فصلنامه دنیای میکروب ها
سال دهم شماره 4 (پیاپی 33، زمستان 1396)

Acinetobacter spp. are non-fermenting Gram-negative bacteria that are associated with nosocomial infections. They are serious opportunistic pathogens with resistance to many antibiotics due to the presence of Metallo-beta-lactamase (MBL) genes. The aims of this study were to determine antimicrobial susceptibility and frequency of MBLs genes in clinical isolates of Acinetobacter species in Shahid Mohammadi hospital, Bandar Abbas, Iran.
Material & This descriptive- cross-sectional study was carried out on 81 Acinetobacter isolates collected from different clinical samples from Shahid Mohammadi hospital, Bandar Abbas, Iran. The bacteria were identified to the species level by Microgen GNA-ID System kit. The Kirby-Bauer disk diffusion test was used to determine antibiotic resistance pattern. MIC of meropenem was determined by E-test, and MBLs production was detected by imipenem-EDTA synergy test (CDST method). The isolates were then subjected to polymerase chain reaction (PCR) for detection of blaIMP and blaVIM genes.
Out of 81 isolates, 79(97.54%) were identified as A. baumanni, 1 (1.23%) as A. lwoffii and 1(1.23%) as A. haemolyticus. Acinetobacter spp. showed the highest resistance to imipenem and meropenem (81.5%) and the highest susceptibility to polymyxin B (96.3%) and colistin(95.1%), respectively. MIC determination by E-test revealed 77.8% of isolates as meropenem- resistant.76.5% of isolates were identified as MBL- positive by CDST method. Also, 13 (16%) isolates carried blaIMP gene, but none of them had the blaVIM gene.
Dissemination of MBL- producing A. baumannii is worrisome. In order to reduce and control Acinetobacter infections, implementation of strict surveillance, and judicious prescribing of antibiotics is necessary.

Due to antimicrobial properties of plants, lots of attention has been recently paid to the addition of natural ingredients to pharmaceutical, food and healthcare systems. The aim of this study was investigation and synthesis of thyme essential oil - containing nanoparticles as bio-detergents.
Material & Thyme essential oil was extracted and purified using Clevenger apparatus. Then nano-niosomes containing thyme essential oil was prepared by Bangham method using Tween 60, Span 60 and lipid cholesterol. Then, two methods were investigated in order to reduce the particles size (bath and probe sonication). The nanoparticles were characterized in term of release rate, size, zeta potential, morphology, infrared spectra and loading efficiency. The antibacterial properties of the detergent against Staphylococcus aureus were studied in term of the minimum bactericidal concentration (MBC), Minimum Inhibitory Concentration (MIC) and inhibition zone.
The results showed a smaller particle size resulted from probe sonication compared to bath sonication. The essential oil loading efficiency of particles prepared by bath sonication was 4.65% higher than the probe sonication method. Type of sonication did not change the zeta potential of nanoparticles. The essential oil was physically encapsulated in the nano-niosome, without changing its properties during encapsulation. The nanoparticle was uniformly disturbed with spherical structure. The results showed a significant anti-bacterial property of the detergents against Staphylococcus aureus (MBC of 15.625 µg/ml).
Bath sonication is economically recommended compared to probe sonication in preparation of nanoparticles. The results of this preliminary study introduce an anti-bacterial herbal detergent which can be more developed in further studies.

Moderate halophiles are excellent sources of enzymes that are not only salt- stable, but also have optimal activities at a wide range of pH and temperature. The aim of this study was the isolation of moderately halophilic protease-producing bacteria from saline soils in Alborz province.
Material & Screening of the protease- producing halophilic bacteria was carried out by skim milk agar containing 5% NaCl. Enzyme assay was investigated by the colorimetric method and the effect of various parameters such as temperature, pH, and different NaCl concentrations on enzyme activity were assessed. Identification of the isolates was carried out by biochemical as well as molecular methods.
A total of 11 halophilic strains with proteolytic activity were isolated among which the strain B8 with higher clearance zone on skim milk agar and 3.2 Unit/mL supernatant activity was chosen for further analysis. The enzyme exhibited its optimal activity at the temperature of 40◦C, pH of 7.5 and NaCl concentration of 0-0.5 M, although at higher salinities (up to 3 M) activity was still remained. The enzyme was active at a broad pH range, keeping 60% of its activity at pH of 9.5. Phylogenetic analysis based on 16S rRNA gene sequencing identified the isolate as Halomonas. It was deposited in GenBank, with the name of Halomonas sp. strain HM_NG2.
These findings suggest that the protease secreted by the isolate of this study could be a good candidate for biotechnological applications due to its moderate thermo-stability and halloalculophytic properties.

Provision of useful strategies and targeted plans in order to reduce the consumption of available water resources and also create good quality wastewater is necessary due to current lack of water resources. This study was carried out to investigate the removal of ammonium nitrogen and orthophosphate from urban wastewater using two microalgae strains.
Material & For this purpose cultured cells of Chlorella and Oocystis were mixed up with 4% sodium alginate solution. The resulting mixture was added to a solution of calcium chloride in order to form alginate globules containing microalgae cells. To measure cell growth, Neubauer Chamber counting method was used. The amount of nitrogen and orthophosphate removal was measured by light absorption method using Nessler's and Armstrong’s reagents, respectively.
Oocystis removed about 65.2 % of the ammonium nitrogen following 14 days of treatment. Moreover, the overall efficiency of the orthophosphate removal was 69 %. In case of Chlorella, the rate of ammonium nitrogen removal was 74.3 % following 4 days of treatment and reached 100% following 7 days of treatment. The overall orthophosphate removal efficiency was 62.27 %.
The results indicated that Chlorella has the convenient ability to remove nitrogen and phosphorus from wastewater in designed conditions.

It is now realized that fungi, specifically molds, have the potential to eliminate a variety of compounds, especially toxic and heavy hydrocarbons. The aim of this study was to investigate the ability of native mold isolates in biodegradation of petroleum pollutants and also the effect of surface active compounds on the removal efficiency.
Material & Plenty of mold strains were isolated from an oil-contaminated area in Sarkhoon area of Hormozgan state. The capability of these isolates in petroleum biodegradation was studied in a salt-based medium containing one percent crude oil. The superior strain was selected and characterized by Internal transcribed spacer (ITS) gene sequencing analysis. Biodegradation rate of 500 ppm pyrene (heavy aromatic hydrocarbons) and 1% tetracosane (heavy aliphatic hydrocarbons) by selected strain was investigated. Finally, biodegradation rate of these pollutants in the presence of rhamnolipid (0.01%) and tween 80 (0.2%) was studied.
Among 40 different fungal isolates of this study, the F11 strain was selected as the superior one, base on crude oil biodegradation rate. The molecular identification showed 99.52% similarity of F11 strain to Aspergillus calidoustus. In 21 days, A. calidoustus could degrade crude oil, pyrene, and tetracosane about 54.59%, 51.43%, and 58.84%, respectively. Furthermore, crude oil, tetracosane, and pyrene biodegradation were increased to 70.97%, 79.44%, and 62.77% in the presence of rhamnolipid and to 66.78%, 74.74%, and 60.16%, in the presence of tween 80, respectively.
According to the results of this study, A. calidoustus has a great ability in biodegradation of heavy hydrocarbons. Also, it was shown that surfactants can increase the rate of hydrocarbons degradation, with much effect on aliphatic hydrocarbons, such as tetracosane, than aromatic compounds like pyrene.

Pasteurella multocida is a Gram-negative facultative bacterium, causing respiratory diseases in various domestic and wild animals. The aim of this study was isolation and identification of P. multocida and investigation of ompH gene polymorphism of in goats P. multocida isolates.
Material & In a cross-sectional study a total of 160 swab samples from nose and throat of goats infected with Pasteurellosis in Fars province were collected. The ompH gene polymorphism in 26 isolates was genotyped by PCR-RFLP technique. Restriction digestion was performed using HindIII and EcoRI endonuclease enzymes. Each sample was injected into two mice at a concentration of 0.5 McFarland's standard. After ompH gene digestion by endonuclease enzymes, RFLP patterns were compared with mice mean dead time (MDT).
Each HindIII and EcoRI enzymes made different patterns, which were remarkable in comparison with MDT in mice. All lethal isolates had MDT less than 24 hours. Out of 29 P. multocida isolates, 89.6 % were lethal in mice.
According to established patterns, MDT in mice was different. Based on the results, the samples with more frequent patterns killed mice in a shorter time and were more lethal. Enzyme digestion patterns can be used to detect virulent and pathogenic strains and to provide vaccine strains. Considering the variability of these strains, the production of multiple vaccines is necessary.

Probiotics are living microorganisms which when administrated adequately, confer benefits to hosts. In order to estimate the probiotic potential of these microorganisms, it is necessary to assess their health benefits, efficacy, and safety. This study was aimed to evaluate gut adhesion capacity of Lysinibacillus sphaericus DY13 and Bacillus clausii DY14 strains which were previously isolated from healthy human milk, and to assess the effects of natural and commercial prebiotics on bacteriocin production by these two strains.
Material & L. sphaericus DY13 and B. clausii DY14 isolates were evaluated for tolerating the artificial gastrointestinal conditions. Moreover, isolates were examined for auto-aggregation, co-aggregation, and cell surface hydrophobicity properties. The prebiotic effect of mannitol, sorbitol, garlic, onion and honey on the enhancement of bacteriocin production against Escherichia coli, Bacillus cereus, Bacillus subtilis, Pseudomonas aeruginosa and Staphylococcus aureus was also evaluated.
Compared to the control, auto-aggregation potential of DY13 and DY14 was found to be decreased by 4%. Both isolates have demonstrated preeminent auto-aggregation potential. The hydrophobicity percentage of DY13 and DY14 isolates typically ranged between 51-52.7% and 59.1-66.1%, respectively. Comparing the effect of selected prebiotics on bacterial isolates growth and bacteriocin production revealed that honey is the best source to improve the growth of bacterial strain, and also to stimulate bacteriocin production.
Due to considerable adhesion potential of both selected strains, they can be applied as suitable and efficient probiotics, along with honey as prebiotic.

Bean (Phaseolus vulgaris L.) is now widely used as a major food product in many tropical areas and semi-temperate and temperate areas of America, Europe, Africa as well as Asia. Damping off and seed rot are the most frequent and damaging diseases of the legumes worldwide which are caused by Rhizoctonia solani. The purpose of this study was isolation and characterization of rhizosphere bacteria for the biocontrol of the R. solani in the bean.
Material & Four isolated bacteria from bean plants rhizosphere soil in Lorestan province farms were evaluated in vitro as a potential antagonist of the fungal pathogen. In vitro inhibition of R. solani mycelium growth by rhizosphere bacteria were tested on rye agar media. The degree of inhibition in each medium was determined by measuring the halo around the bacterial strains.
Sequencing of 16S rRNA and its comparison with Gen Bank sequence database revealed that antagonistic strains belong to Pseudomonas fluorescens, Pseudomonas aeruginosa, Pseudomonas monteilii, and Pseudomonas putida species. All the strains significantly inhibited R. solani growth, resulting in more than 40% inhibition on potato dextrose agar medium (PDA). The results showed the most inhibition by P. putida, and the lowest by P. aeruginosa.
Rhizoctonia root-rot is a highly destructive disease in most areas of the world. Biological control using natural microorganisms offers a powerful alternative to chemical control of Rhizoctonia root-rot diseases.