Study of isolation and determination of antibiotic resistance, plasmid profiles, protein bands and phenotypic virulence of Shigella flexneri strains

Shigellosis is an acute gastroenteritis caused by Shigella species, including S. dysenteriae, S. flexneri, S. boydi and S. sonnei.The purpose of this study was to isolate and to determine antibiotic resistance, plasmid profile and protein b and s by SDS-PAGE, and also phenotypic virulence by Congo red dye among S. flexneri strains. The isolated bacteria were identified by use of st and ard bacterial and biochemical methods. Antibiotic susceptibility tests were performed according to kirby-Bauer method. Plasmids were isolated by alkaline lysis method. Serological reactions were detected by slide agglutination tests with both polyclonal and monoclonal antisera kits. Virulent strains were isolated on a TSA plate containing Congo red dye. From 350 isolated Shigella spp. 142 [40.57%] were S. flexneri. Of 350 patients 41% were female and 59% male. In 100 S. flexneri isolates, resistance rates to tetracycline, ampicillin, trimethoprim-sulfometoxazol and cephalexin were 95%, 91.3%, 85.6% and 70.3% respectively. All of isolates were sensitive to ciprofloxacin. Most isolates contained multiple plasmid b and s [1-5 plasmid's b and s]. A total of 11 distinct plasmid profile patterns were identified. The results of our study showed that serotype 2 was the most common isolated serotype of S. flexeneri [39%]. In this study, 46% of S. flexneri were Congo red positive and haemolysin positive on blood agar plates. A 120 KDa protein b and was detected on electrophoresis gel. These data showed, pathogenicities of all S. flexneri isolates are not similar. Health care can prevent bacterial diarrhea due to shigella. Therefore laboratories are recommended to be more concerned about isolation of these bacteria. Congo red dye binding test is cheap, simple and rapid, so, it can be used to determine the virulence properties of S. flexneri. Antibiogram tests are recommended to prevent antibiotic resistance

[Lactobacillus as probiotic bacteria]

Introduction: Selected probiotic lactobacilli have inhibitory effect and therefore may be use as biological preservative, so, the aim of this study was to present some data on isolation, growth, antimicrobial activity, effect of pH, heat, and sensitivity to proteolytic enzymes of lactobacillus

Material and Methods: Isolation of lactic acid bacteria from sausage was done by using 1g of samples in MRS medium. Each isolate of lactobacillus species was identified by biochemical tests and comparison of their sugar fermentation pattern. Antibacterial activities was done by an agar spot, well diffusion and blank disk method. Stability of antibacterial activity was measured in boiling water and autoclaving for 15 min. Enzyme sensitivity of supernatant fluid and concentrated cell free culture after treatment with a-amylase, lysozyme and trypsin was determined

Results: The isolated bacteria were Lacto. plantarum, Lacto delbruekii, Lacto. acidophilus, Lacto. brevis. The isolated bacteria had strong activity against indicator strains. The antibacterial activity was stable at 100°C for 10 minutes and at 56°C for 30 minutes, but activity was lost after autoclaving. The maximum production of bacterocin was obtained at 25-30°C at pH 6.5

Discussion: If Lactobacilli that are used to induce sausage fermentation have antimicrobial activity with heat stable bacteriocin, these bacteria may be considered to be a healthy probiotic diet. Lactobacilli originally isolated from meat products are the best candidates as probiotic bacteria to improve the microbiological safety of these foods