Biofilm formation and antibiotic sensitivity in Elizabethkingia anophelis

Elizabethkingia anophelis has recently gained global attention and is emerging as a cause of life-threatening nosocomial infections. The present study aimed to investigate the association between antimicrobial resistance and the ability to form biofilm among E. anophelis isolated from hospitalized patients in China. Over 10 years, a total of 197 non-duplicate E. anophelis strains were collected. Antibiotic susceptibility was determined by the standard agar dilution method as a reference assay according to the Clinical and Laboratory Standards Institute. The biofilm formation ability was assessed using a culture microtiter plate method, which was determined using a crystal violet assay. Culture plate results were cross-checked by scanning electron microscopy imaging analysis. Among the 197 isolates, all were multidrug-resistant, and 20 were extensively drug-resistant. Clinical E. anophelis showed high resistance to current antibiotics, and 99% of the isolates were resistant to at least seven antibiotics. The resistance rate for aztreonam, ceftazidime, imipenem, meropenem, trimethoprim-sulfamethoxazole, cefepime, and tetracycline was high as 100%, 99%, 99%, 99%, 99%, 95%, and 90%, respectively. However, the isolates exhibited the highest susceptibility to minocycline (100%), doxycycline (96%), and rifampin (94%). The biofilm formation results revealed that all strains could form biofilm. Among them, the proportions of strong, medium, and weak biofilm-forming strains were 41%, 42%, and 17%, respectively. Furthermore, the strains forming strong or moderate biofilm presented a statistically significant higher resistance than the weak formers (p < 0.05), especially for piperacillin, piperacillin-tazobactam, cefepime, amikacin, and ciprofloxacin. Although E. anophelis was notoriously resistant to large antibiotics, minocycline, doxycycline, and rifampin showed potent activity against this pathogen. The data in the present report revealed a positive association between biofilm formation and antibiotic resistance, which will provide a foundation for improved therapeutic strategies against E. anophelis infections in the future.

Expert Consensus on Diagnosis and Treatment of End-Stage Liver Disease Complicated with Infections

Abstract

End-stage liver disease (ESLD) is a life-threatening clinical syndrome that markedly increases mortality in patients with infections. In patients with ESLD, infections can induce or aggravate the occurrence of liver decompensation. Consequently, infections are among the most common complications of disease progression. There is a lack of working procedure for early diagnosis and appropriate management for patients with ESLD complicated by infections as well as local and international guidelines or consensus. This consensus assembled up-to-date knowledge and experience across Chinese colleagues, providing data on principles as well as working procedures for the diagnosis and treatment of patients with ESLD complicated by infections.

Ground spiders (Araneae, Gnaphosidae) from Jiangxi Province, China

A list of 26 gnaphosid species belonging to 14 genera collected in Jiangxi Province, China, is provided. Three new species of ground spiders from Jiangxi Province of China are diagnosed, described, and illustrated: Haplodrassusyinae Liu, sp. nov. (♂♀), Hitobiaxiaoxi Liu, sp. nov. (♂), and Zelotesdingnan Liu, sp. nov. (♂♀). Haplodrassusyinae Liu, sp. nov. was previously erroneously recorded in Jiangxi Province as H.montanusYin et al., 2012.

Epidemiology and Genomic Characteristics of Bloodstream Infection Caused by Carbapenem-Resistant Klebsiella pneumoniae With Decreased Susceptibility to Aztreonam/Avibactam in China

Aztreonam/avibactam (AZA), as one of the novel β-lactamases and β-lactamase inhibitor combinations, is considered to be a promising option for bloodstream infection (BSI) of carbapenem-resistant Klebsiella pneumoniae (CR-Kp). However, decreased susceptibility of AZA activity in Enterobacterales has been reported. The aim of this study was to identify the mechanisms of BSI CR-Kp with decreased susceptibility of AZA (minimal inhibitory concentration above 16/4 mg/L) (AZAH-Kp). Nine BSI AZAH-Kp isolates were screened from 317 CR-Kp isolates in Blood Bacterial Resistant Investigation Collaborative System (BRICS) program. Whole genome sequencing, bioinformatics analysis, and the relative expression of bla_KPC, ompK35, and ompK37 were explored for CR-Kp with decreased susceptibility to AZA. The results revealed that elevated inhibitory concentration of AZA has emerged in CR-Kp before previous clinical exposure. In addition, decreased AZA susceptibility was associated with higher KPC expression and changes in OmpK35-37.

Abstract 4123: Real-world data to identify the genomic association with response to CDK4/6i + Endocrine therapy in ER+ breast cancer patients

Background Real-world data (RWD) has been increasingly used for drug development. RWD coupled with genomic data provides an opportunity to identify the association between certain genomic alterations and response to current standard of care (SOC). Such analyses may help identify predictive biomarkers to select patients who will benefit most from SOC, and/or potential therapeutic nodes that can be pharmacologically targeted to overcome resistance to SOC.

Methods We obtained Flatiron CGDB Breast Cancer (as of Q3 2020 release) data set. This data set includes clinical and genomic data from 6,918 breast cancer patients. Time to treatment discontinuation (TTD) was used as real world outcome. We performed two types of genomic-outcome association analysis: 1) Use Cox proportional hazards regression model to identify which baseline mutation (mutation occurred prior to the treatment) could predict the outcome; and 2) use Fisher exact test to identify which mutations are enriched in post-treatment tumors samples, compared to pre-treatment tumor samples.

Result We found TP53 mutation is associated with shorter TTD for Palbociclib + Aromatase inhibitor (AI); Palbociclib + Fulvestrant; and endocrine monotherapy. It is consistent with the reports that TP53 mutation is poor prognostic factor (ref). Interestingly, ESR1 mutation is associated with shorter TTD for Palbociclib + AI and AI monotherapy; but not associated with TTD for Palbociclib + Fulvestrant or Fulvestrant monotherapy. On the other hand, MYC amplification is associated shorter TTD for Palbociclib + Fulvestrant or Fulvestrant monotherapy. We found that genes associated with Palbociclib + Endocrine are by and large same as those associated with endocrine monotherapy; suggesting the association is largely driven by endocrine treatment. Comparison of post-treatment vs. pre-treatment analysis found that ESR1 mutation is enriched in post treatment of AI; but not Fulvestrant.

Conclusion We demonstrated that real-world clinicogenomic data could identify the biologically meaningful genomic biomarkers that are associated with real world response. This study warrants the further investigation of novel genomic biomarkers identified from the analysis.

Citation Format: Kun Yu, Tenghui Chen, Manav Korpal, Ping Zhu, Zhaojie Zhang, Lihua Yu, Yonghong Xiao. Real-world data to identify the genomic association with response to CDK4/6i + Endocrine therapy in ER+ breast cancer patients [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 4123.

Five new species of Synagelides Strand, 1906 from China (Araneae, Salticidae)

Five new species of salticids were collected from China: Synagelidesemangou Liu, sp. nov. (♂, ♀) from Gansu province, and S.jinding Liu, sp. nov. (♂), S.serratus Liu, sp. nov. (♂, ♀), S.shuqiang Liu, sp. nov. (♂), and S.triangulatus Liu, sp. nov. (♀) from Jiangxi Province. All species are described and illustrated with photographs and SEM micrographs, and their distributions are also mapped.

Emergence of Neonatal Sepsis Caused by MCR-9- and NDM-1-Co-Producing Enterobacter hormaechei in China

Mobile colistin resistance (mcr) genes represent an emerging threat to public health. Reports on the prevalence, antimicrobial profiles, and clonality of MCR-9-producing Enterobacter cloacae complex (ECC) isolates on a national scale in China are limited. We screened 3,373 samples from humans, animals, and the environment and identified eleven MCR-9-positive ECC isolates. We further investigated their susceptibility, epidemiology, plasmid profiles, genetic features, and virulence potential. Ten strains were isolated from severe bloodstream infection cases, especially three of them were recovered from neonatal sepsis. Enterobacter hormaechei was the most predominant species among the MCR-9-producing ECC population. Moreover, the co-existence of MCR-9, CTX-M, and SHV-12 encoding genes in MCR-9-positive isolates was globally observed. Notably, mcr-9 was mainly carried by IncHI2 plasmids, and we found a novel ~187 kb IncFII plasmid harboring mcr-9, with low similarity with known plasmids. In summary, our study presented genomic insights into genetic characteristics of MCR-9-producing ECC isolates retrieved from human, animal, and environment samples with one health perspective. This study is the first to reveal NDM-1- and MCR-9-co-producing ECC from neonatal sepsis in China. Our data highlights the risk for the hidden spread of the mcr-9 colistin resistance gene.

Crab spiders (Araneae, Thomisidae) of Jinggang Mountain National Nature Reserve, Jiangxi Province, China

A list of 34 thomisid species belonging to 21 genera collected in Jangxi Province of China is provided. Five new species are described: Angaeusxieluae Liu, sp. nov. (♂♀), Lysitelessubspirellus Liu, sp. nov. (♀), Oxytatemucunica Liu, sp. nov. (♀), Phartalingxiufengica Liu, sp. nov. (♀), Stephanopisxiangzhouica Liu, sp. nov. (♀). A new combination is proposed: Ebelingiaforcipata (Song & Zhu, 1993) comb. nov. (ex. Ebrechtella Dahl, 1907). Previously unknown females of E.forcipata (Song & Zhu, 1993), Oxytatebicornis Liu, Liu & Xu, 2017, and Xysticuslesserti Schenkel, 1963 are described for the first time. Stephanopis O Pickard-Cambridge, 1869, a genus previously known from Australasia and South America, is recorded from the Asian mainland for the first time.

Molecular Characterization of Carbapenem-Resistant Acinetobacter baumannii Isolates Among Intensive Care Unit Patients and Environment

Objective

Methods

Results

Conclusion

It is time to define an organizational model for the prevention and management of infections along the surgical pathway: a worldwide cross-sectional survey

BACKGROUND

The objectives of the study were to investigate the organizational characteristics of acute care facilities worldwide in preventing and managing infections in surgery; assess participants' perception regarding infection prevention and control (IPC) measures, antibiotic prescribing practices, and source control; describe awareness about the global burden of antimicrobial resistance (AMR) and IPC measures; and determine the role of the Coronavirus Disease 2019 pandemic on said awareness.

METHODS

A cross-sectional web-based survey was conducted contacting 1432 health care workers (HCWs) belonging to a mailing list provided by the Global Alliance for Infections in Surgery. The self-administered questionnaire was developed by a multidisciplinary team. The survey was open from May 22, 2021, and June 22, 2021. Three reminders were sent, after 7, 14, and 21 days.

RESULTS

Three hundred four respondents from 72 countries returned a questionnaire, with an overall response rate of 21.2%. Respectively, 90.4% and 68.8% of participants stated their hospital had a multidisciplinary IPC team or a multidisciplinary antimicrobial stewardship team. Local protocols for antimicrobial therapy of surgical infections and protocols for surgical antibiotic prophylaxis were present in 76.6% and 90.8% of hospitals, respectively. In 23.4% and 24.0% of hospitals no surveillance systems for surgical site infections and no monitoring systems of used antimicrobials were implemented. Patient and family involvement in IPC management was considered to be slightly or not important in their hospital by the majority of respondents (65.1%). Awareness of the global burden of AMR among HCWs was considered very important or important by 54.6% of participants. The COVID-19 pandemic was considered by 80.3% of respondents as a very important or important factor in raising HCWs awareness of the IPC programs in their hospital. Based on the survey results, the authors developed 15 statements for several questions regarding the prevention and management of infections in surgery. The statements may be the starting point for designing future evidence-based recommendations.

CONCLUSION

Adequacy of prevention and management of infections in acute care facilities depends on HCWs behaviours and on the organizational characteristics of acute health care facilities to support best practices and promote behavioural change. Patient involvement in the implementation of IPC is still little considered. A debate on how operationalising a fundamental change to IPC, from being solely the HCWs responsibility to one that involves a collaborative relationship between HCWs and patients, should be opened.

Comparative Respiratory Tract Microbiome Between Carbapenem-Resistant Acinetobacter baumannii Colonization and Ventilator Associated Pneumonia

Background

Carbapenem-resistant Acinetobacter baumannii (CRAB) is a common cause of ventilator-associated pneumonia (VAP) in intensive care unit (ICU) patients, but its infection and colonization state are difficult to distinguish. If the judgment is wrong, it may aggravate the abuse of antibiotics and further accelerate the evolution of drug resistance. We sought to provide new clues for the diagnosis, pathogenesis and treatment of CRAB VAP based on lower respiratory tract (LRT) microbiota.

Methods

A prospective study was conducted on patients with mechanical ventilation from July 2018 to December 2019 in a tertiary hospital. Multi-genomics studies (16S rRNA amplicon, metagenomics, and whole-genome sequencing [WGS]) of endotracheal deep aspirate (ETA) were performed.

Results

Fifty-two ICU patients were enrolled, including 24 with CRAB VAP (CRAB-I), 22 with CRAB colonization (CRAB-C), and six CRAB-negative patients (infection-free) (CRAB-N). Diversity of pulmonary microbiota was significantly lower in CRAB-I than in CRAB-C or CRAB-N (mean Shannon index, 1.79 vs. 2.73 vs. 4.81, P < 0.05). Abundances of 11 key genera differed between the groups. Acinetobacter was most abundant in CRAB-I (76.19%), moderately abundant in CRAB-C (59.14%), and least abundant in CRAB-N (11.25%), but its interactions with other genera increased in turn. Metagenomics and WGS analysis showed that virulence genes were more abundant in CRAB-I than in CRAB-C. Multi-locus sequence typing (MLST) of 46 CRAB isolates revealed that the main types were ST208 (30.43%) and ST938 (15.22%), with no difference between CRAB-I and CRAB-C.

Conclusion

Lower respiratory tract microbiota dysbiosis including elevated relative abundance of Acinetobacter and reduced bacterial interactions, and virulence enrichment may lead to CRAB VAP.

Encephalomyelitis Caused by Balamuthia mandrillaris in a Woman With Breast Cancer: A Case Report and Review of the Literature

Balamuthia mandrillaris is one cause of a rare and severe brain infection called granulomatous amoebic encephalitis (GAE), which has a mortality rate of >90%. Diagnosis of Balamuthia GAE is difficult because symptoms are non-specific. Here, we report a case of Balamuthia amoebic encephalomyelitis (encephalitis and myelitis) in a woman with breast cancer. She sustained trauma near a garbage dump 2 years ago and subsequently developed a skin lesion with a Mycobacterium abscessus infection. She experienced dizziness, lethargy, nausea and vomiting, inability to walk, and deterioration of consciousness. Next-generation sequencing of cerebrospinal fluid (CSF) samples revealed B. mandrillaris, and MRI of both brain and spinal cord showed abnormal signals. T-cell receptor (TCR) sequencing of the CSF identified the Top1 TCR. A combination of amphotericin B, flucytosine, fluconazole, sulfamethoxazole, trimethoprim, clarithromycin, pentamidine, and miltefosine was administrated, but she deteriorated gradually and died on day 27 post-admission.

Blood bacterial resistant investigation collaborative system (BRICS) report: a national surveillance in China from 2014 to 2019

BACKGROUND

In this first national bloodstream infection (BSI) surveillance program in China, we assessed the composition of pathogenic bacteria and the trends for antimicrobial susceptibility over a 6-year period in China.

METHODS

Blood bacterial isolates from patients at hospitals participating in the Blood Bacterial Resistant Investigation Collaborative System (BRICS) were collected from January 2014 to December 2019. Only the first isolate of a species per patient was eligible over the full study period. Antibiotic-susceptibility testing was conducted by agar-dilution or broth-dilution methods as recommended by the Clinical and Laboratory Standards Institute (CLSI). WHONET 5.6 was used to analyze data.

RESULTS

During the study period, 27,899 bacterial strains were collected. Gram-positive organisms accounted for 29.5% (8244) of the species identified and Gram-negative organisms accounted for 70.5% (19,655). The most-commonly isolated organisms in blood cultures were Escherichia coli, Klebsiella pneumoniae, Staphylococcus aureus, coagulase-negative Staphylococci, and Acinetobacter baumannii. The prevalence of multidrug-resistant organisms, such as E. coli, K. pneumoniae, A. baumannii was higher in tertiary hospitals, whereas extended-spectrum, β-lactamase-producing E. coli (ESBL-E. coli), carbapenem-resistant A. baumannii were more prevalent in economically-developing areas. The prevalence of methicillin-resistant S. aureus declined from 39.0% (73/187) in 2014 to 25.9% (230/889) in 2019 (p < 0.05). The prevalence of ESBL-E. coli dropped from 61.2% (412/673) to 51.0% (1878/3,683) over time (p < 0.05), and carbapenem-resistant E. coli remained low prevalence (< 2%; 145/9944; p = 0.397). In contrast, carbapenem-resistant K. pneumoniae increased markedly from 7.0% (16/229) in 2014 to 19.6% (325/1,655) in 2019 (p < 0.05).

CONCLUSION

E. coli and K. pneumoniae were the leading causes of BSI during the 6-year study period. The major resistant pathogens declined or remained stable, whereas carbapenem-resistant K. pneumoniae continued to increase, which poses a great therapeutic challenge for BSIs.

Rifaximin Modulates the Gut Microbiota to Prevent Hepatic Encephalopathy in Liver Cirrhosis Without Impacting the Resistome

The gut microbiota has an important role in the pathogenesis of hepatic encephalopathy(HE). Rifaximin, an intestinal non-absorbable antibacterial agent, is effective in the treatment of HE. However, whether long-term prophylactic use induces antibacterial resistance and its mechanism for treating HE remains unclear. This prospective study assessed the impact of 12 weeks rifaximin administration on the gut microbiota and resistome in cirrhotic patients. Fecal sampling was conducted 1 day before the first rifaximin administration and at Weeks 1, 2, 4, 6, 8, 10, 12 of the study. Thirty cirrhotic patients who were in remission from recurrent HE was enrolled to receive rifaximin (400mg TID for 12 weeks). Rifaximin improved hyperammonemia and cognitive function in the 21 patients who completed rifaximin treatment. The dynamic observations showed the gut microbiota diversity, composition and the number of resistance genes, plasmids, insertion sequences did not change significantly during the period(P>0.05). Metabolic pathways such as aromatic amino acids, tryptophan synthesis, urea cycle, and LPS synthesis reduced. No new antimicrobial resistance genes was emergenced. However, the number of aminoglycosides, rifamycin and phenolic resistance genes increased, whereas tetracycline, fosfomycin and cephamycin decreased (P<0.05). Changes in the abundance of E. coli, K. pneumoniae, and B. longum strains correlated with changes of resistance genes. Prophylactic use of rifaximin for 12 weeks improved hyperammonemia and neurophysiological function, maintained gut microbiota diversity, composition and did not change the overall resistome. Rifaximin altered expression of HE-related metabolic pathways. All of these effects could play a key role in preventing HE. Clinical Trial Registration: ChiCTR1900022234 (registered at the Chinese Clinical Trial Registry).

Genomic epidemiology and characterisation of penicillin-sensitive Staphylococcus aureus isolates from invasive bloodstream infections in China: an increasing prevalence and higher diversity in genetic typing be revealed

Many countries have reported increasing rates of penicillin-susceptible methicillin-sensitive Staphylococcus aureus (MSSA-PEN^S). To date, there is relatively little known about the current situation and molecular characteristics of MSSA-PEN^S in China. In this study, we carried out a laboratory-based multi-region retrospective study to investigate the genomic epidemiology and characterisation of MSSA-PEN^S isolated from invasive bloodstream infections (BSIs) across 17 provinces. The prevalence of MSSA-PEN^S isolates increased significantly over the 6-year period, with the proportion increasing from 3.51% in 2014-8.80% in 2019, an average relative increase of 22.14% per year (95% confidence interval 9.67%-34.61%, P for trend <0.001), suggesting that China is experiencing a resurgence of MSSA-PEN^S. Phylogenetic analysis showed a higher strain diversity occurred; the most frequent clonal complexes (CCs) identified were CC188 (17.14%), CC398 (15.71%) and CC5 (15.71%). Over half of MSSA-PEN^S strains were pan-susceptible, with erythromycin the most frequent resistance observed. Moreover, 25 isolates were identified as immune evasion cluster negative, including CC15, CC188 and CC1, and 6 strains encoded the Panton-Valentine leucocidin gene. Importantly, virulence assays showed that MSSA-PEN^S exhibited a level of virulence comparable to that of penicillin-resistant MSSA (MSSA-PEN^R), indicating that more-sensitive strains should not be mistaken for lacking aggressiveness in vivo. Furthermore, 11 of these isolates were confirmed as blaZ positive but phenotype sensitive, with different amino acid changes in blaZ. Our data support the recommendation to clinicians regarding the usage of penicillin in invasive BSIs caused by MSSA-PEN^S, which might create a novel opportunity for better antimicrobial stewardship in the future.

Antibacterial Activity and Optimal Treatment of Ceftazidime-Avibactam and Aztreonam-Avibactam Against Bloodstream Infections Caused by Carbapenem-Resistant Klebsiella pneumoniae

Objectives: This work was to investigate the activity and optimal treatments of ceftazidime-avibactam (CZA) and aztreonam-avibactam (AZA) against bloodstream infections caused by carbapenem resistant Klebsiella pneumoniae (BSIs-CRKP).

Methods: A total of 318 nonduplicate BSIs-CRKP isolates were collected from Blood Bacterial Resistant Investigation Collaborative System (BRICS) program. The minimum inhibitory concentration (MIC) of CZA and AZA were determined by agar dilution method. Carbapenemase genes and multilocus sequence typing were amplified by PCR. Monte Carlo simulation (MCS) was conducted to calculate cumulative fraction of response (CFR) of different CZA or AZA administrations.

Results: The MIC₉₀ of CZA and AZA were 128/4 and 1/4 mg/L, respectively. There are 87.4 and 3.5% isolates carried bla_KPC-2 and bla_NDM-1. A total of 68 ST types were identified and 29 novel ST types. ST11 accounted for 66.6%. Further MCS showed CFR of CZA using two-step infusion therapy (rapid first-step 0.5 h infusion and slow second-step 3 h infusion, TSIT) (2.5 g 0.5 h, 3.75 g every 8 h with 3 h infusion and 3.75 g 0.5 h, 2.5 g every 8 h with 3 h infusion) was above 89%. The CFR of AZA with TSIT was above 96%.

Conclusion: TSIT with sufficient pharmacokinetic conditions could be useful for enhancing the therapeutic efficacy of CZA and AZA against BSIs-CRKP.

Molecular mechanisms underlying bacterial resistance to ceftazidime/avibactam

Ceftazidime/avibactam (CAZ/AVI), a combination of ceftazidime and a novel β-lactamase inhibitor (avibactam) that has been approved by the U.S. Food and Drug Administration, the European Union, and the National Regulatory Administration in China. CAZ/AVI is used mainly to treat complicated urinary tract infections and complicated intra-abdominal infections in adults, as well as to treat patients infected with Carbapenem-resistant Enterobacteriaceae (CRE) susceptible to CAZ/AVI. However, increased clinical application of CAZ/AVI has resulted in the development of resistant strains. Mechanisms of resistance in most of these strains have been attributed to bla_KPC mutations, which lead to amino acid substitutions in β-lactamase and changes in gene expression. Resistance to CAZ/AVI is also associated with reduced expression and loss of outer membrane proteins or overexpression of efflux pumps. In this review, the prevalence of CAZ/AVI-resistance bacteria, resistance mechanisms, and selection of detection methods of CAZ/AVI are demonstrated, aiming to provide scientific evidence for the clinical prevention and treatment of CAZ/AVI resistant strains, and provide guidance for the development of new drugs. This article is categorized under: Infectious Diseases > Molecular and Cellular Physiology.

The missing MIL-101(Mn): geometrically guided synthesis and topologically correlated valence states

Through a geometrically guided approach, i.e. with the aid of pyridyl modulators, the long-sought MIL-101(Mn) structure is finally achieved, which features emergent topologically correlated mixed-valence states that are apt for enzymatic catalysis.

Socioeconomic Burden of Bloodstream Infections Caused by Carbapenem-Resistant Enterobacteriaceae

Background

Although infection with carbapenem-resistant Enterobacteriaceae (CRE) has become an urgent public health threat worldwide, the socioeconomic burden of CRE bloodstream infection (BSI) remains to be clarified.

Methods

This retrospective study included all patients infected with Escherichia coli or Klebsiella pneumoniae who were hospitalized for BSI from 2013 to 2015. Socioeconomic burden, including direct and indirect economic burden, was compared in patients infected with carbapenem-sensitive Enterobacteriaceae (CSE) and CRE following 1:1 propensity score matching (PSM) to control for confounding variables.

Results

Data from 879 patients with Enterobacteriaceae BSI were evaluated, including 152 (17.3%) patients infected with CRE and 727 (82.7%) infected with CSE. PSM yielded 112 pairs of 224 patients. Median hospital length of stay did not differ significantly in the CRE and CSE groups (35 vs 29 days, P = 0.089), but in-hospital 28-day mortality rate was significantly higher in patients infected with CRE than with CSE (45.5% vs 32.1%, P = 0.040). Median direct economic burden was significantly greater in patients with CRE-BSI than with CSE-BSI during hospitalization ($24,940.1 vs 16,864.0, P = 0.017) but not during the period after infection ($10,403.4 vs 8498.0, P = 0.178). Drug expenditure accounted for the largest proportion of costs in both groups. The median disability-adjusted life year (DALY) was higher in CRE-BSI than in CSE-BSI patients, but the difference was not statistically significant (7.9 vs 6.7 years, P = 0.190). Median indirect economic burden did not differ significantly in these two groups ($3848.5 vs 1139.9, P = 0.304), although indirect economic burden increased significantly from 2013 to 2015 in patients with CRE-BSI.

Conclusion

Carbapenem resistance had a major impact on the clinical and socioeconomic burden of patients with Enterobacteriaceae BSI. The higher mortality rate in patients with CRE-BSI was associated with increased direct healthcare burden and indirect socioeconomic loss.

The Monte Carlo Simulation of Three Antimicrobials for Empiric Treatment of Adult Bloodstream Infections With Carbapenem-Resistant Enterobacterales in China

Introduction: The aim of this study was to predict and evaluate three antimicrobials for treatment of adult bloodstream infections (BSI) with carbapenem-resistant Enterobacterales (CRE) in China, so as to optimize the clinical dosing regimen further.

Methods: Antimicrobial susceptibility data of blood isolates were obtained from the Blood Bacterial Resistance Investigation Collaborative Systems in China. Monte Carlo simulation was conducted to estimate the probability target attainment (PTA) and cumulative fraction of response (CFR) of tigecycline, polymyxin B, and ceftazidime/avibactam against CRE.

Results: For the results of PTAs, tigecycline following administration of 50 mg every 12 h, 75 mg every 12 h, and 100 mg every 12 h achieved > 90% PTAs when minimum inhibitory concentration (MIC) was 0.25, 0.5, and 0.5 μg/mL, respectively; polymyxin B following administration of all tested regimens achieved > 90% PTAs when MIC was 1 μg/mL with CRE; ceftazidime/avibactam following administration of 1.25 g every 8 h, 2.5 g every 8 h achieved > 90% PTAs when MIC was 4 μg/mL, 8 μg/mL with CRE, respectively. As for CFR values of three antimicrobials, ceftazidime/avibactam achieved the lowest CFR values. The highest CFR value of ceftazidime/avibactam was 77.42%. For tigecycline and ceftazidime/avibactam, with simulated regimens daily dosing increase, the CFR values were both increased; the highest CFR of tigecycline values was 91.88%. For polymyxin B, the most aggressive dosage of 1.5 mg/kg every 12 h could provide the highest CFR values (82.69%) against CRE.

Conclusion: This study suggested that measurement of MICs and individualized therapy should be considered together to achieve the optimal drug exposure. In particular, pharmacokinetic and pharmacodynamic modeling based on local antimicrobial resistance data can provide valuable guidance for clinicians for the administration of empirical antibiotic treatments for BSIs.

In Vitro Activity Comparison of Ceftazidime-Avibactam and Aztreonam-Avibactam Against Bloodstream Infections With Carbapenem-Resistant Organisms in China

Objectives

The aim of this work was to investigate the activity of ceftazidime–avibactam (CZA) and aztreonam–avibactam (AZA) against bloodstream infections caused by carbapenem-resistant organisms (CROs).

Methods

Non-duplicate CROs, including 56 carbapenem-resistant Escherichia coli (CR-Eco), 318 carbapenem-resistant Klebsiella pneumoniae (CR-Kpn), and 65 carbapenem-resistant Pseudomonas aeruginosa (CR-Pae), were collected using the Blood Bacterial Resistant Investigation Collaborative System (BRICS) program in China. The minimum inhibitory concentrations (MICs) of 24 antibiotics were tested. Carbapenemase genes were amplified for CZA-resistant CROs by PCR. The MICs of CZA and AZA were further determined with avibactam at 8 and 16 mg/L, respectively.

Results

The resistance rate of polymyxin B against CROs was less than 5%. Only one CR-Kpn was resistant to tigecycline. The resistance rates of CZA against CR-Eco, CR-Kpn, and CR-Pae were 75.0%, 12.6%, and 18.5%, respectively. The MIC₉₀ values of AZA against CR-Eco, CR-Kpn, and CR-Pae were 2/4, 1/4, and 64/4 mg/L, respectively. Among the CZA-resistant CROs, 42 (100%) CR-Eco, 24 (60%) CR-Kpn, and 1 (8.3%) CR-Pae isolates harbored metallo-β-lactamase genes. The increase of avibactam concentration enhanced the susceptibility of CZA and AZA against CROs, especially for CR-Eco and CR-Kpn.

Conclusions

The in vitro activity of AZA was superior to that of CZA against CR-Eco and CR-Kpn, whereas CZA showed better effect against CR-Pae.

Rapid increase in occurrence of carbapenem-resistant Enterobacteriaceae in healthy rural residents in Shandong province, China, from 2015 to 2017

OBJECTIVES

The global increase of carbapenem-resistant Enterobacteriaceae (CRE) is a growing concern. Infections caused by CRE are associated with increased mortality and length of hospital stay, emphasizing the health and economic burden posed by these pathogens. Although CRE can inhabit the human gut asymptomatically, colonization with CRE is associated with increased risk of CRE infection and mortality. In this study, we investigated the occurrence and characteristics of CRE in fecal samples from healthy persons in 12 villages in Shandong, China.

METHODS

Screening for CRE in fecal samples was performed by selective cultivation. MICs of meropenem were determined with the agar dilution method. Multilocus sequence type (MLST) and carbapenemase gene carriage of the isolates were determined with whole-genome sequencing. Genetic relatedness of E. coli isolates was determined by core genome MLST.

RESULTS

CRE carriage increased from 2.4% to 13% from 2015 to 2017. Most CRE isolates (93%) were E. coli and all carried NDM-type carbapenemases. The STs among the E. coli were diverse. The single most common was the highly epidemic strain ST167, which was only observed among isolates from 2017.

CONCLUSION

We report a rapid increase in occurrence of CRE from 2.4% to 13% among fecal samples collected from healthy rural residents of Shandong province, China, from 2015 to 2017. Colonization with CRE is known to increase the risk of CRE infection and the worrying deterioration of the epidemiological situation in the region reported here indicate a need for further monitoring and possible interventions.

Comparative genomic and transmission analysis of Clostridioides difficile between environmental, animal, and clinical sources in China

Clostridioides difficile is the most common pathogen causing antibiotic-associated diarrhea. Previous studies showed that diverse sources, aside from C. difficile infection (CDI) patients, played a major role in C. difficile hospital transmission. This study aimed to investigate relationships and transmission potential of C. difficile strains from different sources. A prospective study was conducted both in the intensive care unit (ICU) and six livestock farms in China in 2018–2019. Ninety-eight strains from CDI patients (10 isolates), asymptomatic hospitalized carriers (55), the ICU environment (12), animals (14), soil (4), and farmers (3) were collected. Sequence type (ST) 3/ribotype (RT) 001, ST35/RT046, and ST48/RT596 were dominant types, distributed widely in multiple sources. Core-genome single-nucleotide polymorphism (cgSNP) analysis showed that hospital and farm strains shared several common clonal groups (CGs, strains separated by ≤ 2 cgSNPs) (CG4/ST3/RT001, CG7/ST35/RT046, CG11/ST48/RT596). CDI patients, asymptomatic carriers, and the ICU environment strains also shared several common CGs. The number of virulence genes was not statistically different between strains from different sources. Multi-source strains in the same CG carried identical virulence gene sequences, including pathogenicity genes at the pathogenicity locus and adhesion-related genes at S-layer cassette. Resistance genes (ermB, tetM, etc.) were widespread in multiple sources, and multi-source strains in the same CG had similar resistance phenotypes and carried consistent transposons and plasmid types. The study indicated that interspecies and cross-regional transmission of C. difficile occurs between animals, the environment, and humans. Community-associated strains from both farms and asymptomatic hospitalized carriers were important reservoirs of CDI in hospitals.

Clinical Characteristics of Patients and Whole Genome Sequencing-Based Surveillance of Escherichia coli Community-Onset Bloodstream Infections at a Non-tertiary Hospital in CHINA

Background:Escherichia coli is the most common pathogens in patients with community-onset blood stream infections (COBSI). Knowledge of the epidemiology of this disease is crucial to improve allocation of health resources, formulate isolation strategies that prevent transmission, and guide empirical antibiotic therapy.

Methods: This retrospective observational study examined patients with E. coli COBSI (EC-COBSI) at a non-tertiary hospital in China. Whole-genome sequencing and analysis of the isolates was performed. The relationships of clinical variables with antimicrobial resistance and the genetic background of the isolates were examined.

Results: There were 148 isolates in patients with EC-COBSI. All isolates were susceptible to ceftazidime/avibactam, carbapenems, and tigecycline; 35.1% were positive for extended spectrum β-lactamase (ESBL+); and bla_CTX–M–14 was the most common ESBL gene. Patients with ESBL- isolates were more likely to receive appropriate empiric treatment than those with ESBL+ isolates (61.5% vs. 91.4%, p < 0.001), but these two groups had similar mortality rates. The overall 30-day mortality rate was 9.5%. Phylogenetic analysis showed that the isolates were diverse, and that the main sequence types (STs) were ST95, ST131, and ST69. Intra-abdominal infection was the primary source of disease, and isolates from these patients had lower frequencies of virulence genes.

Conclusion: The mortality rate of patients with EC-COBSI was unrelated to ESBL status of the isolates. Most isolates had low resistance to most of the tested antimicrobial agents. The isolates were diverse, and multiple strains were related. Prevention and control of EC-COBSI should target prevention of patient colonization and the living environment.

Harnessing Shape Complementarity for Upgraded Cyclohexane Purification through Adaptive Bottlenecked Pores in an Imidazole-Containing MOF

Shape complementarity is a biological craft for precisely binding substrates at protein-protein interfaces. An analogy to such a function can be drawn conceptually for crystalline porous solids; yet the manifested entities are rare in reticular chemistry. The bottleneck-shaped pores carved out of a metal-organic framework, Zn(MIBA)₂ (aka. MAF-stu-13), can perfectly accommodate benzene molecules. Remarkably, its framework adapts to the optimal guest binding-the enhanced host-guest interactions in the neck in turn minimize the guest-guest repulsion in the pore to the extent it turns into attraction-as demonstrated by the combined X-ray structural and DFT computational studies. This adaptive material can be used for liquid-phase production of ultrahigh-purity (≥99 %) cyclohexane, achieving a balance between uptake capacity and separation selectivity and surpassing the performances of other porous and nonporous crystals reported recently (e.g. product purity 99.4 % vs. 97.5 % to date).

Utility and applicability of rapid diagnostic testing in antimicrobial stewardship in Asia Pacific: A Delphi consensus

Rapid diagnostic tests (RDTs) facilitate fast and accurate identification of infectious disease microorganisms and are a valuable component of multimodal antimicrobial stewardship (AMS) programs but are currently underutilized in the Asia-Pacific region. An experienced group of infectious diseases clinicians, clinical microbiologists, and a clinical pharmacist used a modified Delphi consensus approach to construct 10 statements, aiming to optimize the utility and applicability of infection-related RDTs for AMS in the Asia-Pacific region. They provide guidance on definition, types, optimal deployment, measuring effectiveness, and overcoming key challenges. The Grading of Recommendations Assessment, Development, and Evaluation system was applied to indicate the strength of the recommendation and the quality of the underlying evidence. Given the diversity of the Asia-Pacific region, the trajectory of RDT development will vary widely; the collection of local data should be prioritized to allow realization and optimization of the full benefits of RDTs in AMS.

Tunicamycin Induces Hepatic Stellate Cell Apoptosis Through Calpain-2/Ca2 +-Dependent Endoplasmic Reticulum Stress Pathway

It has been reported that calpain/caspase-mediated apoptosis induced by endoplasmic reticulum stress (ERS) in hepatic stellate cells (HSCs) by previous studies. At present, the activation of HSC is an important cause of liver fibrosis, and the induction of HSC apoptosis plays an irreplaceable role in reversing liver fibrosis. Therefore, it is of great significance to explore mechanisms of action that can induce HSC apoptosis for the reversal of hepatic fibrosis and the clinical prevention and treatment of hepatic-fibrosis-related diseases such as hepatitis, cirrhosis, and liver cancer. In the current study, we demonstrated that tunicamycin (a novel ERS inducer) can induce the apoptosis of HSCs and increase the concentration of intracellular Ca²⁺ and the expression of ERS protein GRP78, apoptosis protein caspase-12, and Bax, while it can decrease the antiapoptosis protein expression of Bcl-2. Our findings indicate that tunicamycin can induce HSCs apoptosis through calpain-2/Ca²⁺-dependent ERS pathway.

Predicting hosts based on early SARS-CoV-2 samples and analyzing the 2020 pandemic

The SARS-CoV-2 pandemic has raised concerns in the identification of the hosts of the virus since the early stages of the outbreak. To address this problem, we proposed a deep learning method, DeepHoF, based on extracting viral genomic features automatically, to predict the host likelihood scores on five host types, including plant, germ, invertebrate, non-human vertebrate and human, for novel viruses. DeepHoF made up for the lack of an accurate tool, reaching a satisfactory AUC of 0.975 in the five-classification, and could make a reliable prediction for the novel viruses without close neighbors in phylogeny. Additionally, to fill the gap in the efficient inference of host species for SARS-CoV-2 using existing tools, we conducted a deep analysis on the host likelihood profile calculated by DeepHoF. Using the isolates sequenced in the earliest stage of the COVID-19 pandemic, we inferred that minks, bats, dogs and cats were potential hosts of SARS-CoV-2, while minks might be one of the most noteworthy hosts. Several genes of SARS-CoV-2 demonstrated their significance in determining the host range. Furthermore, a large-scale genome analysis, based on DeepHoF's computation for the later pandemic in 2020, disclosed the uniformity of host range among SARS-CoV-2 samples and the strong association of SARS-CoV-2 between humans and minks.

Acquisition of the mcr-1 Gene Lowers the Target Mutation to Impede the Evolution of a High-Level Colistin-Resistant Mutant in Escherichia coli

Objective

The spread of the plasmid-mediated colistin resistance gene mcr-1 poses a significant public health threat. Little information is available on the development of high-level colistin-resistant mutants (HLCRMs) in MCR-1-producing Escherichia coli (MCRPEC). The present study was designed to evaluate the impact of chromosomal modifications in pmrAB, phoPQ, and mgrB combined with mcr-1 on colistin resistance in E. coli.

Methods

Five MCRPEC and three non-MCRPEC (E. coli ATCC25922 and two plasmid-curing) strains were used. The HLCRMs were selected through multi-stepwise colistin exposure. Moreover, two E. coli C600-pMCRs were constructed and used for selection of HLCRMs. Further analysis included mutation rates and DNA sequencing. Transcripts of pmrABC, phoP, mgrB, and mcr-1 were quantified by real-time quantitative PCR.

Results

All tested HLCRMs were successfully isolated from their parental strains. Non-MCRPEC strains had higher minimum inhibitory concentrations (MICs) and mutation rates than MCRPEC strains. Nineteen amino acid substitutions were identified: seven in PmrA, six in PmrB, one in PhoP, three in PhoQ, and two in MgrB. Most were detected in non-MCRPEC strains. Sorting Intolerant From Tolerant predicted that four substitutions, PmrA Gly15Arg, Gly53Arg, PmrB Pro94Gln, and PhoP Asp86Gly, affected protein function. Two HLCRM isolates did not show amino acid substitutions in contrast to their parental MCRPEC isolates. No further mutations were detected in the second- and third-step mutants. Further transcriptional analysis showed that the up-regulation of pmrCAB expression was greater in the mutant of E. coli C600 than in E. coli C600-pMCR.

Conclusion

Acquisition of the mcr-1 gene had a negative impact on the development of HLCRMs in E. coli, but was associated with low-level colistin resistance. Thus, colistin-based combination regimens may be effective against infections with MCR-1-producing isolates.

Evaluation of Ceftazidime/Avibactam Administration in Enterobacteriaceae and Pseudomonas aeruginosa Bloodstream Infections by Monte Carlo Simulation

Purpose

To evaluate the administration regimen of ceftazidime/avibactam (CZA) for bloodstream infections caused by Enterobacteriaceae and Pseudomonas aeruginosa.

Methods

The minimal inhibitory concentrations (MICs) of CZA against Enterobacteriaceae and P. aeruginosa isolated from blood cultures at member hospitals in BRICS (Blood Bacterial Resistant Investigation Collaborative System) in 2019 were determined by broth micro-dilution methodology. A 10,000-patient Monte Carlo simulation (MCS) was used to calculate the probability of target attainment (PTA) and cumulative fraction of response (CFR) for different CZA dosage regimens to evaluate their efficacies and optimize the best initial dosage regimen.

Results

Altogether, 6487 Enterobacteriaceae and P. aeruginosa strains were isolated from the blood cultures. The overall CZA resistance rate was 2.31%, of which the Enterobacteriaceae and P. aeruginosa rates were 1.57% and 14.29%, respectively. The MCS showed that the greater the MIC value, the worse the therapeutic effect. When the CZA MIC was ≤8 mg/L, the standard dose (2.5g iv q8h) achieved 90% PTA in the subset of patients with creatinine clearance (CrCl) values from 51 to 120 mL/min. Although the high-dose regimen (3.75g iv q8h) achieved 90% PTA in patients with CrCl values from 121 to 190 mL/min, implementing the low-dose regimen (1.25g iv q8h) was also effective for patients in the 51–89 mL/min CrCl range. Generally, the high-dose regimen (3.75g iv q8h) reached 90% CFR against all of the strains. Conversely, in patients with CrCl values of 121–190 mL/min, the standard dose (2.5g iv q8h) failed to reach 90% CFR against some Enterobacteriaceae members and P. aeruginosa. When the dose was reduced to the low-dose regimen (1.25g iv q8h), no patients reached 90% CFR against some Enterobacteriaceae members and P. aeruginosa.

Conclusion

CZA has good antibacterial activity against Enterobacteriaceae and P. aeruginosa in bloodstream infections. Clinicians could make individualized treatment regimens in accordance with the sensitivity of the strains and the level of renal function in their patients to best predict the drug-related clinical responses.

Characterization of highly virulent community-associated methicillin-resistant Staphylococcus aureus ST9-SCCmec XII causing bloodstream infection in China

Previous studies have shown that livestock (LA)-MRSA ST398 evolved from a human-adapted methicillin-susceptible S. aureus (MSSA) clone. However, detailed information regarding ST9 is still unclear. Here, we characterized a community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) ST9-SCCmec XII isolate that has not been previously reported to cause serious disease in China. We obtained whole-genome sequences of one ST9-t899-XII isolate—ZY462471—from a patient with bloodstream infection without livestock contact. The antibiotic susceptibilities of ZY462471 were determined and the clinical information was extracted from medical notes and compared with twenty-seven previously sequenced genomes. Phylogenetic reconstruction was performed to investigate the probable host evolutionary origins of ZY462471, and the difference in resistome and virulence factors were investigated. Virulence assay was performed to evaluate the high virulence potential of ZY462471 and compare the virulence between the closest ST9 MSSA neighbours. Clinical data suggested that ZY462471 is a CA-MRSA. Phylogenetic analysis showed a much closer relationship of ZY462471 with human-associated MSSA ST9 isolates than other LA-MRSA ST9 isolates, suggesting that ZY462471 probably evolved from ST9 MSSA predecessors by acquiring an SCCmec cassette. Importantly, virulence assays indicated that ZY462471 was highly virulent and compared with the MSSA ST9 predecessors, ZY462471 did not show attenuated virulence. Finally, we found that ZY462471 harboured an immune evasion cluster (IEC)-carrying βC-Φ, which is typically found in human clinical S. aureus rather than LA-MRSA isolates, suggesting that ZY4762471 obtained the IEC-carrying βC-Φs from human clinical S. aureus strains. Considering its high virulence potential, this strain should be monitored to prevent more widespread dissemination.

Optimal Empiric Polymyxin B Treatment of Patients Infected with Gram-Negative Organisms Detected Using a Blood Antimicrobial Surveillance Network in China

Background

Few pharmacodynamics studies to date have evaluated the efficacy and safety of polymyxin B (PMB) in treating patients with bloodstream infections (BSIs) in China.

Methods

Patients with BSIs were identified using an antimicrobial surveillance network, and their pathogens were isolated. Patients were treated with a loading dose of PMB followed by either a weight-based or weight-independent maintenance dose. Monte Carlo simulation was utilized to calculate the probability of target attainment (PTA) and cumulative fraction of response (CFR) against Gram-negative organisms in patients with normal or decreased renal function.

Results

A total of 10,066 Gram-negative organisms, including 5500 Escherichia coli (Eco), 2519 Klebsiella pneumoniae (Kpn), 501 Acinetobacter baumannii (Aba), were isolated from patients with BSIs. Although these strains were highly resistant to carbapenem, they remained susceptible to PMB. Among patients with renal impairment (mean CrCL, 42 mL/min), a PMB 2.5 mg/kg loading dose followed by a maintenance dose of 60 mg q12h reached ≥90% PTA against isolates with an MIC of 2 mg/L, with a low risk of toxicity. Among patients with normal renal function (mean CrCL, 123 mL/min), all simulated regimens showed PTAs of 25–80%. A weight-based loading dose followed by either a weight-based or weight-independent maintenance dose showed a promising CFR, especially in patients with renal impairment, with CFRs ≥90% against carbapenem-resistant Eco, Kpn, and Aba. Simulated regimens showed a disappointing CFR (<80%) against carbapenem-resistant Pae in patients with normal renal function. Based on the optimal balance of efficacy and toxicity, a fixed maintenance dose of 60 mg q12h among patients with renal impairment yielded a CFR similar to regimens based on total body weight and was associated with a probability of toxicity (12.5%) significantly lower than that of simulations based on total body weight. Among patients with normal renal function, a weight-based maintenance dose of 1.25 mg/kg q12h achieved a higher CFR than a fixed maintenance dose, without significantly increasing toxicity.

Conclusion

A 2.5 mg/kg loading dose of PMB is optimal, regardless of renal function. A fixed maintenance dose of 60 mg q12h is recommended for empirical treatment of patients with renal impairment infected with Eco, Kpn, and Aba, whereas a weight-based maintenance dose of 1.25 mg/kg is recommended for patients with normal renal function.

[Immunogenicity and safety of a boost dose of measles, mumps, and rubella combined vaccine for 4-6 years old children]

Objective: To investigate the immunogenicity and safety of a boost dose of measles, mumps, and rubella combined vaccine (MMR) for children 4 to 6 years old. Methods: Children, aged 4 to 6 years old, had vaccinated with 1 dose of measles and rubella combined vaccine(MR) at the age of 8 months and 1 dose of MMR vaccine at 18-months, were recruited in Shanxi, Inner Mongolia, and Beijing, respectively. All children were assigned into 4, 5 and 6-year-old group. The children who met inclusion and exclusion criteria were vaccinated with 1 dose MMR vaccine, and were collected blood samples before vaccination and 35 to 42 d after the vaccination. During the study period, adverse events were collected at 30 min, 1 d, 2 d, 3 d, 4-12 d, and 13 to 42 days after vaccination. Serum was tested for IgG antibodies against measles, mumps and rubella. Geometric mean concentrations (GMC) of measles, mumps, and rubella antibodies were compared among groups by analysis of variance or non-parametric test. Seropositive rates and adverse event rates were compared among groups by Chi-square test or Fisher exact test. Results: A total of 500 children were included in immunogenicity analysis and 535 children were included in safety analysis. The overall adverse event rate was 20.37%, the most of severity for adverse events was mild. The rates of local and systemic adverse events were 0.37% and 20.00%, respectively. Symptoms of local adverse events were redness. The main systemic adverse events were fever, followed by cough, rash and runny nose. Received a dose of MMR vaccine for booster immunization, the seropositive rates of measles antibody, mumps antibody and rubella antibody were above 99% for all 3 age groups, and there was no significant difference between groups. There were significant differences in mumps antibody GMC among groups (P=0.042), but no significant differences in measles and rubella antibodies GMC. Conclusion: The immunogenicity and safety of a boosted MMR vaccintion in children aged 4, 5 and 6 years were all similar good.

The genetic feature and virulence determinant of highly virulent community-associated MRSA ST338-SCCmec Vb in China

ST59 is the predominant pathotype of community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) in China. As a variant of ST59, there is relatively little known about the detailed information of ST338. To address this issue, here, we described thirteen ST338 CA-MRSA strains isolated from severe bloodstream infection cases, and focused on their epidemiology, genetic features and virulence potential. Phylogenetic analysis showed the earliest isolated strain of this study is likely a predecessor of recent ST338 lineage (after year of 2014). Furthermore, the phylogenetic reconstruction and time estimation suggested that ST338 evolved from ST59 in 1991. Notably, the carrying patten of virulence factors of all ST338 strains were similar, and the genomic islands νSaα, νSaγ and SaPI and the core virulence factors like hla and psm were detected in ST338 isolates. However, all ST338 isolates lacked some adhesion factors such as clfA, clfB, eap, cna and icaD. Additionally, among these ST338 strains, one PVL-negative ST338 isolate was detected. Experiment on mice nose and human alveolar epithelial cell showed that the nasal colonization ability of ST338 was weaker than that of CA-MRSA MW2. In a mouse bloodstream infection model and skin infection model, PVL+ and PVL− strains had the similar virulence, which was dependent on upregulation of toxin genes rather than the presence of mobile genetic elements such as ΦSa2 carrying PVL. Our findings provide important insight into the epidemiology and pathogenicity of the novel and highly virulent ST338-SCCmec Vb clone.

[Knockdown of calreticulin increases intracellular Ca2+ concentration and promotes apoptosis of HSC-LX2 human hepatic stellate cells]

Objective To investigate the effect of silencing calreticulin (CALR) gene on the apoptosis and intracellular Ca²⁺ concentration in HSC-LX2 human hepatic stellate cells. Methods Small interfering RNA (siRNA) targeting CALR was designed and transfected into HSC-LX2 cells by lipofectamine transfection, and then the cells with CALR knockdown were screened out. Apoptosis was detected by flow cytometry combined with annexin V-FITC/PI labeling. The intracellular Ca²⁺ concentration which was loaded with Fluo3-AM (calcium ion fluorescent probe) was observed by laser confocal microscope. The mRNA and protein levels of CALR, Bcl2 and BAX were detected by reverse-transcription PCR and Western blotting. Results Knockdown of CALR led to the increase of intracellular Ca²⁺ concentration, the increased apoptosis of HSC-LX2 cells, the up-regulation of BAX expression, down-regulation of Bcl2 and the obvious raise of BAX/Bcl2 ratio. Conclusion Knockdown of CALR can increase intracellular Ca²⁺ concentration, up-regulate the ratio of BAX/Bcl2 and promote the apoptosis of HSC-LX2 cells.

Socioeconomic burden of bloodstream infections caused by carbapenem-resistant and carbapenem-susceptible Pseudomonas aeruginosa in China

OBJECTIVES

Drug resistance in Pseudomonas aeruginosa (PAE) is a serious health threat. Additionally, it is important to understand the associated socioeconomic burden.

METHODS

Clinical information and hospital cost data for patients with PAE bloodstream infections (BSIs) in a tertiary teaching hospital (2011-2016) were collected retrospectively to estimate the direct economic burden. Socioeconomic loss incurred by patients was calculated using the human capital approach combined with estimating disability-adjusted life years (DALYs). Differences in socioeconomic burden between BSIs caused by carbapenem-resistant (CR) and carbapenem-susceptible (CS) PAE were compared.

RESULTS

This study included data for 220 patients, of which were 29.5% (65/220) CR-PAE BSIs. The median direct economic burden of patients following CR-PAE BSI was significantly higher than following CS-PAE BSI ($5005.94 vs. $1462.86; P < 0.001). The median DALY loss was significantly higher in the CR-PAE group compared with CS-PAE group (0.024 vs. 0.008; P = 0.001). The median indirect socioeconomic loss of patients in the CR-PAE group tended to be significantly higher than in the CS-PAE group ($64.06 vs. $29.71; P = 0.011). The annual economic burden of CR-PAE is higher (up to >1.5 times) than the Chinese annual per capita GDP.

CONCLUSION

The economic burden of PAE BSIs is significant, irrespective of carbapenem resistance. The direct economic burden of CR-PAE BSI was at least three-fold that of CS-PAE BSI. The DALY loss caused by CR-PAE BSI is three-fold that caused by CS-PAE BSI. The indirect socioeconomic loss caused by CR-PAE BSI is more than twice that of CS-PAE BSI.

Diagnosis and Management of Intraabdominal Infection: Guidelines by the Chinese Society of Surgical Infection and Intensive Care and the Chinese College of Gastrointestinal Fistula Surgeons

The Chinese guidelines for IAI presented here were developed by a panel that included experts from the fields of surgery, critical care, microbiology, infection control, pharmacology, and evidence-based medicine. All questions were structured in population, intervention, comparison, and outcomes format, and evidence profiles were generated. Recommendations were generated following the principles of the Grading of Recommendations Assessment, Development, and Evaluation system or Best Practice Statement (BPS), when applicable. The final guidelines include 45 graded recommendations and 17 BPSs, including the classification of disease severity, diagnosis, source control, antimicrobial therapy, microbiologic evaluation, nutritional therapy, other supportive therapies, diagnosis and management of specific IAIs, and recognition and management of source control failure. Recommendations on fluid resuscitation and organ support therapy could not be formulated and thus were not included. Accordingly, additional high-quality clinical studies should be performed in the future to address the clinicians' concerns.

MDR Salmonella enterica serovar Typhimurium ST34 carrying mcr-1 isolated from cases of bloodstream and intestinal infection in children in China

OBJECTIVES

Children are vulnerable to Salmonella infection due to their immature immune system. Cases of infection with mcr-1-harbouring Salmonella in child inpatients have not been reported in China before.

METHODS

Salmonella isolates from gastroenteritis and bacteraemia were screened using primers targeting mcr-1. Complete genome sequences of mcr-1-harbouring isolates were determined using the PacBio RS II platform. The transferability of mcr-1-harbouring plasmids was verified by conjugation.

RESULTS

We investigated two mcr-1-carrying polymyxin-resistant Salmonella enterica serovar Typhimurium ST34 isolates, S61394 and S44712, from bloodstream and intestinal Salmonella infection of two child inpatients, respectively. Both isolates were non-susceptible to commonly used antibiotics for children that compromised the success of clinical treatment and infection control. The mcr-1-harbouring plasmids pLS61394-MCR and pLS44712-MCR (from S61394 and S44712, respectively) were both conjugative pHNSHP45-2-like IncHI2-type epidemic plasmids carrying multiple resistance genes. Compared with pHNSHP45-2, a ∼33 kb insertion region encoding Tn7 transposition protein and heavy metal resistance proteins was identified in pLS61394-MCR, which might enhance adaptation of bacteria carrying this plasmid to various ecological niches. The phylogenetic tree of worldwide mcr-harbouring Salmonella indicated a host preference of mcr and a worldwide and cross-sectoral prevalence of the mcr-positive Salmonella ST34 clone.

CONCLUSIONS

To our knowledge, for the first time we report completed whole genomes of mcr-1-positive MDR Salmonella Typhimurium ST34 isolated from infected children in China, suggesting that improved surveillance is imperative for tackling the dissemination of mcr-harbouring MDR Salmonella Typhimurium ST34.

Identification of novel tetracycline resistance gene tet(X14) and its co-occurrence with tet(X2) in a tigecycline-resistant and colistin-resistant Empedobacter stercoris

Tigecycline is one of the last-resort antibiotics to treat severe infections. Recently, tigecycline resistance has sporadically emerged with an increasing trend, and Tet(X) family represents a new resistance mechanism of tigecycline. In this study, a novel chromosome-encoded tigecycline resistance gene, tet(X14), was identified in a tigecycline-resistant and colistin-resistant Empedobacter stercoris strain ES183 recovered from a pig fecal sample in China. Tet(X14) shows 67.14-96.39% sequence identity to the other variants [Tet(X) to Tet(X13)]. Overexpression of Tet(X14) in Escherichia coli confers 16-fold increase in tigecycline MIC (from 0.125 to 2 mg/L), which is lower than that of Tet(X3), Tet(X4) and Tet(X6). Structural modelling predicted that Tet(X14) shared a high homology with the other 12 variants with RMSD value from 0.003 to 0.055, and Tet(X14) can interact with tetracyclines by a similar pattern as the other Tet(X)s. tet(X14) and two copies of tet(X2) were identified on a genome island with abnormal GC content carried by the chromosome of ES183, and no mobile genetic elements were found surrounding, suggesting that tet(X14) might be heterologously obtained by ES183 via recombination. Blasting in Genbank revealed that Tet(X14) was exclusively detected on the chromosome of Riemerella anatipestifer, mainly encoded on antimicrobial resistance islands. E. stercoris and R. anatipestifer belong to the family Flavobacteriaceae, suggesting that the members of Flavobacteriaceae maybe the major reservoir of tet(X14). Our study reports a novel chromosome-encoded tigecycline resistance gene tet(X14). The expanded members of Tet(X) family warrants the potential large-scale dissemination and the necessity of continuous surveillance for tet(X)-mediated tigecycline resistance.

The potential impact of the COVID-19 pandemic on global antimicrobial and biocide resistance: an AMR Insights global perspective

The COVID-19 pandemic presents a serious public health challenge in all countries. However, repercussions of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infections on future global health are still being investigated, including the pandemic’s potential effect on the emergence and spread of global antimicrobial resistance (AMR). Critically ill COVID-19 patients may develop severe complications, which may predispose patients to infection with nosocomial bacterial and/or fungal pathogens, requiring the extensive use of antibiotics. However, antibiotics may also be inappropriately used in milder cases of COVID-19 infection. Further, concerns such as increased biocide use, antimicrobial stewardship/infection control, AMR awareness, the need for diagnostics (including rapid and point-of-care diagnostics) and the usefulness of vaccination could all be components shaping the influence of the COVID-19 pandemic. In this publication, the authors present a brief overview of the COVID-19 pandemic and associated issues that could influence the pandemic’s effect on global AMR.

Alteration of the Gut Microbiome in Chronic Kidney Disease Patients and Its Association With Serum Free Immunoglobulin Light Chains

Objectives

Gut dysbiosis is associated with chronic kidney disease (CKD), and serum free immunoglobulin light chains (FLCs) are biomarkers for CKD. This study aims to assess the CKD gut microbiome and to determine its impact on serum FLC levels.

Methods

To control for confounders, 100 patients and sex- and age-matched healthy controls (HCs) were recruited. The gut microbiome was assessed by sequencing 16S rRNA gene V3-V4 hypervariable regions. Phylogenetic Investigation of Communities by Reconstruction of Unobserved States was applied to infer functional metabolic pathways. When observing group differences in the microbiome and predicted metabolic pathways, demographic confounders were adjusted using binary logistic regression; when examining impacts of the gut microbiome and metabolic pathways on serum FLCs, factors influencing FLC levels were adjusted using multiple regression.

Results

Principal coordinate analysis revealed a significantly different bacterial community between the CKD and HC groups (P < 0.05). After adjusting for confounders, lower Chao 1, observed species and Shannon indices based on binary logistic regression predicted CKD prevalence. Actinobacteria, Alistipes, Bifidobacterium and Bifidobacterium longum enrichment, upregulation of metabolic pathways of bacterial toxin, chloroalkane and chloroalkene degradation, and Staphylococcus aureus infection also predicted CKD prevalence (P < 0.05). Furthermore, depletion of Actinobacteria and Bifidobacterium and reduced chloroalkane and chloroalkene degradation predicted high levels of FLC λ (P < 0.05).

Conclusions

Gut dysbiosis in CKD patients was confirmed by controlling for confounders in the present study. Additionally, the association between gut dysbiosis and FLC λ levels demonstrates the existence of crosstalk between the microbiome and immune response in CKD.

Optimal empiric treatment for KPC-2-producing Klebsiella pneumoniae infections in critically ill patients with normal or decreased renal function using Monte Carlo simulation

BACKGROUND

Limited clinical studies describe the pharmacodynamics of fosfomycin (FOS), tigecycline (TGC) and colistin methanesulfonate (CMS) in combination against KPC-producing Klebsiella pneumoniae (KPC-Kp). Population pharmacokinetic models were used in our study. Monte Carlo simulation was conducted to calculate probability of target attainment (PTA) and cumulative fraction of response (CFR) of each agent alone and in combination against KPC-Kp in patients with normal or decreased renal function.

RESULTS

The simulated regimen of FOS 6 g q8h reached ≥90% PTA against a MIC of 64 mg/L in patients with normal renal function. For patients with renal impairment, FOS 4 g q8h could provide sufficient antimicrobial coverage against a MIC of 128 mg/L. And increasing the daily dose could result to the cut-off value to 256 mg/L in decreased renal function. For TGC, conventional dosing regimens failed to reach 90% PTA against a MIC of 2 mg/L. Higher loading and daily doses (TGC 200/400 mg loading doses followed by 100 mg q12h/200 mg q24h) were needed. For CMS, none achieved 90% PTA against a MIC of 2 mg/L in normal renal function. Against KPC-Kp, the regimens of 200/400 mg loading dose followed by 100 q12h /200 mg q24h achieved > 80% CFRs regardless of renal function, followed by CMS 9 million IU loading dose followed by 4.5/3 million IU q12h in combination with FOS 8 g q8h (CFR 75-91%).

CONCLUSIONS

The use of a loading dose and high daily dose of TGC and CMS in combination with FOS can provide sufficient antimicrobial coverage against critically ill patients infected with KPC-Kp.

A novel dentin bonding scheme based on extrafibrillar demineralization combined with covalent adhesion using a dry-bonding technique

Dentin bonding is a dynamic process that involves the penetration of adhesive resin monomers into the extrafibrillar and intrafibrillar demineralized collagen matrix using a wet-bonding technique. However, adhesive resin monomers lack the capacity to infiltrate the intrafibrillar space, and the excess water that is introduced by the wet-bonding technique remains at the bonding interface. This imperfectly bonded interface is inclined to hydrolytic degradation, severely jeopardizing the longevity of bonded clinical restorations. The present study introduces a dentin bonding scheme based on a dry-bonding technique, combined with the use of extrafibrillar demineralization and a collagen-reactive monomer (CRM)-based adhesive (CBA). Selective extrafibrillar demineralization was achieved using 1-wt% high-molecular weight (MW) carboxymethyl chitosan (CMCS) within a clinically acceptable timeframe to create a less aggressive bonding substance for dentin bonding due to its selectively extrafibrillar demineralization capacity. CMCS demineralization decreased the activation of in situ collagenase, improved the shrinking resistance of demineralized collagen, and thus provided stronger and more durable bonding than traditional phosphoric acid etching. The new dentin bonding scheme that contained CMCS and CBA and used a dry-bonding technique achieved an encouraging dentin bonding strength and durability with low technical sensitivity. This bonding scheme can be used to improve the stability of the resin-dentin interface and foster the longevity of bonded clinical restorations.

The antibacterial effect and physical performance of pit and fissure sealants based on an antibacterial core-shell nanocomposite

The application of pit and fissure sealants is a well-established method to prevent and treat early childhood caries. Resin-based sealants with antibacterial properties provide additional benefits for caries prevention in a cariogenic oral environment. The objective of this study was to evaluate the effect of an antibacterial core-shell AgBr/cationic polymer nanocomposite (AgBr/BHPVP) on the properties of a resin-based pit and fissure sealant. A commercialized pit and fissure sealant without fluoride, Concise (3M, ESPE, USA), was used as the parent material and negative control. Experimental antibacterial sealants were formulated by the addition of AgBr/BHPVP nanoparticles at mass fractions of 0.5, 1.0, and 1.5 wt% to the parent material. A fluoride-releasing sealant, Clinpro (3M, ESPE), was used as the positive control. Bacterial colony-forming unit (CFU) counts, metabolic activity tests, field emission-scanning electron microscopy (FE-SEM), and confocal laser scanning microscopy (CLSM) observations were used to evaluate the antibacterial properties of AgBr/BHPVP-modified sealants against Streptococcus mutans before and after five months of aging. The Vickers microhardness, degree of conversion, and microleakage level of the sealants were also investigated. According to the results of CFU counts and metabolic tests, sealants containing AgBr/BHPVP showed better contact-killing bactericidal activity against S. mutans than the two commercial sealants, irrespective of aging conditions (both P < 0.05). The AgBr/BHPVP-modified sealants also showed a significant inhibitory effect on the planktonic S. mutans around the cured sealant surfaces. In addition, the Vickers microhardness, degree of conversion, and microleakage level of the parent material were not damaged by modification with AgBr/BHPVP (P > 0.05). AgBr/BHPVP-modified pit and fissure sealant with a dual bactericidal mechanism is a promising option for the prevention of pit and fissure caries.

Change in Antibiotic Use in Secondary and Tertiary Hospitals Nationwide After a National Antimicrobial Stewardship Campaign Was Launched in China, 2011-2016: An Observational Study

BACKGROUND

An antimicrobial stewardship campaign was launched in 2011 by the Ministry of Health. This study aimed to assess the achievements and trends in the clinical use of antibiotics in secondary and tertiary hospitals following this campaign in China.

METHODS

This observational study analyzed nationwide hospital antibiotic procurement and consumption data and antibiotic-resistance surveillance data based on claims filed in 2010-2016.

RESULTS

After a 6-year national campaign, the proportion of outpatients and surgical patients who received antibiotic treatment decreased from 19.5% to 8.5% and from 97.9% to 38.3%, respectively. The intensity of antibiotic use among inpatients decreased from 85.3±29.8 defined daily dosage (DDD) per 100 patient days to 48.5±8.0 DDD per 100 patient days. Moreover, the antibiotic procurement expenditure among hospitals declined from 22.3% of total drug procurement costs in 2010 to 12.1% in 2016, although total drug procurement costs doubled during that time. The incidence of methicillin-resistant Staphylococcus aureus isolates also dropped (from 54.4% in 2010 to 34.4% in 2016), as did the proportion of carbapenem-resistant Pseudomonas aeruginosa isolates (from 30.8% to 22.3%).

CONCLUSIONS

The 6-year campaign successfully reduced antibiotic consumption and irrational drug use in Chinese hospitals which was associated with declines in the prevalence of common antibiotic-resistant bacteria.

A Retrospective Analysis of Risk Factors and Outcomes of Carbapenem-Resistant Klebsiella pneumoniae Bacteremia in Nontransplant Patients

BACKGROUND

Carbapenem-resistant Klebsiella pneumoniae (CRKP) has become a major problem among nosocomial infections, and it is a serious threat to patients. The clinical characteristics and outcome of CRKP bloodstream infection (BSI) in nontransplant patients remains unelucidated. The aim of this study was as follows: identify the risk factors of CRKP infection; generate new ideas for prevention; and generate new ideas for the most effective therapeutic management in nontransplant patients.

METHODS

The study retrospectively analyzed the clinical and microbiological data of nontransplant patients with K pneumoniae (KP) bacteremia from January 2013 to December 2015 to identify risk factors, clinical features, and outcomes using multivariate logistic regression analysis.

RESULTS

Of the 371 patients with KP-BSI in nontransplant patients included in this study, 28.0% (N = 104) had CRKP. The 28-day mortality was higher in patients infected with CRKP (55.8%) than in those with carbapenem-susceptible KP (13.9%) (P < .001). Multivariate analysis showed previous gastric catheterization, previous use of carbapenems, hypoproteinemia, and high Acute Physiologic Assessment and Chronic Health Evaluation II scores as independent risk factors for CRKP-BSIs. Carbapenem-resistant KP infection, severe illness, and tigecycline therapy were independent risk factors for death from KP-BSIs. Taken together, inappropriate antibiotic treatment both in empirical and definitive therapy and imipenem minimum inhibitory concentrations (MICs) of >8 mg/L were associated with poor clinical outcome.

CONCLUSIONS

Nontransplant patients with CRKP-BSI had higher mortality. Carbapenems exposure was an independent risk factor for CRKP infection. Imipenem MICs of >8 mg/L, tigecycline therapy, and inappropriate treatments increased the 28-day mortality of KP-BSI patients.

CaMK II/Ca2+ dependent endoplasmic reticulum stress mediates apoptosis of hepatic stellate cells stimulated by transforming growth factor beta 1

Previous studies by our group have demonstrated that the calcium imbalance in rat hepatic stellate cells (HSCs) can induce endoplasmic reticulum stress (ERS) and promote cell apoptosis. KN-62, an inhibitor of Calmodulin kinase II (CaMK II), can decrease the expression of CaMK II that plays a major role in regulating the steady state of intracellular Ca2+. Uridine triphosphate (UTP) plays a biological role in increasing indirectly the level of intracellular Ca2+. In the experiment, we demonstrate that KN-62 and UTP can inhibit the proliferation and promote the apoptosis in HSCs, increase the level of intracellular Ca2+ and the expression of ERS protein GRP78, and increase the apoptosis protein Caspase-12 and Bax expression, while decrease the expression of Bcl-2 protein. Our findings indicate that the CaMK II/Ca2+ signaling pathway regulates the ERS apoptosis pathway and induces HSC apoptosis.

Wza gene knockout decreases Acinetobacter baumannii virulence and affects Wzy-dependent capsular polysaccharide synthesis

To investigate the virulence of capsular polysaccharide export protein (Wza) in carbapenem-resistant Acinetobacter baumannii and its effect on capsule formation.

wza gene knockout and complementation strains were constructed, and changes in bacterial virulence were observed using in vitro adhesion, antiserum complement killing, anti-oxidation experiments, and infections in Galleria mellonella and mice. The effect of wza knockout on the genes wzb and wzc and wzi were assessed by RT-PCR.

We successfully constructed wza knockout and complementation strains. Compared with wild-type (WT) strains, wza knockout strains displayed lower adhesion to A549 cells (p = 0.044), lower antiserum complement killing ability (p = 0.001), and lower mortality of G. mellonella (p = 0.010) and mice (p = 0.033). Expression levels of wzb, wzc and wzi were decreased in wza knockout strains. The antioxidant capacity of Wza knockout bacteria was only slightly decreased. Complementation of the wza gene returned the adhesion ability, antiserum complement killing ability, and mortality of G. mellonella and mice to WT levels. Expression of wzb, wzc and wzi was also returned to WT levels following wza complementation.

The results clearly demonstrate that Wza is toxic. Wza affects the expression of other proteins of the Wzy capsule polysaccharide synthesis pathway, which affects the assembly, export, and extracellular fixation of capsular polysaccharide, resulting in synergistic effects that decrease bacterial virulence.