فصلنامه دنیای میکروب ها
سال ششم شماره 4 (پیاپی 17، زمستان 1392)

The microbial cellulose which is produced by some strains of Acetobacter and Gluconobacter is structurally similar to plant cellulose. Based on this feature, the microbial cellulose has been used in medical and industrial productions as an important raw material. The aims of this study were to isolate the native bacteria species producing cellulose and to evaluate their production rate. In this study, 65 samples were collected from different types of local vinegars, juices and fruits and were cultivated in Hestrin-Schramm's agar medium. Afterward the isolates with maximum ability to produce cellulose were selected and identified using biochemical tests and PCR method. After purification of the cellulose, enzymatic digestions method by cellulase enzyme and scanning electron microscope were used to confirm the presence of cellulose.   Totally, 20 strains with the cellulose production ability were isolated, of them 5 strains with maximum production ability were selected for further investigation. Base on biochemical tests and sequencing method, theses isolates were classified as Acromobacter spanius, Pseudomonas luteola and Pseudomonas durifulva. In this study, the wet and dried weight of the cellulose production were measured as 16.6 and 0.1g, respectively. According to the findings, the cellulose can be produced by native isolates other than Acetobacter and Gluconobacter. In this study, the new native strains of produced cellulose were introduced for the first time in Iran. Also, the produced cellulose by these species has suitable traits in comparison with standard strains.

Non-tuberculosis Mycobacteria (NTM) are important due to increase in the rate of clinical outbreaks and emerging antibiotic resistance. Mycobacterium fortuitum is the most common NTMs in Iran. This study was aimed to molecular detection and genetic diversity of clinical isolates of M. foruitum in Iran using RAPD-PCR method. This cross-sectional study was carried out on 81 isolates of NTM isolated from various clinical samples. The primary identification of M. fortuitum was performed based on Acid Fast staining and routine biochemical tests. After confirmation of the isolates based on PCR, the PCR products were digested with AvaII, HphI and HpaII. The molecular typing of the M. fortuitum isolates were performed using PAPD analysis. Out of 81 tested NTM, 36 strains were confirmed as M. fortuitum. Based on RAPD primers, these isolates were classified into 10 main clusters. Most of the isolates were distributed into RAPD types of 1 (9 members, 25%), 2 (8 members, 22.2%) and 6 (6 members, 16.6%). In RAPD analysis, the major fragments were 300 bp (94.4%), followed by fragment 1000 bp (66.6%). The results showed high discriminatory ability of RAPD–PCR method. This analysis is able to sufficiently discriminate the genotypic diversity and to prepare epidemiologic information of the M. fortuitum isolates. RAPD techniques is simple, rapid, inexpensive, and is less complicated than most of other molecular typing methods.

Pseudomonas aeruginosa is one of the most common antibiotic resistant bacteria and, therefore, treatments of Pseudomonad-caused infections are complicated. MexAB-OprM pump exports many antimicrobial compounds regardless of their structural and functional similarities. The mexB gene encodes a proton-drug antiporter in MexAB-OprM pump. The present study was aimed to evaluate and detect the quinolone resistance associated with efllux pumps mexAB-oprM in P. aeruginosa isolated from clinical specimens. This cross-sectional study was performed on 104 P. aeruginosa isolated from patients hospitalized in Trauma and Burn Intensive Care Unit (TBICU). The Genera and strains were identified primarily based on biochemical tests. The evaluation of antibiotic resistance pattern was carried out using disk diffusion method for 11 common antibiotics and microdilution broth method for 4 antibiotics. The presence of mexB gene was investigated using PCR method. According to the results, the most antibiotic resistance pattern were seen through treatment with nalidixic acid (86.54%), ceftazidime (82.2%) and ofloxacin (81.78%). Furthermore, the minimum antibiotic resistance were observed through treatment with imipenem (40.91%), piperacillin (44.9%) and tetracycline (48.03%). Based on MIC, the highest and lowest antibiotic sensitivity was recorded for tetracycline and ceftriaxone, respectively. Based on the PCR method, 27% of the clinical isolates harbor the mexAB-oprM operon. Based on the results, there is a significant association between presence of mexB gene and mexAB-oprM pump and antibiotic resistance in P. aeruginosa. Regarding the importance of antibiotic resistance, the study of other efllux pumps, comparison of antibiotic resistance profile and the relationship between efllux pumps and clinical origin of the strains are recommended.

Staphylococcus aureus is one of important etiology of contagious infections in community and hospital (nosocomial infections). Nowadays, an intensive increases in the antibiotic resistance is recorded due to increase in the rate of antibiotic usages worldwide. This study was conducted to track the antibiotic resistant genes in the S. aureus strains isolated from clinical specimens obtained from humans and to determine the antibiotic sensitivity pattern or the strains. In this cross-sectional study, 100 coagulase-positive S. aureus collected from urinary tract infections and skin wounds of the patients hospitalised in the Imam Reza hospital, Kermanshah, through 2012. These strains were selected using laboratory standard methods and culture-specific. The antibiotic susceptibility testing was performed using disk diffusion on plate. Furthermore, the presence of 5 genes responsible for antibiotic resistance, including mecA, aacA-D, tet K, tet M, msrA, ermA, were investigated using multiplex-PCR method. Based on the phenotypic investigation on antibiotic resistance of S. aureus strains, the highest rates were seen in treatment with penicillin (90%), tetracycline (76%), methicillin (64%), ampicillin (55%) while the lowest sensitivity was observed in treatment with nitrofurantoin (8%) and vancomycin (14%). The most prevalent gene was tetM (89%), followed by mecA (58%), ermA (40%), msrA (36%), aacA-D (24%) and  tetK (13%). Our result showed high rates of antibiotic resistance in the S. aureus isolated from this hospital. Therefore, it is recommended to limit the antibiotic uses without prescription or in unnecessary cases in order to decrease rate of microbial resistance to antibiotics.

Listeria monocytogenes is able to cause infections in humans and around 50 species of animals. Meats and their derivatives show a potential role in the transmission of Listeria to humans  and epidemy of listeriosis. The aim of this study was to determine the contamination of poultry meats whit L. monocytogenes and to find out the frequency of ctpA gene.
This cross-sectional study was carried out on 410 samples collected from poultry, including 110 fecal samples and 100 samples from each of liver, spleen and brain samples. Isolation of L. monocytogenes was performed using specific medium. PCR was performed using L. monocytogenes 16S rRNA and ctpA gene specific primers. Also, all of the 410 samples were tested directly using PCR.
Totally, 20.24% of the samples were positive for Listeria in culture method. The presence of Listeria in fecal, liver, spleen and brain specimens were 36.30%, 19%, 19% and 12%, respectively. However, based on PCR, 25.12% out of 410 samples were infected to Listeria. Furthermore, ctpA gene was found in 34.95% of Listeria.
The results indicate that the frequency of L. monocytogenes in the poultry samples of this region is relatively high. PCR techniques make it possible to determine the L. monocytogenes infection directly in fresh samples.

Contamination of soil and groundwater by diesel released from underground storage tanks is an important and extensive environmental challenge in Iran. The aim of this study was to isolate and molecular identification of n-hexadecane-degrading bacteria from compost.

In this study, hexadecane was used as a model for contamination to diesel oil. We used compost in order to isolate hexadecane degrading bacteria. Then, the selected bacteria was identified using PCR method. Finally, the efficiency of isolated bacteria for consumption of hexadecane as sole source of carbon and the growth rate of the bacteria in different concentrations of NaCl were evaluated.

Based on morphology, biochemical tests and sequencing, the isolated bacteria identified as Sphingomonas yanoikuyae. This bacteria could remove 49.69% of n- Hexadecane after 33 days in 30 C. The concentration of n- Hexadecane decreased from 3000 mg to 1510 mg. In addition, the results showed that isolated bacteria can growth on 2.5% salinity.

The results of this study showed that S. yanoikuyae can be used in remediation of petroleum products, especially diesel oil, in tropical and semi-salinity area in Iran. Therefore, further investigations using molecular approaches is recommended.

Nowadays, rice is the foodstuff for half the populations, worldwide. Rice is exposed to fungal and aflatoxin contaminations like other cereal. This study was aimed to investigate and to compare the amount of aflatoxin in rice samples in Rasht city and effects of cooking on the level of toxin.
This cross-sectional study was carried out on 72 samples of consumed rice from domestic and imported productions bought from six stores in Rasht city in both summer and winter. At first aflatoxin was extracted using 80% methanol in three different types of samples including raw, boiled and water cooked. Then aflatoxin content was determined in each sample using the ELISA technique.
Domestic samples were less contaminated than imported ones. Samples collected in the summer were less contaminated than winter. Also, in all cases, the cooked rice was less contaminated than seen in raw rice. This reduction rate of contamination was more effective in cooked water rice than in boiled.
The results showed that all rice was contaminated in different levels. Therefore the needs for constant control and supervision over the contamination of rice must be considered. Since the contamination rate of imported rice was more than domestic one, for the purpose of reduction imported rice, the basic steps in order to increase domestic production of rice should be supported.

In 1910 scientist notified the existence of fungi in rumen. Based on chitin content in their cell wall, they were classified as true fungi referred to as Neocallimastix frontalis. Based on morphological characters such as number of flagellates in zoospore, rhizomycelium, shape of sporangium, ultra structural of zoospore and nucleotide sequences data, these fungi are recently classified into two monocentric and polycentric groups, consisting of six genera.

In the present study, literature search was performed based on search of MeSH keywords, such as phylogeny, monophyletic, Neocallimastigomycota, rumen fungi, in several online research tools, such as Pubmed Medline, Scopus, Google scholar, Elsevier databases, Irandoc, Iranmedex, Magiran, SID and MEDLIB limited to the articles published between 1992 to 2013.

Different characterises of these fungi such as life cycle, reproductive structures, vegetative thallus and molecular data revealed phytogenic relationship of rumen fungi to the members of Chytridiomycota. Phylogenetic analysis of these fungi and their relatives with other eukaryotes using 18S rDNA sequence data, analyses of structural data and the G+C content showed that this fungi are monophyletic organisms.

The investigations on inhibitors and their roles in the interactions between fungi and bacteria can be useful to understand the microbial ecosystem of the rumen. Detection of these factors can be used to determine new ecologic relationships in the rumen. Furthermore, detection of the inhibitors of bacterial activity in the rumen can be used to increase the activity of fungi on plant fibres in this ecologic community.