[Multiple resistance to heavy metals and antibiotics in bacteria isolated from the Riachuelo]

Riachuelo is a heavy contaminated course of water, partially surrounding Buenos Aires city. The presence of bacteria resistant to antibiotics and heavy metals was studied. Among the isolated Gram positive colonies, 65, 59 and 48% were resistant to 60 micrograms/ml of Pb++, Zn++ and Cd++, respectively, and 20% grew in the presence of 50 micrograms/6ml gentamicin. Most of these microorganisms belonged to the order Actinomycetales. Accordingly, high percentages of resistance were detected (among the 11 Gram negative isolates (Enterobacteriaceae and Pseudomonaceae), although only one isolate was gentamicin resistant. Four Gram negative isolates also showed a broad spectrum of resistance to tetracycline, erythromyci, ampicillin, amikacin, chloramphenicol and gentamicin.