Introduction: Rhinoviruses (HRV) are among the leading causes of Severe Acute Respiratory Infection (SARI). Their burden and genetic diversity vary from one region to another and little is known in Northern African regions. This study... more
Introduction: Rhinoviruses (HRV) are among the leading causes of Severe Acute Respiratory Infection (SARI). Their burden and genetic diversity vary from one region to another and little is known in Northern African regions. This study describes epidemiological patterns and genotypic diversity of HRV in SARI cases during a two and half year’s study, in Northern Tunisia. Methodology: A total of 271 SARI cases, admitted into the Pediatric Intensive Care Unit of Bechir Hamza Children's Hospital in Tunis, were collected between September 2015 and December 2017. The investigation concerned 104 samples positive for HRV and/or HEV (Human Enterovirus) obtained among these cases. Specific HRV and HEV detections were assessed by real-time PCRs. The HRV molecular typing was based on the VP4-VP2 genomic region analyses. Results: Among the viral SARI cases, 33.5% and 12.3% were positive for HRV and HEV respectively. Molecular investigations showed high prevalence of HRV-A (63.3%) followed by ...
Research Interests: Medicine and Rhinovirus
Candida albicans colonizes the respiratory tract of patients with Cystic Fibrosis (CF). It competes with CF-associated pathogens, such as Pseudomonas aeruginosa and Staphylococcus aureus, and contributes to disease severity. We serially... more
Candida albicans colonizes the respiratory tract of patients with Cystic Fibrosis (CF). It competes with CF-associated pathogens, such as Pseudomonas aeruginosa and Staphylococcus aureus, and contributes to disease severity. We serially recovered 160 C. albicans clinical isolates over a period of 30 months from the sputum of 23 pediatric and 2 adult antifungal-naive CF patients at Children’s Hospital Tunis and characterized the genotype and phenotype of a subset of strains using multilocus sequence typing (MLST) and growth assays on multiple stress-, filamentous growth- and biofilm-inducing media. Out of 16 patients regularly sampled for at least 9 months, 8 and 4 were chronically and transiently colonized with C. albicans, respectively. MLST analyses of 56 strains originating from 15 patients indicated that each patient was colonized with a single strain, while 8 patients (53%) carried isolates from clade 4 known to be enriched with strains from Middle East-Africa. A subset of thes...
OBJECTIVES We implemented a project named MENINGSTOP in three countries of North Africa (Algeria, Morocco and Tunisia). The main objective was to use real-time PCR to detect, identify and type the three main agents (Neisseria... more
OBJECTIVES We implemented a project named MENINGSTOP in three countries of North Africa (Algeria, Morocco and Tunisia). The main objective was to use real-time PCR to detect, identify and type the three main agents (Neisseria meningitidis, Streptococcus pneumoniae and Haemophilus influenzae) responsible for invasive bacterial infections (IBI). METHODS The protocol of WHO and US CDC for real-time PCR was used to detect and type the three bacterial agents in clinical samples. We also designated two quality exercises using an external interlaboratory study and cross-testing of 10% of randomly selected samples. RESULTS Among the 752 samples tested, 18% were positive for one of the three agents. N. meningitidis was the most frequent globally reaching 9% of all samples (7% to 17% range) followed by S. pneumoniae 8% of all samples (6% to 15%). Group B meningococci was the most frequent (74% of all positive samples for meningococci and ranging from 50% to 90%). Quality assurance showed >85% correlation scores. CONCLUSIONS Real-time PCR can help improving epidemiological surveillance. Data confirm the prevalence of meningococci B. Our project add a reliable tool to enhance surveillance and to help decision making in vaccination strategies against IBI.
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Results: The mean age of the17 patients was 1 year and a half (1 month 13 years). The first bacterial pulmonary infection occurred at the age of 21 months on average (2 months 9 years). The organism was identified in 13 cases. It was... more
Results: The mean age of the17 patients was 1 year and a half (1 month 13 years). The first bacterial pulmonary infection occurred at the age of 21 months on average (2 months 9 years). The organism was identified in 13 cases. It was Staphylococcus aureus (n= 6) of Pseudomonas aeruginosa (n = 5), and Haemophilus Influenzae (n= 3). Subsequent episodes occurred at a rate of 2.3 times / year / child. Eight patients developed diffuse bronchiectasis. Germs isolated during follow-up were: Pseudomonas aeruginosa(n = 10),Staphylococcus aureus (n = 9), Haemophilus Influenzae (n = 8), Klebsiella pneumoniae (n = 1), Serratia Liquefiens (n= 1) and Marcescens (n =1). Chronic colonization with Staphylococcus aureus was found in 3 cases and Pseudomonas aeruginosa in 10 cases. The latter had occurred after an average of 7 years of disease development (11 months -13 years). The Pseudomonas aeruginosa was responsible for an increase in the number of hospitalizations for respiratory exacerbation (n = ...
The aim of this study was to determine the bacteriological characteristics of Haemophilus influenzae (Hi) strains isolated from children, namely serotyping, biotyping and their antibiotic susceptibilities specifying the mechanisms and the... more
The aim of this study was to determine the bacteriological characteristics of Haemophilus influenzae (Hi) strains isolated from children, namely serotyping, biotyping and their antibiotic susceptibilities specifying the mechanisms and the β-lactams resistance genes. This study made use of 138 Hi strains isolated from 2009 to 2010 at the Microbiological Laboratory of the Children’s Hospital in Tunisia. Antimicrobial susceptibility for all Hi isolates was determined as recommended by the CA-SFM (Comité de l'antibiogramme de la Société Française de Microbiologie). Beta-lactam resistance genes (blaTEM,, blaROB and ftsI) were detected by PCR (Polymerase Chain Reaction) as well as their capsular genes (bexA). Ampicillin resistance was 44.92% (62/138) of Hi isolates. PCR showed that all of the strains were identified as non-capsulated. These isolates were subdivided into 3 groups according to the ampicillin resistance molecular mechanisms as follows: the group of β-lactamase positive a...
Rhinoviruses (RV) are a major cause of Severe Acute Respiratory Infection (SARI) in children, with high genotypic diversity in different regions. However, RV type diversity remains unknown in several regions of the world. In this study,... more
Rhinoviruses (RV) are a major cause of Severe Acute Respiratory Infection (SARI) in children, with high genotypic diversity in different regions. However, RV type diversity remains unknown in several regions of the world. In this study, the genetic variability of the frequently circulating RV types in Northern Tunisia was investigated, using phylogenetic and phylogeographic analyses with a specific focus on the most frequent RV types: RV-A101 and RV-C45. This study concerned 13 RV types frequently circulating in Northern Tunisia. They were obtained from respiratory samples collected in 271 pediatric SARI cases, between September 2015 and November 2017. A total of 37 RV VP4-VP2 sequences, selected among a total of 49 generated sequences, was compared to 359 sequences from different regions of the world. Evolutionary analysis of RV-A101 and RV-C45 showed high genetic relationship between different Tunisian strains and Malaysian strains. RV-A101 and C45 progenitor viruses’ dates were e...
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Introduction: Bacterial meningitis is a medical emergency requiring a fast and reliable diagnosis. Molecular methods such as real-time PCR (rt-PCR) offer an attractive alternative. Thus, this study aims to establish multiplex rt-PCRs... more
Introduction: Bacterial meningitis is a medical emergency requiring a fast and reliable diagnosis. Molecular methods such as real-time PCR (rt-PCR) offer an attractive alternative. Thus, this study aims to establish multiplex rt-PCRs detecting N. meningitidis, S. pneumoniae and H. influenzae b from cerebrospinal fluid in Tunisian children beyond neonatal age. Methodology: Using bioinformatic tools and experimentation, we validated the specificity and optimal criteria of PCRs for primers and probes of plyA (S. pneumoniae), ctrA and sodC (N. meningitidis) and bexA genes (H. influenzae b). We performed one multiplex RT-PCR for detection of S. pneumoniae and N. meningitidis targeting plyA and ctrA, sodC genes respectively, simultaneously with a singleplex RT-PCR for H. influenzae b. The sensitivity and specificity of our methods were assessed. Then, we tested our methods for 122 CSF samples collected from suspected meningitis cases between 2014 and 2016 in Bechir Hamza Children’s Hospit...
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The aims of our study were to characterize phenotypically and genotypically erythromycin-resistant Streptococcus pyogenes or group A streptococci (ERGAS) isolates, to evaluate macrolide resistance and to analyze the association between... more
The aims of our study were to characterize phenotypically and genotypically erythromycin-resistant Streptococcus pyogenes or group A streptococci (ERGAS) isolates, to evaluate macrolide resistance and to analyze the association between emm types and virulence factors. Included in this study were all ERGAS strains isolated from 2000 to 2013 at the Children's hospital of Tunis. Antimicrobial susceptibility was performed according to the CA-SFM guidelines. Macrolide resistance genes were revealed by polymerase chain reaction (PCR) method. Virulence factor genes (pyrogenic exotoxin genes and superantigen gene) were detected by PCR, and the emm types were defined by the sequencing of the variable 5' end of the emm gene. Among the 289 GAS isolates collected, 15 (5.2%) were resistant to erythromycin; 7 of the strains were assigned to the cMLSB phenotype (46.6%); 5 harbored ermB gene alone (33.3%); and 2 strains coharbored ermB and mefA (13.3%). The remaining (53.4%) were assigned to the M phenotype and harbored the mefA gene. The frequency of detection of each toxin gene among ERGAS was 13.4% for speA (2 strains), 53.4% for speC (8 strains), and 13.4% for ssa (2 strains). Emm types 1, 58, 11, and 78 were the most frequent among ERGAS strains. The distribution of the cMLSB and M phenotypes changed over the period of investigation with a decrement of cMLSB phenotype and ermB gene that predominated between 2000 and 2006 and an increase of M phenotype and mefA gene between 2007 and 2013, but this difference was nonstatistically significant because of the low number of resistant strains. Emm types 1, 58, and 4 were only present among strains assigned to the M phenotype. However strains assigned to the cMLSB phenotype were associated to emm11, emm22, emm28, emm78, or emm76. There was diversity in emm distribution in ERGAS between the two study periods. There was diversity in emm distribution among ERGAS particularly in 2000-2006. Indeed, from 2000 to 2006, the 6 ERGAS belonged to 5 different emm types (22, 28, 76, 11, and 4), while between 2007 and 2013, seven among the nine ERGAS belonged to only 2 emm types 58 and 1. The speA gene was present only among emm1 isolates, and the ssa gene was associated with emm4 and emm78 types. All emm78, emm28, and emm11 strains harbored speC gene. Our study revealed a low frequency of ERGAS and few emm types were associated with these strains.
Research Interests: Biology, Membrane Proteins, Adolescent, Biological Sciences, Humans, and 15 moreChild, Female, Male, Infant, Streptococcus Pyogenes, Phenotype, Newborn Infant, Genotype, Microbial Sensitivity Tests, Erythromycin, Virulence Factors, microbial drug resistance, Child preschool, Medical and Health Sciences, and Streptococcal infections
Background Community-acquired pleuropneumonia (CPP) is a common complication of pneumonia in children. It is serious given its high morbidity and significant mortality. Aim To study clinical and paraclinical features of CPP in children... more
Background Community-acquired pleuropneumonia (CPP) is a common complication of pneumonia in children. It is serious given its high morbidity and significant mortality. Aim To study clinical and paraclinical features of CPP in children and to establish a common therapeutic strategy. Methods Our retrospective study included patients who were hospitalized for CPP between 2004 and 2012. All data were collected from patients' medical files. Statistical analysis was made by Epi-Info 6. Results One hundred and sixty four patients were registered. The mean age was 32 months (15 days - 14.5 years). The hospital incidence of CPP doubled between 2004 and 2012. The symptomatology was dominated by fever (93.9%), cough (56.7%) and dyspnea (48.1%). The pleural effusion was frequently moderately abundant and loculated. Pleural sample, performed in 53.6% of cases, was the most beneficial bacteriological examination (p=10-6 ). The bacteriological confirmation was attained in 44.5% of cases with ...
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Neisseria meningitidis is one of the major causes of meningitis in children and adolescents, but it is uncommonly found in neonatal meningitis. to report a rare case of meningitis by Neisseria meningitides B. We report the case of... more
Neisseria meningitidis is one of the major causes of meningitis in children and adolescents, but it is uncommonly found in neonatal meningitis. to report a rare case of meningitis by Neisseria meningitides B. We report the case of neonatal meningitis in a 20-day-old girl without shock or purpura. The symptoms were fever and seizures. The culture of cerebrospinal fluid showed to be positive for Neisseria meningitidis B. culture blood was negative. Antibiotic therapy was started at admission and maintained for 3 weeks. The outcome was favourable without neurological sequelae. Early diagnosis and treatment are mandatory for life saving.
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We describe a case of osteomyelitis, in a 7-month-old boy, caused by S. pneumoniae involving the pelvic bone with a purulent collection in the adductor muscle. Osteomyelitis diagnosis was suspected using ultrasound and CT scan... more
We describe a case of osteomyelitis, in a 7-month-old boy, caused by S. pneumoniae involving the pelvic bone with a purulent collection in the adductor muscle. Osteomyelitis diagnosis was suspected using ultrasound and CT scan investigations. This showed a periosteal elevation in the Case Study Ben Marzouk et al.; IJMPCR, 3(3): 68-72, 2015; Article no.IJMPCR.2015.038 69 pelvis and an abscess of the adductor muscle. Culture of the perioperative specimens isolated serotype 19A S. pneumoniae with reduced susceptibility to penicillin and macrolides. The patient was treated successfully with amoxicillin-clavulanate during five weeks, associated with gentamicin during the first week.
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The prevalence of plasmid-mediated quinolone resistance genes [qnr, aac(6′)-Ib-cr and qepA] was sought among Enterobacteriaceae strains obtained from the Children’s Hospital of Tunis (Tunisia). Non-duplicate isolates (n = 278) with... more
The prevalence of plasmid-mediated quinolone resistance genes [qnr, aac(6′)-Ib-cr and qepA] was sought among Enterobacteriaceae strains obtained from the Children’s Hospital of Tunis (Tunisia). Non-duplicate isolates (n = 278) with resistance to extended-spectrum cephalosporins and collected in 2003, 2007, 2008 and 2009 were screened for qnr genes. Forty (14.4 %) isolates were qnr positive and were screened for the presence of the aac(6′)-Ib-cr and qepA genes. qnrB was detected in 21 Klebsiella pneumoniae, 11 Escherichia coli and 6 Enterobacter cloacae isolates. Sequence analysis of the qnrB amplicons revealed variants including 24 qnrB1, 11 qnrB2 and 3 qnrB6. qnrS (qnrS1 allele) was detected only in K. pneumoniae isolates, either alone (two isolates) or with the qnrB gene (one isolate). The qnrA, qnrC and qnrD genes were not found in any of the 278 isolates. No qnr-positive isolates carried the qepA gene. Pyrosequencing results showed that aac(6′)-Ib-cr, a variant of the aac(6′)-Ib...
Research Interests: Medical Microbiology, Biology, Adolescent, Medicine, Biological Sciences, and 15 moreHumans, Child, Escherichia coli, Female, Male, Infant, Enterobacteriaceae, Plasmids, Quinolones, Prevalence, Genetic variation, Klebsiella pneumoniae, Enterobacter cloacae, Child preschool, and Medical and Health Sciences
Research Interests: Microbiology, Medical Microbiology, Public Health, Medicine, Prospective studies, and 15 moreHumans, Tunisia, Hospitalization, Female, Male, Infant, Clinical Sciences, Prevalence, Middle Aged, Adult, Elsevier, Bordetella Pertussis, Child preschool, real time polymerase chain reaction, and Nasopharynx
Despite the introduction of routine vaccination against pertussis for more than a half century, leading to a drastic decline in the number of reported cases, pertussis continues to be an important respiratory disease afflicting... more
Despite the introduction of routine vaccination against pertussis for more than a half century, leading to a drastic decline in the number of reported cases, pertussis continues to be an important respiratory disease afflicting unvaccinated infants and previously vaccinated children as well as adults in whom immunity has waned. The diagnosis of pertussis is challenging and accurate laboratory identification of Bordetella infections remains problematic. Common laboratory diagnostic methods used for pertussis diagnosis include culture, direct-fluorescent-antibody testing (DFA), serology and polymerase chain reaction (PCR). Culture of Bordetella pertussis is highly specific but fastidious and has limited sensitivity. DFA provides a much more rapid result, but has the disadvantage of poor sensitivity and specificity. Serology is not useful in infants. In older persons, it is hampered by the limitations of paired sera and it provides mainly a retrospective diagnosis. Such limitations of conventional diagnosis testing have led to the development of PCR assays. Notwithstanding its lack of standardization, PCR has been found to be more sensitive and more specific than other methods. In this report, we aimed to review current knowledge about the available diagnostic methods and tests that accurately diagnose pertussis.
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Background: Since the 1990s, the epidemiology of bacterial meningitis worldwide has changed thanks to vaccination. In Tunisia, the main causative pathogens were Streptococcus pneumoniae, Neisseria meningitidis and Haemophilus influenzae... more
Background: Since the 1990s, the epidemiology of bacterial meningitis worldwide has changed thanks to vaccination. In Tunisia, the main causative pathogens were Streptococcus pneumoniae, Neisseria meningitidis and Haemophilus influenzae serotype b (Hib). Only Hib vaccination was available during our study period. Objectives: We performed a laboratory case report based-study of suspected bacterial meningitis in Northern Tunisia from January 2014 to June 2017. Methods: CSF samples obtained from children beyond neonatal age with suspicion of meningitis were tested by two real time PCRs, targeting pneumococcus, meningococcus and Hib, and conventional methods. Results: Using real-time PCR, 63 were positive including ten supplementary cases compared to conventional methods. A general decrease of bacterial meningitis cases was demonstrated comparing to previous data. Pneumococcus was predominant (69.84%) followed by meningococcus (28.57%) and Hib (1.59%). The main serotypes were 14, 19F, 6...
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ABSTRACT The duration of ship-generated waves (wake waves) and accelerated currents can generate significant influences on the sediment transport. A 3-D numerical model is presented to estimate these effects. The hydrodynamic model is the... more
ABSTRACT The duration of ship-generated waves (wake waves) and accelerated currents can generate significant influences on the sediment transport. A 3-D numerical model is presented to estimate these effects. The hydrodynamic model is the 3-D Reynolds averaged Navier-Stokes (RANS) equations including the standard k – ɛ model while the 3-D convection-diffusion model is for the resuspended sediment transport. This hydro-sedimentary model is firstly validated with the trench experimental results, and then applied to the open channel with a moving ship. The computed results demonstrate that the resuspension generation mainly depends on ship speeds, barge number, and the relative distance away from ship. The acceleration effects of ship on the sediment transport are analyzed as well.
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We conducted a retrospective study of meningococcal invasive diseases (MID) contracted in children in Tunis between January 1997 and January 2006. The purpose of this study is to specify the clinical, epidemiological, therapeutic and... more
We conducted a retrospective study of meningococcal invasive diseases (MID) contracted in children in Tunis between January 1997 and January 2006. The purpose of this study is to specify the clinical, epidemiological, therapeutic and evolutionary features of these infections and to determine antimicrobial susceptibility and the antigenic formula of N. meningitidis isolates. During the study period, we have collected 79 cases of MID arising in children aged 3 days to 11 years. The majority of children's were less than of 4 years (57.3%). We note a frequency of the MID in winter and in spring. The most frequent clinical shape was meningitis (53%). Twenty one patients (26.6%) had a fulminant meningococcal disease. In our series, the rate of lethality was equal to 17.7%. Among the 46 meningococcal isolates, the most frequent serogroup was the B (73%) followed by C and A. A high heterogeneousness of the antigenic formulae was observed The most frequent phenotype was NT: NST for the g...
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ABSTRACT Le but de cette étude est de déterminer les caractéristiques épidémiologiques des souches de Streptococcus pyogenes ou streptocoque bêtahémolytique du groupe A de Lancefield (SGA) isolées chez des enfants à Tunis, c’est-à-dire la... more
ABSTRACT Le but de cette étude est de déterminer les caractéristiques épidémiologiques des souches de Streptococcus pyogenes ou streptocoque bêtahémolytique du groupe A de Lancefield (SGA) isolées chez des enfants à Tunis, c’est-à-dire la détermination des biotypes ainsi que l’activité de différents antibiotiques (ATB) vis-à-vis de ces souches, et de préciser le support génétique de la résistance aux macrolides. L’étude a concerné 193 souches non répétitives de SGA isolées chez des enfants à l’hôpital d’enfants de Tunis entre 2000 et 2008. Parmi ces souches, 63 provenaient de prélèvements de gorge (32,7 %), 89 de prélèvements de pus (46,2 %), 30 de liquides de ponctions (15,5 %), quatre d’hémocultures (2 %) et sept de prélèvements divers (3,6 %). La détermination des biotypes a été effectuée par l’Api système Rapid ID32 STREP (bioMérieux). L’étude de la sensibilité aux ATB a été faite par la méthode de l’antibiogramme et par la détermination des CMI par la technique E-test. Les gènes de résistance aux macrolides ont été recherchés par la réaction de polymérase en chaîne PCR multiplex. L’étude des biotypes a montré la prédominance du biotype 1 avec 43,5 % (84 souches), suivi du biotype 3 avec 27 % (52 souches). Aucune résistance vis-à-vis des bêtalactamines n’a été observée. En revanche, notre étude met en évidence un taux de résistance aux macrolides de 3,6 % (sept souches) et de 2,6 % (six souches) respectivement pour l’érythromycine et pour la clindamycine. Parmi les sept souches résistantes à l’érythromycine, quatre hébergeaient le gène ermB, un le gène mefA et deux les gènes ermB et mefA simultanément. En conclusion, les biotypes les plus fréquents dans notre collection sont le 1 et le 3. Toutes les souches sont sensibles aux bêtalactamines. La résistance aux macrolides a concerné 3,6 % des souches. L’étude des gènes de résistance aux macrolides montre la prédominance du gène ermB.
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The aims of this study were to determine the contribution of commercial rapid antigen detection test (RADT) in the rapid diagnosis of pharyngitis caused by group A streptococci. A total of 292 children with pharyngitis was included. A... more
The aims of this study were to determine the contribution of commercial rapid antigen detection test (RADT) in the rapid diagnosis of pharyngitis caused by group A streptococci. A total of 292 children with pharyngitis was included. A duplicate throat swabs was taken simultaneously from each patient. One of them was used for RADT achievement and the other for culture. When cultures were positive, a semi-quantitative evaluation was done. Throat culture and RADT were positive in 59 and 72 cases respectively. Fifty four specimens were positive simultaneously with RADT and culture and 215 specimens were negative using both methods. Eighteen specimens were positive only with RADT, 5 of them were treated by amoxicillin. Regarding to the group of patients with a negative RADT and a positive culture (5 cases), all of them had a culture evaluation at "+" or "++". Specificity and sensibility of the RADT were 92.2% and 91.5% respectively. RADT use by physicians can reduce a...
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This study had for aim to define the pattern of Haemophilus influenzae infections in a Tunisian hospital during the prevaccination era. We determined serotypes, biotypes, and antibiotic susceptibility of H. influenzae strains. 187 H.... more
This study had for aim to define the pattern of Haemophilus influenzae infections in a Tunisian hospital during the prevaccination era. We determined serotypes, biotypes, and antibiotic susceptibility of H. influenzae strains. 187 H. influenzae strains were identified in various samples between 1999 and 2002. Strains were isolated essentially from respiratory samples in 63.7% and cerebrospinal fluid in 21.4 %. The mean age of children with invasive infections was 16 months. All invasive strains belong to serotype b. Biotypes I, II and III were the most frequent (84.7%). Ampicillin resistance with betalactamase producing mechanism occurred in 26,7% of isolates, this type of resistance was more frequent among invasive strains (37.2%) than in non-invasive ones (22.8%). All betalactamase producing strains had amoxicillin MICs above 1 mg/l, these strains were susceptible to amoxicillin+clavulanate. Three strains were betalactamase negative ampicillin resistant with ampicillin MICs: 1.5, ...
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... of Medicine of Tunis, Tunis, Tunisia; 2 Laboratory of Bacteriology, Hospital Habib Bourguiba of Sfax, Sfax, Tunisia; 3 Laboratory of Bacteriology, Hospital of Children of Tunis, Tunis, Tunisia. Correspondence: Malek Rachdi... more
... of Medicine of Tunis, Tunis, Tunisia; 2 Laboratory of Bacteriology, Hospital Habib Bourguiba of Sfax, Sfax, Tunisia; 3 Laboratory of Bacteriology, Hospital of Children of Tunis, Tunis, Tunisia. Correspondence: Malek Rachdi (mallouk2008{at}yahoo.fr). ... Tunis Med 81, 167171. ...
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Research Interests: Dogs, Humans, Tunisia, Animals, Visceral Leishmaniasis, and 3 moreIncidence, Phlebotomus, and Insect Vectors
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A 3-D version of the MECCA model (Model of Estuarine and Coastal Circulation Assessment) is used to simulate the dynamics of the Eastern part of the English Channel. This area is characterized by a strong tidal turbulent regime and a... more
A 3-D version of the MECCA model (Model of Estuarine and Coastal Circulation Assessment) is used to simulate the dynamics of the Eastern part of the English Channel. This area is characterized by a strong tidal turbulent regime and a frontal zone identified near the French coast by a low-salinity band. The model uses the upwind scheme to approximate the
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Listeria monocytogenesis a Gram positive facultative intracellular bacterium that can be responsible for severe infections, affecting essentially pregnant women, immunocompromised patients at the early and later stages of life. In... more
Listeria monocytogenesis a Gram positive facultative intracellular bacterium that can be responsible for severe infections, affecting essentially pregnant women, immunocompromised patients at the early and later stages of life. In Tunisia, invasive L. monocytogenes infections are thought to be exceptional and limited data are available about listeriosis. We reported seven cases (five newborn children and two infants) of human listeriosis that occurred in Tunis from 2000 to 2008. The newborn children were hospitalized for suspicion of maternofoetal infections. The two infants were hospitalized for fever associated with digestive signs in one case and neurological signs in the other. L. monocytogenes-was isolated from culture of cerebrospinal fluid in four cases, peripheral samples in two cases and from blood culture in one case. Isolates identification was based on conventional methods. Antimicrobial susceptibility was realized according to the recommendation of the "Comité de l'antibiogramme de la Société française de microbiologie". All L. monocytogenes isolates were sensitive to amoxicillin and aminoside but resistant to 3rd generation cephalosporins. Investigations of the immune system were realized for the two infants including phenotypic analysis of peripheral blood cells by flow cytometry, lymphocyte proliferation assays, phagocytic cell functions and measurement of immunoglobulins as well as complement. All these explorations were normal for both infants. The outcome was fatal in only one case (a newborn child), and all the other patients recovered after adapted antibiotic treatment. In conclusion, our study shows that listeriosis is not exceptional in Tunis. Thus, it is necessary to know how to evoke this diagnosis, at any age, in order to establish an early and adapted antibiotic treatment and to avoid fatal outcome.
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The authors had for aim to analyze pertussis epidemiology in Tunisia by studying nasopharyngeal specimens of infants hospitalized in Tunis. Between march 2007 and march 2008, clinical nasopharyngeal samples were collected from infants... more
The authors had for aim to analyze pertussis epidemiology in Tunisia by studying nasopharyngeal specimens of infants hospitalized in Tunis. Between march 2007 and march 2008, clinical nasopharyngeal samples were collected from infants with a suspected diagnosis of whooping cough, pertussoid cough, or pertussis-like syndrome, admitted at the Tunis children's hospital. The laboratory diagnostic criteria were culture isolation of Bordetella species on Bordet-Gengou medium and real-time PCR. Fifty-nine percent of the 74 investigated children with suspected pertussis were less than two months of age. The diagnosis of pertussis was proved positive by real-time PCR for 41%. Culture was negative in all cases. Whooping cough is still prevalent in Tunisia despite an important vaccination coverage. Real-time PCR is an invaluable tool for the rapid diagnosis of pertussis, however culture must also be associated.
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ABSTRACT A new algorithm for solving the duals of separable convex optimization problems is presented. The algorithm is based on an active set strategy in conjunction with a variable metric method. This first order algorithm is more... more
ABSTRACT A new algorithm for solving the duals of separable convex optimization problems is presented. The algorithm is based on an active set strategy in conjunction with a variable metric method. This first order algorithm is more reliable than Newton's method used in DUAL-2 because it does not break down when the Hessian matrix becomes singular or nearly singular. A perturbation technique is introduced in order to remove the nondifferentiability of the dual function which arises when linear constraints are present in the approximate problem.
ABSTRACT A decomposition approach of the kinematical method of limit analysis is first presented. It is based on a mixed variational approach and on a convex interior point solver, using linear or quadratic discontinuous velocity fields.... more
ABSTRACT A decomposition approach of the kinematical method of limit analysis is first presented. It is based on a mixed variational approach and on a convex interior point solver, using linear or quadratic discontinuous velocity fields. Exposed in plane strain, this method appears rapidly convergent, as verified in the Tresca compressed bar problem. Then the method is applied to the classical problem of the stability factor of a Tresca vertical slope: the upper bound is lowered from 3.882 to 3.7778. This value is to be compared to the lower bound just increased from 3.772 to 3.7752 by using the same solver in the extension of the method to the statical decomposition problem with infinite elements.
A one-dimensional model of the vertical exchange of suspended sediment in a tidal boundary layer is proposed. The model includes two linearized momentum equations for the horizontal velocity components and a series of advection–diffusion... more
A one-dimensional model of the vertical exchange of suspended sediment in a tidal boundary layer is proposed. The model includes two linearized momentum equations for the horizontal velocity components and a series of advection–diffusion equations for concentrations of suspended sediment of specific size. Turbulence generated at the sea-bed is computed with the aid of a two-equation closure describing the time–space
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Streptococcus pneumoniae is one of the major causative agents of invasive infectious disease in children <5 years old globally. The aim of this study was to analyze the antimicrobial resistance and the serotype distribution of S.... more
Streptococcus pneumoniae is one of the major causative agents of invasive infectious disease in children <5 years old globally. The aim of this study was to analyze the antimicrobial resistance and the serotype distribution of S. pneumoniae isolates from the paediatric population in Tunisia and to specify the serotypes coverage by the conjugate pneumococcal vaccines. Antimicrobial susceptibility was determined by the disk diffusion method. Minimal inhibitory concentrations of beta-lactams were determined using the E test method (AB BIODISK). Serotypes were determined by agglutination of latex particles, which identified a subset of serotypes included in pneumococcal conjugate vaccines (1, 3, 4, 5, 14) and some of the serogroups. This was followed by the Neufeld test using monovalent antisera (Statens Serum Institute) specific for the other serotypes included in pneumococcal conjugate vaccines 7, 10 and 13 (PCV7, PCV10, PCV13): 6A, 6B, 7F, 9V, 18C, 19A, 19F and 23F. During the study period, 200 invasive and 310 non-invasive pneumococcal isolates were obtained from paediatric patients ranging in age from newborn to 16 years. Among these 510 isolates, 53.4% had reduced susceptibility to penicillin. Penicillin resistance was higher among S. pneumoniae isolates recovered from samples associated with non-invasive vs. invasive disease (60.6% vs. 45%). All the strains were susceptible to pristinamycin, vancomycin, teicoplanin and fosfomycin. Serotype 14 was the most frequently isolated serotype (22.2%), followed by serotypes 19F (15.5%) and 23F (10.3%). Of all strains typed, the percentage of serotypes covered by PCV7, PCV10 and PCV13 were 66.4%, 73% and 78%, respectively (76.1% for invasive pneumococcal isolates, 79.8% for non invasive pneumococcal isolates for PVC13). Continual surveillance of antibiotic susceptibility and careful use of antibiotics are recommended. The introduction of the new conjugate vaccine should be greatly beneficial for reducing pneumococcal invasive diseases among Tunisian children.
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One hundred of non duplicate Streptococcus pneumoniae resistant to erythromycin collected from three teaching hospitals in Tunisia from January 1998 to December 2004 were investigated to evaluate determine their resistance level to... more
One hundred of non duplicate Streptococcus pneumoniae resistant to erythromycin collected from three teaching hospitals in Tunisia from January 1998 to December 2004 were investigated to evaluate determine their resistance level to different macrolides and the mechanisms involved. Most erythromycin resistant S. pneumoniae were isolated from respiratory tract (34%). Eighty-three percent showed constitutive MLS(B) phenotype with high MICs of macrolides and lincosamides (MIC90 >256 microg/ml), 12% M phenotype with moderately increased MICs of macrolides (MIC90: 12 microg/ml) and low MICs of lincosamides (MIC90=0.75 microg/ml) and 5% inducible MLS(B) with high MICs of macrolides (MIC90 >256 microg/ml) and moderately increased MICs of lincosamides (MIC90=8 microg/ml). All strains were susceptible to quinupristun-dafopristin association and linezolid (MIC90=1 microg/ml). Strains belonging to MLS(B) phenotype were PCR positive for the erm B gene (88%). Twelve percent categorized as M phenotype carried the mef A gene. The rates of associated resistance were 68% to penicillin G, 53% to tetracyclines, 61% to cotrimoxazole, 21% to chloramphenicol and 13% to ciprofloxacin. MLS(B) constitutive phenotype conferring cross resistance to macrolides, lincosamides and streptogramins B with high level of resistance was the most prevalent. Thus, quinupristin-dalfopristin association and linezolid remain the most active molecules.
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Eighty non-repetitive strains of Moraxella catarrhalis, isolated in Tunis Children's Hospital during five years from 1998 to 2002, were tested for their antimicrobial susceptibility, 95% of these strains were isolated from lung... more
Eighty non-repetitive strains of Moraxella catarrhalis, isolated in Tunis Children's Hospital during five years from 1998 to 2002, were tested for their antimicrobial susceptibility, 95% of these strains were isolated from lung samples: 57.5% from trachea products, 35% from sputum and 2.5% from bronchial washings. The majority of strains (72%) were obtained from children under two years old. Antimicrobial susceptibility study showed that 95% of stains were beta-lactamase-producing, therefore they were penicillin G and amoxicillin resistant with high MICs. MIC(90) of penicillin G and amoxicillin of beta-lactamase-producing strains were respectively greater than 32 and 6 mg/l, these MIC decrease with addition of clavulanic acid. In fact, all strains studied were susceptible to the association amoxicillin-clavulanic acid as well as to cefotaxime. Concerning the other antimicrobial groups percentages of resistant strains found were as follows: erythromycin 3.75%, trimethoprim-sulfamethoxazol 12.5% and tetracycline 1.25%. Finally, all strains were susceptible to chloramphenicol, rifampicin and ciprofloxacin.
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... an aluminum prototype of the Amica Star Tracker Support (ASTS) of the AMS_02 (Alpha Magnetic Spectrometer ... with regard to the number of degrees of freedom of the finite element model. The major advantage of the method is its... more
... an aluminum prototype of the Amica Star Tracker Support (ASTS) of the AMS_02 (Alpha Magnetic Spectrometer ... with regard to the number of degrees of freedom of the finite element model. The major advantage of the method is its sensitivity to modifications in system parameters ...
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ABSTRACT The goal of the present paper is to improve our understanding of the response of the in-plane loaded rectangular plates containing initial geometric imperfection. Besides the frequency responses and FFT curves, which were used as... more
ABSTRACT The goal of the present paper is to improve our understanding of the response of the in-plane loaded rectangular plates containing initial geometric imperfection. Besides the frequency responses and FFT curves, which were used as diagnostic tools in previous investigations, the temporal response and the phase diagram have been added to better study the transition zones between two kinds of vibration modes. The phase portrait shows that the plate response has a number of “unusual and perhaps chaotic” characteristics in the transition from one mechanism of vibration of another, which distinguished it from the more classical periodic response. Moreover, the effect of one particular spatial mode of imperfection on a different mode of vibration has been investigated for the first time. It was found that the maximum amplitude of forced vibrations is large when vibration and imperfection are in the same mode while the first mode of vibration is always excited whatever the mode of imperfection is.
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... of Medicine of Tunis, Tunis, Tunisia; 2 Laboratory of Bacteriology, Hospital Habib Bourguiba of Sfax, Sfax, Tunisia; 3 Laboratory of Bacteriology, Hospital of Children of Tunis, Tunis, Tunisia. Correspondence: Malek Rachdi... more
... of Medicine of Tunis, Tunis, Tunisia; 2 Laboratory of Bacteriology, Hospital Habib Bourguiba of Sfax, Sfax, Tunisia; 3 Laboratory of Bacteriology, Hospital of Children of Tunis, Tunis, Tunisia. Correspondence: Malek Rachdi (mallouk2008{at}yahoo.fr). ... Tunis Med 81, 167171. ...