Using the Traditional Ex Vivo Whole Blood Model to Discriminate Bacteria by Their Inducible Host Responses

Whole blood models are rapid and versatile for determining immune responses to inflammatory and infectious stimuli, but they have not been used for bacterial discrimination. Staphylococcus aureus, S. epidermidis and Escherichia coli are the most common causes of invasive disease, and rapid testing strategies utilising host responses remain elusive. Currently, immune responses can only discriminate between bacterial 'domains' (fungi, bacteria and viruses), and very few studies can use immune responses to discriminate bacteria at the species and strain level. Here, whole blood was used to investigate the relationship between host responses and bacterial strains. Results confirmed unique temporal profiles for the 10 parameters studied: IL-6, MIP-1α, MIP-3α, IL-10, resistin, phagocytosis, S100A8, S100A8/A9, C5a and TF3. Pairwise analysis confirmed that IL-6, resistin, phagocytosis, C5a and S100A8/A9 could be used in a discrimination scheme to identify to the strain level. Linear discriminant analysis (LDA) confirmed that (i) IL-6, MIP-3α and TF3 could predict genera with 95% accuracy; (ii) IL-6, phagocytosis, resistin and TF3 could predict species at 90% accuracy and (iii) phagocytosis, S100A8 and IL-10 predicted strain at 40% accuracy. These data are important because they confirm the proof of concept that host biomarker panels could be used to identify bacterial pathogens.

An In Vitro Model to Assess Early Immune Markers Following Co-Exposure of Epithelial Cells to Carbon Black (Nano)Particles in the Presence of S. aureus: A Role for Stressed Cells in Toxicological Testing

The exposure of human lung and skin to carbon black (CB) is continuous due to its widespread applications. Current toxicological testing uses 'healthy' cellular systems; however, questions remain whether this mimics the everyday stresses that human cells are exposed to, including infection. Staphylococcus aureus lung and skin infections remain prevalent in society, and include pneumonia and atopic dermatitis, respectively, but current in vitro toxicological testing does not consider infection stress. Therefore, investigating the effects of CB co-exposure in 'stressed' infected epithelial cells in vitro may better approximate true toxicity. This work aims to study the impact of CB exposure during Staphylococcus aureus infection stress in A549 (lung) and HaCaT (skin) epithelial cells. Physicochemical characterisation of CB confirmed its dramatic polydispersity and potential to aggregate. CB significantly inhibited S. aureus growth in cell culture media. CB did not induce cytokines or antimicrobial peptides from lung and skin epithelial cells, when given alone, but did reduce HaCaT and A549 cell viability to 55% and 77%, respectively. In contrast, S. aureus induced a robust interleukin (IL)-8 response in both lung and skin epithelial cells. IL-6 and human beta defensin (hβD)-2 could only be detected when cells were stimulated with S. aureus with no decreases in cell viability. However, co-exposure to CB (100 µg/mL) and S. aureus resulted in significant inhibition of IL-8 (compared to S. aureus alone) without further reduction in cell viability. Furthermore, the same co-exposure induced significantly more hβD-2 (compared to S. aureus alone). This work confirms that toxicological testing in healthy versus stressed cells gives significantly different responses. This has significant implications for toxicological testing and suggests that cell stresses (including infection) should be included in current models to better represent the diversity of cell viabilities found in lung and skin within a general population. This model will have significant application when estimating CB exposure in at-risk groups, such as factory workers, the elderly, and the immunocompromised.

Contrasting effects of linezolid on healthy and dysfunctional human neutrophils: reducing C5a-induced injury

Methicillin-resistant Staphylococcus aureus (MRSA) is an important cause of ventilator-associated pneumonia (VAP). Patients with VAP have poorly functioning neutrophils, related to increased levels of the complement fragment C5a. The antibiotic linezolid has been useful in controlling MRSA-related VAP infections; however clinical benefit does not always correlate with antimicrobial effect, suggesting the possibility of immunomodulatory properties. Here the effects of linezolid on healthy and dysfunctional neutrophils (modelled by C5a-induced injury) was investigated. Functional assays (killing, phagocytosis, transmigration, and respiratory burst) were used to assess the effects of pre-, co- and post-incubating linezolid (0.4-40 mg/L) with healthy neutrophils relative to those with C5a-induced injury. C5a decreased neutrophil killing, and phagocytosis of MRSA. Furthermore, C5a significantly decreased neutrophil transmigration to IL-8, but did not affect respiratory burst. Co-incubation of linezolid significantly improved killing of MRSA by dysfunctional neutrophils, which was supported by concomitant increases in phagocytosis. Conversely linezolid impaired killing responses in healthy neutrophils. Pre- or post-incubation of linezolid prior or following C5a induced injury had no effect on neutrophil function. This study suggests that linezolid has immunomodulatory properties that protect human neutrophils from injury and provides insight into its mode of action beyond a basic antibiotic.

Temporin A and Bombinin H2 Antimicrobial Peptides Exhibit Selective Cytotoxicity to Lung Cancer Cells

BACKGROUND

Recently, antimicrobial peptides (AMPs) have been investigated for their use in cancer therapy. They have been reported to selectively target and kill cancer cells whilst leaving normal healthy cells unaffected. Certain Anura AMPs have expressed selective cytotoxicity against tumour cells.

AIM

To test the potential of Anura AMPs bombinin H2, bombinin H4, temporin A, and temporin L for use as therapeutic agents for non-small cell lung carcinoma (NSCLC).

METHODS

Cytotoxic effects on NSCLC cell lines A549 and Calu-3 and normal epithelial cell line Beas-2B were tested using the CellTox Green Cytotoxicity Assay. Their haemolytic effects on human erythrocytes were also tested for their clinical relevance. Cell membrane profiling, using MALDI-TOF, was performed to ascertain if membrane characteristics of the NSCLC and Beas-2B cell lines may contribute to the AMPs mode of action.

RESULTS

Bombinin H4 (100-1.5 μM, p < 0.05) and temporin A (100-50 μM, p < 0.05) showed selective cytotoxicity towards the NSCLC cell lines. Furthermore, they exhibited low levels of haemolytic activity (bombinin H4, 0.061%; temporin A, 0.874%) comparable to untreated cells. Cell membrane profiling showed the phospholipid composition of normal epithelial cell line Beas-2B to be divergent from the cancerous cell lines. However, there was an overlap in the phospholipid profiles of the NSCLC cell lines supporting the hypothesis that the AMPs may have a selective affinity via the membrane composition of cancerous cell lines.

CONCLUSION

These results suggest that bombinin H4 and temporin A show potential for application in lung cancer therapies. Further in vitro and in vivo studies are required to develop a greater understanding of their use as anticancer agents.

Recommendations for design and conduct of preclinical in vivo studies of orthopedic device-related infection

Orthopedic device-related infection (ODRI), including both fracture-related infection (FRI) and periprosthetic joint infection (PJI), remain among the most challenging complications in orthopedic and musculoskeletal trauma surgery. ODRI has been convincingly shown to delay healing, worsen functional outcome and incur significant socio-economic costs. To address this clinical problem, ever more sophisticated technologies targeting the prevention and/or treatment of ODRI are being developed and tested in vitro and in vivo. Among the most commonly described innovations are antimicrobial-coated orthopedic devices, antimicrobial-loaded bone cements and void fillers, and dual osteo-inductive/antimicrobial biomaterials. Unfortunately, translation of these technologies to the clinic has been limited, at least partially due to the challenging and still evolving regulatory environment for antimicrobial drug-device combination products, and a lack of clarity in the burden of proof required in preclinical studies. Preclinical in vivo testing (i.e. animal studies) represents a critical phase of the multidisciplinary effort to design, produce and reliably test both safety and efficacy of any new antimicrobial device. Nonetheless, current in vivo testing protocols, procedures, models, and assessments are highly disparate, irregularly conducted and reported, and without standardization and validation. The purpose of the present opinion piece is to discuss best practices in preclinical in vivo testing of antimicrobial interventions targeting ODRI. By sharing these experience-driven views, we aim to aid others in conducting such studies both for fundamental biomedical research, but also for regulatory and clinical evaluation. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 37:271-287, 2019.

Rapid Identification of Staphylococci from Prosthetic Joint Infections Using MALDI-TOF Mass-Spectrometry

Hospital-acquired infections associated with implanted medical devices are most commonly caused by staphylococci. Current methods of species identification are slow, costly, and sometimes unreliable. We evaluated the ability of a Bruker Daltonics Microflex MALDI-TOF/MS in conjunction with MALDI Biotyper software to identify 158 characterized staphylococcal isolates from prosthetic joint infections, including 36 Staphylococcus aureus, 100 Staphylococcus epidermidis, 10 Staphylococcus capitis, 8 Staphylococcus lugdunensis, 2 Staphylococcus warneri, and 2 Staphylococcus haemolyticus isolates using the extraction method recommended by Bruker Daltonics. The suggested species identification by the MALDI Biotyper software was correct for all isolates, indicating reliable differentiation between S. aureus and coagulase-negative staphylococci. Applying the recommended criteria of the MALDI Biotyper software all 158 isolates gave scores ≥2.0, implying secure genus and probable species identification for all isolates. 34/36 S. aureus, 36/100 S. epidermidis, 5/10 S. capitis, 6/8 S. lugdunensis, 2/2 S. haemolyticus, 0/2 S. warneri displayed scores ≥2.3 implying highly probable species identification. For S. epidermidis 25/100 additional isolates had a score close to 2.3. It appears that additional clinically relevant staphylococcal isolates in the data base might aid in identification at scores implying highly probable species identification. The ability of the MALDI Biotyper software to recognize clonally-related strains within a species group (i.e. sub-typing) was investigated, and showed great potential. In conclusion, the MALDI-TOF/MS MALDI Biotyper system provides a promising rapid and reliable method of identifying clinical isolates from prosthetic joint infections to the species level, and has potential for sub-typing.

Disruption of Staphylococcus Epidermidis Biofilms by Medicinal Maggot Lucilia Sericata Excretions/Secretions

Chronic infections are commonly associated with biofilms formed by bacteria such as Staphylococcus epidermidis. With the increase in antibiotic resistant bacteria, maggot debridement therapy has been reintroduced for the treatment of chronic wounds. Studies have shown that the excretion/secretions (ES) of Lucilia sericata larvae (maggots) contain many bioactive compounds which may contribute to the efficacy of maggot therapy. The present study evaluates the effect of L. sericata ES on the formation and disruption of S. epidermidis 7457 and 5179-R1 biofilms. These strains employ either polysaccharide intercellular adhesin (PIA) or accumulation associated protein (Aap) for intercellular adhesion.

A semiquantitative biofilm assay was used to measure the formation/disruption of S. epidermidis 7457 and 5179-R1 biofilms by ES. ES activity was characterized according to concentration, incubation time and temperature, thermal stability, and size. Immunofluorescence microscopy was used to ascertain the effect of ES on PIA and Aap.

In the presence of ES, S. epidermidis 7457 and 5179-R1 nascent bio film formation was inhibited, and pre-formed biofilms disrupted. ES activity was temperature and time dependent, inactivated by heat treatment, and disruption depended on the mechanism of intercellular adhesion. The molecule(s) responsible was >10 kDa in size and appeared to have protease or glucosaminidase activity.

ES interferes with S. epidermidis biofilm formation, specifically degrading factors employed in biofilm accumulation, which would increase bacterial susceptibility to antibiotics and the host's immune system. In purified form, ES-factors may have general applicability for the treatment or prevention of chronic biofilm infections caused by staphylococci.

Limitations in the use of PSMγ, agr, RNAIII, and biofilm formation as biomarkers to define invasive Staphylococcus epidermidis from chronic biomedical device-associated infections

Staphylococcus epidermidis is a common cause of biomedical device-associated infections. Agr is the major quorum sensing system in staphylococci and regulates virulence factors. Four agr-specificity groups exist in S. epidermidis, and chronic S. epidermidis infections are hypothesised to select for agr-negative phenotypes. Therefore, we investigated S. epidermidis strains from prosthetic joint- and catheter-associated infections to establish i) whether an infection selects for an agr-negative phenotype; ii) the importance of PSMγ and iii) if the agr-specificity group is infection dependent. S. epidermidis nasal isolates from healthy volunteers were used as controls. The distribution of agr-specificity groups was significantly different between infection and control episodes, but did not distinguish between the infection types. PSMγ secretion was used to determine agr-activity and HPLC analysis showed that 44% of prosthetic and 32% of catheter-associated episodes produced no PSMγ in comparison to 8% of the control strains. However, PSMγ expression did not always correlate with RNAIII up-regulation, indicating that PSMγ synthesis is likely influenced by additional post-transcriptional control. The data suggests chronic S. epidermidis infections favour agr-specificity group 1 but the results suggest that they do not select for an agr-negative phenotype. Further studies are required to explore the mechanisms underlying the selection and survival of these S. epidermidis phenotypes isolated from biomedical device-associated infections.

Pathogenic Mechanisms and Host Interactions in Staphylococcus epidermidis Device-Related Infection

Staphylococcus epidermidis is a permanent member of the normal human microbiota, commonly found on skin and mucous membranes. By adhering to tissue surface moieties of the host via specific adhesins, S. epidermidis is capable of establishing a lifelong commensal relationship with humans that begins early in life. In its role as a commensal organism, S. epidermidis is thought to provide benefits to human host, including out-competing more virulent pathogens. However, largely due to its capacity to form biofilm on implanted foreign bodies, S. epidermidis has emerged as an important opportunistic pathogen in patients receiving medical devices. S. epidermidis causes approximately 20% of all orthopedic device-related infections (ODRIs), increasing up to 50% in late-developing infections. Despite this prevalence, it remains underrepresented in the scientific literature, in particular lagging behind the study of the S. aureus. This review aims to provide an overview of the interactions of S. epidermidis with the human host, both as a commensal and as a pathogen. The mechanisms retained by S. epidermidis that enable colonization of human skin as well as invasive infection, will be described, with a particular focus upon biofilm formation. The host immune responses to these infections are also described, including how S. epidermidis seems to trigger low levels of pro-inflammatory cytokines and high levels of interleukin-10, which may contribute to the sub-acute and persistent nature often associated with these infections. The adaptive immune response to S. epidermidis remains poorly described, and represents an area which may provide significant new discoveries in the coming years.

Characterization of nasal methicillin-resistant Staphylococcus aureus isolated from international human and veterinary surgeons

PURPOSE

Nasal colonization with methicillin-resistant Staphylococcus aureus (MRSA) is poorly described for surgeons, despite the increased exposure to nosocomial pathogens and at-risk patients. This study investigated the molecular epidemiology and antimicrobial resistance of 26 MRSA isolates cultured from the nares of an international cross-sectional study of 1166 human and 60 veterinary surgeons.

METHODOLOGY

All isolates were subjected to agr, spa and multilocus sequence typing, and the presence of 22 virulence factors was screened for by PCR. Additionally, biofilm-forming ability, haemolytic activity, staphyloxanthin production and antibiotic resistance were determined. The genome of a rifampicin-resistant MRSA was sequenced.

RESULTS

Approximately half of the isolates belonged to well-described clonal lineages, ST1, ST5, ST8, ST45 and ST59, that have previously been associated with severe infections and increased patient mortality. Two of the three veterinarian MRSA belonged to epidemic livestock-associated MRSA clonal lineages (ST398 and ST8) previously associated with high transmission potential between animals and humans. The isolates did not display any consistent virulence gene pattern, and 35 % of the isolates carried at least one of the Panton-Valentine leukocidin (lukFS-PV), exfoliative toxin (eta) or toxic shock syndrome (tst) genes. Resistance to rifampicin was detected in one veterinarian isolate and was found to be due to three mutations in the rpoB gene.

CONCLUSION

Surgeons occupy a critical position in the healthcare profession due to their close contact with patients. In this study, surgeons were found to be colonized with MRSA at low rates, similar to those of the general population, and the colonizing strains were often common clonal lineages.

Biofilm Morphotypes and Population Structure among Staphylococcus epidermidis from Commensal and Clinical Samples

Bacterial species comprise related genotypes that can display divergent phenotypes with important clinical implications. Staphylococcus epidermidis is a common cause of nosocomial infections and, critical to its pathogenesis, is its ability to adhere and form biofilms on surfaces, thereby moderating the effect of the host’s immune response and antibiotics. Commensal S. epidermidis populations are thought to differ from those associated with disease in factors involved in adhesion and biofilm accumulation. We quantified the differences in biofilm formation in 98 S. epidermidis isolates from various sources, and investigated population structure based on ribosomal multilocus typing (rMLST) and the presence/absence of genes involved in adhesion and biofilm formation. All isolates were able to adhere and form biofilms in in vitro growth assays and confocal microscopy allowed classification into 5 biofilm morphotypes based on their thickness, biovolume and roughness. Phylogenetic reconstruction grouped isolates into three separate clades, with the isolates in the main disease associated clade displaying diversity in morphotype. Of the biofilm morphology characteristics, only biofilm thickness had a significant association with clade distribution. The distribution of some known adhesion-associated genes (aap and sesE) among isolates showed a significant association with the species clonal frame. These data challenge the assumption that biofilm-associated genes, such as those on the ica operon, are genetic markers for less invasive S. epidermidis isolates, and suggest that phenotypic characteristics, such as adhesion and biofilm formation, are not fixed by clonal descent but are influenced by the presence of various genes that are mobile among lineages.

Effects of polysaccharide intercellular adhesin (PIA) in an ex vivo model of whole blood killing and in prosthetic joint infection (PJI): A role for C5a

BACKGROUND

A major complication of using medical devices is the development of biofilm-associated infection caused by Staphylococcus epidermidis where polysaccharide intercellular adhesin (PIA) is a major mechanism of biofilm accumulation. PIA affects innate and humoral immunity in isolated cells and animal models. Few studies have examined these effects in prosthetic joint infection (PJI).

METHODS

This study used ex vivo whole blood modelling in controls together with matched-serum and staphylococcal isolates from patients with PJI.

RESULTS

Whole blood killing of PIA positive S. epidermidis and its isogenic negative mutant was identical. Differences were unmasked in immunosuppressed whole blood pre-treated with dexamethasone where PIA positive bacteria showed a more resistant phenotype. PIA expression was identified in three unique patterns associated with bacteria and leukocytes, implicating a soluble form of PIA. Purified PIA reduced whole blood killing while increasing C5a levels. In clinically relevant staphylococcal isolates and serum samples from PJI patients; firstly complement C5a was increased 3-fold compared to controls; secondly, the C5a levels were significantly higher in serum from PJI patients whose isolates preferentially formed PIA-associated biofilms.

CONCLUSIONS

These data demonstrate for the first time that the biological effects of PIA are mediated through C5a in patients with PJI.

Ecological Overlap and Horizontal Gene Transfer in Staphylococcus aureus and Staphylococcus epidermidis

The opportunistic pathogens Staphylococcus aureus and Staphylococcus epidermidis represent major causes of severe nosocomial infection, and are associated with high levels of mortality and morbidity worldwide. These species are both common commensals on the human skin and in the nasal pharynx, but are genetically distinct, differing at 24% average nucleotide divergence in 1,478 core genes. To better understand the genome dynamics of these ecologically similar staphylococcal species, we carried out a comparative analysis of 324 S. aureus and S. epidermidis genomes, including 83 novel S. epidermidis sequences. A reference pan-genome approach and whole genome multilocus-sequence typing revealed that around half of the genome was shared between the species. Based on a BratNextGen analysis, homologous recombination was found to have impacted on 40% of the core genes in S. epidermidis, but on only 24% of the core genes in S. aureus. Homologous recombination between the species is rare, with a maximum of nine gene alleles shared between any two S. epidermidis and S. aureus isolates. In contrast, there was considerable interspecies admixture of mobile elements, in particular genes associated with the SaPIn1 pathogenicity island, metal detoxification, and the methicillin-resistance island SCCmec. Our data and analysis provide a context for considering the nature of recombinational boundaries between S. aureus and S. epidermidis and, the selective forces that influence realized recombination between these species.

Dormant cells of Staphylococcus aureus are resuscitated by spent culture supernatant

We describe the first in vitro model of dormancy in Staphylococcus aureus, showing that cells are generated which can be resuscitated by addition of spent medium supernatant taken from cultures of the same organism. Over 30 days, culturable counts in dormant cultures of S. aureus SH1000 fell from 10(6)-10(7) cfu/ml to <10 cfu/ml as measured by the Most Probable Number method in liquid culture, while total counts as determined by microscopy, and supported by data from RT-qPCR, remained around 10(6)-10(7) cells/ml. Supplementing cultures with 25-50% spent medium resulted in a >600-fold increase in bacterial growth. Resuscitation was a specific effect, greatly reduced by boiling or addition of trypsin to the spent supernatant. Supernatant also effected a reduction in lag phase of dormant cultures. SEM demonstrated the presence of small coccoid cells in dormant cultures. The results are similar to those seen with resuscitation promoting factors (Rpfs) in actinobacteria. This is the first time resuscitation has been demonstrated in Staphylococcus aureus, which is an important human pathogen. A better understanding of control and reactivation of dormant cells could lead to major improvements in managing staphylococcal infections; resuscitation could be an important step in restoring susceptibility to antibiotic treatment.

An extracellular Staphylococcus epidermidis polysaccharide: relation to Polysaccharide Intercellular Adhesin and its implication in phagocytosis

BACKGROUND

The skin commensal and opportunistic pathogen Staphylococcus epidermidis is a leading cause of hospital-acquired and biomaterial-associated infections. The polysaccharide intercellular adhesin (PIA), a homoglycan composed of β-1,6-linked N-acetylglucosamine residues, synthesized by enzymes encoded in icaADBC is a major functional factor in biofilm accumulation, promoting virulence in experimental biomaterial-associated S. epidermidis infection. Extracellular mucous layer extracts of S. epidermidis contain another major polysaccharide, referred to as 20-kDa polysaccharide (20-kDaPS), composed mainly out of glucose, N-acetylglucosamine, and being partially sulfated. 20-kDaPS antiserum prevents adhesion of S. epidermidis on endothelial cells and development of experimental keratitis in rabbits. Here we provide experimental evidence that 20-kDaPS and PIA represent distinct molecules and that 20-kDaPS is implicated in endocytosis of S. epidermidis bacterial cells by human monocyte-derived macrophages.

RESULTS

Analysis of 75 clinical coagulase-negative staphylococci from blood-cultures and central venous catheter tips indicated that 20-kDaPS is expressed exclusively in S. epidermidis but not in other coagulase-negative staphylococcal species. Tn917-insertion in various locations in icaADBC in mutants M10, M22, M23, and M24 of S. epidermidis 1457 are abolished for PIA synthesis, while 20-kDaPS expression appears unaltered as compared to wild-type strains using specific anti-PIA and anti-20-kDaPS antisera. While periodate oxidation and dispersin B treatments abolish immuno-reactivity and intercellular adhesive properties of PIA, no abrogative activity is exerted towards 20-kDaPS immunochemical reactivity following these treatments. PIA polysaccharide I-containing fractions eluting from Q-Sepharose were devoid of detectable 20-kDaPS using specific ELISA. Preincubation of non-20-kDaPS-producing clinical strain with increasing amounts of 20-kDaPS inhibits endocytosis by human macrophages, whereas, preincubation of 20-kDaPS-producing strain ATCC35983 with 20-kDaPS antiserum enhances bacterial endocytosis by human macrophages.

CONCLUSIONS

In conclusion, icaADBC is not involved in 20-kDaPS synthesis, while the chemical and chromatographic properties of PIA and 20-kDaPS are distinct. 20-kDaPS exhibits anti-phagocytic properties, whereas, 20-kDaPS antiserum may have a beneficial effect on combating infection by 20-kDaPS-producing S. epidermidis.

Comparison of bacterial identification by MALDI-TOF mass spectrometry and conventional diagnostic microbiology methods: agreement, speed and cost implications

Identification of microbial pathogens still relies primarily on culture and phenotypic methods, which is labour-intensive and time-consuming. In this study, identification of bacteria with valid standard identification using BD Phoenix, API panels and other recommended procedures is compared to identification with matrix-assisted laser desorption/ionisation-time of flight (MALDI-TOF) mass spectrometry using the MALDI Biotyper (Bruker Daltonics) in the setting of a routine NHS diagnostic microbiology laboratory. In total, 928 bacterial isolates obtained from blood (n=463), wounds and pus (n=208), respiratory tract (n=100), faeces (n=86) and urines (n=71) were analysed. There were 721 (77.7%) isolates with a MALDI Biotyper score > or =2.0, indicating secure genus and probable species identification; and 149 (16.1%) isolates with a score > or =1.7 and <2.0 indicating probable genus identification. The isolates with scores of > or =2.0 and > or =1.7 comprised 31 and 33 genera and 65 and 67 species, respectively. Overall, 99.4% and 99.1% of organism identifications were in agreement between the MALDI Biotyper and conventional identification at the genus level, and 89.3% and 87.8% at species level when analysing organisms with MALDI Biotyper scores > or =2.0 and > or =1.7, respectively. With many but not all organisms, identification at the genus level is sufficient; however, MALDI Biotyper separation of 208 staphylococci into Staphylococcus aureus and coagulase-negative staphylococci was always correct when scores were > or =1.7. First results were obtained after 5-10 min and analysis of a full 96-well target plate was completed in approximately 90 min. Substantial savings of between pounds 1.79 and pounds 2.56 per isolate, depending on the cost model of acquisition of the MALDI Biotyper system and number of isolates tested, would be realised when all 928 isolates were identified using the MALDI Biotyper and disk-susceptibility testing when compared to the cost for 618 Phoenix ID panels and 158 API panels and disk-susceptibility tests only (i.e., not taking into account costs incurred for identification of the remaining 152 mixed isolates). Microbial identification by MALDI Biotyper offers a rare opportunity for significant cost-neutral or even cost-saving quality improvements in medical diagnostics.

Increased vascularity and spontaneous metastasis of breast cancer by hedgehog signaling mediated upregulation of cyr61

The Hedgehog (Hh) pathway is well known for its involvement in angiogenesis and vasculogenesis during ontogeny. The ligand, Sonic hedgehog (SHH), plays an important role in vascular formation during development. However, SHH expression is upregulated on tumor cells and can impact the tumor microenvironment. We have investigated the effects of autocrine as well as paracrine Hh signaling on tumor cells as well as on endothelial cells, respectively.

Upon constitutive expression of SHH, breast cancer cells showed aggressive behavior and rapid xenograft growth characterized by highly angiogenic tumors that were spontaneously metastatic. In these cells, SHH caused activation of the Hh transcription factor, GLI1, leading to upregulated expression of the potent pro-angiogenic secreted molecule, CYR61 (cysteine rich angiogenic inducer 61). Silencing of CYR61 from these SHH-expressing Hh activated cells blunted the malignant behavior of the tumor cells and resulted in reduced tumor vasculature and limited hematogenous metastases. Thus, CYR61 is a critical downstream contributor to the Hh influenced pro-angiogenic tumor microenvironment. We also observed concomitant upregulation of SHH and CYR61 transcripts in tumors from patients with advanced breast cancer, further ratifying the clinical relevance of our findings. In summary, we have defined a novel, VEGF-independent, clinically relevant, pro-angiogenic factor, CYR61, that is a transcriptional target of Hh-GLI signaling.

Rapid differentiation of Staphylococcus aureus, Staphylococcus epidermidis and other coagulase-negative staphylococci and meticillin susceptibility testing directly from growth-positive blood cultures by multiplex real-time PCR

This study evaluated a multiplex real-time PCR method specific for the mecA, femA-SA and femA-SE genes for rapid identification of Staphylococcus aureus, Staphylococcus epidermidis and non-S. epidermidis coagulase-negative staphylococci (CoNS), and meticillin susceptibility testing directly in positive blood cultures that grew Gram-positive cocci in clusters. A total of 100 positive blood cultures produced: 39 S. aureus [12 meticillin-resistant S. aureus (MRSA), 31% of all the S. aureus]; 30 S. epidermidis (56.6% of the CoNS), 8 Staphylococcus capitis (15.1%), 3 Staphylococcus saprophyticus (5.7%), 4 Staphylococcus hominis (7.5%), 3 Staphylococcus haemolyticus (5.7%), 2 Staphylococcus warneri (3.8%), 1 Staphylococcus cohnii (1.9%) and 2 unidentified Staphylococcus spp. (3.8%); and 1 Micrococcus luteus in pure culture. Two blood cultures had no growth on subculture and five blood cultures grew mixed CoNS. For the 95 blood cultures with pure growth or no growth on subculture, there was very good agreement between real-time PCR and the BD Phoenix identification system for staphylococcal species categorization in S. aureus, S. epidermidis and non-S. epidermidis CoNS and meticillin-resistance determination (Cohen's unweighted kappa coefficient κ=0.882). All MRSA and meticillin-susceptible S. aureus were correctly identified by mecA amplification. PCR amplification of mecA was more sensitive for direct detection of meticillin-resistant CoNS in positive blood cultures than testing with the BD Phoenix system. There were no major errors when identifying staphylococcal isolates and their meticillin susceptibility within 2.5 h. Further studies are needed to evaluate the clinical benefit of using such a rapid test on the consumption of glycopeptide antibiotics and the alteration of empiric therapy in the situation of positive blood cultures growing staphylococci, and the respective clinical outcomes.

Rewritable glycochips

We describe microarraying of carbohydrates for protein screening using either disulfide bridge or Schiff base imine immobilization chemistries on plasmachemical deposited functional nanolayers. The commonly observed issue of nonspecific background binding of proteins is overcome by spotting carbohydrates through a protein-resistant overlayer yielding spatially localized interaction with a reactive functional underlayer.

Weak effect of metal type and ica genes on staphylococcal infection of titanium and stainless steel implants

Currently, ica is considered to be the major operon responsible for staphylococcal biofilm. The effect of biofilm on susceptibility to staphylococcal infection of different implant materials in vivo is unclear. The interaction of ica-positive (wild-type (WT)) and ica-negative (ica(-)) Staphylococcus aureus and Staphylococcus epidermidis strains with titanium and both smooth and rough stainless steel surfaces was studied by scanning electron microscopy in vitro and in a mouse tissue cage model during 2 weeks following perioperative or postoperative inoculation in vivo. In vitro, WT S. epidermidis adhered equally and more strongly than did WT S. aureus to all materials. Both WT strains, but not ica(-) strains, showed multilayered biofilm. In vivo, 300 CFUs of WT and ica(-)S. aureus led, in all metal cages, to an infection with a high level of planktonic CFUs and only 0.89% adherent CFUs after 8 days. In contrast, 10(6) CFUs of the WT and ica(-) strains were required for postoperative infection with S. epidermidis. In all metal types, planktonic numbers of S. epidermidis dropped to <100 WT, and adherent CFUs were low in WT-infected cages and absent in ica(-)-infected cages after 14 days. Perioperative S. epidermidis inoculation resulted in slower clearance than postoperative inoculation, and in titanium cages adherent WT bacteria survived in higher numbers than ica(-) bacteria. In conclusion, the metal played a minor role in susceptibility to and persistence of staphylococcal infection; the presence of ica genes had a strong effect on biofilm in vitro and a weak effect in vivo; and S. epidermidis was more pathogenic when introduced during implantation than after implantation.

Living with an imperfect cell wall: compensation of femAB inactivation in Staphylococcus aureus

Background

Synthesis of the Staphylococcus aureus peptidoglycan pentaglycine interpeptide bridge is catalyzed by the nonribosomal peptidyl transferases FemX, FemA and FemB. Inactivation of the femAB operon reduces the interpeptide to a monoglycine, leading to a poorly crosslinked peptidoglycan. femAB mutants show a reduced growth rate and are hypersusceptible to virtually all antibiotics, including methicillin, making FemAB a potential target to restore β-lactam susceptibility in methicillin-resistant S. aureus (MRSA). Cis-complementation with wild type femAB only restores synthesis of the pentaglycine interpeptide and methicillin resistance, but the growth rate remains low. This study characterizes the adaptations that ensured survival of the cells after femAB inactivation.

Results

In addition to slow growth, the cis-complemented femAB mutant showed temperature sensitivity and a higher methicillin resistance than the wild type. Transcriptional profiling paired with reporter metabolite analysis revealed multiple changes in the global transcriptome. A number of transporters for sugars, glycerol, and glycine betaine, some of which could serve as osmoprotectants, were upregulated. Striking differences were found in the transcription of several genes involved in nitrogen metabolism and the arginine-deiminase pathway, an alternative for ATP production. In addition, microarray data indicated enhanced expression of virulence factors that correlated with premature expression of the global regulators sae, sarA, and agr.

Conclusion

Survival under conditions preventing normal cell wall formation triggered complex adaptations that incurred a fitness cost, showing the remarkable flexibility of S. aureus to circumvent cell wall damage. Potential FemAB inhibitors would have to be used in combination with other antibiotics to prevent selection of resistant survivors.

Reduced medical infection related bacterial strains adhesion on bioactive RGD modified titanium surfaces: A first step toward cell selective surfaces

Ideally, implants should inhibit nonspecific protein adsorption, bacterial adhesion, and at the same time, depending on the final application be selective toward cellular adhesion and spreading for all or only selected cell types. Poly(L-lysine)-grafted-poly(ethylene glycol) (PLL-g-PEG) polymers have been shown to adsorb from aqueous solution onto negatively charged metal oxide surfaces, reducing protein adsorption as well as fibroblast, osteoblast and epithelial cell adhesion significantly. PLL-g-PEG can be functionalized with bioligands such as RGD (Arg-Gly-Asp), which then restores host cell adhesion, but the surface remains resistant to nonspecific protein adsorption. Previously, it was also shown that both nonfunctionalized PLL-g-PEG and RGD-peptide functionalized PLL-g-PEG reduced the adhesion of Staphylococcus aureus to titanium (Ti) surfaces. The present study looked at the effect of other implant associated infection relevant bacteria, Staphylococcus epidermidis, Streptococcus mutans and Pseudomonas aeruginosa towards the same surface chemistries. The different surfaces were exposed to the bacteria for 1-24 h, and bacteria surface density was evaluated using scanning electron microscopy (SEM) and fluorescence light microscopy (FM). The adhesion of all bacteria strains tested was reduced on Ti surfaces coated with PLL-g-PEG compared to uncoated Ti surfaces even in the presence of RGD. The percentage reduction in bacterial adhesion over the 24-h culture time investigated was 88%-98%, depending on the bacteria type. Therefore, coating surfaces with PLL-g-PEG/PEG-RGD allows cells such as fibroblasts and osteoblasts to attach but not bacteria, resulting in a selective biointeractive pattern that may be useful on medical implants.

Staphylococcus aureus adhesion to standard micro-rough and electropolished implant materials

Implant-associated infections can cause serious complications including osteomyelitis and soft tissue damage, and are a great problem due to the emergence of antibiotic resistant bacteria such as methicillin-resistant Staphylococcus aureus (MRSA). In some cases, antibiotic-loaded beads which release the antibiotic locally have been used, however such systems may lead to the development of antibiotic-resistant bacteria, as seen with gentamicin-loaded beads. Hence modifying the actual metal implant surface to inhibit or reduce initial bacterial adhesion may be an alternative option. This study describes the visualisation and quantification of S. aureus adhering to standard micro-rough 'commercially pure' titanium (TS) and Ti-6Al-7Nb (NS) surfaces, electropolished titanium (TE) and Ti-6Al-7Nb (NE) surfaces, and standard electropolished stainless steel (SS). Qualitative and quantitative results of S. aureus on the different surfaces correlated with each other, and showed significantly more live bacteria on NS than on the other surfaces, whilst there was no significant difference between the amount of bacteria on TS, TE, NE and SS surfaces. The results showed a significant decrease in the amount of bacteria adhering to the NE compared to standard NS surfaces. Such an observation suggests that the NS surface encouraged S. aureus adhesion, and could lead to higher infection rates in vivo. Hence electropolishing Ti-6Al-7Nb surfaces could be advantageous in osteosynthesis areas in minimising bacterial adhesion and lowering the rate of infection.

Mimicking a Stenocara beetle's back for microcondensation using plasmachemical patterned superhydrophobic-superhydrophilic surfaces

A simple two-step plasmachemical methodology is outlined for the fabrication of microcondensor surfaces. This comprises the creation of a superhydrophobic background followed by pulsed plasma deposition of a hydrophilic polymer array. Microcondensation efficiency has been explored in terms of the chemical nature of the hydrophilic pixels and their dimensions. These results are compared to the hydrophilic-hydrophobic pattern present on the Stenocara beetle's back, which is used by the insect to collect water in the desert. Potential applications include fog harvesting, microfluidics, and biomolecule immobilization.

Polysaccharide intercellular adhesin or protein factors in biofilm accumulation of Staphylococcus epidermidis and Staphylococcus aureus isolated from prosthetic hip and knee joint infections

Nosocomial staphylococcal foreign-body infections related to biofilm formation are a serious threat, demanding new therapeutic and preventive strategies. As the use of biofilm-associated factors as vaccines is critically restricted by their prevalence in natural staphylococcal populations we studied the distribution of genes involved in biofilm formation, the biofilm phenotype and production of polysaccharide intercellular adhesin (PIA) in clonally independent Staphylococcus aureus and Staphylococcus epidermidis strains isolated from prosthetic joint infections after total hip or total knee arthroplasty. Biofilm formation was detected in all S. aureus and 69.2% of S. epidermidis strains. Importantly, 27% of biofilm-positive S. epidermidis produced PIA-independent biofilms, in part mediated by the accumulation associated protein (Aap). Protein-dependent biofilms were exclusively found in S. epidermidis strains from total hip arthroplasty (THA). In S. aureus PIA and proteins act cooperatively in biofilm formation regardless of the infection site. PIA and protein factors like Aap are of differential importance for the pathogenesis of S. epidermidis in prosthetic joint infections (PJI) after THA and total knee arthroplasty (TKA), implicating that icaADBC cannot serve as a general virulence marker in this species. In S. aureus biofilm formation proteins are of overall importance and future work should focus on the identification of functionally active molecules.

Biofilm formation in medical device-related infection

Medical device-associated infections, most frequently caused by coagulase-negative staphylococci, especially Staphylococcus epidermidis, are of increasing importance in modern medicine. Regularly, antimicrobial therapy fails without removal of the implanted device. The most important factor in the pathogenesis of medical device-associated staphylococcal infections is the formation of adherent, multilayered bacterial biofilms. There is urgent need for an increased understanding of the functional factors involved in biofilm formation, the regulation of their expression, and the interaction of those potential virulence factors in device related infection with the host. Significant progress has been made in recent years which may ultimately lead to new rational approaches for better preventive, therapeutic, and diagnostic measures.

Microbial interactions in Staphylococcus epidermidis biofilms

Medical device-associated infections, most frequently caused by coagulase-negative staphylococci, especially Staphylococcus epidermidis, are of increasing importance in modern medicine. The formation of adherent, multilayered bacterial biofilms is the most important factor in the pathogenesis of these infections, which regularly fail to respond to appropriate antimicrobial therapy. Progress in elucidating the factors functional in elaboration of S. epidermidis biofilms and the regulation of their expression with a special emphasis on the role of quorum sensing are reviewed. Significant progress has been made in recent years, which provides the rationale for developing better preventive, therapeutic and diagnostic measures.

Bacteria and cell cytocompatibility studies on coated medical grade titanium surfaces

Acute and chronic osteomyelitis caused by staphylococci can be difficult to treat by conventional means and often has marked consequences for the patient. Current methods of treatment involve the use of systemic antibiotics, the local implantation of nondegradable drug carriers, and surgical debridement. A possible solution that could prevent initial bacterial adhesion could be to modify the implant surface with an antimicrobial coating while maintaining biocompatibility to host cells. This study describes the cytocompatibility evaluation of different coatings (poly(D,L-lactide) (PDLLA), politerefate (PTF), calcium phosphate/anodic plasma-chemical treatment (CaP/APC), polyurethane (PU), and polyvinylpyrollidone (PVP) on titanium surfaces with and without chlorhexidine diacetate (CHA) to Staphylococcus aureus, Staphylococcus epidermidis, and hTERT human fibroblasts. Surface characterization of the coatings showed no significant variation in the roughness or hydrophobicity of the coated surfaces, except the CaP/APC surface that was porous yet the smoothest, and PVP, PVP+CHA, and CaP/APC+CHA that were more hydrophilic in nature than the others. On the surfaces without CHA, both staphylococcal strains and spread fibroblasts were observed, but on the CHA impregnated surfaces few bacteria and no intact fibroblasts were seen. Flow cytometry found fewer bacteria in the media and on the surfaces containing CHA in comparison to the surfaces without CHA. The release kinetics varied from slow (over 200 h) to burst release: PDLLA>PTF>PU>CaP/APC=PVP. This study showed that PDLLA and PTF have the best potential as coatings on implants for drug delivery, as they were cytocompatible to hTERT fibroblasts, eluted CHA effectively, and passed mechanical testing. The actual release kinetics of PDLLA and PTF are important, as the amount of CHA present should remain above the minimal inhibitory concentration value for a limited time before disappearing completely.

Staphylococci and implant surfaces: a review

Surfaces of internal fracture fixation implants are generally designed to encourage soft- and/or hard-tissue adherence, eventually leading to tissue or osseo integration. Unfortunately, this feature may also encourage bacterial adhesion. About half of the two million cases of nosocomial infections per year in the US are associated with indwelling devices. In the UK, implant-associated infections are estimated to cost pound 7-11 million per year, and with the rise in antibiotic-resistant bacteria, are an important issue. Soft-tissue infections and osteomyelitis are serious complications associated with implants, particularly open fractures, external fixation devices, and intramedullary nailing. Consequences of implant-associated infections include prolonged hospitalization with systemic antibiotic therapy, several revision procedures, possible amputation, and even death. This review discusses the issue of implant-associated infections and some of the methods used to prevent bacterial adhesion to osteosynthesis implants.

Biodegradable polyurethane cytocompatibility to fibroblasts and staphylococci

Biodegradable polyurethanes have potential for use as implantable devices (orthopedic, maxillofacial, cardiovascular, wound dressing and plastic surgery) because of their controllable elasticity, and the possibility of changing their chemistry and structure. Studying bacterial and cell adhesion to polyurethanes helps to determine surface cytocompatibility and suitability for in vivo trials. Staphylococcus aureus, Staphylococcus epidermidis and hTERT human fibroblast cells were used to determine the cytocompatibility of experimental biodegradable polyurethanes (PUs) with different hydrophobic-to-hydrophilic (pho:phi) content ratios (100% pho, 70% pho, and 30% pho). Poly(L/DL-lactide) 70/30% (PLDL) and Thermanox were used as control surfaces. Surface characterization using noncontact profilometry, contact angles, and scanning electron microscopy (SEM) showed that the three PU surfaces, PLDL, and Thermanox have different properties. On the 100% PU and 30% PU surfaces, hTERT cells spread less in comparison to the 70% PU, PLDL, and Thermanox surfaces. The adsorption of fibronectin to the surfaces had no effect on the adhesion and spreading of hTERT cells when compared to the uncoated surfaces. The trend for S. aureus was the most adhered on the 70% PU and 30% PU, then Thermanox, followed by 100% PU and PLDL, respectively. The amount of S. epidermidis adhesion followed the trend of the most on 70% PU, then 100% PU, then 30% PU and PLDL, and the least on Thermanox. These results suggest that the 70% PU surface is cytocompatible to hTERT fibroblasts, while the 100% PU and 30% PU were not. All surfaces encouraged S. aureus and S. epidermidis colonization, particularly the 70% PU.

Assessment of the cytocompatibility of different coated titanium surfaces to fibroblasts and osteoblasts

Over the years, many metal and polymer implants have been developed for internal fracture fixation. However, there are always some problems associated with their application, such as implant loosening or infection. This study describes how the morphology and adhesion of both fibroblasts and osteoblasts to two manufactured commercially pure, medical implant-quality anodized titanium surfaces (TS and TSS), and five modified titanium surfaces (TLF, low friction gray anodized titanium; TIG, nitrogen ion implanted TSS; THY, TSS grafted with sodium hyaluronate; TAST, TSS coated with hydrophilic hydrogel; and TT, tiodized TS) were used to obtain an indication of their relative cytocompatibility and to assess which modified surface could potentially be used in vivo. Small variations were observed both qualitatively and quantitatively in the spreading and adhesion of fibroblasts and osteoblasts to the studied surfaces. Overall, fibroblast spreading and adhesion were greatest on the TIG and TLF surfaces. Osteoblast spreading and adhesion were greatest on TS, TIG, and TAST surfaces. No fibroblasts or osteoblasts were found attached to the THY-coated surfaces. Coating medical implant-quality anodized titanium surfaces (TS and TSS) with a TLF, TAST, or more specifically TIG could probably improve soft tissue adhesion and/or osseointegration of bone in vivo. However, it seemed that a hyaluronic acid coating (THY) has potential as a coating in areas where cell adhesion is undesirable, such as orbital fractures, where muscles should avoid adhesion to the implant, and distal radius fractures, where tendons should freely glide over the implant.

Influence of contrast media (iopromide, ioxaglate, gadolinium-DOTA) on blood viscosity, erythrocyte morphology and platelet function

The influence of contrast media on blood viscosity, erythrocyte morphology and platelet function was studied. In vitro blood was incubated with iopromide (Ultravist), ioxaglate (Hexabrix) or gadolinium-DOTA (Dotarem). Plasma viscosity and whole blood viscosity were measured and the mean erythrocyte volume and morphology were assessed. Platelet aggregation was measured with a PFA-100 instrument. In an ex vivo study on patients receiving these contrast media the same measurements as described above were done. All contrast media increased blood viscosity at high shear rate in a dose dependent manner (e.g. with ioxaglate: from 4.9+/-0.2 mPa x s to 8.6+/-0.5 mPa x s at 160 mg I/ml), decreased low shear viscosity (for ioxaglate: from 44.9+/-2.5 to 27.7+/-4.8 mPa x s), increased plasma viscosity (ioxaglate: from 1.2+/-0.1 to 2.8+/-1.3 mPa x s), decreased the mean erythrocytic volume (ioxaglate: from 89.7+/-1.4 to 79.7+/-2.0 fl) and decreased platelet aggregation. Iopromide induced an echinocytic shape transformation of erythrocytes. Ex vivo a decreased hematocrit and a consecutively decreased whole blood viscosity were found with iopromide and ioxaglate. We conclude that contrast media influenced blood rheology, erythrocytes and platelet aggregation in vitro and ex vivo.

Staphylococcus aureus adhesion to titanium oxide surfaces coated with non-functionalized and peptide-functionalized poly(L-lysine)-grafted-poly(ethylene glycol) copolymers

Implanted biomaterials are coated immediately with host plasma constituents, including extracellular matrix (ECM); this reaction may be undesirable in some cases. Poly(L-lysine)-grafted-poly(ethylene glycol) (PLL-g-PEG) has been shown to spontaneously adsorb from aqueous solution onto metal oxide surfaces, effectively reducing the degree of non-specific adsorption of blood and ECM proteins, and decreasing the adhesion of fibroblastic and osteoblastic cells to the coated surfaces. Cell adhesion through specific peptide-integrin receptors could be restored on surfaces coated with PLL-g-PEG functionalized with peptides of the RGD (Arg-Asp-Gly) type. To date, no study has examined the effect of surface modifications by PLL-g-PEG-based polymers on bacterial adhesion. The ability of Staphylococcus aureus to adhere to the ECM and plasma proteins deposited on biomaterials is a significant factor in the pathogenesis of medical-device-related infections. This study describes methods for visualizing and quantifying the adhesion of S. aureus to smooth and rough (chemically etched) titanium surfaces without and with monomolecular coatings of PLL-g-PEG, PLL-g-PEG/PEG-RGD and PLL-g-PEG/PEG-RDG. The different surfaces were exposed to S. aureus cultures for 1-24h and bacteria surface density was evaluated using scanning electron microscopy and fluorescence microscopy. Coating titanium surfaces with any of the three types of copolymers significantly decreased the adhesion of S. aureus to the surfaces by 89-93% for PLL-g-PEG, and 69% for PLL-g-PEG/PEG-RGD. Therefore, surfaces coated with PLL-g-PEG/PEG-RGD have the ability to attach cells such as fibroblasts and osteoblasts while showing reduced S. aureus adhesion, resulting in a selective biointeraction pattern that may be useful for applications in the area of osteosynthesis, orthopaedic and dental implantology.

Staphylococcus aureus adhesion to different treated titanium surfaces

Staphylococcus aureus is a major pathogen, associated with medical-device related infections. Converting biomaterial surfaces into non-interactive surfaces requires a specific surface/interface design. One approach is to polish the surface, and a second is to coat the surface with an antimicrobial or protein resistant coating. This study showed that polishing a titanium surface or coating titanium with various treatments that decreased the surface's coefficient of friction, had no significant effect on minimising S. aureus adhesion to these surfaces under static conditions in comparison to standard medical grade titanium. The cell promoting coating, TAST, was found to increase the S. aureus density on its surface as expected. The only coating that significantly decreased the density of adhering S. aureus was the titanium surface coated with sodium hyaluronate. Thus such a coating could have potential use as a coating for ostoesynthesis, orthopaedic or dental implants.

An introduction to Staphylococcus aureus, and techniques for identifying and quantifying S. aureus adhesins in relation to adhesion to biomaterials: review

The ability of Staphylococcus aureus to adhere to the extracellular matrix and plasma proteins deposited on biomaterials is a significant factor in the pathogenesis of orthopaedic-device related infections. S. aureus possesses many adhesion proteins on its surface, but it is not known how they interact with each other to form stable interactions with the substrate. A novel method was developed for extracting adhesins from the S. aureus cell wall, which could then be further analysed. The protocol involves using a FastPrep instrument to mechanically disrupt the cell walls resulting in native cell walls. Ionically and covalently bound proteins were then solubilised using sodium dodecyl sulphate (SDS) and lysostaphin, respectively. Western blot analysis of covalently bound proteins using anti-protein A and anti-clumping factor A sera showed that S. aureus produces most surface proteins in early growth, and less in post-exponential and stationary growth. Immuno-gold labelling of protein A, and clumping factor A was observed all over the bacteria and showed no distinct surface distribution pattern. However, this labelling showed expression of surface associated proteins varied in a growth-phase dependent and cell-density dependent manner.

Analysis of Ebh, a 1.1-megadalton cell wall-associated fibronectin-binding protein of Staphylococcus aureus

In order for Staphylococcus aureus to adhere to host extracellular matrix (ECM) substrates, it elicits a wide range of surface proteins. We have characterized a novel approximately 1.1-MDa protein in S. aureus, termed Ebh (for ECM-binding protein homologue), which has homology to other ECM-binding proteins. Ebh consists of several domains, including a large central region with 44 imperfect repeats of 126 amino acids. Expression analysis revealed ebh to be growth phase regulated and repressed by agr. A fragment of the central repeat region of Ebh was cloned, overexpressed, and used in ligand-binding studies to determine Ebh function. The recombinant protein was found to specifically bind human fibronectin. Ebh is produced during human infection since serum samples taken from patients with confirmed S. aureus infections were found to contain anti-Ebh antibodies. Localization studies revealed Ebh to be cell envelope associated and is proposed to form a specialized surface structure involved in cellular adhesion.

Measurement of fibroblast and bacterial detachment from biomaterials using jet impingement

Fibroblast and Staphylococcus aureus detachment strength from orthopaedic alloys and a tissue culture plastic (Thermanox) have been investigated with jet impingement. For S. aureus, unlike fibroblasts, detachment is caused more by pressure than shear. For these biomaterials, detachment strength is much higher for S. aureus than fibroblasts. Comparing materials under equivalent flow conditions, S. aureus attach to stainless steel and titanium with equal strength and more strongly than to Thermanox. For fibroblasts, detachment strength from all materials was similar. Fibroblast detachment strength from these biomaterials substantially decreases with time at equal flow rates and increases with flow rate at equal exposure times. Detachment strength is very similar for 3T3 and L929 fibroblasts on Thermanox for equivalent flow rate/time combinations, though enhanced adhesion of 3T3 cells was often noted for metals. Time effects are less evident for S. aureus. S. aureus adhesion to metals is more affected by flow rate than fibroblast adhesion.

Influence of parathyroid hormone, calcitonin, 1,25(OH)2 cholecalciferol, calcium, and the calcium ionophore A23187 on erythrocyte morphology and blood viscosity

Parathyroid hormone and calcitonin, both endocrine modulators of calcium homeostasis, may influence blood rheology. Parathyroid hormone is known to reduce erythrocyte survival, leading to anemia. Calcitonin has been found to have some vascular effects. We have analyzed the Influence of parathyroid hormone (10(-7) to 10(-10) mol/L), calcitonin (10(-6) to 10(-12) mol/L), 1,25(OH)2 cholecalciferol (10(-7) to 10(-10) mol/L), additional calcium in plasma (+1 and 2 mmol/L), and the calcium lonophore A23187 (50 micromol/L) on erythrocyte morphology and blood viscosity at high shear rate (94 s(-1)) and low shear rate (0.1 s(-1)) in vitro. The loading of erythrocytes with calcium by the ionophore A23187 produced a marked echinocytic shape transformation, an increased blood viscosity at high shear rate caused by decreased deformability of these cells, and a decreased viscosity at low shear rate caused by decreased aggregation of echinocytes. In contrast, increasing plasma calcium concentrations, parathyroid hormone, calcitonin, and 1,25(OH)2 vitamin D3 had no effect on erythrocyte morphology and blood viscosity. We conclude that an increase in intraerythrocytic calcium leads to severe echinocytosis and altered blood viscosity. The endocrine modulators of calcium homeostasis--namely, parathyroid hormone, calcitonin, and 1,25(OH)2 vitamin D3--apparently do not influence intraerythrocytic calcium to a significant degree and have, therefore, no influence on cell morphology and blood viscosity.

Influence of nitrovasodilators and endothelin-1 on rheology of human blood in vitro

1. The shear stress of flowing blood profoundly influences the release of endothelium-dependent vasodilative and constrictive factors. Conversely, the influence of these mediators such as nitric oxide (NO) or endothelin-1 (ET-1) on blood rheology remains elusive. In the present study the influence of nitrovasodilators and ET-1 on red blood cell (RBC) shape and whole blood viscosity were investigated. 2. Incubation of whole blood with sodium-nitroprusside (SNP, 10-5 - 10-2 M), glyceryl trinitrate (GTN, 0.0001 - 0.1 mg mL-1), S-nitroso-N-acetylpenicillamine (SNAP, 10-6 - 10-3 M), and the active metabolite of molsidomine (SIN-1, 10-6 - 10-3 M), but not molsidomine (10-6 - 10-3 M), resulted in significantly increased amounts of methaemoglobin, indicating a relevant interaction with RBCs. Treatment with SNP at 10-2 M induced a marked echinocytosis (morphological index: 2.23+/-0.98 vs -0.17+/-0.10; P<0.001) and increased blood viscosity (haematocrit 45%) at a high shear rate of 94.5 s-1 (6.46+/-0.60 vs 5.07+/-0.35 mPa.s; P<0.01) and a low shear rate of 0.1 s-1 (88.6+/-36.8 vs 42.1+/-11.7 mPa.s; P<0.01). Echinocytosis was probably due to cyanide accumulation. SIN-1 at 10-3 M slightly decreased high shear viscosity (4.88+/-0.28 vs 4. 95+/-0.30 mPa.s; P<0.05). SNAP at 10-3 M slightly increased both high (5.14+/-0.23 vs 5.05+/-0.24 mPa.s; P<0.01) and low shear (53.9+/-7.2 vs 51.2+/-5.9 mPa.s; P<0.05) viscosity. Molsidomine and GTN failed to influence whole blood viscosity. ET-1 (10-9 - 10-6 M) had no effect on RBC shape and viscosity. 3. We conclude that the most important modulators of vascular tone, NO and ET-1, do not affect RBC shape and blood viscosity, which is important from both a physiological and a pharmacological point of view.

Spinal and combined spinal epidural techniques for labor analgesia: clinical application in a small hospital

Providing safe and effective analgesia to laboring parturients presents a challenge to anesthesia providers in small hospitals. The necessary time commitment and additional staff needed to provide coverage for the obstetrical area can strain resources. Offering the spinal opioid block as the first choice for labor analgesia and the combined spinal epidural block in selected cases permits a labor anesthesia service to address the needs of the community hospital. Sufentanil injected into cerebral spinal fluid provides effective analgesia for 124 minutes. Adding 2.5 mg of bupivacaine further increases effective analgesia time to 170 minutes. The combined spinal epidural block offers the advantages of spinal opioid analgesia but with the flexibility of having an epidural catheter in place. The epidural catheter can be dosed intermittently for parturients in whom labor is prolonged, who require surgical manipulation for vaginal delivery, or who require cesarean section for delivery. By offering both blocks to laboring parturients, the appropriate block can be applied in each situation.

Community Recovery After Storm Damage: A Case of Facilitation in Primary Succession

Manipulations of early arriving, fast-growing algal stands, which appeared soon after a severe storm denuded a Southern California marine reef habiatat, indicated that the dense cover protected newly settled kelp plants from excessive damage by grazing fishes. This is an example of refuge facilitation in primary succession after a major natural disturbance, a mechanism that may contribute substantially to the regeneration of a kelp forest.

An infraciliary network in statocyst hair cells

Ultrastructural analysis of the statocyst, a primitive vestibular organ, of the nudibranch mollusc Hermissenda crassicornis, indicates that in addition to the basal foot, there is an infraciliary rootlet system between basal bodies of adjacent sensory cilia. These rootlets project perpendicularly from the basal bodies and parallel to the cell surface in an astral array. A polarity within the network also appears to exist; the array is longest and most extensive on the side of the basal body directed away from the cell centre, but the overall arrangement of the basal bodies indicates a multidirectional sensitivity for each of the 13 sensory cells. This rootlet system, in conjunction with the attachment system of the basal bodies to the cell membrane (button anchors), may serve an integrative function for the mechanical stimuli experienced by sensory cells and/or be involved with their transductive processes by maximizing the stress to, and membrane distortion of, the transductive site caused by weighting of the cilia. Evidence was also obtained for the intracellular synthesis of statoconia by the nonsensory supporting cells.

Antarctic Micrometazoa: Fresh-Water Species in the McMurdo Sound Area

The multicellular microfauna in fresh-water bodies of Ross Island and the nearby continental coast of Victoria Land is strikingly impoverished with respect to major groups. Yet there are thriving populations belonging to the Rotifera, Nematoda, Tardigrada, and Turbellaria.

Synxenic and Attempted Axenic Cultivation of Rotifers

Three species of rotifers have now been grown synxenically and, to a limited extent, axenically. Brachionus variabilis thrives in suitable media containing Chlorella pyrenoidosa and a bacterial species. Lecane inermis and Philodina acuticornis var. odiosa are bacteriophagous, the former doing best with two bacterial species (dixenically), the latter doing well with Escherichia coli alone (monoxenically).