Abiotrophia defectiva endophthalmitis with retinal involvement and infiltrative keratitis: case report and review of the literature.

We report the exceptional case of a severe intraocular Abiotrophia defectiva infection which developed after cataract surgery. Retinal involvement as a complication of A. defectiva endophthalmitis or the combination of acute-onset endophthalmitis with infiltrative keratitis caused by this pathogen has not been described. Moreover, our report represents the first documented ocular A. defectiva infection in Germany. A. defectiva was identified using biotyping and 16S ribosomal RNA gene sequence analysis. Despite vigorous antimicrobial therapy and repeated ocular surgery, visual outcome was poor.

Expression and functional characterization of gfpmut3.1 and its unstable variants in Staphylococcus epidermidis.

Reporter gene systems are an invaluable tool for investigation of gene transcription activity in eukaryotes and prokaryotes. In order to analyze the temporal and spatial resolution of gene expression patterns in situ and for quantitatively investigating gene expression, the green fluorescent protein (GFP) appears to be especially useful. GFP has been broadly used in various bacterial species, however, there is only limited knowledge about key biological properties in S. epidermidis. Here, the crucial influence of different ribosomal binding sites (RBS) on gfpmut3.1 translation initiation in S. epidermidis 1457 is demonstrated. Only by using the RBS of the delta-hemolysin promoter, after 24 hours a strong fluorescence signal was obtained. The half-life of GFPmut3.1 in S. epidermidis 1457 was significantly shorter than in E. coli (7 h vs. 24 h). GFPmut3.1 derivatives with shorter half-lives (GFP(AAV) and GFP(ASV)) did not reach sufficient quantitative protein levels, and the resulting low fluorescence limits their use as reporter genes in S. epidermidis. This work provides fundamental insights into gfpmut3.1 expression in S. epidermidis and describes the crucial determinants of its biological behavior in this species. In general, this study underlines the need to accurately characterize key biological properties of this transcription marker in gram-positive hosts.

Identification of three essential regulatory gene loci governing expression of Staphylococcus epidermidis polysaccharide intercellular adhesin and biofilm formation.

The formation of adherent multilayered biofilms embedded into a glycocalyx represents an essential factor in the pathogenesis of Staphylococcus epidermidis biomaterial-related infections. Using biofilm-producing S. epidermidis 1457 and transposon Tn917 carried on plasmid pTV1ts, we isolated nine isogenic biofilm-negative transposon mutants. Transduction by S. epidermidis phage 71 was used to prove the genetic linkage of transposon insertions and altered phenotypes. Mapping of the different transposon insertions by Southern hybridization and pulsed-field gel electrophoresis indicated that these were inserted in four unlinked genetic loci. According to their phenotypes, including quantitative differences in biofilm production in different growth media, in the amount of the polysaccharide intercellular adhesin (PIA) produced, in the hemagglutination titers, and in the altered colony morphology, the mutants could be separated into four phenotypic classes corresponding with the genetic classes. Synthesis of PIA was not detectable with class I and II mutants, whereas the amount of PIA produced reflected the residual degree of biofilm production of class III and IV mutants in different growth media. Chromosomal DNA flanking the transposon insertions of five class I mutants was cloned and sequenced, and the insertions were mapped to different locations of icaADBC, representing the synthetic genes for PIA. Expression of icaADBC from a xylose-dependent promoter in the different isogenic mutant classes reconstituted biofilm production in all mutants. In a Northern blot analysis no icaADBC-specific transcripts were observed in RNA isolated from mutants of classes II, III, and IV. Apparently, in addition to icaADBC, three other gene loci have a direct or indirect regulatory influence on expression of the synthetic genes for PIA on the level of transcription.

Three cases of Arcanobacterium haemolyticum associated with abscess formation and cellulitis.

Arcanobacterium haemolyticum has been described as an unusual pathogen causing pharyngotonsillitis and systemic disease in patients with predisposing conditions. A case of soft tissue abscess with no apparent portal of entry is reported in a healthy 31-year-old man who presented with a breast tumor. A second case of abscess formation in a 50-year-old patient with complicated wound healing is presented. In addition, a case of Arcanobacterium haemolyticum cellulitis in a 25-year-old female is reported. Due to its innocuous, coryneform appearance, this pathogen is probably underreported; therefore, the diagnostic evaluation of this organism is emphasized.

Analysis of the 170-kDa lectin gene promoter of Entamoeba histolytica.

The promoter region driving the gene for the 170-kDa heavy subunit of the Entamoeba histolytica galactose-inhibitable lectin was analysed by transient transfection using the chloramphenicol acetyltransferase gene as reporter. S1 mapping confirmed our previous notion that the promoter is located within a 1.35-kb intergenic sequence preceding the structural lectin gene. Transcripts derived from the chloramphenicol acetyltransferase gene of transfected trophozoites were found to be polyadenylated and the transcriptional start mapped to a position similar to that of the wild-type lectin gene. By deletion analysis the entire promoter was restricted to a fragment covering about 550 bp upstream from the start of transcription. On the other hand, residual promoter activity required a sequence of about 140 bp only, encompassing a newly identified CCAAT-box like element around position -100, as well as the amebic specific TATA-box. This 140-bp fragment as well as a stretch of 15 bp, which is located some 100 nt further upstream, were found to be conserved within the 5' noncoding region of a second E. histolytica lectin gene. Point-mutation analyses indicated that the 15-bp fragment, the likely CCAAT-box, as well as the TATA-box are required for full promoter activity.