A Boudabous

Publications (39)63.95 Total impact

• Article: Faecal enterococci from camels in Tunisia: species, antibiotic resistance and virulent genes.

  N Klibi, A Ben Lagha, K Ben Slama, A Boudabous, C Torres
  The Veterinary record. 01/2013;
• Article: Phenotypic and genotypic characterization of bacteriocins in clinical enterococcal isolates of Tunisia

  N. Klibi, A. Jouini, B. Rojo-Bezares, A. Masmoudi, F. Ruiz-Larrea, A. Boudabous, C. Torres
  [show abstract] [hide abstract]
  ABSTRACT: The presence of bacteriocin structural genes (entA, entB, entP, entQ, entAS-48, entL50A/B, bac31, and cylL) encoding different bacteriocins (enterocin A, enterocin B, enterocin P, enterocin Q, enterocin AS-48, enterocin L50A/B, bacteriocin 31 and cytolysin L, respectively), and the production of bacteriocin activity were analysed in 139 E. faecalis and 41 E. faecium clinical isolates of Tunisia. Forty-eight of 139 E. faecalis isolates (34%) and 7 of 41 of E. faecium isolates (17%) were bacteriocin producers. Sixty-two per cent of the bacteriocin-producing enterococci showed inhibitory activity against L. monocytogenes. Different combinations of entA, entB, entP, and entL50A/B genes were detected among the seven bacteriocin-producer E. faecium isolates, and more that one gene were identified in all the isolates. The entA gene was associated in most of the cases with entB gene in E. faecium isolates. Cyl LS were the unique genes detected among E. faecalis (in 24 of 48 bacteriocin-producer isolates, 50%). A β-hemolytic activity was demonstrated in 19 of the 24 cyl LS -positive E. faecalis isolates (79%), this activity being negative in the remaining five isolates. The presence of different bacteriocin structural genes and the production of antimicrobial activities seems to be a common trait of clinical enterococci.
  World Journal of Microbiology and Biotechnology 04/2012; 24(5):653-657. · 1.53 Impact Factor
• Source

  Available from: Badiaa Essghaier

  Article: Biological control of Botrytis cinerea on stem wounds with moderately halophilic bacteria

  N. Sadfi-Zouaoui, I. Hannachi, D. Andurand, B. Essghaier, A. Boudabous, P. Nicot
  [show abstract] [hide abstract]
  ABSTRACT: Infection of tomato stem wounds by Botrytis cinerea is an important problem which can cause severe economic losses in greenhouse tomato crops. Three moderately halophilic bacteria were tested for their ability to protect pruning wounds from attacks by B.cinerea under growth chamber conditions. The severity of the disease estimated by the length of the rotted stem was used to calculate the area under the disease progress curves (AUDPC). Bacterial antagonists (B1, B2 and B3) were very effective in controlling Botrytis-infection on the tomato stems during the first 6days and later by the end of the experiment. Plants treated with Bacillus subtilis (B1) had the lowest AUDPC (0). It was followed by B.subtilis (B3) and Halomonas sp. (B2) with AUDPC of 9.8 and 17.02, respectively. While the B1 strain best inhibited grey mold development when applied as young culture (24h), the B3 strain performed better as an older culture (48h). In contrast to the results obtained with Bacillus species, the efficacy of the bacterial treatment B2 seems to be independent of the growth phase. The co-cultures with fungal spores and either B.subtilis (B1) or Halomonas sp. (B2) applied as a 24h bacterial culture completely inhibited the germination of B.cinerea after 24h at 21°C.
  World Journal of Microbiology and Biotechnology 04/2012; 24(12):2871-2877. · 1.53 Impact Factor
• Source

  Available from: Vanesa Estepa

  Article: Prevalence and characterisation of extended-spectrum beta-lactamase (ESBL)-producing Escherichia coli isolates in healthy volunteers in Tunisia.

  R Ben Sallem, K Ben Slama, V Estepa, A Jouini, H Gharsa, N Klibi, Y Sáenz, F Ruiz-Larrea, A Boudabous, C Torres
  [show abstract] [hide abstract]
  ABSTRACT: The objective of this investigation was to analyse the carriage rate of extended-spectrum beta-lactamase (ESBL)-producing Escherichia coli in faecal samples of healthy humans in Tunisia and to characterise the recovered isolates. One hundred and fifty samples were inoculated on MacConkey agar plates supplemented with cefotaxime (2 μg/ml) for ESBL-positive E. coli recovery. The characterisation of ESBL genes and their genetic environments, detection of associated resistance genes, multilocus sequence typing (MLST) and phylogroup typing were performed by polymerase chain reaction (PCR) and sequencing. The presence and characterisation of integrons and virulence factors were studied by PCR and sequencing. ESBL-positive E. coli isolates were detected in 11 of 150 faecal samples (7.3%) and one isolate/sample was further characterised. These isolates contained the blaCTX-M-1 (ten isolates) and blaTEM-52c genes (one isolate). The ISEcp1 (truncated by IS10 in four strains) and orf477 sequences were found upstream and downstream, respectively, of all bla (CTX-M-1) genes. Seven different sequence types (STs) and three phylogroups were identified among CTX-M-1-producing isolates [ST/phylogroup (number of isolates)]: ST58/B1 (3), ST57/D (2), ST165/A (1), ST155/B1 (1), ST10/A (1), ST398/A (1) and ST48/B1 (1). The TEM-52-producing isolate was typed as ST219 and phylogroup B2. Six ESBL isolates contained class 1 integrons with the gene cassettes dfrA17-aadA5 (five isolates) and dfrA1-aadA1 (one). Healthy humans in the studied country could be a reservoir of CTX-M-1-producing E. coli.
  European Journal of Clinical Microbiology 11/2011; 31(7):1511-6. · 2.86 Impact Factor
• Article: Molecular analysis and antimicrobial resistance of Salmonella isolates recovered from raw meat marketed in the area of "Grand Tunis", Tunisia.

  I Abbassi-Ghozzi, A Jaouani, S Hammami, J Martinez-Urtaza, A Boudabous, M Gtari
  [show abstract] [hide abstract]
  ABSTRACT: A total of 315 samples of chicken (60), beef (144), minced meat (56), lamb meat (33), merguez (10) and fish (12) were collected from various local outlet stores in the area of "Grand Tunis", Tunisia between 2006 and 2008. Salmonella was recovered from 80 samples with the highest occurrence in chicken (48.3%) followed by beef (29.8%), minced meat (10.7%) and lamb (6.0%). No Salmonella were isolated from 12 fish and 10 merguez samples (typical Tunisian sausages). Nine serovars were identified among the isolates with the predominance of Salmonella Typhimurium (n=25) followed by Salmonella Kentucky (n=14), Salmonella Suberu (n=12) and Salmonella Zanzibar (n=11). Isolated Salmonella were characterized by serotyping, pulsed-field gel electrophoresis (PFGE) analysis, plasmid content and antimicrobial resistance profiling. Sixteen (20.0%) Salmonella isolates displayed resistance to ampicillin (13 isolates), streptomycin (five isolates), cefoperazone (two isolates), furazolodine (two isolates), with seven of these isolates displaying multiple resistance to at least two of these antimicriobal agents. PFGE analysis showed homogenous restriction patterns in each serovar. Compiled serotyping, PFGE analysis, plasmid profiling and antimicrobial resistance data provided additional discrimination.
  Pathologie Biologie 08/2011; 60(5):e49-54. · 1.53 Impact Factor
• Article: Antimicrobial resistance and molecular analysis of non-typhoidal Salmonella isolates from human in Tunisia.

  I Abbassi-Ghozzi, A Jaouani, R B Aissa, J Martinez-Urtaza, A Boudabous, M Gtari
  [show abstract] [hide abstract]
  ABSTRACT: During the period from 2006 to 2007, a total of 32 clinical isolates of Salmonella enterica were isolated from diarrheagenic stool samples and further examined for their susceptibility to various antibiotics. Sixteen of the human isolates were from the capital Tunis, 11 were from Sousse, four were from Nabeul and one was from Mahdia, Tunisia. The isolates were serotyped and identified at the National Centre of Enteropathogenic Bacteria, Pasteur Institute, Tunis (Centre National de Salmonella, Shigella et Vibrio - Institut pasteur de Tunis); nine distinct serovars were identified: Enteritidis (n=20), Typhimurium (n=4), Zanzibar (n=2), Manhattan (n=1), Bovismorbificans (n=1), Amsterdam (n=1), Saint Paul (n=1), Kentucky (n=1) and Muenster (n=1). Our results showed that 25 Salmonella isolates (78.1 %) were resistant to antibiotics with 20 isolates (62.5 %) displayed resistance to ampicillin. Isolates sharing invA gene, as shown by PCR amplification, were further characterized by the techniques of pulsed-field gel electrophoresis (PFGE) using the restriction enzyme XbaI and plasmid analysis to determine possible genetic relationships among Salmonella enterica clinical isolates and to assess genetic diversity. Plasmid profiling identified seven plasmid profiles (with 1-5 plasmids) among the isolates; four isolates (Salmonella Kentucky, Salmonella Muenster, Salmonella Bovismorbificans and Salmonella Zanzibar) did not carry any plasmid. The isolates were differentiated into 10 distinct XbaI-pulsotypes. Our findings show genetic diversity among the different serovars and cluster analysis of compiled serotyping, PFGE, plasmid profiling and antibiotic resistance data provided additional discrimination.
  Pathologie Biologie 08/2011; 59(4):207-12. · 1.53 Impact Factor
• Source

  Available from: Patrice Got

  Article: Survival study of enterotoxigenic Escherichia colistrain in seawater and wastewater microcosms.

  I Boukef Ben Omrane, M El Bour, S Mejri, R Mraouna, P Got, M Troussellier, A Boudabous
  [show abstract] [hide abstract]
  ABSTRACT: In order to survey osmotic and oligotrophic stress consequence on pathogenic enterobacteria discharged in marine areas, we examined enterotoxigenic Escherichia coli (ETEC) and a reference (Ecoli O126:B16) strains during their survival (47 days) in wastewater microcosms, submerged in natural seawater and maintained in laboratory conditions. The results revealed that the survival time for the two strains was prolonged when bacterial cells were previously incubated in wastewater, with less cellular membrane damage. In addition, the wild clinical E. coli strain showed a better survival capacity than the reference E. coli strain one. For both, we noted some modifications in biochemical profiles relatively to the initial state, notably when they were previously incubated in wastewater microcosm.
  Archives de l'Institut Pasteur de Tunis 01/2011; 88(1-4):29-34.
• Article: Survival of Escherichia coli strains in Mediterranean brackish water in the Bizerte lagoon in northern Tunisia.

  I Boukef, M El Bour, N Al Gallas, O El Bahri, S Mejri, R Mraouna, R Ben Aissa, A Boudabous, P Got, M Troussellier
  [show abstract] [hide abstract]
  ABSTRACT: This study investigated survival and virulence of Escherichia coli strains exposed to natural conditions in brackish water. Two E. coli strains (O126:B16 and O55:B5) were incubated in water microcosms in the Bizerte lagoon in northern Tunisia and exposed for 12 days to natural sunlight in June (231 to 386 W/m2, 26 +/- 1 degrees C, 30 g/L) and in April (227 to 330 W/m2, 17 +/- 1 degrees C, 27 g/L) or maintained in darkness for 21 days (17 +/- 1 degrees C, 27 g/L). The results revealed that sunlight was the most significant inactivating factor (decrease of 3 Ulog within 48 hours for the two strains) compared to salinity and temperature (in darkness). Survival time of the strains was prolonged as they were maintained in darkness. Local strain (E. coli O55:B5) showed better survival capacity (T90 = 52 hours) than E. coli O126:B16 (T90 = 11 h). For both, modifications were noted only for some metabolic activities of carbohydrates hydrolysis. Cytotoxicity of the two strains, tested on Vero cell, was maintained during the period of survival.
  Water Environment Research 11/2010; 82(11):2249-57. · 0.88 Impact Factor
• Article: Nasal carriage of Staphylococcus aureus in healthy humans with different levels of contact with animals in Tunisia: genetic lineages, methicillin resistance, and virulence factors.

  K Ben Slama, H Gharsa, N Klibi, A Jouini, C Lozano, E Gómez-Sanz, M Zarazaga, A Boudabous, C Torres
  [show abstract] [hide abstract]
  ABSTRACT: Nasal swabs of 423 healthy humans who showed different levels of contact with animals (frequent, 168; sporadic, 94; no contact, 161) were obtained in Tunisia (2008-2009), and 99 of them presented other associated risk factors. Methicillin-resistant Staphylococcus aureus (MRSA) was detected in one of these 423 samples (0.24%), retrieved from a veterinarian. The MRSA isolate was mecA-positive, typed as ST80-t203-SCCmecIVc-agrIII, and contained tet(K), ant(6)-Ia, and aph(3')-IIIa genes encoding tetracycline, streptomycin, and kanamycin resistance, respectively. This MRSA isolate also contained the lukF/lukS virulence gene encoding Panton-Valentine leukocidin. Fifty-four (12.8%) additional nasal samples contained methicillin-susceptible S. aureus (MSSA) and one isolate/sample was characterized. A high diversity of spa types (n = 43; 4 new) and pulsed-field gel electrophoresis (PFGE) types (n = 37) was detected among the 55 recovered S. aureus strains. The percentages of antimicrobial resistance/detected resistance genes were as follows: tetracycline [22%/tet(K)-tet(L)-tet(M)], erythromycin [5%/msrA], ciprofloxacin [14.5%], trimethoprim-sulfamethoxazole [2%/dfrA], streptomycin [11%/ant(6)-Ia], kanamycin [7%/aph(3')-IIIa], amikacin [5%], and chloramphenicol [2%]. Four and two isolates carried the lukF/lukS and eta and/or etb genes, respectively, and always in individuals with contact with animals. Eleven isolates carried the tst gene and were recovered from individuals with different levels of contact with animals.
  European Journal of Clinical Microbiology 11/2010; 30(4):499-508. · 2.86 Impact Factor
• Article: Detection of unrelated Escherichia coli strains harboring genes of CTX-M-15, OXA-1, and AAC(6')-Ib-cr enzymes in a Tunisian hospital and characterization of their integrons and virulence factors.

  A Jouini, K Ben Slama, L Vinué, E Ruiz, Y Saenz, S Somalo, N Klibi, M Zarazaga, M Ben Moussa, A Boudabous, C Torres
  [show abstract] [hide abstract]
  ABSTRACT: Beta-lactamase characterization was carried out in a collection of 18 extended-spectrum beta-lactamase (ESBL)-positive Escherichia coli isolates from blood (n=8) and urine (n=10) obtained in 2007 in a tunisian Hospital. All isolates were clonally unrelated according to PFGE analysis. Seventeen strains presented the bla(CTX-M-)₁₅ gene associated with bla (OXA-)₁ and four of these strains with the (TEM-)₁(b) gene. The remaining ESBL-positive strain contained the bla (CTX-M-)₉ gene associated with the bla (OXA-)₁ and bla (TEM-)₁(b) genes. The orf477 sequence was identified downstream of the bla(CTX-M-)₁₅ gene in all 17 bla(CTX-M-)₁₅-positive strains, and ISEcp1 upstream in 15 of them (in eight cases truncated by IS26). The presence of a class 1 integron was demonstrated in 4 of the 18 ESBL-positive strains (22.2%), with dfrA17 + aadA5 (3 strains) and dfrA12 + orfF + aadA2 (1 strain) being the gene cassettes identified. The variant aac(6´)-Ib-cr was found in 15 bla(CTX-M-)₁₅-containing strains. All 18 ESBL-positive strains were typed as phylogroup B2 and contained at least three of the eight tested virulence genes (fimA, papGIII, hlyA, cnf1, papC, aer, eae and bfp). Six bla(CTX-M-)₁₅-positive strains were included in the serotype O25b and one of them was typed as ST131. Another bla(CTX-M-)₁₅-positive strain serotype-O25 was typed as ST638. The bla(CTX-M-)₁₅, aac(6')- Ib-cr, and aac(3)-II genes were co-transferred by conjugation from 7 donor strains to E. coli CSH26 recipient strain. The bla(CTXM-)₁₅ gene is prevalent among ESBL-positive E. coli strains in the studied hospital, that is frequently found together with aac(6')- Ib-cr, and aac(3)-II genes. The detection of the clone O25b-St131 in a bla(CTX-M-)₁₅ strain corroborates its worldwide dissemination.
  Journal of chemotherapy (Florence, Italy) 10/2010; 22(5):318-23. · 1.08 Impact Factor
• Article: Esterase as an enzymatic signature of Geodermatophilaceae adaptability to Sahara desert stones and monuments.

  I Essoussi, F Ghodhbane-Gtari, H Amairi, H Sghaier, A Jaouani, L Brusetti, D Daffonchio, A Boudabous, M Gtari
  [show abstract] [hide abstract]
  ABSTRACT: To assess esterase profiling of members of Geodermatophilaceae isolated from desert stones and monuments in Tunisia and Egypt. Members of Geodermatophilaceae family isolated from desert stones and monuments in Tunisia and Egypt were characterized by partial 16S rRNA sequences. Twenty-five strains were clustered in three dissimilar groups of the genera Geodermatophilus (12 strains), Blastococcus (5 strains) and Modestobacter (3 strains). Isolates were also screened and typed based on major groups of esterase hydrolytic activity. Their esterase patterns were determined and compared to those of ten reference strains belonging to Geodermatophilaceae family. Strains exhibited a diverse and complex pattern of electrophoretic esterase bands, and 31 haplotypes were obtained for the 35 investigated strains. Esterases produced by members of Geodermatophilaceae family have an optimal activity around 40 degrees C and at pH 8. Esterases from Geodermatophilus strains display a high resistance to thermal inactivation and alkaline pH and retaining 30 and 20% of activity after heating for 20 min at 120 degrees C and at pH 12, respectively, and were completely inactivated after 30 min at 120 degrees C. Enzyme activity has been strongly activated in the presence of Ca(2+)and Mg(2+) ions and moderately by Zn(2+) and was markedly inhibited by Cu(2+) and Co(2+) ions. Geodermatophilaceae isolates share a rich and particular pool of esterase activities that could be directly linked to harsh conditions characterizing their ecological habitat including high level of aridity, temperature, ionic strength and low nutrient availability. Esterase could be considered as enzymatic signature that outlines adaptability of Geodermatophilaceae in arid area.
  Journal of Applied Microbiology 10/2009; 108(5):1723-32. · 2.34 Impact Factor
• Article: Biodiversity of Trichoderma strains in Tunisia.

  N Sadfi-Zouaoui, I Hannachi, M Rouaissi, M R Hajlaoui, M B Rubio, E Monte, A Boudabous, M R Hermosa
  [show abstract] [hide abstract]
  ABSTRACT: Trichoderma strains were sampled in 4 different bioclimatic zones of Tunisia, a Mediterranean North African country with strong climatic and edaphic variability from north to south, to assess the genetic diversity of endemic species of Trichoderma and their relationship to the bioclimatic zones. In all, 53 strains were isolated and identified at the species level by analysis of their internal transcribed spacers regions 1 and 2 (ITS1 and ITS2) of the rDNA cluster and (or) a fragment of the translation elongation factor 1 (tef1) gene, using an online interactive key for species identification in Trichoderma and ex-type strains and taxonomically established isolates of Trichoderma as references. At least 2 different species were observed in each ecosystem. Trichoderma harzianum clade VI and Trichoderma longibrachiatum were present in forest soils in north Tunisia; Trichoderma atroviride and Trichoderma hamatum were found in cultivated fields in northeast Tunisia; T. harzianum clade VI, a Trichoderma sp. close to the T. harzianum complex, and Trichoderma saturnisporum were isolated from forest soils in central Tunisia; and T. harzianum clade II and T. hamatum were present in oasis soils in south Tunisia.
  Canadian Journal of Microbiology 03/2009; 55(2):154-62. · 1.36 Impact Factor
• Article: Biological control of grey mould in strawberry fruits by halophilic bacteria

  B. Essghaier, M.L. Fardeau, J.L. Cayol, M.R. Hajlaoui, A. Boudabous, H. Jijakli, N. Sadfi-Zouaoui
  [show abstract] [hide abstract]
  ABSTRACT: Aims:  Grey mould caused by Botrytis cinerea is an economically important disease of strawberries in Tunisia and worldwide. The aim of this study was to select effective halophilic bacteria from hypersaline ecosystems and evaluate the abilities of antifungal bacteria to secrete extracellular hydrolytic enzymes, anti-Botrytis metabolites and volatiles.Methods and Results:  Grey mould was reduced in strawberry fruits treated with halophilic antagonists and artificially inoculated with B. cinerea. Thirty strains (20·2%) were active against the pathogen and reduced the percentage of fruits infected after 3 days of storage at 20°C, from 50% to 91·66%. The antagonists were characterized by phenotypic tests and 16S rDNA sequencing. They were identified as belonging to one of the species: Virgibacillus marismortui, B. subtilis, B. pumilus, B. licheniformis, Terribacillus halophilus, Halomonas elongata, Planococcus rifietoensis, Staphylococcus equorum and Staphylococcus sp. The effective isolates were tested for antifungal secondary metabolites.Conclusions:  Moderately halophilic bacteria may be useful in biological control against this pathogen during postharvest storage of strawberries.Significance and Impact of the study:  The use of such bacteria may constitute an important alternative to synthetic fungicides. These moderate halophiles can be exploited in commercial production and application of the effective strains under storage and greenhouse conditions.
  Journal of Applied Microbiology 02/2009; 106(3):833 - 846. · 2.34 Impact Factor
• Article: Biological control of grey mould in strawberry fruits by halophilic bacteria.

  B Essghaier, M L Fardeau, J L Cayol, M R Hajlaoui, A Boudabous, H Jijakli, N Sadfi-Zouaoui
  [show abstract] [hide abstract]
  ABSTRACT: Grey mould caused by Botrytis cinerea is an economically important disease of strawberries in Tunisia and worldwide. The aim of this study was to select effective halophilic bacteria from hypersaline ecosystems and evaluate the abilities of antifungal bacteria to secrete extracellular hydrolytic enzymes, anti-Botrytis metabolites and volatiles. Grey mould was reduced in strawberry fruits treated with halophilic antagonists and artificially inoculated with B. cinerea. Thirty strains (20.2%) were active against the pathogen and reduced the percentage of fruits infected after 3 days of storage at 20 degrees C, from 50% to 91.66%. The antagonists were characterized by phenotypic tests and 16S rDNA sequencing. They were identified as belonging to one of the species: Virgibacillus marismortui, B. subtilis, B. pumilus, B. licheniformis, Terribacillus halophilus, Halomonas elongata, Planococcus rifietoensis, Staphylococcus equorum and Staphylococcus sp. The effective isolates were tested for antifungal secondary metabolites. Moderately halophilic bacteria may be useful in biological control against this pathogen during postharvest storage of strawberries. The use of such bacteria may constitute an important alternative to synthetic fungicides. These moderate halophiles can be exploited in commercial production and application of the effective strains under storage and greenhouse conditions.
  Journal of Applied Microbiology 02/2009; 106(3):833-46. · 2.34 Impact Factor
• Article: Polymorphism in pbp5 gene detected in clinical Enterococcus faecium strains with different ampicillin MICs from a Tunisian hospital.

  N Klibi, Y Sáenz, M Zarazaga, K Ben Slama, A Masmoudi, F Ruiz-Larrea, A Boudabous, C Torres
  [show abstract] [hide abstract]
  ABSTRACT: The polymorphism in pbp5 gene was investigated in nine unrelated clinical gentamicin-resistant Enterococcus faecium strains with different minimal-inhibitory-concentration values for ampicillin (six ampicillin-resistant and three ampicillin-susceptible). Five alleles were detected when the pbp5 C-terminal region was analysed, two of them in the ampicillin-resistant strains showed a new allele characterised by the Thr416Ala and Val462Ala substitutions. Two different alleles were identified when the pbp5 N-terminal region was studied; one of them in the unique strain (E. faecium 83) that presented very low ampicillin MIC (<0.125 microg/ml) and a nucleotidic mutation implicating a stop codon at 451 position. RT-PCR experiments carried out on five E.faecium positive results indication the expression of this gene. Specific mutations in pbp5 gene could be responsible of the high MIC values of some of the E. faecium strains.
  Journal of chemotherapy (Florence, Italy) 08/2008; 20(4):436-40. · 1.08 Impact Factor
• Article: Ability of Moderately Halophilic Bacteria to Control Grey Mould Disease on Tomato Fruits

  N. Sadfi‐Zouaoui, B. Essghaier, M. R. Hajlaoui, M. L. Fardeau, J. L. Cayaol, B. Ollivier, A. Boudabous
  [show abstract] [hide abstract]
  ABSTRACT: Tomato is one of the leading crops in Tunisia in terms of weight consumed (20 kg/per person/year). Preserving the quality of the fruit from field to consumer is essential to successful marketing. Grey mould rot induced by Botrytis cinerea is an important cause of postharvest loss depending on season and handling practices. We describe here the ability of halotolerant to moderately halophilic bacteria isolated from different Tunisian Sebkhas (hypersaline soils) to protect fresh-market tomato fruits from B. cinerea. The tomatoes tested were at two different stages of ripening, (i) mature-green and (ii) red. Six strains significantly reduced growth of the pathogens from 67% to 87%. The effectiveness of these antagonists was also confirmed on green tomatoes; in which the fruit rot protection rate ranged from 74% to 100%. The antagonists were characterized by morphological, biochemical and physiological tests as well as 16S rDNA sequencing. The halotolerant effective isolates were identified as belonging to one of the species Bacillus subtilis (M1-20, J9) or B. licheniformis (J24). One effective moderately halophilic isolate (M2-26) was identified as Planococcus rifietoensis. These strains are a source of hydrolytic enzymes such as chitinases, proteases, laminarinases, amylases, lipases and cellulases. For comparison, 12 halotolerant or moderately halophilic strains obtained from DSM culture collection were also evaluated for their antifungal activity against B. cinerea on tomato fruits. The most effective strains were Halomonas subglaciescola, Halobacillus litoralis, Marinococcus halophilus, Salinococcus roseus, Halovibrio variabilis and Halobacillus halophilus with a percentage of grey mould rot reduction ranging from 71% to 97%. Inoculation of mature-green tomatoes by the bacterial antagonist of Halobacillus trueperi resulted in no disease development. Our results indicate that the use of halotolerant to halophilic micro-organisms should be helpful in reducing grey mould disease of stored tomatoes.
  Journal of Phytopathology 12/2007; 156(1):42 - 52. · 0.79 Impact Factor
• Article: Heteroduplex structures in 16S-23S rRNA intergenic transcribed spacer PCR products reveal ribosomal interoperonic polymorphisms within single Frankia strains.

  M Gtari, L Brusetti, A Cherif, A Boudabous, D Daffonchio
  [show abstract] [hide abstract]
  ABSTRACT: Detection of polymorphisms in intergenic transcribed spacer (ITS) 16S-23S rRNA within single Frankia strains. Polymorphisms in the 16S-23S rRNA ITS were investigated in single-colony subcultures of seven Frankia isolates. Multiple ITS-polymerase chain reaction (PCR) bands were detected solely in isolates BMG5.5 and BMG5.11. The slow-migrating bands in the ITS-PCR agarose gel electrophoresis profiles of the isolates were revealed to be heteroduplexes on the basis of their migration shift in different electrophoretic matrices, southern hybridization and the single-strand DNA mung bean endonuclease digestion. Laser-scanned capillary electrophoresis detected two ITS-PCR fragments differing in length by three and six nucleotide insertions/deletions in strains BMG5.5 and BMG5.11, respectively. Sequence analysis of the cloned ITS showed that in strain BMG5.5 the two ITS differed by the presence of three to four copies of the 3-bp tandem repeat 5'-TGG-3'. In strain BMG5.11, the two ITS differed by the presence of two to three copies of the 6-bp tandem repeat 5'-CTTGGG-3'. We demonstrate the occurrence of ITS 16S-23S rRNa polymorphisms within single Frankia strains. We reported the occurrence of ITS 16S-23S rRNA polymorphisms within single Frankia strains from Elaeagnus host group recognized as the more flexible strains within Frankia genus. Furthermore, we underscored the applied interest of strains BMG5.11 and BMG5.5 in future ecological studies using ITS 16S-23S rRNA as molecular marker.
  Journal of Applied Microbiology 11/2007; 103(4):1031-40. · 2.34 Impact Factor
• Article: Detection of virulence factors in high-level gentamicin-resistant Enterococcus faecalis and Enterococcus faecium isolates from a Tunisian hospital.

  N Klibi, K Ben Slama, Y Sáenz, A Masmoudi, S Zanetti, L A Sechi, A Boudabous, C Torres
  [show abstract] [hide abstract]
  ABSTRACT: Phenotypic and genotypic determination of virulence factors were carried out in 46 high-level gentamicin-resistant (HLGR) clinical Enterococcus faecalis (n=34) and Enterococcus faecium (n=12) isolates recovered from different patients in La Rabta Hospital in Tunis, Tunisia, between 2000 and 2003 (all these isolates harboured the aac(6')-aph(2") gene). The genes encoding virulence factors (agg, gelE, ace, cylLLS, esp, cpd, and fsrB) were analysed by PCR and sequencing. The production of gelatinase and hemolysin, the adherence to caco-2 and hep-2 cells, and the capacity for biofilm formation were investigated in all 46 HLGR enterococci. The percentages of E. faecalis isolates harbouring virulence genes were as follows: gelE, cpd, and ace (100%); fsrB (62%); agg (56%); cylLLS (41.2%); and esp (26.5%). The only virulence gene detected among the 12 HLGR E. faecium isolates was esp (58%). Gelatinase activity was detected in 22 of the 34 E. faecalis isolates (65%, most of them with the gelE+-fsrB+ genotype); the remaining 12 isolates were gelatinase-negative (with the gelE+-fsrB- genotype and the deletion of a 23.9 kb fragment of the fsr locus). Overall, 64% of the cylLLS-containing E. faecalis isolates showed beta-hemolysis. A high proportion of our HLGR E. faecalis isolates, in contrast to E. faecium, showed moderate or strong biofilm formation or adherence to caco-2 and hep-2 cells.
  Canadian Journal of Microbiology 04/2007; 53(3):372-9. · 1.36 Impact Factor
• Article: A novel phenotype based on esterase electrophoretic polymorphism for the differentiation of Lactococcus lactis ssp. lactis and cremoris.

  H Ouzari, A Hassen, A Najjari, B Ettoumi, D Daffonchio, M Zagorec, A Boudabous, D Mora
  [show abstract] [hide abstract]
  ABSTRACT: To evaluate the esterase phenotype in Lactococcus lactis strains isolated from traditional Tunisian dairy products. A collection of 55 L. lactis strains isolated from traditional fermented milk products and three reference strains were identified at species and subspecies level using molecular methods targeted to the 16S rRNA gene and to the histidine operon. The genotypic data obtained allowed the identification of the strains as L. lactis ssp. lactis and L. lactis ssp. cremoris with the prevalence of the ssp. lactis. The phenotypic identification based on arginine hydrolysis, the growth at 40 degrees C and in presence of 4% NaCl showed several discrepancy with the identification data based on genotypic analysis. Additional experiments carried out evaluating the esterase electrophoretic patterns revealed four classes of esterases identified on the basis of their electrophoretic mobility and specific activity on alpha- and beta-naphthyl ester of acetate and propionate. Esterase profiles discriminated the strains in two main groups corresponding to the subspecies cremoris and lactis according to a DNA-based identification. The evaluation of esterase activity represents a novel phenotype for the taxonomic discrimination of the L. lactis ssp. lactis and cremoris. Besides the DNA-based techniques that allow the rapid and accurate species/subspecies identification, the electrophoretic esterase profiles of L. lactis strains represents: (i) a new phenotypic tool to understand the physiology and the ecology of this species; and (ii) a new test for the potential selection of flavour producing strains.
  Letters in Applied Microbiology 11/2006; 43(4):351-9. · 1.62 Impact Factor
• Article: Diversity of structures carrying the aac(6')-aph(2") gene in clinical Enterococcus faecalis and Enterococcus faecium strains isolated in Tunisia.

  N Klibi, K Ben Slama, A Masmoudi, S Gharbi, F Ruiz-Larrea, C Fendri, A Boudabous, C Torres
  [show abstract] [hide abstract]
  ABSTRACT: The diversity of structures carrying the aac(6')-aph(2") gene was studied in 46 high-level gentamicin-resistant Enterococcus faecalis and Enterococcus faecium clinical strains recovered in a Tunisian hospital during the period 2000-2003. The inclusion of the aac(6')-aph(2") gene within the Tn4001 composite element or in its truncated forms (lacking the IS256 at the right, the left or at both sides of the aac(6')-aph(2") gene) was investigated by PCR and sequencing. The aac(6')-aph(2") gene was included in the composite Tn4001 element in 19 of 34 high-level gentamicin-resistant E. faecalis strains (56%) and in 1 of 12 E. faecium strains (12%). A truncated form of Tn4001 lacking IS256 at the left-hand (in 10 E. faecalis and 8 E. faecium), at the right-hand (3 E. faecalis and 2 E. faecium) or at both sides of the aac(6')-aph(2") gene (in 2 E. faecalis and 1 E. faecium) was also detected in 26 of our enterococci. The transference by conjugation of the aac(6')-aph(2") gene, associated with other resistance genes, was demonstrated in seven of the high-level gentamicin-resistant E. faecalis strains.
  Journal of chemotherapy (Florence, Italy) 09/2006; 18(4):353-9. · 1.08 Impact Factor