Molecular epidemiology of clinical isolation of carbapenem-resistant Enterobacterales and application of carbapenemase inhibitor enhancement test / 中南大学学报(医学版)

OBJECTIVES@#The prevalence of carbapenem-resistant Enterobacterales (CRE) presents a significant challenge in clinical anti-infective treatment. This study aims to investigate drug resistance and the molecular epidemiological characteristics of CRE in our area. Additionally, we seek to evaluate practicality of utilizing carbapenemase inhibitor enhancement test in clinical laboratory.@*METHODS@#Non-repeated CREs isolated from clinical specimens at Xiangya Hospital, Central South University, were collected. Minimum inhibitory concentration (MIC) combined with Kirby-Bauer (KB) assay was used to detect the drug susceptibility of the strains, and 13 carbapenemase-producing genes were detected by PCR. The phenotype of 126 strains of carbapenemase-producing Enterobacterales identified by PCR was detected by the carbapenemase inhibitor enhancement test to understand the agreement between the method and the gold standard PCR results.@*RESULTS@#Among 704 CRE strains examined, we observed significant drug resistance in 501 strains dentified as carbapenemase-producing Enterobacterales (CPE). Klebsiella pneumoniae was the predominant CPE strain, followed by Enterobacter cloacae and Escherichia coli. A total of 9 carbapenemase types were detected, including Klebsiella pneumoniae carbapenemase (KPC), New Delhi metallo-β-lactamase (NDM), Verona integron- encoded metallo-β-lactamases (VIM), imipenemase (IMP), oxacillinase-48 (OXA-48), and rare imipenem-hydrolyzing β-lactamase (IMI), adelaide imipenemase (AIM), Bicêtre carbapenemase (BIC), and guiana extended-spectrum β-lactamase (GES). The detection rate of KPC serine carbapenemase was 61.7% (309/501). The carbapenemase inhibitor enhancement test exhibited a 100% consistency rate for the strains producing Class A serine carbapenemase and/or Class B metallo-β-lactamases.@*CONCLUSIONS@#CRE strains in Changsha, Hunan, China, are wide distribution and exhibit carbapenemase production. The main mechanism of carbapenem resistance in these bacterias is predominatly attributed to the production of KPC serine carbapenemase. The presence of GES and IMI genes carried by Enterobacterales has been detected for the first time in this region. The carbapenemase inhibitor enhancement test has been proven to be an accurate method for detecting CRE producing Class A serine carbapenemase and/or Class B metallo-β-lactamases. This method offers simpicity of operation and ease of results interpretation, making it weel-suited meeting the clinical microbiology laboratory's reguirements for the detection of serine carbapenemase and metallo-β-lactamases.

Distribution,antimicrobial resistance of pathogens from blood culture,and risk factors for death of children with leukemia / 中国感染控制杂志

Objective To observe distribution and antimicrobial resistance of pathogens from blood culture of chil-dren with leukemia,and study risk factors.Methods From September 2013 to November 2016,species and antimi-crobial resistance types of 131 strains of pathogens isolated from blood culture of 110 children in a pediatric hemato-logy ward were analyzed,childrens'clinical data were also analyzed statistically.Results 131 strains(5.23%)of pathogens were isolated from 2 505 blood culture specimens,gram-negative bacilli and gram-positive cocci accounted for 52.67% and 43.51% respectively,the top 3 pathogens were Escherichia coli(15.27%),Klebsiella pneumoniae (15.27%),and Staphylococcus hominis(12.98%). Gram-negative bacilli were highly resistant to ampicillin,ce-fazolin,ceftriaxone,and ampicillin/sulbactam,but sensitive to amikacin,cefoperazone/sulbactam,piperacillin/tazobactam,and carbapenems;gram-positive cocci had higher resistance to penicillin,oxacillin,erythromycin,and clindamycin,but were sensitive to tigecycline,linezolid,vancomycin,and quinupristin/dalfopristin. Univariate analysis showed that mixed infection,diarrhea,Pseudomonasaeruginosa infection,and Acinetobacterbaumannii in-fection were related to mortality due to bloodstream infection in children with leukemia.Conclusion Pathogens cau-sing bloodstream infection in children with leukemia is widely distributed,antimicrobial resistance rate is high,it is very im-portant to take active precaution and rational treatment according to antimicrobial susceptibility testing result.

Comparison of antimicrobial resistance of Pseudomonas aeruginosa from intensive care units and general wards in a hospital in 2016 / 中国感染控制杂志

Objective To investigate the distribution and antimicrobial resistance of Pseudomonas aeruginosa (P.aeruginosa) from intensive care units(ICUs) and general wards of a hospital,and provide scientific basis for rational use of antimicrobial agents in clinic.Methods Identification and antimicrobial susceptibility testing of clinically isolated bacteria in this hospital in 2016 were performed by VITEK 2 Compact automatic microbial analysis system,difference in antimicrobial resistance of P.aeruginosa between ICUs and general wards was compared.Results The tested specimens were mainly sputum in both ICUs and general wards,accounting for 78.7％ and 66.5％ respectively.There was no significant difference in the isolation rate of P.aeruginosa between ICUs and general wards (11.7％ vs 11.0％,P＞0.05).P.aeruginosa isolated from ICUs had the highest resistance rate to aztreonam (73.8％),resistance rates to piperacillin/tazobactam,cefoperazone/sulbactam,ceftazidime,imipenem,and meropenem were all up to more than 50％;P.aeruginosa detected in general wards had the highest resistance rate to aztreonam(59.6 ％),followed by piperacillin/tazobactam and imipenem,accounting for 48.0 ％ and 44.3 ％ respectively;resistance rates of P.aeruginosa isolated from ICUs to 12 kinds of antimicrobial agents were all higher thanthose of general wards(P＜0.05).Conclusion Resistance rate of P.aeruginosa from ICUs is higher than that in general wards,which should be paid attention,antimicrobial agents should be selected for clinical treatment of infection according to the results of antimicrobial susceptibility testing result.

Emergence of methicillin-resistant Staphylococcus aureus SCCmec type IV/V epidemic clones in a large teaching hospital in China / 南方医科大学学报

<p><b>OBJECTIVE</b>To investigate the staphylococcal cassette chromosome mec (SCCmec) genotype and molecular epidemiological characteristics of healthcare-associated methicillin-resistant Staphylococcus aureus (HA-MRSA) in a large teaching hospital in China.</p><p><b>METHDOS</b>From January 2012 to December 2012, a total of 71 nonduplicate HA-MRSA were collected in a teaching hospital in Changsha, China. SCCmec types were determined by multiplex PCR, and Panton-Valentine leukocidin (PVL) gene was detected by PCR. The homology among the tested isolates was determined using pulsed-field gel electrophoresis (PFGE).</p><p><b>RESULTS</b>Of the 71 HA-MRSA isolates, 49 (69.0%) carried SCCmec III, 10 (14.1%) carried SCCmec IV, 3 (4.2%) carried SCCmec V and 3 (4.2%) carried SCCmec II; the remaining 6 isolates were not typeable by PCR. Compared with patients having SCCmec I/II/III MRSA infections, those with SCCmec IV/V MRSA infections had a significantly younger age and a similar duration of hospital stay before the first MRSA-positive culture and total hospital stay. PVL genes were strongly associated with SCCmec type IV/V MRSA infections. HA-SCCmec IV/V MRSA strains showed a greater susceptibility to rifampicin, gentamicin, levofloxacin, ciprofloxacin, and tetracycline than HA-SCCmec I/II/III MRSA strains. The 13 HA-SCCmec IV/V MRSA isolates formed one large group at the 55% similarity level. Three PFGE clusters with a similarity index of 85% or more were identified, and unique PFGE profiles were observed in 4 isolates.</p><p><b>CONCLUSION</b>This is the first report of HA-MRSA isolates carrying SCCmec V in Chinese hospitals. SCCmec types IV and V MRSA clones have emerged in Chinese hospitals, which urges more rigorous surveillance of their spread in healthcare facilities in China.</p>

AdeABC efflux pump and resistance of Acinetobacter baumannii against carbapenem / 中南大学学报(医学版)

Objective:To investigate relationship between AdeABC efflux pump and resistance of Acinetobacter baumannii against carbapenem.Methods:Carbapenem-resistant strains were acquired from multistep selection resistance test by meropenem in vitro.The quantitation test for sensitivities of strains before and after induction was determined by the E-test,and carbonylcyanide-m-chlorophenylhydrazone (CCCP) inhibition test was used to screen efflux pump.PCR,sequencing analysis,or real-time PCR was used to analyze the changes of regulatory genes adeR and adeS of the AdeABC efflux pump system,or expressions of adeA,adeB,adeR,and adeS in the strains before and after induction,respectively.Results:The minimal inhibitory concentrations (MICs) of meropenem were at 0.38 μg/mL and 0.25 μg/mL in parental sensitive strain S25595 and S7257,respectively,and the MICs of meropenem for both S25595 and S7257 after induction were more than 32 μg/mL.Compared with parental sensitive strains,the expression level of adeA,adeB,adeR,and adeS mRNA were elevated from 2.45 to 9.44 times,but there were no gene mutations or insertion sequences in the regulatory gene adeS and adeR.Conclusion:High expression of the AdeABC efflux pump system in Acinetobacter baumannii is closely associated with meropenem resistance,The upregulation of adeA and adeB expression is not due to gene mutations in the regulatory gene adeS and adeR and other mechanisms might account for it.

An Outbreak of Infections Caused by a Klebsiella pneumoniae ST11 Clone Coproducing Klebsiella pneumoniae Carbapenemase-2 and RmtB in a Chinese Teaching Hospital / 中华医学杂志(英文版)

<p><b>BACKGROUND</b>Klebsiella pneumoniae carbapenemase (KPC)-producing K. pneumoniae bacteria, which cause serious disease outbreaks worldwide, was rarely detected in Xiangya Hospital, prior to an outbreak that occurred from August 4, 2014, to March 17, 2015. The aim of this study was to analyze the epidemiology and molecular characteristics of the K. pneumoniae strains isolated during the outbreak.</p><p><b>METHODS</b>Nonduplicate carbapenem-resistant K. pneumoniae isolates were screened for blaKPC-2and multiple other resistance determinants using polymerase chain reaction. Subsequent studies included pulsed-field gel electrophoresis (PFGE), multilocus sequence typing, analysis of plasmids, and genetic organization of blaKPC-2locus.</p><p><b>RESULTS</b>Seventeen blaKPC-2-positive K. pneumoniae were identified. A wide range of resistant determinants was detected. Most isolates (88.2%) coharbored blaKPC-2and rmtB in addition to other resistance genes, including blaSHV-1, blaTEM-1, and aac(3)-IIa. The blaKPC-2and rmtB genes were located on the conjugative IncFIB-type plasmid. Genetic organization of blaKPC-2locusin most strains was consistent with that of the plasmid pKP048. Four types (A1, A2, A3, and B) were detected by PFGE, and Type A1, an ST11, was the predominant PFGE type. A novel K. pneumoniae sequence type (ST1883) related to ST11 was discovered.</p><p><b>CONCLUSIONS</b>These isolates in our study appeared to be clonal and ST11 K. pneumoniae was the predominant clone attributed to the outbreak. Coharbing of blaKPC-2and rmtB, which were located on a transferable plasmid, in clinical K. pneumoniae isolates may lead to the emergence of a new pattern of drug resistance.</p>

Research advance in Clostridium difficile vaccine / 中华检验医学杂志

The risk factors of Clostridium difficile infections increased in recent years , such as the underlying disease, hospitalization duration, age, the use of antibiotics, the use of proton pump inhibitors and so on.The rate of Clostridium difficile infection and recurrence are still high despite the appear of new antibiotics such as rifaximin, nitazoxanide, tigecycline, ramoplanin, fidaxomicin, and non-antimicrobial such as drugs toxin neutralizer chamber , biological therapeutic agents , fecal transplantation , systemic antibody method , intravenous immunoglobulin and so on.The vaccine is the most ideal way of prevention and treatment of Clostridium difficile infection.The research in Clostridium difficile vaccine lasted for nearly 20 years.Except the monoclonal antibody vaccine and toxoid vaccine against toxin A and toxin B have achieved better results in the human , some recombinant vaccines against the toxin receptor and the key pathogenic factor of Clostridium difficile also achieved good effect in animal.

Novel species including Mycobacterium fukienense sp. is found from tuberculosis patients in Fujian Province, China, using phylogenetic analysis of Mycobacterium chelonae/abscessus complex / 生物医学与环境科学（英文）

<p><b>OBJECTIVE</b>To identify the novel species 'Mycobacterium fukienense' sp. nov of Mycobacterium chelonae/abscessus complex from tuberculosis patients in Fujian Province, China.</p><p><b>METHODS</b>Five of 27 clinical Mycobacterium isolates (Cls) were previously identified as M. chelonae/abscessus complex by sequencing the hsp65, rpoB, 16S-23S rRNA internal transcribed spacer region (its), recA and sodA house-keeping genes commonly used to describe the molecular characteristics of Mycobacterium. Clinical Mycobacterium isolates were classified according to the gene sequence using a clustering analysis program. Sequence similarity within clusters and diversity between clusters were analyzed.</p><p><b>RESULTS</b>The 5 isolates were identified with distinct sequences exhibiting 99.8% homology in the hsp65 gene. However, a complete lack of homology was observed among the sequences of the rpoB, 16S-23S rRNA internal transcribed spacer region (its), sodA, and recA genes as compared with the M. abscessus. Furthermore, no match for rpoB, sodA, and recA genes was identified among the published sequences.</p><p><b>CONCLUSION</b>The novel species, Mycobacterium fukienense, is identified from tuberculosis patients in Fujian Province, China, which does not belong to any existing subspecies of M. chelonea/abscessus complex.</p>

Antimicrobial resistance and molecular epidemiological characteristics of clinical isolates of Staphylococcus aureus in Changsha area / 中华医学杂志(英文版)

<p><b>BACKGROUND</b>Increasing prevalence of Staphylococcus aureus (S. aureus), particularly methicillin-resistant S. aureus (MRSA) has been reported in China. In this study, we investigated the drug resistance characteristic, genetic background, and molecular epidemiological characteristic of S. aureus in Changsha.</p><p><b>METHODS</b>Between January 2006 and December 2008, 293 clinical isolates of S. aureus were collected from 11 hospitals in Changsha and identified by the Vitek-2 system. All the isolates were verified as MRSA by PCR amplification of both femA and mecA genes. K-B disk method was used to test drug sensitivity of S. aureus to antibiotics. Pulsed-field gel electrophoresis (PFGE) was performed for genotypic and homologous analysis of 115 isolates randomly selected from the original 293 clinical S. aureus isolates.</p><p><b>RESULTS</b>S. aureus was highly resistant to penicillin, ampicillin, erythromycin, and clindamycin with resistant rates of 96.6%, 96.6%, 77.1%, and 67.2% respectively. All the isolates were susceptible to tecoplanin, vancomycin, and linezolid. MRSA accounted for 64.8% (190/293) of all the S. aureus strains. The 115 S. aureus isolates were clustered into 39 PFGE types by PFGE typing, with 13 predominant patterns (designated types A to M) accounting for 89 isolates. The most prevalent PFGE type was type A (n = 56, 48.7%) and 100.0% of type A strains were MRSA. PFGE type A included 13 subtypes, and the most prevalent subtype was subtype A1 (46.4%, 26/56). Strains with PFGE type A were isolated from eight hospitals (8/11), and both subtypes A1 and A4 strains were isolated in a university hospital.</p><p><b>CONCLUSIONS</b>Clinical isolates of S. aureus in Changsha were resistant to multiple traditional antibiotics. There was an outbreak of PFGE type A MRSA in this area and the A1 subtype was the predominant epidemic clone. Dissemination of the same clone was an important reason for the wide spread of MRSA.</p>

NDM-1-producing Klebsiella pneumoniae in mainland China / 中国当代儿科杂志

<p><b>OBJECTIVE</b>To investigate the characteristics of New Delhi metallo-beta-lactamase-1 (NDM-1) gene of Klebsiella pneumoniae (K. pneumoniae) emerging in Hunan, and its relationship to antibiotic resistance.</p><p><b>METHODS</b>The clinical strain was isolated from a sputum sample of a child with severe pnemonia and toxic myocarditis who was admitted into a general hospital of Hunan Province. VITEK-2 compact instrument was used for bacterial identification and antibiotic susceptibility test. Modified Hodge test was used for the screening of carbapenemase. EDTA-synergy test and combination disk diffusion test were used for detection of metallo-β-lactamase (MBL). PCR was performed for amplification of NDM-1 genes and the positive products were sequenced and analyzed with BLAST. Conjugation was also performed to analyze mechanisms of antibiotic resistance. The results of antibiotic susceptibility tests were compared before and after conjugation.</p><p><b>RESULTS</b>The isolated strain was identified as K.pneumoniae. Modified Hodge test, EDTA-synergy test and combination disk diffusion test were all positive for the strain. The homology between gene sequence of PCR amplification products and NDM-1 gene FN396876.1 in the GenBank was 100%. Transconjugant DNA was used as template for the amplification of NDM-1 gene. The amplification products were sequenced and found to be the same as the NDM-1 gene amplification product of the donor strain. The MIC of transconjugant E.coli J53 (NDM-1) to all the β-lactams increased significantly compared with the recipient strain E.coli J53. The MIC of ertapenem and imipenem increased by more than 8 times, while the MIC of ceftazidime and ceftriaxone increased by more than 64 times.</p><p><b>CONCLUSIONS</b>This study first identified a strain of K. pneumoniae carrying NDM-1 in mainland China. NDM-1 gene can be transmitted among different strains and causes extensively drug-resistance to β-lactams.</p>

Cytomegalovirus infection and immunosuppressant treatment in allogeneic hematopoietic stem cell transplantation recipients / 中南大学学报(医学版)

OBJECTIVE@#To explore the correlation between peripheral blood cytomegalovirus (CMV) DNA level and cyclosporine A (CsA) plasma concentration among allogeneic hematopoietic stem cell transplantation (allo-HSCT) recipients who received immunosuppressant treatment, and to evaluate the potential clinical value.@*METHODS@#A total of 32 allo-HSCT patients were enrolled and their data were analyzed retrospectively. Ganciclovir was used to prevent CMV infection before the transplantation. Routine fluorescence PCR was admitted to test the blood CMV DNA level. The patients were divided into 2 groups: a CMV DNA positive group and a CMV DNA negative group. Enzyme multiplied immunoassay technique was adopted regularly to monitor the blood CsA concentration. The correlation between CMV DNA level and CsA concentration was analyzed.@*RESULTS@#The CMV infection rate in patients who received allo-HSCT was 53.13%. The blood CsA concentration in the CMV DNA positive group was significantly higher than that in the CMV DNA negative group (P<0.05). Through the ROC curve, the area under the curve on Day 1, 7, and 14 had statistical significance compared with 0.5, and the corresponding blood CsA concentration was 203.15, 215.55, and 302.65 ng/mL, respectively.@*CONCLUSION@#Immunosuppressive drug concentration can affect the dynamic changes of CMV DNA. High blood CsA concentration may be one of the reasons for CMV infection. Monitoring the blood CsA concentration may provide guidance for clinical treatment.

Emergence of AmpC enzyme and antibiotics resistance in gram-negative bacilli / 中南大学学报(医学版)

OBJECTIVE@#To investigate the relationship between emergence of AmpC enzyme and drug resistance in the gram-negative bacilli in Xiangya Hospital and to provide information for the treatment of antibiotics.@*METHODS@#The bacteria were identified; the susceptibility was determined by Microscan microbiological identification system; and the AmpC enzyme was detected by disc diffusion method.@*RESULTS@#Of the 204 gram-negative strains, the positive rate of AmpC enzyme was 19.61%; AmpC-positive strains resisted to ceftriaxone, piperacillin, ceftazidime, cefotaxime, cefoperazone, aztreonam, piperacillin/tazobactam, cefuroxime, ceftazidime/clavulanic, and cefotaxime/clavulanic. But AmpC-negative strains were susceptible to those antibiotics. There were significant differences, between the two groups (All P < 0.05). Both groups were susceptible to cefepime, imipenem, meropenem, cefoperazone/sulbactam, levofloxacin, and amikacin.@*CONCLUSION@#The detection of AmpC enzyme is helpful to the screen of drug resistant strains. Most bacilli with AmpC enzyme show the resistance to third-generation cephosporins, aztreonam, and the beta-lactamase inhibitors, but susceptible to imipenem, cefepime, meropenem, cefoperazone/sulbactam, levofloxacin, and amikacin, which provides the information for the antibiotic therapy.