Seventeen multiple-antibiotic-resistant nonpathogenic Escherichia coli strains of human, animal, and food origins showed a wide variety of antibiotic resistance genes, many of them carried by class 1 and class 2 integrons. Amino acid changes in MarR and mutations in marO were identified for 15 and 14 E. coli strains, respectively.

TEM-, SHV-, and OXA-type β-lactamases were studied by PCR with 124 ampicillin-resistant (AMP^r)Escherichia coliisolates recovered from foods of animal origin (n= 20) and feces of humans (n= 49) and healthy animals (n= 55). PCR showed that 103 isolates were positive for TEM and negative for SHV and OXA. ThreeE. coliisolates showed a positive reaction for OXA, and one showed a positive reaction for SHV. The remaining 17E. coliisolates were negative for the three enzymes by PCR. Fifty-seven of the 103bla_TEMamplicons were sequenced. Different molecular variants ofbla_TEM-1were found in 52 isolates:bla_TEM-1a(n= 9),bla_TEM-1b(n= 36),bla_TEM-1c(n= 6), andbla_TEM-1f(n= 1). Four inhibitor-resistant TEM (IRT) β-lactamase-encoding genes were also detected:bla_TEM-30c(IRT-2),bla_TEM-34b(IRT-6),bla_TEM-40b(IRT-11), andbla_TEM-51a(IRT-15). A newbla_TEMgene, namedbla_TEM-95b, which showed a mutation in amino acid 145 (P→A) was detected. It was found in a food isolate of chicken origin (AMP^r, amoxicillin-clavulanic acid susceptible). The promoter region in 24bla_TEMamplicons was analyzed, and the weakP3promoter was found in 23 of them (bla_TEM-1in 20 amplicons andbla_TEM-51a,bla_TEM-30c, andbla_TEM-95bin 1 amplicon each). The strongPa/Pbpromoter was found only in thebla_TEM-34bgene. No extended-spectrum β-lactamases were detected. Mutations at position −42 or −32 in theampCgene promoter were demonstrated in 4 of 10E. coliisolates for which the cefoxitin MIC was ≥16 μg/ml. Different variants ofbla_TEM-1and IRTbla_TEMgenes were found among the AMP^rE. coliisolates from foods and the feces of humans and healthy animals, and a new gene,bla_TEM-95b(P3), was detected.

Colonization by Campylobacter strains was investigated in human, broiler, and pig fecal samples from 1997- 1998, as well as in foods of animal origin, and antibiotic susceptibility testing was carried out for these strains. Campylobacter strains were isolated in the foods of animal origin (55 of 101 samples; 54.4%), intestinal samples from broilers (85 of 105; 81%), and pigs (40 of 45; 88.9%). A total of 641 Campylobacter strains were isolated from 8,636 human fecal samples of clinical origin (7.4%). Campylobacter jejuni was the most frequently isolated species from broilers (81%) and humans (84%), and Campylobacter coli was most frequently isolated from pigs (100%). An extremely high frequency of ciprofloxacin resistance was detected among Campylobacter strains, particularly those isolated from broilers and pigs (99%), with a slightly lower result for humans (72%); cross-resistance with nalidixic acid was almost always observed. A higher frequency of resistance to erythromycin (81.1%), ampicillin (65.7%), gentamicin (22.2%), and amikacin (21.6%) was detected in C. coli strains isolated from pigs compared to those isolated from humans (34.5, 29.3, 8.6, and 0%, respectively). A low frequency of erythromycin resistance was found in C. jejuni or C. coli isolated from broilers. A greater resistance to ampicillin and gentamicin (47.4 and 11.9%, respectively) was detected in C. jejuni isolated from broilers than in human strains (38 and 0.4%, respectively). β-Lactamase production was found in 81% of the Campylobacter strains tested, although 44% of them were characterized as ampicillin susceptible. The increasing rates of Campylobacter resistance make advisable a more conservative policy for the use of antibiotics in farm animals.

Objectives To assess the occurrence of extended-spectrum β-lactamases (ESBLs) in Escherichia coli isolates of faecal samples of animals (n = 40) and food samples (n = 38) obtained in Tunisia in 2006, and to characterize the type of ESBLs, their genetic environments and the associated resistance genes.