Cefepime-taniborbactam and CERTAIN-1: Can we treat carbapenem-resistant infections?

Wagenlehner and colleagues1 demonstrated non-inferiority and superiority with respect to a primary endpoint of composite success (microbiological plus clinical) of cefepime/taniborbactam vs. meropenem in treating complicated urinary tract infections and acute pyelonephritis caused by carbapenem-susceptible gram-negative bacteria in adults. A major area of interest in real-world application of cefepime/taniborbactam is its potential role in treating carbapenem-resistant infections, which deserves further investigation.

Prediction of carbapenem-resistant gram-negative bacterial bloodstream infection in intensive care unit based on machine learning.

BACKGROUND: Predicting whether Carbapenem-Resistant Gram-Negative Bacterial (CRGNB) cause bloodstream infection when giving advice may guide the use of antibiotics because it takes 2-5 days conventionally to return the results from doctor's order. METHODS: It is a regional multi-center retrospective study in which patients with suspected bloodstream infections were divided into a positive and negative culture group. According to the positive results, patients were divided into the CRGNB group and other groups. We used the machine learning algorithm to predict whether the blood culture was positive and whether the pathogen was CRGNB once giving the order of blood culture. RESULTS: There were 952 patients with positive blood cultures, 418 patients in the CRGNB group, 534 in the non-CRGNB group, and 1422 with negative blood cultures. Mechanical ventilation, invasive catheterization, and carbapenem use history were the main high-risk factors for CRGNB bloodstream infection. The random forest model has the best prediction ability, with AUROC being 0.86, followed by the XGBoost prediction model in bloodstream infection prediction. In the CRGNB prediction model analysis, the SVM and random forest model have higher area under the receiver operating characteristic curves, which are 0.88 and 0.87, respectively. CONCLUSIONS: The machine learning algorithm can accurately predict the occurrence of ICU-acquired bloodstream infection and identify whether CRGNB causes it once giving the order of blood culture.

Genetic, virulence, and antimicrobial resistance characteristics associated with distinct morphotypes in ST11 carbapenem-resistant Klebsiella pneumoniae.

ST11 is the most common lineage among carbapenem-resistant Klebsiella pneumoniae (CRKP) infections in Asia. Diverse morphotypes resulting from genetic mutations are associated with significant differences in microbial characteristics among K. pneumoniae isolates. Here, we investigated the genetic determinants and critical characteristics associated with distinct morphotypes of ST11 CRKP. An ST11-KL47 CRKP isolate carrying a pLVPK-like virulence plasmid was isolated from a patient with a bloodstream infection; the isolate had the "mcsw" morphotype. Two distinct morphotypes ("ntrd" and "msdw") were derived from this strain during in vitro passage. Whole genome sequencing was used to identify mutations that cause the distinct morphotypes of ST11 CRKP. Transmission electron microscopy, antimicrobial susceptibility tests, growth assays, biofilm formation, virulence assays, membrane permeability assays, and RNA-seq analysis were used to investigate the specific characteristics associated with different morphotypes of ST11 CRKP. Compared with the parental mcsw morphotype, the ntrd morphotype resulted from mutation of genes involved in capsular polysaccharide biosynthesis (wza, wzc, and wbaP), a result validated by gene knockout experiments. This morphotype showed capsule deficiency and lower virulence potential, but higher biofilm production. By contrast, the msdw morphotype displayed competition deficiency and increased susceptibility to chlorhexidine and polymyxin B. Further analyses indicated that these characteristics were caused by interruption of the sigma factor gene rpoN by insertion mutations and deletion of the rpoN gene, which attenuated membrane integrity presumably by downregulating the phage shock protein operon. These data expand current understanding of genetic, virulence, and antimicrobial resistance characteristics associated with distinct morphotypes in ST11 CRKP.

Genomic Landscape Reveals Chromosomally-Mediated Antimicrobial Resistome and Virulome of a High-Risk International Clone II Acinetobacter baumannii AB073 from Thailand.

This study utilized integrative bioinformatics' tools together with phenotypic assays to understand the whole-genome features of a carbapenem-resistant international clone II Acinetobacter baumannii AB073. Overall, we found the isolate to be resistant to seven antibiotic classes, penicillins, ß-lactam/ß-lactamase inhibitor combinations, cephalosporins, carbapenems, aminoglycosides, fluoroquinolones, and folate pathway antagonists. These resistance phenotypes are related to various chromosomal-located antibiotic resistance determinants involved in different mechanisms such as reduced permeability, antibiotic target protection, antibiotic target alteration, antibiotic inactivation, and antibiotic efflux. IC2 A. baumannii AB073 could not transfer antibiotic resistance by conjugation experiments. Likewise, mobilome analysis found that AB073 did not carry genetic determinants involving horizontal gene transfer. Moreover, this isolate also carried multiple genes associated with the ability of iron uptake, biofilm formation, immune invasion, virulence regulations, and serum resistance. In addition, the genomic epidemiological study showed that AB073-like strains were successful pathogens widespread in various geographic locations and clinical sources. In conclusion, the comprehensive analysis demonstrated that AB073 contained multiple genomic determinants which were important characteristics to classify this isolate as a successful international clone II obtained from Thailand.

sRNA expression profile of KPC-2-producing carbapenem-resistant Klebsiella pneumoniae: Functional role of sRNA51.

The emergence of carbapenem-resistant Klebsiella pneumoniae (CRKP) has significant challenges to human health and clinical treatment, with KPC-2-producing CRKP being the predominant epidemic strain. Therefore, there is an urgent need to identify new therapeutic targets and strategies. Non-coding small RNA (sRNA) is a post-transcriptional regulator of genes involved in important biological processes in bacteria and represents an emerging therapeutic strategy for antibiotic-resistant bacteria. In this study, we analyzed the transcription profile of KPC-2-producing CRKP using RNA-seq. Of the 4693 known genes detected, the expression of 307 genes was significantly different from that of carbapenem-sensitive Klebsiella pneumoniae (CSKP), including 133 up-regulated and 174 down-regulated genes. Both the Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment and Gene Ontology (GO) analysis showed that these differentially expressed genes (DEGs) were mainly related to metabolism. In addition, we identified the sRNA expression profile of KPC-2-producing CRKP for the first time and detected 115 sRNAs, including 112 newly discovered sRNAs. Compared to CSKP, 43 sRNAs were differentially expressed in KPC-2-producing CRKP, including 39 up-regulated and 4 down-regulated sRNAs. We chose sRNA51, the most significantly differentially expressed sRNA in KPC-2-producing CRKP, as our research subject. By constructing sRNA51-overexpressing KPC-2-producing CRKP strains, we found that sRNA51 overexpression down-regulated the expression of acrA and alleviated resistance to meropenem and ertapenem in KPC-2-producing CRKP, while overexpression of acrA in sRNA51-overexpressing strains restored the reduction of resistance. Therefore, we speculated that sRNA51 could affect the resistance of KPC-2-producing CRKP by inhibiting acrA expression and affecting the formation of efflux pumps. This provides a new approach for developing antibiotic adjuvants to restore the sensitivity of CRKP.

[Analysis of the virulence and genetic differences of carbapenem-resistant Acinetobacter baumannii epidemic clones].

Objective: To evaluate the virulence levels of carbapenem-resistant Acinetobacter baumannii ST191, ST195, and ST208, and to analyze the differences in virulence factors among these epidemic clones. Methods: The study involved the genomic sequencing of 233 Acinetobacter baumannii strains that were isolated from the Fifth Medical Center of the Chinese People's Liberation Army General Hospital (North Hospital) between 2011 and 2019. The genomic data was cross-referenced with the Virulence Factor Database (VFDB) to examine the presence of virulence genes in the strains. Furthermore, a Galleria mellonella infection survival model was used to evaluate the virulence levels of the strains, and the association between virulence levels and virulence genes was analyzed. Results: The study included 38 strains of the ST191 clone, 104 strains of the ST195 clone, and 91 strains of the ST208 clone. In the Galleria mellonella infection survival experiment, the average mortality rate for ST191 was 23.0%, with 3 (7.9%) highly virulent strains. For ST195, the average mortality rate was 53.0%, with 34 (32.7%) highly virulent strains. For ST208, the average mortality rate was 47.0%, with 20 (21.9%) highly virulent strains. There was a significant statistical difference in mortality rates between ST191 and ST195 (χ2=13.9, P<0.001) as well as between ST191 and ST208 (χ2=15.2, P<0.001). A comparison of the strains with the VFDB revealed significant differences in the virulence genes carried by the clones. Specifically, the type Ⅵ secretion system-related genes (clpV/tssH, hcp/tssD, tagX, tssA, tssB, tssC, tssE, tssF, tssG, tssK, ssL, tssM) and the sugar transferase gene ACICU_RS00475 were found to be universally absent in ST191 strains (0%) while being prevalent in ST195 (100.0%) and ST208 (>82.0%) strains. Statistical analysis revealed an association between the mortality rate of the clones and the presence of virulence genes(clpV/tssH P<0.001, hcp/tssD P=0.001, tagX P<0.001, tssA P<0.001, tssB P=0.001, tssC P=0.001, tssE P=0.001, tssF P=0.001, tssG P<0.001, tssK P<0.001, tssL P<0.001, tssM P=0.001, ACICU_RS00475 P=0.001). Conclusion: Among the carbapenem-resistant epidemic clones of Acinetobacter baumannii, the ST191 clone shows lower mortality rates in Galleria mellonella, possibly because of the lack of type Ⅵ secretion system and sugar transferase genes.

Characterization and efficacy against carbapenem-resistant Acinetobacter baumannii of a novel Friunavirus phage from sewage.

Carbapenem-resistant Acinetobacter baumannii (CRAB) has become a new threat in recent years, owing to its rapidly increasing resistance to antibiotics and new effective therapies are needed to combat this pathogen. Phage therapy is considered to be the most promising alternative for treating CRAB infections. In this study, a novel phage, Ab_WF01, which can lyse clinical CRAB, was isolated and characterized from hospital sewage. The multiplicity of infection, morphology, one-step growth curve, stability, sensitivity, and lytic activity of the phage were also investigated. The genome of phage Ab_WF01 was 41, 317 bp in size with a GC content of 39.12% and encoded 51 open reading frames (ORFs). tRNA, virulence, and antibiotic resistance genes were not detected in the phage genome. Comparative genomic and phylogenetic analyses suggest that phage Ab_WF01 is a novel species of the genus Friunavirus, subfamily Beijerinckvirinae, and family Autographiviridae. The in vivo results showed that phage Ab_WF01 significantly increased the survival rate of CRAB-infected Galleria mellonella (from 0% to 70% at 48 h) and mice (from 0% to 60% for 7 days). Moreover, after day 3 post-infection, phage Ab_WF01 reduced inflammatory response, with strongly ameliorated histological damage and bacterial clearance in infected tissue organs (lungs, liver, and spleen) in mouse CRAB infection model. Taken together, these results show that phage Ab_WF01 holds great promise as a potential alternative agent with excellent stability for against CRAB infections.

Insights and Opinions of Critical Care Healthcare Professionals in the Management of Carbapenem-resistant Enterobacteriaceae Cases and Antibiotic-Resistant Infections in the Intensive Care Unit Setting: A Survey-Based Approach.

INTRODUCTION: A survey-based approach to managing antibiotic-resistant infections in the intensive care unit (ICU) setting, with a focus on carbapenem-resistant Enterobacteriaceae (CRE) cases, was conducted. Among CRE, New Delhi metallo-ß-lactamase 1 (NDM-1) is a carbapenemase that is resistant to ß-lactam antibiotics and has a broader spectrum of antimicrobial resistance than other carbapenemase types. The article explains that healthcare-associated infections (HAIs) are a significant problem, particularly in low- and middle-income countries, and that carbapenem in combination with other antibiotics are the most potent class of antimicrobial agents effective in treating life-threatening bacterial infections, including those caused by resistant strains. AIM: The survey aimed to gather critical care healthcare professionals (HCPs') opinions on their current practices in managing infections acquired in the hospital and ICU settings, with a focus on CRE cases, specifically NDM-1 and other antibiotic-resistant infections. METHODS: Responses from critical care healthcare professionals, including online surveys and in-person interviews, to gain insights into the management of infections caused by multidrug-resistant bacteria. The findings related to the insights on the prevalence of bacterial flora, clinical experiences on efficacy and safety of meropenem sulbactam ethylenediaminetetraacetic acid (EDTA) (MSE) in CRE cases, and various combination therapies of antibiotics used to treat antibiotic-resistant infections in ICU setting were evaluated. RESULTS: Klebsiella pneumoniae bacteria were the most common bacteria in cultures, followed by Escherichia coli, Pseudomonas aeruginosa, and Acinetobacter baumannii. NDM-1 was the type of carbapenemase found in around 50% of CRE patients. MSE is among the most preferred antibiotics besides colistin, polymyxin B, and ceftazidime avibactum for CRE cases and specifically for NDM-1 cases due to its high rate of efficacy and safety. CONCLUSION: The article concludes with a discussion on the antibiotics used in response to CRE cases, reporting that critical care HCP considers MSE with high efficacy and safe antibiotic combination and was used as both monotherapy and in combination with other antibiotics. The survey highlights the need for exploring and better understanding the role of MSE in the management of CRE infections, especially in NDM-1.

Carbapenem-Resistant Pseudomonas aeruginosa Infection and Mixed Infections Are Risk Factors for Poor Outcome After Lung Transplant.

OBJECTIVES: In this study, we analyzed the effects of carbapenem-resistant Pseudomonas aeruginosa infection and mixed infection on the perioperative prognosis of lung transplant recipients and studied statistics on antibiotic resistance in P aeruginosa. MATERIALS AND METHODS: This was a retrospective casecontrol study. We collected data on lung transplant recipients with combined lower respiratory tract P aeruginosa infection within 48 hours after lung transplant at the China-Japan Friendship Hospital from August 2018 to April 2022. We grouped recipients according to P aeruginosa resistance to carbapenem antibiotics and summarized the clinical characteristics of carbapenem-resistant P aeruginosa infection. We analyzed the effects of carbapenemresistant P aeruginosa infection and mixed infections on all-cause mortality 30 days after lung transplant by Cox regression. We used the Kaplan-Meier method to plot survival curves. RESULTS: Patients in the carbapenem-resistant P aeruginosa group had a higher all-cause mortality rate than those in the carbapenem-sensitive P aeruginosa group at both 7 days (6 patients [22.3%] vs 2 patients [4.5%]; P = .022) and 30 days (12 patients [44.4%] vs 7 patients [15.9%]; P = .003) after lung transplant. In multivariate analysis, both carbapenemresistant P aeruginosa infection and P aeruginosa combined with bacterial infection were independent risk factors for death 30 days after transplant in lung transplant recipients (P < .05). In subgroup analysis, carbapenem-resistant P aeruginosa combined with bacterial infection increased the risk of death 30 days after transplant in lung transplant recipients compared with carbapenem-sensitive P aeruginosa combined with bacterial infection (12 patients [60%] vs 6 patients [19.4%]; P < .001). CONCLUSIONS: Combined lower respiratory tract carbapenem-resistant P aeruginosa infection and P aeruginosa combined with bacterial infection early after lung transplant increased the risk of 30-day mortality after lung transplant.

Cerastecins inhibit membrane lipooligosaccharide transport in drug-resistant Acinetobacter baumannii.

Carbapenem-resistant Acinetobacter baumannii infections have limited treatment options. Synthesis, transport and placement of lipopolysaccharide or lipooligosaccharide (LOS) in the outer membrane of Gram-negative bacteria are important for bacterial virulence and survival. Here we describe the cerastecins, inhibitors of the A. baumannii transporter MsbA, an LOS flippase. These molecules are potent and bactericidal against A. baumannii, including clinical carbapenem-resistant Acinetobacter baumannii isolates. Using cryo-electron microscopy and biochemical analysis, we show that the cerastecins adopt a serpentine configuration in the central vault of the MsbA dimer, stalling the enzyme and uncoupling ATP hydrolysis from substrate flipping. A derivative with optimized potency and pharmacokinetic properties showed efficacy in murine models of bloodstream or pulmonary A. baumannii infection. While resistance development is inevitable, targeting a clinically unexploited mechanism avoids existing antibiotic resistance mechanisms. Although clinical validation of LOS transport remains undetermined, the cerastecins may open a path to narrow-spectrum treatment modalities for important nosocomial infections.

[Carbapenemase Genes, Virulence Genes, and Molecular Epidemiology of Carbapenem-Resistant Klebsiella pneumoniae Derived From Bloodstream Infections]. / è¡€æµæ„ŸæŸ“ç¢³é’éœ‰çƒ¯è€è¯è‚ºç‚Žå ‹é›·ä¼¯èŒçš„è€è¯åŸºå› å’Œæ¯’åŠ›åŸºå› åŠåˆ†å­æµè¡Œç— å­¦ç ”ç©¶.

Objective: To investigate the clinical characteristics and molecular epidemiology of carbapenem-resistant Klebsiella pneumoniae (CRKP) isolated from patients with bloodstream infections in a large tertiary-care general hospital in Southwest China. Methods: A total of 131 strains of non-repeating CRKP were collected from the blood cultures of patients who had bloodstream infections in 2015-2019. The strains were identified by VITEK-2, a fully automated microbial analyzer, and matrix-assisted laser desorption ionization-time of flight (MALDI-TOF) mass spectrometry. The minimum inhibitory concentration (MIC) was determined by microbroth dilution method. The common carbapenemase resistant genes and virulence factors were identified by PCR. Homology analysis was performed by multilocus sequencing typing. Whole genome sequencing was performed to analyze the genomic characteristics of CRKP without carbapenemase. Results: The 131 strains of CRKP showed resistance to common antibiotics, except for polymyxin B (1.6% resistance rate) and tigacycline (8.0% resistance rate). A total of 105 (80.2%) CRKP strains carried the Klebsiella pneumoniae carbapenemase (KPC) resistance gene, 15 (11.4%) strains carried the New Delhi Metallo-ß-lactamase (NDM) gene, and 4 (3.1%) isolates carried both KPC and NDM genes. Sequence typing (ST) 11 (74.0%) was the dominant sequence type. High detection rates for mrkD (96.2%), fimH (98.5%), entB (100%), and other virulence genes were reported. One hypervirulent CRKP strain was detected. The seven strains of CRKP that did not produce carbapenemase were shown to carry ESBL or AmpC genes and had anomalies in membrane porins OMPK35 and OMPK36, according to whole genome sequencing. Conclusion: In a large-scale tertiary-care general hospital, CRKP mainly carries the KPC gene, has a high drug resistance rate to a variety of antibiotics, and possesses multiple virulence genes. Attention should be paid to CRKP strains with high virulence.

Chromosomal integration and plasmid fusion occurring in ST20 carbapenem-resistant Klebsiella pneumoniae isolates coharboring blaNDM-1 and blaIMP-4 induce resistance transmission and fitness variation.

To investigate the epidemiology of ST20 carbapenem-resistant Klebsiella pneumoniae (CRKP) in China, and further explore the genomic characteristics of blaIMP-4 and blaNDM-1 coharboring isolates and plasmid contributions to resistance and fitness. Seven ST20 CRKP isolates were collected nationwide, and antimicrobial susceptibility testing was performed. Antimicrobial resistance genes, virulence genes, and plasmid replicons were identified via whole-genome sequencing, and clonality assessed via core-genome multilocus sequence typing. Furthermore, we found four dual-metallo-ß-lactamases (MBL)-harbouring isolates, the gene location was detected by Southern blotting, and plasmid location analysis showed that blaIMP-4 was located on a separate plasmid, a self-conjugative fusion plasmid, or the bacterial chromosome. These isolates were subjected to long-read sequencing, the presence of blaIMP-4 in different locations was identified by genomic comparison, and transposon units were detected via inverse PCR. We subsequently found that blaIMP-4 on the fusion plasmid and bacterial chromosome was formed via intact plasmid recombination by the IS26 and ltrA, respectively, and the circular transposon unit was related to cointegration, however, blaIMP-4 in different locations did not affect the gene stability. The blaNDM-1-harbouring plasmid contributed to the increased resistance to ß-lactams and shortened survival lag time which was revealed in plasmid cured isolates. In summary, the K. pneumoniae ST20 clone is a high-risk resistant clone. With the use of ceftazidime/avibactam, MBL-positive isolates, especially dual-MBL-harbouring isolates, should be given additional attention.

Carbapenemase genes in clinical and environmental isolates of Acinetobacter spp. from Quito, Ecuador.

Carbapenem-resistant Acinetobacter spp. is associated with nosocomial infections in intensive care unit patients, resulting in high mortality. Although Acinetobacter spp. represent a serious public health problem worldwide, there are a few studies related to the presence of carbapenemases in health care facilities and other environmental settings in Ecuador. The main aim of this study was to characterize the carbapenem-resistant Acinetobacter spp. isolates obtained from four hospitals (52) and from five rivers (27) close to Quito. We used the disc diffusion and EDTA sinergy tests to determine the antimicrobial susceptibility and the production of metallo ß-lactamases, respectively. We carried out a multiplex PCR of gyrB gene and the sequencing of partial rpoB gene to bacterial species identification. We performed molecular screening of nine carbapenem-resistant genes (blaSPM, blaSIM, blaGIM, blaGES, blaOXA-23, blaOXA-24, blaOXA-51, blaOXA-58, and blaOXA-143) by multiplex PCR, followed by identification using sequencing of blaOXA genes. Our findings showed that carbapenem-resistant A. baumannii were the main species found in health care facilities and rivers. Most of the clinical isolates came from respiratory tract samples and harbored blaOXA-23, blaOXA-366, blaOXA-72, blaOXA-65, blaOXA-70, and blaOXA-143-like genes. The river isolates harbored only the blaOXA-51 and probably blaOXA-259 genes. We concluded that the most predominant type of carbapenem genes among isolates were both blaOXA-23 and blaOXA-65 among A. baumannii clinical isolates.

A CRISPR/Cas12a-Based System for Sensitive Detection of Antimicrobial-Resistant Genes in Carbapenem-Resistant Enterobacterales.

Antimicrobial-resistant (AMR) bacteria pose a significant global health threat, and bacteria that produce New Delhi metallo-ß-lactamase (NDM) are particularly concerning due to their resistance to most ß-lactam antibiotics, including carbapenems. The emergence and spread of NDM-producing genes in food-producing animals highlight the need for a fast and accurate method for detecting AMR bacteria. We therefore propose a PCR-coupled CRISPR/Cas12a-based fluorescence assay that can detect NDM-producing genes (blaNDM) in bacteria. Thanks to its designed gRNA, this CRISPR/Cas12a system was able to simultaneously cleave PCR amplicons and ssDNA-FQ reporters, generating fluorescence signals. Our method was found to be highly specific when tested against other foodborne pathogens that do not carry blaNDM and also demonstrated an excellent capability to distinguish single-nucleotide polymorphism. In the case of blaNDM-1 carrying E. coli, the assay performed exceptionally well, with a detection limit of 2.7 × 100 CFU/mL: 100 times better than conventional PCR with gel electrophoresis. Moreover, the developed assay detected AMR bacteria in food samples and exhibited enhanced performance compared to previously published real-time PCR assays. Thus, this novel PCR-coupled CRISPR/Cas12a-based fluorescence assay has considerable potential to improve current approaches to AMR gene detection and thereby contribute to mitigating the global threat of AMR.

Molecular Epidemiology of Carbapenem-Resistant Klebsiella aerogenes in Japan.

Information regarding Klebsiella aerogenes haboring carbapenemase in Japan is limited. A comprehensive nationwide survey was conducted from September 2014 to December 2022, and 67 non-duplicate strains of carbapenem-resistant K. aerogenes were isolated from 57 healthcare facilities in Japan. Through genetic testing and whole-genome sequencing, six strains were found to possess carbapenemases, including imipenemase (IMP)-1, IMP-6, New Delhi metallo-ß-lactamase (NDM)-1, and NDM-5. The strain harboring blaNDM-5 was the novel strain ST709, which belongs to the clonal complex of the predominant ST4 in China. The novel integron containing blaIMP-1 featured the oxacillinase-101 gene, which is a previously unreported structure, with an IncN4 plasmid type. However, integrons found in the strains possessing blaIMP-6, which were the most commonly identified, matched those reported domestically in Klebsiella pneumoniae, suggesting the prevalence of identical integrons. Transposons containing blaNDM are similar or identical to the transposon structure of K. aerogenes harboring blaNDM-5 previously reported in Japan, suggesting that the same type of transposon could have been transmitted to K. aerogenes in Japan. This investigation analyzed mobile genetic elements, such as integrons and transposons, to understand the spread of carbapenemases, highlighting the growing challenge of carbapenem-resistant Enterobacterales in Japan and underscoring the critical need for ongoing surveillance to control these pathogens.

A challenging case of carbapenem resistant Klebsiella pneumoniae-related pyogenic liver abscess with capsular polysaccharide hyperproduction: a case report.

BACKGROUND: Carbapenem-resistant Klebsiella pneumoniae (CRKP) infections are a major public health problem, necessitating the administration of polymyxin E (colistin) as a last-line antibiotic. Meanwhile, the mortality rate associated with colistin-resistant K. pneumoniae infections is seriously increasing. On the other hand, importance of administration of carbapenems in promoting colistin resistance in K. pneumoniae is unknown. CASE PRESENTATION: We report a case of K. pneumoniae-related pyogenic liver abscess in which susceptible K. pneumoniae transformed into carbapenem- and colistin-resistant K. pneumoniae during treatment with imipenem. The case of pyogenic liver abscess was a 50-year-old man with diabetes and liver transplant who was admitted to Abu Ali Sina Hospital in Shiraz. The K. pneumoniae isolate responsible for community-acquired pyogenic liver abscess was isolated and identified. The K. pneumoniae isolate was sensitive to all tested antibiotics except ampicillin in the antimicrobial susceptibility test and was identified as a non-K1/K2 classical K. pneumoniae (cKp) strain. Multilocus sequence typing (MLST) identified the isolate as sequence type 54 (ST54). Based on the patient's request, he was discharged to continue treatment at another center. After two months, he was readmitted due to fever and progressive constitutional symptoms. During treatment with imipenem, the strain acquired blaOXA-48 and showed resistance to carbapenems and was identified as a multidrug resistant (MDR) strain. The minimum inhibitory concentration (MIC) test for colistin was performed by broth microdilution method and the strain was sensitive to colistin (MIC < 2 µg/mL). Meanwhile, on blood agar, the colonies had a sticky consistency and adhered to the culture medium (sticky mucoviscous colonies). Quantitative real-time PCR and biofilm formation assay revealed that the CRKP strain increased capsule wzi gene expression and produced slime in response to imipenem. Finally, K. pneumoniae-related pyogenic liver abscess with resistance to a wide range of antibiotics, including the last-line antibiotics colistin and tigecycline, led to sepsis and death. CONCLUSIONS: Based on this information, can we have a theoretical hypothesis that imipenem is a promoter of resistance to carbapenems and colistin in K. pneumoniae? This needs more attention.

Difficult-to-treat (DTR) Pseudomonas aeruginosa harboring Verona-Integron metallo-ß-lactamase (blaVIM): infection management and molecular analysis.

Pseudomonas aeruginosa harboring Verona Integron-encoded metallo-ß-lactamase enzymes (VIM-CRPA) have been associated with infection outbreaks in several parts of the world. In the US, however, VIM-CRPA remain rare. Starting in December 2018, we identified a cluster of cases in our institution. Herein, we present our epidemiological investigation and strategies to control/manage these challenging infections. This study was conducted in a large academic healthcare system in Miami, FL, between December 2018 and January 2022. Patients were prospectively identified via rapid molecular diagnostics when cultures revealed carbapenem-resistant P. aeruginosa. Alerts were received in real time by the antimicrobial stewardship program and infection prevention teams. Upon alert recognition, a series of interventions were performed as a coordinated effort. A retrospective chart review was conducted to collect patient demographics, antimicrobial therapy, and clinical outcomes. Thirty-nine VIM-CRPA isolates led to infection in 21 patients. The majority were male (76.2%); the median age was 52 years. The majority were mechanically ventilated (n = 15/21; 71.4%); 47.6% (n = 10/21) received renal replacement therapy at the time of index culture. Respiratory (n = 20/39; 51.3%) or bloodstream (n = 13/39; 33.3%) were the most common sources. Most infections (n = 23/37; 62.2%) were treated with an aztreonam-avibactam regimen. Six patients (28.6%) expired within 30 days of index VIM-CRPA infection. Fourteen isolates were selected for whole genome sequencing. Most of them belonged to ST111 (12/14), and they all carried blaVIM-2 chromosomally. This report describes the clinical experience treating serious VIM-CRPA infections with either aztreonam-ceftazidime/avibactam or cefiderocol in combination with other agents. The importance of implementing infection prevention strategies to curb VIM-CRPA outbreaks is also demonstrated.

Carbapenem-resistant Gram-negative bacteria (CR-GNB) in ICUs: resistance genes, therapeutics, and prevention - a comprehensive review.

Intensive care units (ICUs) are specialized environments dedicated to the management of critically ill patients, who are particularly susceptible to drug-resistant bacteria. Among these, carbapenem-resistant Gram-negative bacteria (CR-GNB) pose a significant threat endangering the lives of ICU patients. Carbapenemase production is a key resistance mechanism in CR-GNB, with the transfer of resistance genes contributing to the extensive emergence of antimicrobial resistance (AMR). CR-GNB infections are widespread in ICUs, highlighting an urgent need for prevention and control measures to reduce mortality rates associated with CR-GNB transmission or infection. This review provides an overview of key aspects surrounding CR-GNB within ICUs. We examine the mechanisms of bacterial drug resistance, the resistance genes that frequently occur with CR-GNB infections in ICU, and the therapeutic options against carbapenemase genotypes. Additionally, we highlight crucial preventive measures to impede the transmission and spread of CR-GNB within ICUs, along with reviewing the advances made in the field of clinical predictive modeling research, which hold excellent potential for practical application.

Molecular Characterization of Class 1 Integrons and Carbapenem-Resistant Genes in Enterobacter cloacae Complex Isolates.

Enterobacter cloacae complex (ECC) widely exists in the hospital environment and is one of the important conditional pathogens of hospital-acquired infection. To investigate the distribution of integrons and carbapenem-resistant genes in clinical ECC, 70 isolates of ECC from non-sputum specimens were collected. Class 1 and class 2 integron integrase gene intI1 and intI2, as well as common carbapenem-resistant genes, blaKPC, blaVIM, blaIMP, blaNDM, blaGES, and blaOXA-23, were screened. Gene cassette arrays and common promoters of class 1 integron together with subtypes of carbapenem-resistant genes were determined by sequencing. Resistant rates to commonly used antimicrobial agents between class 1 integron-positive and integron-negative ECC isolates were analyzed. The whole-genome of blaNDM-7 harboring Enterobacter hormaechei was sequenced and the sequence around blaNDM-7 was analyzed. Twenty isolates were positive for intI1. Nineteen different antimicrobial-resistant gene cassettes and 11 different gene cassette arrays, including aadA22-lnuF, were detected in this study. Common promoters of class 1 integron PcH1, PcW, PcW-P2, and PcH2 were detected in 12, 4, 3, and 1 isolates, respectively. The rates of antimicrobial resistance of intI1-positive isolates were higher than those of intI1-negative isolates to clinical commonly used antimicrobial agents. Carbapenem-resistant genes blaKPC-2, blaNDM-1, blaNDM-2, and blaNDM-7 were detected in 2, 1, 1, and 1 isolates, respectively. blaNDM-7 was located between bleMBL and IS5. To the best of our knowledge, this study reported for the first time of blaNDM-7 in ECC isolate in China.

Biodiversity of carbapenem-resistant bacteria in clinical samples from the Southwest Amazon region (Rondônia/Brazil).

Brazil is recognized for its biodiversity and the genetic variability of its organisms. This genetic variability becomes even more valuable when it is properly documented and accessible. Understanding bacterial diversity through molecular characterization is necessary as it can improve patient treatment, reduce the length of hospital stays and the selection of resistant bacteria, and generate data for health and epidemiological surveillance. In this sense, in this study, we aimed to understand the biodiversity and molecular epidemiology of carbapenem-resistant bacteria in clinical samples recovered in the state of Rondônia, located in the Southwest Amazon region. Retrospective data from the Central Public Health Laboratories (LACEN/RO) between 2018 and 2021 were analysed using the Laboratory Environment Manager Platform (GAL). Seventy-two species with carbapenem resistance profiles were identified, of which 25 species carried at least one gene encoding carbapenemases of classes A (blaKPC-like), B (blaNDM-like, blaSPM-like or blaVIM-like) and D (blaOXA-23-like, blaOXA-24-like, blaOXA-48-like, blaOXA-58-like or blaOXA-143-like), among which we will highlight Klebsiella pneumoniae, Pseudomonas aeruginosa, Acinetobacter baumannii, Serratia marcescens, and Providencia spp. With these results, we hope to contribute to the field by providing epidemiological molecular data for state surveillance on bacterial resistance and assisting in public policy decision-making.