دو ماهنامه میکروب شناسی پزشکی ایران
سال پانزدهم شماره 1 (بهمن و اسفند 1399)

The 2019 novel coronavirus is another type of known coronaviruses; SARS-CoV-1 and MERS-CoV. The World Health Organization (WHO) has named the virus SARS-CoV-2 and its disease as coronavirus disease 2019 (abbreviated COVID-19). The first case of COVID-19 was reported in December 2019 in Wuhan, China. The epidemiological studies have shown that the disease is transmitted from animal to human, and the spread of the disease from person to person is rapidly expanding. Currently, the most important factor in preventing and controlling the spread of the disease is proper recognition, health care, and control measures. Given the importance of early detection and timely treatment of the disease, the use of nanoscale materials for the production of sensors and drug delivery system can be of great assistance to the researchers. In this context, we aimed to explain the effects of the prevalence of the disease worldwide and consider the different aspects of SARS-CoV-2.

The crisis of antibiotic resistance in bacteria is one of the most important concerns of World Health Organization (WHO), which requires further global research and studies in order to develop more effective antimicrobial compounds. Nanoparticles as an alternative to antibiotics have been widely used to target bacteria and they are useful in the treatment of bacterial infections. In this narrative review study, the advantages of using nanoparticles against bacteria are discussed. Due to their unique properties compared to the bulk form, nanoparticles have a high potential to be used as carriers and adjuvants with the ability to strengthen the immune system and fight bacteria using several mechanisms simultaneously. Recently, a number of nanoparticle-based drugs have been designed and used for clinical use as an alternative to antibiotics. Despite special attention to nanoparticles, their antibacterial mechanisms are not very well known. However, in this study, we have examined in detail a number of accepted antibacterial mechanisms such as oxidative stress induced by ROS and the function of nanoparticles for releasing soluble metal ions. Further over, we also examined important factors affecting the antibacterial properties of nanoparticles, including size, charge, zeta potential, and surface morphology will be investigated too. The limitations of the research will also be discussed.

the aim of this study was the isolation of phages able to lyse some strains of MDR-K. pneumoniae (named vB_Kp1 and vB_Kp2) and E. aerogenes (named vB_Ea1) from swages.

Different Klebsiella pneumoniae and Enterobacter aerogenesis strains isolated from clinical specimens (January to September 2018) in three Hospitals in Amol, (Mazandaran, Iran). Kirby Bauer’s disc diffusion method was used for determination of resistance profiles of these isolates using different antibiotics. The resistant strains to multi tested antibiotics (MDR) were selected to investigate the effect of isolated phages from wastewater and hospital sewage. Presence of phage investigated by plaque formation and after enriching and concentrating the isolated bacteriophages and staining the samples, a transmitting electron microscope (TEM) was used to observe the morphology of the bacteriophages. Phage identification tests including host range and One-step growth were performed.

 TEM analysis revealed that tree phages have an icosahedral capsid and long contractile tail. Therefore, they are a member of the Myoviridae family. Phages were able to lyse 14 (56%) of the 25 strains of multidrug-resistant bacteria isolated. The one-step growth curve showed large burst sizes and short latent times.

The formation of clear plaques shows the high lyse power of phages, so they have good potential for further analysis for clinical use as a therapeutic agent in the future.

Ganoderma lucidum is a traditional medicinal mushroom that has many therapeutic applications. However, the application of this beneficial fungus has been limited due to its secondary metabolite’s low production. Many investigations have been carried out to improve the production of G. lucidum as well as Ganoderic Acid (GA); however, prior studies suffer from the lack of sufficient monitoring platform. A real-time monitoring study could be useful to find more information through cultivation and evaluating secondary metabolite production.

In the current study, aerated shaken flasks (AF) with different culture mediums were used for online measurement of the respiration activity of G. lucidum in small scale bioreactors. Then, to find more information through G. lucidum growth, four factors, including biomass formation, GA, residual sugar, and gene expression were evaluated on different days.

Online monitoring of cell proliferation demonstrated that GA starts to synthesize in the second growth phase as a partially growth-associated metabolite. High maximum biomass and GA production were obtained at an initial glucose concentration of 35 g/L with vitamin and KH2PO4. During fermentation, the YO2/GA and Y O2/X the rate of oxygen consumption rate per GA production and biomass formation, respectively, were introduced as beneficial parameters to scale-up the process.

A novel monitoring strategy was suggested which can be beneficial for future investigations.

Koome as one of the traditional fermented dairy products of ovine milk has long been produced in rural areas around Naein, Iran in sheepskin bags. The present study aimed to isolate Lactobacillus bacteria from the traditional dairy products of Naein and to evaluate the functional characteristics and health of these bacteria as probiotics.      

For the initial isolation of bacteria, de Man, Rogosa, and Sharpe (MRS) agar was used. A total of 15 bacilliform, gram-positive, and catalase-negative colonies were isolated from the culture, and resistance to acid, bile, gastric juice, and intestinal juice was assessed to investigate probiotic characteristics. Bacterial isolates with favorable probiotic characteristics were tested for antimicrobial activity and antibiotic resistance to assess the effect of probiotics on health. Afterwards, seven bacterial isolates were selected and their ability for reducing cholesterol and hydrolyzing bile salts was evaluated. Moreover, the selected isolates were sequenced to identify the strain.    

Our findings demonstrated that six of 15 bacterial isolates had a suitable resistance in pH=2.5. In addition, 60% of the isolates were sensitive to bile salts. The identified Lactobacillus isolates had a high antibiotic resistance and were shown to have a favorable antimicrobial activity against pathogenic bacteria. Furthermore, the selected bacterial isolate could reduce 70% of environmental cholesterol.    

According to the results of the present study, koome is highly potential for isolating probiotic isolates and the nutritional consumption of Lactobacillus isolates s microbial supplement might have positive effects on health.

The expression of most genes involved in pathogenesis in Pseudomonas aeruginosa is controlled and regulated by a gene system called quorum sensing (QS). The purpose of this study was to investigate the quorum quenching of garlic extract in preventing the expression of genes involved in QS system of P. aeruginosa.

In the present cross-sectional study, 12 P. aeruginosa strains were collected from burn wounds, cultured on special media and then confirmed by differential tests. The PCR test was performed to detect the lasI and lasR genes. The expression level of lasI gene was assessed in the presence of garlic extract and tobramycin antibiotic by real-time PCR, and the active ingredient of garlic extract was analyzed by HPLC.

Examination of 12 strains cultured on special and differential media showed that all 12 strains were P. aeruginosa. The PCR results indicated that all strains had 100% lasI and lasR genes. The real-time PCR results also revealed that the garlic extract was able to reduce the expression level of lasI gene in P. aeruginosa. It was found that tobramycin has a greater ability to reduce the expression level of this gene compared with garlic extract.

This study showed that the garlic extract could reduce the expression of lasI gene in P. aeruginosa isolates, and that the active ingredients of this extract could be used to treat infections as an alternative to antibiotic therapy.

 Bacterial enteritis occurred in neonatal lambs, is an economically important disease that can cause high morbidity and mortality in lambs, therefore, emergency antibacterial treatment is necessary. Malva sylvestris L. plays an important role in traditional remedies for medicinal properties. The present study aimed to evaluate the antibacterial activity of M. sylvestris on bacterial pathogens isolated from the stool of diarrhetic lamb.

 The antibacterial activities of M. sylvestris hydroalcoholic extract (MSHE) were evaluated by agar diffusion and microbroth dilution methods against isolates of Salmonella enterica (n=10), Escherichia coli (n=10) and standard strains S. enterica PTCC 1709-CIP104115, E. coli PTCC1270.

 The results of plant extract efficiency against clinically isolated reported as Minimum Inhibitory Concentration (MIC) test and Minimum Bactericidal Concentration (MIC) test toward E. coli (MIC: 11.56±0.0 mg×mL-1 and MBC: 21.25±0.0 mg×mL-1) S. enterica (MIC: 42.50±0.0 mg×mL-1 and MBC: 80.00±0.0 mg×mL-1). The conclusions of this study indicated that M. sylvestris revealed antibacterial properties and this plant could be a good candidate for the generation of new wide spectrum antibacterial agents.

Escherichia coli is an important pathogen and microorganism of the normal intestinal flora of humans and animals. One of the important serotypes of E. coli is O157: H7. Because of the excessive and arbitrary use of antibiotics, multiple drug resistance has increased against these organisms. The main problem in treating infections caused by E. coli is its dependence on the administration of a large number of common antibiotics and the resistance of some strains to antibiotics. Phage therapy refers to the therapeutic use of phages to eliminate bacterial infections. In the first step, it is necessary to separate and identify bacteriophages that affect the target bacteria. Therefore, the present study was performed to isolate the phage that was effective on enterohemorrhagic E. coli isolates.

In this study, after collection of sewage samples, bacteriophages were isolated by filtration and enrichment in an enterohemorrhagic E. coli overnight culture. The presence of bacteriophage was detected by plaque observation in a double layer agar and confirmed by TEM electron microscopy.

The results of the observation with electron microscopy revealed the presence of bacteriophage with the appearance of the Cystoviridae, Myoviridae and Podoviridae families. Unfortunately, although the titration of phages and molecular study were not performed in the current study due to the lack of budget, we found antibacterial activity of isolated phages using plaque formation observation, and the presence of phages belonging to Cystoviridae, Myoviridae and Podoviridae families was confirmed by TEM microscopy. Therefore, the effective phage against O157: H7 was successfully identified, isolated, and purified.