Sodium hypochlorite is more effective than chlorhexidine for eradication of bacterial biofilm of staphylococci and Pseudomonas aeruginosa

PURPOSE

Periprosthetic infection is a common reason for surgical revision. Given the increasing resistance of bacteria to antibiotics (e.g., VRE, 4-MRGN) local antiseptic treatment is gaining in importance. However, no standard guideline-based treatment recommendation is yet available. The aim of this study was to investigate the effectiveness of sodium hypochlorite and chlorhexidine against bacterial biofilms. Furthermore, the toxicity of both antiseptics towards human chondrocytes was examined.

METHODS

Human chondrocytes were isolated, cultivated and treated with sodium hypochlorite and chlorhexidine. The viability of cultures was assessed by determination of cell count, XTT and MTT ELISAs, and fluorescent staining with propidium iodide. Bacterial strains of Staphylococcus aureus, Staphylococcus epidermidis and Pseudomonas aeruginosa were added to liquid media and incubated overnight. After determination of bacterial concentrations polyethylene (PE) devices were inoculated with bacteria for 48 h until biofilms formed. The devices were then washed, treated with antiseptics for 2 and 5 min and subsequently spread on agar plates.

RESULTS

Sodium hypochlorite is more effective than chlorhexidine in penetrating biofilms of S. aureus, S. epidermidis and P. aeruginosa. Both antiseptics are chondrotoxic, but sodium hypochlorite damages human chondrocytes less than chlorhexidine in vitro.

CONCLUSIONS

The findings confirm the effectiveness of sodium hypochlorite and chlorhexidine against bacterial biofilms. Both antiseptics can be recommended for the treatment of periprosthetic infections. The toxic effects of sodium hypochlorite and chlorhexidine towards chondrocytes may mean there is a risk of damage to cartilage tissue.

LEVEL OF EVIDENCE

Controlled experimental study.

S. aureus endocarditis: Clinical aspects and experimental approaches

Infective endocarditis (IE) is a life-threatening disease, caused by septic vegetations and inflammatory foci on the surface of the endothelium and the valves. Due to its complex and often indecisive presentation the mortality rate is still about 30%. Most frequently bacterial microorganisms entering the bloodstream are the underlying origin of the intracardiac infection. While the disease was primarily restricted to younger patients suffering from rheumatic heart streptococci infections, new at risk categories for Staphylococcus (S.) aureus infections arose over the last years. Rising patient age, increasing drug resistance, intensive treatment conditions such as renal hemodialysis, immunosuppression and long term indwelling central venous catheters but also the application of modern cardiac device implants and valve prosthesis have led to emerging incidences of S. aureus IE in health care settings and community. The aetiologic change has impact on the pathophysiology of IE, the clinical presentation and the overall patient management. Despite intensive research on appropriate in vitro and in vivo models of IE and gained knowledge about the fundamental mechanisms in the formation of bacterial vegetations and extracardiac complications, improved understanding of relevant bacterial virulence factors and triggered host immune responses is required to help developing novel antipathogenic treatment strategies and pathogen specific diagnostic markers. In this review, we summarize and discuss the two main areas affected by the changing patient demographics and provide first, recent knowledge about the pathogenic strategies of S. aureus in the induction of IE, including available experimental models of IE used to study host-pathogen interactions and diagnostic and therapeutic targets. In a second focus we present diagnostic (imaging) regimens for patients with S. aureus IE according to current guidelines as well as treatment strategies and surgical recommendations.

Study on the utility of a statewide counselling programme for improving mortality outcomes of patients with Staphylococcus aureus bacteraemia in Thuringia (SUPPORT): a study protocol of a cluster-randomised crossover trial

INTRODUCTION

Staphylococcus aureus bacteraemia (SAB) is a frequent infection with high mortality rates. It requires specific diagnostic and therapeutic management such as prolonged intravenous administration of antibiotics and aggressive search for and control of infectious sources. Underestimation of disease severity frequently results in delayed or inappropriate management of patients with SAB leading to increased mortality rates. According to observational studies, patient counselling by infectious disease consultants (IDC) improves survival and reduces the length of hospital stay as well as complication rates. In many countries, IDC are available only in some tertiary hospitals. In this trial, we aim to demonstrate that the outcome of patients with SAB in small and medium size hospitals that do not employ IDC can be improved by unsolicited ID phone counselling. The SUPPORT trial will be the first cluster-randomised controlled multicentre trial addressing this question.

METHODS AND ANALYSIS

SUPPORT is a single-blinded, multicentre interventional, cluster-randomised, controlled crossover trial with a minimum of 15 centres that will include 250 patients with SAB who will receive unsolicited IDC counselling and 250 who will receive standard of care. Reporting of SAB will be conducted by an electronic real-time blood culture registry established for the German Federal state of Thuringia (ALERTSNet) or directly by participating centres in order to minimise time delay before counselling. Mortality, disease course and complications will be monitored for 90 days with 30-day all-cause mortality rates as the primary outcome. Generalised linear mixed modelling will be used to detect the difference between the intervention sequences. We expect improved outcome of patients with SAB after IDC.

ETHICS AND DISSEMINATION

We obtained ethics approval from the Ethics committee of the Jena University Hospital and from the Ethics committee of the State Chamber of Physicians of Thuringia. Results will be published in a peer-reviewed journal and additionally disseminated through public media.

TRIAL REGISTRATION NUMBER

DRKS00010135.

Cardiac 4D phase-contrast CMR at 9.4 T using self-gated ultra-short echo time (UTE) imaging

BACKGROUND

Time resolved 4D phase contrast (PC) cardiovascular magnetic resonance (CMR) in mice is challenging due to long scan times, small animal ECG-gating and the rapid blood flow and cardiac motion of small rodents. To overcome several of these technical challenges we implemented a retrospectively self-gated 4D PC radial ultra-short echo-time (UTE) acquisition scheme and assessed its performance in healthy mice by comparing the results with those obtained with an ECG-triggered 4D PC fast low angle shot (FLASH) sequence.

METHODS

Cardiac 4D PC CMR images were acquired at 9.4 T in healthy mice using the proposed self-gated radial center-out UTE acquisition scheme (TE/TR of 0.5 ms/3.1 ms) and a standard Cartesian 4D PC imaging sequence (TE/TR of 2.1 ms/5.0 ms) with a four-point Hadamard flow encoding scheme. To validate the proposed UTE flow imaging technique, experiments on a flow phantom with variable pump rates were performed.

RESULTS

The anatomical images and flow velocity maps of the proposed 4D PC UTE technique showed reduced artifacts and an improved SNR (left ventricular cavity (LV): 8.9 ± 2.5, myocardium (MC): 15.7 ± 1.9) compared to those obtained using a typical Cartesian FLASH sequence (LV: 5.6 ± 1.2, MC: 10.1 ± 1.4) that was used as a reference. With both sequences comparable flow velocities were obtained in the flow phantom as well as in the ascending aorta (UTE: 132.8 ± 18.3 cm/s, FLASH: 134.7 ± 13.4 cm/s) and pulmonary artery (UTE: 78.5 ± 15.4 cm/s, FLASH: 86.6 ± 6.2 cm/s) of the animals. Self-gated navigator signals derived from information of the oversampled k-space center were successfully extracted for all animals with a higher gating efficiency of time spent on acquiring gated data versus total measurement time (UTE: 61.8 ± 11.5%, FLASH: 48.5 ± 4.9%).

CONCLUSIONS

The proposed self-gated 4D PC UTE sequence enables robust and accurate flow velocity mapping of the mouse heart in vivo at high magnetic fields. At the same time SNR, gating efficiency, flow artifacts and image quality all improved compared to the images obtained using the well-established, ECG-triggered, 4D PC FLASH sequence.

Evaluation of loop-mediated isothermal amplification for the rapid identification of bacteria and resistance determinants in positive blood cultures

The use of molecular assays to rapidly identify pathogens and resistance genes directly from positive blood cultures (BCs) contribute to shortening the time required for the diagnosis of bloodstream infections. In this work, loop-mediated isothermal amplification (LAMP) assays have been examined for their potential use in BC diagnosis. Three different assays were applied. The commercially available eazyplex® MRSA test detects Staphylococcus aureus, S. epidermidis, mecA, and mecC. Two in-house assays [Gram-positive (GP) and Gram-negative (GN)] have been developed for the detection of streptococci, enterococci, vanA, vanB, Pseudomonas spp., Enterobacteriaceae, and the bla _CTX-M family. A total of 370 positive BCs were analyzed. LAMP test results were obtained within 30 min, including sample preparation. Amplification was measured by real-time fluorescence detection. The threshold time for fluorescence intensity values ranged from 6.25 to 13.75 min. The specificity and sensitivity of the assays varied depending on the target. Overall, from 87.7% of BCs, true-positive results were obtained, compared to routine standard diagnosis. Twenty-one tests were true-negative because of the lack of an appropriate target (5.7%). The concordance of positive test results for resistance genes with subsequent antibiotic susceptibility testing was 100%. From 15 BC bottles with mixed cultures, eazyplex® assays produced correct results in 73% of the cases. This study shows that LAMP assays are fast and cost-saving tools for rapid BC testing in order to expedite the diagnostic report and improve the antibiotic stewardship for sepsis patients.

Post-invasion events after infection with Staphylococcus aureus are strongly dependent on both the host cell type and the infecting S. aureus strain

Host cell invasion is a major feature of Staphylococcus aureus and contributes to infection development. The intracellular metabolically active bacteria can induce host cell activation and death but they can also persist for long time periods. In this study a comparative analysis was performed of different well-characterized S. aureus strains in their interaction with a variety of host cell types. Staphylococcus aureus (strains 6850, USA300, LS1, SH1000, Cowan1) invasion was compared in different human cell types (epithelial and endothelial cells, keratinocytes, fibroblasts, osteoblasts). The number of intracellular bacteria was determined, cell inflammation was investigated, as well as cell death and phagosomal escape of bacteria. To explain strain-dependent differences in the secretome, a proteomic approach was used. Barrier cells took up high amounts of bacteria and were killed by aggressive strains. These strains expressed high levels of toxins, and possessed the ability to escape from phagolysosomes. Osteoblasts and keratinocytes ingested less bacteria, and were not killed, even though the primary osteoblasts were strongly activated by S. aureus. In all cell types S. aureus was able to persist. Strong differences in uptake, cytotoxicity, and inflammatory response were observed between primary cells and their corresponding cell lines, demonstrating that cell lines reflect only partially the functions and physiology of primary cells. This study provides a contribution for a better understanding of the pathomechanisms of S. aureus infections. The proteomic data provide important basic knowledge on strains commonly used in the analysis of S. aureus-host cell interaction.

Staphylococcus aureus develops increased resistance to antibiotics by forming dynamic small colony variants during chronic osteomyelitis

OBJECTIVES

Staphylococcus aureus osteomyelitis often develops to chronicity despite antimicrobial treatments that have been found to be susceptible in in vitro tests. The complex infection strategies of S. aureus, including host cell invasion and intracellular persistence via the formation of dynamic small colony variant (SCV) phenotypes, could be responsible for therapy-refractory infection courses.

METHODS

To analyse the efficacy of antibiotics in the acute and chronic stage of bone infections, we established long-term in vitro and in vivo osteomyelitis models. Antibiotics that were tested include β-lactams, fluoroquinolones, vancomycin, linezolid, daptomycin, fosfomycin, gentamicin, rifampicin and clindamycin.

RESULTS

Cell culture infection experiments revealed that all tested antibiotics reduced bacterial numbers within infected osteoblasts when treatment was started immediately, whereas some antibiotics lost their activity against intracellular persisting bacteria. Only rifampicin almost cleared infected osteoblasts in the acute and chronic stages. Furthermore, we detected that low concentrations of gentamicin, moxifloxacin and clindamycin enhanced the formation of SCVs, and these could promote chronic infections. Next, we treated a murine osteomyelitis model in the acute and chronic stages. Only rifampicin significantly reduced the bacterial load of bones in the acute phase, whereas cefuroxime and gentamicin were less effective and gentamicin strongly induced SCV formation. During chronicity none of the antimicrobial compounds tested showed a beneficial effect on bone deformation or reduced the numbers of persisting bacteria.

CONCLUSIONS

In all infection models rifampicin was most effective at reducing bacterial loads. In the chronic stage, particularly in the in vivo model, many tested compounds lost activity against persisting bacteria and some antibiotics even induced SCV formation.

Cloning and expression of Clostridium difficile toxin A gene (tcdA) by PCR amplification and use of an expression vector

Toxigenic Clostridium difficile isolates harbor a 19 kb pathogenicity locus that encodes the genes for toxins A and B. Toxins A and B are among the largest known bacterial toxins expressing potent cytotoxicity and enterotoxicity, and thus the major virulence factors in C. difficile associated diarrhea. Cloning and sequencing of toxin genes is of interest for studies of molecular pathogenesis. We report the amplification and cloning of the complete toxin A gene into an Escherichia coli expression vector. Ten clones analyzed contained the complete toxin A gene. Four of these clones showed cytotoxic activity in cell culture, and were positive for toxin A as determined by ELISA. Toxin A expression was confirmed by Western immunoblot analysis. The presence of cytotoxic activity in cell culture suggests that toxin A activity is independent of other genes in the pathogenicity locus.

Serial CEA and CA 15-3 measurements during follow-up of breast cancer patients

OBJECTIVE

CEA and CA 15-3 are adequate parameters for the early diagnosis of metastases in breast cancer patients. During the last years serial marker measurements have been discussed controversely and moreover accused of frightening breast cancer patients in the sense of a tumor marker terror. Therefore we evaluated the acceptance and practicability of an intense follow-up program including monthly measurements of CEA and CA 15-3.

MATERIALS AND METHODS

Between 1985 and 1995. 547 breast cancer patients were asked to give blood samples every four weeks for CEA and CA 15-3 measurements. In a field research study using a half-standardized interview by telephone we evaluated the acceptance of serial marker measurements in defined aspects: personal acceptance, blood sampling intervals, form of information, role of the home practitioner, motivation.

RESULTS

280 patients could be analyzed for the acceptance of this follow-up program. 52% of this patient group accepted serial tumor marker measurements, while 48% did not. 99% of the participating patients agreed to monthly blood sampling intervals compared to only 41% of the non-participating patients. 64% of the analyzed patients would have preferred both written and personal information about the role of CEA and CA 15-3 and this kind of follow-up program. Only in 6% of the participating patients the home practitioner had a negative attitude towards monthly tumor marker measurements compared to 36% in non-participating patients. Moreover serial marker measurements led to a feeling of security and reassurance in 85% of the patients.

CONCLUSION

CEA and CA 15-3 measurements are adequate and accepted instruments for the follow-up and early diagnosis of metastases in breast cancer patients. If patients got detailed information and support from their home practitioner, serial CEA and CA 15-3 measurements could lead to a feeling of security in most of the patients.

Safety and cost effectiveness of a 10 x 10(9)/L trigger for prophylactic platelet transfusions compared with the traditional 20 x 10(9)/L trigger: a prospective comparative trial in 105 patients with acute myeloid leukemia

In 105 consecutive patients with de novo acute myeloid leukemia (French-American-British M3 excluded), we compared prospectively the risk of bleeding complications, the number of platelet and red blood cell transfusions administered, and the costs of transfusions using two different prophylactic platelet transfusion protocols. Two hundred sixteen cycles of induction or consolidation chemotherapy and 3,843 days of thrombocytopenia less than 25 x 10(9)/L were evaluated. At the start of the study, each of the 17 participating centers decided whether they would use a 10 x 10(9)/L prophylactic platelet transfusion trigger (group A/8 centers) or a 20 x 10(9)/L trigger (group B/9 centers). Bleeding complications (World Health Organization grade 2-4) during treatment cycles were comparable in the two groups: 20 of 110 (18%) in group A and 18 of 106 (17%) in group B (P = .8). Serious bleeding events (grade 3-4) were generally not related to the patient's platelet count but were the consequence of local lesions and plasma coagulation factor deficiencies due to sepsis. Eighty-six percent of the serious bleeding episodes occurred during induction chemotherapy. No patient died of a bleeding complication. There were no significant differences in the number of red blood cell transfusions administered between the two groups, but there were significant differences in the number of platelet transfusions administered per treatment cycle: pooled random donor platelet concentrates averaged 15.4 versus 25.4 (P < .01) and apheresis platelets averaged 3.0 versus 4.8 (P < .05) for group A versus group B, respectively. This resulted in the cost of platelet therapy being one third lower in group A compared with group B without any associated increase in bleeding risk.

[Intensive post-remission therapy in acute myeloid leukemia. Results of a prospective comparative study by the South Germany Hemoblastosis Group]

BACKGROUND

To study intensive postremission therapy in adult patients with acute myeloid leukemia myeloablative therapy followed by allogeneic or unpurged autologous bone marrow transplantation (BMT) was compared with high-dose cytosine-arabinoside/daunorubicin (HDAC) consolidation.

PATIENTS AND METHODS

148 de novo AML patients of maximum 50 years (median 36 years, range 16 to 50) were enrolled in the trial. Following induction and early consolidation chemotherapy consisting of daunorubicin, cytosine-arabinoside and VP-16 (DAV), patients with an HLA-identical sibling underwent allogeneic BMT. The other patients received (by randomization or patient's decision) either HDAC or high-dose busulfan plus cyclophosphamide followed by autologous BMT.

RESULTS

Hundred and five 105 (70.9%) patients achieved a complete remission. The event-free survival rates after intensive postremission therapy after 72 months were: after BMT (24 patients) 62% (95% confidence interval +/- 19%), after HDAC (44 patients) 36 +/- 16% and after autologous BMT (12 patients) 18 +/- 22%. Thus allogeneic BMT was superior to autologous BMT (p = 0.04), as was HDAC compared to autologous BMT, although not significantly so (p = 0.15). Patients receiving 2 cycles of HDAC had a better 6-year event-free survival rate (47%) and a lower relapse rate (50%) than patients who received only 1 course (29% and 70% respectively).

CONCLUSIONS

High-dose busulfan/cyclophosphamide followed by unpurged autologous BMT early after achieving CR had no advantage over high-dose ara-c/daunorubicin. Two cycles of HDAC yielded better results than 1 cycle. The highest event-free survival rate was reached with myeloablative therapy followed by allogeneic BMT.

[Hand and foot purpura ("glove and sock" syndrome) caused by parvovirus B19 infection]

After a period of general nonspecific symptoms (weakness; nocturnal sweating) for a few days a 29-year-old man suddenly developed a purpura-like rash on both hands and feet ("glove and sock") with mild itching and oedema. A blood count demonstrated leukopenia (2100/microliters) with neutropenia (1100/microliters), thrombocytopenia (81,000/microliters) and reticulocytopenia (1/1000), while haemoglobin content was normal. The bone-marrow showed almost complete reduction of erythropoiesis with the presence of giant proerythroblasts. Granulopoiesis and megakaryopoiesis were unremarkable. Positive tests for IgM and IgG antibodies against parvovirus B19 established the diagnosis of infection with this organism. The rash, blood picture and bone-marrow changes all regressed spontaneously, without any treatment, within a week. The petechial or purpuric "glove and sock" syndrome may be a special form of parvovirus B19 infection.

[Sequential alternating chemotherapy of highly malignant non-Hodgkin's lymphomas with VIM-Bleo and CHOP. Initial results]

54 patients with high grade malignant NHL (stage II 19, stage III 10, stage IV 25 patients, medium age 56 years) were treated in an ongoing study with the VIM-Bleo/CHOP-regimen: Etoposide 100 mg/m2 i.v. days 1-3, Ifosfamide 1.5 g/m2 i.v. days 1-5 with Mesna for prophylaxis of cystitis, Methotrexate 30 mg/m2 i.v. day 3, Bleomycin 10 mg i.v. days 8 and 15, Cyclophosphamide 750 mg/m2 day 22, Adriamycin 50 mg/m2 day 22, Vincristine 1.4 mg/m2 day 22 and prednisolone 100 mg po days 1-5 and 22-26. Cycles were repeated on day 43. After completion of therapy (4 cycles of VIM-Bleo/CHOP), 27 out of 35 patients (77%) were in complete remission. 6 patients (17%) had a partial remission and 2 (6%) progressive disease. After a median follow up of 8 months so far, 6 relapses occurred. Probability of survival at 12 months is 82%. Toxicity of treatment was very low with leukopenia being the main side effect. Only in 2 cycles (3%), major infections were observed. Nausea and vomiting were severe only in 4% of patients. We conclude that VIM-Bleo/CHOP is a well tolerated regimen with good remission rates in high grade malignant NHL. However, longer follow up is necessary for a final evaluation.

[Alfentanil in routine clinical use. A study of 50 patients]

Alfentanil in combination with etomidate and N2O/O2 was given to 50 patients as single dosage (0.024 mg/kg b.w.) or with repeated injections for surgical interventions up to 90 minutes duration. In 68% of these cases sufficient analgesia was obtained. The most frequent side-effects were rigidity of the thorax (54%), quick, extensive changes in blood pressure (32%) and bradycardia (28%). The recovery phase was very short, postoperative sickness and vomiting were seen in 6% of all cases. Still, after repeated injections phases with prolonged sleep can appear. While using Alfentanil, exact monitoring is necessary, as quick and unexpected changes of blood pressure and pulse can appear.

Plasma concentration and E.E.G. after various regimens of etomidate

Etomidate was injected i.v. within 10 or 60 s at various doses. After etomidate 0.3 mg kg-1 the plasma concentration was 1.6 micrograms ml-1 at 1 min after the end of injection. For about 7 min a good hypnotic effect (stages C0-D2) was observed on the e.e.g. recording. For surgical procedures, however, a combination with analgesic drugs appeared to be necessary. When the dose of etomidate was increased (0.1-0.4 mg kg-1) a linear increase in plasma concentration and slow e.e.g. activity was observed concomitantly. Anaesthesia could be prolonged with additional injections or with continuous infusion. Each additional injection produced a steep increase in concentration of short duration with marked deepening of hypnosis. The infusion induced only a moderate increase in plasma concentration, whereas the depth of sleep during the period of infusion remained nearly the same. E.e.g. changes induced by etomidate are similar to those after barbiturates and other i.v. anaesthetics.