Study of the Antimicrobial Potential of Actinomycetes Isolated from Organic and Inorganic Waste.

The main objective of this investigation was to characterize a collection of actinomycetes strains isolated from unexplored polluted ecosystems and to evaluate their antimicrobial potential in order to discover interesting bioactive compounds. Based on morphological and culture characters, 32 different strains were isolated: 20 strains from compost heap, seven strains from manure, and five strains from waste water. As expected, the genus Streptomyces was the most prevalent followed by the genus Micromonospora. Analysis of the antimicrobial activities of the isolated strains showed that those from compost heap were more efficient against the tested microorganisms (Candida albicans, Methicillin-resistant Staphylococcus aureus, Staphylococcus aureus, Acinetobacter baumannii, Pseudomonas aeruginosa, and Escherichia coli). Several bioactive compounds were identified by liquid chromatography (LC) combined with mass spectrometry (MS) and then analyzed by both MEDINA's database, which contains the most common secondary metabolites, and Dictionary of Natural Products Chapman & Hall. Many interesting well-known and unknown biomolecules were identified. Quinomycin A and Daidzein were the most fascinating compounds isolated, respectively, by Streptomyces sp. WW2 and Streptomyces sp. WW4. The most active strain was identified based on 16S rDNA's sequences and it seems to be a new strain. The crude extract of the strain CH12 was analyzed and the UV absorption spectra and mass spectra (MS) of the main active compound were reported. It's an interesting compound (possible purpuromycin) with the molecular formula C26H18O13.

Molecular detection of human noroviruses in influent and effluent samples from two biological sewage treatment plants in the region of Monastir, Tunisia.

Noroviruses (NoVs) are responsible for numerous cases of waterborne and foodborne gastroenteritis every year. They are released in the sewage and their detection in this environment can reflect the epidemiology of the viral strains circulating in the community. A three-year (2007-2010) survey was conducted in order to evaluate the presence of human NoVs using RT-PCR in 518 sewage samples collected at the entrance and exit of two biological sewage treatment plants located in Monastir region, Tunisia. In this study, we aimed to genetically characterize the most prevalent GI and GII NoV strains, in order to obtain a rough estimate of the efficacy of disinfection treatments and to compare the results with clinical data documented in the same area during the same period. This work confirms the wide circulation and the genetic diversity of NoVs in Tunisia and the widespread distribution of NoV variants in both raw and treated wastewater. Indeed, NoV was detected in 192 (37.1%) sewage samples, among them mixed infections with group A rotavirus were detected in 125 (65.1%) cases. The genotypes of the GI NoVs were GI.1, GI.2, GI.4, GI.5, and GI of unassigned genotype (GI.UA), and the genotypes of the GII NoVs were all GII.12. This study enhances the currently poor environmental virological data gathered in Tunisia, demonstrates the benefit of environmental surveillance as a tool to determine the epidemiology of NoVs circulating in a given community, and underlines the need for the design and support of similar long-term studies in our country, in order to compensate for the absence of a national surveillance system for gastroenteric viruses.

Etiology of Acute Diarrhea in Tunisian Children with Emphasis on Diarrheagenic Escherichia coli: Prevalence and Identification of E. coli Virulence Markers.

BACKGROUND: Diarrheal diseases can be caused by viral, bacterial and parasitic infections. This paper provides a preliminary image of diarrhea with regards to etiology and epidemiologic factors in Tunisian children less than five years of age. METHODS: Overall, 124 diarrhoeal stools were collected from patients suffering from acute diarrhea and 54 stool samples from healthy children. All stools were examined for the presence of enteric pathogens. RESULTS: In diarrheagenic children, 107 pathogenic bacteria were isolated (12 Salmonella spp. (9.7%) and 95 diarrheagenic Escherichia coli strains (76.6%): 29 enteroaggregative E.coli (EAEC) (23.4%), 15 enteroinvasive E.coli (EIEC) (12.1%), 17 enteropathogenic E.coli (EPEC) (13.7%), 26 enterotoxigenic E.coli (ETEC) (21%) and 2 enterohemoragic E.coli (EHEC) (1.6%). However, in the control group, 23 pathogenic E.coli strains were isolated (42.6%): 8 EAEC (14.8%), 12 EIEC (22.2%) and 3 EPEC (5.5%). Among diarrheagenic E.coli (DEC), only ETEC strains were significantly recovered from diarrheagenic children than from healthy controls (P < 0.0003). Group A rotavirus was identified in 33.9% (n=42) of diarrheagenic children and in 11.1% among the control group (n=6). Concerning norovirus, 8.9% (n=11) of the samples collected from diarrheagenic children and 9.2% (n=5) from the control group were positive. The prevalence of rotaviruses and Salmonella spp were also significantly higher in patients with diarrhea than in controls (P = 0.002 and P < 0.019, respectively). Finally, enteropathogenic parasites (Entamoeba coli and cryptosporidium Oocystes) were isolated from 4.8% and 9.2% of diarrheagenic and control children, respectively. CONCLUSION: These results provide baseline data about the relative importance of different enteropathogens in Tunisian children.

Prevalence and genetic diversity of norovirus infection in Tunisian children (2007-2010).

Viral gastroenteritis can be a life-threatening disease in infants and young children, especially in developing countries. The aim of this study was to continue the epidemiological surveillance of norovirus (NoV) infections in Tunisian children suffering from acute gastroenteritis. Surveillance was initiated in January 2003, to monitor potential variations in strains over time, in terms of frequency and diversity of NoV genotypes, and more particularly the potential emergence of new GII.4 variants following the 2004 Hunter variant. From April 2007 to April 2010, a total of 407 stool specimens were collected from sporadic cases (238 inpatients and 169 outpatients). Furthermore, 28 stool samples were collected from children involved in 3 gastroenteritis outbreaks. Stool specimens were screened for NoV genogroup I (GI) and II (GII) by RT-PCR. NoV strains were genotyped, and variants identified, based on sequence and phylogenetic analyses of the polymerase and capsid genes. NoVs were detected in 38 sporadic cases (9.3%) and 21 epidemic cases (75%). Great diversity was observed throughout the period, with seven distinct NoV genotypes characterized in sporadic cases, and three in outbreaks. GIIb/II.3 and GII.4 were predominant globally, with fluctuations of their prevalence over time. Interestingly, the Hunter variant, which was the unique GII.4 variant observed from 2003 to April 2007 in the region of Monastir, was replaced by the 2006b variant. NoV is an important enteropathogen responsible for viral gastroenteritis among infants and children in Tunisia, and the infecting strains between 2007 and 2010 were different from those in previous years.

Molecular prevalence of bovine noroviruses and neboviruses detected in central-eastern Tunisia.

Two genetically distinct bovine enteric caliciviruses are known: noroviruses of genogroup III (NoVsGIII), which are genetically related to human noroviruses, and neboviruses, which represent a new calicivirus genus. To investigate the presence of NoVsGIII and nebovirus strains in diarrheic calves in Tunisia, a total of 169 faecal specimens were collected from January 2006 to October 2010 from different cattle herds located in the central-east regions. RT-PCRs and sequencing were carried out using primers targeting the 3' end of the polymerase gene of NoVsGIII and neboviruses. This study revealed that NoVsGIII and nebovirus are endemic in diarrheic calves in Tunisia. NoVsGIII infections, all with genotype 2, had an apparent molecular prevalence of 16.6 % and were more frequent than nebovirus infections. NoVsGIII infections showed clear seasonality, with a peak in winter. Nebovirus infections, with a prevalence of 3.0 %, were all related to the reference strain Bo/Nebraska/80/US.

The molecular epidemiology of circulating rotaviruses: three-year surveillance in the region of Monastir, Tunisia.

BACKGROUND: Rotavirus infection is the most common cause of severe, dehydrating, gastroenteritis among children worldwide. In developing countries, approximately 1440 children die from rotavirus infections each day, with an estimated 527,000 annually. In infants, rotavirus is estimated to cause more than 2 million hospitalizations every year depending on the income level of the country. The purpose of this study was to estimate the proportion of rotavirus gastroenteritis and identify the distribution of circulating G and P genotype rotavirus strains among children consulting several dispensaries in the region of Monastir (outpatients departments) or admitted to Monastir University Hospital (inpatients department) with acute gastroenteritis. METHODS: This study was undertaken during a 3-year period from April 2007 to April 2010 in Tunisian children under 13 suffering from acute gastroenteritis. Group A rotaviruses were detected in stools by ELISA and genotyped using multiplex reverse transcription PCRs with type-specific primers on the basis of their outer capsid proteins. Statistical analyses were performed with SPSS software, version 19. RESULTS: Of the 435 stool samples from children with acute gastroenteritis, 27.6% were positive for rotavirus A. The predominant G type was G1 (37.5%), followed by G3 (25%), G2 (17.5%), G4 (12.5%), G9 (2.5%) and three mixed-G infections G3G4 (2.5%) were identified. Only P[8] (80.8%), P[4] (16.7%) and P[9] (0.8%) genotypes were found. The predominant single G/P combination was G1P[8] (37.5%), followed by G3P[8] (25%), G2P[4] (16.7%), G4P[8] (12.5%), G9P[8] (1.7%) and one case of the unusual combination G9P[9] (0.8%). The G-mixed types G3G4 combined with P[8] (2.5%). Infants less than 3 months of age were most frequently affected. The prevalence of rotavirus infection peaked in the winter season, when temperatures were low, and decreased in summer. CONCLUSIONS: Rotavirus gastroenteritis is a common disease associated with significant morbidity, mortality, and economic burden. Epidemiological knowledge of rotavirus is critical for the development of effective preventive measures, including vaccines. These data will help to make informed decisions as to whether rotavirus vaccine should be considered for inclusion in Tunisia's National Immunisation Programme.