Microbiology of sanitized broiler hatching eggs through the egg production period

Nest-clean and dirty eggs were sampled monthly across the productive period of a commercial broiler breeder flock. Eggshells and membranes were examined for total aerobic bacterial and Enterobacteriaceae counts per egg. Paired nest-clean and dirty eggs were spray sanitized in a two-stage commercial egg sanitizing machine (a chlorine detergent wash followed by a quarternary ammonia sanitizing spray) and tested for bacterial contamination. As the flock aged, numbers of bacteria per nest-clean egg fluctuated without a noticeable trend (from log(10) 0.8 to 3.2 cells total aerobic bacteria and 2 to 5 cells Enterobacteriaceae per egg) regardless of hen age. Those eggs classified as dirty had visible fecal contamination and higher bacterial numbers than nest-clean eggs (log(10) 5.9 to 7.6 cells total aerobic bacteria per egg). After sanitization, previously dirty eggs had bacterial populations comparable to those of sanitized dirty eggs were still microbiologically indistinguishable from sanitized nest-clean eggs, though both groups had higher bacterial contamination levels than had been observed in samples taken immediately following sanitization.