فصلنامه دنیای میکروب ها
سال چهاردهم شماره 4 (پیاپی 49، زمستان 1400)

Xanthan gum is produced by Xanthomonas bacteria. This gum is    widely used in various industries. Random mutagenesis of xanthan-producing strains can increase xanthan production capacity several times. This study aimed to evaluate Xanthomonas mutant strains with high xanthan production capacity.Materials &

The native strain of Xanthomonas citri K37 was affected by nitrogenic acid mutagen and after initial screening, the mutant strains were selected based on the appearance and diameter of the colony formed on the c dye medium. Whey-based production medium was used to produce xanthan gum and then production indices such as beta-galactosidase activity, sugar consumption, production rate, and viscosity of xanthan gum were selected in selected mutant strains.

A total of 8 mutant strains were selected among all treated colonies. Two high-yielding strains named R3 and R8 and two low-yielding strains called M2 and M6 were selected to evaluate the activity of beta-galactosidase enzyme and glucose consumption. Strain R3 increased viscosity and amount of xanthan compared to wild strain equivalent to 200 cp and 2 g / l,  espectively, and mutant M6 lost the ability to produce xanthan.

From the native Xanthomonas citri K37 isolate, a new R3 strain was created during mutagenesis, which can be effective in low cost cheese whey as a xanthan-producing strain.

Soil microorganisms play an important role in the biological control of pathogenic fungi. The aim of this investigation was to isolate soil-borne Bacillus subtilis with the ability to produce antifngal lipopeptides  that are suitable  for suppressing Fusarium graminearum, which contaminates wheat, corn, potato and a wide range of plants.Materials &

B. subtilis was isolated from the rhizospher of healthy plants of park slocated in the five areas north, south, east, west and center of Tehran and was identified based on morphological characteristics, biochemical tests and sequencing of 16S rRNA. The antagonistic activity of isolated strains against F. graminearum was investigated by Well method. The strains that inhibited the growth of fungi and showed the greatest inhibition zone, were selected. Surfactin of selected bacteria was purified by methanol method and bacterial metabolites and pure surfactin (Sigma Company) were compared with, high performance liquid chromatography (HPLC).

Among 60 isolated strains, 27 strains had antifungal activity. Six strains with the highest fungal inhibition zone (8-16 mm) were selected and their yellow color and transparency was a confirmation to HPLC. Two bacteria with the highest amount of surfactin production by  molecular method showed high similarity with B. subtilis.

The results show that Bacillus subtilis isolated from soil are good candidates for biological control of plant pathogenic fungi and therefore can a suitable alternative to chemical fungicides.

Acinetobacter baumannii is the clinically significant bacteria easily capable acquiring multi-resistance to antibiotics. This study aims to evaluate the pattern of         resistance, colistin resistance gene, and the study of genetic diversity of colistin-resistant strains isolated from Shahid Rajaee Hospital in Shiraz.Materials &

This descriptive cross-sectional study was conducted on A. baumannii strains isolated from patients admitted to the intensive care unit ICU of Shahid Rajaei Hospital in Shiraz. A. baumannii strains were identified and confirmed by Microgen kit and blaOXA-51 gene. Antibiotic susceptibility testing was then performed by disk diffusion method according to CLSI 2020 instructions. PCR method was used to study pmrA and pmrB genes and also genetic           diversity of A. baumannii strains was analyzed by SPSS software and NTSYS version2.10e.

Fifty strains of A. baumannii were isolated and identified. These strains had multi-resistance and showed high resistance to most antibiotics. The lowest rate of resistance was observed to colistin and tigecycline antibiotics. In the study of colistin-resistance genes,  colistin-susceptible and colistin-resistant strains of A. baumannii carried pmrA and pmrB genes, respectively. Colistin-resistant strains were placed next to colistin-sensitive strains in a node in the dendrogram.

The results of the present study revealed the frequency of multi-resistant  A. baumannii strains in the hospital. These strains belonged to a common clone and seem to be circulating in the hospital. Infection control programs are required to be implemented in hospital wards.

Background &

Pasteurella multocida is an opportunistic microorganism responsible for haemorrhagic septicaemia in cattle and buffalo and pneumonia in sheep and goats. Adhesion factors play crucial role in attachment to cell surfaces, host invasion and colonization. The aim of this study was to identify the frequency of adhesion genes from P. multocida isolated livestock. Materials &

This study was performed on 50 samples isolated from ailing sheep, goats and cattle. Amplification of kmt1 gene with the aim of determining the molecular identity of the isolates and identifying adhesion genes (fimA, hsf1 and hsf2) were performed by using simple PCR method.

PCR results show that, the frequency of fimA and hsf2 genes were 44% and 80%,  respectively. In addition, hsf1 did not exist in the isolates. hsf2 was the only adhesion gene which was identified in cattle. So it may be plays a crucial role in invasion of this host. Moreover, it was found that there is a significant correlation between hsf2 gene and capsule type D.

In the present study, new information was obtained regarding the frequency of adhesion genes in P.multocida strains isolated from multiple livestock in Shiraz. Investigating the pathogenicity role of adhesion genes in laboratory animals and determine the role of these factors in immunity to pasteurellosis are recommended.

Background &

Toxoplasma gondii is a parasite which definitive hosts, Felid and cats, play a critical role in transmission and distribution of the parasite and their immunization is a proper way to control the infection. The aim of the present study is to evaluate the                       immunogenicity of Toxoplasma gondii attenuated isolate produced in Razi Institute branch of    Shiraz in catsMaterials &

Twelve male DSH (Domestic short hair) kittens aged 3-6 months were  randomly divided into three groups; each contains four cats. The First group received tachyzoites of Toxoplasma gondii attenuated isolate at a dose of 10×106 by injection, the second group         received a dose of 25×106 orally and the last group received culture medium as a control. The  humoral immune responses and Cellular immunity evaluated by modified agglutination and skin test. One month after immunization, all cats were challenged by Toxoplasma's PRU strain, after which the cats' feces were collected and molecular tests were performed for five days.

The results of modified agglutination and skin test showed that administration of oral and injection vaccine had a significant increase in comparison with control. Also, Molecular testing after challenge revealed that immunization of cats by oral and injection way of Toxoplasma gondii attenuated isolate could successfully prohibit oocysts shedding in cats.

In order to the significant immune responses and prevention of oocysts shedding, it is suggested that, using this isolation of Toxoplasma gondii as a possible candidate vaccine for cats in future studies.

Background &

Pseudomonas aeruginosa is one of the most important pathogens of opportunistic infections, which is considered as one of the main causes of nosocomial infections. The aim of this study was to isolate pseudomonas aeruginosa and identify strains with                  bla OXA-23 gene using polymerase chain reaction (PCR) technique.Materials &

In this study, 70 isolates of pseudomonas aeruginosa from various            infections including lung, urine, blood, wound and sputum were collected in north khorasan       hospital, after phenotypic and genotypic confirmation of the isolates, antibiotic discs of doripenem and imipenem (Rosco), meropenem and ciprofloxacin, colistin and amikacin (Mast) were used to perform antibiotic susceptibility testing of bacteria by disk diffusion method.

Isolates showed 32.8%, resistance to amikacin , 47.1% todoripenem, 37.1% to imipenem, 40% to ciprofloxacin, and 10% to colistin. The highest resistance of the strains was related to meropenem 61.4% and the lowest was colistin with 10% resistance.

In this study, the resistance of pseudomonas aeruginosa to the antibiotic meropenem was 61.4% and compared to other studies, including in ethiopia, showed a higher level of           antibiotic resistance, this level of carbapenem resistance indicates an increase in resistance of pseudomonas aeruginosa strains to carbapenems.