Antibiotic-resistant gram-negative bacteria in a virtually closed water reticulation system.

The effect of the effluent from a chicken meat-processing plant on the antibiotic-resistant bacterial profile was investigated in an almost closed water reticulation system. Of the 273 faecal coliform isolates 256 (93%) were resistant to one or more of the eight antibiotics tested. The most prevalent isolates were for the beta-lactam antibiotics ampicillin and cephalothin followed by the sulphonamides sulphatriad and cotrimoxazole. Eleven different resistance patterns were identified with a single pattern, comprising of ampicillin-, cephalothin-, streptomycin-, sulphatriad-, cotrimoxazole- and tetracyclin-resistant isolates, dominating the meat-processing effluent. An apparent correlation was observed between the specific use of certain antibiotics and the prevalence of the corresponding resistant bacterial isolates. The drugs used to treat the occasional infections, belonging to the beta-lactam and sulphonamide group of antibiotics, seemed to have a more pronounced effect on the antibiotic-resistant bacterial profile in the primary water source than those drugs used as feed additives, oxytetracyclin and the aminoglycoside flavomycin.