Search

Escherichia coli infection is the major bacterial disease affecting the poultry industry and the continuous use of antibiotics in poultry farming has resulted in antibiotic resistance. So this study was planned to evaluate the use of an ecologically safe alternative to fight against infections. The leaf gel of the Aloe vera plant was selected based on its antibacterial activity assessed in in-vitro tests. The objective of the present study was to evaluate the effect of A. vera leaf extract supplementation on the severity of clinical signs and pathological lesions, mortality rate, levels of antioxidant enzymes, and immune response in experimentally E. coli-infected broiler chicks. Broiler chicks were supplemented with aqueous Aloe vera Leaf (AVL) extract @ 20 ml per liter of water from day one of age. After seven days of age, they were experimentally infected with E. coli O78 @ 10 7 CFU/0.5 ml intraperitoneally. Blood was collected at weekly intervals up to 28 days and assayed for antioxidant enzyme assays, and humoral and cellular immune response. The birds were observed daily for clinical signs and mortality. Dead birds were examined for gross lesions and representative tissues were processed for histopathology. The activities of antioxidants, Glutathione reductase (GR), and Glutathione-S-Transferase (GST) were significantly higher than the control infected group. The E. coli-specific antibody titer and Lymphocyte stimulation Index were comparatively higher in the AVL extract-supplemented infected group as compared to the control infected group. No considerable change was noted in the severity of clinical signs and pathological lesions, and mortality. Thus, Aloe vera Leaf gel extract enhanced the antioxidant activities and cellular immune responses of infected broiler chicks to combat this infection., Competing Interests: Conflict of Interest The authors declare no conflict of interest., (Copyright © 2023 Elsevier B.V. All rights reserved.)

A periodic jet of carbon dioxide (CO2) aerosols is a very quick and effective mechanical technique to remove biofilms from various substrate surfaces. However, the impact of the aerosols on the viability of bacteria during treatment has never been evaluated. In this study, the effects of high-speed CO2 aerosols, a mixture of solid and gaseous CO2, on bacteria viability was studied. It was found that when CO2 aerosols were used to disperse biofilms of Escherichia coli, they led to a significant loss of viability, with approximately 50% of the dispersed bacteria killed in the process. By comparison, 75.6% of the biofilm-associated bacteria were viable when gently dispersed using Proteinase K and DNase I. Indirect proof that the aerosols are damaging the bacteria was found using a recombinant E. coli expressing the cyan fluorescent protein, as nearly half of the fluorescence was found in the supernatant after CO2 aerosol treatment, while the rest was associated with the bacterial pellet. In comparison, the supernatant fluorescence was only 9% when the enzymes were used to disperse the biofilm. As such, these CO2 aerosols not only remove biofilm-associated bacteria effectively but also significantly impact their viability by disrupting membrane integrity.

The emergence of resistance presents a debilitating change in the management of infectious diseases. Currently, the temporal relationship and interplay between various mechanisms of drug resistance are not well understood. A thorough understanding of the resistance development process is needed to facilitate rational design of countermeasure strategies. Using an in vitro hollow-fiber infection model that simulates human drug treatment, we examined the appearance of efflux pump (acrAB) overexpression and target topoisomerase gene (gyrA and parC) mutations over time in the emergence of quinolone resistance in Escherichia coli. Drug-resistant isolates recovered early (24 h) had 2- to 8-fold elevation in the MIC due to acrAB overexpression, but no point mutations were noted. In contrast, high-level (≥ 64× MIC) resistant isolates with target site mutations (gyrA S83L with or without parC E84K) were selected more readily after 120 h, and regression of acrAB overexpression was observed at 240 h. Using a similar dosing selection pressure, the emergence of levofloxacin resistance was delayed in a strain with acrAB deleted compared to the isogenic parent. The role of efflux pumps in bacterial resistance development may have been underappreciated. Our data revealed the interplay between two mechanisms of quinolone resistance and provided a new mechanistic framework in the development of high-level resistance. Early low-level levofloxacin resistance conferred by acrAB overexpression preceded and facilitated high-level resistance development mediated by target site mutation(s). If this interpretation is correct, then these findings represent a paradigm shift in the way quinolone resistance is thought to develop.

Objectives: Fluoroquinolones are commonly believed to exhibit concentration-dependent killing, but time-kill studies have revealed that fluoroquinolone activity could be a complex combination of concentration-dependent and -independent killing. We had previously developed a mathematical modelling framework to describe the dynamics of bacterial populations under the effect of antimicrobials, which could facilitate the design of optimal dosing regimens. Our objective was to extend the framework to describe the effect of fluoroquinolones on heterogeneous populations of Escherichia coli and Staphylococcus aureus., Methods: A mathematical model was fitted to time-kill data of moxifloxacin (0-128× MIC; MIC = 0.0625 mg/L) against E. coli MG1655 and levofloxacin (0-64× MIC; MIC = 0.25 mg/L) against S. aureus ATCC 29213 over 24 h. Based on the best-fit model parameters, the likelihood of resistance development associated with various dosing regimens was predicted. Subsequently, in vitro studies with a hollow-fibre infection model were selectively performed to validate the mathematical model predictions, using simulated human half-lives (moxifloxacin = 12 h; levofloxacin = 5-7 h)., Results: Bacterial regrowth and resistance development were observed with suboptimal dosing regimens. Parallel time-growth studies substantiated the modelling assumption that there was no significant biofitness cost in resistant mutants. The mechanism of fluoroquinolone resistance was confirmed by PCR., Conclusions: Our model was found to be reasonable in characterizing biphasic killing of fluoroquinolones and predicting dosing regimens to suppress resistance development. Our work demonstrated improvements resulting from using the proposed mathematical modelling as a decision support tool for guiding the design of dosing regimens.

Objectives: Escherichia coli is the leading bacterial species implicated in intra-abdominal infections. In these infections a high bacterial burden with pre-existing resistant mutants are likely to be encountered and resistance could be amplified with suboptimal dosing. Our objective was to investigate the pharmacodynamics of moxifloxacin against a high inoculum of E. coli using an in vitro hollow fibre infection model (HFIM)., Methods: Three wild-type strains of E. coli (ATCC 25922, MG1655 and EC28044) were studied by exposing approximately 2 x 10(8) cfu/mL (20 mL) to escalating dosing regimens of moxifloxacin (ranging from 30 to 400 mg, once daily). Serial samples were obtained from HFIM over 120 h to enumerate the total and resistant subpopulation. Quinolone resistance-determining regions of gyrA and parC of resistant isolates were sequenced to confirm the mechanism of resistance., Results: The pre-exposure MIC of the three wild-type strains was 0.0625 mg/L. Simulated moxifloxacin concentration profiles in HFIM were satisfactory (r(2) >or= 0.94). Placebo experiments revealed natural mutants, but no resistance amplification. Regrowth and resistance amplification was observed between 30 mg/day (AUC/MIC = 47) and 80 mg/day dose (AUC/MIC = 117). Sustained bacterial suppression was achieved at >or=120 mg/day dose (AUC/MIC = 180). Point mutations in gyrA (D87G or S83L) were detected in resistant isolates., Conclusions: Our results suggest that suboptimal dosing may facilitate resistance amplification in a high inoculum of E. coli. The clinical dose of moxifloxacin (400 mg/day) was adequate to suppress resistance development in three wild-type strains. Clinical relevance of these findings warrants further in vivo investigation.

Abstract: An electrochemical genosensor based on 1-fluoro-2-nitro-4-azidobenzene (FNAB) modified octadecanethiol (ODT) self-assembled monolayer (SAM) has been fabricated for Escherichia coli detection. The results of electrochemical response measurements investigated using methylene blue (MB) as a redox indicator reveal that this nucleic acid sensor has 60s of response time, high sensitivity (0.5×10−18 M) and linearity as 0.5×10−18–1×10−6 M. The sensor has been found to be stable for about four months and can be used about ten times. It is shown that water borne pathogens like Klebsiella pneumonia, Salmonella typhimurium and other gram-negative bacterial samples has no significant effects in the response of this sensor. [ABSTRACT FROM AUTHOR]