MOSP - Macao Scientific Publishers

文章

First report on Enterobacter sakazakii from Sudanese patients

Humodi A. Saeed¹* and Rania M. Musallam²

Abstract: Enterobacter sakazakii (E. sakazakii) has been identified as emerging opportunistic pathogens that can cause enterocolitis, bacteraemia, meningitis, brain abscess, and urinary tract infection. They have been particularly associated with meningitis in neonates where infant milk formulae have been epidemiologically linked to the disease. This study was carried out during the period of November 2008 to March 2009; to determine the occurrence of E. sakazakii in clinical specimens and its resistance to traditionally used antimicrobial agents in the Sudan. A total of 389 (311 urine specimens, 11 wound specimens, and 67 stool specimens) were collected from outpatients of three leading hospitals in Khartoum State. The urine specimens and wound swabs were cultured on blood and MacConkey's agars for primary isolation of pathogen, while stool specimens were cultured on selenite F broth and incubated overnight then subcultured on xylose lysine deoxycholate agar. Identification of the E. sakazakii was done by colonial morphology, Grams stain and biochemical tests using API 20E. Modified Kirby-Bauer disc diffusion method was adopted to determine the resistance rate of E. sakazakii to fifteen antimicrobial agents. Minimum inhibitory concentration (MIC) of antimicrobial agents was determined by E-test. The result showed that out of 389 specimens examined, 6 (1.5%) E. sakazakii were recovered, 4 (1.03%) from urine, 1(0.3%) from wound and 1(0.3%) from stool. The results more over revealed that the antimicrobial resistance of E. sakazakii was as follows; ceftazidime, amoxicillin, amoxyclav (100% each), co-trimoxazole, ticarcyline (83.3% each), chloramphenicol, tetracycline, ceftriaxone, nitrofuratoin, cephotaxime, tobramycin (66.7% each), ciprofloxacin, amikacin and nalidixic acid (16.7% each). None of the isolates were found to be resistant to gentamicin. In addition to that, the result indicated that the MIC, MIC50 and MIC90 of different antimicrobial agents range from 0.001 to > 240, 0.1 to > 240 and 0.5 to > 240 µg/ml respectively. The results indicated for the first time the presence of E. sakazakii in the examined clinical specimens in Sudan. The occurrence was high and the antimicrobial resistance of the isolated E. sakazakii was also high.[...] Read More.

Keywords: Enterobacter sakazakii, API 20E, E-Test, Khartoum, Sudan.

Full text

Download：876

文章

Effect of oligosaccharides and isoflavones aglycones in defatted soy meal fermented by Lactobacillus paracasei and Bifidobacterium longum

T. R. Chen*, Q. K. Wei, and Z. X. Chi

Abstract: The study determined bacterial population, pH value, oligosaccharides and isoflavone in defatted soy meal fermented by Lactobacillus paracasei and Bifidobacterium longum at 37°C for 48 h. B. longum and L. paracasei fermented in defatted soy meal has significantly increased the maximum bacterial population over 9.6 log CFU/h and reduced pH to 4.9. Furthermore, content of oligosaccharides, including sucrose, raffinose and stachyose, in FDSM were significantly reduced by L. paracasei (97.7, 98.3 and 98.5%) and B. longum (98.0, 97.5 and 86.3%, P[...] Read More.

Keywords: Oligosaccharides, isoflavones, defatted soy meal, Lactobacillus, Bifidobacterium.

Full text

Download：1014

文章

Characteristics of the secretory expression of pectate lyase A from Aspergillus nidulans in Escherichia coli

Zhihua Han, Qingxin Zhao,*, Huanli Wang, and Yijun Kang,

Abstract: Pectate lyases from Aspergillus spp. are a major kind of industrial pectinases, can improve the surface properties of natural fibers and have promising applications in medicine, food, textile and other industries. Pectate lyases catalyze the eliminative cleavage of de-esterified pectin, which is a major component of the primary cell walls of many higher plants. The Pectate lyase A (PelA) gene without an N-terminal signal peptide sequence from Aspergillus nidulans was recombinantly expressed using Escherichia coli as the host strain and pET-20b(+) as expression vector with a pelB N -terminal signal pepetide. PelA biosynthesis reached the maximum production field (450 U ml-1 medium) at 0.5 mM IPTG, 37°C, 200 rpm, for 2 h and the expressed PelA primarily appeared in extracellular medium. Calcium ion had a more obvious promotion than glycine and SDS to the extracellular enzyme fields, and the C-terminal sequence of Pel A might have an important effect on the transportation through the outer-membrane of E. coli. The time (2h) of reaching the maximum enzyme at 37°C implied that the PelA expression was very significant to pectate lyase industrial production.[...] Read More.

Keywords: Characteristics, extracellular expression, pectate lyase A, Aspergillus nidulans, Escherichia coli.

Full text

Download：929

文章

Screening of the PGPR strains compatible with Cajanus cajan and used as biofertilizer

Full Length Research Paper

Abstract: Plant growth promoting rhizobacteria (PGPR) are beneficial bacteria that colonize plant roots and enhance plant growth by a wide variety of mechanisms. The use of PGPR is steadily increasing in agriculture and offers an attractive way to replace chemical fertilizers and pesticides. Here, we have isolated and characterized PGPR traits from the rhizosphere soil of pigeon pea and tested for the growth enhancement of pigeon pea. Rhizosphere soils were collected from different areas of Samalkot, Pithapuram, Peddapuram and Kakinada in India. A total of 65 isolates have been identified and characterized for their morphological, cultural, staining and biochemical characteristics, of which 35 isolates have been selected for further screening of PGPR traits. Sixteen isolates were successfully characterized for the PGPR traits like indole acetic acid (IAA) production, phosphorus solubilization and 1-aminocyclopropane-1- carboxylate (ACC) deaminase. Among the sixteen isolates, seven were found to be high IAA producing. Six were found to be efficient phosphate solubilizers, two were shown to be promising in both IAA production, phosphate solubilization and mineralizing capacity. These isolates showed growth promotion in pigeon pea for seedling emergence, increase of shoot length, root length, dry matter production, nodule number and nodule mass. Furthermore, PGPR isolates remarkably increased seed germination of pigeon pea. The two promising isolates were identified for 16sRNA sequencing and found to be Bacillus cereus and Enterobacter cancerogens.[...] Read More.

Keywords: Indole acetic acid (IAA), plant growth promoting rhizobacteria (PGPR), phosphorus solubilization, 1-aminocyclopropane-1-carboxylate (ACC) deaminase, polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP), seed germination.

Full text

Download：933

文章

Determination of insecticidal toxicity of three species of entomopathogenic spore -forming bacterial isolates against Tenebrio molitor L. (Coleoptera: Tenebrionidae)

N. Du Rand and M. D. Laing

Abstract: Bioassays were conducted using larvae of mealworms, Tenebrio molitor, to determine lethal concentration for five entomopathogenic strains of spore-forming bacteria. Lethal concentration was determined by feeding T. molitor larvae cabbage discs dipped in whole cell cultures of these five strains of bacteria. The strains of bacteria were isolates of Bacillus cereus, Bacillus thuringiensis and Brevibacillus laterosporus. An isolate of B. cereus required the highest concentration of viable spores (8.531 x 107 spores ml-1) to achieve its LC50, whereas an isolate of B. laterosporus required the lowest concentration of viable spores (3.388 x 106 spores ml-1) to achieve LC50.[...] Read More.

Keywords: Mealworms, spore-forming bacteria, bioassays.

Full text

Download：907

文章

Characterization of biofilm formation by Salmonella enterica Serovar Pullorum strains

Yan Lu, Hongyan Dong, Sujuan Chen, Yiping Chen, Daxin Peng* and Xiufan Liu

Abstract: Salmonella enterica Serovar Pullorum causes acute or persistent infection in chickens, resulting in significant economic losses. The objective of this study was to evaluate the biofilm-forming ability of S. enterica Serovar Pullorum strains and association with the pathogenicity. A total of 62 S. enterica Serovar Pullorum isolates were measured for biofilm formation by crystal violet staining. Thirty-nine out of 62 strains were found to produce biofilm which were further confirmed by observation under light microscopy, field emission scanning electron microscopy. Analysis of the major components for biofilm formation showed that bacterial colonies were smooth phenotype and the architecture of biofilm was composed of exopolysaccharides and curli other than cellulose. In addition, animal experiments were performed to determine the 50% lethal doses (LD50) of four S. enterica Serovar Pullorum isolates with or without biofilm-producing ability. Although the virulence of S. enterica Serovar Pullorum strains was independent of the ability of biofilm formation, prior growth as a biofilm for a biofilm producer of S. enterica Serovar Pullorum lead to enhanced virulence in chickens. The results suggested that biofilm may be one of the important virulence factors for S. enterica Serovar Pullorum infection.[...] Read More.

Keywords: Salmonella enterica Serovar Pullorum, biofilm, curli, virulence.

Full text

Download：1033

文章

Influence of growth conditions and nutritional requirements on the production of hydrogen peroxide by lactic acid bacteria

Abimbola Enitan*, Josiah Adeyemo and S. T. Ogunbanwo

Abstract: Lactic acid bacteria (LAB) were isolated from raw and fermented milk samples. They were evaluated for hydrogen peroxide (H2O2) production. Sixty–three strains of LAB belonging to the genera Lactobacillus, Leuconostoc, Lactococcus and Streptococcus were isolated and all the isolates produce H2O2 with Lactococcus lactis having the highest yield of 0.4279 mg/L in de Mann Rogosa Sharpe (MRS) broth. Among the high–level H2O2-producing strains are Lactobacillus bulgaricus, Lactobacillus casei, L. lactis and Streptococcus thermophiles. They were subsequently selected and their culture supernatants were evaluated at different temperatures, pH values and using different carbon and nitrogen sources. The highest quantity of H2O2 (0.6517 mg/L) was produced at 37°C by S. thermophilus, while L. casei produced the lowest quantity of 0.1132 mg/L at 40°C . S. thermophilus produced the highest quantity of 0.5912 mg/L at pH 5.5, while the lowest quantity of 0.1042 mg/L was produced at pH 7. L. bulgaricus produced the highest concentration of0.6512 mg/L when galactose was used as carbon source and lowest quantity of 0.0210 mg/L was produced by L. lactis in basal medium containing sorbitol as carbon source. L. casei produced both the highest and lowest quantities of 0.1895 and 0.0207 mg/L of H2O2 in medium supplemented with yeast extract and ammonium sulphate as nitrogen sources respectively. The antimicrobial activity of the culture supernatants against Escherichia coli K12, Staphylococcus aureus and Candida albicans using agar well diffusion assay was evaluated. Cell-free supernatant by L. bulgaricus had the highest inhibitory activity against E. coli K12 with 21 mm zone of inhibition and against S. aureus with 15 mm zone of inhibition but showed no antagonistic activity against C. albicans. The study revealed that lactic acid bacteria isolated from raw and fermented milk in South-West Nigeria are capable of producing hydrogen peroxide which has antagonistic effect on pathogenic organisms, thus, may be promising sources of preservative that may in future be applied to food.[...] Read More.

Keywords: Hydrogen peroxide, growth conditions, nutrient utilization, antagonistic activity, lactic acid bacteria (LAB).

Full text

Download：966

文章

Isolation and characterization of a psychrophilic bacterium producing cold active lactose hydrolyzing enzyme from soil of Mt. Himalaya in Nepal

E. S. Nam, Y. H. Kim, K. H. Shon, and J. K. Ahn*

Abstract: Psychrophilic bacteria, which grew on lactose as a carbon source, were isolated from soil of Island Peak area at Mt. Himalaya in Nepal, and identified. 148 bacterial isolates were isolated via X-gal hydrolysis on plate. Among these, three isolates, referred to as KNOUC 401, 402 and 403, displayed good cold-adapted growth and activity for hydrolysis of o-nitrophenyl- -D-galactopyranoside (ONPG) and lactose in cell free extracts. Strain KNOUC403 showing negative activity in -hemolysis was selected and identified. The strain was gram-positive bacilli, non-motile, catalase-positive and aerobic. Optimum growth was done at 20°C and pH 6.5~6.8. Anteiso-C15:0 (68.14%) was predominant in the fatty acid composition of cell. The physiological and biochemical properties, cellular fatty acid composition and sequence of 16S rDNA, suggest that strain KNOUC403 indicate a taxonomic affiliation to Arthrobacter psychrolactophilus. The optimal conditions for ONPG hydrolysis of cell free extracts from the strain were 15°C and pH 6.0, and the enzyme was stable at 4°C for 42 h. Zymogram assay of cell free extract from the strain in nondenaturing polyacrylamide gel showed a distinct band of X-gal hydrolysis.[...] Read More.

Keywords: Psychrophilic bacteria, Arthrobacter psychrolactophilus, cold-active lactose hydrolyzing enzyme, Mt. Himalaya.

Full text

Download：931

文章

Full Length Research Paper

Abstract: Enduro hand sanitizer is a new disinfecting agent that has recently been introduced as an effective antibacterial, antifungal and antiviral agent. Considering the importance of infection control in dentistry, this study aimed to evaluate the antimicrobial effects of the foam and its ability to disinfect dental surfaces and instruments. An experimental study was designed to evaluate the microbial load of 50 samples which were obtained randomly from dental surfaces and instruments before and after application of the disinfecting foam. All samples were cultured in blood agar and nutrient agar culture media and incubated at 37°C for 24 h. Colony count was subsequently performed after an additional 24 h. Furthermore, to evaluate the efficacy of the foam on different bacterial species, a blank disc was coated with foam and approximated with the bacteria. The clear zone around each disc was measured and reported (mm) after 48 h. The significance of differences between the data retrieved before and after applying the foam was determined using the non parametric Chi-square test. None of the species were colonized after the application of the foam. It was also shown to significantly reduce the colonization of resistant bacterial strains and the standard microbial species (P[...] Read More.

Keywords: Antibacterial, disinfecting agent, dental instrument.

Full text

Download：893

文章

Rapid detection of Salmonella species using an improved gel-based DNA microarray method

Xuhong Ye, Yiming Wang, and Xiangui Lin,*

Abstract: Salmonella, widely distributed in nature, is a great human and animal health hazard of a class of pathogens. Culture-based methods may require many days to detect Salmonella. Traditional microbiology could advantageously be replaced by DNA microarray technology. We described an improved 3-D polyacrylamide gel-based DNA microarray assay based on gyrB gene (DNA gyrase B subunit gene) sequences that can be used for the identification of Salmonella species. Primers specific for a gyrB gene region common to all 13 samples were synthesized and used for PCR amplification of purified DNA. An oligonucleotide probe for specific gyrB gene regions was developed for the identification of 7 Salmonella species. Acrylamide-modified oligonucleotides solutions containing acrylamide monomer, glycerol, APS and probe were prepared at the desired concentration. The solutions were spotted on the modified glass slide by ink jet using a microarrayer and then the slide was transferred to a vacuum chamber with TEMED, after that the slide was used for hybridization with fluorescently labeled ssDNA derived from amplified sample DNA to yield a pattern of positive spots. This microarray produced unique hybridization patterns for species of Salmonella and could differentiate closely related bacterial species. The sample preparation and microarray method used in this study increased sensitivity and reduces time-to-result for detection of Salmonella. The described method allowed microarray monitoring for Salmonella contamination of food and manure for aquaculture.[...] Read More.

Keywords: Salmonella, gyrB gene, PCR, DNA microarray, TEMED.

Full text

Download：1383

Search Filter