Antimicrobial alternatives for calf diarrhea: enteric responses to Escherichia coli, deferoxamine, or gallium in neonatal calves

Intestinal malabsorption or transferable resistance in enteric bacteria are potentially serious complications of routine oral administrations of antibiotics. On the basis of reports on antimicrobial effects of host iron sequestration and on synthetic iron chelators or competitors in vitro, 2 iron antagonists were studied for their potential as alternative antimicrobials for Escherichia coli diarrhea. Deferoxamine, a fungal iron chelator used to treat acute iron intoxication, and elemental gallium, a competitive inhibitor of iron activity in metabolic enzyme systems, were examined for their effects on enteric morphology and function in neonatal calves. Twelve male calves were allotted to 4 groups: (1) given nonpathogenic E coli (control); (2) given enterotoxigenic B44 E coli; (3) given deferoxamine (50 mg/kg, twice a day); and (4) given gallium (4 mg/kg, twice a day). Calves were studied for 8 days, including the conduct of oral glucose and lactose tolerance tests on days 1, 3, and 7. By day 7, according to oral glucose and lactose tolerance tests, peak plasma glucose concentrations in all calves of groups 2, 3, and 4 were lower than those values in controls. The frequency of diarrhea was significant in all treated calves, and disease was most severe in the deferoxamine-treated calves. Quantitative cultural examination on day 8 showed significant numerical increases of jejunal and ileal E coli and ileal lactobacilli in deferoxamine-treated calves (group 3) and of ileal streptococci in gallium-treated calves (group 4) and showed jejunal and ileal overgrowths of Saccharomyces yeast in deferoxamine-treated calves.(ABSTRACT TRUNCATED AT 250 WORDS)