M Ben Said

Institut Pasteur de Tunis, Tunis-Ville, Tūnis, Tunisia

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Publications (68)56.45 Total impact

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    ABSTRACT: The overall performance of quantitative assays in the detection of anti-Toxoplasma IgG is satisfactory but discrepancies between assays are not uncommon especially when IgG concentrations are close to the limit of detection of the tests.The purpose of our study was to identify soluble and membrane antigens extracted from T. gondii tachyzoites by immunoblot in order to select the most relevant antigenic bands to be used for qualitative serodiagnosis of acquired toxoplasmosis.We selected 5 relevant bands (98, 36, 33, 32 and 21 kDa) with soluble antigens and 4 relevant bands (42, 35, 32, 30 kDa) with membrane antigens which gave high sensitivity and/or specificity in immunodiagnosis.The association on the same blot of at least 3 out of the 5 relevant bands in the soluble antigen immunoblot showed the highest sensitivity/specificity (97.4% / 99.0% respectively).Our results indicate that immunoblot using soluble tachyzoite extract with simultaneous detection of at least 3 out of the 5 bands (98, 36, 33, 32 and 21 kDa) represents a valuable test for serodiagnosis of acquired toxoplasmosis and should be further evaluated as a confirmatory test for sera which give discrepant results in quantitative assays.This article is protected by copyright. All rights reserved.
    Parasite Immunology 11/2014; · 2.21 Impact Factor
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    ABSTRACT: The determination of the accurate immune status of pregnant women is crucial in order to prevent congenital toxoplasmosis. Equivocal results with conventional serological techniques are not uncommon when IgG titers are close to the cut-off value of the test, so that a confirmatory technique is needed. For this purpose, we developed a homemade immunoblot (IB) using soluble extract of T. gondii tachyzoites and assessed it by testing 154 positive, 100 negative and 123 equivocal sera obtained from pregnant women. In order to select the more valuable bands in terms of sensitivity and specificity, we used the Youden Index (YI). The highest YIs were those given by the 32, 36, 98, 21 and 33 bands. The simultaneous presence on the same blot of at least 3 bands showed a much higher YI (0.964) and was adapted as a positivity criterion. The analysis of results showed that our homemade IB correlated well with the commercial LDBIO Toxo II IgG® kit recently recommended as a confirmatory test (96.74% of concordance).
    The Korean Journal of Parasitology 06/2014; Vol. 52(No. 4):1-7. · 0.88 Impact Factor
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    ABSTRACT: The determination of the accurate immune status of pregnant women is crucial in order to prevent congenital toxoplasmosis. Equivocal results with conventional serological techniques are not uncommon when IgG titers are close to the cut-off value of the test, so that a confirmatory technique is needed. For this purpose, we developed a homemade immunoblot (IB) using soluble extract of Toxoplasma gondii tachyzoites and assessed it by testing 154 positive, 100 negative, and 123 equivocal sera obtained from pregnant women. In order to select the more valuable bands in terms of sensitivity and specificity, we used the Youden Index (YI). The highest YIs were those given by the 32, 36, 98, 21, and 33 bands. The simultaneous presence on the same blot of at least 3 bands showed a much higher YI (0.964) and was adapted as the positivity criterion. The analysis of results showed that our homemade IB correlated well with the commercial LDBIO Toxo II IgG® kit recently recommended as a confirmatory test (96.7% of concordance).
    The Korean Journal of Parasitology 06/2014; 52(5):493-499.. · 0.88 Impact Factor
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    ABSTRACT: Although scarce, available data suggest that the epidemiology of invasive aspergillosis (IA) in North Africa differs from northern countries, where more than 80 % is caused by Aspergillus fumigatus. This study aimed at describing the epidemiology of IA in the region of Sousse, Tunisia, and at assessing the usefulness of the available diagnostic tools. For 2 years, clinical and mycological data were prospectively collected from 175 neutropenia episodes of 91 patients hospitalised in the haematology department at the Farhat Hached hospital in Sousse (Tunisia). Screening for galactomannan antigen was positive in 40 % of neutropenia episodes; Aspergillus PCR was positive in 42 % of the tested sera. Nine patients were classified as probable and two as possible IA according to the EORTC/MSG criteria. Twelve patients who prematurely died, had no CT scan and could not be classified. Fifty-six Aspergillus spp. were isolated in 53 (6.5 %) sputa collected from 35 (20 %) patients. The following species were identified with MALDI-TOF mass spectrometry and DNA sequencing: A. niger, 35 %; A. flavus, 38 %; A. tubingensis, 19 %; A. fumigatus, 4 %; A. westerdijkiae, 2 % and A. ochraceus, 2 %. Our findings highlight the epidemiological features of IA in Tunisia, which is characterised by the predominance of Aspergillus spp. from sections Nigri and Flavi.
    Mycopathologia 04/2014; · 1.65 Impact Factor
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    ABSTRACT: The performance values of available techniques used in serodiagnosis of toxoplasmosis are satisfactory but they raise problems of equivocal and discordant results for very low IgG titers. Recently marketed, LDBio-Toxo II IgG Western blot (IB) showed an excellent correlation with the dye test. We estimated the proportion of equivocal and discordant results between the enzyme immunoassay Platelia Toxo IgG (EIA-IgG) and fluorescent antibody test (FAT) and assessed the usefulness of the IB as a confirmatory test. Out of 2,136 sera collected from pregnant women, 1,644 (77.0%) tested unequivocally positive and 407 (19.0%) were negative in both EIA-IgG and FAT. The remaining 85 (4%) sera showed equivocal or discordant results. Among them, 73 (85.9%) were positive and 12 (14.1%) were negative in IB. Forty-one (89.1%) equivocal sera in EIA-IgG and 46 (86.8%) equivocal sera in FAT were positive in IB. Reducing the cut-off values of both screening techniques improved significantly their sensitivity in detecting very low IgG titers at the expense of their specificity. In conclusion, equivocal results in routine-used techniques and their discordance in determination of the immune status in pregnancy women were not uncommon. IB test appeard to be highly useful in these situations as a confirmatory technique.
    The Korean Journal of Parasitology 08/2013; 51(4):485-8. · 0.88 Impact Factor
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    ABSTRACT: Onychomycosis is one of the most prevalent dermatophytic diseases. Mycological methods used in the conventional diagnosis may not be optimal. Multiplex (MX) PCR was reported as a reliable alternative. Dermatophyte gene sequence records were used to design a MX PCR for detection and identification of dermatophytes in nail specimens. A MX PCR method based on the amplification of the chitin synthase 1 and internal transcribed spacer genes was developed. The study included 93 strains of dermatophytes and non-dermatophytic fungi, six dermatophytic reference strains and 201 nail specimens from patients with dermatophytic onyxis. DNA extraction directly from nail samples was carried out by using the QIAamp DNA extraction kit (Quiagen). A set of primers was designed and their specificity was assessed. MX PCR detected the causal agent in specimens from which Trichophyton rubrum and T. interdigitale grew in culture and also identified a dermatophyte species in an additional 32 specimens that were negative in microscopy and culture. None of the investigated non-dermatophytic strains was positive. Sensitivity of MX PCR was higher as compared to mycological examination (97% vs. 81.1%). MX PCR for direct detection of dermatophytes from nail samples yielded mixed flora in 32.8% of samples. MX PCR proved sensitive and adequate for the diagnosis of dermatophytic onychomycosis. It is much adapted to cases where culture is negative or contaminated by overgrowing moulds, which makes the identification of the causal agent problematic.
    Mycoses 06/2013; · 1.28 Impact Factor
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    ABSTRACT: In Tunisia, despite the absence of a national program of congenital toxoplasmosis prevention, serodiagnosis is regularly carried out in pregnant women for prenatal screening. We report our experience on congenital toxoplasmosis over the last 11 years (2000–2011). Methods We reviewed the clinical, biological and therapeutic features of 21 cases of congenital toxoplasmosis. Results The infection occurred in the first trimester in four cases, in the second trimester in six cases and in the third trimester in four cases. Presumed date of maternal contamination could not be specified in seven cases. Spiramycin was prescribed in 16 cases and pyrimethamine-sulfadiazine in one case with a positive PCR. Fetal ultrasound was poorly contributive in the antenatal screening. It showed intra-uterine growth retardation in one case. At birth, 16 neonates were asymptomatic, four presented neurological symptoms and four presented ocular involvement. The postnatal serology was positive for 21 neonates during the first month of life. IgA were positive in 76.9 % of cases and IgM in 66.6 % of cases. Comparison of immunoblot profiles showed a neo-synthesis of IgG and/or IgM in 57.1 % of cases. Twenty neonates were treated with sulfadoxine-pyrimethamine. The evolution was marked by the early death of two neonates. Conclusion Severe congenital toxoplasmosis is still relevant in our country. The management of pregnant women at risk needs to be improved.
    Journal de Pédiatrie et de Puériculture 04/2013; 26(2):83–89.
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    ABSTRACT: Purpureocillium lilacinum is a saprophytic fungus found in soil and decaying organic matter, but has been reported as an emerging pathogen in immunocompromised patients and following surgical procedures. Infections caused by this mold are often difficult to treat because of its intrinsic resistance to conventional antifungal agents and variable susceptibility to novel triazoles. In immunocompetent subjects, infections caused by P. lilacinum are unusual and mainly involve the skin. We describe herein a case of cutaneous hyalohyphomycosis due to this fungus in an immunocompetent girl without any predisposing risk factors and review the previously reported cases in immunocompetent hosts.
    Medical mycology: official publication of the International Society for Human and Animal Mycology 01/2013; · 2.13 Impact Factor
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    ABSTRACT: Candida albicans is one of the most medically important fungi because of its high frequency as a commensal and pathogenic microorganism causing superficial as well as invasive infections. Strain typing and delineation of the species are essential for understanding its biology, epidemiology and population structure. A wide range of molecular techniques have been used for this purpose including non DNA-based methods (multilocus enzyme electrophoresis), conventional DNA-based methods (electrophoretic karyotyping, random amplified polymorphic DNA, amplified fragment length polymorphism, restriction enzyme analysis with and without hybridization, rep-PCR) and DNA-based methods called exact typing methods because they generate unambiguous and highly reproducible typing data (including microsatellite length polymorphism and multilocus sequence typing). In this review, the main molecular methods used for C. albicans strain typing are summarized and their advantages and limitations are discussed with regard to their discriminatory power, reproducibility, cost and ease of performance. © 2013 The Authors Journal of Applied Microbiology © 2013 The Society for Applied Microbiology.
    Journal of Applied Microbiology 01/2013; · 2.20 Impact Factor
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    ABSTRACT: Discrimination of the Old World Leishmania parasites is important for diagnosis and epidemiological studies of leishmaniasis. We have developed PCR assays that allow the discrimination between L. major, L. tropica and L. infantum Tunisian species. The identification was performed by a simple PCR targeting cysteine protease B (cpb) gene copies. These PCR can be a routine molecular biology tools for discrimination of Leishmania spp. from different geographical origins and different clinical forms. Our assays can be an informative source for cpb gene studying concerning drug, diagnostics and vaccine research. The PCR products of the cpb gene and the N-acetylglucosamine-1-phosphate transferase (nagt) Leishmania gene were sequenced and aligned. Phylogenetic trees of Leishmania based cpb and nagt sequences are close in topology, and present the classic distribution of Leishmania in the Old World. The phylogenetic analysis has enabled the characterization and identification of different strains, using both multicopy (cpb) and single copy (nagt) genes. Indeed, the cpb phylogenetic analysis allowed us to identify the Tunisian L. killicki species, and a group which gathers the least evolved isolates of the L. donovani complex, that was originated from East Africa. This clustering confirms the African origin for the visceralizing species of the L. donovani complex.
    Acta tropica 12/2012; · 2.79 Impact Factor
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    ABSTRACT: Onychomycosis is the most frequently encountered nail disease and may be difficult to diagnose and treat. The objective of this study was to determine the prevalence, the clinical and mycological characteristics of onychomycosis in central Tunisia. It is a retrospective study performed over a 22-year period (1986-2007). It included 7151 patients (4709 women and 2442 men) with suspected fingernails and/or toenails onychomycosis. The patients were referred to the Mycology-Parasitology Laboratory of Farhat Hached hospital in Sousse for mycological examination. Both direct microscopy and culture of the nail material were performed to diagnose and identify the causative fungal species. Onychomycosis was confirmed in 78.6% of investigated patients (5624/7151). The positivity rate was higher in women as compared with men. In both men and women, fingernails were most frequently involved than toenails. No significant relation was found between gender and toenails onychomycosis, whereas fingernails were frequently involved in women. As far as aetiological agents are considered, dermatophytes, yeast and moulds were responsible for 49.9%, 47.4% and 2.7% of onyxis cases respectively. In fingernail infections, yeast were the most frequent fungi (83.6%), Candida albicans being the leading species (51.6%). In contrast, in toenail infections, dermatophytes were more frequent (74.1%). Trichophyton rubrum was by far the dominant species (88.1%). Yeast were observed more frequently in women whereas dermatophytes were more common in men. Moulds were involved in 4.2% of cases. The most frequent species were Aspergillus sp. and Chrysosporium sp. Onychomycosis is a frequent disease in central Tunisia. T. rubrum is the predominant agent in toenails infection and yeast, mainly C. albicans, in fingernails onychomycosis.
    Mycoses 10/2012; · 1.28 Impact Factor
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    ABSTRACT: Onychomycosis is one of the most prevalent dermatophytic diseases. Mycological methods used in the conventional diagnosis may not be optimal. PCR was reported as a reliable alternative in the diagnosis of dermatophytosis. A PCR method based on the amplification of the chitin synthase 1 gene was developed. The study included 119 strains of dermatophytes and non dermatophytic fungi, eight dermatophytic reference strains and 201 nail specimens from patients with dermatophytic onyxis. DNA extraction was carried out by using the QIAamp DNA extraction kit (Quiagen). PCR positivity was based on the production of a specific 432bp fragment. None of the investigated non dermatophytic strains was positive. Sensitivity of PCR was higher as compared to mycological examination (90.5% vs. 81.1%). PCR was positive in 31 onyxis cases with positive direct examination but negative or contaminated culture. In contrast, PCR was negative in 10 cases where both direct examination and culture were found positive. PCR is an adequate tool for the diagnosis of dermatophytic onychomycosis. It is much adapted to cases where culture is negative or contaminated by overgrowing molds, which makes the identification of the causal agent problematic.
    Journal de Mycologie Médicale/Journal of Medical Mycology 09/2012; 22(3):249-55. · 0.74 Impact Factor
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    ABSTRACT: Objective The aim of our study was to evaluate the level of fungal contamination of food served to patients in the hematology unit of Farhat Hached hospital, Sousse (Tunisia).Methods We analyzed 159 food served to 90 patients during the post-chemotherapy aplasia period.ResultsThe overall rate of fungal contamination was 66.6%. Fruits and green salads’ contamination was very high (90 and 100%, respectively). Aspergillus species were the most frequent (48.4%) followed by Candida (25.1%), Penicillium (22%), Rhizopus (17.6%) and Cladosporium (17%). The presence of Aspergillus on fruits (66.6%) represents a real source of contamination by inhalation of spores and the presence of Candida (25.1%) in any type of food is a source of gastrointestinal colonization.Conclusion The diet of neutropenic patients should be submitted to a strict surveillance to reduce the risk of fungal infections of food.
    Nutrition Clinique et Métabolisme. 09/2012; 26(3):114–118.
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    ABSTRACT: Over a period of ten years, a series of 694 Leishmania strains from Tunisian leishmaniasis foci were isolated and identified by isoenzymatic analysis. Strains were obtained from human cutaneous and visceral leishmaniasis in immunocompetent subjects, visceral leishmaniasis in imunocompromised individuals and from dogs with visceral leishmaniasis. Two classically dermotropic species, Leishmania (L.) major and Leishmania killicki were found. L. major with the single zymodeme MON-25 was the most isolated in cutaneous leishmaniasis foci of the Centre and South of Tunisia with a recent northern extension. L. killicki zymodeme MON-8 was sporadically found both in its classical microfocus of Tataouine in southeastern Tunisia as well as in some new foci in Southwestern, Central and Northern Tunisia. Leishmania infantum with its three zymodemes MON-1, MON-24 and MON-80 was isolated from both visceral and cutaneous human cases. The majority of L. infantum strains were found in the Northern part of the country; however, some strains were reported for the first time in the Southern part. L. infantum MON-1 was the only zymodeme isolated from canine leishmaniasis.
    Acta tropica 08/2012; 124(3):221-8. · 2.79 Impact Factor
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    ABSTRACT: Fungemia is classically caused by a single species and the detection of more than one species in blood samples is uncommon. We report four cases of mixed fungemia (MF) diagnosed in the parasitology-mycology laboratory of Farhat-Hached hospital in Sousse, Tunisia. The MF episodes occurred in two neonates and two adults suffering from acute myeloid leukemia. Two fungal species were detected concomitantly within the same blood culture in all cases. Species combination was detected by the subculture of the blood culture on Candida ID(®) chromogenic medium in three cases and on Sabouraud agar in one case. Predisposing factors were: indwelling catheters (4/4), broad-spectrum antibiotics (3/4), neutropenia (2/4), exclusive parenteral nutrition (2/4) and Candida colonization (1/4). Patients presented febrile sepsis with no response to broad-spectrum antibiotic therapy in all cases. Outcome under antifungal treatment was favorable in two cases and the two other patients died. CONCLUSION: MF appears similar to the more common monomicrobial fungemia. The use of chromogenic media in routine can improve the detection of MF episodes allowing appropriate antifungal therapy.
    Journal de Mycologie Médicale/Journal of Medical Mycology 06/2012; 22(2):192-6. · 0.74 Impact Factor
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    ABSTRACT: Fungemia is classically caused by a single species and the detection of more than one species in blood samples is uncommon. We report four cases of mixed fungemia (MF) diagnosed in the parasitology-mycology laboratory of Farhat-Hached hospital in Sousse, Tunisia. The MF episodes occurred in two neonates and two adults suffering from acute myeloid leukemia. Two fungal species were detected concomitantly within the same blood culture in all cases. Species combination was detected by the subculture of the blood culture on Candida ID® chromogenic medium in three cases and on Sabouraud agar in one case. Predisposing factors were: indwelling catheters (4/4), broad-spectrum antibiotics (3/4), neutropenia (2/4), exclusive parenteral nutrition (2/4) and Candida colonization (1/4). Patients presented febrile sepsis with no response to broad-spectrum antibiotic therapy in all cases. Outcome under antifungal treatment was favorable in two cases and the two other patients died. Conclusion MF appears similar to the more common monomicrobial fungemia. The use of chromogenic media in routine can improve the detection of MF episodes allowing appropriate antifungal therapy.
    Journal de Mycologie Médicale / Journal of Medical Mycology. 06/2012; 22(2):192–196.
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    ABSTRACT: The serological tests commonly used for the diagnosis of toxoplasmosis raise the problem of the interpretation of the borderline immunoglobulin G (IgG) levels and discordant results between various tests.Objective The purpose of our study was to evaluate the contribution of the immunoblotting in the detection of specific IgG in acquired toxoplasmosis of immunocompetent patients especially when levels are equivocal or discordant in enzyme-linked immunosorbent assay (Elisa) and indirect fluorescent antigen test (IFAT).Materiel and methodsWe tested three groups of sera. The first included 87 positive sera, the second 33 negative sera, and the last one 29 equivocal sera.ResultsResults obtained with the first and the second group of sera led us to identify the bands 30 kDa and 32 kDa as markers of the toxoplasmic infection. The simultaneous presence of both bands showed a sensitivity of 91.5%, a specificity of 96.9%, a VPP of 98.7%, a VPN of 74.4% and a Youden's index of 0.88. Our findings suggest that the presence of these two bands is a reliable criterion for the confirmation of the presence of anti-toxoplasmic IgG in the corresponding serum. The immunoblot allowed us to ascertain serological status of 27 (93.1%) patients from the third group in which results were discrepant or equivocal in Elisa and/or in IFAT.Conclusion Immunoblot is a useful serological test for detection of very low or equivocal titers.
    Pathologie Biologie 06/2012; 60(3):160–165. · 1.67 Impact Factor
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    ABSTRACT: The aim of our study was to assess epidemiological features of neonatal invasive candidiasis in Farhat Hached hospital of Sousse, Tunisia, including incidence, risk factors, mortality, species distribution and antifungal susceptibility. Laboratory data from 1995 to 2010 and medical records of 127 invasive candidiasis cases were reviewed. We tested the susceptibility of 100 Candida sp isolates by using ATB fungus(®) 3 and to fluconazole by using E-test(®) strips. A total of 252 cases of neonatal invasive candidiasis occurred over the study period. The incidence increased 1.8-fold from 1995 to 2006 and decreased fourfold from 2007 to 2010. Candida albicans was the predominant species up to 2006 and a shift in the species spectrum was observed with increase of the non-albicans species mainly C. parapsilosis. The agreement between the ATB Fungus(®) and the E-test(®) for determining fluconazole susceptibility was high. All tested isolates were susceptible to fluconazole, flucytosine, amphotéricine B and voriconazole and the itraconazole resistance rate was 5%. The mortality rate was 63%. The invasive candidiasis incidence increased from 1995 to 2006 and decreased from 2007 to 2010. The spectrum of Candida species and the lack of fluconazole-resistant strains argue for the usefulness of fluconazole as an empiric treatment.
    Mycoses 03/2012; 55(6):493-500. · 1.28 Impact Factor
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    ABSTRACT: The nosocomial transmission of Candida albicans in neonatal intensive care units (NICUs) is an increasing concern and understanding the route of this transmission is critical for adequate infection control measures. The aim of our study was to assess the likeliness of nosocomial acquisition of C. albicans in the NICU of Farhat Hached hospital in Sousse (Tunisia). We genotyped 82 isolates from 40 neonates and 7 isolates from 5 health care workers (HCWs) with onychomycosis, by using CDC3 microsatellite length polymorphism (MLP) and the high-resolution melting (HRM) analysis. Combined MLP and HRM CD3 analysis led to the delineation of 12 genotypes. Five temporal clustering caused by five genotypes occurred during the study period. Three of these genotypes were isolated in both neonates and HCWs. The first clustering included 28 isolates obtained between January 2003 and May 2004 from 16 neonates and 2 HCWs. The second clustering included three isolates collected in 2004 from three neonates and two HCWs. The third clustering included 11 isolates obtained from 6 neonates and 1 HCW in 2006. The two remaining clustering could not be associated with any HCW's contamination. These results argue for the nosocomial transmission of C. albicans in our NICU. The combined MLP and HRM analysis is a rapid first approach for tracking cross-contamination.
    DNA and cell biology 02/2012; 31(7):1161-6. · 2.28 Impact Factor
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    ABSTRACT: Geotrichum capitatum infection is uncommon, and has been exclusively reported in immunocompromised patients. The prognosis is poor with a mortality rate ranging from 50 to 90%. We report 3 cases of Geotrichum capitatum fungemia in neutropenic patients receiving chemotherapy for acute myeloblastic leukemia.The infection was successfully cured with voriconazole in 1 case and was fatal in the 2 remaining cases despite treatment with amphotericin B.
    Medical Mycology Case Reports. 01/2012; 1(1):88–90.

Publication Stats

132 Citations
56.45 Total Impact Points

Institutions

  • 2014
    • Institut Pasteur de Tunis
      Tunis-Ville, Tūnis, Tunisia
  • 2009–2014
    • Centre Hôpital Universitaire Farhat Hached
      Susa, Sūsah, Tunisia
  • 2012
    • Ministère de la Santé Publique de Tunisie
      Tunis-Ville, Tūnis, Tunisia
  • 2004
    • Faculté de Médecine Ibn El Jazzar de Sousse
      Susa, Sūsah, Tunisia
  • 1991
    • Istituto Superiore di Sanità
      Roma, Latium, Italy
  • 1989
    • Faculty of Medecine of Tunis
      Tunis-Ville, Tūnis, Tunisia