CHROMagar mSuperCARBA performance in carbapenem-resistant Enterobacteriaceae isolates characterized at molecular level and routine surveillance rectal swab specimens

Evaluation of CHROMagar™ B. cepacia agar for the detection of Burkholderia cepacia complex species from sputum samples of patients with cystic fibrosis

INTRODUCTION

Burkholderia cepacia complex (BCC) are non-fermenting Gram-negative bacteria that can chronically colonize the lungs of people with cystic fibrosis (pwCF), causing a severe and progressive respiratory failure, post-transplant complications and epidemic outbreaks. Therefore, rapid and accurate identification of these bacteria is relevant for pwCF, in order to facilitate early eradication and prevent chronic colonization. However, BCCs are often quite difficult to detect on culture media as they have a slow growth rate and can be hidden by other fast-growing microorganisms, including Pseudomonas aeruginosa and filamentous fungi.

MATERIAL AND METHODS

We evaluated the sensitivity of CHROMagar™ B. cepacia agar using 11 isolates from a well-characterized BCC collection, using BCA agar (Oxoid, UK) as a gold standard. We also studied 180 clinical sputum samples to calculate positive (PPV) and negative (NPV) predictive values. Furthermore, we used three of the well-characterized BCC isolates to determine the limit of detection (LOD).

RESULTS

Eleven isolates grew on CHROMagar™ B. cepacia at 37ºC after 48 h. The NPV and PPV of CHROMagar™ B. cepacia were 100% and 87.5%, respectively. The LOD of CHROMagar™ B. cepacia was around 1 × 103 CFU/ml, requiring a ten-fold dilution lower bacterial load than BCA for BCC detection.

CONCLUSION

CHROMagar™ B. cepacia agar proved to have a very good sensitivity and specificity for the detection of clinical BCCs. Moreover, the chromogenic nature of the medium allowed us to clearly differentiate BCC from other Gram-negative species, filamentous fungi and yeasts, thereby facilitating the identification of contaminants.

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.

Perinatal colonization with extended-spectrum beta-lactamase-producing and carbapenem-resistant Gram-negative bacteria: a hospital-based cohort study

BACKGROUND

Antimicrobial resistance (AMR) is a growing global health threat that contributes to substantial neonatal mortality. Bangladesh has reported some of the highest rates of AMR among bacteria causing neonatal sepsis. As AMR colonization among newborns can predispose to infection with these bacteria, we aimed to characterize the frequency of and risk factors for colonization of mothers and newborns during hospitalization for delivery.

METHODS

We enrolled pregnant women presenting for delivery to a tertiary care hospital in Faridpur, Bangladesh. We collected vaginal and rectal swabs from mothers pre- and post-delivery, rectal swabs from newborns, and swabs from the hospital environment. Swabs were plated on agars selective for extended-spectrum-beta-lactamase producing bacteria (ESBL-PB) and carbapenem-resistant bacteria (CRB). We performed logistic regression to determine factors associated with ESBL-PB/CRB colonization.

RESULTS

We enrolled 177 women and their newborns during February-October 2020. Prior to delivery, 77% of mothers were colonized with ESBL-PB and 15% with CRB. 79% of women underwent cesarean deliveries (C-section). 98% of women received antibiotics. Following delivery, 98% of mothers and 89% of newborns were colonized with ESBL-PB and 89% of mothers and 72% of newborns with CRB. Of 290 environmental samples, 77% were positive for ESBL-PB and 69% for CRB. Maternal pre-delivery colonization was associated with hospitalization during pregnancy (RR for ESBL-PB 1.24, 95% CI 1.10-1.40; CRB 2.46, 95% CI 1.39-4.37). Maternal post-delivery and newborn colonization were associated with C-section (RR for maternal CRB 1.31, 95% CI 1.08-1.59; newborn ESBL-PB 1.34, 95% CI 1.09-1.64; newborn CRB 1.73, 95% CI 1.20-2.47).

CONCLUSIONS

In this study, we observed high rates of colonization with ESBL-PB/CRB among mothers and newborns, with pre-delivery colonization linked to prior healthcare exposure. Our results demonstrate this trend may be driven by intense use of antibiotics, frequent C-sections, and a contaminated hospital environment. These findings highlight that greater attention should be given to the use of perinatal antibiotics, improved surgical stewardship for C-sections, and infection prevention practices in healthcare settings to reduce the high prevalence of colonization with AMR organisms.

Active Surveillance for Carbapenem-Resistant Enterobacterales (CRE) Colonization and Clinical Course of CRE Colonization among Hospitalized Patients at a University Hospital in Thailand

Optimal measures for preventing and controlling carbapenem-resistant Enterobacterales (CRE) depend on their burden. This prospective observational study investigated the prevalence and clinical course of CRE colonization in hospitalized patients at Siriraj Hospital, the largest university hospital in Thailand. Stool/rectal swab samples were collected from the patients upon admission, once weekly during hospitalization and every 1–3 months after discharge, to determine the presence of CRE in the stool. Between 2018 and 2021, a total of 528 patients were included. The prevalence of CRE colonization upon admission was 15.5%, while 28.3% of patients who tested negative for CRE on admission acquired CRE during their hospitalization. CRE colonization upon admission was usually associated with prior healthcare exposure. Among CRE-colonized patients, 4.7% developed a CRE clinical infection, with 60% mortality. No cutoff period that ensured that patients were free of CRE colonization in stool was identified, and isolation precautions should only be ceased if stool tests are negative for CRE. In conclusion, the prevalence of CRE colonization among hospitalized patients at Siriraj Hospital is high. CRE-colonized patients are at risk of developing subsequent CRE infection. To prevent CRE transmission within the hospital, patients at high risk of colonization should undergo CRE screening upon admission.

Epidemiology of Carbapenem-Resistant Enterobacterales Infection and Colonization in Hospitalized Patients at a University Hospital in Thailand

Purpose

To investigate the epidemiology of carbapenem-resistant Enterobacterales (CRE) colonization or CRE infection relative to the natural history and clinical course of CRE colonization or CRE infection in hospitalized patients during admission and after discharge.

Material and Methods

Two adult cohorts were enrolled. Cohort I comprised hospitalized patients who had CRE isolated from their clinical specimens during 2018–2020. CRE colonization or CRE infection was based on the absence/presence of clinical features of infection. Information regarding the natural history and clinical course of these patients was collected during hospitalization. Stool samples were evaluated for CRE once a week during hospitalization, and then once every few months after discharge until negative for CRE. Cohort II comprised patients who had CRE isolated from clinical specimens during hospitalization and who were discharged during 2015–2018. CRE in stool samples collected from these patients every few months was assessed to determine duration of CRE in stool.

Results

CRE in stool was detected in 69.7% of 353 patients in cohort I. K. pneumoniae was the predominant CRE isolated from clinical samples (76.8%) and stool samples (65.7%). Among the 225 CRE-colonized patients, 20.4% developed subsequent CRE infections with a median duration from CRE colonization to CRE infection of 14 days. Among 174 CRE-infected patients, the most common infection was pneumonia with mortality at discharge of 47.7%. Duration of CRE colonization in stool was <1 year in 50.0% of cohort I patients, and <2 years in 91.4% of patients in cohort II.

Conclusion

CRE isolated from clinical specimens in hospitalized patients are more likely to cause colonization than infection. Patients with CRE colonization are at risk of subsequent CRE infection with high mortality. Stool culture for CRE is needed to verify if contact precautions can be discontinued because the duration of CRE colonization in stool varied from days to years.

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.

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.

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.

A global multinational survey of cefotaxime-resistant coliforms in urban wastewater treatment plants

The World Health Organization Global Action Plan recommends integrated surveillance programs as crucial strategies for monitoring antibiotic resistance. Although several national surveillance programs are in place for clinical and veterinary settings, no such schemes exist for monitoring antibiotic-resistant bacteria in the environment. In this transnational study, we developed, validated, and tested a low-cost surveillance and easy to implement approach to evaluate antibiotic resistance in wastewater treatment plants (WWTPs) by targeting cefotaxime-resistant (CTX-R) coliforms as indicators. The rationale for this approach was: i) coliform quantification methods are internationally accepted as indicators of fecal contamination in recreational waters and are therefore routinely applied in analytical labs; ii) CTX-R coliforms are clinically relevant, associated with extended-spectrum β-lactamases (ESBLs), and are rare in pristine environments. We analyzed 57 WWTPs in 22 countries across Europe, Asia, Africa, Australia, and North America. CTX-R coliforms were ubiquitous in raw sewage and their relative abundance varied significantly (<0.1% to 38.3%), being positively correlated (p < 0.001) with regional atmospheric temperatures. Although most WWTPs removed large proportions of CTX-R coliforms, loads over 10³ colony-forming units per mL were occasionally observed in final effluents. We demonstrate that CTX-R coliform monitoring is a feasible and affordable approach to assess wastewater antibiotic resistance status.

Evaluation of presumptive identification of Enterobacterales using CHROMagar Orientation medium and rapid biochemical tests

Background

The use of matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry is gradually spreading among large‐scale laboratories; however, this method is impractical for small‐scale laboratories. In laboratories without access to these rapid identification methods, problems related to them remain unsolved. In this study, we aimed to develop a rapid and inexpensive method to presumptively identify Enterobacterales using CHROMagar Orientation medium.

Methods

The algorithm for presumptive identification of Enterobacteriaceae using CHROMagar Orientation medium was based on our previous studies. Modified property tests for indole, lysine decarboxylase, ornithine decarboxylase, and hydrogen sulfide were performed to evaluate the differentiation of the bacterial species.

Results

Using the type strains and clinical isolates, it was possible to conduct the property tests at a low cost, within 4 hours. The spot indole test was performed without any nonspecific reactions for the bacteria forming colored colonies. The presumptive identification of bacteria was thereby possible within 24 hours after specimen submission.

Conclusion

All these results suggest that the rapid presumptive identification of Enterobacterales is possible with this new identification method using CHROMagar Orientation medium. This is therefore a prompt and economical method that can be used in routine laboratory work.

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.

CHROMagar™ ESBL/mSuperCARBA bi-plate medium for detection of ESBL- and carbapenemase-producing Enterobacteriaceae from spiked stools

The recently released CHROMagar™ ESBL/CHROMagar™ mSuperCARBA bi-plate medium was evaluated for the detection of ESBL- and carbapenemase-producing Enterobacteriaceae. Spiked stools were used to mimic in vivo stool colonization. Two-hundred enterobacterial isolates were tested. Respective sensitivities of 93.9% and 97.8% were obtained for the detection of ESBL and carbapenemase producers.

A survey on practices for active surveillance of carriage of multidrug-resistant bacteria in hospitals in the Autonomous Community of Valencia, Spain

A questionnaire-based cross-sectional study was conducted to gather information on current microbiological practices for active surveillance of carriage of multidrug-resistant (MDR) bacteria in hospitals from 14 health departments of the Autonomous Community of Valencia (ACV), Spain, which together provided medical attention to 3,271,077 inhabitants in 2017, approximately 70% of the population of the ACV. The survey consisted of 35 questions on MDR bacteria screening policies, surveillance approach chosen (universal vs. targeted), and microbiological methods and processes in use for routine detection and reporting of colonization by MDR bacteria, including the anatomical sites scheduled to be sampled for each MDR bacterial species, and the methodology employed (culture-based, molecular-based, or both). Our study revealed striking differences across centers, likely attributable to the lack of consensus on optimal protocols for sampling, body sites for screening, and microbiological testing, thus underscoring the need for consensus guidelines on these issues.

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.

A Decade of Development of Chromogenic Culture Media for Clinical Microbiology in an Era of Molecular Diagnostics

In the last 25 years, chromogenic culture media have found widespread application in diagnostic clinical microbiology. In the last decade, the range of media available to clinical laboratories has expanded greatly, allowing specific detection of additional pathogens, including Pseudomonas aeruginosa, group B streptococci, Clostridium difficile, Campylobacter spp., and Yersinia enterocolitica. New media have also been developed to screen for pathogens with acquired antimicrobial resistance, including vancomycin-resistant enterococci, carbapenem-resistant Acinetobacter spp., and Enterobacteriaceae with extended-spectrum β-lactamases and carbapenemases. This review seeks to explore the utility of chromogenic media in clinical microbiology, with particular attention given to media that have been commercialized in the last decade. The impact of laboratory automation and complementary technologies such as matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) is also assessed. Finally, the review also seeks to demarcate the role of chromogenic media in an era of molecular diagnostics.

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

A new chromogenic-based medium (mSuperCARBA™) was tested for screening carbapenemase-producing Enterobacteriaceae (CPE). mSuperCARBA™ was more sensitive (83%) in detecting CPE isolates (n=69, including KPC, NDM, OXA-48, VIM, and IMI) compared with CHROMAgar™-KPC (65%) and MacConkey agar with Imipenem (69%) with comparable specificity for non carbapenemase-producing, carbapenem-resistant Enterobacteriaceae (n=29).