Objectives: To assess the occurrence of extended-spectrum b-lactamases (ESBLs) in Escherichia coli isolates of faecal samples of animals (n 5 40) and food samples (n 5 38) obtained in Tunisia in 2006, and to characterize the type of ESBLs, their genetic environments and the associated resistance genes.Methods: Samples were inoculated in supplemented media (2 mg/L cefotaxime) for isolation of broadspectrum cephalosporin-resistant E. coli isolates (one isolate/sample). ESBLs and their genetic environments as well as integrons and their gene cassette composition were characterized by PCR and sequencing.Results: ESBL-producing E. coli isolates were detected in 10 of the 38 food samples analysed (26%) and in none of the tested animal faecal samples. Genes found were as follows (number of isolates): bla CTX-M-1 (5), bla CTX-M-1 1 bla TEM-1b (1), bla CTX-M-14 1 bla TEM-1b (2), bla CTX-M-8 (1) and bla SHV-5 (1). All ESBL-positive isolates showed unrelated PFGE patterns. ISEcp1 and IS903 were detected surrounding bla CTX-M-14 , and ISEcp1/IS26 and orf477 surrounding some of the bla CTX-M-1 genes. Four of the ESBLpositive strains harboured class 1 integrons including different gene cassette combinations.Conclusions: ESBLs, mainly of the CTX-M class, are detected in E. coli of food origin in Tunisia, being the first time that this mechanism has been detected in food E. coli strains in Africa.

Aims: Detection and identification of new antagonistic activities towards Bacillus cereus and relatives. Methods and Results: Twenty Bacillus thuringiensis strains were screened for their capacity to express bacteriocin‐like agents. Strain BMG1.7, isolated from soil, showed an antagonistic activity called thuricin 7. Thuricin 7 was active against several species of the genus Bacillus, including three of the four known B. thuringiensis/B. cereus bacteriocin producers, as well as against Streptococcus pyogenes and Listeria monocytogenes strains. Antimicrobial activity was lost after treatment with proteinase K. The active protein had an apparent molecular weight of 11·6 kDa, and was secreted at the end of the exponential growth phase. Thuricin 7 retained 55% of the activity after incubation at 98°C for 30 min. The mode of action of thuricin 7 was shown to be bactericidal and bacteriolytic. Conclusions: Thuricin 7 is a novel bacteriocin produced by a newly isolated Bacillus thuringiensis strain BMG1.7. Significance and Impact of the Study: The characteristics of thuricin 7 indicate that it is a new bacteriocin which may have interesting biotechnological applications due to its relatively large activity spectrum.

In the last few years, different surveillances have been published in Africa, especially in northern countries, regarding antimicrobial resistance among husbandry animals. Information is still scarce, but the available data show a worrying picture. Although the highest resistance rates have been described against tetracycline, penicillins and sulphonamides, prevalence of plasmidmediated quinolone resistance genes and extended spectrum b-lactamase (ESBL) are being increasingly reported. Among ESBLs, the CTX-M-1 group was dominant in most African surveys. Within this group, CTX-M-15 was the main variant both in animals and humans, except in Tunisia where CTX-M-1 was more frequently detected among Escherichia coli from poultry. Certain bla CTX-M-15 -harbouring clones (ST131/B2 or ST405/D) are mainly identified in humans, but they have also been reported in livestock species from Tanzania, Nigeria or Tunisia. Moreover, several reports suggest an inter-host circulation of specific plasmids (e.g. bla CTX-M-1 -carrying IncI1/ST3 in Tunisia, IncY-and Incuntypeable replicons co-harbouring qnrS1 and bla CTX-M-15 in Tanzania and the worldwide distributed bla CTX-M-15 -carrying IncF-type plasmids). International trade of poultry meat seems to have contributed to the spread of other ESBL variants, such as CTX-M-14, and clones. Furthermore, first descriptions of OXA-48-and OXA-181-producing E. coli have been recently documented in cattle from Egypt, and the emergent plasmid-mediated colistin resistance mcr-1 gene has been also identified in chickens from Algeria, Tunisia and South Africa. These data reflect the urgent need of a larger regulation in the use of veterinary drugs and the implementation of surveillance programmes in order to decelerate the advance of antimicrobial resistance in this continent.

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