Additionally, given the high rate of infectivity of SARS-CoV-2, we almost certainly would see cases of reinfection after documented resolution at this level of global spread and caseload, while we currently have none documented obviously I am not suggesting that reinfection is not possible, for it is most certainly possible, because some unlucky folks who might be able to fight off the acute virus lack fully function immune systems. In my opinion, the search for the golden specific immunoglobulin and titer that denotes immunity is not as important as simply defining how robust post-resolution immunity is.
We should build models for how infection would spread with these various levels of reinfection, then continually run and reiterate the model based on the enormous case-load building thanks to now millions of infections, even within the US. I think our researchers are losing the forest for the trees on this, focusing on the fundamental, academic immunity, instead of looking at this fire burning throughout the human population and using contact tracing and predictive data analytics to adjust our knowledge based on these conclusions.
This type of thinking will be necessary to allow for some return to a new form of normalcy including little things that keep us going like socialization and procreation.
It is also worth noting that all of the above data, whether the specific immunity-indicating antibody or the general reinfection rate, are based on the current proteomic structure of the outside of the virus, which is obviously subject to change. The rate of change and probability of change even themselves are subject to change, and increasing as the total infected pool of humans increases. Long story short, we are defining an evolving entity, and our tools to define it must evolve similarly.
Steven Reid, M. Doctor Lifeline. Are there examples of other coronavirus infections in which a vaccine produces longer lasting or more effective immunity than that achieved after recovery from an infection with the wild virus?
If we know so little about the natural course of immunity following infection from SARS-CoV-2, what is the basis for the optimism regarding the efficacy of an as yet non-existent vaccine? Is it reasonable to maintain a lockdown scenario until such time as this hoped-for vaccine becomes available? I ask these questions non-rhetorically out of genuine ignorance, concern, and curiosity. WHO reports ten million cases of covid in the world since the beginning of the pandemic.
The authors note "to date, no human reinfections with SARS-CoV-2" and conclude that it may be possible that antibodies protect against reinfection "at least temporarily. A more balanced treatment would acknowledge that antibodies protect humans against the vast majority of viral diseases and the lack of observed covid recurrences suggests that antibodies are likely to explain this—as is cell-mediated immunity.
Of course, more research is needed. By emphasizing our lack of knowledge and not acknowledging evidence that antibodies are usually protective, the authors do a disservice. This is the kind of excessive caution that cost CDC its reputation at the beginning of the pandemic. Access your subscriptions. Access through your institution. Add or change institution. Free access to newly published articles. Purchase access. Rent article Rent this article from DeepDyve.
Access to free article PDF downloads. Save your search. Customize your interests. Create a personal account or sign in to:. Privacy Policy. Interestingly, analysis of the spent medium using an Agrobacter tumefaciens indicator strain failed to detect AHLs.
Nevertheless, the authors concluded that P. Although quorum sensing signalling molecules have been detected in cold stored milk and milk derivatives, their exact role in the spoilage process is still not clear and further work on this topic is clearly warranted Bai and Rai, Bai AJ, Rai VR Bacterial quorum sensing and food industry. Specifically, the topic of inter-species communication via broad range signalling molecules e.
The genus Pseudomonas is the most heterogeneous and ecologically significant group of known bacteria. Owing to the fact that the nutritional requirements of Pseudomonas spp. Ann Microbiol — As such, it is not surprising that members of the genus Pseudomonas have long been recognised as the predominant group of psychrotrophic bacteria recovered from spoiled refrigerated milk Chen et al.
Among the pseudomonads, P. Microbiol Res — Furthermore, these species are able to proliferate in milk, an environment where the concentration of free iron is low, due to the production of the diffusible fluorescent pigment pyoverdine, which acts as a siderophore, allowing the bacteria to effectively sequester iron from lactoferrin Mcphee and Griffiths, Mcphee JD, Griffiths MW Psychrotrophic bacteria Pseudomonas spp.
De Jonghe et al. The numbers of Pseudomonas were similar during the first 72 h of storage at either temperature. Unfortunately, direct comparisons between the work of De Jonghe et al. In this context, the importance of the choice of strain was highlighted in the work of Jaspe et al. Environ Microbiol — Similarly, He et al. Pseudomonads also predominated in the microbiota cultured from the crevices of cleaned devices sampled at a milk processing plant, demonstrating their potential roles as post-collection contaminants Cleto et al.
The ability of this group of microbes to resist cleaning is linked to the fact that many species are effective biofilm producers Bai and Rai, Bai AJ, Rai VR Bacterial quorum sensing and food industry.
The complex and multi-layered structures of biofilms allow the bacterial communities to live in a sessile and protected environment.
Yet, when population densities in the biofilms become high, bacteria are released into the environment, providing a continuous source of planktonic bacteria capable of replication within milk Bai and Rai, Bai AJ, Rai VR Bacterial quorum sensing and food industry.
This was particularly the case for fluorescent pigment-producing pseudomonads, where the biochemical results were considered to be doubtful.
In view of this controversy, the authors recommended the use of genotypic identification systems in future studies. A comparative evaluation of phenotypic and genotypic methods for the identification of food-associated psychrotrophic Pseudomonas spp. In this study, phenotypic data identified the bacteria as P. The study of Hantsis-Zacharov and Halpern Hantsis-Zacharov E, Halpern M Culturable psychrotrophic bacterial communities in raw milk and their proteolytic and lipolytic traits.
Pseudomonas and Acinetobacter were recorded as the predominant genera among the Gram-negatives, with 33 and 29 isolates, respectively. Marchand et al. The authors recommended the increased application of genotypic identification methods to ensure accuracy, and they also called for a revision of the taxonomic status of P.
Furthermore, they considered it likely that misidentification of many proteolytic isolates as P. Using phenotypic methods, the authors identified the highly proteolytic Pseudomonas strain 1A4R as either P.
In view of the divergent data, strain 1A4R was classified as a Pseudomonas sp. Improvements in identification at the species and sub-species levels should become possible through the use of highly specific typing methods such as the Multilocus Sequence Typing MLST scheme developed by Andreani et al.
However, it should be noted that the elevated costs of such sequencing-based methods is likely to limit their use, at least in the short term, to academic studies. Indigenous bacterial communities in raw milk, including potentially lipolytic and proteolytic psychrotrophs, are already present when the milk arrives at the dairy plant, making the rapid and accurate identification of the raw milk microbiota a necessary prerequisite for the elaboration of methods to circumvent spoilage Van Der Vossen and Hofstra, Van Der Vossen JMBM, Hofstra H DNA based typing, identification and detection systems for food spoilage microorganisms: development and implementation.
Based on the observation that initial psychrotrophic counts of milk are frequently very low Mcphee and Griffiths, Mcphee JD, Griffiths MW Psychrotrophic bacteria Pseudomonas spp. Traditional microbiological approaches to the study of psychrotrophs in milk based on phenotypic characterisation are time consuming, lack discriminatory power and sensitivity and are often ineffective in establishing a causal relationship between the contamination of the finished product and the environmental source Dogan and Boor, Dogan B, Boor KJ Genetic diversity and spoilage potentials among Pseudomonas spp.
Furthermore, the inability to discriminate between closely related organisms can lead to misidentification, and the slow turnaround time of the results makes phenotypic testing useful mainly for retrospective evaluation Ercolini, Ercolini D PCR-DGGE fingerprinting: novel strategies for detection of microbes in food.
J Microbiol Methods — Molecular analyses of microbes offer some advantages over phenotypic methods, including speed and the ability to provide precise identification of microorganisms from the genus to the strain level, depending on the system used. The discrimination between subspecies and strains is helpful for investigating the routes and sources of contamination Ercolini, Ercolini D PCR-DGGE fingerprinting: novel strategies for detection of microbes in food. The concept of viable but non-culturable VBNC bacteria refers to bacteria with metabolic activity and the ability to reproduce under suitable conditions, but which lack the capability to produce visible growth under standard conditions.
Interest in the role of VBNC in food spoilage has increased due to the observation that some disinfection procedures such as pasteurisation of milk and chlorination of water can cause bacteria to switch to the VBNC form Ozcakir, Ozcakir O Viable but non-culturable form of bacteria.
Mikrobiyol Bul — High-throughput sequencing of 16S rDNA and real-time quantitative PCR qPCR analysis were used in combination with flow cytometry to examine the microbial content of raw and pasteurised cow milk Quigley et al. In contrast to findings from culture-based studies Ranieri et al. Interestingly, the presence of pseudomonads in pasteurised milk has traditionally been considered to be the result of post-pasteurisation contamination Van Tassell et al.
However, it is worth considering that the survival and subsequent transition from VBNC to fully viable cells may explain, at least in part, the frequent isolation of this genus from pasteurised milk.
They will be labeled with the letters A, B, C, D, and E, so as to keep them anonymous and to avoid influencing the reader with any preconceptions that might be created about the textbooks evaluated in this study. However, readers will be able to implement the procedure explained below to critically review the textbooks they use with their learners. Many scholars indicate that textbooks seem to be the main teaching resources in EFL classrooms.
Patricia Byrd claims most teachers depend on textbooks - often as a required tool - because they provide content and activities that shape what happens in the classroom.
EFL textbooks are, indeed, a major necessity for most teachers, because the bulk of them feature an eclectic approach based on the current theories proposed by communicative trends. For instance, Task-based approach engages learners in problem-solving tasks. Content-based approach also offers opportunities to deal with interesting topics and subject matter, rather than coping with grammar-oriented lessons.
Moreover, collaborative learning encourages students to work in groups, as an ideal way to exchange information socially and meaningfully. According to Richards and Rodgers , textbooks are designed in such a way that their tables of contents suggest a gradual development of language forms and functions, going from the most basic to the most complex. All these approaches and features are intended to develop the use of communicative language. However, despite considerable effort on the part of text designers, editors, and publishing houses, a range of grammar-oriented activities and mechanical practice continues to prevail.
As a first step, it is crucial to differentiate the three main types of language practice found in most English instructional materials, according to Richards: 15 :. Mechanical practice refers to controlled activities that involve repetition and substitution drills. They are designed to practice the use of particular grammatical items In many textbooks, this practice demands sentence completion usually with grammar activities in isolation , but lacks authentic language negotiation.
Meaningful practice refers to activities in which language still is controlled and "students are required to make meaningful choices when carrying out practice" Communicative practice embodies those activities in which language "is not totally predictable. These three types of language practice essentially define the kinds of activities often featured in communicative textbooks. All three are expected to be included in the methodological sequence of the various units that constitute English textbook, mainly because students need to go through a process of controlled-practice, by first working on easy-guided mechanical activities, before eventually reaching a degree of free language practice that embraces communicative interaction.
Therefore, if textbooks are designed to develop language competence, one can assume they should contain a well-balanced number of activities pertaining to the three types of language practice described above. To confirm this assumption, we will determine if the five EFL textbooks chosen for this analysis truly provide opportunities to negotiate meaning in different contexts, based on the notion that most of the activities are contextualized in situations where, as Richards 15 suggests, real information is exchanged.
As English teachers, we need to be aware of the frequency of these types of practice in English textbooks, in order to be sure the classroom material we use is effective for our communicative purposes.
Also, it is important for us to undertake a critical evaluation of textbooks with an eye towards improving our teaching practices. Therefore, let us determine if the three language practices previously listed are well-balanced in the textbooks we often use to teach English.
To begin with, I will explain the procedure that was used to analyze the five selected textbooks. Five representative English textbooks were selected for this analysis. The criterion for their choice was based on the fact that they are currently used for upper secondary and university instruction and are offered by recognized publishing houses. They are employed in classrooms where the main goal is to develop communicative competence. Three representative units from each of the five EFL textbooks were chosen to examine the three types of practice proposed by Richards for CLT; that is, mechanical, meaningful, and communicative practice.
Three units were selected as representative data for each textbook, since all the units included in each book follow a model pattern. In other words, all the units include the same sections, approximately the same number of activities, and the same types of practice based on a unit model that publishing houses often provide to designers and authors.
Accordingly, it was not necessary to take data from all the material, since the same pattern is repeated in all the units of the textbooks. The activities in each unit were classified in a table, pursuant to the categories of mechanical, meaningful, and communicative practice.
They also were categorized with respect to the four communicative skills: reading, listening, speaking, and writing, plus grammar and vocabulary. See the data collection instrument in Appendix 1. The number of activities classified in relation to each type of practice was tallied and averaged per unit see Appendix 1. The data collected clearly show which practice is used more often in the textbooks and which is used less.
The figures also show which communicative skills are practiced the most and which are practiced the least. The average percentage of mechanical, meaningful, and communicative practice per unit is summarized and included in the table below, along with the average percentage of each type of practice in the textbook as a whole.
Table 2. The following are the results for Textbook A , which was the first one analyzed:. Out of the sample of the units in Textbook A , In all, These proportions are shown graphically below.
Textbook C Mechanical practice ranks second, with Textbook D showed a variation. The most frequent practice activities are mechanical, with The second most common activity is meaningful practice, with As in textbooks A, B and C, communicative practice accounts for the lowest proportion, with only Textbook E was the last one analyzed and also reflects a difference.
Meaningful practice accounts for the largest average share, with The following table broadly summarizes the three types of language practice developed in the five English-language textbooks examined for this study. Global Average for all the Textboooks. The results show Textbook A is the most grammar-oriented, with mechanical practice accounting for The data also reveal that Textbook D occupies second place, with a high degree of mechanical practice Textbooks A and D are the two with the largest amount of mechanical practice.
We can conclude from the data that only two of the five textbooks: A and D, are characterized primarily by a large degree of mechanical language practice, while B, C, and E tend to be more communicative.
The following is an example of mechanical practice in one of the textbooks. Learners are asked to compose sentences in isolation, without a relevant context. By in large, it features a repetition drill model:. Complete the prompts in bold, using the present perfect and just or never, as in the examples. Textbook D has the least amount of meaningful practice: only As for to textbooks A and B , they provide a moderate proportion of meaningful practice: between Moreover, it is important to emphasize that although the proportion of meaningful practice in Textbook A is This is an example of meaningful practice taken from one of the textbooks.
It requests learners to answer several questions about a girl's personal information. It is a meaningful activity in a context. However, the context is quite limited. The instructions should offer more contextualization to make the activity more relevant.
Language is controlled, seeing as it focuses on simple present tense usage. The following example also is a type of meaningful practice. It provides a context, and learners are required to make choices to complete a story.
The language is controlled as well, because it focuses on the correct use of simple past tense. Although the language is placed in a context, it is important to consider whether it is truly meaningful to the learner. As illustrated, all five textbooks provide limited opportunities for communicative practice.
Textbook E includes the most communicative practice, Textbook A provides the fewest opportunities for communicative practice 7. The following is an example of communicative practice taken from one of the textbooks. It provides a meaningful context, because learners are asked to choose their favorite sports star. Although it suggests that learners make wh questions, the language is not totally predictable, because it allows learners to make their own decisions.
Also, language production is more spontaneous and authentic, since learners are required to interview a classmate and, thus, engage in a process of meaning negotiation in a real communicative context where real information is shared. After the interview, learners are asked to write a report. The overall analysis shows Textbook E tends to be meaningful for the most part, because there is less concentration on mechanical practice However, Textbook E has more meaningful practice than communicative practice.
Friends text to keep up with each other and coordinate events. Parents do it to reach their kids who barely answer calls. Brands text to share information and send reminders. Texting has been such a hit, in fact, that almost any app you open on your phone has a messaging feature.
You can send a million messages because every major carrier has an unlimited messaging plan. In the end, people tend to enjoy typing instead of talking. The numbers of texts sent every day were based mostly on two reports, one by Experian and one by Statistic Brain.
Then I took cell phone usage data from Pew Research Center to piece together per-capita and total sent numbers. So how many texts did people send every day? On average in , American adults sent and received an estimated 32 texts per day.
Later on I found a report by Informate that gave similar numbers. With about million adults in the U. On average, American adults sent and received 32 texts per day, totaling 18 billion texts every day, billion texts every month, and 6. What are they doing now?
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