Delta-toxin peak in spectra from clinical strains.

<p>Whole-Cell Matrix Assisted Laser Desorption Ionization – Time-of-Flight mass spectrometry analysis of 6 representative clinical strains from the collection of 168. BE1103 3028 and BE1046 1395 are two delta-toxin positive strains showing 3005±5 Thomson (Th) peak; BE1104 4293 and BE1050 5040 are 2 strains expressing a mutated G10S delta-toxin; they exhibited no peak at 3005±5 Th but an additional peak at 3035±5 Th; BE1106 5397 and BE1048 2354 are two delta-toxin negative strains showing no peak at 3005±5 Th or at 3035±5 Th. Settings of the mass spectrometer are the same as in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0040660#pone-0040660-g001" target="_blank">Figure 1</a>.</p

Determination of delta-toxin status of clinical strains.

a<p>Th: Thomson.</p>b<p>MALDI-TOF MS: Matrix Assisted Laser Desorption Ionization Time-Of-Flight mass spectrometry.</p>c<p><i>hld</i>: gene encoding delta-toxin.</p>d<p>NT: not tested.</p>e<p>G10S: mutated delta-toxin with glycine 10 replaced by a serine.</p>f<p>WT: wild type delta-toxin.</p>g<p>MALDI/TOF-TOF MS: Matrix Assisted Laser Desorption Ionization Time-Of-Flight/Time-Of-Flight mass spectrometry.</p

Multivariate analysis of <i>accessory gene regulator</i> status for 154 infecting isolates.

a<p><i>agr</i>: accessory gene regulator;</p>b<p>OR: odd ratio;</p>c<p>CI: confidence interval;</p>d<p>GISA: glycopeptide intermediate <i>Staphylococcus aureus</i> strains - hGISA: heterogeneous GISA;</p>e<p>Reference;</p>f<p>χ² (1 degree of freedom)  =  -2 log likelihood (model 2 - model 1)  = 0.608; <i>p</i> = 0.413;</p>g<p>MSSA: methicillin-sensitive <i>Staphylococcus aureus</i>;</p>h<p>MRSA: methicillin-resistant <i>Staphylococcus aureus.</i></p

Northern blot analysis of <i>accessory gene regulator</i>-RNAIII.

<p>Lane 1, positive control isolate (delta-toxin producer); lanes 2 to 18 correspond to the 17 delta-toxin negative clinical isolates. 5S rRNA was used as loading control.</p

Identification of the delta-toxin peak using purified delta-toxin and isogenic strains.

<p>Purified delta-toxin from wild-type <i>Staphylococcus aureus</i> (500 ng) or strains mutated in the <i>accessory gene regulator (agr)</i> locus were spotted on the target and analysed in the Matrix Assisted Laser Desorption Ionization – Time-of-Flight mass spectrometer with a mass-to-charge ratio (<i>m</i>/<i>z</i>) range of 2800 to 3200 Thomson (Th). Setting were as follows: mass range 2000–20000 Th; laser power 80 Volts; pulse extraction 8330 Th; number of laser fires per sample 500; noise cut off 10 mVolts with a minimum resolution of 300; Auto quality mode activated. The settings of the detector were according to the linear mode with a positive source of 20000 Th and a negative pulsed extraction at 2100 Th. The arrow in panel A indicates delta-toxin; additional peaks of 3024, 3040 and 3056 Th correspond to contaminants resulting from the purification of the toxin from <i>S. aureus</i> culture supernatant. Isogenic strains were: RN6390 (delta positive strain) RN6911 (full <i>agr knock-out</i>, delta negative strain) and LUG 950 (<i>rna</i>III <i>knock-out</i>, delta negative strain).</p

Microbiological and patient characteristics stratified by <i>accessory gene regulator</i> function.

a<p>*<i>p</i> value on univariate analysis.</p>b<p>Fisher’s exact test.</p>c<p>GISA: Glycopeptides Intermediate <i>Staphylococcus aureus</i>.</p>d<p>hGISA: heterogeneous GISA.</p>e<p>ND: not determined.</p>f<p>mo: month; yrs: years.</p>g<p>Mann-Whitney test.</p>h<p>M: male, F:female.</p>i<p>30-days mortality.</p