Abstract
Objective: To investigate the prevalence of Salmonella Typhi and Paratyphi resistance to quinolones and characterize the underlying mechanism in Jiangsu Province of China. Methods: Antimicrobial susceptibility testing was performed using Kirby-Bauer disc diffusion system. Quinolone resistance-determining region (QRDR), plasmid-mediated quinolone resistance (PMQR) determinant genes were detected by PCR and sequencing. Results: Out of 239 Salmonella isolates, 164 were S. Typhi and 75 were S. Paratyphi. 128 (53.6%) Salmonella isolates were resistant to nalidixic acid; 11 (4.6%) isolates to ciprofloxacin and 66 (27.6%) isolates were intermediate to ciprofloxacin. QRDR were present in 69 S. Typhi isolates, among which mutation at codon 83 (n = 45) and 133 (n = 61) predominated. In S. Paratyphi, the most common mutations were detected in gyrA at codon 83(n = 24) and parC: T57S (n = 8). Seven mutations were first reported in Salmonella isolates including gyrB: S426G, parC: D79G and parE: [S498T, E543K, V560G, I444S, Y434S]. PMQR genes including qnrD1, qnrA1, qnrB4, aac (6′)-Ib-cr4 and qnrS1 were detected in 1, 2, 3, 7 and 9 isolates, relatively. Conclusions: High resistance to quinolones in Salmonella remains a serious problem in Jiangsu, China. The presence of the novel mutations increases the complexity of quinolone-resistant genotypes and poses a threat to public health. Subject terms: Salmonella Typhi, Salmonella Paratyphi, antimicrobial resistance, QRDR, PMQR.
Highlights
Enteric fever, including typhoid and paratyphoid fever, caused by Salmonella enterica serovar Typhi
Between January 2013 to December 2017, altogether 239 Salmonella isolates were collected from Jiangsu, China; 106 (48.6%) were male and 112 (51.4%) were female (21 cases unknown)
Paratyphi isolates obtained from Jiangsu Province of China during 2013–2017
Summary
Enteric fever, including typhoid and paratyphoid fever, caused by Salmonella enterica serovar Typhi Paratyphi) A, B and C, is a global health problem. Typhoid and paratyphoid fever are transmitted primarily by the fecal-oral route and result in a variety of symptoms, including gradual onset of sustained fever, chills, nausea, rash, anorexia, abdominal pain and hepatosplenomegaly[1]. Despite the improvement in personal hygiene provision of clean water and sanitation systems, the global burden of typhoid and paratyphoid fever remains considerable. An estimated 11.9–20.6 million cases of typhoid fever occur in developing countries and cause approximately 129,000–223,000 deaths, with the majority occurring in South Asia[2]
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