Detection of Staphylococcus aureus delta-toxin production by whole-cell MALDI-TOF mass spectrometry.
The aim of the present study was to detect the Staphylococcus aureus delta-toxin using Whole-Cell (WC) Matrix Assisted Laser Desorption Ionization-Time-of-Flight (MALDI-TOF) mass spectrometry (MS), correlate delta-toxin expression with accessory gene regulator (agr) status, and assess the prevalence of agr deficiency in clinical isolates with and without resistance to methicillin and glycopeptides. The position of the delta-toxin peak in the mass spectrum was identified using purified delta-toxin and isogenic wild type and mutant strains for agr-rnaIII, which encodes delta-toxin. Correlation between delta-toxin production and agr RNAIII expression was assessed by northern blotting. A series of 168 consecutive clinical isolates and 23 unrelated glycopeptide-intermediate S. aureus strains (GISA/heterogeneous GISA) were then tested by WC-MALDI-TOF MS. The delta-toxin peak was detected at 3005±5 Thomson, as expected for the naturally formylated delta toxin, or at 3035±5 Thomson for its G10S variant. Multivariate analysis showed that chronicity of S. aureus infection and glycopeptide resistance were significantly associated with delta-toxin deficiency (p = 0.048; CI 95%: 1.01-10.24; p = 0.023; CI 95%: 1.20-12.76, respectively). In conclusion, the S. aureus delta-toxin was identified in the WC-MALDI-TOF MS spectrum generated during routine identification procedures. Consequently, agr status can potentially predict infectious complications and rationalise application of novel virulence factor-based therapies.
Hospices Civils de Lyon, Centre National de Référence des Staphylocoques, Centre de Biologie et de Pathologie Est, Bron, France.
Julie
J
Gagnaire
Olivier
O
Dauwalder
Sandrine
S
Boisset
David
D
Khau
Anne-Marie
AM
Freydière
Florence
F
Ader
Michèle
M
Bes
Gerard
G
Lina
Anne
A
Tristan
Marie-Elisabeth
ME
Reverdy
Adrienne
A
Marchand
Thomas
T
Geissmann
Yvonne
Y
Benito
Géraldine
G
Durand
Jean-Philippe
JP
Charrier
Jerome
J
Etienne
Martin
M
Welker
Alex
A
Van Belkum
François
F
Vandenesch
D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D001427:Bacterial Toxins / Q000096:biosynthesis* / Q000737:chemistry / Q000302:isolation & purification; D024881:Drug Resistance, Bacterial / Q000235:genetics; D006801:Humans; D015203:Reproducibility of Results; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D013203:Staphylococcal Infections / Q000175:diagnosis* / Q000378:metabolism; D013211:Staphylococcus aureus / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism; D037521:Virulence Factors / Q000235:genetics / Q000378:metabolism
C095698:Agr protein, Staphylococcus aureus; D001426:Bacterial Proteins; D001427:Bacterial Toxins; D015534:Trans-Activators; D037521:Virulence Factors; C025971:staphylococcal delta toxin