Humans ; Microbial Sensitivity Tests ; Pneumoconiosis ; microbiology ; Sputum ; microbiology ; beta-Lactam Resistance ; beta-Lactamases ; analysis

OBJECTIVETo investigate the occurrence and drug resistance of extended-spectrum beta-lactamases (ESBLs)-producing strains of Shigella in pediatric patients, so as to provide information for clinical treatment.

METHODA total of 59 strains of Shigella were isolated from stool specimens of hospitalized children with shigellosis from January 2004 to December 2008. The broth dilution test recommended by Clinical and Laboratory Standards Institute (CLSI) was performed to detect the ESBLs producers. Susceptibility test was carried out by agar dilution method. Escherichia coli ATCC25922 and Klebsiella pneumonia ATCC700603 were used as quality control strains.

RESULTOf the 59 isolates, 21 (35.6%) strains were identified as ESBLs producers. All of the 21 strains were detected by cefotaxime and cefotaxime/clavulanic acid, only 5 (23.8%) were detected by ceftazidime and ceftazidime/clavulanic acid. Both ESBLs and non-ESBLs producers showed high resistance to penicillins. The resistance of ESBLs-producing strains to third and fourth-generation cephalosporins, aztreonam was significantly higher than that of non-ESBLs-producing strains, as well as sulphonamides and quinolones. The drugs sensitive to ESBLs producers were imipenem, meropenem, piperacillin/tazobactam, cefoperazone/sulbactam and cefoxitin, with resistance rate of 0.0%, 0.0%, 14.3%, 9.5%, 14.3%, respectively.

CONCLUSIONThe prevalence of ESBLs-producing Shigella in pediatric patients is at a high level in this area, and the enzyme-producing strains are multidrug resistant. It is recommended that the detection of ESBLs in Shigella should be carried out by microbiological laboratories. Any of the above 5 antibiotics of low resistance should be used according to the patient's condition.

Child ; Feces ; microbiology ; Humans ; Microbial Sensitivity Tests ; Shigella ; Shigella dysenteriae ; drug effects ; isolation & purification ; beta-Lactam Resistance

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

OBJECTIVETo investigate drug-resistant genes associated with beta-lactams and aminoglycosides in clinically isolated Pseudomonas aeruginosa.

METHODSTwenty strains of Pseudomonas aeruginosa were isolated from wound excretion of hospitalized burn patients. The strains resistant to 14 antibiotics were selected for detection of 16 kind of drug-resistant genes (TEM, SHV, OXA-10 cluster, PER, VEB, GES, CARB, CTX-M- I, IMP, VIM, SPM, GIM, DHA, MOX, FOX, oprD2) and 6 kind of aminoglycoside modification genes (aac(3)- I, aac(3)-II, aac(6')-I, aac(6')-II, ant (3")- I , ant(2")- I) in them by PCR.

RESULTSAmong the 20 strains resistant to beta-lactam , all of them were TEM and GES positive (100%), oprD2 gene depletion in 5 strains (25%). All other genes were negative. Among aminoglycoside resistant genes, 20 strains were aac (6') - I positive (100%), 7 were ant (2") - I positive (35%), and negative for other stains.

CONCLUSIONThere were very high existence rates of TEM, GES and aac (6')- I genes in Pseudomonas aeruginosa isolated from clinical burn patients. The fact that GES-5 gene has also been detected in Pseudomonas aeruginosa, suggesting this organism is highly drug resistant in our burn unit.

Aminoglycosides ; pharmacology ; Drug Resistance, Multiple, Bacterial ; genetics ; Humans ; Pseudomonas aeruginosa ; drug effects ; genetics ; isolation & purification ; beta-Lactam Resistance ; genetics ; beta-Lactams ; pharmacology

To study the resistant mechanism and clinical significance of pseudomonas aeruginosa to beta-lactam antibiotics, the outer membrane permeability rate of 30 P. aeruginosa strains to 5 beta-lactam antibiotics was measured and their production of beta-lactamase and the beta-lactamase genes they carried detected. Furthermore, the relationship between the permeability, beta-lactamase and the clinical effects of beta-lactam antibiotics was observed. By using 14C-penicillin and liquid-scintillant isotope assay, the affinity of penicillin binding proteins (PBPS) was measured and their roles in the resistant mechanism studied. It was revealed that the permeability rate was higher in sensitive strains than in resistant ones (P < 0.05). All strains harbored 1-4 beta-lactamase genes and produced beta-lactamase. Higher permeability rate and higher degree of stability to beta-lactamase indicated better clinical therapeutic effects. The affinity of PBPs changed little without regard to the permeability and beta-lactamase. These results suggested that the permeability of outer membrane and beta-lactamase, but not PBPs, played important roles in the resistant mechanism of P. aeruginosa to beta-lactam antibiotics and affected the clinical therapeutic effectiveness of some patients.
Anti-Bacterial Agents/*pharmacology ; Bacterial Outer Membrane Proteins/metabolism ; Microbial Sensitivity Tests ; Permeability ; Pseudomonas aeruginosa/*drug effects ; beta-Lactam Resistance/*genetics ; beta-Lactamases/metabolism ; beta-Lactams/*pharmacology

To study the resistant mechanism and clinical significance of pseudomonas aeruginosa to beta-lactam antibiotics, the outer membrane permeability rate of 30 P. aeruginosa strains to 5 beta-lactam antibiotics was measured and their production of beta-lactamase and the beta-lactamase genes they carried detected. Furthermore, the relationship between the permeability, beta-lactamase and the clinical effects of beta-lactam antibiotics was observed. By using 14C-penicillin and liquid-scintillant isotope assay, the affinity of penicillin binding proteins (PBPS) was measured and their roles in the resistant mechanism studied. It was revealed that the permeability rate was higher in sensitive strains than in resistant ones (P < 0.05). All strains harbored 1-4 beta-lactamase genes and produced beta-lactamase. Higher permeability rate and higher degree of stability to beta-lactamase indicated better clinical therapeutic effects. The affinity of PBPs changed little without regard to the permeability and beta-lactamase. These results suggested that the permeability of outer membrane and beta-lactamase, but not PBPs, played important roles in the resistant mechanism of P. aeruginosa to beta-lactam antibiotics and affected the clinical therapeutic effectiveness of some patients.
Anti-Bacterial Agents ; pharmacology ; Bacterial Outer Membrane Proteins ; metabolism ; Humans ; Microbial Sensitivity Tests ; Permeability ; Pseudomonas aeruginosa ; drug effects ; beta-Lactam Resistance ; genetics ; beta-Lactamases ; metabolism ; beta-Lactams ; pharmacology

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 beta-lactamase was identified. The objective gene 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.
Bacterial Proteins/*genetics ; DNA, Bacterial/genetics ; Point Mutation/*genetics ; Pseudomonas aeruginosa/enzymology ; Pseudomonas aeruginosa/*genetics ; Sequence Analysis, DNA ; beta-Lactam Resistance/*genetics ; beta-Lactamases/*genetics

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

There have been conflicting data about the interactions between vancomycin and beta-lactam agents against Staphylococcus aureus strains with heterogeneous resistance to vancomycin. We evaluated the efficacy of these combinations against Mu 3 and heterogeneously vancomycin-resistant S. aureus (hetero-VRSA) strains which were isolated from Korean patients using a population analysis method. Antagonistic effects were observed when less than 1 g/mL of beta-lactam antibiotics was combined with vancomycin, whereas synergistic effects were noticed with more than 4 microgram/mL of beta-lactam antibiotics. The antagonistic effects at low concentrations of beta-lactams were most prominent at 2 microgram/mL of vancomycin, which were the vancomycin MICs of tested hetero-VRSA strains. This study showed the variable effects of vancomycin- beta-lactam combinations depending on the concentrations of beta-lactam antibiotics and this property could be used to develop screening methods for hetero-VRSA strains.
Anti-Bacterial Agents/*pharmacology ; Cefotaxime/pharmacology ; Drug Synergism ; Human ; In Vitro ; Microbial Sensitivity Tests ; Oxacillin/*pharmacology ; Staphylococcus aureus/*drug effects ; Vancomycin/*pharmacology ; Vancomycin Resistance ; beta-Lactam Resistance

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