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.

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.

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.

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: 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 bla_TEM 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.

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 bla_CTX-M, bla_SHV, and bla_TEM 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 bla_CTX-M, bla_SHV, and bla_TEM 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 bla_TEM and bla_CTX-M genes in 61.5% and 19.2% of the isolates, respectively. However, the bla_SHV gene was not detected in any of the isolates. In addition, 16.4% of the isolates harbored the bla_TEM and bla_CTX-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.

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.

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.

Background and Objectives: Moraxella catarrhalis is considered as an emerging pathogen and a new nosocomial infection agent. This study was conducted to isolate and identify M. catarrhalis from clinical samples (respiratory tracts) and assess them for antimicrobial susceptibility patterns.
      Methods: In total, 280 samples were collected from patients with respiratory tract infection, and 120 samples were obtained from healthy individuals in the control group. The isolates were identified by phenotyping and genotyping methods, and their antibiotic susceptibility was  evaluated using disk diffusion methods. The presence of β-lactamase and efflux pump activity were specified via phenotypic methods. Finally, Bro and acrA genes in the isolates were detected by PCR technique.
      Results: The frequency of this bacterium was 9.64% (27 out of 280) in patients with respiratory tract infection and 4.16% (5 out of 120) in the control group. Although the isolates were resistant to penicillin, they had various responses against other antibiotics. The results obtained from molecular method showed that 90.6% and 84.3% of the isolates possessed Bro and acrA genes, respectively. There was a significant relationship (P<0.05) between the presence of Bro and acrA genes and antibacterial resistance to ampicillin, amoxicillin, cefazolin, cefuroxime, and chloramphenicol.
      Conclusion: Our findings confirmed the existence of M. catarrhalis in patients with respiratory diseases and the high prevalence of antibiotic resistant genes in M. catarrhalis isolates. Therefore, timely diagnosis and successful treatment can play important roles in preventing their spread.

Pasteurella species are one of the most common pathogenic bacteria in domestic animals, and they are seen more in people with weak immune systems. This research aims to investigate a case of a patient with multiple sclerosis from whose sputum Pasteurella multocida (P. multocida) was isolated. The patient was a 28-year-old man with multiple sclerosis who had persistent coughs due to food being stuck in his throat. The patient was a 28-year-old man with multiple sclerosis who had persistent coughs due to food being stuck in his throat. The primary diagnosis was pneumonia hydropneumothorax and complete collapse of the left lung. The patient's sputum culture after the first visit to the hospital was positive for P. multocida, which was not found in a second culture. In the subsequent cultures of the patient, Acinetobacter, Klebsiella, Pseudomonas aeruginosa (P. aeruginosa), and Citrobacter were found, which had extensive drug resistance to all antibiotics. In the secondary computerized tomography (CT) scan, mild pleural effusion on the left side, pneumothorax, and complete collapse with bronchiectasis was seen. Despite the treatments, the patient finally died of cardiac arrest and bradycardia. Infection with P. multocida was found in a patient with multiple sclerosis. Also, hospital-acquired infections with drug resistance caused by the weakness of the patient's system appeared in the patient who was hospitalized in the intensive care unit (ICU), and finally, the patient died. According to antibiotic patterns, the best antibiotic to which the bacteria is sensitive can be considered the primary treatment to avoid irrational antibiotic prescriptions.
 

Background: Acinetobacter baumannii (A. baumannii) has emerged as the predominant etiological agent responsible for bloodstream infections among hospitalized patients. The objective of this study was to evaluate antibiotic resistance in A. baumannii isolates identified from blood cultures.
Methods: A retrospective cohort evaluation was conducted on 117 A. baumannii isolates obtained from blood cultures collected between 2018 and 2019 at the Microbiology Laboratory of Tokat Gaziosmanpaşa University Hospital (Türkiye). The blood culture samples were incubated using the BACT-ALERT 3D system (bioMérieux, Durham, NC, USA). Microorganism identification and antibiotic susceptibility testing were performed using the VITEK 2 (bioMérieux, France) automated system.
Results: Of the 117 samples, 59.8% were obtained from males and 40.2% from females. A total of 90.6% of blood culture samples were collected from the intensive care unit, and 88.9% of isolates were identified as multidrug-resistant (MDR). The highest resistance was observed against meropenem (99.1%), while the lowest resistance was noted for colistin (17.1%) and tigecycline (27.3%). Resistance to amikacin was 74.4%, while resistance levels to gentamicin, tobramycin, cefoxitin, and cefotaxime were within the range of 80–90%. Resistance to imipenem, amoxicillin/clavulanic acid, ampicillin/sulbactam, ceftazidime, cefepime, ciprofloxacin, levofloxacin, meropenem, and ertapenem exceeded 90%.
Conclusion: The increasing number of MDR A. baumannii isolates poses a significant threat to all hospitalized patients. However, colistin and tigecycline remain preferable options for the treatment of MDR A. baumannii infections. Considering the increasing prevalence of MDR A. baumannii isolates, periodic analysis of epidemiological data in healthcare centers is important for managing resistance to colistin and tigecycline.
 

Background: Tigecycline susceptibility testing and reporting remain enigmatic due to the lack of established guidelines. Disc diffusion, as a method of performing susceptibility testing, is more widely accepted worldwide due to its ease of use. Limited published literature is available from India on the utility of this method, especially in a cancer care setting. Hence, this study was conducted to evaluate the performance characteristics of disc diffusion by comparing its results with those of the VITEK-2 COMPACT, considering the latter as the standard.
Methods: Disc diffusion was performed using Kirby-Bauer’s method on Mueller-Hinton agar with a HiMedia 15 mcg TGC disc, following FDA and EUCAST breakpoints. According to CLSI criteria, disc diffusion breakpoints can be considered acceptable when categorical agreement is ≥ 90%, the very major error is ≤ 1.5%, and the major error is ≤ 3%.
Results: Using Cohen’s kappa coefficient, the kappa value was 0.328, with a p-value of <0.05. The agreement percentage observed was 60.84%. Two strains reported as resistant by VITEK-2 COMPACT were misclassified as sensitive by disc diffusion, resulting in a very major error rate of 0.76%. A major error rate of 9.5% and a minor error rate of 27.7% were noted, as 25 strains reported as susceptible were identified as resistant.
Conclusion: Since poor agreement was observed, exceeding the acceptable performance rate, the disc diffusion method was unacceptable according to CLSI criteria. There is a gap in uniformity and a lack of streamlined, harmonized TST, which might become an alarming cause for concern.