Minimum Inhibitory Concentration Of Amoxicillin Research Articles

Combined impact of antibiotics and Cr(VI) on antibiotic resistance, ARGs, and growth of Bacillussp. SH-1: A functionl analysis from gene to protease

The simultaneous selection of antibiotic resistance genes (ARGs) induced by heavy metals and antibiotics has emerged as a growing environmental problem. This study investigated the combined effects of chromium (Cr(VI)) and antibiotics on the ARGs of Bacillus cereus SH-1. As Cr(VI) concentration increased, it triggered reactive oxygen species oxidative stress in SH-1, increased antioxidant enzyme activity, enhanced plasmid conjugative transfer, and reduced the efficiency of Cr(VI) removal by SH-1. Antibiotic resistance varied with increasing tetracycline and amoxicillin minimum inhibitory concentrations (MICs), whereas azithromycin and chloramphenicol MICs decreased with Cr(VI) induction. The overexpression of eight genes of the HAE-1 family of efflux pumps was detected using metagenomics and proteomics. Co-contamination with Cr(VI) and antibiotics has led to the emergence and spread of antibiotic-resistant bacteria. Therefore, resistance gene contamination resulting from Cr(VI)-polluted environments cannot be overlooked.

Outcomes of Enterococcus faecalis infective endocarditis according to MIC of amoxicillin: a multicentric study.

The incidence of Enterococcus faecalis infective endocarditis is increasing over time. Data on the impact of minimum inhibitory concentration (MIC) of amoxicillin on treatment outcomes are scarce. The objective of this study was to describe the epidemiology of E. faecalis infective endocarditis and to evaluate whether the MIC of amoxicillin might influence mortality. We retrospectively included all consecutive patients diagnosed with definite E. faecalis infective endocarditis between 2013 and 2020 in 11 French hospitals. We extracted data from the local diagnosis-related group (DRG) database and matched these data with microbiological results. Amoxicillin MIC was determined by Etest strip. The primary endpoints were endocarditis-related mortality and risk factors for endocarditis-related mortality including amoxicillin MIC. A total of 403 patients with definite E. faecalis infective endocarditis were included. Patients were predominantly male (76.4%) with a median age of 74 years (67-82). Embolic complications occurred in 170 (42.1%) patients. Cardiac surgery was performed in 158 (61.5%) patients. The endocarditis-related mortality rate was 28.3% and the median delay between mortality and onset of hospitalization was 24 (9; 41) days. E. faecalis MIC of amoxicillin was available for 246 (61%) patients. The median MIC was 0.5 mg/L (0.4-0.7). Amoxicillin MIC was not found to be associated with in-hospital mortality. None of the variables included in the multivariate model were identified as a risk factor for mortality and there was no correlation between mortality and the duration of treatment for 4 weeks versus 6 weeks. Higher amoxicillin MIC was not a risk factor leading to endocarditis-related mortality in definite E. faecalis infective endocarditis. However, further studies are needed to assess the effect of amoxicillin MIC on relapse.

Enhancing Antibiotic Efficacy: Exploring Synergistic Interactions between Plant Extracts and Conventional Antibiotics

Medicinal herbs including Senna alata, Ricinus communis, and Lannea barteri have been utilized for centuries to cure a variety of illnesses caused by microbial infections. This study looked at the synergistic effects of these drugs with traditional antibiotics on clinical isolates of Candida albicans, Staphylococcus aureus, Pseudomonas aeruginosa, and Escherichia coli. The test bacteria were chosen based on their minimal potential for monotherapy and susceptibility to at least one antibiotic with a known genetic basis. The interactions of plant extracts with antibiotics against the chosen pathogenic microorganisms were investigated using the agar well diffusion, broth microdilution, and checkerboard methods. Calculated fractional inhibitory concentration index (FICI) values were used to describe how the extracts and antibiotics interacted. All the extracts from the three plants combined with fluconazole exhibited a synergistic interaction against C. albicans (FICI < 0.5). The minimum inhibitory concentration (MIC) of ampicillin against E. coli was demonstrated to be reduced by the combination of the ethanol extract of S. alata with ampicillin, with a FICI value of 0.4 indicating a synergistic effect. With a synergistic action (FICI ˂ 0.5) against P. aeruginosa, the ethanol extract of S. alata and amoxicillin were successful in reducing the MIC of amoxicillin from 0.32 to 0.17 mg/mL. Aqueous L. barteri extract combined with amoxicillin exhibited synergism (FICI < 0.2) against S. aureus with a reduction of MIC from 0.20 to 0.03 mg/mL. The current study is the first to investigate the aforementioned plants in combination with conventional antibiotics for their antimicrobial activities. The findings of this study could be used to create a useful, applicable, feasible, and alternative source of novel antimicrobial agents.

Enhancing Commercial Antibiotics with Trans-Cinnamaldehyde in Gram-Positive and Gram-Negative Bacteria: An In Vitro Approach.

One strategy to mitigate the emergence of bacterial resistance involves reducing antibiotic doses by combining them with natural products, such as trans-cinnamaldehyde (CIN). The objective of this research was to identify in vitro combinations (CIN + commercial antibiotic (ABX)) that decrease the minimum inhibitory concentration (MIC) of seven antibiotics against 14 different Gram-positive and Gram-negative pathogenic bacteria, most of them classified as ESKAPE. MIC values were measured for all compounds using the broth microdilution method. The effect of the combinations on these microorganisms was analyzed through the checkboard assay to determine the type of activity (synergy, antagonism, or addition). This analysis was complemented with a kinetic study of the synergistic combinations. Fifteen synergistic combinations were characterized for nine of the tested bacteria. CIN demonstrated effectiveness in reducing the MIC of chloramphenicol, streptomycin, amoxicillin, and erythromycin (94-98%) when tested on Serratia marcescens, Staphylococcus aureus, Pasteurella aerogenes, and Salmonella enterica, respectively. The kinetic study revealed that when the substances were tested alone at the MIC concentration observed in the synergistic combination, bacterial growth was not inhibited. However, when CIN and the ABX, for which synergy was observed, were tested simultaneously in combination at these same concentrations, the bacterial growth inhibition was complete. This demonstrates the highly potent in vitro synergistic activity of CIN when combined with commercial ABXs. This finding could be particularly beneficial in livestock farming, as this sector witnesses the highest quantities of antimicrobial usage, contributing significantly to antimicrobial resistance issues. Further research focused on this natural compound is thus warranted for this reason.

Synergistic effect of commercial mangosteen extract (Garcinia mangostana L.) and amoxicillin against methicillin-resistant Staphylococcus aureus (MRSA)

Antibiotic resistance occurs worldwide, and has become a threat to humankind. Previous data have shown that antimicrobial resistance is a global issue demanding immediate resolution because it threatens the environment and society. The present work thus investigated the synergistic effects of commercial Garcinia mangostana L. (GML) extract and amoxicillin on the growth of methicillin-resistant Staphylococcus aureus (MRSA) bacterial cells. A commercial GML extract was screened for phytochemical properties, and the presence of α-mangostin was detected using high-performance liquid chromatography (HPLC). The antibacterial activity of the commercial GML extract with amoxicillin was analysed by minimum inhibitory concentration (MIC) and checkerboard assays. The morphology ultrastructure of bacteria was observed using transmission electron microscopy (TEM), after treatment with commercial GML extract, either single or in combination with amoxicillin. The MICs of amoxicillin and commercial GML extract against MRSA bacteria were 250.00 and 137.50 μg/mL, respectively. The checkerboard assay showed synergistic activity in the combination of commercial GML extract (34.38 µg/mL) and amoxicillin (62.50 µg/mL) at fractional inhibitory concentration (FIC) index of < 0.5. Damage to the structure of bacteria occurred due to the commercial GML extract plus amoxicillin. It was observed that the loss of bacterial cell membranes led to an irregular bacterial structure. These findings provided evidence that the combination of commercial GML extract and amoxicillin could reverse bacterial resistance in order to determine the susceptibility of traditional drugs.

ANTIBIOTIC SUSCEPTIBILITY TEST OF PSEUDOMONAS AERUGINOSA AND STAPHYLOCOCCUS AUREUS WITH DISK DIFFUSION AND DILUTION METHOD

The susceptibility test is a test used to measure bacteria's sensitivity and vulnerability towards antibiotics. This study was to determine sensitivity of Pseudomonas aeruginosa and Staphylococcus aureus towards amoxicillin, neomycin, and sulfanilamide. In this study, the methods used in susceptibility tests are disk diffusion method and serial dilution. The disk diffusion method is a method with paper disks that already saturated the antibiotics, with one paper disk for each antibiotic, put the disk on the agar media that had been inoculated by the bacteria, then incubated and measured the inhibition zone. The dilution method was done by making a series of antibiotic dilutions in liquid media which added microbes inside. This test is to estimate the smallest concentration or Minimum Inhibitory Concentration (MIC) in the dilution series with no bacterial growth. The diffusion test shows no clear visible zone at all, so Pseudomonas aeruginosa and Staphylococcus aureus are resistant to amoxicillin, neomycin and sulfanilamide. The dilution test shows the clearest sample was on 0,25% concentrate, so amoxicillin's Minimum Inhibitory Concentration towards Staphylococcus aureus is 0,25%.

Efficacy and safety of low-dose rifabutin-based 7-day triple therapy as a third- or later-line Helicobacter pylori eradication regimen.

BackgroundRifabutin‐based regimens are used as rescue therapy for refractory Helicobacter pylori infection; however, the duration for which treatment is required and side effects are concerning. This study assessed the efficacy and safety of 7‐day rifabutin, amoxicillin, and vonoprazan triple therapy as third‐ or later‐line treatment for H. pylori infection.Materials and MethodsPatients who did not respond to second‐line therapy were enrolled. After H. pylori infection was confirmed with the culture method, the patients received rifabutin‐containing triple therapy (20 mg vonoprazan b.i.d., 500 mg amoxicillin q.i.d., and 150 mg rifabutin q.d.) for 7 days. Twelve weeks after the eradication therapy, successful eradication was confirmed using a 13C urea breath test or the H. pylori stool antigen test. The results obtained from our previous study that reported a 10‐day or 14‐day esomeprazole based rifabutin‐containing triple therapy as a third‐ or fourth‐line rescue therapy treated patients were used as historical control. We determined the minimum inhibitory concentrations of amoxicillin and rifabutin. We also evaluated whether the patients were positive for the mutation of the rpoB gene.ResultsIntention‐to‐treat and per‐protocol analyses showed that our regimen resulted in a high eradication rate (91.2%, 95% CI: 84%–99% and 92.7%, 95% CI: 86%–100%, respectively). Adverse events occurred in 31.6% of the patients, and two patients discontinued the therapy.ConclusionsThis is the first study to evaluate the efficacy and safety of a 7‐day low‐dose rifabutin‐based triple therapy with vonoprazan and amoxicillin. Our results suggest that our regimen was effective and safe as a third‐ or later‐line H. pylori eradication regimen. To clarify what component in this regimen are critical, subsequent studies using a factorial design (comparing vonoprazan‐amoxicillin dual therapy vs. vonoprazan‐rifabutin triple therapy) will be needed.

Analysis of epidemiology and novel mutation of Helicobacter pylori antibiotic resistance in South Korea

BackgroundHelicobacter pylori is a Gram‐negative bacterium associated with upper gastrointestinal disease, peptic ulcer, mucosa‐associated lymphoid tissue lymphoma and eradication treatment is recommended because it is one of the causes of gastric cancer. However, resistance to some antibiotics used for treatment has developed, the eradication rate is declining worldwide. This study focused on antibiotic susceptibility test (AST) of H. pylori isolated from patient clinical specimens. The aim of this study is to identify the resistance epidemiology of H. pylori and to elucidate the resistance mechanism through gene analysis.methodsH. pylori isolated from patient clinical specimens is identified and AST for amoxicillin (AMX) and clarithromycin (CLR) are performed, and the results are analyzed through Whole Genome Sequencing (WGS) and MultiLocus Sequence Typing (MLST), respectively. The strain type of the MLST result is compared with the CLR resistance minimum inhibitory concentration (MIC) value to analyze the significant points.H. pylori is cultured on EYE Agar plate and incubated in Anaerobic Jar for 2~5 days with microaerophilic air condition (5% O2, 10% CO2, 85% N2). Cultured isolates are identified by MALDI‐TOF system and performed AST using Epsilometer test to determining MIC.Results366 H. pylori were isolated from 1952 clinical patients, and 36 AMX‐resistant H. pylori and 101 CLR‐resistant H. pylori were identified. Among the identified H. pylori, 9 AMX high MIC strains were selected and WGS was performed, and 12 CLR high MIC strains were selected and MLST was performed.As the WGS result of 9 clinical strains resistant to AMX, single nucleotide polymorphism (SNP) of the potential target gene was analyzed with reference to ATCC 26695. Six genes, Penicillin binding protein1A (PBP1), PBP2, NhaC, hofH, hofC, and hefC, were selected as potential target genes. As a result of the analysis, 8, 7, 4, 9, 16, and 2 SNPs were found, respectively, and it was specifically confirmed that there were many SNPs in the outer membrane component Gene. However, No correlation was found between AMX MIC value and target SNP.12 For the CLR resistance strain, MLST was performed using 7 housekeeping genes (atpA, efp, trpC, ppa, mutY, yphC, Ure1). In 12 strain, 10 CLR‐resistance H. pylori are not identified strain type(ST) to The National Center for Biotechnology Information(NCBI) database because they have a lots of mutation in 7 housekeeping gene. 2 CLR‐resistance H. pylori are identified the new type strains.ConclusionIn this study, we conclude that hofC, hofH related to outer membrane protein component may be associated to the AMX resistance. And additional research is continued to need about other resistance potential gene, especially hopC.

Minimum inhibitory concentrations of commonly used antibiotics against Helicobacter Pylori: A multicenter study in South China.

AimTo determine the minimum inhibitory concentrations (MICs) of commonly used antibiotics against Helicobacter Pylori (H. pylori) in South China and compare their resistance rates by using EUCAST breakpoints and other breakpoints.MethodsPatients who had not previously received H. pylori treatment in clinical centers in South China were enrolled in this study from 2017 to 2020. Gastric biopsies were obtained for H. pylori culture. The MICs of amoxicillin (AMX), clarithromycin (CLA), metronidazole (MTZ), levofloxacin (LEV), tetracycline (TET) and furazolidone (FZD) were tested by broth microdilution method and assessed by two different breakpoints. ATCC43504 standard strain served as a control.ResultsA total of 208 H. pylori strains were isolated from patients’ biopsy samples. The MICs of AMX, CLA, MTZ, LEV, TET and FZD for H. pylori were 0.0156-256mg/L (MIC50 0.125mg/L, MIC90 4mg/L), 0.0156- >256 mg/L (MIC50 0.0312mg/L, MIC90 64mg/L), 0.0156- >256mg/L (MIC50 8mg/L, MIC90 256mg/L), 0.0156-256mg/L (MIC50 0.25mg/L, MIC90 16mg/L), 0.0156-256mg/L (MIC50 0.0625mg/L, MIC90 4mg/L), and 0.0156- >256mg/L (MIC50 0.0312mg/L, MIC90 2mg/L), respectively. The MICs of AMX, CLA, MTZ, LEV, TET and FZD for ATCC43504 strain were 0.25mg/L, 0.0625mg/L, 64mg/L, 0.5mg/L, 1mg/L and 0.25mg/L, respectively. The resistance rate of FZD was 11.05%. The overall resistance rates according to EUCAST breakpoints and other breakpoints were 57.21% and 14.90% for AMX (p<0.001), 38.94% and 38.94% for CLA (p = 1), 39.42% and 50.96% for MTZ (p<0.001), 12.98% and 10.58% for TET (p = 0.025), 35.10% and 35.10% for LEV (p = 1), respectively.ConclusionsOur results demonstrate that AMX, FZD, and TET, but not MTZ, CLR or LEV, showed good anti-H. pylori activity in vitro in South China. When different breakpoints were used, similar results were found with CLA, and LEV, but not with AMX, MTZ, or TET.

Bioactive constituents with antibacterial, resistance modulation, anti-biofilm formation and efflux pump inhibition properties from Aidia genipiflora stem bark

BackgroundAntimicrobial resistance is a global health challenge. The involvement of bacterial biofilms and efflux pumps in the development of multidrug resistance (MDR) is well established. Medicinal plants have been proposed as alternatives for combating MDR focusing on their bioactive constituents with resistance modulatory activities. This study was aimed at investigating the stem bark of Aidia genipiflora for bioactive constituents with anti-biofilm, efflux pump inhibition and resistance modulatory activities.MethodThe crude methanol extract was purified by column chromatography and isolated compounds characterized by mass and nuclear magnetic resonance spectrometry. Antibacterial activity was determined by the High-throughput spot culture growth inhibition and the broth micro-dilution assay. The ethidium bromide accumulation assay was used to determine efflux pump inhibition property. Biofilm inhibition was determined in a microplate crystal violet retention assay.ResultsPurification of the ethyl acetate fraction led to the isolation of oleanonic acid (1), 4-hydroxy cinnamic acid docosyl ester (2), β-stigmasterol/β-sitosterol (mixture 3a/b) and D-mannitol (4). The minimum inhibitory concentrations (MICs) ranged from 250 to > 500 μg/mL for extracts and fractions and from 15 to 250 μg/mL for compounds. In the presence of sub-inhibitory concentrations of the compounds, the MIC of amoxicillin against E. coli (20 μg/mL) and P. aeruginosa (320 μg/mL) was reduced by 32 and 10 folds respectively. The whole extract demonstrated anti-biofilm formation and efflux pump inhibition in E. coli, S. aureus and P. aeruginosa. The sterol mixture (3a/b) at concentration of 100 μg/mL caused the highest inhibition (73%) of biofilm formation in S. aureus. Oleanonic acid (1) demonstrated remarkable efflux pump inhibition at MIC of 7.8 μg/mL in E. coli better than the standard drugs verapamil and chlorpromazine.ConclusionThis study confirms the prospects of A. genipiflora as a source of new antibacterial agents and adjuvants that could interact with some resistance mechanisms in bacteria to enhance the activity of hitherto ineffective antibiotics. “A small portion of the study has been presented in a conference in the form of poster”.

Enhanced antimicrobial activity of the combination of silver nanoparticles and different β Lactam antibiotics against methicillin resistant Staphylococcus aureus isolates

Methicillin resistant Staphylococcus aureus (MRSA) has emerged as a major problem worldwide. Strong synergistic action of antibiotics combined with silver nanoparticles (AgNPs) presents a potential solution for this problem. AgNPs was prepared by Gamma- irradiation method. Eighty staphylococcus spp. were obtained out of 45 different clinical specimens; 21(46.6 %) isolates were identified as MRSA and chosen to test their susceptibility to plain AgNPs, β-lactam antibiotics and mixed solution of AgNPs /antibiotics by disc diffusion method and broth microdilution assay for detection of minimum inhibitory concentration (MIC) as well as minimum bactericidal concentrations. All MRSA isolates were full resistant to amoxicillin, ceftazidime, cefotaxime, ceftriaxone, cefepime, while 3(14.2%) were susceptible to meropenem and imipenem with MIC ≤ 20µg/ml. Plain AgNPs showed potential anti-MRSA activity, the range of inhibition zones of AgNPs ranged from 7.5 to 12 mm. Broth microdilution assay revealed that 8(38.1%) and 5(23.8%) were inhibited at concentration of 31.25 and 7.81µg/ml of AgNPs, respectively. Disc diffusion assay showed the enhancement of activity of amoxicillin/AgNPs, imipenem/AgNPs and meropenem/AgNPs combinations, the fold increase areas ranging between 33.3 to 100, 0 to 166.6 and 0 to 166.6 respectively. Additionally, MIC of amoxicillin in amoxicillin/AgNPs mixture was decreased from more than 5120 μg/ml to reach 1.95 μg/ml in 28.5% of MRSA and 0.97 μg/mL in 19 % of MRSA isolates. The enhanced activity of antibiotics, especially amoxicillin, combined with AgNPs was very high against the resistant isolates, so utilizing combination therapy is one the proposed approaches to treat MRSA bacterial infections.

Efficacy of Tegoprazan for Improving the Susceptibility of Antimicrobial Agents against Antibiotic-Resistant Helicobacter pylori.

Background/AimsFavorable outcomes of potassium-competitive acid blocker (PCAB)-containing eradication therapy have been reported. In fact, tegoprazan, a recently developed PCAB, was presumed to show good eradication efficacy even for resistant Helicobacter pylori. We aimed to investigate the anti-H. pylori efficacy of tegoprazan compared with that of vonoprazan.MethodsA total of 220 resistant clinical H. pylori isolates were utilized. The anti-H. pylori efficacy of PCABs was determined by evaluating the minimum inhibitory concentrations (MICs) of clarithromycin, fluoroquinolone, metronidazole, and amoxicillin in combination with vonoprazan or tegoprazan by the agar dilution method. The impact of the mutations responsible for resistance development, such as 23S rRNA, gyrA, rdxA, frxA, and pbp1 mutations, was also analyzed.ResultsH. pylori growth was significantly inhibited in a medium containing 1 μg/mL clarithromycin with tegoprazan (128 μg/mL). The MICs of clarithromycin (46.3%), fluoroquinolone (46.7%), metronidazole (55.6%), and amoxicillin (34.5%) against resistant H. pylori isolates improved after tegoprazan administration. Tegoprazan demonstrated more frequent susceptibility acquisition with metronidazole than with vonoprazan (20.6% vs 4.7%, p=0.014). However, there were no significant differences depending on the mutational status of each antimicrobial agent.ConclusionsTegoprazan administration may improve the susceptibility of antimicrobial-resistant H. pylori, independent of acid suppression.

Examination of the minimum inhibitory concentration of amoxicillin and marbofloxacin against Streptococcus suis using standardised methods

The results of the antimicrobial susceptibility testing of clinical isolates Streptococcus suis to amoxicillin and marbofloxacin obtained by the agar dilution method and broth microdilution method with the results obtained by the commercially available E-test were compared. Comparisons between the methods based on the determination of the minimal inhibitory concentration (MIC) of the antimicrobials were assessed based on the degree and frequency of the categorical agreement (Agar dilution method as a reference system) and the percentage of the categorical agreement and error rate. A statistical evaluation was determined using the Bland-Atman method. The presented MIC values, determined for the isolates in the E-test, were slightly different from the MIC values determined by the dilution tests, mainly due to the different defined testing concentrations. For the E-test as the test system and agar-dilution method as the reference system, no error of any class was detected (very major, major and minor error) and a complete categorical agreement was obtained between the evaluated methods for amoxicillin. For amoxicillin, the regression and correlation analysis show linear relationships between the E-test and the two dilution methods with significant coefficients of determination (0.62 and 0.75). The slopes of the equality and regression lines were not significantly different. However, the E-test tends to slightly overestimate the MIC values when compared to the microdilution. The reverse is true when compared with the agar dilution. There was good agreement between the E-test and the dilution methods with a low bias (0.001 3 and −0.005 0), all the experimental data were within the computed limits of agreement. For marbofloxacin, the same trends were observed with lower coefficients of determination (0.42 and 0.73) and a less favourable agreement. The E-test constantly underestimated the MIC values when compared to the two dilution methods. No significant difference between the microdilution and agar dilution was obtained.

Phenolic-rich green tea extract increases the antibacterial activity of amoxicillin against Staphylococcus aureus by in vitro and ex vivo studies

Context: Methicillin-resistant Staphylococcus aureus (MRSA) has been a significant challenge in health problems. Aims: To investigate synergistic properties of green tea extract that can potentially enhance the antibacterial activity of amoxicillin against methicillin-resistant Staphylococcus aureus (MRSA) in vitro and ex vivo. Methods: Green tea coarse powder was extracted by distilled water using high-pressure extraction. The total of phenolic and tannin contents was determined using spectrophotometry, and epigallocatechin gallate (EGCG) content was analyzed using Ultra-Fast Liquid Chromatography. Minimum Inhibitory Concentration (MIC) against MRSA was determined using a microdilution assay. Antibacterial assay of the combination of the extract and amoxicillin was performed using employing-checkerboard microdilution and agar diffusion assays. Results: The results exhibited that the green tea extract (GTE) contained total phenolic content of 545.6 ± 4.7 mg GAE/g extract; total tannin content of 356.6 ± 4.1 mg EGCG equivalent /g extract and EGCG of 221.1 ± 11.6 mg/g extract. The MICs combinatorial of GTE and ¼ MIC of amoxicillin was 75 µg/mL. Fractional Inhibitory Concentration Index value was 0.28, indicating that there was a synergy effect between amoxicillin and green tea extract. Essentially, the inhibitory zone diameter obtained by amoxicillin combined with ¼ MIC of GTE was two-fold than the zone produced by only amoxicillin. Although not significant, in ex vivo study, this combination was able to enhance the antibacterial activity of rat’s plasma against MRSA in vivo after the oral administration of GTE and amoxicillin. Conclusions: The results presented here serve as proof of concept for the enhancement of the antimicrobial activity of synthetic antibiotics when combined with a natural product.

Pharmacokinetic profile of amoxicillin and its glucuronide-like metabolite when administered subcutaneously to koalas (Phascolarctos cinereus).

Amoxicillin was administered as a single subcutaneous injection at 12.5mg/kg to four koalas and changes in amoxicillin plasma concentrations over 24hr were quantified. Amoxicillin had a relatively low average±SD maximum plasma concentration (Cmax ) of 1.72±0.47µg/ml; at an average±SD time to reach Cmax (Tmax ) of 2.25±1.26hr, and an elimination half-life of 4.38±2.40hr. The pharmacokinetic profile indicated relatively poor subcutaneous absorption. A metabolite was also identified, likely associated with glucuronic acid conjugation. Bacterial growth inhibition assays demonstrated that all plasma samples other than t=0hr, inhibited the growth of Escherichia coli ATCC 25922 and Staphylococcus aureus ATCC 29213 to some extent. Calculated pharmacokinetic indices were used to predict whether this dose could attain a plasma concentration to inhibit some susceptible Gram-negative and Gram-positive pathogens. It was predicted that a twice daily dose of 12.5 mg/kg would be efficacious to inhibit susceptible bacteria with an amoxicillin minimum inhibitory concentration (MIC)≤0.75µg/ml such as susceptible Bordetella bronchiseptica, E.coli, Staphylococcus spp. and Streptococcus spp. pathogens.

Nationwide antibiotic resistance mapping of Helicobacter pylori in Korea: A prospective multicenter study.

The eradication rates for Helicobacter pylori have decreased in Korea although the prevalence of this bacterium has also decreased. Antibiotic resistance is likely to be a crucial factor in H.pylori eradication success, and we therefore mapped these resistance patterns nationwide in Korea. Five hundred and ninety adult subjects were prospectively enrolled from 2017 to 2018 from 15 centers across six geographic areas of Korea. A total of 580 biopsy tissues had been sampled from these patients during an upper endoscopy and were frozen at -80°C and delivered to a central laboratory. The agar dilution method was used to determine the minimum inhibitory concentration of amoxicillin, clarithromycin, metronidazole, tetracycline, ciprofloxacin, and levofloxacin for each H.pylori isolate. The culture success rate was 60.2% (349/580). Resistance rates against clarithromycin, metronidazole, amoxicillin, tetracycline, levofloxacin, and ciprofloxacin were 17.8%, 29.5%, 9.5%, 0%, 37.0%, and 37.0%, respectively. The geographic distribution of metronidazole and quinolone resistance was highly variable. Some subjects had multiple H.pylori strains in the antrum and body of the stomach and showed a heterogeneous resistance profile between these anatomic areas. The H.pylori multidrug resistance (MDR) rate was 25.2% (88/349) among amoxicillin, clarithromycin, metronidazole, tetracycline, and quinolone and 11.2% (39/349) among four of these major antibiotics except for quinolone. The Seoul and Chungcheong areas showed a relatively lower MDR rate. The antibiotic resistance of H.pylori differs by drug and geographic area in Korea. Detailed nationwide antibiotic resistance mapping is needed to develop an effective H.pylori eradication strategy.

Comparative Emergence of Resistance to Clofoctol, Erythromycin, and Amoxicillin against Community-Acquired Bacterial Respiratory Tract Pathogens in Italy

Due to increasing bacterial resistance and poor availability of new antibiotics, physicians need to use old, still active antibiotics more frequently. In this study, we focused on clo­foctol and aimed to verify the emergence of clofoctol resistance over time. Additionally, the ability of clofoctol to induce resistance under static and dynamic conditions was evaluated. The minimum inhibitory concentration (MIC) values measured in pathogens isolated from 1990 to 1995 were compared to those isolated from 2017 to 2018. The behaviour of clofoctol is similar to that of amoxicillin, while erythromycin shows a different behaviour with an increase in MIC. A rapid decline in CFUs with complete eradication at 96 and 120 h in the case of clofoctol and amoxicillin, respectively, was observed in a dynamic in vitro model of a pharmacokinetic simulation. Erythromycin provides a reduction in CFUs of approximately one order of magnitude for up to 72 h, and then re-growth is observed. The MIC trend was observed during 5 days of kinetic simulation. The clofoctol MICs remain almost stable up to 96 h, after which the colonies are no longer detectable. The MICs of amoxicillin show a 2-fold increase starting from 36 h; however, at 120 h the colonies are no longer detectable. The MICs of erythromycin show a progressive increase starting from 72 h and reaching 32-fold. Clofoctol maintains its activity towards the common pathogens of respiratory tract infections and, similarly to amoxicillin, does not induce resistance in a strain of Streptococcus pneumoniae, resulting in complete eradication, while erythromycin was able to select resistant mutants.

Pharmacodynamics of amoxicillin against field isolates ofStreptococcus parauberisfrom olive flounder (Paralichthys olivaceus)

Olive flounder is the most important species for the Northeast Asian fish farming industry. However, this species is substantially affected by multiple infectious agents, including Streptococcus parauberis. Evaluation of antibiotics before their application is critical to treat infections and prevent drug resistance. Therefore, in this study, the pharmacodynamics of amoxicillin (AMX) and other antimicrobials against the planktonic- and biofilm-forming bacteria were assessed. The minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC) and Time–kill curve assay were analysed using micro-dilution method. The minimum biofilm eradicating concentration (MBEC) was determined using the Calgary Biofilm device. The effects of temperature, pH, hardness and salinity were detected for both planktonic- and biofilm-forming bacteria. The MIC of AMX ranged from 0.015 to 2 μg/ml, whereas that of cephalexin (CEP), enrofloxacin (ENR) and oxytetracycline (OTC) ranged from 0.125 to 256, 0.125 to >512 and 0.25 to >512 μg/ml respectively. No bacteria were resistant against AMX, while the percentage of resistance to CEP, OTC and ENR were 68.7%, 52.6% and 11.1% respectively. The IC50 of AMX, CEP, ENR and OTC was 0.03, 0.091, 0.015 and 0.213 μg/ml respectively. The MBEC of amoxicillin against S. parauberis ranged from 0.5 to 16 μg/ml. Higher rates of bacterial growth were obtained at 30°C, pH = 8 and salinity of 7.5–10 ppt. The hardness of the media suppressed the bacterial growth. In conclusion, AMX was found to be effective against both the planktonic and the biofilm forms of the prominent fish pathogen, S. parauberis.

In vitro study and characterization of cotton fabric PLA composite as a slow antibiotic delivery device for biomedical applications

Wound treatment remains a challenge to many clinicians because of the complexities of the wound healing process. The choice of dressing depends on a number of factors such as wound type, location, and injury extension, as well as the patient's health status. All of these factors increase the complexity and difficulty of utilizing a single type of dressing. The focus of this study was centered on developing a woven cotton fabric polylactic acid (PLA) composite as a low drug delivery device for biomedical applications. A hand weaving method was employed in developing the fabric to control its porosity. Fabrics with three different pore sizes 0.5 mm, 1.0 mm, and 1.5 mm were developed with a natural cotton yarn of 36 Tex and the resulting fabrics were used for composite development. Three different PLA concentrations 0.01 g/mL, 0.03 g/mL, and 0.06 g/mL were used to study the effects of the PLA/fabric ratio on the mechanical properties. The antibiotic amoxicillin was used in the study. This drug release study was monitored by UV-Vis spectrophotometry, while mechanical testing was performed with the Instron 5566 universal materials testing system. The results suggested that drug-loading capacity increases with decreasing fabric porosity. The release profiles from these devices followed a two-stage pattern, and the release mechanism appears to be a mixed transport system. This includes diffusion and possibly super case II kinetics, as well as a release due to damage to the composite surface through dissolution. The amount of released concentration exceeded the minimum inhibitory concentration of amoxicillin against Staphylococcus aureus. Degradation of the fabric composites is suggested as influencing the drug release rate. The water absorption ability of composites decreases with increasing PLA concentrations. The mechanical properties of composites were consistent with the fabric's density and weight. To design the ideal wound dressing materials, consideration of all these aforementioned properties are required in order to incorporate the desired functions to support tissue regeneration and healing while limiting bacterial infections. The findings from this research suggest that the developed devices could be used for wound dressing applications on sites where a water-resistant dressing is required, thus aiding in the prevention of bacterial contamination of the primary dressing.

Study of Multidrug Resistance Pattern among Escherichia coli isolated from patients with Urinary tract infection

Objective: Urinary tract infections (UTIs) are some of the most common bacterial infections encountered in community and cause of significant morbidity and high medical cost. Escherichia coli is the most common pathogen belongs to Enterobacteriaceae family responsible for majority of UTI infections. Antimicrobial drugs have been routinely prescribed for empirical treatment of UTIs which has led to a dramatic increase in antibiotic resistance pattern of E. coli. The aim of present study was to analyse the multidrug resistance patterns (MDR) of E. coli isolated from UTI patients.Methods: A total of 80 urine samples collected from the patients suspected of having UTI attending Maharishi Markandeshwar Institute of Medical Sciences and Research (MMIMSR), Mullana, Ambala were cultured using standard microbiological techniques. Antibiotic susceptibility testing of E.coli was done by using minimum inhibitory concentration (MIC). MIC of tetracycline, doxycycline, azithromycin, erythromycin, ciprofloxacin, levofloxacin, ampicillin, amoxicillin and amikacin was done by agar dilution method.Results: Of the total 46 isolates contributing 33 females and 13 males were confirmed as E. coli. About 51.34% of the female patients belonged to the age group 21-40 yr and 53.84% of the male population belonged to 41-80 yr were found to be more susceptible to UTI infection. All isolates confirmed as E.coli were found to be multidrug resistant. 80% of the isolates exhibited MICs higher than 1000mg/L against β-lactams. 20% of the E. coli isolates exhibited MICs higher than 1000mg/L against ciprofloxacin, amikacin and erythromycin. 23% and 95% of E. coli isolates exhibited MICs less than 128 mg/L against doxycycline and levofloxacin respectively.Conclusion: The present study revealed the decreased susceptibility of the E.coli to all drugs. E. coli resistance profile to beta lactams, quinolones, macrolides, tetracyclines and aminoglycosides were also found to be quite high in this study emphasizing the need to educate public about appropriate use of antibiotics.NA