OBJECTIVETo investigate the drug resistance of enteric bacilli and its relation to the drug resistance gene cassette in the variable region and molecular evolution of class-I integron.

METHODSK-B assay was applied to measure the drug resistance of E.coli, E.cloacae and A.baumannii isolated against twelve antibiotics. The class-I integron and drug resistance gene cassettes in the variable region of the integron were detected by PCR and sequencing of amplification products. The molecular evolution of drug resistance genes in the class-I integrons was analyzed using Clustal X and MEGA software.

RESULTS54.2%-100% of A.baumannii isolates were resistant to the penicillin and cephem antibiotics, while E.coli and E.cloacae isolates had resistance rates of 41.6%-62.5% to cephem antibiotics. 62.5%(15/24) of E.coli, 67.9%(19/28) of E.cloacae and 83.3%(20/24) of A.baumannii isolates were positive for class-I integrons. 81.5% (44/54) of class-I integrons showed 4 different single band spectrums and the other class-I integrons displayed 3 different double band spectrums. In the drug resistance gene cassettes in variable regions of class-I integrons there were 7 types in 4 groups of drug resistance genes, including aac(6'), sad(3"), aad(2"), cat(4') and dfr (types 7, A13 and 15), which induced the resistance to aminoglycosides and sulfamido antibiotics and chloromycin. The class-I integrons in the isolates might be divided into 4 molecular evolution groups according to the diversity of dihydrofolate reductase encoding gene sequences.

CONCLUSIONThe enteric bacilli have a high drug resistance and frequently carry class-I integrons with 7 drug resistance gene cassettes which present 4 different evolutionary pathways.

Anti-Bacterial Agents ; pharmacology ; Drug Resistance, Multiple, Bacterial ; genetics ; Enterobacteriaceae ; drug effects ; genetics ; Evolution, Molecular ; Integrons ; genetics

OBJECTIVETo investigate antibiotic resistance and carriage class 1 and 2 integrons in clinical isolates of Acinetobacter baumannii (A. baumannii) from Tehran, Iran.

METHODSAntimicrobial susceptibility testing was performed according to the Clinical and Laboratory Standards Institute. The presence of integrons was investigated by PCR using specific primers.

RESULTSAmong isolated A. baumannii strains, 82% were multidrug resistant, 27 samples (54%) were resistant to three or more than three antibiotics and 16 samples (32%) showed resistance to two antibiotics. Integrons were detected from 44 of 50 isolates (88%), with classes 1 and 2 being observed in 42% (21/50) and 82% (41/50) of isolates, respectively. Integron-positive A. baumannii isolates showed higher antibiotic resistance than integron-negative isolates and all showed a multidrug-resistant phenotype.

CONCLUSIONSOur findings show that classes 1 and 2 integrons, and especially classes 2 integrons are widely disseminated among A. baumannii strains isolated from Tehran and these structures are playing a major role in the acquisition of multidrug resistance in these strains. So monitoring of drug resistance with investigating carriage class 1 and 2 integrons is very important to plan specific infection control measures due to multidrug resistance A. baumannii in Iran hospitals.

Acinetobacter baumannii ; drug effects ; genetics ; Anti-Bacterial Agents ; pharmacology ; Drug Resistance, Multiple, Bacterial ; genetics ; Integrons ; genetics ; Iran ; Microbial Sensitivity Tests

OBJECTIVETo investigate the homology and resistant mechanism of vancomycin-resistant Enterococci (VRE) isolates.

METHODSA total of 9 VRE isolates were collected from 2006 to 2007 at PUMC hospital. The susceptibility of these isolates to 10 different antibiotics including vancomycin was tested by E-test. These strains were processed by brain heart infusion agar screening in the presence of vancomycin (6 microg/ml), and were analyzed for genotypic characteristics using the multiplex PCR. The homology of the isolates was determined by pulsed-field gel electrophoresis (PFGE).

RESULTSAll the 9 VRE isolates were identified as Enterococci faecium. The visual analysis of PFGE patterns revealed 6 different PFGE types. The vanA gene was confirmed by PCR and sequencing in 9 VRE isolates, which were consistent between phenotype and genotype for glycopeptides resistance.

CONCLUSIONSOnly vanA genotype was detected in PUMC hospital. Clonal dissemination, horizontal gene transfer, and the selective pressure of antimicrobial agents may contribute to the increase of VRE.

Bacterial Proteins ; genetics ; Bacterial Typing Techniques ; Drug Resistance, Multiple, Bacterial ; Enterococcus faecium ; classification ; drug effects ; genetics ; isolation & purification ; Gram-Positive Bacterial Infections ; microbiology ; Humans ; Vancomycin Resistance

Acinetobacter baumannii ; classification ; genetics ; isolation & purification ; Drug Resistance, Multiple, Bacterial ; genetics ; Humans ; Phylogeny

OBJECTIVETo detect the enterotoxin genes of Staphylococcus aureus (SA) isolated from clinical specimens and analyze the correlation between enterotoxin genes and drug resistance of SA.

METHODSThe mecA gene and enterotoxin genes A-F of clinical SA isolates were identified by polymerase chain reaction (PCR), and the genes were sequenced to investigate the correlation of these genes to drug resistance.

RESULTSThe detection rate of enterotoxin genes was 100% in 67 methicillin- resistant SA (MRSA), showing no significant difference from the rate in 57 methicillin-sensitive SA (MSSA) (83.5%, χ(2)=0.203, P>0.05). Of the 116 strains carrying enterotoxin genes (93.5%), the detection rates of SEA, SEB, SEC, SED and SEF were 90.5%, 6.9%, 61.3%, 5.2%, 25.9% and 93.5%, respectively, and none of the strains were positive for SEE gene. In these strains, 78 (67.2%) carried 2 or more enterotoxin genes, and the main genotypes were SEA and SEC (33.6%), SEA and SEF (7.8%), and SEA and SEC and SEF (13.8%). Compared with the strains carrying a single enterotoxin gene, those with multiple enterotoxin genes showed a higher drug resistance rate, among which 75% of the SA strains carrying SEA+SEC+SEF were resistant to SXT, significantly higher than the rates of SA carrying SEA (28.6%) and SEA+SEC (38.7%) (P<0.05). The SA strains carrying SEA+SEC+SEF and SEA+SEF showed significantly higher amikacin resistance rates than SA strain carrying SEA (75.0%, 77.0%, 21.5%, respectively, P<0.05).

CONCLUSIONClinical isolates of SA carrying multiple enterotoxin genes have a higher drug resistance rate than those with a single enterotoxin gene, suggesting the the important role of enterotoxin in multidrug resistance.

Drug Resistance, Multiple, Bacterial ; genetics ; Enterotoxins ; genetics ; Humans ; Staphylococcal Infections ; microbiology ; Staphylococcus aureus ; drug effects ; genetics ; isolation & purification

Animals ; Anti-Bacterial Agents ; pharmacology ; Bacteria ; drug effects ; genetics ; isolation & purification ; Bacterial Infections ; microbiology ; Bacterial Proteins ; genetics ; Drug Resistance, Multiple, Bacterial ; Environmental Microbiology ; Genomics ; Humans

OBJECTIVETo determine the distribution and the predominant gene carrying model of drug inactive enzyme genes in bacterial isolates, and the mechanism of its induction and inhibition.

METHODSThe β-lactam, aminoglycosides and macrolides inactive enzyme genes were detected by PCR and sequencing in S. aureus, E.coli, K. pneumoniae, A. baumannii and E. cloacae isolates. The expression of inactive enzyme genes were examined by real-time fluorescent quantitative RT-PCR when the bacterial isolates were treated with antibiotics or a histidine kinase blocker closantel.

RESULTSIn 63 isolates of E.coli, 4 kinds of β-lactam, 2 aminoglycosides and 1 macrolides inactive enzyme-encoding genes were detected and the predominant gene-carrying models were [TEM+CTX-M]+aac(3)-II+mphA (25.4 %) and [TEM+CTX-M]+ aac (6')-I b (20.6%). In 24 isolates of S.aureus, 2 kinds of β-lactam and 3 aminoglycosides inactive enzyme-encoding genes were detected and the predominant gene-carrying models were aph (3')(41.7%) or aac (6)-I e-aph (2)-I a (25.0%). In 28 isolates of K.pneumoniae, 4 kinds of β-lactam and 2 aminoglycosides inactive enzyme-encoding genes were detected and the predominant gene-carrying models were [TEM+SHV]+[aac(6')-I b+aac (3)-II](28.6 %) and [TEM+SHV]+[aac(6')-I b+aac (3)-II]+ mphA (17.8 %). The isolates of A.baumannii and E.cloacae also had a predominant model to carry 2 or 3 kinds of inactive enzyme-encoding genes. 1/4 MIC of penicillin, cefotaxime or streptomycin induced the up-regulation of expression of 3 β-lactam or 4 aminoglycosides inactive enzyme-encoding genes (P<0.05), and this effect was inhibited by closantel (P<0.05).

CONCLUSIONThe bacterial isolates frequently carry multiple kinds of inactive enzyme-encoding genes with different predominant gene-carrying models.Low concentration antibiotics can induce the up-regulation of inactive enzyme gene expression, which can be inhibited by histidine kinase blocker.

Anti-Bacterial Agents ; pharmacology ; Bacteria ; enzymology ; genetics ; Drug Resistance, Multiple, Bacterial ; genetics ; Gene Expression Regulation, Bacterial ; Up-Regulation ; drug effects ; beta-Lactamases ; genetics

OBJECTIVETo research the bacteriostatic effects of Qingkailing Injection Extract (QKLIE) and combination therapy of Qingkailing Injection (QKLI) and antibiotics on bacteria carrying New Delhi metallo-3-lactamase 1 (NDM-1) blaNDM-1 resistance gene, and to determine their minimal inhibitory concentrations (MIC).

METHODSThe antimicrobial experiments of QKLIE (Radix Isatidis, baicalin, gardenia, honeysuckle) and combination therapy of QKLI and antibiotics were performed by using the agar dilution method and K-B method. The MIC was determined from each extract.

RESULTSThere were different degrees of inhibitory effects on resistant bacteria carrying blaNDM-1 by extracts from main components of QKLI. Of them, the inhibitory effect of baicalin was the best and the MIC of the resistant bacteria was 0.015 g/mL to WD, 0.020 g/mL to WX, 0. 005 g/mL to WJ, and more than 0.020 g/mL to pGEX-4T-NDM-1/DH5alpha (GST-NDM-1), respectively. The MIC value of each extract was sequenced from high to low as baicalin, honeysuckle, gardenia, and Radix Isatidis. Furthermore, combination therapy of QKLI and antibiotics greatly enhanced the antimicrobial activity of each antibiotics when used alone, showing very obvious antibacterial effects on multidrug resistant bacteria carrying blaNDM-1 gene. Of them, the optimal effects were obtained when combined with penicillins (penicillin G, mezlocillin, piperacillin/ tazobactam, ampicillin/sulbactam), with the antibacterial effects improved by 10 folds. The antibacterial effects of other kinds of antibiotics were improved to some extent. Conclusions QKLIE and combination therapy of QKLI and antibiotics showed better bacteriostatic effects on resistant bacteria carrying blaNDM-1 gene. This study provided theoretical bases for drug development, medication and treatment for super-resistant bacteria carrying blaNDM-1.

Anti-Bacterial Agents ; pharmacology ; Bacteria ; drug effects ; genetics ; Drug Resistance, Multiple, Bacterial ; drug effects ; genetics ; Drug Therapy, Combination ; Drugs, Chinese Herbal ; pharmacology ; beta-Lactamases ; genetics

Antitubercular Agents ; pharmacology ; Drug Resistance, Multiple, Bacterial ; genetics ; Humans ; Microbial Sensitivity Tests ; methods ; Mycobacterium tuberculosis ; drug effects ; genetics

Pathogenic bacteria have increasingly been resisting to antimicrobial therapy. Recently, resistance problem has been relatively much worsened in Gram-negative bacilli. Acinetobacter spp. are typical nosocomial pathogens causing infections and high mortality, almost exclusively in compromised hospital patients. Acinetobacter spp. are intrinsically less susceptible to antibiotics than Enterobacteriaceae, and have propensity to acquire resistance. A surveillance study in Korea in 2009 showed that resistance rates of Acinetobacter spp. were very high: to fluoroquinolone 67%, to amikacin 48%, to ceftazidime 66% and to imipenem 51%. Carbapenem resistance was mostly due to OXA type carbapenemase production in A. baumannii isolates, whereas it was due to metallo-beta-lactamase production in non-baumannii Acinetobacter isolates. Colistin-resistant isolates were rare but started to be isolated in Korea. Currently, the infection caused by multidrug-resistant A. baumannii is among the most difficult ones to treat. Analysis at tertiary care hospital in 2010 showed that among the 1,085 isolates of Acinetobacter spp., 14.9% and 41.8% were resistant to seven, and to all eight antimicrobial agents tested, respectively. It is known to be difficult to prevent Acinetobacter spp. infection in hospitalized patients, because the organisms are ubiquitous in hospital environment. Efforts to control resistant bacteria in Korea by hospitals, relevant scientific societies and government agencies have only partially been successful. We need concerted multidisciplinary efforts to preserve the efficacy of currently available antimicrobial agents, by following the principles of antimicrobial stewardship.
Acinetobacter/classification/*drug effects/genetics/metabolism ; Anti-Bacterial Agents/pharmacology ; Bacterial Proteins/metabolism ; Drug Resistance, Multiple, Bacterial/genetics ; beta-Lactamases/metabolism