ABSTRACT
Since the appearance of the first case of COVID-19 in Morocco on March, 02, 2020, the cumulative number of reported infectious cases continues to increase and, up to date, the peak-time of infection is not reached yet. In this study, we propose a Susceptible-Asymptomatic-Infectious deterministic model to evaluate the impact of compulsory containment imposed in Morocco on March, 21 on the spread of COVID-19 epidemic across the country. The model takes account of the unconfined individuals that continue to work or to leave their home for urgent needs and the existence of infectious asymptomatic and unreported individuals within susceptible population. Furthermore, the model is able to predict the peak-size, peak-time, final size and epidemic duration according to different rates of containment. Advanced knowledge of these details will be of great interest to establish an optimal plan-of-action to control or eradicate the epidemic. Indeed, mitigating and delaying the epidemic peak allow the official health authorities to anticipate and control the spread of COVID-19. Moreover, prediction of the epidemic duration can help the government to predict the end time of containment to avoid consequent social-economic damages as well. Using our model, the basic reproduction number R 0 is estimated to be 2.9949, with C I ( 2.6729 - 3.1485 ) , reflecting a high speed of spread of the epidemic. The model shows that the compulsory containment can be efficient if more than 73% of population are confined. In the absence of other efficient measure of control, even with 90% of containment, the end-time is estimated to happen on July, 4, 2020 with 7558 final cumulative cases. Furthermore, a threshold value of containment rate, below which the epidemic duration is postponed, has been determined. Finally, the sensitivity analysis is performed and showed that the COVID-19 dynamics strongly depends on the asymptomatic duration as well as the contact and containment rates. Our previsions can help the government to adjust its plan-of-action to fight the disease and to face the social-economic shock induced by the containment.
ABSTRACT
Lactic acid bacteria (LAB) synthesize a wide variety of biochemical compounds during food fermentation. Carotenoids provide important biological functions for bacteria, and their consumption by humans has many beneficial effects. In this study, the presence of several genes involved in the production of carotenoids was determined by BLAST analysis and PCR in a collection of 156 LAB isolated from traditional amylaceous African fermented foods. Only the crtE gene and the crtNM operon were present and detected in Lactobacillaceae. Most of the strains with positive PCR detection of the operon crtNM produced carotenoid-like compounds when grown in MRS broth. The carotenoids produced differed from compounds previously identified in other LAB except for one peak, which was closely related to 4,4'-diaponeurosporene already reported in the literature in Lactobacillus plantarum species. Most producing strains belonged to Lactobacillus fermentum and L. plantarum species but a few Pediococcus acidilactici were also producers. Furthermore, the most efficient L. plantarum was able to synthesize carotenoids in a cereal fermented food. Genetic screening was shown to be efficient since, in all cases, it eliminated the need for biochemical analysis of strains in which no amplicons of the operon crtNM were obtained.
