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author:("massoudi, aff")
1.  Primary resistance to clarithromycin, metronidazole and amoxicillin of Helicobacter pylori isolated from Tunisian patients with peptic ulcers and gastritis: a prospective multicentre study 
The frequency of primary resistance to antibiotics in H. pylori isolates is increasing worldwide. In Tunisia, there are limited data regarding the pattern of H. pylori antibiotic primary resistance.
To evaluate the primary resistance of H. pylori to clarithromycin, metronidazole and amoxicillin and to detect the mutations involved in clarithromycin resistance.
Materials and methods
273 strains isolated from adults and children were enrolled. The primary resistance to clarithromycin, metronidazole and amoxicillin was evaluated by means of E-test minimal inhibitory concentration (MIC). The real-time PCR using Scorpion primers was performed in all cases to assess clarithromycin primary resistance and point mutations involved.
No resistance to amoxicillin was detected. For adults, resistance to clarithromycin and metronidazole was found respectively in 14.6% and 56.8%, and respectively in 18.8% and 25% in children. Overall, the rates of global primary resistance to clarithromycin and metronidazole in Tunisia were respectively determined in 15.4% and 51.3%.
By the use of Scorpion PCR, the A2143G was the most frequent point mutation observed (88.1%), followed by the A2142G (11.9%); the A2142C was not found and 18 of 42 patients (42.8%) were infected by both the resistant and the susceptible genotype.
The association of clarithromycin resistance with gender was not statistically significant, but metronidazole resistant strains were isolated more frequently in females (67.8%) than in males (32.2%) and the difference was significant. As for gastroduodenal diseases, the difference between strains isolated from patients with peptic ulceration and those with non peptic ulceration was not statistically significant. When about the distribution of resistant strains to clarithromycin and metronidazole between the three Tunisian cities (Tunis, Menzel Bourguiba and Mahdia), the difference was not statistically significant.
Local data regarding the primary resistance of H. pylori to clarithromycin, metronidazole and amoxicillin and the main genetic mutation involved in clarithromycin resistance in vivo (A2143G) are necessary to prove a clear need for a periodic evaluation of antibiotic consumption and new therapeutic strategies in Tunisia in order to avoid the emergence of resistant strains.
PMCID: PMC2928169  PMID: 20707901
2.  Prevalence of Helicobacter pylori vacA, cagA, iceA and oipA genotypes in Tunisian patients 
Distinct virulence factors of H. pylori have been described: the vaculating cytotoxin (vacA), the cytotoxin associated gene (cagA), the induced by contact with epithelium factor Antigen (iceA gene) and the outer membrane protein oipA. In Tunisia, there are no data regarding the pattern of H. pylori genotypes; therefore, this prospective and multicentre study was the first to be done in Tunisia and aimed to investigate the prevalence of the vacA, cagA, iceA and oipA genotypes of H. pylori isolates from Tunisian patients with peptic ulceration, gastric cancer, MALT lymphoma and gastritis.
H. pylori was cultured from endoscopic biopsies obtained from 281 Tunisian patients. The vacA alleles, cagA, iceA and oipA genotypes were determined by PCR.
The vacA s1m1, s1m2 and s2m2 were respectively found in 10.7%, 12.5% and 45.6% of strains. The s2m1 genotype was not detected in our study. The cagA was found in 61.6% of isolates. The iceA1 and the iceA2 genotypes were respectively isolated in 60.2% and in 16% of strains. The oipA genotype was detected in 90.8% of strains. Considering the vacA and iceA genotypes, the presence of multiple H. pylori strains in a single biopsy specimen was found respectively in 31.4% and 23.8%. The comparison between strains isolated from antrum and fundus showed that Tunisian patients were infected with two or more strains of different cagA, vacA, iceA and oipA genotypes and the discordance was respectively in 9.6%, 4.6%, 8.9% and 8.5% of strains.
Our results showed that in 46% (131 strains among 281), the H. pylori strains were highly virulent in relation of the three or four virulent factors they could carry. These finding were described before in the literature. Tunisian patients were colonized by one or multiple strains of H. pylori in the same time in relation of presence of vacA m1/m2 and iceA1/iceA2 in the same biopsy. The discordance between strains isolated from antrum and fundus was high, and it is in favour of multicolonization.
PMCID: PMC2855517  PMID: 20302630
3.  Characterization of Tunisian Mycobacterium tuberculosis Rifampin-Resistant Clinical Isolates▿  
Journal of Clinical Microbiology  2007;45(9):3095-3097.
Analysis of the gene encoding the β-subunit of Mycobacterium tuberculosis RNA polymerase (rpoB) has demonstrated a small region that harbors the mutations most frequently associated with rifampin resistance. In this study, we determined the occurrence of rifampin resistance in 544 Tunisian clinical M. tuberculosis strains isolated in a university hospital between 2004 and 2006 by using the standard-proportion agar method, the INNO-LiPA Rif.TB assay, and DNA sequencing.
PMCID: PMC2045245  PMID: 17652484
4.  A Novel Extended-Spectrum TEM-Type β-Lactamase, TEM-138, from Salmonella enterica Serovar Infantis 
A novel natural TEM β-lactamase with extended-spectrum activity, TEM-138, was identified in a ceftazidime-resistant clinical isolate of Salmonella enterica serovar Infantis. Compared to TEM-1, TEM-138 contains the following mutations: E104K, N175I, and G238S. The blaTEM-138 gene was located on a 50-kb transferable plasmid. Expression studies with Escherichia coli revealed efficient ceftazidimase and cefotaximase activities for TEM-138.
PMCID: PMC1563563  PMID: 16940125
5.  Characterization of Gentamicin-Susceptible Strains of Methicillin-Resistant Staphylococcus aureus Involved in Nosocomial Spread 
We report an outbreak of epidemic Staphylococcus aureus strains characterized by an unusual heterogeneous resistance to methicillin and resistance to tobramycin but susceptibility to gentamicin (gentamicin-susceptible methicillin-resistant S. aureus [GS-MRSA]), contrasting with gentamicin-resistant homogeneous MRSA (GR-MRSA) that have been endemic in our hospital since the 1970s. A total of 97 GS-MRSA strains, which were shown by DNA hybridization to carry the mecA and ant(4′)-Ia genes, were studied. The 40 GS-MRSA strains isolated at the beginning of the outbreak (January 1992 to June 1993) were typed by using resistance patterns, phage typing, serotyping, and pulsed-field gel electrophoresis and were compared with GR-MRSA and methicillin-susceptible S. aureus (MSSA) strains isolated during the same period. Two dominant clones, A::1 and B::3, and one minor clone, C::5, were identified among the 40 GS-MRSA strains, according to pulsotypes (A to C) and their resistance patterns (1, 3, and 5), which were distinguishable from those of GR-MRSA and MSSA strains. A selection of 57 GS-MRSA strains, isolated from 1994 to 1996, were clustered in the same three clones. However, their distribution had changed in comparison with that in the 1992 to 1993 period: clone A::1 remained dominant (47 versus 42.5%), whereas clone B::3 progressively declined (5 versus 35%) and clone C::5, the most susceptible to antibiotics, spread (44 versus 2.5%). Epidemiological investigations revealed that some clones had been introduced via patients transferred from other hospitals and that cross-infection occurred within and between wards. Major changes in the use of antibiotics, especially aminoglycosides, cyclines, and macrolides, likely played a role in the emergence and spread of GS-MRSA strains.
PMCID: PMC124812  PMID: 9431925

Results 1-5 (5)