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Background Carbapenem-resistant Acinetobacter species have emerged as notorious pathogens causing nosocomial infections. Several phenotypic methods have been developed for detecting carbapenemase production in Enterobacteriaceae. The accuracy of these methods in the prediction of carbapenemase production in Acinetobacter species has not been studied well. Methods This retrospective study enrolled adult patients with Acinetobacter bacteremia from four medical centers in Taiwan between 2012 and 2016. Their demographics and clinical outcomes were recorded. The carbapenem susceptibility of the Acinetobacter species was determined using the agar diffusion method. The carbapenemase genes were detected by PCR. Four phenotypic methods, including the modified Hodge test (MHT), modified carbapenem inactivation method (mCIM), Carba NP test, and CarbAcineto NP test were carried out to determine the production of carbapenemase. Results We analyzed 257 adults who received initial carbapenem monotherapy for the treatment of Acinetobacter bacteremia. Shock within three days of bacteremia and acquisition of carbapenem non-susceptible isolates were independently associated with a higher 14-day and 30-day mortality in patients with Acinetobacter bacteremia. Among the four phenotypic tests for carbapenemase detection, MHT using the imipenem disc displayed the greatest sensitivity (94%; 95% confidence interval [CI], 89–97%) and specificity (81%; 95% CI, 73–88%) for predicting imipenem non-susceptibility. Conclusion Carbapenem non-susceptibility and shock were independent risk factors for mortality in patients with Acinetobacter bacteremia. The MHT could predict the carbapenem susceptibility of Acinetobacter isolates. It is a cheap and quick assay, which could be applied in clinical practice.

Purpose: To investigate the increasing prevalence of colistin resistance in animal Escherichia coli isolates and their mcr-1-carrying plasmids, especially those shared by isolates from human and retail meats. Methods: E. coli from diseased swine and poultry recovered between 2012 and 2016 were studied. Susceptibility was determined using broth microdilution method or Vitek II system. Fifty-eight mcr-1-positive isolates were randomly selected for further testing, including pulsed-field gel electrophoresis (PFGE) for clonality determination, S1- or I-CeuI-PFGE and Southern blotting for localization of mcr-1, and conjugation for transmissibility. Whole genome sequencing (WGS) was performed for the genetic structure of plasmids. Results: Among the 1234 E. coli isolates from diseased swine, colistin resistance increased from 14.6% (14/96) in 2012 to 43.8% (63/144) in 2016 with a paralleled increase in mcr-1-positivity from 12.5% (12/96) to 33.3% (48/144) in 2016 (P

The higher 14-day mortality rate for patients with Acinetobacter bacteremia receiving tigecycline appropriately compared to other appropriate antibiotics (36.4% versus 14.2%, P = 0.028) was due to the poor effect of tigecycline for isolates with a minimum inhibitory concentration of 2 μg/mL (63.6% of 11 versus 14.2% of 127, P = 0.001).

Background/purpose Patients with Acinetobacter pittii and Acinetobacter nosocomialis bacteremia have lower mortality rates than those with Acinetobacter baumannii bacteremia. However, it is unknown whether these organisms differ in outcomes of bacteremic patients. We conducted this study to answer this question. Methods In this retrospective study conducted at a teaching hospital in Taiwan, we enrolled all 86 patients who had developed A. pittii bacteremia and those with A. nosocomialis bacteremia from 2000 to 2008 while matching for age, sex, Acute Physiology and Chronic Health Evaluation II score, and appropriate antimicrobial therapy. After adjustment, we accessed the clinical characteristics and 14- and 28-day mortalities. Results We found that the patients with A. pittii bacteremia had multiple comorbidities less often and received invasive procedures less frequently. The 14-day mortality rate of patients with A. pittii or A. nosocomialis bacteremia was 14% and 7%, respectively, whereas their 28-day mortality rate was 17% and 9%, respectively. Using the mortality rate in patients with A. nosocomialis bacteremia as a reference, the odds ratios for the 14- and 28-day crude morality in those with A. pittii were 2.16 [95% confidence interval (CI), 0.77–6.05] and 2.06 (95% CI, 0.82–5.15), respectively, whereas the adjusted odds ratios for 14- and 28-day mortality were 1.89 (95% CI, 0.56–6.14) and 1.67 (95% CI, 0.59–4.78) respectively. Conclusion Our 8-year study showed that the mortality rate of A. pittii bacteremia was higher but the difference was not statistically significant.

Background and purpose Amino acid substitutions in GyrA and ParC are associated with resistance to quinolones in Acinetobacter baumannii ( A baumannii ), but this association is rarely elucidated in Acinetobacter genomic species (AGS) 13TU. This study aims to compare the association of amino acid substitutions in GyrA and ParC with quinolone resistance in A baumannii and AGS 13TU in Taiwan. Methods Eleven representative strains of A baumannii and 13 strains of AGS 13TU were selected from 402 bacteremic isolates. The sequences of quinolone resistance determining regions of gyrA and parC were determined. Minimal inhibitory concentrations (MICs) of nalidixic acid, ciprofloxacin, levofloxacin and moxifloxacin were determined by agar dilution method. Results Ser83Leu substitution in GyrA in A baumannii (one strain) was associated with resistance to all tested quinolones. This substitution plus a Ser80Leu or Ser80Tyr in ParC in A baumannii (four strains) and AGS 13TU (two strains) were associated with higher MICs of all quinolones. All but one quinolone MICs of A baumannii (one strain) and AGS 13TU (two strains) carrying a single substitution Ser56Asn in ParC remained in the susceptibility breakpoint. The Ser83Leu substitution in GyrA, even with additional Ser56Asn substitution in ParC, was associated with resistance to only nalidixic acid, but not other newer quinolones in AGS 13TU (two strains). Conclusion A baumannii and AGS 13TU possessed similar quinolone resistance associated with amino acid substitutions in GyrA and ParC. Further study with more strains is needed to determine whether a single Ser83Leu substitution in GyrA was associated with a high level of quinolone MIC only in A baumannii , but not in AGS 13TU.

BackgroundIt is still controversial whether carbapenem-resistant Acinetobacter baumannii (CRAB) is an independent risk factor for mortality. This study aimed to determine the risk factors and outcomes of patients with CRAB bacteremia, compared to those with carbapenem-susceptible A. baumannii (CSAB) bacteremia.MethodsThis retrospective cohort study was conducted in Taipei Veterans General Hospital, Taiwan. Patients with bacteremia due to A. baumannii during June 2002 and December 2007 were included.ResultsA total of 62 patients with CRAB and 164 with CSAB bacteremia were included. Among these patients, the independent risk factors for acquiring CRAB bacteremia were hematological malignancy [odds ratio (OR): 4.04; 95% confidence interval (CI): 1.29–12.70; p = 0.017], previous use of cefepime (OR: 2.60; 95% CI 1.11–6.08; p = 0.028) and use of total parenteral nutrition (OR: 3.06; 95% CI 1.12–8.39; p = 0.029). The patients with CRAB bacteremia had higher mortality rate than those with CSAB bacteremia. However, multivariate analysis showed that among patients with A. baumannii bacteremia, acquisition of CRAB by itself was not an independent risk factor for 14-day mortality. Instead, the independent factors predicting14-day mortality were Acute Physiology and Chronic Health Evaluation (APACHE) score > 20 (OR: 6.33; 95% CI: 2.32–17.26; p

Background To determine whether the susceptibilities and the trends of nonsusceptibility of imipenem, meropenem, sulbactam, and colistin differed among Acinetobacter baumannii , Acinetobacter genomic species 3 (AGS 3), and Acinetobacter genomic species 13TU (AGS 13TU) over 11 years. Methods A total of 1,039 nonduplicate blood isolates of A baumannii complex from bacteremic patients between 1997 and 2007 were collected at Taipei Veterans General Hospital and were identified to the species level using a multiplex polymerase chain reaction method and sequence analysis of 16S–23S intergenic spacer. The minimal inhibitory concentrations of antibiotics were determined by the agar dilution method. Results The nonsusceptibility rates of carbepenems and sulbactam were highest in A baumannii , which also showed a trend toward increasing rate of carbapenems nonsusceptibility over the 11-year period of the study. AGS 13TU had the highest nonsusceptible rate to colistin, comparably increasing trend of carbapenem nonsusceptiblity as that of A baumannii , and is the only species with increasing sulbactam nonsusceptibility. AGS 3 had the lowest rate of nonsusceptibility to all four antimicrobial agents. Conclusion Although A baumannii had the highest nonsusceptibility rate to imipenem, meropenem, and sulbactam over the years, the higher rate of colistin nonsusceptibility and the emergence of nonsusceptibility of carbapenems and sulbactam in AGS 13TU suggested that this species might cause a great problem in the near future.

Background Tigecycline was approved for the treatment of complicated intra-abdominal and complicated skin/skin structure infections. Because of its in vitro effectiveness for multidrug-resistant (MDR) isolates, tigecycline has been prescribed more broadly. This study evaluated tigecycline use after its first introduction in Taiwan and experience with tigecycline for the treatment of MDR Acinetobacter baumannii (MDRAB) infection, especially for ventilator-associated pneumonia. Methods Patients treated with tigecycline were collected retrospectively from February 2008 to July 2008 in Taipei Veterans General Hospital, a 2,900-bed tertiary care medical center in Taiwan. Patients were divided into three groups according to the indications: Group 1, Food and Drug Administration–approved indications; Group 2, health care–associated pneumonia (HAP); and Group 3, urinary tract infection, osteomyelitis, bacteremia, etc. Cases of MDRAB were also identified. Results Among 66 cases, indications for the administration of tigecycline included Food and Drug Administration–approved indications (12, 18.2%), HAP (38, 57.6%), bacteremia (3, 4.5%), catheter-related infections (3, 4.5%), urinary tract infection (4, 6.1%), osteomyelitis (4, 6.1%), and others (2, 3%). Clinical outcome was positive in 20 cases, with higher clinical success rate for Group 1 than Group 2, which may correlate with higher Sequential Organ Failure Assessment score, older age, and more frequent intensive care admission in Group 2. Of the microbiologically evaluable cases, MDRAB predominated (33/51, 64.7%). Among infections with MDRAB (excluding pneumonia without ventilator), the clinical success rate was 12% (3/25). Conclusions The most common indication for the prescription of tigecycline was HAP. Success rate for MDRAB infection was lower than that previously reported, possibly because of serious underlying conditions and comorbidities in our patients. Because of limited choices, physicians should weigh the risk and benefit for prescribing tigecycline.