Carbapenemase-producing Organisms Research Articles

102. Carbapenemase producing organisms in Positive Blood and urine Cultures in a large New York Health System Reveals Emergence of NDM-Harboring Organisms and Associated Morbidity and Mortality

Abstract Background Infections caused by organisms harboring carbapenemase genes are a significant cause of morbidity and mortality. The prevalence of carbapenemase producing organisms (CPO) has been increasing for several years, with the majority of isolates originating in healthcare settings and containing one of the five most prevalent carbapenemase genes (blaKPC, blaOXA-48-like, blaNDM, blaVIM, blaIMP). Management of patients with CPOs is particularly challenging and knowledge of the specific carbapenemase gene harbored by these organisms is imperative for proper treatment. Methods We conducted a retrospective multicenter study of hospitalized patients with blood and urine cultures positive for a CPO from January 2021 to December 2023 (2021-2023 blood, 2023 for urine). Blood culture PCR results were utilized to identify carbapenemase genes from these specimens. For urine specimens, phenotypic carbapenemase production was assessed by a lateral flow immunoassay (NG-Test CARBA 5). Clinical outcomes including time to appropriate therapy, length of hospital stay, 30-day hospital readmission, and patient mortality were evaluated. Results A total of 71 CPO-positive blood cultures and 50 CPO-positive urine cultures from 10 hospitals were included. Klebsiella pneumoniae was the predominant CPO isolated from both blood and urine samples, urinary tract infections was the most common source of CPO bacteremia. Of the carbapenemase resistance genes detected, blaNDM comprised 39% of CPO isolated from blood and 46% of CPO isolated from urine. Median time to appropriate therapy was 3.9 hours for blood cultures and 16 hours for urine cultures. The median length of hospital stay was 20 days for blood infections and 13 days for urine infections. Thirty-day readmission rates were 16% for blood infections and 50% for urine infections, with mortality rates of 39% for blood infections and 6% for urine infections. Conclusion Timely identification and differentiation of carbapenem resistance genes are crucial for informing adjustments in antimicrobial therapy. Despite appropriate clinical interventions patients with CPO bacteremia had elevated mortality rates, 42% in 2022 and 33% in 2023. Notably, the primary contributor to these high mortality rates was NDM, with rates reaching 54% in 2022 and 50% in 2023. Disclosures All Authors: No reported disclosures

P-1179. Investigations of carbapenemase-producing bacteria among children in U.S. healthcare settings: review of CDC consultations, 2015–2023

Abstract Background The US Centers for Disease Control and Prevention (CDC) provides technical assistance (consultations) to health departments responding to single cases and clusters of carbapenemase-producing organisms (CPOs). We aimed to characterize consultations involving pediatric patients.Figure 1.Flow diagram of screening of CDC consultations for pediatric CPO cases requiring public health responses or clusters with suspected or confirmed transmission.Abbreviations: AR, antimicrobial resistance; CPO, carbapenemase-producing organism; HAI, healthcare-associated infection.*Includes one additional recent consultation not yet added to database at time of query.†One consultation involved two unrelated single cases and another consultation included 3 subclusters.‡Applicable public-health response components were contact screening, site visit/infection control assessment, and/or environmental sampling. Methods We searched CDC databases of healthcare-associated infection (HAI) consultations (November 2001 to January 25, 2024) using pediatric key-word patterns. We reviewed this subset for CPO investigation consultations with at least one pediatric case (age < 18 years with a CPO-positive clinical or screening specimen) or involving a pediatric healthcare facility. We classified CPO consultations as either (a) a cluster with likely transmission or (b) a single case with a public-health response (Figure 1). We abstracted and descriptively analyzed consultation characteristics regarding microbiology, healthcare setting, index patient characteristics, public-health response, and likely transmission mechanisms.Figure 2.Number of CDC consultations for CPOs by year among children in U.S. healthcare settings, 2015–2023. Results Among 2338 HAI consultations, 271 (12%) related to pediatric cases or facilities were reviewed (Figure 1). Thirty-three consultations from 2015–2023 across 20 states were included, which comprised 16 single cases and 20 clusters (Figure 2). Eight (40%) clusters only involved pediatric cases and the remainder included both pediatric and adult cases. Most commonly, for 17 (47%) index cases, Enterobacterales was identified in a clinical specimen from an acute-care hospital patient in an intensive care unit (e.g., burn unit; Table 1). The most common carbapenemases were NDM (53%), KPC (28%), and VIM (22%). Among the 16 clusters with available information, the most common transmission mechanisms were gaps in core infection control practices (9, 56%) and premise plumbing (3, 19%). Overall, 9 (56%) single cases and 6 (30%) clusters had history of international healthcare or travel for the index case-patient.Table 1.Microbiologic, healthcare setting, index patient, and public health response characteristics of consultations of CPO among children in U.S. healthcare settings, by consultation type, 2015–2023 Abbreviations: ACH, acute care hospital; CPO, carbapenamase-producing organism; ICU, intensive care unit; IPC, infection prevention and control; LTACH, long-term acute-care hospital; PFGE, pulse field gel electrophoresis; SNF, skilled nursing facility; WGS, whole genome sequencing. a Proportions may not add to 100% as values may not be mutually exclusive per consultation and/or rounding error. b Three clusters of VIM–P. aeruginosa in different facilities were part of multistate outbreak linked to artificial tears. c Denominator for clusters is 16 ACHs. “Other” includes one each of surgery, pediatrics, medicine, and adult ICU units. d Includes three single cases and one cluster where index case was a US-born patient in a neonatal ICU whose mother had history of international healthcare or travel. e Includes hand hygiene, Transmission-Based Precautions, and cleaning and disinfection of high-touch surfaces in patient rooms. Conclusion Review of CDC consultations for CPOs in pediatric patients identified multiple cases and clusters among high-risk inpatient units. Links to healthcare outside the U.S. were common. Admission screening, particularly on high-risk units, and adherence to core infection control practices may prevent future outbreaks. Disclosures All Authors: No reported disclosures

P-363. Containing an Outbreak of Carbapenemase-producing Organisms in a Singapore Hospital

Abstract Background Tan Tock Seng Hospital is a 1700-bed academic teaching hospital in Singapore. Active surveillance using rapid PCR for the detection of asymptomatic carriage of carbapenemase-producing organisms (CPO) is routinely performed (Fig. 1). Where available, identified carriers are cohorted or isolated under contact precautions. We describe a hospital-wide multispecies OXA-48-like and NDM outbreak, findings from epidemiological investigations and the subsequent infection prevention and control (IPC) measures. Existing and intensified CPO screening strategies Methods Initial response included additional intensified contact tracing (Fig. 1), expansion of isolation bed capacity and audits of IPC practices. Case-control analysis involved 280 cases and 995 controls. Universal admission screening was conducted to validate the accuracy of existing high risk screening (HRS) criteria. Wards with high transmission underwent environmental sampling. Results The CPO screening positivity rate was observed to be on a steady increase during 2022/23, from a baseline of 1.3-1.7% in 2020/21, peaking at 6.5% in June 2023 (Fig. 2). Spot audits demonstrated a decrease in hand hygiene compliance, improper cleaning of shared equipment, and poor IPC practices especially during diaper changes. Isolates were predominantly Klebsiella pneumoniae and sequence type 307. OXA was the commonest carbapenemase, followed by NDM. Risk factors for acquisition were presence of an indwelling urinary catheter for OXA (adjusted odds ratio [AOR] 1.62, 95% CI 1.02-2.48, p = 0.028), exposure to third-generation cephalosporins for NDM (AOR 3.83, 95% CI, 1.86-7.92, p < 0.001) and length of stay of 15-21 days for both (AOR 3.19, 95% CI, 2.05-4.96, p < 0.001). 4.8% of OXA carriers developed clinical infection within a median of 17 days (Fig. 3). Sensitivity of HRS criteria was 70%, though compliance to screening was only 60-80%. Periods of higher transmission were associated with lower rates of CPO cohorting (Fig. 4). CPO was found in 6.9% (9/130) of environmental samples. Rate and time to onset of clinical infection for asymptomatic carriers according to CPO genotype Conclusion Drivers of the outbreak were lower rates of CPO cohorting/isolation, a decrease in IPC standards, the inadequate compliance to HRS and the introduction of a highly transmissible bacterial clone. Early detection coupled with isolation remains a key strategy to control the spread of CPO. Epidemiologic curve of the CPO outbreak in relation to cohorting efforts (%) Disclosures Darius Beh, MBBS (S'pore) MMed (Int Med) MRCP (UK), AstraZeneca: Conference Sponsorship|Gilead: Conference Sponsorship

P-401. Cost-Effectiveness of Different Screening Strategies to Control the Spread of Carbapenemase-producing Organisms

Abstract Background The transmission of carbapenemase-producing organisms (CPO) in healthcare facilities is associated with increased morbidity and mortality. Recommended control measures include early detection of asymptomatic carriers coupled with isolation and contact precautions. Such measures can be costly and need to be balanced against the disruption of hospital operations. We assessed the effectiveness of different screening strategies at averting potential CPO infections and the corresponding cost savings. Methods A basic infectious disease transmission model was used to characterize colonization and transmission with inputs parameterized based on 2023 data from a 1700-bed academic teaching hospital (Fig. 1). Three strategies were compared to the baseline viz. high-risk screening (HRS) but at 70% compliance (based on previous audits) (Fig. 2): (i) HRS at 100% compliance (cHRS); Universal screening on admission (US); Long-stayer screening (LSS) of all inflight patients at every 10 days of stay till 30 days (where applicable) on top of HRS. Once CPO carriage is identified, we assumed no onward transmission, as per institution policy, timely isolation with contact precautions would be implemented. Outcomes included the monthly number of CPO infections and estimated cost of screening (using rapid PCR) and treatment. All costs were converted to US dollars at an exchange rate of USD$1 = SGD$1.343. Results The baseline strategy resulted in 17 infections/month with an estimated cost of USD$443,000 (Fig. 3). Among the three strategies, cHRS gave the best value with potential cost savings USD$39,000/month and 5 infections averted/month. In comparison, LSS in addition to HRS would similarly avert 5 infections/month but at an estimated cost of USD$74,000 (Fig. 4). For US, 8 infections/month would be averted at a cost of USD$79,000 (Fig. 4). Conclusion Improving compliance to HRS was the most cost-effective option to limit the spread of CPO. Disclosures Darius Beh, MBBS (S'pore) MMed (Int Med) MRCP (UK), AstraZeneca: Conference Sponsorship|Gilead: Conference Sponsorship

P-1432. Assessing Equitable Access to Carbapenemase Production Testing in Los Angeles County Hospitals

Abstract Background Carbapenemase producing organisms (CPO) are the cause of difficult-to-treat infections that result in substantial morbidity and mortality. Due to this and because CPOs can spread quickly between patients, hospital microbiology laboratories should be incentivized to test for carbapenemase production (CP), yet testing costs have stifled uptake. In Los Angeles County (LAC), laboratory professional organizations and the LAC Department of Public Health have broadly promoted CP testing, without emphasis on hospitals that accept patients of highest risk of acquiring a CPO, including patients with a history of long-term care. This analysis assesses CP testing uptake in LAC hospitals and association with patient population and social vulnerability. Methods CP testing in hospitals was assessed using the 2022 National Healthcare Safety Network Annual Facility Survey. We assessed patient origin from the Centers for Medicare and Medicaid Services claims and Minimum Data Set and patient characteristics from the California Department of Health Care Access and Information Healthcare Utilization. Frequencies, logistic regression, and Fisher’s exact tests were performed to evaluate the relationship between CP testing and hospital patient and facility-level characteristics. Results Of the 79 surveyed hospitals in LAC, 51 (65%) tested for CP. No significant relationship was identified between access to CP testing and the number of patient transfers from high-risk facilities (OR=1.00 , 95% CI [1.00, 1.00]), area poverty (OR=1.01 , 95% CI [0.95, 1.07]), the percent of patients with Medicaid or Medicare (OR=0.94 , 95% CI [0.91, 0.98]), the percent of non-white patients (OR=1.01 , 95% CI (0.99, 1.03]), and hospital ownership (p=0.66). Conclusion Access to CP testing was lower among hospitals serving more patients with public insurance and did not differ based on number of high-risk patients. This analysis is limited in that testing capacity was assessed, but data were not available on frequency of testing or implementation of a process to test at-risk individuals. Testing performed at the LAC Public Health Laboratory can supplement testing gaps for facilities of high need. More outreach to hospitals serving highest risk patients to support access to CP testing is needed. Disclosures All Authors: No reported disclosures

P-365. Outbreak of Carbapenemase-Producing Organisms in the Cardiovascular ICU Linked to "Hoppers"

Abstract Background Between June and October 2023, a Canadian cardiac centre recognized a growing number of carbapenemase producing organisms (CPO) in patients in the cardiovascular intensive care unit (CVICU). The organisms were mainly KPC-producing Enterobacterales. Following declaration of an outbreak in the CVICU at the Mazankowski Heart Institute, we investigated the sources of CPO across the unit and in patient rooms to determine environmental reservoirs and mechanisms of patient transmission. Methods We employed prevalence screening to identify cases, environmental sampling to identify source, and comparison of patient strains utilizing whole genome sequencing (WGS) during the investigation. Results Between June and October 2023, five patients were identified as being colonized or infected with CPO-KPC. WGS of patient samples confirmed clonality with less than 10 SNV differences in the plasmid . Environmental sampling revealed drains in the hand-hygiene sinks and medical sinks used for disposal of liquid clinical waste (“hoppers”) harboured CPO. Using GlowGermTM, we found that the faucets of the hoppers resulted in a ∼30cm splash zone causing contamination of medical supplies and health care workers. GlowGermTM did not reveal splash from drains of hand hygiene sinks. Because the hoppers were the only temperature controlled water source on the unit, the majority of faucet use was to collect warm water for bathing patients. As a solution, the unit was equipped with single-use packages of chlorhexidine wipes in warmers for patient bathing. To prevent accidental use of the hoppers, the faucet handles were removed. Since implementing these changes, prevalence screening has not identified any further cases of CPO carriage or infection over 5 months. Conclusion A CPO-KPC outbreak in CVICU was linked to splashback from faucets of hoppers primarily used to collect warm water for sponge-bathing. The outbreak was ended by cessation of faucet use and transition to chlorhexidine wipes for patient bathing. Disclosures All Authors: No reported disclosures

P-2085. Optimizing GAIHN-AR Network Microbiology Laboratory Assets for Early Detection of Carbapenemase-Producing Organisms in Limited Resources Settings: Argentine Experience

Abstract Background The Global Action in Healthcare Network-Antimicrobial Resistance Module (GAIHN-AR), led by the U.S. CDC, enhances prevention, detection and response in low-resource hospital settings (LRS) against emerging antimicrobial resistance (AR) threats, with an initial focus on carbapenemase-producing organisms. GAIHN-AR includes a lab. component for improving early AR detection, an infection prevention and control program, and a communication platform for rapid response coordination. We describe the implementation verification/validation of new AR diagnostic methods and their integration into clinical workflow Table Methods Prior to GAIHN-AR initiation in two hospitals in Argentina in January 2023, validation of CPO diagnostic techniques was conducted. For this, reference strains characterized by WGS from the CDC & FDA AR-Bank and Argentina-NRL repository were used. Evaluation followed manufacturer specifications, with GeneXpert also tested with alternative Dacron swabs. Pure colonies were used for validation of all methods, except for GENEXPERT®Carba-R where contrived fecal sample were also used. Methodologies were acceptable with sensitivity, specificity, and precision values ≥ 95%.The following methodologies were verified for carbapenemase detection in Enterobacterales, P. aeruginosa, and Acinetobacter spp. (ACI): (i) GENEXPERT®Carba-R; (ii) NG-Test®CARBA-5 lateral flow (ACI excluded); (iii) CHROMagar mSuperCARBA® chromogenic medium for carbapenem resistance detection; (iv) RAPIDEC® CARBA-NP. Additionally, the GENEXPERT®Carba-R was validated for: i) KPC variants with ceftazidime/avibactam resistance, ii) local circulation metallo-β-lactamase IMP variants Results The methodologies under evaluation achieved performance between 95-100%, except for the IMP variants with GenXpert Carba-R where sensitivity was reduced to 44% (Table). Conclusion Verification/validation process demonstrated that most methods had acceptable performance, allowing integration into lab workflows to facilitate prompt diagnosis and rapid communication with IPC teams. Results benefited not only GAIHN-AR hospitals but also other LRS facilities with whom they were shared through the NRL, offering valuable lessons for similar settings Disclosures All Authors: No reported disclosures

100. Genomic epidemiology of carbapenemase-producing Enterobacter species in Toronto, Canada, 2007-2021

Abstract Background Identification of transmission networks of carbapenemase-producing organisms (CPO) is critical to identifying their reservoirs and limiting their spread. This study aimed to use whole-genome sequencing to identify genomic relationships between CP Enterobacter (CP-Ent) in Ontario, Canada over a 15-year period. Methods All CP-Ent cases identified by prospective population-based surveillance in the Toronto/Peel Region from first isolate in 2007 to 2021, from hospital sinks (2016-2019), and wastewater treatment plants and surface water sites (2015-2017) were included. CPO isolates were identified by phenotypic screening (ertapenem MIC > 1mg/L or meropenem disc diffusion diameter ≤ 25mm), confirmed as Enterobacter by MALDI-TOF MS and as positive for carbapenemase genes by PCR, and sequenced by Illumina. Genomics analysis utilized a custom pipeline combining Snippy, IQ-Tree, and ClonalFrameML. Results Overall, 182 isolates from 127 patients, 61 isolates from 40 sinks, and 155 isolates from 9 wastewater plants/surface water sites were available (Table 1). Thirty-one of 127 (24%) patients had > 1 sequenced isolate: in 29 patients all isolates were highly related (median SNV distance 3.5, range 0-13); one patient had two CP-Ent species ∼1.5 years apart, and one had 2 sequence types (STs) 86 days apart. Of 12 (30%) sinks with > 1 isolate, 5 had 2 STs recovered at different times (4 with different carbapenemases). Multiple species, STs, and carbapenemases were recovered from sewage trunks and surface water. Using a ≤ 20 SNV threshold between any one pair of isolates, 14 multi-patient putative clusters involving 39 patients were identified; 1 added cluster was identified and 4 expanded when the threshold was increased to 40 SNVs (Table 2). At the 40 SNV threshold, the median number of patients per cluster was 2 (range 2-9), and the median number of hospitals with at least one first identified patient in each cluster was 1.5 (range 1-4). In total, 35% (45/127) patients were part of a cluster. Conclusion CP-Ent in Ontario are diverse, but a significant minority of affected patients are part of genomically-defined clusters. Genomic clusters may reflect undetected transmission of CP-Ent in healthcare, exposure to water, or other as yet unidentified sources. Disclosures Allison McGeer, MD, AstraZeneca: Honoraria|GSK: Honoraria|Merck: Honoraria|Moderna: Honoraria|Novavax: Honoraria|Pfizer: Grant/Research Support|Pfizer: Honoraria|Roche: Honoraria|Seqirus: Grant/Research Support|Seqirus: Honoraria

99. Impact of Covid-19, Divergent Genomic Modes of Transmission and Strain Replacement of Carbapenem-Resistant Organisms in a Single Hospital in Singapore over 12 years

Abstract Background Much remains unknown about the different genomic characteristics of transmission comparing Carbapenem-Resistant Enterobacterales (CREs), Carbapenem-Resistant A. baumannii (CRAB) and Carbapenem-Resistant P. aeruginosa (CRPA). In this study, we examine the genomic characteristics and transmission dynamics of Carbapenemase-producing Organisms (CPOs) isolated in a single hospital from 2010 to 2022.Table 1.Genomic characterization of CPOs detected between 2010 and 2022 Methods All Carbapenemase-Producing Enterobacterales (CPE) (n=160) identified between 2010 and 2015 and all CRE (n=2,573), carbapenem-resistant Acinetobacter spp. (n=500) and carbapenem-resistant Pseudomonas spp. (n=1,434) identified between 2019 and 2022 were whole-genome-sequenced. An outbreak was defined as monthly count greater than 2 SD above the mean. Two or more isolates of a unique species-ST combination formed an ST-cluster.Table 2.Outbreak periods among three major groups of CPOs between 2010 and 2022. Results Of the total 4,667 WGS isolates, 2,828 (60.6%) were surveillance and 1,839 (39.4%) were clinical cultures. The predominant species-ST and carbapenemase gene detected between 2010 and 2015 was E. coli ST131 (n=31, 19.3%) and blaNDM-1 (n=100, 62.5%), respectively, while K. pneumoniae ST76 (n=172, 6.7%) and blaOXA-48-like (n=1,577, 70.7%) was the predominant species-ST and carbapenemase gene detected among CPEs isolated between 2019 and 2022 (Table 1). The majority of CRE (87.0%), CRAB (99.4%) and CRPA (54.0%) were carbapenemase-producers. During outbreaks, ST-clusters accounted for the majority of A. baumannii (92.6% – 100%) and P. aeruginosa (87.5% – 97.1%). ST-clusters accounted for approximately half of CPE outbreaks (37.5% – 55.2%) (Table 2). CRAB and CRPA numbers declined during Covid-19 (2020 to 2021) and remained low (2022) while CRE numbers increased post-Covid-19 (2022) (Figure 1).Figure 1.Monthly incidence rates of carbapenem-resistant Enterobacterales, A. baumannii and P. aeruginosa from 2019 to 2022. Conclusion Clonal transmission accounted for the vast majority of CRAB and CRPA transmission while horizontal gene transfer, likely via plasmid-mediated transmission, accounted for significant CPE transmission. The varying genomic transmission modes is a possible factor for the different trends observed for CRAB, CRPA and CRE transmission pre- and post-Covid-19. Bacterial strain replacement accounted for the carbapenemase gene replacement observed over the 12-year period, possibly due to plasmid-bacterial host factors. Disclosures Shawn Vasoo, MBBS, MRCP, D(ABP), D(ABIM) (Inf Dis), FRCPath, bioMerieux: In-kind, for this study|Rosco Diagnostica: In-kind, for this study

P-1348. Acquired Carbapenemase-Producing Gram-Negative Organisms (CPOs) Across the Pond: Surveillance of Antibiotic Resistance in CPOs in England from 2020-2023

Abstract Background Acquired carbapenemase-producing Gram-negative organisms (CPOs) threaten viable antibiotic treatment options. This is the first national look at CPO phenotypic antimicrobial resistance (AMR) rates since becoming statutorily notifiable in England on 01/10/2020.Table 1.Summary of all big-5 CPO isolates reported from October 2020 to December 2023 Methods All acquired big-5 (NDM, KPC, OXA-48-like, VIM, IMP) CPO reported specimens and antibiotic susceptibilities were extracted from national laboratory surveillance databases between Oct-2020 to Dec-2023. Records were deduplicated by patient, specimen group (invasive/screening/other), bacterial species and CPO mechanism per year. Regional big-5 CPO population rates were calculated; 2023 AMR data were assessed by mechanism and species.Figure 1.Regional notifications per 100,000 population of acquired CPOs by big-5 carbapenemase mechanisms in England, 2023 Results In total, 13,022 episodes from 9,945 patients were reported; median age was 70y, 54% were male. The dominant mechanisms were OXA-48-like (n=4,884; 37.6%), NDM (n=3,927; 30.2%) and KPC (n=3,045; 23.4%); (Table 1) with large regional variation (Figure 1). NDMs became more dominant in 2023 than OXA-48-like. Screening samples accounted for 72% (n=9,378), and < 5% (n=591) were from invasive samples. Thirty-three patients with invasive samples had dual-mechanisms detected: 61% were NDM & OXA-48-like; Klebsiella pneumoniae was the dominant species (patients=21). In 2023, the lowest reported resistance for the most frequently isolated species (n=5,535/5,711; Table 2) was for colistin (4-7%R) for all big-5 mechanisms in Escherichia coli, Enterobacter spp., Citrobacter spp., whilst higher for Klebsiella spp. and Pseudomonas spp. (10-17%R). Similarly, lower Enterobacterales resistance was observed for KPC and OXA-48-like to ceftazidime/avibactam (9-12%R) and amikacin (7-8%R), except for Klebsiella spp., which was higher (22%R). Ciprofloxacin and gentamicin had ≥ 35% resistance. Fosfomycin resistance in E. coli was low (≤ 9%). Proportion of big-5 CPO isolates (n=5,535) resistant to other antimicrobials by most frequently isolates species in England, 2023 Conclusion Continued national CPO and associated AMR surveillance is crucial, particularly for new antimicrobials, to inform guidance and local, empiric prescribing by region, given the geographical variation in CPO mechanism. Further enhancement via data linkage to ethnicity and clinical characteristics to identify risk factors, and tracking changes in patients’ antibiograms over time would help further target national guidance. Disclosures All Authors: No reported disclosures

P-1068. Inhibitory Effect of EDTA on Metallo β-Lactamase Producing Gram-Negative Pathogens Recovered from Cancer Patients with Bloodstream Infections

Abstract Background The spread of metallo β-lactamase (Mβ-L) producing Gram negative pathogens is an important worldwide medical problem. It presents the broadest-spectrum β-lactam resistance of all carbapenemase-producing organisms leaving few remaining treatment options. Previously, adding EDTA, a potent metallo-chelator, was shown to restore activity for antibiotic combinations against Mβ-L pathogens isolated from patients with urinary tract and bronchial infections. In this study, we evaluated in vitro efficacy of EDTA alone and in combination with different β-lactam/β-lactamase inhibitors against Mβ-L isolates recovered from cancer patients with bloodstream infections (BSIs). Methods : EDTA over its concentration range was tested alone and in combination with cefepime (FEP)/Avibactam (AVI), and FEP/Tazobactam (TAZ) against ten Mβ-L blood clinical isolates {E.coli (n=6), K. oxytoca (n=2), P. aeruginosa (n=1), and E. cloacae (n=1)}. CLSI approved broth microdilution methods were used to measure MIC. MIC50, MIC90, MIC ranges, and susceptibility rate calculations were made according to CLSI 2022. The provisional breakpoints susceptibilities of FEP/AVI, FEP/AVI/EDTA are ≤8/4 while the provisional breakpoints for FEP/TAZ, and FEP/TAZ /EDTA are =≤2/4. Statistically, significant differences were determined using Fisher’s exact test (P≤0.05 is considered significant). Results Table 1. presents MIC50, MIC90, MIC ranges, susceptibility rates, and P values comparing EDTA with different concentrations alone and in combination with a range of FEP/AVI, and FEP/TAZ dilutions against ten Mβ-L bloodstream isolates. Conclusion EDTA alone at 100 mg/L, and 300 mg/L concentrations inhibited 100% of Mβ-L blood isolates, while 10 mg/L, and 50 mg/L inhibited 10%, and 90% of tested isolates respectively. The combination of 10 mg/L EDTA with FEP/AVI, and FEP/TAZ, synergistically improved the susceptibility rates from only10% (without EDTA) to 100% (at only10 mg/L EDTA). The differences in MICs, and susceptibility rates between the triple and double combinations were highly significant (P < 0.0001). Further studies are needed to show the synergy against a larger number of Mβ-L Gram negative BSI pathogens as well as to clinically verify these benefits. Disclosures All Authors: No reported disclosures

Prevalence and Molecular Characterization of Carbapenemase-Producing Multidrug-Resistant Bacteria in Diabetic Foot Ulcer Infections.

Background: Diabetic foot ulcers (DFUs) represent severe complications in diabetic patients, often leading to chronic infections and potentially resulting in nontraumatic lower-limb amputations. The increasing incidence of multidrug-resistant (MDR) bacteria in DFUs complicates treatment strategies and worsens patient prognosis. Among these pathogens, carbapenemase-producing pathogens have emerged as particularly concerning owing to their resistance to β-lactam antibiotics, including carbapenems. Methods: This study evaluated the prevalence of MDR bacteria, specifically carbapenemase-producing pathogens, in DFU infections. A total of 200 clinical isolates from DFU patients were analyzed via phenotypic assays, including the modified Hodge test (MHT) and the Carba NP test, alongside molecular techniques to detect carbapenemase-encoding genes (blaKPC, blaNDM, blaVIM, blaIMP, and blaOXA-48). Results: Among the isolates, 51.7% were confirmed to be carbapenemase producers. The key identified pathogens included Klebsiella pneumoniae, Pseudomonas aeruginosa, Acinetobacter baumannii, and Escherichia coli. The most commonly detected carbapenemase genes were blaKPC (27.6%) and blaNDM (24.1%). Carbapenemase-producing isolates presented high resistance to β-lactam antibiotics, whereas non-carbapenemase-producing isolates presented resistance through mechanisms such as porin loss and efflux pumps. Conclusions: The findings of this study highlight the significant burden of MDR infections, particularly carbapenemase-producing organisms, in DFUs. MDR infections were strongly associated with critical clinical parameters, including pyrexia (p = 0.017), recent antibiotic use (p = 0.003), and the severity of infections. Notably, the need for minor amputations was much higher in MDR cases (p < 0.001), as was the need for major amputations (p < 0.001). MDR infections were also strongly associated with polymicrobial infections (p < 0.001). Furthermore, Wagner ulcer grade ≥II was more common in MDR cases (p = 0.002). These results emphasize the urgent need for enhanced microbiological surveillance and the development of tailored antimicrobial strategies to combat MDR pathogens effectively. Given the high prevalence of carbapenem resistance, there is an immediate need to explore novel therapeutic options to improve clinical outcomes for diabetic patients with DFUs.

Modified Carba PBP test for rapid detection and differentiation between different classes of carbapenemases in Enterobacterales.

An advanced biochemical assay named modified Carba PBP test was innovated to identify and differentiate distinct categories of clinically significant carbapenemases (Ambler classes A, B, and D) within the Enterobacterales. The mechanism of mCarba PBP hinges on two core attributes: (i) the hydrolysis of the meropenem substrate by various carbapenemases, (ii) the immobilized penicillin and free meropenem in their affinity to interact with a limited quantity of penicillin-binding protein (PBP). Specific inhibitors for class A (phenylboronic acid, PBA) and class B (ethylenediaminetetraacetic acid, EDTA) were employed to inhibit the hydrolysis activity of carbapenemase and facilitate the classification of carbapenemase classes within 25min. A comprehensive evaluation was undertaken using 94 clinical Enterobacterales isolates, comprising 75 carbapenemase-producing strains and 19 non-carbapenemase-producing strains. Its overall specificity and sensitivity were 100% and 97.3%, respectively, including detection of all types of OXA-48-like carbapenemases. For precise carbapenemase type identification, the assay exhibited remarkable sensitivities for class A, class B, and class D detection at 94.7%, 100%, and 100%, respectively. This user-friendly test presents a promising tool for carbapenemase identification, refining the selection of β-lactam/β-endoenzyme inhibitor combinations for effectively treating infections due to carbapenemase-producing organisms.

Diagnostic advances in sepsis: A comparative analysis of syndromic approaches and molecular biology techniques in clinical bacteremia

Sepsis remains a leading cause of morbidity and mortality. This retrospective study, conducted at Avicenne Military Hospital in Marrakech over ten years, analyzed 3721 blood cultures, identifying 420 cases of bacteremia (11.3% positivity rate). The predominant isolates included Staphylococcus aureus, coagulase-negative staphylococci, Escherichia coli, Klebsiella spp., and Acinetobacter baumannii, with significant resistance patterns observed. Notably, 50% of S. aureus were methicillin-resistant (MRSA), while extended-spectrum beta-lactamase (ESBL) production was found in 30% of E. coli and Klebsiella pneumoniae isolates. The FilmArray multiplex PCR system was utilized to enhance rapid pathogen identification, reducing turnaround time from 72 hours to under 2 hours, and demonstrated high concordance with conventional cultures. The molecular diagnostics identified various resistant strains, including carbapenemase-producing organisms in K. pneumoniae and multidrug-resistant A. baumannii, underscoring the critical need for effective antimicrobial stewardship. Overall, this study emphasizes the evolving epidemiology of bacteremia, the rising antimicrobial resistance, and the utility of rapid molecular diagnostics in guiding timely and appropriate treatment, ultimately aiming to improve patient outcomes in sepsis management.

Longitudinal genomic surveillance of a UK intensive care unit shows a lack of patient colonisation by multi-drug-resistant Gram-negative bacterial pathogens.

Vulnerable patients in an intensive care unit (ICU) setting are at high risk of infection from bacteria including gut-colonising Escherichia coli and Klebsiella species. Complex ICU procedures often depend on successful antimicrobial treatment, underscoring the importance of understanding the extent of patient colonisation by multi-drug-resistant organisms (MDROs) in large UK ICUs. Previous work on ICUs globally uncovered high rates of colonisation by transmission of MDROs, but the situation in UK ICUs is less understood. Here, we investigated the diversity and antibiotic resistance gene (ARG) carriage of bacteria present in one of the largest UK ICUs at the Queen Elizabeth Hospital Birmingham (QEHB), focusing primarily on E. coli as both a widespread commensal and a globally disseminated multi-drug-resistant pathogen. Samples were taken during highly restrictive coronavirus disease 2019 (COVID-19) control measures from May to December 2021. Whole-genome and metagenomic sequencing were used to detect and report strain-level colonisation of patients, focusing on E. coli sequence types (STs), their colonisation dynamics and antimicrobial resistance gene carriage. We found a lack of multi-drug resistance (MDR) in the QEHB. Only one carbapenemase-producing organism was isolated, a Citrobacter carrying bla KPC-2. There was no evidence supporting the spread of this strain, and there was little evidence overall of nosocomial acquisition or circulation of colonising E. coli. Whilst 22 different E. coli STs were identified, only 1 strain of the pandemic ST131 lineage was isolated. This ST131 strain was non-MDR and was found to be a clade A strain, associated with low levels of antibiotic resistance. Overall, the QEHB ICU had very low levels of pandemic or MDR strains, a result that may be influenced in part by the strict COVID-19 control measures in place at the time. Employing some of these infection prevention and control measures where reasonable in all ICUs might therefore assist in maintaining low levels of nosocomial MDR.

Temporal dynamics of extended-spectrum β-lactamase-producing Escherichia coli and carbapenemase-producing Gram-negative bacteria in hospital wastewater

Hospital wastewater is a reservoir for the environmental spread of clinically relevant antimicrobial-resistant bacteria and resistance genes. The aim of this study was to quantify total Escherichia coli, extended-spectrum β-lactamase (ESBL)-producing E. coli, and carbapenemase-producing organisms (CPOs) and perform whole-genome sequencing-based characterization of these bacterial isolates in hospital wastewater samples collected bimonthly in Japan from January to November 2021. Total E. coli counts were 8.1 × 103–8.8 × 104 colony-forming units (CFU)/mL. ESBL-producing E. coli were detected in the sampling months of January, March, May, and July, with the ratio of ESBL-producing E. coli to total E. coli being remarkably highest (95 %) in July. In contrast, DHA-1 Ambler class C β-lactamase (AmpC)-producing E. coli was detected in September and November, accounting for 28 % and 3 % of total E. coli counts, respectively. All 140 ESBL-producing E. coli isolates harbored the blaCTX-M genes, with blaCTX-M-14 being the most common genotype (94.3 %), the vast majority of which were associated with the human virulent B2-O25b: H4-ST131-fimH30R/non-Rx. In September, E. coli clade I-O8:H33-ST3910-fimH1074 was primarily associated with blaDHA-1. Among 26 representative CPO isolates, Aeromonas caviae (34.6 %) and A. hydrophila subsp. hydrophila (30.8 %) were dominant. The most frequently detected carbapenemase gene was blaIMP-1 (57.7 %), followed by blaGES-24 (34.6 %) and blaGES-4 (7.7 %). Estimated bacterial counts of CPOs ranged from 4.0 × 10−1 to 4.7 × 103 CFU/mL over the six sampling months. blaIMP-1-positive A. hydrophila subsp. hydrophila ST860, which was repeatedly detected over the five sampling months, accounted for the highest total number of this bacterial clone (79 %).Overall, this study provides insights into the overwhelming presence and persistence of E. coli B2-O25b:H4-ST131-H30R/non-Rx with blaCTX-M-14 and Aeromonas spp. with blaIMP-1 in hospital wastewater, and the change in the dynamics of resistance gene prevalence from blaCTX-M-positive E. coli to blaDHA-1-positive E. coli.

Evaluation of gradient strip diffusion for susceptibility testing of aztreonam-avibactam in metallo-β-lactamase-producing Enterobacterales.

The emergence of metallo-β-lactamase (MBL)-producing Enterobacterales presents unique clinical treatment challenges. Recently developed β-lactam/ β-lactamase inhibitor combination agents, while effective against other carbapenemase-producing organisms, are notably ineffective against MBL producers. While MBLs do not hydrolyze monobactams (aztreonam), many MBL-producing organisms are resistant to aztreonam through alternate mechanisms, leaving cefiderocol as the sole monotherapy treatment option recommended for MBL producers. Recent guidelines for the treatment of MBL-harboring organisms have added combination therapy with aztreonam and ceftazidime-avibactam, using ceftazidime-avibactam as a source of the β-lactamase inhibitor avibactam. Current laboratory testing options for the combination of aztreonam-avibactam are limited to broth microdilution (BMD) and broth disk elution (BDE) methods, which are not practical in most clinical laboratories. In this study, we evaluated the performance of aztreonam/avibactam gradient strips on 103 MBL-producing Enterobacterales patient isolates as well as an additional 31 isolates from the CDC AR Bank. All MBL Enterobacterales patient isolates included in this study harbored a New Delhi metallo-β-lactamase (blaNDM) gene. Essential agreement of gradient strip minimal inhibitory concentrations (MICs) for patient isolates compared to BMD was 93.2%. While there are no established breakpoints for aztreonam-avibactam, category agreement (CA) for patient isolates was 97.1% when using the CLSI aztreonam breakpoints. There were no major or very major errors observed. There were three minor errors. Precision for aztreonam-avibactam gradient strip diffusion was 100%. These data demonstrate that the use of gradient strip diffusion for aztreonam-avibactam MIC determination in MBL-producing Enterobacterales is a viable option for clinical laboratories.

Identification and characterisation of colistin-resistant Acinetobacter colistiniresistens co-producing IMP-1 and OXA-58 carbapenemases

BackgroundCarbapenem-resistant Acinetobacter is of increasing global concern because infections are challenging to treat with standard antibiotics. Here, we identified a previously uncharacterised Acinetobacter sp. clinical isolate as Acinetobacter colistiniresistens co-producing IMP-1 and OXA-58. We also examined expression of genes related to antibiotic susceptibility and drug resistance, including blaIMP. MethodsThe isolate was deposited at the National Institute of Technology and Evaluation (NITE) as Acinetobacter sp. NBRC 110496. Susceptibility was defined according to the Clinical and Laboratory Standards Institute (CLSI) breakpoints. Genomic and clonal analyses were performed to identify species and resistance genes. ResultsThe isolate was resistant to β-lactams, including broad-spectrum cephalosporins and carbapenems, polymyxins, and trimethoprim/sulfamethoxazole. Genomic analysis identified the isolate as A. colistiniresistens harbouring blaIMP-1, blaOXA-58, blaOXA-670, aac(6′)-Ib, aac(6′)-Ij, ant(3”)-II, aph(3’)-VI, msrE, mphE, and sul1. Colistin resistance was associated with the eptA-like gene, which encodes a lipid A-modifying enzyme. SNP-based phylogenetic analysis revealed that the strain clustered with other strains isolated in Japan. The IMP-1/OXA-58-producing strain described in this study has a novel integron structure surrounding blaIMP-1, aacA and sul1. ConclusionsColistin-resistant IMP-1/OXA-58-co-producing A. colistiniresistens was identified in a patient. This isolate could serve as a reservoir for carbapenemase-producing organisms. This study suggests that screening for colistin-resistant isolates is crucial to preserve colistin as a therapeutic agent for multidrug-resistant bacteria. Identification of this MDR isolate in Asia, and the danger of it spreading worldwide, should raise serious concerns.

Evaluation of the Xpert Carba-R assay for quantifying carbapenemase-producing bacterial load in stool samples.

The spread of Carbapenemase-producing Organisms (CPO) remains a major threat globally. Within clinical settings, the existing method of determining gene load involves traditional culture to determine bacterial load and polymerase-chain-reaction-based Xpert Carba-R Assay to determine carbapenemase gene type. However, there is a need for a fast and accurate method of quantifying CPO colonisation to study the risk of persistent CPO carriage. This study evaluated the accuracy of Xpert Carba-R Ct value in estimating carbapenamase producing bacterial loads in stool samples. Stool samples were obtained from an ongoing study investigating the household transmission of CPO in Singapore. Stool samples lacking carbapenemase producing organisms were spiked with organism carrying a single carbapenemase gene (blaKPC, blaNDM, blaVIM, blaOXA-48(-like) or blaIMP-1) and serially diluted before being subjected to Xpert Carba-R assay and traditional culture. Standard curves with regression lines showing correlation between Ct values and plate counts were generated. The standard curves were validated with stool samples collected from patients. The limit of detection of blaNDM, blaKPC, and blaOXA-48 was approximately 103 cfu/mL, while that of blaIMP-1 and blaVIM was approximately 104 cfu/mL. Validation of the blaNDM and blaOXA-48 curves revealed average delta values of 0.56 log(cfu/mL) (95% CI 0.24-0.88) and 0.80 log(cfu/mL) (95% CI 0.53-1.07), respectively. Our validation data for stool positive for blaNDM and blaOXA-48-type suggests that bacterial loads can be estimated within a reasonable range of error.

Initial empirical antibiotic therapy in kidney transplant recipients with pyelonephritis: A global survey of current practice and opinions across 19 countries on six continents.

Despite the burden of pyelonephritis after kidney transplantation, there is no consensus on initial empirical antibiotic management. We surveyed clinicians throughout the world on their practice and opinions about the initial empirical therapy of post-transplant pyelonephritis, using clinical vignettes. A panel of experts from 19 countries on six continents designed this survey, and invited 2145 clinicians to participate. A total of 721 clinicians completed the survey (response rate: 34%). In the hypothetical case of a kidney transplant recipient admitted with pyelonephritis but not requiring intensive care, most respondents reported initiating either a 3rd-generation cephalosporin (37%) or piperacillin-tazobactam (21%) monotherapy. Several patient-level factors dictated the selection of broader-spectrum antibiotics, including having a recent urine culture showing growth of a resistant organism (85% for extended-spectrum ß-lactamase-producing organisms, 90% for carbapenemase-producing organisms, and 94% for Pseudomonas aeruginosa). Respondents attributed high importance to the appropriateness of empirical therapy, which 87% judged important to prevent mortality. Significant practice and opinion variations were observed between and within countries. High-quality studies are needed to guide the empirical management of post-transplant pyelonephritis. In particular, whether prior urine culture results should systematically be reviewed and considered remains to be determined. Studies are also needed to clarify the relationship between the appropriateness of initial empirical therapy and outcomes of post-transplant pyelonephritis.