Implementation and evaluation of methods for the optimal detection of carbapenem-resistant and colistin-resistant Pseudomonas aeruginosa and Acinetobacter baumannii from stools

Claudine Fournier,Laurent Poirel,Patrice Nordmann

doi:10.1016/j.diagmicrobio.2020.115121

Abstract

Carbapenem-resistant Acinetobacter baumannii (CRAB) and Pseudomonas aeruginosa (CRPA), as well as polymyxin-resistant A. baumannii (PMR-AB) and P. aeruginosa (PMR-PA), were used to test different enrichment strategies from spiked stools. Three procedures were compared, namely, direct inoculation on selective plates and plating after a 24-h enrichment step in tryptic soy broth with or without antibiotics. Selective agar plates were used including CHROMagar-Pseudomonas supplemented with meropenem (2 mg/L), and CHROMagar-MDR-Acinetobacter agar and CHROMagar COL-APSE plates. Use of enrichment broths significantly enhanced the recovery of CRAB, CRPA, PMR-AB, and PMR-PA. However, supplementing or not the pre-enrichment broth with antibiotics had no impact. The proposed strategy for screening multidrug-resistant nonfermenters is of low cost, is easy to implement, and might be useful for outbreak containment.

Highlights

Carbapenem-resistant Acinetobacter baumannii (CRAB) and multidrug-resistant Pseudomonas aeruginosa such as carbapenemresistant P. aeruginosa (CRPA) have been recently classified, respectively, as urgent and serious threats by the CDC (2019) and of priority pathogens by the WHO (2017a)
For carbapenemase-producing A. baumannii, the CHROMagarAcinetobacter-MDR medium showed the best performance in term of bacterial yield recovery and was used
By evaluating the performances of detection of CRPA, PMR-PA, CRAB, and polymyxinresistant A. baumannii (PMR-AB), remarkable differences were observed between direct plating and precultures in nonselective/selective broth enrichment

Summary

Introduction

Carbapenem-resistant Acinetobacter baumannii (CRAB) and multidrug-resistant Pseudomonas aeruginosa such as carbapenemresistant P. aeruginosa (CRPA) have been recently classified, respectively, as urgent and serious threats by the CDC (2019) and of priority pathogens by the WHO (2017a). Those multidrug-resistant (MDR) bacteria constitute the main sources of carbapenem-resistant Gramnegative bacilli worldwide (Gniadek et al, 2016; Nordmann and Poirel, 2019), being sources of hospital-acquired infections and causing a significant mortality and morbidity in high risk-patient populations. Implementation of screening strategies is required for instance in the context of outbreaks (Martischang et al, 2019)

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