Mutations in the rpoB locus confer conformational changes leading to defective binding of rifampin (RIF)

Background:Multidrug resistance Pseudomonas aeruginosa (MDR-P. aeruginosa) is a worldwide threat for public health. Hyperexpression of efflux pump systems (MexAB-OprM and MexCD-OprJ), which is a well-known mechanisms for MDR emerging, is controlled by regulatory genes, mexR and nfxB, respectively. The aim of this study was to evaluate point mutations in mexR and nfxB genes in MDR- P. aeruginosa isolated from wound infections.Materials and Methods:A total of 34 P. aeruginosa cultures obtained from wound infections were analyzed. Among them eight isolates identified as MDR-P. aeruginosa and were subjected to determination of mutations in mexR and nfxB genes.Results:We detected eight-point mutations in mexR and 12-point mutations in nfxB. The most common mutations were common G327-A (eight isolates), G384-A (eight isolates), G411-A (eight isolates). Mutations in A371-C and A372-C were the predominant substitution which was seen in nfxB. Amino acid substitutions were also found at position 124 and 126 for NfxB and MexR, respectively.Conclusions:P. aeruginosa isolates with mutation in efflux pump regulatory genes such as mexR and nfxB could be a main factor contributed to antibiotic resistance and must be considered in antibiotic treatment.

Overuse and misuse of Carbapenems among Klebsiella pneumoniae isolates have caused Carbapenem-Resistant Klebsiella Pneumonia (CRKP) during recent years. Colistin is one of the last available options, and there are increasing concerns about the dosage and resistance to this agent in long-term monotherapies. This study was designed to identification of carbapenemase producing isolates of K. pneumoniae via phenotypic and genotypic methods as well as evaluation of colistin-meropenem combination therapy potential. This study was carried out in Isfahan, of Iran on 100 samples from Alzahra and Khorshid hospitals in 2017. The Modified Hodge Test (MHT) was used to investigate the carbapenemase presence. The minimum inhibitory concentration (MIC) and the Fractional Inhibitory Concentration (FIC) were determined using broth macrodilution and checkerboard assays (respectively) for both meropenem and colistin. The bla-KPC gene was studied by polymerase chain reaction (PCR).The highest and the lowest rate of resistance were observed for piperacillin (84%) and ertapenem (50%) respectively. 68 isolates by MHT were CRKP, but None of them were positive for bla-KPC gene. 21 isolates from CRKP cases were high resistant to used antimicrobial agents in the study that both MIC and FIC results showed significant synergy for this antibiotics in checkerboard test (p-value < 0.05). 21 resistant isolates from CRKP cases showed statistically significant synergy potential for meropenem and colistin. The meropenem-colistin combination therapy can be applied as a suitable antibiotic synergy but it requires further investigation in clinical assay. Regarding to our findings, Probably other mechanisms of resistance to Carbapenems ,except bla-kpc genes are involved.

Background:Since 2003, the incidence of community associated Clostridium difficile infection (CA-CDI) has increased; different types of food have been supposed to be the vectors of C. difficile strains. The purpose of this study is to investigate the occurrence of C. difficile strains in ready-to-eat salads distributed in food services.Materials and Methods:A total of 106 ready-made salad specimens were sampled from different restaurants and food services located in Isfahan, in the center of Iran. Positive isolates of C. difficile were identified and confirmed for the existence of three genes including tpi, tcdA and tcdB by multiplex PCR.Results:A total of six (5.66%) samples were positive for C. difficile strains. Of which, one strain (16.6%) was positive for A and B toxins.Conclusion:The existence of toxigenic C. difficile in ready-made salads could be a caution for public health. Further investigation is required to assess the relationship between the isolated strains in our study and those from diarrheic patients through molecular typing.

Background: Klebsiella pneumoniais producer of carbapenemase (KPC) an emerging pathogen with propensity to malady in weak patients, increasing their morality rates.Carbapenemaseis an enzyme that destroys all beta-lactam antibiotics and is the therapeutic choice for infections with extended-spectrum beta-lactamase (ESBL)-producing organisms.ESBLESBLs are penicillin, narrow spectrum also third-generation cephalosporin, and monobactams hydrolyser and checkrein by clavulanic acid. Objectives: The present study was performed to separate and identify the carbapenemase resistance pattern of multidrug-resistant (MDR) and ESBL-positive K.pneumoniaas well as its prevalence among different wards and various clinical specimens in Isfahan. Patients and Methods: Over 500 different clinical samples were collected from different sections of great teaching hospitals in Isfahan, in which K. pneumonia isolates were identified by IMVIC and urease standard biochemical tests and also were confirmed by determination of the ureD Gene. Antimicrobial susceptibility tests were performed as standard disk-diffusion on Mueller-Hinton agar (Merck, Germany) based on the instructions of Clinical Laboratory Standards Institute (CLSI, 2013). Sieving and phenotype conformation of ESBL isolates were performed by double disc synergy test (DDST), and then, the strains identified as ESBL were test by carbapenem, ertapenem, imipenem andmeropenem. Finally, the statistical analyses were performed using the WHONET software version 5.6. Results: Of clinical isolates of K.pneumonia, 142 were confirmed using biochemical methods and then the molecular confirmation was performed by PCR of the ureD gene. Of the total isolates, 57% were from males and 43% from females; 120(84%) of isolates were recognized as MDR. The highest rates of resistance were related to piperacillin (80%), ceftazidime (76%), and cefotaxime (73%). Among these MDR isolates, 101 (71%) were detected as ESBL, using DDST. The ward and the clinical specimen with the most prevalence were ICU with 55 (38.7%) and urine with 61(42.9%) samples, respectively. The lowest prevalence was related to the neurosurgery ward with 8 (5.6%) samples and the clinical specimen with the lowest prevalence was cerebrospinal fluid (CSF) with 2 (1.4%) samples. The susceptibility patterns to carbapenem agents were as follows: ertapenem50.7%, meropenem 44.8% and imipenem35.8%. Conclusions: In this study, the prevalence of carbapenem-resistant K.pneumoniae was high in positive ESBL isolates, which can create significant therapeutic problems. According to the resistance pattern of ESBL-positive isolates for carbapenems in this research, ertapenem can probably serve as a suitable therapeutic option for uncomplicated infections by ESBL-producing K.pneumoniae instead of imipenem and meropenem.