Mouna Ben Nejma

Characterization of ST80 Panton-Valentine leukocidin-positive community-acquired methicillin-resistant Staphylococcus aureus clone in Tunisia

The spread of community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) has been reported in communities worldwide. In this study, we characterized 64 Tunisian CA-MRSA by agr typing, polymerase chain reaction assay for 20 virulence genes, staphylococcal chromosomal cassette mec (SCCmec) typing, pulsed-field gel electrophoresis (PFGE), multilocus sequence typing (MLST), and protein A gene (spa) typing. All our isolates were lukS-PV-lukF-PV positive, etd positive, and edin positive. They harbored SCCmec type IV and belonged to agr group 3. PFGE typing showed that our isolates were distributed in 11 different pulsotypes. spa typing and MLST, performed with isolates representative of each PFGE pattern, revealed that all isolates had a unique spa type (t044) and a common sequence type (ST80). The isolates showed susceptibility to the majority of antibiotics, and resistance to kanamycin, erythromycin, and tetracycline, but intermediate resistance to fusidic acid. Full analysis of our results revealed that our isolates were nonmultiresistant and belonged to a single clonal type ST80.

Adhesive properties and extracellular enzymatic activity of Staphylococcus aureus strains isolated from oral cavity

Staphylococcus aureus is one of prominent bacterial pathogen that occurs in oral region. In this study, 21 strains of S. aureus isolated from the oral cavity of Tunisian patients were investigated for slime production using Congo red agar method (CRA) and adherence assay. Biofilm formation of oral isolates on orthodontic biomaterials (Bis-GMA and PMMA) was also evaluated by MTT reduction assay. In addition, the production of hydrolytic enzymes by S. aureus strains was analyzed and the presence of protease, lipase and β-hemolysin genes (sspA, sspB, geh, hlb) was achieved by polymerase chain reaction (PCR). Qualitative biofilm production tested on CRA revealed that 91% of strains were slime producers. The result of OD570 showed that five strains isolated from the oral cavity were highly biofilm positive. The metabolic activity of S. aureus biofilm formed on Bis-GMA and PMMA did not differ between tested strains. The atomic force micrographs demonstrated that biofilm formed by S. aureus strains was organized in typical cocci cells attached to each other through production of exopolymeric substances. The production of hydrolytic enzymes showed that all S. aureus strains were protease positive. Lipase (77%) and beta hemolytic (59%) activities were also detected. Among the tested strains, 17 were positive for sspA, sspB and hlb genes. While only ten S. aureus strains harbor the geh gene (48%). These data highlight the importance of evaluation of biofilm formation and exoenzyme production in oral S. aureus isolates to investigate the role of this pathogen and its impact in oral pathology.

Association of the Met-196-Arg Variation of Human Tumor Necrosis Factor Receptor 2 (TNFR2) with Paranoid Schizophrenia

Research has provided strong evidence for oligodendrocyte and myelin-related genes dysfunction in schizophrenia. Several studies have suggested abnormalities in the expression of myelin-related genes including tumor necrosis factor receptor 2 (TNFR2) involved in the neurodegeneration and remyelination. In order to further assess the role of TNFR2 in schizophrenia, we examined a functional bi-allelic polymorphism associated with an impaired NF-KB signaling and cell survival. In the present case/control study, 220 patients with schizophrenia and 176 healthy controls were genotyped by RFLP-PCR for the T/G polymorphism at the position 676 in exon 6 of the TNFR2 gene. We found a trend towards over-representation of TNFR2 676G in the patients compared to the controls (p = 0.19 and 0.09 respectively). Interestingly, when we evaluated the association between this genetic polymorphism and the clinical variables of schizophrenia, our findings indicated that the frequencies of the G/G genotype and the G allele were significantly higher in paranoid (p = 0.014 and p = 0.012 respectively) and adult-onset paranoid (p = 0.004 and p = 0.004 respectively) schizophrenia patient group compared to the controls. The potential association was confirmed by a logistic regression model only for development of the paranoid form of schizophrenia (p = 0.022) indicating a substantially increased risk for paranoid schizophrenia with inheritance of the TNFR2(G) allele. In conclusion, this polymorphism in TNFR2 or a gene in proximity seems to be associated specifically with paranoid schizophrenia, at least in the Tunisian population. A replication of our findings in other and larger populations could be of particular importance to establish TNFR2 as one of the susceptibility genes of paranoid schizophrenia.

High potential of adhesion to biotic and abiotic surfaces by opportunistic Staphylococcus aureus strains isolated from orthodontic appliances.

Orthodontic and other oral appliances act as reservoir of opportunistic pathogens that can easily become resistant to antibiotics and cause systemic infections. The aim of this study was to investigate the ability of Staphylococcus aureus strains isolated from healthy patients with orthodontic appliances, to adhere to biotic (HeLa cells) and abiotic surfaces (polystyrene and dental alloy). Adhesive ability to polystyrene was tested by crystal violet staining and quantitative biofilm production on dental alloy surfaces was evaluated by MTT reduction assay. In addition, the presence of icaA and icaD genes was achieved by polymerase chain reaction (PCR). Qualitative biofilm production revealed that 70.6% of strains were slime producers. The metabolic activity of S. aureus biofilms on dental alloy surfaces was high and did not differ between tested strains. Moreover, all the isolates were adhesive to HeLa cells and 94% of them harbor icaA and icaD genes. Considerable adhesion and internalization capacity to the epithelial HeLa cells and strong biofilm production abilities together, with a high genotypic expression of icaA/icaD genes are an important equipment of S. aureus to colonize orthodontic appliances and eventually to disseminate towards other body areas.

Genotyping of Methicillin Resistant Staphylococcus aureus Strains Isolated from Hospitalized Children

Community associated methicillin resistant Staphylococcus aureus (CA-MRSA) is an emerging pathogen increasingly reported to cause skin and soft tissue infections for children. The emergence of highly virulencet CA-MRSA strains in the immunodeficiency of young children seemed to be the basic explanation of the increased incidence of CA-MRSA infections among this population. The subjects of this study were 8 patients hospitalized in the Pediatric Department at the University Hospital of Monastir. The patients were young children (aged from 12 days to 18 months) who were suffering from MRSA skin infections; two of them had the infections within 72 h of their admission. The isolates were classified as community isolates as they all carried the staphylococcal cassette chromosome mec (SCCmec) IV and pvl genes. Epidemiological techniques, pulsed-field gel electrophoresis (PFGE) and multilocus sequence typing (MLST), were applied to investigate CA-MRSA strains. Analysis of molecular data revealed that MRSA strains were related according to PFGE patterns and they belonged to a single clone ST80. Antimicrobial susceptibility tests showed that all strains were resistant to kanamycin and 2 strains were resistant to erythromycin.

A gender-specific association of interleukin 1 receptor antagonist polymorphism with schizophrenia susceptibility.

Objective Recent genetic studies have revealed that the interleukin (IL) 1 gene complex is associated with schizophrenia in the Caucasian population; however, data from the North African population are limited. To further assess the role of interleukin 1 receptor antagonist protein (IL1Ra) in schizophrenia, we examined a functional multiallelic polymorphism localised in intron 2 of this receptor gene associated with an altered level of IL1Ra. Methods In the present case–control study, we have analysed the (86 bp)n polymorphism of the interleukin 1 receptor antagonist (IL1RN) gene (RS 1794068) by polymerase chain reaction genotyping in 259 patients with schizophrenia and 178 healthy controls from the Tunisian population. Results We showed that the frequencies of the IL1RN*2/2 genotype and allele 2 were higher in the patient group compared with the control group, and the difference was statistically significant [13.5% vs. 5.6%, p = 10−3, odds ratio (OR) = 3.2% and 32.8% vs. 21.9%, p = 3 × 10−4, OR = 1.76, respectively). When we evaluated the association between this genetic polymorphism and the clinical variables of schizophrenia, we found that the frequencies of the 2/2 genotype and allele 2 were significantly higher in the male patient group (p = 10−4 and 10−5, respectively) compared with the male control group, indicating a substantially increased risk for sex-onset schizophrenia with inheritance of the IL1RN2 allele. When the association between the genotypes and outcome was evaluated by multiple logistic regression analysis, the adjusted OR for the IL1RN genotypes remained statistically significant [1.39; 95% confidence interval (CI) = 1.11–1.73; p = 0.003]. Conclusion The intron 2 polymorphism in IL1RN or a genetic polymorphism at proximity seems to be associated specifically with schizophrenia in the Tunisian male population.

Molecular identification of four Salmonella serovars isolated from food in Tunisia based on the sequence of the ribosomal RNA genes

In this study, the 5′-end of the 16S-23S intergenic spacer regions and domains II and III of the 23S ribosomal DNA (rDNA) of six Salmonella strains were analyzed. These strains belong to four serovars: Agona, Amesterdam, Corvallis and Enteritidis, and were isolated from food samples. Polymerase chain reaction (PCR) products were then sequenced on both strands and the sequences obtained were aligned using the “Clustal W” program. The comparative sequence analysis revealed that the 5′-end of the 16S-23S spacer region rDNA is highly conserved among the four Salmonella serovars tested. All of these sequenced spacer regions contained a tRNA Ile gene. For the domains II and III of the 23S rDNA, the sequence analysis showed the presence of both conservative and variable regions. Some mutations, substitutions and deletions were also detected. This work supports the hypothesis that the 23S rRNA genes are useful for the definition of serovar-specific probes for the detection of Salmonella in food.

Community-acquired methicillin resistantStaphylococcus aureus isolated in dermatology department

Community-acquired methicillin-resistantStaphylococcus aureus (CA-MRSA) strains, known as a nosocomial pathogen, have emerged in the community worldwide. CA-MRSA infects frequently young children and is implicated in skin and soft tissue infections. In the present study, we reported the isolation of CA-MRSA strains from elderly patients admitted to the dermatology department at University Hospital of Monastir. The relatedness of these isolates was investigated by PFGE typing which indicated that all strains were clonally related. MRSA strains were thoroughly characterized by molecular methods which revealed that all isolates possessed the unique sequence type ST80 as well as a single spa type t044. Whole genotypic results suggest that all isolates were PVL producing CA-MRSA and were closely related and belonging to the ST80 clone.