Importance of host factors in human salmonellosis caused by multiresistant strains of Salmonella.

Antimicrobial resistance patterns of Salmonella isolates from persons in randomly selected urban and rural counties in the United States were examined along with clinical and epidemiological characteristics of the host. Multiresistant strains, isolated from 66 (12.2%) of 542 persons evaluated, were associated with five of 20 variables in univariate analyses: serotype heidelberg, host of Hispanic origin, host exposure to penicillins within four weeks before stool culture, age greater than or equal to 60 years, and regular antacid use. By multiple linear regression, the first three variables were each significantly associated with infections due to multiresistant Salmonella. One or more of the last three variables, thought to be host factors that may promote disease, were present for persons yielding 38% of multiresistant strains but only 12% of sensitive strains (P less than .001). The relatively large proportion of multiresistant Salmonella among isolates from persons with these risk factors suggests that to cause disease, resistant organisms are more dependent than are sensitive organisms on host characteristics.