MALDI-TOF: A useful tool for laboratory identification of uncommon glucose non-fermenting Gram-negative bacteria associated with cystic fibrosis

Abstract

The predisposition of patients with cystic fibrosis (CF) for recurrent pulmonary infections can result in poor prognosis of the disease. Although the clinical significance in CF of microorganisms, such as Staphylococcus aureus, Haemophilus influenzae and Pseudomonas aeruginosa, is well established, the implication of uncommon glucose non-fermenting Gramnegative bacilli (UGNF-GNB) in respiratory samples from CF patients is still unclear. Because of limitations of traditional methods used in most clinical laboratories, the accurate identification of these microbes is a challenge. Matrix-assisted laser desorption ionization-time of flight (MALDI-TOF) is an alternative tool for efficient identification of bacteria. This was a retrospective study to evaluate different identification methods in a collection of UGNF-GNB isolated from children with CF during a period of three years. The performance of MALDI-TOF was compared to that of 16S rDNA gene sequencing and to a conventional and automated phenotypic identification. The discriminatory power of MALDI-TOF (75.0 % agreement) was superior to automated techniques (67.1 % agreement) and to conventional phenotypical identification (50.0 % agreement). MALDI-TOF also demonstrated high accuracy in identifying Stenotrophomonas maltophilia, Achromobacter xylosoxidans and Chryseobacterium indologenes, but had limited utility in identifying Pandoraea spp. and some species of Acinetobacter and Chryseobacterium (other than C. indologenes). Although MALDI-TOF identified only 75 % of the isolates in comparison with 16S rDNA gene sequencing, the prompt identification and high discriminatory power exhibited by MALDI-TOF make it a useful tool for the characterization of micro-organisms that are difficult to identify using routine methods.

Characterization of Achromobacter Species in Cystic Fibrosis Patients: Comparison of bla OXA-114 PCR Amplification, Multilocus Sequence Typing, and Matrix-Assisted Laser Desorption Ionization–Time of Flight Mass Spectrometry

“…The MALDI-TOF MS results were 39% discordant with MLST identification. All A. ruhlandii (n ϭ 9), A. dolens (n ϭ 1), and A. insuavis (n ϭ 1) isolates were incorrectly identified as A. xylosoxidans (Table 1), probably due to limitations of the database used, such as the lack of identification spectra for the reference strains (6). In our samples, we found ST2 and ST13, STs that were detected in CF patients in the United States between 2009 and 2010.…”

“…Most Achromobacter clinical isolates are designated as Achromobacter xylosoxidans; however, the commonly used phenotypic tests are not reliable (1)(2)(3). Matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) analysis is used in clinical microbiology laboratories as an emerging technology for bacterial species identification (4)(5)(6)(7)(8). Genotypic methods have also been developed for Achromobacter species.…”

Evaluation of matrix-assisted laser desorption ionization–time-of-flight mass spectrometry for typing of methicillin-resistant Staphylococcus aureus and a review of the literature

“…MALDI-TOFMS is a powerful tool for the identification of bacteria including Gram-positive and Gram-negative strains and yeasts at the species and subspecies level [24][25][26][27][28][29][30]. In recent studies, MALDI-TOFMS coupled with ClinProTools has been used to detect the typespecific bio-markers.…”

Ritkábban előforduló, alsó légúti fertőzést okozó Gram-negatív nem fermentáló pálcák

“…által fertőzött CF-betegek nagyobb valószínűséggel fertőzöttek P. aeruginosával vagy a B. cepacia complex valamely tagjával is [13]. Karbapenemekkel és aminoglikozidokkal szemben természetes rezisztenciát mutatnak [13,14]. A CIP, LEV, SXT és FEP eseteink ≥90%-ában hatékonynak bizonyult.…”