Isolation of Cronobacter spp. (formerly Enterobacter sakazakii) from infant food, herbs and environmental samples and the subsequent identification and confirmation of the isolates using biochemical, chromogenic assays, PCR and 16S rRNA sequencing

BACKGROUND: Cronobacter spp. (formerly Enterobacter sakazakii), are a group of Gram-negative pathogens that have been implicated as causative agents of meningitis and necrotizing enterocolitis in infants. The pathogens are linked to infant formula; however, they have also been isolated from a wide range of foods and environmental samples. RESULTS: In this study, 233 samples of food, infant formula and environment were screened for the presence of Cronobacter spp. in an attempt to find its source. Twenty nine strains were isolated from samples of spices, herbs, infant foods, and dust obtained from household vacuum cleaners. Among the 76 samples of infant food, infant formula, milk powder and non-milk dairy products tested, only one sample of infant food contained Cronobacter spp. (1.4%). The other Cronobacter spp. isolates recovered include two from household vacuum dust, and 26 from 67 samples of herbs and spices. Among the food categories analyzed, herbs and spices harbored the highest number of isolates, indicating plants as a possible reservoir of this pathogen. Initial screening with API 20E test strips yielded 42 presumptive isolates. Further characterization using 3 chromogenic media (α-MUG, DFI and EsPM) and 8 sets of PCR primers detecting ITS (internal transcribed spacer sequences), 16S rRNA, zpx, gluA, gluB, OmpA genes followed by nucleotide sequencing of some PCR amplicons did not confirm the identity of all the isolates as none of the methods proved to be free of both false positives or false negatives. The final confirmation step was done by 16S rRNA sequence analysis identifying only 29 of the 42 isolates as Cronobacter spp. CONCLUSION: Our studies showed that Cronobacter spp. are highly diverse and share many phenotypic traits with other Enterobacteriaceae members highlighting the need to use several methods to confirm the identity of this pathogen. None of the biochemical, chromogenic or PCR primers proved to be a reliable method for confirmation of the identity of the isolates as all of them gave either false positives or false negatives or both. It is therefore concluded that 16S rRNA sequencing is pivotal to confirm the identity of the isolates

The Hazard Content of Cadmium, Lead, and Other Trace Elements in Some Medicinal Herbs and Their Water Infusions

54 samples belonging to 23 herbal species (15 individuals and 8 mixtures) were analyzed for their contents of heavy metals in the raw materials and in their water infusions. Trace and toxic elements in these samples were determined by using inductively coupled plasma-atomic emission spectrometry (ICP-OES) following acid digestion. The order of decreasing mean metal concentrations in raw materials (mg/kg) was found to be as follows: Fe (440) > Mn (162) > Zn (45.8) > Cu (12) > Pb (10.4) > Ni (5.4) > Cr (2.9) > Co (0.91) > Cd (0.5). It was found that 21% of the analyzed samples contain both Cd and Pb above their permissible limits. However, the infusions produced from these plants were found to contain fewer amounts of metals than the raw materials. Studied metals had the following mass transfer percentages to the infusion solutions (Fe: 3.5%, Cd: 14%, Cr: 15%, Pb: 20%, Co: 29%, Ni: 31%, Zn: 36%, Cu: 48%, and Mn: 53%). The estimated daily intake calculated for the toxic elements Pb and Cd through the consumption of herbal infusions was far below the tolerable daily intake set by the World Health Organization (WHO)

Advanced determination of piezoelectric properties of AlN thin films on silicon substrates

Piezoelectric deformations of thin, aluminum nitride (AlN) layers, on top of a silicon substrate, were studied by numerical calculations and interferometric measurements. Our calculation by finite element method demonstrates that substrate deformation under the top electrode may be comparable to the electric field induced deformation in the thin AlN layer, for a given applied voltage. Simulations also show the effect of a clamped or free substrate condition and the relative contributions of d33 and d31 piezoelectric constants. A Laser scanning vibrometry technique was used to measure deformations in the top surface with sub-picometer vertical resolution. By comparing calculations and experimental data, quantitative information about both d33 and d31 constants can be obtained

The Phenomenon of Leadership Among Middle Management Leaders in Public Schools in Bahrain: Aspects of Performance, Personality Pattern Analysis, Impact Strategies, and Challenges

The concept of middle school management leadership refers to teachers who teach and have leadership roles. This study aimed to investigate the phenomenon of leadership among middle management leaders in the Kingdom of Bahrain who occupy the positions of heads or coordinators of school departments in public schools. The current study followed the qualitative methodology by analyzing the final projects of teachers who finished the Understanding Leadership course for teachers in 2022. The study sample consisted of (21) projects (presented by 5 males and 16 females) who occupy middle leadership positions in public schools. The study instrument was an analysis sheet that included the dimensions to be studied, the aspects of performance to be changed, personal leadership styles according to international standards and self-reflection, the impact strategies used, and the challenges and strategies used to confront them. The results of the study indicated that the most important aspects of schoolwork that these leaders believe to be the first to change our professional development for teachers, employment of digital empowerment tools, and meeting the needs of new teachers. The most practiced personal leadership styles according to international scales are democracy, diplomacy and transformational, while according to self-reflection they were democracy, transformational and servant. Finally, the most challenges faced by leaders were many educational and administrative tasks and dealing with negative personality patterns for teachers, and resistance to change. The most used strategies to confront these challenges were organizing work, managing time, and following up on the impact of professional development activities and development sessions. The study recommended adopting and implementing a national professional development program for these leaders and proposing complementary studies for this study

Impact of Integrated Learning Strategy on Language Skills Academic Achievement among University of Jordan Female Students

This purpose of this study is to analyze the impact of integrated learning strategy on language Skills educational achievement among female students at the University of Jordan. A quasi experimental study design was applied. Participants (n=40) were enrolled in Language Skills course for undergraduate students throughout the first semester of the academic year 2018/2019. Based on data provided by the Admission and Registration Unit in the University of Jordan, The students were randomly assigned to two groups: experimental (n=20) as well as control (n=20). To achieve the study goals an achievement test was applied as pre-test and post-test. ANCOVA analysis revealed a statistical differences at the significance level (α=0.05) within the research groups in overall average accomplishment test scores, with differences favoring the experimental group taught using an integrated learning strategy

Piezoelectric characterization of ain thin films on silicon substrates

The electric field induced deformations of thin piezoelectric, aluminium nitride (AlN) layers, on top ofa silicon substrate, were studied by numerical calculations and interferometric measurements. Our calculationby finite element method demonstrates that substrate deformation under the top electrode may be comparableto the deformation in the thin AlN layer, for a given applied voltage. Simulations also show the effect of aclamped or free substrate condition and the relative contributions of d33 and d31 piezoelectric constants. ALaser scanning vibrometry technique was used to measure deformations in the top surface with sub-picometervertical resolution. By comparing calculations and experimental data, quantitative information about both d31and d33 constants can be obtained

Simulation and laser vibrometry characterization of piezoelectric AlN thin films

In this paper, the electric field induced deformations of sputter-deposited piezoelectric aluminum nitride thin films sandwiched between electrodes on top of a silicon substrate are studied by numerical calculations and scanning laser interferometric measurements. In our calculations based on the finite element method, the results show the displacement of the top and bottom surfaces of both the thin film and the substrate, for either a free or a perfectly clamped structure. The confirmation that the bottom surface of the film is deformed reveals the limitations of techniques that only access the top surface, as well as the double-beam interferometric configuration, under specific conditions. In addition, the simulations demonstrate the dependence of the displacements on the size of the upper electrode and the contribution of the transverse piezoelectric coefficient d31 to the features of the displacement profiles. A laser scanning vibrometry technique was used to measure deformations on the top surface with subpicometer vertical resolution. By comparing the calculated and the experimental displacement profiles, an advanced approach is discussed to obtain accurate quantitative information of both coefficients d31 and d33

An Evolutionary Reduction Principle for Mutation Rates at Multiple Loci

A model of mutation rate evolution for multiple loci under arbitrary selection is analyzed. Results are obtained using techniques from Karlin (1982) that overcome the weak selection constraints needed for tractability in prior studies of multilocus event models. A multivariate form of the reduction principle is found: reduction results at individual loci combine topologically to produce a surface of mutation rate alterations that are neutral for a new modifier allele. New mutation rates survive if and only if they fall below this surface - a generalization of the hyperplane found by Zhivotovsky et al. (1994) for a multilocus recombination modifier. Increases in mutation rates at some loci may evolve if compensated for by decreases at other loci. The strength of selection on the modifier scales in proportion to the number of germline cell divisions, and increases with the number of loci affected. Loci that do not make a difference to marginal fitnesses at equilibrium are not subject to the reduction principle, and under fine tuning of mutation rates would be expected to have higher mutation rates than loci in mutation-selection balance. Other results include the nonexistence of 'viability analogous, Hardy-Weinberg' modifier polymorphisms under multiplicative mutation, and the sufficiency of average transmission rates to encapsulate the effect of modifier polymorphisms on the transmission of loci under selection. A conjecture is offered regarding situations, like recombination in the presence of mutation, that exhibit departures from the reduction principle. Constraints for tractability are: tight linkage of all loci, initial fixation at the modifier locus, and mutation distributions comprising transition probabilities of reversible Markov chains.Comment: v3: Final corrections. v2: Revised title, reworked and expanded introductory and discussion sections, added corollaries, new results on modifier polymorphisms, minor corrections. 49 pages, 64 reference