Carbapenemase-producing Enterobacteriaceae Infections Research Articles

Characterization of an NDM-1-Producing Citrobacter koseri Isolate from China.

The continuous rise in carbapenemase-producing Enterobacteriaceae infections is a major public health concern. However, there is limited information available on New Delhi metallo-β-lactamase-1 (NDM-1) producing Citrobacter koseri. In this study, we isolated a blaNDM-1-carrying C. koseri from a stool sample of an inpatient. Our aim was to investigate the phenotypic and genomic features of this clinically derived carbapenem-resistant C. koseri isolate and to characterize the transmission pattern of the IncFII/IncN plasmid that carries the blaNDM-1 gene. S1-PFGE, Southern blot and conjugation assay confirmed the presence of blaNDM-1 gene in a conjugative plasmid. C. koseri L2395 and transconjugant L2395-EC600 strains showed similar resistance spectrum. Whole-genome analysis revealed that pL2395_NDM is an IncFII/IncN plasmid with a length of 67,839 bp. Moreover, blaNDM-1 gene was found encoded in the ISKpn19-blaNDM-1-ble-tnpF-dsbD-cutA-ISKpn19 cassette array. Phylogenetic analysis revealed that strain L2395 was close to an IMP-4-bearing C. koseri from Australia. Ongoing surveillance will be essential to control and prevent the spread of carbapenem-resistant Citrobacter spp. in the future.

Characterization of 29 newly isolated bacteriophages as a potential therapeutic agent against IMP-6-producing Klebsiella pneumoniae from clinical specimens.

Carbapenemase-producing Enterobacteriaceae (CPE) are one of the most detrimental species of antibiotic-resistant bacteria globally. Phage therapy has emerged as an effective strategy for the treatment of CPE infections. In western Japan, the rise of Klebsiella pneumoniae strains harboring the pKPI-6 plasmid encoding bla IMP-6 is of increasing concern. To address this challenge, we isolated 29 phages from Japanese sewage, specifically targeting 31 K. pneumoniae strains and one Escherichia coli strain harboring the pKPI-6 plasmid. Electron microscopy analysis revealed that among the 29 isolated phages, 21 (72.4%), 5 (17.2%), and 3 (10.3%) phages belonged to myovirus, siphovirus, and podovirus morphotypes, respectively. Host range analysis showed that 18 Slopekvirus strains within the isolated phages infected 25-26 K. pneumoniae strains, indicating that most of the isolated phages have a broad host range. Notably, K. pneumoniae strain Kp21 was exclusively susceptible to phage øKp_21, whereas Kp22 exhibited susceptibility to over 20 phages. Upon administering a phage cocktail composed of 10 phages, we observed delayed emergence of phage-resistant bacteria in Kp21 but not in Kp22. Intriguingly, phage-resistant Kp21 exhibited heightened sensitivity to other bacteriophages, indicating a "trade-off" for resistance to phage øKp_21. Our proposed phage set has an adequate number of phages to combat the K. pneumoniae strain prevalent in Japan, underscoring the potential of a well-designed phage cocktail in mitigating the occurrence of phage-resistant bacteria. IMPORTANCE The emergence of Klebsiella pneumoniae harboring the bla IMP-6 plasmid poses an escalating threat in Japan. In this study, we found 29 newly isolated bacteriophages that infect K. pneumoniae strains carrying the pKPI-6 plasmid from clinical settings in western Japan. Our phages exhibited a broad host range. We applied a phage cocktail treatment composed of 10 phages against two host strains, Kp21 and Kp22, which displayed varying phage susceptibility patterns. Although the phage cocktail delayed the emergence of phage-resistant Kp21, it was unable to hinder the emergence of phage-resistant Kp22. Moreover, the phage-resistant Kp21 became sensitive to other phages that were originally non-infective to the wild-type Kp21 strains. Our study highlights the potential of a well-tailored phage cocktail in reducing the occurrence of phage-resistant bacteria.

In Vitro Activities and Inoculum Effects of Cefiderocol and Aztreonam-Avibactam against Metallo-β-Lactamase-Producing Enterobacteriaceae.

Cefiderocol and aztreonam-avibactam (ATM-AVI) both had activity against carbapenem-resistant Gram-negative bacilli, including those that produce metallo-β-lactamases (MBLs). We compared the in vitro activities and inoculum effects of these antibiotics against carbapenemase-producing Enterobacteriaceae (CPE), especially MBL-producing isolates. The MICs of cefiderocol and ATM-AVI were determined using broth microdilution method for a 2016 to 2021 collection of Enterobacteriaceae isolates which produced MBL, KPC, or OXA-48-like carbapenemases. MICs with high bacteria inoculum were also evaluated for susceptible isolates. A total of 195 CPE were tested, including 143 MBL- (74 NDM, 42 IMP, and 27 VIM), 38 KPC-, and 14 OXA-48-like-producing isolates. The susceptible rates of MBL-, KPC-, and OXA-48-like producers to cefiderocol were 86.0%, 92.1%, and 92.9%, respectively, and that to ATM-AVI were 95.8%, 100%, and 100%, respectively. NDM producers displayed lower susceptibility and higher MIC50s/MIC90s of cefiderocol (78.4%, 2/16 mg/L) than IMP (92.9%, 0.375/4 mg/L) and VIM (96.3%, 1/4 mg/L) producers. NDM- and VIM-producing Escherichia coli showed lower susceptibility to ATM-AVI (77.3% and 75.0%, respectively) compared to MBL-CPE of other species (100% susceptible). Inoculum effects for cefiderocol and ATM-AVI were observed among 95.9% and 95.2% of susceptible CPE, respectively. A switch from susceptible to resistant category was observed in 83.6% (143/171) of isolates for cefiderocol and 94.7% (179/189) for ATM-AVI. Our results revealed that NDM-producing Enterobacteriaceae had lower susceptibility to cefiderocol and ATM-AVI. Prominent inoculum effects on both antibiotics were observed for CPE, which suggested a risk of microbiological failure when they were used for CPE infections with high bacteria burden. IMPORTANCE The prevalence of infections caused by carbapenem-resistant Enterobacteriaceae is increasing worldwide. Currently, therapeutic options for metallo-β-lactamase (MBL)-producing Enterobacteriaceae remain limited. We demonstrated that clinical metallo-β-lactamase (MBL)-producing Enterobacteriaceae isolates were highly susceptible to cefiderocol (86.0%) and aztreonam-avibactam (ATM-AVI) (95.8%). However, inoculum effects on cefiderocol and ATM-AVI were observed for over 90% of susceptible carbapenemase-producing Enterobacteriaceae (CPE) isolates. Our findings highlight a potential risk of microbiological failure when using monotherapy with cefiderocol or ATM-AVI to treat severe CPE infection.

Epidemiology and Risk Factors of Carbapenemase-Producing Enterobacteriaceae Acquisition and Colonization at a Korean Hospital over 1 Year.

Background: Carbapenemase-producing Enterobacteriaceae (CPE) are known to be primarily responsible for the increasing spread of carbapenem-resistant Enterobacteriaceae and have therefore been targeted for preventing transmission and appropriate treatment. This study aimed to describe the clinical and epidemiological characteristics and risk factors of CPE infection in terms of acquisition and colonization. Methods: We examined patients' hospital data, including active screening on patients' admission and in intensive care units (ICUs). We identified risk factors for CPE acquisition by comparing the clinical and epidemiological data of CPE-positive patients between colonization and acquisition groups. Results: A total of 77 CPE patients were included (51 colonized and 26 acquired). The most frequent Enterobacteriaceae species was Klebsiella pneumoniae. Among CPE-colonized patients, 80.4% had a hospitalization history within 3 months. CPE acquisition was significantly associated with treatment in an ICU [adjusted odds ratio (aOR): 46.72, 95% confidence interval (CI): 5.08-430.09] and holding a gastrointestinal tube (aOR: 12.70, 95% CI: 2.61-61.84). Conclusions: CPE acquisition was significantly associated with ICU stay, open wounds, holding catheters or tubes, and antibiotic treatment. Active CPE screening should be implemented on admission and periodically for high-risk patients.

Long-term ecological and evolutionary dynamics in the gut microbiomes of carbapenemase-producing Enterobacteriaceae colonized subjects

Long-term colonization of the gut microbiome by carbapenemase-producing Enterobacteriaceae (CPE) is a growing area of public health concern as it can lead to community transmission and rapid increase in cases of life-threatening CPE infections. Here, leveraging the observation that many subjects are decolonized without interventions within a year, we used longitudinal shotgun metagenomics (up to 12 timepoints) for detailed characterization of ecological and evolutionary dynamics in the gut microbiome of a cohort of CPE-colonized subjects and family members (n = 46; 361 samples). Subjects who underwent decolonization exhibited a distinct ecological shift marked by recovery of microbial diversity, key commensals and anti-inflammatory pathways. In addition, colonization was marked by elevated but unstable Enterobacteriaceae abundances, which exhibited distinct strain-level dynamics for different species (Escherichia coli and Klebsiella pneumoniae). Finally, comparative analysis with whole-genome sequencing data from CPE isolates (n = 159) helped identify substrain variation in key functional genes and the presence of highly similar E. coli and K. pneumoniae strains with variable resistance profiles and plasmid sharing. These results provide an enhanced view into how colonization by multi-drug-resistant bacteria associates with altered gut ecology and can enable transfer of resistance genes, even in the absence of overt infection and antibiotic usage.

Outbreak of Carbapenemase-Producing Enterobacteriaceae in a Regional Burn Center.

Antimicrobial resistance is an increasing problem in hospitals worldwide; however, the prevalence of carbapenemase-producing Enterobacteriaceae (CPE) in our region is low. Burn patients are vulnerable to infection because of the loss of the protective skin barrier, thus burn centers prioritize infection prevention and control (IP&C). This report describes a CPE outbreak in a regional burn center. In a period of 2.5 months, four nosocomial cases of CPE were identified, three containing the Klebsiella pneumoniae carbapenemase (KPC) gene and one Verona integrin-encoded metallo-β-lactamase (VIM) gene. The first two cases were identified while there was no CPE patient source on the unit. CPE KPC gene was then isolated in sink drains of three rooms. In addition to rigorous IP&C practices already in place, we implemented additional outbreak measures including restricting admissions to patients with complex burns or burns ≥10% TBSA, admitting patients to other in-patient units, and not permitting elective admissions. We began cohorting patients using nursing team separation for CPE-positive and -negative patients and geographical separation on the unit. Despite aggressive IP&C measures already in place, hospital-acquired CPE colonization/infection occurred. Given that CPE contaminated sinks of the same enzyme were identified, we believe hospital sink drains may the source. This highlights the importance of sink design and engineering solutions to prevent the formation of biofilm and reduce splashing. CPE infections are associated with poor outcomes in patients and significant health system costs due to a longer length of stay and additional institutional resources.

Frecuencia de enterobacterias productoras de carbapenemasas en hisopados anales de adultos en una unidad de cuidados críticos

The carbapenemase-producing enterobacteriaceae (CPE) are one of the main concerns of global health, mainly those that are encoded by plasmids. The aim was to describe the progress of colonization by CPE in anal swabs of patients of intensive care unit (ICU) and COVID-ICU in an adult hospital from Chaco province, Argentina. A descriptive retrospective study was carried out between 2021 January to August. 379 anal swabs were studied, in 26% (n=98) CPE were detected. K. pneumoniae was the more frequent isolate. In January, in COVID-ICU, 18% of anal swabs where positive, being all identified as KPC carbapenemase. In August, in COVID-ICU, the total of positive anal swab raised to 81% and all detected carbapenemase were MBL type. In ICU, the percentage of positive anal swabs increased from 14% in January to 49% in August, where both KPC and MBL carbapenemases were detected. Of The total of colonized patients, 15% developed CPE infection. Active surveillance and control measures are necessary to keep down the spread of CPE.

Probabilistic microsimulation to examine the cost-effectiveness of hospital admission screening strategies for carbapenemase-producing enterobacteriaceae (CPE) in the United Kingdom

BackgroundAntimicrobial resistance has been recognised as a global threat with carbapenemase- producing-Enterobacteriaceae (CPE) as a prime example. CPE has similarities to COVID-19 where asymptomatic patients may be colonised representing a source for onward transmission. There are limited treatment options for CPE infection leading to poor outcomes and increased costs. Admission screening can prevent cross-transmission by pre-emptively isolating colonised patients.ObjectiveWe assess the relative cost-effectiveness of screening programmes compared with no- screening.MethodsA microsimulation parameterised with NHS Scotland date was used to model scenarios of the prevalence of CPE colonised patients on admission. Screening strategies were (a) two-step screening involving a clinical risk assessment (CRA) checklist followed by microbiological testing of high-risk patients; and (b) universal screening. Strategies were considered with either culture or polymerase chain reaction (PCR) tests. All costs were reported in 2019 UK pounds with a healthcare system perspective.ResultsIn the low prevalence scenario, no screening had the highest probability of cost-effectiveness. Among screening strategies, the two CRA screening options were the most likely to be cost-effective. Screening was more likely to be cost-effective than no screening in the prevalence of 1 CPE colonised in 500 admitted patients or more. There was substantial uncertainty with the probabilities rarely exceeding 40% and similar results between strategies. Screening reduced non-isolated bed-days and CPE colonisation. The cost of screening was low in relation to total costs.ConclusionThe specificity of the CRA checklist was the parameter with the highest impact on the cost-effectiveness. Further primary data collection is needed to build models with less uncertainty in the parameters.

Validation of the Giannella Risk Score for the Prediction of Infection by Carbapenemase-producing Enterobacteriaceae in the Pediatric Population.

Despite efforts made to prevent the spread of multi-drug-resistant bacteria, carbapenemase-producing Enterobacteriaceae (CPE) has become one of the most dangerous threat worldwide. However, data on the epidemiology of CPE and on the correlation between CPE colonization and infection are scanty. The objectives of this study were first to describe the epidemiologic characteristics of colonizations and invasive CPE infections in the pediatric population, and second, to apply the Giannella Risk Score (GRS) to the pediatric population for the assessment of the risk of invasive CPE infection in patients with already known colonization. Pediatric patients with evidence of colonization by CPE were retrospectively enrolled. For each colonized patient, the subsequent development of an infection by CPE was then assessed for a 90-day period after the first CPE isolation; GRSs were compared between patients who had developed any type of CPE infection and those without infection. A total of 215 patients (113 males and 102 females) with at least 1 isolation of CPE during hospitalization were analyzed. Median age was 5.6 years [interquartile range (IQR), 1.89-12.2 years]. Overall, 28 CPE infections (13%) were documented: 23 blood stream infections and 5 complicated urinary tract infections. The 30-day mortality of invasive CPE infections was 34.8%. The GRS values in patients with any CPE infection were statistically higher than in noninfected patients: median GRS 9 (IQR, 4-12.5) versus 4 (IQR, 2-4), respectively; P < 0.0001. The analysis of the receiver operating characteristic curves identified a GRS cut-off value ≥8 as the best predictor of CPE infection. The likelihood ratio of the results was <2 and the informedness of the test had a value <0.50. Our study confirms that the spread of CPE is an impelling problem also in the pediatric population, with a high mortality rate of invasive infections. However, the application of the GRS appears to be poorly informative in the pediatric setting; it might sometimes help to identify patients at very low-risk of CPE infection, in whom it is reasonable to spare targeted antimicrobial treatments.

Carbapenem-resistant bacteria in an intensive care unit during the coronavirus disease 2019 (COVID-19) pandemic: A multicenter before-and-after cross-sectional study.

To assess the incidence of colonization and infection with carbapenemase-producing Enterobacteriaceae (CPE) and carbapenem-resistant Acinetobacter baumannii (CR-Ab) in the ICUs of our city hospitals before and during the coronavirus disease 2019 (COVID-19) pandemic. We conducted a multicenter, before-and-after, cross-sectional study to compare the rates of colonization and infection with CPE and/or CR-Ab in 2 study periods, period 1 (January-April 2019) and period 2 (January-April 2020). Incidence rate ratios (IRRs) and 95% confidence intervals (CIs) of weekly colonization and infection rates for each period were compared for the 2 study periods using Poisson regression. Weekly trends in the incidence of colonization or infection for each study period were summarized using local weighted (Loess) regression. We detected no significant change in either IRR and weekly trend in CPE colonization and infection during the 2 study periods. A shift from KPC to other CPE mechanisms (OXA-48 and VIM) was observed during period 2. Compared to period 1, during period 2 the IRR of colonization and infection with CR-Ab increased 7.5- and 5.5-fold, respectively. Genome sequencing showed that all CR-Ab strains belonged to the CC92/IC2 clonal lineage. Clinical strains clustered closely into a single monophyletic group in 1 of the 3 centers, whereas they segregated in 2 different clusters in the other 2 centers, which strongly indicates horizontal transmission. Our findings indicate the need to conduct infection control activities targeted against the spread of antimicrobial resistance between and within hospitals during the COVID-19 pandemic, and if necessary, remodulating them according to the new organizational structures imposed by the pandemic.

Genomic and clinical characterisation of multidrug-resistant carbapenemase-producing ST231 and ST16 Klebsiella pneumoniae isolates colonising patients at Siriraj hospital, Bangkok, Thailand from 2015 to 2017

BackgroundInfections caused by carbapenemase-producing Enterobacteriaceae (CPE) have continually grown as a global public health threat, with significant mortality rates observed across the world. We examined the clinical data from patients with CPE infections and their outcomes, concentrating on Klebsiella pneumoniae isolates. We analysed the clinical information, performed antimicrobial susceptibility testing, and conducted molecular epidemiological and genomic analyses on the isolates to identify patterns in the data.MethodsThe clinical characteristics of 33 hospitalised patients with confirmed CPE, including patient-related factors associated with the development of CPE infections, were examined. Patients were divided according to whether they were “colonised” or “infected” with CPE and by the timing and frequency of their rectal swab collections, from which 45 swabs were randomly selected for analysis. CPE isolates were purified, and antimicrobial susceptibility tests performed. Whole genome sequences of these isolates were determined and analysed to compute bacterial multilocus sequence types and plasmid replicon types, infer phylogenetic relationships, and identify antimicrobial resistance and virulence genes.ResultsAltogether, 88.9% (40/45) of the CPE isolates were K. pneumoniae. The most abundant carbapenemase gene family in the K. pneumoniae isolates (33/39) was blaOXA-232, with blaNDM-1 additionally identified in 19 of them. All CPE isolates carrying either blaOXA-232 or blaNDM-1 were resistant to meropenem, but only 40 from 45 were susceptible to colistin. Among the CPE-infected patients (n = 18) and CPE-colonised patients who developed CPE infections during the study (n = 3), all but one received standard colistin-based combination therapy. Phylogenetic analysis revealed the polyclonal spread of carbapenemase-producing K. pneumoniae (CPKP) within the patient population, with the following two major subclades identified: ST16 (n = 15) and ST231 (n = 14). CPKP-ST231 had the highest virulence score of 4 and was associated with primary bacteraemia. The siderophores yersiniabactin and aerobactin, considered to be important virulence factors, were only identified in the CPKP-ST231 genomes.ConclusionsThis study has revealed the genomic features of colonising CPE isolates, focusing on antimicrobial resistance and virulence determinants. This type of multi-layered analysis can be further exploited in Thailand and elsewhere to modify the regimes used for empirical antibiotic treatment and improve the management strategies for CPE infections in hospitalised patients.

Carbapenemase-producing Enterobacteriaceae in transplant patients.

Carbapenemase-producing Enterobacteriaceae (CPE) are a serious public health concern and represent a major threat to immunocompromised hosts, including solid organ (SOT) and stem cell transplant (HSCT) recipients. Transplant patients are at particular risk of developing CPE colonization and/or infection due to their frequent exposure to prolonged courses of broad-spectrum antibiotics, altered immunocompetence and exposure to invasive procedures and immunosuppressive drugs. Gut colonization with CPE, in particular carbapenem-resistant Klebsiella pneumoniae, may occur before or after SOT in 2%-27% of patients and among 2%-9% of HSCT and has been associated with increased risk of developing CPE infections. In endemic areas, CPE infections occur in up to 18% of SOT, and HSCT patients can account for 5%-18% of all patients with CPE bacteraemia. Mortality rates up to 70% have been associated with CPE infections in both patient populations. The rapid initiation of an active therapy against CPE is advocated in these infections. Therapeutic options, however, are limited by the paucity of novel compounds that are currently available and by potential antibiotic-associated toxicities. Therefore, a multidisciplinary approach involving infection control and antimicrobial stewardship programmes still represents the mainstay for the management of CPE infections among transplant patients. The evidence for the use of prevention strategies such as CPE-targeted perioperative prophylaxis or gut decolonization is still scarce. Large, multicentre trials are required to better define prevention strategies and to guide the management of CPE infections in the transplant setting.

Treatment of invasive IMP-4 Enterobacter cloacae infection in transplant recipients using ceftazidime/avibactam with aztreonam: A case series and literature review.

Infections caused by carbapenemase-producing Enterobacteriaceae (CPE) are an emerging threat in both solid organ and stem cell transplant recipients. Invasive CPE infections in transplant recipients are associated with a high mortality, often due to limited therapeutic options and antibacterial toxicities. One of the most therapeutically challenging group of CPE are the metallo-β-lactamase (MBL)-producing Gram-negative bacteria, which are now found worldwide, and often need treatment with older, highly toxic antimicrobial regimens. Newer β-lactamase inhibitors such as avibactam have well-established activity against certain carbapenemases such as Klebsiella pneumoniae carbapenemases (KPC), but have no activity against MBL-producing organisms. Conversely, aztreonam has activity against MBL-producing organisms but is often inactivated by other co-existing β-lactamases. Here, we report four cases of invasive MBL-CPE infections in transplant recipients caused by IMP-4-producing Enterobacter cloacae who were successfully treated with a new, mechanism-driven antimicrobial combination of ceftazidime/avibactam with aztreonam. This novel antimicrobial combination offers a useful treatment option for high-risk patients with CPE infection, with reduced drug interactions and toxicity.

Risk factors for the development of infections associated with carbapenemase-producing Enterobacteriaceae among previously colonized patients: A retrospective cohort study.

Not all patients who acquire carbapenemase-producing Enterobacteriaceae (CPE) develop infections by these organisms; many remain only colonized. Of 54 CPE-colonized patients, 16 (30%) developed CPE infections. We identified indwelling urinary catheter exposure, exposure to intravenous colistin, and overseas transfer as variables associated with CPE infection development among colonized patients.

Analysis of Paradoxical Efficacy of Carbapenems against Carbapenemase-Producing Escherichia coli in a Murine Model of Lethal Peritonitis.

The clinical benefit of carbapenems against carbapenemase-producing Enterobacteriaceae (CPE) remains in question. MICs of imipenem (IMP) and ertapenem (ERT) against isogenic derivatives of the wild-type strain Escherichia coli CFT073 producing KPC-3, OXA-48, or NDM-1 were 0.25, 2, 16, and 64 mg/liter for IMP and 0.008, 0.5, 8, and 64 mg/liter for ERT, respectively. Swiss ICR-strain mice with peritonitis were treated for 24 h with IMP or ERT. Despite a limited duration of time during which free antibiotic concentrations were above the MIC (down to 0% for the NDM-1-producing strain), IMP and ERT significantly reduced bacterial counts in spleen and peritoneal fluid at 24 h (P < 0.005) and prevented mortality. Several possible explanations were investigated. Addition of 4% albumin or 50% normal human serum did not modify IMP activity. Bacterial fitness of resistant strains was not altered and virulence did not decrease with resistance. In the presence of subinhibitory concentrations of ERT, growth rates of OXA-48, KPC-3, and NDM-1 strains were significantly decreased and filamentation of the NDM-1 strain was observed. The expression of blaNDM-1 was not decreased in vivo compared to in vitro No zinc depletion was observed in infected mice compared with Mueller-Hinton broth. In conclusion, a paradoxical in vivo efficacy of IMP and ERT against highly resistant carbapenemase-producing E. coli was confirmed. Alternative mechanisms of antibacterial effects of subinhibitory concentrations of carbapenems may be involved to explain in vivo activity. These results are in agreement with a potential clinical benefit of carbapenems to treat CPE infections, despite high carbapenem MICs.

Epidemiología, tratamiento y mortalidad en pacientes infectados por enterobacterias productoras de carbapenemasas: estudio retrospectivo

Carbapenemase-producing Enterobacteriaceae (CPE) has become a significant problem in terms of public health and clinical outcome. To assess the epidemiology, treatment and mortality in patients with infection due to CPE. A retrospective analysis of 163 patients with CPE infection was carried out in a university hospital from July 2013 to October 2015. A total of 163 patients were included over the study period. Klebsiella pneumoniae was isolated in 95.1% of cases, and most of carbapenemases belonged to the OXA-48 group (93.0%). Acquisition was nosocomial in 124 cases (77.0%), healthcare-associated in 30 (18.6%), and 7 cases (4.3%) were community-acquired. The most frequent infections identified in this study were urinary tract (48.4%) and respiratory (19.5%) infections. Approximately half of the patients received antibiotic monotherapy. The 30-day mortality rate was 23.3%. Multivariate analysis revealed that the presence of septic shock at diagnosis (OR 4.2; IC 95% 1.5-11) was independently associated with an increase in death during the first month, unable to identify association with inappropriate antibiotic treatment. Further studies are needed to clarify whether antibiotic treatment of EPC infections should be combined or if monotherapy might be sufficient in mild infections.

In vitro effect of an antimicrobial combination therapy without colistin and tigecycline for CPE and non-CPE

IntroductionThis study aimed to investigate the in vitro effects of a combination of antimicrobials other than colistin (CL) and tigecycline (TGC) on carbapenem-resistant Enterobacteriaceae (CRE). MethodsWe used 72 CRE strains including 65 carbapenemase-producing Enterobacteriaceae (CPE) that produce IMP-1, IMP-6, NDM, KPC, and OXA-48-like carbapenemases; and 7 carbapenemase-nonproducing Enterobacteriaceae (non-CPE) strains. These strains were assessed using antimicrobial susceptibility testing, breakpoint checkerboard (BC) plate method, and kill curve experiment to determine the effect of the combination therapy. ResultsNDM, KPC, and OXA-48-like carbapenemase-producers showed higher MICs of carbapenem and aminoglycosides, and lower MICs of minocycline, compared to non-CPE and IMP-1/-6-producers. The results of the BC plate method suggested that the suitability of combinations of antimicrobials differ depending on the type of carbapenemases. Killing curve experiments demonstrated bactericidal or bacteriostatic action of the combination of antimicrobials even in sub-MIC concentrations of drugs. Our results suggest that the most effective antimicrobial combinations for each carbapenemase-producers are as follows; IMP-1 (tobramycin + tazobactam/piperacillin), IMP-6 (gentamicin + meropenem), NDM (minocycline + biapenem), KPC (arbekacin + doripenem) and OXA-48-like (minocycline + imipenem). ConclusionThese results suggest that the combination of antimicrobials other than CL and TGC may be another candidate for the treatments of CPE infections, even though we have to choose effective antimicrobial combinations depending on the type of carbapenemase.

Outbreak of carbapenemase-producing Enterobacteriaceae associated with a contaminated water dispenser and sink drains in the cardiology units of a Korean hospital

Concerns are growing over the importance of the hospital water environment for the transmission of carbapenemase-producing Enterobacteriaceae (CPE). To report a large outbreak in the cardiology units involving intensive care units (ICUs) and wards at a tertiary-care hospital. This was a contact tracing, case-control study to find the risk factors for acquisition of CPE and environmental sampling was performed during a CPE outbreak between July and December 2018. A total of 87 patients with CPE infection or colonization were identified in the cardiology units of the Asan Medical Centre. Diverse organisms were identified containing blakpc, blaNDM-1, blaVIM or blaIMP, blaOXA-48, and co-producing organisms. A case-control study indicated that using the sinks in the ward patient room bathroom for teeth brushing was associated with CPE acquisition (83% vs 30%; P=0.03). The environment was cultured and Klebsiella pneumoniae carbapenemase (KPC)-producing Escherichia coli was isolated from a water dispenser and New Delhi metallo-beta-lactamase (NDM) 1-producing Citrobacter freundii and Enterobacter cloacae from sinks in patient rooms. Pulsed-field gel electrophoresis (PFGE) analysis of KPC-producing E.coli from patients and the water dispenser in ICU and NDM-1-producing E.cloacae from the patient and sink drain showed the same pulsotypes. The water dispenser and sink drain were suspected as possible reservoirs of CPE in this outbreak. Close contacts with contaminated water such as tooth brushing were identified as risk factors for CPE acquisition. Education for the adequate use of the water environment system as well as the control of the hospital water environment should be implemented to prevent the CPE outbreaks.

Comparison of the inoculum size effects of antibiotics on IMP-6 β-lactamase-producing Enterobacteriaceae co-harboring plasmid-mediated quinolone resistance genes.

Almost all cases of carbapenemase-producing Enterobacteriaceae infections in Japan are caused by blaIMP-positive Enterobacteriaceae (especially blaIMP-6) and infections caused by other types of carbapenemase-producing Enterobacteriaceae are quite rare. We examined drug resistance genes co-harboring with blaIMP-6 and their inoculum size effects. We screened β-lactamase genes, plasmid-mediated quinolone resistance (PMQR) genes, and aminoglycoside-modifying enzyme genes by PCR and performed sequencing for 14 blaIMP-6-positive Enterobacteriaceae. Further, all PMQR-positive isolates were submitted to conjugation and inoculum effect evaluation. Our data showed that 13 of the 14 isolates harbored CTX-M-2 and one co-harbored CTX-M-2 and CTX-M-1 as extended-spectrum β-lactamases. All isolates carried one or more PMQRs; aac(6’)-Ib-cr was the most prevalent (92.8%), and was followed by oqxA (64.3%), qnrS (50%), oqxAB (21.4%), and qnrB (14.3%). However, Klebsiella pneumoniae contains chromosomal OqxAB. Inoculum size effects were significant in all strains for meropenem, 13 strains for imipenem, 7 for levofloxacin, and 3 for amikacin. We observed that 11 of the experimental strains (100%), 8 strains (72.7%), and 1 strain showed inoculum size effects for meropenem, imipenem, and amikacin, respectively. However, four strains harbored qnr genes and two strains harbored qnr genes and QRDR mutations concurrently; no inoculum size effect was seen for levofloxacin. The blaIMP-6-positive Enterobacteriaceae that we studied was found to harbor at least one plasmid-mediated drug resistance gene. The inoculum size effect for carbapenems was thought to be mainly due to IMP-6-type metallo-β-lactamase; however qnrB and qnrS also had a minimal impact on the inoculum size effect for levofloxacin.

2455. Outbreak of carbapenemase-producing Enterobacteriaceae in cardiology units associated with contaminated water dispenser and sink drain in Korea

BackgroundThere is a growing concern about the importance of hospital water environment for the transmission of carbapenemase-producing Enterobacteriaceae (CPE). Herein, we report a large outbreak in cardiology units involving intensive care units (ICU) and wards at a tertiary care hospital.MethodsDuring a CPE outbreak between July and December 2018, contact tracing and environmental sampling were performed. For outbreak control, we performed education to healthcare workers, hand hygiene enforcement, active surveillance test, preemptive isolation, chlorhexidine bathing for CPE positive patients, and deep terminal cleaning including UV and hydrogen peroxide non-touch disinfection. Patients with CPE were isolated at a single room with dedicated staffs, contact precaution was implemented, and when case patients were located in multi-patient room, we performed surveillance culture for exposed patients in the room.ResultsA total of 87 patients with CPE infection or colonization were identified at two cardiology ICUs and three cardiology wards. CPE from the first two index patients were identified from sputum culture suspecting pneumonia, and the remaining 85 patients were identified to harbor CPE through surveillance culture (exposed patients n = 22, active surveillance test n = 63). Diverse organisms were identified; organisms with blakpc (n = 13), blaNDM-1 (n = 55), blaVIM or blaIMP (n = 12), blaOXA-48 (n = 3), and co-producing organisms (n = 4). We performed environmental culture; KPC-producing Escherichia coli was isolated from water dispenser in ICU and NDM-1 producing Citrobacter freundii and Enterobacter cloacae were isolated from sinks in the patient room. Outbreak ended after the removal of water dispenser and the replacement of sink drain with pouring bleach to the sink drain.ConclusionWater dispenser and sink drain were suspected for the possible reservoirs of CPE in this outbreak. Replacement of plumbing system and use of bleach for pouring to sink as well as the removal of water dispenser was needed to control outbreak. Investigation of water system is warranted for finding the source of CPE. Disclosures All authors: No reported disclosures.