دو ماهنامه میکروب شناسی پزشکی ایران
سال دوازدهم شماره 3 (امرداد و شهریور 1397)

Extracellular vesicles are nanoscale particles which were identified about fifty years ago. The studies have shown that all of the gram-negative bacteria secrete extracellular vesicles during their normal growth. Today, the production of membrane vesicles has been reported by gram-positive bacteria, parasites, fungi, and mycobacteria. Since these nanoscale particles carry many of the bacterial components such as DNA, RNA, protein, endotoxin, and virulence molecules, they play a very important role in interacting with the environment and other bacteria. For this reason, many of these vesicles are considered as the transmission of pathogens, antigenic protein compounds, and the development of non-cellular vaccines, as well as drug delivery agents. The studies, have been carried in this field so far, have been focused on the pathogenic and physiological roles of these nanostructures in cross-species relationships. The focus of this article is on the role of extracellular bacterial vesicles and pathological and physiological functions which contribute to the interactions between bacteria and bacterium-host. Since these nanostructures play significant role in pathogenesis, gene transduction, regulation of gene expression, immune response regulation, and cellular signaling, further studies are needed on the medical application of these nanostructures as a new generation of vaccines, adjuvants, drug delivery agents.

Staphylococcus aureus is the most common and important nosocomial pathogens and due to potential virulence and increasing resistance to anti-microbial medicines, they become one of the most important health problems through worldwide. So the aim of this study was identification and characterization of S. aureus resistant to Methicillin and Vancomycin from patients hospitalized in Razi hospital of Ghaemshahr and Shahid Zare of Sari and characteristics antibiotics susceptibility pattern in 2015. In this cross-sectional descriptive study, 134 strains of Staphylococcus aureus from hospitalized patients in infectious diseases and burns were collected randomly from the hospital laboratory and transferred to the research laboratory. The specimens were incubated in Blood Agar medium for 24 hours at 37 ° C. The colonies were examined for morphology, biochemical properties, resistance to polymixin and sensitivity to Novobiocin. For isolates, antibiotic test was performed using disk diffusion method and PCR detection was performed. PCR results were approved for sequencing. 100 out of 134 samples were positive for S. aureus; 51 samples were methicillin-resistant and 2 samples were resistant to all of the antibiotics and Vancomycin with vanA and vanB resistance gene. Determination of new resistance factor in nosocomial infection is one of the major challenges in treating these infections. 25.37% of the samples, weren’t S. aureus. This study showed 51% prevalence of methicillin-resistance.

Clindamycin is one of the selective drugs for treatment of staphylococcal infections. Molecular methods can complete phenotypic methods to diagnosis induction resistance to clindamycin. The aim of this study was to identify the genes responsible for the resistance to clindamycin and erythromycin, and determine their antibiotic resistance pattern. 100 isolates of Staphylococcus epidermidis and Staphylococcus saprophyticus were isolated from 466 different clinical specimens using biochemical tests. Using the disc diffusion method, Antibiogram susceptibility test was conducted to determinate lincosamides and tetracycline resistance pattern. Then ermA, ermB, ermC and msrA genes were identified and investigated by PCR method. Out of 100 strains of coagulase-negative staphylococci isolated from clinical specimens, 5 isolates were identified as S. saprophyticus (5%) and 55 isolates of S. epidermidis (55%), respectively. Out of the 5 isolated of S. saprophyticus, 2 (40%) isolates were resistant to methicillin and one (20%) isolate had D phenotype. In addition, 1 isolate had ermA gene and 1 isolate had ermB. Out of the 55 isolates of S. epidermidis, 25 (45.45%) isolates were resistant to methicillin, of which nine (36%) isolates had D phenotype. Also, 4 (16%) isolates had ermA gene, 3 (12%) isolates had ermB, 6 (24%) isolates had ermC and 1 (4%) isolate was carrying the msrA. The phenotypic pattern of resistance to macrolide- lincosamides groups does not have a high degree of accuracy in detecting methicillin-resistant MLSB strains.

The application of bacteriophage to control and removal of bacterial biofilm is a novel method. The goal of this study was to investigate the effect of the Salmonella typhimurium bacteriophage against biofilm of a multidrug resistance (MDR) Salmonella formed on stainless steel in beef broth. One and 7 days old biofilm were grown at 15, 8 and 4 °C, on the stainless steel in beef broth and the effects of different bacteriophage concentrations (103, 105 and 107 PFU/mL) with two contact times (10 and 15 min) were assayed. Results showed that Salmonella can adhere to stainless steel and form biofilm in the beef broth which was significantly influenced by temperature. Higher biomass of biofilm was developed at 15, 4 and 8 °C, respectively. One-day-old is less dense (~1 logarithmic cycle) than 7-day-old biofilm. No significant difference (P>0.05) in biofilm reduction was observed in samples treated with different concentration as compared with control. Statistical differences were also not observed in the different contact time (10 and 15 min). These results indicated that there was no significant reduction in MDR Salmonella biofilm population developed on stainless steel in the beef broth after using the bacteriophage; it is needed to investigate some combination procedures or increase contact time to improve the biofilm removal activity of bacteriophage.

Pseudomonas aeruginosa is a potent pathogen for humans using multiple virulence factors. The purpose of this study was to investigate the effect of Saccharomyces cerevisiae lysates and supernatants on biofilm, alginate factors. First, the supernatant extract and lysate were prepared from the native strain of Saccharomyces cerevisiae and turned into dry powder. Then, supernatant and lysate extracts were admixed with Pseudomonas aeruginosa strain PAO1 and strain M 8821, respectively, and biofilm in the strain PAO1 and alginate in strain 8821 M by Colorimetric method is measured by reading Optical Density(OD) also mention to the wave length. Supernatant with MIC concentration of 1/2 in both experiments and all concentrations of lysates in biofilm test and the highest concentration of lysates in alginate test were used. Supernatant of Saccharomyces cerevisiae at a concentration of 1 / 2MIC (0.512 mg / ml) with P <0.05 significantly reduced the production of alginate in Pseudomonas aeruginosa 8821 M strain, but did not affect biofilm in Pseudomonas aeruginosa PAO1 strain respectively, with all concentrations and the highest concentration (8.192 mg / ml) with P <0.05 significantly reduced the production of biofilms in Pseudomonas aeruginosa strain PAO1 and alginate in Pseudomonas aeruginosa 8821 M strain. Saccharomyces cerevisiae is one of the options that probiotic studies can examine its effects on virulence pathogens, but requires the ultimate goal of producing probiotic drugs.

The aim of this study was to evaluate the protective effect of specific egg yolk immunoglobulin (IgY) against aflatoxin on reducing the defects of aflatoxin by adding to the drinking water of 192 day Ross 308 broiler chickens from 1 to 42 days old. The experiment was based on a completely randomized design with 6 treatments, 4 replications, and 8 observations (chicks). First egg yolks were immunized against aflatoxin by injecting aflatoxin-BSA conjugate to laying hens. Also extracted immunoglobulin with 1 and 0.5 percent /volume concentration was added to broilers' drinking water. The experimental treatments were: 1) control (without any additives); 2) ration contaminated with 1 mg kg-1 aflatoxin B1 (negative control treatment); 3) negative control + 0.5% (V/V) immunized yolk against AFB1, 4) negative control + 0.5% (V/V) unimmunized yolk against AFB1; 5) negative control + 1% (V/V) immunized yolk against AFB1 and 6) negative control + 1% (V/V) unimmunized yolk against AFB1. Using aflatoxin contaminated diet significantly increased serum cholesterol, and decreased serum total protein and albumin concentration (P<0.05). Also, histopathologic lesions observed in the liver. Adding 1 % (V/V) of immunized egg yolk to the drinking water (treatment 5) reduced serum cholesterol and increased total protein concentration compared to treatment 2 (P<0.05). The length and width of the villi and the villi surface area of chicks receiving treatment 5 were higher than treatment 2 (P<0.05). Liver tissue in chicken receiving treatment 3 and 5, was almost normal and few changes were observed in hepatocytes. The results indicate that specific IgY against AFB1 can be effective in reducing the defects of experimental aflatoxicosis as a detoxification agent.

The growing concern about bacterial strains resistant to antibiotics reveals the urgent need to discover and develop new types of bactericidal agents. In the present study, in a pioneering step to phycosynthesis of magnetic iron oxide nanoparticles (Fe3O4 MNPs) with antimicrobial potency, the process was initially exploited using an aqueous extract of green marine algae Ulva prolifera, and further evaluated the antimicrobial activity of biosynthetic magnetite nanoparticles against eight bacterial strains and three strains of fungi. In the present study, the U. prolifera/Fe3O4-MNPs showed a strong inhibitory effect on gram-positive bacteria and relatively modest antifungal activity than fungal pathogenic agents. The highest antibacterial activity compared to strain Staphylococcus epidermidis (19 ± 0.6 mm) and consequently in Bacillus subtilis (18 ± 0.03 mm) and Bacillus pumulis (18 ± 0.2 mm) were observed. However, the bactericidal effects of magnetite nanoparticles were more effective than gram-positive bacteria compared to gram-negative ones. In the present study, we also observed a relatively modest antifungal activity in the anesthetized nanoparticles compared to Saccharomyces cervisiae (11 ± 0.4 mm), and this was the most sensitive fungal strain relative to the fungicidal activity of these nanoparticles. The results of this study indicated that biosynthetic magnetite nanoparticles can be introduced as a new antibacterial to the pharmaceutical field and medicine.

Oncolytic viruses (OVs) are a new approach in treatment of cancer. Antitumor efficacy of OVs were limited due to insufficient and non-specific viral delivery to tumor sites. To overcome this issue, mesenchymal stem cells (MSCs) were used for their ability to specifically homing into tumors. The main aim of this study was to use MSCs as carriers and investigate the effect of oncolytic reovirus infection in MSCs, induction of apoptosis, nitric oxide (NO) secretion and their effects for selectively killing tumor cells, to use in future. MSCs isolated from mice adipose tissue and confirmed. Then, the ability of the virus to infect MSCs and the effect of reovirus infection in induction of apoptosis and NO secretion in MSCs were evaluated. The results demonstrate that reovirus could replicate on MSCs. The finding indicated that the NO production significantly was higher at 72 h post infection with different MOI in comparison to the control cells. Also, reovirus induced high level of apoptosis in the MSCs at 48 h post infection compared with the control cells. Based on observed results, reovirus increased the secretion of iNOS (inducible nitric oxide) in the infected MSCs at 48 h post infection; therefore, high amounts of NO and reovirus replication were found to trigger apoptosis at 48 h post infection. Therefore, by optimizing the replication time of virus in the MSCs, specific viral delivery to tumor sites are available and causes cancer cells’ death.