Colibacillosis caused by avian pathogenic E. coli (APEC) is considered as a major hindrance in poultry farming worldwide. This study aimed to characterize the genetic content and the relatedness between multidrug-resistant E. coli isolates from broiler chickens died due to colibacillosis in three farms from Tunisia. One hundred samples were collected from chickens' fresh carcasses from 3 poultry farms in Tunisia. E. coli isolation and identification were performed. Then, antimicrobial susceptibility regarding antibiotics, the ability to produce β-lactamases and Minimal Inhibitory Concentration for colistin were determined according to CLSI guidelines. β-lactams and non-β-lactams antimicrobial resistance genes, integrons, virulence genes, and phylogenetic groups were investigated by PCRs. The genetic relatedness of the E. coli isolates was analyzed by PFGE and MLST. A high infection rate of E. coli (50%) in infected organs of chickens was observed. The majority of E. coli isolates were multidrug-resistant (96%) among them 24% were colistin-resistant and 30% were ESBL- producing isolates. Seven out of 12 colistin-resistant isolates harbored the mcr-1 gene among them, 10 were ESBL- producing and carried blaCTX-M-1, blaTEM and blaSHV β-lactamases encoding genes. E coli isolates were assigned to different phylogroups but most of them (74%) belonged to the pathogenic phylogroup B2. Molecular typing by PFGE showed that some E. coli isolates harboring ESBL-mcr-1 genes were clonally related. MLST revealed the presence of 4 different ST lineages among ESBL- and mcr-1 carrying E. coli: ST4187, ST3882; ST5693 and ST8932 with clonal dissemination of E. coli ST4187 between two farms. This is the first report of ESBL-mcr-1 carrying E. coli isolates of a clinically relevant phylogenetic group (B2) from chickens having died due to colibacillosis in Tunisian poultry farms.

Bovine herpes virus type 1 (BHV-1) still causes great economic loss to the livestock industry and trade because there aren’t any available drugs that proved to be fully effective against it. In this study, the cytotoxicity and the antiviral activities of the Thymus capitata extracts were evaluated for the development of new, non toxic and specific anti-herpesvirus drug. Aqueous extracts (AE), ethanolic extracts (EE) and essential oil (EO) of the aerial parts of Thymus capitata were analyzed to determine their chemical compositions by gas chromatography, and high performance liquid chromatography combined with mass spectrometry. Their cytotoxicity and antiviral activities against Bovine Herpesvirus type 1 (BHV-1) were evaluated by quantifying the reduction of the viral cytopathic effect using Madin-Darby Bovine Kidney cell line with colorimetric assay. T. capitata extracts were added at different stages of the viral infection to investigate and better quantify their potential inhibitory effects. Polyphenols and flavonoids were the major compounds found in T. capitata EO, EE and AE. The cytotoxic concentrations at 50% were 48.70, 189 and 289 μg ml−1 for EO, EE and AE, respectively. The inhibitor concentrations at 50% for the EO, EE and AE, were 3.36, 47.80 and 164 μg ml−1, respectively. The selectivity index anti-BHV-1 values were 14.49, 3.95 and 1.81 for EO, EE and AE, respectively. Thus, the EO extracts were the most efficient antiviral compounds. T. capitata extracts affect mainly the adsorption of BHV-1 virus to host cells. T. capitata extracts inhibit the viral replication by interfering with the early stages of viral adsorption and replication. Thus, T. capitata is a potential candidate for anti-herpesvirus treatment.

Background: Escherichia coli (E. coli) is one of the main etiological agents responsible for bovine mastitis (BM), neonatal calf diarrhea (NCD), and avian colibacillosis (AC). This study aimed to assess resistance and virulence genes content, biofilm-forming ability, phylogenetic groups, and genetic relatedness in E. coli isolates recovered from clinical cases of BM, NCD, and AC. Materials/Methods: A total of 120 samples including samples of milk (n = 70) and feces (n = 50) from cows with BM and calves with NCD, respectively, were collected from different farms in Northern Tunisia. Bacterial isolation and identification were performed. Then, E. coli isolates were examined by disk diffusion and broth microdilution method for their antimicrobial susceptibility and biofilm-forming ability. PCR was used to detect antimicrobial resistance genes (ARGs), virulence genes (VGs), phylogenetic groups, and Enterobacterial repetitive intergenic consensus PCR (ERIC-PCR) for their clonal relationship. Results: Among the 120 samples, 67 E. coli isolates (25 from BM, 22 from AC, and 20 from NCD) were collected. Overall, 83.6% of isolates were multidrug resistant. Thirty-six (53.73%) isolates were phenotypically colistin-resistant (CREC), 28.3% (19/67) were ESBL producers (ESBL-EC), and forty-nine (73.1%) formed biofilm. The bla_TEM gene was found in 73.7% (14/19) of isolates from the three diseases, whilst the bla_CTXM-g-1 gene was detected in 47.3% (9/19) of isolates, all from AC. The most common VG was the fimA gene (26/36, 72.2%), followed by aer (12/36, 33.3%), cnf1 (6/36, 16.6%), papC (4/36, 11.1%), and stx1 and stx2 genes (2/36; 5.5% for each). Phylogenetic analysis showed that isolates belonged to three groups: A (20/36; 55.5%), B2 (7/36; 19.4%), and D (6/36; 16.6%). Molecular typing by ERIC-PCR showed high genetic diversity of CREC and ESBL E. coli isolates from the three animal diseases and gave evidence of their clonal dissemination within farms in Tunisia. Conclusion: The present study sheds new light on the biofilm-forming ability and clonality within CREC and ESBL-EC isolated from three different animal diseases in Tunisian farm animals.