Antimicrobial Resistance Mechanisms Research Articles

Characterization of plasmids carrying blaCTX-M genes among extra-intestinal Escherichia coli clinical isolates in Ethiopia

CTX-Ms are encoded by blaCTX-M genes and are widely distributed extended-spectrum β-lactamases (ESBLs). They are the most important antimicrobial resistance (AMR) mechanism to β-lactam antibiotics in the Enterobacteriaceae. However, the role of transmissible AMR plasmids in the dissemination of blaCTX-M genes has scarcely been studied in Africa where the burden of AMR is high and rapidly spreading. In this study, AMR plasmid transmissibility, replicon types and addiction systems were analysed in CTX-M-producing Escherichia coli clinical isolates in Ethiopia with a goal to provide molecular insight into mechanisms underlying such high prevalence and rapid dissemination. Of 100 CTX-Ms-producing isolates obtained from urine (84), pus (10) and blood (6) from four geographically distinct healthcare settings, 75% carried transmissible plasmids encoding for CTX-Ms, with CTX-M-15 being predominant (n = 51). Single IncF plasmids with the combination of F-FIA-FIB (n = 17) carried the bulk of blaCTX-M-15 genes. In addition, IncF plasmids were associated with multiple addiction systems, ISEcp1 and various resistance phenotypes for non-cephalosporin antibiotics. Moreover, IncF plasmid carriage is associated with the international pandemic E. coli ST131 lineage. Furthermore, several CTX-M encoding plasmids were associated with serum survival of the strains, but less so with biofilm formation. Hence, both horizontal gene transfer and clonal expansion may contribute to the rapid and widespread distribution of blaCTX-M genes among E. coli populations in Ethiopian clinical settings. This information is relevant for local epidemiology and surveillance, but also for global understanding of the successful dissemination of AMR gene carrying plasmids.

Coexistence Of Blaoxa-48, Blavim, And Blashv Genes In Klebsiella Pneumoniae And Escherichia Coli Isolated From Urinary Tract Infections: Microbiological And Epidemiological Analysis.

To investigate antimicrobial resistance mechanisms of isolated bacterialstrains, and their correlation with virulence profile. The cross-sectional study was conducted in January 2020 at outpatient health centres in Kafrelsheikh Governorate of Egypt, and comprised urine samples from patients regardless of age and gender. Midstream samples were collected into sterile swaps which were kept in ice-cooled boxes until transported to the laboratory within 5h. Antimicrobial resistance profile of the isolated Enterobacteriaceae was done using Kirby-Bauer disk diffusion method and was confirmed withVitek compact 2. The phenotypic of carbapenemases and extended-spectrum beta lactamase was determined, and polymerase chain reaction was used, as appropriate. Data was analysed using SPSS 20. Of the 199 patients, 101(50.7%) were females and 98(49.3%) were males. The majority 73(36.6%) were aged 30-50 years. Urinary tract infection was found in 68(34.2%) patients. In 28(41.2%) of these patients, there were 32 isolates of Enterobacterales; 21(65.62%) Klebsiella pneumoniae, 7(21.87%) Escherichia coli and 4(12.5%) Enterobacter cloacae. Of the 28(41.2%) patients, 24(85.7%) were infected with a single strain; 17(70.8%) Klebsiella pneumoniae, 4(16.7%) Escherichia coli and 3(12.5%) Enterobacter cloacae. In 3(10.7%) cases, there was co-infection with Escherichia coli and Klebsiella pneumoniae, and 1(3.6%)sample had mixed infection with Klebsiella pneumoniae and Enterobacter cloacae. The other 40(58.8%) patients had other causative agents. Housewives, agricultural workers and those aged >50 years had a higher risk of urinary tract infections(p<0.05) Among Klebsiella pneumonia isolates, 6(28.5%) possessed carbapenemase-related genes and 4(19.1%) extended-spectrum beta lactamase-related genes. The carbapenemase related genes were bla-Verona integron-encoded metallo beta lactamase 6(100%) bla-New Delhi metallo beta lactamase-1 4(66.6%) and bla-oxacillinase-48 2(33.3%). The 4(19.1%) cases of extended-spectrum beta lactamase related genes had bla-temoneira gene 3(75%) and bla-sulfhydryl variable gene 4(100%). In Escherichia coli isolates, bla-oxacillinase-48 and bla-Cefotaximase genes were observed in 2(28.5%) cases.Virulence genes uridine diphosphate glucose 4-epimerase, fimbrial adhesion and mannose-resistance adhesin of Klebsiella spp genes in Klebsiella pneumoniae isolates were positive in in 16(76.2%), 14(66.7%) and 10(47.6%) cases, respectively. All 21(100%) isolates of Klebsiella pneumoniae were negative for mucoviscosity-associated gene A. There was evidence of the coexistence of bla- oxacillinase-48, bla-Verona integron-encoded metallo beta lactamase and bla-sulfhydryl variable genes in Klebsiella pneumoniae and Escherichia coli isolates from mixed urinary tract infection samples.

ESKAPE and Beyond: The Burden of Coinfections in the COVID-19 Pandemic.

The ESKAPE group constitute a threat to public health, since these microorganisms are associated with severe infections in hospitals and have a direct relationship with high mortality rates. The presence of these bacteria in hospitals had a direct impact on the incidence of healthcare-associated coinfections in the SARS-CoV-2 pandemic. In recent years, these pathogens have shown resistance to multiple antibiotic families. The presence of high-risk clones within this group of bacteria contributes to the spread of resistance mechanisms worldwide. In the pandemic, these pathogens were implicated in coinfections in severely ill COVID-19 patients. The aim of this review is to describe the main microorganisms of the ESKAPE group involved in coinfections in COVID-19 patients, addressing mainly antimicrobial resistance mechanisms, epidemiology, and high-risk clones.

Drug Resistance Mechanism and Detection Method of Salmonella

As an important zoonotic food-borne pathogen, Salmonella is a concern for public health authorities. In particular, bacteria that are resistant to multiple antimicrobials can confuse the efficacy of treatment for infectious diseases. Drug-resistant bacteria have a variety of drug-resistant molecular and cellular mechanisms. These antimicrobial resistance mechanisms include antibiotic efflux, permeability changes in cell membranes, enzymatic drug inactivation, biofilm formation, drug target changes, and protection of antimicrobial targets. In this paper, the mechanisms of antimicrobial resistance in salmonella and the techniques of detecting antibiotic resistance by traditional and molecular methods are reviewed, with emphasis on their advantages and disadvantages, as well as the validity and reliability of the results.

Burkholderia contaminans Bacteriophage CSP3 Requires O-Antigen Polysaccharides for Infection.

The Burkholderia cepacia complex is a group of opportunistic pathogens that cause both severe acute and chronic respiratory infections. Due to their large genomes containing multiple intrinsic and acquired antimicrobial resistance mechanisms, treatment is often difficult and prolonged. One alternative to traditional antibiotics for treatment of bacterial infections is bacteriophages. Therefore, the characterization of bacteriophages infective for the Burkholderia cepacia complex is critical to determine their suitability for any future use. Here, we describe the isolation and characterization of novel phage, CSP3, infective against a clinical isolate of Burkholderia contaminans. CSP3 is a new member of the Lessievirus genus that targets various Burkholderia cepacia complex organisms. Single nucleotide polymorphism (SNP) analysis of CSP3-resistant B. contaminans showed that mutations to the O-antigen ligase gene, waaL, consequently inhibited CSP3 infection. This mutant phenotype is predicted to result in the loss of cell surface O-antigen, contrary to a related phage that requires the inner core of the lipopolysaccharide for infection. Additionally, liquid infection assays showed that CSP3 provides suppression of B. contaminans growth for up to 14 h. Despite the inclusion of genes that are typical of the phage lysogenic life cycle, we saw no evidence of CSP3's ability to lysogenize. Continuation of phage isolation and characterization is crucial in developing large and diverse phage banks for global usage in cases of antibiotic-resistant bacterial infections. IMPORTANCE Amid the global antibiotic resistance crisis, novel antimicrobials are needed to treat problematic bacterial infections, including those from the Burkholderia cepacia complex. One such alternative is the use of bacteriophages; however, a lot is still unknown about their biology. Bacteriophage characterization studies are of high importance for building phage banks, as future work in developing treatments such as phage cocktails should require well-characterized phages. Here, we report the isolation and characterization of a novel Burkholderia contaminans phage that requires the O-antigen for infection, a distinct phenotype seen among other related phages. Our findings presented in this article expand on the ever-evolving phage biology field, uncovering unique phage-host relationships and mechanisms of infection.

Epidemiological and Antimicrobial Resistant Patterns, and Molecular Mechanisms of Carbapenem-Resistant Klebsiella pneumoniae Infections in ICU Patients.

To study the epidemiological and antimicrobial resistant patterns, clinical characteristics and risk factors of critically ill patients infected with carbapenem-resistant Klebsiella pneumoniae (CRKP) from intensive care units (ICUs). The potential molecular mechanisms of antimicrobial resistance and virulence of CRKP were investigated through evaluation of associated genes. Totally, 201 ICU patients infected with K. pneumoniae were recruited from January 2020 through January 2021. K. pneumoniae strains were collected from diverse clinical specimens and identified by microbial cultures and matrix-assisted laser desorption ionization-time-of-flight mass spectrometry. Antimicrobial resistance was measured through broth micro-dilution or Kirby-Bauer assays. The carbapenemase-, virulence-, and capsular serotype-associated genes of CRKP were individually detected by PCR and sequencing. Demographic and clinical profiles were acquired from hospital databases to evaluate the correlation of CRKP infection incidence with clinical risk factors. Of the 201 K. pneumoniae strains, CRKP accounted for 41.29%. Seasonal bias existed in local prevalence of CRKP infections. CRKP strains mounted significantly strong resistance against major antimicrobial agents except ceftazidime-avibactam, tigecycline and minocycline. Recent exposure to certain antibiotics and prior treatment with invasive interventions were prone to increase CRKP infection risks with worsened infectious outcomes. The local top carbapenemase-encoding and virulence-associated genes of CRKP were blaKPC and irp2, respectively. Nearly half of CRKP isolates harbored a capsular polysaccharide serotype of K14.K64 (wzi-64) which preferentially emerged in the cohort with worse outcomes of infection. Featured epidemiology and typical clinical characteristics existed extensively in K. pneumoniae infections among ICU patients. The CRKP cohort exhibited substantially high antimicrobial resistance. Distinctive carbapenemase-, virulence-, and serotype-associated genes were intensively involved in the spread and pathogenesis of CRKP. These findings supported careful management of critically ill patients potentially infected with virulent CRKP in the ICUs.

The vanRCd Mutation 343A>G, Resulting in a Thr115Ala Substitution, Is Associated with an Elevated Minimum Inhibitory Concentration (MIC) of Vancomycin in Clostridioides difficile Clinical Isolates from Florida.

Clostridioides difficile, the primary cause of nosocomial antibiotic-associated diarrhea, has a complex relationship with antibiotics. While the use of broad-spectrum antibiotics disrupts the gut microbiota and increases the risk of C. difficile infection (CDI), antibiotics are also the primary treatment for CDI. However, only a few antibiotics, including vancomycin, fidaxomicin, and rifaximin, are effective against CDI, and resistance to these antibiotics has emerged recently. In this study, we report the identification of two RT027 C. difficile clinical isolates (TGH35 and TGH64) obtained from symptomatic CDI-diagnosed patients in Tampa, Florida in 2016. These two strains showed an elevated minimum inhibitory concentration (MIC) of vancomycin (MIC = 4 μg/mL, compared to the EUCAST breakpoint of 2 μg/mL) and contained a vanRCd 343A>G mutation resulting in a Thr115Ala substitution in the VanRCd response regulator. This mutation was absent in the vancomycin-sensitive control epidemic strain RT027/R20291. TGH64 was also resistant to rifaximin (MIC ≥ 128 μg/mL) and carried the previously reported Arg505Lys and Ile548Met mutations in RpoB. Furthermore, we report on the antimicrobial resistance (AMR) and genomic characterization of additional C. difficile isolates, including RT106/TGH120, RT017/TGH33, and RT017/TGH51, obtained from the same patient sample cohort representing the highly prevalent and regionally distributed C. difficile ribotypes worldwide. Considering that the VanRCd Thr115Ala mutation was also independently reported in seven C. difficile clinical isolates from Texas and Israel in 2019, we recommend epidemiological surveillance to better understand the impact of this mutation on vancomycin resistance. IMPORTANCE The perpetually evolving antimicrobial resistance (AMR) of C. difficile is an important contributor to its epidemiology and is a grave concern to global public health. This exacerbates the challenge of treating the infections caused by this multidrug-resistant causative organism of potentially life-threatening diarrhea. Further, the novel resistance-determining factors can be transferred between different strains and species of bacteria and cause the spread of AMR in clinical, environmental, and community settings. In this study, we have identified a mutation (vanRCd 343A>G) that causes a Thr115Ala substitution and is linked to an increased MIC of vancomycin in clinical isolates of C. difficile obtained from Florida in 2016. Understanding the mechanisms of AMR, especially those of newly evolving strains, is essential to effectively guide antibiotic stewardship policies to combat antibiotic resistance as well as to discover novel therapeutic targets.

Multiple Dosing and Preactivation of Mesenchymal Stromal Cells Enhance Efficacy in Established Pneumonia Induced by Antimicrobial-Resistant Klebsiella pneumoniae in Rodents.

Antimicrobial-resistant (AMR) bacteria, such as Klebsiella species, are an increasingly common cause of hospital-acquired pneumonia, resulting in high mortality and morbidity. Harnessing the host immune response to AMR bacterial infection using mesenchymal stem cells (MSCs) is a promising approach to bypass bacterial AMR mechanisms. The administration of single doses of naïve MSCs to ARDS clinical trial patient cohorts has been shown to be safe, although efficacy is unclear. The study tested whether repeated MSC dosing and/or preactivation, would attenuate AMR Klebsiella pneumonia-induced established pneumonia. Rat models of established K. pneumoniae-induced pneumonia were randomised to receive intravenous naïve or cytomix-preactivated umbilical cord MSCs as a single dose at 24 h post pneumonia induction with or without a subsequent dose at 48 h. Physiological indices, bronchoalveolar lavage (BAL), and tissues were obtained at 72 h post pneumonia induction. A single dose of naïve MSCs was largely ineffective, whereas two doses of MSCs were effective in attenuating Klebsiella pneumosepsis, improving lung compliance and oxygenation, while reducing bacteria and injury in the lung. Cytomix-preactivated MSCs were superior to naïve MSCs. BAL neutrophil counts and activation were reduced, and apoptosis increased. MSC therapy reduced cytotoxic BAL T cells, and increased CD4+/CD8+ ratios. Systemically, granulocytes, classical monocytes, and the CD4+/CD8+ ratio were reduced, and nonclassical monocytes were increased. Repeated doses of MSCs-particularly preactivated MSCs-enhance their therapeutic potential in a clinically relevant model of established AMR K. pneumoniae-induced pneumosepsis.

Human Salmonellosis: A Continuous Global Threat in the Farm-to-Fork Food Safety Continuum.

Salmonella is one of the most common zoonotic foodborne pathogens and a worldwide public health threat. Salmonella enterica is the most pathogenic among Salmonella species, comprising over 2500 serovars. It causes typhoid fever and gastroenteritis, and the serovars responsible for the later disease are known as non-typhoidal Salmonella (NTS). Salmonella transmission to humans happens along the farm-to-fork continuum via contaminated animal- and plant-derived foods, including poultry, eggs, fish, pork, beef, vegetables, fruits, nuts, and flour. Several virulence factors have been recognized to play a vital role in attaching, invading, and evading the host defense system. These factors include capsule, adhesion proteins, flagella, plasmids, and type III secretion systems that are encoded on the Salmonella pathogenicity islands. The increased global prevalence of NTS serovars in recent years indicates that the control approaches centered on alleviating the food animals' contamination along the food chain have been unsuccessful. Moreover, the emergence of antibiotic-resistant Salmonella variants suggests a potential food safety crisis. This review summarizes the current state of the knowledge on the nomenclature, microbiological features, virulence factors, and the mechanism of antimicrobial resistance of Salmonella. Furthermore, it provides insights into the pathogenesis and epidemiology of Salmonella infections. The recent outbreaks of salmonellosis reported in different clinical settings and geographical regions, including Africa, the Middle East and North Africa, Latin America, Europe, and the USA in the farm-to-fork continuum, are also highlighted.

A novel Outer Membrane Vesicle-mediated mechanism of antimicrobial resistance of &lt;i&gt;Klebsiella pneumoniae&lt;/i&gt;

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Antimicrobial resistance and plasmid-mediated colistin resistance mechanism of diarrheagenic Escherichia coli recovered from foods in parts of China in 2020

Objective: To investigate the antimicrobial resistance of food-borne diarrheagenic Escherichia coli (DEC) and the prevalence of mcr genes that mediates mobile colistin resistance in parts of China, 2020. Methods: For 91 DEC isolates recovered from food sources collected from Fujian province, Hebei province, Inner Mongolia Autonomous Region and Shanghai city in 2020, Vitek2 Compact biochemical identification and antimicrobial susceptibility testing platform was used for the detection of antimicrobial susceptibility testing (AST) against to 18 kinds of antimicrobial compounds belonging to 9 categories, and multi-polymerase chain reaction (mPCR) was used to detect the mcr-1-mcr-9 genes, then a further AST, whole genome sequencing (WGS) and bioinformatics analysis were platformed for these DEC isolates which were PCR positive for mcr genes. Results: Seventy in 91 isolates showed different antimicrobial resistance levels to the drugs tested with a resistance rate of 76.92%. The isolates showed the highest antimicrobial resistance rates to ampicillin (69.23%, 63/91) and trimethoprim-sulfamethoxazole (59.34%, 54/91), respectively. The multiple drug-resistant rate was 47.25% (43/91). Two mcr-1 gene and ESBL (extended-spectrum beta-lactamase) positive EAEC (enteroaggregative Escherichia coli) strains were detected. One of them was identified as serotype of O11:H6, which showed a resistance profile to 25 tested drugs referring to 10 classes, and 38 drug resistance genes were predicted by genome analysis. The other one was O16:H48 serotype, which was resistant to 21 tested drugs belonging to 7 classes and carried a new variant of mcr-1 gene (mcr-1.35). Conclusion: An overall high-level antimicrobial resistance was found among foodborne DEC isolates recovered from parts of China in 2020, and so was the MDR (multi-drug resistance) condition. MDR strains carrying multiple resistance genes such as mcr-1 gene were detected, and a new variant of mcr-1 gene was also found. It is necessary to continue with a dynamic monitoring on DEC contamination and an ongoing research into antimicrobial resistance mechanisms.

Automatic Discrimination of Species within the Enterobacter cloacae Complex Using Matrix-Assisted Laser Desorption Ionization-Time of Flight Mass Spectrometry and Supervised Algorithms.

The Enterobacter cloacae complex (ECC) encompasses heterogeneous clusters of species that have been associated with nosocomial outbreaks. These species may have different acquired antimicrobial resistance and virulence mechanisms, and their identification is challenging. This study aims to develop predictive models based on matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) profiles and machine learning for species-level identification. A total of 219 ECC and 118 Klebsiella aerogenes clinical isolates from three hospitals were included. The capability of the proposed method to differentiate the most common ECC species (Enterobacter asburiae, Enterobacter kobei, Enterobacter hormaechei, Enterobacter roggenkampii, Enterobacter ludwigii, and Enterobacter bugandensis) and K. aerogenes was demonstrated by applying unsupervised hierarchical clustering with principal-component analysis (PCA) preprocessing. We observed a distinctive clustering of E. hormaechei and K. aerogenes and a clear trend for the rest of the ECC species to be differentiated over the development data set. Thus, we developed supervised, nonlinear predictive models (support vector machine with radial basis function and random forest). The external validation of these models with protein spectra from two participating hospitals yielded 100% correct species-level assignment for E. asburiae, E. kobei, and E. roggenkampii and between 91.2% and 98.0% for the remaining ECC species; with data analyzed in the three participating centers, the accuracy was close to 100%. Similar results were obtained with the Mass Spectrometric Identification (MSI) database developed recently (https://msi.happy-dev.fr) except in the case of E. hormaechei, which was more accurately identified with the random forest algorithm. In short, MALDI-TOF MS combined with machine learning was demonstrated to be a rapid and accurate method for the differentiation of ECC species.

Within-host resistance evolution of a fatal ST11 hypervirulent carbapenem-resistant Klebsiella pneumoniae.

Hypervirulent carbapenem-resistant Klebsiella pneumoniae (hv-CRKp) has become a great threat to public health. This study reported an hv-CRKp-associated fatal infection and revealed its mechanisms of antimicrobial resistance and within-host evolution. A carbapenem-susceptible K. pneumoniae (CSKp) and 11 KPC-producing CRKp strains were isolated from a lung transplant recipient receiving continual antimicrobial therapy for 1.5 years. Pulsed-field gel electrophoresis (PFGE) separated two clusters between CSKp and CRKp. Further whole genome sequencing analysis found that all 11 CRKp were ST11-KL64 clones, while the CSKp was ST412-KL57. Among these 11 CRKp strains, three and one were resistant to colistin and ceftazidime/avibactam (CAZ/AVI), respectively. Three different mechanisms were found to be responsible for the colistin resistance, including the insertions of two different IS (ISKpn74 and IS903B) into the same position of mgrB and one related to the efflux pump system. CAZ/AVI resistance was associated with blaKPC-2 mutation, and it was also found that increasing blaKPC-2 expression increased the MICs of CAZ/AVI, but not at the resistance level. All these 12 strains had iucABCDiutA virulence cluster and rmpA/rmpA2 genes, with higher siderophore production than a reference classic K. pneumoniae (cKp), which were thought to be hypervirulent K. pneumoniae (hvKp). However, only the CSKp showed higher mucoviscosity according to the mucoviscosity assay. Genomic analysis showed that the rmpA variation (interrupted by ISKpn26) existed in all CRKp strains except the CSKp strain, demonstrating that hypermucoviscous phenotype assays could not accurately identify hvKp. This study depicted a rapid and diverse within-host evolution of resistance in hv-CRKp of ST11-KL64 clone.

Antimicrobials from Medicinal Plants: Key Examples, Success Stories and Prospects in Tackling Antibiotic Resistance

Abstract: The rising statistics of antimicrobial resistance pose an alarming concern for the mankind. The extensive/injudicious use of antibiotics in the environment, animal husbandry, and health care have led to the alarming rise of infectious microbes developing resistance against conventional drugs. The use of phytotherapeutics defines an attractive approach to tackling drug-resistant microbes, attributed to their ability to target major antimicrobial resistance mechanisms, including efflux pumps, biofilms, and cell membranes, among others. In recent times, the discovery and bioprospection of plants for value-added metabolites have witnessed a tremendous upsurge, with several phytomolecules demonstrating bactericidal and drug-resistance reversal properties. However, several existing challenges, including their low concentration in plants, climatic variations, overutilization of plant resources, and deforestation, have limited the utilization of phytotherapeutics. Discussing the growing concern of drug-resistant microbes and antimicrobial resistance, the thematic article discusses the existing and emerging scenarios of antimicrobial resistance in microbes. In the post-antibiotic era, phytotherapeutics defines enormous potential to tackle the growing threat of antimicrobial resistance, addressed through genetic engineering of microbes/plant systems for enhanced antimicrobial production. The success stories of antimicrobials from medicinal plants, as exemplified by key examples, associated challenges, possible strategies, and prospects of antimicrobials in drug discovery, form the key underlying theme of the article.

An overview of the role of Zingiber officinale as an antimicrobial resistance (AMR) solution and a source of antioxidants

In this review, we describe the known mechanisms of antimicrobial resistance which was increasing in this era, due to the misuse of antimicrobial agents such as antibiotics, or genetic and phenotypic mechanisms. In this review, the concerns, especially addressed by designated researchers in their study and WHO in their observations and reports, regarding the types or strains of bacteria with antimicrobial resistances were described. In addition, the predicted mechanisms that promote the development and occurrence of antimicrobial resistances, such as bacterial biofilm formation, horizontal gene transfer, genetic mutations, free DNA which contains antimicrobial resistance genes, plasmids transfer through transformation or conjugation from bacterial cell to cell were well described. In addition, we also tried to describe the use of Z. officinale. The antimicrobial capabilities of this herbal plant are attributed to its capacity to create many secondary metabolites with rather complicated structures that have antibacterial and antioxidant characteristics. Z. officinale had been used for many kinds of diseases treatment traditionally. And along the way, the advance techniques of research in chemistry and biology fields had found out the composition and bioactive compound. In this review, the common online databases such as PubMed, Semantic Scholar, Crossref, Medline, Scopus, and Web of Science (WoS) were utilized to conduct literature searches. According to recent progress of antimicrobial cases observed, the efforts to strengthen the surveillance, general health systems, tightened the antimicrobial medicine distribution rules, and education for public are indeed needed.

Global scenario of the RmtE pan-aminoglycoside-resistance mechanism: emergence of the rmtE4 gene in South America associated with a hospital-related IncL plasmid.

Antimicrobial resistance (AMR) mechanisms, especially those conferring resistance to critically important antibiotics, are a great concern for public health. 16S rRNA methyltransferases (16S-RMTases) abolish the effectiveness of most clinically used aminoglycosides, but some of them are considered sporadic, such as RmtE. The main goals of this work were the genomic analysis of bacteria producing 16S-RMTases from a 'One Health' perspective in Venezuela, and the study of the epidemiological and evolutionary scenario of RmtE variants and their related mobile genetic elements (MGEs) worldwide. A total of 21 samples were collected in 2014 from different animal and environmental sources in the Cumaná region (Venezuela). Highly aminoglycoside-resistant Enterobacteriaceae isolates were selected, identified and screened for 16S-RMTase genes. Illumina and Nanopore whole-genome sequencing data were combined to obtain hybrid assemblies and analyse their sequence type, resistome, plasmidome and pan-genome. Genomic collections of rmtE variants and their associated MGEs were generated to perform epidemiological and phylogenetic analyses. A single 16S-RMTase, the novel RmtE4, was identified in five Klebsiella isolates from wastewater samples of Cumaná. This variant possessed three amino acid modifications with respect to RmtE1-3 (Asn152Asp, Val216Ile and Lys267Ile), representing the most genetic distant among all known and novel variants described in this work, and the second most prevalent. rmtE variants were globally spread, and their geographical distribution was determined by the associated MGEs and the carrying bacterial species. Thus, rmtE4 was found to be confined to Klebsiella isolates from South America, where it was closely related to ISVsa3 and an uncommon IncL plasmid related with hospital environments. This work uncovered the global scenario of RmtE and the existence of RmtE4, which could potentially emerge from South America. Surveillance and control measures should be developed based on these findings in order to prevent the dissemination of this AMR mechanism and preserve public health worldwide.

Gene network interaction analysis to elucidate the antimicrobial resistance mechanisms in the Clostridiumdifficile

Antimicrobial resistance has caused chaos worldwide due to the depiction of multidrug-resistant (MDR) infective microorganisms. A thorough examination of antimicrobial resistance (AMR) genes and associated resistant mechanisms is vital to solving this problem. Clostridium difficile (C. difficile) is an opportunistic nosocomial bacterial strain that has acquired exogenous AMR genes that confer resistance to antimicrobials such as erythromycin, azithromycin, clarithromycin, rifampicin, moxifloxacin, fluoroquinolones, vancomycin, and others. A network of interactions, including 20 AMR genes, was created and analyzed. In functional enrichment analysis, Cellular components (CC), Molecular Functions (MF), and Biological Processes (BP) were discovered to have substantial involvement. Mutations in the rpl genes, which encode ribosomal proteins, confer resistance in Gram-positive bacteria. Full erythromycin and azithromycin cross-resistance can be conferred if more than one of the abovementioned genes is present. In the enriched BP, rps genes related to transcriptional regulation and biosynthesis were found. The genes belong to the rpoB gene family, which has previously been related to rifampicin resistance. The genes rpoB, gyrA, gyrB, rpoS, rpl genes, rps genes, and Van genes are thought to be the hub genes implicated in resistance in C. difficile. As a result, new medications could be developed using these genes. Overall, our observations provide a thorough understanding of C. difficile AMR mechanisms.

Satisfactory In Vitro Activity of Ceftolozane-Tazobactam against Carbapenem-Resistant Pseudomonas aeruginosa But Not against Klebsiella pneumoniae Isolates.

Background: Gram-negative rods are one of the most commonly isolated bacteria within human infections. These microorganisms are typically opportunistic pathogens that pose a serious threat to public health due to the possibility of transmission in the human population. Resistance to carbapenems is one of the most important antimicrobial resistance mechanisms amongst them. The aim of this study was to evaluate ceftolozane-tazobactam in vitro activity against carbapenem-resistant Pseudomonas aeruginosa and Klebsiella pneumoniae clinical strains. Information on the antimicrobial activity of this antimicrobial against Gram-negative rods was also supplemented with a brief review of the relevant literature. Methods: The research involved 316 strains of Gram-negative rods: P. aeruginosa-206 and K. pneumoniae-110. Results: Of the tested strains, 86.0% P. aeruginosa and 30.0% K. pneumoniae remained susceptible to ceftolozane-tazobactam. Conclusions: Therefore, ceftolozane-tazobactam might be a good option in the treatment of infections caused by carbapenem-resistant P. aeruginosa strains, including those in ICU patients. Meanwhile, due to dissemination of ESBLs among K. pneumoniae strains, infections with this etiology should not be treated with the ceftolozane-tazobactam combination.

Genomic characterization of a multidrug-resistant Salmonella Rissen ST469 carrying blaCTX-M-55 gene and Tn6777 isolated from a paediatric patient in China

Here we report a complete genome sequence of a multidrug-resistant Salmonella Rissen, carrying blaCTX-M-55 and Tn6777, isolated from a Chinese paediatric patient. Whole genome of S. Rissen S1905 was sequenced using the Oxford Nanopore MinION and Illumina NovaSeq 6000 platforms. Unicycler was used to perform a de novo assembly of Illumina and Nanopore reads. The genome sequence was annotated using the NCBI Prokaryotic Genome Annotation Pipeline. In silico multilocus sequence typing, plasmid replicons, antimicrobial resistance genes and virulence factors were identified from the genome sequence by multiple bioinformatics tools. Core genome multilocus sequence typing analysis between S. Rissen S1905 and all retrieved from the NCBI GenBank database was performed using BacWGSTdb 2.0 server. Six contigs totaling 5 056 896 bp make up the complete genome sequence of S. Rissen S1905, which includes 1 chromosome and 5 plasmids. The blaCTX-M-55 was embedded in the ISEcp1-blaCTX-M-55-wbuC transposition unit located in an 85 991-bp IncI1 plasmid. However, the pco-sil operon and other eight antimicrobial resistance genes were carried by Tn6777 in the chromosome. There are 162 virulence genes in S1905. S. Rissen S1905 belongs to ST469; the closest relative was another isolate originating from a human faecal specimen in Shanghai, China, which differed by 60 core genome multilocus sequence type alleles. These data on the multidrug-resistant S. Rissen carrying blaCTX-M-55 and Tn6777 can provide a foundation for further studies on the molecular epidemiological characteristics, pathogenicity, antimicrobial resistance mechanisms, and dissemination mechanism of Salmonella.

2nd Workshop in Microbial Molecular Biology

2nd Workshop in Microbial Molecular Biology