Childhood-Onset Lupus Nephritis in the Childhood Arthritis and Rheumatology Research Alliance Registry: Short-Term Kidney Status and Variation in Care

OBJECTIVE

The goal was to characterize short-term kidney status and describe variation in early care utilization in a multicenter cohort of patients with childhood-onset systemic lupus erythematosus (cSLE) and nephritis.

METHODS

We analyzed previously collected prospective data from North American patients with cSLE with kidney biopsy-proven nephritis enrolled in the Childhood Arthritis and Rheumatology Research Alliance (CARRA) Registry from March 2017 through December 2019. We determined the proportion of patients with abnormal kidney status at the most recent registry visit and applied generalized linear mixed models to identify associated factors. We also calculated frequency of medication use, both during induction and ever recorded.

RESULTS

We identified 222 patients with kidney biopsy-proven nephritis, with 64% class III/IV nephritis on initial biopsy. At the most recent registry visit at median (interquartile range) of 17 (8-29) months from initial kidney biopsy, 58 of 106 patients (55%) with available data had abnormal kidney status. This finding was associated with male sex (odds ratio [OR] 3.88, 95% confidence interval [95% CI] 1.21-12.46) and age at cSLE diagnosis (OR 1.23, 95% CI 1.01-1.49). Patients with class IV nephritis were more likely than class III to receive cyclophosphamide and rituximab during induction. There was substantial variation in mycophenolate, cyclophosphamide, and rituximab ever use patterns across rheumatology centers.

CONCLUSION

In this cohort with predominately class III/IV nephritis, male sex and older age at cSLE diagnosis were associated with abnormal short-term kidney status. We also observed substantial variation in contemporary medication use for pediatric lupus nephritis between pediatric rheumatology centers. Additional studies are needed to better understand the impact of this variation on long-term kidney outcomes.

Sustainability analysis of bioethanol production from grain and tuber starchy feedstocks

A comparative sustainability study of bioethanol production from selected starchy feedstocks that are abundantly available was carried out in this work. This is to ensure the safe, reliable, and efficient production and consumption of fuel-grade bioethanol. The analysis utilised the established economic minimum bioethanol plant capacity of 158,000 m³/annum. The processing flowsheet model utilised was the same for each feedstock. The sustainability study's economic, environmental, and energy perspectives were investigated. The economic and environmental indices were assessed using Superpro Designer and openLCA sustainability software, respectively. Exergy and lost work were subsequently estimated manually with Microsoft Excel. The economic analyses showed that the plants using cassava and sweet potato initially had the highest return on investment (ROI) of 64.41 and 41.96% respectively at a minimum of 80% plants' capacity utilisation. The break-even point occurs at a bioethanol price of $3.27 per gallon, beyond which positive net present values were obtained for the four processes. The least profitable plant was based on sorghum recording an ROI value of 34.11%. The environmental assessment on the four selected feedstocks showed that the processes based on cassava, corn, sweet potato, and sorghum recorded encouraging global warming potential (GWP) of 0.2452, 0.2067, 2.5261, and 0.2099 kg CO₂ equivalent respectively. Cassava and corn emerged as the two most economically viable feedstocks when economic parameters were adjusted to include pollutants emission/discharge costs but with a slight decrease in profitability indices. The lost work analyses showed that distillation columns were the least energy-efficient units in the four bioethanol production routes assessed, recording loss work of about 61, 68, 34, and 49 MW for cassava, sweet potato, corn, and sorghum processing plants respectively. However, the net energy balance (NEB) and energy renewability results of the four production routes showed that the processes utilising the four selected starchy biomass feedstocks are more sustainable compared to fossil fuels.

Intraarticular steroids as DMARD-sparing agents for juvenile idiopathic arthritis flares: Analysis of the Childhood Arthritis and Rheumatology Research Alliance Registry

BACKGROUND

Children with juvenile idiopathic arthritis (JIA) who achieve a drug free remission often experience a flare of their disease requiring either intraarticular steroids (IAS) or systemic treatment with disease modifying anti-rheumatic drugs (DMARDs). IAS offer an opportunity to recapture disease control and avoid exposure to side effects from systemic immunosuppression. We examined a cohort of patients treated with IAS after drug free remission and report the probability of restarting systemic treatment within 12 months.

METHODS

We analyzed a cohort of patients from the Childhood Arthritis and Rheumatology Research Alliance (CARRA) Registry who received IAS for a flare after a period of drug free remission. Historical factors and clinical characteristics and of the patients including data obtained at the time of treatment were analyzed.

RESULTS

We identified 46 patients who met the inclusion criteria. Of those with follow up data available 49% had restarted systemic treatment 6 months after IAS injection and 70% had restarted systemic treatment at 12 months. The proportion of patients with prior use of a biologic DMARD was the only factor that differed between patients who restarted systemic treatment those who did not, both at 6 months (79% vs 35%, p < 0.01) and 12 months (81% vs 33%, p < 0.05).

CONCLUSION

While IAS are an option for all patients who flare after drug free remission, it may not prevent the need to restart systemic treatment. Prior use of a biologic DMARD may predict lack of success for IAS. Those who previously received methotrexate only, on the other hand, are excellent candidates for IAS.

Social determinants of health influence disease activity and functional disability in Polyarticular Juvenile Idiopathic Arthritis

BACKGROUND

Social determinants of health (SDH) greatly influence outcomes during the first year of treatment in rheumatoid arthritis, a disease similar to polyarticular juvenile idiopathic arthritis (pJIA). We investigated the correlation of community poverty level and other SDH with the persistence of moderate to severe disease activity and functional disability over the first year of treatment in pJIA patients enrolled in the Childhood Arthritis and Rheumatology Research Alliance Registry.

METHODS

In this cohort study, unadjusted and adjusted generalized linear mixed effects models analyzed the effect of community poverty and other SDH on disease activity, using the clinical Juvenile Arthritis Disease Activity Score-10, and disability, using the Child Health Assessment Questionnaire, measured at baseline, 6, and 12 months.

RESULTS

One thousand six hundred eighty-four patients were identified. High community poverty (≥20% living below the federal poverty level) was associated with increased odds of functional disability (OR 1.82, 95% CI 1.28-2.60) but was not statistically significant after adjustment (aOR 1.23, 95% CI 0.81-1.86) and was not associated with increased disease activity. Non-white race/ethnicity was associated with higher disease activity (aOR 2.48, 95% CI: 1.41-4.36). Lower self-reported household income was associated with higher disease activity and persistent functional disability. Public insurance (aOR 1.56, 95% CI 1.06-2.29) and low family education (aOR 1.89, 95% CI 1.14-3.12) was associated with persistent functional disability.

CONCLUSION

High community poverty level was associated with persistent functional disability in unadjusted analysis but not with persistent moderate to high disease activity. Race/ethnicity and other SDH were associated with persistent disease activity and functional disability.

Sourdough Bread from the Blend of Cassava, Sweet Potato, and Soybean Flours Using Lactobacillus Plantarum and Pichia Kudriavzevii

Sourdough is specialty bread made from a combination of flour, lactic acid bacteria, and yeasts. Composite flour of cassava, sweet potato, and soybean was used for the production of sourdough bread employing autochthonous lactic acid bacteria and yeasts isolated from the composite dough. The flour samples were assessed for functional properties, while the sourdough breads were evaluated for nutritional composition and organoleptic properties. The flour samples possessed good proximate profiles and phenolic contents. The lactic acid bacterium and yeast with the most desirable properties were identified as Lactobacillus plantarum and Pichia kurdriazevii. Fermentation improved the nutritional indices of the composite sourdough bread samples. Lactobacillus plantarum SLC21 and P. kudriavzevii SYD17 bread had a shelf life of 7 days, while the control bread lasted for at least 4 days. Lactobacillus plantarum SLC21 and Pichia kudriavzevii SYD17 bread had the best overall acceptability. Utilisation of these local crops in a composite blend for sourdough will increase commercial profit for local farmers and developing economy. The composite blend will be of great importance in the preparation of pastries that do not require high gluten content. The strains exhibited great potentials for a better nutritional composition of the composite sourdough bread.

Abstract PD8-05: Comparative analysis of the genomic landscape of breast cancers from women of African and European ancestry

Objectives: Paucity of data on populations of African Ancestry in clinical trials continues to limit our ability to design and implement innovative solutions to narrow the breast cancer survival gap amongst Africans, African Americans, and European Americans. We have developed a cross-continent research infrastructure to examine the spectrum of genomic alterations in breast tumors from West Africa and subsequently, to compare them to tumors from African American women and women of European Ancestry in The Cancer Genome Atlas (TCGA) database.

Methods: Consecutive women with breast cancer presenting for treatment at the University College Hospital, Ibadan and at Lagos State University Teaching Hospital, Lagos, Nigeria gave informed consent and were recruited to the West African Breast Cancer Study (WABCS) between 2013-2016. Tumor-normal pairs were subjected to exome and/or high-depth (90x) genome sequencing. High confidence somatic mutations (substitutions, insertions/deletions and structural variants) were obtained by using multiple variant callers. Furthermore, 1,089 exomic and 80 genomic breast tumor-normal pairs from TCGA were harmonized with WABCS samples, resulting in a cohort of 147 West Africans (147 exome; 40 genome), 154 African Americans (154 exome; 31 genome), and 776 Caucasians (776 exome; 43 genome).

Results: Across the exomes, genes commonly altered in breast cancer in TCGA are also altered in women of African ancestry, but the mutational spectrum is quite different, demonstrating overrepresentation of tumors with aggressive phenotypes. Overall, TP53 (65%), ERBB2 (27%), and GATA3 (17%) showed statistically significant higher alteration frequencies in West Africans and African Americans. In contrast, PIK3CA (24%) was less frequently mutated. Of note, GATA3 mutation was statistically significantly more frequent in Nigerians (39%) and African Americans (16.7%) compared to Caucasians (10.5%), in ER-positive cancers. Analysis on Structural Variants (SV), on the other hand, has shown that the genome-wide SV counts among three populations are comparable in ER-negative cancers, while Nigerians have significantly more SV counts compared to African Americans (P=0.0013) or European Americans (P=2.9x10-5) in ER-positive cancers. Similarly, genome-wide substitution patterns in ER+ and ER- cancers varied widely by race/ethnicity. In ER- cases, West Africans carried the highest proportion of canonical APOBEC-associated substitutions, particularly C&gt;T transitions. Conversely, European Americans with ER+ disease showed a higher proportion of C&gt;T than both West Africans (Welch t-test P = 0.044) and African Americans (Welch t-test P = 0.011). Mutation signature analyses highlighted multiple APOBEC signatures, with notable contribution differences across ancestry and ER status. A signature likely corresponding to DNA damage repair correlated with the proportion of genetic ancestry, being most prevalent in European Americans and least common in Nigerians, particularly in ER-negative cancers, with African Americans showing a degree of this signature's contribution in between the two populations (linear model adjusted for age, P=1.0x10-10).

Conclusions: Overall, our data suggests mutation spectra differences in across race/ethnicity and geography. Identification of molecular characteristics such as higher rates of HER2 enriched tumors and higher rates of GATA3 mutations in ER positive tumors are beginning to reveal the genomic basis of race-associated phenotypes and outcomes in breast cancer. Population differences in frequency and spectrum of mutations should now inform the design of innovative clinical trials that improve health equity and accelerate Precision Oncology care in diverse populations.

Citation Format: Olopade OI, Pitt JJ, Riester M, Odetunde A, Yoshimatsu T, Labrot E, Ademola A, Sanni A, Okedere B, Mahan S, Nwosu I, Leary R, Ajani M, Johnson RS, Sveen E, Zheng Y, Wang S, Fitzgerald DJ, Grundstad J, Tuteja J, Clayton W, Khramtsova G, Oludara M, Omodele F, Benson O, Adeoye A, Morhason-Bello O, Ogundiran T, Babalola C, Popoola A, Morrissey M, Chen L, Huo D, Falusi A, Winckler W, Obafunwa J, Papoutsakis D, Ojengbede O, White KP, Ibrahim N, Oluwasola O, Barretina J. Comparative analysis of the genomic landscape of breast cancers from women of African and European ancestry [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr PD8-05.

Abstract P6-03-17: Genomic landscape of breast cancers from women of African ancestry across the diaspora

Objectives: Of all ethnic/racial groups, age-standardized mortality rate from breast cancer is highest for African American women in the US for reasons that remain understudied. The paucity of genomic studies of breast tumors across the African Diaspora further restricts our understanding of the biology of breast cancer in underserved populations. To gain a better understanding of the genomic landscape of breast cancer in women of African Ancestry, we have developed a cross continent translational research infrastructure to examine the spectrum of genetic alterations in breast tumors from West Africa compared to the spectrum of alterations observed in tumors from African-American and other women who are predominantly white in The Cancer Genome Atlas (TCGA) dataset.

Methods: Peripheral blood and breast cancer biopsy tissues were collected from 214 patients enrolled in the West Africa Breast Cancer Study (WABCS) at the University of Ibadan/University College Hospital (UI/UCH) and at Lagos State University Teaching Hospital (LASUTH). Blood DNA as well as breast cancer tissue DNA and RNA were extracted at the Novartis Institutes for Biomedical Research (NIBR), UI/UCH, and LASUTH using a modified protocol of PAXgene Tissue DNA and RNA extraction method. Whole-exome (WES) and transcriptome (RNA-seq) sequencing were performed on the Illumina HiSeq2000 platform at NIBR. Single Nucleotide Variants (SNVs) and insertions/deletions (indels) were called using MuTect and Pindel, while Copy Number Alterations (CNAs) were called using an in-house implementation of the ABSOLUTE method. Observed mutations were compared against those reported in the TCGA dataset. ER, PR and HER2 status were determined by immunohistochemistry (IHC) at UI/UCH, LASUTH and UChicago.

Results: WES data for 95 tumors have been analyzed thus far. Genes commonly mutated in breast cancer in TCGA are also mutated in WABCS but the mutational spectrum is vastly different. TP53 (64%), MYC (31%), and GATA3 (26%), showed significantly higher alteration frequencies in WABCS and African Americans. In contrast, PIK3CA (20%), CDH1 (2%), and MAP3K1 (2%) were less frequently mutated in women of African ancestry. In addition to the high proportion with TP53 mutations, the proportion with HER2 positive subtype of 42.1% and triple-negative subtype of 37.9% suggest that tumors with the most aggressive features are overrepresented in breast cancer patients in West Africa.

Conclusions: In the first study of its kind, high throughput genomic analysis of the largest cohort of women of African ancestry has uncovered alterations in cancer genes, some of which may be amenable to treatment with targeted therapies. Furthermore, we provide evidence that population differences in frequency and spectrum of mutations should drive the design and deployment of precision medicine initiatives. Only then can we develop innovative interventions to reduce the unacceptably high rates of mortality from breast cancer in underserved and under resourced populations.

Citation Format: Olopade OI, Odetunde A, Riester M, Yoshimatsu T, Labrot E, Ademola A, Sanni A, Okedere B, Mahan S, Nwosu I, Leary R, Ajani M, Johnson RS, Sveen E, Zheng Y, Clayton W, Khramtsova G, Oludara M, Omodele F, Benson O, Adeoye A, Morhason-Bello O, Ogundiran T, Babalola C, Popoola A, Morrissey M, Huo D, Falusi A, Winckler W, Obafunwa J, Papoutsakis D, Ojengbede O, Ibrahim N, Oluwasola O, Barretina J. Genomic landscape of breast cancers from women of African ancestry across the diaspora. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P6-03-17.

Analysis of the contrast between natural occurrence of toxigenic Aspergilli of the Flavi section and aflatoxin B1 in cassava

Aflatoxin B1 (AFB1) is a carcinogenic mycotoxin produced by Aspergilli of the section Flavi that may contaminate food, in the field or during storage. Cassava represents an important staple food in sub-Saharan Africa. The analysis of aflatoxigenic fungi in 36 cassava samples obtained from producers in Benin indicated that 40% were contaminated by Aspergilli of the section Flavi. Upon morphological and molecular characterization of the 20 isolates, 16 belonged to Aspergillus flavus, 2 to Aspergillus parvisclerotigenus and 2 to Aspergillus novoparasiticus. This is the first time that this latter species is isolated from food. Although most of these isolates were toxigenic on synthetic media, no AFB1 contamination was observed in these cassava samples. In order to determine the action of cassava on AFB1 synthesis, a highly toxigenic strain of A. flavus, was inoculated onto fresh cassava and despite a rapid development, no AFB1 was produced. The anti-aflatoxin property was observed with cassava from different geographical origins and on other aflatoxigenic strains of the section Flavi, but it was lost after heating, sun drying and freezing. Our data suggest that fresh cassava is safe regarding AFB1 contamination, however, processing may alter its ability to block toxinogenesis leading to secondary contamination.

A review on aflatoxin contamination and its implications in the developing world: a sub-Saharan African perspective

Mycotoxins contamination in some agricultural food commodities seriously impact human and animal health and reduce the commercial value of crops. Mycotoxins are toxic secondary metabolites produced by fungi that contaminate agricultural commodities pre- or postharvest. Africa is one of the continents where environmental, agricultural and storage conditions of food commodities are conducive of Aspergillus fungi infection and aflatoxin biosynthesis. This paper reviews the commodity-wise aetiology and contamination process of aflatoxins and evaluates the potential risk of exposure from common African foods. Possible ways of reducing risk for fungal infection and aflatoxin development that are relevant to the African context. The presented database would be useful as benchmark information for development and prioritization of future research. There is need for more investigations on food quality and safety by making available advanced advanced equipments and analytical methods as well as surveillance and awareness creation in the region.

Technological properties and probiotic potential of Enterococcus faecium strains isolated from cow milk

AIM

To identify enterococci from the fermentation of milk for the production of nono, an African fermented dairy product, to determine the technological properties for suitability as starter cultures and safety as probiotics.

METHODS AND RESULTS

Enterococcus faecium CM4 and Enterococcus faecium 2CM1 were isolated from raw cow's milk. The strains were phenotypically and genotypically identified. Technological properties, safety investigations, in vitro adherence properties and antimicrobial characteristics were carried out. Strong acidification and tolerance to bile salts were recorded. The strains were bile salts hydrolytic positive and no haemolysis. There was no resistance to clinically relevant antibiotics. The strains exhibited adherence to human collagen type IV, human fibrinogen and fibronectin. The bacteriocins were active against Bacillus cereus DSM 2301, Bacillus subtilis ATCC 6633, Micrococcus luteus and Listeria monocytogenes. Bacteriocins were stable at pH 4-9 and on treatment with lipase, catalase, α-amylase and pepsin, while their activity was lost on treatment with other proteases. The bacteriocins produced were heat stable at 100°C for 10 min. The bacteriocin produced by the strains was identified as enterocin A.

CONCLUSIONS

The E. faecium strains in this study exhibited probiotic activity, and the safety investigations indicate their suitability as good candidates for a starter culture fermentation process.

SIGNIFICANCE AND IMPACT OF THE STUDY

The use of bacteriocin-producing E. faecium strains as starter cultures in fermented foods is beneficial but, however, their safety investigations as probiotics must be greatly emphasized.

[Major salmonellosis in Benin]

Although salmonellosis is a common endemo-epidemic disease in Benin, there is a paucity of data about it. The purpose of this cross-sectional study was to determine the incidence of major salmonellosis requiring hospitalizaton and to describe its epidemiological, clinical, and serologic features as well as treatment and outcome. Consecutive cases observed at the Medical Department of Parakou University Hospital in Benin between January 1, 2005 and December 31 2007 were included. Salmonellosis was defined on the basis of clinical and serological criteria. Among the 2,520 patients hospitalized during the study period, salmonellosis was diagnosed in 135 (5.4% [95% CI 4.5%-6.3%]). Highest incidences were observed in January, July, October and November. The main symptoms were headache, fever, fatigue and abdominal pain. The Salmonella typhi serotype was identified in 94.8% of patients. Two patients presented co-infection, i.e., Salmonella typhi with paratyphi A in one case and Salmonella typhi with paratyphi B in the other. Fluoroquinolones were used for treatment in 79.3% of patients. Outcome was favorable in 62.2%. The main complications were,typhoid digestive perforation in 11.1%, and gastrointestinal bleeding in 8.1%. The mortality rate was 4.4% (n=6). These data are consistent with previous reports in the literature and confirm the frequency and severity of salmonellosis in Benin.

Antibacterial activity and phytochemical study of six medicinal plants used in Benin

The ethanol extracts obtained from Psidium guajava, Flacourtia flavescens Boswellia dalzielii, Ficus exasperata, Pavetta corymbosa and Hybanthus enneaspermus, six species traditionally used in Benin to treat several infectious diseases, were evaluated for their in vitro antimicrobial activity against Staphylococcus aureus, Enteroccocus feacalis, Escherichia coli and Pseudomonas aeruginosa. The minimum inhibitory concentration of extracts was determinate using the microplate dilution method. The presence of major phytoconstituents was detected qualitatively. The diphenylpicrylhydrazine radical scavenging activity was also performed. The extracts exhibited antibacterial activities against the tested bacteria. Boswellia dalzielii, Psidium guayava, Pavetta corymbosa and Flacourtia flavescens exibited the lowest minimum inhibitory concentration values (0.313-2.5 mg mL(-1)). Pseudomonas aeruginosa was the lest sensitive microorganism with MIC values higher than 10 mg mL(-1). In antioxidant assay the crude extracts of B. dalzielii and P. corymbosa appeared to be as potent as quercetol with an inhibition percentage of 83 and 75.3% at 10 microg mL(-1) which is comparable to 75.9% for quercetol at the same concentration.

[Production lead time of coagulase in 180 Staphylococcus aureus strains collected at Abidjan]

INTRODUCTION

The pathogenic capacity of S. aureus is related.to the production of many virulence factors of which the coagulase. Several genotypes of coagulase were described and are associated to various populations of S. aureus. According the susceptibility to methicillin, methicillin-resistant strains of S. aureus, are described. The aim of this subject was to study the coagulase expression of Staphylococcus aureus according to the site of infection, patient origin and the resistance against methicillin.

MATERIAL AND METHODS

The study is related about 180 strains of S. aureus collected in the three University Teaching Hospital of Abidjan. S. aureus are identified with laboratory classical methods. Coagulase delay was determined by the test of the coagulase on citrated rabbit plasma at 2, 4 and 18 hours. The resistance against methicillin was researched by disc diffusion agar technique.

RESULTS

In 60% of cases, the bacterial strains gave a coagulum at the end of four hours, fast coagulase, against 40% of strains whose coagulating activity appeared at 18 h, slow coagulase. Fast coagulase strains are isolated from the majority of infections (55% to 71%), in hospital patients (66%) and in paediatrics (58%). Fast coagulase strains are methicillin-resistant in 65% of cases against 48.5% of methicillin-susceptible and low coagulase strains (p < 0.0001).

CONCLUSION

According to the production lead time of the coagulase, fast coagulase and slow coagulase variants of S. aureus coexisted. The expression of the coagulase is not related to the site of infection and the origin of the patients. On the other hand, the type of coagulase is associated to resistance of methicillin. However, the time of formation of the coagulum typed by the test of the coagulase, didn't constitute a sufficient discriminating factor in the medical following and the treatment of infections caused by S. aureus.

Incidence d'infections liées à Escherichia coli producteur de bêta lactamase à spectre élargi au Centre hospitalier départemental du Zou et Collines au Bénin

OBJECTIVES

Over a 6-month period, extended-spectrum betalactamase (ESBL)-producing isolates of Escherichia coli (EC) were collected from in-patients and their environment at the Zou-Collines Hospital Centre (CHDZ/C) in Benin. The aim of this study was to determine the incidence of ESBL and to describe their phenotypic susceptibility to antibiotics in a secondary hospital (500 beds) in Benin.

METHODS

From 15 May to 15 November 2005, clinical informations and samples were collected from patients suspected to have nosocomial infections. The isolates were identified, tested for antimicrobial susceptibility and analysed for the presence of ESBL genes blaTEM and blaSHV by PCR.

RESULTS

One hundred ninety-seven enterobacteria were isolated from the clinical samples of 342 patients, these isolates included 143 EC and 32/143 (22%) of these isolates produced ESBL. Forty-six EC were isolated from the environment and 7 (15%) of them produced ESBL. Except for Imipenem for which the difference was not significant, the isolates producing ESBL were more resistant to the other antibiotics (especially to third generation cephalosporins: Ceftriaxone, Cefotaxime, Ceftazidime (P<0.00001)) than non-ESBL producing isolates. Both ESBL genes blaSHV and blaTEM were identified in the EC ESBL strains from patient and from the environment.

CONCLUSION

This study shows the presence of ESBL genes among EC in various wards of the CHDZ/C hospital proving that there is a need to implement a strict hospital infection control program and a regular surveillance of resistance to antimicrobial agents.

Diabetic donors as a source of non-heart-beating renal transplants

Due to the organ shortage, many renal transplantation centers attempt to increase the donor pool by using non-heart-beating donors (NHBDs). These kidneys are generally regarded as "marginal" grafts. Many centers do not consider transplantation from an NHBD with a history of diabetes as it is a more suboptimal donor. We began our NHBD program in 1998 and have performed 5 renal transplants from diabetic NHBDs. Viability testing identified kidneys suitable for single or dual transplantation. Although kidneys from brain stem dead donors with diabetes have been used successfully, our data suggested that kidneys from diabetic NHBDs can also be used although we still need long-term results.

Donor risk factors for renal graft thrombosis

Graft thrombosis is one of the most devastating complications of transplantation. In obtaining consent prior to transplant, it is useful to share potential risk factors with the recipient. In order to do this, we explored the impact of different risk factors that could contribute to this complication. Using multivariate analysis we found that neither multiple vessels nor vascular injury had a bearing on the risk of graft thrombosis but atheroma did (P < .02).

Donation after cardiac death kidneys with low severity pre-arrest acute renal failure

The widening gap between supply and demand for renal transplantation has prompted many centers to use donors after cardiac death. Some of these donors exhibit signs of acute renal failure (ARF) prior to cardiac arrest. Concern has been expressed about poor quality of graft function from such donors. In response to this perception, we reviewed 49 single renal transplant recipients from category III donors after cardiac death between 1998 and 2005, at our center. All kidneys but one had hypothermic machine perfusion and viability testing prior to transplantation. According to the RIFLE criteria, nine recipients had kidneys from donors with "low severity pre-arrest ARF". The remainder of the recipients were used as control group. There was no statistical significant difference in delayed graft function and rejection rates between these two groups. Recipients GFR at 12 months was 44.4 +/- 17.1 and 45.2 +/- 14.7 (mL/min/1.73m(2)) from donors with ARF and without ARF, respectively (p = 0.96). In conclusion, low severity ARF in kidneys from controlled after cardiac death donors can be a reversible condition after transplantation. Short-term results are comparable to the kidneys from same category donors without renal failure, providing that some form of viability assessment is implemented prior to transplantation.

Renal transplants from category III non-heart-beating donors with evidence of pre-arrest acute renal failure

Kidneys transplanted from non-heart-beating donors (NHBDs) have been exposed to varying degrees of ischemic damage after death. Category III donors have invariably been managed, treated, and investigated in a hospital setting prior to arrest and death. Some therefore exhibit evidence of renal dysfunction and even acute renal failure (ARF) before death. Many surgeons would regard a NHBD with pre-arrest evidence of ARF as too marginal for renal transplantation. This retrospective study examines five Maastricht category III NHBD donors with evidence of pre-arrest ARF. We compare 3- and 12-month GFR outcome data from the nine resulting transplants with 40 category III NHBD transplants with normal pre-arrest renal function. The mean GFR at 3 months was 45.4 and 43.8 for the ARF and normal group, respectively. At 12 months the GFR was 42.2 and 44.7 in the ARF and normal groups, respectively. Thus evidence of ARF pre-arrest does not preclude successful category III NHBD renal transplantation.

Dual renal transplantation for kidneys from marginal non-heart-beating donors

Kidneys transplanted from non-heart-beating donors (NHBD) are generally regarded as marginal or extended criteria grafts due to the associated period of warm ischemia. The most prolonged periods occurring in the category II (uncontrolled) donor. This potential for injury can adversely affect the glomular filtration rate (GFR), which in severe cases results in primary nonfunction. Viability testing can identify a group of kidneys that, although unsuitable for solitary transplantation, may be considered for dual transplant. This retrospective study examined a series of 11 dual renal transplants, comparing 3- and 12-month GFR outcome data with 81 single NHBD transplants. The mean GFR at 3 months in the dual group was 47.6 and at 12 months was 48.6. In the single group the GFR at 3 months was 40.6 and at 12 months was 41.9. Thus using viability testing to identify NHBD kidneys suitable for dual transplant appears reliable and predictable.

Agonal period in potential non-heart-beating donors

The shortage of donor kidneys for renal transplantation is becoming more severe as the gap between the number of patients waiting for renal transplantation and the number of cadaveric organs available continues to widen. Therefore, many centres have started using non-heart-beating (NHB) donors. There was no clear plan for maximal duration of agonal period in Maastricht category NHB donors after withdrawal of treatment in Newcastle. This withdrawal has been audited in retrospect. Our current wait time is now a maximum of 5 hours; however, previously there have been some considerably longer periods. Concern has always been expressed about poor quality with protracted periods. Nonuse in this review of 58 kidneys can be expressed against time: 0 to 2 hours 13%, 2 to 5 hours 33%, and >5 hours 45%. Therefore, though the nonuse rate was significantly different between 0 to 2 hours and >5 hours (P < .05, chi-square), there were 16 transplants performed with kidneys >2 hours and 12 transplanted >5 hours. In conclusion, although good usable kidneys can still be used with protracted withdrawal, there are considerable logistical difficulties with our 5-hour cut-off, which means that one third of potential kidneys will not be utilized.

Renal Graft Function After Prolonged Agonal Time in Non–Heart-Beating Donors

To deal with the increasing gap between organ demand and supply for kidney transplantation, many centers have started to use non-heart-beating (NHB) donors. When we initiated our program to utilize kidneys from such donors in 1998, we had no protocol for the maximal agonal period. This however was audited in retrospect. Our current wait time is now a maximum of 5 hours. Concern has been expressed in the past about possible deterioration in the quality of the organs with a protracted agonal time. We aimed in this study to examine the effect of prolonging agonal period on the quality of kidneys retrieved from Maastricht category III donors: A total of 40 kidneys were transplanted from 29 category III donors between 1998 and 2004. Eleven kidneys had donor agonal times of >5 hours; the remainder, agonal times <5 hours. Both groups were matched for donor and recipient factors. The mean glomerular filtration rates at 12 months for <5 hours versus >5 hours agonal time were 43.8 +/- 4.4 versus 49.8 +/- 5.8, respectively (P = .24) and at 24 months, 46.83 +/- 8.99 versus 37.67 +/- 3.85, respectively (P = .24). In conclusion, intermediate graft function is comparable to ones with shorter agonal time, although we await long-term results.

Predisposing Factors for Biliary Complications Following Liver Transplantation

INTRODUCTION

Biliary complications remain a major cause of morbidity and mortality in patients following liver transplantation. We sought to identify possible risk factors predisposing to biliary complications after OLT using duct-to-duct biliary reconstruction.

MATERIALS AND METHODS

We retrospectively reviewed 5 years of prospectively collected donor and recipient data between April 1999 and April 2004. We evaluated the presence of biliary complications, donor and recipient age, cold ischemia time, hepatic artery thrombosis, non-heart-beating donor (NHBD), and graft steatosis (>30%). The results were compared with a control group of OLT patients without biliary complications.

RESULTS

Among 173 OLT recipients, biliary complications occurred in 28 patients (16.2%), of whom 12 were leaks, 15 strictures, and 1 a nonanastomotic intrahepatic stricture. The mortality following biliary complications was 11%, compared to 6% in the control group.

CONCLUSION

Biliary complications remain a persistent problem in OLT. Analysis of risk factors identified hepatic artery thrombosis and steatosis as predisposing factors. With greater experience, NHBD livers may also prove to be at greater risk of biliary complications.

[Incidence of meticillin-resistant Staphylococcus aureus in neonatal care unit of departmental hospital centre of Zou Collines in Benin]

Meticillin resistant Staphylococcus aureus (MRSA) is among the most important causes of nosocomial infections. It possesses a particular ability to spread in hospitals worldwide.

OBJECTIVE

To analyze the proportion of MRSA among S. aureus isolated from specimen taken for diagnosis purposes. To make the medical staff aware of the problem of MRSA infections and to take a better care of patients.

PATIENTS AND METHODS

During 3 months, a prospective study was carried out in the neonatal unit of centre hospitalier départemental du Zou et Collines in Benin. We identified newborn carriers of SA, particularly MRSA and factors associated with the carriage. Two hundred and ninety patients were admitted in the 3 divisions of the neonatal unit. From 195 specimens examined for diagnosis purposes 48 h after hospitalization, 112 patients were detected by nose swabbing. Concurrently, swabbing of environment was achieved.

RESULTS

Among patients'specimens, 141 isolations of S. aureus were observed. The proportion of MRSA was 36% amongst diagnostic specimens. MRSA represented 39% of the environment specimens. None of the isolated MRSA produces Panton Valentine leukocidin.

CONCLUSION

Our survey revealed a high level of MRSA among S. aureus isolated from diagnostic specimens. Consecutive to such findings and for decreasing nosocomial infection, an appropriate prevention program was installed, including intensive promotion of hands hygiene, correct sterilization and disinfection of materials and patients.

Site-directed mutagenesis to assess the binding capacity of class s protein of Staphylococcus aureus leucotoxins to the surface of polymorphonuclear cells

Staphylococcal leucotoxins result from the association of class S components and class F component inducing the activation and the permeabilization of the target cells. Like alpha-toxin, the leucotoxins are pore-forming toxins with more than 70% beta-sheet. This was confirmed by attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy. In addition, threonine 28 of a predicted and conserved beta-sheet at the N-terminal extremity of class S proteins composing leucotoxins aligns with histidine 35 of alpha-toxin, which has a key role in oligomerization of the final pore. Flow cytometry was used to study different aminoacid substitutions of the threonine 28 in order to evaluate its role in the biological activity of these class S proteins. Finally, results show that threonine 28 of the leucotoxin probably plays a role similar to that of histidine 35 of alpha-toxin. Mutations on this threonin largely influenced the secondary interaction of the class F component and led to inactive toxin.

Iatrogenic femoropopliteal graft entrapment leading to thrombus formation

Femoropopliteal bypass graft entrapment by the gastrocnemius muscle and tendons is an unusual cause of graft stenosis or thrombosis. Before graft occlusion occurs, reduced flow may be seen either with the knee in extension or hyperextension or by passive dorsiflexion of the ankle. We report a case of a femoropopliteal bypass graft entrapment causing a thrombus in the distal graft. Duplex imaging, angiography, MRI and graft surveillance programs are useful diagnostic tools. Treatment options include dividing the occluding muscles and tendons and rerouting the graft.

Magnesium content in seminal fluid as an indicator of chronic prostatitis

Magnesium and zinc are both involved in a high number of enzymic activities vital for mammals. They are found in prostate in remarkably high concentrations and released into seminal fluid. Furthermore, drastic reduction of Zn and Mg concentrations in the semen fluid may lead to disorders in male fertility. We aimed to analyse the differences in Mg and Zn levels in the seminal plasma of 213 males including 48 normozoospermic, 30 azoospermic, 28 oligoasthenozoospermic, 22 asthenozoospermic and 85 chronic prostatitis. Mg and Zn concentrations were measured using an atomic absorption spectrophotometer. While zinc levels did not show correlation either with the volume of the sperm or the percentage of pathological forms, magnesium concentrations in seminal plasma were significantly decreased in chronic prostatitis patients as compared to other groups or normozoospermic patients (p<0.001). We propose therefore magnesium as a marker of prostatitis.

The nucle(ol)ar Tif6p and Efl1p are required for a late cytoplasmic step of ribosome synthesis

Deletion of elongation factor-like 1 (Efl1p), a cytoplasmic GTPase homologous to the ribosomal translocases EF-G/EF-2, results in nucle(ol)ar pre-rRNA processing and pre-60S subunits export defects. Efl1p interacts genetically with Tif6p, a nucle(ol)ar protein stably associated with pre-60S subunits and required for their synthesis and nuclear exit. In the absence of Efl1p, 50% of Tif6p is relocated to the cytoplasm. In vitro, the GTPase activity of Efl1p is stimulated by 60S, and Efl1p promotes the dissociation of Tif6p-60S complexes. We propose that Tif6p binds to the pre-60S subunits in the nucle(ol)us and escorts them to the cytoplasm where the GTPase activity of Efl1p triggers a late structural rearrangement, which facilitates the release of Tif6p and its recycling to the nucle(ol)us.

[No influence of season of transmission nor age of patients on the complexity and genetic diversity of Plasmodium falciparum infection in Cotonou, Benin]

The aim of the present study was to determine the genetic diversity and allelic frequencies of the genes encoding for the merozoite surface protein-1 (MSP-1) and protein-2 (MSP-2) of P. falciparum collected from Beninese patients during the high and low transmission seasons in Cotonou, in South Benin. Sixty and twenty-four patients were sampled during the dry and wet seasons, respectively Parasite DNA was analysed using allele-specific primers to amplify block2 of MSP-1 and central variable region of MSP-2. A total of 12 (K1, Mad20, Ro33) MSP-1 and 23 (3D7, FC27 and hybrids) MSP-2 alleles were detected. Neither age nor transmission season modified the genetic diversity of P. falciparum nor the distribution of MSP-1 and MSP-2 alleles. Combining the results of MSP-1 and MSP-2 genotyping, multiple P. falciparum infections were observed in 57% and 70% of isolates during the wet and dry seasons, respectively. The complexity of infections defined as the number of parasite genotype per isolate was 2.4 and it was not affected either by the season or by the age of the host. We conclude that change of season did not influence the permanent turn-over of parasites and the complexity of infections. Data obtained here will serve as a baseline for future studies, such as the impact of malaria control measures on parasite populations, to be conducted in Cotonou.

Aspartame prevents the karyomegaly induced by ochratoxin A in rat kidney

Ochratoxin A (OTA) is a mycotoxin produced by Aspergillus ochraceus as well as other moulds. This mycotoxin contaminates animal feed and food. OTA is immunosuppressive, genotoxic, teratogenic, carcinogenic and is nephrotoxic in all animal species studied so far. OTA inhibits protein synthesis and induces lipid peroxidation. Since it seems impossible to avoid completely contamination of foodstuffs by toxigenic fungi, it is necessary to investigate the possible ways of limiting such toxicity. An attempt to prevent OTA-induced nephrotoxic and genotoxic effects, mainly the karyomegaly, has been made in vivo using aspartame (L-aspartyl-L-phenylalanine methyl ester), a structural analogue of both OTA and phenylalanine. Aspartame (25 mg/kg body weight) prevented most of the nephrotoxic effects induced by OTA (289 microg/kg body weight). It also showed some utility in preventing morphological and histological damage, mainly the karyomegaly. The protective effects of aspartame on OTA-induced nephrotoxicity could be based on several mechanisms related to competitive binding to plasma proteins, to transport or tissue distribution in the kidney or to the elimination of the toxin in the urine.

No influence of the transmission season on genetic diversity and complexity of infections in Plasmodium falciparum isolates from Benin

The principal goals of the present study were to determine the genetic diversity of the merozoite surface protein-1 (MSP-1) and protein-2 (MSP-2) genes and the complexity of infections in P. falciparum isolates collected from Beninese patients during high and low transmission season at Cotonou, in South Benin. Sixty and twenty-four patients were sampled during dry and wet season respectively. Parasite DNA was analysed using allele-specific primers to amplify block 2 of MSP-1 and central variable region of MSP-2 genes. A total of 12 (K1, Mad20, Ro33) MSP-1 and 13 (3D7 and FC27) MSP-2 alleles were detected in overall samples. Neither influence of age nor transmission season was observed in the genetic diversity of parasites and in the distribution ofMSP-1 and MSP-2 alleles. Combining the results of MSP-1 and MSP-2 genotyping, we observed 57% and 70% of multiple infections during dry and wet season respectively. The complexity of infections 2.4 fragments/individual was not affected either by the season or by the age of the host. We speculate that in an area with perennial transmission, change of season did not influence the permanent turn-over of parasites and the number of parasite genotype per person. Data obtained here will be serve as a baseline for future studies which will carried out at Cotonou to analyse the impact of any malaria control measures on parasite populations.

Molecular characterisation of Plasmodium reichenowi apical membrane antigen-1 (AMA-1), comparison with P. falciparum AMA-1, and antibody-mediated inhibition of red cell invasion

Apical membrane antigen 1 is a candidate vaccine component for malaria. It is encoded by a single copy gene and has been characterised in a number of malaria species as either an 83-kDa de novo product (Plasmodium falciparum; Pf AMA-1) or a 66-kDa product (all other species). All members of the AMA-1 family are expressed during merozoite formation in maturing schizonts and are initially routed to the rhoptries. Processed forms may subsequently be associated with the merozoite surface. Because of the unique occurrence of the 83-kDa form in P. falciparum we were interested to determine whether the phylogenetically closely related chimpanzee malaria Plasmodium reichenowi shared characteristics with Pf AMA-1. Here we show that the molecular structure, the localisation and processing are similar to that of Pf AMA-1 and that in vitro growth inhibitory mAbs reactive with Pf AMA-1 also inhibit P. reichenowi growth in an in vitro assay. Polymorphism in the 83-kDa AMA-1 family was analysed through comparison of Pr ama-1 with Pf ama-1 alleles, which showed the most significant evidence for selection maintaining polymorphism in Domains I-III of AMA-1 in P. falciparum. The most substantial divergence between Pr AMA-1 and Pf AMA-1 sequences was in the N-terminal region unique to the 83-kDa form of AMA-1. It was confirmed that the specific Pr ama-1-type allele was not present among P. falciparum parasites in an African population, and an allele coding for lysine at amino acid 187 was uniquely associated with field isolates in this population.

Implications of oxidative stress and inflammatory process in the cytotoxicity of capsaicin in human endothelial cells: lack of DNA strand breakage

Capsaicin, a natural product of Capsicum species is known to induce excitation of nociceptive terminals involved in pain perception. Nevertheless, it is utilized by topical application in humans, giving rise to blood capsaicin concentration up to 10-20 microM. The effect of capsaicin on human endothelial cells ECV 304 has been investigated. The cytotoxicity and inflammatory properties of capsaicin were evaluated by measuring the capsaicin-stimulated release of soluble intercellular adhesion molecule-1 levels (sICAM-1) into the culture medium; production of reactive oxygen species measured by quantification of lipoperoxidation in endothelial cell membranes; and genotoxicity measured using the comet assay and the DNA fragmentation assay. The concentration inhibiting protein synthesis by 50% after 24-h incubation was found to be 175 microM. Capsaicin induced an increase of sICAM-1 release into the culture medium at concentration >/=100 microM. Lipoperoxidation measured by malondialdehyde production increased at capsaicin concentration >/=200 microM. The comet test and DNA fragmentation assay clearly suggested that capsaicin does not induce significant DNA strand breaks within the range of concentrations used. Because the inflammatory reaction and lipid peroxidation may affect cellular functions and lead to cell death, the present data may have important implications for the possible health threats of capsaicin, specially in the case of unreasonable use of capsaicin preparations in pathological situations.

Combined effects of okadaic acid and cadmium on lipid peroxidation and DNA bases modifications (m5dC and 8-(OH)-dG) in Caco-2 cells

Okadaic acid (OA) is a marine toxin, a tumour promoter and an inducer of apoptosis. It mainly inhibits protein-phosphatases, protein synthesis and enhances lipid peroxidation. Cadmium (Cd) is known to be carcinogenic in animals and humans (group 1 according to the International Agency for Research on Cancer (IARC) classification). Cd also induces oxidative stress in living organisms. Since they are sometimes found simultaneously in mussels, we have evaluated in the present investigation, the lipid peroxidation, as malondialdehyde (MDA) production, in the variation of the ratios of 8-(OH)-dG/10(5)dG and m5dC/(dC + m5dC) induced by OA and/or Cd in Caco-2 cells. When cells were treated exclusively by OA (15 ng/ml) or Cd (0.625 and 5 microg/ml) for 24 h, protein synthesis was inhibited (by 42 +/- 5%, 18 +/- 13%, and 90 +/- 4% respectively) while MDA production was 2,235 +/- 129, 1710 +/- 20, and 11,496 +/-1,624 pmol/mg protein respectively. In addition, each toxicant induced modified bases in DNA; increases in oxidised bases and methylated dC. The combination of OA and cadmium was more cytotoxic and caused more DNA base modifications; the ratio m(5)dC/(m(5)dC + dC) was increased from 3 +/- 0.15 to 9 +/- 0.15 and the ratio 8-(OH)-dG/10(5) dG also (from 36 +/- 2 to 76 +/- 6). The combination of OA and Cd also increased the level of MDA (1,6874 +/- 2,189 pmole/mg protein). The present results strongly suggest that DNA damage resulting from the oxidative stress induced by these two toxicants may significantly contribute to increasing their carcinogenicity via epigenetic processes.

Prevention by vitamin E of DNA fragmentation and apoptosis induced by fumonisin B1 in C6 glioma cells

Fumonisin B1 (FB1), produced by the fungus Fusarium moniliforme, belongs to a class of sphingosine analogue mycotoxins that occur widely in the food chain. Epidemiological studies have associated consumption of Fusarium moniliforme-contaminated food with human oesophageal cancer in China and South Africa. FB1 also causes equine leucoencephalomalacia. Evidence for induction of apoptosis by FB1 was first obtained when C6 glioma cells were incubated with fumonisin B1 (3-27 microM) causing DNA fragmentation profiles showing DNA laddering in gel electrophoresis and apoptotic bodies revealed by chromatin staining with acridine orange and ethidium bromide. Further confirmation experiments and comet assays have been performed under similar conditions. The results of the comet test show that FB1 at 9 and 18 microM induces respectively 50 +/- 2% and 40 +/- 1% of cells with a comet with an increased tail length of 93 +/- 9 microm and 102 +/- 17 microm respectively. Under these concentrations, FB1 induced DNA fragmentation and laddering and many apoptotic bodies. Pre-incubation of the cells with vitamin E (25 microM) for 24 h before FB1 (18 microM) significantly reduced DNA fragmentation and apoptotic bodies induced by FB1.

Concentrations of riboflavin and related organic acids in children with protein-energy malnutrition

BACKGROUND

Riboflavin, flavin mononucleotide (FMN), and flavin adenine dinucleotide (FAD) concentrations have been little studied in cases of malnutrition.

OBJECTIVE

Our objective was to investigate the effects of malnutrition on riboflavin status and riboflavin's relation with thyroid hormones and concentrations of urinary organic acids.

DESIGN

Malnourished children from the savannah in Benin (group S, n = 30) and the coast in Togo (group C, n = 30), as well as 24 control subjects from both regions, were studied. Blood riboflavin, FMN, and FAD were analyzed by HPLC; urinary organic acids were analyzed by gas chromatography-mass spectrometry.

RESULTS

Children in group S were more severely malnourished than children in group C. Triiodothyronine concentrations were lower in group S than in group C or the control group (1.12 +/- 0.24 compared with 1.74 +/- 0.18 and 2.92 +/- 0.19 nmol/L, respectively; P < 0.0001). Plasma riboflavin concentrations in group S were higher than those in group C or the control group (66.90 +/- 12.75 compared with 28.09 +/- 9.12 and 20.08 +/- 3.03 nmol/L, respectively; P < 0.001). Plasma FAD concentrations in group S were lower than those in group C or the control group (31.57 +/- 10.19 compared with 59.02 +/- 5.60 and 65.35 +/- 5.23 nmol/L, respectively; P < 0.0001). Dicarboxylic aciduria was higher in group C than in group S or the control subjects.

CONCLUSIONS

Children in group S had low triiodothyronine concentrations and low conversion of plasma riboflavin into its cofactors, leading to a plasma FAD deficiency. Plasma FAD was not correlated with urinary dicarboxylic acid concentrations.

Discoupling the Ca(2+)-activation from the pore-forming function of the bi-component Panton-Valentine leucocidin in human PMNs

The consecutive cell activation, including Ca(2+)-channel opening, and pore formation leading to human neutrophil lysis were the two functions of the staphylococcal Panton-Valentine leucocidin attempted to be discoupled by site-directed mutagenesis. In a first approach consisting in deletions of the cytoplasmic extremity of the transmembranous domain, we produced a LukF-PV DeltaSer125-Leu128 with a slightly reduced Ca(2+) induction but with a significantly lowered lytic activity when combined with its synergistic protein LukS-PV. The second approach consisted in the modification of charges and/or introduction of a steric hindrance inside the pore, which also led to interesting mutated proteins: LukF-PV G131D, G131W and G130D. The latter had an intact Ca(2+) induction ability while the lytic one was 20-fold diminished. Binding properties and intrinsic pore diameters of these discoupled toxins remained comparable to the wild-type protein. The mutated proteins promoted interleukin-8 secretion, but they were rather inactive in an experimental model. New insights are brought concerning the role of the two functions in the virulence of this bi-component leucotoxin.