Multicenter evaluation of the RAPIDEC® CARBA NP assay for the detection of carbapenemase production in clinical isolates of Enterobacterales and Pseudomonas aeruginosa

Risk factors, impact on outcomes, and molecular epidemiology of infections caused by carbapenem-resistant Enterobacterales in intensive care patients: a multicenter matched case-control study in Brazil

OBJECTIVE

To evaluate risk factors, molecular profiles, and hospital mortality of carbapenem-resistant Enterobacterales (CRE) infections in intensive care unit patients.

METHODS

In this retrospective, multicenter cohort study, intensive care unit admissions from 52 intensive care units between January 2019 and December 2020 were analyzed in a nested case-control design. Patients with carbapenem-resistant Enterobacterales infections were propensity score-matched 1:1 to those with carbapenem-susceptible Enterobacterales infections. Hierarchical conditional logistic regression identified risk factors for carbapenem-resistant Enterobacterales, and multivariable logistic regression assessed the association of carbapenem-resistant Enterobacterales with 60-day in-hospital mortality. Molecular genotyping was also conducted.

RESULTS

Matching resulted in 250 carbapenem-resistant Enterobacterales patients and 250 carbapenem-susceptible Enterobacterales patients. Sepsis was more common in the carbapenem-resistant Enterobacterales group (58% versus 35%; p < 0.001). Risk factors for carbapenem-resistant Enterobacterales included major premorbid assistance requirements (OR 1.72, 95%CI 0.99 - 3.01; p = 0.06) and intensive care unit readmission (OR 1.87, 95%CI 1.00 - 3.49; p = 0.05), although with weak associations. Acute COVID-19 (OR 3.55, 95%CI 1.96 - 6.45; p < 0.001) also increased the odds of resistance. Carbapenem-resistant Enterobacterales infection was associated with twice the likelihood of 60-day mortality after adjusting for covariates (OR 1.95, 95%CI 1.26 - 3.02; p < 0.001). The predominant bacteria and carbapenemase resistance genes included Klebsiella pneumoniae (79%), Klebsiella pneumoniae carbapenemase (73%), New Delhi metallo-beta-lactamase (13%), and xacillinase-48 (9%).

CONCLUSION

Carbapenem-resistant Enterobacterales-related infections in intensive care unit patients were associated with major premorbid dependence, intensive care unit readmission, and acute COVID-19. In addition, carbapenem-resistant Enterobacterales infections were independently associated with poorer hospital outcomes. This study also characterized the resistance profile of Enterobacterales in Brazilian intensive care units, which are dominated by K. pneumoniae with high rates of carbapenemase and increased rates of New Delhi metallo-beta-lactamase, in comparison with previous reports.

New Microbiological Techniques for the Diagnosis of Bacterial Infections and Sepsis in ICU Including Point of Care

Purpose of Review

The aim of this article is to review current and emerging microbiological techniques that support the rapid diagnosis of bacterial infections in critically ill patients, including their performance, strengths and pitfalls, as well as available data evaluating their clinical impact.

Recent Findings

Bacterial infections and sepsis are responsible for significant morbidity and mortality in patients admitted to the intensive care unit and their management is further complicated by the increase in the global burden of antimicrobial resistance. In this setting, new diagnostic methods able to overcome the limits of traditional microbiology in terms of turn-around time and accuracy are highly warranted. We discuss the following broad themes: optimisation of existing culture-based methodologies, rapid antigen detection, nucleic acid detection (including multiplex PCR assays and microarrays), sepsis biomarkers, novel methods of pathogen detection (e.g. T2 magnetic resonance) and susceptibility testing (e.g. morphokinetic cellular analysis) and the application of direct metagenomics on clinical samples. The assessment of the host response through new “omics” technologies might also aid in early diagnosis of infections, as well as define non-infectious inflammatory states.

Summary

Despite being a promising field, there is still scarce evidence about the real-life impact of these assays on patient management. A common finding of available studies is that the performance of rapid diagnostic strategies highly depends on whether they are integrated within active antimicrobial stewardship programs. Assessing the impact of these emerging diagnostic methods through patient-centred clinical outcomes is a complex challenge for which large and well-designed studies are awaited.

Genetic Diversity, Biochemical Properties, and Detection Methods of Minor Carbapenemases in Enterobacterales

Gram-negative bacteria, especially Enterobacterales, have emerged as major players in antimicrobial resistance worldwide. Resistance may affect all major classes of anti-gram-negative agents, becoming multidrug resistant or even pan-drug resistant. Currently, β-lactamase-mediated resistance does not spare even the most powerful β-lactams (carbapenems), whose activity is challenged by carbapenemases. The dissemination of carbapenemases-encoding genes among Enterobacterales is a matter of concern, given the importance of carbapenems to treat nosocomial infections. Based on their amino acid sequences, carbapenemases are grouped into three major classes. Classes A and D use an active-site serine to catalyze hydrolysis, while class B (MBLs) require one or two zinc ions for their activity. The most important and clinically relevant carbapenemases are KPC, IMP/VIM/NDM, and OXA-48. However, several carbapenemases belonging to the different classes are less frequently detected. They correspond to class A (SME-, Nmc-A/IMI-, SFC-, GES-, BIC-like…), to class B (GIM, TMB, LMB…), class C (CMY-10 and ACT-28), and to class D (OXA-372). This review will address the genetic diversity, biochemical properties, and detection methods of minor acquired carbapenemases in Enterobacterales.