Chloramphenicol-ResistantSalmonella newportTraced through Hamburger to Dairy Farms

Abstract

Animal-to-human transmission of drug-resistant salmonella and the role of antimicrobial use in food animals in the emergence of these bacteria are controversial subjects. Investigation of a 4.9-fold increase in Salmonella newport isolations from Californians in 1985 showed that 87 percent of the isolates had an unusual antimicrobial-resistance pattern (including chloramphenicol resistance) and a single, identical plasmid. Interviews of 45 patients and 89 matched controls in Los Angeles County showed that illness was associated with penicillin or tetracycline use during the month before onset (P less than 0.001) and with eating ground beef during the week before onset (P = 0.052). The epidemic strain was isolated from hamburger products eaten by cases, abattoirs where the animals from which the meat came were slaughtered, dairies that sent cows for slaughter on days when culture-positive products were processed, and ill dairy cows. Isolation of salmonella from beef carcasses in abattoirs correlated with the proportion of dead or moribund animals received for slaughter (r = 0.60, P less than 0.05). Isolation of chloramphenicol-resistant salmonella from dairy farms was associated with the use of chloramphenicol at those dairies. We conclude that food animals are a major source of antimicrobial-resistant salmonella infections in humans and that these infections are associated with antimicrobial use on farms.

Changes in Tetracycline Susceptibility of Enteric Bacteria following Switching to Nonmedicated Milk Replacer for Dairy Calves

“…Epidemiological investigations have provided evidence for the transmission of antimicrobial-resistant Salmonella spp. from cattle to humans through direct contact or consumption of contaminated beef (7,18,19,39). Drug-resistant Campylobacter spp.…”

Molecular Characterization of Cephalosporin-Resistant Salmonella enterica Serotype Newport Isolates from Animals in Pennsylvania

“…Salmonella serotype Newport has been isolated from food sources such as potato salad (11), hamburger (7,26), chicken (1), precooked roast beef (24), ham or pork (13,16), fish and seafood (10), and alfalfa sprouts (29,30). In the United States, serotype Newport has been implicated in several large outbreaks of human salmonellosis, and this serotype is consistently among the top 10 salmonella serotypes isolated from human infection.…”

Typhoidal Salmonella and Emerging Resistance in Outbreak Proportions

“…Salmonella infections are associated with poverty; therefore, they tend to cause infections in families and communities. 23 Travelers to tropical destinations are increasingly at risk of Salmonella infections when traveling to villages or remote rural areas of the countryside where diagnostic and treatment facilities may be far and few. Special precautions are required for travelers with pre-existing bowel/systemic problems such as irritable bowel syndrome, inflammatory bowel disease, poorly controlled diabetes, hepatic cirrhosis, or renal impairment.…”