نشریه میکروب شناسی پزشکی ایران
سال دوازدهم شماره 6 (بهمن و اسفند 1397)

The most important factor for pathogenicity of Staphylococcus epidermidis is the ability to produce biofilm. Identification of biofilm-forming strains using an appropriate method and recognizing the mechanisms of biofilm formation can help understand the proper use of artificial medical equipment and prevent increased drugs resistance . The aim of this study was to 1) evaluate the biofilm formation of S. epidermidis isolates using phenotypic methods such as Tube Method (TM), Congo Red Agar Method (CRA) and Microtiter Plates Method (MTP) as well as PCR of the genes icaA and icaD 2) determine the drug resistance pattern of S. epidermidis isolates and its association with biofilm formation among clinical specimens and samples of healthy carriers. A total of 90 strains of S. epidermidis including 50 clinical isolates and 40 strains from healthy carriers were studied using the phenotypic methods TM, CRA and MTP, and the molecular PCR of the genes icaA and icaD. Antibiotic resistance profile of the strains was performed using disk diffusion method according to the CLSI standards. A total of 90 strains ( 63.34% by TM, 37.78% by CRA method and 67.79% of MTP method) were able to form biofilm. No significant differences were found between the healthy and carriers groups in terms of antibiotic resistance. The icaA and icaD genes were detected among 100% and 85.24% of the biofilm forming strains, respectively. Comparing the phenotypic and molecular methods for the detection of biofilm formation among S. epidermidis isolatesshowed that MTP is the best method with the highest sensitivity and specificity and its simultaneous use with molecular methods is recommended.

Mycoplasma pneumoniae is one of the most important pathogens causing human respiratory tract infection; especially in community-acquired pneumonia (responsible for 10 – 40% of these infections).The aim of this study was to evaluate the prevalence of Mycoplasma pneumonia in patients with respiratory infections from Mostafa Khomeini and Khatam hospitals, by culture and molecular methods. In this study, 100 samples of throat swab from patients with respiratory infections were collected. All samples were cultured in PPLO broth and PPLO agar. After culture and genomic DNA extraction, PCR was carried out using specific M. pneumoniae primers. In this study, 14 (14%) colonies of Mycoplasma were isolated on PPLO agar medium. Using specific primers, 17 samples (17%) were detected as Mycoplasma genus and 6 samples (6%) were confirmed to be M. pneumoniae species. Based on the results of this study, For the detection of M. pneumoniae among the respiratory infections cases PCR is a highly reliable and sensitive method compared to the culture media. Using specific primers, PCR can confidently detect and separate infectious agents even in the genesis and species level.

Many bacteria including Escherichia coli may enter into a viable but non-culturable (VBNC) state under unfavorable stresses, which are unable to be detected by culture-based methods. In this study, the use of Reverse Transcription PCR (RT-PCR) for detection of VBNC state of E. coli O157:H7 was investigated.  Escherichia. coli O157:H7 was inoculated in distilled water and 30 percent salt water at room temperature. The cultivability of bacteria was determined using routine culture and colony counting on MacConkey agar. The RT-PCR of 16S rRNA gene involved direct extraction and purification of RNA, DNase I treatment for removing DNA contamination, cDNA synthesis and electrophoresis of PCR products of cDNA was used to detect viable E. coli O157:H7 under studied treatments and was compared with the results of RT-PCR of 16S rRNA gene of heat- killed bacteria. The cultivability of bacteria was maintained during the study period in distilled water; however, the use of 30percent NaCl caused the bacteria to be non-cultivable on day 4. The RT-PCR of 16S rRNA showed the positive expression of this gene in cultivable and non-cultivable bacteria during the study period, whereas heat-killed bacteria were negative for this gene, which indicated the efficacy of RT-PCR of 16S rRNA in differentiation of alive from dead bacteria. Escherichia coli O157:H7 entered into the VBNC under 30 percent NaCl which can be associated with serious human health problems. RT-PCR can be used to detect bacteria in the VBNC state.

Bacteriophages are mandatory bacterial parasites that are harmless to human and animal, which are used by dipping or spraying in food as natural antimicrobial agents. The use of these methods leads to wasting or trapping of phage in food, but its immobilization on the polymer surface facilitates the contact of phage with the host cell at the food surface. Therefore, the aim of this study was to immobilize the lytic phage of Escherichia coli on the cellulose acetate film and investigate of its antimicrobial effect. Escherichia.coli bacteria was incubated at 37°C for 24 hours, and the antimicrobial effect of phages was evaluated through plaque forming. The cellulose acetate film was prepared by casting, then modificated by plasma, and immersed in a suspension of phage (1010 PFU/ml) and incubated at 37 °C for 24 hours with slow shaking, then the number of immobilized phages was estimated. To confirm the immobilization, FESEM was done. The antimicrobial effect of the active film was evaluated by disk diffusion and the release rate and antimicrobial activity of immobilized phages were investigated in 14 days. Phages formed clear plaques against E.coli. Modification of film by plasma resulted in uniform immobilization (108 PFU/ml) that FESEM revealed it. The active film (with zone diameter 12 mm) showed stronger antimicrobial effect than the antibiotic ampicillin (positive control sample with zone diameter 8 mm). 11 days after the immobilization, the number of immobilized phages decreased from 108 to 106 (PFU/ml) and released from the film surface, afterwards did not release. The antimicrobial activity of active film was decreased due to the absence of host bacteria continuously in 15 days, so that the host bacteria population increased from 3 to 5.3 LOG CFU/ml. In spite of reducing the antimicrobial activity of cellulose acetate active film over the time, due to the presence of host bacteria at food surface and its high potential in destroying the host bacteria, it can be used to increase of food safety in food packaging.

Marine Actinomycetes are gram-positive bacteria that sometimes are free, saprophytic or plant and animal-associated, including marine sponges. More than 75% of antibiotics and antimicrobial compounds are produced by actinomycetes. In recent years, due to the need for new drugs, marine microorganisms have been considered as new sources of potential production of significant metabolites. The purpose of this study is isolation and identification of marine sponge-associated Actinomycete and investigation of its antibacterial activity. The Actinomycete was isolated from the marine Sponge collected from the depths of coastal waters in Bushehr and screened for antibacterial activity on pathogenic microorganisms of Escherichia coli، Bacillus cereus، Klebsiella spp.، Salmonella spp. and Proteus spp. using a Disk Diffusion Method. For molecular identification, genomic DNA was first extracted from isolate and then, the16S rDNA gene was amplified by PCR and Sequenced. The results were analyzed using bioinformatic programs, Bioedit and MEGA6. In this study, based on phylogeny studies, it was determined that the isolate belonged to thegenus Streptomyces, and biochemical studies showed that all tests except catalase and gram were negative; antibacterial activity study showed significant activity against three pathogenic bacteria, E. coli, Bacillus cereus and Salmonella spp. It was more active against Salmonella spp. (around 16mm inhibition zone diameter). The results showed that depths of the Bushehr coastal waters have marine sponge associated actinomycetes, which are a source of secondary metabolites with biological activity.

Cyanobacteria are considered as favorable source for new pharmaceutical compounds. To date, the majority of bioactive metabolites isolated from cyanobacteria are either polyketides (PKSs) or non-ribosomal peptides. Despite of several worldwide studies on prevalence of PKSs, none of them included the terrestrial cyanobacteria of the Lavasan. Therefore, this study aimed to detectthe PKS genes and correlation of the presence of these genes with antimicrobial compounds synthesis. Morphological and molecular identification of the terrestrial strains was performed after culture and purification. Amplification of polyketide synthase and phylogenetic trees were used for ‎phylogenetic analysis. Nucleotide and protein sequences were deposited in GenBank. Lastly, to show the correlation of this gene with antimicrobial compounds synthesis, antibiogram bioassay was used. Phylogentic analysis revealed that most of the identified 16SrRNA genes and PKS domains had more than 90% similarity to their closest matches in the Gen-Bank. In addition, antibiogram assessment showedthe different pattern of inhibition, indicating the involvement of variety antimicrobial substances. According to the results of this sudy, it seems the antibiogram bioassay and molecular detection of polyketide synthase genes are useful techniques for the assessment of productive species of natural products and the possible role of polyketide synthase enzyme complexes in the biosynthesis of biologically active compounds.

Candidiasis is a fungal infection caused by Candida albicans. Uncontrolled use of antibiotics has resulted in drug resistance. This study has been conducted to find a suitable alternative for these drugs. Primarily, standard and clinical isolates of C.albicans were collected. In order to indentify clinical isolates from lambs, the conventional mycological methods CHROM candida agar and germ tube production were used. The Antifungal effects of experimental treatments were evaluated against C.albicans by disk diffusion and measuring the growth inhibition zone in well diffusion method. Moreover, the MIC and MFC of experimental treatments were determined by microdilution method. The results of the well and disk diffusion methods showed that in both tests, the highest growth inhibition zone of the "Nano selenium-loaded lactobacillus" treatment was 29/41 and 27.64 mm, respectively on the standard strain of C.albicans. The results of MIC and MFC determination showed that in all experimental periods, "Nano selenium-loaded lactobacillus" and "Nano selenium+Lactobacillus" treatments with 473.80 and 511.91 μg/ml for MIC and 807.66 and 845.28 μg/ml for MFC had the lowest amounts compared to other treatments (P<0.05). The results of microbial tests on C.albicans confirm the antifungal ability of "Nano selenium-loaded lactobacillus" treatment. Therefore, provided that this test is repeated in future studies and the accuracy of these results is ensured, manufacturing of this product or industrial supplements with this formulation may be advised for prevention or treatment of fungal infections.

Hydatidosis is one of the most important zoonotic parasitic diseases. Hydatidosis is endemic in Iran and is the cause of hospitalization of almost 1% of patients in surgical wards. The purpose of this study is to examine the epidemiologic status of hydatid cyst in patients undergoing surgery in Golestan hospital of Ahvaz during 2002-2011 using archived files of the patients. This research is a cross-sectional study. During the mentioned period, 2002 until 2011, 55 patients in Ahvaz Golestan hospital have undergone hydatid cyst surgery and the information in the patients' files were examined by referring to the relevant archives in the mentioned hospital. Among the 55 patients studied, 37 (67.3%) were female and 18 patients (32.7%) were male. The highest incidence rate was found in liver with 47 cases (85.5%), followed by lung with 5 cases (9%). Considering the results, the highest prevalence rate was found among urban residents (n=33 ,60%) whilst 22 cases(40%) belonged to the rural residents. The results of this study indicate that the occurrence of the disease was significant in Khuzestan province during the mentioned period which reflects the necessity of more comprehensive and updated studies.