Volume 3, Number 3—September 1997 Emerging Quinolone-Resistant
Salmonella in the United States We conducted a national survey
of antimicrobial resistance in human clinical isolates of
Salmonella between July 1, 1994, and June 30, 1995. Every tenth
nontyphoidal Salmonella isolate received at state public health
laboratories in the United States during this period was tested
for resistance to 12 antimicrobial agents, including two
quinolones, nalidixic acid, and ciprofloxacin. Emerging
quinolone resistance was detected; of 4,008 isolates tested, 21
(0.5%) were resistant to nalidixic acid, and one (0.02%) was
resistant to ciprofloxacin. Continued surveillance for
quinolone-resistant Salmonella is necessary, particularly after
the recent approval of a fluoroquinolone for use in animals
intended for food in the United States. Each year, an estimated
2 to 4 million human Salmonella infections occur in the United
States (1,2). Although most of these infections cause a mild,
self-limiting illness, serious sequelae, i