The Synbiotic Effect of Probiotics and Dried Spirulina platensis or Phycocyanin on Biofilm Formation by Salmonella Typhimurium and Staphylococcus aureus

This study aimed to evaluate the synbiotic effect of probiotics and dried Spirulina platensis or phycocyanin on autoaggregation, coaggregation, and the inhibition of biofilm formation by Salmonella Typhimurium and Staphylococcus aureus on 96-well microtiter plates and Human colon carcinoma cells-116 surfaces. The results showed that the probiotics strains cultured in the presence of S. platensis exhibited the highest autoaggregation values, ranging between 68.5 and 74.2% after 24 h. All probiotic strains with or without S. platensis and phycocyanin showed coaggregation abilities with S. Typhimurium and S. aureus. Interestingly, significant effect of S. platensis and phycocyanin supplementation was observed on the inhibition of the biofilm formation by the selected pathogens during the competition, exclusion, and displacement on abiotic and biotic surfaces.

Protective effects of dietary Kefir against aflatoxin B1-induced hepatotoxicity in Nile tilapia fish, Oreochromis niloticus

The effect of dietary Kefir supplementation on the biometric, biochemical, and histological parameters of Nile tilapia (Oreochromis niloticus) exposed to aflatoxin B1 (AFB1, 200 µg/kg diet) contamination was studied. The yeasts were dominant in Kefir followed by lactic and acetic acid bacteria. The Kefir showed relatively interesting antioxidant potential in the DPPH• (IC50 = 0.9 ± 0.02 mg/ml) and ABTS•+ (IC50 = 2.2 ± 0.03 mg/ml) scavenging activities, Fe3+-reducing power (EC0.5 = 1.2 ± 0.01 mg/ml), and β-carotene bleaching assay (IC50 = 3.3 ± 0.02 mg/ml). Three hundred and sixty Nile tilapia weighing 23 ± 5 g were divided into four groups (30 fish/group with 3 replicates), and fed with diets containing Kefir (D2), AFB1 (D3), and Kefir+AFB1 (D4) for 4 weeks, whereas D1 was kept as control group where fish were fed with basal diet. The Kefir supplementation in D4 group significantly increased (p < .05) the percent weight gain as compared to D3 group. Moreover, Kefir improved the antioxidant enzymes in the liver, such as catalase (CAT), glutathione peroxidase (GPx), and superoxide dismutase (SOD) activities, that significantly increased (p < .05) by 2-, 3-, and 1.5-folds, respectively, as compared to D3 group. The Kefir treatment significantly decreased (p < .05) the liver malonaldehyde content by ~50% as compared to D3 group. Histopathological analysis revealed the hepatoprotective effects of Kefir by showing normal liver histological architecture in D4 group, as compared to degenerative changes observed in D3 group. These results suggest that Kefir could be considered as a potential probiotic in Nile tilapia feed to mitigate the AFB1 harmful effects.

Does probiotic Kefir reduce dyslipidemia, hematological disorders and oxidative stress induced by zearalenone toxicity in wistar rats?

Zearalenone (ZEA) is a toxic metabolite of the genus Fusarium, which causes hepatotoxicity and induces oxidative stress. Kefir is an important probiotic dairy-product showing important in vitro antioxidant potential. In this study, the effect of Kefir supplementation to mitigate ZEA toxicity in rats was investigated. Animals were divided into four groups of five rats each, which received sterile milk (200 μL/day) during the first week. Then, they were switched to Kefir (200 μL/day), ZEA (40 mg/kg b. w./day) and Kefir + ZEA for the second week. Hematological and biochemical parameters, as well as liver histological analysis were determined. Kefir administration prevented the changes occurred in the count of all blood cells, and improved the antioxidant enzymes in the liver, such as catalase, glutathione peroxidase and superoxide dismutase activities that increased by 6, 4.5 and 1.3 folds, respectively, compared to ZEA group. Interestingly, the concurrent regimen Kefir + ZEA removed ZEA residues in the serum and liver. Furthermore, the Kefir + ZEA group showed a reduction in the levels of bilirubin, alanine aminotransferase, aspartate aminotransferase, alkaline phosphatase and hepatic malonaldehyde by ∼82, 54, 66, 50 and 36%, respectively, compared to the ZEA group. The histopathological analysis showed a normal liver histological architecture in Kefir + ZEA group, while degenerative changes were observed in ZEA group. These results suggest that Kefir as probiotic consortium may have a hepatoprotective effect against ZEA poisoning.

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Zearalenone caused oxidative stress and liver damage in rats.

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Zearalenone induced disruption of hematological and biochemical parameters.

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Kefir improved the antioxidant defense systems in rats subjected to Zearalenone.

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Kefir prevented Zearalenone-induced hepatotoxicity in rats.

Control of Staphylococcus aureus methicillin resistant isolated from auricular infections using aqueous and methanolic extracts of Ephedra alata

In the current study the potential use of aqueous and methanolic extracts of Ephedra alata aerial parts as biological control agent against pathogenic bacteria and especially Staphylococcus aureus methicillin resistant isolated from auricular infections was evaluated. Chemical tests and spectrophotometric methods were used for screening and quantification of phytochemicals. The assessment of the antioxidant activity was accomplished by DPPH and ABTS radicals scavenging assays. Extracts were evaluated for their antibacterial efficacy by diffusion and microdilution methods. Biofilm inhibition was tested using XTT assay and the cytotoxicity of extracts was carried out on Vero cell line. The GC-FID analysis revealed that E. alata was rich in unsatured fatty acids. In addition, the aqueous extract had the highest flavonoid and protein contents (30.82 mg QE /g dry extract and 98.92 mg BSAE/g dry extract respectively). However, the methanolic extract had the highest phenolic, sugars and tannins. The antioxidant activity demonstrated that the aqueous extract exhibited the strong potency (IC50 ranged between 0.001 and 0.002 mg/mL).

Both extracts displayed antimicrobial activity on Gram negative and positive strains. They were effective against S. aureus isolated from auricular infections. The tested extracts were able to inhibit biofilm formation with concentration-dependent manner.

Moreover, no cytotoxic effect on Vero cells line was demonstrated for the extracts. Overall, our findings highlight the potential use of E. alata extract as a novel source of bioactive molecules with antioxidant, antibacterial and antiobiofilm effects for the control of infectious disease especially those associated to S. aureus methicillin resistant.

Pathogenic Impacts of Bacillus cereus Strains on Crassostrea gigas

Regarding the economic importance of bivalve farming, a great deal of interest has recently been devoted to studying the pathogenesis of infectious diseases of these mollusks to prepare for public health emergencies. Bacillus cereus is one of these pathogens; it is a ubiquitous soil bacterium responsible for many types of gastrointestinal diseases associated with food. This study was conducted to determine the pathogenic effect of B. cereus on Crassostrea gigas. This effect was studied by assessing hemocytes death using flow cytometry analysis. The results showed that only ∼15% of C. gigas were able to survive after B. cereus artificial infection with 10⁸ CFU (colony-forming unit)/oyster. Evenly, the percentage of nonviable hemocytes gradually increased with the concentration of B. cereus, with a peak value of ∼40% after infection. Indeed, findings showed that this strain is harmful to C. gigas.

Atypical Salmonella Typhimurium persistence in the pacific oyster, Crassostrea gigas, and its effect on the variation of gene expression involved in the oyster's immune system

Salmonella is one of the most important pathogens involved in food intoxication outbreaks, and in many cases, the intoxication has been linked to shellfish which is typically consumed raw. While much is understood about the interactions between Salmonella and vertebrates, much less is known about its relationships with invertebrates, which could be an overlooked and important aspect to better understand the Salmonella interaction with its diversified hosts. The aim of this study was to investigate the effect of preadaptation in seawater microcosms during 12 months on Salmonella Typhimurium by determining its survival capacity within this mollusk over a period of 30 days. The results showed that the stressed bacteria are able to survive in this mollusk at a higher concentration even after thirty days of infection compared to bacteria in the normal state. In order to minimize the effect of an experimental device for one month on the survival of Salmonella, we carried out an in vitro study to determine the number of viable Salmonella in the hemocytes of oysters. Interestingly, we evaluated the effect of the antibacterial activity of different extracts of C. gigas using the solvents (Methanol, Ethanol and acetic acid) specifically against stressed and unstressed Salmonella. Furthermore, we compared the expression of three genes in the oyster Cg-big-def1, timp and sod in response to experimental infections of this mollusk with Vibrio splendidus kb133 and S. Typhimurium LT2DT104 in normal and stressed states. These findings are very important to contribute to explaining several questions about the persistence of S. Typhimurium for a long time in C. gigas and the host's immune response to this microorganism which is considered to be non-virulent for molluscs.

Legionella pneumophila sg1-sensing signal enhancement using a novel electrochemical immunosensor in dynamic detection mode

This work presents a comparison between static and dynamic modes of biosensing using a novel microfluidic assay for continuous and quantitative detection of Legionella pneumophila sg1 in artificial water samples. A self-assembled monolayer of 16-amino-1-hexadecanethiol (16-AHT) was covalently linked to a gold substrate, and the resulting modified surface was used to immobilize an anti-Legionella pneumophila monoclonal antibody (mAb). The modified surfaces formed during the biosensor functionalization steps were characterized using electrochemical measurements and microscopic imaging techniques. Under static conditions, the biosensor exhibited a wide linear response range from 10 to 10⁸ CFU/mL and a detection limit of 10 CFU/mL. Using a microfluidic system, the biosensor responses exhibited a linear relationship for low bacterial concentrations ranging from 10 to 10³ CFU/mL under dynamic conditions and an enhancement of sensing signals by a factor of 4.5 compared to the sensing signals obtained under static conditions with the same biosensor for the detection of Legionella cells in artificially contaminated samples.

Dietary administration effects of exopolysaccharide from potential probiotic strains on immune and antioxidant status and nutritional value of European sea bass (Dicentrarchus labrax L.)

The use of biological immunostimulants is considered a valuable practice to improve culture conditions in aquaculture sector that may help to increase production and maintain healthy environment. We undertook this study in order to evaluate the potential effect of the administration of two exopolysaccharides (EPS) "EPLB" and "EPB" derived from potential probiotic strains on immune and antioxidant status of European sea bass (Dicentrarchus labrax L.) larvae. In order to find out if the EPSs have an effect on the biochemical composition during the trial period, the nutritional value has been evaluated. The results revealed that expression levels of immune-relevant genes (infg, Il1b, Il8, Il6 and tcr-β) in the gut and head kidney and the scavenging enzymes (cat, sod, gr) genes in the liver were modulated. In fact, the dietary supplementation with the tested EPSs, significantly enhances the expression of immune-associated genes in the head-kidney, particularly infg and tcrβ, as well as catalase gene in liver. During the period of study, EPSs administration did not affect the fatty acid profiles of larvae, which is balanced. This is confirmed by the Docosahexaenoic acid / Eicosapentaenoic acid ratio and demonstrates that EPLB and EPB can be administrated without any negative effect on biochemical composition of European sea bass. The present findings provided evidence that the tested EPSs with antibacterial and antioxidant activities can enhance immune response without negative effect on the biochemical composition. The used EPSs can be considered as a good source of natural functional aquafeed ingredients for European sea bass.

Fermented Seeds ("Zgougou") from Aleppo Pine as a Novel Source of Potentially Probiotic Lactic Acid Bacteria

Microorganisms inhabiting fermented foods represent the main link between the consumption of this food and human health. Although some fermented food is a reservoir of potentially probiotic microorganisms, several foods are still unexplored. This study aimed at characterizing the probiotic potential of lactic acid bacteria isolated from zgougou, a fermented matrix consisting of a watery mixture of Aleppo pine's seeds. In vitro methods were used to characterize the safety, survival ability in typical conditions of the gastrointestinal tract, and adherence capacity to surfaces, antimicrobial, and antioxidant activities. Strains belonged to the Lactobacillus plantarum group and Enterococcus faecalis showed no DNase, hemolytic, and gelatinase activities. In addition, their susceptibility to most of the tested antibiotics, satisfied some of the safety prerequisites for their potential use as probiotics. All the strains tolerated low pH, gastrointestinal enzymes, and bile salts. They displayed a good antibacterial activity and antibiofilm formation against 10 reference bacterial pathogens, especially when used as a cell-free supernatant. Furthermore, the lactic acid bacteria (LAB) strains inhibited the growth of Aspergillus flavus and Aspergillus carbonarius. Finally, they had good antioxidant activity, although depending on the strain. Overall, the results of this work highlight that zgougou represents an important reservoir of potentially probiotic LAB. Obviously, future studies should be addressed to confirm the health benefits of the LAB strains.

[Molecular characterization of invasive Haemophilus influenzae strains isolated in Tunisia]

We reported a molecular characterization of 25 Haemophilus influenzae strains derived from cases of meningitis and sepsis in children aged less than five years hospitalized in pediatric wards from three hospitals in the Sahel area (Tunisia) during the period 1997-2002. These strains were biotyped and subjected to a capsular typing by Slide agglutination serotyping and Polymerase Chain Reaction (PCR). The genetic polymorphism of these strains was also studied in Arbitrarily Primed Polymerase Chain Reaction (AP-PCR) with two sets of primers: RAP IV and 217 delta(2) as in Pulsed Field Gel Electrophoresis after digestion of the total DNA with the restriction enzyme SmaI (PFGE SmaI). Nineteen strains among 25 (76%) were of biotype I. The bexA gene was highlighted in 13 strains (52%) and in all the cases it was of the type b. Twelve strains (48%) were shown to be unencapsulated by PCR. AP-PCR RAP IV (23 genotypes/25 with a discrimination index ID=0.993) had shown nearly the same discriminatory power than PFGE (20 genotypes/21 strains with a discrimination index ID=0.995). We thus note, how capsular typing by PCR is more sensitive than slide agglutination serotyping. We also note the genetic diversity of the invasive strains isolated with a remarkable presence of non typable strains. AP PCR seems to be an alternative of choice for the epidemiologic follow-up of the Haemophilus influenzae invasive infections.

[Epidemiologic markers in Haemophilus influenzae]

Twenty-six strains of Haemophilus influenzae, isolated from diverse pathological products in two different hospitals in the center of Tunisia (Sousse-Monastir) have been compared with two different genotypic techniques: AP-PCR and pulsed-field gel electrophoresis. These two techniques showed a high discriminating power. The combination of the results of both techniques were complementary and have individualized twenty-five heterogeneous patterns among the twenty-six strains. Among the strains of respiratory origin, only two were identical, they have been isolated from two patients hospitalized in the same period and the same hospital. Excepted the two above mentioned cases, this study showed a high genetical heterogeneity of the strains.

Nosocomial outbreak caused by Salmonella enterica serotype Livingstone producing CTX-M-27 extended-spectrum beta-lactamase in a neonatal unit in Sousse, Tunisia

In this study, we report an outbreak of Salmonella enterica serotype Livingstone resistant to extended-spectrum cephalosporins that occurred in a neonatal ward of the maternity department of Farhat Hached Hospital, Sousse, Tunisia, in 2002. A total of 16 isolates were recovered from 16 babies hospitalized in the ward during the period 1 to 16 July. All these babies developed diarrhea, and three of them developed septicemia. All the isolates demonstrated resistance to ceftriaxone and ceftazidime due to the production of an extended-spectrum beta-lactamase (ESBL). The isolates were also resistant to aminoglycosides (kanamycin, tobramycin, netilmicin, gentamicin, and amikacin) and sulfamethoxazole-trimethoprim. DNA profiles were determined by pulsed-field gel electrophoresis using the XbaI and SpeI endonucleases and by ribotyping with PstI digestion. They yielded the same patterns, showing that the outbreak was caused by a single clone. The ESBL was identified as CTX-M-27 by sequencing of PCR products and by isoelectric focusing. The ESBL resistance was transferred by a 40-kb conjugative plasmid. The mobile insertion sequence ISEcp1 was found to be located upstream of bla(CTX-M-27) in the same position as that known for a bla(CTX-M-14) sequence. A new gene named dfrA21, encoding resistance to trimethoprim and carried by a 90-kb plasmid, was characterized. The dfrA21 gene was inserted as a single resistance cassette in a class I integron. The babies were treated with colistin, and all except two recovered. The outbreak came to an end when appropriate actions were taken: patient isolation, hand washing, and disinfection of the ward.

Investigation of the clonal dissemination of Klebsiella pneumoniae isolates producing extended-spectrum beta-lactamases in a neonatal ward, Sousse, Tunisia

This study was designed to investigate the spread of extended-spectrum beta-lactamase producing Klebsiella pneumoniae (ESBL-Kp) strains in Sousse hospital, during 7-month period by using phenotypic and genotypic markers. A total of 57 clinical isolates of ESBL-Kp, 22 strains recovered from seriously infected neonates and 35 strains recovered from colonized neonates and hospitalized in the neonatal ward of Sousse hospital, Tunisia, was subjected to 99 carbon source utilization tests, ribotyping and pulse-field gel electrophoresis (PFGE) profiles of total genomic DNA. Biotyping, ribotyping and PFGE typing showed that four different clones circulated in the neonatal ward between January and July 1997 and suggested that the epidemic strain belonged to the same biotype, ribotype and PFGE pattern, and was represented by 18 isolates from infected neonates and 28 isolates from colonized neonates. Biotyping, ribotyping and PFGE typing appeared to be reliable methods for distinguishing K. pneumoniae strains. Biotyping, which has the advantage of simplicity and rapidity, may be used as a first screening method.

[Bacteriologic features of urinary tract infections in children in the Sousse area, Tunisia]

Urinary tract infection (UTI) is frequent in childhood. Our purpose is to determine the bacteriologic profile of UTI in children through a retrospective study of 1281 urinary specimens analysed in the Laboratory of Microbiology of F. Hached University hospital of Sousse between 1997 and 2002 (2000 except). The most frequent pathogens recovered were E. coli (71%), K. pneumoniae (10%) P. mirabilis (8%), Staphylococcus (1.6%), P. aeruginosa (1%) and others (2%). E. coli susceptibility to antibiotics was characterised by the high resistance percentage to amoxicillin (60%), to amoxicilline - acid clavulanic (54%) and to cotrimoxazole (40%). The resistance percentage to third generation cephalosporins, to aminoglycosides and to nitrofurane remained very low, respectively of 1.5%, 1% and 1%. High resistance rates among K. pneumoniae strains towards to amoxicillin - acid clavulanic and Cefotaxim, respectively of 63 and 39% were noticed. The resistance percentages to amikacin and cotrimoxazole were respectively of 17 and 65%, but only of 4% to nitrofurane. 70% of P. mirabilis strains were resistant to amoxicillin, 63% of them remained susceptible to amoxicillin - acid clavulanic. No resistance was shown to amikacin against 31% towards cotrimoxazole.

[Contribution of phage typing and ribotyping in investigating a typhoid fever outbreak in Tunisia]

A study was carried out to investigate an outbreak of typhoid fever that occurred in Sousse city and in the vicinity of Sousse (Tunisia) during summer 1999. Twenty four isolates of Salmonella enterica serotype Typhi were isolated in hospitalized patients with a typhoid fever in two hospitals (Farhat Hached Sousse and M'saken) and were studied with the help of two molecular typing methods: phage typing and automated ribotyping. Twenty one isolates with the Vi antigen had profile DVS (Degraded Vi Strain), one isolate with the Vi antigen belonged to phage type A and two isolates were non phage typable (no Vi antigen). The same ribotype was found in 22 out of 24 isolates. The results suggested that ribotyping is more discriminative than phage typing in this case in distinguishing strains and the strains shared the same source of the contamination. Unfortunately the precise source of the contamination could not be determined.

Group A streptococci in children with acute pharyngitis in Sousse, Tunisia

A 1-year prospective study in 2 paediatric outpatient clinics in Sousse, Tunisia, aimed to determine the presence of group A streptococci in acute pharyngitis cases and carriers, and the distribution of the serotypes and biotypes. Group A streptococci were found in 9.0% of throat swabs from 155 controls and 17.7% from 474 patients (P < 0.05). Of 43 strains isolated from patients and submitted for typing, 15 different types were identified, the most common being M75 (14 strains; 32.5%), M9 (6 strains; 14.0%), M76 (5 strains; 11.6%) and M12 (4 strains; 9.3%). Three strains were non-typeable (7.0%). Biotyping of the strains showed 3 predominant biotypes: biotype 3 (n = 14), biotype 2 (n = 11), and biotype 1 (n = 7).

Outbreak of Pseudomonas putida bacteraemia in a neonatal intensive care unit

During the period of 9-27 March 2001, Pseudomonas putida strains were recovered from 10 neonates hospitalized in the neonatal intensive care unit of Farhat Hached Hospital, Sousse (Tunisia). Seven neonates developed bacteraemia, and three had an umbilical catheter-related infection (without bacteraemia). A total of 18 isolates were cultured from blood (N = 11) and catheters (N = 7). These isolates were identified as P. putida by routine biochemical methods (API 20 NE, bioMérieux, Lyon, France). Restriction endonuclease DNA profiles were determined by pulsed-field gel electrophoresis using two endonucleases XbaI and SpeI. They yielded the same patterns showing that the outbreak was caused by a single clone of P. putida. Although the antiseptic solutions used to clean the umbilicus were implicated circumstantially as probable sources, they were not sampled and so this could not be confirmed.

[The reduction of methicillin resistance in Streptococcus aureus in a hospital environment in Sousse (Tunisia)]

The sensitivity of Staphylococcus aureus to the principal antibiotics has been studied in a hospital environment during the period of 1989 to 1992. The resistance to methicillin was important in 1989, 1990, and 1991 (respectively 20.5; 24 and 25%). It showed an important decrease in 1992: 5%. The outstanding point over this last period is the appearance of a lower number of multi-resistant strains: M penicillin, aminoglycosides, macrolides. These strains represented 9, 10 and 11.5% in 1989, 1990 and 1991 and only 4% in 1992. This study indicates the need for increased control of the ecology and distribution of resistant strains.