Intestinal Carriage of Carbapenemase-Producing Organisms: Current Status of Surveillance Methods

Identification of carbapenemase-producing Enterobacteriaceae reservoirs in wet hospital environments as a potential factor in patient acquisition: A cross-sectional study in a French university hospital in 2023

OBJECTIVES

Wet hospital environments have been documented as potential reservoirs for Carbapenemase-producing Enterobacteriaceae (CPE), possibly contributing to outbreaks among inpatients. Our objectives were to assess the prevalence of CPE reservoirs in a hospital's wet environments and to investigate the contamination of adjacent dry surfaces.

METHODS

From March to August 2023, we conducted a cross-sectional study in two hospital wards experiencing ongoing large outbreaks. Sampling of the environment was undertaken in two distinct phases. During phase 1, 38 shower drains and 38 toilet bowls, defined as the wet environment, were sampled using swabs. Phase 2 consisted in sampling adjacent dry surfaces, using wipes in rooms that had tested positive during phase 1. Samples were plated on a selective medium (chromID®CARBASMART, bioMérieux). Species were identified using the matrix-assisted laser desorption/ionization-time of flight (MALDI-TOF) technique. Carbapenemases were detected by OKNVI RESIST-5® (CORIS BioConcept).

RESULTS

From the 38 patient rooms, 76 samples were taken during phase 1. All in all, 33 (86.8%) rooms presented at least one CPE reservoir in the wet environment; there were 32 (84.2%) contaminated shower drains and six (15.8%) contaminated toilet bowls. Among 57 identified CPEs, the most frequent strain was Enterobacter cloacae VIM (13, 22.8%). During phase 2, 11 (8.3%) out of 132 samples tested positive for CPE. Enterobacter cloacae complex VIM accounted for six (54.5%) of the CPE strains.

CONCLUSION

These findings suggest that the wet hospital environments were broadly contaminated with CPE, mostly Enterobacter cloacae VIM. The spread of CPE from wet environments to dry surfaces seemed limited.

Development and Validation of the MAST ISOPLEX®VTEC Kit for Simultaneous Detection of Shiga Toxin/Verotoxin 1 and 2 (stx1/vt1 and stx2/vt2) with Inhibition Control (IC) in a Rapid Loop-Mediated Isothermal Amplification (LAMP) Multiplex Assay

Loop-mediated isothermal amplification (LAMP) is a cost-effective, rapid, and highly specific method of replicating nucleic acids. Adding multiple targets into a single LAMP assay to create a multiplex format is highly desirable for clinical applications but has been challenging due to a need to develop specific detection techniques and strict primer design criteria. This study describes the evaluation of a rapid triplex LAMP assay, MAST ISOPLEX®VTEC, for the simultaneous detection of Shiga toxin/verotoxin 1 and 2 (stx1/vt1 and stx2/vt2) genes in verotoxigenic Escherichia coli (E. coli) (VTEC) isolates with inhibition control (IC) synthetic DNA using a single fluorophore-oligonucleotide probe, MAST ISOPLEX®Probes, integrated into the primer set of each target. MAST ISOPLEX®Probes used in the MAST ISOPLEX®VTEC kit produce fluorescent signals as they integrate with reaction products specific to each target, allowing tracking of multiple amplifications in real time using a real-time analyzer. Initial validation on DNA extracts from fecal cultures and synthetic DNA sequences (gBlocks) showed that the MAST ISOPLEX®VTEC kit provides a method for sensitive simultaneous triplex detection in a single assay with a limit of detection (LOD) of less than 100 target copies/assay and 96% and 100% sensitivity and specificity, respectively.

Accuracy of Xpert Carba-R Assay for the Diagnosis of Carbapenemase-producing Organisms from Rectal Swabs in Asia: a Diagnostic Meta-analysis

The Cepheid Xpert Carba-R assay has been demonstrated to be reliable for rapid detection of carbapenemase-producing orgnisms (CPO) directly from rectal swabs but the performance of which remains unclear in Asia.We searched PubMed, EMBASE and Cochrane Library databases to identify studies according to predetermined criteria. STATA 13.0 software was used to analyze the tests for sensitivity, specificity, positive likelihood ratio (PLR), negative likelihood ratio (NLR), area under the summary receiver operating characteristic curves (AUC). QUADAS-2 was used to assess the quality of included studies with RevMan 5.2. A total of 5 unique studies involving 10807 samples met the inclusion criteria. The pooled sensitivity, specificity, PLR, NLR, and the AUC with 95% CIs of Xpert Carba-R were 0.91 (0.72-0.97), 0.99 (0.96-1.00), 71.24 (25.41-199.73), 0.09 (0.03-0.32), 0.99 (0.98-1.00), respectively. Deeks'funnel plot showed no publication bias.The present meta-analysis showed the Xpert Carba-R assay had good sensitivity and perfect specificity for detecting CPOs on rectal swabs.

Carbapenemase producing Gram negative bacteria: Review of resistance and detection methods

Gram negative bacilli that are carbapenem resistant have emerged and are spreading worldwide. Infections caused by carbapenem resistant isolates posses a significant threat due to their high morbidity and mortality rates. Carbapenemases production by multi-drug resistant pathogens severely restricts treatment choices for illnesses caused by bacteria that are resistant to both carbapenems and majority of β-lactam antibiotics. Various phenotypic and genotypic methods for identification can distinguish between different classes of carbapenemase and identify pathogens that are resistant to carbapenems. The establishment of a quick, accurate and reliable test for identifying the clinical strains that produce the carbapenemase enzyme is essential for optimum diagnosis of microbial pathogens and management of the global rise in the prevalence of carbapenemase producing bacterial strains. The aim of this review was to summarize the mechanisms of carbapenem resistance and to provide an overview of different carbapenemase detection methods for carbapenem resistant Gram negative bacilli.

Combined Use of Phenotypic Screening and of a Novel Commercial Assay (REALQUALITY Carba-Screen) for the Rapid Molecular Detection of Carbapenemases: A Single-Center Experience

Carbapenem resistance is a serious public health threat, causing numerous deaths annually primarily due to healthcare-associated infections. To face this menace, surveillance programs in high-risk patients are becoming a widespread practice. Here we report the performance of the combined use of a recently approved commercial multiplex real-time PCR assay (REALQUALITY Carba-Screen kit) with conventional phenotypic screening. In this three-month study, 479 rectal swabs from 309 patients across high-risk units were evaluated by combining the two approaches. Although the molecular assay showed a higher positivity rate than phenotypic screening (7.1% vs. 5%), it should be noted that the molecular method alone would have missed eight carbapenem-resistant isolates, while using only phenotypic screening would not have detected sixteen isolates. This demonstrates the complementary strengths of each method. Our study confirms the need for a combined approach to maximize the possible clinical impact of this kind of screening, ensuring a more comprehensive detection of resistant strains.

Retrospective Tertiary Care-Based Cohort Study on Clinical Characteristics and Outcomes of Ceftazidime-Avibactam-Resistant Carbapenem-Resistant Klebsiella pneumoniae Infections

Introduction

The advent of ceftazidime-avibactam (CAZ-AVI)-resistant carbapenem-resistant Klebsiella pneumoniae (CRKP) isolates has been steadily documented in recent years. We aimed to identify risk factors of CAZ-AVI-resistant CRKP infection and assess clinical outcomes of patients.

Methods

The study retrospectively examined the clinical and microbiological data of patients with ceftazidime avibactam susceptible and ceftazidime avibactam-resistant Klebsiella pneumonia carbapenem-resistant enterobacteriaceae infection to identify risk factors, clinical features, and outcomes using multivariate logistic regression analysis.

Results

A total of 152 patients with CRKP infection were enrolled in this study. Patients with CAZ-AVI-resistant CRKP isolates (20/34 = 58.8%) had prior exposure to carbapenems (p=0.003) and had more tracheostomies (16/34 = 47.1%) (p=0.001). Only 8/28 (28.6%) patients with CAZ-AVI susceptible CRKP isolates died amongst those administered ceftazidime-avibactam compared to 49/90 (54.4%) who did not receive the same (p=0.016). 1/9 (11.1%) patients with CAZ-AVI-resistant CRKP isolates who received colistin died compared to 13/25 (52%) who did not receive colistin (p=0.03). There was no association between presence of CAZ-AVI-resistant CRKP isolates and overall mortality (odds ratio: 0.7; 95% CI: 0.3, 1.6), and no independent predictors of risk factors to overall mortality in the group with CAZ-AVI-resistant CRKP isolates were noted.

Conclusion

Early advent of CAZ-AVI resistance in CRE isolates highlights the dynamic necessity of routine CAZ-AVI resistance laboratory testing and antimicrobial stewardship programmes focusing on the utilization of all antibiotics. Consolidating the hospital infection control of tracheostomies may help to prevent CAZ resistance in CRKP. Colistin may aid in decreasing of mortality rates among patients with CAZ-AVI CRKP isolates.

Utilization of an immunochromatographic lateral flow assay for rapid detection of carbapenemase production in gram negative bacilli

BACKGROUND

Rapid detection of carbapenemase production in gram negative bacilli has important treatment considerations.

OBJECTIVE

We evaluated a lateral flow assay (LFA) for carbapenemase production compared with molecular detection of 5 (blaKPC, blaNDM, blaVIM, blaIMP, and blaOXA-48) carbapenemase genes.

METHODS

A total of 218 carbapenem nonsusceptible strains, including species of Enterobacterales, Pseudomonas aeruginosa isolated from clinical cultures were tested using the Cepheid Xpert Carba-R assay and the NG Biotech Carba-5 lateral flow immunoassay.

RESULTS

Overall agreement with LFA was 98.2% with accuracy for each target >99% compared with polymerase chain reaction. Results were available within 15 minutes compared with 1 hour for molecular detection.

CONCLUSION

The use of accurate, rapid diagnostics compliments antimicrobial stewardship programs.

Tigecycline-Rifampicin Restrains Resistance Development in Carbapenem-Resistant Klebsiella pneumoniae

The goal of this study was to clarify the synergistic antibacterial activity of the combination of tigecycline (TGC) and rifampicin (RIF). Additionally, the study sought to investigate the impact of this combination on the development of mutational resistance and to assess its efficacy in an in vivo model using Galleria mellonella. Through a checkerboard test, we found that the combination of TGC and RIF showed synergistic antibacterial activity against carbapenem-resistant Klebsiella pneumoniae (CRKP). The fractional inhibition concentration index (FICI) was found to be ≤0.5, confirming the potency of the combination. Additionally, this synergistic effect was further validated in vivo using the G. mellonella infection model. TGC-RIF treatment had a lower mutant prevention concentration (MPC) than that of monotherapy, indicating its potential to reduce the development of mutational resistance. We observed a substantial variation in the MPCs of TGC and RIF when they were measured at different proportions in the combinations. Furthermore, during the resistant mutant selection window (MSW) test, we noticed a correlation between strains with low FICI and low MSW. The expression of efflux-pump-related genes, namely rarA and acrB, is significantly decreased in the combination therapy group. This indicates that altered expression levels of certain efflux pump regulator genes are associated with a combined decrease in bacterial mutation resistance. In conclusion, the combination of TGC and RIF effectively suppresses antibiotic resistance selection in CRKP. This study establishes a paradigm for evaluating drug-resistant mutant suppression in antimicrobial combination therapy.

Nutritional drinks and enteral feeds promote the growth of carbapenemase-producing Enterobacterales in conditions that simulate disposal in hospital sinks

BACKGROUND

Studies have shown that nutritional products are discarded via handwash sinks by healthcare workers, and this practice may promote bacterial growth, including growth of pathogens such as carbapenemase-producing Enterobacterales (CPE). Outbreaks and acquisition of CPE in nosocomial settings are associated with negative outcomes for patients and hospitals.

OBJECTIVES

To investigate the potential growth-promoting effect of nutritional support drinks (NSDs) and enteral tube-feed products (ETFPs) on CPE.

METHODS

Six different CPE strains were grown in five different diluted NSDs, five different diluted ETFPs, Mueller-Hinton broth (MHB) and M9 minimal salts media to simulate discarding a small volume of nutritional product in a u-bend, already containing liquid. CPE were enumerated at 0 h, 6 h and 24 h, and compared using two-way analysis of variance and Dunett test, with confidence levels at 95%. Spearman's r was used to measure the strength of correlation between component concentrations in nutritional products and CPE growth.

RESULTS

All NSDs and ETFPs promoted CPE growth that exceeded both M9 (negative growth control) and MHB (positive growth control). In several cases, growth in NSDs/ETFPs was significantly greater compared with growth in MHB.

CONCLUSION

Nutritional products support CPE growth under in-vitro conditions. The propensity of CPE to survive in drain pipework suggests that inappropriate product disposal may further nourish established CPE in these environmental reservoirs. The growth observed in diluted NSDs and ETFPs shows that modifiable practices should be optimized to mitigate the potential risk of CPE transmission from these reservoirs.

Comparison of Risk Stratification Approaches to Identify Patients with Clostridioides difficile Infection at Risk for Multidrug-Resistant Organism Gut Microbiota Colonization

INTRODUCTION

Multidrug-resistant organisms (MDRO) commonly colonize the gut microbiota of patients with Clostridioides difficile infection (CDI). This increases the likelihood of systemic infections with these MDROs. To help guide MDRO screening and/or empiric antibiotic therapy, we derived and compared predictive indices for MDRO gut colonization in patients with CDI.

METHODS

This was a multicenter, retrospective cohort study of adult patients with CDI from July 2017 to April 2018. Stool samples were screened for MDRO via growth and speciation on selective antibiotic media and confirmed using resistance gene polymerase chain reaction. A regression-based risk score for MDRO colonization was constructed. Predictive performance via area under the receiver operating characteristic curve (aROC) of this index was compared with two other simplified risk stratification approaches: (1) prior healthcare exposure and/or high-CDI risk antibiotics; (2) number of prior high-CDI risk antibiotics.

RESULTS

50 (20.8%) of 240 included patients had MDRO colonization; 35 (14.6%) VRE, 18 (7.5%) MRSA, 2 (0.8%) CRE. Prior fluoroquinolone (aOR 2.404, 95% CI 1.095-5.279) and prior vancomycin (1.996, 95% CI 1.014-3.932) were independently associated with MDRO colonization while prior clindamycin (aOR 3.257, 95% CI 0.842-12.597) and healthcare exposure (aOR 2.138, 95% CI 0.964-4.740) were retained as explanatory variables. The regression-based risk score significantly predicted MDRO colonization (aROC 0.679, 95% CI 0.595-0.763), but was not significantly more predictive than prior healthcare exposure + prior antibiotics (aROC 0.646, 95% CI 0.565-0.727) or number of prior antibiotic exposures (aROC 0.642, 95% CI 0.554-0.730); P > 0.05 for both comparisons.

CONCLUSION

A simplified approach using prior healthcare exposure and receipt of prior antibiotics known to increase CDI risk identified patients at risk for MDRO gut microbiome colonization as effectively as individual patient/antibiotic risk modeling.

Transmission of Carbapenem-Resistant Enterobacterales in an Overcrowded Emergency Department: Controlling the Spread to the Hospital

BACKGROUND

Overcrowded emergency departments (EDs) may increase the risk of carbapenem-resistant Enterobacterales (CRE) transmission.

METHODS

We conducted a quasi-experimental study divided into 2 phases (baseline and intervention) to investigate the impact of an intervention on the acquisition rate and identify risk factors for CRE colonization in an ED of a tertiary academic hospital in Brazil. In both phases, we did universal screening with rapid molecular test (blaKPC, blaNDM, blaOXA48, blaOXA23, and blaIMP) and culture. At baseline, both screening test results were not reported, and patients were put under contact precautions (CP) based on previous colonization or infection by multidrug-resistant organisms. During the intervention, all patients hospitalized in the ED were placed in empiric CP and the result of CRE screening was reported; if negative, patients were released from CP. Patients were rescreened if they stayed >7 days in the ED or were transferred to an intensive care unit.

RESULTS

A total of 845 patients were included: 342 in baseline and 503 in intervention. Colonization at admission was 3.4% by culture and molecular test. Acquisition rates during ED stay dropped from 4.6% (11/241) to 1% (5/416) during intervention (P = .06). The aggregated antimicrobial use in the ED decreased from phase 1 to phase 2 (804 defined daily doses [DDD]/1000 patients to 394 DDD/1000 patients, respectively). Length of stay >2 days in the ED was a risk factor for CRE acquisition (adjusted odds ratio, 4.58 [95% confidence interval, 1.44-14.58]; P = .01).

CONCLUSIONS

Early empiric CP and rapid identification of CRE-colonized patients reduce cross-transmission in ED. Nevertheless, staying >2 days in ED compromised efforts.

Intestinal colonization with multidrug-resistant Enterobacterales: screening, epidemiology, clinical impact, and strategies to decolonize carriers

The clinical impact of infections due to extended-spectrum β-lactamase (ESBL)- and/or carbapenemase-producing Enterobacterales (Ent) has reached dramatic levels worldwide. Infections due to these multidrug-resistant (MDR) pathogens-especially Escherichia coli and Klebsiella pneumoniae-may originate from a prior asymptomatic intestinal colonization that could also favor transmission to other subjects. It is therefore desirable that gut carriers are rapidly identified to try preventing both the occurrence of serious endogenous infections and potential transmission. Together with the infection prevention and control countermeasures, any strategy capable of effectively eradicating the MDR-Ent from the intestinal tract would be desirable. In this narrative review, we present a summary of the different aspects linked to the intestinal colonization due to MDR-Ent. In particular, culture- and molecular-based screening techniques to identify carriers, data on prevalence and risk factors in different populations, clinical impact, length of colonization, and contribution to transmission in various settings will be overviewed. We will also discuss the standard strategies (selective digestive decontamination, fecal microbiota transplant) and those still in development (bacteriophages, probiotics, microcins, and CRISPR-Cas-based) that might be used to decolonize MDR-Ent carriers.

A Pooling Strategy for Detecting Carbapenem Resistance Genes by the Xpert Carba-R Test in Rectal Swab Specimens

Rapid and accurate detection of carriers of carbapenemase-producing organisms (CPO) in hospitalized patients is critical for infection control and prevention. This study aimed to evaluate a pooling strategy for the detection of carbapenem resistance genes (CRG) in multiple specimens using the Xpert Carba-R test. Two rectal swabs each were collected from 415 unique patients. One swab was tested by Carba-R on the five specimen-pooled strategy. The other swab was tested individually by culture followed by DNA sequence analysis for CRG as the reference. At the first 5:1 pooling testing, 22 of 83 pools were positive, which yielded 34 positives from individual specimens when positive pools were subsequently retested. All individual specimens in the 61 negative pools were retested as negative by Carba-R. Among the 34 Carba-R-positive samples, 30 and four were positive and negative, respectively, by culture and sequencing. The remaining 381 Carba-R-negative specimens were also negative by culture and sequencing. Overall sensitivity, specificity, positive predictive value, and negative predictive value of the 5:1 pooled screening were 100.0% (95% confidence interval [CI] = 85.9% to 100%), 99.0% (95% CI = 97.2% to 99.7%), 88.2% (95% CI = 71.6% to 96.2%), and 100.0% (95% CI = 98.8% to 100%), respectively. Using the 5:1 pooling strategy, our study completed CRG screening in 414 patients with 193 reagents with significant cost savings. The 5:1 pooling strategy using the Carba-R test showed a potential method for screening CRG from rectal swabs with good sensitivity and decreased cost.

An interventional quasi-experimental study to evaluate the impact of a rapid screening strategy in improving control of nosocomial extended-spectrum beta-lactamase-producing Enterobacterales and carbapenemase-producing organisms in critically ill patients

Introduction

Rapid molecular tests could accelerate the control of extended-spectrum beta-lactamase-producing Enterobacterales (ESBL-PE) and carbapenemase-producing organisms (CPO) in intensive care units (ICUs).

Objective and methods

This interventional 12-month cohort study compared a loop-mediated isothermal amplification (LAMP) assay performed directly on rectal swabs with culturing methods (control period, 6 months), during routine ICU screening. Contact precautions (CP) were implemented for CPO or non-E. coli ESBL-producing Enterobacterales (nEcESBL-PE) carriers. Using survival analysis, we compared the time intervals from admission to discontinuation of unnecessary preemptive CP among patients at-risk and the time intervals from screening to implementation of CP among newly identified carriers. We also compared diagnostic performances, and nEcESBL-PE/CPO acquisition rates. This study is registered, ISRCTN 23588440.

Results

We included 1043 patients. During the intervention and control phases, 92/147 (62.6%) and 47/86 (54.7%) of patients at-risk screened at admission were candidates for early discontinuation of preemptive CP. The LAMP assay had a positive predictive value (PPV) of 44.0% and a negative predictive value (NPV) of 99.9% for CPO, and 55.6% PPV and 98.2% NPV for nEcESBL-PE. Due to result notification and interpretation challenges, the median time from admission to discontinuation of preemptive CP increased during the interventional period from 80.5 (95% CI 71.5–132.1) to 88.3 (95% CI 57.7–103.7) hours (p = 0.47). Due to the poor PPV, we had to stop using the LAMP assay to implement CP. No difference was observed regarding the incidence of nEcESBL-PE and CPO acquisition.

Conclusion

A rapid screening strategy with LAMP assays performed directly on rectal swabs had no benefit for infection control in a low-endemicity setting.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13054-022-04027-8.

An Overview on Phenotypic and Genotypic Characterisation of Carbapenem-Resistant Enterobacterales

Improper use of antimicrobials has resulted in the emergence of antimicrobial resistance (AMR), including multi-drug resistance (MDR) among bacteria. Recently, a sudden increase in Carbapenem-resistant Enterobacterales (CRE) has been observed. This presents a substantial challenge in the treatment of CRE-infected individuals. Bacterial plasmids include the genes for carbapenem resistance, which can also spread to other bacteria to make them resistant. The incidence of CRE is rising significantly despite the efforts of health authorities, clinicians, and scientists. Many genotypic and phenotypic techniques are available to identify CRE. However, effective identification requires the integration of two or more methods. Whole genome sequencing (WGS), an advanced molecular approach, helps identify new strains of CRE and screening of the patient population; however, WGS is challenging to apply in clinical settings due to the complexity and high expense involved with this technique. The current review highlights the molecular mechanism of development of Carbapenem resistance, the epidemiology of CRE infections, spread of CRE, treatment options, and the phenotypic/genotypic characterisation of CRE. The potential of microorganisms to acquire resistance against Carbapenems remains high, which can lead to even more susceptible drugs such as colistin and polymyxins. Hence, the current study recommends running the antibiotic stewardship programs at an institutional level to control the use of antibiotics and to reduce the spread of CRE worldwide.

Prevalence and incidence of carbapenem-resistant K. pneumoniae colonization: systematic review and meta-analysis

BACKGROUND

Klebsiella pneumoniae is a gram-negative rod belonging to the order Enterobacterales and having a wide distribution in the environment, including the human colon. Recently, the bacterium is one of the known problems in the healthcare setting as it has become resistant to last-resort drugs like carbapenems. The colonized person can serve as a reservoir for his/herself and others, especially in the healthcare setting leading to nosocomial and opportunistic infections. Therefore, we aimed to quantitatively estimate the rate of prevalence and incidence of colonization with carbapenem-resistant K. pneumoniae.

METHODS

A literature search was conducted on PubMed/MEDLINE, Google Scholar, Science Direct, Cochrane Library, WHO Index Medicus, and university databases. The study includes all published and unpublished papers that addressed the prevalence or incidence of K. pneumoniae colonization. Data were extracted onto format in Microsoft Excel and pooled estimates with a 95% confidence interval calculated using Der-Simonian-Laird random-effects model. With the use of I² statistics and prediction intervals, the level of heterogeneity was displayed. Egger's tests and funnel plots of standard error were used to demonstrate the publication bias.

RESULTS

A total of 35 studies were included in the review and 32 records with 37,661 patients for assessment of prevalence, while ten studies with 3643 patients for incidence of colonization. The prevalence of carbapenem-resistant K. pneumoniae colonization varies by location and ranges from 0.13 to 22%, with a pooled prevalence of 5.43%. (3.73-7.42). Whereas the incidence of colonization ranges from 2 to 73% with a pooled incidence of 22.3% (CI 12.74-31.87), both prevalence and incidence reports are majorly from developed countries. There was a variation in the distribution of carbapenem resistance genes among colonizing isolates with KPC as a prominent gene reported from many studies and NDM being reported mainly by studies from Asian countries. A univariate meta-regression analysis indicated continent, patient type, study design, and admission ward do not affect the heterogeneity (p value>0.05).

CONCLUSION

The review revealed that colonization with K. pneumoniae is higher in a healthcare setting with variable distribution in different localities, and resistance genes for carbapenem drugs also have unstable distribution in different geographic areas.

The Molecular Characterization of Nosocomial Carbapenem-Resistant Klebsiella pneumoniae Co-Harboring blaNDM and blaOXA-48 in Jeddah

Carbapenem-resistant Klebsiella pneumoniae (CRKP)-associated infections have become a major concern and life-threatening worldwide. Understanding the epidemiology of CRKP using a reliable molecular technology can help to develop an effective infection control policies. In the western region of Saudi Arabia, there are no sufficient data on the prevalence of CRKP and its carbapenem-resistant determinants. Therefore, this study aimed to determine the molecular epidemiology of CRKP and identify the most common carbapenemase genes. In the current study, a total of 191 CRKP isolates were collected and obtained from clinical specimens of patients at King Fahad Armed Forces Hospital (KFAFH), Jeddah, Saudi Arabia. All isolates that were resistant or intermediately susceptible to either of the carbapenem antimicrobials (imipenem, meropenem, or ertapenem) were included. All CRKP showed resistance to ceftazidime, cefepime, and piperacillin/tazobactam, whereas low (14%) and moderate (37.7%) levels of resistance were reported against tigecycline and colistin, respectively. The most common carbapenemase genes identified were blaOXA-48 (n = 157 [82.2%]), followed by blaNDM in 27 (14%) isolates. The blaVIM and blaKPC were reported in only one isolate each and no blaIMP producers were detected among all tested isolates. The high prevalence of OXA-48 among K. pneumoniae isolates reported in the current study may reflect that OXA-48 has become an endemic in Saudi Arabian hospitals. The second major finding was that the identification of CRKP co-harbors both blaNDM and blaOXA-48, and such isolates can be threating for healthcare societies (patients and healthcare workers) due to their high level of resistance to carbapenems. These results suggest that the use of molecular diagnostic methods and proper surveillance programs are required to monitor and control the spread of all multidrug-resistant (MDR) bacteria, including CRKP. Therefore, further research is recommended to expand the study and further analyze the genotyping of the most common clones of CRKP in other hospitals in the western regions of Saudi Arabia.

High frequency of colonization by extended-spectrum beta-lactamase-producing Gram-negative bacilli in hemodialysis patients and their household contacts in Colombia: dissemination between the community and the hospital

OBJECTIVES

Increasing colonization by beta-lactam-resistant Gram-negative bacilli (BR-GNB) represents a risk for infections and bacterial resistance spread, both in hospitals and the community. Hemodialysis patients and their household contacts regularly transit between these environments. This study investigated the clinical and epidemiological characteristics of BR-GNB colonization in hemodialysis patients and their household contacts, as well as the genetic relationship between their isolates.

METHODS

A cross-sectional study was conducted on hemodialysis patients at a hospital-associated dialysis center in Medellín, Colombia and their household contacts. Clinical and epidemiological information was collected. Colonization was assessed from stool or rectal swab samples. Bacterial identification and susceptibility were determined using chromogenic media and Vitek-2. Molecular characterization included beta-lactamase detection by polymerase chain reaction, multiple-locus sequence typing (MLST), pulsed-field gel electrophoresis, and identification of Escherichia coli phylogroups by the Clermont protocol.

RESULTS

This study included 36 hemodialysis patients and 90 household contacts. Colonization by BR-GNB occurred in 58.3% of patients and 22.2% of household contacts. The main beta-lactamase detected was CTX-M group-1 (40.5%). In 3 of the 9 homes that had more than 1 colonized individual, a genetic relationship was found. MLST showed a high diversity in E. coli isolates, and the most frequent phylogroups were B1 and B2.

CONCLUSIONS

These results show a high frequency of colonization and the presence of potentially pathogenic BR-GBN both in hospitals and the community. This highlights the importance of populations who move between those 2 environments, and the need to prevent the spread of bacterial resistance outside hospitals.

Bacteremia with Carbapenemase-Producing Enterobacterales in Immunocompromised Patients Colonized with These Bacteria

We aimed to analyze rates and risk factors for carbapenemase-producing Enterobacterales (CPE) bloodstream infection (BSI) in CPE-colonized patients with malignancies or following hematopoietic cell transplantation. We retrospectively collected data on demography, underlying disease, colonizing CPE, treatment, intensive care unit (ICU) hospitalization, CPE-BSI, and mortality in CPE-colonized immunocompromised patients (2014-2020). Two hundred twenty-one patients were colonized with 272 CPE: 254 (93.4%) carried one carbapenemase [KPC (50.4%), NDM (34.6%), OXA-48-like (5.2%), and VIM (3.3%)]; 18 (6.6%) carried two carbapenemases. Twenty-eight (12.7%) patients developed CPE-BSI. Univariate analysis revealed CPE-BSI-associated factors: younger age, carbapenem or aminoglycoside exposure, ICU admission, neutropenia, carrying serine carbapenemase-producing, and specifically KPC-producing bacteria, colonization with several CPE, and detection of several carbapenemases. None of 23 auto-HSCT recipients developed CPE-BSI. In multivariate analysis, ICU hospitalization was significantly associated with CPE-BSI (odds ratio [OR] 2.82, 95% CI 1.10-7.20; p = 0.042); solid tumor diagnosis was protective (OR 0.21, 95% CI 0.05-1.01; p = 0.038). One-year crude mortality was 108/221 (48.8%), including 19/28 (67.9%) and 89/193 (46.1%) in patients with and without CPE-BSI, p = 0.104. To conclude, CPE-BSI is rare in CPE-colonized patients with solid tumors and following auto-HSCT. ICU hospitalization increased CPE-BSI risk. These data can help to guide empirical anti-CPE antibiotic therapy in patients colonized with these bacteria.

An animal model of limitation of gut colonization by carbapenemase-producing Klebsiella pneumoniae using rifaximin

Current knowledge suggests that infection by carbapenem-resistant enterobacteria is preceded by gut colonization. It is hypothesized that colonization is eradicated by non-absorbable antibiotics like rifaximin. We investigated the effect of rifaximin against carbapenem-resistant Klebsiella pneumoniae (CRKP) in vitro and in a mouse model. We studied the in vitro efficacy of rifaximin against 257 CRKP clinical isolates, 188 KPC producers and 69 OXA-48 producers, by minimum inhibitory concentration and time-kill assays. We then developed a model of gut colonization by feeding 30 C57Bl6 mice with 10⁸ cfu of one KPC-KP isolate for 7 days; mice were pre-treated orally with saline, omeprazole or ampicillin. Then, another 60 mice with established KPC-2 gut colonization received orally for 7 consecutive days rifaximin 180 mg/kg dissolved in ethanol and 4% bile or vehicle. On days 0, 3 and 7 stool samples were collected; mice were sacrificed for determination of tissue outgrowth. At a concentration of 1000 μg/ml rifaximin inhibited 84.8% of CRKP isolates. Α 3 × log₁₀ decrease of the starting inoculum was achieved by 100, 250 and 500 μg/ml of rifaximin after 24 h against 25, 55 and 55% of isolates. Pre-treatment with ampicillin was necessary for gut colonization by KPC-KP. Treatment with rifaximin succeeded in reducing KPC-KP load in stool and in the intestine. Rifaximin inhibits at clinically meaningful gut concentrations the majority of CRKP isolates and is efficient against gut colonization by KPC-KP.

Outbreak of NDM-1-Producing Escherichia coli in a Coronavirus Disease 2019 Intensive Care Unit in a Mexican Tertiary Care Center

Emergency department areas were repurposed as intensive care units (ICUs) for patients with acute respiratory distress syndrome during the initial months of the coronavirus disease 2019 (COVID-19) pandemic. We describe an outbreak of New Delhi metallo-β-lactamase 1 (NDM-1)-producing Escherichia coli infections in critically ill COVID-19 patients admitted to one of the repurposed units. Seven patients developed infections (6 ventilator-associated pneumonia [VAP] and 1 urinary tract infection [UTI]) due to carbapenem-resistant E. coli, and only two survived. Five of the affected patients and four additional patients had rectal carriage of carbapenem-resistant E. coli. The E. coli strain from the affected patients corresponded to a single sequence type. Rectal screening identified isolates of two other sequence types bearing bla_NDM-1. Isolates of all three sequence types harbored an IncFII plasmid. The plasmid was confirmed to carry bla_NDM-1 through conjugation. An outbreak of clonal NDM-1-producing E. coli isolates and subsequent dissemination of NDM-1 through mobile elements to other E. coli strains occurred after hospital conversion during the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic. This emphasizes the need for infection control practices in surge scenarios.

IMPORTANCE The SARS-CoV-2 pandemic has resulted in a surge of critically ill patients. Hospitals have had to adapt to the demand by repurposing areas as intensive care units. This has resulted in high workload and disruption of usual hospital workflows. Surge capacity guidelines and pandemic response plans do not contemplate how to limit collateral damage from issues like hospital-acquired infections. It is vital to ensure quality of care in surge scenarios.

Rapid detection of a novel B1-β-lactamase gene, blaAFM-1 using a loop-mediated isothermal amplification (LAMP) assay

Background

BlaAFM-1 (GenBank Accession No. 143105.1) is a new B1 subclass metallo-β-lactamase gene discovered by our group, and isolated from an Alcaligenes faecalis plasmid that renders carbapenem antibiotics ineffective. In this study, we generated a fast and reliable assay for blaAFM-1 detection.

Methods

We designed optimum loop-mediated isothermal amplification (LAMP) primers and constructed a recombinant plasmid AFM-1 to specifically detect blaAFM-1. Optimal LAMP primers were used to assess sensitivity of the recombinant plasmid AFM-1 and blaAFM-1-supplemented samples (simulated sputum and simulated feces). Fifty two samples, without blaAFM-1, were used to assess LAMP real-time assay specificity; these samples were verified by conventional PCR and sequencing for the absence of blaAFM-1. Three hundred clinical Gram-negative carbapenem-resistant strains were tested by LAMP assay for strains carrying blaAFM-1, which were confirmed by conventional PCR and Sanger sequencing. We calculated the sensitivity and its 95% confidence interval (95% CI), specificity and its 95% CI, and predictive values of the LAMP assay and conventional PCR/sequencing by investigating positive and negative clinical strains.

Results

The lowest limit of detection for the recombinant plasmid AFM-1 and blaAFM-1-supplemented samples (in both simulated sputum and simulated feces) was 10¹ copies/reaction. All amplification curves of the 52 blaAFM-1-free bacteria strains were negative, suggesting the LAMP assay had excellent specificity for detecting blaAFM-1. Among the 300 clinical strains, eight were positive for blaAFM-1 using LAMP. These LAMP results were consistent with conventional PCR and Sanger sequencing data. As with conventional PCR/sequencing, the LAMP method exhibits 100% sensitivity (95% CI 59.8–100%) and 100% specificity (95% CI 98.4–100%) for blaAFM-1 detection. The LAMP assay is also time-efficient (1 h) for blaAFM-1 detection.

Conclusions

We established a new LAMP assay with high sensitivity and specificity to detect the novel B1-β-lactamase gene, blaAFM-1.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12941-021-00486-z.

Intestinal Dominance by Serratia marcescens and Serratia ureilytica among Neonates in the Setting of an Outbreak

(1) Background: We determined the relevance of intestinal dominance by Serratia spp. during a neonatal outbreak over 13 weeks. (2) Methods: Rectal swabs (n = 110) were obtained from 42 neonates. Serratia spp. was cultured from swabs obtained from 13 neonates (Group 1), while the other 29 neonates were culture-negative (Group 2). Total DNA was extracted from rectal swabs, and quantitative PCRs (qPCRs) using Serratia- and 16SrRNA-gene-specific primers were performed. relative intestinal loads (RLs) were determined using ΔΔC_t. Clonality was investigated by random amplified polymorphic DNA analysis and whole-genome sequencing. (3) Results: The outbreak was caused by Serratia marcescens during the first eight weeks and Serratia ureilytica during the remaining five weeks. Serratia spp. were detected by qPCR in all Group 1 neonates and eleven Group 2 neonates. RLs of Serratia spp. were higher in Group 1 as compared to Group 2 (6.31% vs. 0.09%, p < 0.05) and in the first swab compared to the last (26.9% vs. 4.37%, p < 0.05). Nine neonates had extraintestinal detection of Serratia spp.; eight of them were infected. RLs of the patients with extraintestinal spread were higher than the rest (2.79% vs. 0.29%, p < 0.05). (4) Conclusions: Intestinal dominance by Serratia spp. plays a role in outbreaks and extraintestinal spread.

[Infections in patients colonized with carbapenem-resistant Gram-negative bacteria in a medium Spanish city]

OBJECTIVE

Because there are few studies on the clinical implications of colonization by carbapenem-resistant gram-negative bacteria (CRB) this was analyzed in rectal smears (RS) and pharyngeals (PS) and its ability to predict infection/colonization.

METHODS

A cross-sectional, retrospective study from adult inpatients between January 2016 and December 2019 was conducted. The isolates were characterized by MicroScan and spectrometry of masses applying EUCAST 2018 cutoff points. The detection of carbapenemases was performed by PCR and Sanger sequencing; sequencies was assigned by MLST. The genetic relationship between the clinical isolates was made by pulsed field electrophoresis using the enzymes Xbal, Spel or Apal.

RESULTS

A total of 308 (86.03%) RS and 50 (13.97%) positive PS were detected, the RS had a 85% sensibility, 100% specificity, 100% positive predictive value and 97% negative predictive value. In RS, the following were isolated: 44% (n=135) Acinetobacter baumannii, 26% (n =80) Enterobacterales (20 KPC, 29 OXA-48, 22 VIM, 2 IMP, 7 NDM), 17% (n=53) Pseudomonas aeruginosa and 13% (n=40) Stenotrophomonas maltophilia. In the PS were isolated 44% (n=22) S. maltophilia, 40% (n = 20) A. baumannii, 8% (n=4) P. aeruginosa and 8% (n=4) Enterobacterales (3 VIM, 1 OXA). From the patients with simultaneous RS and PS, 41 (40.6%) had positivity in both smears, 45 (44.6%) only in RS and 15 (14.9%) only in PS. Colonization preceded infection in 81.3% (n=13) of the isolates; association between infection and colonization was found (p<0.001; χ2); and the episodes where the information was found all the isolates from the clinical samples and from the smears were similar.

CONCLUSIONS

The probability of predicting infection through the CRB colonized in different clinical samples is feasible. The RS has a major sensibility to detect colonization.

Rapid identification from rectal swabs of the clinically most relevant carbapenemase genes from gram-negative bacteria using the BD MAX Check-Points CPO Assay

We conducted an international multicentre evaluation to assess the clinical performance characteristics of the new multiplex PCR-based BD MAX Check-Points CPO assay to detect the 5 major carbapenemase families: KPC, VIM/IMP (tested simultaneously), NDM and OXA-48 compared to a reference method consisting of 2 culture methods (to improve recovery of CPO isolates from the rectal swabs), followed by carbapenem susceptibility testing and sequencing of target carbapenemase genes. Tests were performed from rectal swab specimens in ESwab collection and transport devices. Positive percent agreement (PPA) for BD MAX Check-Points CPO for KPC and OXA-48 were 88.2% (95% CI:72.6-96.7) and 96.2% (95% CI:80.4-99.9), respectively. Negative percent agreement was ≥99% for each gene. Insufficient samples (≤10) were positive for VIM/IMP or NDM tests to calculate meaningful PPA values. The BD MAX Check-Points CPO assay represents an accurate tool for rapid recognition of patients with rectal colonization by the most commonly encountered CPOs.

Accuracy of Xpert Carba-R Assay for the Diagnosis of Carbapenemase-Producing Organisms from Rectal Swabs and Clinical Isolates: A Meta-Analysis of Diagnostic Studies

The Cepheid Xpert Carba-R assay has demonstrated a promising value for the detection of carbapenemase-producing organisms, but its diagnostic performance remains unclear. Studies were retrieved from Cochrane Library, EMBASE, and PubMed databases according to predetermined selection criteria. The specificity, sensitivity, negative likelihood ratio, positive likelihood ratio, and area under the summary receiver operating characteristic curves of Xpert Carba-R were analyzed by STATA version 13.0. The quality of each study was examined by Quality Assessment of Diagnostic Accuracy Studies using RevMan version 5.2. In total, 17 unique studies involving 15,972 samples met the inclusion criteria. Nine studies performed Xpert Carba-R on rectal swabs. The pooled sensitivity, specificity, and area under the curve were as follows: 0.95 (95% CI, 0.91-0.97; I² = 90.80%), 0.99 (95% CI, 0.97-0.99; I² = 97.17%), and 0.99 (95% CI, 0.98-1.00), respectively. The sensitivity and specificity of Xpert Carba-R in high-risk populations were 0.99 (95% CI, 0.76-1.00; I² = 78.51%) and 0.98 (95% CI, 0.97-0.99; I² = 84.95%), respectively. The sensitivity and specificity in low-prevalence regions were 0.96 (95% CI, 0.88-0.99; I² = 74.58%) and 0.99 (95% CI, 0.98-0.99; I² = 77.66%), respectively. Eight studies performed Xpert Carba-R on clinical isolates. The pooled sensitivity and specificity were 1.00 (95% CI, 0.97-1.00; I² = 97.43%) and 0.98 (95% CI, 0.97-0.99; I² = 55.27%), respectively. This meta-analysis indicates that Xpert Carba-R assay has excellent diagnostic accuracy for diagnosing carbapenemase-producing organisms on rectal swabs and clinical isolates, especially for high-risk populations and low-prevalence regions.

Preventing infections caused by carbapenemase-producing bacteria in the intensive care unit - Think about the sink

OBJECTIVE

Outbreaks caused by carbapenemase-producing bacteria (CPB) are challenging to manage in critical care settings and can be protracted due to inadvertent and ubiquitous ecological niches within the built unit environment, such as handwashing sinks. We discuss evidence from a narrative review on transmission pathways and interventions for critical care practitioners.

METHODS

A literature review was undertaken using Pubmed, CINAHL and Embase and included outbreaks of CPB, and equivalent bacteria in critical care units, between 1998 and May 2020. Intervention studies targeting elements of sinks that were employed in response to outbreaks in critical care units were included (n = 30).

FINDINGS

We found control measures included sink removal, use of physical barriers or design modification to protect patients from sinks, engineering controls to mitigate bacterial dispersal and administrative controls. A multi-disciplinary approach involving practitioners from critical care, infection prevention and control, engineering and other staff, should be involved in ongoing measures and in outbreak control activities. Ascertaining the optimal method to end CPB outbreaks in critical care is challenging due to the lack of prospective studies available. However, the literature suggests that sinks can and do serve as reservoirs of CPB near critically ill patients, and should be considered hazardous, especially when sub-optimally designed or used.

Identification and infection control of carbapenem-resistant Enterobacterales in intensive care units

Infections with multidrug-resistant organisms among patients in intensive care units (ICUs) are associated with high mortality. Among multidrug-resistant organisms, carbapenem-resistant Enterobacterales (CRE) harbor important pathogens for healthcare-associated infections, including pneumonia, bacteremia, and urinary tract infections. Risk factors for CRE colonization include underlying comorbid conditions, prior antibiotics exposure, prior use of healthcare facilities, device use, and longer ICU stay. The mortality rate due to invasive CRE infection is 22%–49%, and CRE colonization is associated with an approximately 10-fold increased risk of CRE infection. Infection control measures include hand hygiene, contact precautions, minimizing the use of devices, and environmental control. Additionally, implementing active surveillance of CRE carriage should be considered in ICU settings.

Metallo-β-lactamases in the Age of Multidrug Resistance: From Structure and Mechanism to Evolution, Dissemination, and Inhibitor Design

Antimicrobial resistance is one of the major problems in current practical medicine. The spread of genes coding for resistance determinants among bacteria challenges the use of approved antibiotics, narrowing the options for treatment. Resistance to carbapenems, last resort antibiotics, is a major concern. Metallo-β-lactamases (MBLs) hydrolyze carbapenems, penicillins, and cephalosporins, becoming central to this problem. These enzymes diverge with respect to serine-β-lactamases by exhibiting a different fold, active site, and catalytic features. Elucidating their catalytic mechanism has been a big challenge in the field that has limited the development of useful inhibitors. This review covers exhaustively the details of the active-site chemistries, the diversity of MBL alleles, the catalytic mechanism against different substrates, and how this information has helped developing inhibitors. We also discuss here different aspects critical to understand the success of MBLs in conferring resistance: the molecular determinants of their dissemination, their cell physiology, from the biogenesis to the processing involved in the transit to the periplasm, and the uptake of the Zn(II) ions upon metal starvation conditions, such as those encountered during an infection. In this regard, the chemical, biochemical and microbiological aspects provide an integrative view of the current knowledge of MBLs.

Evaluation of the BD Phoenix CPO detect panel for prediction of Ambler class carbapenemases

Rapid detection of carbapenemases as a cause of resistance is beneficial for infection control and antimicrobial therapy. The BD Phoenix NMIC-502 panel and CPO detect test identifies presence of carbapenemases in Enterobacterales such as Klebsiella pneumoniae and assigns them to Ambler classes. To evaluate the performance of the CPO detect panel, we employed a European collection of 1222 K. pneumoniae including carbapenem non-susceptible and susceptible clinical isolates from 26 countries, for which draft genomes were available after Illumina sequencing and the presence of carbapenemase genes had been identified by ARIBA gene calling. The CPO panel detected 488 out of 494 carbapenemase-encoding isolates as positive and six as negative. One-hundred and two isolates were tested positive for carbapenemase in the absence of any carbapenemase gene. The CPO panel identified 229 out of 230 KPC-positive isolates as carbapenemase producing and classified 62 of these as class A enzyme. Similarly, the CPO panel correctly specified 167 of 182 as class D. Regarding metallo-beta-lactamases, the CPO panel assigned 78 of 90 MBL positive isolates to class B enzymes. The sensitivity of the CPO panel in detecting carbapenemase activity was 99.5%, 97.7% and 98.3% for class A, B and D enzymes, respectively. The sensitivity in assignation to Ambler class A, B and D was 27%, 86% and 91%, respectively. An overall sensitivity of 98.8% and specificity of 86% in unclassified detection of carbapenemases was observed, with frequent false positive detection of carbapenemase producing organisms, thus rendering further confirmatory tests necessary.

Combined selective culture and molecular methods for the detection of carbapenem-resistant organisms from fecal specimens

Detection of patients with intestinal colonization of carbapenem-resistant organisms (CRO), or more specifically carbapenemase-producing (CP) CRO, can prevent their transmission in healthcare facilities and aid with outbreak investigations. The objective of this work was to further develop and compare methods that combine selective culture and/or PCR to rapidly detect and recover CRO from fecal specimens. Molecularly characterized Gram-negative bacilli (n = 62) were used to spike fecal samples to establish limit of detection (LOD; n = 12), sensitivity (n = 28), and specificity (n= 21) for 3 methods to detect CP-CRO: direct MacConkey (MAC) plate and Xpert Carba-R (Cepheid) on growth, MAC broth and Carba-R testing of the broth, and direct testing by Carba-R. This was followed by a clinical study comparing methods in parallel for 286 fecal specimens. The LOD ranged from 10^2-10⁵ CFU/mL depending on the carbapenemase gene and method. Combined culture/PCR methods had a sensitivity of 100%, whereas direct Carba-R testing had a sensitivity of 96% for the detection of CP-CRO. All methods had specificities of 100%. The prevalence of CP-CRO (0.7%) and non-CP-CRO (5.2 %) were low in the clinical study, where all methods demonstrated 100% agreement. The three methods performed comparably in detecting CP-CRO. Direct Carba-R testing had a higher LOD than the combined selective culture methods, but this may be offset by its rapid turnaround time for detection of CP-CRO. The selective culture methods provide the benefit of simultaneously isolating CP-CRO in culture for follow-up testing and detecting non-CP-CRO.

Isolation Procedure for CP E. coli from Caeca Samples under Review towards an Increased Sensitivity

Due to the increasing reports of carbapenemase-producing Enterobacteriaceae (CPE) from livestock in recent years, the European Reference Laboratory for Antimicrobial Resistances (EURL-AR) provided a protocol for their recovery from caecum and meat samples. This procedure exhibited limitations for the detection of CPE with low carbapenem MIC values. Therefore, it was modified by a second, selective enrichment in lysogeny broth with cefotaxime (CTX 1 mg/L) and with meropenem (MEM 0.125 mg/L) at 37 °C under microaerophilic conditions. By Real-time PCR, these enrichments are pre-screened for the most common carbapenemase genes. Another adaptation was the use of in-house prepared MacConkey agar with MEM and MEM+CTX instead of commercial selective agar. According to the EURL-method, we achieved 100% sensitivity and specificity using the in-house media instead of commercial agar, which decreased the sensitivity to ~75%. Comparing the method with and without the second enrichment, no substantial influence on sensitivity and specificity was detected. Nevertheless, this enrichment has simplified the CPE-isolation regarding the accompanying microbiota and the separation of putative colonies. In conclusion, the sensitivity of the method can be increased with slight modifications.

Four-Hour Immunochromatographic Detection of Intestinal Carriage of Carbapenemase-Producing Enterobacteriaceae: a Validation Study

The increasing incidence of carbapenemase-producing Gram-negative bacilli (C-PGNB) represents a major public health challenge. Rapid detection of digestive colonization with C-PGNB is fundamental to control their spread. We performed the validation of a rapid protocol for C-PGNB detection directly on rectal swabs. We developed a protocol combining enrichment by a rapid selective subculture of the rectal swab medium and realization of a Resist-4 O.K.N.V. K-SeT test on the bacterial pellet obtained. The limit of detection and performances of this protocol were validated in vitro on 52 C-PGNB strains spiked on a calibrated sample suspension and confirmed in clinical settings on 144 rectal swabs sampled from patients with C-PGNB digestive colonization (n = 48) and controls (patients with extended-spectrum beta-lactamase [ESBL] colonization [n = 48] and without carbapenemase/ESBL [n = 48]). The protocol detected, with 100% sensitivity, the presence of the 15 OXA-48-, 14 KPC-, 13 NDM-, and 10 VIM-producing GNB from 10³ CFU/ml. The limit of detection was 2 × 10² CFU/ml. Among the 48 C-PGNB-containing rectal swabs of the validation cohort, 46 were accurately detected. False negative were observed for 1 NDM-producing Acinetobacter baumannii strain and 1 OXA-48-producing Escherichia coli strain. The 96 control swabs were negative. Sensitivity and specificity for C-PGNB detection were 97.7% (95% confidence interval [CI], 87.7 to 100) and 100% (95% CI, 96.2 to 100). The negative likelihood ratio was 0.04 (95% CI, 0.01 to 0.16). Considering a C-PGNB digestive colonization prevalence between 0.01% and 0.1%, positive and negative predictive values were 100%. Our protocol is a rapid and low-cost method detecting accurately the digestive colonization with carbapenemase-producing Enterobacteriaceae in 4 h without any requirement for specific equipment.

Detection of KPC, NDM and VIM-Producing Organisms Directly from Rectal Swabs by a Multiplex Lateral Flow Immunoassay

We report a preliminary evaluation of the NG-Test CARBA 5 immunochromatographic assay for detecting carbapenemases directly from rectal swabs on the same day of sampling. Thirty fecal swabs were examined for carbapenemase-producing organisms (CPOs) by conventional culture, PCR, and NG-Test CARBA 5. Each sample was tested by the immunochromatographic assay five times, including direct testing and incubation in trypticase soy broth for 1, 2, 3, and 4 h. Twenty patients yielded CPOs by culture. Immunochromatographic and PCR results were concordant and detected the same 25 carbapenemases (11 KPC, 8 VIM, and 6 NDM). In five cases, we detected co-carriage of KPC and VIM. Compared with PCR, the sensitivity of NG-Test CARBA 5 for the detection of KPC, VIM, and NDM was 80% without incubation, 88% with one hour, 92% with two, and 100% with three hours incubation, while specificity was 100% for all time points. All samples containing adequate fecal content were detected by NG-Test CARBA 5 concordantly with PCR, without incubation. NG-Test CARBA 5 is a reliable test that rapidly detects the presence of carbapenemases at the same day of sampling, directly from rectal swabs. It thus provides early information to guide antimicrobial treatment and infection control interventions.

Potential Effectiveness of Piperacillin/Tazobactam in Treating Pediatric Patients Infected with IMP-Type Carbapenemase-Producing Enterobacteriaceae

Background: The resistance rate of carbapenem-resistant Enterobacteriaceae (CRE) is increasing yearly but rarely reported in children. Objectives: This retrospective study analyzed the characteristics of isolated CRE strains in pediatric patients, intending to explore reasonable antimicrobial treatment options. Methods: Some CRE isolates were collected from infected pediatric patients in Liaocheng People’s Hospital from January 2014 to December 2019. The strain identification and antimicrobial susceptibility testing were conducted using Vitek mass spectrometry and the Vitek 2 system, respectively. The carbapenemase genotypes of blaKPC, blaIMP, blaVIM, blaNDM-1, and blaOXA-48 were each detected by polymerase chain reaction and sequencing. The molecular homology analysis of strains was conducted via Pulse-field Gel Electrophoresis (PFGE). The clinical data of CRE-infected pediatric patients were collected from the hospital’s medical data information system. Results: Twenty CRE strains were isolated from 1945 infected pediatric patients with Enterobacteriaceae. All CRE strains showed multiple resistance to commonly used antimicrobials. Twelve strains of imipenemase (IMP)-4 and seven strains of IMP-8 carbapenemase were confirmed. Besides, PFGE revealed that two strains of Escherichia coli and three of Klebsiella pneumoniae had indistinguishable patterns. Sixteen patients were cured, including 10 patients using piperacillin/tazobactam. Conclusions: This study found the major sources of resistance were IMP carbapenemases. Piperacillin/tazobactam is potentially effective for the treatment of CRE infection, despite insensitivity in vitro.

Molecular characterization of carbapenem-resistant Enterobacterales in thirteen tertiary care hospitals in Saudi Arabia

BACKGROUND

Carbapenems are the antibiotics of last-resort for the treatment of bacterial infections caused by multidrug-resistant organisms. The emergence of resistance is a critical and worrisome problem for clinicians and patients. Carbapenem-resistant Enterobacterales (CRE) are spreading globally, are associated with an increased frequency of reported outbreaks in many regions, and are becoming endemic in many others.

OBJECTIVES

Determine the molecular epidemiology of CRE isolates from various regions of Saudi Arabia to identify the genes encoding resistance and their clones for a better understanding of the epidemio-logical origin and national spread.

DESIGN

Multicenter, cross-sectional, laboratory-based study.

SETTING

Samples were collected from 13 Ministry of Health tertiary-care hospitals from five different regions of Saudi Arabia.

METHODS

Isolates were tested using the GeneXpert molecular platform to classify CRE.

MAIN OUTCOME MEASURES

Prevalence of various types of CRE in Saudi Arabia.

SAMPLE SIZE

519 carbapenem-resistant isolates.

RESULT

Of 519 isolates, 440 (84.7%) were positive for CRE, with Klebsiella pneumoniae (410/456, 90%) being the most commonly isolated pathogen. The distribution of the CRE-positive K pneumoniae resistance genes was as follows: OXA-48 (n=292, 71.2%), NDM-1 (n=85, 20.7%), and NDM+OXA-48 (n=33, 8%). The highest percentage of a single blaOXA-48 gene was detected in the central and eastern regions (77%), while the blaNDM-gene was the predominant type in the northern region (27%). The southern regions showed the lowest percentages for harboring both blaOXA-48 and blaNDM genes (4%), while the western region isolates showed the highest percentage of harboring both genes (14%).

CONCLUSION

The results illustrate the importance of molecular characterization of CRE isolates for patient care and infection prevention and control. Larger multicenter studies are needed to critically evaluate the risk factors and trends over time to understand the dynamics of spread and effective methods of control.

LIMITATIONS

Lack of phenotypic susceptibility and clinical data.

CONFLICT OF INTEREST

None.

Molecular Characterization of New Delhi Metallo-ß-Lactamases-Producing Bacteria in the Gastrointestinal Tract of Intensive Care Unit Patients

Background: The emergence of carbapenem-resistance in the gut flora of patients in the intensive care unit (ICU) poses a significant risk for infection with these types of pathogens.

Materials and methods: New Delhi metallo-ß-lactamase 1 (NDM-1) in the gut flora of ICU patients was detected in cultures of a single rectal swab from each patient admitted to the ICU for a minimum period of 48 hrs. Samples were processed in the microbiology laboratory using blood agar and MacConkey agar. Identification of pathogens, carbapenem resistance, and metallo-ß-lactamase production was made using standard laboratory procedures. Bacterial isolates were also used for the determination of the NDM-1 gene by molecular methods.

Results: One hundred twenty-two patients with different clinical presentations were recruited in the study. Two hundred nine bacteria were isolated, with Escherichia coli being the most common isolate. A total of 54/122 (44.3%) patients harbored carbapenem-resistant organisms (CRO), 36/122 (29.5%) carried metallo-β-lactamase-producing organisms (MBLO), and 30/122 (24.6%) carried bacteria with the NDM-1 gene. Patients who harbored CRO and MBLO had longer mean duration of stay in the ICU and hospital than those not harboring CRO and MBLO. All the metallo-β-lactamases were simultaneously resistant to other groups of antibiotics also. Use of invasive devices, three or more classes of antibiotics, hospitalization during the previous six months, comorbidities, and hospital stay for ≥48 hours before ICU admission had a significant association with colonization with CRO.

Conclusion: Patients admitted in ICU or with serious diseases should be screened for gastrointestinal carriage of carbapenem-resistant organisms. Irrational use of antibiotics must be stopped to prevent the emergence and spread of such organisms. 

Confronting Ceftolozane-Tazobactam Susceptibility in Multidrug-Resistant Enterobacterales Isolates and Whole-Genome Sequencing Results (STEP Study)

Ceftolozane-tazobactam (C/T) is frequently used for infections caused by multidrug-resistant (MDR)-Enterobacterales isolates. Whole-genome sequencing (WGS, Illumina-Hiseq 4000/NovaSeq 6000, OGC, UK) was used to study the population structure, the resistome and the virulome of C/T-susceptible and -resistant MDR Escherichia spp. (n=30) and Klebsiella spp. (n=78) isolates, recovered from lower respiratory, intra-abdominal and urinary tract infections of ICU patients from 11 Portuguese Hospitals (STEP study, 2017-2018). Minimum inhibitory concentrations (MICs) were determined (ISO-broth microdilution, breakpoints EUCAST-2020). In Escherichia spp., a weak concordance between the phenotypic and the WGS method (P=0.051) was observed in the carbapenemase detection (3/30) [bla_VIM-2 (2/3), bla_KPC-3 (1/3)]; VIM-2-Escherichia coli isolates were C/T-susceptible and only the KPC-3-Escherichia marmotae producer showed C/T-resistance. Overall, CTX-M-15-E. coli-ST131-O25:H4-H30-Rx (11/30) was the most frequent subclone, followed by CTX-M-27-E. coli-ST131-O25:H4-H30 (4/4). Moreover, a wide resistome and virulome were detected in all E. coli isolates. Among Klebsiella spp. isolates [K. pneumoniae (67/78), K. aerogenes (7/78), K. oxytoca (2/78), K. variicola (2/78)], concordance (P<0.001) was observed between the phenotypic and the genomic carbapenemase detection (21/78) [bla_KPC-3 (14/21), bla_OXA-48 (3/21), bla_OXA-181 (3/21)]. A high correlation between C/T-resistance and carbapenemase detection was established (P<0.05). Overall, a high clonal diversity was observed, mainly in KPC-3-producing K. pneumoniae isolates. An extensive resistome was detected in Klebsiella spp. isolates, whereas virulence determinants were mostly identified in carbapenemase producers (P<0.001). WGS is a powerful tool for typing characterization and microbiological study of MDR-Enterobacterales pathogens. Furthermore, carbapenemase genes are associated with C/T-resistance in Klebsiella spp., but other mechanisms might also be involved.

Prevalence of carbapenem-resistant Enterobacteriaceae and emergence of high rectal colonization rates of blaOXA-181-positive isolates in patients admitted to two major hospital intensive care units in Kuwait

BACKGROUND

Fecal colonization by carbapenem-resistant Enterobacteriaceae (CRE) can be the main reservoir for transmission of these resistant organisms especially in the Intensive Care Units (ICUs).

AIM

This study was conducted to evaluate the rate of rectal carriage and molecular characterization of CRE in patients hospitalized in the ICUs of 2 major hospitals (Adan and Mubarak Al Kabeer Hospitals) in Kuwait.

MATERIALS AND METHODS

Rectal swabs were collected from all patients at admission, 48 h after admission and once weekly from April 2017- March 2018. Initial CRE screening was carried out on MacConkey agar on which meropenem disc 10μg was placed. Identification of isolates was by API 20E. Susceptibility testing was performed using the E-test method. Polymerase chain reaction (PCR) was used to detect the carbapenemase-encoding genes. Clonal relationship was investigated by pulsed-field electrophoresis (PFGE). Genes of blaOXA-181 and blaNDM-5-carrying plasmids were detected in some strains.

RESULTS

A total of 590 patients were recruited into the study. Of these, 58 were positive for CRE, giving a prevalence of 9.8%; 25/320 (7.8%) in Adan and 33/270 (12.2%) in Mubarak Al Kabeer Hospitals. All isolates were resistant to multiple antibiotics. Resistance rates to colistin and tigecycline were 17% and 83%, respectively. Single genes of blaOXA-181 were detected in isolates from 38 (65.5%) out of 58 patients and in 5 patients colonized by blaOXA-48-positive CRE. A combination of 2 genes was detected in 12 isolates; 5 blaKPC-2 and blaOXA-181, 4 blaVIM-1 and blaOXA-181, and 3 blaNDM-5 and blaOXA-181. PFGE showed an overall level of similarity of 38%. Southern hybridization studies localized the blaOXA-181 and blaNDM-5 genes to a large plasmid of 200kb in 3 K. pneumoniae isolates and a small plasmid of 80kb in 2 E. coli isolates, respectively.

CONCLUSION

The prevalence of CRE colonization in the 2 hospital ICUs was relatively high and the emergence of blaOXA-181-mediated CRE is a cause for concern as there is the possibility of rapid horizontal spread among hospital patients in Kuwait. Active surveillance of CRE in the ICUs is highly recommended to stem its spread.

The microcolony detection method (MCD), a simple and rapid screening test for antimicrobial resistance bacteria on positive blood cultures

Rapid detection of antibiotic-resistant bacteria in blood cultures is critical for the timely treatment of patients with sepsis. The aim of this study was to develop a simple method for the rapid detection of drug-resistant bacteria from blood cultures and to evaluate its performance. We developed an optical microscopy-based microcolony detection method (MCD) for the rapid detection of antibiotic-resistant bacterial colonies in media. This method was tested using staphylococci resistant to methicillin and gram-negative bacilli resistant to third-generation cephalosporins and carbapenem. The results of the investigations of clinical samples using this method were compared with the drug susceptibility testing results for each of the 457 isolates, which included 134 staphylococci and 323 g-negative bacilli. The MCD was successful in detecting antibiotic-resistant bacterial growth from culture-positive blood samples in approximately 3 h. The sensitivity/specificity for methicillin-resistant staphylococci was 100%/97.2%. In the case of gram-negative bacilli, the sensitivity/specificity values for bacteria resistant to ceftriaxone, ceftazidime, and carbapenem were 100%/98.7%, 100%/89.3%, and 100%/90.9%, respectively. Therefore, MCD is a clinically useful screening method for the efficient and rapid detection of antibiotic-resistant bacteria and can be easily implemented in laboratories.

The effect of transport temperature and time on the recovery of antimicrobial-resistant Enterobacterales in stool

Surveillance for antibiotic-resistant (AR) bacteria is challenging. We evaluated AR Enterobacterales survival in stool over various transport conditions. Stool in Cary-Blair medium was spiked with AR Enterobacterales, held at 3 °C, 20 °C, or 37 °C, and cultured on days 3, 8, and 15. Stool from US international travelers sent through the US mail was also screened. We compared recovery rates using Fisher's exact tests and linear regression models. AR Enterobacterales recovery reduced with time (86% versus 75% versus 61% at days 3, 8, and 15; Beta for linear trend=-0.02, r²=0.99, P=0.02) and colder temperatures [56% (3 °C) versus 89% (20 °C) versus 86% (37 °C); P=0.003]. Traveler sample recovery also reduced with transport time (Beta for linear trend=-0.03, r²=0.70, P=0.01) but not with season [20% (cold) versus 22% (warm), P=0.7]. AR Enterobacterales are found over variable transport conditions, providing rationale for expanding surveillance sample processing timelines.

Molecular Detection and PCR-RFLP Analysis of Mucoviscosity-Associated Gene A (magA) in Clinical Isolates of Multidrug-Resistant Klebsiella pneumoniae in Bangladesh

Background and Objective:

The mucoviscosity associated gene A (magA) in the hypermucoviscous variants of K. pneumoniae is reported to be associated with invasive infections and considered a virulence factor. We sought to analyze the magA genes in K. pneumoniae isolates in the clinical specimen collected from Bangladesh.

Methods:

We established a multicenter cohort of patients with Klebsiella infection hospitalized at 05 different hospitals between September 2016 and April 2017. We collected 313 K. pneumoniae isolates from patients who consented to participate in the study. The isolates were evaluated for harboring the magA genes using a single-tube multiplexed polymerase chain reaction. The magA genes were analyzed by PCR-RFLP technique using two enzymes, namely PciI and SmaI. Antibiogram assay using 12 commercially available antibiotic discs was performed on all the isolates.

Results:

The presence of K. pneumoniae specific gene (ureD) was confirmed in all the isolates. The percentage of isolates harboring the magA gene was 7.34%(23 isolates), the majority of which was collected from the patients admitted in intensive care units (16 isolates, 69.6%), and infectious diseases wards (5 isolates, 21.7%). PCR-RFLP analysis revealed that for 7 out of 23 isolates, where Sma1 could not cleave the magA gene. All the isolates showed resistance to ampicillin, carbenicillin cefradine, chloramphenicol, erythromycin, kanamycin, and sulphamethoxazole, though the extent was varying. However, imipenem showed 100% sensitivity to all the tested isolates.

Conclusion:

This study demonstrates the presence of the magA gene in multidrug-resistant clinical isolates of K. pneumoniae collected from Bangladesh.

ChromID® CARBA Agar Fails to Detect Carbapenem-Resistant Enterobacteriaceae With Slightly Reduced Susceptibility to Carbapenems

After first detections of carbapenemase-producing Enterobacteriaceae (CPE) in animals, the European Union Reference Laboratory for Antimicrobial Resistance has provided a protocol for the isolation of carbapenemase-producing Escherichia (E.) coli from cecum content and meat. Up to now, only few isolates were recovered using this procedure. In our experience, the choice of the selective agar is important for the efficacy of the method. Currently, the use of the prevailing method fails to detect CPE that exhibit a low resistance against carbapenems. Thus, this study aims to evaluate the suitability of selective media with antibiotic supplements and commercial ChromID^® CARBA agar for a reliable CPE detection. For comparative investigations, detection of freeze-dried carbapenemase-resistant bacteria was studied on different batches of the ChromID^® CARBA agar as well as on MacConkey agar supplemented with 1 mg/L cefotaxime and 0.125 mg/L meropenem (McC+CTX+MEM). The suitability of the different media was assessed within a time of 25 weeks, starting at least six weeks before expiration of the media. Carbapenem-resistant isolates exhibiting a serine-based hydrolytic resistance mechanism (e.g., bla _KPC genes) were consistently detected over 25 weeks on the different media. In contrast, carbapenemase producers with only slightly reduced susceptibility and exhibiting a zinc-catalyzed activity (e.g., bla _VIM, bla _NDM, and bla _IMP) could only be cultivated on long-time expired ChromID^® CARBA, but within the whole test period on McC+CTX+MEM. Thus, ChromID^® CARBA agar appears to be not suitable for the detection of CPE with slightly increased minimum inhibitory concentrations (MIC) against carbapenems, which have been detected in German livestock and thus, are of main interest in the national monitoring programs. Our data are in concordance with the results of eleven state laboratories that had participated in this study with their ChromID^® CARBA batches routinely used for the German CPE monitoring. Based on the determined CPE detection rate, we recommend the use of McC+CTX+MEM for monitoring purposes. This study indicates that the use of ChromID^® CARBA agar might lead to an underestimation of the current CPE occurrence in food and livestock samples.

Clinical and Molecular Epidemiologic Characteristics of Ceftazidime/Avibactam-Resistant Carbapenem-Resistant Klebsiella pneumoniae in a Neonatal Intensive Care Unit in China

Background

Ceftazidime/avibactam (CZA)-resistant carbapenem-resistant Klebsiella pneumoniae (CRKP) infections occur in adults worldwide but are rarely observed in neonates. We evaluated the activities of CZA against CRKP and described the clinical and molecular epidemiology of CZA-resistant CRKP in a NICU prior to CZA approval in China.

Methods

A laboratory-based surveillance of CRKP was conducted from July 2017 to June 2018. Clinical data were initially reviewed. Antimicrobial susceptibility was determined by the broth microdilution method. CZA-resistant CRKP isolates were submitted to carbapenemase types screening and multilocus sequence typing.

Results

Over 23.3% (10/43) of CRKP strains were resistant to CZA, MIC₅₀ and MIC₉₀ values being 0.5 μg/mL and >32μg/mL, respectively. Most neonates shared similar clinical features with cesarean (n=8), preterm birth (n=6), low birth weight (n=5), and exposure to carbapenems/β-lactam (n=8). All CZA-resistant CRKP isolates were highly resistant to most tested drugs except for polymyxin B (POL) and tigecycline (TGC). CZA-resistant CRKP isolates showed greater sensitivity to amikacin (AMK), nitrofurantoin (NIT), levofloxacin (LVX) and ciprofloxacin (CIP), compared with CZA-sensitive CRKP. All CZA-resistant CRKP isolates harbored carbapenemase genes, bla_kpc-2 (n=5) being predominant, followed by bla_NDM-1 (n=4) and bla_NDM-5 (n=2). Among these CZA-resistant CRKP isolates, a total of eight different STs were identified. CRKP harboring KPC belonged to ST1419, ST37 and ST11, while NDM types were assigned to ST784, ST1710, ST37 and ST324. Furthermore, other β-lactamase genes including bla_SHV and bla_CTX-M were also found.

Conclusion

Over 23.3% of CRKP strains isolated from neonates were resistant to CZA. Cesarean, preterm birth, low birth weight, and exposure to carbapenems/β-lactam were similar clinical features of most neonates with CZA-resistant CRKP. The predominant carbapenemases of CZA-resistant CRKP were KPC-2 and NDM-1, and KPC-2 producing K. pneumoniae assigned into 3 STs, which indicate the genetic diversity of clinical CZA-resistant CRKP isolates.

Toilet drain water as a potential source of hospital room-to-room transmission of carbapenemase-producing Klebsiella pneumoniae

BACKGROUND

Carbapenemase-producing Enterobacterales (CPE) have rapidly emerged in Europe, being responsible for nosocomial outbreaks.

AIM

Following an outbreak in the burn unit of Ghent University Hospital, we investigated whether CPE can spread between toilets through drain water and therefrom be transmitted to patients.

METHODS

In 2017, the burn centre of our hospital experienced an outbreak of OXA-48-producing Klebsiella pneumoniae that affected five patients staying in three different rooms. Environmental samples were collected from the sink, shower, shower stretcher, hand rail of the bed, nursing carts, toilets, and drain water to explore a common source. Whole-genome sequencing and phylogenetic analysis was performed on K. pneumoniae outbreak isolates and two random K. pneumoniae isolates.

FINDINGS

OXA-48-producing K. pneumoniae was detected in toilet water in four out of six rooms and drain water between two rooms. The strain persisted in two out of six rooms after two months of daily disinfection with bleach. All outbreak isolates belonged to sequence type (ST) 15 and showed isogenicity (<15 allele differences). This suggests that the strain may have spread between rooms by drain water. Unexpectedly, one random isolate obtained from a patient who became colonized while residing at the geriatric ward clustered with the outbreak isolates, suggesting the outbreak to be larger than expected. Daily application of bleach tended to be superior to acetic acid to disinfect toilet water; however, disinfection did not completely prevent the presence of carbapenemase-producing K. pneumoniae in toilet water.

CONCLUSION

Toilet drain water may be a potential source of hospital room-to-room transmission of carbapenemase-producing K. pneumoniae.