Comparative genomic analysis reveals a high prevalence of inter-species in vivo transfer of carbapenem-resistance plasmids in patients with haematological malignancies

Towards unraveling antimicrobial resistance dynamics: a longitudinal exploration of rectal swab metagenomes

The increasing prevalence of antimicrobial resistance (AMR) poses significant challenges in clinical settings. In particular, early screening and detection of colonization by multidrug-resistant organisms (MDROs) in patients at admission is crucial. In this context, the clinical use of metagenomics (mNGS) holds promise for fast and untargeted diagnostic methods. Here, we aimed to evaluate the long-term stability of the rectal microbiome and the diagnostic accuracy of mNGS in comparison to culture and whole-genome sequencing (WGS) of MDROs. We analyzed rectal swabs from 26 patients with two consecutive admissions over a four-year period. The detected antimicrobial resistance genes and assembled metagenomes were compared to those obtained via classical culture-based antimicrobial susceptibility testing and WGS of isolated MDROs. Our results showed that the rectal microbiome is variable during the two timepoints, highlighting the variability in the niche. Nevertheless, we also observed strong co-occurrence of taxa, suggesting that the rectal swab microbiome is also a regulated environment with cooperative biotic interactions. In total, we isolated and sequenced 6 MDROs from 6 patients at individual timepoints. Almost all AMR genes from the genomes of the isolates (median: 100%, range: 84.6-100%) could be detected by mNGS of the rectal swabs at the time of isolation of the MDRO but not at the time of culture negativity. In addition, we detected AMR genes and potentially pathogenic species in patients with negative cultures. In conclusion, our study showed that, in principle, mNGS of rectal swabs can detect clinically relevant AMR profiles. However, the cooccurrence of AMR genes and potentially-pathogenic species does not always correlate with culture-based diagnostic results but rather indicates a potential risk of horizontal AMR gene transfer. However, it is unclear whether the observed discrepancies are due to transient or locally confined colonization of MDROs, limits of detection, or variability of the sampling method and specimens.

Preliminary insights on carbapenem resistance in Enterobacteriaceae in high-income and low-/middle-income countries

The emergence of carbapenem-resistant Enterobacteriaceae in the hospital sector as well as in the natural environment is a problem that affects both high-income countries (HICs) and low-/middle-income countries (LMICs). The observed differences in the prevalence of carbapenem-resistant strains between HICs and LMICs can be attributed mainly to antibiotic consumption in healthcare facilities and the quantity of treated wastewater. Hospital wastewater is a major hotspot for the spread of carbapenem-resistant Enterobacteriaceae (CRE) and carbapenem resistance genes (CRGs) between the hospital sector and the environment. In this review article, attempts were made to describe and compare antibiotic consumption in hospitals, antimicrobial concentrations in both hospital and municipal wastewater, and the prevalence of CRE and CRGs in patients and in hospital and municipal wastewater in HICs and LMICs. A review of the literature has shown that carbapenems are more widely used in LMICs, but Saudi Arabia, an HIC, is a country with the highest carbapenem consumption in the world. The results of research conducted in both groups of countries indicate that Klebsiella sp./K. pneumoniae is the most common CRE in samples isolated from patients. Escherichia coli was the dominant pathogen in hospital and municipal wastewater in HICs, whereas Enterobacter spp. were most prevalent in LMICs. An analysis of the prevalence of CRGs demonstrated that the same genes are present in both groups of countries (blaKPC, blaKPC-2, blaVIM, blaVIM-1,2, blaNDM, blaIMP, blaIMP-8, blaOXA-48,181, blaNDM-1,5, blaGES, blaGES-5,6, blaIMI-1). The fact that the same CRGs are most prevalent in countries with different levels of economic development could suggest that these genes have a high potential to persist in the natural environment. These findings underscore the need for enhanced monitoring, effective control techniques, and a better understanding of carbapenem resistance pathways to mitigate public health hazards, notwithstanding the constraints of data analysis.

Comparative genome analysis reveals putative and novel antimicrobial resistance genes common to the nosocomial infection pathogens

The 21st century has witnessed several clinical outcomes regarding AMR. One health concept has been foreseen as a standard global public health initiative in ensuring human, animal and environmental health. The present study explores critical Gram-negative ESKAPE pathogens encompassing Acinetobacter baumannii (ACB), Klebsiella pneumoniae (KPX) and Pseudomonas aeruginosa (PAE). A comparative genomic analysis approach was utilized for identifying novel and putative genes coercing global health consequences stressing the significance of the above iatrogenic and nosocomial pathogens. O findings reveal that Pseudomonas aeruginosaPAO1 (PAE) possesses the largest genome, measuring 62,64,404 base pairs, containing 14,342 protein-coding genes and an elevated count of ORFs, surpassing other organisms. Notably, P. aeruginosa PAO1 exhibits a comprehensive metabolic landscape with 355 pathways and 1659 metabolic reactions, encompassing 200 biosynthesis and 132 degradation pathways. Transferases are the predominant enzyme category across all three genomes, followed by oxidoreductases and hydrolases. The pivotal role of beta-lactamase in conferring resistance against antibiotics is also evident in all three microbes. This investigation underscores the PAE genome harbours genes and enzymes associated with heightened virulence in antibiotic resistance. The holistic review combined with comparative genomics underlines the significance of delving into the genomes of these antimicrobial-resistant organisms. In silico methodologies are increasingly stressed in aiding the successful accomplishment of the United Nations Sustainable Development Goal -3: Good Health and Well-being. The prominent findings establish Carbapenem resistance and evolutionary lineages of the MCR-1 gene conferring AMR landscapes for future research.

Evaluation of screening algorithms to detect rectal colonization with carbapenemase-producing Enterobacterales in a resource-limited setting

Objectives

To improve and rationalize the detection of carbapenemase-producing Enterobacterales (CPE) in rectal swabs in a high-prevalence and resource-constrained setting, addressing surveillance challenges typically encountered in laboratories with limited resources.

Methods

A point prevalence survey (PPS) was conducted on 15 August 2022, in a provincial children's hospital in northern Vietnam. Rectal swab samples of all admitted children were collected and plated on a selective medium for carbapenem-resistant Enterobacterales (CRE). Species identification and antimicrobial susceptibility testing (AST) were performed by MALDI-TOF, and VITEK2 XL and interpreted according to CLSI breakpoints (2022). Carbapenemases were detected by the carbapenem inactivation method (CIM) and quantitative real-time PCR (qRT-PCR).

Results

Rectal swab samples were obtained from 376 patients. Of 178 isolates growing on the CRE screening agar, 140 isolates were confirmed as Enterobacterales of which 118 (84.3%) isolates were resistant to meropenem and/or ertapenem. CIM and PCR showed that 90/118 (76.3%) were carbapenemase producers. Overall, 83/367 (22.6%) were colonized by CPE. Klebsiella pneumoniae, Escherichia coli and Enterobacter cloacae complex were the most common CPE detected, with NDM as the predominant carbapenemase (78/90; 86.7%). Phenotypic resistance to meropenem was the best predictor of CPE production (sensitivity 85.6%, specificity 100%) compared with ertapenem resistance (95.6% sensitivity, 36% specificity). CIM was 100% concordant with PCR in detecting carbapenemases.

Conclusions

These findings underscore the effectiveness of meropenem resistance as a robust indicator of the production of carbapenemases and the reliability of the CIM method to detect such carbapenemases in resource-limited settings where the performance of molecular methods is not possible.

Airway commensal bacteria in cystic fibrosis inhibit the growth of P. aeruginosa via a released metabolite

In cystic fibrosis (CF), Pseudomonas aeruginosa infection plays a critical role in disease progression. Although multiple studies suggest that airway commensals might be able to interfere with pathogenic bacteria, the role of the distinct commensals in the polymicrobial lung infections is largely unknown. In this study, we aimed to identify airway commensal bacteria that may inhibit the growth of P. aeruginosa. Through a screening study with more than 80 CF commensal strains across 21 species, more than 30 commensal strains from various species have been identified to be able to inhibit the growth of P. aeruginosa. The underlying mechanisms were investigated via genomic, metabolic and functional analysis, revealing that the inhibitory commensals may affect the growth of P. aeruginosa by releasing a large amount of acetic acid. The data provide information about the distinct roles of airway commensals and provide insights into novel strategies for controlling airway infections.

Carbapenem-Resistant NDM and OXA-48-like Producing K. pneumoniae: From Menacing Superbug to a Mundane Bacteria; A Retrospective Study in a Romanian Tertiary Hospital

BACKGROUND

Carbapenem-resistant Klebsiella pneumoniae (Cr-Kpn) is becoming a growing public health problem through the failure of adequate treatment. This study's objectives are to describe the sources of Cr-Kpn in our hospital over 22 months, associating factors with the outcome of Cr-Kpn-positive patients, especially those with NDM+OXA-48-like (New Delhi Metallo-β-Lactamase and oxacillinase-48), and the effectiveness of the treatments used.

METHODS

A retrospective observational cohort study including all hospitalized patients with Cr-Kpn isolates. We reported data as percentages and identified independent predictors for mortality over hospital time through multivariate analysis.

RESULTS

The main type of carbapenemases identified were NDM+OXA-48-like (49.4%). The statistical analysis identified that diabetes and co-infections with the Gram-negative, non-urinary sites of infection were factors of unfavorable evolution. The Cox regression model identified factors associated with a poor outcome: ICU admission (HR of 2.38), previous medical wards transition (HR of 4.69), and carbapenemase type NDM (HR of 5.98). We did not find the superiority of an antibiotic regimen, especially in the case of NDM+OXA-48-like.

CONCLUSIONS

The increase in the incidence of Cr-Kpn infections, especially with NDM+OXA-48-like pathogens, requires a paradigm shift in both the treatment of infected patients and the control of the spread of these pathogens, which calls for a change in public health policy regarding the use of antibiotics and the pursuit of a One Health approach.

Cross-contamination of carbapenem-resistant Gram-negative bacteria between patients and the hospital environment in the first year of a newly built surgical ward

BACKGROUND

Transmission and outbreaks of carbapenem-resistant Gram-negative bacteria (CRGN) in hospitals are often associated with contamination of the wastewater environment. We performed a prospective observational study to investigate the colonization of the hospital wastewater environment during the first year of occupancy of the surgical intermediate and intensive care units of a newly constructed building at the University Hospital of Heidelberg, Germany.

METHODS

We performed monthly screening of the wastewater system (toilets and sinks) for 12 months, starting 1 month before opening (1st October 2020 to 30th October 2021). Admission and weekly rectal screening of patients for CRGN were also performed in parallel. Bacterial isolates were characterized by whole-genome sequencing.

RESULTS

Twenty-seven of 1978 (1.4%) admitted patients were colonized/infected with CRGN. A total of 29 CRGN isolates from 24 patients and 52 isolates were available for sequencing. Within the first month of occupancy, we identified seven patients colonized/infected with CRGN, while none were found in the environmental reservoirs. The first detection of CRGN isolates in the sewage system started five months after the first occupancy. Two previously non-colonized patients were colonized/infected with Pseudomonas aeruginosa strains colonizing the sewage system. The significant identity of plasmids carrying the carbapenemase gene suggests that long-term colonization of the sewage system facilitates the emergence of new carbapenem-resistant clones.

CONCLUSION

Cross-contamination between patients and the hospital environment is bidirectional. Our study demonstrated that contamination of the hospital wastewater environment may lead to persistent colonization and may serve as a reservoir for nosocomial acquisition of CRGN.

Proton pump inhibitors increase the risk of carbapenem-resistant Enterobacteriaceae colonization by facilitating the transfer of antibiotic resistance genes among bacteria in the gut microbiome

Carbapenem-resistant Enterobacteriaceae (CRE) pose a global health threat; however, there is still limited understanding of the risk factors and underlying mechanisms of CRE colonization in the gut microbiome. We conducted a matched case-control study involving 282 intensive care unit patients to analyze influencing covariates on CRE colonization. Subsequently, their effects on the gut microbiome were analyzed in a subset of 98 patients (47 CRE carriers and 51 non-CRE carriers) using whole metagenome sequences. The concomitant use of proton pump inhibitors (PPIs) and antibiotics was a significant risk factor for CRE colonization. The gut microbiome differed according to PPI administration, even within the CRE and non-CRE groups. Moreover, the transfer of mobile genetic elements (MGEs) harboring carbapenem resistance genes (CRGs) between bacteria was higher in the PPI-treated group than in the PPI-not-treated group among CRE carriers. The concomitant use of PPIs and antibiotics significantly alters the gut microbiome and increases the risk of CRE colonization by facilitating the transfer of CRGs among bacteria of the gut microbiome. Based on these findings, improved stewardship of PPIs as well as antibiotics can provide strategies to reduce the risk of CRE colonization, thereby potentially improving patient prognosis.

Risk factors for nosocomial rectal colonisation with carbapenem-resistant Gram-negative bacilli in children with haematological malignancies: a case-control study

BACKGROUND

Rectal colonisation with carbapenem-resistant Gram-negative bacilli (CR-GNB) may cause CR-GNB infection in children with haematological malignancies (HMs) haematological. To date, information on its epidemiology is limited. This study aimed to assess the the risk factors for rectal colonisation with CR-GNB in children with HMs.

METHODS

A case-control study in a tertiary children's hospital in Hangzhou City, was conducted between July 2019, and September 2021. Based on the hospitalisation date, children in the CR-GNB colonisation group and control groups were matched at a ratio of 1:2. Conditional logistic regression models were used to compute the adjusted odds ratios (aORs) and 95% confidence intervals (CIs) of the risk factors for CR-GNB rectal colonisation in children with HMs.

RESULTS

A total of 85 non-duplicated CR-GNB isolates were collected from rectal swab samples of 69 children with HMs. The 30-day mortality rates were 5.8% in the CR-GNB colonisation group and 0% in the control group (P = 0.020).colonisation In the conditional logistic regression model, the aORs were 6.84 (95% CI 1.86-25.20) for acute myeloid leukemia (AML) or acute lymphoblastic leukemia (ALL), 4.16 (95% CI 1.17-14.84) for prior concomitant infections within the last 1 month, 2.33 (95% CI 1.16-4.69) for prior carbapenems usage within the last 1 month and 7.46 (95% CI 1.81-30.67) for prior hematopoietic stem-cell transplantation (HSCT).

CONCLUSION

AML/ALL, prior concomitant infections within the last 1 month, prior carbapenems usage within the last 1 month, and prior HSCT are associated with an increased risk of rectal colonisation with CR-GNB in children with HMs.

Development of a Risk Prediction Model of Subsequent Bloodstream Infection After Carbapenem-Resistant Enterobacteriaceae Isolated from Perianal Swabs in Hematological Patients

Purpose

Patients with hematological diseases are at high risk of carbapenem-resistant Enterobacteriaceae (CRE) infection, and CRE-related bloodstream infection (BSI) is associated with high mortality risk. Therefore, developing a predictive risk model for subsequent BSI in hematological patients with CRE isolated from perianal swabs could be used to guide preventive strategies.

Methods

This was a single-center retrospective cohort study at a tertiary blood diseases hospital, including all hematological patients hospitalized from 10 October 2017 to 31 July 2021. We developed a predictive model using multivariable logistic regression and internally validated it using enhanced bootstrap resampling.

Results

Of 421 included patients with CRE isolated from perianal swabs, BSI due to CRE occurred in 59. According to the multivariate logistic analysis, age (OR[odds ratio]=1.04, 95% CI[confidence interval]: 1.01-1.06, P=0.004), both meropenem and imipenem minimal inhibitory concentration (MIC) of the isolate from perianal swabs>8ug/mL (OR=5.34, 95% CI: 2.63-11.5, P<0.001), gastrointestinal symptoms (OR=3.67, 95% CI: 1.82-7.58, P<0.001), valley absolute neutrophil count (10⁹/L)>0.025 (OR=0.07, 95% CI: (0.02-0.19, P<0.001) and shaking chills at peak temperature (OR=6.94, 95% CI: (2.60-19.2, P<0.001) were independently associated with CRE BSI within 30 days and included in the prediction model. At a cut-off of prediction probability ≥ 21.5% the model exhibited a sensitivity, specificity, positive predictive value and negative predictive value of 79.7%, 85.6%, 96.27% and 47.47%. The discrimination and calibration of the prediction model were good on the derivation data (C-statistics=0.8898; Brier score=0.079) and enhanced bootstrapped validation dataset (adjusted C-statistics=0.881; adjusted Brier score=0.083). The risk prediction model is freely available as a mobile application at https://liujia1992.shinyapps.io/dynnomapp/.

Conclusion

A prediction model based on age, meropenem and imipenem MIC of isolate, gastrointestinal symptoms, valley absolute neutrophil count and shaking chills may be used to better inform interventions in hematological patients with CRE isolated from perianal swabs.

The acquisition of transferable extrachromosomal fec operon is associated with a cefiderocol MIC increase in Enterobacterales

BACKGROUND

Cefiderocol is a novel siderophore cephalosporin active against MDR Gram-negative bacilli, including MBL-harbouring Enterobacterales. The detection of multiple cefiderocol-resistant blaVIM-carrying Enterobacterales isolates (MIC = 4 mg/L) from a single patient suggested an additional, potentially transferable, resistance determinant as blaVIM typically does not elevate cefiderocol MIC above the resistance threshold.

METHODS

Transfer of a mobile genetic element was performed in liquid mating experiments. All donor isolates and transconjugants were characterized by short-read WGS to identify potential resistance determinants. mRNA expression of siderophore receptors was determined by quantitative RT-PCR. Validation was performed by transformation. Antibiotic susceptibility was determined by broth microdilution.

RESULTS

Liquid mating experiments indicated the presence of transferable resistance determinants. Comparative genomic analysis of the clinical isolates and their respective transconjugants revealed the transfer of an accessory fec operon (fecABCDEIR). Transformation of the fec operon-containing vector into a TOP10 Escherichia coli led to an elevation of the cefiderocol MIC by at least 16-fold. Higher expression of fecA as a proxy for the fec operon mRNA expression was associated with phenotypic cefiderocol resistance. Both VIM and the accessory fec operon contribute to the elevation of cefiderocol MIC beyond the resistance threshold. The acquisition of an accessory fec operon via liquid mating confers phenotypic cefiderocol resistance in both E. coli J53 and Pseudomonas aeruginosa PAO1, indicating a broad-host-range nature of this mobile resistance determinant.

CONCLUSIONS

The emergence of a transferable cefiderocol resistance determinant without prior exposure to the substance is worrisome and should be monitored closely.

Canary in the Coal Mine: How Resistance Surveillance in Commensals Could Help Curb the Spread of AMR in Pathogenic Neisseria

Antimicrobial resistance (AMR) is widespread within Neisseria gonorrhoeae populations. Recent work has highlighted the importance of commensal Neisseria (cN) as a source of AMR for their pathogenic relatives through horizontal gene transfer (HGT) of AMR alleles, such as mosaic penicillin binding protein 2 (penA), multiple transferable efflux pump (mtr), and DNA gyrase subunit A (gyrA) which impact beta-lactam, azithromycin, and ciprofloxacin susceptibility, respectively. However, nonpathogenic commensal species are rarely characterized. Here, we propose that surveillance of the universally carried commensal Neisseria may play the role of the "canary in the coal mine," and reveal circulating known and novel antimicrobial resistance determinants transferable to pathogenic Neisseria. We summarize the current understanding of commensal Neisseria as an AMR reservoir, and call to increase research on commensal Neisseria species, through expanding established gonococcal surveillance programs to include the collection, isolation, antimicrobial resistance phenotyping, and whole-genome sequencing (WGS) of commensal isolates. This will help combat AMR in the pathogenic Neisseria by: (i) determining the contemporary AMR profile of commensal Neisseria, (ii) correlating AMR phenotypes with known and novel genetic determinants, (iii) qualifying and quantifying horizontal gene transfer (HGT) for AMR determinants, and (iv) expanding commensal Neisseria genomic databases, perhaps leading to the identification of new drug and vaccine targets. The proposed modification to established Neisseria collection protocols could transform our ability to address AMR N. gonorrhoeae, while requiring minor modifications to current surveillance practices. IMPORTANCE Contemporary increases in the prevalence of antimicrobial resistance (AMR) in Neisseria gonorrhoeae populations is a direct threat to global public health and the effective treatment of gonorrhea. Substantial effort and financial support are being spent on identifying resistance mechanisms circulating within the gonococcal population. However, these surveys often overlook a known source of resistance for gonococci-the commensal Neisseria. Commensal Neisseria and pathogenic Neisseria frequently share DNA through horizontal gene transfer, which has played a large role in rendering antibiotic therapies ineffective in pathogenic Neisseria populations. Here, we propose the expansion of established gonococcal surveillance programs to integrate a collection, AMR profiling, and genomic sequencing pipeline for commensal species. This proposed expansion will enhance the field's ability to identify resistance in and from nonpathogenic reservoirs and anticipate AMR trends in pathogenic Neisseria.

Rapid Development of Cefiderocol Resistance in Carbapenem-resistant Enterobacter cloacae During Therapy Is Associated With Heterogeneous Mutations in the Catecholate Siderophore Receptor cirA

We report a case of resistance development toward cefiderocol in a patient with intra-abdominal and bloodstream infections caused by carbapenemase-producing Enterobacter cloacae within 21 days of cefiderocol therapy. Whole genome sequencing revealed heterogeneous mutations in the cirA gene, encoding a catecholate siderophore receptor, conferring phenotypic resistance to cefiderocol.

Comparative Genomic Reveals Clonal Heterogeneity in Persistent Staphylococcus aureus Infection

Persistent infections caused by Staphylococcus aureus remain a clinical challenge. Adaptational mechanisms of the pathogen influencing infection persistence, treatment success, and clinical outcome in these types of infections by S. aureus have not been fully elucidated so far. We applied a whole-genome sequencing approach on fifteen isolates retrieved from a persistent S. aureus infection to determine their genetic relatedness, virulome, and resistome. The analysis of the genomic data indicates that all isolates shared a common clonal origin but displayed a heterogenous composition of virulence factors and antimicrobial resistance. This heterogeneity was reflected by different mutations in the rpoB gene that were related to the phenotypic antimicrobial resistance towards rifampicin and different minimal inhibitory concentrations of oxacillin. In addition, one group of isolates had acquired the genes encoding for staphylokinase (sak) and staphylococcal complement inhibitor (scn), leading to the truncation of the hemolysin b (hlb) gene. These features are characteristic for temperate phages of S. aureus that carry genes of the immune evasion cluster and confer triple conversion by integration into the hlb gene. Modulation of immune evasion mechanisms was demonstrated by significant differences in biofilm formation capacity, while invasion and intracellular survival in neutrophils were not uniformly altered by the presence of the immune evasion cluster. Virulence factors carried by temperate phages of S. aureus may contribute to the course of infection at different stages and affect immune evasion and pathogen persistence. In conclusion, the application of comparative genomic demonstrated clonal heterogeneity in persistent S. aureus infection.

Commensal Bacteria in the Cystic Fibrosis Airway Microbiome Reduce P. aeruginosa Induced Inflammation

Chronic Pseudomonas aeruginosa infections play an important role in the progress of lung disease in patients suffering from cystic fibrosis (CF). Recent studies indicate that polymicrobial microbiome profiles in the airway are associated with less inflammation. Thus, the hypothesis was raised that certain commensal bacteria might protect the host from inflammation. We therefore performed a screening study with commensals isolated from CF airway microbiome samples to identify potential beneficial commensals. We isolated more than 80 aerobic or facultative anaerobic commensal strains, including strains from genera Streptococcus, Neisseria, Actinomyces, Corynebacterium, Dermabacter, Micrococcus and Rothia. Through a screening experiment of co-infection in human epithelial cell lines, we identified multiple commensal strains, especially strains belonging to Streptococcus mitis, that reduced P. aeruginosa triggered inflammatory responses. The results were confirmed by co-infection experiments in ex-vivo precision cut lung slices (PCLS) from mice. The underlying mechanisms of the complex host-pathogen-commensal crosstalk were investigated from both the host and the bacterial sides with a focus on S. mitis. Transcriptome changes in the host in response to co-infection and mono-infection were evaluated, and the results indicated that several signalling pathways mediating inflammatory responses were downregulated by co-infection with S. mitis and P. aeruginosa compared to P. aeruginosa mono-infection, such as neutrophil extracellular trap formation. The genomic differences among S. mitis strains with and without protective effects were investigated by whole genome sequencing, revealing genes only present in the S. mitis strains showing protective effects. In summary, through both in vitro and ex vivo studies, we could identify a variety of commensal strains that may reduce host inflammatory responses induced by P. aeruginosa infection. These findings support the hypothesis that CF airway commensals may protect the host from inflammation.

Genomic Investigation and Successful Containment of an Intermittent Common Source Outbreak of OXA-48-Producing Enterobacter cloacae Related to Hospital Shower Drains

The hospital environment has been reported as a source of transmission events and outbreaks of carbapenemase-producing Enterobacterales. Interconnected plumbing systems and the microbial diversity in these reservoirs pose a challenge for outbreak investigation and control. A total of 133 clinical and environmental OXA-48-producing Enterobacter cloacae isolates collected between 2015 and 2021 were characterized by whole-genome sequencing (WGS) to investigate a prolonged intermittent outbreak involving 41 patients in the hematological unit. A mock-shower experiment was performed to investigate the possible acquisition route. WGS indicated the hospital water environmental reservoir as the most likely source of the outbreak. The lack of diversity of the blaOXA-48-like harbouring plasmids was a challenge for data interpretation. The detection of blaOXA-48-like-harboring E. cloacae strains in the shower area after the mock-shower experiment provided strong evidence that showering is the most likely route of acquisition. Initially, in 20 out of 38 patient rooms, wastewater traps and drains were contaminated with OXA-48-positive E. cloacae. Continuous decontamination using 25% acetic acid three times weekly was effective in reducing the trap/drain positivity in monthly environmental screening but not in reducing new acquisitions. However, the installation of removable custom-made shower tubs did prevent new acquisitions over a subsequent 12-month observation period. In the present study, continuous decontamination was effective in reducing the bacterial burden in the nosocomial reservoirs but was not sufficient to prevent environment-to-patient transmission in the long term. Construction interventions may be necessary for successful infection prevention and control. IMPORTANCE The hospital water environment can be a reservoir for a multiward outbreak, leading to acquisitions or transmissions of multidrug-resistant organisms in a hospital setting. The majority of Gram-negative bacteria are able to build biofilms and persist in the hospital plumbing system over a long period of time. The elimination of the reservoir is essential to prevent further transmission and spread, but proposed decontamination regimens, e.g., using acetic acid, can only suppress but not fully eliminate the environmental reservoir. In this study, we demonstrated that colonization with multidrug-resistant organisms can be acquired by showering in showers with contaminated water traps and drains. A construction intervention by installing removable and autoclavable shower inserts to avoid sink contact during showering was effective in containing this outbreak and may be a viable alternative infection prevention and control measure in outbreak situations involving contaminated shower drains and water traps.

Invasiveness of Escherichia coli Is Associated with an IncFII Plasmid

Escherichia coli is one of the most prevalent pathogens, causing a variety of infections including bloodstream infections. At the same time, it can be found as a commensal, being part of the intestinal microflora. While it is widely accepted that pathogenic strains can evolve from colonizing E. coli strains, the evolutionary route facilitating the commensal-to-pathogen transition is complex and remains not fully understood. Identification of the underlying mechanisms and genetic changes remains challenging. To investigate the factors involved in the transition from intestinal commensal to invasive E. coli causing bloodstream infections, we compared E. coli isolated from blood culture to isolates from the rectal flora of the same individuals by whole genome sequencing to identify clonally related strains and potentially relevant virulence factors. in vitro invasion assays using a Caco- 2 cell intestinal epithelial barrier model and a gut organoid model were performed to compare clonally related E. coli. The experiments revealed a correlation between the presence of an IncFII plasmid carrying hha and the degree of invasiveness. In summary, we provide evidence for the role of an IncFII plasmid in the transition of colonization to invasion in clinical E. coli isolates.

The Impact of Discontinuing Contact Precautions and Enforcement of Basic Hygiene Measures on Nosocomial Vancomycin-Resistant Enterococcus faecium Transmission

OBJECTIVES

Vancomycin-resistant Enterococcus faecium (VREfm) has emerged as a pathogen of major public health concern. Although definitive evidence is lacking, contact precautions have been a crucial element in infection prevention and control (IPC) strategies designed to limit nosocomial VRE transmissions. This study investigates the effect of discontinuing contact precautions while enforcing basic hygiene measures, including hand hygiene, environmental cleaning, and antiseptic body washing, for VRE patients at ICUs on prevention of nosocomial VRE transmission causing bacteraemia.

METHODS

Contact precaution was discontinued in January 2018. A total of 96 VREfm isolates from 61 ICU patients with VREfm bacteraemia and/or colonization from 8 ICUs in 2016 and 2019 in a tertiary care hospital were characterized by whole genome sequenicng. VRE transmission was investigated using patient movement data and admission screening for reliable identification of nosocomial acquisition.

RESULTS

Discontinuation of contact precautions did not increase VREfm transmission events (8 in 2016 vs 1 in 2019). While the rate of endogenous VREfm was similar in both years (38% vs 31%), the number of non-colonized patients prior to VREfm bacteraemia was 16 (16/29; 55%) in 2019, which was significantly higher than in 2016 (8/32; 25%). The mean incidence density for VREfm bacteraemia was similar for both years; 0.26 versus 0.31 per 1000 patient days in 2016 and 2019, respectively.

CONCLUSION

Our data suggest that discontinuation of contact precaution, while enforcing the basic hygiene measures did not lead to an increase of nosocomial bloodstream infection rates due to transmissions of VREfm in hyperendemic ICU settings.

Pitfalls in genotypic antimicrobial susceptibility testing caused by low expression of blaKPC in Escherichia coli

BACKGROUND

There is a growing interest in the rapid genotypic identification of antimicrobial resistance (AMR). In routine diagnostics, we detected multiple KPC-positive Escherichia coli (KPC-Ec) with discordant phenotypic meropenem susceptibility from a single patient's blood cultures, which prompted a more thorough investigation.

OBJECTIVES

We investigated the potential clinical relevance of, and the mechanism behind, discordant phenotypic and genotypic meropenem susceptibility in KPC-Ec.

METHODS

WGS was used to perform a comparative analysis of the isolates' genetic characteristics and their blaKPC-2 locus. Expression of blaKPC-2 was determined by quantitative PCR and the potency of meropenem hydrolysis was determined using a semi-quantitative carbapenem inactivation method. An in vivo infection assay using Galleria mellonella was performed to assess the potential clinical relevance of KPC expression in E. coli.

RESULTS

Despite the presence of blaKPC-2, three of five isolates were susceptible to meropenem (MICVITEK2 ≤ 0.25 mg/L), while two isolates were resistant (MICVITEK2 ≥ 16 mg/L). The isolates with high MICs had significantly higher blaKPC-2 expression, which corresponds to phenotypic meropenem inactivation. The genetic environment of blaKPC-2, which may impact KPC production, was identical in all isolates. In vivo infection assay with G. mellonella suggested that meropenem was effective in reducing mortality following infection with low-expressing KPC-Ec.

CONCLUSIONS

Our findings clearly highlight a limitation of genotypic AMR prediction for blaKPC. For the time being, genotypic AMR prediction requires additional analysis for accurate antibiotic therapy decision-making.

Challenges in interpretation of WGS and epidemiological data to investigate nosocomial transmission of vancomycin-resistant Enterococcus faecium in an endemic region: incorporation of patient movement network and admission screening

OBJECTIVES

VRE are listed, by the WHO, among the leading resistant pathogens causing greatest public concern; hence the spread and transmission of VRE, especially in hospitalized patients, need to be monitored. Despite the advancements in typing methods since the implementation of WGS for outbreak investigations, data interpretation, especially for vancomycin-resistant Enterococcus faecium (VREfm) in an endemic setting, remains challenging. In this study we explored the potential added benefit of incorporating patient movement data and admission screening to accurately estimate the magnitude of an outbreak.

METHODS

We sequenced 73 VREfm isolates from patients with bacteraemia (n = 43) and rectal colonization (n = 30/32). Genetic relatedness was determined by SNP distance (≤10) between isolates. Patient movements were visualized in a movement network, along with contact intensity and rectal colonization status prior to infection onset.

RESULTS

ST117, ST80 and ST203 were the predominant STs in our study population. Forty-four percent (18/41) of VREfm bacteraemia cases were of endogenous origin. SNP analysis of infection and colonization isolates revealed nine clonal groups. Eighty-six percent (37/43) of the patients were visualized in a transmission network due to spatiotemporal overlap. Nineteen out of 43 (44%) belonged to five transmission clusters. Incorporation of prior colonization status revealed that transmission was very likely in only 63% (12/19) of patients in these transmission clusters.

DISCUSSION

Although interpretation of WGS data is challenging, incorporation of patient movement data and colonization status by admission screening of high-risk patients may provide additional resolution when interpreting the magnitude of an outbreak in an endemic setting.

Acquisition and Transmission of Carbapenemase-Producing (blaKPC-2) Enterobacter cloacae in a Highly Frequented Outpatient Clinic

The role of outpatient clinics as a potential transmission ground for multidrug-resistant organisms has not been adequately investigated. Here, we report a transmission cluster of blaKPC-2-positive Enterobacter cloacae among patients treated in a highly frequented outpatient department.

Emergence of carbapenem-resistant ST131 Escherichia coli carrying bla OXA-244 in Germany, 2019 to 2020

The dissemination of carbapenem-producing Gram-negative bacteria is a major public health concern. We report the first detection of OXA-244-producing ST131 O16:H5 Escherichia coli in three patients from two tertiary hospitals in the south-west of Germany. OXA-244 is emerging in Europe. Because of detection challenges, OXA-244-producing E. coli may be under-reported. The emergence of carbapenem resistance in a globally circulating high-risk clone, such as ST131 E. coli is of clinical relevance and should be monitored closely.

Identification and Elimination of the Clinically Relevant Multi-Resistant Environmental Bacteria Ralstonia insidiosa in Primary Cell Culture

In times of spreading multidrug-resistant bacteria, species identification and decontamination of cell cultures can be challenging. Here, we describe a mobile cell culture contaminant with “black dot”-like microscopic appearance in newly established irreplaceable hybridoma cell lines and its identification. Using 16S rRNA gene sequencing, species-specific PCRs, whole genome sequencing (WGS), and MALDI-TOF mass spectrometry, the contaminant was identified as the ubiquitous environmental and clinically relevant Gram-negative bacterium Ralstonia insidiosa (R. insidiosa), a strong biofilm producer. Further characterizations by transmission electron microscopy (TEM) and biochemical API test were not conclusive. Whole genome sequencing of our R. insidiosa isolate revealed numerous drug-resistance determinants. Genome-wide comparison to other Ralstonia species could not unambiguously designate our isolate to R. insidiosa (<95% average nucleotide identity) suggesting a potential novel species or subspecies, closely related to R. insidiosa and R. pickettii. After determining the antibiotic susceptibility profile, the hybridoma cell culture was successfully decontaminated with ciprofloxacin without affecting antibody production.

Entry of Panton-Valentine leukocidin-positive methicillin-resistant Staphylococcus aureus into the hospital: prevalence and population structure in Heidelberg, Germany 2015-2018

Staphylococcus aureus is one of the major pathogens causing community—and healthcare-acquired infections. The presence of the virulence factor Panton–Valentine leukocidin (PVL) is associated with recurrent infection and clinical severity and generally regarded as a feature of community associated-methicillin-resistant Staphylococcus aureus (MRSA). To date, the focus of PVL-positive MRSA in hospitalized patients has been on outbreaks. We aimed to investigate whether PVL-positive MRSA has penetrated the community-hospital barrier by determining the prevalence of PVL in MRSA of hospitalized patients. MRSA strains isolated from patients hospitalized > 48 h in Heidelberg University Hospital between 2015 and 2018 Isolates were analysed for the presence of PVL and subjected to spa-typing. PVL-positive MRSA were then characterized by whole genome sequencing. We analysed 740 MRSA isolates in the study period and identified 6.2% (n = 46) PVL-positivity. 32.6% of PVL-positive MRSA met the criteria for nosocomial acquisition. The most frequent clones among the PVL-positive strains were ST80-t044 (21.7%, n = 10/46) and ST8-t008 (19.5%, n = 9/46). WGS identified three possible transmission clusters involving seven patients. In conclusion, we found successful epidemic PVL-positive MRSA clones entering the hospital and causing nosocomial infections. Preventive measures and constant surveillance should be maintained to prevent transmissions and clonal outbreaks.

Whole-genome sequencing disproves two suspected transmission events of blaNDM between Pseudomonas aeruginosa and Enterobacterales in hospitalized patients

New Delhi metallo-β-lactamase (bla_NDM) acquisition by Gram-negative bacteria is a primary concern due to its broad-host-range distribution. This study investigated two potential in-vivo horizontal gene transfers (HGTs) of bla_NDM between Enterobacterales and Pseudomonas aeruginosa, initially indicated by polymerase chain reaction. Whole-genome sequencing showed independent parallel acquisition of two different bla_NDM variants (NDM-1 and NDM-5) in P. aeruginosa and Enterobacterales, respectively. The data show that short-read sequencing provides the necessary resolution to confirm or dispute HGT by the comparison of genetic elements surrounding the gene of interest, and thus provide a timely response to potential outbreaks.

Low prevalence of combined linezolid- and vancomycin-resistant Enterococcus faecium from hospital admission screening in an endemic region in Germany

BACKGROUND

The emergence and spread of linezolid and combined linezolid/vancomycin resistance in Enterococcus faecium (LVRE) is a major therapeutic challenge. Due to the unavailability of standardized selective culture media for LVRE screening, the detection of LVRE is laborious and costly. Systematic data on LVRE prevalence are scarce, and therefore, supportive evidence for the correct implementation of preemptive strategies is lacking.

OBJECTIVE

We investigated the prevalence of LVRE in a vancomycin-resistant enterococci (VRE) endemic area in Germany in admission screening of high-risk patients for multidrug-resistant organisms to assess the necessity of LVRE screening.

METHODS

We performed phenotypic testing for linezolid susceptibility in all patients (n = 2572) admitted to our hospital in the months of January, April, July and October 2018 with a positive VRE culture in their rectal admission screening swab. Eight isolates from seven patients with LVRE colonization were characterized by whole genome sequencing.

RESULTS

Twenty-eight percent (712/2572) of screened patients were colonized by VRE. Seventy percent (497/712) of the isolates were available for testing and whole genome sequencing. A total of 1.4% (7/497) of VRE were LVRE, predominantly due to mutations of 23S rRNA. optrA, poxtA or cfr genes were not detected. Patients with LVRE colonization did not develop LVRE infections during their stay.

CONCLUSION

LVRE prevalence was low, and there was no evidence for the dissemination of linezolid resistance genes. Due to the low prevalence and the low risk of infection due to endogenous LVRE, we do not see the immediate necessity to introduce routine LVRE screening in our hospital.