Investigation of Plasmid-Mediated Colistin Resistance Genes (mcr-1-8) in Enterobacterales Isolates.

Background The escalating global rise in multidrug-resistant gram-negative bacteria presents an increasingly substantial threat to patient safety. Over the past decade, carbapenem-resistant Enterobacterales (CRE) have emerged as one of the most critical pathogens in hospital-acquired infections, notably within intensive care units. Colistin has become one of the last-resort antimicrobial agents utilized to combat infections caused by CRE. However, the use of colistin has been accompanied by a notable increase in the prevalence of colistin-resistant bacteria. This study aimed to investigate plasmid-mediated colistin resistance genes ranging from mcr-1 to mcr-8 among members of the Enterobacterales order. Materials and methods This prospective study was conducted in the microbiology laboratory of Afyonkarahisar Health Sciences University Health Research and Practice Center between May 1, 2021 and July 31, 2022. A total of 2,646 Enterobacterales isolates were obtained from all culture-positive clinical samples sent from various clinics. Of these, 79 isolates exhibiting resistance to carbapenem antibiotics were included in the study. Among the 79 isolates, the presence of mcr-1 to mcr-8 genes was investigated in 27 isolates that were shown to be resistant to colistin. The identification of bacteria at the species level and antibiotic susceptibility tests were conducted using the VITEK 2 automated system (bioMérieux, USA). Colistin resistance among Enterobacterales strains exhibiting carbapenem resistance was evaluated using the broth microdilution technique (ComASP™ Colistin, Liofilchem, Italy), in accordance with the manufacturer's instructions. Results In our in vitro investigations, the minimum inhibitory concentration (MIC) values for meropenem were determined to be >8 µg/ml, whereas for colistin, the MIC50 value was >16 µg/ml and the MIC90 value was 8 µg/ml. A total of 27 colistin-resistant strains were identified among the 79 carbapenem-resistant Enterobacterales strains analyzed. The most prevalent agent among colistin-resistant strains was Klebsiella pneumoniae (K. pneumoniae), representing 66.7% of the isolates. This was followed by Proteus mirabilis (P. mirabilis) with 29.6% and Escherichia coli (E. coli) with 3.7%. The colistin resistance rate among carbapenem-resistant strains was found to be 34.2%, with colistin MIC values in strains tested by the broth microdilution method ranging from 4 to >16 µg/ml concentrations. In polymerase chain reaction (PCR) studies, the mcr-1 gene region was successfully detected by real-time PCR in the positive control isolate. Nevertheless, none of the gene regions from mcr-1 to mcr-8 were identified in our study investigating the presence of plasmid-mediated genes using a multiplex PCR kit. Conclusion Although our study demonstrated the presence of increased colistin resistance rates in carbapenem-resistant Enterobacterales isolates, it resulted in the failure to detect genes from mcr-1 to mcr-8 by the multiplex PCR method. Therefore, it is concluded that the colistin resistance observed in Enterobacteriaceae isolates in our region is not due to the mcr genes screened, but to different resistance development mechanisms.

Optimizing Treatment for Carbapenem-Resistant Acinetobacter baumannii Complex Infections: A Review of Current Evidence.

Carbapenem-resistant Acinetobacter baumannii complex (CRAB) poses a significant global health challenge owing to its resistance to multiple antibiotics and limited treatment options. Polymyxin-based therapies have been widely used to treat CRAB infections; however, they are associated with high mortality rates and common adverse events such as nephrotoxicity. Recent developments include numerous observational studies and randomized clinical trials investigating antibiotic combinations, repurposing existing antibiotics, and the development of novel agents. Consequently, recommendations for treating CRAB are undergoing significant changes. The importance of colistin is decreasing, and the role of sulbactam, which exhibits direct antibacterial activity against A. baumannii complex, is being reassessed. High-dose ampicillin-sulbactam-based combination therapies, as well as combinations of sulbactam and durlobactam, which prevent the hydrolysis of sulbactam and binds to penicillin-binding protein 2, have shown promising results. This review introduces recent advancements in CRAB infection treatment based on clinical trial data, highlighting the need for optimized treatment protocols and comprehensive clinical trials to combat the evolving threat of CRAB effectively.

Transcriptomic investigations of polymyxins and colistin/sulbactam combination against carbapenem-resistant Acinetobacter baumannii.

Carbapenem-resistant Acinetobacter baumannii (CRAB) is a Priority 1 (Critical) pathogen urgently requiring new antibiotics. Polymyxins are a last-line option against CRAB-associated infections. This transcriptomic study utilized a CRAB strain to investigate mechanisms of bacterial killing with polymyxin B, colistin, colistin B, and colistin/sulbactam combination therapy. After 4 h of 2 mg/L polymyxin monotherapy, all polymyxins exhibited common transcriptomic responses which primarily involved disruption to amino acid and fatty acid metabolism. Of the three monotherapies, polymyxin B induced the greatest number of differentially expressed genes (DEGs), including for genes involved with fatty acid metabolism. Gene disturbances with colistin and colistin B were highly similar (89 % common genes for colistin B), though effects on gene expression were generally lower (0-1.5-fold in most cases) with colistin B. Colistin alone (2 mg/L) or combined with sulbactam (64 mg/L) resulted in rapid membrane disruption as early as 1 h. Transcriptomic analysis of this combination revealed that the effects were driven by colistin, which included disturbances in fatty acid synthesis and catabolism, and inhibition of nutrient uptake. Combination therapy produced substantially higher fold changes in 72 % of DEGs shared with monotherapy, leading to substantially greater reductions in fatty acid biosynthesis and increases in biofilm, cell wall, and phospholipid synthesis. This indicates synergistic bacterial killing with the colistin/sulbactam combination results from a systematic increase in perturbation of many genes associated with bacterial metabolism. These mechanistic insights enhance our understanding of bacterial responses to polymyxin mono- and combination therapy and will assist to optimize polymyxin use in patients.

Clinical Outcome Assessment of Colistin Sulfate in Children with Carbapenem-Resistant Organism Infections: First Data from China.

OBJECT: Colistin sulfate for injection (CSI) became clinically available in China in July 2019. To date, there is no published data regarding its usage in children. Our research group has been following data on the efficacy and safety of CSI in Chinese pediatric patients with carbapenem-resistant organism (CRO) infections. The purpose of this short communication is to provide a brief overview of the findings to date. METHODS: We reviewed the electronic medical records of pediatric patients (aged 9-17 years) who were administered CSI during their hospital stay at Tongji Hospital in Wuhan, China, between June 2021 and November 2023. Drug efficacy was evaluated based on clinical and microbiological outcomes, while drug safety was assessed using surveillance markers that reflect adverse reactions. RESULTS: A total of 20 patients met the inclusion criteria. The predominant pathogens were Klebsiella pneumoniae (8 strains), followed by Acinetobacter baumannii (5 strains) and Pseudomonas aeruginosa (2 strains). The clinical response rate of CSI was 85%, with a bacterial clearance rate of 79%. None of the patients experienced colistin-related nephrotoxicity or neurotoxicity during the treatment. CONCLUSION: In this real-world setting, CSI demonstrated a high level of clinical response and was well tolerated for the treatment of CRO infections in Chinese children.

Epidemiology of Citrobacter spp. infections among hospitalized patients: a systematic review and meta-analysis.

BACKGROUND: Infections due to Citrobacter species are increasingly observed in hospitalized patients and are often multidrug-resistant. Yet, the magnitude and burden of Citrobacter spp. resistance in the hospital setting have not been reported. We aimed to evaluate the epidemiology of Citrobacter spp. infections among hospitalized patients, their main resistance patterns and Citrobacter spp. involvement in hospital outbreaks. METHODS: We conducted a systematic review and meta-analysis of published literature (PROSPERO registration Jan-2023, CRD42023390084). We searched Embase, Medline and grey literature for studies on hospitalized patients diagnosed with Citrobacter spp. infections, and nosocomial outbreaks due to Citrobacter spp. published during the years 2000-2022. We included observational, interventional, surveillance studies and outbreak reports. Outcomes of interest were the frequency of Citrobacter spp. infections among hospitalized patients and 3rd generation cephalosporin and/or carbapenem resistance percentages in these infections. We used random-effects models to generate pooled outcome estimates and evaluated risk of bias and quality of reporting of outbreaks. RESULTS: We screened 1609 deduplicated publications, assessed 148 full-texts, and included 41 studies (15 observational, 13 surveillance and 13 outbreak studies). Citrobacter spp. urinary tract- and bloodstream infections were most frequently reported, with Citrobacter freundii being the main causative species. Hospital-acquired infection occurred in 85% (838/990) of hospitalized patients with Citrobacter infection. After 2010, an increasing number of patients with Citrobacter spp. infections was reported in observational studies. Pooled frequency estimates for Citrobacter spp. infections could not be generated due to lack of data. The pooled prevalence of ESBL and carbapenemase producers among Citrobacter isolates were 22% (95%CI 4-50%, 7 studies) and 18% (95%CI 0-63%, 4 studies), respectively. An increased frequency of reported Citrobacter outbreaks was observed after 2016, with an infection/colonization ratio of 1:3 and a case-fatality ratio of 7% (6/89 patients). Common outbreak sources were sinks, toilets, contaminated food and injection material. Implemented preventive measures included environmental cleaning, isolation of positive patients and reinforcement of hand hygiene. Only seven out of 13 outbreaks (54%) were definitively controlled. CONCLUSION: This review highlights the clinical importance of endemic and epidemic Citrobacter spp. in healthcare settings. As an emerging, multidrug­resistant nosocomial pathogen it requires heightened awareness and further dedicated surveillance efforts.

Clinical Characteristics and Molecular Insights of Carbapenem-Resistant Klebsiella pneumoniae Isolates from Patients in Intensive Care Units.

Background: Carbapenem-resistant Klebsiella pneumoniae (CRKP), a significant worldwide public health threat, is common in patients in intensive care units. Methods: A retrospective study was conducted over a period of 22 months to assess the risk factors associated with infection caused by CRKP isolates. Strain identification was performed using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS), and antimicrobial sensitivity was assessed using the micro broth dilution method and Kirby-Bauer test. The genes blaKPC, blaOXA-48, blaNDM, blaVIM, and blaGES were amplified using polymerase chain reaction (PCR), followed by sequencing of the PCR products. The polymerase hypermucoviscosity phenotype was determined using the string test. Capsular serotypes (K1, K2) and presence of the virulence gene (rmpA) in positive isolates were investigated using phenotypic tests followed by PCR. Results: Length of hospitalization and use of carbapenems were associated with CRKP infection. CRKP isolates exhibited extensive drug resistance, but retained sensitivity to colistin and ceftazidime-avibactam (CZA). The main gene detected in 35 CRKP isolates was blaKPC-2. In addition, 11 strains were positive in the string test, and two of these strains carried rmpA. Conclusions: Prolonged hospitalization and carbapenem exposure increased the risk of CRKP infection in intensive care unit (ICU) patients. The prevalence of CRKP carrying the blaKPC-2 gene was high, and suspected hypervirulent carbapenem-resistant K. pneumoniae isolates were scattered.

Molecular characteristics and evaluation of the phenotypic detection of carbapenemases among Enterobacterales and Pseudomonas via whole genome sequencing.

Background/purposes: The continuously increasing carbapenem resistance within Enterobacterales and Pseudomonas poses a threat to public health, nevertheless, the molecular characteristics of which in southern China still remain limited. And carbapenemase identification is a key factor in effective early therapy of carbapenem-resistant bacteria infections. We aimed to determine the molecular characteristics of these pathogens and compare commercial combined disc tests (CDTs) with the modified carbapenem inactivation method (mCIM) and EDTA-CIM (eCIM) in detecting and distinguishing carbapenemases using whole genome sequencing (WGS). Methods: A total of 78 Enterobacterales, 30 Pseudomonas were obtained from two tertiary hospitals in southern China. Susceptibility tests were conducted using an automated VITEK2 compact system with confirmation via the Kirby-Bauer method. The WGS was conducted on all clinical isolates and the molecular characteristics were analyzed by screening the whole genome sequences. CDTs with or without cloxacillin, mCIM, and eCIM, were performed and compared by taking WGS results as the benchmark. Results: A total of 103 carbapenem non-susceptible and 5 carbapenem susceptible bacteria were determined, with Klebsiella pneumoniae (42.7%), Pseudomonas aeruginosa (23.3%) and Escherichia coli (18.4%) being most prevalent. Carbapenemase genes were detected in 58 (56.3%) of the 103 carbapenem-non-susceptible clinical isolates, including 46 NDM, 6 KPC, 3 IMP, 1 IPM+VIM,1NDM+KPC, and 1 OXA-181. Carbapenemase-producing isolates were detected more frequently in Enterobacterales (76.3%). Among K. pneumoniae, the major sequence types were st307 and st11, while among E. coli and P. aeruginosa, the most prevalent ones were st410 and st242 respectively. For carbapenemase detection in Enterobacterales, the mCIM method achieved 100.00% (95% CI, 92.13-100.00%) sensitivity and 94.44% (70.63-99.71%) specificity (kappa, 0.96); for Pseudomonas, detection sensitivity was 100% (5.46-100.00%), and 100% (84.50-100.00%) specificity (kappa, 0.65). Commercial CDT carbapenemase detection sensitivity for Enterobacterales was 96.49% (86.84-99.39%), and 95.24% (74.13-99.75%) specificity (kappa, 0.90); for Pseudomonas, carbapenemase detection sensitivity was 100.00% (5.46-100.00%) and 37.93% (21.30-57.64%) specificity (kappa, 0.04). When cloxacillin testing was added, CDT specificity reached 84.61% (64.27-94.95%). Conclusion: The molecular epidemiology of carbapenem-non-susceptible isolates from pediatric patients in Southern China exhibited distinctive characteristics. Both the mCIM-eCIM combination and CDT methods effectively detected and differentiated carbapenemases among Enterobacterales isolates, and the former performed better than CDT among Pseudomonas.

Characterization of carbapenemase-producing Enterobacterales from rectal swabs of patients in the intensive care units of a tertiary hospital in Cali-Colombia.

Background: Carbapenemase-producing Enterobacterales (CPE) represents a significant threat to global health. This study aimed to characterize clinically and molecularly the CPE isolated from rectal swabs of patients in the intensive care units (ICUs) of a tertiary hospital in Cali, Colombia. Methods: This was a cross-sectional observational study. Rectal swabs from patients admitted to the ICUs were collected. Bacterial identification and carbapenemase production were determined using phenotypic and molecular methods. Demographic and clinical data were extracted from electronic medical records. Results: The study included 223 patients. Thirty-six patients (36/223, 16.14 %) were found to be colonized or infected by CPE. Factors such as prolonged stay in the ICU, previous exposure to carbapenem antibiotics, use of invasive procedures, and admission due to trauma were associated with CPE. Klebsiella pneumoniae (52.5 %) was the most prevalent microorganism, and the dominant carbapenemases identified were KPC (57.8 %) and NDM (37.8 %). Conclusion: Distinguishing carbapenemase subtypes can provide crucial insights for controlling dissemination in ICUs in Cali, Colombia.

Risk factors for mortality in Acinetobacter baumannii bloodstream infections and development of a predictive mortality model.

BACKGROUND: Acinetobacter baumannii nosocomial infections represent a serious hazard to public health, given high mortality rates and rapid spread of multidrug-resistance. METHODS: Between 2019 and 2023, all consecutive hospitalized adult patients with bacteraemia due to A. baumannii were retrospectively enrolled at a single-centre. OBJECTIVES: The primary outcome was to evaluate predictors of 14- and 30-day mortality in bloodstream infections (BSIs) due to both carbapenem-resistant and carbapenem-sensitive Acinetobacter. Secondary endpoints were to identify risk factors for BSIs due to carbapenem-resistant A. baumannii (CRAB) and to develop a predictive model for mortality in CRAB-related BSIs. RESULTS: 126 episodes of BSI caused by A. baumannii were recorded, 89.7% of which were due to CRAB. Recent burn injuries, older age, previous CRAB colonization and antibiotics exposure were identified as risk factors for acquiring CRAB BSI. Overall, 14-day mortality was observed in 26.1% patients and 30-day mortality in 30.9% patients. On multivariate analysis, the Sequential Organ Failure Assessment (SOFA) score was associated with both 14- and 30-day mortality, while burn injuries correlated with 30-day survival. Concurrent Coronavirus disease (COVID) was associated with mortality, although not reaching statistical. No major impact of receiving appropriate treatment was observed. Based on these findings, a multivariable model to predict mortality among patients with CRAB BSI was built and internally validated. CONCLUSIONS: A. baumannii BSIs are characterized by poor outcomes and the limited therapeutic options. This study aimed to assist physicians in prompt identification of patients who are at greater risk of death, contributing to more informed clinical decision-making.

A retrospective study of the efficacy of sulbactam in the treatment of patients with extensively drug-resistant Acinetobacter baumannii infections.

PURPOSE: Sulbactam (SBT) is one of the most significant treatments for patients with extensively drug-resistant Acinetobacter baumannii (XDR-AB). However, the efficacy and safety of SBT and its high dose regimen has not been well documented. This retrospective study aimed to assess the efficacy and safety of SBT-based treatment, particularly at high-dose (≥ 6 g/day), for XDR-AB infection. METHOD: A total of 52 XDR-AB infected patients treated with intravenous SBT at Peking Union Medical College Hospital were included. The primary outcome was 28-day all-cause mortality, while the secondary outcome was 14-day clinical response and the time of response. The formulation of SBT in our study is 0.5 g per vial. RESULTS: Among the patients, the 28-day all-cause mortality rate was 36.5% (19/52), and the favorable 14-day clinical response rate was 59.6% (31/52). The 28-day mortality was independently associated coinfection with gram-positive bacteria (GPB) and a shorter duration of therapy. Patients with intracranial infection might have a longer survival time. A favorable 14-day clinical response was associated with the dose of SBT, and a longer treatment duration. However, the higher creatinine clearance (CrCl) associated with a worse clincal response. In addition, a higher SBT dosage was significantly correlated with a shorter time to clinical response. No adverse effects related were reported. CONCLUSION: The single-agent formulation of SBT emerges as a promising alternative for the treatment of XDR-AB infection, such as intracranial infection, particularly at high doses (≥ 6 g/day). Besides, longer duration of treatment correlates with higher survival rate and better favorable clinical response. Higher CrCl negatively correlates with favorable clinical response.

Co-colonization of different species harboring KPC or NDM carbapenemase in the same host gut: insight of resistance evolution by horizontal gene transfer.

Introduction: The dissemination of carbapenem-resistant Enterobacteriales (CRE) in nosocomial settings is primarily associated with the horizontal transfer of plasmids. However, limited research has focused on the in-host transferability of carbapenem resistance. In this study, ten isolates were collected from gut specimens of five individuals, each hosting two different species, including Escherichia coli, Klebsiella pneumoniae, Klebsiella aerogenes, Enterobacter cloacae, or Citrobacter koseri. Methods: Species identification and antimicrobial susceptibility were determined by MALDI-TOF MS and broth microdilution method. Carbapenemase genes were detected and localized using PCR, S1-PFGE and southern blot. The transferability of carbapenemase genes between species was investigated through filter mating experiments, and the genetic contexts of the plasmids were analyzed using whole genome sequencing. Results and discussion: Our results revealed that each of the ten isolates harbored a carbapenemase gene, including bla NDM-5, bla NDM-1, or bla KPC-2, on a plasmid. Five different plasmids were successfully transferred to recipient cells of E. coli, K. pneumoniae or A. baumannii by transconjugation. The genetic contexts of the carbapenemase gene were remarkably similar between the two CRE isolates from each individual. This study highlights the potential for interspecies plasmid transmission in human gut, emphasizing the colonization of CRE as a significant risk factor for the dissemination of carbapenemase genes within the host. These findings underscore the need for appropriate intestinal CRE screening and colonization prevention.

Adult acute leukemia patients with gram-negative bacteria bloodstream infection: Risk factors and outcomes of antibiotic-resistant bacteria.

This study aims to analyze the risk factors for the development of multidrug-resistant (MDR) and carbapenem-resistant (CR) bacteria bloodstream infection (BSI) in a patient with acute leukemia (AL) and the mortality in gram-negative bacteria (GNB) BSI. This is a retrospective study conducted at West China Hospital of Sichuan University, which included patients diagnosed with AL and concomitant GNB BSI from 2016 to 2021. A total of 206 patients with GNB BSI in AL were included. The 30-day mortality rate for all patients was 26.2%, with rates of 25.8% for those with MDR GNB BSI and 59.1% for those with CR GNB BSI. Univariate and multivariate analyses revealed that exposure to quinolones (Odds ratio (OR) = 3.111, 95% confidence interval (95%CI): 1.623-5.964, p = 0.001) within the preceding 30 days was an independent risk factor for MDR GNB BSI, while placement of urinary catheter (OR = 6.311, 95%CI: 2.478-16.073, p < 0.001) and exposure to cephalosporins (OR = 2.340, 95%CI: 1.090-5.025, p = 0.029) and carbapenems (OR = 2.558, 95%CI: 1.190-5.497, p = 0.016) within the preceding 30 days were independently associated with CR GNB BSI. Additionally, CR GNB BSI (OR = 2.960, 95% CI: 1.016-8.624, p = 0.047), relapsed/refractory AL (OR = 3.035, 95% CI: 1.265-7.354, p = 0.013), septic shock (OR = 5.108, 95% CI: 1.794-14.547, p = 0.002), platelets < 30 × 109/L before BSI (OR = 7.785, 95% CI: 2.055-29.492, p = 0.003), and inappropriate empiric antibiotic therapy (OR = 3.140, 95% CI: 1.171-8.417, p = 0.023) were independent risk factors for 30-day mortality in AL patients with GNB BSI. Prior antibiotic exposure was a significant factor in the occurrence of MDR GNB BSI and CR GNB BSI. CR GNB BSI increased the risk of mortality in AL patients with GNB BSI.

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.

Development and validation of a novel prediction model for Carbapenem-resistant organism infection in a large-scale hospitalized patients.

Carbapenem-resistant organism (CRO) are defined as gram-negative bacteria. The lack of safe and effective antibiotics has led to an increase in incidence rate. The purpose of this study is to establish and determine a risk nomogram to predict CRO infection in hospitalized patients. Hospitalized patients' information were collected from the electronic medical record system of hospital between January 2019 and December 2022. Based on the inclusion and exclusion criteria, we identified 131390 inpatients who met the criteria for this study. For the training cohort, the area under the curves (AUC) for predicting the CRO infection was 0.935. For the validation cohort, the AUC for predicting the CRO infection was 0.937. We have developed the first novel nomogram to predict CRO infection in hospitalized patients, which is reliable and high-performance. The nomogram performs well among hospitalized patients and has good predictive ability.

Clinical outcomes of carbapenem-resistant gram-negative bacterial bloodstream infection in patients with end-stage renal disease in intensive care units: a multicenter retrospective observational study.

BACKGROUND: Carbapenem-resistant gram-negative bacteria (CRGNB) present a considerable global threat due to their challenging treatment and increased mortality rates, with bloodstream infection (BSI) having the highest mortality rate. Patients with end-stage renal disease (ESRD) undergoing renal replacement therapy (RRT) face an increased risk of BSI. Limited data are available regarding the prognosis and treatment outcomes of CRGNB-BSI in patients with ESRD in intensive care units (ICUs). METHODS: This multi-center retrospective observational study included a total of 149 ICU patients with ESRD and CRGNB-BSI in Taiwan from January 2015 to December 2019. Clinical and microbiological outcomes were assessed, and multivariable regression analysis was used to evaluate the independent risk factors for day-28 mortality and the impact of antimicrobial therapy regimen on treatment outcomes. RESULTS: Among the 149 patients, a total of 127 patients (85.2%) acquired BSI in the ICU, with catheter-related infections (47.7%) and pneumonia (32.2%) being the most common etiologies. Acinetobacter baumannii (49.0%) and Klebsiella pneumoniae (31.5%) were the most frequently isolated pathogens. The day-28 mortality rate from BSI onset was 52.3%, and in-hospital mortality was 73.2%, with survivors experiencing prolonged hospital stays. A higher Sequential Organ Failure Assessment (SOFA) score (adjusted hazards ratio [aHR], 1.25; 95% confidence interval [CI] 1.17-1.35) and shock status (aHR, 2.12; 95% CI 1.14-3.94) independently predicted day-28 mortality. Colistin-based therapy reduced day-28 mortality in patients with shock, a SOFA score of ≥ 13, and Acinetobacter baumannii-related BSI. CONCLUSIONS: CRGNB-BSI led to high mortality in critically ill patients with ESRD. Day-28 mortality was independently predicted by a higher SOFA score and shock status. In patients with higher disease severity and Acinetobacter baumannii-related BSI, colistin-based therapy improved treatment outcomes.

Solithromycin in Combination with Other Antimicrobial Agents Against the Carbapenem Resistant Klebsiella pneumoniae (CRKP).

Klebsiella pneumoniae is considered as the most common pathogen of hospital-acquired pneumonia. K. pneumoniae has emerged as the superbug which had shown multidrug resistance (MDR) as well as extensively drug resistance. Carbapenem resistant K. pneumoniae (CRKP) has become a menace for the treatment with monotherapy of the patients mainly admitted in intensive care units. Hence, in the present study we collected total 187 sputum isolates of K. pneumoniae and performed the antimicrobial susceptibility testing by using the automated Vitek-2 system and broth micro-dilution method (67 CRKP). The combination study of solithromycin with meropenem, colistin, cefotaxime, piperacillin and tazobactam, nitrofurantoin, tetracycline, levofloxacin, curcumin and nalidixic acid was performed by using checkerboard assay. We observed the high rate of resistance towards ampicillin, cefotaxime, ceftriaxone, cefuroxime and aztreonam. The colistin and tigecycline were the most sensitive drugs. The CRKP were 36%, maximum were from the patients of ICUs. The best synergistic effect of solithromycin was with meropenem and cefotaxime (100%), colistin and tetracycline (80%). So, these combinations can be a choice of treatment for the infections caused by MDR CRKP and other Gram-negative bacteria where the monotherapy could not work.

Molecular epidemiology and risk factors for carbapenem-resistant Enterobacteriaceae infections during 2020-2021 in Northwest China.

OBJECTIVES: Severe infection caused by Carbapenem-resistant Enterobacteriaceae (CRE) is a challenge for clinical anti-infective therapy, and clinical intervention to improve control of CRE is of great significance. The study aims to determine the molecular epidemiology and risk factors of CRE infections to provide evidence for effective control of nosocomial infection in patients with CRE. METHODS: A total of 192 non-repetitive CRE strains were collected from January 2020 to December 2021 in Northwest China. To explore the risk factors of CRE infection by univariate and Logistic regression analysis, 1:1 case-control study was used to select Carbapenem sensitive Enterobacteriaceae (CSE) infection patients at the same period as the control group. RESULTS: Among the 192 CRE strains, the most common isolates included Klebsiella pneumoniae (Kpn) and Enterobacter cloacae (Ecl). The CRE strain showed the lowest rate of resistance to amikacin at 58.3. 185 CRE strains carried carbapenemase resistance genes of concern in this study. KPC-2 (n=94) was the most common carbapenemase, followed by NDM-1 (n=69), NDM-5 (n=22) and IMP-4 (n=5). OXA-48 and VIM were not detected. And KPC-2 was the most common in all strains. Logistic regression analysis implicated days of invasive ventilator-assisted ventilation (OR=1.452; 95 % CI 1.250～1.686), antibiotic combination therapy (OR=2.149; 95 % CI 1.128～4.094), hypoalbuminemia (OR=6.137; 95 % CI 3.161～11.913), history of immunosuppressant use (OR=25.815; 95 % CI 6.821～97.706) and days of hospitalization (OR=1.020; 95 % CI 1.006～1.035) as independent risk factors associated with CRE infection. Age (OR=0.963; 95% CI 0.943～0.984) and history of hormone use (OR=0.119; 95 % CI 0.028～0.504) were protective factors for CRE infection (P < 0.05). CONCLUSIONS: The resistance of commonly used antibiotics in clinical is severe, and CRE strains mainly carry KPC-2 and NDM-1. Multiple risk factors for CRE infection and their control can effectively prevent the spread of CRE.

The Rising Tide of Antibiotic Resistance: A Study on Extended-Spectrum Beta-Lactamase and Carbapenem-Resistant Escherichia coli and Klebsiella pneumoniae.

BACKGROUND: The global spread of extended-spectrum beta-lactamase (ESBL)-producing and carbapenem-resistant Enterobacterales (CRE) poses a significant concern. Acquisition of antimicrobial resistance genes leads to resistance against several antibiotics, limiting treatment options. We aimed to study ESBL-producing and CRE transmission in clinical settings. METHODS: From clinical samples, 227 ESBL-producing and CRE isolates were obtained. The isolates were cultured on bacterial media and confirmed by VITEK 2. Antibiograms were tested against several antibiotics using VITEK 2. The acquired resistance genes were identified by PCR. RESULTS: Of the 227 clinical isolates, 145 (63.8%) were Klebsiella pneumoniae and 82 (36.1%) were Escherichia coli; 76 (33.4%) isolates were detected in urine, 57 (25.1%) in pus swabs, and 53 (23.3%) in blood samples. A total of 58 (70.7%) ESBL-producing E. coli were resistant to beta-lactams, except for carbapenems, and 17.2% were amikacin-resistant; 29.2% of E. coli isolates were resistant to carbapenems. A total of 106 (73.1%) ESBL-producing K. pneumoniae were resistant to all beta-lactams, except for carbapenems, and 66.9% to ciprofloxacin; 38 (26.2%) K. pneumoniae were resistant to carbapenems. Colistin emerged as the most effective antibiotic against both bacterial types. Twelve (20.6%) E. coli isolates were positive for blaCTX-M, 11 (18.9%) for blaTEM, and 8 (33.3%) for blaNDM. Forty-six (52.3%) K. pneumoniae isolates had blaCTX-M, 27 (18.6%) blaTEM, and 26 (68.4%) blaNDM. CONCLUSION: This study found a high prevalence of drug-resistant ESBL-producing and CRE, highlighting the need for targeted antibiotic use to combat resistance.

Inhibitory Potential of Bifidobacterium longum FB1-1 Cell-Free Supernatant against Carbapenem-Resistant Klebsiella pneumoniae Drug Resistance Spread.

The widespread dissemination of carbapenem-resistant Klebsiella pneumoniae (CRKP) and its drug resistance transfer poses a global public health threat. While previous studies outlined CRKP's drug resistance mechanism, there is limited research on strategies inhibiting CRKP drug resistance spread. This study investigates the potential of Bifidobacterium longum (B. longum) FB1-1, a probiotic, in curbing the spread of drug resistance among CRKP by evaluating its cell-free supernatant (CFS) for antibacterial activity. Evaluating the inhibitory effect of FB1-1 CFS on CRKP drug resistance spread involved analyzing its impact on drug resistance and virulence gene expression; drug resistance plasmid transfer FB1-1 CFS exhibited an MIC range of 125 µL/mL against CRKP. After eight hours of co-culture, CFS achieved a 96% and 100% sterilization rate at two and four times the MIC, respectively. At sub-inhibitory concentrations (1/2× MIC), FB1-1 CFS reduced the expression of the bla_KPC gene, which is pivotal for carbapenem resistance, by up to 62.13% across different CRKP strains. Additionally, it markedly suppressed the expression of the uge gene, a key virulence factor, by up to 91%, and the fim_H gene, essential for bacterial adhesion, by up to 53.4%. Our study primarily focuses on determining the inhibitory effect of FB1-1 CFS on CRKP strains harboring the bla_KPC gene, which is a critical resistance determinant in CRKP. Furthermore, FB1-1 CFS demonstrated the ability to inhibit the transfer of drug resistance plasmids among CRKP strains, thus limiting the horizontal spread of resistance genes. This study highlights FB1-1 CFS's inhibitory effect on CRKP drug resistance spread, particularly in strains carrying the bla_KPC gene, thus offering a novel idea and theoretical foundation for developing antibacterial drugs targeting CRKP resistance.

Dissemination of clinical Escherichia coli strains harboring mcr-1, blaNDM-7 and siderophore-producing plasmids in a Chinese hospital.

BACKGROUND: Carbapenem-resistant E. coli (CREco) pose a significant public health threat due to their multidrug resistance. Colistin is often a last-resort treatment against CREco; however, the emergence of colistin resistance gene mcr-1 complicates treatment options. METHODS: Two E. coli strains (ECO20 and ECO21), recovered from hospitalized patients in distinct wards, exhibited resistance to carbapenems and colistin. Whole-genome sequencing and phenotypic characterization were employed to study resistance patterns, plasmid profiles, transferability of resistance and virulence genes, and siderophore production capabilities. Comparative genome analysis was used to investigate the genetic environment of mcr-1, blaNDM-7, and virulence clusters. RESULTS: Both E. coli strains exhibited thr presence of both mcr-1 and blaNDM-7 genes, showing high resistance to multiple antibiotics. Genomic analysis revealed the clonal transmission of these strains, possessing identical plasmid profiles (pMCR, pNDM, and pVir) associated with colistin resistance, carbapenem resistance, and virulence factors. Conjugation experiments confirmed the transferability of these plasmids, indicating their potential to disseminate resistance and virulence traits to other strains. Comparative genomic analyses unveiled the distribution of mcr-1 (IncX4-type) and blaNDM (IncX3-type) plasmids across diverse bacterial species, emphasizing their adaptability and threat. The novelty of pVir indicates its potential role in driving the evolution of highly adaptable and pathogenic strains. CONCLUSIONS: Our findings underscore the co-occurrence of mcr-1, blaNDM-7, and siderophore-producing plasmids in E. coli, which poses a significant concern for global health. This research is crucial to unravel the complex mechanisms governing plasmid transfer and recombination and to devise robust strategies to control their spread in healthcare settings.