OBJECTIVETo study the changes in expression of quorum sensing gene aba I in Acinetobacter baumannii (AB) strains isolated from burn patients during biofilm formation process, and its influences on the extracellular matrix of biofilm and drug resistance of AB.

METHODSSix drug-resistant and five drug-sensitive AB strains isolated from wound excretion, blood and venous catheter were collected from burn patients hospitalized in Ruijin hospital of Shanghai Jiao Tong University School of Medicine from January to October 2011. The AB standard strain ATCC 19606 was used as control. (1) Clinical strains and standard strain were normally cultured 10, 24, and 48 h respectively in vitro. The bacteria samples were stained with propidium iodide to measure biofilm thickness with confocal laser scanning microscope. (2) Clinical strains and standard strain were cultured in tubes 10, 24, and 48 h respectively in vitro under shaking condition. The bacteria floating in the medium were regarded as free bacteria, while those adhered to the tube wall as the bacteria within biofilm (biofilm bacteria). Relative expression value of genes aba I and pgaB was detected by real-time fluorescent quantitative PCR with the expression value of the standard strain set at 1. Data were processed with analysis of variance.

RESULTS(1) At post culture hour (PCH) 10, 24, 48, biofilm thickness of clinical strains was thicker than that of standard strain; biofilm thickness of drug-resistant strains [(28.8 ± 0.6), (31.7 ± 1.1), and (38.1 ± 3.1) µm] was respectively thicker than that of drug-sensitive strains [(17.1 ± 0.4), (20.1 ± 1.6), and (25.8 ± 1.7) µm, with F value respectively 1274.38, 206.60, and 61.73, P values all below 0.05]. (2) Biofilm bacteria: at PCH 10, 24, 48, expression values of aba I in drug-resistant strains (6.6 ± 1.7, 25.7 ± 3.5, 9.8 ± 3.6) were much higher than those of drug-sensitive strains (2.7 ± 1.0, 15.0 ± 3.5, 4.7 ± 3.2, with F value respectively 21.82, 25.24, and 6.22, P values all below 0.05); expression values of pgaB in drug-resistant strains (37.4 ± 1.1, 44.5 ± 3.6, 33.1 ± 11.5) were obviously higher than those of drug-sensitive strains (14.6 ± 0.8, 20.0 ± 6.9, 18.7 ± 6.8, with F value respectively 1488.44, 57.26, and 6.01, P values all below 0.05). (3) Free bacteria: at PCH 10, 24, 48, there was no significant statistical difference between drug-resistant strains and drug-sensitive strains in expression value of aba I (with F value respectively 0.24, 2.33, and 0.11, P values all above 0.05); expression values of pgaB in drug-resistant strains (13.8 ± 3.8, 12.5 ± 2.9, 23.7 ± 2.1) were obviously higher than those of drug-sensitive strains (7.0 ± 5.9, 5.0 ± 1.3, 15.6 ± 6.7, with F value respectively 5.44, 28.42, and 7.76, P values all below 0.05). (4) Comparison between biofilm bacteria and free bacteria in resistant strains: expression value of aba I in biofilm bacteria at each time point was respectively higher than that of free bacteria (with F value respectively 43.69, 286.61, and 9.98, P values all below 0.05); expression values of pgaB in biofilm bacteria at PCH 10, 24 were higher than those in free bacteria (with F value respectively 214.26 and 283.20, P values below 0.05). (5) Comparison between biofilm bacteria and free bacteria in sensitive strains: expression value of aba I in BF bacteria at PCH 24 was higher than that of free bacteria (F = 70.28, P < 0.05); expression values of pgaB in biofilm bacteria at PCH 10, 24 were higher than those of free bacteria (with F value respectively 8.03 and 22.62, P values below 0.05).

CONCLUSIONSDuring biofilm formation process, the increasing expression of quorum sensing gene aba I in drug-resistant AB strains isolated from burn patients may up-regulate the expression of gene pgaB, which leads to high production of extracellular matrix and biofilm formation, and enhances drug resistance of AB.

Acinetobacter Infections ; Acinetobacter baumannii ; genetics ; isolation & purification ; Biofilms ; Burns ; microbiology ; Drug Resistance, Bacterial ; Genes, Bacterial ; Humans

OBJECTIVETo observe expressions of pgaABC gene clusters and changes in biofilm (BF) phenotype in Acinetobacter baumannii (AB) isolated from burn patients.

METHODSFrom January 2009 to October 2010, 24 strains of AB isolated from burn patients hospitalized in our burn wards were collected for the study, while the standard strain ATCC 19606 was used as control. Expressions of pgaABC gene clusters were detected by real time fluorescence quantitative RT-PCR. All strains were cultured for 16 hours in vitro, BF with semi-quantitative detection was respectively evaluated by modified microtiter-plate test under stable condition and tube test under shaking condition for expression of absorbance value. All strains were cultured for 48 hours in vitro, then stained with fluorescent agent and collected for measurement of BF thickness with confocal laser scanning microscopy (CLSM). Data were processed with t test.

RESULTS(1) The expression of pgaB gene (27.91 ± 7.93) in clinical AB strains was much higher than that of standard strain ATCC 19606 (1.00, t = 5.77, P < 0.05). There was no statistical difference in expression of pgaA and pagC genes between standard strain ATCC 19606 (1.00) and clinical AB strains (1.01 ± 0.28, 1.15 ± 0.38, with t value respectively 0.04, 0.64, P values all above 0.05). (2) After being cultured for 16 hours, BF of clinical AB strains cultured under shaking condition formed distinct "purple circle", and its absorbance value (1.25 ± 0.31) was higher than that in standard strain ATCC 19606 (0.76 ± 0.03, t = 2.67, P < 0.05). There was no obvious difference in absorbance value between clinical AB strains and standard strain ATCC19606 cultured under stable condition. (3) After being culture for 48 hours, green fluorescence intensity and distribution in extracellular matrix of clinical AB strains were stronger as compared with those of standard strain ATCC 19606, and BF thickness in clinical AB strains [(27.3 ± 9.4)µm] was thicker than that in standard strain ATCC 19606 [(15.6 ± 1.7) µm, t = 2.09, P < 0.05].

CONCLUSIONSThe high expression of pgaB gene in AB strains isolated from burn patients can induce production of extracellular matrix, which may be related to increase in the ability and thickness of BF formation.

Acinetobacter Infections ; microbiology ; Acinetobacter baumannii ; genetics ; isolation & purification ; Biofilms ; Burns ; microbiology ; Genes, Bacterial ; Humans ; Multigene Family

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

BACKGROUND: We evaluated the effectiveness of isolation measures using cohorting rooms and antimicrobial use in reducing the isolation rate of methicillin-resistant Staphylococcus aureus (MRSA) and multidrug-resistant Acinetobacter baumannii (MDR-AB). METHODS: Four cohorting rooms (16 beds) for patients colonized or infected with multidrug-resistant organisms (MDRO) have been created in the general wards of our 894-bed hospital since October 2003. We prospectively evaluated the isolation rates of MRSA and MDR-AB, and amount of antimicrobial use during the 8-year study period. We also investigated the relationship between antimicrobial use density (AUD) and the isolation rates of MRSA and MDR-AB. RESULTS: After creating cohorting rooms, the isolation rates of MRSA decreased from 1.56 cases per 1,000 patient-days from 2004-2005 to 1.24 from 2006-2007 (P=0.57). The isolation rates of MDR-AB also decreased from 0.72 from 2004-2005 to 0.36 from 2010-2011 (P<0.01). The mean quarterly AUDs of glycopeptides and carbapenems were 30.17+/-6.80 and 19.5+/-7.10, respectively. There were no significant correlations between AUD values and the isolation rate of MRSA or MDR-AB. CONCLUSION: This study suggests that isolation measures using cohorting rooms to help limit the transmission of MDRO infection and colonization, especially MDR-AB, in resource-limited settings is feasible and efficacious.
Acinetobacter ; Acinetobacter baumannii ; Carbapenems ; Cohort Studies ; Colon ; Drug Resistance ; Glycopeptides ; Humans ; Methicillin Resistance ; Methicillin-Resistant Staphylococcus aureus ; Patient Isolation ; Patients' Rooms ; Prospective Studies

OBJECTIVETo investigate the clinical features of ventilator-associated pneumonia (VAP) caused by acinetobacter.

METHODSThe clinical manifestations of 45 cases with ventilator-associated pneumonia caused by acinetobacter between 1995 and 2002 were analyzed. Bacterial susceptibility of acinetobacter strains was determined by Kerby-Bauer method.

RESULTSThe mean age of the subjects was 58 +/- 13 years with 31 patients older than 60 years. All the patients had underlying diseases, most of which were respiratory diseases (37.8%), nervous system diseases (22.2%), and trauma (22.2%). Thirteen cases (28.9%) were mixed infections with other bacteria. The main manifestations were fever, purulent secretion, and solidification in the lung. X-ray revealed inflammatory infiltration in lower lobes of both sides. The mortality was 37.8%. The in vitro activity tests of 28 antibiotics against the acinetobacter strains showed that they were multiresistant. Polymysin B, imipenem, minocycline, ofloxacin, and amikacin were relatively active.

CONCLUSIONThe patients with VAP caused by acinetobacter usually had underlying diseases without unique features and high mortality, and the isolated strains were often mutiresistant. It is necessary to make early diagnosis, select the appropriate agents, and improve the disinfection of the breath loop in the ventilator.

Acinetobacter ; isolation & purification ; Acinetobacter Infections ; microbiology ; Aged ; Cross Infection ; etiology ; Drug Resistance, Bacterial ; Female ; Humans ; Male ; Middle Aged ; Pneumonia, Bacterial ; microbiology ; Ventilators, Mechanical ; microbiology

Acinetobacter Infections ; etiology ; Acinetobacter baumannii ; drug effects ; isolation & purification ; Child, Preschool ; Drug Resistance, Bacterial ; Female ; Humans ; Infant ; Intensive Care Units, Pediatric ; Male ; Risk Factors

OBJECTIVETo study the transferrable character of Acinetobacter baumannii (AB) plasmids with 3 types of beta-lactamase gene.

METHODSThe plasmid of multi-drug resistant AB (donor) isolated from burn wound were transferred to E. coil ATCC25922 (receptor) through conjugation, and drug sensitivity was also observed. Drug-resistant gene and stability of filial generation and zygote were analyzed by PCR.

RESULTSThe drug-resistance of donor plasmids to Sulfamethoxazole, Ampicillin, Cefalotin, Cefpodoxime, Cefuroxime, Imipenem/Cilastatin and Ampicillin/Sulbactam, and three types of beta-lactamase gene were transferred to the receptor, and were also stably transmitted for passages. The minimum inhibitor concentration of receptor to Sulfamethoxazole was > 2 mg/L after conjugation with donor, and inhibitory character could be transferred to next generation.

CONCLUSIONbla(TEM-1), bla(PER-1) and bla(OXA-23) genes carried in the plasmid of AB can be transferred through conjugation and stably transmitted for passages, and it is one of the molecular mechanisms for AB with multi-drug resistance after burn infections.

Acinetobacter Infections ; Acinetobacter baumannii ; enzymology ; genetics ; isolation & purification ; Burns ; microbiology ; Drug Resistance, Multiple, Bacterial ; genetics ; Genes, Bacterial ; Humans ; Microbial Sensitivity Tests ; Plasmids ; beta-Lactamases ; genetics

Acinetobacter Infections ; microbiology ; Acinetobacter baumannii ; drug effects ; isolation & purification ; Anthracosis ; microbiology ; Anti-Bacterial Agents ; pharmacology ; Drug Resistance, Bacterial ; Fosfomycin ; pharmacology ; Humans ; Imipenem ; pharmacology ; Pneumonia, Bacterial ; microbiology

OBJECTIVE: To explore the expression level of class I integrase (intI 1) mRNA in Acinetobacter baumannii from biofilm cells and planktonic cultured cells ,and to analyze the drug-resistance of Class I integron positive strains. METHODS: Acinetobacter baumannii were collected from hospitals,and Class I integron strains were screened by gene amplification. Total RNA of Class I integron positive strains was extracted, and the intI1 mRNA expression in the bioflim cells and planktonic cultured cells was measured by RT-PCR. Susceptibilities to antibiotics of Class I integron positive strains were also examined. RESULTS: The intI1 gene mRNA was expressed under 2 conditions, and the mRNA expressed in the biofilm cells was about 4 times higher than that in the planktonic cultured cells. Among the 64 strains of Acinetobacter baumannii, 46 strains were Class I integron positive strains. The antibiotic resistance of intI1 gene cassette-positive strains was higher than that of gene cassette-negative strains. CONCLUSION The intI1 gene mRNA can be up-regulated in Acinetobacter baumannii biofilm cells.Class I integron plays an important role in drug resistance. It is much easier to capture gene cassettes for bacteria under biofilm condition.
Acinetobacter Infections ; microbiology ; Acinetobacter baumannii ; genetics ; isolation & purification ; Base Sequence ; Biofilms ; Drug Resistance, Multiple ; genetics ; Humans ; Integrases ; biosynthesis ; genetics ; Molecular Sequence Data ; RNA, Messenger ; biosynthesis ; genetics

No abstract available.
Acinetobacter/*isolation & purification ; Acinetobacter Infections/*drug therapy/*microbiology ; Anti-Bacterial Agents/*therapeutic use ; Cross Infection/*microbiology/*therapy ; Female ; Humans ; Male ; Meningitis, Bacterial/*drug therapy/*microbiology ; Staphylococcal Infections/*drug therapy/*microbiology ; Staphylococcus/*isolation & purification