Incidence, characteristics, and risk factors of hypofibrinogenemia induced by generic tigecycline: a retrospective study.

The objective of this study was to evaluate the incidence, clinical features, and risk factors of generic tigecycline-associated hypofibrinogenemia. A single-center retrospective study was conducted in adult patients treated with generic tigecycline. Clinical data were extracted from the electronic medical records. The endpoint was tigecycline-related hypofibrinogenemia, defined as a condition with no abnormality in fibrinogen before tigecycline application, but developing hypofibrinogenemia upon prescription. The risk factors were determined by logistic regression analysis, and the ROC curve was subsequently established. A total of 240 adults prescribed generic tigecycline from May 1st to November 30th 2023 were included. It was shown that hypofibrinogenemia is a frequent side effect of generic tigecycline, with an adverse reaction rate of 42.9% (103/240). However, the incidence of adverse reactions to generic drugs was lower than in previous studies. The cumulative dose of tigecycline (OR:1.002, 95%CI 1.001-1.002, P < 0.001), baseline FIB (OR:0.995, 95%CI 0.992-0.997, P < 0.001), baseline PT (OR:1.247, 95%CI 1.071-1.452, P = 0.004) and baseline ALB (OR:0.931, 95%CI 0.879-0.986, P = 0.025) were identified as independent prognostic factors of tigecycline-related hypofibrinogenemia. We recommend intensive monitoring of coagulation function in patients exhibiting the aforementioned risk factors for generic tigecycline-associated hypofibrinogenemia to ensure patients safety.

Global genomic epidemiology and transmission dynamics of plasmid-borne tmexCD-toprJ-carrying Klebsiella pneumoniae in a one health context.

The emergence of tmexCD-toprJ, a novel plasmid-mediated resistance-nodulation-division (RND) type efflux pump gene cluster, poses a significant threat to public health by diminishing bacterial susceptibility to the last-resort antibiotics, including tigecycline. Between 2020 and 2022, 18 Klebsiella pneumoniae strains carrying the tmexCD-toprJ gene were recovered from over 30,000 human stool samples collected from patients across five hospitals in China. Phylogenetic analysis of these 18 strains revealed clonal transmission of tmexCD-toprJ-carrying K. pneumoniae among patients and hospital settings. Comparative analysis of the 18 tmexCD-toprJ-carrying plasmids showed conservation in the genetic backgrounds of tmexCD-toprJ, despite the diverse backbone structures among the plasmids. The inactive suppressor, TNfxB1, is located in front of all tmexCD1-toprJ1, while TNfxB3 is located upstream of tmexCD3-toprJ3. Conjugation experiments demonstrated the transferability of plasmids from three strains to the recipient Escherichia coli J53. Among all 237 globally distributed tmexCD-toprJ-carrying strains, the majority (92.83 %) were from China. These strains encompassed 50 sequence types, with the most prevalent being ST11 (12.66 %), ST37 (11.81 %), and ST15 (11.39 %). Samples originated from various sources: 47.26 % from human, 38.82 % from livestock, and 13.08 % from the environment. The most common tmexCD-toprJ genotype was tmexCD1-toprJ1 (86.92 %, n = 206), followed by tmexCD2-toprJ2 (8.86 %, n = 21) and tmexCD3-toprJ3 (4.22 %, n = 10). The tmexCD1-toprJ1 gene was found in livestock (44.66 %, n = 92), humans (39.81 %, n = 82), and environmental samples (15.05 %, n = 31). In contrast, tmexCD2-toprJ2 and tmexCD3-toprJ3 were only found in human samples. Additionally, tmexCD-toprJ has been detected in 79 strains of K. pneumoniae harboring carbapenem-resistance genes. Given the presence of tmexCD-toprJ across various hosts and environments, establishing a comprehensive surveillance system from a One Health perspective is particularly vital.

Clinical outcomes and safety of polymyxin B versus tigecycline combination therapy for pneumonia of carbapenem-resistant Klebsiella pneumoniae: a retrospective cohort study.

PURPOSE: Infection by carbapenem-resistant Klebsiella pneumoniae (CRKP) has high mortality. There is no clear optimal therapeutic choice for pneumonia caused by CRKP. The aim of this study was to compare the clinical outcomes and safety of the standard doses of polymyxin B-based regimens vs tigecycline-based regimens and to identify risk factors for mortality. METHODS: This retrospective cohort study included patients with pneumonia caused by CRKP between January 1, 2020 and December 31, 2022. The primary outcomes were 7-day bacterial eradication rate and 14- and 28-day all-cause mortality. The secondary outcome was incidence of acute kidney injury. RESULTS: Seventy-three patients were included in this study, 29 in the polymyxin B-based combination therapy group and 44 in tigecycline-based combination therapy group. There were no significant differences between the two groups in terms of the 7-day bacterial eradication rate (31.03% vs 20.45%, p = 0.409), the 14-day all-cause mortality (37.93% vs 22.73%, p = 0.160), and the incidence of acute kidney injury (14.29% vs 6.82%, p = 0.526). The 28-day all-cause mortality in the polymyxin B-based therapy group was higher than in the tigecycline-based group (75.86% vs 45.45%, p = 0.010). Binary logistic regression analysis revealed that male and previous use of carbapenems were independent factors associated with 28-day all-cause mortality for patients treated with polymyxin B (p < 0.05). CONCLUSIONS: Polymyxin B-based combination therapy at the standard dose should be used with caution for patients with CRKP-induced pneumonia, especially for men who used carbapenems prior to CRKP detection.

Identification of novel Tet(X6)-Tet(X2) recombinant variant in Elizabethkingia meningoseptica from a bullfrog farm and downstream river in China.

Introduction: The dissemination of strains producing tetracyclines monooxygenase Tet(X) from breeding farms to the natural environment poses a potential threat to public health. Methods: Antimicrobial susceptibility testing and WGS were performed to identify resistance phenotypes and genotypes. Cloning experiments, sequence alignment, and homology modeling were used to characterize the function and formation mechanisms of the recombinant variant. The mobilization potential of Tet(X) was assessed by collinearity analysis, conjugation experiments, and phylogenetic analysis. Results: Three tet(X)-producing Elizabethkingia meningoseptica strains were isolated from bullfrog breeding ponds, the sewage outlet, and downstream river in Zhejiang Province, China. These strains carry a novel Tet(X) variant, differing from Tet(X6) by seven residues, and possess the ability to degrade tetracyclines. Interestingly, the novel Tet(X) is a recombinant variant formed by homologous recombination of Tet(X6) and the C-terminal of Tet(X2). Further analysis revealed that Tet(X6) formed several Tet(X) variants, including Tet(X5), through homologous recombination. The novel tet(X) gene is located on a circularizable integrative and conjugative element (ICEEmeChn3), with ISwz1 participating in the recombination of its multi-drug resistance region, potentially facilitating the mobilization and recombination of tet(X) in early hosts. These three strains were clonally transmitted and shared a close genetic relationship (SNP < 62) with a clinically-sourced strain isolated from the same province. Discussion: To our knowledge, this is the first report of homologous recombination between Tet(X) variants with differing activities. These clonal strains provide evidence of the transmission of tet(X)-positive strains from aquaculture sewage to the natural environment, highlighting the need to strengthen the monitoring and management of this emerging farming model.

Coexistence of plasmid-mediated tmexCD2-toprJ2, blaIMP-4, and blaNDM-1 in Klebsiella quasipneumoniae.

Klebsiella quasipneumoniae is a potential pathogen that has not been studied comprehensively. The emergence of multidrug-resistant (MDR) K. quasipneumoniae, specifically strains resistant to tigecycline and carbapenem, presents a significant challenge to clinical treatment. This investigation aimed to characterize MDR K. quasipneumoniae strain FK8966, co-carrying tmexCD2-toprJ2, blaIMP-4, and blaNDM-1 by plasmids. It was observed that FK8966's MDR was primarily because of the IncHI1B-like plasmid co-carrying tmexCD2-toprJ2 and blaIMP-4, and an IncFIB(K)/IncFII(K) plasmid harboring blaNDM-1. Furthermore, the phylogenetic analysis revealed that IncHI1B-like plasmids carrying tmexCD2-toprJ2 were disseminated among different bacteria, specifically in China. Additionally, according to the comparative genomic analysis, the MDR regions indicated that the tmexCD2-toprJ2 gene cluster was inserted into the umuC gene, while blaIMP-4 was present in transposon TnAs3 linked to the class 1 integron (IntI1). It was also observed that an ΔTn3000 insertion with blaNDM-1 made a novel blaNDM-1 harboring IncFIB(K)/IncFII(K) plasmid. The antimicrobial resistance prevalence and phylogenetic analyses of K. quasipneumoniae strains indicated that FK8966 is a distinct MDR branch of K. quasipneumoniae. Furthermore, CRISPR-Cas system analysis showed that many K. quasipneumoniae CRISPR-Cas systems lacked spacers matching the two aforementioned novel resistance plasmids, suggesting that these resistance plasmids have the potential to disseminate within K. quasipneumoniae. Therefore, the spread of MDR K. quasipneumoniae and plasmids warrants further attention.IMPORTANCEThe emergence of multidrug-resistant K. quasipneumoniae poses a great threat to clinical care, and the situation is exacerbated by the dissemination of tigecycline- and carbapenem-resistant genes. Therefore, monitoring these pathogens and their resistance plasmids is urgent and crucial. This study identified tigecycline- and carbapenem-resistant K. quasipneumoniae strain, FK8966. Furthermore, it is the first study to report the coexistence of tmexCD2-toprJ2, blaIMP-4, and blaNDM-1 in K. quasipneumoniae. Moreover, the CRISPR-Cas system of many K. quasipneumoniae lacks spacers that match the plasmids carried by FK8966, which are crucial for mediating resistance against tigecycline and carbapenems, indicating their potential to disseminate within K. quasipneumoniae.

Proteomic analysis of carbapenem-resistant Klebsiella pneumoniae outer membrane vesicles under the action of phages combined with tigecycline.

BACKGROUND: Klebsiella pneumoniae is the most commonly encountered pathogen in clinical practice. Widespread use of broad-spectrum antibiotics has led to the current global dissemination of carbapenem-resistant K. pneumoniae, which poses a significant threat to antibacterial treatment efficacy and public health. Outer membrane vesicles (OMVs) have been identified as carriers capable of facilitating the transfer of virulence and resistance genes. However, the role of OMVs in carbapenem-resistant K. pneumoniae under external pressures such as antibiotic and phage treatments remains unclear. METHODS: To isolate and purify OMVs under the pressure of phages and tigecycline, we subjected K. pneumoniae 0692 harboring plasmid-mediated blaNDM-1 and blaKPC-2 genes to density gradient separation. The double-layer plate method was used to isolate MJ1, which efficiently lysed K. pneumoniae 0692 cells. Transmission electron microscopy (TEM) was used to characterize the isolated phages and extract OMV groups for relevant morphological identification. Determination of protein content of each OMV group was conducted through bicinchoninic acid assay (BCA) and proteomic analysis. RESULTS: K. pneumoniae 0692 released OMVs in response to different environmental stimuli, which were characterized through TEM as having the typical structure and particle size of OMVs. Phage or tigecycline treatment alone resulted in a slight increase in the mean protein concentration of OMVs secreted by K. pneumoniae 0692 compared to that in the untreated group. However, when phage treatment was combined with tigecycline, there was a significant reduction in the average protein concentration of OMVs compared to tigecycline treatment alone. Proteomics showed that OMVs encapsulated numerous functional proteins and that under different external stresses of phages and tigecycline, the proteins carried by K. pneumoniae 0692-derived OMVs were significantly upregulated or downregulated compared with those in the untreated group. CONCLUSIONS: This study confirmed the ability of OMVs to carry abundant proteins and highlighted the important role of OMV-associated proteins in bacterial responses to phages and tigecycline, representing an important advancement in microbial resistance research.

Tigecycline-Based Regimens for Complicated Urinary Tract Infections Caused by Carbapenem-Resistant Gram-Negative Bacteria: Case Series.

There is existing controversy regarding the efficacy of tigecycline (TG) in treating complicated urinary tract infections (cUTIs) because of its pharmacokinetic concerns. We present three patients with cUTIs caused by carbapenem-resistant gram-negative (GN) pathogens successfully treated with high-dose tigecycline (HDT)-based regimens, as cefiderocol and aztreonam were not available in our country. The first case describes a 67-year-old patient with diabetes, prostate cancer, and double J ureteral stenting who was hospitalized with a febrile, complicated urinary tract infection (cUTI). Urine and blood cultures were positive for metallo-beta-lactamases (MBL)-producing extensively drug-resistant (XDR) Klebsiella pneumoniae (cefiderocol-susceptible). The synergy between TG and colistin using the in vitro E-test was demonstrated, and the patient was started on this regimen using HDT. Clinical and microbiological cures were achieved, and the patient was discharged home. The second case presents a 70-year-old patient with urethral pathology who was hospitalized with the diagnosis of a lower cUTI caused by an MBL-producing pan-drug-resistant (PDR) Klebsiella pneumoniae. The in vitro E-test showed synergy between TG and colistin, and our patient was successfully treated with this HDT-based combination. The third case emphasizes a 63-year-old patient with insulin-dependent diabetes, Child B cirrhosis, and a right double J ureteral stent who was hospitalized with a febrile cUTI. Urine and blood cultures were positive for carbapenem-resistant XDR Acinetobacter baumannii (susceptible to colistin and TG). Colistin was administered for only 96 hours because of stage II acute kidney injury, and we continued the treatment with HDT in monotherapy. The patient was discharged home, and no urinary tract infection relapse was seen for six months. Favorable clinical and microbiological outcomes were achieved with TG-based regimens in our cUTI cases. We highlight the role of antibiotic synergy determined by the in vitro E-test in two cases of MBL-producing XDR/PDR Klebsiella pneumoniae.

Correlation of RND efflux pump expression and AdeRS mutations in tigecycline-resistant Acinetobacter baumannii from Thai clinical isolates.

Tigecycline-resistant Acinetobacter baumannii (TRAB) is increasing in Thailand, complicating antibiotic treatment due to limited antibiotic options. The specific resistance mechanism behind tigecycline resistance is still unclear, necessitating further investigation. We investigated the presence of OXA-type carbapenemases, the antimicrobial susceptibility profile, the inhibitory effect of carbonyl cyanide m-chlorophenylhydrazone (CCCP) on tigecycline susceptibility, the expression levels of RND-type efflux pumps and amino acid substitutions within a two-component regulatory system on 30 Thai clinical isolates. Our investigation revealed that most of (73.3%) TRAB isolates expressed at least one member of the Ade efflux pumps. The adeB was most frequently expressed (63.3%), followed by adeR (50%), adeS (43.3%), adeJ (30%) and adeG (10%). Overexpression of the AdeABC was associated with increased tigecycline minimum inhibitory concentrations (MICs) and amino acid substitutions within the AdeRS. Notably, isolates harbouring simultaneous mutations in these genes exhibited an increase in the transcription level of the adeB. Our findings highlight the significant role of the AdeABC system in tigecycline resistance among Thai clinical TRAB isolates. This is supported by point mutations within the AdeRS and upregulated expression of the adeB. These results provide valuable insights for understanding resistance mechanisms and developing novel therapeutic strategies.

Small RNA-regulated expression of efflux pump affects tigecycline resistance and heteroresistance in clinical isolates of Klebsiella pneumoniae.

Tigecycline and the newly Food and Drug Administration-approved tetracyclines, including eravacycline and omadacycline, are regarded as last-resort treatments for multidrug-resistant Enterobacterales. However, tigecycline resistance in Klebsiella pneumoniae has increased, especially the underlying mechanism of heteroresistance is unclear. This study aimed to elucidate the mechanisms underlying tigecycline resistance and heteroresistance in clinical K. pneumoniae isolates. A total of 153 clinical K. pneumoniae isolates were collected, and identified 15 tigecycline-resistant and three tigecycline-heteroresistant isolates using broth microdilution and population analysis profile methods, respectively. Total RNAs from K. pneumoniae ATCC13883 and the laboratory-induced tigecycline-resistant strain were extracted and sequenced on an Illumina platform. Differentially expressed genes and regulatory small RNAs (sRNAs) were analyzed and validated in clinical isolates of K. pneumoniae using quantitative real-time PCR. RNA sequencing results showed that mdtABC efflux pump genes were significantly upregulated in the tigecycline-resistant strains. Overexpression of mdtABC was observed in a clinical K. pneumoniae isolate, which increased tigecycline minimum inhibitory concentrations (MICs) and was involved in tigecycline heteroresistance. Sequencing analysis of sRNA demonstrated that candidate sRNA-120 directly interacted with the mdtABC operon and was downregulated in tigecycline-resistant strains. We generated an sRNA-120 deletion mutation strain and a complemented strain of K. pneumoniae. The sRNA-120 deletion strain displayed increased mRNA levels of mdtA, mdtB, and mdtC and an increase in MICs of tigecycline. The complemented strain of sRNA-120 restored the mRNA levels of these genes and the susceptibility to tigecycline. RNA antisense purification and parallel reaction monitoring mass spectrometry were performed to verify the interactions between sRNA-120 and mdtABC. Collectively, our study highlights that the post-transcriptional repression of mdtABC through sRNA-120 may provide an additional layer of efflux pump gene expression control, which is important for resistance and heteroresistance in clinical K. pneumoniae isolates.

In vitro antimicrobial activity of doxycycline, minocycline, and tigecycline against Mycobacterium abscessus complex: A meta-analysis study.

PURPOSE: Mycobacterium abscessus complex (MABC) infections are increasing worldwide. Furthermore, these infections have a low treatment success rate due to their resistance to many current antibiotics. This study aimed to determine the overall in vitro activity of the tetracyclines doxycycline (DOX), minocycline (MIN), and tigecycline (TGC) against MABC clinical isolates. PATIENTS AND METHODS: A systematic review of PubMed/MEDLINE, Web of Science, and Embase was conducted up to August 28, 2023. Studies applying the drug susceptibility testing standards of the Clinical and Laboratory Standards Institute were considered. A random effects model was used to assess the total in vitro resistance rates of the MABC clinical isolates to DOX, MIN, and TGC. The I2 and Cochran's Q statistics were employed to evaluate the origins of heterogeneity. All analyses were conducted using CMA V.3 software. RESULTS: Twenty-six publications (22, 12, and 11 studies on DOX, MIN, and TGC, respectively) were included. The pooled in vitro resistance rates of the MABC clinical isolates to DOX and MIN at the breakpoint of 8 µg/mL were 93.0 % (95 % CI, 89.2 %-95.5 %) and 87.2 % (95 % CI, 76.5 %-93.4 %), respectively. In the case of TGC, the breakpoints of 2, 4, and 8 µg/mL were associated with pooled resistance rates of 2.5 % (95 % CI, 0.5 %-11.6 %), 7.2 % (95 % CI, 4.0 %-12.5 %), and 16.8 % (95 % CI, 4.7 %-45.0 %), respectively. CONCLUSION: Among the three examined tetracyclines, MABC exhibited extremely high resistance rates to DOX and MIN, thereby limiting their use in treating MABC infections. Conversely, MABC showed an increased susceptibility rate to TGC, highlighting TGC administration as a viable treatment option for patients with MABC infections.

Genomic characterization revealing the high rate of tet(X4)-positive Escherichia coli in animals associated with successful genetic elements.

Introduction: The rapid spread of plasmid-mediated tet(X4) conferring high tigecycline resistance poses a significant threat to public health. Escherichia coli as the most common pathogen which carries tet(X4) has been widely disseminated in China. Thus, comprehensive investigations are required to understand the mechanism of transmission of tet(X4)-positive E. coli. Methods: In this study, a total of 775 nonduplicate samples were collected in Guangdong, China from 2019 to 2020. We screened for tet(X4)-positive E. coli by PCR amplification and species identification. Furthermore, we analyzed the phylogenetics and genetic context of tet(X4)-positive E. coli through whole-genome sequencing and long-reads sequencing. Results: Overall, 146 (18.84%) tet(X4)-positive E. coli were isolated, comprising 2 isolates from humans and 144 isolates from pigs. The majority of tet(X4)-positive E. coli exhibited resistance to multiple antibiotics but all of them were susceptible to amikacin and colistin. Phylogenetic analysis showed that ST877, ST871, and ST195 emerged as the predominant sequence types in tet(X4)-positive E. coli. Further analysis revealed various genetic environments associated with the horizontal transfer of tet(X4). Notably, a 100-kbp large fragment insertion was discovered downstream of tet(X4), containing a replicon and a 40-kbp gene cluster for the bacterial type IV secretion system. Discussion: The high colonization rate of tet(X4)-positive E. coli in animals suggests that colonization as a key factor in its dissemination to humans. Diverse genetic context may contribute to the transfer of tet(X4). Our findings underline the urgent need for controlling the spread of plasmid-mediated tigecycline resistance.

Third-Generation Tetracyclines: Current Knowledge and Therapeutic Potential.

Tetracyclines constitute a unique class of antibiotic agents, widely prescribed for both community and hospital infections due to their broad spectrum of activity. Acting by disrupting protein synthesis through tight binding to the 30S ribosomal subunit, their interference is typically reversible, rendering them bacteriostatic in action. Resistance to tetracyclines has primarily been associated with changes in pump efflux or ribosomal protection mechanisms. To address this challenge, tetracycline molecules have been chemically modified, resulting in the development of third-generation tetracyclines. These novel tetracyclines offer significant advantages in treating infections, whether used alone or in combination therapies, especially in hospital settings. Beyond their conventional antimicrobial properties, research has highlighted their potential non-antibiotic properties, including their impact on immunomodulation and malignancy. This review will focus on third-generation tetracyclines, namely tigecycline, eravacycline, and omadacycline. We will delve into their mechanisms of action and resistance, while also evaluating their pros and cons over time. Additionally, we will explore their therapeutic potential, analyzing their primary indications of prescription, potential future uses, and non-antibiotic features. This review aims to provide valuable insights into the clinical applications of third-generation tetracyclines, thereby enhancing understanding and guiding optimal clinical use.

A promising metabolite, 9-aminominocycline, restores the sensitivity of tigecycline against tet(X4)-positive Escherichia coli.

The emergence and widespread of tigecycline resistance undoubtedly poses a serious threat to public health globally. The exploration of combination therapies has become preferred antibacterial strategies to alleviate this global burden. In this study, tigecycline-resistant tet(X4)-positive Escherichia coli were selected for adjuvant screening. Interestingly, 9-aminominocycline (9-AMC), one of the tigecycline metabolites, exhibits synergistic antibacterial activity with tigecycline using checkerboard assay. The efficacy in vitro and in vivo was evaluated, and the synergistic mechanism was further explored. The results suggested that 9-AMC combined with tigecycline could inhibit the growth of antibiotic resistant bacteria, efficiently retard the evolution of tet(X4) gene and narrow the drug mutant selection window. In addition, the combination of tigecycline and 9-AMC could destroy the normal membrane structure of bacteria, inhibit the formation of biofilm, remarkably reduce the level of intracellular ATP level, and accelerate the oxidative damage of bacteria. Furthermore, 9-AMC is more stable in the bind of Tet(X4) inactivating enzyme. The transcriptomics analysis revealed that the genes related to the 9-AMC and tigecycline were mainly enriched in ABC transporters. Collectively, the results reveal the potentiation effects on tigecycline and the probability of 9-AMC as a novel tigecycline adjuvant against tet(X4)-positive Escherichia coli, which provides new insights for adjuvant screening.

Intrathecal Tigecycline in the Treatment of Hospital-Acquired Meningitis: A Review of Four Cases.

Objectives: Carbapenem-resistant A. baumannii is a common cause of nosocomial meningitis, and it presents a challenge in terms of treatment because of limited therapeutic options. Intravenous tigecycline has been considered a potential salvage therapy against multi-drug-resistant Acinetobacter baumannii. However, its effectiveness is limited by its poor ability to cross the blood-brain barrier. As an alternative treatment option, intrathecal tigecycline has shown promise with its minimal side effects and high concentration in cerebrospinal fluid. Methods: In this report, we present a series of four cases infected with multi-drug-resistant A. baumannii following neurosurgery and treated with intrathecal tigecycline, including antimicrobial therapy. Results: The rate of successful microbiological response was 2 out of 3 cases (66%) in whom microbiological response could be tested anytime during the intrathecal therapy, whereas the 30-day survival rate after treatment completion was » (25%). Conclusion: Although intrathecal tigecycline treatment has shown relative efficacy in achieving microbiological response, its impact on overall survival is still uncertain. Further studies involving larger groups of patients are necessary to evaluate the outcomes of intrathecal tigecycline therapy.

Emergence of plasmid-mediated tigecycline resistance tet(X4) gene in Enterobacterales isolated from wild animals in captivity.

Background: Over the past few decades, antimicrobial resistance (AMR) has emerged as a global health challenge in human and veterinary medicine. Research on AMR genes in captive wild animals has increased. However, the presence and molecular characteristics of tet(X)-carrying bacteria in these animals remain unknown. Methods: Eighty-four samples were collected from captive wild animals. tet(X) variants were detected using polymerase chain reaction and the isolates were identified using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. All isolated strains were subjected to antimicrobial susceptibility testing and whole-genome sequencing. The virulence of an Escherichia coli strain carrying enterotoxin genes was assessed using a Galleria mellonella larval model. Results: We isolated two tet(X4)-positive E. coli strains and one tet(X4)-positive Raoultella ornithinolytica strain. Antimicrobial susceptibility tests revealed that all three tet(X4)-carrying bacteria were sensitive to the 13 tested antimicrobial agents, but exhibited resistance to tigecycline. Notably, one tet(X4)-carrying E. coli strain producing an enterotoxin had a toxic effect on G. mellonella larvae. Whole-genome sequencing analysis showed that the two tet(X4)-carrying E. coli strains had more than 95% similarity to tet(X4)-containing E. coli strains isolated from pigs and humans in China. Conclusion: The genetic environment of tet(X4) closely resembled that of the plasmid described in previous studies. Our study identified tet(X4)-positive strains in wildlife and provided valuable epidemiological data for monitoring drug resistance. The identification of enterotoxin-producing E. coli strains also highlights the potential risks posed by virulence genes.

Multidrug-Resistant Acinetobacter baumannii mediastinitis.

INTRODUCTION: Mediastinitis remains one of the most serious complications of cardiac surgery. The reported incidence is 1-4%, while the related mortality varies from 10-47%. CASE PRESENTATION: A patient with triple vessel disease (TVD) was hospitalized at our clinic for coronary artery bypass graft (CABG) surgery. The preoperative examination results were normal. We performed standard CABG under extracorporeal circulation. The patient had a favorable postoperative course. On the fifth postoperative day, the wound showed seropurulent drainage. The treatment of the patient's wound continued with open dressing, negative wound pressure device, debridement, minimal muscle plasticity, and total bilateral muscle pectoral flap plasticity. The infecting microorganism was identified as multidrug-resistant Acinetobacter baumani, and systemic antibiotic therapy was initiated. The patient had "per secundum closure" of the wound after all these efforts. The wound healed completely 2 months after discharge, and the patient was in good health. CONCLUSIONS: Mediastinitis is associated with high mortality and high financial and human costs. The occurrence of this high-risk complication can be prevented through constant vigilance at every step from admission to discharge.

Severe hypoglycemia induced by Tigecycline in a diabetic and hemodialysis patient.

INTRODUCTION: Tigecycline has a broad spectrum of activity, including activity against drug-resistant Gram-positive and -negative microorganisms. Its side effects are significant, but hypoglycemia is a rare finding during treatment. We aim to present an event of severe hypoglycemia in a patient with type 2 diabetes mellitus with replacement renal therapy, and hemodialysis after initiating tigecycline. CASE PRESENTATION: A 54-year-old female diagnosed with type 2 diabetes mellitus was under treatment with basal-bolus insulin therapy and oral antihypertensive drugs. She started hemodialysis 24 months ago. She complained of recurrent fever for the last seven months and was treated with several antibiotics. In two separate blood cultures, she tested positive for methicillin-resistant Staphylococcus epidermidis (MRSE). Based on the antibiogram, we started treatment with tigecycline 100 mg/day. After 6-8 hours from the first dose, the patient is complicated with events of hypoglycemia and then continues with severe hypoglycemia (40-47 mg/dL). The patient continued to have hypoglycemia for about 16-18 hours after the last dose. We didn't find any reasons to explain the cause of episodes of hypoglycemia. She did not have high blood insulin levels (insulin 4.11 mIU/L [range 2.6-24.9]). We followed her for six months and the patient did not experience episodes of hypoglycemia. CONCLUSIONS: The association of severe hypoglycemia with tigecycline treatment is a very rare event and published papers on this topic are limited. Clinicians should be aware of this rare event when administering tigecycline and should routinely check blood glucose level during the treatment.

Characteristics of multidrug-resistant hypervirulent Klebsiella pneumoniae strains ST29 and K212 harbouring tmexC2-tmexD2-toprJ2.

OBJECTIVES: This study aimed to characterize a tigecycline-resistant hypervirulent Klebsiella pneumoniae (HvKP) strain, identified as KLZT, which carries the tigecycline resistance gene cluster tmexC2-tmexD2-toprJ2 belonging to ST29 and serotype K212. METHODS: Antimicrobial susceptibility and virulence phenotypes were assessed, followed by whole-genome sequencing (WGS) using PacBio II and MiSeq sequencers. Genome annotation was carried out using the RAST server and bioinformatics analysis revealed the genetic characteristics of this strain. RESULTS: Antimicrobial and virulence phenotype testing indicated that K. pneumoniae strain KLZT could be considered as a multidrug-resistant HvKP. WGS analysis showed that KLZT has a single 5,536,506-bp chromosome containing three plasmids 290,963 bp (pKLZT-1), 199,302 bp (pKLZT-2), and 4820 bp (pKLZT-3) in size, and also includes the ST29 and K212 serotypes. Four (blaSHV-187, oqxA, oqxB, and fosA6) and six resistance genes (tmexC2-tmxeD2-toprJ2, blaOXA-1, aac(6')-Ib-cr, catB3, arr-3, and blaLEN27) were identified from chromosomal and plasmid pKLZT-1, respectively. Gene-based analysis of the resistance genes of plasmid pKLZT-1 showed that the tigecycline resistance gene cluster-carrying region was flanked by umuC and umuD (umuD-hps-IS5-tmexC2-tmexD2-toprJ2-umuC), as well as other resistance genes and virulence factors (ureB, ureC, and ureG), which were carried by IS5075-Tn3-intI1 -aac(6')-Ib-cr-blaOXA-1-catB3-arr-3-blaLEN27-Tn3-ISkpn26-ureBCG-IS5075. CONCLUSIONS: WGS has revealed that a multidrug-resistant strain, HvKP KLZT, belonging to ST29 with capsular serotype K212, contains a multidrug-resistance plasmid.

Prevalence and characterization of an integrative and conjugative element carrying tet(X) gene in Elizabethkingia meningoseptica.

OBJECTIVES: To investigate the tet(X) gene, a determinant of tigecycline resistance, in the emerging pathogen Elizabethkingia meningoseptica and its association with an integrative and conjugative element (ICE). METHODS: All E. meningoseptica genomes from the National Center for Biotechnology Information (n = 87) were retrieved and annotated for resistome searches using the CARD database. A phylogenic analysis was performed based on the E. meningoseptica core genome. The ICE was identified through comparative genomics with other ICEs occurring in Elizabethkingia spp. RESULTS: Phylogenetic analysis revealed E. meningoseptica genomes from six countries distributed across different lineages, some of which persisted for years. The common resistome of these genomes included blaBlaB, blaCME, blaGOB, ranA/B, aadS, and catB (genes associated with resistance to ß-lactams, aminoglycosides, and chloramphenicol). Some genomes also presented additional resistance genes (dfrA, ereD, blaVEB, aadS, and tet(X)). Interestingly, tet(X) and aadS were located in an ICE of 49 769 bp (ICEEmSQ101), which was fully obtained from the E. meningoseptica SQ101 genome. We also showed evidence that the other 27 genomes harboured this ICE. The distribution of ICEEmSQ101, carrying tet(X), was restricted to a single Chinese lineage. CONCLUSIONS: The tet(X) gene is not prevalent in the species E. meningoseptica, as previously stated for the genus Elizabethkingia, since it is present only in a single Chinese lineage. We identified that several E. meningoseptica genomes harboured an ICE that mobilized the Elizabethkingia tet(X) gene and exhibited characteristics similar to the ICEs of other Flavobacteria, which would favour their transmission in this bacterial family.