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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.

The continuous emergence of carbapenem-resistant Escherichia coli (CRECO) presents a great challenge to public health. New Delhi metallo-lactamase (NDM) variants are widely disseminated in China, so the research on the prevalence and transmission of diverse blaNDM variants is urgently needed. In the present study, 54 CRECO isolates were collected from 1,185 Escherichia coli isolates in five hospitals in Northern Jiangsu Province, China from September 2015 to August 2016. Antimicrobial susceptibility tests, PCR detection of resistance determinants, multi-locus sequence typing (MLST) and pulsed-field gel electrophoresis (PFGE) were performed to characterize these strains. Plasmid conjugation experiments were carried out to determine the transferability of resistant genes from selected isolates. PCR-based replicon typing (PBRT), S1 nuclease-PFGE, and Southern blotting were conducted for plasmid profiling. Carbapenemase genes were detectable in all CRECO isolates, among which thirty-one CRECO isolates were found to carry blaNDM−5 (54.7%), while, blaNDM−1, blaNDM−7, blaNDM−4, blaNDM−9, and blaKPC−2 were identified in 14, five, two, one, and one isolates, respectively. MLST results revealed 15 different STs and four new STs were first reported to be linked with NDM-producing isolates. PFGE typing showed that no more than two isolates with the same ST appeared to the same band pattern except three ST410 isolates. Twenty-six selected NDM-producing isolates were successfully transferred to E. coli J53 by conjugation experiments. Notably, 50.0% (13/26) of blaNDM variants were found to be carried by ~55 kb IncX3 plasmid. Our study reported a high prevalence of blaNDM variants, especially blaNDM−5, in Northern Jiangsu province, China. Diverse blaNDM variants were mainly carried by ~55 kb IncX3 plasmids, suggesting that the fast evolution and high transferability of this kind of plasmid promote the high prevalence of blaNDM variants. Therefore, large-scale surveillance and effective infection control measures are also urgently needed to prevent diverse blaNDM variants from becoming epidemic in the future.

BackgroundThe ability of Shigella to invade, colonize, and eventually kill host cells is influenced by many virulence factors. However, there is no analysis of related genes in Jiangsu Province of China so far. Shigella flexneri was collected from 13 cities of Jiangsu Province through the provincial Centers for Disease Control (CDC) for analysis of distribution of major virulence genes (ipaH, ipaBCD, ial, virF, virB, sigA, set1A, sepA, sat, pic, set1B and sen) detected by PCR technology.ResultsA total of 545 isolates received were confirmed as S. flexneri which belongs to 11 serotypes of S. flexneri, among which serotype 2a was the most predominant (n = 223, 40.9%). All isolates were positive for ipaH gene, followed by sat (94.1%), sigA (78.9%), set1B (78.0%), pic (77.6%), set1A (74.5%), virF (64.8%), sepA (63.5%), sen (56.9%), ipaBCD (50.5%), ial (47.0%) and virB (47.0%). The presence of virulence genes in different serotypes was distinct. The existence of virulence genes of serotype 1b was generally lower than other serotype-the positive rate for virulence genes was between 0.0 and 14.1% except for ipaH and sat. In addition, virulence genes also fluctuated in different regions and at different times in Jiangsu province. The result of analysis on the relationship between virulence genes of S. flexneri showed that the existence of virulence genes of Shigella could be well represented by multiplex PCR combination ipaH + ial + set1A, which had a high clinical value.ConclusionsThe present study was designed to explore the prevalence of 12 S. flexneri-associated virulence genes. The data showed high diversity of virulence genes with regard to periods, regions and serotypes in Jiangsu Province of China.Electronic supplementary materialThe online version of this article (10.1186/s13099-017-0222-9) contains supplementary material, which is available to authorized users.

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Background: The ability of Shigella to invade, colonizes, and eventually kill host cells is influenced by many virulence factors. The aims of this study were to assess the presence of 11 virulence genes of S. sonnei strains isolated in this country. Methods: A total of 166 S. sonnei was collected from 13 cities of Jiangsu province through the provincial Centers for Disease Control (CDC) from 2010 to 2015 and then the distribution of virulence genes was detected by polymerase chain reaction (PCR) technology. Results: Invasive virulence genes included ipaH and ial, in which the positive rate of ipaH was 100% while the positive rate of ial was 15.1% in S. sonnei. The classic pathway of regulating expression of Shigella virulence gene involved virF and virB gene, which positive rates were 33.7% and 24.1% respectively. The most common serine protease autotransporters of Enterobacteriaceae among S. sonnei were sigA (100%), followed by sepA (3.0%), sat (3.0%), pic (1.2%). Shigella enterotoxin genes include sen, set1A, set1B were found in 16.3%, 6.0% and 1.8% of the isolates, respectively. Conclusions: This study provides baseline information on the distribution of virulence genes in clinical S. sonnei trains in Jiangsu province in China, which will be important for implementation of effective control strategies.