Comparison of the bactericidal effects of quinolones against low-susceptible Haemophilus influenzae

2021 ◽  
Vol 70 (6) ◽  
Author(s):  
Kosei Mizoi ◽  
Takeaki Wajima ◽  
Emi Tanaka ◽  
Hidemasa Nakaminami ◽  
Norihisa Noguchi
Keyword(s):  
Haemophilus Influenzae ◽  
Type Species ◽  
Antimicrobial Agents ◽  
Content Type ◽  
Log Reduction ◽  
Link Type ◽  
Bactericidal Effects ◽  
Kill Curve ◽  
Time Kill

The increasing incidence of Haemophilus influenzae with decreased susceptibility to quinolones (quinolone low-susceptible H. influenzae ) in Japan has raised concerns about therapeutic failure. Thus, assessment of effective antimicrobial agents is necessary to establish an effective therapeutic strategy against resulting infections. In this study, in vitro bactericidal effects of quinolones on low-susceptible H. influenzae strains were evaluated using time-kill curve analysis. For tosufloxacin, log reduction values for low-susceptible strains were significantly lower than those for susceptible strains at both Cmax and 1/2 Cmax. Conversely, although the log reduction values were lower for susceptible strains, the Cmax of levofloxacin and β-lactams (amoxicillin and cefditoren) indicated bactericidal effects. In addition, higher concentrations of tosufloxacin at 2×Cmax and 4×Cmax had bactericidal effects on not only susceptible but also low-susceptible strains. These data strongly suggest that we should consider the presence of low-susceptible strains and reconsider the appropriate dosage of tosufloxacin for treatment, especially for paediatric patients.

scholarly journals In vitro synergy of 5-nitrofurans, vancomycin and sodium deoxycholate against Gram-negative pathogens

2021 ◽  
Author(s):  
Catrina Olivera ◽  
Vuong Van Hung Le ◽  
Catherine Davenport ◽  
Jasna Rakonjac
Keyword(s):  
Growth Inhibition ◽  
Type Species ◽  
Sodium Deoxycholate ◽  
Gram Positive ◽  
Bacterial Killing ◽  
Gram Negative ◽  
Content Type ◽  
Link Type ◽  
Time Kill

Introduction. There is an urgent need for effective therapies against bacterial infections, especially those caused by antibiotic-resistant Gram-negative pathogens. Hypothesis. Synergistic combinations of existing antimicrobials show promise due to their enhanced efficacies and reduced dosages which can mitigate adverse effects, and therefore can be used as potential antibacterial therapy. Aim. In this study, we sought to characterize the in vitro interaction of 5-nitrofurans, vancomycin and sodium deoxycholate (NVD) against pathogenic bacteria. Methodology. The synergy of the NVD combination was investigated in terms of growth inhibition and bacterial killing using checkerboard and time-kill assays, respectively. Results. Using a three-dimensional checkerboard assay, we showed that 5-nitrofurans, sodium deoxycholate and vancomycin interact synergistically in the growth inhibition of 15 out of 20 Gram-negative strains tested, including clinically significant pathogens such as carbapenemase-producing Escherichia coli , Klebsiella pneumoniae and Acinetobacter baumannii , and interact indifferently against the Gram-positive strains tested. The time-kill assay further confirmed that the triple combination was bactericidal in a synergistic manner. Conclusion. This study demonstrates the synergistic effect of 5-nitrofurans, sodium deoxycholate and vancomycin against Gram-negative pathogens and highlights the potential of the combination as a treatment for Gram-negative and Gram-positive infections.

In vitro activity of bedaquiline against Mycobacterium avium complex

2021 ◽  
Vol 70 (10) ◽  
Author(s):  
Vitaly Litvinov ◽  
Marina Makarova ◽  
Dmitry Kudlay ◽  
Nikolai Nikolenko ◽  
Julia Mikhailova
Keyword(s):  
Mycobacterium Avium ◽  
Type Species ◽  
Antimicrobial Agents ◽  
Nontuberculous Mycobacteria ◽  
Common Species ◽  
Multidrug Resistant ◽  
Content Type ◽  
Link Type ◽  
Extensively Drug Resistant

Introduction. Nontuberculous mycobacteria (NTM) are widespread in the environment and can cause various diseases in humans, especially immunocompromised patients. Hypothesis. Treatment of diseases caused by NTM is a complicated issue, mainly due to the resistance of the pathogen to most antimicrobial agents. Bedaquiline (Bdq) is now widely used for the treatment of multidrug-resistant (MDR) and extensively drug-resistant (XDR) tuberculosis (TB). Aim. The main goal of our study was to evaluate the activity of Bdq against Mycobacterium avium complex (MAC), the most common species among NTM. Methodology. A total of 166 MAC cultures (124 Mycobacterium avium and 42 Mycobacterium intracellulare ) were studied. The minimum inhibitory concentrations (MICs) of Bdq for M. avium and M. intracellulare were obtained by twofold serial dilutions in the Middlebrook 7H9 medium. MIC ranges were determined and the MIC50, MIC90 and ECOFF values were obtained. Results. The MICs in respect of M. avium ranged from 0.003 to 1.0 µg ml−1; those for M. intracellulare ranged from 0.003 to 0.5 µg ml−1. The Bdq MIC50 and MIC90 values were found to be 0.015 and 0.12 µg ml−1 , respectively, for M. avium and 0.007 and 0.06 µg ml−1, respectively, for M. intracellulare . The tentative ECOFF values for M. avium and M. intracellulare were 0.12 and 0.06 µg ml−1, respectively. Conclusion. The main bedaquiline susceptibility parameters for MAC strains isolated in the Moscow region were determined.

Impact of pH on growth of Staphylococcus epidermidis and Staphylococcus aureus in vitro

2021 ◽  
Vol 70 (9) ◽  
Author(s):  
Vidula Iyer ◽  
Janhavi Raut ◽  
Anindya Dasgupta
Keyword(s):  
Staphylococcus Aureus ◽  
Growth Kinetics ◽  
Staphylococcus Epidermidis ◽  
Type Species ◽  
Ph Dependence ◽  
Skin Microbiome ◽  
Content Type ◽  
Link Type ◽  
Kinetics Of

The pH of skin is critical for skin health and resilience and plays a key role in controlling the skin microbiome. It has been well reported that under dysbiotic conditions such as atopic dermatitis (AD), eczema, etc. there are significant aberrations of skin pH, along with a higher level of Staphylococcus aureus compared to the commensal Staphylococcus epidermidis on skin. To understand the effect of pH on the relative growth of S. epidermidis and S. aureus , we carried out simple in vitro growth kinetic studies of the individual microbes under varying pH conditions. We demonstrated that the growth kinetics of S. epidermidis is relatively insensitive to pH within the range of 5–7, while S. aureus shows a stronger pH dependence in that range. Gompertz’s model was used to fit the pH dependence of the growth kinetics of the two bacteria and showed that the equilibrium bacterial count of S. aureus was the more sensitive parameter. The switch in growth rate happens at a pH of 6.5–7. Our studies are in line with the general hypothesis that keeping the skin pH within an acidic range is advantageous in terms of keeping the skin microbiome in balance and maintaining healthy skin.

In vitro effectiveness of biapenem against IMP-producing Enterobacteriaceae

2021 ◽  
Vol 70 (10) ◽  
Author(s):  
Kazuyoshi Gotoh ◽  
Makoto Miyoshi ◽  
I Putu Bayu Mayura ◽  
Koji Iio ◽  
Osamu Matsushita ◽  
...  
Keyword(s):  
Therapeutic Option ◽  
Small Data ◽  
Limited Data ◽  
Data Set ◽  
Content Type ◽  
Link Type ◽  
Almost All ◽  
New Treatments ◽  
Time Kill

The options available for treating infections with carbapenemase-producing Enterobacteriaceae (CPE) are limited; with the increasing threat of these infections, new treatments are urgently needed. Biapenem (BIPM) is a carbapenem, and limited data confirming its in vitro killing effect against CPE are available. In this study, we examined the minimum inhibitory concentrations (MICs) and minimum bactericidal concentrations (MBCs) of BIPM for 14 IMP-1-producing Enterobacteriaceae strains isolated from the Okayama region in Japan. The MICs against almost all the isolates were lower than 0.5 µg ml−1, indicating susceptibility to BIPM, while approximately half of the isolates were confirmed to be bacteriostatic to BIPM. However, initial killing to a 99.9 % reduction was observed in seven out of eight strains in a time–kill assay. Despite the small data set, we concluded that the in vitro efficacy of BIPM suggests that the drug could be a new therapeutic option against infection with IMP-producing CPE.

Cell-free supernatants produced by lactic acid bacteria reduce Salmonella population in vitro

Microbiology ◽  
2021 ◽  
Vol 167 (11) ◽  
Author(s):  
Alberto Gonçalves Evangelista ◽  
Jessica Audrey Feijó Corrêa ◽  
João Vitor Garcia dos Santos ◽  
Eduardo Henrique Custódio Matté ◽  
Mônica Moura Milek ◽  
...  
Keyword(s):  
Antimicrobial Activity ◽  
Lactic Acid ◽  
Antimicrobial Resistance ◽  
Lactic Acid Bacteria ◽  
Type Species ◽  
Feed Additives ◽  
Poultry Feed ◽  
Content Type ◽  
Link Type

The genus Salmonella is closely associated with foodborne outbreaks and animal diseases, and reports of antimicrobial resistance in Salmonella species are frequent. Several alternatives have been developed to control this pathogen, such as cell-free supernatants (CFS). Our objective here was to evaluate the use of lactic acid bacteria (LAB) CFS against Salmonella in vitro. Seventeen strains of LAB were used to produce CFS, and their antimicrobial activity was screened towards six strains of Salmonella . In addition, CFS were also pH-neutralized and/or boiled. Those with the best results were lyophilized. MICs of lyophilized CFS were 11.25–22.5 g l–1. Freeze-dried CFS were also used to supplement swine and poultry feed (11.25 g kg–1) and in vitro simulated digestion of both species was performed, with Salmonella contamination of 5×106 and 2×105 c.f.u. g−1 of swine and poultry feed, respectively. In the antimicrobial screening, all acidic CFS were able to inhibit the growth of Salmonella . After pH neutralization, Lactobacillus acidophilus Llorente, Limosilactobacillus fermentum CCT 1629, Lactiplantibacillus plantarum PUCPR44, Limosilactobacillus reuteri BioGaia, Lacticaseibacillus rhamnosus ATCC 7469 and Pediococcus pentosaceus UM116 CFS were the only strains that partially maintained their antimicrobial activity and, therefore, were chosen for lyophilization. In the simulated swine digestion, Salmonella counts were reduced ≥1.78 log c.f.u. g–1 in the digesta containing either of the CFS. In the chicken simulation, a significant reduction was obtained with all CFS used (average reduction of 0.59±0.01 log c.f.u. ml–1). In general, the lyophilized CFS of L. fermentum CCT 1629, L. rhamnosus ATCC 7469 and L. acidophilus Llorente presented better antimicrobial activity. In conclusion, CFS show potential as feed additives to control Salmonella in animal production and may be an alternative to the use of antibiotics, minimizing problems related to antimicrobial resistance.

scholarly journals Genetic regulation, biochemical properties and physiological importance of arginase from Sinorhizobium meliloti

Microbiology ◽  
2020 ◽  
Vol 166 (5) ◽  
pp. 484-497 ◽  
Author(s):  
Alejandra Arteaga Ide ◽  
Victor M. Hernández ◽  
Liliana Medina-Aparicio ◽  
Edson Carcamo-Noriega ◽  
Lourdes Girard ◽  
...  
Keyword(s):  
Type Species ◽  
Sinorhizobium Meliloti ◽  
Arginase Activity ◽  
Wild Type ◽  
Mobility Shift ◽  
Content Type ◽  
Link Type ◽  
Arginine Catabolism

In bacteria, l-arginine is a precursor of various metabolites and can serve as a source of carbon and/or nitrogen. Arginine catabolism by arginase, which hydrolyzes arginine to l-ornithine and urea, is common in nature but has not been studied in symbiotic nitrogen-fixing rhizobia. The genome of the alfalfa microsymbiont Sinorhizobium meliloti 1021 has two genes annotated as arginases, argI1 (smc03091) and argI2 (sma1711). Biochemical assays with purified ArgI1 and ArgI2 (as 6His-Sumo-tagged proteins) showed that only ArgI1 had detectable arginase activity. A 1021 argI1 null mutant lacked arginase activity and grew at a drastically reduced rate with arginine as sole nitrogen source. Wild-type growth and arginase activity were restored in the argI1 mutant genetically complemented with a genomically integrated argI1 gene. In the wild-type, arginase activity and argI1 transcription were induced several fold by exogenous arginine. ArgI1 purified as a 6His-Sumo-tagged protein had its highest in vitro enzymatic activity at pH 7.5 with Ni2+ as cofactor. The enzyme was also active with Mn2+ and Co2+, both of which gave the enzyme the highest activities at a more alkaline pH. The 6His-Sumo-ArgI1 comprised three identical subunits based on the migration of the urea-dissociated protein in a native polyacrylamide gel. A Lrp-like regulator (smc03092) divergently transcribed from argI1 was required for arginase induction by arginine or ornithine. This regulator was designated ArgIR. Electrophoretic mobility shift assays showed that purified ArgIR bound to the argI1 promoter in a region preceding the predicted argI1 transcriptional start. Our results indicate that ArgI1 is the sole arginase in S. meliloti , that it contributes substantially to arginine catabolism in vivo and that argI1 induction by arginine is dependent on ArgIR.

A review of in vitro attempts to develop the axenic culture of Treponema pallidum and genomics-based suggestions to achieve this elusive goal

2021 ◽  
Vol 70 (7) ◽  
Author(s):  
Souad Belkacemi ◽  
Maryam Tidjani Alou ◽  
Saber Khelaifia ◽  
Didier Raoult
Keyword(s):  
Microscopic Observation ◽  
Type Species ◽  
Culture Media ◽  
Treponema Pallidum ◽  
Axenic Culture ◽  
Dark Field ◽  
Content Type ◽  
Link Type ◽  
Oral Microbiology

To date, the axenic culture of Treponema pallidum remains a challenge in the field of microbiology despite countless attempts. Here, we conducted a comprehensive bibliographic analysis using several databases and search engines, namely Pubmed, Google scholar, Google, Web of Science and Scopus. Numerous unsuccessful empiric studies have been conducted and evaluated using as criteria dark-field microscopic observation of motile spiral shaped cells in the culture and virulence of the culture through rabbit infectivity. All of these studies failed to induce rabbit infectivity, even when deemed positive after microscopic observation leading to the misnomer of avirulent T. pallidum . In fact, this criterion was improperly chosen because not all spiral shaped cells are T. pallidum . However, these studies led to the formulation of culture media particularly favourable to the growth of several species of Treponema, including Oral Microbiology and Immunology, Zürich medium (OMIZ), Oral Treponeme Enrichment Broth (OTEB) and T-Raoult, thus allowing the increase in the number of cultivable strains of Treponema . The predicted metabolic capacities of T. pallidum show limited metabolism, also exhibited by other non-cultured and pathogenic Treponema species, in contrast to cultured Treponema species. The advent of next generation sequencing represents a turning point in this field, as the knowledge inferred from the genome can finally lead to the axenic culture of T. pallidum .

Environment in the lung of cystic fibrosis patients stimulates the expression of biofilm phenotype in Mycobacterium abscessus

2022 ◽  
Vol 71 (1) ◽  
Author(s):  
Bailey F. Keefe ◽  
Luiz E. Bermudez
Keyword(s):  
Cystic Fibrosis ◽  
Host Cell ◽  
Biofilm Formation ◽  
Type Species ◽  
Divalent Cations ◽  
Mycobacterium Abscessus ◽  
Content Type ◽  
Link Type ◽  
Populations At Risk

Introduction. Pulmonary infections caused by organisms of the Mycobacterium abscessus complex are increasingly prevalent in populations at risk, such as patients with cystic fibrosis, bronchiectasis and emphysema. Hypothesis. M. abscessus infection of the lung is not observed in immunocompetent individuals, which raises the possibility that the compromised lung environment is a suitable niche for the pathogen to thrive in due to the overproduction of mucus and high amounts of host cell lysis. Aim. Evaluate the ability of M. abscessus to form biofilm and grow utilizing in vitro conditions as seen in immunocompromised lungs of patients. Methodology. We compared biofilm formation and protein composition in the presence and absence of synthetic cystic fibrosis medium (SCFM) and evaluated the bacterial growth when exposed to human DNA. Results. M. abscessus is capable of forming biofilm in SCFM. By eliminating single components found in the medium, it became clear that magnesium works as a signal for the biofilm formation, and chelation of the divalent cations resulted in the suppression of biofilm formation. Investigation of the specific proteins expressed in the presence of SCFM and in the presence of SCFM lacking magnesium revealed many different proteins between the conditions. M. abscessus also exhibited growth in SCFM and in the presence of host cell DNA, although the mechanism of DNA utilization remains unclear. Conclusions. In vitro conditions mimicking the airways of patients with cystic fibrosis appear to facilitate M. abscessus establishment of infection, and elimination of magnesium from the environment may affect the ability of the pathogen to establish infection.

scholarly journals Dysgonomonas macrotermitis sp. nov., isolated from the hindgut of a fungus-growing termite

2014 ◽  
Vol 64 (Pt_9) ◽  
pp. 2956-2961 ◽  
Author(s):  
Ying-jie Yang ◽  
Ning Zhang ◽  
Shi-qi Ji ◽  
Xin Lan ◽  
Kun-di Zhang ◽  
...  
Keyword(s):  
Type Species ◽  
Antimicrobial Agents ◽  
Novel Species ◽  
Rrna Gene ◽  
Gram Stain ◽  
Cultivation Temperature ◽  
Biochemical Tests ◽  
Content Type ◽  
Link Type ◽  
Bile Resistance

A Gram-stain-negative, facultatively anaerobic, non-motile and coccoid- to short-rod-shaped bacterium, designated strain Dys-CH1T, was isolated from the hindgut of a fungus-growing termite Macrotermes barneyi. The optimal pH and cultivation temperature of strain Dys-CH1T were pH 7.2–7.6 and 35–37 °C, respectively. Sequence analysis of 16S rRNA gene showed that Dys-CH1T shared 94.6 % and 90.9 % similarity with Dysgonomonas capnocytophagoides JCM 16697T and Dysgonomonas gadei CCUG 42882T, respectively. Strain Dys-CH1T was found to be different from other species of the genus Dysgonomonas with validly published names with respect to taxonomically important traits, including habitat, biochemical tests, DNA G+C content, bile resistance, fatty-acid composition and susceptibility to antimicrobial agents. On the basis of these characteristics, strain Dys-CH1T represents a novel species of the genus Dysgonomonas for which the name Dysgonomonas macrotermitis sp. nov. is proposed. The type strain is Dys-CH1T ( = JCM 19375T = DSM 27370T).

scholarly journals nosX is essential for whole-cell N2O reduction in Paracoccus denitrificans but not for assembly of copper centres of nitrous oxide reductase

Microbiology ◽  
2020 ◽  
Vol 166 (10) ◽  
pp. 909-917 ◽  
Author(s):  
Sophie P. Bennett ◽  
Maria J. Torres ◽  
Manuel J. Soriano-Laguna ◽  
David J. Richardson ◽  
Andrew J. Gates ◽  
...  
Keyword(s):  
Nitrous Oxide ◽  
Type Species ◽  
Paracoccus Denitrificans ◽  
Pseudomonas Stutzeri ◽  
Reduction Reaction ◽  
Nitrous Oxide Reductase ◽  
Content Type ◽  
Link Type ◽  
Reverse Transcription Pcr

Nitrous oxide (N2O) is a potent greenhouse gas that is produced naturally as an intermediate during the process of denitrification carried out by some soil bacteria. It is consumed by nitrous oxide reductase (N2OR), the terminal enzyme of the denitrification pathway, which catalyses a reduction reaction to generate dinitrogen. N2OR contains two important copper cofactors (CuA and CuZ centres) that are essential for activity, and in copper-limited environments, N2OR fails to function, contributing to rising levels of atmospheric N2O and a major environmental challenge. Here we report studies of nosX, one of eight genes in the nos cluster of the soil dwelling α-proteobaterium Paraccocus denitrificans. A P. denitrificans ΔnosX deletion mutant failed to reduce N2O under both copper-sufficient and copper-limited conditions, demonstrating that NosX plays an essential role in N2OR activity. N2OR isolated from nosX-deficient cells was found to be unaffected in terms of the assembly of its copper cofactors, and to be active in in vitro assays, indicating that NosX is not required for the maturation of the enzyme; in particular, it plays no part in the assembly of either of the CuA and CuZ centres. Furthermore, quantitative Reverse Transcription PCR (qRT-PCR) studies showed that NosX does not significantly affect the expression of the N2OR-encoding nosZ gene. NosX is a homologue of the FAD-binding protein ApbE from Pseudomonas stutzeri , which functions in the flavinylation of another N2OR accessory protein, NosR. Thus, it is likely that NosX is a system-specific maturation factor of NosR, and so is indirectly involved in maintaining the reaction cycle of N2OR and cellular N2O reduction.

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