Clonal relationship and the association of the ST218 strain harboring bla(OXA-72) gene to mortality in carbapenem-resistant Acinetobacter baumannii bacteremia.

In 2017, the World Health Organization categorized carbapenem-resistant Acinetobacter baumannii (CRAB) as a priority 1, critical antibiotic-resistant bacteria. This study analyzed the clinical outcomes and investigated the molecular epidemiology of CRAB bacteremia in a medical center in Northern Taiwan. We collected 62 blood isolates from patients with CRAB bacteremia from January 2014 to December 2015 at MacKay Memorial Hospital and determined the clonal relationship using the PCR-based technique for molecular epidemiology. Medical charts were reviewed for clinical outcomes. Fifty-six isolates harbored the blaOXA-51-like and blaOXA-23-like carbapenemase genes, 4 isolates harbor the blaOXA-51-like and blaOXA-24-like carbapenemase genes and 2 isolates harbored only the blaOXA-51-like gene. After sequencing, all four isolates of blaOXA-24-like carbapenemase gene were confirmed to be isolates of blaOXA-72 carbapenemase genes. In multivariate analysis in the 60 patients, the independent mortality risk factors of CRAB bacteremia included ≥65 years (elderly) (Odds ratio, 4.04, 95% CI, 1.10-14.83, p = 0.035), chronic kidney disease (4.36, 1.14-16.72, p = 0.032). Isolates harboring the blaOXA-72 gene had the same sequence type (ST218) and PFGE pulsotype raising the possibility of intra-hospital transmission, and all infected patients died. This study showed the clonal relationship of isolates harboring the carbapenemase gene in CRAB bacteremia. Patients with the ST218 strain harboring blaOXA-72 gene had high mortality. This warrants further research to determine the mechanism of virulence and risk factors in order to reduce mortality.

Liu CP ，Lu HP ，Luor T 《-》

Prevalence of different carbapenemase genes among carbapenem-resistant Acinetobacter baumannii blood isolates in Taiwan.

Wang TH ，Leu YS ，Wang NY ，Liu CP ，Yan TR ... -  《Antimicrobial Resistance and Infection Control》

Phenotypic and molecular characterization of Acinetobacter baumannii isolates causing lower respiratory infections among ICU patients.

Multi-drug resistant Acinetobacter baumannii has emerged as important nosocomial pathogen associated with various infections including lower respiratory tract. Limited therapeutic options contribute to increased morbidity and mortality. Acinetobacter baumannii has the ability to persist in the environment for prolonged periods. Breach in infection control practices increases the chances of cross transmission between patients and inter/intraspecies transmission of resistance elements. The present prospective work was conducted among patients with lower respiratory tract infections (LRTI) in the intensive care unit (ICU) to study the etiology with special reference to Acinetobacter baumannii and the role of immediate patient environment in the ICU as possible source of infection. Acinetobacter baumannii were characterized for antimicrobial susceptibility, mechanism of carbapenem resistance and virulence determinants. Molecular typing of the clinical and environmental isolates was undertaken to study the probable modes of transmission. Appropriate respiratory samples from 107 patients with LRTI admitted to ICU during September 2016 to March 2017 were studied for likely bacterial pathogens. Environmental samples (n = 71) were also screened. All the samples were processed using conventional microbiological methods. Consecutive Acinetobacter spp. isolated from clinical and environmental (health care workers and environment from ICU) samples were included in the study. Antimicrobial susceptibility was performed as per CLSI guidelines. Carbapenem resistance, mediated by carbapenemase genes (blaOXA-23-like,blaOXA-24-like,blaOXA-58-like and blaNDM-1) were studied by PCR. Biofilm forming ability was tested phenotypically using microtitre plate method. Pulse Field Gel Electrophoresis (PFGE) was used to study clonality of the clinical and environmental isolates. The prevalence of Acinetobacter baumannii was 26.2% (28/107) and 11.26% (8/71) among patients with LRTI and environmental samples respectively. The carbapenem resistance was high, 96.42% (27/28) and 87.5% (7/8) in clinical and environmental isolates respectively. The most common carbapenemase associated with resistance was blaOXA-23-like gene followed by blaNDM-1 among both the clinical and environmental isolates. All isolates were sensitive to colistin (MIC ≤ 1 μg/ml). Biofilm production was observed among all clinical (n = 28) and 87.5% (7/8) of the environmental isolates. Line listing of the cases suggests the occurrence of infections throughout the study period with no significant clustering. On PFGE, 12 clusters were observed and 16/36 isolates were present in one single cluster that included both clinical and environmental isolates which were either carbapenem resistant or sensitive. Carbapenem resistant Acinetobacter baumannii (CRAB) is an important cause of LRTI in the ICU. PFGE suggests spread of carbapenem resistant isolates via cross transmission among patients and the environment. The detection of blaNDM-1 gene among Acinetobacter baumannii and existence of carbapenem resistant and sensitive isolates within the same clones suggests horizontal transmission of resistant genes among various bacterial species. The ability of Acinetobacter baumannii to form biofilms may contribute to its persistence in the environment. This along with breach in infection control practices are the likely factors contributing to this transmission. This information can be used to strengthen and monitor infection control (IC) and the hospital cleaning and disinfection practices to prevent spread of resistant organisms within the ICU. Colistin remains drug of choice for management of CRAB.

Jain M ，Sharma A ，Sen MK ，Rani V ，Gaind R ，Suri JC ... -  《-》

Emergence of carbapenem-resistant Acinetobacter baumannii ST787 in clinical isolates from blood in a tertiary teaching hospital in Northern Taiwan.

The purpose of this study is to investigate the predominant clones of carbapenem-resistant Acinetobacter baumannii (CRAB) in our hospital in Taiwan by pulsed-field gel electrophoresis (PFGE) and multilocus sequence typing (MLST) technique. We collected 108 non-duplicate A. baumannii clinical blood isolates from January 2012 to December 2013 in MacKay Memorial Hospital. PFGE and MLST were used for typing the A. baumannii isolates and for investigation of the predominant clones. Bacteria isolates were screened by polymerase chain reaction for the presence of the carbapenemase-encoding genes. All 108 isolates were classified as 33 pulsotypes by PFGE. The predominant clones were pulsotype 10 (12.04%) in 2012 and pulsotype 8 (16.67%) in 2013, respectively. The 31 predominant pulsotype isolates were typed by MLST, and ST787 (54.84%) and ST455 (45.16%) were identified. All isolates carried blaOXA-51-like genes, and blaOXA-23-like genes was founded in 101 isolates (93.52%). Other identified resistance genes included blaOXA-24-like and blaOXA-IMP. To the best of our knowledge, this study is the first to describe the microbiological characteristics of CRAB ST787, which carried high genetic resistance to carbapenem, but remained susceptible to colistin. CRAB ST787 was the predominant clone in our hospital in the study period.

Hu YF ，Hou CJ ，Kuo CF ，Wang NY ，Wu AY ，Leung CH ，Liu CP ，Yeh HI ... -  《-》

Molecular Epidemiology of Emerging bla(OXA-23-Like)- and bla(OXA-24-Like)-Carrying Acinetobacter baumannii in Taiwan.

The rate of recovery of carbapenem-resistant Acinetobacter baumannii (CRAB) isolates has increased significantly in recent decades in Taiwan. This study investigated the molecular epidemiology of CRAB with a focus on the mechanisms of resistance and spread in isolates with blaOXA-23-like or blaOXA-24-like All 555 CRAB isolates in our multicenter collection, which were recovered from 2002 to 2010, were tested for the presence of class A, B, and D carbapenemase genes. All isolates with blaOXA-23-like or blaOXA-24-like were subjected to pulsed-field gel electrophoresis, and 82 isolates (60 isolates with blaOXA-23-like and 22 isolates with blaOXA-24-like) were selected for multilocus sequence typing to determine the sequence type (ST) and clonal group (CG) and for detection of additional β-lactamase and aminoglycoside resistance genes. The flanking regions of carbapenem and aminoglycoside resistance genes were identified by PCR mapping and sequencing. The localization of blaOXA was determined by S1 nuclease and I-CeuI assays. The numbers of CRAB isolates carrying blaOXA-23-like or blaOXA-24-like, especially those carrying blaOXA-23-like, increased significantly from 2008 onward. The blaOXA-23-like gene was carried by antibiotic resistance genomic island 1 (AbGRI1)-type structures located on plasmids and/or the chromosome in isolates of different STs (CG92 and novel CG786), whereas blaOXA-24-like was carried on plasmids in CRAB isolates of limited STs (CG92). No class A or B carbapenemase genes were identified. Multiple aminoglycoside resistance genes coexisted in CRAB. Tn6180-borne armA was found in 74 (90.2%) CRAB isolates, and 58 (70.7%) isolates had Tn6179 upstream, constituting AbGRI3. blaTEM was present in 38 (46.3%) of the CRAB isolates tested, with 35 (92.1%) isolates containing blaTEM in AbGRI2-type structures, and 61% of ampC genes had ISAba1 upstream. We conclude that the dissemination and spread of a few dominant lineages of CRAB containing various resistance island structures occurred in Taiwan.

Kuo SC ，Huang WC ，Huang TW ，Wang HY ，Lai JF ，Chen TL ，Lauderdale TL ... -  《-》