Discovery of seven novel mutations of gyrB, parC and parE in Salmonella Typhi and Paratyphi strains from Jiangsu Province of China

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.

Comparison of xMAP Salmonella Serotyping Assay With Traditional Serotyping and Discordance Resolution by Whole Genome Sequencing

“…In this study, we evaluated the performance of the xMAP SSA in comparison to the traditional SAT on 255 isolates from human and environmental or food samples from Zhejiang Province of southeast China. We selected all the serovars in our database to test the typeability of serovars in our collection by SSA, including Paratyphi A which was not tested in previous study in southern China (Liang et al, 2016 ) but was a common serovar in China (Lu et al, 2017 ; Qian et al, 2020 ). In this study, we had tested 30 serovars that are listed in the xMAP SSA information sheet as typable, of which 14 serovars were fully typed and 16 serovars were partially typed.…”

The molecular basis of extensively drug-resistant Salmonella Typhi isolates from pediatric septicemia patients

“…We found that, unlike antibiotic-susceptible S. Typhi ISP2825, all XDR S. Typhi isolates tested encode qnrS (Figure 3A). Fluoroquinolone-resistant Salmonella strains have been reported to carry point mutations in gyrA, gyrB, parC, and/or parE, which exhibits variations depending on geographical locations (10,(12)(13)(14)(15)(16)(17)(18)(19)(20) (Table 4). Specific primer sets for the known mutations on these four genes were designed for PCR and PCR amplicon sequencing (Table 3).…”

“…For instance, several point mutations occurred in gyrA have been correlated to resistance to fluoroquinolones, including M52L, G81C, D82G, S83F/Y/L, D87N/G/A/Y/H, and A119E (10,(12)(13)(14)(15)(16). Point mutations in gyrB, parC, and parE have also been reported, while some variants have been reported only from certain geographical locations (13,(15)(16)(17)(18)(19)(20). Some of those mutation sites are near the quinolone binding site, which in many cases results in the inhibition of the binding of antibiotics to topoisomerases (21).…”

Antimicrobial Susceptibility Pattern of Salmonella spp. Isolated from Enteric Fever Patients in Nepal

“…Enteric fever (typhoid and paratyphoid fever) is a serious bloodstream infection caused by Salmonella enteric serovar Typhi ( S. Typhi) and Paratyphi ( S. Paratyphi) A, B and C [ 1 ]. Enteric fever is transmitted predominantly by the fecal–oral route and manifests with several clinical outcomes including malaise, fever, chills, nausea, abdominal discomfort, transient rash, and hepatosplenomegaly [ 2 ]. In spite of increased sanitation, personal hygiene, and availability of effective treatment, enteric fever remains as a serious health problem in developing countries.…”

“…Antimicrobials such as chloramphenicol, ampicillin, co-trimoxazole and fluoroquinolones are the choice of drugs in the treatment of enteric fever and have proven to be the most effective agents [ 7 ]. The case fatality rate is estimated to be 10%–30% without antibiotic therapy, while the fatality rate falls to 1%–4% with the proper treatment course [ 2 ]. However, extensive and irrational prescription and use of these drugs have led to the emergence and spread of drug-resistance, often referred as multidrug-resistance (MDR) in the pathogenic strains of Salmonella [ 6 ].…”