Comparison of the ASTA MicroIDSys and VITEK MS matrix-assisted laser desorption/ionization time-of-flight mass spectrometry systems for identification of clinical bacteria and yeasts.

The ASTA MicroIDSys system (ASTA, Suwon, Korea) is a newly developed Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) system for identification of microorganisms. We compared the performance of the ASTA MicroIDSys system with that of the VITEK MS system (bioMérieux, Marcy l'Etoile, France) for identifying clinical microorganisms. A total 2055 isolates including 1910 bacteria and 145 yeasts were tested. Among them, the VITEK MS correctly identified 1999 (97.3%) isolates to species level and 26 (1.3%) to the genus level. The ASTA MicroIDSys correctly identified 1988 (96.7%) isolates to species level and 28 (1.4%) to the genus level. The VITEK MS and ASTA MicroIDSys misidentified one isolate and four (0.2%) isolates, respectively, and provided no identification for 29 (1.4%) and 35 (1.7%) isolates, respectively. The performance of the ASTA MicroIDSys was comparable to that of the VITEK MS for identification of clinically relevant bacterial and yeast isolates.

Performance of a Novel Fluorogenic Assay for Detection of Carbapenemase-Producing Enterobacteriaceae from Bacterial Colonies and Directly from Positive Blood Cultures.

Rapid and accurate detection of carbapenemase-producing Enterobacteriaceae (CPE) is critical for appropriate treatment and infection control. We compared a rapid fluorogenic assay using a carbapenem-based fluorogenic probe with other phenotypic assays: modified carbapenem inactivation method (mCIM), Carba NP test (CNP), and carbapenemase inhibition test (CIT). A total of 217 characterized isolates of Enterobacteriaceae were included as follows: 63 CPE; 48 non-carbapenemase-producing carbapenem-resistant Enterobacteriaceae (non-CP-CRE); 53 extended-spectrum ß-lactamase producers; and 53 third-generation-cephalosporin-susceptible isolates. The fluorogenic assay using bacterial colonies (Fluore-C) was conducted by lysing the isolates followed by centrifugation and mixing the supernatant with fluorogenic probe. In addition, for the fluorogenic assay using spiked blood culture bottles (Fluore-Direct), pellets were obtained via the saponin preparation method, which can directly identify the pathogens using matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS). The fluorescence signal was measured over 50 min using a fluorometer. The fluorescent signal of CPE was significantly higher than that of non-CPE in both Fluore-C (median relative fluorescence units [RFU] [range], 5,814 [240 to 32,009] versus 804 [36 to 2,480], respectively; P < 0.0001) and Fluore-Direct (median RFU [range], 10,355 [1,689 to 31,463] versus 1,068 [428 to 2,155], respectively; P < 0.0001) tests. Overall, positive and negative percent agreements of Fluore-C, mCIM, CNP, CIT, and Fluore-Direct were 100% and 98.7%, 98.3% and 97.5%, 88.1% and 100%, 96.4% and 98.7%, and 98.3% and 98.1%, respectively. The relatively lower positive percent agreement (PPA) of CNP was mainly observed in OXA-type CPE. The fluorogenic assay showed excellent performance with bacterial colonies and also directly from positive blood cultures. We included many non-CP-CRE isolates for strict evaluation. The fluorogenic assay will be a useful tool for clinical microbiology laboratories.

Clinical usefulness of iQ200/iChem Velocity workstation for screening of urine culture.

BACKGROUND: Clinical microbiology laboratories are asked to process large numbers of urine specimens for culture, but only 20-40% of them are positive. Therefore, a rapid, reliable screening method is necessary to speed up the reporting of a negative result. In this study, we evaluated the iQ200/iChem workstation, which is a combination of digital imaging software and a strip reader to predict negative urine culture. METHOD: A total of 1942 urine specimens were processed through both culture and iQ200/ iChem workstation. We analyzed the performance using two definition of positive urine culture; one or two potential uropathogens at a concentration of ≥105 CFU/ml and ≥ 104 CFU/ml. We assessed combinations of parameters (ASP; all small particles, WBC; leukocyte, BACT; bcteria, LE; leukocyte esterase) applying various cut-offs which can achieve the negative predictive value (NPV) ≥97% and culture reduction rate ≥ 50%. RESULTS: The culture positive rate was 12.8 and 18.4% applying the criteria of ≥105 CFU/ml and ≥ 104 CFU/ml, respectively. The area under the curve (AUC) of each parameter for ≥105 CFU/ml / ≥104 CFU/ml bacteriuria was 795 /0.719 for WBC, 0.722 / 0.701 for ASP and 0.740 /0.704 for bacteria. Therefore, we investigated the combination of the parameters. With the fixed parameter of BACT≥1/HPF and positive LE, the combinations of WBC ≥ 4/HPF and ASP ≥8500/µl or WBC ≥ 6/HPF and ASP≥5500/µl showed good performance for detecting ≥105 CFU/ml uropathogen. The ranges of sensitivity, specificity, negative predictive value and culture reduction rate were 91.5-92.3%, 49.8-52.6%, 97.7-97.9% and 50.4-53.0%, respectively. However, none of the combined setting yielded acceptable range of NPV for detecting ≥104 CFU/ml uropathogen (NPV 92.9-94.9%). Enterococcus spp. was the most common uropathogen causing the false negative results (55.7%), and also the main pathogen among the positive culture of 104-5 CFU/ml bacteriuria (45%). CONCLUSIONS: iQ200/iChem workstation was excellent in detection of ≥105 CFU/ml uropathogen, but unsatisfactory in detection of 104-5 CFU/ml uropathogen and Enterococcus spp. It can be useful for screening of urine specimens to reduce bacterial culture. However, notice from clinician will be necessary for specimens from the patients with high risk for UTI, such as pregnant woman, infant, elderly or immune compromised patients.

Comparative Evaluation of Seegene Allplex Gastrointestinal, Luminex xTAG Gastrointestinal Pathogen Panel, and BD MAX Enteric Assays for Detection of Gastrointestinal Pathogens in Clinical Stool Specimens.

CONTEXT.­: Infectious gastroenteritis is caused by various pathogens, including bacteria, viruses, and parasites. OBJECTIVE.­: To compare the performance of Seegene Allplex Gastrointestinal (24 targets: 13 bacteria, 5 viruses, and 6 parasites in 4 panels), Luminex xTAG Gastrointestinal Pathogen Panel (15 targets: 9 bacteria, 3 viruses, and 3 parasites), and BD MAX Enteric panel (5 bacteria and 3 parasites). We estimated the agreement among 3 molecular assays. DESIGN.­: A total of 858 stool samples (554 bacterial/parasite and 304 viral pathogens) were included. A consensus positive/negative was defined as concordant results from at least 2 tests. To evaluate the agreement among the assays, κ value was calculated. RESULTS.­: The overall positive percentage agreements of Seegene, Luminex, and BD MAX were 94% (258 of 275), 92% (254 of 275), and 78% (46 of 59), respectfully. For Salmonella, Luminex showed low negative percentage agreement because of frequent false positives (n = 31) showing low median fluorescent intensity. For viruses, positive/negative percentage agreements of Seegene and Luminex were 99%/96% and 93%/99%, respectively. Compared with routine microbiology testing, Seegene, Luminex, and BD MAX additionally identified 39, 40, and 12 pathogens, respectively. Sixty-one cases (16 cases with Seegene, 51 cases with Luminex, and 1 case with BD MAX) showed positive results for multiple pathogens, but only 3 were consensus positive. CONCLUSIONS.­: These multiplex molecular assays appear to be promising tools for the detection and identification of multiple gastrointestinal pathogens simultaneously. However, careful interpretation of positive results for multiple pathogens is required.

Evaluation of modified saponin preparation method for the direct identification and antimicrobial susceptibility testing from positive blood culture.

BACKGROUND: We evaluated the two in-house sample preparation methods (saponin method (SAP) and [saponin + Sputazyme] method (SSPZ)) for direct identification of microorganisms using MALDI-TOF MS from positive blood culture bottles. Also, we evaluated the [saponin + Sputazyme] method for direct antimicrobial susceptibility testing (AST) using Vitek 2 system. METHODS: For direct identification, 163 prospective, monomicrobial positive blood culture bottles and 25 contrived blood culture bottles spiked with 25 infrequently isolated bacterial strains were included. For direct AST, pellets obtained by SSPZ method from 102 prospective blood culture bottles were tested. The results from the direct identification and AST were compared with those from the routine diagnostic method performed with colonies sub cultured on solid media. RESULTS: In 163 prospective specimens, SAP method correctly identified 132/163 (81.0%) isolates and SSPZ method correctly identified 148/163 (90.8%) isolates (P = .018). Among the 92 Gram-positive isolates, the correct identification rate was significantly higher with the SSPZ method than the SAP method (92.4% vs. 81.5%), respectively (P = .041). However, the SSPZ method failed to identify Streptococcus pneumoniae. Among the 64 Gram-negative isolates, the correct identification rate was 82.8% (53/64) and 87.5% (56/64) for the former and the latter method, respectively (P = .491). Compared with standard methods direct AST showed 98.5% (1523/1547) agreement. CONCLUSION: The addition of Sputazyme improved the identification of commonly isolated bacteria, especially for Gram-positive isolates and yeasts and can be applied for direct antimicrobial susceptibility testing of bacteria. Although SAP method showed better results for Campylobacter spp. and anaerobic bacteria, considering their very low incidence, routine use of SSPZ will be more practical.

In Vitro Evaluation of Betafoam, a New Polyurethane Foam Dressing.

BACKGROUND: A new polyurethane foam dressing impregnated with 3% povidone-iodine (Betafoam; Genewell, Seoul, Korea) was recently developed based on the hypothesis that its physical properties, including improved moisture-retention capacity and antimicrobial activity, are at least as good as those achieved with the current foam dressings that contain silver, but also associated with reduced cost and cytotoxicity to host cells. The purpose of this in vitro study was to evaluate the efficacy of Betafoam by comparing its physical properties, antimicrobial activity, and cytotoxicity with those of 3 silver foam dressings (Allevyn-Ag [Smith & Nephew, Hull, United Kingdom]; Mepilex-Ag [Mölnlycke Health Care, Gothenburg, Sweden]; and PolyMem-Ag [Ferris MFG Corp, Burr Ridge, Illinois]) used worldwide. METHODS: This study measured each dressing's pore size, fluid absorption time, fluid absorption capacity, fluid retention capacity, antimicrobial activity against Staphylococcus aureus and Pseudomonas aeruginosa, and cytotoxicity to mouse fibroblasts. RESULTS: Betafoam had the smallest pore size, the fastest fluid absorption time, greatest fluid absorption, and best retention capacities among the tested foam dressings. Antimicrobial activity was not significantly different among the dressings. However, Betafoam also demonstrated the lowest cytotoxicity to the fibroblasts. CONCLUSIONS: Betafoam may result not only in desirable rapid regulation of exudation but also antimicrobial activity with minimal cytotoxicity to host cells that are key requirements for wound healing.

Evaluation of BD MAX Staph SR Assay for Differentiating Between Staphylococcus aureus and Coagulase-Negative Staphylococci and Determining Methicillin Resistance Directly From Positive Blood Cultures.

BACKGROUND: We evaluated the performance of the BD MAX StaphSR Assay (SR assay; BD, USA) for direct detection of Staphylococcus aureus and methicillin resistance not only in S. aureus but also in coagulase-negative Staphylococci (CNS) from positive blood cultures. METHODS: From 228 blood culture bottles, 103 S. aureus [45 methicillin-resistant S. aureus (MRSA), 55 methicillin-susceptible S. aureus (MSSA), 3 mixed infections (1 MRSA+Enterococcus faecalis, 1 MSSA+MRCNS, 1 MSSA+MSCNS)], and 125 CNS (102 MRCNS, 23 MSCNS) were identified by Vitek 2. For further analysis, we obtained the cycle threshold (Ct) values from the BD MAX system software to determine an appropriate cutoff value. For discrepancy analysis, conventional mecA/mecC PCR and oxacillin minimum inhibitory concentrations (MICs) were determined. RESULTS: Compared to Vitek 2, the SR assay identified all 103 S. aureus isolates correctly but failed to detect methicillin resistance in three MRSA isolates. All 55 MSSA isolates were correctly identified by the SR assay. In the concordant cases, the highest Ct values for nuc, mecA, and mec right-extremity junction (MREJ) were 25.6, 22, and 22.2, respectively. Therefore, we selected Ct values from 0-27 as a range of positivity, and applying this cutoff, the sensitivity/specificity of the SR assay were 100%/100% for detecting S. aureus, and 97.9%/98.1% and 99.0%/95.8% for detecting methicillin resistance in S. aureus and CNS, respectively. CONCLUSIONS: We propose a Ct cutoff value for nuc/mec assay without considering MREJ because mixed cultures of MSSA and MRCNS were very rare (0.4%) in the positive blood cultures.

Performance of a novel fluorogenic chimeric analog for the detection of third-generation cephalosporin resistant bacteria.

Resistance to third generation cephalosporins is widely disseminated in Enterobacteriaceae mainly due to extended-spectrum-ß-lactamases, plasmid AmpC ß-lactamases, and hyperproduction of chromosomal AmpC ß-lactamases. Here we evaluated the performance of a novel fluorogenic probe rapid test and compared the results with the phenol red assay using a total of 77 characterized organisms (44 extended-spectrum-ß-lactamases, 33 chromosomal or plasmid AmpC ß-lactamases) and 46 susceptible organisms. The fluorescent assay showed higher sensitivity than the phenol red assay in cefotaximase type extended-spectrum-ß-lactamases, non- cefotaximase type extended-spectrum-ß-lactamases, chromosomal AmpC ß-lactamases, and plasmid AmpC ß-lactamases (96.7% vs. 90.0%, p=0.157; 71.4% vs. 7.1%, p=0.003; 100.0% vs. 64.7%, p<0.001; 100.0% vs. 6.3%, p<0.001). The fluorescent assay had a positive correlation with the exponents of cefotaxime and ceftazidime minimum inhibitory concentrations (p<0.001 for both). The new fluorescent assay will be very useful for the rapid detection of resistance to third generation cephalosporins that originates from various ß-lactamases.

Effects of Panax ginseng extract on human dermal fibroblast proliferation and collagen synthesis.

Current studies of Panax ginseng (or Korean ginseng) have demonstrated that it has various biological effects, including angiogenesis, immunostimulation, antimicrobial and anti-inflammatory effects. Therefore, we hypothesised that P. ginseng may also play an important role in wound healing. However, few studies have been conducted on the wound-healing effects of P. ginseng. Thus, the purpose of this in vitro pilot study was to determine the effects of P. ginseng on the activities of fibroblasts, which are key wound-healing cells. Cultured human dermal fibroblasts were treated with one of six concentrations of P. ginseng: 0, 1, 10 and 100 ng/ml and 1 and 10 µg/ml. Cell proliferation was determined 3 days post-treatment using the 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyl tetrazolium bromide assay, and collagen synthesis was evaluated by the collagen type I carboxy-terminal propeptide method. Cell proliferation levels and collagen synthesis were compared among the groups. The 10 ng/ml to 1 µg/ml P. ginseng treatments significantly increased cell proliferation, and the 1 ng/ml to 1 µg/ml concentrations significantly increased collagen synthesis. The maximum effects for both parameters were observed at 10 ng/ml. P. ginseng stimulated human dermal fibroblast proliferation and collagen synthesis at an optimal concentration of 10 ng/ml.

Direct Identification and Antimicrobial Susceptibility Testing of Bacteria From Positive Blood Culture Bottles by Matrix-Assisted Laser Desorption/Ionization Time-of-Flight Mass Spectrometry and the Vitek 2 System.

BACKGROUND: We evaluated the reliability and accuracy of the combined use of matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) bacterial identification and Vitek 2 antimicrobial susceptibility testing (AST) for bacteria from positive blood culture bottles. METHODS: Direct identification and AST were performed in parallel to the standard methods in monomicrobial positive blood culture bottles. In total, 254 isolates grown on aerobic and/or anaerobic bottles were identified with MALDI-TOF Vitek MS (bioMérieux, France), and 1,978 microorganism/antimicrobial agent combinations were assessed. For isolates from anaerobic bottles, an aliquot of the culture broth was centrifuged, washed, and filtered through a nylon mesh. For isolates from aerobic/pediatric bottles, a lysis step using 9.26% ammonium chloride solution and 2% saponin solution was included. RESULTS: The overall correct identification rate was 81.8% (208/254) and that for gram-positive/gram-negative isolates was 73.9%/92.6%, respectively, and it was 81.8%, 87.6%, and 57.9% for isolates from aerobic, anaerobic, and pediatric bottles, respectively. Identification was not possible in 45 cases, and most of these isolates were streptococci (N=14) and coagulase-negative staphylococci (N=11). Misidentification occurred only in one case. Compared with standard methods, direct AST showed 97.9% (1,936/1,978) agreement with very major error of 0.25%, major error of 0.05%, and minor error of 1.8%. CONCLUSIONS: This simple and cost-effective sample preparation method gives reliable results for the direct identification and AST of bacteria. For the identification of streptococci and coagulase-negative staphylococci, the method should be further improved.

Recurrent Extranodal NK/T-Cell Lymphoma Presenting as a Perforating Palatal Ulcer and Oro-Nasal Fistula.

Nasal-type extranodal natural killer/T-cell lymphoma (ENKTL) is a rare disease presenting with non-specific symptoms, typically originating in the nasal cavity, palate, or midfacial region. Oral cavity is an extremely rare site for this type of lymphoma. In this report, we present a case of palatal perforation and oro-nasal fistula as a manifestation of recurrent ENKTL. Complicated disease entity should be considered when surgeons deal with palatal perforation and oro-nasal fistula.

Atypical Facial Filler Granuloma: Comparative Histologic Analysis with Paraffinoma.

Dermal fillers are generally accepted as safe and well-tolerable cosmetic tools. However, adverse reactions have been reported in the literature. Here, we present a case of atypical facial filler granuloma and compare its histologic features with those of the classic paraffinoma.

Genotypes of Ciprofloxacin-Resistant Klebsiella pneumoniae in Korea and Their Characteristics According to the Genetic Lineages.

We investigated the molecular genotypes of ciprofloxacin-resistant Klebsiella pneumoniae and their characteristics according to the genetic lineages. For 160 K. pneumoniae collected in 2013, ciprofloxacin minimum inhibitory concentrations (MICs) were determined by agar dilution method. The genotypes of ciprofloxacin-resistant K. pneumoniae isolates were determined by multilocus sequence typing (MLST) and wzi gene typing. The presence of plasmid-mediated resistance determinants [qnrA, qnrB, qnrS, aac(6')-Ib-cr, blaCTX-M, and blaSHV] was investigated. The gyrA and parC genes were sequenced. Fifty-seven isolates showed ciprofloxacin resistance. By MLST, four major sequence types (STs) or clonal complexes (CCs), that is, ST307, CC11, CC147, and ST15, were found and the two most prevalent STs were ST307 (14/57, 24.6%) and ST11 (12/57, 21.1%). By wzi gene sequencing, 46 of the 57 isolates could be differentiated. All the ST307 isolates had an identical wzi sequence and harbored qnrB. The majority of them harbored aac(6')-Ib-cr (85.7%) and CTX-M-15 (92.9%). In contrast, 12 ST11 isolates were divided into five sublineages by wzi sequence and qnrB, qnrS, and aac(6')-Ib-cr were carried by nine, seven, and three isolates, respectively. They harbored SHV-type extended-spectrum ß-lactamase more frequently than CTX-M-15 (nine and four isolates, respectively). The prevalence of CTX-M-15, qnrB1, and aac(6')-Ib-cr was significantly higher in ST307 than in ST11 (p=0.003, p=0.000, and p=0.002, respectively). Both clones had identical amino acid substitution in gyrA (S83I) and parC (S80I). K. pneumoniae ST307 and ST11 were the two most common clones, and the ST307 isolates were highly homogeneous, suggesting their recent emergence.

Direct Identification of Urinary Tract Pathogens From Urine Samples Using the Vitek MS System Based on Matrix-Assisted Laser Desorption Ionization-Time of Flight Mass Spectrometry.

BACKGROUND: We evaluated the coincidence rate between Vitek MS system (bioMérieux, France) and Vitek 2 in identifying uropathogens directly from urine specimens. METHODS: Urine specimens submitted to our microbiology laboratory between July and September 2013 for Gram staining and bacterial culture were analyzed. Bacterial identification was performed by using the conventional method. Urine specimens showing a single morphotype by Gram staining were processed by culturing and matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS). Of 2,370 urine specimens, 251 showed a single morphotype on Gram staining, and among them, 202 were available for MALDI-TOF MS. RESULTS: In these 202 specimens, colony growth was observed in 189 specimens, and 145 specimens had significant growth of single-colony morphotype in culture. One hundred and ten (75.9%) of them had colony counts of ≥10(5) colony-forming units (CFU)/mL and included 71 enteric gram-negative bacteria (GNB), 5 glucose-non-fermenting GNB, 9 gram-positive cocci (GPC), and 25 yeasts. Furthermore, 70 (98.6%), 3 (60.0%), 4 (44.4%), and 5 (20.0%), respectively, of these were correctly identified by Vitek MS. Thirty-one specimens (21.4%; 11 GNB, 7 GPC, 12 yeasts, and 1 gram-positive bacillus) had colony counts of 10(4)-10(5) CFU/mL. Four specimens (2.8%) yielded colony counts of 10(3)-10(4) CFU/mL. CONCLUSIONS: Vitek MS showed high rate of accuracy for the identification of GNB in urine specimens (≥10(5) CFU/mL). This could become a rapid and accurate diagnostic method for urinary tract infection caused by GNB. However, for the identification of GPC and yeasts, further studies on appropriate pre-treatment are warranted.

Evaluation of 3 automated real-time PCR (Xpert C. difficile assay, BD MAX Cdiff, and IMDx C. difficile for Abbott m2000 assay) for detecting Clostridium difficile toxin gene compared to toxigenic culture in stool specimens.

We evaluated the performance of the 3 automated systems (Cepheid Xpert, BD MAX, and IMDx C. difficile for Abbott m2000) detecting Clostridium difficile toxin gene compared to toxigenic culture. Of the 254 stool specimens tested, 87 (48 slight, 35 moderate, and 4 heavy growth) were toxigenic culture positive. The overall sensitivities and specificities were 82.8% and 98.8% for Xpert, 81.6% and 95.8% for BD MAX, and 62.1% and 99.4% for IMDx, respectively. The specificity was significantly higher in IMDx than BD MAX (P= 0.03). All stool samples underwent toxin A/B enzyme immunoassay testing, and of the 254 samples, only 29 samples were positive and 2 of them were toxigenic culture negative. Considering the rapidity and high specificity of the real-time PCR assays compared to the toxigenic culture, they can be used as the first test method for C. difficile infection/colonization.

Rapid detection of Gram-negative bacteria and their drug resistance genes from positive blood cultures using an automated microarray assay.

We evaluated the performance of the Verigene Gram-negative blood culture (BC-GN) assay (CE-IVD version) for identification of Gram-negative (GN) bacteria and detection of resistance genes. A total of 163 GN organisms (72 characterized strains and 91 clinical isolates from 86 patients) were tested; among the clinical isolates, 86 (94.5%) isolates were included in the BC-GN panel. For identification, the agreement was 98.6% (146/148, 95% confidence interval [CI], 92.1-100) and 70% (7/10, 95% CI, 53.5-100) for monomicrobial and polymicrobial cultures, respectively. Of the 48 resistance genes harbored by 43 characterized strains, all were correctly detected. Of the 19 clinical isolates harboring resistance genes, 1 CTX-M-producing Escherichia coli isolated in polymicrobial culture was not detected. Overall, BC-GN assay provides acceptable accuracy for rapid identification of Gram-negative bacteria and detection of resistance genes, compared with routine laboratory methods despite that it has limitations in the number of genus/species and resistance gene included in the panel and it shows lower sensitivity in polymicrobial cultures.

Performance of chromID Clostridium difficile agar compared with BBL C. difficile selective agar for detection of C. difficile in stool specimens.

We evaluated the performance of a new chromogenic medium for detection of Clostridium difficile, chromID C. difficile agar (CDIF; bioMérieux, France), by comparison with BBL C. difficile Selective Agar (CDSA; Becton Dickinson and Company, USA). After heat pre-treatment (80℃, 5 min), 185 diarrheal stool samples were inoculated onto the two media types and incubated anaerobically for 24 hr and 48 hr for CDIF and for 48 hr and 72 hr for CDSA. All typical colonies on each medium were examined by Gram staining, and the gram-positive rods confirmed to contain the tpi gene by PCR were identified as C. difficile. C. difficile was recovered from 36 samples by using a combination of the two media. The sensitivity with CDIF 48 hr was highest (100%) and was significantly higher than that with CDIF 24 hr (58.3%; P<0.001), because samples with a low burden of C. difficile tended to require prolonged incubation up to 48 hr (P<0.001). The specificity of CDIF 24 hr and CDIF 48 hr (99.3% and 90.6%, respectively) was significantly higher than that of CDSA 48 hr and CDSA 72 hr (72.5% and 67.1%, respectively; P<0.001). CDIF was effective for detecting C. difficile in heat-pretreated stool specimens, thus reducing unnecessary testing for toxin production in non-C. difficile isolates and turnaround time.

Risk factors for mortality in patients with Pseudomonas aeruginosa bacteremia; retrospective study of impact of combination antimicrobial therapy.

BACKGROUND: Whether the combination of antimicrobial therapy is a factor in mortality in Pseudomonas aeruginosa bacteremia remains to be elucidated. This study investigated the risk factors for mortality in P. aeruginosa bacteremia patients and the influence of adequate antimicrobial therapy and combination therapy on clinical outcomes. METHODS: This retrospective study analyzed data of 234 patients with P. aeruginosa bacteremia at a 1,200-bed tertiary teaching university hospital in South Korea between January 2010 and December 2012. Factors associated with mortality were determined. Mortality was compared in patients with adequate empirical and targeted combination therapy, and monotherapy, and inappropriate therapy. RESULTS: A total of 141 (60.3%) patients were given appropriate empirical antibiotic treatment (combination therapy in 38 and monotherapy in 103). Among 183 patients (78.2%) who finally received appropriate targeted treatment, 42 had combination therapy and 141 had monotherapy. The percentage of patients receiving empirical combination therapy was slightly, but not significantly higher, in the survivor group than in the nonsurvivor group (17.0% [31/182] vs. 13.5% [7/52], p = 0.74). A similar tendency was demonstrated for targeted combination therapy (19.8% [36/182] vs. 11.5% [6/52], respectively; p = 0.31). However, in a subgroup analysis of data from patients (n = 54) with an absolute neutrophil count less than 500/mm3, the patients who had appropriate empirical or targeted combination therapy showed better outcomes than those who underwent monotherapy or inappropriate therapy (p < 0.05). Mechanical ventilation (odds ratio [OR], 6.93; 95% confidence interval [CI], 2.64-18.11; p = 0.0001), the use of a central venous catheter (OR, 2.95; 95% CI, 1.35-6.43; p = 0.007), a high Acute Physiology and Chronic Health Evaluation II score (OR, 4.65; 95% CI, 1.95-11.04; p = 0.0001), and presence of septic shock (OR, 2.91; 95% CI, 1.33-6.38; p = 0.007) were independent risk factors for 14-day mortality. CONCLUSIONS: Disease severity was a critical factor for mortality in our patients with P. aeruginosa bacteremia. Overall, combination therapy had no significant effect on 14-day mortality compared with monotherapy. However, appropriate combination therapy showed a favorable effect on survival in patients with febrile neutropenia.

Rates of fecal transmission of extended-spectrum ß-lactamase-producing and carbapenem-resistant Enterobacteriaceae among patients in intensive care units in Korea.

BACKGROUND: We investigated the rates of fecal transmission of extended-spectrum ß-lactamase (ESBL)-producing Enterobacteriaceae (ESBL-E) and carbapenem-resistant Enterobacteriaceae (CRE) among patients admitted to intensive care units (ICUs). METHODS: From June to August 2012, rectal cultures were acquired from all patients at ICU admission. For patients not carrying ESBL-E or CRE at admission, follow-up cultures were performed to detect acquisition. A chromogenic assay was used to screen for ESBL-E and CRE. Bacterial species identification and antibiotic susceptibility tests were performed using the Vitek 2 system (bioMérieux, France). ESBL genotypes were determined by PCR, and clonal relatedness of the isolates was assessed by pulsed-field gel electrophoresis. RESULTS: Out of 347 ICU admissions, 98 patients were found to be carriers of ESBL-E (28.2%, 98/347). Follow-up cultures were acquired from 91 of the patients who tested negative for ESBL-E at admission; the acquisition rate in this group was 12.1% (11/91), although none was a nosocomial transmission. For CRE, the prevalence of fecal carriage was 0.3% (1/347), and the acquisition rate was 2.9% (4/140). None of the CRE isolates were carbapenemase-producers. CONCLUSIONS: The high prevalence of ESBL-E carriage on admission (28.2%), coupled with rare nosocomial transmission and the very low carriage rate of CRE (0.3%), challenge the routine use of active surveillance in non-epidemic settings. Nevertheless, passive surveillance measures, such as rapid and accurate screening of clinical specimens, will be critical for controlling the spread of CRE.