QUINOLONE-RESISTANT SALMONELLA-TYPHI IN VIET-NAM - MOLECULAR-BASIS OFRESISTANCE AND CLINICAL-RESPONSE TO TREATMENT

Nalidixic acid-resistant Salmonella typhi (NARST) was first isolated i n Viet Nam in 1993, Analysis of the quinolone resistance-determining r egion of gyrA in 20 NARST isolates by polymerase chain reaction and si ngle-stranded conformational polymorphism yielded two novel patterns: pattern II corresponding to a point mutation at nucleotide 87 Asp --> Gly (n = 17), and pattern III corresponding to a point mutation at nuc leotide 83 Ser --> Phe (n = 3). In trials of short-course ofloxacin th erapy for uncomplicated typhoid, 117 (78%) of 150 patients were infect ed with multidrug-resistant S. typhi, 18 (15%) of which were NARST, Th e median time to fever clearance was 156 hours (range, 30-366 hours) f or patients infected with NARST and 84 hours (range, 12-378 hours) for those infected with nalidixic acid-susceptible strains (P < .001). Si x (33.3%) of 18 NARST infections required retreatment, whereas 1 (0.8% ) of 132 infections due to susceptible strains required retreatment (r elative risk = 44; 95% confidence interval = 5.6-345; P < .0001). We r ecommend that short courses of quinolones not be used in patients infe cted with NARST.