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A Cherif

Publications and source records attributed to A Cherif.

At least 19 recordsLinked to original sources
PubMed2006

[Nosocomial respiratory infection due to an imipenem-resistant Pseudomonas aeruginosa O: 12 strain in a Tunis's neonatal intensive care unit].

OBJECTIVE: Investigation of an outbreak caused by an imipenem-resistant Pseudomonas aeruginosa strain and research of its hospital reservoir. PATIENTS AND METHODS: Nine strains isolated from protected tracheal specimens during 14 weeks (October 2004 to January 2005) from 8 infants, and one strain from vacuum interrupter were studied. Epidemiological study was investigated by determination of antibiotics susceptibility, serotyping and Pulsed-field gel electrophoresis (PFGE). RESULTS: Strains were of O:12 serotype, they have the same antibiotype characterised by imipenem resistance. Strains were indistinguishable or closely related as determined by PFGE. The common source of P. aeruginosa O:12 strains was not determined, however eradication of the epidemic strain was obtained by amelioration of hygiene conditions and the change of disinfectors. CONCLUSION: Outbreak of respiratory infections due to an imipenem-resistant P. aeruginosa O:12. The common source of the epidemic strain was not determined.

Anti-Bacterial Agents↗
PubMed2005

The autolytic phenotype of the Bacillus cereus group.

AIM: To determine the autolytic phenotype of five species in the Bacillus cereus group. METHODS AND RESULTS: The autolytic rate of 96 strains belonging to five species in the B. cereus group was examined under starvation conditions at pH 6, 6.5 and 8.5 in different buffers. The autolytic rate was strain-dependent with a wide variability at pH 6, but higher and more uniform at pH 6.5. At pH 8.5, and respect to the extent of autolysis at pH 6.5, it was relatively low for most of the strains with the lowest values between 13 and 52% in Bacillus mycoides and Bacillus pseudomycoides. Peptidoglycan hydrolase patterns evaluated by renaturing sodium dodecyl sulfate-polyacrylamide gel electrophoresis using cells of Bacillus thuringiensis ssp. tolworthi HD125 as an indicator, revealed complex profiles with lytic bands of about 90, 63, 46, 41, 38, 32, 28 and 25 kDa in B. cereus, B. thuringiensis and Bacillus weihenstephanensis. Bacillus mycoides and B. pseudomycoides had simpler profiles with lytic bands of 63, 46 and 38 kDa. Changes in the autolytic pattern were observed for cells harvested at the stationary phase of growth (72 h) showing an increase in the intensity of the 25 kDa band in the case of B. cereus, B. thuringiensis and B. weihenstephanensis, while no changes were observed for B. mycoides. Using Micrococcus lysodeicticus and Listeria monocytogenes as indicators lytic activity was retained by proteins of 63, 46, 38, 32 and 25 kDa and a new one of about 20 kDa in B. mycoides. Growth in the different media did not affect the autolytic pattern. NaCl abolished the activity of all the peptidoglycan hydrolases except for those of B. mycoides and B. weihenstephanensis. Lytic activity was retained in the presence of MgCl(2), MnCl(2) and EDTA and increased at basic pH. CONCLUSIONS: Bacillus cereus/B. thuringiensis/B. weihenstephanensis showed a high extent of autolysis around neutral pH, even though they presented relatively complex autolysin profiles at alkaline pH. Bacillus mycoides/B. pseudomycoides had a higher extent of autolysis at acidic pH and a simpler autolysin pattern. SIGNIFICANCE AND IMPACT OF THE STUDY: Information on the autolytic phenotype expand the phenotypic characterization of the different species in the B. cereus group.

Bacillus cereus↗
PubMed2004

The autolytic phenotype of Bacillus thuringiensis.

AIMS: To evaluate the autolytic phenotype of Bacillus thuringiensis. METHODS AND RESULTS: The autolytic rate of 87 strains belonging to different subsp. of B. thuringiensis was examined at pH 6, 6.5 and 8.5 in different buffers under starvation conditions. At pH 6 the extent of autolysis (average in the strain collection 38.3 +/- 21.1) was strain-dependent with wide variability, while at pH 6.5 and 8.5 (averages 72.0 +/- 9.0 and 63.1 +/- 8.2, respectively) it was much more uniform with only a few strains showing low autolytic rates. Forty-one per cent of the strains showed high resistance (>/=80%) to mutanolysin, a commercial muramidase from Streptomyces. The peptidoglycan hydrolase pattern was evaluated by renaturing SDS-PAGE using cells of B. thuringiensis subsp. tolworthi HD125 as indicator. The strain collection showed seven major lytic bands of about 90, 63, 46, 38, 32, 28 and 25 kDa, and in the stationary growth phase (72 h) there was a more intense 25 kDa band in the autolytic pattern. Using Micrococcus lysodeicticus and Listeria monocytogenes as the indicators lytic activity was retained, as seen by the bands of 63, 46, 38, 32 and 25 kDa. Growth in the different media did not affect the autolytic pattern. NaCl abolished the activity of all the peptidoglycan hydrolases in the gel, but in the presence of KCl, MgCl(2), MnCl(2) and EDTA some activity was retained. At basic pH the lytic activity increased. CONCLUSIONS: The autolytic phenotype of B. thuringiensis was found to be strain-dependent, and different proteins exibited peptidoglycan hydrolase activity, particularly at alkaline pH. Several of these proteins retained lytic activity against other bacterial species. SIGNIFICANCE AND IMPACT OF THE STUDY: The characterisation of the autolytic phenotype of B. thuringiensis should expand the prospects of using this species in bacterial bio-control and field applications.

Bacillus thuringiensis↗
PubMed2003

[Pharmacologic study of monohydrated caffeine in the treatment of apnoea of premature infant].

UNLABELLED: Monohydrated caffeine was the only respiratory xanthine available in our country to treat apnea of premature infant. The aim of this study was to evaluate plasma levels of this molecule at dosages of 20 mg/kg (equal to 18 mg/kg of caffeine base) as a loading dose and 5 mg(-1) kg(-1) (equal to 4.5 mg(-1) kg(-1) of caffeine base) as a maintenance dose. PATIENTS AND METHODS: The study was prospective including premature infants less than 34 weeks of gestational age born between the 1st of july 2001 and 15th december 2001 and receiving monohydrated caffeine to prevent apnea. Each premature infant has received orally a loading dose of 20 mg/kg in the first hours of life followed, 24 h after, by a maintenance dose orally once a day of 5 mg/kg until 35 weeks of post-conceptional age. Caffeinemia plasma levels were measured by high performance liquid chromatography immediately before the second dose to determine the loading residual rate and immediately before the sixth dose to determine the maintenance residual rate. RESULTS: Twenty-one premature infants were included. Their medium term was 31.4 weeks (27.4-33.3 weeks), birth weight was 1684 g (1000-2800 g) and sex-ratio M/F was 1.3. Fifteen infants (71.4%) have presented apnea with an average of 4.1 episodes per infant and per day. Tolerance of the medicament was good in all cases. The medium loading residual rate was 3.26 microg/ml (1.75-7.80) and the medium maintenance residual rate was 4.26 microg/ml (2.13-7.64). CONCLUSION: Prescribed at a dosage close to twice the recommendations of the literature, monohydrated caffeine does not provide efficient plasma rates. This is probably due to a difference in its oral bio-availability compared with caffeine citrate and further study with greater dosages is needed to appreciate its efficacy.

Administration, Oral↗
PubMed2003

Genetic relationship in the 'Bacillus cereus group' by rep-PCR fingerprinting and sequencing of a Bacillus anthracis-specific rep-PCR fragment.

AIMS: To evaluate the genetic relationship in the Bacillus cereus group by rep-PCR fingerprinting. METHODS AND RESULTS: A collection of 112 strains of the six species of the B. cereus group was analysed by rep-PCR fingerprinting using the BOX-A1R primer. A relative genetic distinctness was found among the species. Cluster analysis of the rep-PCR patterns showed clusters of B. thuringiensis strains quite separate from those of B. cereus strains. The B. anthracis strains represented an independent lineage in a B. cereus cluster. The B. mycoides, B. pseudomycoides and B. weihenstephanensis strains were clustered into three groups at some distance from the other species. Comparison of sequences of AC-390, a typical B. anthracis rep-PCR fragment, from 27 strains of B. anthracis, B. cereus, B. thuringiensis and B. weihenstephanensis, representative of different clusters identified by rep-PCR fingerprinting, confirmed that B. anthracis diverges from its related species. CONCLUSIONS: The genetic relationship deduced from the rep-PCR patterns indicates a relatively clear separation of the six species, suggesting that they can indeed be considered as separate units. SIGNIFICANCE AND IMPACT OF THE STUDY: rep-PCR fingerprinting can make a contribution in the clarification of the genetic relationships between the species of the B. cereus group.

Bacillus anthracis↗
PubMed2003

Detection and characterization of the novel bacteriocin entomocin 9, and safety evaluation of its producer, Bacillus thuringiensis ssp. entomocidus HD9.

AIMS: To identify and characterize new bacteriocins from a collection of 41 strains belonging to 27 subspecies of Bacillus thuringiensis, and to evaluate the safety of the producers. METHODS AND RESULTS: Bacillus thuringiensis ssp. entomocidus HD9 produced in the culture supernatant an antimicrobial activity against Gram-positive bacteria including Listeria monocytogenes, one of four pathogenic Pseudomonas aeruginosa and several fungi. Production of the antibacterial activity, named entomocin 9, started during mid-logarithmic growth reaching its maximum at the early stationary phase. Entomocin 9 retained more than 72% of activity after incubation for 20 min at 121 degrees C. Activity was lost after proteinase K treatment, it was stable in a pH range between 3 and 9, and resistant to lyophilization. After partial purification with ammonium sulphate precipitation followed by gel-filtration and anion-exchange chromatography, an active protein of ca 12.4 kDa was isolated. The mode of action of entomocin 9 was bactericidal and caused cell lysis of growing cells. Despite the presence of a range of virulence related genes, including haemolysin BL, nonhaemolytic enterotoxin, cytotoxin K and several hydrolytic activities, B. thuringiensis HD9 was not toxic against Vero cells. CONCLUSIONS: Entomocin 9 is a novel heat-stable, bacteriocin produced by B. thuringiensis HD9. The absence of toxicity against Vero cells suggests the suitability of strain HD9 for a safe application in antimicrobial treatments. SIGNIFICANCE AND IMPACT OF THE STUDY: New finding on entomocin 9 would make B. thuringiensis attractive in biotechnological applications as an antimicrobial agent in agriculture and food industry.

Animals↗
PubMed2003

[Diastematomyelia: antenatal diagnosis with successful outcome, two cases].

To discuss, through a review of the literature, clinical signification and antenatal and postnatal management of diastematomyelia. We present two cases highlighting the clinical presentation and discuss management options. The first case was diagnosed in a 32-year-old primagravida female physician. The conssanguinous couple had a history of primary hypofertility. Antenatal magnetic resonance imaging revealed the presence of a sagittal spinal spur separating two asymmetrical hemi cords. Pregnancy was not interrupted due to the lack of factors of poor prognosis. The infant was delivered at term and outcome has been favorable at 18 months follow-up. Ultrasonography performed at 22 weeks gestation provided the diagnosis in the second case. The mother was a 30-year-old primagravida anesthesist who had been addressed for suspected spina bifida. The consanguinous couple had a history of male hypoferility. The ultrasound scan revealed an echogenic spinal spur and integrity of the skin. Pregnancy was not interrupted due to the lack of factors of poor prognosis. The infant was delivered at term and outcome has been favorable at 18 months follow-up. Diastematomyelia is a rare malformation which can be diagnosed antenatally. Careful ultrasonography can distinguish diastematomyelia from myelomeningocele. Antenatal assessment is essential to identify forms with good prognosis because the neonatal outcome of isolated diastematomyelia is generally good, even if surgical repair is required.

Adult↗
PubMed2002

Autolytic phenotype of Lactococcus lactis strains isolated from traditional Tunisian dairy products.

AIMS: To evaluate the autolytic properties of Lactococcus lactis strains isolated from artisan Tunisian dairy products, their peptidoglycan hydrolase content and their activity spectrum. METHODS AND RESULTS: The autolytic phenotype of Lactococcus strains was evaluated under starvation conditions in potassium phosphate buffer. The results obtained highlighted a high degree of diversity among the strains analysed, allowing the identification of high and low autolytic Lactococcus lactis strains. Peptidoglycan hydrolase content was evaluated by renaturing SDS-PAGE using cells of Micrococcus lysodeikticus as a target for the enzymatic activity. A major activity band migrating at about 45 kDa was observed. The lytic activity, evaluated in the presence of different chemicals, was retained in 8% NaCl, 15 mmol l(-1) CaCl2, and in a pH range between 5 and 9.5. The substrate specificity of peptidoglycan hydrolase from Lactococcus strains was evaluated in renaturing SDS-PAGE incorporating cells of different bacterial species. The major autolysin of Lactococcus lactis was active against cells of Lactococcus lactis subsp. lactis, Streptococcus thermophilus, Lactobacillus delbrueckii subsp. bulgaricus, Lactobacillus helveticus and Listeria monocytogenes. CONCLUSIONS: Autolytic activity is widely distributed in Lactococcus lactis and the rate of autolysis is strain-dependent. The major peptidoglycan hydrolase showed a wide spectrum of activity against several lactic acid bacteria and bacterial species involved in food-related infection. SIGNIFICANCE AND IMPACT OF THE STUDY: The autolytic phenotype of Lactococcus lactis strains isolated from Tunisian artisan dairy products has been determined, and the data obtained should allow the selection of strains of technological interest in the cheese-ripening process.

Bacteriolysis↗
PubMed2002

Characterization of a repetitive element polymorphism-polymerase chain reaction chromosomal marker that discriminates Bacillus anthracis from related species.

AIMS: To identify a chromosomal marker with signature nucleotides specific for Bacillus anthracis. METHODS AND RESULTS: Repetitive element polymorphism-polymerase chain reaction with BOX-A1R primer was used to discriminate 52 strains of all six species of the 'B. cereus group'. A B. anthracis signature fragment, named AC-390, was cloned and sequenced. The deduced amino acid sequence was homologous to that of YwfK of B. subtilis. Using two internal primers, the AC-390 fragment was sequenced from two other B. anthracis strains as well as from strains of B. cereus and B.thuringiensis which have an AC-390 fragment homologous to that of B. anthracis as shown by Southern hybridization experiments. CONCLUSIONS: Two new signature sequences specific for B. anthracis were identified on a chromosomal fragment homologous to YwfK, a transcriptional regulator of B. subtilis. SIGNIFICANCE AND IMPACT OF THE STUDY: These results show a new chromosomal DNA trait useful for distinguishing B. anthracis from the related species of the B. cereus group, regardless of the presence of the virulence plasmids pXO1 and pXO2.

Amino Acid Sequence↗
PubMed2001

Microbial characterization during composting of municipal solid waste.

This study investigates the prevailing physico-chemical conditions and microbial community; mesophilic bacteria, yeasts and filamentous fungi, bacterial spores, Salmonella and Shigella as well as faecal indicator bacteria: total coliforms, faecal coliforms and faecal Streptococci, present in a compost of municipal solid waste. Investigations were conducted in a semi-industrial pilot plant using a moderate aeration during the composting process. Our results showed that: (i) auto-sterilization induced by relatively high temperatures (60-55 degrees C) caused a significant change in bacterial communities. For instance, Escherichia coli and faecal Streptococci populations decreased, respectively, from 2 x 10(7) to 3.1 x 10(3) and 10(7) to 1.5 x 10(3) cells/g waste dry weight (WDW); yeasts and filamentous fungi decreased from 4.5 x 10(6) to 2.6 x 10(3) cells/g WDW and mesophilic bacteria were reduced from 5.8 x 10(9) to 1.8 x 10(7) bacteria/g WDW. On the other hand, the number of bacterial spores increased at the beginning of the composting process, but after the third week their number decreased notably; (ii) Salmonella disappeared completely from compost by the 25th day as soon as the temperature reached 60 degrees C; and (iii) the bacterial population increased gradually during the cooling phase. While Staphylococci seemed to be the dominant bacteria during the mesophilic phase and at the beginning of the thermophilic phase, bacilli predominated during the remainder of the composting cycle. The appearance of gram-negative rods (opportunistic pathogens) during the cooling phase may represent a serious risk for the sanitary quality of the finished product intended for agronomic reuse. Compost sonication for about 3 min induced the inactivation of delicate bacteria, in particular gram-negatives. By contrast, gram-positive bacteria, especially micrococcus, spores of bacilli, and fungal propagules survived, and reached high concentrations in the compost.

Biodegradation, Environmental↗
PubMed2001

Thuricin 7: a novel bacteriocin produced by Bacillus thuringiensis BMG1.7, a new strain isolated from soil.

AIMS: Detection and identification of new antagonistic activities towards Bacillus cereus and relatives. METHODS AND RESULTS: Twenty Bacillus thuringiensis strains were screened for their capacity to express bacteriocin-like agents. Strain BMG1.7, isolated from soil, showed an antagonistic activity called thuricin 7. Thuricin 7 was active against several species of the genus Bacillus, including three of the four known B. thuringiensis/B. cereus bacteriocin producers, as well as against Streptococcus pyogenes and Listeria monocytogenes strains. Antimicrobial activity was lost after treatment with proteinase K. The active protein had an apparent molecular weight of 11.6 kDa, and was secreted at the end of the exponential growth phase. Thuricin 7 retained 55% of the activity after incubation at 98 degrees C for 30 min. The mode of action of thuricin 7 was shown to be bactericidal and bacteriolytic. CONCLUSION: Thuricin 7 is a novel bacteriocin produced by a newly isolated Bacillus thuringiensis strain BMG1.7. SIGNIFICANCE AND IMPACT OF THE STUDY: The characteristics of thuricin 7 indicate that it is a new bacteriocin which may have interesting biotechnological applications due to its relatively large activity spectrum.

Bacillus cereus↗
PubMed2001

Heterogeneity among infecting strains of Pseudomonas aeruginosa in diverse departments of a large Tunisian hospital.

Clinical isolates of Pseudomonas aeruginosa were obtained during a half-year screening period of five different wards of the La Rabta Hospital (Tunis). Distinct clinical isolates (N= 82) were obtained from patients, 40 (48%) of which originated from the Department of Otolaryngology. In order to define the local epidemiology of this opportunistic organism, all strains were serotyped, analysed for pyocin production and genetically characterized with the help of pulsed-field gel electrophoresis (PFGE). The data show that, despite the frequent occurrence of identical serotypes, most of the isolates represent unique pyocin types (N= 53) and genotypes (N= 64). A combination of the pyocin and PFGE data showed that nearly all strains were of unique types, except for two pairs of strains. A limited number of strain clusters was observed on the basis of DNA typing data alone. This involved eight genotypes, some of which were clustered with respect to clinical environment or time. Genotype 22 occurred most frequently (6/83, 7%) and independently of time and locale, indicating that it may represent either a clonal type constituting a major fraction of all P. aeruginosa isolates in the region or a more prevalent organism. Despite a relatively high incidence of P. aeruginosa infections, the polyclonality of these strains shows that, in La Rabta Hospital, pseudomonal infections are not primarily due to excessive spread of a single bacterial genotype.

Cross Infection↗
PubMed2001

[Severe pulmonary hypertension in ostium secundum atrial septal defect].

Between 1969 and 1999, 149 patients underwent cardiac catheterization for ostium secundum atrial septal defect, in hemodynamics department. Age average was 21.5 +/- 16 years (2-67). Systolic pulmonary arterial pressure average was 35 +/- 15.6 mm Hg (15-140). The atrial septal defect was closed in 108 patients (by surgery in 107 cases, and by interventional catheterization in one case). Mean follow-up was 8 +/- 7 years (1-20). Overall mortality rate was 2.7%. Severe pulmonary hypertension (systolic pressure > or = to 50 mm Hg) was seen in 13.4% of cases. It was present at all ages, but more frequent above 20 years. Obstructive pulmonary vascular disease was noticed in 2% of patients. Clinical and haemodynamic data analysis showed that, severe pulmonary hypertension is a frequent, and unpredictible complication of secundum atrial septal defect; it might occur at any age and worsen considerably the cardiac disease prognosis. Because of atrial septal defect hemodynamic profile, and current rise of percutaneous closure technics, invasive investigation should be more and more routinely performed, in order to define the best therapeutic option. Early and systematic closure of secundum atrial septal defects, should prevent, or at least minimize pulmonary vascular lesions.

Adolescent↗
PubMed2000

Homoduplex and heteroduplex polymorphisms of the amplified ribosomal 16S-23S internal transcribed spacers describe genetic relationships in the "Bacillus cereus group".

Bacillus anthracis, Bacillus cereus, Bacillus mycoides, Bacillus pseudomycoides, Bacillus thuringiensis, and Bacillus weihenstephanensis are closely related in phenotype and genotype, and their genetic relationship is still open to debate. The present work uses amplified 16S-23S internal transcribed spacers (ITS) to discriminate between the strains and species and to describe the genetic relationships within the "B. cereus group," advantage being taken of homoduplex-heteroduplex polymorphisms (HHP) resolved by polyacrylamide gel electrophoresis and silver staining. One hundred forty-one strains belonging to the six species were investigated, and 73 ITS-HHP pattern types were distinguished by MDE, a polyacrylamide matrix specifically designed to resolve heteroduplex and single-strand conformation polymorphisms. The discriminating bands were confirmed as ITS by Southern hybridization, and the homoduplex or heteroduplex nature was identified by single-stranded DNA mung bean nuclease digestion. Several of the ITS-HHP types corresponded to specific phenotypes such as B. anthracis or serotypes of B. thuringiensis. Unweighted pair group method arithmetic average cluster analysis revealed two main groups. One included B. mycoides, B. weihenstephanensis, and B. pseudomycoides. The second included B. cereus and B. thuringiensis, B. anthracis appeared as a lineage of B. cereus.

Bacillus↗
PubMed2000

[Evolution after 5 years of percutaneous pulmonary valvulotomy: report of 47 cases].

47 patients aged from 2 to 59 years affected by valvular congenital or mixed pulmonary stenosis including three fallot trilogies and one patient with right congestive cardiac failure are treated by percutaneous pulmonary valvulotomy between october 1986 and december 1990. All patients have been controlled with a mean follow-up of 6.5 +/- 1.1 years. The total gradient rate between pulmonary artery and right ventricule decrease from 112 +/- 55 mm Hg to 20 +/- 8 mm Hg on the last control with disappearance of infundibular inflammation and inter auricular shunt in all the concerned cases. We observe the regression of right cardiac failure symptoms with disappearance of tricuspid insufficiency in the cases of advanced pulmonary stenosis with right ventricular dysfunction. Percutaneous pulmonary valvulotomy by its simplicity and harmlessness, its long term efficiency is a good method of treatment of pure valvular or mixed pulmonary stenosis.

Adolescent↗
PubMed2000

[Study of the incidence and cost of nosocomial infections in general surgery].

Nosocomial infection incidence and its cost were study. We have identified 61 infected patients and 75 infectious episodes, is an incidence of 9.4% infected for 100 hospitalized by trimester. Operative site infections are the most frequent (60%), operative site infection (9.1%), inferior respiratory ways infections (2.2%). Incriminated germs are represented essentially by negative gram Bacillus (77.3%) with predominance of enterobacterias (59%). Invasive technique usage, surgery types and contamination classes have been identified as risk factors of nosocomial infection occurrence. The supplementary stay duration estimated by simple comparison between infected group and no-infected one is 9.3% days, responsible of an over cost of 336 TD by infected patient and 273 TD by infectious episode. The curative antibiotic costs have been estimated at 70 TD by infected patient being equivalent to two hospitalization days and to 57 TD by infectious episode.

Adult↗