جستجوی مقالات مرتبط با کلیدواژه « باکتری های لاکتیک اسید » در نشریات گروه « زیست شناسی »

Probiotics have some beneficial effects on health so these microorganisms are added to dairy products and other foods as well. Lactobacillus bacteria are the most commonly used for this purpose. The aim of this study was to find native Lactobacillus bacteria which has the potentiality for using as probiotic. For isolating lactobacilli، gram strain reaction and catalase test were performed on separated bacteria from 40 local yoghurt samples: after isolating، the acid resistance ability of isolates were evaluated by placing isolates in pH=2. 5 for 2 hours and culturing samples on medium and colony counts. Then، among 18 acid resistant bacteria، by gel diffusion method the inhibitory effect of isolates on pathogens bacteria such as E. coli and Pseudomonas aeruginosa were investigated. The results were compared to the results of investigated commercial strains. The results revealed that S4 isolate had the most inhibitory effect، it showed %80 good-inhibitory and %20 strong-inhibitory effect on pathogenic bacteria، which were completely consistent with results for commercial Lactobacillus gasseri strain. Also، the lowest inhibitory effect against pathogens was related to (Y4-Y5-Y11-Y14-Y15) isolates that all of them had weak-inhibitory effect on pathogens. Other strains were classified in good-inhibitor group. Discussion and Considering daily increasing of drug resistance relating to pathogenic bacteria، today، the use of probiotics، especially lactobacilli as an appropriate alternative of antibiotics is important. The investigated bacteria in this study were able to inhibit pathogens’s growth to some extent، but for investigating the results more accurately، some methods with more sensitivity، for instance، two layers method and MIC method can be used as well.

Streptococcosis /Entrococcosisis important disease in aquaculturewhich are duo to gram positive bacteria such as cocci in fresh and salty water fish and cause infectious and septicemia. In recent decades the mentioned diseases caused economic damages. One of the most important cocci are lactic acid bacteria. They invaded to fish farms and caused to death of them. The aim of this research was identification of gram positive and pathogenic cocci form bacteria in rainbow trout farms in North West area of Fars province by cultivation and PCR methods. At first 90 samples of rainbow trout were collected from farms where might be contaminated. Then dead and sick fish were identified and their clinical profiles were recorded. Sampling from their kidney was done for cultivating bacteria and doing biochemical test to identify them. In the next step for determination of antibiotic that was effective on identified bacteria antibiogram test was done. At the end identification of bacteria was done by PCR method in the base of 16srRNA gene. In this research 43 gram positive cocci were identified they included: 4. 6% Streptococcus iniae، 23. 3 % Lactococcus graviae، and 72. 1 % Streptococcus milleri. The result of PCR test showed that identified bacteria belonged to lactic acid bacteriathat caused diseases in the fish. As regards the diseases are common between human and aquaculture and they cause economical damages so identification and treatment of these infectious agents are important. Clinical symptoms of bacteria which cause the diseases are similar so the best method for identification of them is PCR.