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Showing 22 results for Drug Resistance

M Fatemi Motlagh, H Varham, N Mansori,
Volume 4, Issue 2 (10-2010)
Abstract

Abstract Background and objectives: "The comb antibiotic sensitivity test" is a quick, reliable and cost effective method to determine the susceptibility of bacteria to different antibiotics. The purpose of this study is to design a plate that is easy and quick to use, and enable to be interpreted easily without the need for measurement of the margins with a ruler. Material and Methods: First, Clinical and Laboratory Standards Institute data about the maximum growth inhibitory haloes formed with antibiotics and various micro-organisms were statistically examined and determined that the most (99.7%) zone of inhibition growth is formed in the range of 42 mm. Accordingly, the obtained number (42 mm) and conventional plate size (100 mm) used for testing sensitivity were punched into Solid works software which was used to determine the best place of strip and shoulder plates. After that the efficacy this media were examined by determination of MIC Staphylococcus aureus and Klebsiella pneumonia, non-graded and graded plate shoulders were searched and compared. Results: Has been placed two combs MIC in a plate in this method and didn’t create growth inhibitory haloes interferences. Obtained MIC for Nitrofurantoin( 10 µg/ml) , Amikacin(0.5 µg/ml), Gentamicin(1 µg/ml) , and Amoxicillin (0.5 µg/ml) against S.aureus , MIC Nalidicsic Acid, Amikcin, Gentamicin and Nitrofurantoin against K.pneumonia was 0.1, 0.5, 0.5 and 10 µg/ml ,respectively. Conclusion:The comparison between this new innovative method and standard methods (Clinical Laboratory Standards Institute - CLSI) shows that there a marked reduction in the interference of antibiotic therapy and will also reduce time of interpretation. Key words: Plate, Antibiogram Comb, MIC, Antibiotics, Drug resistance.
Derakhshan, S, Najar Peerayeh, Sh, Fallah, F, Bakhshi, B,
Volume 8, Issue 4 (1-2015)
Abstract

Abstract Background and Objective: Multiple drug resistance has increased in recent years in Klebsiella pneumoniae isolates. The Integrons are mobile genetic elements that carry antibiotics resistance genes. The aim of this study was to determine antibiotic susceptibility and the prevalence of class 1, 2, and 3 integrons in clinical Klebsiella pneumoniae isolated from clinical specimens. Material and Methods: A total of 108 K. pneumoniae isolates were collected between April and December 2011 from different clinical specimens of Loghman hospital in Tehran and identified by biochemical tests. Susceptibility of isolates to 14 antibiotic disks was determined by disk diffusion method. The template DNA was extracted by freeze-thaw method and the presence of class 1, 2, and 3 integrons was investigated by PCR method. Level of resistance to antibiotics in integron-positive and integron-negative isolates was determined. Results: The highest level of resistance was seen for cefotaxime, ceftriaxone, and amoxicillin-clavulanic acid (55.5%). In 79 isolates (73.14%) class 1 integron and in 57 of 79 isolates (72.15%) resistance to at least two classes of drugs were seen. The class 2 and 3 integrons were not detected. Among integron-negative isolates, 8 isolates (27.58%) had resistance to at least one antibiotic. Conclusion: The prevalence of class 1 integron in resistant K. pneumoniae is high therefore, the monitoring of drug resistance and limiting the use of antibiotics are necessary. Keywords: Klebsiella Pneumoniae, Integron, Multi-Drug Resistance


Sedighi, I, Alikhani, My, Nakhaee, S, Karami, P,
Volume 8, Issue 4 (1-2015)
Abstract

Abstract Background and Objective: Escherichia coli is the most common cause of urinary tract infections in children and the leading cause of intra-abdominal infections (peritonitis and abscess) followed intestinal injuries. Urinary tract infection, including cystitis and pyelonephritis, is a common childhood infection. E. coli causes more than 90 percent of the community acquired and 50% of hospital acquired urinary tract infections therefore, the determination of E. coli antibiotic susceptibility is a paramount importance to clinical and epidemiological purposes. Material and Methods: In this cross-sectional study, 50 E. coli strains isolated from urine samples of children less than 7 years of age with urinary tract infections. They were compared for drug susceptibility testing by disc diffusion method with 50 strains of Escherichia coli isolated from stool samples of healthy children with the same age and sex pattern. Results: The actual amount of drug sensitivity of uropathogenic and intestinal Escherichia coli strains to amikacin was 94 and 100%, nitrofurantoin 90 and 88%, gentamicin 66 and 94%, cefixime 56 and 60%, nalidixic acid 38 and 44% and to cotrimoxazole 28 and 32%, respectively. Conclusion: the rate of resistance to gentamicin, Cefixime and nalidixic acid in urinary tract infection isolates were more than intestinal strains. The highest rate of drug resistance in urinary Escherichia coli isolates was associated with cotrimoxazole and the lowest one with amikacin. Keywords: Escherichia Coli, Intra-Abdominal Infection, Drug Resistance, Urinary Tract Infection, Children


Ebrahim Zade, A, Zare Bidaki, M, Saber Hosseini, Sn, Gh Shariatzadeh, Derayati, Z,
Volume 8, Issue 4 (1-2015)
Abstract

Abstract Background and Objective: Streptococcus pneumoniae is the most common cause of acquired bacterial infections in the respiratory system. In recent years, a high incidence of pneumococcal resistance to different antibiotics has also been appeared. This study was conducted to evaluate the in vivo and in vitro resistance of pneumococcal pneumonia to ceftriaxone, azithromycin and co-amoxiclave in clinical setting and laboratory. Material and Methods: In this single-blind clinical trial study, the participants were the patients with the diagnosis of pneumonia referred to infectious diseases clinic in Vali-e-Asr hospital of Birjand university of Medical Sciences, October 2012 - April 2014. The patients were randomly allocated to one of the three therapeutic regimes including azithromycin, ceftriaxone, and co-amoxiclave. After 48-72 hours that the infection was confirmed by paraclinical findings, the patients with pneumococcal pneumonia remained in the study and their in vivo and in vitro resistance to the above mentioned antibiotics were compared. Results: The most in vitro drug resistance was to co-amoxiclave (41.5%) and the least to ceftriaxone (20.8%) (P>0.05). For In vivo, the most resistance was to azithromycin (47.4%) and the least one to ceftriaxone (6.7%) (p<0.05). The agreement coefficient between the laboratory antibiogram test and the clinical responses to therapeutic regimes of azithromycin, co-amoxiclave and ceftriaxone was 0.25 (p=0.26), 0.46 (p=0.02) and 0.44 (p=0.04), respectively. Conclusion: With regard to the demographic characteristics of the patients in this study, the resistance of Streptococcus pneumoniae to ceftriaxone is less than that of co-amoxiclave and azithromycin in both clinical setting and laboratory. Keywords: Drug Resistance, Streptococcus Pneumonia, Azithromycin, Ceftriaxone, Co-Amoxiclave


Soltan Dallal, Mm, Rahbar, M, Douraghi, M, Rahimi Forooshani, A, Khan Babaei, Gt, Mobarhan, M, Ghasemi, F,
Volume 8, Issue 5 (1-2015)
Abstract

Abstract Background and Objective: Cystic fibrosis (CF) is an autosomal recessive genetic disease and Pseudomonas aeruginosa is one of the most common bacteria colonized in CF patients. Growing resistance of this bacterium to antibiotics now a day is a challenge of controlling infection in CF patient. In this study colonization of CF patients with Pseudomonas aeruginosa and antibiotic susceptibility pattern of isolated strains were examined. Material and Methods: From 100 CF patients, during a year, sputum and bronchial swabs were collected. After culturing the samples, some of them were reported as Pseudomonas aeruginosa using biochemical tests. Mucoid strains of Pseudomonas aeruginosa were identified the same as non-producing alginate strains while for catching single pure colony, repeated passage was used. For determining antibiotic resistance of Pseudomonas aeruginosa to some antimicrobial agents Kirby-Bauer method based on CLSI was used. Results: Of 100 samples, 40 (40%) were positive for Pseudompnas aeruginosa. The prevalence of P. aeruginosa was 23.8, 36.84 and 80% at the age of 1-3, 4-12 and 13, respectively. Conclusion: Statistically, there is a significant difference between age and contracting with Pseudomonas aeruginosa in that the higher the age the more colonization with Pseudomonas aeruginosa. Key words: Pseudomonas Aeruginosa, Cystic Fibrosis, Drug Resistance
Monadi, M, Kargar, M, Naghiha, A, Najafi, A, Mohammadi, R,
Volume 9, Issue 1 (4-2015)
Abstract

Abstract Background and Objective: Salmonellosis is the most common type of food poisoning in developed and developing countries that is caused by Salmonella serotype. Hence, we aimed to identify the Salmonella serovars in eggs obtained from Kohgiluyeh and Boyerahmad province and to evaluate antibiotic resistance of the isolated strains. Material and Methods: In this study, 210 eggs were collected from Kohgiluyeh and Boyerahmad Province. The bacteria were isolated and identified using biochemical tests. After extraction of genomic DNA, Salmonella gender, Salmonella enteritidis and Salmonella typhimurium were investigated by invA, fliC and sefA primers, respectively, using Multiplex PCR method. Results: Of 210, 14 (6.66%) were contaminated with Salmonella. Of these, 12 (5.71%) were Salmonella typhimurium and 2 (0.95%) were related to Salmonella spp. None of the samples were contaminated with Salmonella enteritidis. The highest resistance was related to penicillin (100%) and neomycin (78.57%). Conclusion: Salmonella typhimurium is the predominant serovar causing contamination in the eggs of this Province. Given the wide spread of antibiotic resistance in different serotypes of Salmonella, we recommend avoiding of indiscriminate use of antibiotics in livestock and poultry. Keywords: Salmonella, Drug Resistance, Antibiotic, Multiplex PCR, Kohgiluyeh and Boyerahmad
Behshood, P, Karbasizade, V, Naghavi, Ns,
Volume 9, Issue 2 (7-2015)
Abstract

Abstract

Background and Objective: Methicillin-resistant Staphylococcus aureus (MRSA) is a major pathogen involved in nosocomial infections. Because of increasing antibiotic resistance of these strains, treatment of these infections has become very difficult. This study aimed to determine the frequency and drug resistance pattern of MRSA isolates from nosocomial infections in hospitals.

Material and Methods: the isolates of S.aureus (n= 100) isolated from clinical samples such as: urine, blood, wound, throat, sputum, cerebrospinal fluid, catheter and other purulent discharge from in patients were identified using biochemical tests. MRSA strains were isolated by using agar screening method and then drug resistance pattern of them was determined by disk diffusion method.

Results: Out of 100 S.aureus strains, 65 (65%) were MRSA. Drug resistance of MRSA isolates to most antibiotics were high: penicillin100%, oxacillin 100%, nitrofurantoin 80%, tetracycline 63%, erythromycin 58.4%, gentamicin 46.1%, clindamycin 33.8%, cotrimoxazole 35.3% and ciprofloxacin 26.1%. Also 35 of MRSA isolates were multiple drug resistance (MDR).

Conclusion: The prevalence of MRSA isolates and also their resistance to other antibiotics were high.

Keywords: Drug Resistance, Methicillin-Resistant Staphylococcus Aureus, Multi-Drug Resistant


J Vazirzadeh, H Ghajavand , L Heidari , P Behshood ,
Volume 9, Issue 3 (9-2015)
Abstract

Abstract

Background and Objective: Acinetobacter species are opportunistic important pathogens responsible for many nosocomial infections. The purpose of this study was to determine the drug resistan pattern Acinetobacter baumannii and prevalence of ESBL producing strains in Intensive Care Unit patients in Isfahan city hospitals.

Material and Methods: The study was conducted on 100 Acinetobacter baumannii strains isolated from clinical samples.  The Isolates were identified by standard methods and confirmed by PCR method. Drug resistance pattern of isolates was determined by standard disk diffusion method according to CLSI. To identify ESBL producing strains, a Combined Disk phenotypic method was used.

Results: Hundred percent of Acinetobacter baumannii strains was MDR and the maximum antibiotics resistance was shown to cefepime, co-trimoxazole, ciprofloxacin, meropenem and ceftazidime. According to initial screening, 4.5% of strains were producing Extended Spectrum Beta Lactamase enzyme.

Conclusion: The percent of ESBLs producing strains is low. Thus, Combined Disk for initial screening of ESBLs strains and multiplex PCR for rapid detection of ESBLs strains are recommended.   This issue can be a new step in preventing from the spread of Acinetobacter Baumannii Strains in hospitals particularly in intensive care unit.

Keywords: Beta-Lactamases; Acinetobacter Baumannii; Drug Resistance


Izadpanah, Mr, Asadpour, L,
Volume 9, Issue 3 (9-2015)
Abstract

Abstract

Background and Objective: Staphylococcus aureus is an important opportunistic pathogen causing a wide range of infections in human .Most clinical isolates of S.aureus are resistant to a number of antibiotics. For appropriate antimicrobial therapy, this study was conducted to determine antibacterial drug resistance patterns of S.aureus isolates obtained from different clinical samples in Rasht.

Material and Methods:  the clinical isolates of S.aureus were collected from different clinical laboratories in Rasht. Thirty coagulase positive S.aureus strains were identified using biochemical tests and amplification of 23SrRNA and coa genes by polymerase chain reaction.  Finally, the resistance pattern of the isolates to 16 selected antimicrobial agents was evaluated by disk diffusion method.

Results:  the S.aureus isolates (75%) were resistant to methicillin and all of them were multidrug resistance. The isolates were high resistance to ampicillin (73%), amoxicillin (60%), cloxacillin (53%) and low resistance to vancomycin (7%) and gentamicin (10%).

Conclusion: given the high prevalence of methicillin resistant, multi drug resistant and presence of vancomycin resistant S.aureus isolates in Rasht, continuously monitoring of drug resistance pattern of S.aureus isolates is recommended for having appropriate therapeutic regime.

Keywords: Staphylococcus Aureus, Coagulase, Drug Resistance, PCR


Saeideh Sadat Shobeiri , Saeid Abediankenari (phd), Mohtaram Nasrollahi , Mohammad Khademlou, Maryam Sarabijamab ,
Volume 10, Issue 3 (5-2016)
Abstract

Background and objective: Implementation of standard methods for accurate detection of bacteria, correct antibiotic susceptibility testing and effective treatment of bacterial infections play important roles in development of public health and prevention of drug resistance. This study aimed to detect bacteria using standard methods and compare the results with the results obtained in teaching hospitals’ laboratories.

Methods: Positive culture plates containing bacteria isolated from patients in hospital laboratories in city of Sari were transferred to microbiology laboratory of Faculty of Medicine at Mazandaran University of Medical Sciences, after determining the genus and species of bacteria and antibiotic susceptibility testing of the isolates. The samples were re-examined based on standard protocols, and antibiotic susceptibility testing was done using the Kirby-Bauer method.

Results: Of 101 patients, 20% of bacteria and 22.5% of antibiotic sensitivity results reported by the hospital laboratories were incorrect. There were significant differences between the two study groups in terms of bacterial species detection and sensitivity to some drugs (P<0.05).

Conclusion: In the present study, lack of implementation of internal quality control programs in some hospital laboratories and lack of proper monitoring by regulatory authorities in different departments of the hospital have caused 20% false-detection results in hospital reports. Inconsistency in results of laboratories, false antibiograms and subsequent false laboratory reports cause drug resistance in some patients. This indicates the necessity of continuous training in the field of Microbiology and implementation of standard protocols and methods for detection of bacterial species and antibiotic susceptibility testing.


Zahra Rahimi , Mansour Salehi , Abbas Dousti ,
Volume 11, Issue 3 (5-2017)
Abstract

ABSTRACT
         Background and objective: Approximately 50 million people worldwide (1% of the world's population) suffer from epilepsy. Among 700 thousand people with epilepsy in Iran, 20% have refractory epilepsy. Accumulation of leukocytes in patients' brain parenchyma is thought to be related to different types of epilepsy. Recent clinical observations suggest that therapeutic strategies that interfere with leukocytes or cause them to migrate may have therapeutic efficacy in epilepsy. The aim of this study was to identify treatment-resistant patients, and investigate the association between polymorphism rs1024611 in CCL2 gene and drug resistance in patients with epilepsy in Isfahan, Iran.
        Methods: Blood samples were taken from 50 patients with intractable epilepsy (case group) and 50 drug-responsive patients with epilepsy (control group). Genomic DNA was extracted from peripheral blood by salting out method. Specific primers were designed by Oligo 7 software to investigate polymorphism rs1024611 using PCR-RFLP. The preliminary results for a number of samples were confirmed by sequencing.
        Results: The results of this study showed that there was a significant relationship between intractable epilepsy and presence of C allele.
        Conclusion: Similar to previous study, we found a significant association between CCL2 gene polymorphism and drug-resistant epilepsy.
        Keywords: Epilepsy, Drug Resistance, Polymorphism, CCL2.
 
 
Hamid Vaez , Vahid Vaez , Farzad Khademi ,
Volume 11, Issue 6 (11-2017)
Abstract

ABSTRACT
           Background and Objectives: Pseudomonas aeruginosa is an important non-fermenting gram-negative hospital-acquired pathogen. Treatment of P. aeruginosa infections has become more challenging due to overexpression of efflux pumps. The aim of the present study was to apply in silico analysis to evaluate the structure of the efflux pump regulatory protein, MexR, and impact of mutation on its stability and function.
         Methods: Different bioinformatics tools including EXPASY, PROTEER, TECCOFFE, iStable, I-Mutant 2, STRING, ESPript, GOR IV, and PDB were used in the study.
          Results: Aliphatic and instability indices were 104.15, and 46.52, respectively, indicating that the protein has a relatively short half-life. Most mutations decreased protein stability. Twenty-four mutations were identified as deleterious, with negative impact on the protein’s function.
         Conclusion: Determination of structure, variability, and function of MexR could be useful for modeling of treatment and control of multidrug resistant P. aeruginosa, with overexpressed efflux pump. We found that MexR is a relatively unstable and conserved protein and the majority of mutations decrease its stability.

         Keywords: Pseudomonas aeruginosa, MexR protein, Drug resistance, drug resistance multiple.


Hasan Vahidi Emami , Mohaddeseh Khalilian, Narges Yadollahi Movahhed ,
Volume 12, Issue 1 (1-2018)
Abstract

ABSTRACT
         Background and Objectives: Acinetobacter species are responsible for a wide range of clinical complications in hospitalized patients. Antimicrobial treatment of clinical strains of Acinetobacter baumannii may be compromised due to multiple-drug resistance to b-lactams. Aim of this study was to determine antibiotic resistance patterns and frequency of PER and VEB genes in A. baumannii isolates from hospitalized patients.
          Methods: In this cross-sectional study, 100 clinical strains of A. baumannii were isolated from patients hospitalized in Qom (Iran) using specific culture media and biochemical tests. The disk diffusion method was performed to determine resistance to some antibiotics. Minimum inhibitory concentration (MIC) for cefepime and ceftazidime was evaluated. Identification of ESBL-producing strains and presence of the PER and VEB genes were determined by combined disk test and polymerase chain reaction, respectively.
         Results: The isolates were highly resistant against cefixime, ceftriaxone and cefepime. Lowest level of resistance was against polymyxin B. In addition, 70% of the isolates were multi-drug resistant. MIC<128 µg/ml to ceftazidime and cefepime was observed in 84% and 91% of the strains, respectively. Moreover, 21% of the strains were ESBL-positive and frequency of the PER and VEB genes was 47% and 32%, respectively.
        Conclusion: Majority of A. baumannii isolates are highly resistant to the tested antibiotics. Due to presence of the PER and VEB genes in the isolated strains, there is the possibility of resistance spread to other bacteria. Therefore, it is recommended to modify the consumption pattern for antibiotics and pay more attention to standards of nosocomial infection control.
         Keywords: Acinetobacter baumannii, Drug resistance, PER, VEB.

Afsaneh Sikarchi , Leila Fozouni ,
Volume 12, Issue 2 (3-2018)
Abstract

 
ABSTRACT
           Background and Objectives: Helicobacter pylori is the most common cause of gastritis and ulcer worldwide. Treatment of such infections may lead to failure due to drug resistance. This study aimed to investigate the antimicrobial effects of bacteria present in camel milk on the growth of drug-resistant clinical isolates of H. pylori.
           Methods: In this cross-sectional study, biopsy samples from 75 patients with digestive symptoms were transferred to laboratory in transport medium containing homogeneous compounds. In order to isolate H. pylori, urease-positive biopsies were promptly cultured in brucella agar enriched with defibrinated sheep blood and fetal calf serum. Disk diffusion agar test was used to evaluate antibiotic susceptibility and agar well diffusion method was applied to study the antagonistic effect of probiotics isolated from camel milk on the H. pylori isolates.
           Results: The frequency of H. pylori isolates was 42.7%. The highest rate of resistance was observed against metronidazole (56.3%). In addition, the rate of resistant to amoxicillin, ciprofloxacin, and clarithromycin and tetracycline was 31.3%, 18.8%, 15.6%, respectively. Lactobacillus plantarum (59.3%) was more frequent than other Lactobacillus species. L. plantarum, Lactobacillus fermentum and Lactobacillus casei showed favorable inhibitory effects against the H. pylori isolates, but L. plantarum (with inhibition zone diameter of 20.3 mm) showed the highest inhibitory effect.
           Conclusion: Considering the increasing rate of drug resistance and the inhibitory effect of probiotics isolated from milk, health providers recommend that promoting consumption of probiotic food seems beneficial for the general population and those suffering from gastrointestinal disorders.
           Keywords: Helicobacter pylori, Drug resistance, Camel, milk, Probiotics.

Zahra Salimizadeh, Seyed Masoud Hashemi Karouei , Farzaneh Hosseini,
Volume 12, Issue 4 (7-2018)
Abstract

ABSTRACT
            Background and objectives: The present study was conducted to detect class 1 integrons and evaluate antibiotic susceptibility patterns among clinical isolates of P. aeruginosa.
            Methods: Sixty clinical samples from blood, tracheal wounds, burns and urinary tract infections were collected from three general hospitals in Tehran, Iran. Culture of specimens was performed on common bacteriological culture media. Bacteria were  identified based on mobility, pigment production, growth at 42 oC, and oxidase and catalase tests. Overall, 21 P.  aeruginosa strains were isolated. Antimicrobial susceptibility of was evaluated via the disk diffusion method (Kirby-Bauer) according to the CLSI guidelines. Presence of the intI1, sul1, aadA2 and aadB gene cassettes was investigated using PCR. The collected data were analyzed using SPSS software (version 21).
            Results: The most effective antimicrobial agents against P. aeruginosa isolates were tetracycline and gentamicin. All P. aeruginosa isolates were multidrug re­sistant. Moreover, the intI1, sul1, aadA2 and aadB genes were found in 90.5%, 90.5%, 47.6% and 19% of the P. aeruginosa isolates, respectively.
            Conclusion: The results indicate that the presence of aadB, aadA2 and sul1 gene cassetes may play an important role in the dissemination of antimicrobial resistance determinants.
          Keywords: Pseu­domonas aeruginosa, integron, multidrug resistance.
ABSTRACT
            Background and objectives: The present study was conducted to detect class 1 integrons and evaluate antibiotic susceptibility patterns among clinical isolates of P. aeruginosa.
            Methods: Sixty clinical samples from blood, tracheal wounds, burns and urinary tract infections were collected from three general hospitals in Tehran, Iran. Culture of specimens was performed on common bacteriological culture media. Bacteria were  identified based on mobility, pigment production, growth at 42 oC, and oxidase and catalase tests. Overall, 21 P.  aeruginosa strains were isolated. Antimicrobial susceptibility of was evaluated via the disk diffusion method (Kirby-Bauer) according to the CLSI guidelines. Presence of the intI1, sul1, aadA2 and aadB gene cassettes was investigated using PCR. The collected data were analyzed using SPSS software (version 21).
            Results: The most effective antimicrobial agents against P. aeruginosa isolates were tetracycline and gentamicin. All P. aeruginosa isolates were multidrug re­sistant. Moreover, the intI1, sul1, aadA2 and aadB genes were found in 90.5%, 90.5%, 47.6% and 19% of the P. aeruginosa isolates, respectively.
            Conclusion: The results indicate that the presence of aadB, aadA2 and sul1 gene cassetes may play an important role in the dissemination of antimicrobial resistance determinants.
          Keywords: Pseu­domonas aeruginosa, integron, multidrug resistance.
ABSTRACT
            Background and objectives: The present study was conducted to detect class 1 integrons and evaluate antibiotic susceptibility patterns among clinical isolates of P. aeruginosa.
            Methods: Sixty clinical samples from blood, tracheal wounds, burns and urinary tract infections were collected from three general hospitals in Tehran, Iran. Culture of specimens was performed on common bacteriological culture media. Bacteria were  identified based on mobility, pigment production, growth at 42 oC, and oxidase and catalase tests. Overall, 21 P.  aeruginosa strains were isolated. Antimicrobial susceptibility of was evaluated via the disk diffusion method (Kirby-Bauer) according to the CLSI guidelines. Presence of the intI1, sul1, aadA2 and aadB gene cassettes was investigated using PCR. The collected data were analyzed using SPSS software (version 21).
            Results: The most effective antimicrobial agents against P. aeruginosa isolates were tetracycline and gentamicin. All P. aeruginosa isolates were multidrug re­sistant. Moreover, the intI1, sul1, aadA2 and aadB genes were found in 90.5%, 90.5%, 47.6% and 19% of the P. aeruginosa isolates, respectively.
            Conclusion: The results indicate that the presence of aadB, aadA2 and sul1 gene cassetes may play an important role in the dissemination of antimicrobial resistance determinants.
          Keywords: Pseu­domonas aeruginosa, integron, multidrug resistance.

Majid Komijani, Khashayar Shahin, Mohadeseh Barazandeh, Mehdi Sajadi,
Volume 12, Issue 5 (9-2018)
Abstract

ABSTRACT
            Background and Objectives: Pseudomonas aeruginosa is an opportunistic pathogen resistant to various antibiotics. The aim of the present study was to study resistant patterns in clinical isolates of P. aeruginosa, classify them into pandrug resistance (PDR), extensive drug resistance (XDR) and multidrug resistance (MDR) groups, and identify extended-spectrum β-lactamase (ESBL)-positive isolates using the phenotypic and genotypic methods.
            Methods: This cross-sectional study was conducted on 161 P. aeruginosa isolates collected from the city of Isfahan, Iran. Antibiotic susceptibility tests were performed using 11 antimicrobial agents. ESBL-positive strains were identified using the phenotypic and genotypic methods.
            Results: The highest level of antibiotic resistance was observed against ceftazidime (77.64%). None of the isolates was resistant to polymyxin B. In the phenotypic method, 64 isolates (39.75%) were found as ESLB-positive, whereas 132 isolates (81.98%) were ESBL-positive in the genotypic method. The number of ESBL-positive isolates in the genotypic method was significantly higher than in the phenotypic method. The frequency of XDR and MDR isolates was 50.93% and 27.32%, respectively. None of the isolates was PDR. The frequency of the blaTEM gene was significantly higher than other genes (P<0.0001).
            Conclusion: It was revealed that the genotypic method was much more accurate in identifying ESBL-positive strains than the phenotypic method. Therefore, use of the molecular method may increase the chance of successful treatment with antibiotics of the β-lactam family.
            Keywords: Drug Resistance,  β-lactamases, Pseudomonas aeruginosa.

Shadi Beladi Ghannadi , Maryam Ghane , Laleh Babaeekhou ,
Volume 13, Issue 2 (3-2019)
Abstract

ABSTRACT
             Background and Objectives: The emergence of extended-spectrum β-lactamase (ESBL)-producing Shigella spp. is becoming a health concern worldwide. This study aimed to investigate antibiotic resistance pattern and frequency of blaCTX-M, blaSHV, and blaTEM genes among Shigella isolates from patients in hospitals of Tehran, Iran.
             Methods: In this cross-sectional study, 52 non-repeated Shigella strains were isolated from hospitalized patients in Milad, Emam Khomeini and Shariati hospitals in Tehran (Iran) from November 2015 to December 2016. Bacterial identification, serotyping, and antimicrobial susceptibility testing were performed according to the standard guidelines. The blaCTX-M, blaSHV, and blaTEM resistance genes were identified using multiplex polymerase chain reaction.
             Results: Among 52 Shigella isolates, S. sonnei (44.2%) was the predominant species, followed by S. flexneri and S. dysenteriae (23%). Over 67% of the isolates were multidrug resistant. The highest rates of resistance were observed against cefalotin (67.3%), tetracycline (67.3%), amikacin (63.5%), trimethoprim-sulphamethoxazole (48.1), and ampi­cillin (42.3%). The lowest resistance rate was against ciprofloxacin (1.9%). We detected the blaTEM and blaCTX-M genes in 61.5% and 19.2% of the isolates, respectively. However, the blaSHV gene was not detected in any of the isolates. In addition, 16.4% of the isolates harbored the blaTEM and blaCTX-M genes simultaneously. Ciprofloxacin was the most effective antibiotics according to the ESBL genes distribution.
             Conclusion: Our findings indicate the high prevalence of multidrug resistance and ESBL genes in Shigella isolates, which elucidates the need for appropriate infection control measures for limiting the spread of resistant strains.
             Keywords: Shigella, Multiplex Polymerase Chain Reaction, Drug Resistance.

Leila Fozouni, Hamideh Askari, Hamid Reza Pordeli,
Volume 13, Issue 4 (7-2019)
Abstract

ABSTRACT
            Background and Objectives: Enterococcus faecalis is a major cause of bacterial prostatitis, which can increase the risk of developing prostate cancer if mistreated or left untreated. The aim of this study was to evaluate resistance of E. faecalis strains isolated from patients with prostatitis to three fluoroquinolones.
            Methods: In this cross-sectional study, we collected urine specimen from 164 patients hospitalized in six hospitals in the Golestan Province, Iran. Biochemical and bacteriological tests were carried out to identify E. faecalis strains. Pattern of resistance to ciprofloxacin, levofloxacin and norfloxacin was studied using the agar disk diffusion method (Kirby-Bauer method). The broth microdilution test was performed to determine minimum inhibitory concentrations (MICs) of fluoroquinolones according to the CLSI M100-S25 (2015) criteria.
            Results: Of 164 isolates, 39 (23.8%) were identified as E. faecalis. Frequency of resistance to ciprofloxacin, norfloxacin and levofloxacin was 12.8%, 12.8% and 2.6%, respectively. The MIC90 of ciprofloxacin against the isolates was 4 μg/ml, which was 4-fold lower than that of norfloxacin (MIC90=16μg/ml) and 2-fold lower than that of levofloxacin (MIC90=8μg/ml). We found no significant difference between the isolates in terms of resistant to the fluoroquinolones (P>0.01). 
            Conclusion: Our results show that E. faecalis is one of the most common causes of bacterial prostatitis, and fluoroquinolones are still effective for treating the infection despite the reports of fluoroquinolones resistance in Iran. Moreover, levofloxacin may be a more suitable and effective antibiotic than ciprofloxacin and norfloxacin for treatment of this infection.
            Keywords: Enterococcus faecalis, Prostatitis, Drug Resistance, Iran.

Farzaneh Mohammadzadeh Rostami, Saman Shalibeik, Morteza Rabi Nezhad Mousavi,
Volume 14, Issue 1 (1-2020)
Abstract

ABSTRACT
          Background and objectives: Nosocomial infections caused by antibiotic resistant bacteria is a life threatening health challenge. This study aimed to determine the frequency of antibiotic resistance genes in clinical isolates from hospitals of Zahedan, southeast of Iran.
           Methods: Overall, 818 isolates were collected from different hospital wards. The isolates were identified using conventional microbiological and biochemical tests. Antibiotic susceptibility pattern was assessed by agar disc diffusion method and determination of minimum inhibitory concentration of a number of antibiotics. Multiplex PCR was performed using specific primers for the detection of resistance genes.
           Results: The most common species were Staphylococcus aureus (25%), Klebsiella pneumoniae (22%) and Pseudomonas aeruginosa (14%). The rate of methicillin resistance among S. aureus, S. epidermidis and S. saprophyticus was 60%, 43% and 24%, respectively. In addition, 28.5% of enterococci isolates were vancomycin resistant. Among gram-negative bacteria, 45% of A. baumannii and 24% of P. aeruginosa were identified as ESBL. A high level of resistance to ampicillin (96%), cefotaxime (89%), gentamicin (89%) and sulfamethoxazole-trimethoprime (60%) was observed in K. pneumoniae.
           Conclusion: Our results highlight the urgent need for an eradication program and a surveillance plan for preventing increased emergence of antibiotic resistant bacteria in the study area.
           Keywords: Bacterial Infections, Drug resistance, Zahedan.

Behnoush Khasheii, Pezhman Mahmoodi, Abdolmajid Mohammadzadeh,
Volume 15, Issue 5 (9-2021)
Abstract

Increasing antibiotic resistance is a global health problem. In recent years, due to the indiscriminate use of antibacterial compounds, many bacterial pathogens, including staphylococci, members of the Enterobacteriaceae family including Klebsiella pneumoniae and bacteria such as Pseudomonas aeruginosa and Acinetobacter baumannii have become multi-drug resistant. Consequently, it is important to explore alternative approaches for eliminating resistant strains. Bacteria synthesize low-weight molecules called siderophores to chelate iron from the environment as a vital element for their growth and survival. One way to deal with resistant bacterial strains is to utilize siderophore-mediated iron uptake pathways as entrance routes for drug delivery. Therefore, the production of drugs with Trojan horse strategy in the form of conjugated siderophore-antibiotic complexes has recently received much attention for dealing with resistant isolates. In this review, we discuss the efficacy of siderophore-antibiotic conjugates as a Trojan horse strategy for eliminating drug-resistant pathogens.

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