Rapid Identification and Multiple Susceptibility Testing of Pathogens from Positive-Culture Sterile Body Fluids by a Combined MALDI-TOF Mass Spectrometry and Vitek Susceptibility System.

Yueru Tian,Bei Wang,Bing Zheng,Yong Lin,Min Li

doi:10.3389/fmicb.2016.00523

Abstract

Infections of the bloodstream, central nervous system, peritoneum, joints, and other sterile areas are associated with high morbidity and sequelae risk. Timely initiation of effective antimicrobial therapy is crucial to improving patient prognosis. However, standard final identification and antimicrobial susceptibility tests (ASTs) are reported 16–48 h after a positive alert. For a rapid, effective and low-cost diagnosis, we combined matrix-assisted laser desorption/ionization time of flight mass spectrometry with a Vitek AST system, and performed rapid microbial identification (RMI) and rapid multiple AST (RMAST) on non-duplicated positive body fluid cultures collected from a hospital in Shanghai, China. Sterile body fluid positive culture and blood positive culture caused by Gram negative (GN) or polymicrobial were applied to the MALDI–TOF measurement directly. When positive blood culture caused by Gram positive (GP) bacteria or yeasts, they were resuspended in 1 ml brain heart infusion for 2 or 4 h enrichment, respectively. Regardless of enrichment, the RMI (completed in 40 min per sample) accurately identified GN and GP bacteria (98.9 and 87.2%, respectively), fungi (75.7%), and anaerobes (94.7%). Dominant species in multiple cultures and bacteria that failed to grow on the routing plates were correctly identified in 81.2 and 100% of cases, respectively. The category agreements of RMAST results, determined in the presence of various antibiotics, were similarly to previous studies. The RMI and RMAST results not only reduce the turnaround time of the patient report by 18–36 h, but also indicate whether a patient's antibiotic treatment should be accelerated, ceased or de-escalated, and adjusted the essential drugs modification for an optimized therapy.

Highlights

Infections of the bloodstream, central nervous system, peritoneum, joints, and other sterile areas are associated with high morbidity and risk of sequelae (Thigpen et al, 2011; Goto and Al-Hasan, 2013; Chon et al, 2014; Ascione et al, 2015; Bagheri-Nesami et al, 2015)
Sterile body fluids, including blood, cerebrospinal fluid (CSF), pleural fluid, ascitic fluid, pericardial effusion, joint cavity fluid, and vitreous fluid, were injected into blood culture bottles to improve the positive rate of clinical samples
Regardless of enrichment, the rapid microbial identification (RMI) test of each sample was completed in 40 min (15 min for the pellet collection/washing/centrifugation steps, 15 min for the extraction procedure, 5 min for the sample spotting/drying steps, 5 min for MALDI–TOF MS measurement)

Summary

Introduction

Infections of the bloodstream, central nervous system, peritoneum, joints, and other sterile areas are associated with high morbidity and risk of sequelae (Thigpen et al, 2011; Goto and Al-Hasan, 2013; Chon et al, 2014; Ascione et al, 2015; Bagheri-Nesami et al, 2015). BSIs have become a major cause of death in European intensive care units, incurring a mortality rate of 30–50% (Vincent et al, 2006) To improve this prognosis, timely initiation of effective antimicrobial therapy is essential (Kumar et al, 2006; Vincent et al, 2006; Dellinger et al, 2013; Chon et al, 2014; Ascione et al, 2015; Bagheri-Nesami et al, 2015). Standard final identification (ID) and ASTs are reported 16–48 h after a positive alert During this delay, the clinician must administer an empirical antimicrobial therapy, typically a broad-spectrum antibiotic or an antibiotic cocktail to cover all likely pathogens. The long-term use of dispensable broad-spectrum antibiotics promotes antibiotic resistance and spread, increases cost and lengthens hospital stays (Blot et al, 2002; Tumbarello et al, 2010)

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