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Aims: Methicillin-resistant Staphylococcus aureus (MRSA) is recognized as an important health problem worldwide. To counteract the human innate immunity, S. aureus produces a number of immune evasion cluster (IEC) including staphylokinase (SAK), staphylococcal enterotoxin P (SEP), staphylococcal enterotoxin A (SEA), staphylococcal complement inhibitor (SCIN), and chemotaxis inhibitory protein (CHIP) encoded by sak, sep, sea, scn, and chp genes, respectively. These genes are carried by β-hamolysin-converting bacteriophages. The present study was conducted to determine the IEC phage types and antibiotic resistance patterns in 145 clinical MRSA isolates from Khuzestan Province, Iran.
Methods: All the isolates were investigated by disc diffusion method and PCR assay of sak, sep, sea, scn, and chp genes.
Findings: The assessment of antibiotic resistance showed the highest rate of resistance towards penicillin (97.25%), followed by methicillin (95.8%), ceftazidime (81.4%), erythromycin (71.8%), clindamycin (61.4%), ciprofloxacin (60.7%), gentamycin (56%), imipenem (56.55%), and vancomycin (0%), respectively. Also, the frequency of IEC types was as follows: type A (4.8%), type B (9%), type C (13.1%), type D (12.4%), type E (27.6%), type F (1.4%), type G (0.7%), and type H (6.9%). On the other hand, 24.1% of the isolates did not show any of the IEC types.
Conclusion: The findings showed that IEC-carrying bacteriophages are highly prevalent among MRSA strains, resulting in the adaptation and counteraction of bacteria to the human immune system. Therefore, understanding the role of IEC in the virulence of bacteria can improve our knowledge about the evolution, vaccination, and treatment of S. aureus infection.

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Aims: Following the emergence of methicillin-resistant Staphylococcus aureus (MRSA) isolates, the use of other antibiotics especially vancomycin in S. aureus infections has become inevitable, leading to the emergence of vancomycin-resistant S. aureus (VRSA) strains, which is considered as a major public health concern. This study aimed to determine the vancomycin susceptibility patterns of S. aureus clinical isolates in order to evaluate the current status of vancomycin resistance in the southwest of Iran.
Materials & Methods: In this study, 100 S. aureus clinical strains were collected from the hospitals of Khuzestan province in the southwest of Iran. Next, antibiotic susceptibility, vancomycin resistance, and the presence of mecA, vanA, vanB, vanC, and vanD genes were investigated in these isolates.
Findings:  It was found that 1 and 2 isolates were vancomycin-intermediate S. aureus (VISA) and VRSA, respectively. All three strains showed methicillin-resistance pattern and carried mecA gene. vanA gene was detected in VRSA strains, whereas vanB, vanC, and vanD genes were detected in none of these isolates.
Conclusion: This study findings could be alarming regarding the emergence and spread of VRSA strains; therefore, the principles of infection control should be employed in the healthcare systems to prevent the spread of VRSA strains in healthcare facilities.
 

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Aims: The present study aimed to determine the prevalence of nosocomial infections and their bacterial agents in patients admitted to Poursina Medical and Educational Center of Rasht.
Materials & Methods: The present retrospective descriptive study was conducted by referring to the Infection Control Unit of Poursina hospital and investigating the records of patients with culture-positive nosocomial infections from April 2013 until the end of September 2015. Bacterial agents were diagnosed based on the standard microbiological tests.
Results: During the research period, urinary tract and blood infections were reported as the highest and lowest nosocomial infections, respectively. The most common strains causing nosocomial infections were Acinetobacter spp. (24.7%) (as the most common strain causing respiratory infection), Escherichia coli (22.9%) (as the most common strain causing urinary tract infection), and Enterobacter spp. (19.9%) (as the most common strain causing postoperative infection). Based on the frequency distribution of bacterial strains in hospital wards, Acinetobacter spp was reported as the most common strain isolated from patients in the intensive care unit.
Conclusion: According to the present study results, Acinetobacter spp was the most common strain isolated, and UTIs were the most common type of infection. Due to the prevalence of UTIs and the financial, physical, and social damage they impose to the whole country and the constant change of common pathogens and their susceptibility and antibiotic resistance patterns, it is necessary to conduct studies on this issue in the academic centers of each province at regular intervals.
 

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Aims: Numerous microbial agents have been identified as the causative agents of UTIs, such as Escherichia coli. The spread of antibiotic resistance is increasing among strains causing UTIs. The present study aimed to investigate the prevalence of etiological agents of UTIs and their antibiotic resistance patterns and to determine related risk factors and treatment outcomes of antibiotic resistance in Razi teaching hospital, Guilan, North of Iran.
Material & Methods: This retrospective cross-sectional study was performed from April 2017 to September 2018. All patients with clinical symptoms of UTI were included. The patients’ complete medical records were assessed. Moreover, bacterial isolation and identification were performed by conventional bacteriological and standard biochemical tests. Antibiotic susceptibility testing was performed using the disk diffusion method based on the CLSI recommendation.
Findings: Gram-negative bacilli were identified as the most common causative agents of UTIs in all cases (140, 100%), of which E. coli had the highest isolation rate with 76 cases (54.3%), followed by Klebsiella spp. with 23 cases (16.4%).  Antibacterial susceptibility tests revealed that 64.3% of the isolates were resistant to three antibiotics of different classes (MDR phenotype).
Conclusion: In conclusion, Gram-negative bacilli were the most common causative agents of UTIs, and E. coli had the highest isolation rate (54.3%). Regarding the high prevalence of antibiotic resistance and MDR phenotype, paying attention to drug resistance patterns of pathogens and proper and correct administration of antibiotics as well as proper and timely monitoring of treatment, could help physicians decrease the patients’ mortality rate.

 

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Background: This study aimed to evaluate the frequency of extensively drug-resistant (XDR) uropathogenic Escherichia coli (UPEC) isolates and to detect their metallo-beta-lactamase (MBL) genes.
Materials & Methods: Three hundred urine samples collected from patients with suspected urinary tract infection (UTI) were evaluated for the presence of UPEC isolates. These isolates were subjected to antibiotic susceptibility testing to determine multidrug-resistance (MDR) and XDR profiles. Imipenem or meropenem-resistant isolates were evaluated for MBL production using modified carbapenem inactivation (mCIM) and EDTA-CIM (eCIM) methods. PCR was carried out to identify the presence of MBL genes, including bla_GIM, bla_SIM, bla_VIM-1, bla_VIM-2, bla_SPM-1, bla_IMP-1, bla_IMP-2, bla_NDM, and bla_KPC.
Findings: Out of 300 urine samples, 200 (66.66%) were positive for UTI. Among these, 150 were caused by UPEC. The highest antimicrobial resistance was against cefepime (88%) and ampicillin (85.3%), while the highest susceptibility was against imipenem (91.7%) and fosfomycin (84%). MDR and XDR profiles were detected in 145 (96.66%) and 5 (3.33%) isolates, respectively.  Overall, five UPEC isolates were XDR and resistant to imipenem and meropenem. All these isolates were positive for mCIM, while four were positive for eCIM. The bla_NDM gene was found in all five isolates, while the other MBL genes were not found.
Conclusion: The existence of MDR and XDR bacteria poses a significant risk to public health. bla_NDM is circulating in UPEC strains at least in Nasiriya province, Iraq. This could lead to increased resistance to carbapenems among Enterobacteriaceae, a serious threat to public health.

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In this paper, modeling and design of a trajectory tracking control system for a novel multi-rotor UAV (Unmanned Aerial Vehicle) is developed. The UAV is similar to a quadrotor with an extra no feedback propeller which is added to center of vehicle. The additional rotor improves the ability of lifting heavier payloads, and anti-crosswind capability for quadrotor. For validation, the dynamic model is obtained via both Newton Euler and Lagrange approaches. The dynamical model is under actuated, nonlinear, and has strongly coupled terms. Therefore, an appropriate control system is necessary to achieve desired performance. The proposed nonlinear controller of this paper is an input-output feedback linearization companioned with an optimal LQR controller for the linearized system. The controller involves high-order derivative terms and turns out to be quite sensitive to un-modeled dynamics. Therefore, precise model of UAV is derived by considering actuator’s dynamics. To compensate the actuator’s dynamic and moreover, to avoid complexity in the controller, a second control loop is utilized. The obtained simulation results confirm that the proposed control system has a promising performance in terms of stabilization and position tracking even in presence of external disturbances.

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In this paper, modeling and tow type of nonlinear controller for trajectory tracking of a novel five-rotor UAV (Unmanned Aerial Vehicle) is developed. Because of the very simple structure and high maneuverability, quadrotors are one of the most preferred types of UAVs but the main problem of them is their small payload. In the proposed novel model, one propeller is added to the center of vehicle to improve the ability of lifting heavier payloads, and to excel anti-crosswind capability of quadrotor. The dynamic model is obtained via Newton Euler approach. The model is under actuated, nonlinear, and has strongly coupled terms. Also, two types of nonlinear controllers are presented. First one is a conventional input-output feedback linearization controller which involves high-order derivative terms and turns out to be quite sensitive to sensor noise as well as modeling uncertainty. Second controller is a BackStepping controller based on the hierarchical control strategy that yields easier controller. The obtained simulation results confirm that the performance of BackStepping controller is convenient in terms of stability, position tracking and it is robust in presence of disturbance.

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In this paper, modeling and feedback linearization controller for trajectory tracking of a novel six-rotor UAV (Unmanned Aerial Vehicle) is developed. Because of the very simple structure and high maneuverability, quadrotors are one of the most preferred types of UAVs but the main problem of them is their small payload. In the proposed novel model, two coaxial propellers are added to the center of vehicle to improve the ability of lifting heavier payloads, and to excel anti-crosswind capability of quadrotor, while the dynamic and steering principle is preserved. The dynamic model is obtained via Newton Euler approach. Model is under actuated, nonlinear, and has strongly coupled terms. Also, two types of nonlinear controllers are presented. First one is a conventional input-output feedback linearization controller which involves high-order derivative terms and turns out to be quite sensitive to sensor noise as well as modeling uncertainty. Second controller is a feedback linearization based on the hierarchical control strategy that yields easier controller. To compensate actuator’s dynamic and moreover, to avoid complexity of controller, a two-stage algorithm is utilized. The obtained simulation results confirm that the performance of hierarchical controller is more convenient in terms of position tracking and disturbance rejection than conventional controller.