Magnificines A and B, Antimicrobial Marine Alkaloids Featuring a Tetrahydrooxazolo[3,2-a]azepine-2,5(3H,6H)-dione Backbone from the Red Sea Sponge Negombata magnifica

Investigation of the Red Sea sponge Negombata magnifica gave two novel alkaloids, magnificines A and B (1 and 2) and a new β-ionone derivative, (±)-negombaionone (3), together with the known latrunculin B (4) and 16-epi-latrunculin B (5). The analysis of the NMR and HRESIMS spectra supported the planar structures and the relative configurations of the compounds. The absolute configurations of magnificines A and B were determined by the analysis of the predicted and experimental ECD spectra. Magnificines A and B possess a previously unreported tetrahydrooxazolo[3,2-a]azepine-2,5(3H,6H)-dione backbone and represent the first natural compounds in this class. (±)-Negombaionone is the first β-ionone of a sponge origin. Compounds 1-3 displayed selective activity against Escherichia coli in a disk diffusion assay with inhibition zones up to 22 mm at a concentration of 50 µg/disc and with MIC values down to 8.0 µM. Latrunculin B and 16-epi-latrunculin B inhibited the growth of HeLa cells with IC50 values down to 1.4 µM.

Download Full-text

Comparison of Antimicrobial Resistance in Escherichia coli, Staphylococcus aureus, and Listeria monocytogenes Strains Isolated from Organic and Conventional Poultry Meat

Journal of Food Protection ◽

10.4315/0362-028x-71.12.2537 ◽

2008 ◽

Vol 71 (12) ◽

pp. 2537-2542 ◽

Cited By ~ 38

Author(s):

J. M. MIRANDA ◽

B. I. VÁZQUEZ ◽

C. A. FENTE ◽

P. CALO-MATA ◽

A. CEPEDA ◽

...

Keyword(s):

Escherichia Coli ◽

Staphylococcus Aureus ◽

Listeria Monocytogenes ◽

Antimicrobial Resistance ◽

Intestinal Bacteria ◽

Poultry Meat ◽

E Coli ◽

Disk Diffusion Assay ◽

Multiresistant Strains ◽

Diffusion Assay

The presence of Escherichia coli, Staphylococcus aureus, and Listeria monocytogenes was determined in 55 samples of organic poultry meat and in 61 samples of conventional poultry meat. A total of 220 E. coli, 192 S. aureus, and 71 L. monocytogenes strains were analyzed by an agar disk diffusion assay for their resistance to ampicillin, cephalothin, chloramphenicol, ciprofloxacin, doxycycline, fosfomycin, gentamicin, nitrofurantoin, streptomycin, and sulfisoxazole (E. coli); chloramphenicol, ciprofloxacin, clindamycin, doxycycline, erythromycin, gentamicin, nitrofurantoin, oxacillin, and sulfisoxazole (S. aureus); and chloramphenicol, doxycycline, erythromycin, gentamicin, sulfisoxazole, and vancomycin (L. monocytogenes). The results indicated a significantly higher (P < 0.0001) prevalence of E. coli but not of S. aureus and L. monocytogenes in organic poultry meat as compared with conventional poultry meat. E. coli isolated from organic poultry meat exhibited lower levels of antimicrobial resistance against 7 of the 10 antimicrobials tested as compared with isolates recovered from conventional meat. In the case of S. aureus and L. monocytogenes isolated from conventional poultry, antimicrobial resistance was significantly higher only for doxycycline as compared with strains isolated from organic poultry. In the case of E. coli, the presence of multiresistant strains was significantly higher (P < 0.0001) in conventional poultry meat as compared with organic poultry meat. Organically farmed poultry samples showed significantly lower development of antimicrobial resistance in intestinal bacteria such as E. coli.

Download Full-text

Discovery of a Gene Conferring Multiple-Aminoglycoside Resistance in Escherichia coli

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.01743-09 ◽

2010 ◽

Vol 54 (6) ◽

pp. 2666-2669 ◽

Cited By ~ 59

Author(s):

Margaret A. Davis ◽

Katherine N. K. Baker ◽

Lisa H. Orfe ◽

Devendra H. Shah ◽

Thomas E. Besser ◽

...

Keyword(s):

Escherichia Coli ◽

16S Rrna ◽

Dna Microarray ◽

Protein Sequence ◽

Gram Negative Bacteria ◽

Aminoglycoside Resistance ◽

Gram Negative ◽

Disk Diffusion Assay ◽

High Level ◽

Diffusion Assay

ABSTRACT Bovine-origin Escherichia coli isolates were tested for resistance phenotypes using a disk diffusion assay and for resistance genotypes using a DNA microarray. An isolate with gentamicin and amikacin resistance but with no corresponding genes detected yielded a 1,056-bp DNA sequence with the closest homologues for its inferred protein sequence among a family of 16S rRNA methyltransferase enzymes. These enzymes confer high-level aminoglycoside resistance and have only recently been described in Gram-negative bacteria.

Download Full-text

Identifying Small Molecules That Promote Quasipalindrome-Associated Template-Switch Mutations in Escherichia coli

G3 Genes|Genome|Genetics ◽

10.1534/g3.120.401106 ◽

2020 ◽

Vol 10 (5) ◽

pp. 1809-1815 ◽

Cited By ~ 1

Author(s):

Julie A. Klaric ◽

Eli L. Perr ◽

Susan T. Lovett

Keyword(s):

Escherichia Coli ◽

Small Molecules ◽

Mutational Event ◽

Template Strand ◽

Dna Repeat ◽

Mutational Hotspots ◽

Small Molecule Libraries ◽

Disk Diffusion Assay ◽

Switch Mechanism ◽

Template Switch

DNA can assemble into non-B form structures that stall replication and cause genomic instability. One such secondary structure results from an inverted DNA repeat that can assemble into hairpin and cruciform structures during DNA replication. Quasipalindromes (QP), imperfect inverted repeats, are sites of mutational hotspots. Quasipalindrome-associated mutations (QPMs) occur through a template-switch mechanism in which the replicative polymerase stalls at a QP site and uses the nascent strand as a template instead of the correct template strand. This mutational event causes the QP to become a perfect or more perfect inverted repeat. Since it is not fully understood how template-switch events are stimulated or repressed, we designed a high-throughput screen to discover drugs that affect these events. QP reporters were engineered in the Escherichia coli lacZ gene to allow us to study template-switch events specifically. We tested 700 compounds from the NIH Clinical Collection through a disk diffusion assay and identified 11 positive hits. One of the hits was azidothymidine (zidovudine, AZT), a thymidine analog and DNA chain terminator. The other ten were found to be fluoroquinolone antibiotics, which induce DNA-protein crosslinks. This work shows that our screen is useful in identifying small molecules that affect quasipalindrome-associated template-switch mutations. We are currently assessing more small molecule libraries and applying this method to study other types of mutations.

Download Full-text

Spectrum and theIn VitroAntifungal Susceptibility Pattern of Yeast Isolates in Ethiopian HIV Patients with Oropharyngeal Candidiasis

International Journal of Microbiology ◽

10.1155/2016/3037817 ◽

2016 ◽

Vol 2016 ◽

pp. 1-8 ◽

Cited By ~ 10

Author(s):

Birhan Moges ◽

Adane Bitew ◽

Aster Shewaamare

Keyword(s):

Antifungal Agents ◽

Antifungal Susceptibility ◽

Antifungal Drugs ◽

Assay Method ◽

Cryptococcus Laurentii ◽

Susceptibility Pattern ◽

Test Procedures ◽

Disk Diffusion Assay ◽

Diffusion Assay

Background.In Ethiopia, little is known regarding the distribution and thein vitroantifungal susceptibility profile of yeasts.Objective.This study was undertaken to determine the spectrum and thein vitroantifungal susceptibility pattern of yeasts isolated from HIV infected patients with OPC.Method.Oral pharyngeal swabs taken from oral lesions of study subjects were inoculated onto Sabouraud Dextrose Agar. Yeasts were identified by employing conventional test procedures and the susceptibility of yeasts to antifungal agents was evaluated by disk diffusion assay method.Result.One hundred and fifty-five yeast isolates were recovered of which 91 isolates were from patients that were not under HAART and 64 were from patients that were under HAART.C. albicanswas the most frequently isolated species followed byC. glabrata, C. tropicalis, C. krusei, C. kefyr, Cryptococcus laurentii, and Rhodotorulaspecies. Irrespective of yeasts isolated and identified, 5.8%, 5.8%, 12.3%, 8.4%, 0.6%, and 1.3% of the isolates were resistant to amphotericin B, clotrimazole, fluconazole, ketoconazole, miconazole, and nystatin, respectively.Conclusion.Yeast colonization rate of 69.2% and 31% resistance to six antifungal agents was documented. These highlight the need for nationwide study on the epidemiology of OPC and resistance to antifungal drugs.

Download Full-text

Antimicrobial Activities in Pistacia atlantica—Aphids Make a Difference!

Proceedings ◽

10.3390/proceedings2020066009 ◽

2020 ◽

Vol 66 (1) ◽

pp. 9

Author(s):

Yoram Gerchman

Keyword(s):

Secondary Metabolites ◽

Essential Oils ◽

Organic Solvents ◽

Antimicrobial Properties ◽

Antimicrobial Activities ◽

Disk Diffusion ◽

Pistacia Atlantica ◽

Disk Diffusion Assay ◽

Bacteria And Fungi ◽

Diffusion Assay

Plants have been explored and used as sources for antimicrobial extract and compounds for many years, but galls—specialized structures forms on such by diversity of organisms—have been explored much less. Aphid galls host many insects in closed, humid and sugar rich environments for long periods. We have tested the antimicrobial properties of Slavum wertheimae aphid galls on Pistacia atlantica. Secondary metabolites were extracted from leaves and galls with organic solvents, and essential oils with Clevenger, and tested by disk diffusion assay and volatile effect on bacteria and fungi, respectively. The results demonstrated that gall extracts/essential oils had much stronger activity against the diversity of bacteria and fungi. The large diversity of galls suggest they could be explored as source for novel compounds.

Download Full-text

ISOLATION AND CHARACTERIZATION OF ACTINOMYCETES FROM SOIL OF AD-DAWADMI, SAUDI ARABIA AND SCREENING THEIR ANTIBACTERIAL ACTIVITIES

International Journal of Pharmacy and Pharmaceutical Sciences ◽

10.22159/ijpps.2017v9i10.15402 ◽

2017 ◽

Vol 9 (10) ◽

pp. 276 ◽

Cited By ~ 3

Author(s):

Gouse Basha Sheik ◽

Muazzam Sheriff Maqbul ◽

Gokul Shankar S. ◽

Ranjith M S

Keyword(s):

Escherichia Coli ◽

Staphylococcus Aureus ◽

Antibacterial Activity ◽

Antibacterial Activities ◽

Soil Samples ◽

Streptomyces Sp ◽

Crude Extracts ◽

Test Organisms ◽

Inhibition Zones

Objective: To isolate and characterize novel actinomycetes and to evaluate their antibacterial activity against drug-resistant pathogenic bacteriaMethods: In the present study, 19 soil samples were collected from different localities of Ad-Dawadmi, Saudi Arabia. Actinomycetes were isolated from these samples using serial dilution and plating method on Actinomycetes isolation agar supplemented with nalidixic acid and actidione to inhibit bacteria and fungi. Crude extracts of potential actinomycetes were produced by submerged fermentation. The antimicrobial activity of crude extracts of actinomycetes was tested against different bacteria using the agar well diffusion method. Characterization of the isolates was done by morphological, physiological and biochemical methods.Results: A total of 9 (47%) isolates of actinomycetes were isolated from 19 different soil samples tested. Among them, 4 (44%) isolates confirmed as Streptomyces sp. showed potential antimicrobial activity against one or more test organisms. Crude extracts were made from these 4 actinomycetes isolates(DOM1, DOM3, DP3, DP4)and tested for their antibacterial activities against 4 different clinical bacterial strains (Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus and Enterococcus). Crude extract from DP3 isolate showed highest antibacterial activity against all the four test organisms (28 mm, 21 mm, 20 mm and 18 mm) respectively and DP4 showed lowest antibacterial activity against all the four test organisms (14 mm, 12 mm, 0 mm, 6 mm) respectively. The highest zone of inhibition was shown by DP3 against Staphylococcus aureus (28 mm) and Escherichia coli was resistant for DP4. Most of the Inhibition zones produced by crude extracts showed significant differences when compared with control, tested against test organisms (P<0.05). Inhibition zones produced by DP3 and DOM1 against Staphylococcus aureus were 28 mm and 23 mm, respectively which were strong active when compared with control Ciprofloxacin (18 mm).Conclusion: Further studies for purification of bioactive metabolites and molecular characterization analysis of isolated Streptomyces sp. are in progress which would be helpful in discovering novel compounds of commercial value.

Download Full-text

Molecular Characterization of Plasmid-Mediated Non-O157 Verotoxigenic Escherichia coli Isolated from Infants and Children with Diarrhea

Baghdad Science Journal ◽

10.21123/bsj.2020.17.3.0710 ◽

2020 ◽

Vol 17 (3) ◽

pp. 0710

Author(s):

Md Fazlul Karim Khan ◽

Shah Samiur Rashid

Keyword(s):

Escherichia Coli ◽

Virulence Gene ◽

Multidrug Resistant ◽

Plasmid Curing ◽

Health Issues ◽

E Coli ◽

Disk Diffusion Assay ◽

Microbiological Techniques ◽

Polymerase Chain

A significant increase in the incidence of non-O157 verotoxigenic Escherichia coli (VTEC) infections have become a serious health issues, and this situation is worsening due to the dissemination of plasmid mediated multidrug-resistant microorganisms worldwide. This study aims to investigate the presence of plasmid-mediated verotoxin gene in non-O157 E. coli. Standard microbiological techniques identified a total of 137 E. coli isolates. The plasmid was detected by Perfectprep Plasmid Mini preparation kit. These isolates were subjected to disk diffusion assay, and plasmid curing with ethidium bromide treatment. The plasmid containing isolates were subjected to a polymerase chain reaction (PCR) for investigating the presence of plasmid mediated verotoxin gene (VT1 and VT2) in non-O157 E. coli. Among the 137 E. coli isolates, 49 isolates were non-O157 E. coli while 29 (59.1%) isolates were verotoxin producing non-O157 serotypes and 26 non-O157 VTEC isolates possessed plasmids. Certain isolates harboured single sized plasmid while others had multiple plasmids with different size varied from 1.8kb to 7.6kb. A plasmid containing all (100%) the isolates was multidrug-resistant. Eight isolates changed their susceptibility patterns while three isolates were found to lose plasmid after post plasmid curing treatment and the rest of the isolates (15) remained constant. Different PCR sets characterized 3 plasmid-mediated verotoxins producing non-O157 E. coli. This current study demonstrated the occurrence of plasmid mediated verotoxin gene in non-O157 E. coli. To the best of our knowledge, this is the first report in the global literature on plasmid-mediated verotoxin gene in non-O157 E. coli. Timely diagnosis and surveillance of VTEC infections should prioritize to stop or slow down the virulence gene for dissemination by plasmid-mediated gene transfer amongst the same bacteria or other species.

Download Full-text

Mono- and Dimeric Xanthones with Anti-Glioma and Anti-Inflammatory Activities from the Ascidian-Derived Fungus Diaporthe sp. SYSU-MS4722

Marine Drugs ◽

10.3390/md20010051 ◽

2022 ◽

Vol 20 (1) ◽

pp. 51

Author(s):

Senhua Chen ◽

Heng Guo ◽

Minghua Jiang ◽

Qilin Wu ◽

Jing Li ◽

...

Keyword(s):

High Resolution Mass Spectrometry ◽

2D Nmr ◽

Crystallographic Analysis ◽

Selective Cytotoxicity ◽

X Ray ◽

Planar Structures ◽

Spectroscopic Analyses ◽

Ic50 Values ◽

Anti Inflammatory ◽

Resolution Mass

Seven new xanthones, diaporthones A−G (1−7), together with 13 known analogues, including five mono- (8−14) and six dimeric xanthones (15−20), were obtained from the ascidian-derived fungus Diaporthe sp. SYSU-MS4722. Their planar structures were established by extensive spectroscopic analyses, including 1D and 2D NMR and high-resolution mass spectrometry (HR-ESIMS). The absolute configurations of 1−7 were clearly identified by X-ray crystallographic analysis and calculation of the ECD Spectra. Compounds 15−20 showed significant anti-inflammatory activity with IC50 values between 6.3 and 8.0 μM. In addition, dimeric xanthones (15−20) showed selective cytotoxicity against T98G cell lines with IC50 values ranging from 19.5 to 78.0 μM.

Download Full-text

In Vitro Activity of Essential Oils Against Planktonic and Biofilm Cells of Extended-Spectrum β-Lactamase (ESBL)/Carbapenamase-Producing Gram-Negative Bacteria Involved in Human Nosocomial Infections

Antibiotics ◽

10.3390/antibiotics9050272 ◽

2020 ◽

Vol 9 (5) ◽

pp. 272 ◽

Cited By ~ 1

Author(s):

Ramona Iseppi ◽

Alessandro Di Cerbo ◽

Piero Aloisi ◽

Mattia Manelli ◽

Veronica Pellesi ◽

...

Keyword(s):

Antibacterial Activity ◽

Klebsiella Pneumoniae ◽

Essential Oils ◽

Disk Diffusion ◽

Mentha Piperita ◽

Thymus Vulgaris ◽

Extended Spectrum ◽

Disk Diffusion Assay ◽

Diffusion Assay

The aim of this study was to analyze the antibacterial activity of four essential oils (EOs), Melaleuca alternifolia, Eucalyptus globulus, Mentha piperita, and Thymus vulgaris, in preventing the development and spread of extended-spectrum β-lactamase (ESBL)-producing Escherichia coli and Klebsiella pneumoniae, metallo-beta-lactamase (MBL)-producing Pseudomonas aeruginosa and carbapenemase (KPC)-producing Klebsiella pneumoniae. A total of 60 strains were obtained from the stock collection from the Microbiology Laboratory of Hesperia Hospital, Modena, Italy. Twenty ESBL-producing E. coli, 5 K. pneumoniae, 13 KPC-producing K. pneumoniae, and 20 MBL-producing P. aeruginosa were cultured and reconfirmed as ESBL and carbapenamase producers. Polymerase chain reaction was used for the detection of genes responsible for antibiotic resistance (ESBL and KPC/MBL). Antibacterial activity of the EOs was determined using the agar disk diffusion assay, and minimal inhibitory concentrations (MICs) were also evaluated. Lastly, adhesion capability and biofilm formation on polystyrene and glass surfaces were studied in 24 randomly selected strains. M. alternifolia and T. vulgaris EOs showed the best antibacterial activity against all tested strains and, as revealed by agar disk diffusion assay, M. alternifolia was the most effective, even at low concentrations. This effect was also confirmed by MICs, with values ranging from 0.5 to 16 µg/mL and from 1 to 16 µg/mL, for M. alternifolia and T. vulgaris EOs, respectively. The EOs’ antibacterial activity compared to antibiotics confirmed M. alternifolia EO as the best antibacterial agent. T. vulgaris EO also showed a good antibacterial activity with MICs lower than both reference antibiotics. Lastly, a significant anti-biofilm activity was observed for the two EOs (*P < 0.05 and **P < 0.01 for M. alternifolia and T. vulgaris EOs, respectively). A good antibacterial and anti-biofilm activity of M. alternifolia and T. vulgaris EOs against all selected strains was observed, thus demonstrating a future possible use of these EOs to treat infections caused by ESBL/carbapenemase-producing strains, even in association with antibiotics.

Download Full-text

Primary antibiotic resistance of Helicobacter pylori among a Chinese Tibetan population

Future Microbiology ◽

10.2217/fmb-2020-0206 ◽

2020 ◽

Vol 15 (14) ◽

pp. 1353-1361

Author(s):

Xiaoqiong Tang ◽

Xiaohong Chen ◽

Yalin Shen ◽

Tiankuo Yang ◽

Renwei Hu ◽

...

Keyword(s):

Helicobacter Pylori ◽

Antibiotic Resistance ◽

Primary Resistance ◽

Tibetan Population ◽

Disk Diffusion Assay ◽

Treatment Naïve ◽

Gastric Biopsies ◽

H Pylori ◽

Resistance Rates ◽

Diffusion Assay

Aim: To evaluate the primary antibiotic resistance in Helicobacter pylori strains isolated from a Chinese Tibetan population. Methods & materials: Gastric biopsies from 400 H. pylori treatment-naive Tibetan patients were collected for H. pylori isolation. Susceptibility to amoxicillin (AML)/clarithromycin (CLR)/levofloxacin (LEV)/metronidazole (MTZ)/tetracycline (TET)/rifampicin (RIF)/furazolidone (FZD) was determined by E-test or a disk diffusion assay. Results: Biopsies from 117 patients were H. pylori culture positive (29.3%). The primary resistance rates to MTZ, CLR, LEV, RIF, AML, TET and FZD were 90.6, 44.4, 28.2, 69.2, 7.7, 0.8 and 0.8%, respectively. Interestingly, 42.7% of the strains had simultaneous resistance to CLR and MTZ. Conclusion: Among Tibetan strains, primary resistance rates were high for CLR/MTZ/LEV, whereas primary resistance rates to AML/TET/FZD were low. The high resistance to RIF is a concerning finding.

Download Full-text