With the abuse of antimicrobial agents in developing countries, increasing number of carbapenem-resistant Enterobacteriaceae (CRE) attracted considerable public concern. A retrospective study was conducted based on 242 CRE strains from a tertiary hospital in Hangzhou, China to investigate prevalence and drug resistance characteristics of CRE in southeast China. Bacterial species were identified. Antimicrobial susceptibility was examined by broth microdilution method or epsilometer test. Resistant β-lactamase genes were identified by polymerase chain reaction and sequencing. Genotypes were investigated by phylogenetic analysis. Klebsiella pneumoniae and Escherichia coli were the most prevalent types of species, with occurrence in 71.9% and 21.9% of the strains, respectively. All strains exhibited high resistance (> 70%) against β-lactam antibiotics, ciprofloxacin, trimethoprim-sulfamethoxazole, and nitrofurantoin but exhibited low resistance against tigecycline (0.8%) and minocycline (8.3%). A total of 123 strains harbored more than two kinds of β-lactamase genes. bla, bla, bla, and bla were the predominant genotypes, with detection rates of 60.3%, 61.6%, 43.4%, and 16.5%, respectively, and were highly identical with reference sequences in different countries, indicating potential horizontal dissemination. IMP-4 was the most frequent class B metallo-lactamases in this study. In conclusion, continuous surveillance and effective prevention should be emphasized to reduce spread of CRE.
Anti-Bacterial Agents ; therapeutic use ; Carbapenem-Resistant Enterobacteriaceae ; drug effects ; enzymology ; genetics ; China ; epidemiology ; Enterobacteriaceae Infections ; epidemiology ; microbiology ; Genotype ; Humans ; Microbial Sensitivity Tests ; Phylogeny ; Prevalence ; Retrospective Studies ; beta-Lactam Resistance ; beta-Lactamases ; genetics

OBJECTIVETo analyze the distribution of Enterobacteriaceae isolated from West China Hospital, investigate the antibiotic resistance profile of Enterobacteriaceae with decreased susceptibility to carbapenems and explore the molecular mechanism.

METHODSForty-five Enterobacteriaceae strains resistant or with reduced susceptibility to carbapenems were isolated from patients in West China Hospital. The antimicrobial susceptibility and carbapenemase-producing phenotypes of the bacteria were examined and specific PCR were performed to determine the molecular mechanism.

RESULTSOf the 45 isolates, 17, 21 and 36 were resistant or intermediate strains to imipenem, meropenem and ertapenem, respectively. The majority of these isolates showed resistance to cephalosporins. The modified Hodge test resulted in the highest positivity rate (77.8%), followed by EDTA disc test (57.8%) and PBA disc test (22.2%). BlaTEM, blaSHV and blaCTX-M were detected in 60.0%, 53.3% and 15.6% of these strains with reduced susceptibility. The rate of strains carrying 2 or more genes was 44.4%, and the detection rate of blaIMP was 48.9%. BlaKPC was identified in 4 (8.9%) high-level resistant strains and confirmed to locate on the plasmid.

CONCLUSIONProduction of carbapenemase contributes to reduced susceptibility of carbapenems in Enterobacteriaceae. The presence of blaKPC, MBL and ESBL, and their possible combinations can be the main factor contributing to carbapenem resistance or reduced susceptibility in Enterobacteriaceae. The KPC-2 carbapenemase gene located on the plasmids we found in this study can cause potential horizontal transmission across strains.

Anti-Bacterial Agents ; pharmacology ; Bacterial Proteins ; genetics ; metabolism ; Carbapenems ; pharmacology ; Cephalosporins ; pharmacology ; Enterobacteriaceae ; drug effects ; enzymology ; genetics ; Gene Amplification ; Imipenem ; pharmacology ; Microbial Sensitivity Tests ; Polymerase Chain Reaction ; Thienamycins ; pharmacology ; beta-Lactam Resistance ; beta-Lactamases ; genetics ; metabolism ; beta-Lactams ; pharmacology

OBJECTIVETo investigate the role of AdeABC efflux pump in carbapenems resistance of Acinetobacter baumannii in light of the phenotype and genetype of the efflux pump.

METHODSThe phenotype of the efflux pump was detected in 138 clinical isolates of A.baumannii using the efflux pump inhibitor carbonyl cyanide 3-chlorophenylhydrazone (CCCP). The mRNA expression of pump-encoding gene adeB in the strains was detected using quantitative real-time RT-PCR.

RESULTSOf the 138 strains, 28 showed positivities for AdeABC efflux pump identified by Mueller-Hinton Broth with CCCP. Of the 39 strains resistant to meropenem, 15 (38.4%) showed positive results in CCCP assay, a rate significantly higher than that among the 99 sensitive strains (13.1%, 13/99) (X(2)=12.477(b), P=0.01). The mRNA expression of efflux pump-encoding gene adeB was detected by real-time RT-PCR at a level of 0.899∓∓1.172 in meropenem-sensitive strains, significantly lower than the level of 21.101∓∓21.443 in meropenem-resistant strains (t=4.403, P=0.000).

CONCLUSIONSEfflux plays a role in carbapenems resistance in the clinical isolates of A. baumannii. The AdeABC efflux pump may be an important factor in reducing carbapenems sensitivity in A. baumannii.

Acinetobacter baumannii ; drug effects ; isolation & purification ; Bacterial Proteins ; genetics ; metabolism ; Carbapenems ; pharmacology ; Humans ; Membrane Transport Proteins ; genetics ; metabolism ; beta-Lactam Resistance ; genetics

OBJECTIVEThis study aimed to investigate drug resistance and genotypes of the extended spectrum β-lactamase (ESBLs) and AmpC β-lactamase-producing Escherichia coli and Klebsiella pneumoniae isolated from Uygur and Han newborns in Urumqi.

METHODSDisk diffusion test (Kirby-Bauer) was used for detecting drug resistance of 299 strains to twenty two kinds of antibiotics. Resistance genes of the ESBLs and AmpC β-lactamase-producing strains were amplified by multiplex PCR and subtypes were confirmed by DNA sequence analysis. Total 148 strains were selected with random number table and sequenced, which included TEM-, SHV-, CTX-M-1-, or CTX-M-9-positive ESBLs-producing strains and DHA-, or CIT-positive AmpC β-lactamase-producing strains. Antibiotic resistant rates were analyzed by Whonet 5.4 and statistic analysis was performed by chi-square (χ(2)) test with PEMS 3.1.

RESULTSThe antibiotic resistant rates between Uygur and Han newborns significantly differ in ESBLs-producing Klebsiella pneumoniae to Sulfamethoxazole-Trimethoprim (80.0% (40/50) and 56.0% (28/50), χ(2) = 6.6176, P = 0.0101), in ESBLs-producing Escherichia coli to Sulbactam and Cefoperazone (54.2% (32/59) and 94.0% (47/50), χ(2) = 21.4512, P = 0.0000), and in AmpC &beta;-lactamase-producing Klebsiella pneumoniae to Sulbactam and Cefoperazone (100.0% (20/20) and 72.2% (26/36), χ(2) = 6.7633, P = 0.0093) and to Amikacin (65.0% (13/20) and 25.0% (9/36), χ(2) = 8.6246, P = 0.0033). Although SHV gene of ESBLs-producing Escherichia coli was detected from Uygur newborns at only 3.4% (2/59) and not detectable from Han newborns, TEM, CTX-M-1, and CTX-M-9 group genes were all detected over 38.0% (19/50). Among the detected strains, the subtypes of TEM and CTX-M-1 were mainly TEM-1 and CTX-M-15, respectively; whereas the subtypes of SHV and CTX-M-9 included SHV-1, 2, 11, 12, 27, 61, 99 and CTX-M-9, 14, 24, 27, 65, respectively. The strains of Escherichia coli and Klebsiella pneumoniae carrying two or more kinds of ESBLs genotypes were 56.7% (42/74) - 90.0% (63/70). Two species carrying the AmpC gene in two kinds of newborns were only grouped in the subtypes of DHA-1 and CMY-44, and other subtypes were not detected at all. Moreover, TEM-positive ESBLs-producing Escherichia coli were detected from Uygur newborns at the higher rate than that from Han newborns (71.2% (42/59) and 50.0% (25/50), χ(2) = 5.1291, P = 0.0235), while there was no difference in other genotypes detected between two kinds of newborns (χ(2) < 3.7780, P > 0.05).

CONCLUSIONThere were significant differences in antibiotic resistance and genotype distribution of Klebsiella pneumoniae and Escherichia coli between two nationality newborns, and these two bacteria detected in this study carried multi-resistance genes and showed high resistant to &beta;-lactamase antibiotics.

Bacterial Proteins ; metabolism ; China ; Escherichia coli ; drug effects ; genetics ; isolation & purification ; Escherichia coli Infections ; microbiology ; Ethnic Groups ; Genotype ; Humans ; Infant, Newborn ; Klebsiella Infections ; microbiology ; Klebsiella pneumoniae ; drug effects ; genetics ; isolation & purification ; Microbial Sensitivity Tests ; beta-Lactam Resistance ; genetics ; beta-Lactamases ; metabolism

OBJECTIVETo observe the effect of amino acid substitution in conserved sequence of penicillin-binding protein (PBP) 1A, 2B, 2X on antimicrobial activity of beta-lactams against Streptococcus pneumoniae (SP).

METHODMinimal inhibitory concentration (MIC) of 6 beta-lactams was determined by the E-test in 59 SP strains. The penicillin-binding protein genes pbp1a, 2b, 2x in every SP strain were amplified by nested-polymerase chain reaction (nPCR), then the PCR products were sequenced using automatic genetic analyzer directly. To analyze the amino acid substitutions, the DNA sequences were converted to protein sequences and aligned by Clustalx software. According to amino acid substitution in conserved sequence of PBP2B, 3 phenotypes were observed, including: PBP2B phenotype I (no amino acid substitution); PBP2B phenotype II (Glutamine 432-->Leucine and/or Threonine 445/451-->Alanine/Serine, Glutamic 481-->Glycine, 1 strain had proline insertion between residues 431/432); PBP2B phenotype III (Alanine 624-->Glycine with the addition of phenotype II). According to amino acid substitution in conserved sequence of PBP1A, 3 phenotypes were observed, including: PBP1A phenotype I (no amino acid substitution); PBP1A phenotype II (Threonine 574-->Asparagine, Serine 575-->Threonine, Glutamine 576-->Glycine, Phenylalanine 577-->Tyrosine, 574TSQF-->NTGY); PBP1A III (Threonine 371-->Alanine/Serine, Proline 432-->Threonine with the addition of 574TSQF-->NTGY). According to amino acid substitution in conserved sequence of PBP2X, 4 phenotypes were observed, including: PBP2X phenotype I (no amino acid substitution); PBP2X phenotype II (Histidine 394-->Leucine or Threonine 338-->Alanine); PBP2X phenotype III (Threonine 338-->Alanine, Isoleucine 371-->Threonine, Arginine 384-->Glycine and Leucine 546-->Valine); PBP2X phenotype IV (Methionine 339-->Phenylalanine, Methionine 400-->Threonine with the addition of PBP2X phenotype III).

RESULTAmong 59 SP strains antibacterial activities distribution (sensitive strains, intermediate strains and resistant strains) of 6 beta-lactams were penicillin (12, 29, 18); amoxicillin(49, 9, 1); cefuroxime (16, 16, 27); ceftriaxone (47, 1, 11); cefotaxime (47, 3, 9); imipenem (49, 10, 0). beta-lactam antibiotics insensitive strains (intermediate + resistant strain) in PBP2B phenotype III, PBP1A phenotype III, PBP2X phenotype III and IV were significantly increased, the MIC(50) of these strains were significantly higher than that of the others.

CONCLUSIONThe amino acid substitutions in or vicinal conserved sequence of PBP of SP increase MIC for beta-lactam antibiotics.

Amino Acid Substitution ; Aminoacyltransferases ; genetics ; Anti-Bacterial Agents ; pharmacology ; Bacterial Proteins ; genetics ; Microbial Sensitivity Tests ; Penicillin-Binding Proteins ; genetics ; Peptidyl Transferases ; genetics ; Streptococcus pneumoniae ; drug effects ; beta-Lactam Resistance ; genetics ; beta-Lactams ; pharmacology

Anti-Bacterial Agents ; metabolism ; pharmacology ; Bacterial Proteins ; genetics ; metabolism ; Biological Evolution ; Enterobacteriaceae ; enzymology ; pathogenicity ; Gene Transfer, Horizontal ; Host-Parasite Interactions ; Humans ; beta-Lactam Resistance ; drug effects ; genetics ; beta-Lactamases ; genetics ; metabolism

OBJECTIVETo investigate the molecular mechanism of carbapenem resistance in the clinical isolates of Acinetobacter baumannii from Xi'an and their profile of carbapenemase production.

METHODSA total of 146 Acinetobacter baumannii strains were isolated from 6 general hospitals in Xi'an. Antimicrobial susceptibility test was performed for all the strains, followed by detection of imipenem resistance using E-test for metallo-beta-lactamase (MBL) and NaCl inhibition test for OXA type carbapenemase. Bla(OXA-23)and bla(OXA-58) were amplified by PCR, and the positive products were sequenced.

RESULTSFrom the collected strains, 15 non-repetitive imipenem-resistant Acinetobacter baumannii strains were identified, among which 14 yielded negative results in E-test for MBL production. All the resistant strains showed increased sensitivity to imipenem after NaCl inhibition, suggesting the presence of carbapenemase production. Eleven of the strains harbored OXA -23 type gene and 1 harbored OXA -58 type gene. The concordance rate of the results by NaCl inhibition test and PCR was 85.7%.

CONCLUSIONSProduction of OXA-type carbapenemase is the most important reason for carbapenem resistance in Acinetobacter baumannii in Xi'an. The OXA-58 type gene is a novel carbapenemase genotype in China. NaCl inhibition test is a convenient and cost-effective method for detecting carbapenemase in Acinetobacter baumannii.

Acinetobacter baumannii ; drug effects ; genetics ; isolation & purification ; Anti-Bacterial Agents ; pharmacology ; Bacterial Proteins ; genetics ; China ; Humans ; Imipenem ; pharmacology ; beta-Lactam Resistance ; beta-Lactamases ; genetics

OBJECTIVETo construct prokaryotic expression systems of TCS genes comD/comE/comC of Streptococcus pneumoniae, and to determine the correlation of ComD and ComC with the drug resistance.

METHODSThe entire comD, comE and comC genes were amplified by PCR and their prokaryotic expression systems were established by routine genetic engineering technique. SDS-PAGE and Bio-Rad Agarose Image Analyzor was applied to measure the outputs of target recombinant proteins rComD, rComE and rComC. Rabbits were immunized with these recombinant proteins to prepare antisera. The resistance of S.pneumoniae strains to penicillin and cefotaxime was examined after ComD and ComC were blocked by antisera.

RESULTCompared with the reported sequences, similarities of nucleotide and amino acid sequences of the cloned comD, comE and comC genes were 98.4% approximately 99.3% and 99.1% approximately 100%, respectively. The constructed engineering bacteria E.coli BL21DE3(pET42a-comD), E.coli BL21DE3(pET42a-comE) and E.coli BL21DE3(pET42a-comC) were able to efficiently express the target recombinant proteins and the outputs of rComD, rComE and rComC were 28%, 25% and 35% of the total bacterial proteins, respectively. The double immunodiffusion titers of rabbit antisera against rComD, rComE or rComC were 1:4, 1:4 and 1:8, respectively. After the ComD and/or ComC were blocked by the antisera, the cefotaxime-sensitive S. pneumoniae strains became to resistant to antibiotics but there were no changes for cefotaxime-resistant strains and resistance to penicillin for all tested strains.

CONCLUSIONThe prokaryotic expression systems of S.pneumoniae comD/come/comC genes have been successfully constructed, and the study also indicates that both the ComD and ComC are involved in the drug resistance of S. pneumoniae to cefotaxime.

Animals ; Bacterial Proteins ; biosynthesis ; genetics ; Cefotaxime ; pharmacology ; Escherichia coli ; genetics ; metabolism ; Rabbits ; Recombinant Proteins ; biosynthesis ; genetics ; Recombination, Genetic ; Signal Transduction ; Streptococcus pneumoniae ; drug effects ; genetics ; beta-Lactam Resistance ; genetics

OBJECTIVETo construct prokaryotic expression systems of Streptococcus pneumoniae ciaH and ciaR genes,and to determine their correlation with drug resistance.

METHODSThe total length of ciaH and ciaR genes was amplified by PCR and their prokaryotic expression systems were established by using routine genetic engineering technique. SDS-PAGE was applied to measure the outputs of target recombinant proteins rCiaH and rCiaR. Rabbits antisera and IgGs against rCiaH and rCiaR were prepared. The resistance to penicillin and cefotaxime of S.pneumoniae strains was examined after CiaH and CiaR were extracellularly and intracellularly blocked by the IgGs.

RESULTThe homogeneity of nucleotide and amino acid sequences of the cloned ciaH and ciaR genes with the reported sequences was 99.9-100% and 100%, respectively. The recombinant bacteria E.coli BL21DE3pET42a-ciaH and E.coli BL21DE3pET42a-ciaR were able to express the target recombinant proteins rCiaH and rCiaR with efficiency. The outputs of rCiaH and rCiaR were 33% and 45% of the total bacterial proteins, respectively. The double immunodiffusion titers of rCiaH antiserum,rCiaR antiserum,rCiaH-IgG and rCiaR-IgG were 1:4,1:4,1:1 and 1:1, respectively. After CiaH was extracellularly or intracellularly blocked by CiaH-IgG, and CiaR was intracellularly blocked by CiaR-IgG, the penicillin-sensitive or cefotaxime-sensitive strains developed resistance to the two antibiotics; but the blocks did not change that of penicillin-resisting or cefotaxime-resisting strains.

CONCLUSIONThe prokaryotic expression systems of S. pneumoniae ciaH/ciaR genes have been successfully constructed in this study. Both the CiaH and CiaR may be involved in penicillin and cefotaxime resistance of the bacterium.

Animals ; Bacterial Proteins ; genetics ; metabolism ; Cefotaxime ; pharmacology ; Escherichia coli ; genetics ; metabolism ; Gene Expression Regulation, Bacterial ; Genetic Vectors ; Penicillin Resistance ; genetics ; Protein Kinases ; genetics ; metabolism ; Rabbits ; Recombinant Fusion Proteins ; genetics ; metabolism ; Signal Transduction ; Streptococcus pneumoniae ; drug effects ; enzymology ; genetics ; beta-Lactam Resistance ; genetics

OBJECTIVETo investigate the resistance genes and antibiotic resistance patterns against beta-lactams in Pseudomonas aeruginosa prevalent in burn ward.

METHODSK-B method was performed to test bacterial resistance patterns against 9 species of beta-lactams in Pseudomonas aeruginosa isolated from wounds and dressings of the patient in burn wards. Seven species of resistance genes against beta-lactams were detected with PCR. Tazobactam-inhibited piperacillin resistance test was performed to study whether the above strains produce extended spectrum beta-lactams.

RESULTSAll 12 strains of bacteria with resistance genes detected were resistant to penicillin and cephalosporins (100%), among them 11 were resistant to all antibiotics. Tazobactam-inhibited piperacillin resistance test demonstrated that all strains with resistance genes were ESBLs.

CONCLUSIONHigh incidence of beta-lactams resistance genes is found in Pseudomonas aeruginosa isolated from burn ward, and they have close relationship with the occurrence of multiple drug-resistance.

Burn Units ; Burns ; microbiology ; Genes, Bacterial ; Humans ; Pseudomonas aeruginosa ; drug effects ; genetics ; isolation & purification ; beta-Lactam Resistance ; genetics