Postharvest control of Aspergillus niger in mangos by means of essential oils

The use of essential oil as an alternative mean to synthetic fungicides has been considered in the past years for management of the postharvest decay of fruits in order to ensure more safe and long storage life of these perishable commodities. Aspergillus niger is one of the most dangerous fungal pathogen which can cause postharvest diseases in fresh mangos. The aim of this study was to assess the effectiveness of essential oil from four aromatic plants (Thymus vulgaris, Salvia mirzayanii, Artemisa persica, and Rosmarinus officinalis) in comparison to fungicide ‘Mancozeb’ against A. niger under in vitro and in vivo conditions. After inoculation of mango fruits with an isolate of A. niger followed by curative treatments with essential oil, the main physical and chemical attributes of mangoes were determined under postharvest condition. The in vitro results showed that colonies of A. niger were totally inhibited by application of essential oil of T. vulgaris (at all the tested concentrations) and A. persica (1500 μl/l). While, S. mirzayanii showed the lowest effect at 1000 μl/l if compared with the other essential oils. The results of the in vivo experiments showed that treatments with T. vulgaris and S. mirzayanii essential oil had significant (P<0.05) effects in preventing fruit decay at 1000 μl/l after 10 days of storage, while, R. officinalis essential oil significantly (P<0.05) reduced deterioration of mango fruits at 500 μl/l, followed by A. persica. Rosemary also showed the highest fruit firmness in comparison with other treatments. Also, the essential oils maintained higher chlorophyll content. The results of this work showed that application of essential oil on mangos assurance both a significant preservation on their quality attributes by controlling, at the same time, decaying caused by A. niger during the postharvest phase

Isolation of a Penicillin Acylase Producing E.coli and Kinetic Characterization of the Whole Cell Enzyme Activity

ABSTRACT Penicillin acylase (EC 3.5.1.11) has been a target of study for a long time because of its pivotal role in the deacylation of the penicillin into the 6-aminopenicillanic acid (6-APA) and the side-chain organic acids. This property of penicillin acylase has been exploited commercially for large scale production of 6-APA, which is the key intermediate in the manufacture of semi-synthetic penicillins. Due to the worldwide demand for semi-synthetic penicillins, production of 6-APA has been increased up to 7000 tons in recent years. In this study, Sixty-five strains of E. coli were investigated for penicillin acylase activity using fluorescamine method. The 6-aminopenicillanic acid formed in the reaction mixture was developed on thin layer chromatography. One-minute beta-lactamase test was carried out to follow any trace of penicillinase activity. Only one sample designated as E.coli PPA78 was found to be penicillin acylase producer. The optimal pH and temperature of penicillin acylase activity of the whole cells were determined to be 8.0 and 57°C, respectively. Km value and activation energy of the enzymatic hydrolysis reaction of penicillin G by intracellular enzyme were estimated as 0.004 mmol and 6.2 Kcal/mol, respectively. Iran. Biomed. J. 6 (2 & 3): 93-96, 200

rep-PCR Genotyping and Antibiogram Pattern of Clinical Isolates of Pseudomonas aeruginosa in Shahid Mohammadi Hospital, Bandar Abbas, Iran

Background and Objectives: Pseudomonas aeruginosa is one of the multi-drug resistant pathogens and a cause of opportunistic neusocomial infections. Different methods have been used for investigating genetic diversity of P. aeruginosa. rep-PCR typing has been introduced as a rapid and low-cost method with high discriminatory power. The aim of this study was to investigate distribution, genotypic relatedness, and antibiotic resistance in clinical isolates of P. aeruginosa. Methods: This cross-sectional study was conducted on 67 P. aeruginosa clinical isolates at Shahid Mohammadi Hospital, Bandar Abbas, Iran, between May 2012 and June 2013. Identification of strains and determination of antibiotic resistance pattern were conducted by conventional biochemical tests and Kirby-Bauer method, respectively. Genetic similarity was investigated by rep-PCR. The correlation between molecular types and antimicrobial resistance patterns was determined by Pearson's chi-square test. p≤0.05 was considered to be the level of significance. Results: rep-PCR results exhibited seven genotypic clusters with 76% similarity. Genotypes A and C were the most prevalent types with 16 (23.8%) frequency. ICU had the most distribution and diversity of rep-PCR types. The majority of isolates were obtained from sputum (29.8%). Most isolates were resistant to cotrimoxazole (80.6%) and susceptible to ciprofloxacin (85.1%), as the most effective antibiotic. Conclusion: The result of this study showed that P. aeruginosa rep-PCR types A and C were the predominant strains in the studied hospital. Because drug resistance is considered a serious challenge ahead for treatment of nosocomial infections, it is necessary to implement the guidelines of infection control to reduce P. aeruginosa infections