Exploring the relationship between problematic internet use and emotion regulation skills in tunisian medical students

Introduction

There is paucity of researches addressing the relationship between individuals struggling to identify, express and communicate their emotions and problematic internet use, especially among medical students.

Objectives

To assess problematic internet use in Tunisian medical students and to address its relationship with emotion regulation skills.

Methods

First to fifth-year undergraduate medical students registered in the medical school of Sousse, Tunisia, were offered to answer an online questionnaire survey, involving sociodemographic and clinical data, Internet Addiction Test (IAT) and Difficulties in Emotion Regulation Scale (DERS).

Results

A total of 175 medical students participated in the study with a median age of 22 (20-23) years and a gender ratio of 0.3. Median score of IAT was 40 (30-48). Twenty-four percent of medical students (n=42) reported problematic Internet use. Higher scores of IAT were significantly associated with the perception of an unsatisfactory relationship with parents, not having a leisure activity, family history of psychiatric disorders, personal health conditions and regular alcohol consumption. Scores of IAT were strongly and positively correlated with the following DERS subscores: Non acceptance of emotional responses (r=0.328**), Difficulties engaging in goal directed behaviors (r=0.366**), Impulse control difficulties (r=0.238**), Limited access to emotional regulation strategies (r=0.311**), and Lack of emotional clarity (r=0.311**).

Conclusions

Problematic internet use seems to emerge as part of a cluster of symptoms related to ineffective emotion regulation skills. Hence, training for affective regulation abilities appears strategically useful in the control of Internet use.

Characterization of a Colletotrichum population causing anthracnose disease on Olive in northern Tunisia

AIMS

To phenotypically, physiologically and molecularly characterize the causal agent of olive anthracnose in the northern Tunisia and to study its genetic variability and pathogenicity.

METHODS AND RESULTS

A total of 43 isolates were obtained from symptomatic olives collected from four regions in northern Tunisia. A range of morphological and physiological characteristics was recorded; and a phylogenetic study, based on the sequence analysis of both internal transcribed spacers and TUB2 gene regions, was performed. Of the 43 isolates, 41 were identified as Colletotrichum acutatum s.s, and only two were affiliated to Colletotrichum gloeosporioides s.s. Two more representative Spanish isolates, included for comparison, were identified as Colletotrichum godetiae. Using six inter-simple-sequence-repeat markers, homogeneity between isolates from different locations and within the same species was recorded. In pathogenicity and virulence studies, C. gloeosporioides s.s was found to be less virulent, while the Spanish C. godetiae isolate was significantly more virulent than the Tunisian C. acutatum s.s.

CONCLUSIONS

Olive anthracnose in the North of Tunisia is mainly caused by C. acutatum s.s species.

SIGNIFICANCE AND IMPACT OF THE STUDY

This is the first study of olive anthracnose in Tunisia, which combines both phenotypic and molecular approaches. Colletotrichum acutatum s.s group was recorded for the first time in the country as the causal agent of olive anthracnose.

First Report of Botryosphaeria dothidea, Diplodia seriata, and Neofusicoccum luteum Associated with Canker and Dieback of Grapevines in Tunisia

In 2011, common symptoms of grapevine dieback were frequently observed in 2- to 5-year-old table grape (Vitis vinifera L.) cvs. in four vineyards located in northern Tunisia. The symptoms included dead spur and cordons, shoot dieback, and sunken necrotic bark lesions, which progressed into the trunk resulting in the death of large sections of the vine. Longitudinal and transversal sections of cordons and spurs from symptomatic vines revealed brown wedge-shaped cankers of hard consistency. Twelve symptomatic samples from spur and cordons were collected, surface disinfected by dipping into 5% (v/v) sodium hypochlorite for 2 min, and small pieces from the edge of necrotic and healthy tissue were removed and plated onto potato dextrose agar (PDA) at 25°C in the dark. Based on colony and conidia morphological characteristics, isolates were divided in three species, named Diplodia seriata, Botryosphaeria dothidea, and Neofusicoccum luteum. D. seriata colonies were gray-brown with dense aerial mycelium producing brown cylindric to ellipsoid conidia rounded at both ends and averaged 22.4 × 11.7 μm (n = 50). B. dothidea colonies were initially white with abundant aerial mycelium, gradually becoming dark green olivaceous. Conidia were fusiform to fusiform elliptical with a subobtuse apex and averaged 24.8 × 4.7 μm (n = 50). N. luteum colonies were initially pale to colorless, gradually darkening with age and becoming gray to dark gray producing a yellow pigment that diffuses into the agar. Conidia were hyaline, thin-walled, aseptate, fusiform to fusiform elliptical, and averaged 19.8 × 5.5 μm (n = 50). Identity of the different taxa was confirmed by sequence analyses of the internal transcribed spacer (ITS1-5.8S-ITS2) region of the rDNA and part of the elongation factor 1-alpha (EF1-α) gene. BLAST analysis of sequences indicated that six isolates were identified as D. seriata (GenBank: AY259094, AY343353), one isolate as B. dothidea (AY236949, AY786319) and one isolate as N. luteum (AY259091, AY573217). Sequences were deposited in GenBank under accessions from KC178817 to KC178824 and from KF546829 to KF546836 for ITS region and EF1-α gene, respectively. A pathogenicity test was conducted on detached green shoots cv. Italia for the eight Botryosphaeriaceae isolates. Shoots were inoculated by placing a colonized agar plug (5 mm diameter) from the margin of a 7-day-old colony on fresh wound sites made with a sterilized scalpel. Each wound was covered with moisturized cotton and sealed with Parafilm. Control shoots were inoculated using non-colonized PDA plugs. After 6 weeks, discoloration of xylem and phloem and necrosis with average length of 38.8, 17.6, and 11.2 mm were observed from inoculated shoots with D. seriata, N. luteum, and B. dothidea, respectively, and all three fungi were re-isolated from necrotic tissue, satisfying Koch's postulates. Control shoots showed no symptoms of the disease and no fungus was re-isolated. In Tunisia, Botryosphaeria-related dieback was reported only on citrus tree caused by B. ribis (2), on Pinus spp. caused by D. pinea (4), on Quercus spp. caused by D. corticola (3), and on olive tree (Olea europea) caused by D. seriata (1). To our knowledge, this is the first report of D. seriata, B. dothidea, and N. luteum associated with grapevine dieback in Tunisia. References: (1) M. Chattaoui et al. Plant Dis. 96:905, 2012. (2) H. S. Fawcett. Calif. Citrogr. 16:208, 1931. (3) B. T. Linaldeddu et al. J. Plant Pathol. 91:234. 2009. (4) B. T. Linaldeddu et al. Phytopathol. Mediterr. 47:258, 2008.

First Report of Fire Blight Caused by Erwinia amylovora on Pear in Tunisia

In the spring of 2012 and 2013, symptoms similar to those of fire blight were observed on pear trees (Pyrus communis cv. Alexandrine, Williams) in Tunisia at flowering stages. Disease symptoms appeared in 2012 in the region of Mornag and in the following year extended to the regions of Manouba and Tebourba. More recently, the disease was observed in the regions of Bizerte, Zaghouan, and Beja. The percentages of orchard areas that had infected plants varied from 10 to 40%. Some orchards in Mornag region exhibited more than 75% disease incidence. Symptoms were observed on flowers and young shoots. Blighted blossoms appeared wilted, shriveled, and brown, and dead flowers remained on the stems. Infected shoots wilted rapidly and often formed shepherd's crooks at their tips. Samples of diseased young shoots and flowers were subjected to pathogen isolation and identification. Bacteria were isolated from washed tissues on King's B medium (KB) (1). Colonies with morphology similar to that of Erwinia amylovora were purified by sub-culturing on KB. The strains were first characterized based on morphology and biochemical tests (1). Sixteen strains produced white colonies on KB, were gram-negative, did not produce a fluorescent pigment on KB, did not grow at 35°C, and induced a hypersensitive reaction when infiltrated into tobacco leaves (cv. Xanthi). These strains were identified as E. amylovora by double-antibody sandwich indirect-ELISA and immunofluorescene microscopy using a polyclonal antibody (2) and nested PCR targeting the pEA29 plasmid (3). Pathogenicity was tested using a detached-fruit assay (1). Each strain was inoculated onto three pear fruit (cv. Alexandrine) wounded with a scalpel dipped in a 10⁹ CFU/ml bacterial suspension. The inoculated fruit were incubated at 25°C and 80% relative humidity in plates with sterile 1% agar. Negative controls consisted of fruit wounded with a scalpel dipped in sterile distilled water. Seven days after inoculation, symptoms of discoloration, browning, and production of bacterial ooze appeared at the inoculated points. No symptoms developed on negative controls. Reisolation of bacteria yielded colonies with characteristics of E. amylovora. Purified amplicons from nested PCR were sequenced (KF302525, KF302526) and a BLAST search of the GenBank database revealed 98% homology with E. amylovora strain HF560643.1. References: (1) Anonymous. OEPP/EPPO Bull. 34:159, 2004. (2) M. T. Gorris et al. Acta Hortic. 411:41, 1996. (3) P. Llop et al. Appl. Environ. Microbiol. 66:2071, 2000.

First Report of Agrobacterium vitis as Causal Agent of Crown Gall Disease of Grapevine in Tunisia

Since October 2011, a serious outbreak of crown gall disease was observed on 1- and 2-year-old grapevines (Vitis vinifera L.) cv. Superior Seedless in several vineyards located in the region of Regueb in the center of Tunisia. Fifty isolates of Agrobacterium were isolated on a tartrate medium from galls of affected plants. To prepare template DNA, cell suspensions were lysed in 0.25% sodium-azide (NaN₃) buffer prepared in 1% Triton X-100 by heating the samples at 95°C for 10 to 15 min (1). The strains were differentiated using a multiplex PCR assay with a combination of VIRFF₁/VIRFR₂ and VIRD2S4F₇₁₆/VIRD2S4R₁₀₃₆ primers (2), which detect regions of virF and virD2 genes, respectively, in A. vitis strains carrying octopine or nopaline Ti plasmids and A. vitis vitopine strains. In order to differentiate A. vitis strains from A. tumefaciens strains, PGF/PGR (4), a polygalacturonase specific primer set, was added to the mixture in multiplex PCR. The isolates segregated into three main groups. The first group carries octopine type Ti plasmids, the second carries vitopine type Ti plasmids, and the third group carries both octopine and vitopine type Ti plasmids. The polygalacturonase gene sequence from 10 isolates showed 94 to 97% identity to the sequences of A. vitis previously deposited in the NCBI GenBank database (Accession No. CP000633.1gb). The biochemical test results corresponded to the results of genetic analysis. The ability to aerobically convert lactose to 3-ketolactose was tested by spotting bacteria onto medium containing lactose and flooding plates with a layer of Benedict's reagents after incubation at 28°C for 48 h. Acid production from glucose was tested by spotting bacterial strains onto potato dextrose agar (PDA) medium supplemented with CaCO₃. Alkali production from L-tartrate was tested by streaking bacteria on AB minimal medium supplemented with L-tartrate and growth in salt medium was tested by streaking on nutrient broth supplemented with 2% NaCl. All isolates except one were negative in 3-ketolactose. They were negative in acid clearing on PDA-CaCO₃, grew in 2% NaCl, and produced alkali from tartarate. Pathogenicity of all 50 strains was tested on 1-month-old tomato plants (Lycopersicum esculentum cv. Riograndi). Plants were inoculated on the stem by pricking one to three times through a drop of inoculum (10⁸ CFU/ml) at three inoculation sites. Sterile distilled water was used as control treatment. Plants were grown for 4 weeks at 23 ± 3°C and symptoms were recorded. Typical tumors developed at the inoculation sites and no symptoms were observed on the control plants. In Tunisia, crown gall disease was observed only on stone fruit trees and only A. tumefaciens Biovar 1 have been reported and assigned to four genomic species G4, G6 G7, and G8 basically on the recA sequencing (3). To our knowledge, this is the first report of A. vitis determined as the causal agent of grapevine crown gall in Tunisia. References: (1) A. Abolmaaty et al. Microbios 101:181, 2000. (2) F. Bini et al. Vitis 47:181, 2008. (3) D. Costechareyre et al. Microb. Ecol. 60:862, 2010. (4) E. Szegedi and S. Bottka. Vitis 41:37, 2002.

First Report of Botryosphaeria obtusa as Causal Agent of Olive Tree Branch Dieback in Tunisia

A branch dieback of olive trees (Olea europaea L. cv. Manzanilla de Sevilla) was observed in 2010 in an orchard (50 ha), located in the Testour region of northern Tunisia. More than 50% of trees were severely damaged by the disease. Symptomatic trees presented dead branches and wilted leaves, which remained attached to the shoots, and the affected tissues appeared abnormally dark compared with the inner bark of healthy branches. Numerous pycnidia were observed on the surface of the infected branches. For diagnosis, symptomatic stems were collected and small pieces of discolored tissues were excised from lesion margins, surface sterilized in 0.5% sodium hypochlorite for 1 min, rinsed and dried on sterilized filter paper, then placed on acidified Difco potato dextrose agar plates (APDA; 2.5 ml of 25% lactic acid per liter). Plates were incubated at 25°C for 4 to 5 days, and hyphal tips from developing fungal colonies were transferred to PDA and placed under fluorescent light (12 h/day). A fastgrowing, pycnidia-producing fungus was consistently isolated, with conidia exuding onto the agar surface of 10-day-old cultures. On the basis of colony characteristics, isolates were identified as Botryosphaeria obtusa (3). Conidia were large, dark brown, aseptate, rounded at both ends or truncate at base, and 25 to 26.8 × 10.5 to 12.03 μm. Pathogenicity tests were performed on detached stems of cv. Manzanilla by 7-mm diameter mycelial plugs cut from actively growing cultures of the fungus. Stems (30 cm length) were cleaned, surface sterilized with sodium hypochlorite (0.25% for 2 min), and wounded with a sterilized scalpel. Mycelial disks were placed over wounds and wrapped with Parafilm to prevent desiccation. Control stems were mock inoculated with sterile agar plugs. Inoculated and control stems were placed in polyethylene boxes and incubated at 25°C. After 45 days, inoculated stems developed brown discoloration, and small dark pycnidia appeared on stem surfaces. Controls remained healthy. Koch's postulates were verified by isolating the fungus from symptomatic stems. To confirm the identification, DNA of one isolate was extracted and the fungal primers ITS1 and ITS4 (4) were used to amplify the internal transcribed spacer region of rDNA. Purified amplicons were sequenced and a BLAST search of the GenBank database revealed 99% homology with B. obtusa isolate HO166525.1. The anamorph of the fungus, Diplodia seriata, has been recognized as the cause of fruit rot of olive (1) and branch canker or dieback (2). To our knowledge, this is the first report of a canker disease of olive trees caused by B. obtusa in Tunisia. References: (1) J. Moral et al. Plant Dis. 92:311, 2008. (2) J. Moral et al. Phytopathology 100:1340, 2010. (3) A. Taylor et al. Australas. Plant Pathol. 34:187, 2005. (4) T. J. White et al. Page 315 in: PCR Protocols: A Guide to Methods and Applications. Academic Press, San Diego, CA, 1990.

First Report of Fruit Rot of Olives Caused by Botryosphaeria dothidea in Tunisia

During the summer of 2010, unfamiliar symptoms of fruit rot were frequently observed on different Tunisian olive (Olea europaea) cultivars. These symptoms appeared to be associated with the damage caused by the olive fruit fly (Bactrocera oleae). At first, infected olives showed a brown color and then fruits begin to depress until they become completely mummified and fall immaturely. This problem was more pronounced on table olive cultivars (Ascolana, Meski, and Picholine) in the northern Tunisian regions (Nabeul), with an infection incidence of 65%. Infected Ascolana olives were disinfected with 70% ethanol for 2 min, rinsed in sterile distilled water, and air dried. Several pieces were cut and placed on acidified (2.5 ml of a 25% [vol/vol] solution of lactic acid per liter of medium) potato dextrose agar medium (PDA). All plates were incubated at 25°C for 4 days under continuous fluorescent light. A fast-growing fungus with an abundant, aerial mycelium, which was gradually veering from white to dark gray, was constantly isolated. On the reverse side of the colonies, an olive green coloration spread to the edge and became darker from the center until the underside was completely black. Conidia produced on the PDA plate were hyaline, single or double cell, ellipsoid, with a subobtuse apex and a truncate base, and averaged 22.70 × 5.32 μm. Conidiophores were hyaline, cylindrical, smooth, branched at the base, with an average of 14 to 24 × 2 to 3 μm. Pathogenicity of an isolate was conducted by dipping 20 olives wounded by a sterilized scalpel in a conidial suspension (10⁵ conidia/ml), covering inoculated olives with moisture filter paper, and incubating them in a polyethylene bag under darkness at 25°C. Controls however, were wounded and dipped in sterile distillated water. Seven days after the inoculation, olives showed a brown color covering half of the fruit. Later (15 days after), this browning was accentuated and several black pycnidia were observed. Forty days after inoculation, fruits were completely dried out and the kernel was already appearing. Controls, however, remained totally healthy. Koch's postulates was then verified and showed that pure cultures were obtained after reisolations from inoculated olives, whereas the controls were free of the fungus. BLAST analysis of the internal transcribed spacer region (ITS) of rDNA of one isolate showed 99% identity with the ITS sequence of Botryosphaeria dothidea (GenBank Accession No. FM955381.1). Species of the family of Botryosphaeriaceae are common pathogens causing fruit rot and dieback of many woody plants (3). Drupe rot problem caused by B. dothidea was reported on olives in Greece (4) and southern Italy (2). It was reported that the fungus invades the drupes through the wounds caused by the olive fruit fly and may even be transmitted by it (1), and recently Moral et al. (3) suggested that the olive fruit fly is essential for the initiation of the disease on the fruit. To our knowledge, this is the first report of fruit rot of olives caused by B. dothidea in Tunisia. References: (1) N. González et al. Bol. San. Veg. Plagas 32:709, 2006. (2) C. Lazzizera et al. Plant Pathol. 57:948, 2008. (3) J. Moral et al. Phytopathology 100:1340, 2010. (4) A. J. L Phillips et al. Mycopathology 159:433, 2005.

First Report of a Branch Dieback of Olive Trees in Tunisia Caused by a Phoma sp

From 2007 to 2008, a new dieback of branches of olive trees was observed in several orchards in central and southern Tunisia. The appearance of this new syndrome coincided with warm temperatures and frequent rainfall from February to April 2007. Affected trees were observed in seven commercial orchards; disease incidence ranged from 1 to 9% and affected trees were randomly distributed in each orchard. Symptoms included abundant dead branches and wilted leaves remained attached. Distinct brown areas appeared on the bark of current-year shoots as well as on larger branches. Cankers on branches that were >2 years old were difficult to detect but were conspicuous in current-year shoots. To determine the etiology of this new syndrome, a study was carried out on samples of affected branches collected from 2007 to 2008 from different areas of the country. Unidentified species of Chaetomium and Phoma were isolated from the margins of the cankers. Koch's postulates were performed with one isolate each of a Chaetomium sp. and a Phoma sp on 2-year-old olive trees, cv. Chemlali, grown in 13-cm-diameter pots containing a sand/lime/peat mixture. Stems were inoculated by placing 10 μl of conidial suspension (10⁶ conidia/ml) on 1-cm-long longitudinal stem wounds that had been made with a sterile scalpel. Control plants were wounded, but inoculum was replaced with sterile distilled water. Three sets of 10 plants each were wound inoculated with each of the fungi on the same day. Inoculated plants were covered with a polyethylene plastic bag to retain moisture and incubated for 2 months at 30°C with a 12-h photoperiod. After 45 days, only branches inoculated with the Phoma isolate showed brown discoloration areas at the inoculation sites. A Phoma sp. was recovered from necrotic bark from each of the 10 inoculated plants. Conidia were hyaline, unicellular, slightly ellipsoidal, and 4.8 to 6.3 × 1.8 to 2.2 μm. To confirm the identification, DNA extraction was done with hyphae collected from a 7-day-old culture on PDA after incubation at 25°C (1). Fungal primers ITS1 and ITS4 (3) were used for amplification. Purified amplicons were directly sequenced using the ITS1 and ITS4 primers for the internal transcribed spacer region of rDNA. A BLAST search of the GenBank database revealed 96% homology with Phoma sp. isolate (AJ972865.1) and 98% homology with Phoma medicaginis isolate (DQ026014.1). P. incompta has been reported as responsible for branch dieback of olive tree in Italy (2). To our knowledge, this is the first report of a canker disease of olive caused by a Phoma sp. in Tunisia. References: (1) S. R. Tendulkar et al. Biotechnol. Lett. 22:1941, 2003. (2) L. Tosi and A. Zazzerini. Petria 4:161, 1994. (3) T. J. White et al. Page 315 in: PCR Protocols: A Guide to Methods and Applications. Academic Press, San Diego, CA, 1990.

Optimization and biochemical characterization of a bacteriocin from a newly isolated Bacillus subtilis strain 14B for biocontrol of Agrobacterium spp. strains

AIMS

The identification of a new compound active against Agrobacterium tumefaciens.

METHODS AND RESULTS

The culture conditions of a newly isolated Bacillus subtilis strain, designed 14B, were optimized, as a first step, to produce its bacteriocin (termed Bac 14B) for the biocontrol of Agrobacterium spp., the causal agents of the crown gall disease. Bac 14B was then partially purified and biochemically characterized. Bacillus subtilis 14B was observed to produce an antibacterial compound having a protinaceous nature. As estimated by sodium dodecyl sulfate-polyacrilamide gel electrophoresis (SDS-PAGE), the semi-purified bacteriocin substance was found to be a monomeric protein with a molecular weight of 21 kDa. While the latter's antimicrobial activity was completely stable during exposure to a temperature range of up to 100 degrees C for 2 h, its initial activity was totally lost at 121 degrees C for 20 min. The maximum bacteriocin production (4096 AU ml(-1)) was recorded after 96 h-incubation in an optimized Luria Bertani medium supplemented with 10 g l(-1) glucose, 15 g l(-1) K(2)HPO(4) and 5 g l(-1) MgSO(4) 7H(2)O at 30 degrees C in a shaking flask culture. Interestingly, the B. subtilis 14B culture supernatant that contained the bacteriocin under study was proved efficient in reducing both the percentage of galled plants and the number of galls in tomato.

CONCLUSION

The findings revealed that B. subtilis 14B and its bacteriocin are efficient in reducing the percentage of infections in plants caused by Ag. tumefaciens.

SIGNIFICANCE AND IMPACT OF THE STUDY

The results could be useful for the nurserymen who are particularly interested in the biocontrol of the crown gall disease.

Delineation of Pseudomonas savastanoi pv. savastanoi strains isolated in Tunisia by random-amplified polymorphic DNA analysis

AIMS

To investigate the genetic diversity of Pseudomonas savastanoi pv. savastanoi strains and to look whether these strains were distributed to geographical location.

METHODS AND RESULTS

Random amplification of polymorphic DNA (RAPD) was used to discriminate between 58 Tunisian strains and 21 strains from various other countries of P. savastanoi pv. savastanoi, the causal agent of olive knot disease. Isolates were separated into three groups by cluster analysis and principal coordinate analysis of RAPD fingerprint data obtained with three primers (OPR-12, OPX-7 and OPX-14). Group 1 contained isolates from the southeast of Tunisia and European strains. Group 2 comprised strains isolated from the north of Tunisia exclusively while group 3 encompassed the majority of isolates obtained from five orchards located in the centre of Tunisia.

CONCLUSIONS

The results indicated that isolates of P. savastanoi pv. savastanoi were genetically distinct according to geographic regions. RAPD grouped isolates derived from the same orchard as identical.

SIGNIFICANCE AND IMPACT OF THE STUDY

This is the first application of RAPD in the delineation of P. savastanoi pv. savastanoi strains.

Genetic diversity of Tunisian figs (Ficus carica L.) as revealed by nuclear microsatellites

The present study portrays the achievement of the genetic polymorphism surveying and the establishment of an ecotypes identification key on the basis of simple sequence repeats data. Seventy-two Tunisian fig ecotypes in situ and ex situ conserved were analyzed using six microsatellite loci. A total of 58 alleles and 124 genotypes were revealed and permitted to evidence high degree of genetic diversity mainly explained at the intra group level. Cluster analysis based on genetic distances proved that a typical continuous genetic diversity characterizes the local germplasm. In addition, the microsatellite multilocus genotyping has permitted to unambiguously distinguish 70 well-defined ecotypes (resolving power of 97.22%). Data are discussed in relation with the reliability of the used markers to check the conformity of the plant material and to rationally manage the conservation of this crop.