Detection of KPC directly from positive blood cultures by MALDI-TOF: From research to the clinical microbiology laboratory routine

Natália Kehl Moreira; Camila Mörschbächer Wilhelm; Gabriela da Silva Collar; Aymê Duarte Echevarria; Júlia Becker; Afonso Luís Barth; Juliana Caierão

doi:10.1016/j.mimet.2024.106940

Detection of KPC directly from positive blood cultures by MALDI-TOF: From research to the clinical microbiology laboratory routine

J Microbiol Methods. 2024 Jun:221:106940. doi: 10.1016/j.mimet.2024.106940. Epub 2024 May 1.

Authors

Natália Kehl Moreira¹, Camila Mörschbächer Wilhelm², Gabriela da Silva Collar³, Aymê Duarte Echevarria⁴, Júlia Becker⁵, Afonso Luís Barth², Juliana Caierão³

Affiliations

¹ Programa de Pós-Graduação em Ciências Farmacêuticas, Faculdade de Farmácia, Universidade Federal do Rio Grande do Sul, Porto Alegre, Rio Grande do Sul, Brazil; Laboratório de Pesquisa em Bacteriologia Clínica, Universidade Federal do Rio Grande do Sul, Porto Alegre, Rio Grande do Sul, Brazil; Laboratório de Pesquisa em Resistência Bacteriana, Hospital de Clínicas de Porto Alegre, Porto Alegre, Rio Grande do Sul, Brazil. Electronic address: natkehl@hotmail.com.
² Programa de Pós-Graduação em Ciências Farmacêuticas, Faculdade de Farmácia, Universidade Federal do Rio Grande do Sul, Porto Alegre, Rio Grande do Sul, Brazil; Laboratório de Pesquisa em Resistência Bacteriana, Hospital de Clínicas de Porto Alegre, Porto Alegre, Rio Grande do Sul, Brazil.
³ Programa de Pós-Graduação em Ciências Farmacêuticas, Faculdade de Farmácia, Universidade Federal do Rio Grande do Sul, Porto Alegre, Rio Grande do Sul, Brazil; Laboratório de Pesquisa em Bacteriologia Clínica, Universidade Federal do Rio Grande do Sul, Porto Alegre, Rio Grande do Sul, Brazil.
⁴ Laboratório de Pesquisa em Resistência Bacteriana, Hospital de Clínicas de Porto Alegre, Porto Alegre, Rio Grande do Sul, Brazil.
⁵ Laboratório de Pesquisa em Bacteriologia Clínica, Universidade Federal do Rio Grande do Sul, Porto Alegre, Rio Grande do Sul, Brazil.

PMID: 38702032
DOI: 10.1016/j.mimet.2024.106940

Abstract

Bloodstream infections (BSI) caused by carbapenem-resistant Gram-negative bacilli (CR-GNB) are a subject of major clinical concern, mainly those associated with carbapenemase-producing isolates. Matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS) has been proposed to detect specific β-lactamases, including KPC. We aimed to detect KPC enzyme directly from positive blood cultures using MALDI-TOF MS. Overall, 146 clinical Gram-negative bacilli (46 CR-GNB) recovered from consecutive blood cultures were evaluated. Proteins were extracted using formic acid, isopropyl alcohol, and water and spotted onto a steel target plate using the double-layer sinapinic acid method. The relative ions intensity ≥120 arbitrary units (a.u.) of a peak close to 28,700 m/z indicated the presence of KPC. The results were compared to HRM-qPCR methodology. This specific peak was observed in 11/14 blood bottles with bla_KPC positive isolates (78.6% sensitivity), with 3 false-positive results (97.7% specificity). Analysis from colonies reached identical sensitivity (78.6%), but higher specificity (100%). The detection of KPC peaks directly from positive blood cultures using MALDI-TOF MS is feasible and rapid. It's excellent specificity indicates that positive results are consistently associated with the presence of a KPC producer in positive blood culture.

Keywords: Blood culture; KPC; MALDI-TOF MS.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

Anti-Bacterial Agents / pharmacology
Bacteremia / diagnosis
Bacteremia / microbiology
Bacterial Proteins* / genetics
Blood Culture* / methods
Carbapenems / pharmacology
Gram-Negative Bacteria / classification
Gram-Negative Bacteria / enzymology
Gram-Negative Bacteria / genetics
Gram-Negative Bacteria / isolation & purification
Gram-Negative Bacterial Infections / blood
Gram-Negative Bacterial Infections / diagnosis
Gram-Negative Bacterial Infections / microbiology
Humans
Sensitivity and Specificity
Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization* / methods
beta-Lactamases* / genetics

Substances

carbapenemase