Characterization of Extensively Drug-Resistant Salmonella enterica Serovar Kentucky Sequence Type 198 Isolates from Chicken Meat Products in Xuancheng, China.

The purpose of this study was to characterize extensively drug-resistant Salmonella enterica serovar Kentucky sequence type 198 (ST198) isolates from chicken meat products. Ten S. Kentucky strains obtained from chicken meat products in Xuancheng, China, carried 12 to 17 resistance genes, such as blaCTX-M-55, rmtB, tet(A), floR, and fosA3, combined with mutations within gyrA (S83F and D87N) and parC (S80I), resulting in resistance to numerous antimicrobial agents, including the clinically important antibiotics cephalosporin, ciprofloxacin, tigecycline, and fosfomycin. These S. Kentucky isolates shared a close phylogenetic relationship (21 to 36 single-nucleotide polymorphisms [SNPs]) and showed close genetic relatedness to two human clinical isolates from China. Three S. Kentucky strains were subjected to whole-genome sequencing using Pacific Biosciences (PacBio) single-molecule real-time (SMRT) technology. All antimicrobial resistance genes were located on their chromosomes and clustered in one multiresistance region (MRR) and Salmonella genomic island (SGI) SGI1-K. The MRRs in three S. Kentucky strains were bounded by IS26 at both ends and were inserted downstream of the bcfABCDEFG cluster with 8-bp direct repeats. The MRRs were related to those of IncHI2 plasmids but differed by insertions, deletions, and rearrangements of multiple segments involving resistance genes and plasmid backbones. This finding suggests that the MRR fragment possibly originates from IncHI2 plasmids. Four SGI1-K variants with slight differences were identified in 10 S. Kentucky strains. Mobile elements, particularly IS26, play an essential role in forming distinct MRRs and SGI1-K structures. In conclusion, the emergence of extensively drug-resistant S. Kentucky ST198 strains containing numerous chromosomally located resistance genes is alarming and needs continued surveillance. IMPORTANCE Salmonella spp. are important foodborne pathogens, and multidrug-resistant (MDR) Salmonella strains have become a serious threat to clinical therapy. MDR S. Kentucky ST198 strains have been increasingly reported from various sources and have become a global risk. In this study, we described extensively drug-resistant S. Kentucky ST198 strains from chicken meat products from a city in China. Numerous resistance genes are clustered in the chromosomes of S. Kentucky ST198 strains, possibly acquired with the help of mobile elements. This would facilitate the spread of numerous resistance genes as intrinsic chromosomal genes within this global epidemic clone, with the potential to capture more resistance genes. The emergence and dissemination of extensively drug-resistant S. Kentucky ST198 pose a severe clinical and public health threat; therefore, continuous surveillance is warranted.

Chromosomally Located fosA7 in Salmonella Isolates From China.

This study aimed to investigate the prevalence of fosfomycin fosA7 in Salmonella enterica isolates from food animals and retail meat products in China and the impact of fosA7 on bacterial fitness. A total of 360 Salmonella isolates collected from 11 provinces and cities in China were detected for fosA7. All fosA7-positive Salmonella isolates were determined minimum inhibitory concentrations (MICs) and sequenced by Illumina Hiseq. The fosA7 gene of S. Derby isolate HA2-WA5 was knocked out. The full length of fosA7 was cloned into vector pBR322 and then transformed into various hosts. MICs of fosfomycin, growth curves, stability, and fitness of fosA7 were evaluated. The fosA7 gene was identified in S. Derby (ST40, n = 30) and S. Reading (ST1628, n = 5). MICs to fosfomycin of 35 fosA7-positive isolates were 1 to 32 mg/L. All fosA7 were located on chromosomes of Salmonella. The deletion of fosA7 in HA2-WA5 decreased fosfomycin MIC by 16-fold and slightly affected its fitness. The acquisition of plasmid-borne fosA7 enhanced MICs of fosfomycin in Salmonella (1,024-fold) and Escherichia coli (16-fold). The recombinant plasmid pBR322-fosA7 was stable in Salmonella Typhimurium, S. Pullorum, S. Derby, and E. coli, except for Salmonella Enteritidis, and barely affected on the growth of them but significantly increased biological fitness in Salmonella. The spread of specific Salmonella serovars such as S. Derby ST40 will facilitate the dissemination of fosA7. fosA7 can confer high-level fosfomycin resistance and enhance bacterial fitness in Salmonella if transferred on plasmids; thus, it has the potential to be a reservoir of the mobilized fosfomycin resistance gene.

Coexistence of bla OXA-58 and tet(X) on a Novel Plasmid in Acinetobacter sp. From Pig in Shanghai, China.

The purpose of this study was to characterize the complete sequence of a novel plasmid carrying tigecycline resistance gene tet(X) and carbapenemase gene bla OXA-58 from a swine Acinetobacter sp. strain SH19PTT10. Minimal inhibitory concentration (MIC) was performed using microbroth dilution method. The isolate SH19PTT10 was highly resistant (16 mg/L) to tigecycline, and also exhibited resistance to ampicillin, streptomycin, tetracycline, chloramphenicol, florfenicol, ciprofloxacin, and sulfamethoxazole/trimethoprim. Although SH19PTT10 harbored bla OXA-58, it was susceptible to cefotaxime and meropenem. The genome sequence of SH19PTT10 was determined using PacBio single-molecule real-time sequencing. Plasmid pYUSHP10-1 had a size of 174,032 bp and showed partial homology to several plasmids found in Acinetobacter isolates. It contained two repA genes, putative toxin-antitoxin systems (HipA/HipB, RelE/RelB, and BrnT/BrnA), partitioning genes (parA and parB), and heavy metal resistance-associated genes (copA/copB, nrp, and czcA/czcD) but the transfer region or proteins was not found. pYUSHP10-1 carried 16 resistance genes, mainly clustered in two mosaic multiresistance regions (MRRs). The first MRR contained sul3, qacI-aadA1-clmA1-aadA2-blaCARB-2-dfrA16 cassette, aac(3)-IId, and bla OXA-58. The bla OXA-58 gene was associated with ISAba3, as previously described. The second MRR is the tet(X) region (ISAcsp12-aph(3')-Ia-IS26-ΔxerD-tet(X)-res-ISCR2-sul2) related to the corresponding region in other tet(X)-bearing plasmids. The pdif sites, as well as mobile elements, play an important role in mobilization of DNA modules and plasmid evolution. Coexistence of numerous resistance genes on a single plasmid may contribute to the dissemination of these genes under pressure posed by different agents, which may explain the presence of clinically crucial resistance genes tet(X) and bla OXA-58 in livestock. Thus, rational drug use and continued surveillance of tet(X) and bla OXA-58 in livestock are warranted.

Emergence of 16S rRNA Methylase Gene rmtB in Salmonella Enterica Serovar London and Evolution of RmtB-Producing Plasmid Mediated by IS26.

This study aimed to characterize 16S rRNA methylase genes among Salmonella and to elucidate the structure and evolution of rmtB-carrying plasmids. One hundred fifty-eight Salmonella isolates from one pig slaughterhouse were detected as containing 16S rRNA methylase genes; two (1.27%) Salmonella London isolates from slaughtered pigs were identified to carry rmtB. They were resistant to gentamicin, amikacin, streptomycin, ampicillin, tetracycline, florfenicol, ciprofloxacin, and sulfamethoxazole/trimethoprim. The complete sequences of RmtB-producing isolates were obtained by PacBio single-molecule real-time sequencing. The isolate HA1-SP5 harbored plasmids pYUHAP5-1 and pYUHAP5-2. pYUHAP5-1 belonged to the IncFIBK plasmid and showed high similarity to multiple IncFIBK plasmids from Salmonella London in China. The rmtB-carrying plasmid pYUHAP5-2 contained a typical IncN-type backbone; the variable region comprising several resistance genes and an IncX1 plasmid segment was inserted in the resolvase gene resP and bounded by IS26. The sole plasmid in HA3-IN1 designated as pYUHAP1 was a cointegrate of plasmids from pYUHAP5-1-like and pYUHAP5-2-like, possibly mediated by IS26 via homologous recombination or conservative transposition. The structure differences between pYUHAP1 and its corresponding part of pYUHAP5-1 and pYUHAP5-2 may result from insertion, deletion, or recombination events mediated by mobile elements (IS26, ISCR1, and ISKpn43). This is the first report of rmtB in Salmonella London. IncN plasmids are efficient vectors for rmtB distribution and are capable of evolving by reorganization and cointegration. Our results further highlight the important role of mobile elements, particularly IS26, in the dissemination of resistance genes and plasmid evolution.

Three-dimensional morphological analysis of acromioclavicular joint in patients with and without subacromial erosion after hook plate fixation.

Objective To investigate the role of acromioclavicular joint morphology in the presence of subacromial erosion after hook plate fixation. Methods We retrospectively analyzed the clinical data of 36 patients (17 men, 19 women; mean age, 48.7 years; range, 21-76 years) treated with hook plate fixation for distal clavicular fractures (n = 20) or acromioclavicular joint dislocation (n = 16) from August 2011 to March 2013. The patients were divided into two groups: the subacromial erosion group (18 patients) and the normal group (18 patients). Differences in multiple anatomical parameters between the two groups were measured and compared. Results The distal clavicle-acromion angle was significantly larger in the subacromial erosion group (mean, 51.37° ± 5.59°) than in the normal group (mean, 44.20° ± 3.83°), as was the distal clavicle-coronal angle (mean, 25.44° ± 2.51° vs. 21.67° ± 4.06°, respectively). The thickness of the acromion was significantly different between men and women (9.72 ± 1.13 vs. 8.16 ± 1.89 mm, respectively). Conclusion The results of this study indicate that the distal clavicle-acromion angle and distal clavicle-coronal angle are closely correlated with the occurrence of subacromial erosion after hook plate fixation.

Neonatal exposure to fluoxetine and fluvoxamine alteres spine density in mouse hippocampal CA1 pyramidal neurons.

Some women in childbearing ages take selective serotonin reuptake inhibitors (SSRIs) such as fluoxetine and fluvoxamine for treating psychiatric symptoms. However, these compounds may cause some side effects to their children. It has been identified that early life exposure to SSRIs increased the chance of developing mood disorders and the biological basis is still unclear. Here, we studied the effects of neonatal exposure to SSRIs on neuronal morphology. We used GFP-transgenic mice to investigate the acute and long-lasting effects of early life exposure to SSRIs on dendritic spine density of CA1 neurons. We found that 18-day drug applications of fluoxetine and fluvoxamine significantly reduced spine density of basal dendrites at postnatal day 22 (P22), but only fluvoxamine caused a reduction of spine density of apical dendrites. Interestingly, compared with the control group, the spine densities of basal dendrites after fluoxetine and fluvoxamine exposure and the spine density of apical dendrites after fluoxetine exposure increased in adult mice at the age of P90. We also observed impaired locomotor activity in adult mice after exposure to SSRIs. Our findings demonstrated that neonatal exposure to SSRIs was capable of influencing the morphological plasticity of excitatory synapses. It raised the caution for clinical use of SSRIs.