Starting in 1975, an abrupt decline in ampicillin resistance of Salmonella typhimurium (the most common and antibiotic-resistant serotype) occurred in New York City. The present lower rate of 5% to 7.9% at our hospitals represents a return to the 1965 level. At the same time, the ampicillin resistance in S typhimurium from calves and other farm animals from upper New York State, which has been rising since 1972, has reached 75%. Substantial differences between levels of resistance in Escherichia coli from animals and humans were also noted. The divergence of the trends in S typhimurium from these two sources in New York State suggests a substantial degree of separation of the respective reservoirs of Salmonella and of antibiotic resistance.
(JAMA 242:439-442, 1980)
Cherubin CE, Timoney JF, Sierra MF, Ma P, Marr J, Shin S. A Sudden Decline in Ampicillin Resistance in Salmonella typhimurium. JAMA. 1980;243(5):439-442. doi:10.1001/jama.1980.03300310027017