Identification and distribution of the clinical isolates of imipenem-resistant Pseudomonas aeruginosa carrying metallo-β-lactamase and/or class 1 integron genes

To investigate the distribution of the genes of two major metallo-β-1actamases （MBL;i.e.,IMP and VIM） and class 1 integrons （intI） in the clinical imipenem-resistant Pseudomonas aeruginosa, a total of 65 isolates, from a university hospital in Sichuan between December 2004 and April 2005 were screened for MBL genes by PCR using primers specific for blaIMP-1, blaVIM and blaVIM-2 genes. The MBL-positive isolates were further assessed for class 1 integrons by PCRusing specific primers. The nucleotide sequences of several PCR products were also determined. The results revealed that the blaVIM gene was found in 81.5% （53/65） of all isolates, blaVIM-2 gene was found in only 1 isolate and the intl gene was observed in 45.3% （24/53） of blaVIM-positive isolates. One isolate carried simultaneously both blaIMP-1 and intl genes, and to the best of our knowledge this is the first report of such isolate in southwest China. These observations highlight that the genes for VIM β-1actamase and class 1 integrons were predominantly present among the imipenem-resistant P. aeruginosa tested, confirming the current widespread threat of imipenem-resistant, integron-borne P.aeruginosa.     

Characterization of multidrug-resistant and metallo-beta- lactamase-producing Pseudomonas aeruginosa isolates from a paediatric clinic in China

Background In the present study, we characterized multidrug-resistant Pseudomonas aeruginosa （MDRP） clinical isolates from a paediatric facility and investigated the types and features of the metallo-β-lactamases （MBLs） produced by carbapenem-resistant strains. Methods Four hundred and ninety-eight strains of Pseudomonas aeruginosa were isolated from patients at Beijing Children＇s Hospital between January 2005 and December 2006. The minimal inhibition concentrations （MICs） of the strains for 13 antibiotics were measured. A combination of the E test and PCR amplification/DNA sequencing was used to define the carbapenem-resistant strains. Results We found that 24.1% （120/498） of the isolates were MDRP. The frequencies of resistance to imipenem and meropenem were 34.2% and 35.8%, respectively, and the MIC50 and MIC90values for the two antibiotics were identical at 4 pg/ml and 32 pg/ml, respectively. The detection rate for carbapenem resistance was 49.2% （59/120）. Among the 59 carbapenem-resistant Pseudomonas aeruginosa strains, 39 （66.1%） were positive for the MBL genotype; 35 （89.7%） strains carried the blaiMp gene and 4 （10.3%） strains carried the blavm gene. Neither blasPM nor blaGiM was amplified from any of the 59 isolates. DNA sequencing revealed that IMP-1 was present in 35 IMP-producing isolates and VIM-2 was detected in four VIM-producing isolates. Conclusions These MDRP isolates exhibited high frequencies of resistance to carbapenems among clinical isolates from a paediatric facility in Beijing, China. The production of MBL appears to be an important mechanism for carbapenem resistance in Pseudomonas aeruginosa.     

Characterization of Class 1 Integron Gene Cassettes among Clinical Bacteria Isolated from One Large Hospital in Northern China

The class 1 integron and complex gene cassettes among different species of clinical isolates in northern China were characterized in this study. 383 clinical isolates were obtained from northern China, and class 1 integrons containing gene cassettes widely distributed among gram negative clinical isolates was observed. We find that the class 1 integron showed positive correlation with multidrug resistance phenotype of gram negative bacteria. In addition, we find that isolates belonged to one species harbored different types of gene cassette arrays, while same types of gene cassette arrays were observed in different species of isolates. The diversity of gene cassette arrays among the isolates indicated the complexity of multidrug resistance in clinical isolates in northern China.     

Prevalence of β-lactamase and Antimicrobial Resistance among Clinical Pseudomonas Aeruginosa Isolates

Pseudomonas aeruginosa is the most common pathogen with an increasing resistance to antimicrobials. The objective of this study was to investigate the prevalence of β-lactamases and their relationships to β-lactam resistance in clinical isolates of P. aeruginosa. A total of 101 consecutive, non-duplicate isolates of P. aeruginosa were studied. Minimum inhibitory concentrations （MICs） of eight kinds of antibacterial agents were determined by the agar dilution method. AmpC was identified by the AmpC disk test and metallo-β-lactamases by the inhibitor-potentiated disk diffusion （IPD） test. PCR amplification and sequencing of Ambler class A and D genes were performed. The MICs of all antibacterial agents used in this study were quite high. The MIC90 of piperacillin/tazobactam was achieving to 256μg/ml, and cefoperazone/sulbactam and imipenem MIC90 values were 128μg/ml and 32μg/ml, respectively. The most effective antimicrobial agent was meropenem, however, it still only inhibited 80.2% of P. aeruginosa strains. A total of 56 isolates （55.4%） yielded one or more kinds of β-lactamase and were more resistant than β-lactamase negative isolates. In conclusion, resistance of P. aeruginosa to β-lactams seems very common in our hospital and β-1actamase is a major mechanism. The early recognition of β-1actamase producers is critical for selection of antimicrobial agents in the treatment of clinical infection and for the prevention of their widespread dissemination.     

Subcloning,sequencing and expressing of conserved blocks of P190 gene of Plasmodium falciparum FCC1/HN strain

190-kilodalton glycoprotein (P190) of Plasmodium falciparum,precursor of themajor surface protein of merozoites,is considered a promising candidate for blood stage malarialvaccine.Six primers were designed according to the sequence of MAD20 strain,with a GCclamp and BamH Ⅰ site at the 5'-end of each one,and a GC clamp and Xba Ⅰ site at the 3'-endof each one.The primers were synthesized by phosphoramidite approach (User's Manual ofABI Company) and purified using HPLC.Three fragments in the second,third and fourth con-served regions of P190 gene of Plasrnodium falciparum FCC1/HN strain isolated from theblood of patients in Hainan Province of China were amplified by the polymerase chain reaction(PCR).The amplified fragments were suhcloned into pUC18 vectors and sequenced using thedideoxy chain termination method.All three regions of P190 gene of FCC1/HN strain also werehighly conservative as compared with P190 gene of MAD20 (Papua New Guinea isolate),K1(Thailand isolate),Wellcome (West Africa isolate) and CAMP (Malaysia) strains ofPlasmodium falciparum.The C at position 81 in the second conserved block of P190 gene ofFCC1/HN isolate was substituted by T,which did not change the amino acid determined by thecodon corresponding to the substitution.The genes sequenced were cloned into rpGEX-2T,aglutathione S-transferase gene fusion system for expression.     

Class Ⅰ integron with a novel cassette array in an ESBL-producing multidrug-resistant Klebsiella pneumoniae isolate

Objective： To analyze the molecular mechanism of integron mediated mulfi-resistanc, e in an ESBL-producing K. pneumoniae NJ 12 isolate. Methods： Susceptibility test was carried out by Kirby-Bauer method. Class Ⅰ, Ⅱ and Ⅲ integrons were detected by integrase gene PCR with primers that annealed to conserved regions of integron-encoded integrase genes intll, intl2 and intl3. The variable region of integron was amplified by integron PCR with primers that targeted the conserved flanking regions, and the product was sequenced. Six aminoglycoside modifying-enzyme genes, including ant（2＂）-Ⅰ, ant（3＂）- Ⅰ, aac（3）- Ⅰ, aac（3）-Ⅱ, aac （6＇）-Ⅰ, and aac（6＇）-Ⅱ , were detected. Results： K. pneumoniae NJ 12 was resistant to nine antibiotics, including piperacillin, ampicillin, cefuroxime, ceftazidime, cefotaxime, aztreonam, streptomycin, gentamicin and amikacin. This isolate was shown that there was positive with class Ⅰ integron, ant（2＂）- Ⅰ , ant（3＂）- Ⅰ , aac（3）-Ⅱ and aac（6＇）- Ⅰ modifying-enzyme genes. Neither class Ⅱ nor Ⅲ integron was detected; DNA sequencing of the fragment amplified by integron PCR revealed a novel cassette array aadR-cat-blaoxa-10/ aadA1. Conclusion： Class I integron with a novel cassette array in an ESBL-producing multidrug-resistant K. pneumon/ae NJ 12 isolate was reported from Nanjing area of China, with the GenBank accession number DQ141319.     

Detection of Multi-drug Resistant Acinetobacter Lwoffii Isolated from Soil of Mink Farm

正There were 4 Acinetobacter lwoffii obtained from soil samples.The antimicrobial susceptibility of the strains to 16 antimicrobial agents was investigated using K-B method.Three isolates showed the multi-drug resistance.The presence of resistance genes and integrons was determined using PCR.The aadA 1,aac(3’)-IIc,aph(3')-VII,aac(6’)-Ib,sul2,cat2,floR,and tet(K)genes were detected,respectively.Three class 1 integrons were     

Transconjugation and genotyping of the plasmid-mediated AmpC β-lactamase and extended-spectrum β-lactamase genes in Klebsiella pneumoniae

Bsckgroud AmpC β-lactamases and extended-spectrum β-lactamases （ESBLs） are becoming predominant causes of resistance to third and forth-generation cephalosporins in Klebsiella pneumoniae （K. pneumoniae）. It is very difficult to treat infectious diseases caused by multidrug-resistant K. pneumoniae. The purpose of the present study was to investigate transconjugation and characteristics of β-lactamase genes in K. pneumoniae producing AmpC β-lactamases and ESBLs.
Methods AmpC β-lactamases were detected by three-dimension test and ESBLs by disc confirmatory test. Minimum inhibitory concentrations （MICs） were determined by agar dilution. Transfer of resistance to EC600 （Rifr） was attempted by conjugation in broth and screened on agar containing cefotaxime （2 μg/ml） plus rifampin （1024 μg/ml）. The genes encoding AmpC or ESBLs and their transconjugants were detected by PCR and verified by DNA sequencing.
Results The resistant rates to ampicillin and piperacillin were 100% in 18 isolates of K. pneumoniae. However, imipenem was still of great bactericidal activity on K. pneumoniae, and its MIC50 was 0.5 μg/mL. Eleven β-lactamase genes, including TEM-1, TEM-11, SHV-13, SHV-28, CTX-M-9, CTX-M-22, CTX-M-55, OXA-1, LEN, OKP-6 and DHA-1, were found from 18 isolates. And at least one β-lactamase gene occurred in each isolate. To our surprise, there were six β-lactamase genes in the CZ04 strain. Among 18 isolates of K. pneumoniae, the partial resistant genes in 8 isolates were conjugated successfully, which had 100% homological sequence with donors by sequence analysis. Compared with donors, 8 transconjugants had attained resistance to most β-lactams, including ampicillin, piperacillin, cefoxitin, cefotaxime and aztreonam, or even amikacin and gentamicin.
Conclusions R plasmids can be easily transferred between the resistant and sensitive negative bacilli. It is very difficult to block and prevent the spread of antimicrobial resistance. So more attention should be paid to reducing the frequency, times and dosage of antimicrobials, especially third or fourth cephalosporins.     

Multi-drug resistance and characteristic of integrons in Shigella spp. isolated from China

Objective To investigate the characteristic of integrons and the relationship between integrons and antimicrobial resistance in Shigella spp. Methods Ninety Shigella strains (83 S. flexneri and 7 S. sonnei) were isolated from the stools of patients in China. Susceptibility to 8 antimicrobials was tested for all isolated strains. PCR, RFLP and sequencing analysis of integrons were applied to all of them. Results High prevalence of multi‐drug resistance (95.6%) was identified. Of the isolates 79 (87.8%) carri...     

Emergence of Klebsiella pneumoniae carbapenemase-producing Escherichia coli sequence type 131 in Hangzhou, China

Background Klebsiella pneumoniae carbapenemase （KPC）-producing Escherichia （E.） coil has been reported in China since 2008.However,there is no information about the molecular epidemiology of KPC-producing E.coil in China.In this study,we aimed to investigate the sequence type （ST） and characteristics of KPC-producing E.coil isolates in China.Methods Three carbapenem-resistant isolates of E.coil （E1,E2,and E3） from one teaching hospital in Hangzhou covering a one year period were analyzed.Antibiotic susceptibility was determined by Etest.Pulsed-field gel electrophoresis （PFGE） and multilocus sequence typing （MLST） were used for epidemiological analysis.The genetic structure around blaKPC,the major plasmid incompatibility typing,and the identification of 3-lactamase gene types were performed by PCR and the positive products were subsequently sequenced.Plasmids were analyzed by transformation,restriction,and Southern blotting.Results PFGE demonstrated that patterns of isolates E1 and E2 were clonally-related and designated as patterns A1 and A2; pattern of isolate E3 was different and designated as pattern B.MLST analysis showed that the three isolates displayed one common sequence type ST131.The identification of bla gene types by PCR and sequencing showed that blaKPC-2,blaCTX-M-14,and blaTEM-1 were detected in all three isolates.All three isolates carried a KPC-2-encoding plasmid of the IncN replicon.Plasmid analysis and hybridization experiments showed that the isolates were found simultaneously to carry two or four plasmids.The blaKPc-2 gene in E1 and E2 was located in a plasmid with size of ca.50 kb.However,the blaKPC-2 gene in E3 was located in a plasmid with size of ca.130 kb.Conclusions E.coil ST131 with KPC-2 β-1actamase has emerged in China,which enlarges the geographical area where the ST131 KPC-oroducing E.coil strains have diffused.     

Genetic environment of β-lactamase genes of extended-spectrum β-lactamase-producing Klebsiella pneumoniae isolates from patients with lower respiratory tract infection in China

Background Extended-spectrum β-lactamase （ESBL）-producing Klebsiella pneumoniae （K.pneumoniae） is one of the most popular pathogens that cause refractory respiratory tract infection.The genetic environment,including insertion sequences and the types of promoter,plays a key role in exploration of the mechanism of prevalence and dismission of the ESBL-producing K.pneumoniae isolates.The aim of the investigation was to target analysis the genetic environment and promoter sequences of blaCTX-M,blaSHV and blaTEM,the most popular β-lactamase genes harbored by ESBL-producing K.pneumoniae isolates.Methods From February 2010 to July 2011,158 of 416 K.pneumoniae isolates producing ESBL from patients with lower respiratory tract infection were collected from seven tertiary hospitals from Beijing,Anhui,Fujian,Liaoning,Hebei and Inner Mongolia Autonomous Region in China.The genetic environment including promoters of 10 types of blaCTX-M,18 types of blaSHVand 2 types of blaTEM were analyzed by amplification and direct sequencing with various sets of PCR primers.Results ISEcp1 was located upstream of the 5＇ end of the blaCTX-M gene in 130 （97.0％） out of 134 K.pneumoniae isolates harboring blaCTX-M and provided a conserved promoter to blaCTX-M.A non-coding sequence preceded by kdpC and recF was identified in all of the blaSHV genes except blaSHV-12 and blaSHV-2a.IS26 was also found upstream of 1 blaCTX-M-15,10 blaSHV-1 strains,4 blaTEM-1 and all of the blaSHV-2,blaSHV-2a,blaSHV-5 and blaSHV-12.Eighty-seven of 91 strains harboring blaTEM-1 carried a copy of Tn2 and IS26-blaTEM-1 fragments were also detected in 4 strains.With respect to K.pneumoniae,the genetic environment of blaCTX-M-38,blaSHV-142 and blaTEM-135 were firstly elaborated,and four kinds of novel genetic environment of blaCTX-M-3,blaCTX-M-15 and blaTEM-1 have been detected as well.Conclusions Perfective implementation of the genetic environment information of β-lactamase gene needs to be further explored and supplemented.ISEcp1 and IS26 elements ar     

Analysis of AmpC β-lactamase Gene in Pseudomonas aeruginosa

The gene and the amino acid sequence of the structural and regulatory region of the Pseudomonas aeruginosa with different resistance patterns were analyzed. Six strains with different resistance patterns were selected and the AmpC β-lactamase was identified. The objectivegene fragment was amplified by colonies PCR. The sequences of the PCR-products were analyzed. The DNA sequence of the structural gene ampC and the regulatory genes ampR, ampD and ampE was detected. The 6 strains and the wild-type Pseudomonas aeruginosa are highly homogeneous in structural and regulatory region. Some new mutant points were found.     

Phylogenetic and Molecular Analysis of an H7N7 Avian Influenza Virus Isolated in East Dongting Lake in 2012

Objective In March 2012, an H7N7 subtype avian influenza virus (AIV) named A/wild goose/Dongting/PC0360/2012 (H7N7) (DT/PC0360) was recovered from a wild goose in East Dongting Lake. We performed whole-genome sequencing of the isolate, and analyzed the phylogenetic and molecular characterization.
Methods RNA was extracted from environment samples (including fecal samples from wild bird or domestic ducks, and water samples) for detecting the presence of Influenza A Virus targeting Matrix gene, using realtime RT-PCR assay. The positive samples were performed virus isolation with embryonated eggs. The subtype of the isolates were identified by RT-PCR assay with the H1-H16 and N1-N9 primer set. The whole-genome sequencing of isolates were performed. Phylogenetic and molecular characterizations of the eight genes of the isolates were analyzed.
Results Our results suggested that all the eight gene segments of DT/PC0360 belonged to the Eurasian gene pool, and the HA gene were belonged to distinct sublineage with H7N9 AIV which caused outbreaks in Mainland China in 2013. The hemagglutinin cleavage site of HA of DT/PC0360 showed characterization of low pathogenic avian influenza virus.
Conclusion Strengthening the surveillance of AIVs of wild waterfowl and poultry in this region is vital for our knowledge of the ecology and mechanism of transmission to prevent an influenza pandemic.     

Construction of Prokaryotic Expressing Vector of Antisense Nucleic Acid of lasR and Its Effect on the Virulence of Pseudomonas Aeruginosus

To construct a pUCP18/lasRantisense plasmid carrying the reversed gene and analyze its effect on the virulence of Pseudomonas aeruginosus,LasR gene was amplified from the genome of Pseudomonas aeruginosus by PCR and reversely recombined with plasmid pUCP18.The recombi-nant pUCP18/lasRantisense was verified by enzyme digestion,PCR and sequencing.The biological ef-fects of pUCP18/lasRantisense were examined by using RT-PCR,NAD method and the assay of pyo-cyanin.Our results showed that the expected full length lasR fragment(721 bp) was extended from Pseudomonas aeruginosus gene with PCR.And it is consistent with LasR gene of Pseudomonas aeruginosa in GenBank(No.NC-002516).The recombinant plasmid was successfully constructed and transferred into Pseudomonas aeruginosus.The antisense nucleic acid of LasR gene could reduce the virulence of Pseudomonas aeruginosus and might serve as a new target site for treatment purpose.     

A study on detecting and identifying enteric pathogens with PCR

Objective To develop a rapid and definite diagnostic test of bacterial enteritis caused by pathogenic enterobacteria, the most frequent etiologic agent of infectious enteritis in the world.Methods A set of conventional PCR assays were applied to detect and identify salmonella, shigella,and E. coli O157:H7 directly from pure culture and fecal samples.The general primers of pathogenic enterobacteria were located on the uidA gene, which were found not only in E. coli nuclear acid, but also in Shigella and salmonella genes.Shigella primer was from ipaH gene whose coded invasive plasmid relative antigen existed both in plasmid and in genome.The primers of salmonella were designed from the 16SrRNA sequence.The primer of E.coli O157:H7 was taken from eaeA gene.Five random primers were selected for RAPD. The detection system included common PCR,semi-nested PCR and RAPD. Results This method was more sensitive, specific and efficient and its processing was rapid and simple. For example, the method could be used to specifically detect and identify salmonella, shigella, and E. coli O157:H7,and its sensitivity ranged from 3 to 50CFU, and its detection time was 4 hours. Conclusion This PCR method, therefore, can serve as a routine and practical protocol for detecting and identifying pathogenic microorganisms from clinical samples.     

Detection and amplification of Helicobacter pylori urease gene A in gastric biopsies by using nested polymerase (?)hain reaction

A nested polymerase chain reaction(N-PCR)for the spegific detection of Helicobacterpylori(H.pylori)was developed with two primer pairs(nested primers)derived from ureasegene A of H.pylori.The N-PCR was used to detect 21 different samples of H.pylori including20 clinical isolates and 1 reference strain NCTC 14126,but it was negative for other bacterialspecies,showing the N-PCR assay to be 100% specific.Tenfold serial dilution experiments re-vealed the detection of as little as 0.1 fg of H.pylori DNA by N-PCR.To evaluate the PCR as-say for clinical samples,gastric biopsies were tested with N-PCR,and the results were comparedwith those of culture,urease test and histologic examination(reference standard,RS).In 30biopsy specimens,H.pylori DNA sequences were detected by PCR in all of 20(100%)positivetissue and none of the 10 negative tissues.PCR is a specific and sensitive method that can detectthe presence of H.pylori without the need for culture and would have significant importance di-agnostically and epidemiologically.     

Construction and identification of recombinant lentivirus-mediated gene transfer system for rat transducer of regulated CREB activity 1

Objective:To construct a recombinant lentivirus vector which carries SD rat transducer of regulated CREB activity-1(TORC1) gene and examine its ability to express the TORC1 gene in vitro.Methods:The coding sequence of SD rat TORC1 gene was amplified using PCR and cloned into pGC-FU vector.293T cells were transfected using Lipofectamine 2000 and packaged for the recombinant lentivirus particles.When the cloned sequence was identified to be right,the recombinant lentivirus particles were amplified in a large quantity.The titer of virus was determined by real-time PCR and the level of TORC1 expression was examined by Western blot. Results:The recombinant lentivirus vector carrying TORC1 was constructed successfully and could express TORC1 at a high level in 293T cells in vitro,and the titer determined by real-time PCR was 2×108 TU/ml.Conclusion:The recombinant lentivirus vector could express TORC1 gene at a high level,and was very helpful in the study of exploring the effect of TORC1 on spinal cord injury.     

Cloning and sequencing of core gene cDNA of Chinese hepatitis C virus

A hepatitis C virus(HCV)cDNA fragment,534bp in length and designated asQ534,was obtained by PCR amplification with self-designed primers.Q534 was cloned in-to Hinc Ⅱ site of pUC18 and the recombinant plasmid pQ534 was then selected from thebacterial transformants.The sequence analysis indicated that Q534 was a cDNA fragmentof HCV core gene,and located in HCV genome from positions 320 to 853 incorrespondence with Chiron's prototype sequence.The homologies between Q534 and theprototype at the levels of nucleotides and amino acids were 90.0% and 97.6%,respectively.The homologies of Q534 with Japanese HCV-J and HCV-BK strains were 96.6% and97.0% at the nucleotide level,and 98.2% and 98.8% at the amino acid level.In terms ofthe sequence,this Chinese HCV isolate should belong to HCV group Ⅱ.