Accuracy of American Thoracic Society/Infectious Diseases Society of America criteria in predicting infection or colonization with multidrug-resistant bacteria at intensive-care unit admission
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Acinetobacter baumannii
Stenotrophomonas maltophilia
Background: Multidrug resistant (MDR) Pseudomonas aeruginosa, Acinetobacter baumannii and Stenotrophomonas maltophilia have a leading role in nosocomial infections, including lower respiratory tract (LRT) infections. When polymicrobial infection by these three bacteria occurs, colistin against MDR P. aeruginosa and A. baumannii and trimethoprim/sulfamethoxazole (SXT) against S. maltophilia can be an optional antimicrobial strategy. Objectives: The aim of this study was to investigate the potential synergic effect of colistin-plus-SXT against those MDR P. aeruginosa, A. baumannii and S. maltophilia isolates that were isolated at the same time, from the same LRT sample of patients. Methods: Sixty connected isolates from 20 different patients were collected in a two-year study period. The checkerboard method and time-kill assays were used for synergy testing. Results: All P. aeruginosa and A. baumannii strains were susceptible to colistin, whereas all S. maltophilia isolates were resistant to it. Fifteen percent of MDR A. baumannii strains and all S. maltophilia isolates were susceptible to SXT. By the checkerboard method, colistin-plus-SXT showed synergy in 50%, 35% and 45% of S. maltophilia, MDR P. aeruginosa and MDR A. baumannii strains, respectively. Antagonistic effect was not found. A time-kill assay was performed on strains which showed synergy by the checkerboard method: 70%, 57% and 56% of S. maltophilia, P. aeruginosa and A. baumannii strains showed the same results. Synergic activity of the combination was already detected after 6 h incubation in 86% of S. maltophilia isolates and 50% of P. aeruginosa strains. Regrowth of A. baumannii after 24 hour in the presence of colistin was prevented by the combination. The results gained by CB and TKA methods correlated in 61% of cases, but the ΣFIC values did not correlate with the rate of log10 decrease in TKA. Colistin-plus-SXT combination had synergic effect on 35% of S. maltophilia, 20% of P. aeruginosa and 25% A. baumannii strains by both methods. Conclusions: According to our in vitro results, colistin-plus-SXT combined therapy can be used efficiently in clinical practice as no antagonistic effect was detected. In certain cases colistin-plus-SXT has a synergic effect against MDR P. aeruginosa, A. baumannii and S. maltophilia.
Colistin
Sulfamethoxazole
Respiratory tract
Trimethoprim
Gram
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Background and Objective : Acinetobacter baumannii is an important cause of hospital-derived infection or nosocomial infections in many hospitals. The bacterium has an ability to survive for a long time on common surfaces including medical equipments and drug resistant isolates have been increasingly reported. Bacillusamyloliquefaciens N3-8 was isolated from soil. The secondary metabolites that were produced from this organism showed inhibition againstseveral pathogens including A. baumannii . This study aimed toobserve the range of inhibition and to set a model investigating the ability of crude proteinsproduced from B. amyloliquefaciens inkilling A. baumannii on plastic surface. Material and Methods: The inhibition activity of crude proteins from B. amyloliquefaciens N3-8 was observed against 28isolates of A. baumannii by agar well diffusion. Imipenem, the drug of choice, was used as a positive control. The efficiency of crude proteinsfrom theN3-8 to kill or prevent A. baumannii contamination was done on plastic surface and observed by colony count and streak plate methods using A. baumannii N5, which is a drug resistant isolate.Chlorhexidine of 1.5% was used as a positive control. Results: Thecrude proteins could inhibit 71% (20/28) while imipenem could inhibit only 21% (6/28) of total A. baumannii isolates. Seven isolates showed no inhibition by both compounds, 15 isolates were inhibited by crude proteins but not imipenem, 5 were inhibited by both compounds and 1 isolate was inhibited by imipenem but not the crude proteins. Crude protein at concentrations of1, 2, 4, 8, 16 and 32 mg/ml that spread overthe 5x10 6 CFU/ml of N5 or the other way round could completely kill the bacterium. When N5 was applied before and after the crude proteins, the concentrations of2, 4, 8, 16 and 32 mg/ml could completely kill the N5 similar to 1.5% chlorhexidine. Conclusion: These may be no advantage to use the crude proteins from B.amyloliquefaciens N3 - 8 for antiseptic purpose but they were superior to imipenem in killing the majority of A. baumannii isolates. Further purification and characterization may lead to the discovery of a new drug for treatment of A. baumannii .
Acinetobacter baumannii
Bacillus amyloliquefaciens
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Proper identification of the causative organism in pediatric sepsis is crucial for early diagnosis and prevention of septic shock and organ failure.The aim of the present study was to evaluate the multiplex polymerase chain reaction (PCR) for detection of Acinetobacter baumannii, Pseudomonas aeruginosa, and Stenotrophomonas maltophilia from positive blood cultures for these pathogens isolated from children with hospital- acquired sepsis compared to the conventional biochemical reactions for identification of these organisms.This study was a cross-sectional study performed on 100 isolates from pediatric blood cultures, including Acinetobacter baumannii, Pseudomonas aeruginosa, and Stenotrophomonas maltophilia. The study also included 100 isolates of Escherichia coli as a negative control. All isolates were identified by API 20NE and the multiplex PCR with primers specific to the 3 tested bacteria.Multiplex PCR was positive in 96% of isolates and 4 isolates had negative results. Falsepositive results were reported with three E. coli strains. Multiplex PCR identified all the isolates of Acinetobacter baumannii, 29 isolates of Pseudomonas aeruginosa and 27 isolates of Stenotrophomonas maltophilia. The diagnostic value of the multiplex PCR compared to the biochemical identification revealed sensitivity 96.04%, specificity 96.9%, positive predictive value 97.00%, negative predictive value 96.00% and accuracy 96.50%.The present study highlights the diagnostic value of multiplex PCR to identify Acinetobacter baumannii, Pseudomonas aeruginosa, and Stenotrophomonas maltophilia from positive blood cultures. Multiplex PCR was sensitive, specific and accurate. The accuracy differs according to the organisms with 100% accuracy for Acinetobacter baumannii.
Stenotrophomonas maltophilia
Acinetobacter baumannii
Multiplex
Stenotrophomonas
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Twenty blood isolates of Acinetobacter baumannii were studied, representing eight pulsed-field gel electrophoresis patterns and all different antimicrobial susceptibility patterns observed during 1995–97 at the University Hospital Virgen Macarena, Seville, Spain. The MIC90s (mg/L) of imipenem and meropenem decreased from 16 to 0.5 and from 8 to 4, respectively, in the presence of BRL 42715 (BRL) but not clavulanic acid. Hydrolysing activity (nmol/min/mg) of bacterial supernatants against cefaloridine ranged from 8.8 to 552.3 for A. baumannii type I (imipenem MICs ≤ 2), which expressed only a β-lactamase of pI ≥ 9, and from 12.3 to 1543.5 for A. baumannii type II (imipenem MICs ≥ 4), which expressed a β-lactamase of pI ≥ 9 and two others of pI 6.3 and 7. The hydrolysing activities of A. baumannii type II against imipenem, meropenem and oxacillin were higher than those observed for A. baumannii type I. Ten outer membrane protein (OMP) profiles (A. baumannii types I and II) were visualized on 10% SDS–PAGE gels with 6 M urea, whereas only five OMP profiles (A. baumannii types I and II) were differentiated in 12% SDS–PAGE gels. Five A. baumannii with OMP profile type B, characterized by the absence of a 22.5 kDa OMP, were resistant to meropenem and/or imipenem. Twelve penicillin-binding protein (PBP) patterns were observed. PBP patterns of A. baumannii type II were characterized by the absence of a 73.2 kDa band (PBP 2). We concluded that production of β-lactamases of pI 6.3 and 7.0 and reduced expression of PBP 2 are the most frequently observed mechanisms of resistance to carbapenems. In some isolates, loss of a 22.5 kDa OMP is also related to resistance to carbapenems.
Acinetobacter baumannii
Penicillin binding proteins
Carbapenem
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Background: Multidrug resistant (MDR) Pseudomonas aeruginosa, Acinetobacter baumannii and Stenotrophomonas maltophilia have a leading role in nosocomial infections, including lower respiratory tract (LRT) infections. When polymicrobial infection by these three bacteria occurs, colistin against MDR P. aeruginosa and A. baumannii and trimethoprim/sulfamethoxazole (SXT) against S. maltophilia can be an optional antimicrobial strategy. Objectives: The aim of this study was to investigate the potential synergic effect of colistin-plus-SXT against those MDR P. aeruginosa, A. baumannii and S. maltophilia isolates that were isolated at the same time, from the same LRT sample of patients. Methods: Sixty connected isolates from 20 different patients were collected in a two-year study period. The checkerboard method and time-kill assays were used for synergy testing. Results: All P. aeruginosa and A. baumannii strains were susceptible to colistin, whereas all S. maltophilia isolates were resistant to it. Fifteen percent of MDR A. baumannii strains and all S. maltophilia isolates were susceptible to SXT. By the checkerboard method, colistin-plus-SXT showed synergy in 50%, 35% and 45% of S. maltophilia, MDR P. aeruginosa and MDR A. baumannii strains, respectively. Antagonistic effect was not found. A time-kill assay was performed on strains which showed synergy by the checkerboard method: 70%, 57% and 56% of S. maltophilia, P. aeruginosa and A. baumannii strains showed the same results. Synergic activity of the combination was already detected after 6 h incubation in 86% of S. maltophilia isolates and 50% of P. aeruginosa strains. Regrowth of A. baumannii after 24 hour in the presence of colistin was prevented by the combination. The results gained by CB and TKA methods correlated in 61% of cases, but the ΣFIC values did not correlate with the rate of log10 decrease in TKA. Colistin-plus-SXT combination had synergic effect on 35% of S. maltophilia, 20% of P. aeruginosa and 25% A. baumannii strains by both methods. Conclusions: According to our in vitro results, colistin-plus-SXT combined therapy can be used efficiently in clinical practice as no antagonistic effect was detected. In certain cases colistin-plus-SXT has a synergic effect against MDR P. aeruginosa, A. baumannii and S. maltophilia.
Acinetobacter baumannii
Stenotrophomonas maltophilia
Colistin
Sulfamethoxazole
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Data of patients infected imipenem-resistant Acinetobacter baumannii were get from the HIS system,results of bacterial culture,susceptibility test,patients' general information and treatment effects were analyzed.From January of 2008 to December of 2010,427 strains of Acinetobacter baumannii were detected in patients,among them there were 234 imipenem-resistant strains.There was a yearly increasing trend,which was especially remarkable in 2010.Among the 234 patients infected imipenem-resistant Acinetobacter baumannii,10 died,72 were not healed and 15 gave up treatment.It can concluded that infection of imipenem-resistant Acinetobacter baumannii is with high mortality and poor effect of treatment,antimicrobial drug must be rationally used so as to delay the resistance of antibiotics.
Acinetobacter baumannii
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Objective To compare the two detection methods of metallo-β-lactamase produced by imipenem-resistant Acinetobacter Baumannii.Methods Metallo-β-lactamase produced by imipenem-resistant Acinetobacter Baumannii was detected by modified Hodge test and Etest MBL test.Resistance of Acinetobacter Baumanni to imipenem was assayed with McrioScan WalkAway 96.Results The metallo-β-lactamase was detected in 40 imipenem-resistant Acinetobacter Baumannii strains with the two methods.The metallo-β-lactamase was detected in 36 out of the 40 imipenem-resistant Acinetobacter Baumannii strains by modified Hodge test and in 38 imipenem-resistant Acinetobacter Baumannii strains by Etest MBL test,with a positive detection rate of 90% and 95%,respectively.Conclusion The two detection methods are simple,rapid and accurate for detecting the metallo-β-lactamase produced by imipenem-resistant Acinetobacter Baumannii.
Acinetobacter baumannii
Etest
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We investigated the mechanisms involved in imipenem resistance in 23 clinical strains of Acinetobacter baumannii. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) analysis showed the presence of a 30-kDa protein in imipenem-intermediate A. baumannii (IIAB) and imipenem-resistant A. baumannii (IRAB) strains; this protein was almost undetectable in imipenem-susceptible A. baumannii (ISAB) strains. The 30-kDa protein was identified as an OXA-51-like carbapenemase using two-dimensional gel electrophoresis and mass spectrometry. Similar to other recent findings, bla(OXA-51-like) genes were found to exist in all 23 clinical strains; however, the transcript levels of bla(OXA-51-like) in the IIAB and IRAB were higher than in the ISAB strains using reverse transcriptase PCR (RT-PCR) and real-time RT-PCR assays. This change was due to the presence of an insertion sequence, ISAba1, upstream of bla(OXA-51-like) in the IIAB and IRAB strains that was not present in the ISAB strains. The introduction of bla(OXA-66) (a bla(OXA-51)(-like) gene), identified in ISAB ab1254 and IRAB ab1266, into Escherichia coli TOP10 cells resulted in 3.95-fold and 7.90-fold elevations in resistance to imipenem, respectively. Furthermore, when ISAB ab8 and ISAB ab1254 and their in vitro-selected imipenem-resistant mutants ISAB ab8(r) and ISAB ab1254(r) were compared, the results showed no change in the bla(OXA-66)/bla(OXA-51-like) gene sequences, in expression of the gene, and in the outer membrane protein profiles. However, there was a four- to eightfold reduction in imipenem resistance upon adding carbonyl cyanide m-chlorophenylhydrazone. Taken together, these results suggest that the OXA-66/OXA-51-like carbapenemase contributes to intrinsic resistance to imipenem; however, drug export by an efflux pump may be more important and/or occur more frequently in imipenem-resistant A. baumannii. Furthermore, this is the first report of a Taiwanese strain of an OXA-66/OXA-51-like carbapenemase that confers imipenem resistance in A. baumannii.
Acinetobacter baumannii
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The susceptibility of 20 clinical isolates of Stenotrophomonas maltophilia to the carbapenems imipenem and meropenem was investigated by various methods. S. maltophilia appeared sensitive to meropenem but resistant to imipenem by disc testing in Iso-sensitest agar. Agar dilution MICs were performed using Iso-sensitest agar and with incubation under three sets of atmospheric conditions. MICs of meropenem were considerably lower than those of imipenem; this effect was maximal after incubation in 5% CO2 when the MIC of meropenem was approximately 64 times less than that of imipenem. Induction experiments showed that both carbapenems could induce production of the L1 carbapenemase. However, disc approximation tests showed that imipenem could induced resistance to meropenem. Partially stably derepressed mutants were readily selected in vitro. We conclude that, although S. maltophilia may give large zones of inhibition to meropenem on disc testing, resistant mutants are readily selected and therefore standard sensitivity tests may be poorly predictive of clinical outcome of treatment of S. maltophilia infections with meropenem.
Stenotrophomonas maltophilia
Agar dilution
Carbapenem
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Acinetobacter baumannii
Silver nanoparticle
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