Biofilm formation is an important virulence trait of many bacterial pathogens. It has been reported in the literature that only two of the reference strains of the swine pathogen Actinobacillus pleuropneumoniae, representing serotypes 5b and 11, were able to form biofilm in vitro. In this study, we compared biofilm formation by the serotype 1 reference strain S4074 of A. pleuropneumoniae grown in five different culture media. We observed that strain S4074 of A. pleuropneumoniae is able to form biofilms after growth in one of the culture conditions tested brain heart infusion (BHI medium, supplier B). Confocal laser scanning microscopy using a fluorescent probe specific to the poly-N-acetylglucosamine (PGA) polysaccharide further confirmed biofilm formation. In accordance, biofilm formation was susceptible to dispersin B, a PGA hydrolase. Transcriptional profiles of A. pleuropneumoniae S4074 following growth in BHI-B, which allowed a robust biofilm formation, and in BHI-A, in which only a slight biofilm formation was observed, were compared. Genes such as tadC, tadD, genes with homology to autotransporter adhesins as well as genes pgaABC involved in PGA biosynthesis and genes involved in zinc transport were up-regulated after growth in BHI-B. Interestingly, biofilm formation was inhibited by zinc, which was found to be more present in BHI-A (no or slight biofilm) than in BHI-B. We also observed biofilm formation in reference strains representing serotypes 3, 4, 5a, 12 and 14 as well as in 20 of the 37 fresh field isolates tested. Our data indicate that A. pleuropneumoniae has the ability to form biofilms under appropriate growth conditions and transition from a biofilm-positive to a biofilm-negative phenotype was reversible.

Please cite this article as: Monecke S, Engelmann I, Archambault M, Coleman DC, Coombs GW, Cortez de Jäckel S, Pelletier-Jacques G, Schwarz S, Shore AC, Slickers P, Ehricht R, Distribution of SCCmecassociated phenol-soluble modulin in staphylococci, Molecular and Cellular Probes (2012), doi: 10.1016/ j.mcp.2012 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. AB547236.1) and S. vitulinus (AB546780.1).The aim of this study was to screen staphylococcal isolates for the presence of PSM-mec in order to obtain more data on its distribution. 102 S. aureus isolates and 38 coagulase-negative staphylococci were genotyped using DNA microarrays (StaphyType, Alere Technologies GmbH, Jena, Germany, [7,9]). This allowed characterising their SCCmec elements [10]. In addition, SCCmec elements of some isolates have previously been studied comprehensively [11,12]. PCR primers pr_psmMEC_02 (5'-CGAAAGCCTGAATGCAAGTCT-3') and pr_psmMEC_03(5'-GGATTTCACTGGTGTTATTACAAGC-3') were used to detect PSM-mec. Reaction conditions included an initial denaturation (2 min at 96°C) followed by 35 cycles (20 sec at 96°C, 20 sec at 70°C and 20 sec at 72°C). A second PCR covered a region spanning from xylR to PSMmec (pr_psmMEC_02 and pr_xylR_04, 5'-AAGCGTCATCTTCTCATTTAGTTGA-3') and a third PCR covered the region from PSM-mec to mecR1 (pr_mecR_01, 5'-CCAGAAAGTAAACAACGATATTCACC-3' and pr_psmMEC_03). Both reactions comprised denaturation (2 min at 96°C) followed by 35 cycles (20 sec at 96°C, 20 sec at 55°C and 70 sec at The results are summarised in Table 1 vitulinus. The presence of PSM-mec did not depend on the host species, and was found in isolates from humans, dogs, cats, goats, cattle, pigs and turkeys. PSM-mec was absent in SCCmec types I, IIC, IIE, IV, V or XI and in SCC elements lacking the mec complex. Some isolates, including CC12-MRSA, WA-MRSA-59, harboured SCCmec elements comprising mecR1 but lacking xylR.These strains were PSM-mec-negative.There was no evidence for alternative locations of PSM-mec. Isolates lacking SCCmec elements, or harbouring SCCmec types I, IIC, IIE, IV and V were PSM-mec-negative regardless of clonal complex or species affiliation. A PCR covering the region from xylR to PSM-mec using primers pr_psmMEC_02/pr_xylR_04 yielded results which were in all cases but one in accordance with the PSM-mec PCR. In a PSM-mec-positive CC5-MRSA, xylR was absent, and primer pair pr_psmMEC_02/pr_xylR_04 did not yield a result.Results of a third PCR (pr_psmMEC/pr_mecR_01) differed from those of the other two PCRs by yielding negative results for ST8-MRSA-IIA or -IID, and for deletion variants of this strain. This can be attrib...