Effect of iron on the expression of sirR and sitABC in biofilm-associated Staphylococcus epidermidis

BACKGROUND: Different gene expression patterns correlate with the altered phenotype in biofilm-associated bacteria. Iron and iron-linked genes are thought to play a key-role in biofilm formation. The expression of Fe-linked genes (sirR, sitABC operon) in Staphylococcus epidermidis, was compared in planktonic versus sessile bacteria in vitro and in vivo in a subcutaneous foreign body rat model. RESULTS: In vitro in a Fe-limited environment, the planktonic form of S. epidermidis produces siderophores and grows slower than in Fe-rich environment. The expression of sirR in planktonic bacteria, in vitro, was not different in medium without Fe or with 1 μM FeCl(3). High Fe concentrations (25 μM FeCl(3)) increased expression of sirR transiently during the early phase of incubation. Expression of sitC in vitro, in planktonic bacteria, was inversely correlated with sirR expression in medium with 25 μM FeCl(3): sitC expression decreased for the first 3 hours followed by an up regulation. In sessile bacteria in vitro, sirR expression was high and independent of the Fe concentration. The expression of sitC was not inversely correlated to sirR expression. In vivo, expression levels of sirR and of sitABC were high during the initial phase after implantation and, after a transient decrease, remained stable over a period of two weeks. CONCLUSION: Our data suggest that the expression of sirR and the regulatory effect of sirR on the sitABC operon are different in planktonic and sessile bacteria

Pseudomonas aeruginosa Population Structure Revisited

At present there are strong indications that Pseudomonas aeruginosa exhibits an epidemic population structure; clinical isolates are indistinguishable from environmental isolates, and they do not exhibit a specific (disease) habitat selection. However, some important issues, such as the worldwide emergence of highly transmissible P. aeruginosa clones among cystic fibrosis (CF) patients and the spread and persistence of multidrug resistant (MDR) strains in hospital wards with high antibiotic pressure, remain contentious. To further investigate the population structure of P. aeruginosa, eight parameters were analyzed and combined for 328 unrelated isolates, collected over the last 125 years from 69 localities in 30 countries on five continents, from diverse clinical (human and animal) and environmental habitats. The analysed parameters were: i) O serotype, ii) Fluorescent Amplified-Fragment Length Polymorphism (FALFP) pattern, nucleotide sequences of outer membrane protein genes, iii) oprI, iv) oprL, v) oprD, vi) pyoverdine receptor gene profile (fpvA type and fpvB prevalence), and prevalence of vii) exoenzyme genes exoS and exoU and viii) group I pilin glycosyltransferase gene tfpO. These traits were combined and analysed using biological data analysis software and visualized in the form of a minimum spanning tree (MST). We revealed a network of relationships between all analyzed parameters and non-congruence between experiments. At the same time we observed several conserved clones, characterized by an almost identical data set. These observations confirm the nonclonal epidemic population structure of P. aeruginosa, a superficially clonal structure with frequent recombinations, in which occasionally highly successful epidemic clones arise. One of these clones is the renown and widespread MDR serotype O12 clone. On the other hand, we found no evidence for a widespread CF transmissible clone. All but one of the 43 analysed CF strains belonged to a ubiquitous P. aeruginosa “core lineage” and typically exhibited the exoS+/exoU− genotype and group B oprL and oprD alleles. This is to our knowledge the first report of an MST analysis conducted on a polyphasic data set

Immunoprophylaxis and immunotherapy of Staphylococcus epidermidis infections: challenges and prospects

Previously considered a human commensal, Staphylococcus epidermidis is a frequent cause of nosocomial infections and the most common cause of device-related infections. Because the expression of toxins and other obvious virulence factors is less in S. epidermidis, the biofilm-forming capacity is its major virulence factor. Biofilm growth is characterized by high resistance to antimicrobial agents and host immune responses, making biofilm eradication tremendously difficult. The increasing prevalence of multidrug-resistant S. epidermidis strains additionally hampers antimicrobial therapy. Therefore, immunoprophylaxis and immunotherapy targeting factors expressed at some point in biofilm formation might offer new tools to combat S. epidermidis infections. So far, a limited number of targets have been examined for their immunotherapeutic potential. In this review, we focus on the already tested and possible targets for vaccine development, discuss the accompanying challenges and speculate on future possibilities with respect to immunotherapeutic solutions to deal with S. epidermidis infections.status: publishe

Metabolic Activity of Staphylococcus epidermidis Is High during Initial and Low during Late Experimental Foreign-Body Infection

Foreign-body infection (FBI) is notoriously resistant to eradication by antibiotic treatment. It is hypothesized that reduced bacterial metabolic activity contributes to this resistance. We examined the metabolic activity of Staphylococcus epidermidis in 204 samples recovered during in vitro foreign-body colonization and in 424 samples recovered during in vivo FBI in a rat model. Metabolic activity was measured by determining the amount of 16S rRNA per genome by quantitative PCR. The initial foreign-body-associated growth proved to be a metabolically active process, both in vitro and in vivo. The initial 16S rRNA content was similar to that observed during in vitro exponential-growth phase. However, during late in vivo FBI, a 114-fold (P ≪ 0.0001) decrease in the 16S rRNA content was observed, indicating that there was markedly decreased metabolic activity. This decreased metabolic activity during late FBI can explain at least in part why such infections are so difficult to eradicate with conventional antibiotic treatment

Compliance with evidence-based guidelines for the prevention of central line-associated bloodstream infections in a Belgian home care setting: An observational study

This study assessed the compliance of Belgian home care nurses with good practice recommendations to prevent central line-associated bloodstream infections. The compliance to 3 care bundles was 0% (0 out of 7), 13.3% (2 out of 15), and 22.2% (2 out of 9), respectively. This finding is important given the increasing number of home care patients with an intravascular catheter and underscores the need for quality improvement strategies to prevent central line-associated bloodstream infections in home care.status: publishe

Performance of qualitative urinary hCG assays

Significant differences in the sensitivity of eight frequently used qualitative urine human chorionic gonadotropin (hCG) tests in Belgium were observed in this study. Although most manufacturers claimed to detect hCG levels as low as 25 mIU/ml, only two out of six tests for home use and one out of two tests for professional use only, achieved the claimed detection limit. According to a survey, we performed among 20 acute care hospitals, 80% of the surveyed hospitals claimed to use these types of hCG analysis in a diagnostic setting. Unsatisfactory performance of these point-of-care testing (POC) assays for urinary hCG could have major consequences in a hospital setting, exposing the early pregnant woman to harmful diagnostic and therapeutic procedures. Although qualitative urine hCG tests are rapid and convenient, determination of hCG in blood remains the gold standard for the diagnosis of pregnancy.peerreview_statement: The publishing and review policy for this title is described in its Aims & Scope. aims_and_scope_url: http://www.tandfonline.com/action/journalInformation?show=aimsScope&journalCode=yacb20status: publishe

Cervicofacial actinomycosis following third molar removal: case-series and review

Actinomycosis is an opportunistic infection caused by bacteria of the Actinomyces spp., commonly A. israelii. These are non-pathogenic commensals in the mouth, gut, and female genital tract. An infection may arise following trauma or surgery, such as tooth extraction. More than half of cases of actinomycosis occur in the perimandibular area and are termed cervicofacial actinomycosis. Initially, the infection develops as a painful, rapidly progressive swelling. The lesion may then indurate and is often painless while the overlying skin discolors red to purple-blue. Prolonged treatment with antibiotics and surgery are often required for resolution, unless treatment is promptly started. However, diagnosis may be delayed or missed because of difficult bacterial culturing and frequent confusion with malignancy and other infections. This case study describes six patients who developed cervicofacial actinomycosis following third molar extraction. The purpose of this study is to inform clinicians on this stubborn and deceitful disease entity and to highlight the importance of clinical recognition for quick resolution with minimal morbidity.status: publishe

Colonization of hard and soft surfaces by Aggregatibacter actinomycetemcomitans under hydrodynamic conditions

Introduction: Oral bacteria must attach to hard and soft tissues to colonize the oral cavity in the presence of a variety of forces caused by shear and flow. In vitro models mimicking this dynamic process are indispensable to study factors that might interfere with the first step towards infection. For extrapolation purposes the comparability between the dynamics of colonization on hard vs. soft surfaces needs to be evaluated.status: publishe