System for real-time monitoring of mutation-in-progress

Aims:  There has been an increasing number of pathogens becoming resistant to multiple classes of antibiotics. The study on how mutation emerges is therefore crucial to promote further understanding in this area. Conventional methods for such studies involve the monitoring of growth by standard plate count and biomolecular sequencing. This is however tedious and not cost effective. The aim of this paper is thus to introduce a novel system that enables real-time monitoring of bacterial ‘mutation-in-progress’. Methods and Results:  This system provides real-time data, thus enabling confirmatory and further work to be performed at the important points when mutation is initiated. The system integrates spectroscopic techniques as the detection system and various supporting systems, such as a nutrient replenishing system, a pH control system and a waste system to allow for extended monitoring. In this paper, the feasibility of monitoring the emergence of ciprofloxacin resistance in Staphylococcus aureus was demonstrated as an initial example. The integrated system was found to require significantly less material resource and manpower compared with conventional techniques. Conclusions:  The novel system to monitor bacterial mutation-in-progress is presented. The work reported herein demonstrates such a system to be effective and efficient in performing real-time monitoring of mutation-in-progress, especially in extended time frames for mutation into the weeks and months. Significance and Impact of the Study:  With the successful optimization of this system, researchers can learn about the dynamics of antibiotic resistance and further understand how the mutation of bacteria occurs.     

Promising antibacterial agents against multidrug resistant Staphylococcus aureus

Rapid emergence of multidrug resistant Staphylococcus aureus infections has created a critical health menace universally. Resistance to all the available chemotherapeutics has been on rise which led to WHO to stratify Staphylococcus aureus as high tier priorty II pathogen. Hence, discovery and development of new antibacterial agents with new mode of action is crucial to address the multidrug resistant Staphylococcus aureus infections. The egressing understanding of new antibacterials on their biological target provides opportunities for new therapeutic agents. This review underlines on various aspects of drug design, structure activity relationships (SARs) and mechanism of action of various new antibacterial agents and also covers the recent reports on new antibacterial agents with potent activity against multidrug resistant Staphylococcus aureus. This review provides attention on in vitro and in vivo pharmacological activities of new antibacterial agents in the point of view of drug discovery and development.     

The influence of green fluorescent protein incorporation on bacterial physiology: a note of caution

AIMS: To investigate the effect of green flourescent protein (GFP) incorporation on bacterial physiology. METHODS AND RESULTS: Comparisons were made between four different isogenic pairings of non-GFP-containing parents and their GFP-containing transformants with respect to growth rate and antimicrobial susceptibility. For the latter, sensitivities to 12 different antibiotics were measured initially by disc-diffusion assay, and then subsequently by generation of dose-dependent survival curves for 1 h exposure to different concentrations of tetracycline, ciprofloxacin and cetrimide USP. Whilst no significant difference in growth rate was observed, GFP-containing strains were uniformly and significantly more sensitive to all antimicrobial agents tested, excluding the beta-lactams, than their respective non-GFP-containing counterparts. CONCLUSIONS: GFP incorporation has a significant effect on bacterial physiology and can modulate antimicrobial susceptibility. SIGNIFICANCE AND IMPACT OF THE STUDY: Transformation with GFP can affect the physiology of bacterial cells. This may therefore affect the quality and accuracy of data generated depending on the application for which GFP is used.     

Biosorption Behavior of Ciprofloxacin onto Enteromorpha prolifera: Isotherm and Kinetic Studies

The studies aimed at the feasibility of using Enteromorpha prolifera for the removal of ciprofloxacin from aqueous solutions. Batch experiments were carried out for the biosorption of ciprofloxacin onto Enteromorpha prolifera. The factors affecting the biosorption process such as the initial concentration, dosage, pH and the contact time were studied. Enteromorpha prolifera exhibited a maximum biosorption capacity of 21.7 mg/g. The pseudo-second-order kinetic model described the ciprofloxacin biosorption process with a good fitting. The optimum pH of ciprofloxacin adsorbed by Enteromorpha prolifera was 10. Biosorption equilibrium studies demonstrated that the biosorption followed Freundlich isotherm model, which implied a heterogeneous biosorption phenomenon.     

Chemical composition and synergistic effect of three Moroccan lavender EOs with ciprofloxacin against foodborne bacteria: a promising approach to modulate antimicrobial resistance

The aim of this study was to determine the chemical profile of the essential oils (EOs) of three Moroccan lavender species (Lavandula pedunculata, LP; Lavandula angustifolia, LA; and Lavandula maroccana, LM) and to investigate, for the first time, the synergistic effect of the optimal mixture of the EOs with conventional antibiotic ciprofloxacin against three pathogenic foodborne bacteria. Gas chromatography/mass spectrometry analysis showed that eucalyptol (39·05%), camphor (24·21%) and borneol (8·29%) were the dominant compounds of LA-EO. LP-EO was characterized by the abundance of camphor (74·51%) and fenchone (27·06%), whereas carvacrol (42·08%), camphor (17·95%) and fenchone (12·05%) were the main constituents of LM-EO. EOs alone or combined showed a remarkable antimicrobial activity against the tested bacteria with minimum inhibitory concentrations (MICs) ranging from 3·53 to 15·96 mg ml⁻¹. The optimal mixture, calculated using a mixture design, corresponded to 19% LA, 38% LP and 43% LM. All combination of the EOs and the best EO mixture with ciprofloxacin exhibited a total synergism with fractional inhibitory concentration index values ranging from 0·27 to 0·37. The best EO mixture showed the highest gain of 128-fold, especially against Salmonella spp., more than that found testing the EOs separately. These findings should be taken into consideration for a possible application in the pharmaceutical and food industries.     

Selecting for development of fluoroquinolone resistance in a Campylobacter jejuni strain 81116 in chickens using various enrofloxacin treatment protocols

Aims: To determine the effect of various enrofloxacin dose regimes on the colonization and selection of resistance in Campylobacter jejuni strain 81116P in experimentally colonized chickens. Methods and Results: Two experiments were undertaken, in which 14‐day‐old chickens were colonized with 1 × 10⁷–1 × 10⁹ CFU g^?1Camp. jejuni strain 81116P and then treated with enrofloxacin at 12–500 ppm in drinking water for various times. Caecal colonization levels were determined at various time‐points after start‐of‐treatment, and the susceptibility of recovered isolates to ciprofloxacin was monitored. Resistance was indicated by growth on agar containing 4 μg ml^?1 ciprofloxacin, MICs of 16 μg ml^?1 and the Thr86Ile mutation in gyrA. Enrofloxacin at doses of 12–250 ppm reduced Camp. jejuni colonization over the first 48–72 h after start‐of‐treatment. The degree of reduction in colonization was dose, but not treatment time, dependent. In all cases, maximal colonization was re‐established within 4–6 days. Fluoroquinolone‐resistant organisms were recoverable within 48 h of start‐of‐treatment; after a further 24 h all recovered isolates were resistant. In contrast, a dose of 500 ppm enrofloxacin reduced colonization to undetectable levels within 48 h, and the treated birds remained Campylobacter negative throughout the remaining experimental period. By high pressure liquid chromatography, for all doses, the maximum concentrations of enrofloxacin and ciprofloxacin in the caecal contents were detected at the point of treatment completion. Thereafter, levels declined to undetectable by 7 days post‐treatment withdrawal. Conclusions: In a model using chickens maximally colonized with Camp. jejuni 81116P, treatment with enrofloxacin, at doses of 12–250 ppm in drinking water, enables the selection, and clonal expansion, of fluoroquinolone‐resistant organisms. However, this is preventable by treatment with 500 ppm of enrofloxacin. Significance and impact of the study: Treatment of chickens with enrofloxacin selects for resistance in Camp. jejuni in highly pre‐colonized birds. However, a dose of 500 ppm enrofloxacin prevented the selection of resistant campylobacters.     

Synthesis and antibacterial activity of a new series of 3-[3-(substituted phenyl)-1-phenyl-1H-pyrazol-5-yl]-2H-chromen-2-one derivatives

A series of 3-[3-(substituted phenyl)-1-phenyl-1H-pyrazol-5-yl]-2H-chromen-2-one (4a–k) were synthesized by reaction of 3-[2,3-dibromo-3-(substituted phenyl)propanoyl]-2H-chromen-2-one (3 a-k) with phenyl hydrazine in presence of triethylamine in absolute ethanol, characterized by spectral data and screened for their in vitro antibacterial activity against gram-positive and gram-negative bacteria. Among the series, compounds 4d, 4h and 4i displayed an encouraging antibacterial activity profile as compared to reference standard drug ciprofloxacin against tested bacterial strains.     

新疆西北地区原奶和手工奶酪中屎肠球菌耐药性及毒力基因分析

对来源于新疆西北地区的动物原奶和手工奶酪中的屎肠球菌的抗生素耐药性及毒力基因进行分析。采用纸片法检测屎肠球菌对13种不同抗生素敏感性以及PCR检测毒力基因的分布。原奶中屎肠球菌对环丙沙星、红霉素、四环素的耐药率为80%、15%、5%,此外,原奶中还出现3种耐药谱。奶酪中的屎肠球菌对环丙沙星、链霉素、利福平的耐药率分别为84.3%、40%和37.1%,但对其余抗生素的耐药率均低于9%,其中对万古霉素的耐药率为4.3%。此外,奶酪中屎肠球菌表现出17种耐药谱,其中一种耐药谱含10种抗生素。毒力基因agg(31.4%)、esp(34.3%)、gelE(37.1%)、efaAfm(32.9%)、cylA(30%)、cylB(7.1%)、cylM(8.6%)在奶酪中都有检测到,而在原奶中仅检测到gelE(15%)和efaAfm(65%)基因。原奶和手工奶酪中屎肠球菌的耐药性和毒力基因的分布显示手工奶酪对消费者身体健康具有安全隐患。