA, 5.4 × 10(4) CFU/ml, or approximately 120 CFU per reaction mixture of bacteria. The sensitivity of the pentaplex PCR assay was further improved following preincubation of the stool samples in gram-negative broth. A preliminary study with 30 diarrhoeal specimens resulted in no cross-reaction with other non-Shigella strains tested. We conclude that the developed pentaplex PCR assay is robust and can provide information about the four target genes that are essential for the identification of the Shigella genus and the three Shigella species responsible for the majority of shigellosis cases.

Matched MeSH terms: Gram-Negative Bacteria/isolation & purification
Fulltext Bioactive compounds and biological activities of Jatropha curcas L. kernel meal extract

Oskoueian E, Abdullah N, Ahmad S, Saad WZ, Omar AR, Ho YW

Int J Mol Sci, 2011;12(9):5955-70.
PMID: 22016638 DOI: 10.3390/ijms12095955

Defatted Jatropha curcas L. (J. curcas) seed kernels contained a high percentage of crude protein (61.8%) and relatively little acid detergent fiber (4.8%) and neutral detergent fiber (9.7%). Spectrophotometric analysis of the methanolic extract showed the presence of phenolics, flavonoids and saponins with values of 3.9, 0.4 and 19.0 mg/g DM, respectively. High performance liquid chromatography (HPLC) analyses showed the presence of gallic acid and pyrogallol (phenolics), rutin and myricetin (flavonoids) and daidzein (isoflavonoid). The amount of phorbol esters in the methanolic extract estimated by HPLC was 3.0 ± 0.1 mg/g DM. Other metabolites detected by GC-MS include: 2-(hydroxymethyl)-2 nitro-1,3-propanediol, β-sitosterol, 2-furancarboxaldehyde, 5-(hydroxymethy) and acetic acid in the methanolic extract; 2-furancarboxaldehyde, 5-(hydroxymethy), acetic acid and furfural (2-furancarboxaldehyde) in the hot water extract. Methanolic and hot water extracts of kernel meal showed antimicrobial activity against both Gram positive and Gram negative pathogenic bacteria (inhibition range: 0-1.63 cm) at the concentrations of 1 and 1.5 mg/disc. Methanolic extract exhibited antioxidant activities that are higher than hot water extract and comparable to β-carotene. The extracts tended to scavenge the free radicals in the reduction of ferric ion (Fe(3+)) to ferrous ion (Fe(2+)). Cytotoxicity assay results indicated the potential of methanolic extract as a source of anticancer therapeutic agents toward breast cancer cells.

Matched MeSH terms: Gram-Negative Bacteria/drug effects; Gram-Negative Bacteria/growth & development
Cyclopenta[b]benzofuran and Secodammarane Derivatives from the Stems of Aglaia stellatopilosa

Othman N, Pan L, Mejin M, Voong JC, Chai HB, Pannell CM, et al.

J Nat Prod, 2016 Apr 22;79(4):784-91.
PMID: 26974604 DOI: 10.1021/acs.jnatprod.5b00810

Four new 2,3-secodammarane triterpenoids, stellatonins A-D (3-6), together with a new 3,4-secodammarane triterpenoid, stellatonin E (7), and the known silvestrol (1), 5‴-episilvestrol (2), and β-sitosterol, were isolated from a methanol extract of the stems of Aglaia stellatopilosa through bioassay-guided fractionation. The structures of the new compounds were elucidated using spectroscopic and chemical methods. The compounds were evaluated for their cytotoxic activity against three human cancer cell lines and for their antimicrobial activity using a microtiter plate assay against a panel of Gram-positive and Gram-negative bacteria and fungi.

Matched MeSH terms: Gram-Negative Bacteria/drug effects
Antibacterial evaluation of silver nanoparticles synthesized from lychee peel: individual versus antibiotic conjugated effects

Perveen S, Safdar N, Chaudhry GE, Yasmin A

World J Microbiol Biotechnol, 2018 Jul 14;34(8):118.
PMID: 30008019 DOI: 10.1007/s11274-018-2500-1

This paper describes the extracellular synthesis of silver nanoparticles from waste part of lychee fruit (peel) and their conjugation with selected antibiotics (amoxicillin, cefixim, and streptomycin). FTIR studies revealed the reduction of metallic silver and stabilization of silver nanoparticles and their conjugates due to the presence of CO (carboxyl), OH (hydroxyl) and CH (alkanes) groups. The size of conjugated nanoparticles varied ranging from 3 to 10 nm as shown by XRD. TEM image revealed the spherical shape of biosynthesized silver nanoparticles. Conjugates of amoxicillin and cefixim showed highest antibacterial activity (147.43 and 107.95%, respectively) against Gram-negative bacteria i.e. Alcaligenes faecalis in comparison with their control counterparts. The highest reduction in MIC was noted against Gram-positive strains i.e. Enterococcus faecium (75%) and Microbacterium oxydans (75%) for amoxicillin conjugates. Anova two factor followed by two-tailed t test showed non-significant results both in case of cell leakage and protein estimation between nanoparticles and conjugates of amoxicillin, cefixime and streptomycin. In case of MDA release, non-significant difference among the test samples against the selected strains. Our study found green-synthesized silver nanoparticles as effective antibacterial bullet against both Gram positive and Gram negative bacteria, but they showed a more promising effect on conjugation with selected antibiotics against Gram negative type.

Matched MeSH terms: Gram-Negative Bacteria/drug effects
Synergistic antibacterial actions of graphene oxide and antibiotics towards bacteria and the toxicological effects of graphene oxide on human epidermal keratinocytes

Pulingam T, Thong KL, Appaturi JN, Nordin NI, Dinshaw IJ, Lai CW, et al.

Eur J Pharm Sci, 2020 Jan 15;142:105087.
PMID: 31626968 DOI: 10.1016/j.ejps.2019.105087

Graphene oxide (GO) has displayed antibacterial activity that has been investigated in the past, however, information on synergistic activity of GO with conventional antibiotics is still lacking. The objectives of the study were to determine the combinatorial actions of GO and antibiotics against Gram-positive and Gram-negative bacteria and the toxicological effects of GO towards human epidermal keratinocytes (HaCaT). Interactions at molecular level between GO and antibiotics were analyzed using Attenuated Total Reflectance-Fourier-transform infrared spectroscopy (ATR-FTIR). Changes in the antibacterial activity of antibiotics towards bacteria through the addition of GO was investigated. Toxicity of GO towards HaCaT cells were examined as skin cells play a role as the first line of defense of the human body. The ATR-FTIR characterizations of GO and antibiotics showed adsorption of tested antibiotics onto GO. The combinatorial antibacterial activity of GO and antibiotics were found to increase when compared to GO or antibiotic alone. This was attributed to the ability of GO to disrupt bacterial membrane to allow for better adsorption of antibiotics. Cytotoxicity of GO was found to be dose-dependent towards HaCaT cell line, it is found to impose negligible toxic effects against the skin cells at concentration below 100 μg/mL.

Matched MeSH terms: Gram-Negative Bacteria/drug effects*
Graphene oxide exhibits differential mechanistic action towards Gram-positive and Gram-negative bacteria

Pulingam T, Thong KL, Ali ME, Appaturi JN, Dinshaw IJ, Ong ZY, et al.

Colloids Surf B Biointerfaces, 2019 Sep 01;181:6-15.
PMID: 31103799 DOI: 10.1016/j.colsurfb.2019.05.023

The antibacterial nature of graphene oxide (GO) has stimulated wide interest in the medical field. Although the antibacterial activity of GO towards bacteria has been well studied, a deeper understanding of the mechanism of action of GO is still lacking. The objective of the study was to elucidate the difference in the interactions of GO towards Gram-positive and Gram-negative bacteria. The synthesized GO was characterized by Ultraviolet-visible spectroscopy (UV-vis), Raman and Attenuated Total Reflectance-Fourier-transform infrared spectroscopy (ATR-FTIR). Viability, time-kill and Lactose Dehydrogenase (LDH) release assays were carried out along with FESEM, TEM and ATR-FTIR analysis of GO treated bacterial cells. Characterizations of synthesized GO confirmed the transition of graphene to GO and the antibacterial activity of GO was concentration and time-dependent. Loss of membrane integrity in bacteria was enhanced with increasing GO concentrations and this corresponded to the elevated release of LDH in the reaction medium. Surface morphology of GO treated bacterial culture showed apparent differences in the mechanism of action of GO towards Gram-positive and Gram-negative bacteria where cell entrapment was mainly observed for Gram-positive Staphylococcus aureus and Enterococcus faecalis whereas membrane disruption due to physical contact was noted for Gram-negative Escherichia coli and Pseudomonas aeruginosa. ATR-FTIR characterizations of the GO treated bacterial cells showed changes in the fatty acids, amide I and amide II of proteins, peptides and amino acid regions compared to untreated bacterial cells. Therefore, the data generated further enhance our understanding of the antibacterial activity of GO towards bacteria.

Matched MeSH terms: Gram-Negative Bacteria/cytology; Gram-Negative Bacteria/drug effects*
Fulltext Preliminary screening of endophytic fungi from medicinal plants in malaysia for antimicrobial and antitumor activity

Radu S, Kqueen CY

Malays J Med Sci, 2002 Jul;9(2):23-33.
PMID: 22844221 MyJurnal

The screening of antimicrobial activity against Gram-positive bacteria, Gram-negative bacteria, yeast and fungi was carried out on isopropanol extracts prepared from 121 isolates of endophytic fungi isolated from medicinal plants in Malaysia. Sensitivity was found to vary among the microorganisms. Bacillus subtilis, Saccharomyces cerevisiae and Alternaria sp. were susceptible to extracts from three, two and two isolates of endophytic fungi, respectively. None were found effective against Salmonella typhimurium. Sixteen endophytic fungal isolates tested were also found to exhibit antitumor activity in the yeast cell-based assay.

Matched MeSH terms: Gram-Negative Bacteria
Ocular surface infections in northeastern state of malaysia: a 10-year review of bacterial isolates and antimicrobial susceptibility

Rahman ZA, Harun A, Hasan H, Mohamed Z, Noor SS, Deris ZZ, et al.

Eye Contact Lens, 2013 Sep;39(5):355-60.
PMID: 23982472 DOI: 10.1097/ICL.0b013e3182a3026b

Ocular surface infections that include infections of conjunctiva, adnexa, and cornea have the potential risk of causing blindness within a given population. Empirical antibiotic therapy is usually initiated based on epidemiological data of common causative agents. Thus, the aims of this study were to determine the bacterial agents and their susceptibility patterns of isolates from ocular surface specimens in our hospital.

Matched MeSH terms: Gram-Negative Bacteria/drug effects*; Gram-Negative Bacteria/isolation & purification
Fulltext Microbiology of diabetic foot infections in a teaching hospital in Malaysia: a retrospective study of 194 cases

Raja NS

J Microbiol Immunol Infect, 2007 Feb;40(1):39-44.
PMID: 17332905

Diabetes mellitus is a progressive disease with chronic complications. Foot infections are a major complication of diabetes and eventually lead to development of gangrene and lower extremity amputation. The microbiological characteristics of diabetic foot infections have not been extensively studied in Malaysia. This study investigated the microbiology of diabetic foot infections and their resistance to antibiotics in patients with diabetic foot infections treated at University of Malaya Medical Centre in Kuala Lumpur, Malaysia.

Matched MeSH terms: Gram-Negative Bacteria/classification; Gram-Negative Bacteria/drug effects; Gram-Negative Bacteria/isolation & purification*

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