Transferable antibiotic resistance among Salmonella strains isolated from surface waters

Resistance to 20 antimicrobials was tested in 79 Salmonella strains isolated from river and lake waters in northern Greece. Of the strains, 19 (24.1%) exhibited resistance to one or more of the antibiotics while single, double and multiple resistances were oberved in 12.7, 6.3 and 5.1% of the isolates, respectively. Streptomycin resistance was the most common and nine different antibiotic resistance patterns were recorded in total. All of the strains were susceptible to amoxycillin-clavulanate, cefuroxime, ciprofloxacin, colistin, amikacin and apramycin. Among the resistant salmonellas, five (26.3%) were able to transfer R factors to the Escherichia coli recipient. Resistance to ampicillin and ticarcillin was transferable in four cases, resistance to chloramphenicol, trimethoprim and sulfafurazole in two cases, whereas resistance to gentamicin, tobramycin, spectinomycin, kanamycin and tetracycline was transferable in one case. Chloramphenicol resistance, in one of the two cases, was transferable only after mobilization with the X+ factor while streptomycin resistance, although prevailing, was not found to be transferable even after mobilization. The geometric means of the fecal indicator bacteria, i.e. total coliforms, fecal coliforms and fecal streptococci did not significantly differ between samples with antibiotic sensitive and resistant Salmonella isolates.