Mixed Broth Research Articles

Real time microcalorimetric profiling of prebiotic inulin metabolism

The in vitro assessment of prebiotics involves elaborate microbiological techniques or a combination of culture techniques and molecular methods. In this study, the isothermal microcalorimeter, an instrument which can monitor the real time growth of bacteria was applied to investigate the prebiotic effect of inulin in real time. Fresh and standardized frozen faecal slurries were prepared, placed and monitored in the isothermal microcalorimeter. The faecal samples and commercial probiotic strains Lactobacillus acidophilus LA-5®, Bifidobacterium lactis BB-12® were cultured in a mixed medium of cooked meat medium (CMM) and brain heart infusion (BHI) broth with and without supplementation with inulin and monitored in the microcalorimeter. The results showed power-time (p-t) curves that were characteristic for the samples. The p-t curves of the fresh and frozen faecal samples were similar. Augmented microbial activity was observed when the faecal sample was inoculated into CMM-BHI mixed broth with significant enhancement of microbial activity detected in the presence of inulin which was reproducible. Deconvoluted p-t curves showed multiple peaks with time and intensity variance depending on presence or absence of inulin suggesting possible differences in utilization of inulin by the different groups of bacteria in the polymicrobial sample. P-t curves of the pure species did not show any significant change when inulin was supplemented into the medium likely due to the inability of the bacteria to primarily utilize inulin.

Comparison of Genotypic and Phenotypic Predictions for Heavy Metal Resistance in Salmonella enterica and Escherichia coli

Salmonella enterica and Escherichia coli are two pathogenic bacteria of worldwide importance that can infect the gastrointestinal tract. Contamination in the food supply chain is an area of concern. Animal feed may be supplemented with essential trace elements, which function as nutritional additives to promote growth & health and optimize production. Bacteria have acquired many metal resistance genes to adapt to the exposure of metals. In this study, our objectives were to evaluate in S. enterica and E. coli, the correlation between the resistance genotype and phenotype to certain heavy metals, and the ability of conjugative plasmids to transfer antimicrobial resistance genes (AMRGs) and heavy metal resistance genes (HMRGs). A total of 10 strains, five S. enterica and five E. coli, were used for this study. Minimal inhibitory concentrations (MICs) were determined for heavy metals: copper, silver, arsenic, and tellurite. The tested isolates showed resistance to copper (5/10; 50%), arsenic (7/10; 70%), and silver (9/10; 90%). Cohen’s Kappa statistics were used to analyze genotype to phenotype agreements. Among the 10 strains sampled, the accordance between geno- and phenotypic heavy metal resistance was fair for copper (kappa = 0.4), none to slight for arsenic (kappa = 0.19) and tellurite (kappa = 0), and no agreement for silver (kappa = -0.19). The transfer of HMRGs was determined in a conjugation experiment performed for all five Salmonella strains as donors using mixed broth cultures. Transconjugants were obtained only from the genotypically tellurite-resistant strain PSU-3260, which yielded a transfer frequency of 10⁻³ transconjugants per donor. In such strain, the tellurite-resistant genes reside on an IncHI2-type plasmid that shares high DNA sequence identity with known HMRG-disseminating Salmonella plasmids. Our results indicated no considerable correlation between the geno- and phenotypic resistance towards heavy metals in the sampled S. enterica and E. coli. The necessity of research in this area is supported by the lack of standardized protocols and MIC clinical breakpoints for heavy metals. KEYWORDS: Heavy metal; resistance; Salmonella; E. coli; agriculture; genotype; phenotype; MIC

Lactic Acid Bacteria from Gamecock and Goat Originating from Phitsanulok, Thailand: Isolation, Identification, Technological Properties and Probiotic Potential.

From independent swab samples of the cloaca of indigenous gamecocks (CIG), anus of healthy baby goats (AHG), and vagina of goats (VG) originating from Phitsanulok, Thailand, a total of 263 isolates of lactic acid bacteria (LAB) were collected. Only three isolates, designated C707, G502, and V202, isolated from CIG, AHG, and VG, respectively, exhibited an excellent inhibitory zone diameter against foodborne pathogenic bacteria when evaluated by agar spot test. Isolates C707 and G502 were identified as Enterococcus faecium, whereas V202 was identified as Pediococcus acidilactici, based on 16S rRNA sequence analysis. When foodborne pathogenic bacteria were co-cultured with chosen LAB in mixed BHI-MRS broth at 39°C, their growth was suppressed. These LAB were found to be capable of surviving in simulated stomach conditions. Only the isolate G502 was able to survive in the conditions of simulated intestinal juice. This research suggests that selected LAB could be used as a food/feed supplement to reduce foodborne pathogenic bacteria and improve the safety of animal-based food or feed.

Developing a food waste biorefinery: Lactic acid extraction using anionic resin and impacts on downstream biogas production

Coupling lactic acid (LA) production with food waste (FW) anaerobic digestion (AD) can facilitate the next generation biorefinery to increase revenue and economic viability of FW AD. For this, LA should be effectively extracted from complex fermentation broths with minimal adverse effects on subsequent AD to maximise economic benefit. This study evaluated LA recovery by adsorption using a polymeric resin (BA765), not previously tested for LA, to explore adsorption capacity and kinetics. Furthermore, biochemical methane potential (BMP) tests were utilised to assess the effect of LA extraction on subsequent AD by measuring biogas production from the solid and liquid extraction residues. Optimal adsorption conditions yielded a maximum capacity of 0.21 gLA·g−1resin from pure solutions at pH 2–4, which was insensitive to temperature. However, real mixed fermentation broth impurities reduced LA uptake by 37%. BMP tests showed that the solid and liquid extraction residues had significant methane potential, with only a 21% reduction in overall methane yield compared to the raw fermentation broth prior to LA extraction. LA production outweighed the loss in methane energy in terms of relative value and indicated a FW biorefinery concept could be commercially attractive and technically feasible.

Accumulation of Astaxanthin by Co-fermentation of Spirulina platensis and Recombinant Saccharomyces cerevisiae.

This study aimed to explore an effective, simple, and time-saving method for astaxanthin accumulation. Wild-type Saccharomyces cerevisiae as a bioreactor, the SpcrtR gene was first ligated with the signal peptide S to construct pYES2/NT-A-S-SpcrtR plasmid in Saccharomyces cerevisiae. The detection of SDS-PAGE and Western blotting protein proved that SpCRTR was successfully extracellular expressed in Saccharomyces cerevisiae. The target product astaxanthin was produced by co-fermentation of Spirulina platensis and recombinant Saccharomyces cerevisiae. The test results showed that after 18h of fermentation, the astaxanthin concentration was highest in the mixed fermentation broth with 4% Spirulina platensis and recombinant Saccharomyces cerevisiae, and the content of astaxanthin was 0.25 ± 0.02μg/mL. In addition, the source of astaxanthin was explored. During the fermentation process of the Saccharomyces cerevisiae strain, SpCRTR enzyme catalyzed the Spirulina platensis canthaxanthin, which almost completely converted into astaxanthin, providing a simple method for astaxanthin synthesis. Compared with culture of Haematococcus pluvialis, this culture route not only shortens culture time, but also eliminates the limitation of the conditions in the culture process.

Nematicidal Effect of Methyl Palmitate and Methyl Stearate against Meloidogyne incognita in Bananas.

Banana plants (Musa spp.) are susceptible to infection by many plant-parasitic nematodes, including Meloidogyne incognita. In this study, a mixed fermentation broth of chicken manure (CM) and cassava ethanol wastewater (CEW) was used to inhibit M. incognita by reducing egg hatching and by having a lethal effect on second-stage juvenile nematodes (J2s). It also alleviated nematode damage and promoted banana plant growth. Using gas chromatography-mass spectrometry (GC-MS), we identified methyl palmitate and methyl stearate as bioactive compounds. These bioactive compounds repelled J2s and inhibited egg hatching; reduced root galls, egg masses, and nematodes in soil; and downregulated the essential parasitic nematode genes Mi-flp-18 and 16D10. A Caenorhabditis elegans offspring assay showed that low concentrations of the fermentation broth, methyl palmitate, and methyl stearate were safe for its life cycle. This study explored the effective and environmentally safe strategies for controlling root-knot nematodes.

A Potent Burkholderia Endophyte against Boxwood Blight Caused by Calonectria pseudonaviculata.

Calonectria pseudonaviculata (Cps) poses an increasing threat to boxwood, a major nursery crop and iconic landscape plant worldwide. Here, we report on a potent biocontrol agent that produces small sage green (SSG) colonies on potato dextrose agar. SSG is a bacterial strain recovered from Justin Brouwers boxwood leaves with unusual response to Cps inoculation. Water-soaked symptoms developed on leaves 2 days after inoculation then disappeared a few days later. This endophyte affected several major steps of the boxwood blight disease cycle. SSG at 107 cfu/mL lysed all conidia in mixed broth culture. SSG at 108 cfu/mL reduced blight incidence by >98% when applied one day before or 3 h after boxwood were inoculated with Cps. Its control efficacy decreased with decreasing bacterial concentration to 103 cfu/mL and increasing lead time up to 20 days. When applied on diseased leaf litter under boxwood plants, SSG reduced Cps sporulation and consequently mitigated blight incidence by 90%. SSG was identified as a new member of the Burkholderia cepacia complex with distinct characters from known clinical strains. With these protective, curative, and sanitizing properties, this Burkholderia endophyte offers great promise for sustainable blight management at production and in the landscape.

Mixed bacterial fermentation can control the growth and development of Verticillium dahliae

Verticillium wilt is a severe disease caused by Verticillium dahliae, which afflicts many crops, particularly cotton in the Xinjiang province of China. Chemical fungicides are harmful to the environment, and biological control agents against the fungal pathogens of plants provide an alternative to chemicals. Biological control agents include antagonistic bacteria or metabolic products. We investigated the inhibitory effects of two plant-growth-promoting rhizobacterial (PGPR) strains, namely Bacillus tequilensis C-9 and Sphingobacterium A1, against V. dahliae in vitro and in the field. We used the mixed fermentation of two bacteria to inhibit V. dahliae. Antimicrobial assays were performed and showed that spore production and germination, and the virulence protein of V. dahliae were reduced after treatment with cell-free mixed fermentation broth. In field studies, there was improvement in the disease severity, along with declined incidence and index after the treatment in the bud and bell stages. To explore the molecular mechanisms of this inhibition, we studied six metabolism-related genes by real-time quantitative polymerase chain reaction (qRT-PCR). The results showed that in response to mixed fermentation broth, some genes related to growth and development were significantly upregulated, explaining the structural changes observed in V. dahliae. Some genes that regulate oxidative stress were also dramatically induced, indicating that mixed bacterial fermentation had a significant impact on V. dahliae. These results support the idea that the cell-free mixed fermentation broth of Bacillus tequilensis C-9 and Sphingobacterium A1, when applied for biocontrols, can inhibit V. dahliae in vitro and in vivo.

In vitro inhibitory activity of Bifidobacterium longum BB536 and Lactobacillus rhamnosus HN001 alone or in combination against bacterial and Candida reference strains and clinical isolates

Bifidobacterium longum BB536 and Lactobacillus rhamnosus HN001 are two strains frequently used as probiotic components in food supplements. The decrease of potentially pathogenic gastrointestinal microorganisms is one of their claimed mechanisms. The aim of this study was to investigate their ability, alone or in combination, to inhibit in vitro the growth of Gram-negative, Gram-positive and Candida reference strains and clinical isolates, using different methods.The cell-free supernatants were obtained by centrifugation and filtration from single or mixed broth cultures and the inhibitory activity was tested using both agar-well diffusion and broth microdilution methods. In order to get some preliminary information about the chemical nature of the active metabolites released in the supernatants, the inhibitory activity was investigated after neutralization, heat and proteolytic treatments.The highest inhibitory activity was shown by the untreated supernatant obtained from broth culture of the two probiotic strains, especially against bacterial reference strains and clinical isolates. This supernatant showed inhibitory activity towards Candida species, too. A decreased inhibitory activity was observed for the supernatants obtained from single cultures and after proteolytic treatment, against bacterial reference strains.The study suggests that the combination of B. longum BB536 and L. rhamnosus HN001 could represent a possible alternative against gastrointestinal and urinary pathogens either as prophylaxis or as treatment.

Positive "Surprise" Broth Cultures in Nonunion Surgery Do Not Require Antibiotic Treatment.

The objective of this study was to review the efficacy of a treatment approach for patients with positive intraoperative cultures during fracture nonunion surgery. The authors performed a retrospective case series at a level I trauma center. In this series, 60 patients without preoperative concern for infection were surgically treated for fracture nonunion. The treatment course of patients after fracture nonunion surgery, including culture results, antibiotic administration, and the presence of clinical infection and radiographic union, was studied. Sixty patients underwent fracture nonunion surgery. Twenty-four patients had a positive intraoperative culture. Fourteen patients had only a positive broth culture, 6 had only a positive routine culture, and 4 had positive mixed (routine and broth) cultures. The most common bacteria was coagulase-negative staphylococci, isolated in 19 of 24 patients, and the only isolated organism in 13 of 24 patients. Patients with a positive broth culture were not treated with antibiotics. Four of 10 patients with either a positive routine or mixed culture grown within 3 days of surgery were treated with antibiotics. All patients achieved clinical healing without signs of infection, and all but 2 patients achieved radiographic union at a mean follow-up of approximately 5 years. In the setting of fracture nonunion surgery, patients with only a positive broth culture and those with only a positive routine or mixed cultures that grew in a delayed fashion (>3 days postoperatively) did not require antibiotic treatment to achieve healing. [Orthopedics. 2019; 42(6):e532-e538.].

Mixed culture fermentation between Rhizopus nigricans and Trichoderma pseudokoningii to control cucumber Fusarium wilt

Fusarium wilt, caused by Fusarium oxysporum, is a devastating soilborne fungal disease. Compared to traditional chemical pesticides, biological control has been attracting increasing attention recently, owing to its eco-friendly features. This study investigated the potential use of mixed culture fermentation of Rhizopus nigricans and Trichoderma pseudokoningii (MCF) to control Fusarium oxysporum f.sp.cucumerinum (FOC). At first, the tablet confrontation experiment using bio-control fungi and F. oxysporum showed that the suppression rate of R. nigricans and T. pseudokoningii were more than 60% higher than that of individual fermentations. Furthermore, the inhibitory effect of MCF on the pathogen was higher than that of single fermentation broth, both in vitro and in greenhouse experiment. At the molecular level, MCF had better control on the number of pathogens in the plant tissue and soil, as seen by the real-time PCR assay. In the pot experiment, increased activities of the defense enzymes involved in PAL, SOD, and POD indicated that mixed broth treatment could increase the plant-induced resistance. In the field experiment, after two-year treatment by the mixed broth, the relative control effect on cucumber Fusarium wilt was 76.5%. Through this study, we demonstrated that co-fermentation of R. nigricans and T. pseudokoningii has synergistic effect on the control of F. oxysporum, which may promote more reasonable and effective utilization of biocontrol agents in future.

Usefulness of matrix-assisted laser desorption ionization time-of-flight mass spectrometry to identify pathogens, including polymicrobial samples, directly from blood culture broths.

Matrix-assisted laser desorption ionization time-of-flight mass spectrometry (TOF-MS) is now widely used to detect pathogens in clinical settings in Japan. Here, we report the ability of TOF-MS to detect bacteria from blood culture (BC) broths, and compare the efficacy of TOF-MS to that of conventional culture methods. Bacteria were correctly detected from 63 monomicrobial samples within 80 minutes; results matched those obtained by conventional BC methods, although the conventional methods took 2–3 days. In addition to the 63 monomicrobial samples, another three polymicrobial samples were tested; notably, the infecting bacteria were not correctly identified in two of these three samples. To better assess the TOF-MS detection of polymicrobial samples, we tested various ratios of mixed broth samples, including combinations of the bacteria that we were unable to detect in clinical samples. Combinations of Enterobacter cloacae and Pseudomonas aeruginosa were correctly detected at a culture ratio of 2:1, but not in the 3:1 mixture. These results suggested that TOF-MS is a strong tool for the rapid and correct detection of pathogens from monomicrobial BC samples, though results need to be carefully checked when handling known or suspected polymicrobial samples.

Efficacy of mealworm and super mealworm larvae probiotics as an alternative to antibiotics challenged orally with Salmonella and E. coli infection in broiler chicks

This study was conducted to evaluate dry mealworm (Tenebrio molitor) (DMLP) and super mealworm (Zophobas morio) (DSMLP) larvae probiotics as alternatives to antibiotics in broiler chicks. A total of 240 one-day old Ross 308 male broiler chicks were randomly assigned to three dietary treatments consisting of ten replications with eight birds each in a completely randomized design. The dietary treatments were, (i) control (basal diet), (ii) 0.4% DMLP (basal diet + 0.4% DMLP, DM basis), and (iii) 0.4% DSMLP (basal diet + 0.4% DSMLP, DM basis). On day one, 1 mL of mixed broth agar consisting of 2.4 × 107 cfu Salmonella enteritidis KCTC 2021 and 3.7 × 107 cfu Escherichia coli KCTC 2571 was injected orally into each chick. After one week, growth performance, immunity, mortality, internal organ weight, and cecal and fecal microbiota were investigated. Average daily gain (ADG) and average daily feed intake (ADFI) increased, while feed conversion ratio (FCR) (g intake/g gain per bird) decreased in response to DMLP and DSMLP supplementation (P < 0.05). Additionally, mortality decreased (P < 0.05), while IgG and IgA levels increased following DMLP and DSMLP supplementation (P < 0.05). Internal organs remained unaffected, except for a reduced bursa of Fabricius weight in DSMLP supplementation (P < 0.05). Cecal E. coli and Salmonella contents were reduced in DMLP and DSMLP supplementation (P < 0.05), while fecal microbiota contents and pH of cecal and fecal digesta remained unaffected. In conclusion, dietary supplementation with DMLP and DSMLP increased ADG and IgG and IgA levels, while reducing FCR, mortality and cecal E. coli and Salmonella spp. contents. Thus, DMLP and DSMLP can be utilized as an alternative to antibiotics in broiler diets.

Investigating the interaction between Gluconobacter oxydans and Bacillus megaterium for 2-keto-L-gulonic acid biosynthesis in the two-step vitamin C fermentation

In the two-step vitamin C fermentation process, its precursor 2-keto-L-gulonic acid was synthesized from L-sorbose by mixed culture of Gluconobacter oxydans and Bacillus megaterium. The interaction between Gluconobacter oxydans and Bacillus megaterium remains unclear and it is a challenge to mathematically model the mixed growth of these two strains. The Monod-type equations were previously proposed to describe the coupled growth of Gluconobacter oxydans and Bacillus megaterium. However, in this study, we modeled the interaction of these two strains in a macroscopic view by introducing the population theory. Taking account of the fact that the density or concentration of Gluconobacter oxydans or Bacillus megaterium was hardly to measure accurately in the mixed culture broth, the data of concentrations of the substrate and product were used to indirectly investigate the relation between these two strains. Three batch experiments were used to validate our model. And according to the values of identified parameters, the type of interaction between Gluconobacter oxydans and Bacillus megaterium was concluded to be predation, where Gluconobacter oxydans was predator, and Bacillus megaterium was prey.

A New Coumarin Produced by Mixed Fermentation of Two Marine Fungi

A new coumarin, 7-(γ,γ-dimethylallyloxy)-6-hydroxy-4-methylcoumarin (1), was isolated from the mixed fermentation broth of two mangrove fungi (strain No. K38 and E33) isolated from the South China Sea coast. The structure of 1 was determined by comprehensive spectroscopic methods, especially 2D NMR techniques. Primary bioassays showed that compound 1 at 0.25 mM has no inhibitory activity against Fusarium graminearum, Gloeosporium musae, Rhizoctonia solani, and Phytophthora sojae.

Effect of substrate concentration and pH on biohydrogen production kinetics from food industry wastewater by mixed culture

Kinetics of batch anaerobic hydrogen production using mixed culture was investigated in this study. The mixed culture broth was the effluent from the CSTR which had been inoculated with the Li-Ming wastewater treatment sludge. The batch reactor had a volume of 2 L and was operated at a temperature of 35 °C. The initial volumes of the mixed culture broth and the substrate were 200 ml and 1800 ml, respectively. The initial substrate concentrations were controlled at 20, 30, 40, 60 and 100 g total sugar/L. The peak specific growth rate of the mixed culture (μ = 0.28 h−1) was obtained at a substrate concentration of 40 g total sugar/L and pH 5.5. Finally, three inhibition models were used to obtain the kinetic parameters by curve fitting. The Haldane model is appropriate in this study. The effect of pH was then studied for modifying the established biohydrogen production by the three-parameter model. The established model can be used for further designing of a biohydrogen production fermenter for food industry wastewater by mixed culture.

Molecular epidemiology of KPC-2-producing Proteus mirabilis

Objective To investigate the molecular epidemiology and resistance mechanism of reduced carbapenem susceptibility of Proteus mirabilis from intensive care unit (ICU). Methods Nineteen carbapenem resistance or reduced carbapenem susceptibility of Proteus mirabilis were isolated from two ICUs in Second Affiliated Hospital of Zhejiang University from August 2010 to October 2010.Pulsed-field gel electrophoresis (PFGE) was performed to analyze the molecular epidemiology of isolates.Antibiotic susceptibilities were determined by agar dilution method.Conjugation experiments were carried out in mixed broth cultures.Plasmid DNAs were obtained by using an alkalinelysis technique.Specific polymerase chain reaction （PCR） and DNA sequencing were preformed to confirm the genotype of β-1actamases. Results Nineteen Proteus mirabilis showed resistance or reduced carbapenem susceptibility, and were resistant or susceptible to cephalosporins.PFGE analysis indicated that nineteen carbapenem-non-susceptible Proteus mirabilis belonged to 3 clones, named as clone A (14 isolates), clone B (2 isolates of subclone B1 and 2 isolates of subclone B2) and clone C (1 isolate).Fourteen clone A isolates were indistinguishable, and subclone B1 and subclone B2 were closely related with only one fragment disparity.Escherichia coli (EC600) acquired an approximately 45 000 bp，54 000 bp and 45 000 bp plasmids from clone A, subclone B1 and subclone B2 isolates separately by conjugation studies.PCRs and DNA sequence analysis confirmed that all Proteus mirabilis isolates and their transconjugants produced the KPC-2 carbapenemase. Conclusion Carbapenem-non-susceptible Proteus mirabilis were epidemic in two ICUs in our hospital，and were clonally disseminated.（Chin J Lab Med,2012,35:349-353） Key words: Proteus infections; Proteus mirabilis; Disease outbreaks; Carbapenems; beta-lactamases

Detection of plasmid-mediated carbapenem-hydrolyzing β-lactamase KPC-2 in Morganella morganii

Objective To investigate the molecular epidemiology and mechanisms of carbapenem resistance of Morganella morganii.Methods Seven carbapenem-non-susceptible M.morganii were isolated from Hangzhou Traditional Chinese Medicine Hospital from October 2010 to February 2011.Pulsed-field gel electrophoresis (PFGE) was performed to analysis the molecular epidemiology of isolates.Antibiotic susceptibilities were determined by agar dilution method.Conjugation experiments were carried out in mixed broth cultures.Plasmid DNA was obtained by an alkalinelysis technique and examined by electrophoresis.Specific PCRs and DNA sequencing were preformed to confirm the genotype of β-lactamases.Results PFGE indicated that 6 M.morganii isolates from emergency care unit were indistinguishable or closely related and 1 isolate from intensive care unit was distinguishable.Seven M.morganii showed similar antibiotic susceptibility patterns.M.morganii isolates were resistant to imipenem,were susceptible to meropenem,and were susceptible or intermediate resistant to ertapenem,with MICs of 8 μg/ml,1 μg/ml,and 0.25-0.50 μg/ml,respectively.M.morganii isolates were resistant to penicillins,aztreonam,and ciprofloxacin,were resistant or susceptible to cephalosporins,and were susceptible to amikacin.E.coli (EC600) acquired an approximately 60 kb plasmid from M.morganii by conjugation studies and resistant or intermediate resistant to carbapenems and other β-lactams.PCRs and DNA sequence analysis confirmed that all M.morganii isolates and their E. coli transconjugants produced the KPC-2 carbapenemase and carried the qnrS1 gene.Conclusion It is the first detection of KPC-2 in M.morganii isolates.Production of KPC-2 mainly contributed to the carbapenem resistance in M.morganii. Key words: Morganella morganii; Carbapenems; Antibiotic resistance; Klebsiella pneumoniae carbapenemase

A new diimide derivative from the co-culture broth of two mangrove fungi (strain no. E33 and K38)

A new diimide derivative, named ( − )-byssochlamic acid bisdiimide (1), was isolated from the mixed broth of two mangrove fungi (strain no. K38 and E33) from the South China sea coast. The structure of 1 was determined by comprehensive spectroscopic methods, including 1D and 2D NMR (COSY, HMQC, and HMBC) and semi-synthesis. Primary bioassays showed that 1 had weak cytotoxic activity against Hep-2 and HepG2 cells.

Providencia stuartii with VIM-1 metallo-β-lactamase

Providencia stuartii with VIM-1 metallo-β-lactamase