The quality of Nile tilapia (Oreochromis niloticus) produced in Algeria was assessed after refrigerated (4°C) storage as well as ambient temperature (30°C) keeping, corresponding to usual fish selling conditions in Algeria. Sensorial, microbial and biochemical analyzes were conducted in parallel. Moreover, the nutritional quality of fresh tilapia was also assessed by determining the proximate composition and the fatty acids profile. Results of lipid oxidation, namely hydroperoxydes and thiobarbituric acid-reactive substances (TBARS), proteolysis, represented by total volatile basic nitrogen (TVB-N) and trimethylamine (TMA-N), sensory assessment and bacterial load were highly correlated. They demonstrated that the shelf life of tilapia is limited to 12 h and five days of storage at 30 and 4°C respectively. After these period of time, fish was rejected by sensorial analysis and all the parameters thresholds (fixed in the present study at 0.85 mg MDA kg -1 of wet weight for TBARS, 35 mg TVB-N 100 g -1 of flesh, 8 mg TMA-N 100 g -1 of flesh and 6 log cfu g -1 for total viable count) were exceeded.

A relevant analytical strategy was developed by combining a microbiological screening and an LC-UV chromatographic method for the identification and the quantification of oxolinic acid (OXO) in tilapia (Oreochromis niloticus) flesh. The sensitivity, accuracy and specificity of the test were 100% for OXO. The detection capacity (CCß) of the screening test was 0.75 times the maximum residue limits for OXO (100 µg kg −1 ). The performance parameters of the LC-UV method were satisfactory in terms of linearity within the range of 2.5 to 1000 µg kg −1 (R 2 = 0.99), precision (< 23%), accuracy (− 20% to + 10%), selectivity and specificity. The limit of quantification (LOQ) and detection (LOD) was 5 and 2.5 µg kg −1 respectively. The withdrawal of OXO in tilapia is estimated for 8 days after treatment of six successive days with a dose of 12 mg kg −1 body weight per day. The strategy used in this study is simple, inexpensive and practical for the control of oxolinic acid residues in fishery products and foodstuffs.

Tuberculosis (TB) is considered one of the most widespread and devastating zoonotic diseases in low-income countries, with a cosmopolitan distribution. The aim of this 10-year retrospective survey (from 2011 to 2020) was to determine the frequency of bovine, ovine, and goat tuberculosis in different local slaughterhouses across Constantine Province, Algeria. The control of livestock carcasses was systematically performed by veterinarian inspectors, after each stage of the slaughter process. The routine abattoir inspection included the detection of visible abnormalities on different organs and lymph nodes. The overall prevalence of tuberculosis recorded in slaughtered animals was 0.83%, with the following distribution among species: 2.73% in cattle, 0.001% in sheep, and 0.0% in goats. During the study period, there was a strong correlation (R = 0.82) (p < 0.01) between tuberculosis occurrence and the number of slaughtered cattle. Fluctuations in monthly TB prevalence ranged from 2% to 24.8% between 2018 and 2020, although there were no statistically significant correlations between infection and the age or gender of the animals, except for the year 2020 when a significantly higher (p = 0.017) percentage of TB cases were recorded in female cattle compared to male cattle. The average monthly weight of the confiscated livers and lungs ranged significantly (p ≤ 0.05) from 150 kg to 350 kg. The study results provide baseline data regarding livestock tuberculosis monitoring in the area of Constantine, Algeria, indicating that the disease incidence is not highly alarming, yet remains a serious public and animal health issue in the screened region.

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Background: Marine actinobacteria are a potential resource for natural products; their secondary bioactive metabolites have shown several biological activities. Most of the isolated and identified actinobacteria in Algeria were usually explored from caves, Saharan soil or palm groves. The marine ecosystem is poorly explored and documented. Methods: Five Streptomyces strains producing bioactive compounds were isolated from Rachgoun Island located in Western Algeria and characterised phenotypically and genotypically using microbiological and 16S rRNA sequencing methods, respectively. The crude extract of the most representative strain “Streptomyces sp. strain SM2.4” and its seven active fractions were characterised by GC/MS analysis. Results: Streptomyces sp. strain SM2.4 revealed the strongest activity against the Gram-positive bacteria Staphylococcus aureus and Bacillus subtilis, the fungus Aspergillus niger and was inactive against Gram-negative bacteria. GC/MS analysis of the methylated crude extract of Streptomyces sp. strain SM2.4 revealed the presence of 11 major compounds including fatty acids methyl ester (12-methyltridecanoic acid methyl ester, 9-hexadecenoic acid methyl ester, hexadecanoic acid methyl ester, 14-methylhexadecanoic acid methyl ester and 16-methylheptadecanoic acid methyl ester), 2,4-di-tert-butylphenol, (4S,4aS,8aR)-4,8a-dimethyloctahydro-4a(2H)-naphthalenol (geosmin), 2,4-dimethylbenzaldehyde, 3,4-difluorobenzaldehyde, dimethylfuran-2,4-dicarboxylate and pyrrolo(1,2-a)pyrazine-1,4-dione, hexahydro-3-(2-methylpropyl)-. Partial purification of the crude extract by Thin-layer chromatography provided seven active fractions which were tested by radial diffusion assay. GC/MS analysis of the active TLC-fractions revealed the presence of a mixture of active compounds from which 2-(bromomethyl)-2-(2-methylphenyl)-1,3-dioxolane was found to be a new 1,3 dioxolane derivative. Furthermore, 3,4-dimethylbenzamide and pyrido[2,3-d] pyridazine-1,4-dione, hexahydro-3-(2-methylpropyl)-, were extracted for the first time from a natural source. Conclusion: Our study reveals that marine Streptomyces sp. strain SM2.4 has an interesting antimicrobial potential due to its panel of bioactive compounds.