# Clinical effect of in-house rapid diagnostic process on patients with bloodstream infections due to carbapenem-resistant bacteria or methicillin-resistant Staphylococcus aureus: a prospective cohort study

## TL;DR

A new rapid diagnostic method for bloodstream infections caused by drug-resistant bacteria significantly reduces mortality by speeding up effective antibiotic treatment.

## Contribution

The study demonstrates the clinical benefits of an in-house rapid diagnostic workflow for drug-resistant bloodstream infections.

## Key findings

- The in-house process reduced the time to identification and susceptibility results compared to conventional methods.
- The rapid workflow increased the adjustment rate of effective antibiotics from 56.09% to 70.33%.
- 28-day mortality decreased from 19.57% to 9.34% with the in-house rapid diagnostic process.

## Abstract

Bloodstream infections caused by multidrug-resistant bacteria result in a high mortality rate. Little research has been carried out to analyze the clinical effects of laboratory-based rapid identification and susceptibility tests of the types of organisms responsible for these infections. We previously developed an ammonium chloride-based in-house workflow for direct pathogen identification and susceptibility testing from positive blood cultures, eliminating the need for subsequent overnight subculturing. In this study, we carried out a prospective single-center cohort study evaluating the outcomes associated with in-house rapid detection of carbapenem-resistant bacterial strains or methicillin-resistant Staphylococcus aureus directly from positive blood cultures. From 2018 to 2023, 584 patients with clinically significant monomicrobial bloodstream infections due to these strains were enrolled. Among the 584 patients, 412 were included in the final analysis, with 182 in the in-house group and 230 in the conventional group. The median time from positive blood culture to identification and susceptibility results was significantly shorter for the in-house rapid process than for the conventional process (P < 0.01). A decrease in laboratory report time improved the time to effective antibiotic therapy and increased the adjustment rate of effective antibiotics from 56.09% (129/230) to 70.33% (128/182) (P < 0.01). The 28-day all-cause mortality after occurrence of a bloodstream infection markedly decreased from 19.57% (45/230) to 9.34% (17/182) (P = 0.005). Our results indicate that the in-house rapid process improves the time to effective antibiotic therapy and significantly decreases patient mortality. This information should encourage the implementation of our in-house rapid diagnostic process for bloodstream infections.

In this study, we included only patients whose bloodstream infection was caused by carbapenem-resistant bacterial strains or methicillin-resistant Staphylococcus aureus, avoiding the interference of empirical treatment for sensitive strains and allowing a clearer evaluation of the effects of laboratory-based rapid workflows. Moreover, this study covered all bloodstream infection cases from 1 January 2018 to 30 June 2023, with patients randomly grouped to minimize confounding factors. The results of this study demonstrated that this laboratory-based rapid workflow significantly shortened laboratory reporting times, which led to improvements in the rate and timing of adjustment of effective antibiotic therapy and a significant decrease in the mortality of patients with bloodstream infections. To the best of our knowledge, few studies have employed such a procedure to analyze clinical effects. Therefore, we believe that our research findings will encourage the implementation of laboratory-based rapid diagnosis for bloodstream infections.