Yih-Ru Shiau

Complete Nucleotide Sequence of pK245, a 98-Kilobase Plasmid Conferring Quinolone Resistance and Extended-Spectrum-beta-Lactamase Activity in a Clinical Klebsiella pneumoniae Isolate

ABSTRACT A plasmid containing the qnrS quinolone resistance determinant and the gene encoding the SHV-2 β-lactamase has been discovered from a clinical Klebsiella pneumoniae strain isolated in Taiwan. The complete 98-kb sequence of this plasmid, designated pK245, was determined by using a whole-genome shotgun approach. Transfer of pK245 conferred low-level resistance to fluoroquinolones in electroporant Escherichia coli epi300. The sequence of the immediate region surrounding qnrS in pK245 is nearly identical (>99% identity) to those of pAH0376 from Shigella flexneri and pINF5 from Salmonella enterica serovar Infantis, the two other qnrS-carrying plasmids reported to date, indicating a potential common origin. Other genes conferring resistance to aminoglycosides (aacC2, strA, and strB), chloramphenicol (catA2), sulfonamides (sul2), tetracycline (tetD), and trimethoprim (dfrA14) were also detected in pK245. The dfrA14 gene is carried on a class I integron. Several features of this plasmid, including three separate regions containing putative replicons, a partitioning-control system, and a type II restriction modification system, suggest that it may be able to replicate and adapt in a variety of hosts. Although no critical conjugative genes were detected, multiple insertion sequence elements were found scattered throughout pK245, and these may facilitate the dissemination of the antimicrobial resistance determinants. We conclude that pK245 is a chimera which acquired its multiple antimicrobial resistance determinants horizontally from different sources. The identification of pK245 plasmid expands the repertoire of the coexistence of quinolone and extended-spectrum-β-lactam resistance determinants in plasmids carried by various species of the family Enterobacteriaceae in different countries.

Emergence of extensively drug-resistant Acinetobacter baumannii complex over 10 years: Nationwide data from the Taiwan Surveillance of Antimicrobial Resistance (TSAR) program

BackgroundAcinetobacter baumannii complex (ABC) has emerged as an important pathogen causing a variety of infections. Longitudinal multicenter surveillance data on ABC from different sources in Taiwan have not been published. Using data from the Taiwan Surveillance of Antimicrobial Resistance (TSAR) conducted biennially, we investigated the secular change in resistance of 1640 ABC from 2002 to 2010 (TSAR period III to VII) to different antimicrobial agents and identified factors associated with imipenem-resistant and extensively drug-resistant ABC (IRABC and XDRABC).MethodsIsolates were collected by TSAR from the same 26 hospitals located in all 4 regions of Taiwan. Minimum inhibitory concentrations (MIC) were determined by reference broth microdilution method. Isolates nonsusceptible to all tested aminoglycosides, fluoroquinolones, β-lactam, β-lactam/β-lactam inhibitors, and carbapenems were defined as extensively drug-resistant (XDR). Multivariate logistic regression analysis was performed to assess the relationship between predictor variables among patients with resistant ABC and patients with non-resistant ABC.ResultsThe prevalence of IRABC increased from 3.4% in 2002 to 58.7% in 2010 (P < 0.001; odds ratio [OR], 2.138; 95% confidence interval [CI], 1.947 to 2.347) and that of XDRABC increased from 1.3% in 2002 to 41.0% in 2010 (P < 0.001; OR, 1.970; 95% CI, 1.773-2.189). The rates of non-susceptibility to other antimicrobial agents remained high (>55%) over the years with some fluctuations before and after TSAR V (2006) on some agents. Multivariate analysis revealed that recovery from elderly patients, origins other than blood, from ICU settings, or geographic regions are independent factors associated with IRABC and XDRABC. Although the prevalence of XDRABC increased in all four regions of Taiwan over the years, central Taiwan had higher prevalence of XDRABC starting in 2008. Susceptibility to polymyxin remained high (99.8%).ConclusionsThis longitudinal multicenter surveillance program revealed significant increase and nationwide emergence of IRABC and XDRABC in Taiwan over the years. This study also identified factors associated with IRABC and XDRABC to help guide empirical therapy and at-risk groups requiring more intense interventional infection control measures with focused surveillance efforts.

Vancomycin-Resistant Enterococci from Humans and Retail Chickens in Taiwan with Unique VanB Phenotype-vanA Genotype Incongruence

ABSTRACT Vancomycin resistant enterococci (VRE) with VanB phenotype-vanA genotype incongruence were found in all 39 VRE isolated from chicken carcasses and four human VRE isolates in Taiwan. Three identical mutations in the vanS gene were found in the VanB phenotype-vanA genotype VRE sequenced. This finding indicates possible transmission of glycopeptide resistance among different hosts.

Comparative In Vitro Activities of Nemonoxacin (TG-873870), a Novel Nonfluorinated Quinolone, and Other Quinolones against Clinical Isolates

ABSTRACT The in vitro antibacterial activities of nemonoxacin (TG-873870), a novel nonfluorinated quinolone, against 770 clinical isolates were investigated. Nemonoxacin (tested as its malate salt, TG-875649) showed better in vitro activity than ciprofloxacin and levofloxacin against different species of staphylococci, streptococci, and enterococci, Neisseria gonorrhoeae, and Haemophilus influenzae. The in vitro activity of TG-875649 was also comparable to or better than that of moxifloxacin against these pathogens, which included ciprofloxacin-resistant, methicillin-resistant Staphylococcus aureus and levofloxacin-resistant Streptococcus pneumoniae.

Methicillin-resistant Staphylococcus aureus in Taiwan

We found a virulent closely related clone (Panton-Valentine leukocidin–positive, SCCmec V:ST59) of methicillin-resistant Staphylococcus aureus in inpatients and outpatients in Taiwan. The isolates were found mostly in wounds but were also detected in blood, ear, respiratory, and other specimens; all were susceptible to ciprofloxacin, gentamicin, and trimethoprim-sulfamethoxazole.

Sequencing and Comparative Genomic Analysis of pK29, a 269-Kilobase Conjugative Plasmid Encoding CMY-8 and CTX-M-3 β-Lactamases in Klebsiella pneumoniae

ABSTRACT A 269-kilobase conjugative plasmid, pK29, from a Klebsiella pneumoniae strain was sequenced. The plasmid harbors multiple antimicrobial resistance genes, including those encoding CMY-8 AmpC-type and CTX-M-3 extended-spectrum β-lactamases in the common backbone of IncHI2 plasmids. Mechanisms for dissemination of the resistance genes are highlighted in comparative genomic analyses.

mecA-Positive Staphylococcus aureus with Low-Level Oxacillin MIC in Taiwan

ABSTRACT Although the presence of mecA is the genotypic determinant of methicillin-resistant Staphylococcus aureus (MRSA), certain MRSA strains, especially community-associated MRSA (C-MRSA), can display an oxacillin MIC in the Clinical and Laboratory Standards Institute susceptible breakpoint range (≤2 μg/ml). Among 91 and 180 isolates thought to be methicillin-susceptible S. aureus (MSSA) with oxacillin MICs of 2 and 1 μg/ml as determined by the Sensititre broth microdilution test initially, 52 (57.1%) and 6 (3.3%), respectively, were mecA positive. These mecA-positive low-oxacillin-MIC isolates belong to the dominant Taiwan C-MRSA clone (clonal complex [CC] 59), 56 of which carried SCCmec type V and were pvl positive, and 43 of which belonged to spa CC t437. All 271 isolates were retested by Sensititre, as well as by Vitek II and disk diffusion (DD). Based on the oxacillin results, the sensitivities of the Sensititre, Vitek II, and DD methods were 48.3% (28/58), 46.6% (27/58), and 89.6% (52/58), respectively. Although cefoxitin was better at detecting these isolates, 12.1, 10.4, and 5.2% of these isolates were still misidentified as MSSA by Sensititre, Vitek II, and DD, respectively. These results highlight the difficulty in the accurate identification of MRSA with borderline oxacillin MICs in the CC59:SCCmec V clone, which likely has contributed to its spread in the health care and community settings. Since this clone has now been detected in other countries, and since other C-MRSA lineages have also been found to have low-level β-lactam resistance, the findings of the present study may be relevant to other regions. Further studies are warranted to determine the extent and clinical impact of such misidentification.

A multicenter surveillance of antimicrobial resistance on Stenotrophomonas maltophilia in Taiwan

BACKGROUND Stenotrophomonas maltophilia has emerged as an important opportunistic pathogen in debilitated hosts. Clinical management of S. maltophilia is challenging due to its intrinsic resistance to a variety of antibiotics. This study investigated the trend and prevalence of antimicrobial resistance in S. maltophilia from a nationwide surveillance study in Taiwan. METHODS S. maltophilia isolates were collected biennially between 1998 and 2008 as part of the Taiwan Surveillance of Antimicrobial Resistance (TSAR) program from medical centers and regional hospitals throughout Taiwan. Minimal inhibitory concentrations (MIC) were determined using the Clinical and Laboratory Standards Institute reference broth microdilution method. RESULTS A total of 377 non-duplicate S. maltophilia isolates were collected from 38 hospitals. The majority of the isolates were from the respiratory tract (256, 67.9%), followed by blood (48, 12.7%). Overall, 376 (99.7%) isolates were susceptible to minocycline, 362 (96%) to tigecycline, 311 (82.5%) to trimethoprim/sulfamethoxazole (TMP-SMX), 300 (79.6%) to levofloxacin, 92 (24.4%) to ceftazidime, and 70 (18.6%) to ticarcillin-clavulanic acid. The MIC(50)/MIC(90) of minocycline, tigecycline, TMP-SMX, levofloxacin, ceftazidime, and ticarcillin-clavulanic acid, were ≤0.5/1 μg/mL, 0.25/1 μg/mL, ≤0.25/8 μg/mL, 1/4 μg/mL, 32/128 μg/mL, and 64/128 μg/mL, respectively. A trend of increased non-susceptibility to levofloxacin (p=0.014) was observed over the 10-year study period. Compared to TMP-SMX-susceptible isolates, TMP-SMX-resistant isolates were less susceptible to levofloxacin (54.5% vs. 84.9%, p<0.001). CONCLUSION In this 10-year study, minocycline and TMP-SMX remained the two antimicrobials with better in vitro activities against S. maltophilia than ceftazidime, levofloxacin, and ticarcillin-clavulanic acid. The activity of levofloxacin against S. maltophilia in Taiwan declined during the past 10 years.

Epidemiology and Molecular Characterization of Macrolide-Resistant Streptococcus pyogenes in Taiwan

ABSTRACT Our multicenter nationwide surveillance data indicated that erythromycin (ERY) resistance among group A Streptococcus (GAS) isolates in Taiwan declined from 53.1% in 1998 and 2000 to 14.6% in 2002 and 2004 and 10.7% in 2006 to 2010 (P < 0.01). The present study aimed to assess the epidemiology of GAS in Taiwan and identify factors associated with ERY resistance. All 127 ERY-resistant (ERYr) isolates and 128 randomly selected ERY-susceptible (ERYs) isolates recovered from 1998 to 2010 were emm typed. ERYr isolates were also characterized by ERY resistance phenotype and mechanisms and pulsed-field gel electrophoresis (PFGE). Multilocus sequence typing was performed on selected ERYr isolates. The predominant emm types in ERYr isolates were emm22 (n = 33, 26.0%), emm12 (n = 24, 18.9%), emm4 (n = 21, 16.5%), and emm106 (n = 15, 11.8%). In ERYs isolates, emm12 (n = 27, 21.9%), emm1 (n = 18, 14.1%), emm106 (n = 16, 12.5%), and emm11 (n = 9, 7.1%) predominated. The most common ERY resistance phenotype was the M phenotype (resistant to macrolides) (70.9%), with all but one isolate carrying mef(A), followed by the constitutive macrolide-lincosamide-streptogramin B resistance (cMLSB) phenotype (26.8%), with isolates carrying erm(B) or erm(TR). ERYr isolates of the emm12-sequence type 36 (ST36) lineage with the cMLSB phenotype were mostly present before 2004, while those of the emm22-ST46 lineage with the M phenotype predominated in later years. Recovery from respiratory (throat swab) specimens was an independent factor associated with ERY resistance. emm1 and emm11 GAS isolates were significantly associated with ERYs, while emm22 was detected only in ERYr GAS. In addition, emm106 isolates were prevalent among the abscess/pus isolates, whereas emm12 isolates were strongly associated with a respiratory (throat) origin. In addition to identifying factors associated with ERY resistance in GAS, our study provides helpful information on the changing GAS epidemiology in Taiwan.

High rates of multidrug resistance in Enterococcus faecalis and E. faecium isolated from inpatients and outpatients in Taiwan

Longitudinal national data on resistance in Enterococcus faecalis and E. faecium from different sources in Taiwan are rare. The present study analyzed data from the Taiwan Surveillance of Antimicrobial Resistance program to address this issue. Between 2002 and 2010, a total of 1696 E. faecalis and 452 E. faecium isolates were studied. Although these 2 species together comprised similar percentages of all enterococci in each study year (94.1-97.2%, P = 0.19), the proportion of E. faecium increased from 12.4% in 2002 to 27.3% in 2010 (P < 0.001). The most noteworthy change in susceptibilities of these 2 species was vancomycin resistance in E. faecium (VREfm), which increased from 0.3% in 2004 to 24.9% in 2010 (P < 0.001). VREfm prevalence differed significantly between geographic regions, patient age groups, and locations. Multidrug resistance was very common in both species even in isolates from outpatients (82.7% for E. faecalis and 98.1% for E. faecium), at rates similar to those from intensive care unit (ICU) and non-ICU patients (80.5-80.9% in E. faecalis and 97.2-98.6% in E. faecium). Nonsusceptibility to linezolid was <0.5% in both species. All tested isolates were susceptible to daptomycin. Continuous surveillance of VRE prevalence and survey of community reservoirs of multidrug-resistant enterococci are warranted.