Arginine-Enhanced Antimicrobial Activity of Nanozymes against Gram-Negative Bacteria

The continuous reduction of clinically available antibiotics has made it imperative to exploit more effective antimicrobial therapies, especially for difficult-to-treat Gram-negative pathogens. Herein, it is shown that the combination of an antimicrobial nanozyme with the clinically compatible basic amino acid L-arginine affords a potent treatment for infections with Gram-negative pathogens. In particular, the antimicrobial activity of the antimicrobial nanozyme is dramatically increased by ≈1000-fold after L-arginine stimulation. Specifically, the combination therapy enhances bacterial outer and inner membrane permeability and promotes intracellular reactive oxygen species (ROS) generation. Moreover, the metabolomic and transcriptomic results reveal that combination treatment leads to the increased ROS-mediated damage by inhibiting the tricarboxylic acid cycle and oxidative phosphorylation, thereby inducing an imbalance of the antioxidant and oxidant systems. Importantly, L-arginine dramatically significantly accelerates the healing of infected wounds in mouse models of multidrug-resistant peritonitis-sepsis and skin wound infection. Overall, this work demonstrates a novel synergistic antibacterial strategy by combining the antimicrobial nanozymes with L-arginine, which substantively facilitates the nanozyme-mediated killing of pathogens by promoting ROS production.

A new variant of the colistin resistance gene MCR-1 with co-resistance to β-lactam antibiotics reveals a potential novel antimicrobial peptide

The emerging and global spread of a novel plasmid-mediated colistin resistance gene, mcr-1, threatens human health. Expression of the MCR-1 protein affects bacterial fitness and this cost correlates with lipid A perturbation. However, the exact molecular mechanism remains unclear. Here, we identified the MCR-1 M6 variant carrying two-point mutations that conferred co-resistance to β-lactam antibiotics. Compared to wild-type (WT) MCR-1, this variant caused severe disturbance in lipid A, resulting in up-regulation of L, D-transpeptidases (LDTs) pathway, which explains co-resistance to β-lactams. Moreover, we show that a lipid A loading pocket is localized at the linker domain of MCR-1 where these 2 mutations are located. This pocket governs colistin resistance and bacterial membrane permeability, and the mutated pocket in M6 enhances the binding affinity towards lipid A. Based on this new information, we also designed synthetic peptides derived from M6 that exhibit broad-spectrum antimicrobial activity, exposing a potential vulnerability that could be exploited for future antimicrobial drug design.

Antibiotic-Polymer Self-Assembled Nanocomplex to Reverse Phenotypic Resistance of Bacteria toward Last-Resort Antibiotic Colistin

Colistin is the last-resort antibiotic to treat multidrug-resistant (MDR) Gram-negative bacterial infections that are untreatable by other clinically available antibiotics. However, the recently merged plasmid-borne gene mobilized colistin resistance (mcr) leads to modification of the colistin target (i.e., bacterial membrane), greatly compromising the therapy outcome of colistin. To address this unmet clinical need, a nanocomplex (CMS-pEt_20 NP) of anionic prodrug colistin methanesulfonate (CMS) and guanidinium-functionalized cationic polymer pEt_20 is developed through facile self-assembly for co-delivering an antibiotic and antimicrobial polymer with membrane affinity to reverse colistin resistance. The CMS-pEt_20 NP formation enables reversal of colistin resistance and complete killing of clinically isolated mcr-positive colistin-resistant bacteria including MDR E. coli and K. pneumoniae, while monotreatment of polymer or antibiotic at equivalent doses exhibits no antibacterial activity. Mechanistic studies reveal that the CMS-pEt_20 NP enhanced the affinity of delivered CMS to the modified membrane of colistin-resistant bacteria, reviving the membrane lytic property of colistin. The increased membrane permeability caused by colistin in turn promotes an influx of pEt_20 to generate intracellular ROS stress, resulting in elimination of colistin-resistant bacteria. More importantly, a colistin-resistant mouse peritonitis-sepsis infection model demonstrates the excellent therapeutic efficacy of CMS-pEt_20 NP with 100% survival of the infected mouse. In addition, the nanocomplex is proven not toxic both in vitro and in vivo. Taken together, the self-assembled antibiotic-polymer nanocomplex with two complementary antibacterial mechanisms successfully reverses the colistin resistance phenotype in bacteria, and it can be a potential strategy to treat untreatable colistin-resistant MDR bacterial infections.

Comparative Genomic Analysis of Hypervirulence Carbapenem-Resistant Klebsiella pneumoniae from Inpatients with Infection and Gut Colonization, China

Background

The emergence and spread of hypervirulent carbapenem-resistant Klebsiella pneumoniae (hv-CRKP) is a potential epidemiological threat that needs to be monitored. However, the transmission and pathogenic characteristics of hv-CRKP in China remain unclear. We investigated the epidemiological characteristics of gut colonized hv-CRKP in a hospital in Guangdong Province, China.

Methods

A total of 46 gut colonized hv-CRKP isolates were collected from Sun Yat-Sen Memorial Hospital (Guangzhou, China) from August 31st to December 31st, 2021. Minimum inhibitory concentrations (MICs) were obtained for 15 antibiotics for 46 hv-CRKP isolates. BALB/C mice infection model and mucoviscosity assay was used to evaluate the virulence of the isolates. The characteristics of genome, phylogenetic relationship and the structure of the plasmid of 46 gut colonized hv-CRKP isolates were compared with pathogenic isolates from GeneBank based on whole-genome data.

Results

The hv-CRKP isolation rate of all gut colonized carbapenem-resistant Klebsiella pneumoniae was 17% (46/270), and the intestinal colonization rate of hv-CRKP was irrelevant to the sex, age, department of hospitalization, and history of antibiotic use of the host. The gut colonized hv-CRKP showed pandrug resistance and hypervirulence. The gut colonized hv-CRKP and pathogenic hv-CRKP prevalent in China were mainly ST11 hv-CRKP and had two major epidemic clades. The similarities in genomic characteristics between gut colonized hv-CRKP and pathogenic hv-CRKP were consistent. The gut colonized hv-CRKP carried an incomplete structure pK2044 virulence plasmid from hypervirulent K. pneumoniae NTUH-K2044 by analyzing the virulence plasmid structure.

Conclusion

Our results suggest that the gut colonized ST11 hv-CRKP may serve as a reservoir for the clinical pathogenic ST11 HV-CRKP. It is necessary to further strengthen the monitoring of gut colonized hv-CRKP and research the potential mechanism of infection caused by gut colonized hv-CRKP.

MCR-1-dependent lipid remodelling compromises the viability of Gram-negative bacteria

The global dissemination of the mobilized colistin resistance gene, mcr-1, threatens human health. Recent studies by our group and others have shown that the withdrawal of colistin as a feed additive dramatically reduced the prevalence of mcr-1. Although it is accepted that the rapid reduction in mcr-1 prevalence may have resulted, to some extent, from the toxic effects of MCR-1, the detailed mechanism remains unclear. Here, we found that MCR-1 damaged the outer membrane (OM) permeability in Escherichia coli and Klebsiella pneumonia and that this event was associated with MCR-1-mediated cell shrinkage and death during the stationary phase. Notably, the capacity of MCR-1-expressing cells for recovery from the stationary phase under improved conditions was reduced in a time-dependent manner. We also showed that mutations in the potential lipid-A-binding pocket of MCR-1, but not in the catalytic domain, restored OM permeability and cell viability. During the stationary phase, PbgA, a sensor of periplasmic lipid-A and LpxC production that performed the first step in lipid-A synthesis, was reduced after MCR-1 expression, suggesting that MCR-1 disrupted lipid homeostasis. Consistent with this, the overexpression of LpxC completely reversed the MCR-1-induced OM permeability defect. We propose that MCR-1 causes lipid remodelling that results in an OM permeability defect, thus compromising the viability of Gram-negative bacteria. These findings extended our understanding of the effect of MCR-1 on bacterial physiology and provided a potential strategy for eliminating drug-resistant bacteria.

Carriage of distinct blaKPC-2 and blaOXA-48 plasmids in a single ST11 hypervirulent Klebsiella pneumoniae isolate in Egypt

Background

Carbapenem-resistant hypervirulent K. pneumoniae (CR-hvKP) causes serious infections with significant morbidity and mortality. However, the epidemiology and transmission mechanisms of CR-hvKP and the corresponding carbapenem-resistant plasmids require further investigation. Herein, we have characterized an ST11 K. pneumoniae strain EBSI041 from the blood sample encoding both hypervirulence and carbapenem resistance phenotypes from a patient in Egypt.

Results

K. pneumoniae strain EBSI041 showed multidrug-resistance phenotypes, where it was highly resistant to almost all tested antibiotics including carbapenems. And hypervirulence phenotypes of EBSI041 was confirmed by the model of Galleria mellonella infection. Whole-genome sequencing analysis showed that the hybrid plasmid pEBSI041-1 carried a set of virulence factors rmpA, rmpA2, iucABCD and iutA, and six resistance genes aph(3′)-VI, armA, msr(E), mph(E), qnrS, and sul2. Besides, bla_OXA-48 and bla_SHV-12 were harboured in a novel conjugative IncL-type plasmid pEBSI041-2. The bla_KPC-2-carrying plasmid pEBSI041-3, a non-conjugative plasmid lacking the conjugative transfer genes, could be transferred with the help of pEBSI041-2, and the two plasmids could fuse into a new plasmid during co-transfer. Moreover, the emergence of the p16HN-263_KPC-like plasmids is likely due to the integration of pEBSI041-3 and pEBSI041-4 via IS26-mediated rearrangement.

Conclusion

To the best of our knowledge, this is the first report on the complete genome sequence of KPC-2- and OXA-48-coproducing hypervirulent K. pneumoniae from Egypt. These results give new insights into the adaptation and evolution of K. pneumoniae during nosocomial infections.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12864-021-08214-9.

Prevalence of mcr-1 in Colonized Inpatients, China, 2011-2019

In response to the spread of colistin resistance gene mcr-1, China banned the use of colistin in livestock fodders. We used a time-series analysis of inpatient colonization data from 2011-2019 to accurately reveal the associated fluctuations of mcr-1 that occurred in inpatients in response to the ban.

Molecular characterization of carbapenem-resistant and virulent plasmids in Klebsiella pneumoniae from patients with bloodstream infections in China

Bloodstream infections (BSIs) caused by carbapenem-resistant Klebsiella pneumoniae (CRKP) are potentially life-threatening and an urgent threat to public health. The present study aims to clarify the characteristics of carbapenemase-encoding and virulent plasmids, and their interactions with the host bacterium. A total of 425 Kp isolates were collected from the blood of BSI patients from nine Chinese hospitals, between 2005 and 2019. Integrated epidemiological and genomic data showed that ST11 and ST307 Kp isolates were associated with nosocomial outbreak and transmission. Comparative analysis of 147 Kp genomes and 39 completely assembled chromosomes revealed extensive interruption of acrR by ISKpn26 in all Kp carbapenemase-2 (KPC-2)-producing ST11 Kp isolates, leading to activation of the AcrAB-Tolc multidrug efflux pump and a subsequent reduction in susceptibility to the last-resort antibiotic tigecycline and six other antibiotics. We described 29 KPC-2 plasmids showing diverse structures, two virulence plasmids in two KPC-2-producing Kp, and two novel multidrug-resistant (MDR)-virulent plasmids. This study revealed a multifactorial impact of KPC-2 plasmid on Kp, which may be associated with nosocomial dissemination of MDR isolates.

Prevalence, genomic characteristics, and transmission dynamics of mcr-1-positive Salmonella enterica Typhimurium from patients with infectious diarrhea

BACKGROUND

Previous studies reported the prevalence of mcr-1 among clinical infected Salmonella isolates in China. However, the transmission dynamics of mcr-1 in different ecological niches were not well investigated. Our objective is to exhibit the transmission dynamics of mcr-1 in Salmonella.

METHODS

598 Salmonella isolates were recovered from ten hospitals; besides 936 pig faces and 167 pork samples were collected from January 2015 to December 2017 in Guangzhou, China. PCR and sequencing were used to identify mcr-1-positive Salmonella. Antimicrobial susceptibility testing was performed with 16 antimicrobials. Conjugation, S1-PFGE, and Southern blot were used to determine the transferability and location of mcr-1. Whole-genome sequencing was used to investigate pangenome, phylogeny, plasmid, and transposon.

RESULTS

Eleven mcr-1-positive Salmonella isolates were identified from patients with infectious diarrhea. Five pig fecal samples and three pork samples contained mcr-1-positive Salmonella isolates. All isolates were multi-drug resistant. The mcr-1 genes were located on ∼210-250 kb IncHI2-pST3 plasmids, and 12 mcr-1 genes were transferable. All isolates were assigned to ST34 or its genetically closed STs. The distribution of the core-genome network was significantly correlated with source distributions. The accessory genes-based network demonstrated that the diverse clonal complexes could share highly similar accessory genomes.

CONCLUSIONS

The prevalence of mcr-1-positive Salmonella among different sources was low. Clonal transmission could not be the main reason for the expansion of mcr-1-positive Salmonella, but be attributed to the horizontal transfer of IncHI2-pST3 plasmid. Continuous surveillance on Salmonella should be performed to investigate the response of colistin banning in food-producing animals by mcr-1-positive Salmonella populations.

Emergence of a Hypervirulent Carbapenem-Resistant Klebsiella pneumoniae Co-harbouring a blaNDM-1-carrying Virulent Plasmid and a blaKPC-2-carrying Plasmid in an Egyptian Hospital.. [DOI: 10.1101/2021.02.26.433140] [Citation(s) in RCA: 0] [Impact Index Per Article: 0]

The emergence of carbapenem-resistant Klebsiella pneumoniae (CRKP) isolates in Egyptian hospitals has been reported. However, the genetic basis and the analysis of the plasmids associated with CR-hypervirulent-KP (CR-HvKP) in Egypt are not presented. Therefore, we attempt to decipher the plasmids sequences, which are responsible for transferring the determinants of carbapenem-resistance, particularly the blaNDM-1 and blaKPC-2. Out of 34 K. pneumoniae isolates collected from two tertiary hospitals in Egypt, 31 were CRKP. Whole-genome sequencing revealed that our isolates were related to 13 different sequence types (STs). The most prevalent ST was ST101, followed by ST383, and ST11. Among the CRKP isolates, one isolate named EBSI036 has been reassessed using Nanopore sequencing. Genetic environment analysis showed that EBSI036 carried 20 antibiotic resistance genes and was identified as CR-HvKP strain, it harboured four plasmids, namely; pEBSI036-1-NDM-VIR, pEBSI036-2-KPC, pEBSI036-3, and pEBSI036-4. The two carbapenemase genes, blaNDM-1 and blaKPC-2, were located on plasmids pEBSI036-1-NDM-VIR and pEBSI036-2-KPC, respectively. The IncFIB:IncHI1B hybrid plasmid pEBSI036-1-NDM-VIR also carried some virulence factors, including regulator of the mucoid phenotype (rmpA), the regulator of mucoid phenotype 2 (rmpA2), and aerobactin (iucABCD, iutA). Thus, we set out this study to analyse in-depth the genetic basis of pEBSI036-1-NDM-VIR and pEBSI036-2-KPC plasmids. We reported for the first time a high-risk clone ST11 KL47 serotype of CR-HvKP strain isolated from the blood of a 60-year-old hospitalised female patient from the ICU in a tertiary-care hospital in Egypt, which showed the cohabitation of a novel hybrid plasmid coharbouring the blaNDM-1 and virulence genes, besides a blaKPC-2-carrying plasmid.

IMPORTANCE

CRKP had been registered in the critical priority tier by the World Health Organization and became a significant menace to public health. Therefore, we set out this study to analyse in-depth the genetic basis of pEBSI036-1-NDM-VIR and pEBSI036-2-KPC plasmids. Herein, we reported for the first time (to the best of our knowledge) a high-risk clone ST11 KL47 serotype of CR-HvKP strain isolated from the blood of a 60-year-old hospitalised female patient in a tertiary-care hospital from the ICU in Egypt, which showed the cohabitation of a novel hybrid plasmid co-harbouring the blaNDM-1 and virulence genes, besides a blaKPC-2-carrying plasmid. Herein, the high rate of CRKP might be due to the continuous usage of carbapenems as empirical therapy, besides the failure to implement an antibiotic stewardship program in Egyptian hospitals. Thus, this study serves to alert the contagious disease clinicians to the presence of hypervirulence in CRKP isolates in Egyptian hospitals.

Colistin and its role in the Era of antibiotic resistance: an extended review (2000-2019)

Increasing antibiotic resistance in multidrug-resistant (MDR) Gram-negative bacteria (MDR-GNB) presents significant health problems worldwide, since the vital available and effective antibiotics, including; broad-spectrum penicillins, fluoroquinolones, aminoglycosides, and β-lactams, such as; carbapenems, monobactam, and cephalosporins; often fail to fight MDR Gram-negative pathogens as well as the absence of new antibiotics that can defeat these "superbugs". All of these has prompted the reconsideration of old drugs such as polymyxins that were reckoned too toxic for clinical use. Only two polymyxins, polymyxin E (colistin) and polymyxin B, are currently commercially available. Colistin has re-emerged as a last-hope treatment in the mid-1990s against MDR Gram-negative pathogens due to the development of extensively drug-resistant GNB. Unfortunately, rapid global resistance towards colistin has emerged following its resurgence. Different mechanisms of colistin resistance have been characterized, including intrinsic, mutational, and transferable mechanisms.In this review, we intend to discuss the progress over the last two decades in understanding the alternative colistin mechanisms of action and different strategies used by bacteria to develop resistance against colistin, besides providing an update about what is previously recognized and what is novel concerning colistin resistance.

Genomic patterns and characterizations of chromosomally-encoded mcr-1 in Escherichia coli populations

The emergence and transmission of the mobile colistin resistance gene (mcr-1) threatened the extensive use of polymyxin antimicrobials. Accumulated evidence showed that the banning of colistin additive in livestock feed efficiently reduce mcr-1 prevalence, not only in animals but also in humans and environments. However, our previous study has revealed that a small proportion of Escherichia coli could continually carry chromosomally-encoded mcr-1. The chromosomally-encoded events, indicated the existence of stabilized heritage of mcr-1 and revealed a potential threat in the antimicrobial stewardship interventions, are yet to be investigated. In this study, we systematically investigated the genetic basis of chromosomally-encoded mcr-1 in prevalence and potential mechanisms of lineage, plasmid, insertion sequence, and phage. Our results demonstrated that the emergence of chromosomally-encoded mcr-1 could originate from multiple mechanisms, but mainly derived through the recombination of ISApl1/Tn6330. We reported a specific transmission mechanism, which is a phage-like region without lysogenic components, could associate with the emergence and stabilization of chromosomally-encoded mcr-1. These results highlighted the potential origin and risks of chromosomally-encoded mcr-1, which could be a heritable repository and thrive again when confronted with new selective pressures. To the best of our knowledge, this is the first study to systematically reveal the genomic basis of chromosomally-encoded mcr-1, and report a specific transmission pattern involved in phage-like region. Overall, we demonstrate the origin mechanisms and risks of chromosomally-encoded mcr-1. It highlights the need of public attention on chromosome-encoded mcr-1 to prevent from its reemergence.

Co-Occurrence of mcr-9 and bla NDM-1 in Enterobacter cloacae Isolated from a Patient with Bloodstream Infection

Background

Bloodstream infection (BSI) caused by carbapenem-resistant Enterobacteriaceae are potentially life-threatening related to poorer outcomes. Colistin is considered one of the last-resort treatments against human infections caused by multidrug-resistant (MDR) Gram-negative bacteria. Therefore, emergence of strains from the blood that co-harboring mcr and carbapenem resistance genes were considered as a serious problem.

Purpose

In this study, two mcr-9-harboring MDR Enterobacter cloacae isolates BSI034 and BSI072 recovered from BSI patients were identified, one of which co-harbored mcr-9 and bla_NDM-1. The genetic characteristics of the MDR plasmid needed to be clarified.

Methods

S1-PFGE and Southern blotting were conducted to determine the location of mcr-9. Whole-genome sequencing was performed to obtain the complete genome and plasmid sequences. The resistome and virulence genes of the strains, accompanied by the genetic characteristics of mcr-9- and bla_NDM-1-harboring plasmids, were analyzed.

Results

Whole-genome sequencing showed that BSI034 harbored mcr-9-carrying IncHI2-type pBSI034-MCR9 and bla_NDM-1-carrying IncX3-type pBSI034-NDM1. The 278,517 bp pBSI034-MCR9 carried mcr-9 along with the other 19 resistance genes. mcr-9 was flanked by IS903B (1057 bp) and IS26 (820 bp) in the same orientation. In addition to resistance genes, strain BSI034 also carried a chromosome-located Yersinia high-pathogenicity island, which harbored genes of yersiniabactin biosynthesis operon ybtSXQPAUTE, irp1/2, and fyuA.

Conclusion

We described the complete genome and mcr-9/bla_NDM-1-co-harboring plasmid of E. cloacae from a BSI patient. Notable differences were observed within mosaic modules between pBSI034-MCR9 and other mcr-9-harboring plasmids due to extensive recombination via horizontal gene transfer.

High Rates of Human Fecal Carriage of mcr-1-Positive Multidrug-Resistant Enterobacteriaceae Emerge in China in Association With Successful Plasmid Families

Background

mcr-1-mediated colistin resistance in Enterobacteriaceae is concerning, as colistin is used in treating multidrug-resistant Enterobacteriaceae infections. We identified trends in human fecal mcr-1-positivity rates and colonization with mcr-1-positive, third-generation cephalosporin-resistant (3GC-R) Enterobacteriaceae in Guangzhou, China, and investigated the genetic contexts of mcr-1 in mcr-1-positive 3GC-R strains.

Methods

Fecal samples were collected from in-/out-patients submitting specimens to 3 hospitals (2011-2016). mcr-1 carriage trends were assessed using iterative sequential regression. A subset of mcr-1-positive isolates was sequenced (whole-genome sequencing [WGS], Illumina), and genetic contexts (flanking regions, plasmids) of mcr-1 were characterized.

Results

Of 8022 fecal samples collected, 497 (6.2%) were mcr-1 positive, and 182 (2.3%) harbored mcr-1-positive 3GC-R Enterobacteriaceae. We observed marked increases in mcr-1 (0% [April 2011] to 31% [March 2016]) and more recent (since January 2014; 0% [April 2011] to 15% [March 2016]) increases in human colonization with mcr-1-positive 3GC-R Enterobacteriaceae (P < .001). mcr-1-positive 3GC-R isolates were commonly multidrug resistant. WGS of mcr-1-positive 3GC-R isolates (70 Escherichia coli, 3 Klebsiella pneumoniae) demonstrated bacterial strain diversity; mcr-1 in association with common plasmid backbones (IncI, IncHI2/HI2A, IncX4) and sometimes in multiple plasmids; frequent mcr-1 chromosomal integration; and high mobility of the mcr-1-associated insertion sequence ISApl1. Sequence data were consistent with plasmid spread among animal/human reservoirs.

Conclusions

The high prevalence of mcr-1 in multidrug-resistant E. coli colonizing humans is a clinical threat; diverse genetic mechanisms (strains/plasmids/insertion sequences) have contributed to the dissemination of mcr-1, and will facilitate its persistence.

Multiplex loop-mediated isothermal amplification (multi-LAMP) assay for rapid detection of mcr-1 to mcr-5 in colistin-resistant bacteria

Purpose: The discovery of the plasmid-mediated colistin resistance genes, mcr, revealed a mechanism of transmission of colistin resistance, which is a major, global public health concern especially among individuals infected with carbapenem-resistant Gram-negative bacteria. To monitor the spread and epidemiology of mcr genes, a convenient and reliable method to detect mcr genes in clinical isolates is needed, especially in the primary care institutions. This study aimed to establish a restriction endonuclease-based multiplex loop-mediated isothermal amplification (multi-LAMP) assay to detect mcr genes (mcr-1 to mcr-5) harbored by colistin-resistant bacteria.

Methods: A triple-LAMP assay for mcr-1, mcr-3, and mcr-4 and a double-LAMP assay for mcr-2 and mcr-5 were established. The sensitivity and specificity of the LAMP reactions were determined via electrophoresis and visual detection.

Results: The sensitivity of the LAMP assay was 10-fold greater than that of PCR, with high specificity among the screened primers. Specific mcr genes were distinguished in accordance with band numbers and the fragment length of the digested LAMP amplification products. Furthermore, the LAMP assay was confirmed as a rapid and reliable diagnostic technique upon application for clinical samples, and the results were consistent with those of conventional PCR assay.

Conclusion: The multi-LAMP assay is a potentially promising method to detect mcr genes and will, if implemented, help prevent infections by drug-resistant bacteria in primary-care hospitals due to rapid and reliable surveillance. To our knowledge, this is the first study to report the application of LAMP to detect mcr-2 to mcr-5 genes and the first time that multi-LAMP has been applied to detect mcr genes.

Antimicrobial resistance, virulence genes profiling and molecular relatedness of methicillin-resistant Staphylococcus aureus strains isolated from hospitalized patients in Guangdong Province, China

Purpose

The main objective of this study was to decipher the prevalence, antimicrobial resistance, major virulence genes and the molecular characteristics of methicillin-resistant Staphylococcus aureus (MRSA) isolated from different clinical sources in southern China.

Materials and methods

The present study was performed on 187 non-duplicate S. aureus clinical isolates collected from three tertiary hospitals in Guangdong Province, China, 2010–2016. Antimicrobial susceptibility testing was performed by the disk diffusion method and by measuring the minimum inhibitory concentration. Screening for resistance and virulence genes was performed. Clonal relatedness was determined using various molecular typing methods such as multilocus sequence typing, spa and staphylococcal chromosomal cassette mec (SCCmec) typing. Whole genome sequencing was performed for three selected isolates.

Results

Out of 187 isolates, 103 (55%) were identified as MRSA. The highest prevalence rate was found among the skin and soft tissue infection (SSTI) samples (58/103), followed by sputum samples (25/103), blood stream infection samples (15/103) and others (5/103). Antimicrobial susceptibility results revealed high resistance rates for erythromycin (64.1%), clindamycin (48.5%), gentamicin (36.9%) and ciprofloxacin (33.98%). All isolates were susceptible to vancomycin. Resistance genes and mutation detected were as follows: aac(6’)-aph(2”) (24.3%), dfrG (10.7%), rpoB (21.4%), cfr (0%), fexA (1.94%), gyrA (35.92%), gyrB (0.97%), grlA (20.4%), grlB (10.68%), ermA (21.4%), ermB (18.44%), ermC (21.4%) and lnuA (18.44%). Profiling of virulence genes revealed the following: sea (11.7%), seb (21.4%), sec (0.97%), sed (0.97%), hla (86.41%), hlb (17.48%), hlg (10.68%), hld (53.4%), Tsst-1 (3.9%) and pvl (27.2%). Clonal relatedness showed that ST239-SCCmecA III-t37 clone was the most prevalent clone.

Conclusion

Our study elucidated the prevalence, antibiotic resistance, pathogenicity and molecular characteristics of MRSA isolated from various clinical sources in Guangdong, China. We found that the infectious rate of MRSA was higher among SSTI than other sources. The most predominant genotype was ST239-SCCmecA III-t37 clone, indicating that ST239-t30 clone which was previously predominant had been replaced by a new clone.

[Effect of connecting airbag in different filling state at the front end of piezometric tube in noninvasive ventilation circuit on man-machine synchronization]

Objective: To investigate the effect of connecting airbag in different filling state at the front end of piezometric tube in the noninvasive ventilation circuit on pressure transmission and human-machine synchronization. Method: In test 1, the airbag was connected to a piezometric tube which was placed in a closed container, the filling state of the airbag was regulated, and the pressure inside the container was changed to observe the corresponding pressure change in the piezometric tube. In test 2, the airbag in different filling state was connected at the front end of piezometric tube in noninvasive ventilation circuit. Twelve subjects were connected to the ventilator such that dynamic changes in the pressure inside the mask (Pmask) and piezometric tube (Ptube) could be measured. Data with normal distribution was analyzed by t test, while data with abnormal distribution was analyzed by K-W test. Results: In test 1, the pressure inside the container changed between 0 and 50 cmH(2)O(1 cmH(2)O=0.098 kPa), when the big airbag was filled at 1/5, 2/5, 3/5, 4/5, the medium-sized airbag was filled at 3/5, 4/5, 5/5, and the small airbag was filled at 4/5, the pressure inside the piezometric tube changed synchronously with the pressure inside the container with no statistically significant difference(P>0.05). In a state of no filling in the small airbag and the medium-sized airbag, and filled at 1/5 in the small airbag, the pressure inside the piezometric tube no longer changed with the pressure in the container when the pressure reached a certain level .When the small airbag was filled at 1/5, 2/5, 3/5, 5/5, the medium-sized airbag at 1/5, 2/5, and the big airbag at 5/5, and all the airbags were in the state of no filling , the difference in the pressure between the piezometric tube and the container was statistically significant. In test 2, respiratory ventilation parameters were set on 10/4 cmH(2)O-30/14 cmH(2)O , and the connecting airbag at the front end of piezometric tube in noninvasive ventilation circuit. The platform pressure in the mask was slightly higher than that in the piezometer tube, and the baseline pressure in the mask was slightly lower than that of the piezometer tube. When the big airbag was filled at 1/5, 2/5, 3/5, 4/5 and medium-sized airbag at 2/5, 3/5, 4/5, the pressure difference between Pmask and Ptube was less than 0.5 cmH(2)O, which was acceptable clinically. When the big airbag was filled at 1/5, 2/5, 3/5 and the medium-sized airbag at 2/5, 3/5, there was no significant difference in trigger work before and after connecting the airbag at the front end of the piezometric tube(P>0.05). Conclusion: Connecting the airbag at the front end of the piezometric tube could avoid the forming of condensate in piezometric tube. The airbag showed good properties of pressure conductivity under ideal size and filling state.

Co-production of MCR-1 and NDM-5 in Escherichia coli isolated from a colonization case of inpatient

Colistin is increasingly used as an antibiotic of last resort for treating carbapenem-resistant Enterobacteriaceae. Mobile colistin resistance gene mcr-1 has been increasingly reported in Enterobacteriaceae around the world. Of particular concern is the spread of mcr-1 into carbapenemase-producing Enterobacteriaceae, which results in highly drug-resistant strains that are potentially untreatable. Notably, such mcr-1-carrying isolates harboring carbapenemase genes have been reported in animals and patients with infection. Here, we report an Escherichia coli strain carrying co-transferable mcr-1-harboring IncX4 and bla_NDM-5-harboring IncX3 plasmids, which was recovered in the context of fecal colonization.

Spread of MCR-3 Colistin Resistance in China: An Epidemiological, Genomic and Mechanistic Study

BACKGROUND

Mobilized resistance to colistin is evolving rapidly and its global dissemination poses a severe threat to human health and safety. Transferable colistin resistance gene, mcr-3, first identified in Shandong, China, has already been found in several countries in multidrug-resistant human infections. Here we track the spread of mcr-3 within 13 provinces in China and provide a complete characterization of its evolution, structure and function.

METHODS

A total of 6497 non-duplicate samples were collected from thirteen provinces in China, from 2016 to 2017 and then screened for the presence of mcr-3 gene by PCR amplification. mcr-3-positive isolates were analyzed for antibiotic resistance and by southern blot hybridization, transfer analysis and plasmid typing. We then examined the molecular evolution of MCR-3 through phylogenetic analysis. Furthermore, we also characterized the structure and function of MCR-3 through circular dichroism analyses, inductively coupled plasma mass spectrometry (ICP-MS), liquid chromatography mass spectrometry (LC/MS), confocal microscopy and chemical rescue tests.

FINDINGS

49 samples (49/6497 = 0.75%) were mcr-3 positive, comprising 40 samples (40/4144 = 0.97%) from 2017 and 9 samples (9/2353 = 0.38%) from 2016. Overall, mcr-3-positive isolates were distributed in animals and humans in 8 of the 13 provinces. Three mcr-3-positive IncP-type and one mcr-1-bearing IncHI2-like plasmids were identified and characterized. MCR-3 clusters with PEA transferases from Aeromonas and other bacteria and forms a phylogenetic entity that is distinct from the MCR-1/2/P(M) family, the largest group of transferable colistin resistance determinants. Despite that the two domains of MCR-3 not being exchangeable with their counterparts in MCR-1/2, structure-guided functional mapping of MCR-3 defines a conserved PE-lipid recognizing cavity prerequisite for its enzymatic catalysis and its resultant phenotypic resistance to colistin. We therefore propose that MCR-3 uses a possible "ping-pong" mechanism to transfer the moiety of PEA from its donor PE to the 1(or 4')-phosphate of lipid A via an adduct of MCR-3-bound PEA. Additionally, the expression of MCR-3 in E. coli prevents the colistin-triggered formation of reactive oxygen species (ROS) and interferes bacterial growth and viability.

INTERPRETATION

Our results provide an evolutionary, structural and functional definition of MCR-3 and its epidemiology in China, paving the way for smarter policies, better surveillance and effective treatments.

[Thoracoscopy in diagnosis and treatment of pleural diseases in children]

Objective: To investigate the value of thoracoscopy in diagnosis and treatment of pleural diseases in children. Method: Clinical manifestations and treatment outcomes of 19 patients who had refractory pleural diseases treated with thoracosocy during May 2011 to August 2016 in Hunan Provincial People's Hospital were retrospectively analyzed. In 19 cases, 15 were male and 4 were female, with an average age of (4.8±2.0) years. Thirteen patients had left pleural lesion, while 5 patients had right lesion, and 1 had bilateral lesions. Result: All cases were successfully treated with thoracoscopy without emergent thoracotomy. Pre- and post operative diagnosis was compatible in 10 cases, including 8 cases of empyema (Streptococcus pneumoniae infection in 6 cases, and Staphylococcus Aureus infection in 2 cases), and 2 cases of tuberculous pleuritis. Nine patients who had not been clearly diagnosed before surgery were diagnosed to be empyema (4 case), tuberculous pleuritic (3 cases), mycoplasma infection (1 case), and foreign body with infection (1 case) by thoracoscopy. The average duration of post-op closed thoracic drainage was (4.7±2.3) days. The average time to get normal temperature was (2.4±2.6) days. And the average length of hospital stay was (6.7±1.8) days. No hemothorax, chylothorax, or need for analgesic occurred. Conclusion: Thoracoscopy can be recommended for diagnosis and treatment of refractory pleural lesions diseases in children, with minimal trauma and complications.

[SOX10 mutation is relevant to inner ear malformation in patients with Waardenburg syndrome]

Objective: To determine the relevance between the SOX10 mutation and Waardenburg syndrome (WS) accompanied with inner ear abnormality by analyzing the inner ear imaging results and molecular and genetic results of the WS patients with the SOX10 mutation. Methods: This study included 36 WS in patients during 2001 and 2015 in the department of otorhinolaryngology head and neck surgery, Chinese Peoples's Liberation Army General Hospital. The condition of the inner ear of each patient was assessed by analyzing HRCT scans of the temporal bone and MRI scans of the brain and internal auditory canal. Meanwhile, the possible pathogenic genes of WS, including SOX10, MITF, and PAX3, were also screened. Patients were divided into two groups according to SOX10 mutation.The Fisher accuracy test was used to determine statistical difference of inner ear deformation incidence between the two groups. Results: Among all 36 patients, 12 were found to have inner ear abnormality. Most abnormalities were posterior semicircular canal deformations, some accompanied with cochlear deformation and an enlarged vestibule. Among all patients, 9 patients were SOX10 heterozygous mutation carriers, among which six showed bilateral inner ear abnormality. Fisher accuracy test results suggested a significant correlation between the SOX10 mutation and inner ear abnormality in WS patients (P=0.036). Conclusion: This study found that WS patients with the SOX10 mutation are more likely to have deformed inner ears when compared to WS patients without the SOX10 mutation.

Prevalence, risk factors, outcomes, and molecular epidemiology of mcr-1-positive Enterobacteriaceae in patients and healthy adults from China: an epidemiological and clinical study

BACKGROUND

The mcr-1 gene confers transferable colistin resistance. mcr-1-positive Enterobacteriaceae (MCRPE) have attracted substantial medical, media, and political attention; however, so far studies have not addressed their clinical impact. Herein, we report the prevalence of MCRPE in human infections and carriage, clinical associations of mcr-1-positive Escherichia coli (MCRPEC) infection, and risk factors for MCRPEC carriage.

METHODS

We undertook this study at two hospitals in Zhejiang and Guangdong, China. We did a retrospective cross-sectional assessment of prevalence of MCRPE infection from isolates of Gram-negative bacteria collected at the hospitals from 2007 to 2015 (prevalence study). We did a retrospective case-control study of risk factors for infection and mortality after infection, using all MCRPEC from infection isolates and a random sample of mcr-1-negative E coli infections from the retrospective collection between 2012 and 2015 (infection study). We also did a prospective case-control study to assess risk factors for carriage of MCRPEC in rectal swabs from inpatients with MCRPEC and mcr-1 negative at the hospitals and collected between May and December, 2015, compared with mcr-1-negative isolates from rectal swabs of inpatients (colonisation study). Strains were analysed for antibiotic resistance, plasmid typing, and transfer analysis, and strain relatedness.

FINDINGS

We identified 21 621 non-duplicate isolates of Enterobacteriaceae, Acinetobacter spp, and Pseudomonas aeruginosa from 18 698 inpatients and 2923 healthy volunteers. Of 17 498 isolates associated with infection, mcr-1 was detected in 76 (1%) of 5332 E coli isolates, 13 (<1%) of 348 Klebsiella pneumoniae, one (<1%) of 890 Enterobacter cloacae, and one (1%) of 162 Enterobacter aerogenes. For the infection study, we included 76 mcr-1-positive clinical E coli isolates and 508 mcr-1-negative isolates. Overall, MCRPEC infection was associated with male sex (209 [41%] vs 47 [63%], adjusted p=0·011), immunosuppression (30 [6%] vs 11 [15%], adjusted p=0·011), and antibiotic use, particularly carbapenems (45 [9%] vs 18 [24%], adjusted p=0·002) and fluoroquinolones (95 [19%] vs 23 [30%], adjusted p=0·017), before hospital admission. For the colonisation study, we screened 2923 rectal swabs from healthy volunteers, of which 19 were MCRPEC, and 1200 rectal swabs from patients, of which 35 were MCRPEC. Antibiotic use before hospital admission (p<0·0001) was associated with MCRPEC carriage in 35 patients compared with 378 patients with mcr-1-negative E coli colonisation, whereas living next to a farm was associated with mcr-1-negative E coli colonisation (p=0·03, univariate test). mcr-1 could be transferred between bacteria at high frequencies (10^-1 to 10^-3), and plasmid types and MCRPEC multi-locus sequence types (MLSTs) were more variable in Guangdong than in Zhejiang and included the human pathogen ST131. MCRPEC also included 17 unreported ST clades.

INTERPRETATION

In 2017, colistin will be formally banned from animal feeds in China and switched to human therapy. Infection with MRCPEC is associated with sex, immunosuppression, and previous antibiotic exposure, while colonisation is also associated with antibiotic exposure. MLST and plasmid analysis shows that MCRPEC are diversely spread throughout China and pervasive in Chinese communities.

FUNDING

National Key Basic Research Program of China, National Natural Science Foundation of China/Zhejiang, National Key Research and Development Program, and MRC, UK.

[Establishment of a mathematical model for calculating cochlear length]

OBJECTIVE

To compare the cochlear length of the miniature pig calculated by 3-dimensional reconstruction technique and an Archimedean spiral model, and to evaluate the feasibility of determining the length of the cochlea using a mathematical model.

METHODS

The temporal bones of three miniature pigs with normal hearing were selected and scanned by micro-CT. The pictures were input into Mimics software, the 3D structure of the inner ear was reconstructed, and the following parameters were determined through Mimics: cochlear length, diameter of each turn, cochlear height, and apical turn angle. The cochlear length was calculated using the Archimedean spiral model.

RESULTS

The length of the cochlea was (35.30±0.88)mm based on the three-dimensional reconstruction technique compared to (34.85±0.64)mm based on the Archimedean spiral model. The differences between the two values were not statistically significant. The height of the cochlea is (2.64±0.24)mm. The capsule of the cochlea had 3.67 turns.

CONCLUSIONS

The three-dimensional reconstruction technique provides accurate and reliable results, but the reconstruction process is time-consuming and is unsuitable for clinical application. The Archimedean spiral model method is simple, feasible, reliable, and therefore suitable for clinical applications, in particular to provide references for cochlear implantation surgeries.

NDM-1-Producing Citrobacter freundii, Escherichia coli, and Acinetobacter baumannii Identified from a Single Patient in China

We identified New Delhi metallo-β-lactamase (NDM-1)-producing Citrobacter freundii GB032, Escherichia coli GB102, and Acinetobacter baumannii GB661 in urine and stool samples from a single patient in China. Plasmid profiling and Southern blotting indicated that blaNDM-1 from GB032 and that from GB102 were likely located on the same plasmid, while blaNDM-1 from GB661 was located on a very large (>400-kb) plasmid. This case underscores the broad host range of blaNDM-1 and its potential to spread between members of the family Enterobacteriaceae and A. baumannii.

Expression of anti-inflammatory mediator lipoxin A4 and inflammation responsive transcriptive factors NF-kappa B in patients with preeclampsia

OBJECTIVE

To evaluate the role of lipoxin A4 (LXA4), NF-kappaB p65 in preeclampsia.

MATERIALS AND METHODS

LXA4 in blood serum and the lipoxin A4 receptor (ALX-R), NF-kappaB p65 mRNA, protein expressions in placenta-specific tissues were obtained from patients with preeclampsia and normal pregnancy.

RESULTS

Levels of lipoxin A4 in women with mild preeclampsia was significantly high (p < 0.05). There was no significant statistical difference between normal pregnancy and severe preeclampsia (p > 0.05). The mRNA expression of ALX-R was significantly low in women with preeclampsia than in control group (p < 0.01) and mRNA expression of NF- kappaB p65 was significantly high in preeclampsia (p < 0.01). The immunohistochemical staining of NF-kappaB p65 protein was stronger in severe preeclampsia group whereas staining of ALX-R in placental tissue was weaker than in control group (p < 0.01). ALX-R mRNA was negatively correlated with NF-kappaB (p < 0.0001), but there was no correlation between LXA4 and ALX-R mRNA.

CONCLUSION

There was an excessive maternal inflammatory response in preeclampsia. LXA4, ALX-R, and NF-kappaB p65 may be involved in the disease process ofpreeclampsia.