Introduction: The virulent Escherichia coli strains responsible for extraintestinal infections were mainly belonged to B2 and D phylogroups. However, no past studies have determinate via the presence of virulence genes the frequency of E. coli pathovars recovered from animals housed in farms in Tunisia. The aims of this study were to investigate 26 E. coli isolated from healthy and diarrheic animals and to determinate via the presence of virulence genes the frequency of pathovars. Methodology: Twenty-six E. coli isolates of phylogroups B2 (n = 14), B2₂ (n = 9), B2₃ (n = 5), and D₂ (n = 12) were characterized. Genes encoding virulence factors (fimH,eaeA,aggC,papC, papG allele III, hlyA, east1, cnf1, exhA,stx1, stx2, iutA, fyuA, ibeA,and ipaH), and antibiotic resistance as well as class 1 and 2 integrons were searched by polymerase chain reaction (PCR). The genetic relationship of isolates was done by PFGE. Results: According to the occurrence of specific genes the 26 isolates were classified as:9 EAEC, 2 EHEC, 4 UPEC, 3 EPEC/EHEC and 1 NTEC. Therefore, 2 Ex-PEC and 5 APEC were presented amongst our strains. Some isolates (12) were clonal and the remaining was unrelated. Conclusions: Higher diversity of pathovars which carried diverse combinations of virulence genes in healthy isolates. In addition, it seems that the infections were caused by different mechanisms.

Background/Objectives: Multidrug-resistant (MDR) Escherichia coli resistant to third-generation cephalosporins are a growing One Health concern, but data on extraintestinal pathogenic E. coli (ExPEC) from wildlife in North Africa remain scarce. We aimed to characterize ESBL/AmpC-producing ExPEC from captive wild mammals in Tunisia and to situate these isolates in a global genomic context. Methods: In 2018, 30 fecal samples from 14 captive wild mammals in a private farm were screened on cefotaxime agar. Four cefotaxime-resistant E. coli isolates were recovered from a llama, lion, hyena, and tiger. Antimicrobial susceptibility testing and Illumina whole-genome sequencing were combined with in silico typing, resistome and virulome profiling, plasmid and mobile element analysis, human pathogenicity prediction and core-genome MLST-based minimum-spanning trees. Results: All isolates were MDR but remained susceptible to carbapenems, colistin and tigecycline. Two ST162/B1 isolates from the llama and tiger carried bla_CMY-2, whereas two ST69/D isolates from the lion and hyena harbored bla_CTX-M-15 and qnrS1. Genomes encoded 61–68 antimicrobial resistance genes and 114–131 virulence-associated genes, together with IncF-, IncI1- and IncY-type plasmids and IS26-rich insertion sequence profiles. Mating-out assays yielded cefotaxime-resistant transconjugants, supporting plasmid transferability of bla_CMY-2 or bla_CTX-M-15. PathogenFinder predicted a ≥0.93 probability of human pathogenicity for all isolates. cgMLST-based trees showed that Tunisian ST69 and ST162 clustered within internationally disseminated lineages containing human, animal and food isolates, rather than forming wildlife-restricted branches. Conclusions: Captive wild mammals in Tunisia can harbor high-risk ExPEC lineages combining ESBL/AmpC production, multidrug resistance and extensive virulence and mobility gene repertoires. These findings highlight captive wildlife as potential reservoirs and sentinels of clinically relevant E. coli and underscore the need for integrated WGS-based One Health surveillance at the human–animal–environment interface in North Africa.

In our previous work, we reported for the first time the presence of enterocin-encoding genes in novel Lacticaseibacillus paracasei (L. paracasei) and Levilactobacillus brevis (Lev. brevis) strains isolated from artisanal dairy products made from raw cow milk. The aim of this study was to isolate enterocin-positive lactic acid bacteria (LAB) from artisanal dairy products and assess their technological characteristics and safety for potential application in food systems. LAB isolates were characterized using phenotypic tests, Matrix-Assisted Laser Desorption/Ionization Time-of-Flight (MALDI-TOF) identification, and PCR detection of enterocin genes, followed by evaluation of their physiological and technological properties and a comprehensive safety assessment, including antimicrobial resistance, virulence, biogenic amine, and integron genes. Two strains, L. paracasei S2 and Lev. brevis S62, carried enterocin genes (entAS-48 and entQ) and exhibited strong acidifying and proteolytic activities, along with antibacterial effects against foodborne pathogens and reference strains. Both isolates tolerated environmental stresses, including low pH, and lacked virulence factors, clinically relevant antibiotic resistance genes, biogenic amine production, and integron elements. These results indicate that the strains are safe, multifunctional, and suitable for developing regionally adapted dairy products, highlighting artisanal dairy products as a valuable source of novel LAB with promising biotechnological applications.

This numerical study investigates the thermo-hydraulic and thermodynamic performance of a rectangular-channel heat exchanger incorporating isothermal circular tubes, with particular emphasis on geometric design strategies suitable for compact thermal systems. Two configurations with identical total heat transfer surfaces are analyzed: baseline geometry comprising four aligned tubes (G1) and an optimized geometry consisting of eight tubes arranged in two parallel rows (G2) maintaining the same exchange surface. Laminar forced convection is also considered. For the baseline configuration, results show a pronounced thermal shadowing effect, leading to a reduction of nearly 50% in the heat transfer contribution of downstream tubes.In contrast, optimized geometry significantly improves flow redistribution and temperature field uniformity. An optimal inter-row spacing, equal to 0.1, is identified as a robust design parameter, maximizing the total average Nusselt number. At this spacing, all heated surfaces actively contribute to heat transfer, resulting on an overall heat transfer enhancement of approximately 20–40% compared to the baseline configuration. Entropy production analysis shows that increasing Re strongly intensifies thermal irreversibility, while viscous irreversibility exhibits a moderate increase. The impact of nanoparticles addition, carried out on the optimal configuration of G2, shows that heat transfer increases by about 8% for a nanoparticle concentration of 4% at high Re values, with an insignificant change in the Bejan number. The present findings demonstrate that geometric optimization represents a more effective and energetically sustainable enhancement strategy than nanofluid addition for compact tubular heat exchangers.

Background/Objectives: Carbapenem-resistant Klebsiella pneumoniae (CRKP) is a major nosocomial pathogen. Although newer agents have reduced colistin use in high-income countries, this polymyxin remains important in many low- and middle-income settings. Colistin resistance in K. pneumoniae is most commonly associated with chromosomal alterations affecting the MgrB–PhoPQ pathway, or with plasmid-mediated mcr genes. This study aimed to investigate chromosomally mediated colistin resistance in CRKP clinical isolates from a Tunisian tertiary hospital. Methods: Between 2010 and 2015, 317 non-duplicate CRKP isolates were collected at Charles Nicolle Hospital, Tunis. Colistin MICs were determined by broth microdilution. Phenotypic tests and PCR characterized carbapenemases, extended-spectrum β-lactamases, AmpC, plasmid-mediated quinolone resistance, mcr and virulence genes. Porins (OmpK35/OmpK36) and the mgrB, phoP and phoQ loci were analyzed by SDS-PAGE and sequencing. Clonal relatedness was assessed by ERIC-PCR and multilocus sequence typing. We additionally compared colistin-resistant isolates with a panel of colistin-susceptible CRKP controls and assessed phenotypic stability after serial passages without colistin. Results: Five isolates (1.6%) were colistin-resistant. All were multidrug-resistant, produced OXA-48, and two also carried NDM-1. The isolates belonged to five distinct sequence types, including high-risk clones (ST11, ST101, ST147). No mcr genes were detected. Four isolates carried disruptive mutations in mgrB, and the remaining strain harbored inactivating mutations in both phoP and phoQ with an intact mgrB. Truncating alterations in PhoP/PhoQ and frequent loss or truncation of OmpK35/OmpK36 were observed. No mgrB/phoP/phoQ alterations were detected among colistin-susceptible controls, and colistin MICs remained stable after 7 days of drug-free passaging. Conclusions: In Tunisian CRKP, colistin resistance was associated with chromosomal alterations, predominantly involving disruption of the MgrB–PhoPQ pathway, in the absence of mcr genes. These mechanisms in both high-risk and emerging sequence types underscore the adaptability of CRKP and the need for surveillance where colistin remains an important therapeutic option.

Background/Objectives: Multidrug-resistant (MDR) Escherichia coli resistant to third-generation cephalosporins are a growing One Health concern, but data on extraintestinal pathogenic E. coli (ExPEC) from wildlife in North Africa remain scarce. We aimed to characterize ESBL/AmpC-producing ExPEC from captive wild mammals in Tunisia and to situate these isolates in a global genomic context. Methods: In 2018, 30 fecal samples from 14 captive wild mammals in a private farm were screened on cefotaxime agar. Four resistant E. coli were recovered from a llama, lion, hyena and tiger. Antimicrobial susceptibility testing and Illumina whole-genome sequencing were combined with in silico typing, resistome and virulome profiling, plasmid and mobile element analysis, human pathogenicity prediction and core-genome MLST-based minimum-spanning trees. Results: All isolates were MDR but remained susceptible to carbapenems, colistin and tigecycline. Two ST162/B1 isolates from the llama and tiger carried bla_CMY-2, whereas two ST69/D isolates from the lion and hyena harbored bla_CTX-M-15 and qnrS1. Genomes encoded 61–68 antimicrobial resistance genes and 114–131 virulence-associated genes, together with IncF-, IncI1- and IncY-type plasmids and IS26-rich insertion sequence profiles. PathogenFinder predicted a ≥0.93 probability of human pathogenicity for all isolates. cgMLST-based trees showed that Tunisian ST69 and ST162 clustered within internationally disseminated lineages containing human, animal and food isolates, rather than forming wildlife-restricted branches. Conclusions: Captive wild mammals in Tunisia can harbor high-risk ExPEC lineages combining ESBL/AmpC production, multidrug resistance and extensive virulence and mobility gene repertoires. These findings highlight captive wildlife as potential reservoirs and sentinels of clinically relevant E. coli and underscore the need for integrated WGS-based One Health surveillance at the human–animal–environment interface in North Africa.