Prevalence and accessory gene regulator (agr) analysis of vancomycin-intermediate Staphylococcus aureus among methicillin-resistant isolates in Taiwan--SMART program, 2003.

The prevalence of methicillin-resistant Staphylococcus aureus (MRSA) in nosocomial staphylococcal infections in Taiwan has exceeded 50% since 2000. However, little relevant data has been available concerning vancomycin-intermediate S. aureus (VISA) and heteroresistant VISA (hVISA). We collected 1,000 MRSA isolates from ten medical center hospitals in Taiwan during 2003. All were initially screened for reduced susceptibility to vancomycin on brain heart infusion (BHI) agar containing 5 mg/L vancomycin. Among 34 MRSA isolates that grew on the screening plates, two VISA isolates (0.2%) and seven hVISA isolates (0.7%) were evident. Vancomycin-resistant S. aureus was not detected. The accessory gene regulator (agr) typing of all 1,000 MRSA strains were typed by multiplex polymerase chain reaction (PCR); 919 strains (91.9%) including the VISA and hVISA isolates belonged to agr group I, 78 strains (7.8%) were agr group II, two strains (0.2%) were agr group III, and one isolate (0.1%) was agr group IV. There was no relationship between sample sites and agr typing. In 2003, the incidence of hVISA and VISA in Taiwan was low. Continued surveillance is recommended, given the implementation of new Clinical and Laboratory Standards Institute (CLSI) criteria for S. aureus and the increasing clinical use of glycopeptides.

In vitro activities of doripenem and other carbapenems against clinically important bacteria isolated in intensive care units: nationwide data from the SMART Programme.

This nationwide surveillance of clinically important bacteria from the intensive care units (ICUs) of major teaching hospitals throughout Taiwan investigated the susceptibilities to doripenem and other comparator carbapenems from September through November 2005. Minimum inhibitory concentrations (MICs) were determined for 1,311 clinical isolates using the broth microdilution method according to Clinical and Laboratory Standards Institute (CLSI) 2005 guidelines. Doripenem showed similar (within four-fold difference of MICs) in vitro activity to meropenem for Enterobacteriaceae and probably comparable activity to meropenem against important nosocomial non-fermentative Gram-negative bacilli (NFGNBs), including Pseudomonas aeruginosa, Acinetobacter baumannii and Burkholderia cepacia. Among the four carbapenems analysed, doripenem and meropenem exhibited better in vitro activity than imipenem or ertapenem against extended-spectrum beta-lactamase (ESBL)-producing Klebsiella pneumoniae and Escherichia coli isolates. However, the meropenem MIC(90) against ESBL-producing K. pneumoniae isolates was 2 microg/ml. Besides, doripenem with the MIC(90) of 0.5 microg/ml to Streptococcus pneumoniae possibly suggested its potential therapeutic effect regarding community-acquired pneumonia. Because of the heavy resistance burden in Taiwan, closely monitoring the evolutionary trend of carbapenem susceptibilities against clinically important pathogens is crucial in the future.

Nationwide surveillance of antimicrobial resistance among Haemophilus influenzae and Streptococcus pneumoniae in intensive care units in Taiwan.

A nationwide susceptibility surveillance of Streptococcus pneumoniae and Haemophilus influenzae isolates collected from patients treated at the intensive care units (ICUs) of ten Taiwanese major teaching hospitals was conducted from September 2005 through November 2005. High rates of resistance (intermediate/resistant) of S. pneumoniae to penicillin (85% resistance), ceftriaxone (46%/20%), and cefepime (43%/15%) by meningitis criteria, and in contrast, non-susceptibilities (intermediate/resistant) to penicillin (0%/0%), ceftriaxone (20%/0%) and cefepime (15%/0%) by non-meningitis criteria were noted (p values < 0.05) by the Clinical and Laboratory Standards Institute 2008. Resistant rate of S. pneumoniae to azithromycin was also high (63%). S. pneumoniae isolates were significantly more susceptible to ertapenem (87%) than to imipenem (39%) and meropenem (44%) (p values < 0.05). Rates of non-susceptibilities of H. influenzae isolates to ampicillin and cefaclor were high (55% and 45%, respectively). No beta-lactamase-negative ampicillin-resistant (BLNAR) H. influenzae isolates were found. Imipenem has a notably higher MIC(90) value (8 microg/ml) for H. influenzae than that of the other two carbapenems. Tigecycline showed good in vitro activities against these two respiratory pathogens. High rates of resistance among isolates of S. pneumoniae and H. influenzae continue to exist in the ICUs of Taiwan.

Nationwide surveillance of antimicrobial resistance among Enterobacteriaceae in intensive care units in Taiwan.

To determine the antimicrobial resistance profiles among clinical isolates of Enterobacteriaceae in Taiwanese intensive care units (ICUs), a national surveillance of antibiotic resistance among important Enterobacteriaceae was conducted from September 2005 through November 2005 at the ICUs of ten major teaching hospitals in Taiwan. A total of 574 Enterobacteriaceae isolates recovered from various clinical samples of our ICU patients were submitted for in vitro test. Minimum inhibitory concentrations (MICs) of these isolates to 18 antimicrobial agents were determined by the broth microdilution method. The prevalences of Enterobacteriaceae isolates with phenotypic extended-spectrum beta-lactamase (ESBL) production were 26% in Klebsiella pneumoniae, 16% in Serratia marcescens, 14% in Escherichia coli, and 13% in Proteus mirabilis, in which a significantly rising prevalence of ESBL production among K. pneumoniae was noted (p = 0.002) when compared with a previous Taiwanese survey in 2000. Heterogeneous resistance to various fluoroquinolones was found among our Enterobacteriaceae isolates, except for Enterobacter cloacae. Emergence of ertapenem-resistant isolates of E. coli, K. pneumoniae, E. cloacae, and S. marcescens was noted. Gradually increasing rates of drug-resistant Enterobacteriaceae were noted in Taiwanese ICUs. Periodic surveillance of the evolutionary trend of antimicrobial resistance among ICU isolates is crucial for starting appropriately empirical antimicrobial therapy in the future.

Changes in macrolide resistance among respiratory pathogens after decreased erythromycin consumption in Taiwan.

Measures to alleviate the growing problem of macrolide resistance in Taiwan resulted in a decrease in macrolide consumption, from 0.629 defined daily doses/1000 inhabitants per day (DIDs) in 1999 to 0.301 DIDs in 2003 (a reduction of 52%). A linear relationship was observed between the decline in erythromycin consumption and the decline in erythromycin resistance in Streptococcus pyogenes (46% in 1999 vs. 17% in 2003; p < 0.001) and azithromycin resistance in Haemophilus influenzae (31% in 2000 vs. 0% in 2003; p < 0.001). However, the rate of erythromycin resistance in Streptococcus pneumoniae showed a continued increase, from 80.2% in 1999 to 92% in 2003.

Multicenter surveillance of antimicrobial resistance of Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis in Taiwan during the 1998-1999 respiratory season.

A susceptibility surveillance study of 276 isolates of Streptococcus pneumoniae, 301 of Haemophilus influenzae, and 110 of Moraxella catarrhalis was carried out from November 1998 to May 1999 in Taiwan. High rates of nonsusceptibility to penicillin (76%), extended-spectrum cephalosporins (56%), azithromycin (94%), clarithromycin (95%), and trimethoprim-sulfamethoxazole (TMP-SMX) (65%) for S. pneumoniae isolates and high rates of nonsusceptibility to amoxicillin (58%) and TMP-SMX (52%) for H. influenzae isolates were found. Higher percentages of S. pneumoniae isolates nonsusceptible to aminopenicillins, extended-spectrum cephalosporins, macrolides, and TMP-SMX were observed among penicillin-intermediate and -resistant isolates. All quinolones tested were active in vitro against these three organisms.

Use of restriction endonuclease analysis of plasmids and pulsed-field gel electrophoresis to investigate outbreaks of methicillin-resistant Staphylococcus aureus infection.

We used restriction endonuclease analysis of plasmids (REAP) and pulsed-field gel electrophoresis (PFGE) to investigate clusterings of methicillin-resistant Staphylococcus aureus (MRSA) infections in our orthopedic unit, neurosurgery unit, intensive care unit, and burn unit. Fourteen different strain types were identified by REAP and 10 different strain types were identified by PFGE among 25 MRSA isolates collected during these incidents of infection. Though neither technique was clearly superior to the other for typing MRSA isolates, REAP is recommended as a relatively simple and reproducible technique for the preliminary investigation of MRSA infection outbreaks in clinical settings.

Epidemiological typing of Flavimonas oryzihabitans by PCR and pulsed-field gel electrophoresis.

Flavimonas oryzihabitans has emerged as a potential nosocomial pathogen in recent years. The typing method for characterization of this species has never been reported before. Pulsed-field gel electrophoresis (PFGE) and enterobacterial repetitive intergenic consensus (ERIC)-based PCR were used to generate DNA fingerprints for 14F. oryzihabitans isolates obtained from eight episodes of nosocomial infections during a 2-year period. Both techniques successfully classified these clinical isolates into eight distinct genotypes, thus indicating that all of these episodes of infections were independent. In contrast, repeated isolates from the same patient were assigned to identical genotypes. The reproducibility of both techniques was good. Therefore, we conclude that both PFGE and ERIC-PCR have comparable reproducible and discriminatory powers for the typing of F. oryzihabitans and may be useful for clarifying the epidemiology of this species; however, ERIC-PCR has the advantages of both speed and simplicity.

Comparison of different PCR approaches for characterization of Burkholderia (Pseudomonas) cepacia isolates.

In this study, we evaluated three PCR methods for epidemiological typing of Burkholderia (Pseudomonas) cepacia--PCR-ribotyping, arbitrarily primed PCR (AP-PCR) and enterobacterial repetitive intergenic consensus sequence PCR (ERIC-PCR)--and compared them with pulsed-field gel electrophoresis. The analysis was performed with 31 isolates of B. cepacia, comprising 23 epidemiologically unrelated isolates and 8 isolates collected from the same patient during two episodes of bacteremia. Pulsed-field gel electrophoresis, ERIC-PCR, and AP-PCR identified 23 distinct types among the 23 unrelated isolates, while PCR-ribotyping only identified 12 strain types, even after AluI digestion of the amplification products. Among the eight isolates collected from the same patient, all typing techniques revealed two clones of strains. The day-to-day reproducibilities of PCR-ribotyping and ERIC-PCR were good, while greater day-to-day variations were noted in the fingerprints obtained by AP-PCR. We conclude that all three PCR techniques are useful for rapid epidemiological typing of B. cepacia, but ERIC-PCR seems to be more reproducible and discriminative.

DNA fingerprinting of Pseudomonas aeruginosa serotype O11 by enterobacterial repetitive intergenic consensus-polymerase chain reaction and pulsed-field gel electrophoresis.

We report the use of pulsed-field gel electrophoresis (PFGE) and enterobacterial repetitive intergenic consensus (ERIC)-based polymerase chain reaction (PCR) to characterize clinical isolates of Pseudomonas aeruginosa serotype O11 collected from an incident of hospital-acquired infection. Both typing techniques differentiated 20 different strain types among seven epidemiologically related isolates and 22 epidemiologically unrelated isolates. There was complete concordance between these two techniques. Our results indicate that the ERIC-based PCR technique represents a rapid and simple means for typing P. aeruginosa serotype O11 with a level of discrimination equivalent to that of PFGE.

Analysis of clonal relationships among isolates of Shigella sonnei by different molecular typing methods.

Shigella sonnei is a major cause of diarrheal disease in developed as well as in developing countries. Epidemiologic studies of this organism have been limited by the lack of a simple and effective method for comparing strains. In this study, we have compared different molecular typing methods, i.e., plasmid profile analysis, restriction endonuclease analysis of plasmids, rRNA gene restriction analysis (ribotyping), pulsed-field gel electrophoresis (PFGE), and enterobacterial repetitive intergenic consensus (ERIC) sequence-based PCR (ERIC-PCR) for typing 20 clinical isolates of S. sonnei collected from six incidents of infection. PFGE and ERIC-PCR fingerprintings had the highest discriminatory power for discrimination of epidemiologically related isolates from epidemiologically unrelated strains of S. sonnei, and both gave seven distinct strain types among these isolates and the type strain of the species. Plasmid study and ribotyping produced only six and typing techniques demonstrated two distinct patterns, respectively, among these strains. All of these molecular an identical fingerprint for eight temporally related sporadic isolates. It is possible that these temporally related isolates belonged to a single bacterial clone and circulated obscurely through the community. Our results indicate that the ERIC-PCR technique represents a rapid and simple means for typing S. sonnei with a level of discrimination equivalent to that of PFGE but greater than those of plasmid profile analysis, restriction endonuclease analysis of plasmids, and ribotyping.

Comparison of susceptibility to extended-spectrum beta-lactam antibiotics and ciprofloxacin among gram-negative bacilli isolated from intensive care units.

The in vitro activities of extended-spectrum beta-lactam antibiotics (including piperacillin, cefotaxime, ceftriaxone, ceftazidime, cefepime, imipenem, and meropenems) were assessed and compared with the activity of ciprofloxacin against 366 clinical Gram-negative bacilli isolates from the intensive care units of Taichung Veterans General Hospital. The most prevalent species isolated were Pseudomonas aeruginosa and Acinetobacter baumannii. The activities of ceftazidime, cefepime, imipenem, and meropenem against these isolates were comparable to that of ciprofloxacin. Meropenem was found to be the most potent extended-spectrum beta-lactam antibiotic tested and the MIC50s and MIC90s for most of these multiresistant strains were lower than those of imipenem, ceftazidime, and cefepime, except for Stenotrophomonas maltophilia. The extended-spectrum beta-lactam antibiotics that were still active against S. maltophilia were piperacillin and ceftazidime. More than 50% of Enterobacter spp. were resistant to third-generation cephalosporins and piperacillin, but they remained susceptible to carbapenems and cefepime.