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 study the mode of transmission and molecular characteristics on carbapenem-resistant Acinetobacter baumannii strain. Strains were isolated from different parts of samples in various patients.

METHODSClinical information of carbapenem-resistant Acinetobacter baumannii isolates were stored and analyzed by WHONET 5.4 software. The transmission and pathopoiesis of the strains were learned through case file review. Genotypes of isolates were identified by pulse-field gel electrophoresis (PFGE) and genes of carbapenemase were detected by multiple PCR, in order to find molecular characteristics and relatedness between strains.

RESULTS29 stains of Acinetobacter baumannii resistant to carbapenem were isolated from 2 or more kinds of samples among 13 patients'. Two genotypes were identified by PFGE: genotype A was obtained from 22 isolates in 11 patients and genotype B was obtained from 7 isolates in 4 patients. PCR amplification showed that all strains possessed OXA-23 gene except 1, and all strains possessed Integrase gene I except 3.

CONCLUSIONThere were 2 different genotypes from 29 strains of carbapenem-resistant Acinetobacter baumannii with Genotype A as the main type. OXA-23 carbapenemase gene and integrase gene I were detected from most of the isolates. All the strains could be easily transmitted in the body of the patients and among patients, hence becoming the epidemic pathogen of iatrogenic infection.

Acinetobacter Infections ; microbiology ; transmission ; Acinetobacter baumannii ; classification ; drug effects ; genetics ; Carbapenems ; pharmacology ; Cross Infection ; microbiology ; transmission ; Drug Resistance, Bacterial ; genetics ; Genotype ; Humans

OBJECTIVETo monitor genotypes and drug-resistance trend of Acinetobacter baumannii (AB) isolated from burn wards.

METHODSTwenty-six strains of AB isolated from wound secretion, venous catheter, and blood were collected from burn patients hospitalized in our burn wards from November 2008 to February 2009, and June to September 2010. Homogeneous genotype analysis was performed with repetitive extragenic palindromic PCR, and drug-resistance rate to 13 antibiotics including amikacin, gentamicin, etc., which were commonly used in clinic, was tested by K-B paper disk diffusion. The data of drug-resistance rate were processed with chi-square test.

RESULTS(1) Sixteen AB strains were multi-drug resistant (MDR), 9 AB strains were pan-drug resistant (PDR). Among all strains, the resistance rate to gentamicin, piperacillin, piperacillin/tazobactam, cefuroxime, cefotaxime, ceftazidime, cefepime, ciprofloxacin, imipenem, and meropenem was respectively higher than 90.00%; the resistance rate against cefoperazone/sulbactam was the lowest (11/26, 42.31%). There were obvious difference among the drug-resistance rates of AB strains to 13 antibiotics (with rates from 42.31% to 100.00%, χ(2) = 97.371, P < 0.05). (2) There were 7 genotypes among 26 AB strains, respectively type A (17), type B (3), type C (2), type D (1), type E (1), type F (1), and type G (1). Out of the 17 AB strains in A genotype, 1 strain was from 2008, 1 strain was from 2009, 15 strains were from 2010, and among them 11 strains were collected from wound secretion and 6 strains were obtained from blood and venous catheter.

CONCLUSIONSAB strains in A genotype are dominant in our burn wards in recent years, which are MDR or PDR to commonly used antibiotics. Cefoperazone/sulbactam is the drug of choice for burn patients with AB infection.

Acinetobacter Infections ; epidemiology ; microbiology ; Acinetobacter baumannii ; drug effects ; genetics ; Burns ; microbiology ; Cross Infection ; epidemiology ; microbiology ; Drug Resistance, Multiple, Bacterial ; Genes, Bacterial ; Humans

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 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

OBJECTIVETo investigate antibiotic resistance, clonal relatedness and carbapenemase genotype among carbapenem-resistant Acinetobacter baumannii collected from 3 comprehensive hospitals in Ningbo city, Zhejiang province.

METHODS28 strains of carbapenem resistant Acinetobacter baumannii were collected from Ningbo Li Hui-li Hospital, Ningbo Li Hui-li Hospital, Ningbo First Hospital, and N ingbo Second Hospital. The minimum inhibitory concentrations (MIC) of these strains were examined by agar dilution and E-test method. Homology of these isolates was analyzed by pulse-field gel electrophoresis (PFGE) and Genotype of carbapenemases were analyzed by PCR and verified by DNA sequencing.

RESULTS28 strains of Acinetobacter baumanii were highly resistant to all of the antibiotics except polymyxin E. They were classified into 4 clones based on PFGE pattern. Clone A and B had been spreading widely. All of the 28 strains produced carbapenemases which were confirmed as OXA-23 by PCR and sequencing. Metallo-beta-lactamase was not detected in any of the isolates.

CONCLUSIONAll of t hecarbapenem-resistant Acinetobacter baumannii collected from Ningbo were producing OXA-23 carbapenemase, suggesting that the transmission of clones had occurred in the 3 hospitals.

Acinetobacter Infections ; drug therapy ; epidemiology ; Acinetobacter baumannii ; drug effects ; genetics ; metabolism ; Bacterial Proteins ; genetics ; China ; Drug Resistance, Microbial ; Genotype ; Hospitals ; Humans ; Molecular Epidemiology ; Polymerase Chain Reaction ; beta-Lactamases ; genetics

BACKGROUND: The aims of this study were to understand the molecular epidemiology of integron-associated gene cassettes in Acinetobacter baumannii across four hospitals in northern Taiwan and to clarify the relationship between the presence of integrons and antibiotic-resistant phenotypes. METHODS: Sixty-five A. baumannii isolates, collected from the patients of four regional hospitals in northern Taiwan in 2009, were tested for the presence of integrons and their associated gene cassettes. The susceptibility difference between integron-positive and integron-negative A. baumannii strains was analyzed. Antibiotic-resistant phenotypes among A. baumannii with different types of gene cassette array combinations were also compared. RESULTS: Around 72% of the A. baumannii isolates carried class 1 integrase genes. Despite this, only three gene cassette arrays were found in the integrons. Integron-positive strains were significantly more resistant to all the tested antibiotics than the integrase-negative strains. All the four types of A. baumannii with different gene cassette array combinations were multidrug-resistant in nature. Gene cassette array aacA4-catB8-aadA1 existed in all the integron-positive A. baumannii isolates. Repetitive-sequence-based PCR (rep-PCR) results revealed the prevalence of one major cluster of imipenem-resistant A. baumannii strains (84%) in the four regional hospitals. CONCLUSIONS: The presence of integrons with associated antimicrobial resistance gene cassettes can be used as a representative marker of multidrug resistance in A. baumannii. Some prevalent gene cassette arrays may exist among epidemiologically unrelated A. baumannii strains.
Acinetobacter Infections/epidemiology/*microbiology ; Acinetobacter baumannii/drug effects/*genetics/isolation & purification ; Anti-Bacterial Agents/pharmacology ; Bacterial Proteins/genetics ; DNA, Bacterial/analysis ; Drug Resistance, Bacterial ; Humans ; Imipenem/pharmacology ; Integrases/genetics ; Integrons/*genetics ; Microbial Sensitivity Tests ; Multiplex Polymerase Chain Reaction ; Taiwan/epidemiology

OBJECTIVE: To study the antibiotic resistance evolution, homology, phenotypes and genotypes of carbapenemase in Acinetobacter baumannii from clinical isolates. METHODS: A total of 72 strains of Acinetobacter baumannii were isolated from Xiangya Hospital of Central South University from March to May 2012. Antimicrobial susceptibility test was carried out by automatic microorganism clinical analytical system VITEK-II. The homology of the 72 strains was analyzed by enterobacterial repetitive intergenic consensus-PCR (ERIC-PCR). Modified Hodge test was used to screen carbapenemases of the strains. Carbapenemase genes blaOXA-23, blaOXA-40 and blaOXA-58 were also amplified and sequenced. RESULTS: The 72 strains of Acinetobacter baumannii remained sensitive to cefoperazone/sulbactam (resistance rate 8.33%), followed by Amikacin. Otherwise, they were resistant to most of the antimicrobial agents (resistance rate more than 70%). The 72 strains were identified as 7 epidemic clones, A-G, by means of ERIC-PCR and the phylogenetic relationship among D, E, F and G was very close, suggesting a nosocomial infection possibility. Totally 56 strains produced carbapenemase; 61 strains were positive for carbapenemase gene blaOXA-23 and 1 strain positive for blaOXA-58. All strains were negative for carbapenemase gene blaOXA-40. CONCLUSION Acinetobacter baumannii strains isolated clinically are resistant to most of the antimicrobial agents and nosocomial infection had been observed. Most of the strains produce carbapenemase, among which, blaOXA-23 gene is the main carbapenemase gene. blaOXA-58 gene exists in the Acinetobacter baumannii isolates from Hunan Province.
Acinetobacter Infections ; microbiology ; Acinetobacter baumannii ; drug effects ; enzymology ; genetics ; Anti-Bacterial Agents ; pharmacology ; Bacterial Proteins ; genetics ; Base Sequence ; Drug Resistance, Multiple, Bacterial ; genetics ; Genotype ; Humans ; Imipenem ; pharmacology ; Microbial Sensitivity Tests ; Molecular Sequence Data ; Sequence Homology, Nucleic Acid ; beta-Lactamases ; genetics

OBJECTIVE: To survey antibiotic resistance of clinical isolates of Acinetobacter baumannii in Changsha and to investigate molecular epidemiological characteristics of carbapenem-resistant Acinetobacter baumannii. METHODS: A total of 205 non-duplicated, clinical isolates of Acinetabacter baumannii from 10 general hospitals in Changsha were collected from March 2010 to December 2010. The K-B disk diffusion method was applied for the drug-susceptibility test; a modified, double-disk synergy test was used to detect metallo-β-lactamase (MBL), and a modified Hodge test was used for the screening of carbapenemase. PCR was used to amplify carbapenemase genes (including OXA-23, OXA-24, OXA-51, IMP-1, and VIM-2) and the positive products were sequenced. Enterobacterial repetitive intergenic consensus PCR (ERIC-PCR) was used for DNA typing and test of homology. RESULTS: Of the 18 antibiotics tested, 14 had a high rate of resistance (>50% of the isolates tested), with piperacillin the highest (80.5% of strains), and cefoperazone/sulbactam the lowest (2.5%). In total, 115 carbapenem-resistant Acinetobacter baumannii strains were confirmed, but their MBL phenotype and genes were all negative. Seventy-one positive strains were detected by the modified Hodge test, among which 64 strains were OXA-23-positive. All the 115 strains were positive for the amplification of the OXA-51 gene, and no strain was found which carried OXA-24 or OXA-58 gene. Seven genomic types were included in the 115 Acinetobacter baumannii. The major prevalence types were Type B ( 72 strains) and Type A (19 strains). CONCLUSION Multiple drug resistance of clinically isolated Acinetobacter baumannii is a serious problem in Changsha. Production of OXA-23 and OXA-51 carbapenemases is an important mechanism of resistance to carbapenem antibiotics, and there is prevalence of the same clones in these carbapenem-resistant strains.
Acinetobacter Infections ; epidemiology ; microbiology ; Acinetobacter baumannii ; drug effects ; genetics ; isolation & purification ; Carbapenems ; pharmacology ; China ; epidemiology ; DNA, Bacterial ; genetics ; Drug Resistance, Multiple, Bacterial ; genetics ; Humans ; Molecular Epidemiology ; Piperacillin ; pharmacology ; Polymerase Chain Reaction ; methods

BACKGROUNDAcinetobacter baumannii is one of the main gram-negative bacilli in clinical practice. Nosocomial infections caused by multi-drug resistance Acinetobacter baumannii is very difficult to treat. This study was designed to investigate the antimicrobial resistance characteristics and four resistant gene expressions of aminoglycoside-modifying enzymes including N-acetyltransferases and O-phosphotransferases in Acinetobacter baumannii.

METHODSBacterial identification and antimicrobial susceptibility test were performed by Phoenix system in 247 strains of Acinetobacter baumannii. Minimal inhibitory concentrations (MICs) of seven aminoglycosides including gentamicin, amikacin, kanamycin, tobramycin, netilmicin, neomycin and streptomycin in 15 strains of multi-drug resistant Acinetobacter baumannii were detected by agar dilution. Four aminoglycoside-modifying enzyme genes were amplified by polymerase chain reaction (PCR) and verified by DNA sequencer.

RESULTSThe resistance rates of 247 strains of Acinetobacter baumannii against cefotaxime, levofloxacin, piperacillin, aztreonam, tetracycline, ciprofloxacin and chloramphenicol were more than 50%. Imipenem and meropenem showed high antibacterial activities with resistance rates of 3.2% and 4.1%. MIC50 and MIC90 of gentamicin, amikacin, streptomycin and kanamycin in 15 strains of multi-drug resistant Acinetobacter baumanii were all more than 1024 mg/L, and the resistance rates were 100%, 100%, 100% and 93.3%, respectively. But their resistance rates to tobramycin, netilmicin and neomycin were 86.7%, 93.3% and 46.7%, respectively. Three modifying enzyme genes, including aacC1, aacC2 and aacA4 genes, were found in 15 strains, but aphA6 had not been detected. Their positive rates were 93.3%, 20.0% and 20.0%, respectively. These three genes existed simultaneously in No.19 strain. Nucleotide sequences of aacC1, aacC2 and aacA4 genes shared 100%, 97.9% and 99.7% identities with GenBank genes (AY307113, S68058 and AY307114).

CONCLUSIONMulti-drug resistant Acinetobacter baumannii strains are rapidly spreading in our hospital, and their resistance to aminoglycosides may be associated with aminoglycoside-modifying enzyme gene expressions.

Acinetobacter baumannii ; drug effects ; enzymology ; genetics ; Aminoglycosides ; metabolism ; pharmacology ; Base Sequence ; Drug Resistance, Multiple, Bacterial ; Gene Expression Regulation, Bacterial ; Genotype ; Microbial Sensitivity Tests ; Molecular Sequence Data