Propagation of TEM- and PSE-Type β-Lactamases among Amoxicillin-Resistant Salmonella spp. Isolated in France

Abstract

A survey conducted between 1987 and 1994 at the University Hospital of Besançon, France, demonstrated a dramatic increase (from 0 to 42.5%) in the prevalence of amoxicillin resistance amongSalmonella spp. Of the 96 resistant isolates collected during this period (including 77 Typhimurium), 54 were found to produce TEM-1 β-lactamase, 40 produced PSE-1 (equivalent to CARB-2), one produced PSE-1 plus TEM-2, and one produced OXA-1 in isoelectric focusing and DNA hybridization experiments. Plasmids coding for these β-lactamases were further characterized by (i) profile analysis, (ii) restriction fragmentation pattern analysis, (iii) hybridization with anspvCD-orfE virulence probe, and (iv) replicon typing. In addition, isolates of S. typhimurium were genotypically compared by pulsed-field gel electrophoresis ofXbaI-macrorestricted chromosomal DNA. Altogether, these methods showed that 40 of the 41 PSE-1 producers were actually the progeny of a single epidemic S. typhimurium strain lysotype DT104. Isolates of that strain were found to harbor RepFIC virulence plasmids with somewhat different restriction profiles, but which all carried the bla PSE-1 gene. Of these virulence/resistance plasmids, 15 were transmissible toEscherichia coli. TEM-1-producing S. typhimurium displayed much greater genotypic and plasmidic diversities, suggesting the acquisition of thebla TEM-1 gene from multiple bacterial sources by individual strains. In agreement with this, 32 of the 35 S. typhimurium plasmids encoding TEM-1 were found to be conjugative. These data show that development of amoxicillin resistance amongSalmonella, especially in serovar Typhimurium, results from both gene transfers and strain dissemination.

Molecular characterisation and mechanisms of resistance of multidrug-resistant human serovar Typhimurium isolated in Amiens (France)

“…The fact that this PCR product was observed in isolates 49 and 50 of phenotype C S T R indicated that the flo ST gene also conferred resistance to tetracycline, which is in agreement with literature data [7,13]. In total, a resistance plasmid conferring multiresistance to chloramphenicol, streptomycin, sulphonamide and tetracycline described elsewhere in DT 104 isolates [5,6,23,27] has been found in this study, in addition to resistance mediated by ␤-lactamase production.…”

“…These results are in line with those observed by Gallardo et al [15] who found 52% TEM-1, 39% PSE-1 and 8% OXA-1 ␤-lactamase-producing strains. The percentages of our isolates producing either PSE-1 or TEM-1 was quite similar to those found by Llanes et al [23] with respect to PSE-1 (48% versus 42.5%) and TEM-1 (44% versus 57.4%). From our results, it seems clear that multiresistant S. Typhimurium isolates presented various genotypes and produced various plasmid-mediated ␤-lactamases.…”

“…Llanes et al [23] showed in their study that, in ampicillinresistant S. Typhimurium, the bla TEM-1 gene was detected on transferable plasmids, which is demonstrated by the observation that TEM-1 ␤-lactamase is met with increasing frequencies in other Gram-negative enteric species such as E. coli [30]. Thus, Salmonella may inherit the bla TEM-1 gene from intestinal flora of humans [31].…”

“…3) show that the collected isolates belong to five clones designated S1-S5 (similarity percentage between 30% and 59%). Clone S2 included 21 (47.8%) isolates, of which 13 belonged to pulsotype F (18,19,(22)(23)(24)(25)(26)(27)(28)31, 34, 37 and 41), 7 to pulsotype A (14, 28, 29, 32, 33, 35 and 38) and 1 to pulsotype E (36). Clone S4 consisted of 12 (27.3%) isolates, of which 4 belonged to pulsotype A (1, 2, 6 and 8), 4 to pulsotype C (10, 11, 13 and 42), 2 to pulsotype B (4 and 5), 1 to pulsotype D (12) and 1 to pulsotype F (3).…”

Detection of integrons and antibiotic-resistance genes in Salmonella enterica serovar Typhimurium isolates with resistance to ampicillin and variable susceptibility to amoxicillin-clavulanate

“…This phenotype has already been attributed in Salmonella to the simultaneous production of TEM-1 and PSE-1 ␤-lactamases [10,20]. By using PCR primers specific for the pse-1 gene (encoding PSE-1 ␤-lactamase) we were able to amplify the expected DNA fragment from 17 Salmonella strains (two amoxicillin-clavulanate-resistant strains, 10 moderately susceptible and five susceptible).…”