Economic evaluation of endometrial scratching before the second IVF/ICSI treatment: a cost-effectiveness analysis of a randomized controlled trial (SCRaTCH trial).

STUDY QUESTION: Is a single endometrial scratch prior to the second fresh IVF/ICSI treatment cost-effective compared to no scratch, when evaluated over a 12-month follow-up period? SUMMARY ANSWER: The incremental cost-effectiveness ratio (ICER) for an endometrial scratch was €6524 per additional live birth, but due to uncertainty regarding the increase in live birth rate this has to be interpreted with caution. WHAT IS KNOWN ALREADY: Endometrial scratching is thought to improve the chances of success in couples with previously failed embryo implantation in IVF/ICSI treatment. It has been widely implemented in daily practice, despite the lack of conclusive evidence of its effectiveness and without investigating whether scratching allows for a cost-effective method to reduce the number of IVF/ICSI cycles needed to achieve a live birth. STUDY DESIGN, SIZE, DURATION: This economic evaluation is based on a multicentre randomized controlled trial carried out in the Netherlands (SCRaTCH trial) that compared a single scratch prior to the second IVF/ICSI treatment with no scratch in couples with a failed full first IVF/ICSI cycle. Follow-up was 12 months after randomization.Economic evaluation was performed from a healthcare and societal perspective by taking both direct medical costs and lost productivity costs into account. It was performed for the primary outcome of biochemical pregnancy leading to live birth after 12 months of follow-up as well as the secondary outcome of live birth after the second fresh IVF/ICSI treatment (i.e. the first after randomization). To allow for worldwide interpretation of the data, cost level scenario analysis and sensitivity analysis was performed. PARTICIPANTS/MATERIALS, SETTING, METHODS: From January 2016 until July 2018, 933 women with a failed first IVF/ICSI cycle were included in the trial. Data on treatment and pregnancy were recorded up until 12 months after randomization, and the resulting live birth outcomes (even if after 12 months) were also recorded.Total costs were calculated for the second fresh IVF/ICSI treatment and for the full 12 month period for each participant. We included costs of all treatments, medication, complications and lost productivity costs. Cost-effectiveness analysis was carried out by calculating ICERs for scratch compared to control. Bootstrap resampling was used to estimate the uncertainty around cost and effect differences and ICERs. In the sensitivity and scenario analyses, various unit costs for a single scratch were introduced, amongst them, unit costs as they apply for the United Kingdom (UK). MAIN RESULTS AND THE ROLE OF CHANCE: More live births occurred in the scratch group, but this also came with increased costs over a 12-month period. The estimated chance of a live birth after 12 months of follow-up was 44.1% in the scratch group compared to 39.3% in the control group (risk difference 4.8%, 95% CI -1.6% to +11.2%). The mean costs were on average €283 (95% CI: -€299 to €810) higher in the scratch group so that the point average ICER was €5846 per additional live birth. The ICER estimate was surrounded with a high level of uncertainty, as indicated by the fact that the cost-effectiveness acceptability curve (CEAC) showed that there is an 80% chance that endometrial scratching is cost-effective if society is willing to pay ∼€17 500 for each additional live birth. LIMITATIONS, REASONS FOR CAUTION: There was a high uncertainty surrounding the effects, mainly in the clinical effect, i.e. the difference in the chance of live birth, which meant that a single straightforward conclusion could not be ascertained as for now. WIDER IMPLICATIONS OF THE FINDINGS: This is the first formal cost-effectiveness analysis of endometrial scratching in women undergoing IVF/ICSI treatment. The results presented in this manuscript cannot provide a clear-cut expenditure for one additional birth, but they do allow for estimating costs per additional live birth in different scenarios once the clinical effectiveness of scratching is known. As the SCRaTCH trial was the only trial with a follow-up of 12 months, it allows for the most complete estimation of costs to date. STUDY FUNDING/COMPETING INTEREST(S): This study was funded by ZonMW, the Dutch organization for funding healthcare research. A.E.P.C., F.J.M.B., E.R.G. and C.B. L. reported having received fees or grants during, but outside of, this trial. TRIAL REGISTRATION NUMBER: Netherlands Trial Register (NL5193/NTR 5342).

Is home-based monitoring of ovulation to time frozen embryo transfer a cost-effective alternative for hospital-based monitoring of ovulation? Study protocol of the multicentre, non-inferiority Antarctica-2 randomised controlled trial.

STUDY QUESTION: The objective of this trial is to compare the effectiveness and costs of true natural cycle (true NC-) frozen embryo transfer (FET) using urinary LH tests to modified NC-FET using repeated ultrasound monitoring and ovulation trigger to time FET in the NC. Secondary outcomes are the cancellation rates of FET (ovulation before hCG or no dominant follicle, no ovulation by LH urine test, poor embryo survival), pregnancy outcomes (miscarriage rate, clinical pregnancy rates, multiple ongoing pregnancy rates, live birth rates, costs) and neonatal outcomes (including gestational age, birthweight and sex, congenital abnormalities or diseases of babies born). WHAT IS KNOWN ALREADY: FET is at the heart of modern IVF. To allow implantation of the thawed embryo, the endometrium must be prepared either by exogenous oestrogen and progesterone supplementation (artificial cycle (AC)-FET) or by using the NC to produce endogenous oestradiol before and progesterone after ovulation to time the transfer of the thawed embryo (NC-FET). During an NC-FET, women visit the hospital repeatedly and receive an ovulation trigger to time FET (i.e. modified (m)NC-FET or hospital-based monitoring). From the woman's point of view, a more natural approach using home-based monitoring of the ovulation with LH urine tests to allow a natural ovulation to time FET may be desired (true NC-FET or home-based monitoring). STUDY DESIGN SIZE DURATION: This is a multicentre, non-inferiority prospective randomised controlled trial design. Consenting women will undergo one FET cycle using either true NC-FET or mNC-FET based on randomisation. PARTICIPANTS/MATERIALS SETTING METHODS: Based on our sample size calculation, the study group will consist of 1464 women between 18 and 45 years old who are scheduled for FET. Women with anovulatory cycles, women who need ovulation induction and women with a contra indication for pregnancy will be excluded. The primary outcome is ongoing pregnancy. Secondary outcomes are cancellation rates of FET, pregnancy outcomes (including miscarriage rate, clinical pregnancy, multiple pregnancy rate and live birth rate). Costs will be estimated by counting resource use and calculating unit prices. STUDY FUNDING/COMPETING INTERESTS: The study received a grant from the Dutch Organisation for Health Research and Development (ZonMw 843002807; www.zonmw.nl). ZonMw has no role in the design of the study, collection, analysis, and interpretation of data or writing of the manuscript. F.B. reports personal fees from member of the external advisory board for Merck Serono, grants from Research support grant Merck Serono, outside the submitted work. A.E.P.C. reports and Unrestricted grant of Ferring B.V. to the Center for Reproductive medicine, no personal fee. Author up-to-date on Hyperthecosis. Congress meetings 2019 with Ferring B.V. and Theramex B.V. M.G. reports Department research and educational grants from Guerbet, Merck and Ferring (location VUMC) outside the submitted work. E.R.G. reports personal fees from Titus Health Care, outside the submitted work. C.B.L. reports grants from Ferring, grants from Merck, from Guerbet, outside the submitted work. The other authors have none to declare. TRIAL REGISTRATION NUMBER: Dutch Trial Register (Trial NL6414 (NTR6590), https://www.trialregister.nl/). TRIAL REGISTRATION DATE: 23 July 2017. DATE OF FIRST PATIENT'S ENROLMENT: 10 April 2018.

Endometrial scratching in women with one failed IVF/ICSI cycle-outcomes of a randomised controlled trial (SCRaTCH).

STUDY QUESTION: Does endometrial scratching in women with one failed IVF/ICSI treatment affect the chance of a live birth of the subsequent fresh IVF/ICSI cycle? SUMMARY ANSWER: In this study, 4.6% more live births were observed in the scratch group, with a likely certainty range between -0.7% and +9.9%. WHAT IS KNOWN ALREADY: Since the first suggestion that endometrial scratching might improve embryo implantation during IVF/ICSI, many clinical trials have been conducted. However, due to limitations in sample size and study quality, it remains unclear whether endometrial scratching improves IVF/ICSI outcomes. STUDY DESIGN, SIZE, DURATION: The SCRaTCH trial was a non-blinded randomised controlled trial in women with one unsuccessful IVF/ICSI cycle and assessed whether a single endometrial scratch using an endometrial biopsy catheter would lead to a higher live birth rate after the subsequent IVF/ICSI treatment compared to no scratch. The study took place in 8 academic and 24 general hospitals. Participants were randomised between January 2016 and July 2018 by a web-based randomisation programme. Secondary outcomes included cumulative 12-month ongoing pregnancy leading to live birth rate. PARTICIPANTS/MATERIALS, SETTING, METHODS: Women with one previous failed IVF/ICSI treatment and planning a second fresh IVF/ICSI treatment were eligible. In total, 933 participants out of 1065 eligibles were included (participation rate 88%). MAIN RESULTS AND THE ROLE OF CHANCE: After the fresh transfer, 4.6% more live births were observed in the scratch compared to control group (110/465 versus 88/461, respectively, risk ratio (RR) 1.24 [95% CI 0.96-1.59]). These data are consistent with a true difference of between -0.7% and +9.9% (95% CI), indicating that while the largest proportion of the 95% CI is positive, scratching could have no or even a small negative effect. Biochemical pregnancy loss and miscarriage rate did not differ between the two groups: in the scratch group 27/153 biochemical pregnancy losses and 14/126 miscarriages occurred, while this was 19/130 and 17/111 for the control group (RR 1.21 (95% CI 0.71-2.07) and RR 0.73 (95% CI 0.38-1.40), respectively). After 12 months of follow-up, 5.1% more live births were observed in the scratch group (202/467 versus 178/466), of which the true difference most likely lies between -1.2% and +11.4% (95% CI). LIMITATIONS, REASONS FOR CAUTION: This study was not blinded. Knowledge of allocation may have been an incentive for participants allocated to the scratch group to continue treatment in situations where they may otherwise have cancelled or stopped. In addition, this study was powered to detect a difference in live birth rate of 9%. WIDER IMPLICATIONS OF THE FINDINGS: The results of this study are an incentive for further assessment of the efficacy and clinical implications of endometrial scratching. If a true effect exists, it may be smaller than previously anticipated or may be limited to specific groups of women undergoing IVF/ICSI. Studying this will require larger sample sizes, which will be provided by the ongoing international individual participant data-analysis (PROSPERO CRD42017079120). At present, endometrial scratching should not be performed outside of clinical trials. STUDY FUNDING/COMPETING INTEREST(S): This study was funded by ZonMW, the Dutch organisation for funding healthcare research. J.S.E. Laven reports grants and personal fees from AnshLabs (Webster, Tx, USA), Ferring (Hoofddorp, The Netherlands) and Ministry of Health (CIBG, The Hague, The Netherlands) outside the submitted work. A.E.P. Cantineau reports 'other' from Ferring BV, personal fees from Up to date Hyperthecosis, 'other' from Theramex BV, outside the submitted work. E.R. Groenewoud reports grants from Titus Health Care during the conduct of the study. A.M. van Heusden reports personal fees from Merck Serono, personal fees from Ferring, personal fees from Goodlife, outside the submitted work. F.J.M. Broekmans reports personal fees as Member of the external advisory board for Ferring BV, The Netherlands, personal fees as Member of the external advisory board for Merck Serono, The Netherlands, personal fees as Member of the external advisory for Gedeon Richter, Belgium, personal fees from Educational activities for Ferring BV, The Netherlands, grants from Research support grant Merck Serono, grants from Research support grant Ferring, personal fees from Advisory and consultancy work Roche, outside the submitted work. C.B. Lambalk reports grants from Ferring, grants from Merck, grants from Guerbet, outside the submitted work. TRIAL REGISTRATION NUMBER: Registered in the Netherlands Trial Register (NL5193/NTR 5342). TRIAL REGISTRATION DATE: 31 July 2015. DATE OF FIRST PATIENT'S ENROLMENT: 26 January 2016.

The SUPER study: protocol for a randomised controlled trial comparing follicle-stimulating hormone and clomiphene citrate for ovarian stimulation in intrauterine insemination.

OBJECTIVE: To study the effectiveness of four cycles of intrauterine insemination (IUI) with ovarian stimulation (OS) by follicle-stimulating hormone (FSH) or by clomiphene citrate (CC), and adherence to strict cancellation criteria. SETTING: Randomised controlled trial among 22 secondary and tertiary fertility clinics in the Netherlands. PARTICIPANTS: 732 women from couples diagnosed with unexplained or mild male subfertility and an unfavourable prognosis according to the model of Hunault of natural conception. INTERVENTIONS: Four cycles of IUI-OS within a time horizon of 6 months comparing FSH 75 IU with CC 100 mg. The primary outcome is ongoing pregnancy conceived within 6 months after randomisation, defined as a positive heartbeat at 12 weeks of gestation. Secondary outcomes are cancellation rates, number of cycles with a monofollicular or with multifollicular growth, number of follicles >14 mm at the time of ovulation triggering, time to ongoing pregnancy, clinical pregnancy, miscarriage, live birth and multiple pregnancy. We will also assess if biomarkers such as female age, body mass index, smoking status, antral follicle count and endometrial aspect and thickness can be used as treatment selection markers. ETHICS AND DISSEMINATION: The study has been approved by the Medical Ethical Committee of the Academic Medical Centre and from the Dutch Central Committee on Research involving Human Subjects (CCMO NL 43131-018-13). Results will be disseminated through peer-reviewed publications and presentations at international scientific meetings. TRIAL REGISTRATION NUMBER: NTR4057.

Cost-effectiveness analysis of lifestyle intervention in obese infertile women.

STUDY QUESTION: What is the cost-effectiveness of lifestyle intervention preceding infertility treatment in obese infertile women? SUMMARY ANSWER: Lifestyle intervention preceding infertility treatment as compared to prompt infertility treatment in obese infertile women is not a cost-effective strategy in terms of healthy live birth rate within 24 months after randomization, but is more likely to be cost-effective using a longer follow-up period and live birth rate as endpoint. WHAT IS KNOWN ALREADY: In infertile couples, obesity decreases conception chances. We previously showed that lifestyle intervention prior to infertility treatment in obese infertile women did not increase the healthy singleton vaginal live birth rate at term, but increased natural conceptions, especially in anovulatory women. Cost-effectiveness analyses could provide relevant additional information to guide decisions regarding offering a lifestyle intervention to obese infertile women. STUDY DESIGN, SIZE, DURATION: The cost-effectiveness of lifestyle intervention preceding infertility treatment compared to prompt infertility treatment was evaluated based on data of a previous RCT, the LIFEstyle study. The primary outcome for effectiveness was the vaginal birth of a healthy singleton at term within 24 months after randomization (the healthy live birth rate). The economic evaluation was performed from a hospital perspective and included direct medical costs of the lifestyle intervention, infertility treatments, medication and pregnancy in the intervention and control group. In addition, we performed exploratory cost-effectiveness analyses of scenarios with additional effectiveness outcomes (overall live birth within 24 months and overall live birth conceived within 24 months) and of subgroups, i.e. of ovulatory and anovulatory women, women <36 years and ≥36 years of age and of completers of the lifestyle intervention. Bootstrap analyses were performed to assess the uncertainty surrounding cost-effectiveness. PARTICIPANTS/MATERIALS, SETTINGS, METHODS: Infertile women with a BMI of ≥29 kg/m2 (no upper limit) were allocated to a 6-month lifestyle intervention programme preceding infertility treatment (intervention group, n = 290) or to prompt infertility treatment (control group, n = 287). After excluding women who withdrew informed consent or who were lost to follow-up we included 280 women in the intervention group and 284 women in the control group in the analysis. MAIN RESULTS AND THE ROLE OF CHANCE: Total mean costs per woman in the intervention group within 24 months after randomization were €4324 (SD €4276) versus €5603 (SD €4632) in the control group (cost difference of -€1278, P < 0.05). Healthy live birth rates were 27 and 35% in the intervention group and the control group, respectively (effect difference of -8.1%, P < 0.05), resulting in an incremental cost-effectiveness ratio of €15 845 per additional percentage increase of the healthy live birth rate. Mean costs per healthy live birth event were €15 932 in the intervention group and €15 912 in the control group. Exploratory scenario analyses showed that after changing the effectiveness outcome to all live births conceived within 24 months, irrespective of delivery within or after 24 months, cost-effectiveness of the lifestyle intervention improved. Using this effectiveness outcome, the probability that lifestyle intervention preceding infertility treatment was cost-effective in anovulatory women was 40%, in completers of the lifestyle intervention 39%, and in women ≥36 years 29%. LIMITATIONS, REASONS FOR CAUTION: In contrast to the study protocol, we were not able to perform the analysis from a societal perspective. Besides the primary outcome of the LIFEstyle study, we performed exploratory analyses using outcomes observed at longer follow-up times and we evaluated subgroups of women; the trial was not powered on these additional outcomes or subgroup analyses. WIDER IMPLICATIONS OF THE FINDINGS: Cost-effectiveness of a lifestyle intervention is more likely for longer follow-up times, and with live births conceived within 24 months as the effectiveness outcome. This effect was most profound in anovulatory women, in completers of the lifestyle intervention and in women ≥36 years old. This result indicates that the follow-up period of lifestyle interventions in obese infertile women is important. The scenario analyses performed in this study suggest that offering and reimbursing lifestyle intervention programmes in certain patient categories may be cost-effective and it provides directions for future research in this field. STUDY FUNDING/COMPETING INTEREST(S): The study was supported by a grant from ZonMw, the Dutch Organization for Health Research and Development (50-50110-96-518). The department of obstetrics and gynaecology of the UMCG received an unrestricted educational grant from Ferring pharmaceuticals BV, The Netherlands. B.W.J.M. is a consultant for ObsEva, Geneva. TRIAL REGISTRATION NUMBER: The LIFEstyle RCT was registered at the Dutch trial registry (NTR 1530). http://www.trialregister.nl/trialreg/admin/rctview.asp?TC = 1530.

[Can I still get pregnant? Options for fertility preservation in young women diagnosed with cancer]. / Kan ik nog zwanger worden?

- In 2015 around 2300 women under the age of 40 years were diagnosed with cancer in the Netherlands.- Cancer treatment can have a negative effect on fertility.- Due to improving survival rates, discussing this effect and the options for fertility preservation has become an important part of counselling these patients.- Cryopreservation of oocytes and embryos is standard procedure in fertility preservation in the Netherlands.- Cryopreservation of ovarian tissue is a new, rapidly-developing technique. Recently, the first child following autotransplantation of thawed ovarian tissue was born in the Netherlands.- If gonadotoxic treatment has to be given, it is important to talk well in advance with the patient about fertility preservation.

Heat inactivation data for Mycobacterium avium subsp. paratuberculosis: implications for interpretation.

AIMS: We discuss several factors that are critical for heat inactivation experiments and which should be taken into account for future research. METHODS AND RESULTS: On the basis of examples from the literature we discuss critical factors influencing the calculated heat inactivation of Mycobacterium avium subsp. paratuberculosis (MAP). Furthermore, using a modelling approach, we show that tailing of the inactivation curve of MAP is caused by the presence of cell clumps and not by a more heat-resistant cell fraction. CONCLUSIONS: The experimental conditions of the MAP heat inactivation studies of different research groups vary significantly and lead to considerable differences in results and conclusions. Therefore, a more consensual approach should be employed in future studies. In addition, our model on clumping of MAP can be used to predict the decimal reduction of MAP during heat treatment and to study the effect of clumping on other lethal effects. SIGNIFICANCE AND IMPACT OF THE STUDY: We discuss several factors that should be carefully considered in heat resistance experiments. This is essential for a thorough interpretation of results from experiments and should be given proper attention in future experiments and publications on this topic.

Analysis of intestinal flora development in breast-fed and formula-fed infants by using molecular identification and detection methods.

BACKGROUND: An obvious difference between breast-fed and formula-fed newborn infants is the development of the intestinal flora, considered to be of importance for protection against harmful micro-organisms and for the maturation of the intestinal immune system. In this study, novel molecular identification methods were used to verify the data obtained by traditional culture methods and to validate the culture independent fluorescent in situ hybridization (FISH) technique. METHODS: From each of six breast-fed and six formula-fed newborn infants, six fecal samples were obtained during the first 20 days of life. The microbial compositions of the samples were analyzed by culturing on specific media and by FISH, by using specific 16S rRNA-targeted oligonucleotide probes. The colonies growing on the media were identified by random amplified polymorphic DNA pattern analysis and by polymerase chain reaction amplification and subsequent analysis of the 16S rRNA gene. RESULTS: Molecular identification of the colonies showed that the selective media are insufficiently selective and unsuitable for quantitative analyses. Qualitative information from the culturing results combined with the data obtained by the FISH technique revealed initial colonization in all infants of a complex (adult-like) flora. After this initial colonization, a selection of bacterial strains began in all infants, in which Bifidobacterium strains played an important role. In all breast-fed infants, bifidobacteria become dominant, whereas in most formula-fed infants similar amounts of Bacteroides and bifidobacteria (approximately 40%) were found. The minor components of the fecal samples from breast-fed infants were mainly lactobacilli and streptococci; samples from formula-fed infants often contained staphylococci, Escherichia coli, and clostridia. CONCLUSIONS: This study confirms the differences in development of intestinal flora between breast-fed and formula-fed infants. The results obtained from the FISH technique were consistent. Although the repertoire of probes for this study was not yet complete, the FISH technique will probably become the method of reference for future studies designed to develop breast-fed-like intestinal flora in formula-fed infants.

Characteristics of pedicle screw loading. Effect of surgical technique on intravertebral and intrapedicular bending moments.

STUDY DESIGN: A static nondestructive bending analysis of pedicle screws inserted into vertebral analogues was conducted. Pedicle screw load was studied as a function of variables in insertion technique. OBJECTIVES: To determine how the sagittal bending moment in pedicle screws is affected by changes in pedicle screw length, insertional depth, and sagittal placement. BACKGROUND DATA: An unexpectedly high rate of clinical failure has been observed in pedicle screws used in short-segment instrumentation for unstable burst fractures. The majority of screws fail in sagittal bending within the pedicle. Little is known of the insertion technical factors that affect in situ loads incurred by pedicle screws. METHODS: Synthetic vertebral analogues were fabricated. Pedicle screws internally instrumented with strain gauges were used as load transducers to determine screw bending moments within the pedicle and body of the analogue. Analogues were loaded in compression to simulate loading of an unstable burst fracture. RESULTS: Screw bending moments within the pedicle increased 33% and 52% when screws were left 3 mm and 5 mm short of full insertion. Intrapedicular moments increased 20% to 29% in screws inserted superiorly or inferiorly within the pedicle. Thirty-five-millimeter screws developed intrapedicular moments 16% higher than 40-mm and 45-mm screws. CONCLUSIONS: In situ pedicle screw loads increased significantly as a direct result of variations in surgical technique. Screws left short of full insertion, placed off center in the sagittal plane of the pedicle, or less than 40 mm long developed increased intrapedicular bending moments.

The effect of bone quality on pedicle screw loading in axial instability. A synthetic model.

STUDY DESIGN: In this biomechanical analysis of pedicle screw bending moments, custom-fabricated vertebral analogues were loaded in axial compression to produce sagittal bending forces. Moments were measured directly from internally instrumented pedicle screws. OBJECTIVES: To establish the role of cancellous vertebral modulus on pedicle screw bending moments within the vertebral body and the vertebral pedicle. SUMMARY OF BACKGROUND DATA: Pedicle screws are often used to manage axial instability of the spine. Clinical studies report a high incidence of screw bending failure, resulting in kyphosis and pain in some patients. Factors predisposing to bending failure are not well understood, although recent studies have shown that vertebral morphometry is important. METHODS: Axially canullated 7.0-mm pedicle screws, internally instrumented with paired strain gauges, were inserted into analogue vertebrae of uniform dimension. Cancellous modulus was varied from 25-100 MPa. Screws were rigidly mounted to a vertical testing frame, and axial loads were applied to the superior vertebral endplate, producing sagittal bending moments. Moments were recorded from gauges applied in the intrapedicular and intravertebral portions of the screw. Mean moments were compared using a Student's t test, with significance defined as P < 0.05. RESULTS: Cancellous modulus did not affect bending moments experienced in either the intrapedicular or intravertebral portions of the pedicle screws. Gauge accuracy was excellent, and with no gauge drift. CONCLUSIONS: Although small changes in pedicle morphometry can alter screw bending moments significantly, changes in cancellous modulus had no measurable impact on bending moments at these same loads. Bone density is likely to play a limited role in screw bending failure.

The effect of pedicle morphometry on pedicle screw loading. A synthetic model.

STUDY DESIGN: Static nondestructive bending analysis of pedicle screws inserted into vertebral analogues was conducted. Pedicle screw bending load was studied as a function of pedicle morphometry. OBJECTIVES: To determine how sagittal bending moment in pedicle screws is affected by changes in pedicle height, length, and width. BACKGROUND DATA: An unexpectedly high rate of clinical failure has been observed in pedicle screws used in short-segment instrumentation for axially unstable fractures. The majority of screws fail in sagittal bending within the pedicle. To date, little is known of the exogenous factors that affect in situ loads incurred by pedicle screws. METHODS: Synthetic vertebral analogues were fabricated, varying pedicle height, length, or width independently. Pedicle screws internally instrumented with strain gages were used as load transducers to determine screw bending moments within the pedicle and body of the analogue. Analogues were loaded in compression to simulate loading of an unstable burst fracture. RESULTS: Screw bending moments within the pedicle increased incrementally with increasing pedicle length, rising 30% as length increased from 8.0 mm to 12.0 mm. Screw moment increased 20% when pedicle height dropped below 15.0 mm, consistent with a threshold effect. Changes in pedicle width did not affect screw loads within the pedicle. CONCLUSIONS: In situ pedicle screw loads increased significantly as pedicle length increased and as pedicle height decreased. Pedicle screws instrumented internally with strain gages are an effective research instrument allowing measurement of in situ loading along the axis of the screw.

Discrimination between Bacillus cereus and Bacillus thuringiensis using specific DNA probes based on variable regions of 16S rRNA.

Identification of Bacillus cereus and differentiation between B. cereus and closely related species are currently based on biochemical tests. The main problem is to discriminate between B. cereus and B. thuringiensis. Sequencing part of the 16S rRNA showed that several B. cereus isolates present in food and involved in food poisoning, confirmed according to the classical biochemical methods, were in fact B. thuringiensis. As this organism is the most commonly used microbial insecticide worldwide, the results of this study emphasize the need for accurate identification methods and for careful screening of strains for use as insecticides. Therefore, specific DNA probes based on the variable region VI of 16S rRNA of B. cereus and B. thuringiensis were designed. The probes were used in hybridization experiments with the variable region amplified using the polymerase chain reaction. In this way, a rapid and sensitive method was developed to distinguish B. cereus and B. thuringiensis.

Identification of Clostridium tyrobutyricum as the causative agent of late blowing in cheese by species-specific PCR amplification.

Butyric acid fermentation, the late-blowing defect in cheese, caused by the outgrowth of clostridial spores present in raw milk, can create considerable loss of product, especially in the production of semihard cheeses like Gouda cheese, but also in grana and Gruyère cheeses. To demonstrate the causative relationship between Clostridium tyrobutyricum and late blowing in cheese, many cheesemaking experiments were performed to provoke this defect by using spores from several strains of the major dairy-related clostridia. A method of PCR amplification of a part of the 16S rRNA gene in combination with hybridization with species-specific DNA probes was developed to allow the specific detection of clostridial sequences in DNAs extracted from cheeses. The sensitivity was increased by using nested PCR. Late blowing was provoked in experimental cheeses with 28 of the 32 C. tyrobutyricum strains tested, whereas experimental cheeses made with spores from C. beijerinckii, C. butyricum, and C. sporogenes showed no signs of butyric acid fermentation. In all experimental and commercial cheeses with obvious signs of late blowing, DNA from C. tyrobutyricum was detected; in some cheeses, signals for C. beijerinckii were also found. It was concluded that only C. tyrobutyricum strains are able to cause butyric acid fermentation in cheese.

Genetic marking of Lactococcus lactis shows its survival in the human gastrointestinal tract.

A human feeding study was performed with Lactococcus lactis TC165.5, which is genetically marked by insertion of the sucrose-nisin conjugative transposon Tn5276 and chromosomal resistance to rifampin and streptomycin. The fate of strain TC165.5 and its nucleic acids was monitored by conventional plating methods and by molecular detection techniques based on specific PCR amplification of the nisin (nisA) gene from DNA extracted from human feces. A method was developed for the efficient extraction of microbial DNA from human feces. The results show that a fraction of viable cells of L. lactis TC165.5 survived passage through the human gastrointestinal tract. Only cells that passed within 3 days of ingestion could be recovered from the feces of the volunteers, and they accounted for approximately 1% of the total number of cells consumed. The presence of nisA in DNA extracted from feces could be detected up to 4 days, when viable cells were no longer present.

Detection and characterization of lactose-utilizing Lactococcus spp. in natural ecosystems.

The presence of lactose-utilizing Lactococcus species in nondairy environments was studied by using identification methods based on PCR amplification and (sub)species-specific probes derived from 16S rRNA sequences. Environmental isolates from samples taken on cattle farms and in the waste flow of a cheese production plant were first identified to the genus level, using a Lactococcus genus-specific probe. Isolates which showed a positive signal with this probe were further identified to the (sub)species level. Lactococcus lactis isolates were also characterized at the phenotypic level for the ability to hydrolyze arginine, to ferment citrate, and to produce proteases and bacteriocins. With specific PCR amplifications, the presence of sequences related to citP, coding for citrate permease; prtP, coding for protease; and nisA or nisZ, the structural genes for production of nisin A or nisin Z, respectively, was verified. By these methods, it was possible to isolate lactococci from various environmental sources, such as soil, effluent water, and the skin of cattle. The strains of L. lactis isolated differed in a number of properties, such as the ability to hydrolyze arginine or the absence of citP-related sequences, from those found in industrial starter cultures. The results indicate that the majority of the industrially produced lactococci do not survive outside the dairy environment, although natural niches are available. However, from those niches strains with the potential to be developed into novel starter cultures may be isolated.

Identification of mesophilic lactic acid bacteria by using polymerase chain reaction-amplified variable regions of 16S rRNA and specific DNA probes.

Specific DNA probes based on variable regions V1 and V3 of 16S rRNA of lactic acid bacteria were designed. These probes were used in hybridization experiments with variable regions amplified by using the polymerase chain reaction. In this way, a rapid and sensitive method was developed for the identification and classification of Lactococcus and Leuconostoc species.