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Bacterial efflux pumps confer multidrug resistance by transporting diverse antibiotics from the cell. In Gram-negative bacteria, some of these pumps form multi-protein assemblies that span the cell envelope. Here, we report the near-atomic resolution cryoEM structures of the Escherichia coli AcrAB-TolC multidrug efflux pump in resting and drug transport states, revealing a quaternary structural switch that allosterically couples and synchronizes initial ligand binding with channel opening. Within the transport-activated state, the channel remains open even though the pump cycles through three distinct conformations. Collectively, our data provide a dynamic mechanism for the assembly and operation of the AcrAB-TolC pump.

Background Acral lentiginous melanoma (ALM) is a highly malignant and invasive type of melanoma with unique locations of onset. Its incidence is increasing and early diagnosis is challenging. Reflectance confocal microscopy (RCM) is a non‐invasive technique that provides an accurate image of tissue pathology. There are few reports on the use of RCM for the assessment of ALM. Materials and methods In this retrospective study, data from 31 patients with a clinical diagnosis of ALM were collected. RCM image features were compared with histopathological findings to determine the concordance between the two methods. The sensitivity, specificity, positive predictive value, and negative predictive value of RCM for the diagnosis of ALM were evaluated. Results RCM and histopathology findings were concordant in 29 of 31 patients (93.5%). There were no false‐negative results, although there were two false positives in RCM diagnosis. The sensitivity of RCM for diagnosing ALM was 100%, specificity was 50%, positive predictive value was 93.1%, and negative predictive value was 100%. Conclusions RCM showed substantial concordance with histopathology in the diagnosis of ALM. It is a reliable and valuable non‐invasive diagnostic tool that holds promise for the early diagnosis of ALM.

Gastrointestinal (GI) colonization by Klebsiella pneumoniae is a risk factor for subsequent infection as well as transmission to other patients. Additionally, colonization is achieved by many strain types that exhibit high diversity in genetic content. Thus, we aimed to study strain-specific requirements for K. pneumoniae GI colonization by applying transposon insertion sequencing to three classical clinical strains: a carbapenem-resistant strain, an extended-spectrum beta-lactamase-producing strain, and a non-epidemic antibiotic-susceptible strain. The transposon insertion libraries were screened in a murine model of GI colonization. At 3 days post-inoculation, 27 genes were required by all three strains for colonization. Isogenic deletion mutants for three genes/operons ( acrA , carAB , and tatABCD ) confirmed colonization defects in each of the three strains. Additionally, deletion of acrA reduced bile tolerance in vitro , while complementation restored both bile tolerance in vitro and colonization ability in vivo . Transposon insertion sequencing suggested that some genes were more important for the colonization of one strain than the others. For example, deletion of the sucrose porin-encoding gene scrY resulted in a colonization defect in the carbapenemase-producing strain but not in the extended-spectrum beta-lactamase producer or the antibiotic-susceptible strain. These findings demonstrate that classical K. pneumoniae strains use both shared and strain-specific strategies to colonize the mouse GI tract. Klebsiella pneumoniae is a common cause of difficult-to-treat infections due to its propensity to express resistance to many antibiotics. For example, carbapenem-resistant K. pneumoniae has been named an urgent threat by the United States Centers for Disease Control and Prevention. Gastrointestinal colonization in patients with K. pneumoniae has been linked to subsequent infection, making it a key process to control in the prevention of multidrug-resistant infections. However, the bacterial factors which contribute to K. pneumoniae colonization are not well understood. Additionally, individual strains exhibit large amounts of genetic diversity, begging the question of whether some colonization factors are strain dependent. This study identifies the enteric colonization factors of three classical strains using transposon mutant screens to define a core colonization program for K. pneumoniae as well as detecting strain-to-strain differences in colonization strategies.

Bacillary dysentery, commonly called shigellosis, is a common infectious illness in underdeveloped nations that is caused by the Shigella flexneri . According to the World Health Organization, it was the second most common cause of diarrhea in 2010 with about 212,000 deaths. The immediate development of a new vaccine candidate against dysentery is required due to the high prevalence of this disease. Here, we report on the endeavor to create a chimeric vaccine against S. flexneri by employing a computational subtractive genome-based vaccine design with the references strain (UP000001884). Ultimately, the acriflavin resistance protein AcrA was identified as non-homologous, non-paralogous, and antigenic vaccine candidate and thus was used for the vaccine designing. Subsequently, it was discovered that just two of the identified epitopes were very efficient and were used to create potential vaccines. Eight distinct vaccination models were evaluated, and the results indicated that the V5 candidate was antigenic, non-allergenic, and stable. The molecular docking and simulations reveal a significant interaction energy between the proposed vaccine candidate and the HLAs and TRL2/4 immunological receptors. Afterward, a plasmid vector for the Escherichia coli K12 strain was constructed utilizing the vaccine cDNA sequence. The simulations showed that V5 elicited significant immune responses, indicating its strong immunogenicity. The adoption of SF-designed ( S. flexneri ) vaccines has the potential to cut vaccine development times and costs in half. Although these findings show potential, further study is required (both in vivo and in vitro experiments) to confirm the proposed vaccine's biological effectiveness against S. flexneri .

Clustered, regularly interspaced short palindromic repeats (CRISPRs) and their related genes (Cas) are prevalent in the genomes of several bacteria and serve as a defense mechanism against external attackers, such as plasmids and viruses. This study aimed to examine the frequency of the CRISPR/Cas system in naturally occurring strains of Klebsiella pneumoniae sub spp pneumoniae confirmed by Vitek 2 biochemical test, in the hospital setting and determine its correlation with antibiotic resistance both phenotypically and genetically (antibiotic-resistant genes, namely blaTEM and AcrA efflux pump gene). The research was conducted at Medical College/ Mosul University 23 multi-drug resistant K. pneumoniae sub spp. pneumoniae that were obtained from 230 clinical samples from  infected patients with different types of infections attending  Al-Salam and Al-Jumhoree Teaching hospitals. PCR was used to detect blaTEM, AcrA genes, and CRISPR/Cas system genes (CAS1A and CAS1B) among the clinical isolates. The correlation between the CRISPR/Cas system and antibiotic-resistance was determined. All the isolates were multiple drug-resistant strains, and the blaTEM gene was detected in all clinical isolates, whereas AcrA gene was detected in 94% of the isolates. The frequency of CAS1A and CAS1B was 21.73% and 86.95% respectively. There was an inverse correlation between the CAS1A gene and phenotypic antibiotic resistance Disc diffusion test results, so isolates carrying CAS1A gene were less resistant to different antibiotics studied in this research. In contrast, there was no significant correlation between CRISPR / Cas genes, blaTEM, and AcrA genes at the genetic level.  

Undergraduate training continues to be a challenge to train entrepreneurial specialists with research-oriented attitudes. Depending on the level of func-tional development of the brain, the level of learning will be different in re-lation to chronological age. The ACRA learning strategies scales (Román & Gallego, 2001) allow verifying the frequency, type of strategy and specific technique used by students, the coding strategies being the most important for effective performance throughout life; although there is an abbreviated and validated version of this scale applicable only at the university level by De la Fuente and Justicia (2003); In the study, the 2001 version of Román & Gallego is applied to analyze, according to age, the correspondence between the learning strategies used by the students with their academic performance, as well as to verify if there is a difference by gender, during a period of three years . Technical sheets and final grades of the students were also ap-plied; a multiple linear regression analysis; it is a mixed type investigation. It is observed that the Coding strategies are not used very frequently. In Aca-demic Performance (AR), only 7.85% of the students obtained a final score of 14 or more, the use score coinciding with scales that measure the same learning strategies. The type of strategies and the age (18-19 years) registered influence the RA and only the Acquisition strategies show a slight relation-ship with the RA. There is no gender relationship.

Efflux pumps are a relevant factor in antimicrobial resistance. In E. coli, the tripartite efflux pump AcrAB-TolC removes a chemically diverse set of antibiotics from the bacterium. Therefore, small molecules interfering with efflux pump function are considered adjuvants for improving antimicrobial therapies. Several compounds targeting the periplasmic adapter protein AcrA and the efflux pump AcrB have been identified to act synergistically with different antibiotics. Among those, several 4(3-aminocyclobutyl)pyrimidin-2-amines have been shown to bind to both proteins. In this study, we intended to identify analogs of these substances with improved binding affinity to AcrA using virtual screening followed by experimental validation. While we succeeded in identifying several compounds showing a synergistic effect with erythromycin on E. coli, biophysical studies suggested that 4(3-aminocyclobutyl)pyrimidin-2-amines form colloidal aggregates that do not bind specifically to AcrA. Therefore, these substances are not suited for further development. Our study emphasizes the importance of implementing additional control experiments to identify aggregators among bioactive compounds.