Carbapenem Resistance Research Articles

An Economic Model to Assess the Cost Impact of Using Xpert Carba-R to Screen Carbapenemase-Producing Enterobacterales in Comparison with Standard of Care, in a National Health Service Setting.

Carbapenemase-producing Enterobacterales (CPE) are bacteria that produce carbapenemases, enzymes that destroy carbapenem antibiotics and result in carbapenem resistance. Early identification of individuals who have been colonised or infected is important to correctly implement infection prevention and control procedures. Chromogenic media culture is traditionally the most common method of screening for high-risk patients. However, there is a long wait for results, which has substantial cost and operational implications. Xpert Carba-R is a rapid molecular test that provides CPE screening results in 50min. This study aimed to assess the cost impact of high-risk CPE screening with Xpert Carba-R compared with media culture. An economic model was developed using a probabilistic cost-comparison approach to estimate the costs associated with Xpert Carba-R, from a National Health Service and personal social services perspective. The model cohort was individuals at high risk of CPE colonisation and used an 8.30-day mean time horizon for all patients to cover hospitalisation time, with an extra 5.80days added for patients that were truly colonised to cover the time they would spend in isolation (14.10-day time horizon overall). Deterministic sensitivity analysis and scenario analysis were used to determine the robustness of the findings. The model found that Xpert Carba-R is cost saving compared with media culture, with incremental cost savings of £818.28 per person. Despite greater technology costs, there are cost savings associated with preventing unnecessary isolation. The analysis found Xpert Carba-R to be cost saving compared with media culture for CPE screening in high-risk patients. The model did not explore onwards transmission or the opportunity cost of releasing isolation spaces, so the cost savings are likely to be far greater than those demonstrated in this study.

The ongoing antibiotic resistance and carbapenemase encoding genotypes surveillance. The first quarter report of the INVIFAR network for 2024.

Antimicrobial resistance surveillance plays an important role in generating information about the prevalence of resistant microorganisms. In this study, we summarize a surveillance of antimicrobial resistance and carbapenemase-encoding genes for selected pathogens in Mexican healthcare centers. Databases of identification and susceptibility results collected from January 1 to March 31, 2024, from forty-one centers were gathered and analyzed using the WHONET software. Some relevant gram-negatives and gram-positives, which were isolated from relevant clinical specimens were included. Isolates were stratified by patient´s age, clinical specimens, and site of attention, and were classified as multidrug-resistant (MDR). Clinical isolates were collected from January 1 to June 30 and were genotyped for carbapenemase-encoding genes by a polymerase chain reaction test. In total, 8 708 strains were included. Escherichia coli had a higher resistance to carbapenems (p < 0.05) in the 0-17 years group and Klebsiella pneumoniae (p = 0.017), Pseudomonas aeruginosa, and Acinetobacter baumannii (p < 0.05) in the 18-59 years group. P. aeruginosa had higher resistance to ceftazidime-avibactam, ceftolozane-tazobactam, cefepime, and imipenem (p < 0.05) in the 18-59 years group. K. pneumoniae had the highest resistance to carbapenems (p < 0.05) and cefepime (p < 0.001) in clinical isolates recovered from blood. For P. aeruginosa, the highest resistance to cefepime (p = 0.012) and ceftazidime (p < 0.018) was seen in isolates from urine. For Staphylococcus aureus, a higher resistance was observed for cefoxitin in lower respiratory tract specimens (p < 0.05). E. coli had the highest resistance to carbapenems (p < 0.01), and P. aeruginosa for ceftazidime (p = 0.005), cefepime (p = 0.003), piperacillin-tazobactam (p = <0.01), IPM (p = 0.006), and meropenem (p = <0.01) in clinical isolates recovered from patients in the intensive care unit (ICU). For K. pneumoniae, the highest resistance to ertapenem was observed in clinical isolates from the ICU area (p < 0.035). Finally, 67.9% of A. baumannii and 53.8% of E. coli strains were Multidrug-resistant. Candida albicans isolated from blood had susceptibility to caspofungin 100% and 90.2% for voriconazole. Regarding E. coli non-susceptible to meropenem, 16 (59.2%) were carriers of blaNDM, and the blaKPC gene was detected in 2 (40%) strains of K. pneumoniae. In conclusion, carbapenem resistance was higher for E. coli in the 0-17 years group and for K. pneumoniae, P. aeruginosa, and A. baumannii in the 18-59 years group. K. pneumoniae has the highest resistance to carbapenems in blood isolates and the ICU area. E. coli and P. aeruginosa had the highest carbapenem resistance in the intensive care unit. A high multidrug resistance was observed for A. baumannii and E. coli strains. A high susceptibility to caspofungin and voriconazole was observed for Candida albicans collected from blood.

Diagnostic algorithm for the detection of carbapenemases and extended-spectrum β-lactamases in carbapenem-resistant Pseudomonas aeruginosa.

Pseudomonas aeruginosa can acquire carbapenem resistance through various mechanisms, including genomic mutations leading to the overexpression of efflux pumps, intrinsic AmpC-β-lactamase, and/or reduced permeability, and/or through the acquisition of plasmid-mediated carbapenemases and/or extended-spectrum-β-lactamases (ESBLs). Unfortunately, carbapenemase/ESBL-producing-carbapenem-resistant-P. aeruginosa (CP/ESBL-CRPA) cannot be differentiated from non-CP/ESBL-CRPA based solely on susceptibility testing results of conventional β-lactam (BL)-antibiotics. Knowing that these two groups display different activity profiles toward novel BL/β-lactamase-inhibitor (BLI) combinations, we developed and verified a cost-effective and easy-to-use diagnostic algorithm for screening and differentiation of carbapenemase and ESBL production in CRPA. We determined disc diffusion inhibition zones and gradient strip minimal inhibitory concentration values of 136 whole-genome-sequenced CRPA (70 metallo-β-lactamase-[MBL-], 1 GES-5-, 1 KPC-2-, 12 ESBL-, and 53 AmpC-hyper-producing isolates). We used the following BL-BLI combinations: ceftolozane-tazobactam (C-T), ceftazidime-avibactam, imipenem-relebactam (I-R), meropenem-vaborbactam, cefepime-enmetazobactam (C-E), and aztreonam-avibactam. We also included a lateral flow immunoassay (Carba-5, NG-Biotech) for confirmation of MBL production and double disc synergy testing (DDST) to improve ESBL detection. C-T was the most effective screening antibiotic for distinguishing MBL and ESBL producers from AmpC-hyperproducing CRPA, achieving a sensitivity of 100% for both MBL and ESBL producers. I-R reliably confirmed MBL production in C-T positive screened CRPAs, with a sensitivity of 92.8% and specificity of 100%. Incorporating Carba-5 into the phenotypic algorithm improved sensitivity for confirming MBL production to 100%. For the remaining C-T positive but I-R negative isolates, C-E showed 75% sensitivity and 78.6% specificity in detecting ESBL production. The DDST further confirmed ESBL production in six out of nine ESBL producers (66.6%). In conclusion, we established a simple and cost-effective diagnostic algorithm, enabling screening and confirmation of carbapenemase and ESBL production in CRPA.IMPORTANCECarbapenem-resistant Pseudomonas aeruginosa (CRPA) is a major global health threat, and rapid identification of its resistance mechanisms is crucial for effective treatment and infection control. Differentiating between carbapenemase-producing (CP), extended-spectrum β-lactamase-producing (ESBL), and AmpC-hyperproducing CRPA is challenging, as conventional susceptibility testing cannot reliably distinguish these resistance mechanisms. Our study presents a simple, cost-effective, and easy-to-implement phenotypic diagnostic algorithm that enables accurate screening and confirmation of CP and ESBL production in CRPA. This method is particularly valuable for laboratories lacking access to molecular diagnostics, as it provides a practical alternative for routine testing. By facilitating the early detection of resistant P. aeruginosa strains, this approach has the potential to improve patient outcomes, optimize antimicrobial therapy, and enhance global surveillance efforts against multidrug-resistant pathogens.

Performance of disk diffusion, gradient test, and VITEK 2 for carbapenem susceptibility testing in OXA-48-like carbapenemase-producing Enterobacterales: a comparative study.

This study aimed to compare the performance of disk diffusion, gradient test (ETEST), and VITEK 2 (AST-N223, AST-N428, AST-N432 cards) antibiotic susceptibility testing methods with the reference broth microdilution (BMD) for carbapenem susceptibility in OXA-48-like carbapenemase-producing Enterobacterales (CPE). A total of 107 CPE and 142 controls (Enterobacterales that do not produce any type of carbapenemases), all molecularly characterized by whole-genome sequencing, were tested for carbapenem susceptibility using BMD and derivative methods. Essential agreement (EA), categorical agreement (CA), major error, very major error, and bias were evaluated. In the OXA-48-like group, resistance frequencies by BMD for ertapenem, imipenem, and meropenem were 86.9%, 12.1%, and 10.3%, respectively. For OXA-48-like CPE, ETEST showed the highest EA among all methods for meropenem (100/107, 93.5%) and ertapenem (99/107, 92.5%), while EA for VITEK 2 cards were <90%. In contrast, for imipenem, VITEK 2 AST-N428 performed best with an EA of 95/105 (90.5%). CA was higher for ertapenem across all methods (93.5%-98.1%) compared to imipenem (59.8%-81.4%) and meropenem (78.8%-95.3%). The highest CA was achieved with ETEST for ertapenem and meropenem, and with VITEK 2 AST-N223 for imipenem. Significant variability was observed across different tests in resistance frequencies, MICs, EA, and CA for the OXA-48-like group. Ertapenem was the most useful carbapenem for detecting resistance in OXA-48-like CPE across all methods. Laboratories should be aware that susceptibility testing of imipenem leads to more erroneous results compared to the other carbapenems when using derivative methods. Additionally, most derivative methods tend to overcall carbapenem resistance in OXA-48-like CPE.IMPORTANCEOXA-48-like is the most frequent carbapenemase in western Europe, and both its rapid spread and its challenging-to-detect nature are a particular concern for adequate treatment and infection control purposes. Accurate determination of carbapenem minimal inhibitory concentrations (MICs) is of utmost importance, both for the selection of the best therapy and as a marker for carbapenemase detection. However, the performance of derivative susceptibility testing methods is unclear for OXA-48-like isolates. Our study reports on the varying performance of carbapenem susceptibility testing by disk diffusion, gradient test (ETEST), and VITEK 2 in OXA-48-like-producing Enterobacterales. The results of the present study can help to inform about the limitations of current susceptibility testing methods and serve to improve MIC determination in these challenging isolates.

The causes and outcomes of nosocomial meningitis by pathogens for which new antibiotics are urgently needed

BackgroundIn 2017, WHO published a list of bacteria for which new antibiotics are urgently needed. The main bacteria are common causes of nosocomial meningitis. The key focuses are carbapenem resistance, vancomycin resistance, methicillin resistance, and extended-spectrum beta-lactamase (ESBL) production. There are a limited number of appropriate drugs to treat nosocomial meningitis due to resistance and permeability of drugs, we aimed to discuss the urgency by analyzing the causes and related outcomes of antimicrobial resistance in the pathogens.MethodsWe collected 333 patients in whom 854 pathogens were isolated. Poor outcome was defined as a Glasgow Outcome Scale of 1–3. The adjusted analysis of risk factors for poor outcomes was performed using a generalized linear model.ResultsThe main pathogens were Enterobacteriaceae (n = 186, 21.8%), A. baumannii (n = 66, 7.7%), S. aureus (n = 38, 4.4%), E. faecium (n = 27, 3.2%), and P. aeruginosa (n = 16, 1.9%). Vancomycin resistance was found in 0% (0/38) of S. aureus and 22.2% (6/27) of E. faecium. Carbapenem resistance was found in 35.5% (16/186) of Enterobacteriaceae, 80.3% (53/66) of A. baumannii and 37.5% (6/16) of P. aeruginosa. ESBL production occurred in 54.8% (102/186) of Enterobacteriaceae and methicillin resistance occurred in 39.5% (15/38) of S. aureus. Additionally, 136 (40.8%) cases had poor outcomes. Vancomycin or carbapenem resistance (relative risk 1.98, 95% confidence interval [1.72–4.12], p < 0.001) and ESBL production or methicillin resistance (relative risk 1.60, 95% confidence interval [1.10–3.07], p = 0.020) were risk factors for poor outcomes.ConclusionIn nosocomial meningitis, drug-resistant A. baumannii and Enterobacteriaceae were predominant, requiring urgent development of new antimicrobials for treatment.Clinical trialNot applicable.

Genomic analysis of carbapenemase-encoding plasmids and antibiotic resistance in carbapenem-resistant Klebsiella pneumoniae isolates from Vietnam, 2021.

Carbapenem resistance in gram-negative rods is increasing in low- and middle-income countries. We conducted a single-center study to identify carbapenemase-encoding plasmids in carbapenem-resistant Klebsiella pneumoniae isolates causing human infections in Vietnam. The secondary objective was to investigate the prevalence of multidrug-resistant (MDR) and hypervirulent K. pneumoniae in this setting. Our genomic analysis study characterized 105 of 245 clinical K. pneumoniae isolates at the 108 Military Hospital in Hanoi, Vietnam, collected from intensive care unit and regular wards between 1 January 2021 and 31 December 2021. All isolates were characterized using long- and short-read sequencing, followed by hybrid assembly. Comprehensive genomic analysis was performed to identify carbapenemase-encoding plasmids, complemented by extended antibiotic susceptibility testing for commonly used and novel antibiotics. We observed a high prevalence of NDM-4-related carbapenem resistance (30.5%, 32/105) mostly carried by a specific 83-kb IncFII plasmid co-carrying the blaTEM-1 (46.9%, 15/32). The genomic content of the blaNDM-4-harboring plasmids is highly variable. While blaOXA-181 and blaOXA-48 were predominantly located on an IncX3 and an IncL plasmid, respectively, the majority of plasmids harboring blaKPC-2 were not related to any named Inc-type. All isolates exhibited the MDR phenotype; however, the majority remained susceptible to the siderophore-cephalosporin cefiderocol (79%, 83/105). All isolates were susceptible to aztreonam/avibactam. In addition, we identified a hypervirulent, carbapenem-resistant K. pneumoniae ST23 strain, confirmed through both in vitro and in vivo experiments. Our study provides insights into plasmids harboring the carbapenemases New Delhi metallo-β-lactamase, oxacillinase-48 like, and K. pneumoniae carbapenemase-2 circulating in Vietnam.IMPORTANCECarbapenem resistance in Klebsiella pneumoniae is a major public health threat, especially in low- and middle-income countries. This study examined resistant strains from a hospital in Vietnam to understand how they spread and which antibiotics might still work. We found that a significant number of these bacteria carried resistance genes on different types of plasmids. Despite their resistance to many antibiotics, most strains remained susceptible to newer substances like cefiderocol and aztreonam/avibactam. Alarmingly, we also identified a hypervirulent strain that is carbapenem resistant, potentially posing an even greater risk to patients. This research provides insight into the epidemiology of the carbapenemase gene-harboring plasmids in a Vietnamese hospital. Understanding these resistance patterns can help guide antibiotic use and policy decisions to combat the growing threat of multidrug-resistant infections in Vietnam.

Evidence of hypervirulent carbapenem-resistant Klebsiella pneumoniae in cats with urinary affections and associated humans in Egypt

The emergence of hypervirulent and carbapenem-resistant Klebsiella pneumoniae poses a significant threat to the public health of both cats and their owners. Therefore, conducting molecular characterization and phylogenetic analysis of K. pneumoniae strains in both cats and humans in Egypt is crucial. 108 feline and 101 human urine samples were collected and subjected to routine microbiological isolation and molecular identification of K. pneumoniae. Subsequently, phenotypic antimicrobial sensitivity patterns and molecular identification of classical virulence, hypervirulence, and carbapenem resistance genes were examined. A total of 46 K. pneumoniae isolates were recovered, comprising 43.4% (23 out of 53) from diseased humans, 4.17% (2 out of 48) from healthy humans, 22.95% (14 out of 61) from diseased felines, and 14.89% (7 out of 47) from healthy felines. The detection rates for narrow drug-resistant (NDR), multidrug-resistant (MDR), extensively drug-resistant (XDR), and pan drug-resistant (PDR) strains were 41.30%, 54.35%, 2.17%, and 2.17%, respectively. The distribution rates for mrKD, entB, K2, Kfu, and MagA genes were 76.1%, 82.6%, 8.7%, 13.0%, and 0%, respectively. In addition, the distribution of hypervirulence genes was 41.3%, 36.9%, 13.0%, 10.9%, and 17.4% for iucA, iroB, Peg344, rmPA, and rmPA2, respectively, and 43.5%, 30.4%, 19.6%, and 52.2% for NDM, OXA-48, VIM, and KPC resistance genes, respectively. Phylogenetic analysis of the entB gene from four recovered strains revealed a relationship between feline strains and other human strains. In conclusion, this study focused on the molecular characterization and phylogenetic analysis of hypervirulent and carbapenem-resistant K. pneumoniae in companion cats and humans in Egypt.

Inhibitory effects of benzyl isothiocyanate on widespread mcr-1-harbouring IncX4 plasmid transfer

The global dissemination of mobile colistin resistance (mcr) genes represents a significant public health threat due to colistin’s critical role in treating multidrug-resistant (MDR) bacterial infections. We identified high rates of carbapenem resistance in Escherichia coli (27.82%) and Klebsiella pneumoniae (57.98%) and colistin resistance in E. coli (7.52%) and K. pneumoniae (19.68%) among MDR clinical isolates in Thailand. We reported sequences of self-transferable IncX4 plasmids (~ 34 kb) that facilitated the spread of the mcr-1.1 gene among six diverse MDR strains, often co-transferring blaCTX-M-55. Additionally, E. coli ST101 was found to co-transfer mcr-1.1, mcr-3.5, blaCTX-M-55, and tet(X4) via three plasmids (~ 34-kb IncX4, ~ 84-kb IncFII, ~ 278-kb IncHI2), resulting in increases in MICs for colistin, ceftriaxone, and tigecycline. Core SNP analysis revealed that closely related IncX4 plasmids harbouring mcr-1 (< 35 SNP differences) were reported from at least 12 countries. We first demonstrated the inhibitory effects of benzyl isothiocyanate (BITC) on the conjugation of mcr-1-bearing IncX4 plasmids to 1.57 ± 1.00% to 48.86 ± 12.31% relative to control (100%), targeting VirB4 and VirB11 proteins, reducing ATPase activity by over 30%. This study highlights the widespread mcr-1-harbouring IncX4 plasmids and proposes BITC as a potential inhibitor to control the dissemination of colistin resistance.

Detection of a novel SME-6 Carbapenemase in Serratia ureilytica in Germany.

Carbapenem resistance in Serratia species is occasionally mediated by the serine carbapenemase Serratia marcescens enzymes (SMEs). During microbiological diagnostics, we identified a carbapenem-resistant Serratia ureilytica isolate in which resistance was not mediated by any known SME variants or other characterized carbapenemases. To identify and characterize the underlying resistance mechanism in a carbapenem-resistant Serratia ureilytica isolate that lacks known SME variants or other characterized carbapenemases. Antimicrobial susceptibility testing (AST) was performed using Vitek, gradient strips, broth microdilution, and disc diffusion methods. WGS was performed to identify the resistance mechanisms. Growth curve analysis and RT-qPCR were performed at 30°C and 37°C. WGS identified a novel SME variant, SME-6, which differed from a known variant, SME-2, by two amino acids (G117R and G147E). AST showed carbapenem resistance at 30°C but susceptibility at 37°C. Growth curve analysis showed a shorter lag phase at 30°C compared with 37°C, and RT-qPCR showed a ∼3-fold higher blaSME expression at 30°C. To the best of our knowledge, this study reports the first identification of SME-6 and the first detection of an SME-type carbapenemase in Germany. Resistance was found to be temperature-dependent, with faster growth and higher SME-6 expression at lower temperatures contributing to the phenotype. These findings suggest SME variants may be underdiagnosed using current diagnostic protocols, highlighting the need for adjustments to improve detection of temperature-sensitive resistance mechanisms.

Characterization of Enterobacter cloacae and Citrobacter freundii Species Complex Isolates with Decreased Susceptibility to Cephalosporins from United States Hospitals and Activity of Aztreonam–Avibactam and Comparator Agents (2019–2023)

Background: Citrobacter freundii (CFC) and Enterobacter cloacae (ECLC) species complexes represent important causes of hospital-associated infections, frequently are related to outbreaks, and have a great ability to develop antimicrobial resistance. We evaluated a large collection of CFC and ECLC isolates with decreased susceptibility to broad-spectrum cephalosporins (Ceph-DS) from United States (US) hospitals. Methods: A total of 43,325 Enterobacterales (1/patient) were collected in 2019–2023 and susceptibility tested by broth microdilution; among those, 5106 (11.8%) were CFC (n = 1374) or ECLC (n = 3732). Ceph-DS CFC (n = 379) and ECLC isolates (n = 1065), defined as isolates with ceftazidime MICs ≥ 16 mg/L and/or cefepime MICs ≥ 2 mg/L, were screened for β-lactamase genes by whole genome sequencing. Results: The most common ESBLs were CTX-M type (n = 98; 47.6% of ESBL producers), SHV type (n = 94; 45.6%), and OXA type (n = 78; 37.9%); ≥2 ESBLs were identified in 65 isolates (31.6%), mainly OXA-1/30 plus a CTX-M. A carbapenemase was identified in 55 of 64 (85.9%) carbapenem-resistant (CB-R) isolates, including KPC type (40 isolates; 62.5% of CB-R) and NDM-1 (16; 23.4% of CB-R). Aztreonam–avibactam was active against 99.6% of Ceph-DS and 100.0% of ESBL producers and CB-R isolates, including NDM producers. Ceftazidime–avibactam and meropenem–vaborbactam were active against 100.0% of ESBL producers (excluding carbapenemase co-producers) and 70.3–71.9% of CB-R isolates. Cefiderocol was active against 82.8% of CB-R isolates but only 46.7% of MBL producers. Conclusions: Aztreonam–avibactam was highly active against cephalosporin-nonsusceptible ECLC and CFC, including MBL producers. The activities of ceftazidime–avibactam, meropenem–vaborbactam, and cefiderocol were compromised against CB-R isolates due to the high frequency of NDM producers.

Transcriptional response study of auto inducer-2 regulatory system in Escherichia coli harboring blaNDM

BackgroundThe emergence of carbapenem resistance in gram-negative bacteria such as Escherichia coli is one of the world’s most urgent public health problems. E. coli, which encounter a diverse range of niches in host can rapidly adapt to the changes in surrounding environment by coordinating their behavior via production, release and detection of signal molecules called autoinducers through a cell density dependent communication system known as quorum sensing. Here, in this study we investigated whether imipenem, and acyl homoserine lactone quorum sensing signal molecules influence the transcriptional response within lsr and lsrRK operon which are associated with auto inducer-2 mediated quorum sensing in E. coli. Two E. coli isolates carrying blaNDM were treated with 10% SDS for 20 consecutive days, resulting in the successful elimination of the blaNDM encoding plasmid from one isolate. Plasmid was extracted from the isolate and was transformed into recipient E. coli DH5α by electroporation. The native type, plasmid-cured type, transformant, and E. coli DH5α were allowed to grow under eight different inducing conditions and the transcriptional responses of lsr and lsrRK operons were studied by quantitative real-time PCR method.ResultsThe findings of this study highlight the distinct effects of imipenem and AHL on the transcriptional responses of the lsrB,lsrR, and lsrK genes in native type, plasmid cured type, transformant, and E. coli DH5α.ConclusionThis study provides a basis for further research to elucidate different inducing conditions including antibiotics and autoinducers that could switch on the quorum sensing circuit in carbapenem non-susceptible E. coli, one of the world’s most urgent public health threats.

Evaluation of phenotypic and genotypic methods for detecting KPC variants.

Klebsiella pneumoniae carbapenemases (KPCs) have spread and diversified extensively. To date, 242 clinical variants have been identified and harbor different hydrolytic capacities, thereby interfering with rapid diagnostic tests. The accurate detection of KPC variants is crucial to guide treatment and control measures in healthcare settings. We constructed KPC variants to assess the mutational impact on detection capacities of resistance-based tests. KPC variants (n = 45) were characterized phenotypically and used to measure the detection sensitivity of KPC detection methods (two lateral flow immunoassays [LFIAs], three hydrolysis tests, three selective culture media, and two PCR-based tests). We identified four antibiotic susceptibility patterns: "KPC-like" (23/45; 51%), "extended-spectrum beta-lactamase-like" (6/45; 13%), "ceftazidimase" (9/45; 20%), and outlier variants with "mixed-profiles" (5/45; 11%). These phenotypes had different impacts on the detection capabilities of hydrolysis tests (0%-100%), LFIA (44%-100%), and selective culture media (0%-100%), highlighting a risk of misdiagnosis for some KPC variants. All variants were detected with PCR-based tests. To detect the maximum of KPC variants, fecal carriage screening requires a combination of selective media targeting resistance to carbapenems, third-generation cephalosporins, and ceftazidime-avibactam. From antibiotic susceptibility testing, resistance to ceftazidime ± avibactam and specific phenotypic profiles should be used as warnings to track the presence of KPC variants. We recommend LFIA as a first-line test, owing to its high sensitivity in detecting KPC variants. Nevertheless, using a combination of tests may remain wise in some situations. The spread of KPC variants remains a significant concern, particularly as reversion to ancestral phenotype could restore carbapenem resistance and lead to therapeutic failure.

Emergence and characterization of IncFII/IncR plasmids with multiple 5,692 bp- bla KPC-2-bearing tandem repeats in ceftazidime/avibactam non-susceptible Klebsiella pneumoniae strains.

Ceftazidime/avibactam (CAZ/AVI) is widely recognized as an effective treatment for infections caused by KPC-producing Klebsiella pneumoniae (KPC-Kp). However, the prevalence of CAZ/AVI resistance among KPC-Kp isolates has increased rapidly in recent years. In this study, high-level carbapenem resistance and enhanced CAZ/AVI resistance were observed in two hypervirulent carbapenem-resistant K. pneumoniae isolates, KP1878 and KP3034, following prolonged carbapenem use. Virulence phenotypes were confirmed using the string test and a Galleria mellonella larvae infection model. Real-time quantitative PCR revealed that the relative expression of bla KPC-2 in KP1878 and KP3034 was 2.4-fold and 11.6-fold higher, respectively, than that in the CAZ/AVI-susceptible KPC-Kp strain KP1880. Whole-genome sequencing showed that the bla KPC-2 gene resided within an identical 5,692-bp ΔklcA-korC-ΔISKpn6-bla KPC-2-ISKpn8-ΔtnpR-IS26 tandem repeat, which was replicated twice and four times in plasmids pKPC1878 and pKPC3034, respectively. Compared with KP1880, the β-lactamase hydrolysis activities of crude cell lysates derived from KP1878 and KP3034 were significantly higher in their ability to hydrolyze meropenem, ceftazidime, and nitrocefin. S1-nuclease-digested pulsed-field gel electrophoresis, along with Southern blot and restriction fragment length polymorphism fingerprinting, identified plasmid profiles but revealed one or more 5.6-kilobase variations in the regions hybridized with the KPC-specific probe. Further comparative genomic analysis suggested that a potential homologous recombination event occurred between the bla KPC-2-carrying plasmid and the pLVPK-like virulence plasmid of KP3034, leading to the generation of a cointegrated plasmid that combined both virulence and CAZ/AVI resistance.

STUDY OF GENE EXPRESSION IN RESPONSE TO SERIAL EXPOSURE TO MEROPENEM IN BACTEROIDES FRAGILIS

Antibiotic resistance is a major global health concern, and inappropriate antibiotic use contributes significantly to the development of resistance in pathogens. Bacteroides fragilis, an anaerobic bacterium, is commonly treated with β-lactam antibiotics like meropenem. B. fragilis possesses various antibiotic resistance mechanisms, including enzymatic modification of antibiotics, efflux systems, and reduction of cell membrane permeability. The primary mechanism of carbapenem resistance in B. fragilis is linked to the production of a metallo-β-lactamase encoded by the cfiA gene. However, this gene is frequently inactive and requires activation by insertion elements. The study aimed to explore the expression of specific genes in B. fragilis associated with different metabolic pathways in response to exposure to sub-inhibitory concentrations of meropenem. The study used B. fragilis strain BFR KZ01, obtained from a patient with appendicitis and peritonitis. Serial exposure to meropenem was conducted, and gene expression was analyzed using quantitative RT-PCR. Significant and long-lasting alterations in gene expression patterns were observed in B. fragilis following exposure to meropenem, even after removal of the antibiotic. Genes such as cfiA, oxyR, and Ddl showed heightened expression levels even after discontinuation of meropenem. The study discussed the implications of gene expression changes induced by meropenem exposure, highlighting the role of oxidative stress response (oxyR), D-Ala-D-Ala ligase (Ddl), and carbapenemase (cfiA) genes in antibiotic resistance mechanisms. The study concluded that exposure to meropenem induced lasting alterations in gene expression in B. fragilis, contributing to antibiotic resistance. Understanding these mechanisms is crucial for developing strategies to combat antibiotic resistance.

Global and regional burden of bloodstream infections caused by carbapenem-resistant Gram-negative bacteria in 2019: A systematic analysis from the MICROBE database.

Global and regional burden of bloodstream infections caused by carbapenem-resistant Gram-negative bacteria in 2019: A systematic analysis from the MICROBE database.

Genetic Diversity of Carbapenemases-producing Acinetobacter baumannii Isolates at a Tertiary Teaching Hospital in Western India

Abstract Background: Acinetobacter baumannii is an alarming pathogen in hospital-acquired infections, particularly in the intensive care units (ICUs). Carbapenemases production and biofilm formation contribute significantly to the pathogenicity of the organism. Carbapenem resistance in A. baumannii is primarily due to the production of carbapenemases. Aim: The study was conducted to detect the presence of carbapenemase-encoding genes in A. baumannii along with their ability to form biofilm. In addition, this study also investigated the association between biofilm formation and carbapenemase genes harboring A. baumannii isolates. Materials and Methods: One hundred and forty isolates of A. baumannii were collected from the various specimens. Of these, this study included 36 isolates that were carbapenem-resistant, metallo-β-lactamases (MBLs) producing, and extensively drug-resistant (XDR) obtained from ICUs. Identification and antibiotic susceptibility determination was done using VITEK 2. Further, the isolates were confirmed by detecting the bla OXA-51 carbapenemase gene intrinsic to A. baumannii. Polymerase chain reaction was performed to detect carbapenemase-encoding genes, and biofilm formation was examined using the tube method. Results: The bla OXA-51 gene was present in all isolates (n = 36). A. baumannii showed highest sensitivity against colistin (100%) and minocycline (25%). Out of 36 isolates, acquired carbapenemase encoding genes were detected in 35 (97.22%) isolates, as follows: bla OXA-23 (35/36, 97.22%), bla NDM (18/36, 50%), bla IMP (1/36, 2.78%), and bla VIM (28/36, 77.78%). In 33 (91.67%) isolates, oxacillinase (OXA) and MBL genes coexisted. Among the 36 isolates, 30 (83.33%) formed biofilm. Conclusion: The study highlights that colistin and minocycline are the viable antibiotics for treating carbapenem-resistant MBL-producing XDR A. baumannii infections. bla OXA-23 is the commonest carbapenemase gene, and bla VIM is the most frequently found MBL gene prevalent in our hospital and contributes to carbapenem resistance in A. baumannii. The study also showed a higher frequency of co-occurrence of multiple carbapenemase genes in single isolates, and most of these isolates formed biofilm. However, no statistically significant association was found between biofilm formation and carbapenemase genes in A. baumannii. This study emphasizes the molecular diagnostic value of carbapenemase gene detection to reduce the resistance rate in A. baumannii isolates.

Pandemic human-associated extended-spectrum β-lactamase-producing Escherichia coli lineages of ST38, ST131 and ST141 identified in Viennese dogs.

To assess the prevalence of ESBL Enterobacteriaceae among dogs attending a veterinary clinic in Vienna, characterize the isolates in terms of antimicrobial resistance, virulence and phylogenetic relationships. Faecal samples of 88 dogs were streaked on selective plates, species were identified by MALDI-ToF MS, tested for resistance by a combination disk test and VITEK 2®, whole genome-sequenced, bioinformatically genotyped, phylogenetically analysed and screened for resistance and virulence genes. ESBL Escherichia coli carriage rate was 14.8% (95% CI: [8.1-23.9]). No carbapenem resistance was found, but 53.8% of the isolates were classified genotypically as multi-drug resistant. Phylogenetic analyses revealed that half of the isolates belonged to animal and environment-associated phylogroups, while another half was human-associated, and included high-risk international clones of ST38, ST131 and ST141, which clustered primarily with human isolates. All isolates harboured various virulence-associated genes, including four isolates that encoded exotoxins, of which two were from the pandemic ST131 and emerging ST141 lineages. Dogs in Vienna carry ESBL E. coli with high rates of multi-drug resistance and virulence, and a highly diverse population structure that includes pandemic human-associated lineages.

Revisiting fosfomycin to treat urinary tract infections in the era of rising carbapenem resistance

Background: Most of the studies on antibiotic resistance are pre-judiced over the use of last-resort antibiotics for Multidrug resistant organisms (MDRO) and fail to acknowledge the effectiveness of older antibiotics. There is a dearth of information regarding the susceptibility of fosfomycin and nitrofurantoin, which are oral alternatives for such infections. Aims and Objectives: To study the antibiotic susceptibility profile of uropathogenic Escherichia coli and infer whether fosfomycin can be used as an efficient oral option for the management of uncomplicated urinary tract infection (UTI), especially in carbapenem-resistant cases. Materials and Methods: Clean catch midstream urine samples from cases clinically suspected of UTI received for culture were processed using standard guidelines for microbiological procedures. Antimicrobial sensitivity was performed through the Kirby Bauer disc diffusion method. Discrepant results were confirmed with VITEK 2. Results: This study reports antimicrobial susceptibility pattern of 100 E. coli isolated from urine samples of patients with signs and symptoms suggestive of UTI. There was a female predominance in the study population and the most affected age group was 20–40 years (52%). Most specimens were received from the obstetrics and gynecology department (32%) followed by General medicine (28%). Higher sensitivity was observed for fosfomycin (97%), amikacin (80%), and meropenem (79%). Conclusion: Fosfomycin is an oral, safe, and efficient antibiotic for UTI. It is a valuable alternative for outpatient treatment of MDROs causing UTI. Thus, decreasing hospitalization and consequently reducing the financial burden of treatment for the patients.

Carbapenem-Resistant, Virulence Plasmid-Harboring Klebsiella pneumoniae, United States.

Carbapenem-resistant and virulence plasmid-harboring Klebsiella pneumoniae (pVir-CRKP) has emerged and spread globally, yet clinical investigations from the United States remain limited. We conducted a genomic analysis of 884 unique carbapenem-resistant K. pneumoniae isolates from a multicenter US cohort and identified 6 pVir-CRKP isolates, including 2 sequence type (ST) 23, 2 ST893, and 2 ST11 isolates. Patients infected with pVir-CRKP experienced high Pitt bacteremia scores and a 33% 30-day mortality rate. The pVir-CRKP isolates exhibited significant sequence variation in virulence genes and plasmids, along with differences in mucoviscosity, capsule production, survival in normal human serum, resistance to killing by human polymorphonuclear neutrophils, and in vivo pathogenicity. Phylogenetic analyses showed that most pVir-CRKP isolates were genetically similar to strains reported from other global regions. The emergence of pVir-CRKP with higher virulence potential and carbapenem resistance in the United States than the predominant carbapenem-resistant K. pneumoniae clone underscores the need for active global surveillance.

Real-World Use, Effectiveness, and Safety of Intravenous Fosfomycin: The FORTRESS Study.

Intravenous fosfomycin (FOS) is a broad-spectrum antibiotic primarily used in combination therapy to treat severe infections caused by both Gram-positive (GP) and Gram-negative (GN) pathogens, including multi-drug resistant (MDR) bacteria. The aim of this study, the largest to date, was to evaluate the effectiveness, safety, usage patterns, and patient characteristics of FOS in a real-world setting. Interim analysis of an ongoing, prospective, non-interventional, multicentre study in five European countries, involving centres in Germany, Italy, the United Kingdom, Greece, and Austria. A total of 716 patients were enrolled between January 2017 and November 2023 (mean age: 62.8 years, APACHE II: 18.3, SOFA: 6.7). Main indications for FOS were bacteraemia/sepsis (23.6%), complicated urinary tract infections (18.0%), and bone and joint infections (17.4%). Other indications included hospital-acquired/ventilator-associated pneumonia (11.0%), complicated skin and soft tissue infections (9.1%), bacterial meningitis/central nervous system (CNS) infections (7.8%), and infective endocarditis (6.4%). Most common pathogens identified were Staphylococcusaureus (31.4%, including methicillin-resistant S.aureus), Klebsiellaspp. (including K.pneumoniae) (17.2%), Escherichiacoli (14.2%), coagulase-negative staphylococci (12.9%), other Enterobacterales (10.9%), and Pseudomonasaeruginosa (8.4%). In 34.6% of patients, an MDR pathogen was involved. Carbapenem resistance (CR) was high in Klebsiellaspp. infections (59/123, 48.0%). In most patients, FOS was used in combination therapy (90.2%). The median dose was 15 g/day. Overall, clinical success and clinical response were favourable with 75.3% and 83.4% at the end of FOS treatment. Clinical success rates in infections caused by MDR or CR pathogens were 78.0% and 81.8%, respectively. Microbiological cure was achieved in 82.4% of all patients. Electrolyte imbalances were the most frequently observed adverse drug reactions, while gastrointestinal disorders were rare. The results from this study suggest that FOS is a safe and effective option as combination partner in the treatment of patients with severe infections caused by both GP and GN pathogens, including deep-seated infections and/or involvement of MDR bacteria. ClinicalTrials.gov identifier, NCT02979951.