[show abstract][hide abstract] ABSTRACT: OBJECTIVES:Although many epidemiologic studies have shown that Helicobacter pylori (H. pylori) eradication has prophylactic effects on gastric cancer, their results are less clear in high-risk populations. We conducted this study to examine whether H. pylori eradication would affect the occurrence of metachronous gastric cancer after endoscopic resection in patients with early gastric cancer.METHODS:We retrospectively analyzed 2,089 adults who underwent endoscopic resection of gastric low-grade neoplasia, high-grade neoplasia, or differentiated invasive neoplasia from 2004 to 2008 at Asan Medical Center. Of these, a total of 1,007 patients with early gastric cancer were enrolled in this study. We evaluated the demographic data, the pathology, and the incidence of metachronous recurrence by dividing them into three groups: those without active H. pylori infection (Hp negative group, n=340), those who successfully underwent H. pylori eradication (eradicated group, n=485), and those who failed or did not undergo H. pylori eradication (noneradicated group, n=182).RESULTS:Metachronous recurrence was diagnosed in 75 patients, including 17 in the Hp, 34 in the eradicated, and 24 in the noneradicated groups. Median time to metachronous recurrence was 18 months (range, 7-75 months). The incidence of metachronous gastric cancer was 10.9 cases per 1,000 person-years in the Hp negative group, 14.7 cases per 1,000 person-years in the eradicated group, and 29.7 cases per 1,000 person-years in the noneradicated group. The hazard ratios in the noneradicated group compared with the Hp negative and eradicated groups were 2.5 (P<0.01) and 1.9 (P=0.02), respectively. H. pylori eradication reduced metachronous recurrence of gastric neoplasm, which was also shown in the secondary analysis of 1,487 patients with low-grade neoplasia and early gastric cancer.CONCLUSIONS:Successful H. pylori eradication may reduce the occurrence of metachronous gastric cancer after endoscopic resection in patients with early gastric cancer.Am J Gastroenterol advance online publication, 17 December 2013; doi:10.1038/ajg.2013.404.
The American Journal of Gastroenterology 12/2013; · 7.55 Impact Factor
[show abstract][hide abstract] ABSTRACT: Endoscopic forceps biopsy (EFB) is a major diagnostic procedure for gastric epithelial neoplasia (GEN). However, discrepancy between the result of EFB and endoscopic resection (ER) is not uncommon. Thus, there is controversy over whether specimens obtained by EFB are optimal for diagnosis of GEN. We investigated the discrepancy between EFB and ER in the diagnosis of GEN.
A total of 1,850 GEN cases were histologically diagnosed with EFB, including 954 low-grade dysplasias (LGDs), 315 high-grade dysplasias (HGDs), and 581 carcinomas. Following diagnosis with EFB, all patients were treated with ER. We retrospectively reviewed the pathologic findings and patient characteristics and analyzed predictors for the discrepancy between the two procedures (largest diameter, number of biopsy fragments, number of biopsy fragments/largest diameter, location, macroscopic type, color, surface unevenness, and erosion).
The overall discrepancy rate between EFB and ER was 31.7 % (587/1,850). Among the discordant group, 440 (23.9 %) cases showed a higher grade of disease after ER; 229 of the 954 LGDs (24.0 %) were diagnosed as HGD or carcinoma, 166 of the 315 HGDs (52.7 %) as carcinoma, and 45 of the 581 differentiated carcinomas (7.7 %) as undifferentiated carcinoma. In the LGD group with EFB, the largest diameter (≥1.8 cm; P < 0.001), surface unevenness (P = 0.014), and depressed macroscopic type (P < 0.001) were factors associated with discrepancy. In the carcinoma group with EFB, flat macroscopic type (P = 0.043) was the only significant factor. In the HGD group with EFB, there were no significant factors for discrepancy.
EFB can be insufficient for diagnosing GENs, and ER can be considered not only as treatment but also as a diagnostic modality in GEN. It is especially pertinent to all cases of HGD regardless of their endoscopic features and to cases of LGDs with the largest lesion diameter ≥1.8 cm, surface unevenness, or a depressed macroscopic type.
[show abstract][hide abstract] ABSTRACT: The purpose of the present study was to identify the mediating effects of emotion regulation on the association between cumulative childhood trauma and behavior problems in sexually abused children in Korea, using structural equation modeling (SEM). Data were collected on 171 children (ages 6-13 years) referred to a public counseling center for sexual abuse in Seoul, Korea. Cumulative childhood traumas were defined on the basis of number of traumas (physical abuse, witnessing domestic violence, neglect, traumatic separation from parent, and sexual abuse) and the severity and duration of traumas. Children were evaluated by their parents on emotion regulation using the Emotion Regulation Checklist and internalizing and externalizing behavior problems using the Korean-Child Behavior Checklist. SEM analyses confirmed the complete mediation model, in which emotion dysregulation fully mediates the relationship between cumulative childhood traumas and internalizing/externalizing behavior problems. These findings indicate that emotion regulation is an important mechanism that can explain the negative effects of cumulative childhood traumas and that there is a need to focus on emotion regulation in sexually abused children exposed to cumulative trauma.
[show abstract][hide abstract] ABSTRACT: Six gram-negative, non-fermentative bacteria, which were designated as strains 11-0202T, 11-0607, LUH13522, LUH8638, LUH10268, and LUH10288 were isolated from soil in South Korea, from soil of a beetfield in Germany, soil in the Netherlands, and sediment of integrated fish in Malaysia and Thailand, respectively. Based on 16S rRNA, rpoB, and gyrB gene sequences, they represented a novel species of Acinetobacter. Their 16S rRNA gene sequences showed the greatest pairwise similarity to A. beijerinckii (97.9 to 98.4%). A. johnsonii and A. bouvetii were the species showing the greatest similarities with the six strains in rpoB and gyrB gene sequences, but they showed sequence divergences (85.4-87.6 and 78.1-82.7%, respectively). A strains 11-0202T displayed low DNA-DNA reassociation values less than 40% with the closely related Acinetobacter species. The strains utilized 2,3-butanediol, ethanol, and DL-lactate as sole carbon sources. Cellular fatty acid (CFA) analyses showed similarities to those of related Acinetobacter species: summed feature 3 (C16:1 ω7c, C16:1 ω6c)' (26.0-27.0%), C18:1 ω9c (22.1-23.4%), C16:0 (17.3%-22.0%), and C12:0 (9.2-12.4%). On the basis of current findings, it is concluded that the six strains represent a novel species, for which the name Acinetobacter kookii sp. nov. is proposed. The type strain is strain 11-0202T (= KCTC 32033T = JCM 18512T).
INTERNATIONAL JOURNAL OF SYSTEMATIC AND EVOLUTIONARY MICROBIOLOGY 08/2013; · 2.11 Impact Factor
[show abstract][hide abstract] ABSTRACT: The 4-propargylamino-1,8-naphthalimide based fluorescent probe 1 has been explored as a sensor for selective detection of Au(3+). 4-Amino-1,8-naphthalimides, that possess typical intramolecular charge transfer (ICT) electronic characteristics, have been widely used as versatile platforms for fluorescent probes. The newly designed probe 1 contains a propargylamine moiety at C-4 of the naphthalimide chromophore that reacts with Au(3+) to generate a product that has distinctly different electronic properties from 1. Specifically, the probe undergoes a remarkable change in its absorption spectrum upon addition of Au(3+) that is associated with a distinct color change from yellow to light pink. In addition, a blue shift of ca. 56nm also takes place in the emission spectra of the probe. Consequently, 1 serves as a reaction-based sensor or so called chemodosimeter for Au(3+). Importantly, surfactants enhance the rate of reaction of 1 with Au(3+), thus, enhancing its use as a real time sensor. Finally, the results of studies probing its application to bioimaging of Au(3+) in live cells show that the probe 1 has a unique ability to sense Au(3+) in cells and, in particular, in lipid droplets within cells.
[show abstract][hide abstract] ABSTRACT: BACKGROUND: There are insufficient reports on the outcomes and local recurrence rates for gastric neoplasms treated using argon plasma coagulation (APC). The purpose of this study was to analyze the clinical outcomes in early gastric cancer or gastric adenoma patients following APC treatment. METHODS: Seventy-one patients were enrolled and all underwent APC at the Asan Medical Center between July 2007 and August 2011. Clinical and oncological outcomes were analyzed. RESULTS: The median follow-up period was 20 months (interquartile range 13-29 months). Among the 71 patients we evaluated, nonlifting after submucosal saline injection was found in 35 patients and 15 patients (21.2 %) experienced local recurrence with a median period of 10 months (IQR 5-13 months). The rate of local recurrence was higher in the nonlifting group and the 40-W group than in the lifting group and the 60- or 80-W groups (31.4 vs. 11.1 %, p = 0.045 and 31.7 vs. 6.7 %, p = 0.017, respectively). Multivariate analysis showed that the power setting with the 40-W and nonlifting groups after submucosal injection was associated with local recurrence. CONCLUSIONS: APC therapy after submucosal saline injection using high power (60 or 80 W) appears to be an effective alternative in the management of gastric neoplasm.
[show abstract][hide abstract] ABSTRACT: One hundred and twenty-one isolates of S. maltophilia complex were collected from seven Korean hospitals. Species and groups were identified using partial gyrB gene sequences and antimicrobial susceptibility testing was performed using a broth microdilution method. Based on partial gyrB gene sequences, 118 isolates were identified to belong to S. maltophilia complex including S. maltophilia, S. pavanii, Pseudomonas beteli, P. geniculata, and P. hibisciola. S. maltophilia were further divided into three groups, I to III. While S. maltophilia groups II and III were clustered into Clade A with S. pavanii and P. beteli, S. maltophilia group I was clustered into Clade B with P. geniculata and P. hibisciola. For all S. maltophilia complex isolates, resistance rate to trimethoprim/sulfamethoxazole (TMP/SMX) was very high (30.5%). Antimicrobial resistance rates were varied by species or groups of S. maltophilia complex. Isolates of Clade A showed significantly lower antimicrobial resistance rates than those of Clade B; while 25.0% of Clade A isolates were multidrug-resistant, 46.0% of Clade B isolates were multidrug-resistant (P 0.001). In this study, high antimicrobial resistance rates, particularly to TMP/SMX, were identified among S. maltophilia complex isolates from Korea. Distinct groups among S. maltophilia complex isolates were revealed and antimicrobial resistance rates differed among those groups. These data suggest consideration of alternative agents to TMP/SMX to treat S. maltophilia infections and warrant importance of accurate identification of appropriate selection of treatment option.
Journal of Medical Microbiology 02/2013; · 2.30 Impact Factor
[show abstract][hide abstract] ABSTRACT: The purpose of the present study was to explore the effects of multiple interpersonal traumas on psychiatric diagnosis and behavior problems of sexually abused children in Korea. With 495 children (ages 4-13 years) referred to a public counseling center for sexual abuse in Korea, we found significant differences in the rate of psychiatric diagnoses (r = .23) and severity of behavioral problems (internalizing d = 0.49, externalizing d = 0.40, total d = 0.52) between children who were victims of sexual abuse only (n = 362) and youth who were victims of interpersonal trauma experiences in addition to sexual abuse (n = 133). The effects of multiple interpersonal trauma experiences on single versus multiple diagnoses remained significant in the logistic regression analysis where demographic variables, family environmental factors, sexual abuse characteristics, and postincident factors were considered together, odds ratio (OR) = 0.44, 95% confidence interval (CI) = [0.25, 0.77], p < .01. Similarly, multiple regression analyses revealed a significant effect of multiple interpersonal trauma experiences on severity of behavioral problems above and beyond all aforementioned variables (internalizing β =.12, p = .019, externalizing β = .11, p = .036, total β = .14, p =.008). The results suggested that children with multiple interpersonal traumas are clearly at a greater risk for negative consequences following sexual abuse.
Journal of Traumatic Stress 02/2013; 26(1):149-57. · 2.72 Impact Factor
[show abstract][hide abstract] ABSTRACT: A new hydroxypyrene-based sensor 1 was designed and synthesized as a Zn2+ selective colorimetric and fluorescent chemosensor. This chemosensor showed a new UV–vis absorption peak (λmax = 498 nm) with Zn2+, which can be attributed to an internal charge transfer (ICT) mechanism. In addition, Zn2+ induced a highly selective “turn-on” fluorescence enhancement at long wavelength (λmax = 588 nm) in a buffered system. A significant fluorescence enhancement was observed upon the addition of Zn2+. The combination of two phenol groups on the pyrene and phenyl moieties as well as a conjugated hydrazone group can generate a binding pocket for Zn2+. These results also demonstrate that 1-hydroxypyrene-2-carboaldehyde can be a unique platform to introduce various ligands for the colorimetric and fluorescent recognition of metal ions.
Dyes and Pigments 01/2013; 96(1):176–179. · 3.53 Impact Factor
[show abstract][hide abstract] ABSTRACT: BACKGROUND: The main problem in performing endoscopic submucosal dissection (ESD) of gastric neoplasms is that it is technically difficult, especially for beginners. METHODS: A total of 51 patients were randomly assigned to undergo transnasal endoscope-assisted or routine ESD performed by two endoscopists inexperienced in ESD while supervised by one expert. RESULTS: Total procedure time (p = 0.330), complete resection rate (p = 0.977), and complication rate (p = 0.157) were similar for the patients who underwent transnasal endoscope-assisted and routine ESD, but bleeding control time was significantly longer in the transnasal endoscope-assisted ESD group (p = 0.002). Three and six patients in the transnasal endoscope-assisted and routine ESD groups, respectively, were "dropped out" during the procedures (p = 0.291). The endoscopists tended to regard the traction with the transnasal endoscope as more useful for large tumors (p = 0.062). Bleeding control in patients who underwent the transnasal endoscope-assisted ESD was significantly longer for patients with tumors located in the anterior wall, posterior wall, and lesser curvature of the stomach (p = 0.001). CONCLUSION: Transnasal endoscope-assisted ESD does not result in improved outcomes when performed by beginners, except for some large tumors. The traction method used by beginners was not superior to proper supervision and advice by an expert during ESD and allowing the expert to perform the procedure when the risk of complications is high or the procedure is delayed.
[show abstract][hide abstract] ABSTRACT: A new fluorescent receptor composed of two imidazoliums, two pyrenes and a boronic acid has been synthesized and studied for the recognition of 3,4-dihydroxyphenylacetic acid (DOPAC), which is the metabolite of dopamine. Dopamine, l-DOPA and catechol also induced fluorescence quenching effects, however, 1 displayed a largest association constant with DOPAC. In addition, d-fructose, d-glucose and l-phenylalanine did not show any significant fluorescence change. These fluorescence changes were observed at pH 7.4 in HEPES(0.02 M, pH 7.4)–CH3CN (95:5, v/v). As far as we are aware of, our receptor 1 is the first example of fluorescent chemosensor which shows selectivity for DOPAC. The unique intermolecular excimer formation and fluorescence quenching effects with DOPAC and catechol are carefully explained based on the theoretical calculations.
Sensors and Actuators B Chemical 10/2012; 176:611. · 3.54 Impact Factor
[show abstract][hide abstract] ABSTRACT: BACKGROUND: Reducing food residue by proper preparation methods before endoscopy after distal gastrectomy can increase the quality of examination and decrease patient discomfort. We evaluated the risk factors for food residue and proper methods of preparation for endoscopy after distal gastrectomy. METHODS: Follow-up endoscopy with questionnaires was performed on 1,001 patients who underwent distal gastrectomy at Asan Medical Center between December 2010 and July 2011. RESULTS: Endoscopic examination failed in 94 patients (9.4 %) as a result of large amounts of food residue. Rates of failure were significantly higher in patients who ate a regular diet rather than a soft diet at last dinner before examination (13.9 vs. 6.1 %, p = 0.050), and in those who ate lunch rather than not eating lunch on the day before examination (14.6 vs. 7.7 %, p = 0.020). Multivariate analysis showed that the rate of failed examination was lower in patients who had a history of abdominal surgery (p = 0.011), those who ate a soft (p < 0.001) or liquid (p = 0.003) diet as a last meal rather than a regular diet, those who underwent Billroth I rather than Billroth II reconstruction (p = 0.035), patients with longer fasting time (p = 0.009), and those with a longer gastrectomy-to-endoscopy time interval (p < 0.001). CONCLUSIONS: Patients who undergo follow-up endoscopy after surgery should fast more than 18 h and ingest a soft or liquid diet on the day before examination.
[show abstract][hide abstract] ABSTRACT: Background/Aims: We reviewed the clinical outcome of metachronous gastric adenocarcinoma according to the endoscopic interval after curative treatment of squamous esophageal carcinoma by endoscopic resection or surgical resection. Methodology: Eighteen cases with gastric adenocarcinoma after treatment of esophageal carcinoma at Asan Medical Center between March 1994 and March 2010 were analyzed retrospectively. Results: Median interval between treatment of esophageal cancer and detection of metachronous gastric cancer was 44 months (interquartile range [IQR]=25.5-77.8 months), and median endoscopic interval before finding gastric cancer was 15 months (IQR=12.0-44.8 months). In cases with 12 resectable gastric cancers, the median interval of previous endoscopy before gastric cancer was shorter than that for 6 unresectable cancers (12.0 months, IQR=12-16 months vs. 59.5 months, IQR=37.5-68.5 months, p<0.001) and the rate of death was lower (16.7% [2/12] vs. 83.3% [5/6], p=0.006). Logistic regression showed that a shorter duration of endoscopic interval increased the rate of resectability of gastric cancer (p<0.001) and a higher rate of unresectable gastric cancer and longer duration of endoscopic interval increased death (p=0.029 and p=0.004, respectively). Conclusions: After treatment of esophageal cancer, endoscopic examination at 12-month intervals is important to lower the rate of death due to metachronous gastric cancer.
[show abstract][hide abstract] ABSTRACT: This study reports for the first time the AbaR4-type resistance island with the bla(OXA-23) gene in two carbapenem-resistant A. nosocomialis isolates from South Korea and Thailand.
Antimicrobial Agents and Chemotherapy 06/2012; 56(8):4548-9. · 4.57 Impact Factor
[show abstract][hide abstract] ABSTRACT: During multilocus sequence analysis of Acinetobacter calcoaceticus-Acinetobacter baumannii complex, we identified the evidence of recent genetic recombination between 2 Acinetobacter species. While 3 isolates belonged to A. nosocomialis based on 16S rRNA, gyrB, fusA, gdhB, and rplB gene sequences, they showed close relationships with Acinetobacter genomic species 'close to 13TU' in rpoB, recA, cpn60, rpoD, and gltA gene trees.
[show abstract][hide abstract] ABSTRACT: The emergence of colistin or tigecycline resistance as well as imipenem resistance in Acinetobacter baumannii poses a great therapeutic challenge. The bactericidal and synergistic effects of several combinations of antimicrobial agents against imipenem-, colistin- or tigecycline-resistant A. baumannii isolates were investigated by in vitro time-kill experiments. Six imipenem-resistant A. baumannii blood isolates were examined in this study, including colistin- and tigecycline-susceptible, colistin-resistant but tigecycline-susceptible, and colistin-susceptible but tigecycline-resistant isolates. Time-kill studies were performed using five antimicrobial agents singly or in combinations (imipenem plus colistin, imipenem plus ampicillin-sulbactam, colistin plus rifampicin, colistin plus tigecycline, and tigecycline plus rifampicin) at concentrations of 0.5× and 1× their MICs. Only imipenem was consistently effective as a single agent against all six A. baumannii isolates. Although the effectiveness of combinations of 0.5× MIC antimicrobial agents was inconsistent, combination regimens using 1× MIC of the antimicrobial agents displayed excellent bactericidal activities against all six A. baumannii isolates. Among the combinations of 0.5× MIC antimicrobial agents, the combination of colistin and tigecycline showed synergistic or bactericidal effects against four of the isolates. This in vitro time-kill analysis suggests that antimicrobial combinations are effective for killing imipenem-resistant A. baumannii isolates, even if they are simultaneously resistant to either colistin or tigecycline. However, the finding that the combinations of 0.5× MIC antimicrobial agents were effective on only some isolates may warrant further investigation of the doses of combination agents needed to kill resistant A. baumannii.
Journal of Medical Microbiology 03/2012; 61(Pt 3):353-60. · 2.30 Impact Factor
[show abstract][hide abstract] ABSTRACT: Red ginseng (RG, the extract of Panax ginseng Meyer) has various biological and psychological activities and may also alleviate fatigue-related disorders. The present study was undertaken to evaluate what kind of fatigue red ginseng alleviate. Animals were orally administered with 50, 100, 200, 400 mg/kg of RG for 7 days. Before experiments were performed. Physiological stress (swimming, rotarod, and wire test) are behavioral parameters used to represent physical fatigue. Restraint stress and electric field test to a certain degree, induce psychological fatigue in animals. Plasma concentration of lactate and corticosterone (CORT) were also measured after these behavioral assays. RG supplementation (100 mg/kg) increased movement duration and rearing frequency of restrainted mice in comparison with control. 100 and 200 mg/kg of RG increased swimming time in cold water (8±4℃) while at 100 mg/kg, RG increased electric field crossing over frequencies. 50, 100 and 200 mg/kg RG prolonged running time on the rotarod and at 100 mg/kg, it increased balancing time on the wire. RG at those doses also reduced falling frequencies. RG supplementation decreased plasma CORT levels, which was increased by stress. Lactate levels were not significantly altered. These results suggest that RG supplementation can alleviate more the damages induced by psychological than physical fatigue.
Journal of ginseng research 09/2011; 35(3):331-338. · 2.26 Impact Factor
[show abstract][hide abstract] ABSTRACT: Acinetobacter species have emerged as opportunistic nosocomial pathogens in intensive care units. Epidemic spread and outbreaks of multidrug-resistant or carbapenem-resistant Acinetobacter baumannii infections have been described worldwide. Species distribution, antimicrobial resistance and genotypes were investigated for Acinetobacter species isolates collected from a single institution in Korea over 7 years. Two hundred and eighty-seven Acinetobacter species isolates were collected from patients with bloodstream infections in one Korean hospital from 2003 to 2010. Most of them belonged to the Acinetobacter calcoaceticus-baumannii complex (94.4 %). The most frequently isolated species was A. baumannii (44.2 %), followed by Acinetobacter nosocomialis (formerly Acinetobacter genomic species 13TU) (34.1 %). The proportion of A. baumannii increased significantly from 2008 to 2010 (40.4 to 50.0 %). From 2008, imipenem and meropenem resistance rates increased significantly compared with 2003-2007 (12.9 % and 20.5 %, respectively, to 41.4 % and 41.5 %, respectively). An increased carbapenem resistance rate between the two periods was identified more clearly amongst A. baumannii isolates. Polymyxin-resistant A. baumannii isolates emerged in 2008-2010, despite the availability of few isolates. The increase of carbapenem resistance in A. baumannii might be due to the substitution of main clones. Although ST92 and ST69 were the most prevalent clones amongst A. baumannii in 2003-2007 (47.8 % and 15.9 %, respectively), ST75 and ST138 had increased in 2008-2010 (39.7 % and 25.9 %, respectively). Although ST92 showed moderate resistance to carbapenems, most ST75 and ST138 isolates were resistant to carbapenems. All ST75 and ST138 isolates, but only one ST92 isolate, contained the bla(OXA-23-like) gene. Increased carbapenem resistance in Acinetobacter species and A. baumannii isolates might be due to the expansion of specific carbapenem-resistant clones.
Journal of Medical Microbiology 08/2011; 61(Pt 1):71-9. · 2.30 Impact Factor
[show abstract][hide abstract] ABSTRACT: Current guidelines for endoscopic management such as EMR and endoscopic submucosal dissection (ESD) in early gastric cancer (EGC) are in evolution, with broader indication criteria.
To determine the clinical outcomes of endoscopic treatment, based on absolute indication and extended indication criteria and endoscopic methods.
Tertiary-care, academic medical center.
EMR or ESD was performed on 1627 cases of EGC in 1447 patients from July 1994 to January 2009.
EMR and ESD.
Clinical outcomes of EGC after EMR or ESD, based on the indication criteria.
Although the complete resection rate was higher (95.9% vs 88.4%; P < .001), and the complication rate was lower (6.8% vs 9.8%; P = .054) in the absolute than in the extended indication group, there was no between-group difference in the local recurrence rate (0.9% vs 1.1%; P = .783) at a median follow-up period of 32 months (interquartile range 22-48 months). In the extended indication group, ESD resulted in a significantly higher complete resection rate than EMR (83.0% vs 91.1%; P = .006).
ESD in the extended indication group showed acceptable clinical outcomes with a relatively high complete resection rate and a low local recurrence rate.
[show abstract][hide abstract] ABSTRACT: Relationships between the PmrAB two-component system and colistin resistance were investigated in Acinetobacter baumannii. The sequences of pmrA, pmrB and pmrC in 26 colistin-susceptible (ColS) and 7 colistin-resistant (ColR) A. baumannii isolates were determined. In addition, 30 ColR mutants (colistin minimum inhibitory concentration >64 mg/L) were selected in vitro from 10 ColS strains and the pmrA, pmrB and pmrC sequences of the in-vitro-selected ColR mutants were also determined. Expression of pmrA and pmrB was compared between the ColR mutants and their parent ColS strains using a quantitative real-time polymerase chain reaction method. Elevated expression of pmrA and pmrB genes was evident both in wild-type and in in-vitro-selected ColR strains. However, no amino acid differences in the pmrA, pmrB and pmrC genes were found between wild-type ColR and ColS isolates. Although six kinds of amino acid alterations in pmrB were identified in in-vitro-selected ColR mutants, no changes were found in some of the mutants. These findings indicate that increased expression of the PmrAB system is essential for colistin resistance in A. baumannii but that amino acid alterations might be only partially responsible for resistance.
International journal of antimicrobial agents 06/2011; 37(6):525-30. · 3.03 Impact Factor