Emergence of silent NDM-1 carbapenemase gene in carbapenem-susceptible Klebsiella pneumoniae: Clinical implications and epidemiological insights.

The global dissemination of carbapenemase genes, particularly blaNDM-1, poses a significant threat to public health. While research has mainly focused on strains with phenotypic resistance, the impact of silent resistance genes has been largely overlooked. This study documents the first instance of silent blaNDM-1 in a cluster of clonally related carbapenem-susceptible K. pneumoniae strains from a single patient. Despite initial effectiveness of carbapenem therapy, the patient experienced four recurrent lung infections over five months, indicating persistent K. pneumoniae infection. Genomic sequencing revealed all strains harbored blaNDM-1 on the epidemic IncX3 plasmid. A deletion within the upstream promoter region (PISAba125) of blaNDM-1 hindered its expression, resulting in phenotypic susceptibility to carbapenems. However, in vitro bactericidal assays and a mouse infection model showed that K. pneumoniae strains with silent blaNDM-1 exhibited significant tolerance to carbapenem-mediated killing. These findings demonstrate that silent blaNDM-1 can mediate both phenotypic susceptibility and antibiotic tolerance. In silico analysis of 1986 blaNDM sequences showed that 1956 (98.5%) retained the original promoter PISAba125. Given that previous genomic sequencing typically targets carbapenem-resistant strains, accurately assessing the prevalence of silent blaNDM remains challenging. This study highlights the hidden threat of silent resistance genes to clinical antimicrobial therapy and calls for enhanced clinical awareness and laboratory detection.

Relationship between virulence and carbapenem resistance phenotype of Klebsiella pneumoniae from blood infection: identification of a carbapenem-resistant and hypervirulent strain. / è¡€æ¶²æ„ŸæŸ“æ¥æºè‚ºç‚Žå ‹é›·ä¼¯èŒæ¯’åŠ›ä¸Žç¢³é’éœ‰çƒ¯ç±»è€è¯è¡¨åž‹çš„å ³ç³»åŠç¢³é’éœ‰çƒ¯ç±»è€è¯é«˜æ¯’åŠ›èŒæ ªçš„é‰´å®š.

OBJECTIVES: To investigate the relationship between the virulence and the carbapenem resistance phenotype of Klebsiella pneumoniae from blood infection, and to identify carbapenem-resistant and hypervirulent Klebsiella pneumoniae (CR-HVKP)strains. METHODS: A total of 192 Klebsiella pneumoniae strains were isolated from blood culture of patients with bloodstream infections from 2016 to 2019, of which 96 isolates were carbapenem-resistant Klebsiella pneumoniae (CRKP) and 96 were carbapenem-sensitive Klebsiella pneumoniae (CSKP). The drug susceptibility was detected by VITEK-2 automatic microbial analyzer; carbapenemase genes, virulence genes and capsule typing were detected by polymerase chain reaction; the high viscosity phenotype of strains was detected by string test, and the genome characteristics of CR-HVKP were detected by whole genome sequencing. Serum killing and biofilm formation test were used to further verify the virulence of CR-HVKP. RESULTS: There were significant differences in drug resistance to common antibiotics, except for minocycline between CSKP and CRKP isolates (all P<0.05). 92 out of 96 CRKP isolates carried carbapenemase genes, mainly blaKPC-2. The string tests were positive in 4 isolates of CRKP and 36 isolates of CSKP (P<0.05). The detection rates of virulence genes Kfu, aerobictin, iutA, ybtS, rmpA, magA, allS, and capsule antigen K1 and K2 in CSKP group were significantly higher than those in CRKP group (all P<0.05). One HVKP strain was detected in the CRKP group (CR-HVKP) and 36 HVKP was detected in the CSKP group (P<0.05). The CR-HVKP strain belonged to the MLST412, serotype K57, expressed iutA, entB, mrkD, fimH, and rmpA virulence genes, and showed strong biofilm formation and significantly increased serum resistance. Whole genome sequencing results showed that this CR-HVKP isolate carried blaSHV-145, blaTEM-1, blaCTX-M-3, fosA6, oqxA5, oqxB26, and aac(3)-IId resistance genes, accompanied by abnormalities in outer membrane protein K (OmpK) 35 and OmpK36. CONCLUSIONS: The drug resistance of CRKP is significantly higher than that of CSKP, while CRKP carrying fewer virulence genes in both number and types compared to CSKP. A new MLST type of carbapenem-resistant and hypervirulent Klebsiella pneumoniae strain has been detected, which requires clinical awareness and epidemiological monitoring.

Evolution of blaKPC Under the Pressure of Carbapenems and Ceftazidime/Avibactam in a Patient With Persistent Bacteremia Caused by Klebsiella pneumoniae.

A 30-year-old Korean man with myelodysplastic syndrome admitted hospital due to undifferentiated fever and recurrent skin lesions. He received combination therapy with high doses of meropenem, tigecycline and amikacin, yielding carbapenem resistant Klebsiella pneumoniae (CRKP) harboring K. pneumoniae carbapenemase (KPC)-2 from blood cultures on hospital day (HD) 23. Ceftazidime/avibactam was started at HD 37 and CRKP was eradicated from blood cultures after 5 days. However, ceftazidime/avibactam-resistant CRKP carrying KPC-44 emerged after 26 days of ceftazidime/avibactam treatment and then ceftazidime/avibactam-resistant, carbapenem-susceptible K. pneumoniae carrying KPC-135 was isolated on HD 65. The 3-D homology of KPC protein showed that hot spot changes in the omega loop could be attributed to ceftazidime/avibactam resistance and loss of carbapenem resistance. Whole genome sequencing of serial isolates supported that phenotypic variation was due to clonal evolution than clonal replacement. The treatment regimen was changed from CAZ/AVI to meropenem-based therapy (meropenem 1 g iv q 8 hours and amikacin 600 mg iv per day) starting with HD 72. CAZ/AVI-susceptible CRKP was presented again from blood cultures on HD 84, and the patient expired on HD 85. This is the first Korean report on the acquisition of ceftazidime/avibactam resistance through the emergence of blaKPC variants.

Evaluation of synergism effect of human glucose-dependent insulinotropic polypeptide (GIP) on Klebsiella pneumoniae carbapenemases (KPC) producer isolated from clinical samples.

Antibiotic resistance is increasing among Gram-negative bacteria, prompting the development of new antibiotics as well as alternative treatment approaches. Klebsiella pneumoniae Carbapenemases (KPC) has become a major concern in the treatment of infections, since KPC-producing bacteria are resistant to a number of ß -lactam and non ß-lactam antibiotics in addition to hydrolyzing carbapenemases. The aim of this study is to examine the synergistic effect of human Glucose-dependent Insulinotropic Polypeptide (GIP) on KPC producer. The K. pneumoniae isolates were identified by using biochemical tests and PCR genotyping. The disc diffusion method was used to assess the antimicrobial susceptibility of each isolate, and the modified Hodge test (MHT) was used to find carbapenemases. Agar well diffusion and minimum inhibitory concentration (MIC) assays were used to validate the synergistic effect of GIP against Klebsiella species. MIC values of chosen antimicrobial compounds demonstrated a considerable synergism impact when combined with human GIP, particularly against KPC strains. The antibacterial activity of the antimicrobial compounds was boosted by 4-16 times due to human GIP, reducing the MIC values. The fractional inhibitory concentration (FIC) ranged from 0.032 to 0.25 for examined antibiotics. Thus, GIP can be considered an antibacterial adjuvant with the potential to supplement the current antibiotic spectrum.

Homology of Escherichia coli isolated from urine and vagina and their antimicrobial susceptibility in postmenopausal women with recurrent cystitis.

Uropathogenic Escherichia coli (UPEC) is a typical cystitis-causing organism that can migrate from the vagina to the bladder and cause recurrent cystitis (RC). Few reports have compared the characteristics of urinary and vaginal UPEC in patients with RC. We carried out molecular biological analyses of Escherichia coli (E. coli) strains and their antimicrobial susceptibility to assess the association between urinary and vaginally UPEC. We included E. coli isolated from urinary and vaginal samples at the onset of cystitis in postmenopausal women with RC between 2014 and 2019 in our hospital. Pulsed-field gel electrophoresis (PFGE) was performed using a restriction enzyme (Xba I). These sequences were compared with 17 antimicrobial susceptibilities determined by a micro-liquid dilution method. Multilocus sequence typing (MLST) and classification of extended-spectrum ß-lactamase (ESBL) genotypes by multiplex polymerase chain reaction (PCR) were performed on ESBL-producing E. coli. We analyzed 14 specimens (each seven urine and vaginal) from seven patients in total. On PFGE, the similarity of urinary and vaginal E. coli per patient ranged from 89.5 to 100 %, including four patients with 100 % matches. MLST demonstrated that 29 % (4/14 specimens) were strain sequence type 131. Two specimens contained ESBL-producing strains and identified the CTX-M-27 genotype for each specimen. For each patient, antimicrobial susceptibilities between urinary and vaginal E. coli were mostly identical. Thus, urinary- and vaginally-derived E. coli were identical in postmenopausal women with RC. Management targeting both urinary and vaginal UPEC is essential for RC, indicating the importance of a vagina-targeted approach.

Structural investigation of the docking domain assembly from trans-AT polyketide synthases.

Docking domains (DDs) located at the C- and N-termini of polypeptides play a crucial role in directing the assembly of polyketide synthases (PKSs), which are multienzyme complexes. Here, we determined the crystal structure of a complex comprising the C-terminal DD (CDDMlnB) and N-terminal DD (NDDMlnC) of macrolactin trans-acyltransferase (AT) PKS that were fused to a functional enzyme, AmpC EC2 ß-lactamase. Interface analyses of the CDDMlnB/NDDMlnC complex revealed the molecular intricacies in the core section underpinning the precise DD assembly. Additionally, circular dichroism and steady-state kinetics demonstrated that the formation of the CDDMlnB/NDDMlnC complex had no influence on the structural and functional fidelity of the fusion partner, AmpC EC2. This inspired us to apply the CDDMlnB/NDDMlnC assembly to metabolon engineering. Indeed, DD assembly induced the formation of a complex between 4-coumarate-CoA ligase and chalcone synthase both involved in flavonoid biosynthesis, leading to a remarkable increase in naringenin production in vitro.

Characterizing carbapenemase-producing Escherichia coli isolates from Spain: high genetic heterogeneity and wide geographical spread.

Introduction: Carbapenemase-Producing Escherichia coli (CP-Eco) isolates, though less prevalent than other CP-Enterobacterales, have the capacity to rapidly disseminate antibiotic resistance genes (ARGs) and cause serious difficult-to-treat infections. The aim of this study is phenotypically and genotypically characterizing CP-Eco isolates collected from Spain to better understand their resistance mechanisms and population structure. Methods: Ninety representative isolates received from 2015 to 2020 from 25 provinces and 59 hospitals Spanish hospitals were included. Antibiotic susceptibility was determined according to EUCAST guidelines and whole-genome sequencing was performed. Antibiotic resistance and virulence-associated genes, phylogeny and population structure, and carbapenemase genes-carrying plasmids were analyzed. Results and discussion: The 90 CP-Eco isolates were highly polyclonal, where the most prevalent was ST131, detected in 14 (15.6%) of the isolates. The carbapenemase genes detected were bla OXA-48 (45.6%), bla VIM-1 (23.3%), bla NDM-1 (7.8%), bla KPC-3 (6.7%), and bla NDM-5 (6.7%). Forty (44.4%) were resistant to 6 or more antibiotic groups and the most active antibiotics were colistin (98.9%), plazomicin (92.2%) and cefiderocol (92.2%). Four of the seven cefiderocol-resistant isolates belonged to ST167 and six harbored bla NDM. Five of the plazomicin-resistant isolates harbored rmt. IncL plasmids were the most frequent (45.7%) and eight of these harbored bla VIM-1. bla OXA-48 was found in IncF plasmids in eight isolates. Metallo-ß-lactamases were more frequent in isolates with resistance to six or more antibiotic groups, with their genes often present on the same plasmid/integron. ST131 isolates were associated with sat and pap virulence genes. This study highlights the genetic versatility of CP-Eco and its potential to disseminate ARGs and cause community and nosocomial infections.

Emergence of carbapenem-resistant Pseudomonas aeruginosa ST179 producing both IMP-16 and KPC-2: a case study of introduction from Peru to Spain.

We describe four cases of a novel carbapenem-resistant Pseudomonas aeruginosa ST179 clone carrying the blaKPC-2 or blaKPC-35 gene together with blaIMP-16, imported from Peru to Spain and isolated from leukemia patients. All isolates were multidrug-resistant but remained susceptible to fosfomycin, cefiderocol, and colistin. Whole-genome sequencing revealed that blaKPC-2 and blaKPC-35 were located in an IncP6 plasmid, whereas blaIMP-16 was in a chromosomal type 1 integron. This study highlights the global threat of multidrug-resistant P. aeruginosa clones and underscores the importance of monitoring and early detection of emerging resistance mechanisms to guide appropriate treatment strategies. The importation and spread of such clones emphasize the urgent need to implement strict infection control measures to prevent the dissemination of carbapenem-resistant bacteria. IMPORTANCE: This is the first documented case of a Pseudomonas aeruginosa ST179 strain carrying the blaKPC-35 gene, and it represents the first report of a P. aeruginosa co-harboring blaIMP-16 and either blaKPC-2 or blaKPC-35, which wre imported from Peru to Spain, highlighting a threat due to the capacity of spreading carbapenem-resistance via plasmid conjugation.

Enhancing resistance, but not virulence attributed to the high mortality caused by carbapenem-resistant Klebsiella pneumoniae.

Carbapenem-resistant Klebsiella pneumoniae (CRKP) has emerged as a global threat due to its high mortality in clinical patients. However, the specific mechanisms underlying this increased mortality remain unclear. The objective of this study is to investigate how the development of a resistance phenotype contributes to the significantly higher mortality associated with this pathogen. To achieve this, a collection of isogeneic strains was generated. The clinical carbapenem-susceptible K. pneumoniae (CSKP) strain HKU3 served as the control isolate, while HKU3-KPC was created through conjugation with a blaKPC-2-bearing plasmid and served as clinical CRKP strain. Using a sepsis model, it was demonstrated that both HKU3 and HKU3-KPC exhibited similar levels of virulence. Flow cytometry, RNA-seq, and ELISA analysis were employed to assess immune cell response, M1 macrophage polarization, and cytokine storm induction, revealing that both strains elicited comparable types and levels of these immune responses. Subsequently, meropenem was utilized to treat K. pneumoniae infection, and it was found that meropenem effectively reduced bacterial load, inhibited M1 macrophage polarization, and suppressed serum cytokine production during HKU3 (CSKP) infection. However, these effects were not observed in the case of HKU3-KPC (CRKP) infection. These findings provide evidence that the high mortality associated with CRKP is attributed to its enhanced survival within the host during antibiotic treatment, resulting in a cytokine storm and subsequent host death. The development of an effective therapy for CRKP infections could significantly reduce the mortality caused by this pathogen.

Oxidized glutathione reverts carbapenem resistance in blaNDM-1-carrying Escherichia coli.

The emergence of drug-resistant Enterobacteriaceae carrying plasmid-mediated ß-lactamase genes has become a significant threat to public health. Organisms in the Enterobacteriaceae family containing New Delhi metallo-ß-lactamase­1 (NDM-1) and its variants, which are capable of hydrolyzing nearly all ß-lactam antibacterial agents, including carbapenems, are referred to as superbugs and distributed worldwide. Despite efforts over the past decade, the discovery of an NDM-1 inhibitor that can reach the clinic remains a challenge. Here, we identified oxidized glutathione (GSSG) as a metabolic biomarker for blaNDM-1 using a non-targeted metabolomics approach and demonstrated that GSSG supplementation could restore carbapenem susceptibility in Escherichia coli carrying blaNDM-1 in vitro and in vivo. We showed that exogenous GSSG promotes the bactericidal effects of carbapenems by interfering with intracellular redox homeostasis and inhibiting the expression of NDM-1 in drug-resistant E. coli. This study establishes a metabolomics-based strategy to potentiate metabolism-dependent antibiotic efficacy for the treatment of antibiotic-resistant bacteria.

Comparative analysis of the antimicrobial resistance and virulence traits in ESBL-producing-Klebsiella pneumoniae ST307 strains colonizing the gastrointestinal tract and causing a fatal bloodstream infection in a leukemia patient.

Klebsiella pneumoniae is an opportunistic pathogen that can colonize the gastrointestinal tract (GIT) of humans. The mechanisms underlying the successful translocation of this pathogen to cause extra-intestinal infections remain unknown, although virulence and antimicrobial resistance traits likely play significant roles in the establishment of infections. We investigated K. pneumoniae strains isolated from GIT colonization (strains Kp_FZcol-1, Kp_FZcol-2 and Kp_FZcro-1) and from a fatal bloodstream infection (strain Kp_HM-1) in a leukemia patient. All strains belonged to ST307, carried a transferable IncF plasmid containing the blaCTX-M-15 gene (pKPN3-307 TypeA-like plasmid) and showed a multidrug-resistance phenotype. Phylogenetic analysis demonstrated that Kp_HM-1 was more closely related to Kp_FZcro-1 than to the other colonizing strains. The Kp_FZcol-2 genome showed 81 % coverage with the Kp_HM-1 246,730 bp plasmid (pKp_HM-1), lacking most of its putative virulence genes. Searching public genomes with similar coverage, we observed the occurrence of this deletion in K. pneumoniae ST307 strains recovered from human colonization and infection in different countries. Our findings suggest that strains lacking the putative virulence genes found in the pKPN3-307 TypeA plasmid are still able to colonize and infect humans, highlighting the need to further investigate the role of these genes for the adaptation of K. pneumoniae ST307 in distinct human body sites.

Genomic characterization of extended-spectrum ß-lactamase-producing Enterobacterales isolated from abdominal surgical patients.

Rectal swabs of 104 patients who underwent abdominal surgery were screened for ESBL producers. Sequence types (STs) and resistance genes were identified by whole-genome sequencing of 46 isolates from 17 patients. All but seven isolates were assigned to recognized STs. While 18 ESBL-producing E. coli (EPEC) strains were of unique STs, ESBL-producing K. pneumoniae (EPKP) strains were mainly ST14 or ST15. Eight patients harboured strains of the same ST before and after abdominal surgery. The most prevalent resistant genes in E. coli were blaEC (69.57%), blaCTX-M (65.22%), and blaTEM (36.95%), while blaSHV was present in only K. pneumoniae (41.30%). Overall, genes encoding ß-lactamases of classes A (blaCTX-M, blaTEM, blaZ), C (blaSHV, blaMIR, and blaDHA), and D (blaOXA) were identified, the most prevalent variants being blaCTX-M-15, blaTEM-1B, blaSHV-28, and blaOXA-1. Interestingly, blaCMY-2, the most common pAmpC ß-lactamase genes reported worldwide, and mobile colistin resistance genes, mcr-10-1, were also identified. The presence of blaCMY-2 and mcr-10-1 is concerning as they may constitute a potentially high risk of pan-resistant post-surgical infections. It is imperative that healthcare professionals monitor intra-abdominal surgical site infections rigorously to prevent transmission of faecal ESBL carriage in high-risk patients.

A practical approach to screening for carbapenemase-producing Enterobacterales- views of a group of multidisciplinary experts from English hospitals.

INTRODUCTION: Carbapenemase-producing Enterobacterales (CPE) are an important public health threat, with costly operational and economic consequences for NHS Integrated Care Systems and NHS Trusts. UK Health Security Agency guidelines recommend that Trusts use locally developed risk assessments to accurately identify high-risk individuals for screening, and implement the most appropriate method of testing, but this presents many challenges. METHODS: A convenience sample of cross-specialty experts from across England met to discuss the barriers and practical solutions to implementing UK Health Security Agency framework into operational and clinical workflows. The group derived responses to six key questions that are frequently asked about screening for CPE. KEY FINDINGS: Four patient groups were identified for CPE screening: high-risk unplanned admissions, high-risk elective admissions, patients in high-risk units, and known positive contacts. Rapid molecular testing is a preferred screening method for some of these settings, offering faster turnaround times and more accurate results than culture-based testing. It is important to stimulate action now, as several lessons can be learnt from screening during the COVID-19 pandemic, as well as from CPE outbreaks. CONCLUSION: Further decisive and instructive information is needed to establish CPE screening protocols based on local epidemiology and risk factors. Local management should continually evaluate local epidemiology, analysing data and undertaking frequent prevalence studies to understand risks, and prepare resources- such as upscaled screening- to prevent increasing prevalence, clusters or outbreaks. Rapid molecular-based methods will be a crucial part of these considerations, as they can reduce unnecessary isolation and opportunity costs.

Cobalt complexes modulate plasmid conjugation in Escherichia coli and Klebsiella pneumoniae.

Antimicrobial resistance genes (ARG), such as extended-spectrum ß-lactamase (ESBL) and carbapenemase genes, are commonly carried on plasmids. Plasmids can transmit between bacteria, disseminate globally, and cause clinically important resistance. Therefore, targeting plasmids could reduce ARG prevalence, and restore the efficacy of existing antibiotics. Cobalt complexes possess diverse biological activities, including antimicrobial and anticancer properties. However, their effect on plasmid conjugation has not been explored yet. Here, we assessed the effect of four previously characterised bis(N-picolinamido)cobalt(II) complexes lacking antibacterial activity on plasmid conjugation in Escherichia coli and Klebsiella pneumoniae. Antimicrobial susceptibility testing of these cobalt complexes confirmed the lack of antibacterial activity in E. coli and K. pneumoniae. Liquid broth and solid agar conjugation assays were used to screen the activity of the complexes on four archetypical plasmids in E. coli J53. The cobalt complexes significantly reduced the conjugation of RP4, R6K, and R388 plasmids, but not pKM101, on solid agar in E. coli J53. Owing to their promising activity, the impact of cobalt complexes was tested on the conjugation of fluorescently tagged extended-spectrum ß-lactamase encoding pCTgfp plasmid in E. coli and carbapenemase encoding pKpQILgfp plasmid in K. pneumoniae, using flow cytometry. The complexes significantly reduced the conjugation of pKpQILgfp in K. pneumoniae but had no impact on pCTgfp conjugation in E. coli. The cobalt complexes did not have plasmid-curing activity, suggesting that they target conjugation rather than plasmid stability. To our knowledge, this is the first study to report reduced conjugation of clinically relevant plasmids with cobalt complexes. These cobalt complexes are not cytotoxic towards mammalian cells and are not antibacterial, therefore they could be optimised and employed as inhibitors of plasmid conjugation.

Clinical manifestations, antimicrobial resistance and genomic feature analysis of multidrug-resistant Elizabethkingia strains.

BACKGROUND: Elizabethkingia is emerging as an opportunistic pathogen in humans. The aim of this study was to investigate the clinical epidemiology, antimicrobial susceptibility, virulence factors, and genome features of Elizabethkingia spp. METHODS: Clinical data from 71 patients who were diagnosed with Elizabethkingia-induced pneumonia and bacteremia between August 2019 and September 2021 were analyzed. Whole-genome sequencing was performed on seven isolates, and the results were compared with a dataset of 83 available Elizabethkingia genomes. Genomic features, Kyoto Encyclopedia of Genes and Genomes (KEGG) results and clusters of orthologous groups (COGs) were analyzed. RESULTS: The mean age of the patients was 56.9 ± 20.7 years, and the in-hospital mortality rate was 29.6% (21/71). Elizabethkingia strains were obtained mainly from intensive care units (36.6%, 26/71) and emergency departments (32.4%, 23/71). The majority of the strains were isolated from respiratory tract specimens (85.9%, 61/71). All patients had a history of broad-spectrum antimicrobial exposure. Hospitalization for invasive mechanical ventilation or catheter insertion was found to be a risk factor for infection. The isolates displayed a high rate of resistance to cephalosporins and carbapenems, but all were susceptible to minocycline and colistin. Genomic analysis identified five ß-lactamase genes (blaGOB, blaBlaB, blaCME, blaOXA, and blaTEM) responsible for ß-lactam resistance and virulence genes involved in stress adaptation (ureB/G, katA/B, and clpP), adherence (groEL, tufA, and htpB) and immune modulation (gmd, tviB, cps4J, wbtIL, cap8E/D/G, and rfbC). Functional analysis of the COGs revealed that "metabolism" constituted the largest category within the core genome, while "information storage and processing" was predominant in both the accessory and unique genomes. The unique genes in our 7 strains were mostly enriched in KEGG pathways related to microRNAs in cancer, drug resistance (ß-lactam and vancomycin), ABC transporters, biological metabolism and biosynthesis, and nucleotide excision repair mechanisms. CONCLUSION: The Elizabethkingia genus exhibits multidrug resistance and carries carbapenemase genes. This study presents a comparative genomic analysis of Elizabethkingia, providing knowledge that facilitates a better understanding of this microorganism.

Emergence of eravacycline heteroresistance in carbapenem-resistant Acinetobacter baumannii isolates in China.

Carbapenem-resistant Acinetobacter baumannii (CRAB) is resistant to almost all antibiotics. Eravacycline, a newer treatment option, has the potential to treat CRAB infections, however, the mechanism by which CRAB isolates develop resistance to eravacycline has yet to be clarified. This study sought to investigate the features and mechanisms of eravacycline heteroresistance among CRAB clinical isolates. A total of 287 isolates were collected in China from 2020 to 2022. The minimum inhibitory concentration (MIC) of eravacycline and other clinically available agents against A. baumannii were determined using broth microdilution. The frequency of eravacycline heteroresistance was determined by population analysis profiling (PAP). Mutations and expression levels of resistance genes in heteroresistant isolates were determined by polymerase chain reaction (PCR) and quantitative real-time PCR (qRT-PCR), respectively. Antisense RNA silencing was used to validate the function of eravacycline heteroresistant candidate genes. Twenty-five eravacycline heteroresistant isolates (17.36%) were detected among 144 CRAB isolates with eravacycline MIC values ≤4 mg/L while no eravacycline heteroresistant strains were detected in carbapenem-susceptible A. baumannii (CSAB) isolates. All eravacycline heteroresistant strains contained OXA-23 carbapenemase and the predominant multilocus sequence typing (MLST) was ST208 (72%). Cross-resistance was observed between eravacycline, tigecycline, and levofloxacin in the resistant subpopulations. The addition of efflux pump inhibitors significantly reduced the eravacycline MIC in resistant subpopulations and weakened the formation of eravacycline heteroresistance in CRAB isolates. The expression levels of adeABC and adeRS were significantly higher in resistant subpopulations than in eravacycline heteroresistant parental strains (P < 0.05). An ISAba1 insertion in the adeS gene was identified in 40% (10/25) of the resistant subpopulations. Decreasing the expression of adeABC or adeRS by antisense RNA silencing significantly inhibited eravacycline heteroresistance. In conclusion, this study identified the emergence of eravacycline heteroresistance in CRAB isolates in China, which is associated with high expression of AdeABC and AdeRS.

High prevalence of plasmid-mediated quinolone resistance in escherichia coli strains producing extended-spectrum beta-lactamases isolated from faeces and urine of pregnant women with acute cystitis.

BACKGROUND: Escherichia coli is the most common etiological agent of urinary tract infections (UTIs). Meanwhile, plasmid-mediated quinolone resistance (PMQR) is reported in E. coli isolates producing extended-spectrum ß-lactamases (ESBLs). Furthermore, the reservoirs and mechanisms of acquisition of uropathogenic Escherichia coli (UPEC) strains are poorly understood. On the other hand, UTIs are common in pregnant women and the treatment challenge is alarming. METHODS AND RESULTS: In the present study, 54 pregnant women with acute cystitis were included. A total of 108 E. coli isolates, 54 isolates from UTI and 54 isolates from faeces of pregnant women (same host) were collected. In the antimicrobial susceptibility test, the highest rate of antibiotic resistance was to nalidixic acid (77%, 83/108) and the lowest rate was to imipenem (9%, 10/108). Among the isolates, 44% (48/108) were ESBLs producers. A high frequency of PMQR genes was observed in the isolates. The frequency of PMQR genes qnrS, qnrB, aac(6')-Ib-cr, and qnrA was 58% (63/108), 21% (23/108), 9% (10/108), and 4% (4/108), respectively. Meanwhile, PMQR genes were not detected in 24% (20/85) of isolates resistant to nalidixic acid and/or fluoroquinolone, indicating that other mechanisms, i.e. chromosomal mutations, are involved in resistance to quinolones, which were not detected in the present study. In ESBL-producing isolates, the frequency of PMQR genes was higher than that of non-ESBL-producing isolates (81% vs. 53%). Meanwhile, UTI and faeces isolates mainly belonged to phylogenetic group B2 (36/54, 67% and 25/54, 46%, respectively) compared to other phylogenetic groups. In addition, virulence factors and multidrug-resistant (MDR) were mainly associated with phylogenetic group B2. However, predominant clones in faeces were not found in UTIs. Rep-PCR revealed the presence of 85 clones in patients. Among the clones, 40 clones were detected only in faeces (faeces-only), 35 clones only in UTI (UTI-only) and 10 clones in both faeces and UTI (faeces-UTI). We found that out of 10 faeces-UTI clones, 5 clones were present in the host's faeces flora. CONCLUSION: This study revealed a high rate of resistance to the quinolone nalidixic acid and a widespread distribution of PMQR genes in MDR E. coli strains producing ESBLs. The strains represented virulence factors and phylogenetic group B2 are closely associated with abundance in UTI and faeces. However, the predominant clones in faeces were not found in UTIs and it is possible that rep-PCR is not sufficiently discriminating clones.

Sulbactam-durlobactam: a ß-lactam/ß-lactamase inhibitor combination targeting Acinetobacter baumannii.

Sulbactam-durlobactam is a pathogen-targeted ß-lactam/ß-lactamase inhibitor combination that has been approved by the US FDA for the treatment of hospital-acquired and ventilator-associated bacterial pneumonia caused by susceptible isolates of Acinetobacter baumannii-calcoaceticus complex (ABC) in patients 18 years of age and older. Sulbactam is a penicillin derivative with antibacterial activity against Acinetobacter but is prone to hydrolysis by ß-lactamases encoded by contemporary isolates. Durlobactam is a diazabicyclooctane ß-lactamase inhibitor with activity against Ambler classes A, C and D serine ß-lactamases that restores sulbactam activity both in vitro and in vivo against multidrug-resistant ABC. Sulbactam-durlobactam is a promising alternative therapy for the treatment of serious Acinetobacter infections, which can have high rates of mortality.

Sulbactam­durlobactam: a drug for treating lung infectionsAcinetobacter is a type of bacteria. One type, called CRAB, causes serious infections and can be fatal. CRAB is very hard to treat because most drugs no longer work. Sulbactam­durlobactam (SUL-DUR) is a drug that can kill CRAB. The US FDA approved SUL-DUR in May of 2023 for treating lung infections (pneumonia) caused by CRAB. This article explains how SUL-DUR works. Use of SUL-DUR and other drugs to treat these types of infections are discussed. In conclusion, SUL-DUR is a promising therapy for serious infections caused by CRAB.

Characteristics of non-carbapenemase producing carbapenem-resistant Klebsiella pneumoniae from a tertiary hospital in China.

INTRODUCTION: The spread of carbapenem-resistant Klebsiella pneumoniae (CRKP) is a substantial severe global public health burden. Non-carbapenemase-producing CRKP (non-CP-CRKP) is increasingly recognized as the source of severe infections. METHODOLOGY: We analyzed the genotypic, and phenotypic profiles of non-CP-CRKP strains with the whole-genome sequences isolated between 2017 and 2019 and the clinical characterization of non-CP-CRKP infection. RESULTS: A total of 91 CRKP strains were collected, of which 5 (5.49%) strains were non-CP-CRKP. Four strains were from male patients; three strains were isolated from the bile of patients who underwent biliary interventional surgery and four had a history of antibiotic exposure. Three strains were sequence type (ST)11, one was ST1, and one was ST5523. The non-CP-CRKP strains were insusceptible to ertapenem. Three strains were susceptible to amikacin. All the strains were susceptible to imipenem, meropenem, tigecycline, ceftazidime/avibatam and polymyxin B. The ß-lactamases of non-CP-CRKP predominantly included blaCTX-M, blaSHV, and blaTEM subtypes. Two site mutations in ompK36 (p.A217S and p.N218H) and four in ompK37 (p.I70M, p.I128M, p.N230G, and m233_None234insQ) were detected accounting for carbapenem resistance. Plasmids IncFI and IncFII were found in most strains. Genes encoding aerobactin, yersiniabactin and allantoin utilization were not detected in several isolates, and all non-CP-CRKP strains did not carry rmpA gene. CONCLUSIONS: Non-CP-CRKP infected patients had a history of previous antibiotic exposure or invasive procedures. Non-CP-CRKP strains were insusceptible to ertapenem. The mechanism of resistance includes ß-lactamases production and the site mutations in ompK36 and ompK37. Several virulence genes were not detected in non-CP-CRKP.