Development of carbapenem resistance in Pseudomonas aeruginosa is associated with OprD polymorphisms, particularly the amino acid substitution at codon 170.

Objectives: Pan-susceptible Pseudomonas aeruginosa (PSPA) clinical isolates carrying an OprD with loop 7 shortening (the group-1A allele) were found to rapidly develop carbapenem resistance under continuous selection pressure. We further studied whether OprD polymorphisms are associated with the potential to develop carbapenem resistance. Methods: OprD amino acid sequences of 126 PSPA clinical isolates were analysed to determine their STs using P. aeruginosa strain PAO1 as the control strain. Site-directed mutagenesis was performed in PAO1 to generate polymorphisms of interest. A disc diffusion method was used to select carbapenem-resistant variants from the mutant strains. Expression levels of oprD were determined by quantitative RT-PCR. MICs of carbapenems were determined by Etest. Results: Forty-eight (38.1%) of the tested isolates carried the group-1A allele. Another two major STs, C1 and C2, both of which harboured an F170L polymorphism, were found in 21 (16.7%) and 39 (31.0%) isolates, respectively. The PAO1 type was also found in 14 (11.1%) isolates. Under continuous selective pressure, isolates of most STs developed carbapenem resistance at different numbers of passaging events; only those belonging to the PAO1 type remained susceptible. However, PAO1 mutants carrying either the oprD group-1A allele or the OprD-F170L polymorphism were able to develop carbapenem resistance. Reduced oprD expression triggered by continuous imipenem challenge was found in PAO1 mutants, but not in the PAO1 WT strain. Conclusions: OprD polymorphisms, particularly the F170L substitution and the specific shortening in loop 7, appear to determine the potential for P. aeruginosa to develop carbapenem resistance.

Antimicrobial resistance in Mycobacterium abscessus complex isolated from patients with skin and soft tissue infections at a tertiary teaching hospital in Taiwan.

Background: Mycobacterium abscessus complex (MABC) is the most common non-tuberculous mycobacterium that causes complicated skin and soft tissue infections (cSSTIs). The selection of antimycobacterial agents for successful treatment of such infections is a critical issue. Objectives: To investigate the antimicrobial susceptibility patterns of MABC isolates from skin and soft tissue to a variety of antimycobacterial agents. Methods: Sixty-seven MABC isolates were collected and partial gene sequencing of secA1, rpoB and hsp65 was used to classify them into three subspecies: M. abscessus subsp. abscessus (MAB), M. abscessus subsp. massiliense (MMA) and M. abscessus subsp. bolletii (MBO). The MICs of 11 antimycobacterial agents for these 67 isolates were determined using a broth microdilution method and commercial Sensititre RAPMYCOI MIC plates, as recommended by CLSI. Results: In total, 28 MAB, 38 MMA and 1 MBO were isolated from patients with cSSTIs at our hospital. Most MABC strains were resistant to ciprofloxacin, doxycycline, imipenem, linezolid, minocycline, moxifloxacin and trimethoprim/sulfamethoxazole. In addition, most MABC strains were intermediately susceptible or resistant to cefoxitin. Eighteen of the 28 MABs and 1 MBO isolate harboured the T28 polymorphism in the erm(41) gene. Two of the 38 MMA isolates had an rrl A2059G point mutation. Most of the MABC strains were susceptible to amikacin and tigecycline. Conclusions: In Taiwan, amikacin, clarithromycin and tigecycline have good activity against MMA and MAB erm(41) C28 sequevar isolates, whereas amikacin and tigecycline, rather than clarithromycin, have good activity against both MBO and MAB erm(41) T28 sequevar isolates. Clinical trials are warranted to correlate these data with clinical outcomes.

Benefit analysis of the auto-verification system of intelligent inspection for microorganisms.

In recent years, the automatic machine for microbial identification and antibiotic susceptibility tests has been introduced into the microbiology laboratory of our hospital, but there are still many steps that need manual operation. The purpose of this study was to establish an auto-verification system for bacterial naming to improve the turnaround time (TAT) and reduce the burden on clinical laboratory technologists. After the basic interpretation of the gram staining results of microorganisms, the appearance of strain growth, etc., the 9 rules were formulated by the laboratory technologists specialized in microbiology for auto-verification of bacterial naming. The results showed that among 70,044 reports, the average pass rate of auto-verification was 68.2%, and the reason for the failure of auto-verification was further evaluated. It was found that the main causes reason the inconsistency between identification results and strain appearance rationality, the normal flora in the respiratory tract and urine that was identified, the identification limitation of the mass spectrometer, and so on. The average TAT for the preliminary report of bacterial naming was 35.2 h before, which was reduced to 31.9 h after auto-verification. In summary, after auto-verification, the laboratory could replace nearly 2/3 of manual verification and issuance of reports, reducing the daily workload of medical laboratory technologists by about 2 h. Moreover, the TAT on the preliminary identification report was reduced by 3.3 h on average, which could provide treatment evidence for clinicians in advance.

Influence of teicoplanin MICs on treatment outcomes among patients with teicoplanin-treated methicillin-resistant Staphylococcus aureus bacteraemia: a hospital-based retrospective study.

OBJECTIVES: Higher vancomycin MIC values (≥1.5 mg/L via Etest) may be associated with vancomycin treatment failure among patients with serious methicillin-resistant Staphylococcus aureus (MRSA) infections. As there were limited similar data for teicoplanin, this retrospective cohort study intended to determine the predictive value of teicoplanin MICs for treatment failure among patients with MRSA bacteraemia. PATIENTS AND METHODS: All patients with at least one blood culture positive for MRSA admitted to the hospital between January 2010 and January 2011 were reviewed. Patients with an age ≥18 years and receipt of teicoplanin therapy throughout the course or receipt of <72 h of vancomycin therapy and then teicoplanin for >3 days were enrolled. Teicoplanin Etest(®) MICs and treatment outcomes for MRSA bacteraemia were reviewed to identify the breakpoint of teicoplanin MICs influencing treatment outcomes. RESULTS: Of the 101 patients enrolled, 56 had a lower teicoplanin MIC (≤1.5 mg/L) for MRSA and 45 had a higher MIC (>1.5 mg/L) for MRSA. A lower teicoplanin MIC was associated with a favourable outcome [37 (66.1%) versus 13 (28.9%); P<0.001] and a lower rate of bloodstream infection-related mortality [15 (26.8%) versus 22 (48.9%); P=0.022]. Patients with chronic obstructive pulmonary disease, bacteraemic pneumonia or higher Pittsburgh bacteraemia score had an unfavourable outcome (P=0.028, 0.022 and <0.001, respectively). Multivariate analysis showed that teicoplanin MIC >1.5 mg/L, higher Pittsburgh bacteraemia score and bacteraemic pneumonia were independent risk factors for unfavourable outcome. CONCLUSIONS: A higher teicoplanin MIC value (>1.5 mg/L) may predict an unfavourable outcome and higher mortality rate among teicoplanin-treated MRSA bacteraemic patients.

Mycoplasma hominis septic arthritis with concomitant gouty arthritis.

We report a rare case of Mycoplasma hominis septic arthritis occurring simultaneously with acute gout. A Taiwanese native aboriginal presented with right ankle swelling, erythema, local tenderness, and limitation of range of motion after a vertebroplasty. He had a history of gout without regular follow-up. Under the polarized light microscopy examination, his synovial fluid revealed neutrophilic leukocytosis and monosodium urate crystals. Subsequently, 2 consecutive anaerobic synovial fluid cultures yielded a cell wall-free microorganism, which was identified as M. hominis based on polymerase chain reaction of its 16S rDNA. He did not defervesce under colchicine and indomethacin treatment until we prescribed a doxycycline and moxifloxacin regimen. He responded well to 6-week doxycycline and moxifloxacin treatment without bone destruction and loss of joint function.

Highly efficient classification and identification of human pathogenic bacteria by MALDI-TOF MS.

Accurate and rapid identification of pathogenic microorganisms is of critical importance in disease treatment and public health. Conventional work flows are time-consuming, and procedures are multifaceted. MS can be an alternative but is limited by low efficiency for amino acid sequencing as well as low reproducibility for spectrum fingerprinting. We systematically analyzed the feasibility of applying MS for rapid and accurate bacterial identification. Directly applying bacterial colonies without further protein extraction to MALDI-TOF MS analysis revealed rich peak contents and high reproducibility. The MS spectra derived from 57 isolates comprising six human pathogenic bacterial species were analyzed using both unsupervised hierarchical clustering and supervised model construction via the Genetic Algorithm. Hierarchical clustering analysis categorized the spectra into six groups precisely corresponding to the six bacterial species. Precise classification was also maintained in an independently prepared set of bacteria even when the numbers of m/z values were reduced to six. In parallel, classification models were constructed via Genetic Algorithm analysis. A model containing 18 m/z values accurately classified independently prepared bacteria and identified those species originally not used for model construction. Moreover bacteria fewer than 10(4) cells and different species in bacterial mixtures were identified using the classification model approach. In conclusion, the application of MALDI-TOF MS in combination with a suitable model construction provides a highly accurate method for bacterial classification and identification. The approach can identify bacteria with low abundance even in mixed flora, suggesting that a rapid and accurate bacterial identification using MS techniques even before culture can be attained in the near future.

Antimicrobial susceptibility of Streptococcus pneumoniae at a university hospital in Taiwan, 2000-07: impact of modified non-meningeal penicillin breakpoints in CLSI M100-S18.

OBJECTIVES: In 2008, a new set of penicillin breakpoints was published in the CLSI revised guideline, M100-S18, to define the susceptibility of non-meningeal isolates of Streptococcus pneumoniae. The impact of the change is studied and discussed. METHODS: Laboratory data on pneumococcal isolates collected from Chang Gung Memorial Hospital during 2000-07 were analysed using the original and modified penicillin CLSI breakpoints. RESULTS: A total of 3729 non-duplicate isolates were identifed, including 43 (1.2%) meningeal isolates showing high rates of penicillin (79.1%) and ceftriaxone (34.9%) resistance. For non-meningeal isolates, penicillin non-susceptibility was reduced significantly from 75.1% (72.4% in 2000-03 increasing to 77.4% in 2004-07) to 16% (28.6% in 2000 decreasing to 2.4% in 2007) if the modified breakpoints were applied. However, isolates for which penicillin MICs were 1-2 mg/L increased significantly from 34.2% in 2000 to 59.8% in 2007. Ceftriaxone non-susceptibility also increased significantly from 2.8% before 2005 to 18.4% thereafter. A quarter (25.7%) of the pneumococcal isolates were recovered from patients <10 years old. Higher resistance to penicillin (89.8% versus 70.4%; or 19.1% versus 13.2% by the modified breakpoints) or ceftriaxone (11.1% versus 5.8%) was found among these isolates, compared with those from older patients. CONCLUSIONS: With the implementation of the new breakpoints, clinicians may continue to use penicillin for the treatment of non-meningeal pneumococcal infections in preference to other drug classes. However, as isolates with borderline penicillin MICs are increasing, continued surveillance of pneumococcal susceptibility to penicillin will be needed.

Clinical manifestations, antibiotic susceptibility and molecular analysis of Mycobacterium kansasii isolates from a university hospital in Taiwan.

OBJECTIVES: Mycobacterium kansasii causes a variety of infections. Although previous reports on the prognosis of antimicrobial therapy have been mostly satisfactory, problems involving treatment failure or relapse have been encountered. The purpose of this study was to establish a relationship between the clinical treatment outcomes of M. kansasii infections and bacterial drug susceptibility, and their clonality. METHODS: A total of 37 M. kansasii clinical isolates and clinical information on 34 patients were retrospectively collected in a tertiary medical centre in Taiwan. Bacterial drug susceptibility was determined by the microdilution method. The phylogenetic relationship was analysed by PFGE analysis. RESULTS: Results of PFGE typing revealed a major cluster (cluster I) and eight other divergent patterns. Two/three strains leading to treatment failure were also multidrug resistant and belonged to cluster I. CONCLUSIONS: A relationship between high drug resistance and genetic relatedness of some M. kansasii strains was established. This was associated with clinical treatment failure.

Rapid identification of mycobacteria from smear-positive sputum samples by nested PCR-restriction fragment length polymorphism analysis.

The rapid identification of mycobacteria from smear-positive sputum samples is an important clinical issue. Furthermore, the availability of a cheap, technically simple, and accurate method also would benefit mycobacterial laboratories in developing countries. In the present study, we aimed to develop an assay allowing the identification of the Mycobacterium tuberculosis complex (MTBC) and other frequently isolated nontuberculous mycobacteria (NTM) directly from smear-positive sputum samples. A nested PCR-restriction fragment length polymorphism analysis (nested-PRA) assay that focuses on the analysis of the hsp65 gene was developed and evaluated for its efficiency compared to that of traditional culture methods and 16S rRNA gene sequencing identification. A total of 204 smear-positive and culture-positive sputum specimens were prospectively collected for analysis between November 2005 and May 2006. The samples were classified according to an acid-fast bacillus (AFB) staining scale as rare/1+, 2+, or 3+. The results of the nested-PRA showed that the identification rate for AFB 3+, AFB 2+, and AFB rare/1+ samples was 100, 95, and 53%, respectively, and that the overall identification rate was 89%. All positive results by the nested-PRA method agreed with the results by culture and 16S rRNA gene sequence analysis. The nested-PRA appears to have clinical applicability when used for the direct identification of mycobacterial organisms (both MTBC and NTM) that are present in smear-positive sputum samples, especially for countries in which MTBC is endemic.

Vancomycin-resistant Enterococcus faecium at a university hospital in Taiwan, 2002-2015: Fluctuation of genetic populations and emergence of a new structure type of the Tn1546-like element.

BACKGROUND/PURPOSES: Vancomycin resistance increased significantly to 31.3% among Enterococcus faecium in 2006 and remained high thereafter at a university hospital in Taiwan. A longitudinal study was retrospectively conducted to characterize these vancomycin-resistant E. faecium (VRE-fm). METHODS: A total of 378 non-repetitive VRE-fm blood isolates collected during 2002-2015 were studied. Multilocus sequence typing, pulsed-field gel electrophoresis, analysis of van genes and the Tn1546 structure, and conjugation experiments were performed. RESULTS: The majority (78.0%) of the isolates were associated with hospital-acquired infections. Molecular typing revealed nine major pulsotypes and five predominant sequence types (STs): ST17 (33.9%), ST78 (18.3%), ST414 (14.6%), ST18 (10.6%), and ST203 (7.4%). Fluctuation of these prevailing STs among the study years in association with some major pulsotypes was noted. All isolates carried vanA genes, except that in four isolates vanB genes were found. Among the vanA-carrying Tn1546-like elements, one predominant structure type (Type I, 55.9%) was noted throughout the study years. Since 2009, another predominant structure type (Type II, 40.1%) has emerged firstly in ST414 and gradually spread to other 11 STs in subsequent years. Isolates carrying these Type II Tn1546-like elements have become the most predominant population since 2014, majorly found in ST78 and ST17. Preliminary experiments indicated that plasmids carrying the Type II Tn1546-like elements demonstrated ten-fold higher efficiency than those carrying the Type I Tn1546-like elements. CONCLUSION: Dissemination of some major STs and horizontal transfer of plasmids carrying two major structure types of Tn1546-like elements may have together contributed to the increase of VRE-fm infection.

The emergence in Taiwan of fluoroquinolone resistance in Salmonella enterica serotype choleraesuis.

BACKGROUND: Salmonella enterica serotype choleraesuis is a cause of serious systemic infections. Because fluoroquinolones are the drug of choice for the treatment of severe salmonella infections, the emergence and dissemination of fluoroquinolone-resistant S. enterica serotype choleraesuis have clinical consequences. METHODS: In Taiwan, a hospital-based surveillance system has been in place since 1987 to monitor the incidence of S. enterica serotype choleraesuis infections and the antimicrobial susceptibility of the isolates. We investigated the rapid emergence of fluoroquinolone resistance in this serotype in 2000 and 2001. Pigs in Taiwan were evaluated as a potential source of the resistant salmonella. RESULTS: A total of 501 clinical isolates of S. enterica serotype choleraesuis were recovered in our hospital from 1987 through 2000. The proportion of total salmonella isolates made up by S. enterica serotype choleraesuis decreased from an average of 8.4 percent before 1995 to 2.7 percent in 1996 through 1998. During 1999 and 2000, this proportion increased significantly, to an average of 5.0 percent. Ciprofloxacin resistance in S. enterica serotype choleraesuis has been observed since 2000. In the third quarter of 2001, 60 percent of isolates were resistant to ciprofloxacin. Molecular typing indicated that the primary source of S. enterica serotype choleraesuis isolates was herds of swine. All the resistant isolates from humans and swine had mutations that led to the substitution of phenylalanine for serine at position 83 and asparagine for aspartic acid at position 87 in the gene for DNA gyrase A. CONCLUSIONS: This investigation in Taiwan indicates that fluoroquinolone-resistant S. enterica serotype choleraesuis can spread from swine to humans. The use of fluoroquinolones in food animals should be prohibited.

CMY-2 beta-lactamase-carrying community-acquired urinary tract Escherichia coli: genetic correlation with Salmonella enterica serotypes Choleraesuis and Typhimurium.

Forty-six cephamycin-resistant Escherichia coli isolates from patients diagnosed with community-acquired urinary tract infection were selected in order to study their resistance mechanism. With the exception of one isolate producing CMY-4, all isolates produced a CMY-2 beta-lactamase. Molecular typing showed that the CMY-2-producing isolates were not related. Cephamycin resistance was plasmid encoded and conjugatively transferred. Plasmid digest profiles suggested that the plasmids were different. Thirty-nine of the 45 CMY-2-producing isolates harboured a plasmid containing a specific DNA fragment, ISEcp1-bla(CMY-2)-blc-sugE, which was identical to those previously published in CMY-2-producing Salmonella enterica serotype Choleraesuis (SCB67) and Salmonella enterica serotype Typhimurium (pNF1358) from Taiwan and the USA, respectively. Among the remaining six isolates, insertion of IS1294 and IS1 at different positions was observed in one and five isolates, respectively. The regions surrounding bla(CMY-2) of the six isolates were identical to the other 39 isolates as well as to SCB67 and pNF1358. Since the present identical transmissible bla(CMY-2)-carrying element was observed in food animal sources both in the USA and Taiwan, its possible transmission to humans, as revealed in this study, is of great concern. Awareness of this mobile resistance element is required to prevent introduction into hospitals and to reduce the spread of this emerging resistance within the community.

Risk factors and clinical significance of bacteremia caused by Pseudomonas aeruginosa resistant only to carbapenems.

BACKGROUND/PURPOSE: Carbapenem-resistant Pseudomonas aeruginosa infections have been a challenge and issue in hospital settings. However, the clinical impact of P. aeruginosa blood isolates resistant only to carbapenems has never been discussed previously. METHODS: To assess the risk factors and clinical significance of bacteremia caused by carbapenem resistance only P. aeruginosa (CROPA), a 6-year retrospective case-control study was conducted. The CROPA strains were defined as isolates susceptible to ciprofloxacin, antipseudomonal penicillins and cephalosporins, and aminoglycosides but resistant to one antipseudomonal carbapenem (imipenem or meropenem) or both. The controls were selected among patients with bacteremia due to P. aeruginosa susceptible to all above classes of antipseudomonal antibiotics, which was defined as all-susceptible P. aeruginosa. RESULTS: Twenty-five patients had at least one blood culture positive for CROPA, and 50 controls had all-susceptible P. aeruginosa bacteremia. CROPA bacteremia had a high 30-day mortality rate (72.0%), as compared to 26.0% for the controls (p < 0.001). Through multivariate analysis, carbapenem exposure was the only risk factor for developing CROPA bacteremia (p = 0.002). A comparison between the surviving and deceased patients with CROPA bacteremia showed that nine (50%) of those who died, but none of the survivors, received carbapenems as the initial empirical therapy (p = 0.027). CONCLUSION: Carbapenem exposure was associated with emergence of CROPA infections. Repeated carbapenem use in such patients might increase rates of inappropriate initial empirical treatment and mortality. Prudent carbapenem use is important to reduce the emergence of CROPA.

Routine identification of microorganisms by matrix-assisted laser desorption ionization time-of-flight mass spectrometry: Success rate, economic analysis, and clinical outcome.

BACKGROUND: Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) has been widely used in microbial identification. This study evaluated the performance of MALDI-TOF MS and investigated the economic and medical impact of MALDI-TOF MS implementation. METHODS: A total of 12,202 clinical isolates collected from April to September 2013 were identified using MALDI-TOF MS, and the success rates in identifying isolates were analyzed. The differences in the processing time, cost of consumables, weight of waste, and clinical impact between MALDI-TOF MS and biochemical reaction were compared. RESULTS: MALDI-TOF MS successfully identified 96% of 12,202 isolates, including 96.8% of 10,502 aerobes, 90.5% of 1481 anaerobes, 93.8% of 81 yeasts, and 90.6% of 138 nontuberculous mycobacteria at the genus level. By using MALDI-TOF MS, the processing time for aerobes decreased from 32.5 hours to 4.1 hours, and that for anaerobes decreased from 71.5 hours to 46 hours. For detection of aerobes and anaerobes, the cost of consumables was estimated to decrease by US$0.9 per isolate, thus saving US$94,500 in total annual isolation. Furthermore, the weight of waste decreased six-fold, resulting in a reduction of 350 kg/month or 4.2 tons/year. MALDI-TOF MS also increased the percentage of correct antibiotics treatment for Escherichia coli and Klebsiella pneumonia from 56.1% to 75% and shortened the initiation time of the correct antibiotic action from 3.3 hours to 2.5 hours. CONCLUSIONS: MALDI-TOF MS is a rapid, reliable, economical, and environmentally friendly method for routine microbial identification and may contribute to early appropriate antibiotic treatment in clinical settings.

Dissemination of extended-spectrum beta-lactamase-producing Enterobacteriaceae in intensive care units of a medical center in Taiwan.

The prevalence of extended-spectrum beta-lactamase (ESBL)-producing Enterobacteriaceae in a tertiary hospital in Taiwan was assessed over a 16-month period. A total of 125 nonrepetitive ESBL-producing isolates of Enterobacter cloacae, Escherichia coli, and Klebsiella pneumoniae were available for investigation using molecular methods. Four predominant intensive care units (ICUs) were identified, and SHV-12 (59%), CTX-M- 3 (36%), and CTX-M-14 (14%) were the three most frequent ESBLs. SHV-12 was predominant among E. cloacae in the burn unit and K. pneumoniae in the other three chest medicine-related ICUs. CTX-M-3 was predominant among E. coli and K. pneumoniae in three other ICUs. The dissemination of ESBL-producing Enterobacteriaceae in four ICUs of a medical center in Taiwan is a consequence of the clonal dissemination of a few epidemic strains along with the horizontal transmission of resistance genes-carrying plasmids among bacterial organisms.

Evolving pneumococcal serotypes and sequence types in relation to high antibiotic stress and conditional pneumococcal immunization.

In Taiwan, beginning in 2013, the 13-valent pneumococcal conjugate vaccine (PCV13) was provided free of charge to children 2-5 years of age. In 2014, this was extended to children 1-5 years old. During 2012-2014, 953 cases of culture-confirmed pneumococcal disease (CCPD), including 104 invasive pneumococcal disease (IPD), were prospectively identified and analyzed at a 3,700-bed hospital in Taiwan. From 2012 to 2014, the incidence per 10,000 admissions decreased from 26.7 to 20.4 for CCPD (P < 0.001) and from 3.2 to 1.9 for IPD (P < 0.05). Significant reduction of PCV13 serotypes was firstly noted in children in 2013 and extended to both paediatric and adult populations in 2014. Simultaneously, the incidence per 10,000 admissions of non-PCV13 serotypes increased from 6.1 in 2012 to 9.3 in 2014 (P < 0.005). The most prevalent non-PCV13 serotypes were 15A, 15B, and 23A, each containing a predominant clone, ST63(15A), ST83(15B), and ST338(23A). From 2012 to 2014, isolates with penicillin minimum inhibitory concentrations >2 mg/L decreased from 27.8% to 8.1% (P < 0.001) among all isolates. PCV13 immunization in young children demonstrated an early protective effect in all ages. However, in the elderly, the effect was compromised by an emergence of non-PCV13 serotypes.

Clinical experience and microbiologic characteristics of invasive Staphylococcus lugdunensis infection in a tertiary center in northern Taiwan.

BACKGROUND/PURPOSE: Staphylococcus lugdunensis is a coagulase-negative staphylococcus that cannot be ignored. This study is a comprehensive analysis of the clinical and microbiological characteristics of S. lugdunensis bacteremia and sterile site infection during hospitalization. METHODS: This retrospective study included 48 patients with invasive S. lugdunensis infection. During the period of March 2002 to July 2012, they had been hospitalized in a tertiary center of northern Taiwan. Demographics, clinical characteristics, and risk factors of mortality were analyzed. All isolates were tested for antimicrobial susceptibility. We identified the staphylococcal cassette chromosome mec (SCCmec) gene for oxacillin nonsusceptible isolates. RESULTS: The incidence of S. lugdunensis in coagulase-negative staphylococci bacteremia was 0.87%. Forty-eight patients were enrolled: S. lugdunensis was present in 41 patients with bacteremia, in the ascites of three patients, in the synovial fluid of two patients, in the pleural effusion of one patient, and in the amniotic fluid of one patient. The three most common sources of infection were primary bacteremia (43.8%), catheter-related infection (18.8%), and vascular graft infection (12.5%). All-cause mortality during hospitalization was 20.8% (10/48). All deceased patients were bacteremic. Risk factors associated with in-hospital mortality included a Pittsburgh bacteremia score of 2 or greater, infective endocarditis, and end-stage renal disease. Ten (20.8%) isolates were resistant to oxacillin, and 8 isolates were classified as SCCmec type V. CONCLUSION: The clinical significance of S. lugdunensis should not be ignored, especially in patients with severe comorbidities. An aggressive search for endocarditis is strongly suggested in S. lugdunensis bacteremic cases.

Reduced production of OprM may promote oprD mutations and lead to imipenem resistance in Pseudomonas aeruginosa carrying an oprD-group 1A allele.

Resistance mechanisms in a group of carbapenemase-negative Pseudomonas aeruginosa that were susceptible to all antibiotics except carbapenems (carbapenem resistance-only P. aeruginosa [CROPA]) were studied. Ten genetically nonrelated CROPA isolates and their carbapenem-susceptible counterparts were further investigated. OprD production was demonstrated by protein electrophoresis in only 1 of the 10 carbapenem-susceptible isolates, while the other 9 isolates showed hyperproduction of OprM. DNA sequencing of oprD revealed a shortened loop 7 domain (group 1A allele) in eight carbapenem-susceptible isolates. Various oprD mutations, leading to early terminations, were found in 9 of the 10 CROPA isolates. RNA analysis demonstrated hyperexpression of oprM with normal expression of mexA in eight of the carbapenem-susceptible isolates, while in seven of their CROPA counterparts, the oprM expression was significantly reduced. Deletion of oprM was performed in two pairs of representative isolates. Selection of imipenem resistant variants by a disc assay indicated that the lost-of-function mutations in oprD occurred relatively faster in the ΔoprM mutants compared with their corresponding parent strains. Under selection pressure, reduced production of OprM may promote the selection of spontaneous changes in oprD, resulting in the carbapenem resistance in a group of pan-susceptible P. aeruginosa isolates characterized by harboring an oprD-group 1A allele.

Mycobacterium marinum infection in Taiwan.

Mycobacterium marinum often causes skin infections, tenosynovitis, arthritis, and osteomyelitis, and occasionally results in severe disseminated infections in immunocompromised patients. In this study, the clinical features of 14 cases of M. marinum infection were retrospectively analyzed. One patient had septic arthritis, the other 13 had skin infections and/or tenosynovitis. It usually took 2 months or longer for a definite diagnosis to be made in these patients. Three of the 14 patients were cured using clarithromycin alone or in combination with rifampin plus ethambutol. Most patients did not respond to conventional antituberculosis agents. Pulsed-field gel electrophoresis and infrequent-restriction-site polymerase chain reaction are efficient tools for the molecular typing of M. marinum. Both methods yielded a concordant result, and 4 of 12 isolates were genetically closely related to each other based on their banding patterns. This study indicates that these isolates were derived from the same clone. Because M. marinum infection is curable, early diagnosis is important. Poor healing of wounds after exposure to aquatic animals appears to be the most important clinical clue indicating the need for culture and inclusion of M. marinum infection in the differential diagnosis.

National surveillance on vancomycin-resistant Enterococcus faecium in Taiwan: emergence and widespread of ST414 and a Tn1546-like element with simultaneous insertion of IS1251-like and IS1678.

Cases of bacteremia caused by vancomycin-resistant E. faecium (VRE-fm) increased significantly in Taiwan. The present multicenter surveillance study was performed to reveal the associated epidemiological characteristics. In 2012, 134 non-repetitive VRE-fm isolates were prospectively collected from 12 hospitals in Taiwan. Antimicrobial susceptibility, pulsed-field gel electrophoresis (PFGE), multilocus sequence typing (MLST), and analysis of van genes and Tn1546 structures were investigated. Two isolates carried vanB genes, while all the remaining isolates carried vanA genes. Three isolates demonstrated a specific vanA genotype - vanB phenotype. Nine (6.7%) isolates demonstrated tigecycline resistance, and all were susceptible to daptomycin and linezolid. Molecular typing revealed 58 pulsotypes and 13 sequence types (STs), all belonged to three major lineages 17, 18, and 78. The most frequent STs were ST17 (n = 48, 35.8%), ST414 (n = 22, 16.4%), and ST78 (n = 16, 11.9%). Among the vanA harboring isolates, eight structure types of the Tn1546-like element were demonstrated. Type I (a partial deletion in the orf1 and insertion of IS1251-like between the vanS - vanH genes) and Type II (Type I with an additional insertion of IS1678 between orf2 - vanS genes) were the most predominant, consisted of 60 (45.5%) and 62 (47.0%) isolates, respectively. The increase of VRE-fm bacteremia in Taiwan may be associated with the inter- and intra-hospital spread of some major STs and horizontal transfer of vanA genes mostly carried on two efficient Tn1546-like elements. The prevailing ST414 and widespread of the Type II Tn1546-like elements are an emerging problem that requires continuous monitoring.