Gene expression regulation plays a critical role in host-pathogen interactions, and RNAs function is essential in this process. miRNAs are small noncoding, endogenous RNA fragments that affect stability and/or translation of mRNAs, act as major posttranscriptional regulators of gene expression. miRNA is involved in regulating many biological or pathological processes through targeting specific mRNAs, including development, differentiation, apoptosis, cell cycle, cytoskeleton organization, and autophagy. Deregulated microRNA expression is associated with many types of diseases, including cancers, immune disturbances, and infection. miRNAs are a vital section of the host immune response to bacterial-made infection. Bacterial pathogens suppress host miRNA expression for their benefit, promoting survival, replication, and persistence. The role played through miRNAs in interaction with host-bacterial pathogen has been extensively studied in the past 10 years, and knowledge about these staggering molecules' function can clarify the complicated and ambiguous interactions of the host-bacterial pathogen. Here, we review how pathogens prevent the host miRNA expression. We briefly discuss emerging themes in this field, including their role as biomarkers in identifying bacterial infections, as part of the gut microbiota, on host miRNA expression.

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Carbapenems are employed to treat infections caused by Gram-negative bacteria including Klebsiella pneumoniae. This research is aimed to perform phenotypic detection of β-lactamases and molecular characterization of NDM-1 positive K. pneumoniae isolates. Another objective is to investigate NDM-1 producing K. pneumoniae among children in Iran. From 2019 to 2020, altogether 60 K. pneumoniae isolates were acquired from various patients in certain Iranian hospitals. Antimicrobial susceptibility testing was performed by disk diffusion and broth microdilution methods. In addition, mCIM and eCIM were used to confirm the production of carbapenemases and metallo-beta-lactamases (MBLs), respectively. Detection of resistance genes namely, blaNDM-1, blaIMP, blaVIM, blaKPC, blaOXA-48-like, blaCTX-M, blaSHV, blaTEM, and mcr-1 was performed by PCR and confirmed by DNA sequencing. Multilocus sequence typing (MLST) was employed to determine the molecular typing of the strains. According to the findings, the highest rate of carbapenem resistance was detected against doripenem 83.3% (50). Moreover, 31.7% (19) were resistant to colistin. Further to the above, altogether 80% (48) were carbapenemase-producing isolates and among them 46.7% (28) of the isolates were MBL and 33.3% (20) isolates were serine β-lactamase producer. According to the PCR results, 14 isolates produced blaNDM-1. Remarkably, four blaNDM-1 positive isolates were detected in children. In addition, these isolates were clonally related as determined by MLST (ST147, ST15). Altogether ten blaNDM-1 positive isolates were ST147 and four blaNDM-1 positive isolates were ST15. Based on the results, the emergence of NDM-producing K. pneumoniae among children is worrying and hence, it is necessary to develop a comprehensive program to control antibiotic resistance in the country.

Background: The opportunistic human pathogen, Pseudomonas aeruginosa, is a critical cause of nosocomial infection with high morbidity and mortality rate. Eradication of P. aeruginosa has been troublesome due to its high capacity to develop strong multidrug resistance (MDR). Objectives: The purposes of this study were to define the pattern of antimicrobial sensitivity, typing, and prevalence of metallo-β-lactamase (MBL) and detect the oprD, blaCTX-M, blaSHV, blaTEM, blaIMP, blaNDM, and blaVIM among clinical isolates of P. aeruginosa collected from Tehran hospitals. Methods: Clinical isolates were collected from hospitalized children in selected hospitals in Tehran from March 2019 to February 2020. The antimicrobial susceptibility test (AST) was performed by the Kirby-Bauer disk diffusion method. Composed disc diffusion tests were performed to screen MBL production. MBLs and extended-spectrum β-lactamases (ESBL) encoding genes were amplified by polymerase chain reaction (PCR). Amplification of the oprD gene were performed for carbapenem-resistant P. aeruginosa. Random amplified polymorphic DNA (RAPD-PCR) Fingerprinting was used for genotyping the isolates. Results: A total of 80 P. aeruginosa isolates were collected. Isolates were resistant to cefepime 35%, ceftazidime 20%, ciprofloxacin 22%, tazobactam 16%. Out of 80 isolates, 16 were carbapenems-resistant. Gentamicin, tobramycin, and amikacin had the highest susceptibilities of 85%,90%, and 90%, respectively. OprD, blaCTX-M, blaSHV, and blaTEM were detected in 80(100%), 36(45%),22 (27.5%), 17 (21.25%), and 1 (1.25%) blaIMP and blaNDM, respectively. In this study, the blaVIM gene was not detected in the isolates, and no mutation was observed regarding the presence of an insertion element in the OprD gene. Isolates were divided into 13 and 14 common and single types, respectively. Conclusions: P. aeruginosa isolates showed a high rate of β- lactamases production, and the prevalence of carbapenem-resistant, which can be related to different mechanisms, was alarming. On the other hand, the results demonstrated that there was beta-lactam antibiotic resistance and clonal spread among the hospital population. This shows the necessity of molecular surveillance in tracking beta-lactamase-producing strains.

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