Treatment strategies include attempts to control predisposing infections or environmental factors and early use of antibacterials indicated by susceptibility tests. Most isolates are resistant to tetracyclines, streptomycin, and sulfa drugs, although therapeutic success can sometimes be achieved with tetracycline. In fact, 90% of clinical isolates are resistant to tetracycline, with 60% of isolates resistant to five or more antibiotics. Fluoroquinolone use is now banned in many countries, including the USA. Commercial bacterins administered to breeder hens or chicks have provided some protection against homologous E coli serogroups.