Predicting the Spread of COVID-19 Using SIR Model Augmented to Incorporate Quarantine and Testing

India imposed a nationwide lockdown from 25th March 2020 onwards to combat the spread of COVID-19 pandemic. To model the spread of a disease and to predict its future course, epidemiologists make use of compartmental models such as the SIR model. In order to address some of the assumptions of the standard SIR model, a new modified version of SIR model is proposed in this paper that takes into account the percentage of infected individuals who are tested and quarantined. This approach helps overcome the assumption of homogenous mixing of population which is inherent to the conventional SIR model. Using the available data of the number of COVID-19 positive cases reported in the state of Kerala, and in India till 26th April, 2020 and 12th May 2020, respectively, the parameter estimation problem is converted into an optimization problem with the help of a least squared cost function. The optimization problem is then solved using differential evolution optimizer. The impact of lockdown is quantified by comparing the rising trend in infections before and during the lockdown. Using the estimated set of parameters, the model predicts that in the state of Kerala, by using certain interventions the pandemic can be successfully controlled latest by the first week of July, whereas the R 0 value for India is still greater than 1, and hence lifting of lockdown from all regions of the country is not advisable.

Multidrug resistant yeasts in synanthropic wild birds

BACKGROUND

The aim of this study was to investigate the presence of multidrug resistant yeasts in the faeces of synanthropic wild birds from the Bangsar suburb of Kuala Lumpur.

METHODS

Species characterisations of yeast isolates and determinations of antimycotic susceptibility profiles were undertaken using the commercial characterization kit, Integral System Yeasts Plus (Liofilchem, Italy).

RESULTS

Fourteen species of yeasts were detected in the bird faecal samples.Candida albicans was present in 28.89% of bird faecal samples, Candida krusei (13.33%), Candida tropicalis (4.44%), Candida glabrata (4.44%), Candida parapsilosis (2.22%), Candida lambica (2.22%), Candida stellatoidea (2.22%), Candida rugosa (2.22%) and Candida lusitaniae (2.22%). Amongst the non-candidal yeast isolates, Cryptococcus laurentii was present in 6.67% of bird faecal samples, Cryptococcus uniguttulatus (4.44%), Saccharomyces cerevisiae (4.44%), Trichosporon pullulans (2.22%), Trichosporon pullulans/Cryptococcus albidus (8.89%) and Rhodotorula rubra/Rhodotorula glutinis (4.44%). Of the isolated yeasts, 18.1% (or 26/144) were found to be resistant to all 11 antimycotic agents they were tested against i.e. Nystatin, Amphotericin B, Flucytosine, Econazole, Ketoconazole, Clotrimazole, Miconazole, Itraconazole, Voriconazole, Fluconazole 16 and Fluconazole 64. 45.8% (or 66/144) of the bird faecal yeast isolates were resistant to four or more of the 11 antimycotic agents they were tested against.

CONCLUSIONS

This finding is of public health significance as these synanthropic wild birds may be reservoirs for transmission of drug resistant yeast infections to humans.

In vitro evaluation of cancer-specific NF-kappaB-CEA enhancer-promoter system for 5-fluorouracil prodrug gene therapy in colon cancer cell lines

Nuclear factor-kappa B (NF-κB) is a transcription factor with high transcriptional activity in cancer cells. In this study, we developed a novel enhancer–promoter system, κB4-CEA205, in which the basal carcinoembryonic antigen (CEA) promoter sequence (CEA205) was placed downstream of the four tandem-linked NF-κB DNA-binding sites (κB4). In combination with a κB4 enhancer, the transcriptional activity of the CEA promoter was significantly enhanced (three- to eight-fold) in cancer cell lines but not in normal cells. In cancer cell lines, the transcriptional activity of κB4-CEA205 was comparable with that of the SV40 promoter. We also constructed vectors in which the thymidine phosphorylase (TP) cDNA was under the control of CEA205, κB4, κB4-CEA205 and CMV promoters, respectively. TP protein and enzyme activity were detected at comparable levels in κB4-CEA205- and CMV-driven TP cDNA-transfected cancer cell lines (H630 and RKO). The κB4-TP and CEA205-TP-transfected cell lines, respectively, only demonstrated negligible and low levels of TP protein and enzyme activity. Both CMV- and κB4-CEA205-driven TP cDNA transiently transfected cells were 8- to 10-fold sensitised to 5-fluorouracil (5-FU) prodrug, 5′-deoxy-5-fluorouradine (5′-DFUR), in contrast to only 1.5- to 2-fold sensitised by the κB4- and CEA205-driven TP cDNA-transfected cells. The bystander killing effect of CMV- and κB4-CEA205-driven TP cDNA-transfected cells was comparable. This is the first report that indicates that the NF-κB DNA-binding site could be used as a novel cancer-specific enhancer to improve cancer-specific promoter activity in gene-directed enzyme prodrug therapy.

Analysis of genes of mitochondrial origin in the genus Entamoeba

The amitochondriate protistan parasite Entamoeba histolytica has lost most mitochondrial functions secondarily but has retained a reduced organelle of mitochondrial origin, the mitosome. We here investigate the presence, origins, and expression in other species of Entamoeba of three genes of mitochondrial origin--pyridine nucleotide transhydrogenase and the mitochondrial-type chaperonins cpn60 and hsp70. The genes appear to be present in all species and specifically related, confirming that the E. histolytica mitosomal genes were not acquired recently by lateral transfer from another organism. Detection of expression was not possible in all cases under the culture conditions used, but several genes were induced during recovery from exposure to a heat shock. This includes the transhydrogenase, which to our knowledge has not been shown previously to be a heat-shock protein.