Optimal detection of carbapenemase-producing Enterobacteriaceae from rectal samples: a role for enrichment?

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.

Rectal screening for carbapenemase-producing Enterobacteriaceae: a proposed workflow

OBJECTIVES

Active screening is a crucial element for the prevention of carbapenemase-producing Enterobacteriaceae (CPE) transmission in healthcare settings. Here we propose a culture-based protocol for rectal swab CPE screening that combines CPE detection with identification of the carbapenemase type.

METHODS

The workflow integrates an automatic digital analysis of selective chromogenic media (WASPLab®; Copan), with subsequent rapid tests for the confirmation of carbapenemase production [i.e. detection of Klebsiella pneumoniae carbapenemase (KPC)-specific peak by matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry (MALDI-TOF/MS) or a multiplex immunochromatographic assay identifying the five commonest carbapenemase types]. To evaluate the performance of this protocol in depth, data for 21 162 rectal swabs submitted for CPE screening to the Microbiology Unit of S. Orsola-Malpighi Hospital (Bologna, Italy) were analysed.

RESULTS

Considering its ability to correctly segregate plates with/without Enterobacteriaceae, WASPLab Image Analysis Software showed globally a sensitivity and specificity of 100% and 79.4%, respectively. Of the plates with bacterial growth (n = 901), 693 (76.9%) were found to be positive for CPE by MALDI-TOF/MS (KPC-specific peak for K. pneumoniae) or by immunochromatographic assay. Only 2.8% (16/570) of KPC-positive K. pneumoniae strains were missed by the specific MALDI-TOF/MS algorithm, being detected by the immunochromatographic assay. The mean turnaround time needed from sample arrival to the final report ranged between 18 and 24 h, representing a significant time saving compared with manual reading.

CONCLUSION

This workflow proved to be fast and reliable, being particularly suitable for areas endemic for KPC-producing K. pneumoniae and for high-throughput laboratories.

Community prevalence of carbapenemase-producing organisms in East London

BACKGROUND

Over the last decade there has been a rapid, worldwide increase in carbapenem resistance, which is of growing concern. The main protagonists, the carbapenemases Klebsiella pneumoniae carbapenemase (KPC), oxacillinase β-lactamase 48 (OXA-48), imipenemase metallo-β-lactamase (IMP), Verona integron-borne metallo-β-lactamase (VIM), and New Delhi metallo-β-lactamase (NDM) have also been reported across the UK. However, these reports are derived from a combination of reactive screening, outbreak control, inpatient surveillance, and diagnostic samples. Therefore, the true community prevalence is unknown.

AIM

To determine the community prevalence of carbapenemase-producing organisms (CPOs) in the area served by Barts Health NHS Trust.

METHODS

Active screening of 200 non-duplicate community stool samples was performed. Patient demographics and foreign travel history were extracted from the laboratory information management system to identify potential risk factors for carriage of CPOs.

FINDINGS

Patients in this study were aged from one to 93 years and were evenly distributed between male and female. Foreign travel in the last year was listed for 46 out of 200 (23%) patients, with the most commonly visited countries including Bangladesh (4%), India (2.5%), Morocco (2%), and Turkey (1.5%). However, only one patient tested positive for a CPO, an NDM-producing Pseudomonas aeruginosa, and this patient had travelled to the Caribbean.

CONCLUSION

To date, there have been no studies investigating the prevalence of CPOs in the UK community. Given the high-risk patient population served by Barts Health NHS Trust, it is reassuring that the prevalence observed here was low. However, it should be highlighted that travel to countries not previously categorized as high risk may also pose a threat.

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.