Action of Ganoderma lucidum mycelial growth filtrates on Erysiphe diffusa and embryotoxicity assessment in a chicken embryo model

This work aimed to evaluate the antimicrobial effect of Ganoderma lucidum mycelial growth filtrates (MGF) on the phytopathogen Erysiphe diffusa and their potential effects on the embryonic development of Gallus gallus. The antimicrobial activity was evaluated on E. diffusa spores by the microdilution broth method. To evaluate embryotoxic and teratogenic effects, fertile eggs of G. gallus received injections of solutions containing the filtrates of G. lucidum through the air chamber. After three days of incubation, we opened the eggs and evaluated egg viability, embryo survival, malformation occurrence, embryonic staging and heart rate. Live embryos were prepared using whole mount technique and the morphological analysis was performed. We used the generalized linear model to fit embryotoxicity and teratogenicity data. We verified that G. lucidum MGF showed inhibitory activity in vitro against E. diffusa and the minimum inhibitory concentrations ranged from 5 to 10 mg/mL. We could also observe that the filtrates did not present embryotoxic or teratogenic effects on the early embryonic development of G. gallus, but induced significant differences in the embryonic mean heart rate and on the stage of embryonic development.

Azole Resistance in Clinical and Environmental Aspergillus Isolates from the French West Indies (Martinique)

The emergence of azole resistant Aspergillus spp., especially Aspergillus fumigatus, has been described in several countries around the world with varying prevalence depending on the country. To our knowledge, azole resistance in Aspergillus spp. has not been reported in the West Indies yet. In this study, we investigated the antifungal susceptibility of clinical and environmental isolates of Aspergillus spp. from Martinique, and the potential resistance mechanisms associated with mutations in cyp51A gene. Overall, 208 Aspergillus isolates were recovered from clinical samples (n = 45) and environmental soil samples (n = 163). They were screened for resistance to azole drugs using selective culture media. The Minimum Inhibitory Concentrations (MIC) towards voriconazole, itraconazole, posaconazole and isavuconazole, as shown by the resistant isolates, were determined using the European Committee on Antimicrobial Susceptibility Testing (EUCAST) microdilution broth method. Eight isolates (A. fumigatus, n = 6 and A. terreus, n = 2) had high MIC for at least one azole drug. The sequencing of cyp51A gene revealed the mutations G54R and TR34/L98H in two A. fumigatus clinical isolates. Our study showed for the first time the presence of azole resistance in A. fumigatus and A. terreus isolates in the French West Indies.

Antimicrobial activity of the essential oils from the leaves and stems of Amomum rubidumLamxay & N. S. Lý

This paper described the chemical compositions and antimicrobial activity of the essential oils from the leaves and stem of Amomum rubidumLamxay & N. S. Lý, collected from Bidoup Nui Ba National Park, Lam Dong, Vietnam. The essential oils were obtained by hydrodisitllation method while antimicrobial activity was evaluetd by microdilution broth susceptibility assay. The main constituents of the leaf essential oil were identified as 1,8-cineole (37.7%), -3-carene (19.5%) and limonene (16.3%) while -3-carene (21.9%), limonene (17.8%) and β-phellandrene (14.6%) dominated in the stem essentialoil. The leaf and stem essential oils displayed stronger inhibition of Pseudomonas aeruginosawith MIC of 25 μg/mLand 50 μg/mLrespectively. The stem essential oil was active against Candida albicans(MIC, 50 μg/mL) while both essential oils inhibited the growth of Fusarium oxysporum(MIC 50 μg/mL). This is the first report on chemical constituents and antimicrobial activity of the essential oils of A. rubidum.

Correlation of Trichosporon asahii genotypes with anatomical sites and antifungal susceptibility profiles: data analyses from 284 isolates collected in the last 22 years across 24 medical centers

Trichosporon asahii is an opportunistic fungal pathogen that can cause severe infections with high mortality rates. Azole derivatives are the best-targeted therapy for T. asahii invasive infections, but azole-resistant isolates have been reported. To investigate peculiarities in the antifungal susceptibility profile (ASP) of T. asahii clinical isolates, we analyzed the genotypes distribution, isolation sources, and ASP of 284 strains collected from 1997 to 2019 in different Brazilian medical centers. Species identification and genotypes characterization were performed by analysis of the intergenic spacer (IGS1) region of the ribosomal DNA (rDNA). Antifungal susceptibility testing (AST) for amphotericin B and azoles were processed using the CLSI M27-4th ed. microdilution broth method. Trends in the ASP of Brazilian T. asahii isolates were investigated using epidemiological cutoff values. Five different genotypes were found among the 284 isolates tested (G1, 76%; G3, 10%; G4, 3%; G5, 7%; G7, 11, 4%). The isolates were collected mainly from urine (55%) and blood/catheter tip samples (25%) where G1 and G7 were the most frequent genotypes found, respectively (p < 0.05). The G7 isolates exhibited the highest MIC90 values for azoles when compared to the other genotypes (p <0.05). Genotype 7 isolates also contributed to the increasing rates of voriconazole non-wild type isolates found in recent years (p=0.02). No significant differences were found among the AST results generated by isolates cultured from different anatomical sites. Monitoring T. asahii genotypes distribution and antifungal susceptibility profiles are warranted to prevent the spread of azole-resistant isolates.

Antimicrobial Activity of Isoniazid in Conjugation with Surface-Modified Magnetic Nanoparticles against Mycobacterium tuberculosis and Nonmycobacterial Microorganisms

Isoniazid, the choice antitubercular agent, has only been employed against Mycobacterium tuberculosis. This study evaluated if the enzyme-mimetic activities of magnetic nanoparticles could accelerate the activation process of isoniazid against mycobacterial and, more importantly, non-mycobacterial microorganisms. First, magnetic nanoparticles were synthesized and coated by lipoamino acid; then, isoniazid was conjugated to synthesized nanoparticles. Antibacterial activities of nanoconjugated isoniazid were evaluated against Mycobacterium tuberculosis and four Gram-positive and Gram-negative nonmycobacterial strains through a microdilution broth process. Results showed that the required amount of isoniazid against Mycobacterium tuberculosis would decrease to 44.8% and 16.7% in conjugation with naked and surface-modified magnetic nanoparticles, respectively. Also, 32 μg/mL and 38 μg/mL of isoniazid in conjugation with naked and surface-modified nanoparticles, respectively, could prevent the growth of Enterococcus faecalis, Escherichia coli, Pseudomonas aeruginosa, and Staphylococcus aureus. Hence, the vicinity of magnetic nanoparticles with isoniazid could declare promising aspects of isoniazid antibacterial capabilities.

Effect of low doses of biocides on the antimicrobial resistance and the biofilms of Cronobacter sakazakii and Yersinia enterocolitica

The susceptibility of Cronobacter sakazakii ATCC 29544 (CS) and Yersinia enterocolitica ATCC 9610 (YE) to sodium hypochlorite (10% of active chlorine; SHY), peracetic acid (39% solution of peracetic acid in acetic acid; PAA) and benzalkonium chloride (BZK) was tested. Minimum inhibitory concentration (MIC) values (planktonic cells; microdilution broth method) of 3,800 ppm (SHY), 1,200 ppm (PAA) and 15 ppm (BZK) for CS, and 2,500 ppm (SHY), 1,275 ppm (PAA) and 20 ppm (BZK) for YE, were found. In some instances, an increase in growth rate was observed in presence of sub-MICs (0.25MIC, 0.50MIC or 0.75MIC) of biocides relative to the samples without biocides. The cultures exhibited an acquired tolerance to biocides and an increase in antibiotic resistance after exposure to sub-MICs of such disinfectants. Strains were able to form strong biofilms on polystyrene after 48 hours (confocal laser scanning microscopy), with average biovolumes in the observation field (14,161 µm2) of 242,201.0 ± 86,570.9 µm3 (CS) and 190,184.5 ± 40,860.3 µm3 (YE). Treatment of biofilms for 10 minutes with disinfectants at 1MIC or 2MIC reduced the biovolume of live cells. PAA (YE) and BZK (CS and YE) at 1MIC did not alter the percentage of dead cells relative to non-exposed biofilms, and their effect of countering biofilm was due principally to the detachment of cells. These results suggest that doses of PAA and BZK close to MICs might lead to the dissemination of live bacteria from biofilms with consequent hazards for public health.

First report on echinocandin resistant Polish Candida isolates

Purpose: Candida spp. are ranked as one of the four major causative agents of fungal infections. The number of infections caused by Candida species resistant to fluconazole, which is applied as the first line drug in candidiasis treatment, increases every year. In such cases the application of echinocandin is necessary. Echinocandin susceptibility testing has become a routine laboratory practice in many countries due to the increasing frequency of clinical failures during treatment with these drugs. Methods: We performed anidulafungin, micafungin and caspofungin susceptibility testing according to the microdilution broth method on 240 Candida isolates collected in Polish hospitals. Results: We identified 12 isolates resistant to all echinocandins within 240 examined isolates. Moreover, 6 of the examined samples were identified as rare Candida species and among them we observed very high echinocandin MIC values. Conclusion: Our research proves that in Poland there is a problem of echinocandin resistance. Moreover, we identified two species of Candida which are rare causative agents of human infections, and there was no reported incidence of such infections in Poland until now.

Analysis of the Mutant Selection Window and Killing of Mycoplasma hyopneumoniae for Doxycycline, Tylosin, Danofloxacin, Tiamulin, and Valnemulin

Mycoplasma hyopneumoniae is the major pathogenic microorganism causing enzootic pneumonia in pigs. With increasing resistance of M. hyopneumoniae to conventional antibiotics, treatment is becoming complicated. Herein, we investigated the mutant selection window (MSW) of doxycycline, tylosin, danofloxacin, tiamulin, and valnemulin for treating M. hyopneumoniae strain (ATCC 25934) to determine the likelihood of promoting resistance with continued use of these antibiotics. Minimum inhibitory concentration (MIC) values against M. hyopneumoniae were determined for each antimicrobial agent and ranged from 105 colony-forming units (CFU)/mL to 109 CFU/mL based on microdilution broth and agar dilution methods. The minimal concentration inhibiting colony formation by 99% (MIC99) and the mutant prevention concentration (MPC) were determined by the agar dilution method with three inoculum sizes. Antimicrobial killing was determined based on MIC99 and MPC values for all five agents. MIC values ranged from 0.001 to 0.25 μg/mL based on the microdilution broth method, and from 0.008 to 1.0 μg/mL based on the agar dilution method. MPC values ranged from 0.0016 to 10.24 μg/mL. MPC/MIC99 values were ordered tylosin >doxycycline >danofloxacin >tiamulin >valnemulin. MPC achieved better bactericidal action than MIC99. Based on pharmacodynamic analyses, danofloxacin, tylosin, and doxycycline are more likely to select resistant mutants than tiamulin and valnemulin.

Successful treatment with daptomycin and ceftaroline of MDR Staphylococcus aureus native valve endocarditis: a case report

Objectives The best therapeutic approach for treating MRSA endocarditis remains unknown, particularly in cases of high vancomycin MICs. We report here a case of daptomycin-non-susceptible, ceftaroline-resistant and fosfomycin-resistant MRSA native left valve endocarditis that was successfully treated with valve repair and a combination of high-dose daptomycin and ceftaroline. Methods Antimicrobial testing of the clinical strain was performed using Etest and microdilution broth methods. Time–kill and chequerboard methodologies were used to test the activity of antibiotic combinations. Results By Etest, the MIC of vancomycin was 2 mg/L, the MIC of daptomycin was 2 mg/L, the MIC of fosfomycin was 1024 mg/L and the MIC of ceftaroline was 1.5 mg/L. At the standard inoculum (105 cfu/mL), the three combinations of daptomycin plus ceftaroline, cloxacillin or fosfomycin were synergistic and bactericidal. However, when these combinations were tested using a higher inoculum (108 cfu/mL), all combinations were synergistic, but only daptomycin plus ceftaroline had bactericidal activity. Conclusions These results confirmed a synergistic effect between daptomycin plus ceftaroline and increased bactericidal activity against MRSA, suggesting that this combination may be effective for the treatment of invasive MRSA infection. Our experience highlights the potential clinical use of synergy testing to guide difficult treatment decisions in patients with MDR MRSA infection.

Phytochemical, antioxidant and antimicrobial properties of Litsea angulata extracts

Background: Litsea angulata is a plant species belonging to Lauraceae family that is distributed throughout Indonesia, Malaysia, and New Guinea. The seeds have been traditionally used by local people in Kalimantan, Indonesia for the treatment of boils; however, there is no information about the potency of its branch, bark and leaves yet. This study aimed to determine the antioxidant, antimicrobial activity as well as the phytochemical constituent of Litsea angulata branch, bark, and leaves. Methods: Extraction was performed by successive maceration method using n-hexane, ethyl acetate, and ethanol solvent. Antioxidant activity was evaluated by DPPH radical scavenging assay. The antimicrobial activity using the 96 well-plate microdilution broth method against Staphylococcus aureus and Streptococcus mutans. Results: Based on the phytochemical analysis, it showed that extract of L. angulata contains alkaloids, flavonoids, tannins, terpenoids, and coumarin. The results showed that all extracts of plant samples displayed the ability to inhibit DPPH free radical formation and all tested microorganisms. Conclusions: L. angulata contains secondary metabolites such as alkaloids, flavonoids, tannins, terpenoids, carotenoids, and coumarin. The antioxidant activity on different plant extracts was a range as very strong to weak capacity. All extracts in this study could inhibit the growth of S. aureus and S. mutans.