Isolation of Salmonella from muscoid flies at commercial animal establishments in San Bernardino County, California.

Adult muscoid flies collected from three dairies and eight commercial poultry ranches in San Bernardino County were tested for Salmonella enteritidis. Of the total 2,686 flies tested, 92.3% were Musca domestica, 5.5% Fannia canicularis, 1.9% Ophyra leucostoma, 0.2% Phaenicia sericata, and <0.1% Muscina stabulans. Whereas flies at the dairies belonged exclusively to M. domestica, faunal composition at the poultry ranches was more diverse, including all five species. Among the five fly species, only M. domestica tested positive for serotypes of S. enteritidis. The six isolates from fly pools (25-50 flies per pool) collected from dairies included five S. enteritidis serotype Kentucky and one S. enteritidis ser. Muenster. Isolates from flies collected at poultry ranches were three S. enteritidis ser. Braenderup, S. enteritidis ser. Kottbus, and S. enteritidis ser. Montevideo. The male to female ratio in M. domestica testing positive for S. enteritidis serotypes, was 3 to 8 pools, showing more female than male flies carrying the organism.