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Severe acute respiratory syndrome coronavirus 2, is the cause of the new Coronavirus 2019 disease, which has caused a severe pandemic that is unprecedented 21st century. The virus has triggered at least seven mutations in the last two years, leading to either an increase in pathogenicity or transmission. Including, Alpha, Beta, Gamma, Eta, Delta, Lambda, and the recent emergence of Omicron variants. Indicating, we have a long way to deal with the complete eradication of this disease. Several scientific evidence show that respiratory droplets and aerosols are the most common route for coronavirus transmission. Using face masks by all people is generally recommended as a simple and inexpensive solution to cut this outbreak as the virus can be transmitted by asymptomatic patient. Many governments and public health organizations around the world have promoted the use of face masks in public places and have made them mandatory, especially in situations where social distancing is not possible; However, the effectiveness of face mask remains a challenge. This paper considers the challenges from three viewpoints: the quality standards of different face masks and the basis of their filtration mechanisms, the quantitative methods available to determine mask integrity and efficiency in particle filtration, and finally disinfection methods for disposable masks that make possible their reuse.

The ELISA technique is an immunochemical method for determining the amount of an antibody or antigen molecule. In this technique, the solid phase is used to create a suitable subs trate for binding to an antigen or antibody. The enzyme attached to the antigenantibody complex is then used to convert the appropriate subs trate into a dye product. The rate of conversion of a colorless subs trate to a dye product by an enzyme, which indicates the presence of an antigen or antibody and also its concentration, it can be determined by measuring the optical density with a spectrophotometer. This s tudy aims to introduce the ELISA technique, its applications, advantages, disadvantages, challenges and important parameters in improving the results.

Neisseria species are gram negative diplococci an important characteristic of these bacteria is resistance against crystal violet. This study was done to investigate the effect of crystal violet on the growth of Neisseria, to observe the outcome of adding this substance in culture media for isolating these organisms, and finally to make a specific medium for isolation of the Nisseria species.

The study was done in 3 phases: 1) Initially urethral discharge from 106 male patients with urethritis was cultured on NYC, chocolate agar and chocolate violet agar with various concentrations of violet from 1:100000 to 1:250000. We also made direct smears for gram stains. 2) Pharyngeal secretions from 230 healthy persons were cultured on chocolate agar, Muller Hinton agar, and Thayer Martin agar with different concentrations of violet between 1:50000 to 1:500000. Also direct smears were made for gram stains. 3) The standard strain of gonococcus (ATCC) were cultured on the three media. Concurrently we added various concentrations of violet from 1:50000 to 1:200000 to the above media and studied the effect of adding crystal violet on the growth of the standard strain.

In first step, 69 out of 106 patients with urethritis were suspicious of gonorrhea, with positive culture of gonococcus on NYC medium from 64 patients. On chocolate agar only 54 positive cultures, (with 84% sensitivity against NCY medium), were seen together with a growth of normal flora. Chocolate agar plus violet in concentration 1:150000, showed 58 positive cultures, (with 91% sensitivity against NYC medium), with minimal growth of normal flora. In second step, 228 out of 230 healthy persons had positive culture of Neisseria, these organisms grew in different concentrations of crystal violet between 1:500000 and 1:50000. However, with minimal concentration of violet, there was a dense growth of normal flora and with gradual increase in concentration, normal flora grew sparsely. In direct exam, 228 cases of gram negative Neisseria like diplococci were observed. In third step, result of growth of the standard Neisseria gonorrhea in chocolate agar, Muller-Hinton agar and Thayer-Martin agar with and without different concentrations of crystal violet are as follow: In all media without crystal violet, the growth of the bacteria was perfect and abundant while in media containing crystal violet, minimum colony count was observed in concentrations of 1:50000 and maximum colony count occurred at concentrations of 1:200000

To isolate pathogenic species of Neisseria, for e.g. gonococcus, we can use a specific chromogen medium like chocolate-violet agar 1:150000, or Thayer-Martin-violet agar or Muller-Hinton-violet agar with a concentration of 1:200000. Although nonpathogenic Neisseria have high resistance to crystal violet and were isolated from cultures with 1:50000 dilutions of this substance, but growth become sparse with higher concentrations. We can make chromogen media of varying strengths by adding different amounts of crystal violet in various media to get the desired results.

Streptokinase has been widely prescribed as a fibrinolytic agent for myocardial infarction. Simple structural characteristics of this protein have provided techniques for production of different recombinant types of this protein. The present study was designed to prepare equisimilisH46A subtype of streptokinase in our country.

Having extracted the DNA, the streptokinase gene was replicated and cloned in pGEX-4T-2. The recombinant product was transformed in BL21(DE3)plysS'. Then the recombinant streptokinase expression and performance was assessed by lasic densitometry and special test for S2251 substrate.

Use of a restriction enzyme for both sides of a gene may facilitate its cloning in different expressive carriers. Expression rate of recombinant protein (45%) confirmed successful cloning.

Use of pGEX-4T-2 carrier was not only associated with active recombinant streptokinase production, added GST to its amine ending that could facilitate purification process.