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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The objective of this investigation was to analyse the carriage rate of extended-spectrum beta-lactamase (ESBL)-producing Escherichia coli in faecal samples of healthy humans in Tunisia and to characterise the recovered isolates. One hundred and fifty samples were inoculated on MacConkey agar plates supplemented with cefotaxime (2 μg/ml) for ESBL-positive E. coli recovery. The characterisation of ESBL genes and their genetic environments, detection of associated resistance genes, multilocus sequence typing (MLST) and phylogroup typing were performed by polymerase chain reaction (PCR) and sequencing. The presence and characterisation of integrons and virulence factors were studied by PCR and sequencing. ESBL-positive E. coli isolates were detected in 11 of 150 faecal samples (7.3%) and one isolate/sample was further characterised. These isolates contained the blaCTX-M-1 (ten isolates) and blaTEM-52c genes (one isolate). The ISEcp1 (truncated by IS10 in four strains) and orf477 sequences were found upstream and downstream, respectively, of all bla (CTX-M-1) genes. Seven different sequence types (STs) and three phylogroups were identified among CTX-M-1-producing isolates [ST/phylogroup (number of isolates)]: ST58/B1 (3), ST57/D (2), ST165/A (1), ST155/B1 (1), ST10/A (1), ST398/A (1) and ST48/B1 (1). The TEM-52-producing isolate was typed as ST219 and phylogroup B2. Six ESBL isolates contained class 1 integrons with the gene cassettes dfrA17-aadA5 (five isolates) and dfrA1-aadA1 (one). Healthy humans in the studied country could be a reservoir of CTX-M-1-producing E. coli.

The prevalence of extended-spectrum beta-lactamase (ESBL)- and plasmidic AmpC-beta-lactamase (pAmpC-BL)-producing Escherichia coli isolates has been studied in food-producing animals at the farm level in Tunisia, and recovered isolates were characterized for the presence of other resistance genes and integrons. Eighty fecal samples of food-producing animals (23 sheep, 22 chickens, 22 cattle, six horses, five rabbits, and two dromedaries) were obtained from 35 different farms in Tunisia in 2011. Samples were inoculated onto MacConkey agar plates supplemented with cefotaxime (2 mg/L) for cefotaxime-resistant (CTX(R)) E. coli recovery. CTX(R) E. coli isolates were detected in 11 out of 80 samples (13.8%), and one isolate per sample was further characterized (10 from chickens and one from a dromedary). The 11 CTX(R) isolates were distributed into phylogroups: B1 (five isolates), A (two isolates), D (three isolates), and B2 (one isolate). The following beta-lactamase genes were detected: bla(CTX-M-1) (seven isolates), bla(CTX-M-1)+bla(TEM-135) (one isolate), bla(CTX-M-1)+bla(TEM-1b) (one isolate), and bla(CMY-2) (two isolates). All ESBL- and pAmpC-BL-producing E. coli strains showed unrelated pulsed-field gel electrophoresis patterns. Seven isolates contained class 1 integrons with four gene cassette arrangements: dfrA17-aadA5 (three isolates), dfrA1-aadA1 (two isolates), dfrA15-aadA1 (one isolate), and aadA1 (one isolate). All isolates showed tetracycline resistance and contained the tet(A) +/- tet(B) genes. Virulence genes detected were as follows (number of isolates in parentheses): fimA (10); aer (eight); papC (two); and papGIII, hly, cnf, and bfp (none). Chicken farms constitute a reservoir of ESBL- and pAmpC-BL-producing E. coli isolates of the CTX-M-1 and CMY-2 types that potentially could be transmitted to humans via the food chain or by direct contact.

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The objective was to determine the location of bla(CTX-M-1) and bla(CMY-2) genes in 33 Escherichia coli isolates previously obtained from healthy humans, pets, and food-producing animals in Tunisia, and to characterize the genetic lineages of isolates. Molecular typing was performed by pulsed-field gel electrophoresis (PFGE)-XbaI and multilocus sequence typing (MLST). Plasmids were analyzed by S1-PFGE, polymerase chain reaction-based replicon typing, and plasmid MLST. Conjugation experiments were performed. The bla(CTX-M-1) and bla(CMY-2) genes were studied by I-Ceu1-PFGE and S1-PFGE, and subsequent hybridization with specific probes. Eighteen different sequence types (STs) were identified among the 30 CTX-M-1-producing isolates, 5 of them being detected in 17 isolates (ST/phylogroup): ST57/D, ST155/B1, ST58/B1, ST10/A, and ST398/A. Most of the bla(CTX-M-1)-positive isolates had different PFGE profiles, with the exception of four human and pet isolates of lineage ST57 with related PFGE profiles (>80% identity). Three CMY-2-producing isolates were typed as ST58/B1, ST117/D, and ST3632/B2. The IncI1 replicon was detected in all the 33 E. coli studied isolates, in many cases in combination with other replicons: IncF, IncX, IncK, IncR, IncY, colE, or IncN. The bla(CTX-M-1) gene was transferred by conjugation in 22 of the 30 positive strains and was located into IncI1 plasmids (ST3-CC3); the bla(CMY-2) gene was located into a conjugative IncI1 plasmid (ST12) of 97 kb in one strain. One bla(CTX-M-1)-positive strain carried the qnrB19 gene in a 33 kb IncX plasmid. Diverse genetic lineages are detected in extended-spectrum beta-lactamase- and AmpC beta-lactamase-producing E. coli from different origins. The bla(CTX-M-1) and bla(CMY-2) genes were associated with conjugative IncI1 (ST3 and ST12, respectively) plasmids in E. coli strains from human and animal origin.