UNASSIGNED: The emergence of carbapenem-resistant Klebsiella pneumoniae (CRKP) has garnered international concern due to its significant antibiotic resistance. Notably, children exhibit distinct resistance mechanisms compared to adults, necessitating a differential approach to antibiotic selection. A thorough analysis of CRKP\'s epidemiology and drug resistance mechanisms is essential for establishing a robust foundation for clinical anti-infection strategies and precise prevention and control measures.
UNASSIGNED: This study involved the collection of 31 non-repetitive strains from pediatric and adult patients at a tertiary hospital in China, spanning from July 2016 to July 2022, testing for resistance genes, antimicrobial susceptibility, and homology analysis.
UNASSIGNED: Infants (0-1 year) were the largest pediatric CRKP group, with 61.3% of cases. The neonatal intensive care unit (NICU) and pediatrics were the main departments affected. Adults with CRKP had a mean age of 67 years, with the highest prevalence in neurology and emergency ICU. Antimicrobial susceptibility testing revealed that adult CRKP strains exhibited higher resistance to amikacin, ciprofloxacin, cotrimoxazole, and aztreonam compared to pediatric strains. Conversely, pediatric strains showed a higher rate of resistance to ceftazidime/avibactam. The predominant resistance genes identified were bla NDM-5 in children (58.1%) and bla KPC-2 in adults (87.1%), with over 93% of both groups testing positive for extended-spectrum beta-lactamase (ESBL) genes. Multilocus Sequence Typing (MLST) indicated ST2735 and ST11 as the predominant types in children and adults, respectively. Pulsed-field gel electrophoresis (PFGE) identified clonal transmission patterns of ST11 bla KPC-2 and ST15 bla OXA-232 across both age groups. Notably, this study reports the first instance of ST1114-type CRKP co-producing bla NDM-5 and bla OXA-181 in the NICU.
UNASSIGNED: This study reveals distinct resistance mechanisms and epidemiology in CRKP from children and adults. The identified clonal transmission patterns emphasize the need for improved infection control to prevent the spread of resistant strains.

BACKGROUND: Carbapenemase-producing Klebsiella pneumoniae (CRKP) presents a significant challenge to antimicrobial therapy, especially when compounded by resistance to colistin. The objective of this study was to explore molecular epidemiological insights into strains of clinical K. pneumoniae that produce carbapenemases and exhibit resistance to colistin. Eighty clinical isolates of CRKP were obtained from Milad Hospital in Tehran, Iran. Antimicrobial susceptibility and colistin broth disk elution were determined. PCR assays were conducted to examine the prevalence of resistance-associated genes, including blaKPC, blaIMP, blaVIM, blaOXA-48, blaNDM and mcr-1 to -10. Molecular typing (PFGE) was used to assess their spread.
RESULTS: Colistin resistance was observed in 27 isolates (33.7%) using the Broth Disk Elution method. Among positive isolates for carbapenemase genes, the most frequent gene was blaOXA-48, identified in 36 strains (45%). The mcr-1 gene was detected in 3.7% of the obtained isolates, with none of the other of the other mcr genes detected in the studied isolates.
CONCLUSIONS: To stop the spread of resistant K. pneumoniae and prevent the evolution of mcr genes, it is imperative to enhance surveillance, adhere rigorously to infection prevention protocols, and implement antibiotic stewardship practices.

Novel beta-lactams/beta-lactamase inhibitors (BIBLI) combinations are commercially available and they have been used for treating carbapenem-resistant Klebsiella pneumoniae (CRKP) infections. Continuous surveillance of susceptibility profile and resistance mechanisms identification are necessary to monitor the evolution of resistance as these agents are used. The purpose of this study was to evaluate susceptibility rates to ceftazidime/avibactam, imipenem/relebactam and meropenem/vaborbactam in CRKP isolates from patients with bloodstream infection screened for a randomized clinical trial in Brazil. Minimum inhibitory concentration (MIC) was determined by gradient diffusion strip method for meropenem, ceftazidime/avibactam, imipenem/relebactam and meropenem/vaborbactam. Carbapenemase genes were detected by multiplex qPCR. KPC-producing isolates showing resistance to any BLBLI and NDM-producing isolates showing susceptibility to any BLBLI were further submitted to whole genome sequencing. From a total of 69 CRKP isolates, 39 were positive for blaKPC, 19 for blaNDM and 11 for blaKPC and blaNDM. KPC-producing isolates demonstrated susceptibility rates above 94% for all BLBLI. Two isolates with resistance to meropenem/vaborbactam showed a Gly and Asp duplication at OmpK36 protein and truncated ompK35 genes. All NDM-producing isolates, including KPC and NDM coproducers, demonstrated susceptibility rates for ceftazidime/avibactam, imipenem/relebactam and meropenem/vaborbactam of 0%, 9.1 to 21.1% and 9.1 to 26.3%, respectively. Five NDM-producing isolates that presented susceptibility to BLBLI also demonstrated alterations in porins. This study demonstrated that, although high susceptibility rates to the BLBLI were found, KPC-2 isolates can also demonstrate resistance due to porin mutations. Additionally, NDM-1 isolates can demonstrate susceptibility in vitro to the BLBLI.

Carbapenemases, a class of enzymes specialized in the hydrolysis of carbapenems, represent a significant threat to global public health. These enzymes are classified into different Ambler\'s classes based on their active sites, categorized into classes A, D, and B. Among the most prevalent types are IMI/NMC-A, KPC, VIM, IMP, and OXA-48, commonly associated with pathogenic species such as Acinetobacter baumannii, Klebsiella pneumoniae, and Pseudomonas aeruginosa. The emergence and dissemination of carbapenemase-producing bacteria have raised substantial concerns due to their ability to infect humans and animals (both companion and food-producing) and their presence in environmental reservoirs. Adopting a holistic One Health approach, concerted efforts have been directed toward devising comprehensive strategies to mitigate the impact of antimicrobial resistance dissemination. This entails collaborative interventions, highlighting proactive measures by global organizations like the World Health Organization, the Center for Disease Control and Prevention, and the Food and Agriculture Organization. By synthesizing the evolving landscape of carbapenemase epidemiology in Portugal and tracing the trajectory from initial isolated cases to contemporary reports, this review highlights key factors driving antibiotic resistance, such as antimicrobial use and healthcare practices, and underscores the imperative for sustained vigilance, interdisciplinary collaboration, and innovative interventions to curb the escalating threat posed by antibiotic-resistant pathogens. Finally, it discusses potential alternatives and innovations aimed at tackling carbapenemase-mediated antibiotic resistance, including new therapies, enhanced surveillance, and public awareness campaigns.

BACKGROUND: This study aimed to assess the performance of three commercial panels, the ERIC Carbapenem-Resistant Enterobacteriaceae Test (ERIC CRE test), the NG-Test CARBA 5 (NG CARBA 5), and the BD Phoenix CPO Detect Panel (CPO panel), for the detection of main types of carbapenemases among carbapenem-resistant Enterobacterales (CRE).
METHODS: We collected 502 isolates of carbapenem-resistant Enterobacterales (CRE) demonstrating intermediate or resistant profiles to at least one carbapenem antibiotic (ertapenem, imipenem, meropenem, or doripenem). Carbapenemase genes and their specific types were identified through multiplex PCR and sequencing methods. Subsequently, the ERIC CRE test, CPO panel, and NG CARBA 5 assay were conducted on these isolates, and the results were compared with those obtained from multiplex PCR.
RESULTS: The results indicated that the ERIC CRE test exhibited an overall sensitivity and specificity of 98.1% and 93.6%, respectively, which were comparable to 99.1% and 90.6% for the NG CARBA 5. However, the CPO panel demonstrated a sensitivity of only 56.2% in identifying Ambler classes, exhibiting the poorest sensitivity for class A. Moreover, while the ERIC CRE test outperformed the NG CARBA 5 in identifying multi-gene isolates with multiple carbapenemase-encoding genes, the CPO panel failed to accurately classify these isolates.
CONCLUSIONS: Our findings support the utilization of the ERIC CRE test as one of the methods for detecting carbapenemases in clinical laboratories. Nonetheless, further optimization is imperative for the CPO panel to enhance its accuracy in determining carbapenemase classification and address limitations in detecting multi-gene isolates.

UNASSIGNED: Meropenem-vaborbactam is a recent and promising option for the treatment of KPC-producing Klebsiella pneumoniae (KPC-Kp) infections, including those resistant to ceftazidime-avibactam.
UNASSIGNED: We conducted a retrospective analysis of observational data from 19 Italian hospitals on use and outcomes of patients treated with meropenem-vaborbactam for at least ≥24 hours for KPC-Kp infections. Crude and propensity-weighted multiple Cox regression models were performed to ascertain risk factors independently associated with 30-day mortality.
UNASSIGNED: The cohort included 342 adults with bloodstream infections (n = 172) and nonbacteremic infections (n = 170), of which 107 were lower respiratory tract infections, 30 were complicated urinary tract infections, and 33 were infections involving other sites. Most infections (62.3%) were managed with meropenem-vaborbactam monotherapy, or in combination with at least 1 other active drug (usually fosfomycin, tigecycline, or gentamicin) (37.7%). The 30-day mortality rate was 31.6% (108/342). In multiple Cox regression model, 30-day mortality was independently associated with septic shock at infection onset, Charlson comorbidity index ≥ 3, dialysis, concomitant COVID-19, and INCREMENT score ≥ 8. Administration of meropenem-vaborbactam within 48 hours from infection onset was a negative predictor of mortality. All predictors, except administration of meropenem-vaborbactam within 48 hours, remained significant when the multiple Cox regression model was repeated after adjustment for the propensity score for receipt of combination therapy.
UNASSIGNED: Despite the limits of a retrospective study, the data derived from this multicenter cohort provide additional evidence on the efficacy of meropenem-vaborbactam in treating severe KPC-Kp infections, even when used as monotherapy.

β-Lactamases are bacterial enzymes that inactivate β-lactam antibiotics and, as such, are the most prevalent cause of antibiotic resistance in Gram-negative bacteria. The ever-increasing production and worldwide dissemination of bacterial strains producing carbapenemases is currently a global health concern. These enzymes catalyze the hydrolysis of carbapenems - the β-lactam antibiotics with the broadest spectrum of activity that are often considered as drugs of last resort. The incidence of carbapenem-resistant pathogens such as Pseudomonas aeruginosa, Acinetobacter baumannii and carbapenemase or extended spectrum beta-lactamase (ESBL)-producing Enterobacterales, which are frequent in clinical settings, is worrisome since, in some cases, no therapies are available. These include all metallo-β-lactamases (VIM, IMP, NDM, SMP, and L1), and serine-carbapenemases of classes A (KPC, SME, IMI, and GES), and of classes D (OXA-23, OXA-24/40, OXA-48 and OXA-58). Consequently, the early diagnosis of bacterial strains harboring carbapenemases is a pivotal task in clinical microbiology in order to track antibiotic bacterial resistance and to improve the worldwide management of infectious diseases. Recent research efforts on the development of chromogenic and fluorescent chemical sensors for the specific and sensitive detection and quantification of β-lactamase production in multidrug-resistant pathogens are summarized herein. Studies to circumvent the main limitations of the phenotypic and molecular methods are discussed. Recently reported chromogenic and fluorogenic cephalosporin- and carbapenem-based β-lactamase substrates will be reviewed as alternative options to the currently available nitrocefin and related compounds, a chromogenic cephalosporin-based reagent widely used in clinical microbiology laboratories. The scope of these new chemical sensors, along with the synthetic approaches to synthesize them, is also summarized.

BACKGROUND: Carbapenem-resistant Pseudomonas aeruginosa (CRPA) is a serious threat to public health. Globally, carbapenemases-producing CRPA isolates mainly belong to \'high-risk\' clones; however, the molecular epidemiology of CRPA isolates circulating in Chile are scarce, where this pathogen is the main aetiological agent of ventilator-associated pneumonia.
OBJECTIVE: To characterize the phylogenomics and molecular features of ST654 CRPA isolates collected in Chile between 2016 - 2022.
METHODS: 89 CRPA isolates collected in different Chilean hospitals from clinical specimens between 2005 and 2022 were analyzed. Antibiotic susceptibility tests and carbapenemases production were carried out on the CRPA ST654 isolates. Also, they were subjected to whole-genome sequencing (WGS) from which in silico analyses were performed.
RESULTS: Thirty-four strains (38.2%) belonged to the ST654 \'high risk\' clone, being the most predominant lineage of the collection. Most of these isolates belonged to a sub-clade including KPC-producers that also clustered with strains from Argentina and the USA, whereas few VIM and NDM co-producers clustered in two different smaller sub-clades. The isolates exhibited a broad resistome encompassing genes mediating resistance to several other clinically relevant drugs. Additionally, all the 34 ST654 isolates were ExoS+ as a virulence factor and associated to the O4-serotype.
CONCLUSIONS: Our report represents the most comprehensive phylogenomic study of CRPA \'high risk\' clone ST654 to date. Our analyses suggest that this lineage is undergoing a divergent evolutionary path in Chile, since most of the isolates were KPC-producers and were O4-serotype, differing from previous descriptions, which underline the relevance of performing molecular surveillance on this pathogen.

BACKGROUND: Acinetobacter baumannii is a serious health concern worldwide, causing high mortality rates and limited medical therapy options. Carbapenem resistance is a significant problem in Acinetobacter baumannii isolates. The synthesis of acquired carbapenemases, such as oxacillinases, IMP, NDM, VIM, and KPC enzymes, causes carbapenem resistance.
METHODS: A total of 106 non-repetitive, Acinetobacter baumannii isolates were collected from four major hospitals in Bahrain including 78 carbapenem-resistant Acinetobacter baumannii (CRAB), and 28 carbapenem-susceptible Acinetobacter baumannii (CSAB) isolates. Three phenotypic tests were investigated in this study: including CARBA NP, modified carbapenem inactivation method (mCIM)/EDTA-CIM (eCIM), and modified Hodge test (MHT).
RESULTS: CARBA NP was positive in 50 tested CRAB isolates (100%), and the sensitivity was 100%. The MHT was positive in 73/106 isolates (68.8%), while the sensitivity and specificity of the MHT were 77.6% and 100%. Moreover, only 38/106 (35.8%) isolates were positive for mCIM/eCIM. The sensitivity and specificity of mCIM were 40.4% and 100%.
CONCLUSIONS: CARBA NP was ideal for phenotypic detection of carbapenemase production, followed by MHT. The m/eCIM demonstrated a lower detection rate in CRAB. Consequently, combining tests would be more accurate. The mCIM/eCIM can easily distinguish between MBLs and serine-carbapenemases due to the frequent co-production of these enzymes in A. baumannii. In hospital setups where molecular characterization tests are not available, CARBA NP seems to be an alternative test in combination with MHT or mCIM/eCIM.

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