Antibacterial Activity of CdTe/ZnS Quantum Dot-ß Lactum Antibiotic Conjugates.

ß-Lactum antibiotics are broad class of antibiotics which kills bacteria by inhibiting the formation of peptidoglycan that constitutes the bacterial cell wall. The resistance that develops in bacteria for antibiotics led the scientific world to think about the future aspects for modifying the way through which antibiotics are acted on the bacteria and become lethal for them. In this consequence, the potential of latest marketed antibiotics e.g. Amoxiciline (I), ceftazidim (II) have been evaluated after being conjugated with quantum dots. The surface of quantum dots has been conjugated with antibiotics by carbodiimide coupling with the help of 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC) and N-hydroxysuccinimide (NHS) as conjugating agent between antibiotic and functionalized quantum dots. The antibacterial properties of QD-conjugated antibiotics have been determined by disc diffusion assay. The potency of QD-conjugated antibiotics has been estimated by determining their MIC50 for the selected strain of Gram-negative (Escherichia coli) and Gram-positive (Staphylococcus aureus) bacteria. Minimum inhibitory concentration study, minimum bactericidal concentration and growth pattern analysis revealed that QD-antibiotic conjugates showed slightly more prospective than pure native antibiotics against both Gram-negative (Escherichia coli) and Gram-positive (Staphylococcus aureus) bacteria.

[The development of a general drug resistance score model based on MIC50 related gene pairs in colorectal cancer cell lines].

Cancer cell line models are widely used for testing drug sensitivity and in screening for drug resistance markers. However, the general level of drug resistance in cancer cell lines is often ignored by researchers, making it difficult to apply many drug efficacy markers in clinical practice. In this study, we examined 48 colorectal cancer (CRC) cell lines to calculate the correlation coefficients between the IC50 values for 265 drugs. The general drug resistance evaluation index MIC50 was constructed using the median value of 265 drugs' IC50 values. Genes with positively correlated expression values and a MIC50 which rose to significance were selected for further study. To analyze the effect of general drug resistance on the response status and prognosis in CRC patients, the general drug resistance scoring model was established based on within-sample relative expression orderings of gene pairs. The results demonstrate that more than 99% of the IC50 correlation coefficients of 265 drugs were significantly positive (FDR<0.05), indicating that CRC cell lines possessed general drug resistance characteristics. Furthermore, we identified 602 general drug resistance related genes, and by using Metascape, we identified four functional modules closely related to tumor resistance. A scoring model of 5-FU-based general drug resistance levels consisting of 21 gene pairs was built. After performing χ 2 test, we found that the general drug resistance level in CRC patients was significantly correlated with the response information after accepting 5-FU-based combination drug therapy. Survival analysis showed that the low scoring cohort of patients had a better prognosis than the higher scoring cohort, indicating that the level of basic drug resistance was closely related to the prognosis and drug response status in these patients. These results provide basic theoretical support for further research on the mechanism of combined chemotherapy resistance and the individualized regimen of clinical drug use in patients with CRC.

Preparation and biological evaluation of ethionamide-mesoporous silicon nanoparticles against Mycobacterium tuberculosis.

Ethionamide (ETH) is an important second-line antituberculosis drug used for the treatment of patients infected with multidrug-resistant Mycobacterium tuberculosis. Recently, we reported that the loading of ETH into thermally carbonized-porous silicon (TCPSi) nanoparticles enhanced the solubility and permeability of ETH at different pH-values and also increased its metabolization process. Based on these results, we synthesized carboxylic acid functionalized thermally hydrocarbonized porous silicon nanoparticles (UnTHCPSi NPs) conjugated with ETH and its antimicrobial effect was evaluated against Mycobacterium tuberculosis strain H37Rv. The activity of the conjugate was increased when compared to free-ETH, which suggests that the nature of the synergy between the NPs and ETH is likely due to the weakening of the bacterial cell wall that improves conjugate-penetration. These ETH-conjugated NPs have great potential in reducing dosing frequency of ETH in the treatment of multidrug-resistant tuberculosis (MDR-TB).

Changes in antimicrobial resistance of Escherichia coli isolated from community-associated urinary tract infection before and during the COVID-19 pandemic in India.

PURPOSE: The impact of the COVID-19 pandemic on antimicrobial resistance (AMR) is largely studied in healthcare settings. There is a need to understand the fluctuations in AMR during pandemic at the community level. With urinary tract infection (UTI) being one of the most common infections in the community, the AMR profile of community-acquired UTI (CA-UTI) is considered representative AMR at the community level. METHODS: The study was taken in a cohort of patients with a clinical diagnosis of CA-UTI. The four study sites represented different community health centres in India. Escherichia coli isolates were analysed phenotypically and genotypically for AMR pre-COVID (October 2019-February 2020) and in the first (March 2020-February 2021) and second waves of COVID-19 (March 2021-December 2021). RESULTS: E. coli was the predominant uropathogen (229, 82%). Increased susceptibility to nitrofurantoin was observed during the pandemic. Reduced susceptibility to first-line oral antibiotics and carbapenems was seen during the second wave, and an increased minimum inhibitory concentration (MIC50) to beta-lactams and fluoroquinolones was seen during the pandemic. Genomic analysis of E. coli isolates showed some AMR genes (aacC1, aacC4, SHV, QepA) only during the second wave. CONCLUSION: One good outcome of the pandemic was increased susceptibility to nitrofurantoin, while drawback was a significant decrease in susceptibility to oral antibiotics during the second wave and increased MIC50 of some antibiotics. Decreased susceptibility to last-resort carbapenems and the occurrence of various AMR genes during the second wave of the pandemic are of great concern.

Hesperetin effect on MLH1 and MSH2 expression on breast cancer cells BT-549.

Due to its genetic and phenotypic heterogeneity, breast cancer is very difficult to eliminate. The harmful consequences of conventional therapies like radiation and chemotherapy have prompted the search for organic-based alternatives. Hesperetin (HSP), a flavonoid, has been discovered to possess the ability to hinder the proliferation of cell associated with breast cancer by acting as an epigenetic agent and modifying gene expression. In this investigation, breast cancer cells (BT-549) and normal cells (MCF-10a) were subjected to the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) test and three different doses (200, 400, and 600 µM/mL) of HSP for real-time polymerase chain reaction and flow cytometry to examine its cytotoxic and anti-malignant potential. HSP was shown to be cytotoxic to both normal and breast cancer cells, but had a more pronounced effect on the cancer cell lines. After 48 h of treatment, the half-maximal inhibitory concentration (IC50) for BT-549 was 279.2 µM/mL, whereas the IC50 for MCF-10a was 855.4 µM/mL. At high HSP concentrations, upregulation of the MLH1 and MSH2 genes was observed in both cell lines. The influence of HSP on MLH1 gene expression was concentration dependent. Moreover, HSP had a concentration-dependent effect on MSH2 gene expression in the BT-549 cell line but not in the MCF-10a cell line. Cell death and early apoptosis were shown to be concentration dependent upon the application of HSP, as determined by flow cytometric analysis. HSP's capacity to cause apoptosis and its stronger impact on the malignant cell line when analyzed with the normal cell line imply that it might be useful as an effective therapeutic approach for combating breast cancer.

Cefotaxime Mediated Synthesis of Gold Nanoparticles: Characterization and Antibacterial Activity.

Cefotaxime (CTX) is a third-generation cephalosporin antibiotic with broad-spectrum activity against Gram negative and Gram positive bacteria. However, like other third-generation cephalosporin antibiotics, its efficacy is declining due to the increased prevalence of multidrug-resistant (MDR) pathogens. Recent advances in nanotechnology have been projected as a practical approach to combat MDR microorganisms. Therefore, in the current study, gold nanoparticles (AuNPs) were prepared using cefotaxime sodium, which acted as a reducing and capping agent, besides having well-established antibacterial activity. The synthesized cefotaxime-loaded gold nanoparticles (C-AuNPs) were characterized by UV-Visible spectroscopy, FTIR, TEM and DLS. In addition, the in vitro antibacterial activity of C-AuNPs was assessed against both Gram-positive and Gram-negative bacteria. UV-Visible spectroscopy verified the formation of C-AuNPs, while TEM and DLS verified their nano-size. In addition, CTX loading onto AuNPs was confirmed by FTIR. Furthermore, the colloidal stability of the synthesized C-AuNPs was ascribed to the higher net negative surface charge of C-AuNPs. Most importantly, the synthesized C-AuNPs showed superior antibacterial activity and lower minimum inhibitory concentration (MIC) values against Gram-negative (Escherichia coli, Klebsiella oxytoca, Pseudomonas aeruginosa) and gram-positive (Staphylococcus aureus) bacteria, compared with pure CTX. Collectively, CTX was successfully adopted, as reducing and capping agent, to synthesize stable, nano-sized spherical C-AuNPs. Furthermore, loading CTX onto AuNPs could efficiently restore and/or boost the antibacterial activity of CTX against resistant Gram-negative and Gram-positive bacteria.

Establishment of Epidemiological Resistance Cut-Off Values of Aquatic Aeromonas to Eight Antimicrobial Agents.

The abuse of antibiotics in aquaculture has led to the increasing rate of antibiotic resistance of aquatic bacteria including Aeromonas, which is an increasing threat to environmental and human health. To date, no epidemiological cut-off values (COWT) for Aeromonas spp. have been established by the Clinical and Laboratory Standards Institute nor the European Commission on Antimicrobial Susceptibility Testing. In this study, commercially prepared minimum inhibitory concentration (MIC) test 96-well plates (dry-form plates) were used to determine the MIC of eight antimicrobial agents against 556 Aeromonas strains. The obtained MIC distributions were simulated and analyzed by NRI and ECOFFinder to obtain tentative COWT values for Aeromonas spp. The COWT values of eight kinds of representative antimicrobial agents including trimethoprim-sulfamethoxazole, erythromycin, doxycycline, neomycin, colistin, florfenicol, enrofloxacin, and ceftazidime for Aeromonas spp. were established and were 0.25, 64/32, 4/2, 8, 4, 1, 0.062/0.125, and 0.5 µg/mL, respectively. Results showed that Aeromonas spp. had a very high proportion of non-wild-type strains to enrofloxacin, florfenicol, and doxycycline, which are the most widely used antimicrobials in aquaculture. The COWT values for Aeromonas spp. obtained in this study can contribute to the final establishment of COWT for Aeromonas spp. internationally.

Land Use Influences the Composition and Antimicrobial Effects of Propolis.

Honey bee propolis is a complex, resinous mixture created by bees using plant sources such as leaves, flowers, and bud exudates. This study characterized how cropland surrounding apiaries affects the chemical composition and antimicrobial effects of propolis. The chemical composition and compound abundance of the propolis samples were analyzed using Gas Chromatography-Mass Spectrometry (GC-MS) and the antimicrobial effects were analyzed using the 50% minimum inhibitory concentration (MIC50) assay against four relevant bee pathogens, Serratia marcescens, Paenibacillus larvae, Lysinibacillus sphaericus, and Klebsiella pneumoniae. Propolis composition varied significantly with apiary, and cropland coverage predicted mean sum abundance of compounds. The apiary with the highest cropland coverage exhibited significantly higher MIC50 values for S. marcescens and K. pneumoniae compared to other apiaries. These results demonstrate that agricultural land use surrounding honey bee apiaries decreases the chemical quality and antimicrobial effects of propolis, which may have implications for the impacts of land use on hive immunity to potential pathogens.

In Vitro Antimicrobial Effects and Inactivation Mechanisms of 5,8-Dihydroxy-1,4-Napthoquinone.

Naphthoquinones are an important class of natural organic compounds that have antimicrobial effects. However, the mechanisms of their action remain to be elucidated. Therefore, the antimicrobial activity of the chemically synthesized naphthoquinone derivative, 5,8-dihydroxy-1,4-naphthoquinone, was investigated in this study against 10 different microorganisms. Its inhibitory activity was evident against Bacillus cereus, Proteus vulgaris, Salmonella enteritidis, Staphylococcus epidermidis, S. aureus, and Candida albicans, and its MIC50 values were determined to be 14, 10, 6, 2, 4, 1.2, and <0.6 µg/mL, respectively. Moreover, the crystal violet uptake, TTC dehydrogenase activity, protein/DNA leakage, and DNA damage of the compound in these microorganisms were also investigated to reveal the antimicrobial mechanisms. In addition, scanning electron microscopy was used to detect physiological damage to the cell membrane of S. epidermidis, S. aureus, and C. albicans, which was most severe in the crystal violet uptake assay. The overall results showed that 5,8-dihydroxy-1,4-naphthoquinone exhibited its effects on S. aureus, S. epidermidis, and C. albicans by various mechanisms, especially membrane damage and membrane integrity disruption. It also caused DNA leakage and damage along with respiratory chain disruption (78%) in C. albicans. Similarly, it caused varying degrees of reduction in the respiratory activity of S. aureus (47%), S. epidermidis (16%), B. cereus (12%), S. enteritidis (9%), and P. vulgaris (8%). Therefore, 5,8-dihydroxy-1,4-naphthoquinone proved to be a very effective antifungal and antibacterial agent and could be considered a new potential drug candidate, inspiring further discoveries in these microorganisms.

Ceftriaxone Mediated Synthesized Gold Nanoparticles: A Nano-Therapeutic Tool to Target Bacterial Resistance.

Ceftriaxone has been a part of therapeutic regime for combating some of the most aggressive bacterial infections in the last few decades. However, increasing bacterial resistance towards ceftriaxone and other third generation cephalosporin antibiotics has raised serious clinical concerns especially due to their misuse in the COVID-19 era. Advancement in nanotechnology has converted nano-therapeutic vision into a plausible reality with better targeting and reduced drug consumption. Thus, in the present study, gold nanoparticles (GNPs) were synthesized by using ceftriaxone antibiotic that acts as a reducing as well as capping agent. Ceftriaxone-loaded GNPs (CGNPs) were initially characterized by UV-visible spectroscopy, DLS, Zeta potential, Electron microscopy and FT-IR. However, a TEM micrograph showed a uniform size of 21 ± 1 nm for the synthesized CGNPs. Further, both (CGNPs) and pure ceftriaxone were examined for their efficacy against Escherichia coli, Staphylococcus aureus, Salmonella abony and Klebsiella pneumoniae. CGNPs showed MIC50 as 1.39, 1.6, 1.1 and 0.9 µg/mL against E. coli, S. aureus, S. abony and K. pneumoniae, respectively. Interestingly, CGNPs showed two times better efficacy when compared with pure ceftriaxone against the tested bacterial strains. Restoring the potential of unresponsive or less efficient ceftriaxone via gold nanoformulations is the most alluring concept of the whole study. Moreover, applicability of the findings from bench to bedside needs further validation.

In Vitro Antimicrobial Activity of Quinolones Against Major Bacterial Isolates from the Ocular Surface Bacterial Flora of Tertiary Hospital Patients in Japan.

Purpose: To determine the in vitro antimicrobial activity of quinolones against major bacterial isolates from the ocular surface bacterial flora of patients in a tertiary hospital for selection of optimal antibiotic eye drop during the perioperative stage. Methods: The conjunctival sac scraping of 933 patients who underwent ophthalmic surgery was cultivated and bacterial species of the isolates were identified. The minimum inhibitory concentrations (MICs) of gatifloxacin (GFLX), moxifloxacin (MFLX), levofloxacin (LVFX), and tosufloxacin (TFLX) were measured by microdilution methods. The cumulative percentages of MICs of 4 quinolones against major bacteria were calculated. The concentrations of quinolones inhibiting 50% (MIC50) and 90% (MIC90) of the major bacteria were compared. Results: The study mainly included 784 patients scheduled for cataract surgery, 73 for vitrectomy, 30 for corneal transplantation, 30 for conjunctival surgery, 11 for eyelid surgery. The most frequently isolated bacterium was coagulase-negative Staphylococci (CNS) (184 strains), followed by Corynebacterium (107 strains), Staphylococcus aureus (33 strains), Streptococcus (18 strains), and Enterococcus (13 strains). The percentages of methicillin-sensitive CNS isolates for which MIC of GFLX, MFLX, LVFX, and TFLX was 0.06 µg/mL or less were 8.0%, 13.4%, 5.4%, and 63.4%, respectively. Similarly, the percentage for Corynebacterium was 23.0%, 23.0%, 0%, and 35.6%, respectively. MIC50 of TFLX for Streptococcus and Enterococcus showed the lowest values, 0.12 and 0.25 µg/mL, respectively. Conclusions: Among 4 quinolones, TFLX has the highest in vitro antimicrobial activity against major bacterial isolates from the ocular surface bacterial flora of patients in a tertiary hospital.

Clinical Distribution Characteristics of 1439 Carbapenem-Resistant Escherichia coli Strains in China: Drug Resistance, Geographical Distribution, Antibiotic MIC50/90.

PURPOSE: To explore the clinical distribution characteristics and antimicrobial susceptibilities of carbapenem-resistant Escherichia coli (CR-ECO) in Hebei Province, China, from 2017 to 2019, and provide data on the treatment of this bacterial infection and the prevention of its spread. MATERIALS AND METHODS: A total of 1439 CR-ECO strains were collected from 2017 to 2019 in Hebei Province, China. Drug sensitivity tests were performed using the minimum inhibitory concentration (MIC) method, and the data were analyzed statistically using WHONET5.6 software. RESULTS: A total of 54,377 strains of Escherichia coli were isolated in Hebei Province from 2017 to 2019, of which 1439 strains were CR-ECO (2.65%). The highest proportion (33.78%) of strains was isolated from urine, and the detection rate showed a slow downward trend over the past 3 years. CR-ECO was mainly detected in densely populated and economically developed areas. Of all the patients, 54.2% were from the medical ward; the ratio of male to female patients with CR-ECO infections was 1.35:1; elderly patients and adults accounted for 59.6% and 30.8%, respectively, whereas minors and newborns accounted for 4.9% and 4.7%, respectively. For CR-ECO, the drug resistance rates to ß-lactams were all higher than 80% and there was an annual increasing trend, while the drug resistance rates to quinolones remained nearly unchanged. The rate of resistance to aminoglycosides was relatively low, especially to amikacin (approximately 22%). The MIC50 of other antibacterial drugs, except amikacin, was equal to or higher than the break point of drug resistance. CONCLUSION: From 2017 to 2019, the isolation rate of CR-ECO in Hebei Province, China, remained stable; however, the drug resistance rate showed an upward trend, primarily in cases of urinary tract infections in older men; the resistance rate to amikacin was the lowest.

Antimicrobial susceptibility pattern of oral isolates of Aggregatibacter actinomycetemcomitans.

BACKGROUND: Aggregatibacter actinomycetemcomitans is involved in the etiology of localized aggressive periodontitis (LAP), a condition that frequently requires supplemental antibiotic therapy. Information on antimicrobial susceptibility pattern and guidelines for oral antibiotic therapy are not available on Indian patients. AIM: The main aim of the present study was to screen clinical isolates on a panel of antibiotics commonly used for oral/systemic therapy. MATERIALS AND METHODS: The study included 40 strains of A. actinomycetemcomitans isolated from patients with LAP. The subgingival plaque was plated onto Trypticase Soy Serum Bacitracin Vancomycin Agar medium and incubated for 72 h, and suspected colonies were confirmed by phenotypic tests. Each isolate was tested against a panel of 12 antibiotics using MIC gradient strip test. ATCC strains of A. actinomycetemcomitans serotype A and C were used as standards. Performance and interpretation of the test were done according to the manufacturers' instructions. Distribution of MICs among isolates (n = 40) were used to calculate concentrations inhibiting 50% (MIC50) and 90% (MIC90) of strains. RESULTS: Moxifloxacin, cefotaxime and ceftriaxone showed excellent activity with 100% growth inhibition followed by amoxicillin, amoxiclav and doxycycline (>90% activity). The bacterial strains were moderately susceptible to cefuroxime, cefazolin and tetracycline but displayed poor susceptibility to clindamycin and azithromycin. All isolates were resistant to metronidazole. CONCLUSION: The isolates of A. actinomycetemcomitans displayed a high level of resistance to azithromycin and clindamycin. Development of resistance against tetracycline also appears to be significant. Variable resistance among the different members of the cephalosporin group is a factor to be investigated further since susceptibility profile against these antibiotics and interpretative criteria for oral bacteria are not available.

Phytochemical profiles, and antimicrobial and antioxidant activities of greater galangal [Alpinia galanga (Linn.) Swartz.] flowers.

Previous studies of galangal (Alpinia galanga) have focussed mostly on rhizomes but seldom on flowers. A comprehensive look at galangal flowers could reveal additional benefits. The chemical composition of galangal flowers was significantly (p < 0.05) different from that of galangal rhizome. Pentadecane and α-humulene were identified as major compounds of galangal flower essential oil. 1'-acetoxyeugenol acetate was identified as the highest compound in flowers and exhibited the strongest antimicrobial activity among all fractions, with MIC50 values of 34 µg/ml against Staphylococcus aureus and 68 µg/ml against Listeria monocytogenes. Galangal flowers had a 3-fold higher total phenols content than had rhizomes (10.5 vs. 3.33 mg GAE/g powder). The antioxidant activities of different flower fractions varied from 2 to 4.45 mmol  trolox/g phenolics. These findings suggest that antimicrobial and antioxidant agents extracted from galangal flowers could potentially be utilized as natural food preservatives or as therapeutic agents.

Screening of Trichoderma isolates for their potential of biosorption of nickel and cadmium.

Fourteen Trichoderma isolates were evaluated for their tolerance to two heavy metals, nickel and cadmium. Three isolates, MT-4, UBT-18, and IBT-I, showed high levels of nickel tolerance, whereas MT-4, UBT-18, and IBT-II showed better tolerance of cadmium than the other isolates. Under nickel stress, biomass production increased up to a Ni concentration of 60ppm in all strains but then decreased as the concentrations of nickel were further increased. Among the nickel-tolerant isolates, UBT-18 produced significantly higher biomass upon exposure to nickel (up to 150ppm); however, the minimum concentration of nickel required to inhibit 50% of growth (MIC50) was highest in IBT-I. Among the cadmium-tolerant isolates, IBT-II showed both maximum biomass production and a maximum MIC50 value in cadmium stress. As the biomass of the Trichoderma isolates increased, a higher percentage of nickel removal was observed up to a concentration of 40ppm, followed by an increase in residual nickel and a decrease in biomass production at higher nickel concentrations in the medium. The increase in cadmium concentrations resulted in a decrease in biomass production and positively correlated with an increase in residual cadmium in the culture broth. Nickel and cadmium stress also influenced the sensitivity of the Trichoderma isolates to soil fungistasis. Isolates IBT-I and UBT-18 were most tolerant to fungistasis under nickel and cadmium stress, respectively.

Isolation of strong constitutive promoters from Lactococcus lactis subsp. lactis N8.

The synthesis of heterologous proteins in Lactococcus lactis is strongly influenced by the promoter selected for the expression. The nisin A promoter is commonly used for induced expression of proteins in L. lactis, whereas few constitutive promoters (P45 and the weaker P32) have been used for protein expression studies. In this study, eight different putative strong constitutive promoters were identified through transcriptional analysis of L. lactis N8 and were investigated for their capability to drive nisZ gene expression with promoters P45 and P32 as control. Four strong promoters (P8, P5, P3 and P2) were identified as having a transcriptional activity that was higher than that of P45 through RT-qPCR and agar-diffusion experiments. In addition, these four promoters were fused to the erythromycin resistant gene (ermC) with promoter P45 as control and inserted into the backbone of the pNZ8048 vector. The transcriptional efficiencies of promoters P8, P5, P2 and P3 were all higher than promoter P45 based on the obtained MIC50 values and they all showed different activity levels. In conclusion, four strong constitutive promoters with a wide range of promoter activities were identified and are suitable for protein production in L. lactis.

Antibacterial and anti-biofilm activities of thiazolidione derivatives against clinical staphylococcus strains.

Both Staphylococcus aureus and Staphylococcus epidermidis can form biofilms on natural surfaces or abiotic surfaces, such as medical implants, resulting in biofilm-associated diseases that are refractory to antibiotic treatment. We previously reported a promising antibacterial compound (Compound 2) and its derivatives with bactericidal and anti-biofilm activities against both S. epidermidis and S. aureus. We have further evaluated the antibacterial activities of four Compound 2 derivatives (H2-38, H2-39, H2-74 and H2-81) against 163 clinical strains of S. epidermidis and S. aureus, including methicillin-susceptible and methicillin-resistant strains, as well as biofilm-forming and non-biofilm-forming strains. The four derivatives inhibited the planktonic growth of all of the clinical staphylococcal isolates, including methicillin-resistant S. aureus and methicillin-resistant S. epidermidis and displayed bactericidal activities against both immature (6 h) and mature (24 h) biofilms formed by the strong biofilm-forming strains. The derivatives, which all target YycG, will help us to develop new antimicrobial agents against multidrug-resistant staphylococci infections and biofilm-associated diseases.

Screening of Trichoderma isolates for their potential of biosorption of nickel and cadmium

Abstract Fourteen Trichoderma isolates were evaluated for their tolerance to two heavy metals, nickel and cadmium. Three isolates, MT-4, UBT-18, and IBT-I, showed high levels of nickel tolerance, whereas MT-4, UBT-18, and IBT-II showed better tolerance of cadmium than the other isolates. Under nickel stress, biomass production increased up to a Ni concentration of 60 ppm in all strains but then decreased as the concentrations of nickel were further increased. Among the nickel-tolerant isolates, UBT-18 produced significantly higher biomass upon exposure to nickel (up to 150 ppm); however, the minimum concentration of nickel required to inhibit 50% of growth (MIC50) was highest in IBT-I. Among the cadmium-tolerant isolates, IBT-II showed both maximum biomass production and a maximum MIC50 value in cadmium stress. As the biomass of the Trichoderma isolates increased, a higher percentage of nickel removal was observed up to a concentration of 40 ppm, followed by an increase in residual nickel and a decrease in biomass production at higher nickel concentrations in the medium. The increase in cadmium concentrations resulted in a decrease in biomass production and positively correlated with an increase in residual cadmium in the culture broth. Nickel and cadmium stress also influenced the sensitivity of the Trichoderma isolates to soil fungistasis. Isolates IBT-I and UBT-18 were most tolerant to fungistasis under nickel and cadmium stress, respectively.