Comparative evaluation of a new commercial media, the CHROMAgar™ mSuperCARBA™, for the detection of carbapenemase-producing Enterobacteriaceae

Characterization of Enterobacterales growing on selective CPE screening plates with a focus on non-carbapenemase-producing strains

Carbapenem-resistant Enterobacterales (CRE) are divided into two distinct groups: carbapenemase-producing (CPE) and non-carbapenemase-producing (non-CPE). The population of non-CPE growing on CPE selective plates during routine screening is usually not reported and is not well defined. This study aimed to characterize non-CPE isolates growing on those plates. Isolates were collected from two medical institutions in Israel between May and November 2022. Species identification and antibiotic susceptibility testing were performed using VITEK systems. Further analyses focused on Klebsiella pneumoniae and Escherichia coli which were the most common isolates. Meropenem MIC was determined by E-test. Fourier-transform infrared spectroscopy (FTIR) was used to analyze phenotypic similarity, and whole genome sequencing was conducted on a subset of non-CPE isolates. Of 260 isolates growing on selective CPE screening plates, 60.4% were non-CPE. The most common non-CP isolates were K. pneumoniae (65.6%) followed by E. coli (20.4%). Of the non-CP K. pneumoniae and E. coli isolates, 78.2% were susceptible to meropenem. All non-CP K. pneumoniae and E. coli isolates were multidrug-resistant (MDR) and belonged to multiple FTIR clusters. The 21 sequenced non-CPE isolates carried multiple mechanisms of resistance. Isolates had multiple beta-lactamases and all had penicillin-binding protein modifications and porin mutations; in meropenem-resistant K. pneumoniae isolates, both Ompk35 and Ompk36 were mutated. The majority of isolates growing on selective CPE screening plates are non-CPE but are MDR. Laboratory reporting of these MDR bacteria might be useful for guiding treatment and prophylaxis when indicated, as well as for infection control.

IMPORTANCE

Selective screening plates for carbapenemase-producing Enterobacterales (CPE) are used to detect CPE carriers for infection control purposes. We characterized non-CPE isolates that grew on selective CPE screening plates, which are intended to filter them out. We found that 60% of isolates that grew on these plates were not CPE. They included both meropenem-susceptible and meropenem-resistant isolates and were multidrug-resistant with multiple resistance mechanisms. These test results, which are usually not reported by laboratories, may be clinically valuable.

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.

Unveiling the hidden threat of carbapenemase-producing Enterobacteriaceae in hospital water environments: A single-center study

This retrospective study examined the presence of carbapenemase-producing Enterobacteriaceae in hospital water environments. Results showed that carbapenemase-producing Enterobacteriaceae was detected in 41.5% of the samples within 1 m of a water source (showers or sinks), with 20.6% of the positive samples associated with shower water sources.

A European multicenter evaluation study to investigate the performance on commercially available selective agar plates for the detection of carbapenemase producing Enterobacteriaceae

The European Food Safety Authority (EFSA) advised to prioritize monitoring carbapenemase producing Enterobacteriaceae (CPE) in food producing animals. Therefore, this study evaluated the performance of different commercially available selective agars for the detection of CPE using spiked pig caecal and turkey meat samples and the proposed EFSA cultivation protocol. Eleven laboratories from nine countries received eight samples (four caecal and four meat samples). For each matrix, three samples contained approximately 100 CFU/g CPE, and one sample lacked CPE. After overnight enrichment in buffered peptone water, broths were spread upon Brilliance™ CRE Agar (1), CHROMID® CARBA (2), CHROMagar™ mSuperCARBA™ (3), Chromatic™ CRE (4), CHROMID® OXA-48 (5) and Chromatic™ OXA-48 (6). From plates with suspected growth, one to three colonies were selected for species identification, confirmation of carbapenem resistance and detection of carbapenemase encoding genes, by methods available at participating laboratories. Of the eleven participating laboratories, seven reported species identification, susceptibility tests and genotyping on isolates from all selective agar plates. Agars 2, 4 and 5 performed best, with 100% sensitivity. For agar 3, a sensitivity of 96% was recorded, while agar 1 and 6 performed with 75% and 43% sensitivity, respectively. More background flora was noticed for turkey meat samples than pig caecal samples. Based on this limited set of samples, most commercially available agars performed adequately. The results indicate, however, that OXA-48-like and non-OXA-48-like producers perform very differently, and one should consider which CPE strains are of interest to culture when choosing agar type.

A hospital-wide outbreak of IMI-17-producing Enterobacter ludwigii in an Israeli hospital

Background

To describe the course and intervention of an hospital-wide IMI-Producing Enterobacter ludwigii outbreak.

Methods

This was an outbreak interventional study, done at a tertiary care center in Tel-Aviv, Israel. Data was collected on the course of the outbreak and the demographic and clinical characteristics of all patients involved in the outbreak. The intervention measures included patients’ cohorting, contact isolation precautions, environmental cleaning and screening of contacts. The molecular features and phylogeny of outbreak-related isolates were studied by whole-genome based analysis.

Results

The outbreak included 34 patients that were colonized by IMI-Producing E. ludwigii and were identified in 24 wards throughout the hospital. Colonization was identified in the first 72 h of admission in 13/34 patients (38.2%). Most patients (91.2%) were admitted from home and had relatively low level of comorbidities. The majority of them (88%) had no recent use of invasive catheters and none had previous carriage of other multi-drug resistant bacteria. All available isolates harbored the bla_IMI-17 allele and belonged to Sequence-Type 385. With the exception of two isolates, all isolates were closely related with less than a 20-SNP difference between them.

Conclusions

This outbreak had most likely originated in the community and subsequently disseminated inside our institution. More studies are required in order to elucidate the epidemiology of IMI-Producing E. ludwigii and the possible role of environmental sources in its dissemination.

Carbapenemase screening in an Irish tertiary referral hospital: Best practice, or can we do better?

BACKGROUND

Carbapenems are a family of end line antibiotics with increasing levels of resistance that are a cause for concern.

AIM

To ascertain whether the CPE screening programme employed in an acute tertiary hospital is fit for purpose.

METHOD

We outlined the current working algorithm employed using a universal screening programme over a 26-month screening period. Rectal swabs are cultured on arrival. Those with suspicious growth are further investigated using NG-Carba 5 lateral flow tests and Vitek 2.0 sensitivity cards. These practices were compared with NHS guidelines.

FINDINGS & CONCLUSIONS

In all, 53 true positives were detected from 45 patients since the screening was implemented in early 2018 (46 OXA-48, 6 KPC, 1 NDM). As the rate of screening increased, the number of positive screens decreased over time. There were a lot of similarities between the HSE guidelines and the published NHS CPE toolkit. It was evident that there is no standard practice being employed across all hospitals. Comparing the MUH to national guidelines it appears to be quicker and more effective with universal screening in place at reducing the potential contacts and identifying carriers. Cost analysis indicates that the need to confirm all positive strains in a reference lab is costly, unnecessary and time consuming. There are adequate confirmatory tests available in-house for routine positive screens. It was concluded that infection prevention and control are key to identifying and controlling possible outbreaks in a hospital setting.

Institutional Burden of Carbapenemase-Producing Enterobacterales: The Effect of Changes in Surveillance Culture Methodology

An essential part of the Israeli intervention program aimed to contain the spread of carbapenemase-producing Enterobacterales (CPE) has been the establishment of national surveillance system, where the institutional rates are determined by both clinical and surveillance cultures. The objectives of the study were to analyze the effect of changes in surveillance culture media on the rates and microbiological characteristics of CPE in a multicenter study. The rates were compared during 2 years in and between four centers. Two centers (Tel-Aviv and Beilinson) had changed their surveillance media to CHROMagar™ mSuperCARBA™ after 1 year, and two centers (Rambam and Hillel-Yaffe) had continued to use CHROMagar KPC. There was an increase in the rates of surveillance CPE in Tel-Aviv and Beilinson following the change in media, whereas the rates remained the same or declined in Rambam and Hillel-Yaffe, respectively. The rates of clinical CPE remained unchanged in Rambam and Hillel-Yaffe, declined in Tel-Aviv, and increased in Beilinson but to a lesser extent compared with the increase in surveillance CPE. The relative composition of the CPE mechanisms and species changed in Tel-Aviv, with an increase in non-Klebsiella pneumoniae species and in carbapenemase other than KPC. Our study shows that changes in surveillance media may contribute to significant changes in the rate of surveillance CPE that may be irrespective of actual epidemiological changes. Therefore, determination of institutional burden of CPE and the assessment of intervention results should be based primarily on the rate of clinical CPE rather than surveillance culture reports.

Utility of CHROMagar mSuperCARBA for surveillance cultures of carbapenemase-producing Enterobacteriaceae

Culture of carbapenemase-producing Enterobacteriaceae (CPE) as part of active surveillance is one of the most useful strategies for successful infection control programmes. Our objective was to compare the recently introduced CHROMagar mSuperCARBA agar for CPE detection in surveillance cultures from perineal swabs with the US Centers for Disease Control and Prevention method. Our results showed that this agar is a useful and affordable alternative (sensitivity 93.05%, specificity 96.21%, diagnostic accuracy 95.2%) to detect CPE in hospital settings.

Evaluation of two commercial real-time PCR assays for detection of carbapenemase genes in Enterobacteriaceae

The implementation of PCR for the detection of carbapenemase genes enables rapid results with significant epidemiological implications. Two commercial real-time PCR assays, the Hylabs Hy-CRE and Sacace MDR MBL+KPC/OXA, were evaluated for the detection of the genes blaKPC, blaVIM, blaNDM, blaIMP and blaOXA-48-carbapenemasein a collection of 96 carbapenem-resistant Enterobacteriaceae strains with different resistant mechanisms. Both assays exhibited excellent diagnostic performance, with 100 % sensitivity and specificity.