Rates of susceptibility of carbapenems, ceftobiprole, and colistin against clinically important bacteria collected from intensive care units in 2007: Results from the Surveillance of Multicenter Antimicrobial Resistance in Taiwan (SMART).

BACKGROUND: Data on susceptibility to ceftobiprole and colistin, and the complete evolutionary trends of minimum inhibitory concentrations (MICs) of important carbapenem agents among important pathogens collected in intensive care units (ICUs) in Taiwan are lacking. METHODS: We surveyed the MIC distribution patterns of ceftobiprole and colistin and susceptibility profiles of some important pathogens collected from patients hospitalized in intensive care units (ICUs) of major teaching hospitals throughout Taiwan in 2007. We also investigated the rates of nonsusceptibility to powerful carbapenems (imipenem, meropenem) among four important species of Enterobacteriaceae (Escherichia coli, Klebsiella pneumoniae, Enterobacter cloacae, and Proteus mirabilis) collected during the same period. MIC breakpoints recommended by the Clinical and Laboratory Standards Institute in 2014 were applied. RESULTS: Colistin showed excellent in vitro activity (susceptibility rate, 96%) against Acinetobacter baumannii isolates but moderate (73-77% susceptibility rate) activity against isolates of Pseudomonas aeruginosa and E. cloacae. The ceftobiprole MIC90 value was 4 µg/mL for methicillin-resistant Staphylococcus aureus and 16 µg/mL for P. aeruginosa. The phenotype of methicillin resistance did not markedly increase the MIC value of ceftobiprole among S. aureus isolates. Interestingly, the proportion of isolates that displayed nonsusceptibility to imipenem was significantly higher among P. mirabilis isolates than among isolates of the other three Enterobacteriaceae species, regardless of the production of extended-spectrum ß-lactamase. CONCLUSION: Continuous monitoring of susceptibility profiles of ICU pathogens to important antibiotics is warranted to provide appropriate antimicrobial regimens against infections in the ICU.

Carbapenem susceptibility among Escherichia coli, Klebsiella pneumoniae, and Enterobacter cloacae isolates obtained from patients in intensive care units in Taiwan in 2005, 2007, and 2009.

To investigate the evolutionary trends in non-susceptibility of carbapenems against the isolates of Escherichia coli, Klebsiella pneumoniae, and Enterobacter cloacae from patients hospitalized in intensive care units (ICUs) of major teaching hospitals throughout Taiwan during 2005-2009, we applied the breakpoints of MICs recommended by Clinical and Laboratory Standards Institute and European Committee on Antimicrobial Susceptibility Testing in 2013. Escalations in imipenem MIC levels for overall E. coli and E. cloacae isolates and extended-spectrum ß-lactamase (ESBL)-producing K. pneumoniae isolates were noted during this period. The overall MIC levels against imipenem and meropenem for subgroups of ESBL producers of 3 Enterobacteriaceae species were significantly higher than those of respective overall groups in 2007 and 2009. Compared with meropenem, we found that significant evidence of imipenem MIC creep and evidence of extraordinarily high rates of non-susceptibility to ertapenem among isolates of 3 species in 2009 existed. The prominent rises in rates of ertapenem non-susceptibility for ESBL-producing E. coli and K. pneumoniae during 2005-2009 and rate of ESBL positivity for E. cloacae between 4 years were notably found. Based on our findings, ertapenem should be used cautiously in management of the ICU infections caused by these potentially ESBL-producing Enterobacteriaceae isolates in Taiwan.

Relationship between the distribution of cefepime minimum inhibitory concentrations and detection of extended-spectrum ß-lactamase production among clinically important Enterobacteriaceae isolates obtained from patients in intensive care units in Taiwan: results from the Surveillance of Multicenter Antimicrobial Resistance in Taiwan (SMART) in 2007.

BACKGROUND: The data on susceptibility of important cephalosporins against four Enterobacteriaceae members producing potential extended-spectrum ß-lactamase (ESBL) collected from Taiwanese intensive care units are lacking. METHODS: Minimum inhibitory concentrations (MICs) of cefotaxime, ceftazidime, and cefepime were determined using agar dilution method, against Escherichia coli (n = 344), Klebsiella pneumoniae (n = 359), Enterobacter cloacae (n = 103), and Proteus mirabilis (n = 78). Susceptibilities of these isolates to three cephalosporins were assessed according to MIC breakpoints recommended by the Clinical and Laboratory Standards Institute (CLSI) and the European Committee on Antimicrobial Susceptibility Testing (EUCAST) in 2013. The double-disk synergy test using disks containing cefepime (30 µg) with or without clavulanate (10 µg) was applied to confirm production of ESBL for isolates with cephalosporin MIC ≥ 2 µg/mL. RESULTS: A total of 175 isolates were verified as ESBL producers. The rates of cefepime susceptibility among the ESBL-producing isolates, according to CLSI (EUCAST) criteria, were 56.7% (22.4%) for E. coli, 61.3% (12.0%) for K. pneumoniae, 57.9% (31.6%) for E. cloacae, and 71.4% (7.1%) for P. mirabilis. Using different cefepime MIC breakpoints (MICs ≥ 16 µg/mL recommended by CLSI criteria and ≥ 2 µg/mL by EUCAST criteria) to define nonsusceptibility, we found that both criteria were poorer at predicting ESBL producers among K. pneumoniae and E. cloacae than among the other two species. In addition, we also found that the cefepime MIC level of 1.0 µg/mL best distinguished non-ESBL- from ESBL-producing K. pneumoniae and E. cloacae. CONCLUSION: To detect ESBLs, CLSI should revise the cefepime MIC breakpoint against Enterobacteriaceae.

Trend in vancomycin susceptibility and correlation with molecular characteristics of methicillin-resistant Staphylococcus aureus causing invasive infections in Taiwan: results from the Tigecycline in vitro Surveillance in Taiwan (TIST) study, 2006-2010.

This study was intended to investigate the trend in vancomycin susceptibility and correlation with molecular characteristics of methicillin-resistant Staphylococcus aureus (MRSA) causing invasive infections. A total of 670 MRSA isolates were collected from patients with invasive infections as part of bacterial collection in the Tigecycline in vitro Surveillance in Taiwan (TIST) from 2006 to 2010. MICs of the isolates to vancomycin were determined using the agar dilution method. Characteristics of staphylococcal cassette chromosome mec (SCCmec), mec-associated hypervariable region (dru), and accessory gene regulator (agr) of the isolates were identified by polymerase chain reaction methods. MRSA isolates with SCCmec types I, II, and III were molecularly defined as hospital-associated MRSA (HA-MRSA), and those with SCCmec types IV, V, and VT were assigned as community-associated MRSA (CA-MRSA). All but 1 MRSA isolates exhibited vancomycin MICs ≤1 mg/L. A declining trend in vancomycin MICs among MRSA isolates was noted, which was associated with the decline in proportion of HA-MRSA. The percentage of CA-MRSA increased from 25.6% in 2006 to 46.0% in 2010. An increase in the geometric mean of vancomycin MICs was found in MRSA with particular molecular types such as SCCmec types II and III, agr groups I and II, and dru10-14. A significant correlation among particular molecular types was found, including SCCmecII-agr group II-dru4, SCCmecIII-agr group I-dru11-14, SCCmecIV-agr group II-dru9, and SCCmecVT-agr group I-dru9 and dru11. There was no vancomycin creep among MRSA isolates, and the declining trend of vancomycin MIC against MRSA was attributed to the increasing prevalence of CA-MRSA over time.

Risk factors for imipenem-nonsusceptible Acinetobacter nosocomialis bloodstream infection.

BACKGROUND: The emergence of imipenem-nonsusceptible (INS) Acinetobacter baumannii complex has had a great impact on healthcare systems worldwide. Understanding the risk factors related to INS infection is useful for infection control. The risk factors for INS A. baumannii have been well documented; however, the risk factors related to INS Acinetobacter nosocomialis infection lack documentation. The purpose of this study was to identify the risk factors associated with INS A. nosocomialis bacteremia. METHODS: This retrospective 9-year study included 329 adults with A. nosocomialis bacteremia in a tertiary medical center in Taiwan. Acinetobacter nosocomialis was identified using a multiplex polymerase chain reaction method and sequence analysis of a 16S-23S intergenic spacer. RESULTS: Among 329 patients with A. nosocomialis bacteremia, 67 had INS isolates (20.4%). Patients with INS isolates tended to have a more severe form of the diseases [with ICU admission and a higher APACHE (Acute Physiology and Chronic Health Evaluation) II score], specific underlying diseases (associated with chronic lung diseases and end-stage renal diseases, but less commonly alcoholism and chemotherapy), multiple invasive procedures, pneumonia as a primary focus of infection, and prior antimicrobial use (sulbactam, antipseudomonal penicillins, aminoglycosides, and carbapenems). Multivariable analysis showed that ICU admission, chronic lung diseases, arterial line catheterization, total parenteral nutrition, and prior use of carbapenems were independent risk factors; prior use of carbapenems was found to be the most influential (odds ratio 6.36, 95% confidence interval 2.00-20.21; p = 0.002). CONCLUSION: To our knowledge, this is the first study describing the risk factors associated with INS A. nosocomialis bacteremia. Regulated antibiotic control policy, especially for carbapenem, and infection control measures targeting patients hospitalized in ICU, with chronic lung diseases and multiple invasive procedures, may be helpful in reducing INS A. nosocomialis infection.

Trends in the antimicrobial susceptibilities and serotypes of Streptococcus pneumoniae: results from the Tigecycline In Vitro Surveillance in Taiwan (TIST) study, 2006-2010.

Isolates of Streptococcus pneumoniae (n = 530) were collected from 20 hospitals in different parts of Taiwan from 2006 to 2010. MICs to 16 antimicrobial agents were determined by broth dilution method and serotypes were identified by latex agglutination. Based on meningitis (non-meningitis) criteria established by the CLSI, 11.7% (63.2%) of all isolates were susceptible to penicillin and 46.0% (83.8%) were susceptible to ceftriaxone. Of the isolates, 94.3% were non-susceptible to azithromycin and 5.8% and 7.2% were non-susceptible to moxifloxacin and levofloxacin, respectively. Susceptibility to penicillin by meningitis criteria increased significantly (P = 0.0012) with year, and that to clindamycin and amoxicillin/clavulanic acid declined significantly (P < 0.05). Six major serotypes were found, namely 19F (24.0%), 23F (18.5%), 14 (13.6%), 6B (12.5%), 19A (7.5%) and 3 (5.1%). Prevalence of serotypes 19F and 14 remained stationary, that of serotype 6B decreased significantly (P < 0.0001) and that of serotype 19A increased significantly (P < 0.0001) with year. The coverage rate of PCV-7 among the pneumococcal isolates declined from 80.5% in 2006 to 50% in 2010 (P < 0.0001) and that of PCV-13 declined from 91.5% in 2009 to 75% in 2010. The non-susceptibility rate to levofloxacin was highest among serotype 23F isolates (13.3%) and lowest among serotype 19A isolates (2.5%). Rates of resistance to the four agents penicillin, ceftriaxone, azithromycin and clindamycin were highest among serotype 19A isolates (70.0%) and 23F isolates (49.0%). All serotype 3 isolates were susceptible to four of the most commonly used antibiotics (penicillin, ceftriaxone, azithromycin and levofloxacin).

Carbapenem susceptibilities and non-susceptibility concordance to different carbapenems amongst clinically important Gram-negative bacteria isolated from intensive care units in Taiwan: results from the Surveillance of Multicentre Antimicrobial Resistance in Taiwan (SMART) in 2009.

To investigate the in vitro susceptibilities to various carbapenems amongst clinical Gram-negative bacteria isolated from patients in intensive care units of ten major teaching hospitals in Taiwan in 2009, a survey was conducted to determine the minimum inhibitory concentrations (MICs) of ertapenem, imipenem, meropenem and doripenem against isolates of Enterobacteriaceae (n = 594), Pseudomonas aeruginosa (n = 185), Acinetobacter baumannii (n = 192) and Burkholderia cepacia (n = 23) using the agar dilution method. Susceptibilities were determined according to 2009, 2011 and 2012 MIC breakpoints recommended by the CLSI as well as 2012 MIC breakpoints recommended by EUCAST. Based on CLSI 2012 criteria, the ertapenem susceptible rate was 93%, 81%, 68% and 92% for Escherichia coli, Klebsiella pneumoniae, Enterobacter cloacae and Serratia marcescens, respectively. All Proteus mirabilis and Morganella morganii isolates were susceptible to ertapenem; however, 64% of P. mirabilis and all M. morganii isolates were non-susceptible to imipenem. Meropenem and doripenem had better activities than imipenem against ertapenem-non-susceptible Enterobacteriaceae isolates. E. coli, K. pneumoniae and E. cloacae with ertapenem MICs≥4 mg/L were synchronously not susceptible to imipenem, meropenem and doripenem. Imipenem susceptibility was 65% and 29% for P. aeruginosa and A. baumannii, respectively. Additionally, P. aeruginosa and A. baumannii isolates with imipenem MICs≥8 mg/L were also not susceptible to meropenem and doripenem. These data provide a better understanding of choosing appropriate carbapenem agents to treat infections caused by ertapenem-non-susceptible Enterobacteriaceae as well as P. aeruginosa and A. baumannii isolates with imipenem MICs≥4 mg/L.

Dissemination of multidrug-resistant Acinetobacter baumannii carrying BlaOxA-23 from hospitals in central Taiwan.

BACKGROUND: Imipenem-resistant Acinetobacter baumannii (IRAB) poses a great threat to healthcare systems. Production of carbapenem-hydrolyzing class D ß-lactamases (CHDLs) is the major mechanism for imipenem resistance. In this study, we found a high prevalence of IRAB carrying a gene encoding CHDL, bla(OxA-23), in central Taiwan and elucidated the molecular characteristics and possible mechanisms of the spread of these isolates. METHODS: During 2007, we collected 291 nonrepetitive A baumannii isolates from 10 teaching hospitals in Taiwan. The antimicrobial susceptibility of the isolates was determined by agar dilution or Etest. The genes encoding carbapenemase and related structure were detected by polymerase chain reaction mapping and sequencing, and the clonal relationship of the isolates was analyzed by pulsed-field gel electrophoresis. Plasmid localization of bla(OxA-23) was determined by extraction of plasmid with commercial kit and Southern blot analysis. RESULTS: Among 142 IRAB isolates, 30 harbored the bla(OxA-23). The prevalence of IRAB with bla(OxA-23) was highest in central Taiwan compared to other areas [24.8% (27/109) vs. 1.6% (3/182); p < 0.001]. These IRAB with bla(OxA-23) were also resistant to other antimicrobial agents, except colistin. The PCR methods showed the presence of bla(OxA-51) in all isolates. We could exclude clonal spreading due to the diversity of the pulsotype. The bla(OxA-23) gene was detected in the plasmids of 6 isolates. Tn2006 was present in 22 (73.3%) isolates, and Tn2008, in 6 other isolates (26.7%). Two strains had bla(oxa-23)-ΔATPase but lacked upstream ISAba1. CONCLUSION: The high prevalence of bla(OxA-23)-harboring IRAB in central Taiwan might be attributed to the transposition event of Tn2006.

In vitro susceptibilities of non-Enterobacteriaceae isolates from patients with intra-abdominal infections in the Asia-Pacific region from 2003 to 2010: results from the Study for Monitoring Antimicrobial Resistance Trends (SMART).

The Study for Monitoring Antimicrobial Resistance Trends (SMART) is an international surveillance study designed to monitor resistance trends among aerobic and facultative Gram-negative bacilli (GNB) isolated from intra-abdominal infections. During 2003-2010, a total of 20710 GNB isolates were collected at medical centers in China, Hong Kong, Korea, New Zealand, and Taiwan. The susceptibility profiles of 2252 isolates of non-Enterobacteriaceae GNB were determined. At least 10 isolates of a given organism were required for that organism to be included in the analysis. Pseudomonas aeruginosa was the leading organism (49.2% of non-Enterobacteriaceae GNB), followed by Acinetobacter baumannii (21.5%), Aeromonas spp. (11.6%), and Stenotrophomonas maltophilia (9.1%). All the other species/genera made up less than 2%. The rates of susceptibility of the four major organisms were examined for two different time periods and according to whether the isolates had been obtained <48 h after hospitalization or ≥ 48 h after hospital admission. P. aeruginosa, Aeromonas spp., and S. maltophilia showed sustained levels of susceptibility to several antimicrobial agents in the two time periods, whereas A. baumannii exhibited very high rates of resistance to most antimicrobial agents including imipenem. Nosocomial P. aeruginosa and A. baumannii were more resistant than community-acquired pathogens, although this was not the case for Aeromonas spp. and S. maltophilia. Worldwide and regional surveillance is necessary to guide empirical antimicrobial therapy for infections due to non-Enterobacteriaceae GNB.

Antimicrobial susceptibility profiles of Gram-negative bacilli isolated from patients with hepatobiliary infections in Taiwan: results from the Study for Monitoring Antimicrobial Resistance Trends (SMART), 2006-2010.

We investigated the trends in antimicrobial resistance among species of Gram-negative bacilli isolated from patients with hepatobiliary tract infections in Taiwan during the period 2006-2010 as part of the Study for Monitoring Antimicrobial Resistance Trends (SMART). During the study period, 1032 isolates of Gram-negative bacilli that had been collected from patients with hepatobiliary infections were tested for susceptibility to 12 antimicrobial agents in accordance with the Clinical and Laboratory Standards Institute guidelines. Enterobacteriaceae accounted for the majority (n = 874, 84.7%) of isolates and Escherichia coli was the most common pathogen (n = 323, 31.3%). There were significantly more E. coli (P = 0.001) and Proteus mirabilis (P = 0.031) isolates collected from patients who had been hospitalized for less than 48 h and significantly more Serratia marcescens (P = 0.035) and Pseudomonas aeruginosa (P = 0.008) isolates collected from patients who had been hospitalized for 48 h or longer. The prevalence of extended-spectrum ß-lactamase (ESBL)-producing pathogens was low. The decline in susceptibility rates with time was remarkable for ceftazidime (P = 0.036), ciprofloxacin (P = 0.029), and levofloxacin (P = 0.018). The most effective antibiotics, i.e., those that were active against more than 90% of Enterobacteriaceae, were amikacin, cefepime, imipenem, ertapenem, and piperacillin-tazobactam. Susceptibility of P. aeruginosa to anti-pseudomonal agents was greater than 80%. In this study, we found an overall increase in resistance to antimicrobial agents among Gram-negative bacilli isolated from patients with hepatobiliary tract infections in Taiwan. Surveillance of antimicrobial susceptibility and updates of treatment guidelines are recommended to help achieve optimal therapy for patients with hepatobiliary infections.

Correlation between carbapenem consumption and resistance to carbapenems among Enterobacteriaceae isolates collected from patients with intra-abdominal infections at five medical centers in Taiwan, 2006-2010.

We investigated the trend in resistance to carbapenems among isolates of Enterobacteriaceae that had been collected from patients with intra-abdominal infections at five medical centers in Taiwan from 2006 to 2010 and evaluated the correlation between resistance to carbapenems and consumption of said agents as part of the Study for Monitoring Antimicrobial Resistance Trends (SMART). During the study period, the usage of ertapenem and that of total carbapenems (ertapenem, imipenem, and meropenem) increased significantly from 6.13 to 13.38 defined daily doses per 1000 patient-days for ertapenem and from 20.43 to 34.25 defined daily doses per 1000 patient-days for total carbapenems. The most common species were Escherichia coli (n = 1095), Klebsiella spp. (n = 663), and Enterobacter spp. (n = 202). The susceptibility of all isolates to ertapenem and to imipenem varied during the study period. For ertapenem, the rates of nonsusceptibility ranged from 3.5% to 10.3% and those for imipenem ranged from 3.5% to 10.7%. Although the use of carbapenems increased during the study period, there was no marked increase in resistance to carbapenems. Continuous monitoring of resistance trends is necessary so that antimicrobial prescription policies can be adjusted and infection control intervention programs can be implemented.

Antimicrobial susceptibility of pathogens isolated from patients with complicated intra-abdominal infections at five medical centers in Taiwan that continuously participated in the Study for Monitoring Antimicrobial Resistance Trends (SMART) from 2006 to 2010.

The Study for Monitoring Antimicrobial Resistance Trends (SMART) is a worldwide surveillance program designed to longitudinally monitor the in vitro activity of antimicrobial agents against pathogens that cause intra-abdominal infections (IAIs). In this study, trends in antimicrobial resistance during the period 2006 to 2010 were analyzed at five tertiary-care hospitals in Taiwan. Enterobacteriaceae accounted for the majority (80.9%) of the 2417 Gram-negative isolates, and the two most common species were Escherichia coli (38.8%) and Klebsiella pneumoniae (23.5%). The rates of susceptibility of Enterobacteriaceae isolates to cephalosporins decreased during the study period. Although carbapenems, fluoroquinolones, piperacillin-tazobactam, and amikacin were active in vitro against more than 80% of the Enterobacteriaceae isolates, the activity of carbapenems declined during the study period. Extended-spectrum ß-lactamase (ESBL) production in E. coli was steady, but that in K. pneumoniae decreased during the study period. The rate of ESBL-producing species was three-fold higher among patients with nosocomial IAIs than among patients with community-acquired IAIs. The majority of isolates from liver were K. pneumoniae (69%) and very few of those isolates were ESBL producers (0.9%). Pseudomonas aeruginosa (9.3%) and Acinetobacter baumannii (3.8%) were the two most common non-Enterobacteriaceae. P. aeruginosa showed improved susceptibility, whereas A. baumannii showed a rapid development of resistance during the study period. There was marked geographic variation in resistance patterns of the isolates obtained during the study period. Northern Taiwan had the highest rate of ESBL producers and the highest rate of ceftazidime resistance among P. aeruginosa isolates. Central Taiwan had the lowest rate of ESBL producers but the highest rates of carbapenem resistance among P. aeruginosa and A. baumannii isolates. Continuous monitoring and regular updates of epidemiological data are needed to guide appropriate empiric antimicrobial therapy.

Epidemiology and antimicrobial susceptibility profiles of Gram-negative bacteria causing urinary tract infections in the Asia-Pacific region: 2009-2010 results from the Study for Monitoring Antimicrobial Resistance Trends (SMART).

In 2009, the Study for Monitoring Antimicrobial Resistance Trends (SMART) was expanded to include surveillance of Gram-negative pathogens causing urinary tract infections (UTIs) in the Asia-Pacific region. A total of 1762 isolates were collected from 38 centers in 11 countries from patients with UTIs in 2009 and 2010. In vitro susceptibilities were determined by the broth microdilution method and susceptibility profiles were determined using minimum inhibitory concentration (MIC) interpretive criteria, as recommended by the Clinical and Laboratory Standards Institute (CLSI) in 2010 (M100-S20), in 2011 (M100-S21), and in 2012 (M100-S22). Enterobacteriaceae comprised 86.0% of the isolates, of which Escherichia coli (56.5%) and Klebsiella pneumoniae (13.8%) were the two most common species. Amikacin was the most effective antibiotic (91.7%), followed by ertapenem (86.9%), imipenem (86.6%), and piperacillin-tazobactam (84.9%). Rates of susceptibility were 50.3% for cefoxitin and ranged from 50.3% to 74.2% for the third- and fourth-generation cephalosporins. For ciprofloxacin and levofloxacin, the susceptibility rates were 51.4% and 54.4%, respectively. Extended-spectrum ß-lactamase (ESBL)-producing Enterobacteriaceae comprised 28.2% of all isolates. We also found a high rate of resistance to carbapenems among Acinetobacter baumannii and Pseudomonas aeruginosa causing UTI. Interestingly, according to 2012 CLSI breakpoints, approximately 33.4% of ESBL producers were still susceptible to ceftazidime. However, this in vitro efficacy of ceftazidime needs to be validated in vivo by clinical data. The lowered CLSI interpretive breakpoints for piperacillin-tazobactam, carbapenems, and some cephalosporins in 2011-2012 for Enterobacteriaceae resulted in an approximate 5% drop in susceptibility rates for each drug, with the exception of imipenem for which the susceptibility rate dropped from 99.4% according to 2010 criteria to 91.2% according to 2011 criteria. With the updated CLSI criteria, the antimicrobial resistance threat from UTI pathogens in the Asia Pacific area was revealed to be more prominent.

Impact of revised CLSI breakpoints for susceptibility to third-generation cephalosporins and carbapenems among Enterobacteriaceae isolates in the Asia-Pacific region: results from the Study for Monitoring Antimicrobial Resistance Trends (SMART), 2002-2010.

This study examined the rates of susceptibility to third-generation cephalosporins and carbapenems among Enterobacteriaceae isolates that had been obtained from patients with intraabdominal infections in the Asia-Pacific region as part of the Study for Monitoring Antimicrobial Resistance Trends (SMART). Susceptibility profiles obtained using 2009 Clinical and Laboratory Standards Institute (CLSI) breakpoints were compared with those obtained using the 2011 CLSI breakpoints. From 2002 to 2010, Escherichia coli and Klebsiella pneumoniae together accounted for more than 60% of the 13714 Enterobacteriaceae isolates analyzed during the study period. Extended-spectrum ß-lactamase (ESBL) producers comprised 28.2% of E. coli isolates and 22.1% of K. pneumoniae isolates in the Asia-Pacific region, with China (55.6% and 33.7%, respectively) and Thailand (43.1% and 40.7%, respectively) having the highest proportions of ESBL producers. Based on the 2011 CLSI criteria, 77.2% of the Enterobacteriaceae isolates, 40.4% of ESBL-producing E. coli, and 25.2% of ESBL-producing K. pneumoniae isolates were susceptible to ceftazidime. Carbapenems showed in vitro activity against >90% of Enterobacteriaceae isolates in all participating countries, except for ertapenem in South Korea (susceptibility rate 82.2%). Marked differences (>5%) in susceptibility of ESBL-producing E. coli and K. pneumoniae isolates to carbapenems were noted between the profiles obtained using the 2009 CLSI criteria and those using the 2011 CLSI criteria. Continuous monitoring of antimicrobial resistance is necessary in the Asia-Pacific region.

Trends in susceptibility of vancomycin-resistant Enterococcus faecium to tigecycline, daptomycin, and linezolid and molecular epidemiology of the isolates: results from the Tigecycline In Vitro Surveillance in Taiwan (TIST) study, 2006 to 2010.

Among the 219 vancomycin-resistant Enterococcus faecium isolates collected in 20 Taiwanese hospitals from 2006 to 2010, all were susceptible to linezolid and daptomycin, and 98.6% were susceptible to tigecycline. There was a shift toward higher tigecycline MIC values (MIC(90)s) from 2006-2007 (0.06 µg/ml) to 2008-2010 (0.12 µg/ml). The MIC(90)s of daptomycin and linezolid remained stationary. Although pulsotypes among the isolates from the 20 hospitals varied, intrahospital spreading of several clones was identified in 13 hospitals.

Comparison of microbiological and clinical characteristics based on SCCmec typing in patients with community-onset meticillin-resistant Staphylococcus aureus (MRSA) bacteraemia.

Molecular identification methods based on the staphylococcal cassette chromosome mec (SCCmec) genotype are more reliable than clinical risk factors and demographic data for differentiating community-acquired and healthcare-associated (HCA) meticillin-resistant Staphylococcus aureus (MRSA). However, patients with community-onset (CO) MRSA infections, defined as a culture-positive sample obtained <48h after admission and from patients with HCA risk factors, have been infrequently studied. This study compared the clinical profiles of different SCCmec genotypes in this group of patients. From 2004 to 2008, the clinical profiles of 122 non-repetitive patients with CO-MRSA infections at a tertiary medical centre in Taiwan were retrospectively recorded and the molecular characteristics of the isolates were examined. The proportion of SCCmec IV/V genotypes increased from 9.5% to 35.3% from 2004 to 2008. There were no differences in demographic data, underlying diseases, invasive procedures or outcomes between the SCCmec II/III and IV/V groups, except that patients with SCCmec II/III genotypes tended to have more HCA risk factors (3.1 vs. 2.4; P=0.008). Multivariate logistic regression analysis revealed that having at least four HCA risk factors was independently associated with SCCmec II/III. The sensitivity of recovering SCCmec IV/V genotypes from patients with less than four HCA risk factors was 89.3%. This study revealed the emergence of SCCmec IV/V genotypes in CO-MRSA infections. Although the clinical characteristic boundaries between SCCmec II/III and IV/V diminished, having at least four HCA risk factors made the presence of SCCmec IV/V genotypes less likely in patients with CO-MRSA infections.

Agreement assessment of tigecycline susceptibilities determined by the disk diffusion and broth microdilution methods among commonly encountered resistant bacterial isolates: results from the Tigecycline In Vitro Surveillance in Taiwan (TIST) study, 2008 to 2010.

The Tigecycline In Vitro Surveillance in Taiwan (TIST) study, initiated in 2006, is a nationwide surveillance program designed to longitudinally monitor the in vitro activity of tigecycline against commonly encountered drug-resistant bacteria. This study compared the in vitro activity of tigecycline against 3,014 isolates of clinically important drug-resistant bacteria using the standard broth microdilution and disk diffusion methods. Species studied included methicillin-resistant Staphylococcus aureus (MRSA; n = 759), vancomycin-resistant Enterococcus faecium (VRE; n = 191), extended-spectrum ß-lactamase (ESBL)-producing Escherichia coli (n = 602), ESBL-producing Klebsiella pneumoniae (n = 736), and Acinetobacter baumannii (n = 726) that had been collected from patients treated between 2008 and 2010 at 20 hospitals in Taiwan. MICs and inhibition zone diameters were interpreted according to the currently recommended U.S. Food and Drug Administration (FDA) criteria and the European Committee on Antimicrobial Susceptibility Testing (EUCAST) criteria. The MIC(90) values of tigecycline against MRSA, VRE, ESBL-producing E. coli, ESBL-producing K. pneumoniae, and A. baumannii were 0.5, 0.125, 0.5, 2, and 8 µg/ml, respectively. The total error rates between the two methods using the FDA criteria were high: 38.4% for ESBL-producing K. pneumoniae and 33.8% for A. baumannii. Using the EUCAST criteria, the total error rate was also high (54.6%) for A. baumannii isolates. The total error rates between these two methods were <5% for MRSA, VRE, and ESBL-producing E. coli. For routine susceptibility testing of ESBL-producing K. pneumoniae and A. baumannii against tigecycline, the broth microdilution method should be used because of the poor correlation of results between these two methods.

Trends in the susceptibility of clinically important resistant bacteria to tigecycline: results from the Tigecycline In Vitro Surveillance in Taiwan study, 2006 to 2010.

The Tigecycline In Vitro Surveillance in Taiwan (TIST) study, a nationwide, prospective surveillance during 2006 to 2010, collected a total of 7,793 clinical isolates, including methicillin-resistant Staphylococcus aureus (MRSA) (n = 1,834), penicillin-resistant Streptococcus pneumoniae (PRSP) (n = 423), vancomycin-resistant enterococci (VRE) (n = 219), extended-spectrum ß-lactamase (ESBL)-producing Escherichia coli (n = 1,141), ESBL-producing Klebsiella pneumoniae (n = 1,330), Acinetobacter baumannii (n = 1,645), and Stenotrophomonas maltophilia (n = 903), from different specimens from 20 different hospitals in Taiwan. MICs of tigecycline were determined following the criteria of the U.S. Food and Drug Administration (FDA) and the European Committee on Antimicrobial Susceptibility Testing (EUCAST-2011). Among drug-resistant Gram-positive pathogens, all of the PRSP isolates were susceptible to tigecycline (MIC(90), 0.03 µg/ml), and only one MRSA isolate (MIC(90), 0.5 µg/ml) and three VRE isolates (MIC(90), 0.125 µg/ml) were nonsusceptible to tigecycline. Among the Gram-negative bacteria, the tigecycline susceptibility rates were 99.65% for ESBL-producing E. coli (MIC(90), 0.5 µg/ml) and 96.32% for ESBL-producing K. pneumoniae (MIC(90), 2 µg/ml) when interpreted by FDA criteria but were 98.7% and 85.8%, respectively, when interpreted by EUCAST-2011 criteria. The susceptibility rate for A. baumannii (MIC(90), 4 µg/ml) decreased from 80.9% in 2006 to 55.3% in 2009 but increased to 73.4% in 2010. A bimodal MIC distribution was found among carbapenem-susceptible A. baumannii isolates, and a unimodal MIC distribution was found among carbapenem-nonsusceptible A. baumannii isolates. In Taiwan, tigecycline continues to have excellent in vitro activity against several major clinically important drug-resistant bacteria, with the exception of A. baumannii.