Zeinab H. Kheiralla

Contribution of different mechanisms to the resistance to fluoroquinolones in clinical isolates of Salmonella enterica

OBJECTIVES To study the potential factors include gene mutation, efflux pump and alteration of permeability associated with quinolone-resistance of Salmonella enterica strains isolated from patients with acute gastroenteritis and to evaluate the degree of synergistic activity of efflux pump inhibitors when combined with ciprofloxacin against resistant isolates. METHODS Antimicrobial resistance patterns of fifty-eight Salmonella isolates were tested. Five isolates were selected to study the mechanism of resistance associated with quinolone group, including mutation in topoisomerase-encoding gene, altered cell permeability, and expression of an active efflux system. In addition, the combination between antibiotics and efflux pump inhibitors to overcome the microbial resistance was evaluated. RESULTS Five Salmonella isolates totally resistant to all quinolones were studied. All isolates showed alterations in outer membrane proteins including disappearance of some or all of these proteins (Omp-A, Omp-C, Omp-D and Omp-F). Minimum inhibitory concentration values of ciprofloxacin were determined in the presence/absence of the efflux pump inhibitors: carbonyl cyanide m-chlorophenylhydrazone, norepinephrin and trimethoprim. Minimum inhibitory concentration values for two of the isolates were 2-4 fold lower with the addition of efflux pump inhibitors. All five Salmonella isolates were amplified for gyrA and parC genes and only two isolates were sequenced. S. Enteritidis 22 had double mutations at codon 83 and 87 in addition to three mutations at parC at codons 67, 76 and 80 whereas S. Typhimurium 57 had three mutations at codons 83, 87 and 119, but no mutations at parC. CONCLUSIONS Efflux pump inhibitors may inhibit the major AcrAB-TolC in Salmonella efflux systems which are the major efflux pumps responsible for multidrug resistance in Gram-negative clinical isolates.

MULTIPLEX-PCR AND PCR-RFLP ASSAYS TO MONITOR WATER QUALITY AGAINST PATHOGENIC BACTERIA

In this work we developed and optimized two molecular-based approaches to monitor rapidly, sensitively and specifically bacterial pathogens from three different genera, Escherichia coli, Pseudomonas aeruginosa, and Salmonella spp., directly in waters. To achieve this aim, firstly a multiplex-PCR assay (M-PCR) was optimized using a primer pair specific for each pathogen. Secondly, as a molecular confirmatory test after isolation of the pathogens by classical microbiological methods, PCR-RFLP of their amplified 16S rDNA genes was performed. It was observed from the results that the developed M-PCR assay has significant impact on the ability to detect sensitively, rapidly and specifically the three pathogens directly in water within a short time (5 h from sampling to obtain final results), therefore it represents a considerable advancement over other known more time-consuming and less-sensitive methods for identification and characterization of these kinds of pathogens.

Effect of incubation time, temperature and substrate on growth and aflatoxin production

Abstract The highest level of aflatoxin produced in broth culture by Aspergillus flavus strains isolated from corn, wheat and rice was observed at 25 or 30°C after 2 weeks. Low levels were produced after 4 weeks at 4°. There was apparently no direct relationship between toxin production and weight of the mycelium. Thirteen substrates were evaluated for aflatoxin production by A. parasiticus NRRL 2999. After incubation for 2 weeks at 30° the highest incidence of aflatoxin, in the range of 29–50 ppm, was observed in raw peanuts, rice, watermelon seeds and sesame seeds, with 11–21 ppm occurring in wheat, wheat flour, corn, corn flour and cow peas and approximately 2–4 ppm in yellow beans, soybeans, lentils and roasted salted peanuts.

In vitro and in vivo genotoxicity and molecular response of silver nanoparticles on different biological model systems

Abstract In vitro and in vivo experiments on human cell lines (breast adenocarcinoma, MCF-7, and liver hepatocellular carcinoma, HepG2), plants (Allium cepa) and bacteria (Staphylococcus aureus and Pseudomonas aeruginosa) displayed cytotoxic and genotoxic impacts of silver nanoparticles (AgNPs). The cell viability assays indicated that AgNPs had inhibitory effects on MCF-7 cell line more effectively than HepG2 cell line. Mitotic indices and distribution of cells in mitotic phases of A. cepa were clearly changed after treatment with three different weight ratios of silver metal (1, 3 and 5%) for 3 and 12 h. With increasing concentration of the nanoparticles a decrease in the mitotic index was detected (from 4.19 to 0.79 after 3 h and from 4.56 to 0.25 after 12 h) and different types of chromosomal aberrations were noticed. Protein electrophoresis results of S. aureus and P. aeruginosa demonstrated the change in the protein profiles of the two bacterial strains and it was more noticeable in P. aeruginosa than S. aureus. RAPD-PCR and ISSR-PCR analyses using different primers (OP-A19, OP-B04, OP-C04, OP-C12, OP-Q18, OP-Z03, 14A, 44B, HB-08, HB-11 and HB-12) demonstrated the impairment of bacterial DNA and induction of genetic variability. The percentage of polymorphism was higher in P. aeruginosa than S. aureus. The present findings revealed an analogous effect of AgNPs induced in in vitro and in vivo experiments, therefore AgNP applications should be given special consideration.

Characterization of biosurfactants produced by Halobacillus dabanensis and Pontibacillus chungwhensi isolated from oil-contaminated mangrove ecosystem in Egypt

The production and properties of biosurfactants synthesized by Halobacillus dabanensis and Pontibacillus chungwhensi, isolated from oil-contaminated mangrove sediments of Avicennia marina, Red Sea (Egypt) have been investigated. The two strains were classified as moderate halophile and halotolerant, respectively. The produced biosurfactants were considered as metabolites associated with the growth of H. dabanensis and P. chungwhensi and were able to reduce the interfacial tension to 20 and 19 mN/m, respectively. The partially purified biosurfactants showed high emulsiflcation value (E24) against n-hexadecane (68 and 72%, respectively). Biological degradation of n-alkane mixture and linear alkyl benzene after incubation of bacteria in Buslinell-Haas medium in presence and absence of the partially purified biosurfactants has been monitored. H. dabanensis and P. chungwhensi were capable of degrading 92.3 and 94.7% of n- alkane mixture and 76.5 and 76.7% of linear alkyl benzene, respectively. The biodegradation of n-alkane, achieved in the presence of biosurfactants was better than its degradation in control. The structural analysis of the biosurfactants proved them to be lipopeptides. Biosurfactant-producing halophilic/halotolerant microorganisms may play a significant role in accelerating remediation of oil-polluted saline environments.

Production and Immobilization of Halophilic Invertase Produced from Honey Isolate Aspergillus niger EM77 (KF774181)

Honey isolate Aspergillus niger EM77 was a good halophilic invertase producer in the presence of wheat bran as a complete medium (114.55 U/g), using solid state fermentation technique. Different parameters influence the enzyme productivity such as different pH values, temperature, incubation period, nitrogen and carbon sources were investigated. The optimum pH, temperature and incubation period for enzyme production were 5.5, 30 o C and 72 hrs, respectively. Sucrose at 2 % was more suitable carbon source for invertase production (144.39 U/g) and (NH 4 ) 2 SO 4 at 0.15 % was the ideal nitrogen source. Among different metals ions MnSO 4 enhanced the enzyme productivity than other tested ions to 194.71 U/g. The partially purified enzyme was successfully entrapped in polyvinyl alcohol sponge shielded with agar starch layer (PVAsp Gs) and achieved 71% immobilization yield. The optimum conditions for immobilization were: pH 5.2, an incubation time of 15 min and a protein concentration of 250 mg/ml. Immobilized enzyme was reused 12 times with 29% activity loss. The free enzyme lost its activity completely at 70EsC after 45 minute and the immobilized form retained 80% of its activity at the same condition.The free and immobilized form reported extreme halophilic property since the highest enzyme activity was obtained between 3.5- 5 M.

One-factor-at-a-time (OFAT) optimization of hemicellulases production from Fusarium moniliforme in submerged fermentation

ABSTRACT Hemicellulose degrading enzymes play an important role in bioconversion of lignocellulosic and agro-industrial wastes. In this study, production of hemicellulase by six fungal isolates was determined under submerged culture using corn cobs xylan as a carbon source and enzyme inducer at different incubation periods. The results indicated that Alternaria tenuis showed the lowest enzyme productivity (156.95 ± 2.07U/l) while the highest enzyme production (2,594.44 ± 62.25 U/l) was obtained by Fusarium moniliforme. One-factor-at-a-time revealed maximum enzyme productivity of 10,950.11 ± 98.45 U/l at corn cobs xylan (6 g/l), yeast extract (4 g/l), inorganic salts (1.5 g/l KH2PO4, 1.0 g/l MgSO4.7H2O, 0.2 g/l CaCl2, 0.4 g/l FeSO4.7H2O, and 0.3 g/l MnSO4.5H2O), initial pH (5), initial inoculum size (4%), 150 rpm, and temperature (30°C) in a submerged fermentation process.

NAP enzyme recruitment in simultaneous bioremediation and nanoparticles synthesis

Graphical abstract Our study aims to exploit the denitrifying bacteria MMT and its NAP enzyme in dual missions, nitrate removal from wastewater and nanoparticles synthesis. Therefore, the crud NAP enzyme was characterized and immobilized by entrapment technique for aforementioned application. To the best of author knowledge, the immobilization for denitrifying bacteria and NAP enzyme for simultaneous bioremediation and bionanoparticles synthesis was not studied previously.

Morphological, molecular and biochemical comparative studies of two novel fungal honey isolates.

Aims and Study Design: The stress honey medium expected to have spores with unique feature. Within this context, two honey isolates were identified, characterized, and evaluated as secondary metabolite producers. Place and Duration of Study: The study was undertaken in the National research center, 33 Al Behous, Dokki, Giza, Egypt. The duration of study was during the period of January 2012 to Original Research Article