Aminoglycoside Resistance Mechanisms Research Articles

Escherichia coli with increased aminoglycoside resistance due to an amino acid substitution at position 85 of HemC

ObjectiveThe mechanism of aminoglycoside resistance due to abnormal hemin synthesis remains unclear. We investigate an Escherichia coli strain with a single amino acid substitution at position 85 of HemC. MethodsAn aminoglycoside-resistant Escherichia coli DH5α was selected by passaging in Lysogeny Broth (LB) medium containing amikacin. Whole genome sequencing was performed to determine the genetic profile of the strain. An isogenic strain of E. coli DH5α was created. Growth rates, drug susceptibilities and expressions of the heme synthetic genes were compared between the original strain and the isogenic strain. ResultsWhole genome sequencing revealed a nucleotide substitution at position 254 of hemC from adenine (A) to thymine (T), resulting in an amino acid substitution at position 85 of HemC from histidine (H) to leucine (L). There were no mutations in other heme synthetic genes, including hemA, hemB, hemC, hemD, hemE, hemF, hemG, hemH, hemL, hemN, hemX and hemY. The isogenic strain of E. coli DH5α with H85L in HemC was less susceptible to aminoglycosides, and its growth was slower than that of E. coli DH5α before passage. Quantitative real-time PCR showed that the expression of hemA was higher and the expressions of hemL, hemG and hemX lower in the isogenic strain than before passage. ConclusionThis is the first report of aminoglycoside resistance due to an amino acid substitution in HemC. These findings suggested that mutations in the heme synthetic genes may indirectly affect the growth rates of E. coli strains and their susceptibilities to aminoglycosides.

Resistance against aminoglycoside antibiotics via drug or target modification enables community-wide antiphage defense.

The ongoing arms race between bacteria and phages has forced bacteria to evolve a sophisticated set of antiphage defense mechanisms that constitute the bacterial immune system. In our previous study, we highlighted the antiphage properties of aminoglycoside antibiotics, which are naturally secreted by Streptomyces. Successful inhibition of phage infection was achieved by addition of pure compounds and supernatants from a natural producer strain emphasizing the potential for community-wide antiphage defense. However, given the dual functionality of these compounds, neighboring bacterial cells require resistance to the antibacterial activity of aminoglycosides to benefit from the protection they confer against phages. In this study, we tested a variety of different aminoglycoside resistance mechanisms acting via drug or target (16S rRNA) modification and demonstrated that they do not interfere with the antiphage properties of the molecules. Furthermore, we confirmed the antiphage impact of aminoglycosides in a community context by coculturing phage-susceptible, apramycin-resistant Streptomyces venezuelae with the apramycin-producing strain Streptoalloteichus tenebrarius. Given the prevalence of aminoglycoside resistance among natural bacterial isolates, this study highlights the ecological relevance of chemical defense via aminoglycosides at the community level.

Prevalence and mechanisms of aminoglycoside resistance among drug-resistant Pseudomonas aeruginosa clinical isolates in Iran

BackgroundAminoglycosides have been a cornerstone of the treatment of nosocomial infections caused by Pseudomonas aeruginosa for over 80 years. However, escalating emergence of resistance poses a significant challenge. Therefore, this study aimed to investigate the prevailing patterns of aminoglycoside resistance among clinical isolates of P. aeruginosa in Iran; as well as the underlying resistance mechanisms observed in patients referred to Ardabil hospitals.MethodsA total of 200 isolates from five hospitals were evaluated. The resistance profiles of P. aeruginosa isolates to tobramycin, amikacin, and netilmicin were determined using the disk diffusion method. The capacity of aminoglycoside-resistant isolates to form biofilms was assessed through a phenotypic assay, and the results were confirmed using the gene amplification technique. The presence of genes associated with aminoglycoside resistance was detected using polymerase chain reaction (PCR). Quantitative reverse transcription PCR (qRT-PCR) was performed to measure the expression levels of genes encoding the MexXY-OprM efflux pump and PhoPQ two-component system (TCS).ResultsThe prevalence of aminoglycoside-resistant P. aeruginosa isolates was 48%, with 94.7% demonstrating multidrug resistance (MDR). All aminoglycoside-resistant P. aeruginosa strains exhibited biofilm-forming capabilities and harbored all the genes associated with biofilm production. Among the nine genes encoding 16S rRNA methylase and aminoglycoside-modifying enzymes, three genes were detected in these isolates: aac(6’)-Ib (85.4%), ant(2’’)-Ia (18.7%), and aph(3’)-VI (3.1%). Additionally, all aminoglycoside-resistant P. aeruginosa isolates carried mexY and phoP genes, although the expression levels of mexY and phoP were 75% and 87.5%, respectively.ConclusionGiven the considerably high prevalence of aminoglycoside-resistant P. aeruginosa strains, urgent measures are warranted to transition towards the use of novel aminoglycosides and to uphold vigilant surveillance of resistance patterns.

Inactivation of the ribosome assembly factor RimP causes streptomycin resistance and impairs motility in Salmonella.

The ribosome is the central hub for protein synthesis and the target of many antibiotics. Although the majority of ribosome-targeting antibiotics inhibit protein synthesis and are bacteriostatic, aminoglycosides promote protein mistranslation and are bactericidal. Understanding the resistance mechanisms of bacteria against aminoglycosides is not only vital for improving the efficacy of this critically important group of antibiotics but also crucial for studying the molecular basis of translational fidelity. In this work, we analyzed Salmonella mutants evolved in the presence of the aminoglycoside streptomycin (Str) and identified a novel gene rimP to be involved in Str resistance. RimP is a ribosome assembly factor critical for the maturation of the 30S small subunit that binds Str. Deficiency in RimP increases resistance against Str and facilitates the development of even higher resistance. Deleting rimP decreases mistranslation and cellular uptake of Str and further impairs flagellar motility. Our work thus highlights a previously unknown mechanism of aminoglycoside resistance via defective ribosome assembly.

Whole-genome sequencing and transcriptome-characterized mechanism of streptomycin resistance in Vibrio parahaemolyticus O10: K4

Streptomycin resistance in V. parahaemolyticus has been widespread in both clinical and environmental isolates. Therefore, it is of great significance to characterize the mechanism of streptomycin resistance in V. parahaemolyticus. O10:K4 has emerged and becoming the new dominant serotype since 2020. In this study, we isolated a total of 36 strains of V. parahaemolyticus O10:K4 from 2020 to 2022 and found that more than half of them were resistant to streptomycin. We obtained streptomycin resistant and sensitive strains by detecting the resistance profiles. Whole-genome sequencing showed that VP_RS10735 and VP_RS05605 were the predominant mutations in streptomycin resistant O10:K4 clinical isolates. In addition, this study provided global insight into the characteristics of the transcriptome signature of streptomycin resistance, revealing that efflux transporters play a key role in streptomycin resistance. Finally, we found that streptomycin resistant strain was more virulent than sensitive strain. The results of this study should advance our understanding of the mechanisms of aminoglycoside resistance.

Prevalence of Aminoglycoside Resistance Genes in Clinical Isolates of Pseudomonas aeruginosa from Taif, Saudi Arabia-An Emergence Indicative Study.

Hospital-acquired infections caused by P. aeruginosa contribute to global distress because of the elevated rates of microbial antibiotic resistance. Aminoglycosides are antipseudomonal agents that are effectively and frequently utilized to eradicate this infection. This current study is a retrospective study investigating plasmid-mediated aminoglycoside resistance by focusing on the prevalence of the genes encoding aminoglycoside-modifying enzymes (AMEs) and 16S rRNA methylase among P. aeruginosa clinical isolates from Taif, Saudi Arabia. A hundred clinical isolates of P. aeruginosa were collected. The isolates were identified from February 2021 to February 2022. Antibiotic susceptibility testing and MICs were determined using (DD) and (BM-MIC) testing, respectively. AMEs and 16S rRNA methylase variants in bacterial isolates were amplified via PCR for genetic detection. A relatively high multiple antibiotic resistance rate corresponding to 10-32% was reported. Eighteen percent of P. aeruginosa isolates were gentamicin-amikacin-tobramycin resistant according to the MIC levels. The aminoglycoside-resistant strains were additionally identified via GyrA gene sequencing. The phylogenic relatedness dendrogram of the sequenced GyrA genes was performed using a neighbor-joining method via MEGAX software version 10.2.6. The most prevalent AME encoding gene was aac(6')-Ib, observed in 94.4% of resistant isolates, while a resistance gene cocktail of [aac(6')-Ib and ant(3″)-I] was a highly frequent combination (27.8%). This study updated the knowledge about aminoglycoside resistance mechanisms in P. aeruginosa, which constitutes an urgent need, especially after the COVID-19 crisis, which was associated with increased antimicrobial use and resistance rates.

Identification and characterization of a novel chromosomal aminoglycoside 3'-O-phosphotransferase, APH(3')-Id, from Kluyvera intermedia DW18 isolated from the sewage of an animal farm.

Aminoglycosides, as important clinical antimicrobials, are used as second-line drugs for treating multidrug-resistant tuberculosis or combined with β-lactam drugs for treating severe infections such as sepsis. Aminoglycoside-modifying enzyme (AME) is the most important mechanism of aminoglycoside resistance and deserves more attention. The bacterium Kluyvera intermedia DW18 was isolated from the sewage of an animal farm using the conventional method. The agar dilution method was used to determine the minimum inhibitory concentrations (MICs) of antimicrobials. A novel resistance gene was cloned, and the enzyme was expressed. The kinetic parameters were measured by a SpectraMax M5 multifunctional microplate reader. Bioinformatic analysis was performed to reveal the genetic context of the aph(3')-Id gene and its phylogenetic relationship with other AMEs. A novel aminoglycoside 3'-O-phosphotransferase gene designated aph(3')-Id was identified in K. intermedia DW18 and shared the highest amino acid identity of 77.49% with the functionally characterized aminoglycoside 3'-O-phosphotransferase APH(3')-Ia. The recombinant plasmid carrying the novel resistance gene (pMD19-aph(3')-Id/E. coli DH5α) showed 1,024-, 512-, 128- and 16-fold increased MIC levels for kanamycin, ribostamycin, paromomycin and neomycin, respectively, compared with the reference strain DH5α. APH(3')-Id showed the highest catalytic efficiency for ribostamycin [kcat/Km of (4.96 ± 1.63) × 105 M-1/s-1], followed by paromomycin [kcat/Km of (2.18 ± 0.21) × 105 M-1/s-1], neomycin [kcat/Km of (1.73 ± 0.20) × 105 M-1/s-1], and kanamycin [kcat/Km of (1.10 ± 0.18) × 105 M-1/s-1]. Three conserved functional domains of the aminoglycoside phosphotransferase family and ten amino acid residues responsible for the phosphorylation of kanamycin were found in the amino acid sequence of APH(3')-Id. No mobile genetic element (MGE) was discovered surrounding the aph(3')-Id gene. In this work, a novel aminoglycoside 3'-O-phosphotransferase gene designated aph(3')-Id encoded in the chromosome of the environmental isolate Kluyvera intermedia DW18 was identified and characterized. These findings will help clinicians select effective antimicrobials to treat infections caused by pathogens with this kind of resistance gene.

Contribution of different mechanisms to aminoglycoside resistance in clinical isolates of Acinetobacter baumannii

The antibiotics overuse for infection treatment was the sparkle in the spreading of multi-drug resistance Acinetobacter baumannii in hospitals. In our study, we evaluated the contribution of the aminoglycoside resistance mechanisms of A. baumannii to the resistance surge in some selected Egyptian hospitals with a checkerboard assay application to retrieve the aminoglycoside activity. The resistance profile analysis of collected 200 A. baumannii isolates revealed a multidrug-resistant pattern with limited susceptibilities to aminoglycosides. Analysis of the prevalence of aminoglycoside-modifying enzyme (AMEs) genes revealed the presence of the six AMEs genes either singly or in combination in selected isolates and aph (3)-VIa gene was the predominant one. At the same time, four efflux pump genes of AdeABC and AdeKJL family showed significant (P < 0.001) up-regulation levels. Moreover, the implementation of combination strategy showed fourteen synergistic activities against two high-level aminoglycoside-resistance (HLAR) A. baumannii isolates. The findings highlighted the alarming levels of aminoglycoside resistance in A. baumannii isolates, which proved that a common enzymatic modification mechanism acts synergistically with decreased antibiotic accumulation in acquiring aminoglycoside resistance. Additionally, the study provides useful information for the promising synergistic combination therapy that reduces the therapeutic dose of aminoglycosides used and subsequently increases their clinical application.

30S subunit recognition and G1405 modification by the aminoglycoside-resistance 16S ribosomal RNA methyltransferase RmtC

Acquired ribosomal RNA (rRNA) methylation has emerged as a significant mechanism of aminoglycoside resistance in pathogenic bacterial infections. Modification of a single nucleotide in the ribosome decoding center by the aminoglycoside-resistance 16S rRNA (m7G1405) methyltransferases effectively blocks the action of all 4,6-deoxystreptamine ring-containing aminoglycosides, including the latest generation of drugs. To define the molecular basis of 30S subunit recognition and G1405 modification by these enzymes, we used a S-adenosyl-L-methionine analog to trap the complex in a postcatalytic state to enable determination of a global 3.0 Å cryo-electron microscopy structure of the m7G1405 methyltransferase RmtC bound to the mature Escherichia coli 30S ribosomal subunit. This structure, together with functional analyses of RmtC variants, identifies the RmtC N-terminal domain as critical for recognition and docking of the enzyme on a conserved 16S rRNA tertiary surface adjacent to G1405 in 16S rRNA helix 44 (h44). To access the G1405 N7 position for modification, a collection of residues across one surface of RmtC, including a loop that undergoes a disorder-to order transition upon 30S subunit binding, induces significant distortion of h44. This distortion flips G1405 into the enzyme active site where it is positioned for modification by two almost universally conserved RmtC residues. These studies expand our understanding of ribosome recognition by rRNA modification enzymes and present a more complete structural basis for future development of strategies to inhibit m7G1405 modification to resensitize bacterial pathogens to aminoglycosides.

Whole-genome sequencing and transcriptome-characterized in vitro evolution of aminoglycoside resistance in Mycobacterium tuberculosis.

Antibiotic resistance of Mycobacterium tuberculosis (Mtb) is a major public health concern worldwide. Therefore, it is of great significance to characterize the mutational pathways by which susceptible Mtb evolves into drug resistance. In this study, we used laboratory evolution to explore the mutational pathways of aminoglycoside resistance. The level of resistance in amikacin inducing Mtb was also associated with changes in susceptibility to other anti-tuberculosis drugs such as isoniazid, levofloxacin and capreomycin. Whole-genome sequencing (WGS) revealed that the induced resistant Mtb strains had accumulated diverse mutations. We found that rrs A1401G was the predominant mutation in aminoglycoside-resistant clinical Mtb isolates from Guangdong. In addition, this study provided global insight into the characteristics of the transcriptome in four representative induced strains and revealed that rrs mutated and unmutated aminoglycoside-resistant Mtb strains have different transcriptional profiles. WGS analysis and transcriptional profiling of Mtb strains during evolution revealed that Mtb strains harbouring rrs A1401G have an evolutionary advantage over other drug-resistant strains under the pressure of aminoglycosides because of their ultra-high resistance level and low physiological impact on the strain. The results of this study should advance our understanding of aminoglycoside resistance mechanisms.

High prevalence of ArmA-16S rRNA methyltransferase among aminoglycoside-resistant Klebsiella pneumoniae bloodstream isolates.

Introduction. Aminoglycosides are used for the treatment of carbapenemase-producing Klebsiella pneumoniae (CPK) infections. 16S rRNA methyltransferases (RMTs) confer resistance to all aminoglycosides and are often cocarried with NDM.Hypothesis/Gap Statement. There is a dart of studies looking at the aminoglycoside resistance mechanisms for invasive CPK isolates, particularly in OXA-48 endemic settings.Aim. We aimed to determine the prevalence of RMTs and their association with beta lactamases and MLSTs amongst aminoglycoside-resistant CPK bloodstream isolates in an OXA-48 endemic setting.Methodology. CPK isolates (n=181), collected as part of a multicentre cohort study, were tested for amikacin, gentamicin and tobramycin susceptibility using custom-made sensititre plates (GN2XF, Thermo Fisher Scientific). All isolates were previously subjected to whole-genome sequencing. Carbapenemases, RMTs, MLSTs and plasmid incompatibility groups were detected on the assembled genomes.Results. Of the 181 isolates, 109(60 %) were resistant to all three aminoglycosides, and 96 of 109(88 %) aminoglycoside-resistant isolates carried an RMT (85 ArmA, 10 RmtC, 4 RmtF1; three isolates cocarried ArmA and RmtC). Main clonal types associated with ArmA were ST2096 (49/85, 58 %) and ST14 (24/85, 28 %), harbouring mainly OXA-232 and OXA-48 +NDM, respectively. RmtC was cocarried with NDM (5/10) on ST395, and NDM +OXA-48 or NDM +KPC (4/10) on ST14, ST15 and ST16. All RMT producers also carried CTX-M-15, and the majority cocarried SHV-106, TEM-150 and multiple other antibiotic resistance genes. The majority of the isolates harboured a combination of IncFIB, IncH and IncL/M type plasmids. Non-NDM producing isolates remained susceptible to ceftazidime-avibactam.Conclusion. Aminoglycoside resistance amongst CPK bloodstream isolates is extremely common and mainly driven by clonal spread of ArmA carried on ST2096 and ST14, associated with OXA-232 and OXA48 +NDM carriage, respectively.

Using Targeted Liquid Chromatography-Tandem Mass Spectrometry to Rapidly Detect β-Lactam, Aminoglycoside, and Fluoroquinolone Resistance Mechanisms in Blood Cultures Growing E. coli or K. pneumoniae.

New and rapid antimicrobial susceptibility/resistance testing methods are required for bacteria from positive blood cultures. In this study, a multiplex-targeted liquid chromatography-tandem mass spectrometry (LC-MS/MS) assay was developed and validated for the detection of β-lactam, aminoglycoside, and fluoroquinolone resistance mechanisms in blood cultures growing Escherichia coli or Klebsiella pneumoniae complex. Selected targets were the β-lactamases SHV, TEM, OXA-1-like, CTX-M-1-like, CMY-2-like, chromosomal E. coli AmpC (cAmpC), OXA-48-like, NDM, VIM, and KPC; the aminoglycoside-modifying enzymes AAC(3)-Ia, AAC(3)-II, AAC(3)-IV, AAC(3)-VI, AAC(6′)-Ib, ANT(2)-I, and APH(3′)-VI; the 16S-RMTases ArmA, RmtB, RmtC, and RmtF; the quinolone resistance mechanisms QnrA, QnrB, AAC(6′)-Ib-cr; the wildtype quinolone resistance determining region of GyrA; and the E. coli porins OmpC and OmpF. The developed assay was evaluated using 100 prospectively collected positive blood cultures, and 148 negative blood culture samples spiked with isolates previously collected from blood cultures or isolates carrying less prevalent resistance mechanisms. The time to result was approximately 3 h. LC-MS/MS results were compared with whole-genome sequencing and antimicrobial susceptibility testing results. Overall, there was a high agreement between LC-MS/MS results and whole-genome sequencing results. In addition, the majority of susceptible and non-susceptible phenotypes were correctly predicted based on LC-MS/MS results. Exceptions were the predictions for ciprofloxacin and amoxicillin/clavulanic acid that matched with the phenotype in 85.9 and 63.7% of the isolates, respectively. Targeted LC-MS/MS based on parallel reaction monitoring can be applied for the rapid and accurate detection of various resistance mechanisms in blood cultures growing E. coli or K. pneumoniae complex.

Aminoglycoside Resistance and Possible Mechanisms in Campylobacter Spp. Isolated From Chicken and Swine in Jiangsu, China.

Campylobacter is a major food-borne pathogen in humans, and previous studies reported a high prevalence of gentamicin-resistant Campylobacter isolates from food-producing animals in China. This study aimed to investigate the aminoglycoside resistance of Campylobacter isolated from chicken and swine in Jiangsu province, China and understand the possible mechanisms responsible for aminoglycoside resistance. One hundred and eighty-five Campylobacter isolates of chicken and swine origins in 2017 and 2018 were analyzed for gentamicin and kanamycin resistance. Some aminoglycoside resistance genes were selected for PCR detection in all strains. The genomic DNAs of two strains with high resistance to gentamicin were used as donors to subject C. jejuni NCTC11168 to natural transformation. The transformants were investigated by whole-genome sequencing and analyzed comparatively with C. jejuni NCTC11168. In total, 30.5% (29/95) of C. jejuni isolates and 42.2% (38/90) of C. coli isolates were resistant to gentamicin and kanamycin. The prevalence of the aph(2")-If gene and aac(6')-Ie/aph(2")-Ia gene was 65.4% (121/185) and 36.2% (67/185) in Campylobacter isolates, respectively. The aadE-sat4-aphA-3 cluster was identified in 8.7% (8/92) and 20.4% (19/93) of all Campylobacter isolates in each year. With each donor DNA, aminoglycoside-resistant transformants were obtained. The transformants showed ≥128-fold increases in the MICs of gentamicin, kanamycin, and tobramycin. A 5200-bp segment was found to be inserted between the highly conserved genes Cj0299 and panB of Campylobacter. A total of 9.7% (18/185) strains showing high resistance to aminoglycosides had this segment by PCR detection. The genetic diversity of the insertion-fragment positive strains was determined by MLST, and seven sequence types were identified for these strains.

Activity of plazomicin against carbapenem-intermediate or -resistant Escherichia coli isolates from the United States and international sites in relation to clonal background, resistance genes, co-resistance, and region.

Emerging carbapenem resistance in Escherichia coli, including sequence type 131 (ST131), threatens therapeutic efficacy. Plazomicin (PLZ), a semisynthetic aminoglycoside approved by the FDA in 2018, overcomes the most common aminoglycoside resistance mechanisms and maintains activity against many carbapenem-intermediate or -resistant (CIR) E. coli strains. To assess plazomicin susceptibility among CIR E. coli in relation to region and multiple bacterial characteristics. We determined broth microdilution MICs for plazomicin and 11 comparators against 343 CIR clinical E. coli isolates, then compared susceptibility results by bacterial characteristics and region. The collection comprised 203 US isolates (2002-17) and 141 isolates from 17 countries in Europe, Latin America, and the Asia-West Pacific region (2003-17). Isolates were characterized for phylogenetic group, resistance-associated sequence types (STs) and subsets thereof, and relevant β-lactamase-encoding genes. Plazomicin exhibited the highest percentage susceptible (89%) after tigecycline (99%). The percentage susceptible to plazomicin varied significantly by phylogroup (63%, group B1; versus >93%, others) and ST131 subclone (92%, H30Rx; versus 87%-89%, H30R1 and non-H30), but not ST. It also varied by resistance genotype [higher with Klebsiella pneumoniae carbapenemase (KPC), lower with metallo-β-lactamases], global region [highest for Latin America (94%), lowest for Asia-West Pacific (69%)], and US region (80%, South, versus 96%-100%, others). Although reduced susceptibility to comparators often predicted reduced susceptibility to plazomicin, even among comparator-intermediate or -resistant isolates the plazomicin-susceptible fraction was ≥77%, except for amikacin (53%). The likely utility of plazomicin against CIR E. coli is high overall, but varies with region and multiple bacterial characteristics.

Healthcare-Associated Laboratory-Confirmed Bloodstream Infections-Species Diversity and Resistance Mechanisms, a Four-Year Retrospective Laboratory-Based Study in the South of Poland.

Introduction: Regardless of the country, advancements in medical care and infection prevention and control of bloodstream infections (BSIs) are an enormous burden of modern medicine. Objectives: The aim of our study was to describe the epidemiology and drug-resistance of laboratory-confirmed BSI (LC-BSIs) among adult patients of 16 hospitals in the south of Poland. Patients and methods: Data on 4218 LC-BSIs were collected between 2016–2019. The identification of the strains was performed using MALDI-TOF. Resistance mechanisms were investigated according to European Committee on Antimicrobial Susceptibility Testing, EUCAST recommendations. Results: Blood cultures were collected from 8899 patients, and LC-BSIs were confirmed in 47.4%. The prevalence of Gram-positive bacteria was 70.9%, Gram-negative 27.8% and yeast 1.4%. The most frequently isolated genus was Staphylococcus (50% of all LC-BSIs), with a domination of coagulase-negative staphylococci, while Escherichia coli (13.7%) was the most frequent Gram-negative bacterium. Over 4 years, 108 (2.6%) bacteria were isolated only once, including species from the human microbiota as well as environmental and zoonotic microorganisms. The highest methicillin resistant Staphylococcus aureus (MRSA) prevalence was in intensive care units (ICUs) (55.6%) but S. aureus with resistance to macrolides, lincosamides and streptogramins B (MLSB) in surgery was 66.7%. The highest prevalence of E. faecalis with a high-level aminoglycoside resistance (HLAR) mechanism was in ICUs, (84.6%), while E. faecium-HLAR in surgery was 83.3%. All cocci were fully glycopeptide-sensitive. Carbapenem-resistant Gram-negative bacilli were detected only in non-fermentative bacilli group, with prevalence 70% and more. Conclusions: The BSI microbiology in Polish hospitals was similar to those reported in other studies, but the prevalence of MRSA and enterococci-HLAR was higher than expected, as was the prevalence of carbapenem-resistant non-fermentative bacilli. Modern diagnostic techniques, such as MALDI-TOF, guarantee reliable diagnosis.

Novel antimicrobial drugs Omadacycline Sarecycline, Eravacycline, and plazomicin: A review

Resistance to antibiotics is a worldwide ongoing issue. Urgent want for brand new antibacterial agents has resulted in substantial studies efforts, with new molecules proposed for use in clinical practice. This review focuses on novel FDA approved antibacterial drugs (2018–2019): are new players in the area of resistant microorganism treatment. Omadacycline Sarecycline, Eravacycline, Plazomicin (2018–2019) are new healing options. This review focuses on novel FDA approved antibacterial agents (2018–2019): are new players in the field of resistant bacteria treatment. Omadacycline is a modernized tetracycline with broad-spectrum activity designed to overcome tetracycline resistance. Eravacycline is a synthetic fluorocycline antibiotic belonging to the tetracycline drug class. It disrupts bacterial protein synthesis by binding the 30S ribosomal subunit, Sarecycline is a new first-in-class tetracycline-derived antibiotic indicated for adults and children aged 9 years and older with non-nodular moderate-to-severe acne vulgaris, Plazomicin has been engineered to overcome aminoglycoside-modifying enzymes, the most common amino glycoside-resistance mechanism in Enterobacteriaceae. Despite of these new developments, there is an ongoing need and urgency to develop novel antibiotic strategies and drugs to overrun the bacterial resistance to antibiotics. Many potential signs are being investigated, broadened and confirmed by future studies. Despite recent progress, it is imperative that new antibiotic drugs and new strategies be developed to com bat antibiotic resistance.

1454. Plazomicin Activity against Enterobacterales Isolates Producing Extended-Spectrum β-Lactamases (ESBLs), Carbapenemases, and Aminoglycoside-Modifying Enzymes (AMEs) from United States (US) Hospitals

BackgroundLimited therapeutic options are available for the treatment of multidrug resistant (MDR) organisms. Plazomicin (PLZ) is an aminoglycoside developed to overcome common aminoglycoside-resistance mechanisms. We evaluated the activity of PLZ and comparators against Enterobacterales isolates collected in 2018-2019 carrying genes encoding ESBLs, carbapenemases, and AMEs.MethodsAmong 3,899 Enterobacterales isolates from US hospitals susceptibility (S) tested using reference broth microdilution method, 619 isolates from selected species displaying elevated MIC values for cephalosporins, carbapenems and/or resistance (CLSI criteria) to amikacin (AMK), gentamicin (GEN) and tobramycin (TOB) were submitted to whole genome sequencing for detection of resistance genes.ResultsMost isolates producing ESBLs (n= 418) carried blaCTX-M (n= 386). The activity of PLZ (99.3% susceptible [S]) was comparable to that of colistin and higher than other comparators against ESBL isolates (Figure). AMK inhibited 96.4% of the isolates and GEN and TOB inhibited 57.9% and 43.5%, respectively. Only 34 isolates produced carbapenemases, including 19 KPC-2, 10 KPC-3, 1 each with VIM-1, OXA-181, NDM-5 and KPC-2-like plus 1 isolate carrying the genes encoding NDM-1 and OXA-232. These isolates displayed higher resistance rates to comparators and only PLZ, and tigecycline inhibited >90% of these isolates. AMK and GEN inhibited 67.6% and 55.9% of these isolates, respectively. PLZ was active against 97.7% of isolates carrying AME genes (n= 306) that carried aac(6’)-Ib-cr (n =177), aac(3)-IIa (n = 159) and aac(3)-IId (n =81), among others. Most of these isolates were resistant to GEN and TOB (only 10.8-14.1% S), but 92.8% were S to AMK. Three K. pneumoniae isolates carried 16S rRNA methyltransferases, 1 armA (also harboring NDM-1) and 2 rmtB1.ConclusionThe activity of PLZ against Enterobacteriaceae isolates carrying AMEs, ESBLs, and carbapenemases was greater than the activity of other aminoglycosides tested and comparable to those of tigecycline and colistin against carbapenemase-producing organisms. Isolates carrying genes encoding ESBLs, AMEs and carbapenemases are usually MDR and PLZ had activity against these organisms collected in the US.Figure 1 DisclosuresMariana Castanheira, PhD, 1928 Diagnostics (Research Grant or Support)A. Menarini Industrie Farmaceutiche Riunite S.R.L. (Research Grant or Support)Allergan (Research Grant or Support)Allergan (Research Grant or Support)Amplyx Pharmaceuticals (Research Grant or Support)Cidara Therapeutics (Research Grant or Support)Cidara Therapeutics (Research Grant or Support)Cipla Ltd. (Research Grant or Support)Cipla Ltd. (Research Grant or Support)Fox Chase Chemical Diversity Center (Research Grant or Support)GlaxoSmithKline (Research Grant or Support)Melinta Therapeutics, Inc. (Research Grant or Support)Melinta Therapeutics, Inc. (Research Grant or Support)Melinta Therapeutics, Inc. (Research Grant or Support)Merck (Research Grant or Support)Merck (Research Grant or Support)Merck & Co, Inc. (Research Grant or Support)Merck & Co, Inc. (Research Grant or Support)Paratek Pharma, LLC (Research Grant or Support)Pfizer (Research Grant or Support)Qpex Biopharma (Research Grant or Support) Rodrigo E. Mendes, PhD, A. Menarini Industrie Farmaceutiche Riunite S.R.L. (Research Grant or Support)Allergan (Research Grant or Support)Allergan (Research Grant or Support)Basilea Pharmaceutica International, Ltd (Research Grant or Support)Cipla Ltd. (Research Grant or Support)Department of Health and Human Services (Research Grant or Support)GlaxoSmithKline (Research Grant or Support)Melinta Therapeutics, Inc. (Research Grant or Support)Merck (Research Grant or Support)Merck (Research Grant or Support)Pfizer (Research Grant or Support) Timothy B. Doyle, Allergan (Research Grant or Support)Allergan (Research Grant or Support)Cipla Ltd. (Research Grant or Support)Melinta Therapeutics, Inc. (Research Grant or Support)Pfizer (Research Grant or Support)Qpex Biopharma (Research Grant or Support) Valerie Kantro, n/a, Cipla Ltd. (Research Grant or Support) Helio S. Sader, MD, PhD, A. Menarini Industrie Farmaceutiche Riunite S.R.L. (Research Grant or Support)Allergan (Research Grant or Support)Allergan (Research Grant or Support)Allergan (Research Grant or Support)Cipla Ltd. (Research Grant or Support)Cipla Ltd. (Research Grant or Support)Melinta (Research Grant or Support)Merck (Research Grant or Support)Merck (Research Grant or Support)Paratek Pharma, LLC (Research Grant or Support)Pfizer (Research Grant or Support) Jaideep Gogtay, n/a, Cipla Ltd. (Employee) Sandhya Das, n/a, Cipla Ltd. (Research Grant or Support)

Expected Plazomicin Susceptibility in India Based on the Prevailing Aminoglycoside Resistance Mechanisms in Gram-Negative Organisms Derived from Whole-Genome Sequencing

AbstractBackground: Aminoglycoside resistance is a growing challenge, and it is commonly mediated by the aminoglycoside-modifying enzymes (AMEs), followed by 16S rRNA methyl transferase. Plazomicin, a novel aminoglycoside agent approved by the Food and Drug Administration for complicated urinary tract infections is proven to overcome resistance mediated by AMEs but not due to 16S rRNA methyl transferase (16SRMTases). We undertook this study to predict the efficacy of plazomicin in India based on the antimicrobial resistance profile derived from whole-genome sequencing (WGS). Methodology: A total of 386 clinical isolates of Escherichia coli, Klebsiella pneumoniae and Acinetobacter baumannii subjected to WGS were screened for aminoglycoside-resistance mechanisms such as AMEs and 16SRMTases and its association with carbapenemases. Results: AMEs was present in all E. coli, A. baumannii and in 90% of K. pneumoniae. In addition, up to 47% of E. coli and 38% of K. pneumoniae co-carried 16SRMTases with AMEs genes. However, A. baumannii showed 87% of isolates co-harbouring 16SRMTase. blaNDM, blaOxa-48-like and blaOxa-23-like were the most predominant carbapenemases in E. coli, K. pneumoniae and A. baumannii, respectively. Notably, 48% of NDM-producing E. coli and 35% of Oxa-48-like producing K. pneumoniae were identified to co-harbour AMEs + RMTAses, where plazomicin may not be useful. Conclusion: Overall, 53%, 62% and 14% of carbapenemase-producing E. coli, K. pneumoniae and A. baumannii harbours only AMEs, indicating the role of plazomicin use. Plazomicin can be used both for ESBLs as “carbapenem-sparing agent” and carbapenemase producers as “colistin-sparing agent.” For optimal use, it is essential to know the molecular epidemiology of resistance in a given geographical region where plazomicin empirical therapy is considered.

New Determinants of Aminoglycoside Resistance and Their Association with the Class 1 Integron Gene Cassettes in Trueperella pyogenes.

Trueperella pyogenes is an important opportunistic animal pathogen. Different antimicrobials, including aminoglycosides, are used to treat T. pyogenes infections. The aim of the present study was to evaluate aminoglycoside susceptibility and to detect aminoglycoside resistance determinants in 86 T. pyogenes isolates of different origin. Minimum inhibitory concentration of gentamicin, streptomycin, and kanamycin was determined using a standard broth microdilution method. Genetic elements associated with aminoglycoside resistance were investigated by PCR and DNA sequencing. All studied isolates were susceptible to gentamicin, but 32.6% and 11.6% of them were classified as resistant to streptomycin and kanamycin, respectively. A total of 30 (34.9%) isolates contained class 1 integrons. Class 1 integron gene cassettes carrying aminoglycoside resistance genes, aadA11 and aadA9, were found in seven and two isolates, respectively. Additionally, the aadA9 gene found in six isolates was not associated with mobile genetic elements. Moreover, other, not carried by gene cassettes, aminoglycoside resistance genes, strA-strB and aph(3’)-IIIa, were also detected. Most importantly, this is the first description of all reported genes in T. pyogenes. Nevertheless, the relevance of the resistance phenotype to genotype was not perfectly matched in 14 isolates. Therefore, further investigations are needed to fully explain aminoglycoside resistance mechanisms in T. pyogenes.

Dissemination of Plasmid-Mediated Aminoglycoside-Modifying Enzymes Among MDR Acinetobacter baumannii Isolates from a Tertiary Care Egyptian Hospital

Background: Acinetobacter baumannii is one of the most challenging multidrug-resistant (MDR) nosocomial pathogens worldwide. Aminoglycosides are used for the treatment of A. baumannii infections, however, resistance to aminoglycosides is currently emerging, limiting therapeutic choices. Objective: In this study, the prevalence of aminoglycoside resistance and plasmid-mediated mechanisms of aminoglycoside resistance were investigated in A. baumannii clinical isolates collected from ICU patients at a tertiary care hospital in Egypt. Methods: The automated Vitek 2 system was used to identify A. baumannii species and determination of the antimicrobial susceptibility pattern. The identification of A. baumannii was confirmed by the detection of the blaOXA-51-like gene intrinsic to this species. Minimum Inhibitory Concentration (MIC) of gentamicin was determined using E-test following the CLSI breakpoints. Isolates were screened for the prevalence and diversity of the plasmid-carried aminoglycoside-modifying enzymes encoding genes aacC1, aadA1, aadB and aphA6. For genetic diversity analysis, the ERIC-PCR method was performed. Results: All A. baumannii isolates were MDR with high resistance rates to tested antimicrobials. The resistance rate to gentamicin was 92.9% with elevated MICs (≥ 32 μg/mL). The gentamicin-resistant isolates harboured one or more of the studied genes with the prevalence of aphA6 (81%). ERIC-based genotyping revealed that there was no evidence of A. baumannii clonal dissemination among isolates. Conclusion: The study concluded that MDR A. baumannii isolates were highly resistant to gentamicin. The plasmid-carried aminoglycoside-modifying enzymes encoding genes were disseminated among isolates with the AphA6 gene, which was the most prevalent one. The acquisition of more than one aminoglycoside resistance gene was associated with an elevated MIC of gentamicin. Thus, regular surveillance studies of the emerging resistance to antimicrobials and strict measures to control the dissemination of resistance determinants genes are warranted.