Toxin-antitoxin Systems: Classification, Biological Function and Application in Biotechnology.

The toxin-antitoxin (TA) systems are systems in which an unstable antitoxin inhibits a stable toxin. This review aims to introduce the TA system and its biological application in bacteria. For this purpose, first we introduce a new classification for the TA systems based on how the antitoxin can neutralize the toxin, we then describe the functions of TA systems and finally review the application of these systems in biotechnology.

Genomic diversity and virulence genes among clinical isolates of Pseudomonas aeruginosa.

BACKGROUND: Typing of nosocomial pathogens is necessary to determine the source of an outbreak. The aim was to determine the genomic variability among Pseudomonas aeruginosa (P. aeruginosa) by random amplification of polymorphic DNA (RAPD) and enterobacterial repetitive intergenic consensus (ERIC) methods. METHODS: Fifty P. aeruginosa isolates were obtained from the hospitals. The source of these isolates were burn wound and urinary tract infections. After detection of P. aeruginosa by biochemical methods, chromosomal deoxyribonucleic acid (DNA) was extracted by a DNA extraction kit. ERIC-PCR and RAPD- PCR was done by standard methods. The polymerase chain reaction (PCR) products were run and visualized in 1.5% agarose gels stained with ethidium bromide. RESULTS: Fifty P. aeruginosa isolates were analyzed by ERIC-PCR and RAPD-PCR methods. Multiple PCR fragment sizes generated by two PCR methods and PCR product size were between 200-3500 bp, and 10 and 7 different PCR patterns were detected by ERIC-PCR and RAPD-PCR, respectively. Eleven isolates were not detected by ERIC-PCR method. Fifteen isolates were typed to a single genotype by the RAPD-PCR method. CONCLUSIONS: We suggested that ERIC and RAPD PCR are equally suitable, inexpensive, fast, reproducible, and discriminatory as rapid DNA typing tools for effective epidemiological surveillance of P. aeruginosa isolates. Our results suggest that these DNA typing tools could be used in routine epidemiological surveillance, outbreak surveillance, and in the identification of the source of transmission of P. aeruginosa.

Prevalence of heteroresistant Helicobacter pylori and treatment follow-up in patients in Ilam, Iran.

Background: Special antibiotics are prescribed against Helicobacter (H.) pylori. However, sometimes the bacteria are not completely eliminated, or they are recurrent. Unlike most infections, it is very difficult to eliminate a H. pylori infection. Heteroresistance is defined as the phenomenon in which subpopulations of the same colony of bacteria exhibit a range of susceptibilities to a particular antibiotic. Because of heteroresistant cells, antibiotic failure and chronic infection can occur; thus, the current research aimed to investigate presence of heteroresistant cells in H. pylori collected from patients reffering to clinic in Ilam, Iran. Subsequently, patients who were infected with heteroresistant H. p ylori were treated with antibiotics effective against heteroresistant subpopulations. Methods: In this cross-sectional descriptive study, 100 patients with clinical symptoms and suspected of being infected with H. pylori were studied in private clinics in Ilam, Iran. Fiftyisolates of H. pylori accompanied by patients' information were obtained from Ilam clinics. We cultured the bacteria to identify heteroresistance and to find the cause of recurrent infection in these patients. Results: Out of a total of 50 samples, 3 were heteroresistant to clarithromycin (6%). Levofloxacin was applied in cases of heteroresistant samples, and the effectiveness was determined after one month of follow-up of patients. Conclusion: Patients with heteroresistance showed sensitivity to levofloxacin. After one month of follow-up, it was found that the effectiveness of this antibiotic was good. Therefore, this antibiotic was introduced as a more effective drug in patients with heteroresistant H. pylori.

Application of proteomics in lab diagnosis.

Proteomics is defined as a large-scale study of proteins, in particular their functions and structures. This review was aimed to introduce the application of proteomics in lab diagnosis. Beforehand, we introduce the methods, which were used in proteomics also the advantages and disadvantages of proteomics are challenged. In the end, the necessity of proteomics for understanding the structure, function, and interaction of proteins in different fields of sciences including biomarkers, drug discovery, etc. will be discussed.

Metabolic engineering of Lactococcus lactis influence of the overproduction of lipase enzyme.

The dairy industry uses lipase extensively for hydrolysis of milk fat. Lipase is used in the modification of the fatty acid chain length, to enhance the flavours of various chesses. Therefore finding the unlimited source of lipase is a concern of dairy industry. Due to the importance of lipase, this study was an attempt to express the lipase from Burkholderia cepacia in Lactococcus lactis. To achieve this, a gene associated with lipase transport was amplified and subcloned in inducible pNZ8148 vector, and subsequently transformed into Lc. lactis NZ9000. The enzyme assay as well as SDS-PAGE and western blotting were carried out to analysis the recombinant lipase expression. Nucleotide sequencing of the DNA insert from the clone revealed that the lipase activity corresponded to an open reading frame consisting of 1092 bp coding for a 37·5-kDa size protein. Blue colour colonies on nile blue sulphate agar and sharp band on 37·5-kD size on SDS-PAGE and western blotting results confirm the successful expression of lipase by Lc. lactis. The protein assay also showed high expression, approximately 152·2 µg/ml.h, of lipase by recombinant Lc. lactis. The results indicate that Lc. lactis has high potential to overproduce the recombinant lipase which can be used commercially for industrially purposes.

Roles of Oxidative Stress and Nrf2 Signaling in Pathogenic and Non-Pathogenic Cells: A Possible General Mechanism of Resistance to Therapy.

The coordinating role of nuclear factor erythroid-2-related factor 2 (Nrf2) in cellular function is undeniable. Evidence indicates that this transcription factor exerts massive regulatory functions in multiple signaling pathways concerning redox homeostasis and xenobiotics, macromolecules, and iron metabolism. Being the master regulator of antioxidant system, Nrf2 controls cellular fate, influencing cell proliferation, differentiation, apoptosis, resistance to therapy, and senescence processes, as well as infection disease success. Because Nrf2 is the key coordinator of cell defence mechanisms, dysregulation of its signaling has been associated with carcinogenic phenomena and infectious and age-related diseases. Deregulation of this cytoprotective system may also interfere with immune response. Oxidative burst, one of the main microbicidal mechanisms, could be impaired during the initial phagocytosis of pathogens, which could lead to the successful establishment of infection and promote susceptibility to infectious diseases. There is still a knowledge gap to fill regarding the molecular mechanisms by which Nrf2 orchestrates such complex networks involving multiple pathways. This review describes the role of Nrf2 in non-pathogenic and pathogenic cells.

Prevalence of genomic island PAPI-1 in clinical isolates of Pseudomonas aeruginosa in Iran.

Pseudomonas aeruginosa, a gram-negative rod-shaped bacterium, is an opportunistic pathogen, which causes various serious diseases in humans and animals. The aims of this study were to evaluate of the presence of genomic island PAPI-1 in Pseudomonas aeruginosa isolated from Reference Laboratory of Ilam, Milad Hospital and Emam Khomeini Hospital, Iran and to study the frequency of extended spectrum beta-lactamases (ESBLs) among isolates. Forty-eight clinical isolates of P. aeruginosa were obtained during April to September 2010, and were evaluated for ESBLs by screening and confirmatory disk diffusion methods and PAPI-1 by PCR. Fifteen of 48 P. aeruginosa isolates were positive for ESBLs and 17 isolates positive for PAPI-1. This was first study of the prevalence of PAPI-1 in clinical isolates of P. aeruginosa in Iran, showing that most of PAPI-1 positive strains had high levels of antibiotic resistance and produced ESBLs.

Comparative analysis of biofilm development among MRSA and MSSA strains.

As the recalcitrance of biofilm-mediated infections to the anti-infective treatment has an adverse effect on patient's health, the main objective of this study was to investigate the capacity of clinical isolates of Staphylococcus aureus with different resistance patterns to form biofilms. S. aureus strains are among the most representative etiology of infections in the health-care environment of Milad hospital in Iran. The results showed that out of 80 analyzed strains, 27 methicillin resistant S. aureus (MRSA) and 29 methicillin susceptible S. aureus (MSSA) were positive for biofilm development ability, without any significant correlation observed between MRSA and biofilm production.

The Prevalence of ESBLs Producing Klebsiella pneumoniae Isolates in Some Major Hospitals, Iran.

Aims of this study were to investigate on antibiotic resistance and molecular epidemiology of K.pneumoniae producing ESBLs isolates of respiratory tract infections in some major hospitals in Iran. K.pneumonaie were obtained of patients with RTI. K. pneumoniae producing ESBLs detected by screening, confirming and PCR methods. During the 12-month period, a total of one hundred and thirteen of K.pneumoniae were found from RTI in three cities in different region of Iran which Sixty seven strains (59.2%) were ESBLs producer. In Ilam hospitals, seventeen strains (43.6%), in Milad hospital, thirty-seven strains (74%) and in Emam Reza hospital, thirteen strains (54.2%) were ESBLs producer. The findings showed that among sixty-seven K.pneumoniae producing ESBLs, Sixty-three strains (94%) were positive for blaSHV, eleven strains (16.4%) contained blaTEM and sixteen strains (23.9%) harbored blaCTX-M. Imipenem was found as an effectiveness antibiotic. In the current study, Majority of the ESBLs production had occurred in Milad hospital in Tehran (74%). In conclusion, spreading ESBL-producing strains is a concern, as it causes limitations to the antimicrobial agents for optimal treatment of patients.