فصلنامه دنیای میکروب ها
سال چهارم شماره 3 (پیاپی 11، پاییز و زمستان 1390)

L-glutaminase is widely used in pharmaceutical and food industries, such as treatment of leukemia. This study aimed to isolate and identify native L-glutaminase producing bacteria in Iran and to study its quantitative activity in submerged fermentation. The L-glutaminase producer bacteria were isolated from soil and water samples of Zayandehrod and Karoon Rivers and also from the sediments of fishing pools. The isolates were screened using minimal glutamine agar (MGA) medium for producing L-glutaminase enzyme. The samples were grown in a submerged fermentation system using mineral salt glutamine (MSG) medium, and the produced enzyme was assayed quantitatively. The best glutaminase producer bacterium was identified by the gram-staining and biochemical tests. In this study, 11 glutaminase producer strains were isolated. Bacillus subtilis CH3-GLU strain showed maximum enzyme productivity 37.91±0.62 U/ml at temperature 45° C after 96 hours. Based on this study, Bacillus subtilis CH3-GLU showed the highest rate of glutaminase production.

E. coli k99 is one of the major causes of diarrhea in neonatal calves. Colicin is an antimicrobial peptide produced by one strain of E. coli to suppress the growth of other strains of E. coli. The aim of this study was to control E. coli k99 infection in mice by oral administration of colicinogenic E. coli (CEC). This experimental study was conducted on two groups of control and treatment infant mice, strain BALB/c. The control group was subdivided into two groups: one group was fed with colicinogenic E. coli (CEC) and the second control group was E. coli k99. The treatment group was administrated with colicinogenic E. coli (CEC) and also with E. coli k99 in intervals. Finally, the mortality rate of the mice was assayed in both treatment and control groups. Results of this study delineated that all mice in the control group who were fed with colicinogenic E. coli was survived while 83% of the second control group (40 cases) died due to production of heat-stable enterotoxin. Our study showed that the mortality rate in the treatment group was significantly reduced, and the reduction rate was increased in higher doses of colicinogenic E. coli (CEC).  Based on the antibacterial activity of CEC against E. coli k99, colicin is an appropriate choice for control of the infection. Furthermore, it is possible to replace colicins instead of conventional antibiotics for control of the intestinal disorder.

Urinary tract infections (UTI) are among the most common infectious diseases. Nowadays, Escherichia coli (E. coli) is counted as the predominant cause of urinary tract infection in 80-90% of patients. Due to increase in the rate of antibiotic usage and subsequent drug resistance, this study was performed to evaluate the antimicrobial resistance pattern of E. coli isolated from patients with suspected urinary tract infection and phylogenetic grouping of these strains. This cross sectional study was conducted on 600 samples of suspected urinary tract infection from Hasheminejad super specialty kidney hospital. To isolate E. coli strains, all samples were examined with biochemical and microbial tests. Then using the standard disc diffusion method (Kirby-Bauer), drug susceptibility test was performed on 8 different antibiotics. Multiplex PCR technique and specific primers of chuA, yjaA genes and TSPE4.C2 fragment were used for phylogenetic grouping of the isolated E. coli strains. In this study the highest rates of resistance to antibiotics were seen against ampicillin (83.83%) and nalidixic acid (71.42%). Also, the lowest rates of resistance were reported against nitrofurantoin (3.12%) and ceftizoxime (11.22%). Based on phylogenetic studies, 65%, 19% and 16% of the isolated strains belonged to group B2, group D and group A, respectively. Also, the majority of antibiotic resistant strains and multi-drug resistant strains belonged to the phylogenetic group B2. As same as other reports around the world, most of the E. coli strains isolated from this region belonged to phylogenetic group B2.

Dipicolinic acid (pyridne 2, 6 dicarboxylic acid) is a major component of bacterial spore and is unique in that it has been found only in bacterial endospore. This study was aim to evaluate the environmental stress on DPA production in Bacillus cereus PTCC1015.  

In this experimental study the effects of environmental stresses including temperature, ethanol, NaCl and pH on the production of DPA by Bacillus cereus PTCC 1015 were evaluated by colorimetric assay (the color complex formed by interaction of ferrous iron with dipicolinic acid) and comparison with standard curves.

The results showed that the amount of DPA in B. cereus decreased upon increase in acidic condition and salt concentration in the medium. DPA formation increased at alkaline pH 8-10. DPA formation decreased in the medium containing 5-55% of ethanol. DPA formation was higher in optimum temperature at 30 ºCin comparison to the reference strains. The cell concentration decreased at 90 ºC and level of DPA detected in this stage.

In stressful condition, DPA formation significantly reduced and these properties can be used in food and dairy industries to control spore production of Bacillus cereus.

Leptospirosis is one of the most significant zoonotic diseases with intensive frequency worldwide. The infection of individuals in any given slaughter house is fortuitous and it will normally occur after a direct contact with animals’ urine or their carcass. This study was aimed to evaluate the rate of serum infection with the various strains of Leptospira interrogance among the industrial slaughter house personnel of Zanjan province. In this cross sectional descriptive study, 98 serum samples were collected from the personnel of the industrial slaughter house placedin Zanjan province throughout 2011. After sampling, all the serum samples were subjected to microscopic agglutination Test (MAT) by seven live Leptospiral serotypes (made by Razi Vaccine and Serum Institute, Karaj, Iran).   The results obtained from study of the serum samples indicated that 34 (34.7%) samples had positive reactions to one or more serovars. The remaining samples (65.3%) were serologically negative.Sejroe Hardjo, Grippotyphosa, and Canicola serovars were the most prevalent serovars of Leptospira with the frequency rates of %47.8, %15.2, and %13, respectively. Since there is a high frequency rate of seropositive cases in the personnel, there is a high possibility for transmitting of the contamination into the food cycle. Therefore, a vaccination program for the personnel is recommended.

Bats, the second largest group of mammals, are the reservoir of Histoplasma capsulatum. This fungus is found in soils enriched by bird droppings and bat guano especially in caves and fields and is transmissible to human beings. In this research, Histoplasma capsulatum infection of bats in the caves placed in Jahrom were investigated. In this study bats were captured with mist-net from 7 caves in Jahrom during 12 months (2010-2011). The bats were identified and classified according to taxonomic key in lab. The samples of skin, mouth, and internal organs of bats, were cultured in BHI media.   168 bats belonging to 11 species and 6 families were identified in Jahrom region but none of them were infected to H. capsulatum. Despite high population and diversity of bat as a source of this fungus and favorable conditions in terms of nutrition, topology and climate, no contamination was detected. This illustrated that some other factors, such as genetic of bats, or physiological and ecologic factors may influence the life cycle of the fungus.