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ABSTRACT With the introduction of ceftazidime-avibactam worldwide, the antimicrobial activity of new β-lactam/β-lactamase inhibitors (BL/BLIs) needs to be investigated. From January 2020 to June 2023, Klebsiella pneumoniae carbapenemase (KPC)-producing Enterobacterales were collected. With a broth microdilution test of new BL/BLIs, cross-activity test with nine combinations of BLs and new BLIs and dose-escalation titration test for non-susceptible isolates were conducted to investigate inhibitory activities of new BLIs. A total of 188 isolates was collected and most isolates (186/188, 98.9%) carried the KPC-2 gene exclusively, while two isolates (1.1%) co-harbored NDM-1. Among the 186 KPC-2-producing isolates, 184 (98.9%) were susceptible to ceftazidime-avibactam, 173 (93.0%) to imipenem-relebactam, and 184 (98.9%) to meropenem-vaborbactam. All isolates non-susceptible to imipenem-relebactam or meropenem-vaborbactam became susceptible when avibactam replaced relebactam or vaborbactam, with 7 of 11 (63.6%) imipenem-relebactam non-susceptible isolates and both (100.0%) of the meropenem-vaborbactam non-susceptible isolates. When the minimum inhibitory concentrations (MICs) of BLs were compared using log2 scales, combinations with avibactam showed statistically significant efficacy in lowering MICs compared to relebactam and vaborbactam (all P < 0.05). In the dose-escalation test of new BLIs, increasing dose of all new BLIs corresponded to increased susceptibility to BLs. Ceftazidime-avibactam exhibited excellent susceptibility against KPC-2-producing Enterobacterales unless co-harboring metallo-β-lactamase. The cross-combination test against non-susceptible isolates suggests that the inhibitory activity of avibactam was superior to those of relebactam or vaborbactam. Increasing the dose of new BLIs produced increased susceptibility to BLs, suggesting that high-concentration regimen need to be developed.IMPORTANCEThis study investigated 188 Klebsiella pneumoniae carbapenemase (KPC)-2-producing Enterobacterales collected from January 2020 to June 2023 in a tertiary care hospital of Korea. Most isolates were susceptible to ceftazidime-avibactam (98.9%) and meropenem-vaborbactam (98.9%), while susceptibility to imipenem-relebactam was lower (93.0%). The cross-combination test using nine combinations of the individual β-lactams (BLs) and new β-lactamase inhibitors (BLIs) showed that the inhibitory activity of avibactam was significantly superior to relebactam or vaborbactam when the Log2 MIC of BLs were compared for each combination with BLIs (all P < 0.05). The dose-escalation test of new BLIs demonstrated that increasing doses of new BLIs corresponded to increased susceptibility to BLs. Taken together, this study illustrates the excellent activity of ceftazidime-avibactam against KPC-2-producing Enterobacterales and suggests further investigation into high-concentration regimens for potentially non-susceptible clinical isolates.

ABSTRACTThe aim of this study was to compare the performance of the newly developed SMG HHV-6 Q Real-Time PCR Kit (SMG assay) with the RealStar HHV-6 PCR Kit (RealStar assay). The analytical sensitivity and specificity, linearity, and precision of the SMG assay were evaluated. The clinical performance of the SMG assay was assessed and compared with that of the RealStar assay using 207 clinical specimens (HHV-6A positive, n = 51; HHV-6B positive, n = 64; HHV-6A/B negative, n = 92). The limit of detection of the SMG assay was 2.92 log10 copies/mL for HHV-6A DNA and 2.88 log10 copies/mL for HHV-6B DNA. The linear range was determined to be 3.40–9.00 log10 copies/mL for both viruses. Intra- and inter-assay variability were below 5% at concentrations ranging from 4 to 9 log10 copies/mL. No cross-reactivity was observed with the 25 microorganisms included in the specificity panel. The clinical sensitivity and specificity of the SMG and RealStar assays compared to in-house polymerase chain reaction and sequencing were as follows: SMG assay, 98.0% and 100% for HHV-6A DNA, respectively, and 96.9% and 100% for HHV-6B DNA, respectively; RealStar assay, 98.0% and 100% for HHV-6A DNA, respectively, and 90.6% and 100% for HHV-6B DNA, respectively. The correlation coefficients between viral loads measured by the two assays were 0.948 and 0.975, with mean differences of 0.62 and 0.32 log10 copies/mL for HHV-6A and HHV-6B DNA, respectively. These results demonstrate that the SMG assay is a sensitive and reliable tool for the quantitative detection and differentiation of HHV-6A and HHV-6B DNA.IMPORTANCEQuantitative real-time PCR (qPCR) that can distinguish between HHV-6A and HHV-6B DNA is recommended for diagnosis of active infection. The SMG HHV-6 Q Real-Time PCR Kit (SMG assay) is a newly developed qPCR assay that can differentiate between HHV-6A and HHV-6B DNA; however, little is known about its performance. In this study, we assessed the performance of the SMG assay and compared it with that of a commercially available qPCR assay, the RealStar HHV-6 PCR Kit (RealStar assay). The SMG assay demonstrated excellent analytical sensitivity and specificity, precision, and linearity. Furthermore, the viral loads measured by the SMG assay were highly correlated with those measured by the RealStar assay. Our results suggest that the SMG assay is a useful diagnostic tool for quantitative detection and differentiation of HHV-6A and HHV-6B DNA.

Abstract In the ongoing global fight against coronavirus disease 2019 (COVID-19), the sample preparation process for real-time reverse transcription polymerase chain reaction (rRT-PCR) faces challenges due to time-consuming steps, labor-intensive procedures, contamination risks, resource demands, and environmental implications. However, optimized strategies for sample preparation have been poorly investigated, and the combination of RNase inhibitors and Proteinase K has been rarely considered. Hence, we investigated combinations of several extraction-free protocols incorporating heat treatment, sample dilution, and Proteinase K and RNase inhibitors, and validated the effectiveness using 120 SARS-CoV-2 positive and 62 negative clinical samples. Combining sample dilution and heat treatment with Proteinase K and RNase inhibitors addition exhibited the highest sensitivity (84.26%) with a mean increase in cycle threshold (Ct) value of + 3.8. Meanwhile, combined sample dilution and heat treatment exhibited a sensitivity of 79.63%, accounting for a 38% increase compared to heat treatment alone. Our findings highlight that the incorporation of Proteinase K and RNase inhibitors with sample dilution and heat treatment contributed only marginally to the improvement without yielding statistically significant differences. Sample dilution significantly impacts SARS-CoV-2 detection, and sample conditions play a crucial role in the efficiency of extraction-free methods. Our findings may provide insights for streamlining diagnostic testing, enhancing its accessibility, cost-effectiveness, and sustainability.

Objectives: It is unclear whether the poor outcome of patients with severe vancomycin-resistant enterococci (VRE) infection is attributable to vancomycin resistance or to Enterococcus faecium (Efm), which predominates among VRE. Methods: Retrospective study of a prospectively identified cohort from nationwide surveillance. A cohort of consecutive, nonduplicate episodes of monomicrobial bloodstream infections (BSIs) caused by Efm in 2016 was selected. The primary outcome was all-cause, 30-day, in-hospital mortality. Inverse probability weighting was applied using the propensity score for vancomycin-resistant Efm (VREfm) BSI. Results: A total of 241 Efm BSI episodes were included, of which 59 (24.5%) were VREfm. Patients with VREfm BSI were younger but had similar comorbidities to those with vancomycin-sensitive Efm (VSEfm) BSI. Multivariable logistic regression revealed that younger age, previous piperacillin-tazobactam use, and steroid use were significant risk factors for VREfm BSI, but 30-day in-hospital mortality did not differ significantly between groups (35.6% and 23.6% for VREfm and VSEfm, respectively; odds ratio, 1.79; 95% confidence interval, 0.95-3.37; P = 0.101). However, Cox regression with inverse probability weighting revealed that vancomycin resistance was independently associated with an increased risk of mortality (adjusted hazard ratio, 2.18; 95% confidence interval, 1.03-4.62; P = 0.041). Conclusion: In patients with Efm BSI, vancomycin resistance was independently associated with mortality.

ABSTRACT In October 2022, we experienced a significant increase in samples showing high galactomannan (GM) indexes ranging from 6.22 to 10.58, as determined by the Platelia Aspergillus antigen immunoassay, also known as the GM test. After reviewing the medical records of nine GM antigenemia cases that did not show evidence of invasive aspergillosis, we found that these patients had received total parenteral nutrition (TPN) products from the same manufacturer, whose supplier of the glucose component had recently changed. The TPN products supplied by the specific manufacturer in October were subjected to a GM assay. The glucose component of the products from three different lot numbers exhibited strong positive results in the GM assay. Microbiological investigations through fungal culture and PCR on the TPN products were negative. The present study demonstrated that the glucose component of the TPN products contained a high level of GM antigen, which caused false-positive GM test results. The source of GM in the glucose component was glucoamylase, which was produced from Aspergillus niger to obtain glucose monohydrate from starch. Investigation of three commercially available glucoamylase products exhibited positive GM and 1,3-β-D-glucan tests with various titers positive up to 1:1,000 dilutions, while fungal cultures were all negative. Quality assurance measures of TPN products to prevent GM contamination should be emphasized during the manufacturing process to avoid unnecessary additional diagnostic procedures and overtreatment of invasive aspergillosis due to false-positive GM tests. IMPORTANCE This manuscript describes an occurrence of false-positive GM tests in patients receiving TPN products from a manufacturer who had recently changed the supplier of the glucose component. We describe the clinical presentation of nine false-positive cases and the results of serologic and microbiological investigations of the TPN products suspected of contamination with GM. Attempts to detect GM in parenteral nutrition products were made since the detection of GM in sodium gluconate-containing solutions in 2007, but none of them identified the source of elevated GM indexes in TPN products. However, the present study demonstrated that the glucose component of the TPN products contained a high level of GM antigen, which caused false-positive GM assay results. The source of GM was glucoamylase, which was derived from A. niger in the manufacturing process. Physicians and clinical microbiology laboratories should be aware of this issue to improve interpretation and patient care.

Introduction: Poor liquefaction of pyogenic liver abscesses, which makes drainage impossible at the time of diagnosis, is not infrequent. The impact of poor liquefaction and subsequent drainage failure on clinical outcomes is unknown. Methods: We conducted a retrospective study with all patients diagnosed with liver abscesses from July 2017 through June 2020. Late drainage (LD) was defined as drainage performed ≥48 h after diagnosis due to poor liquefaction. Logistic regression was performed to identify the factors associated with late or non-drainage (LD/ND). The Cox proportional hazard model was used to identify the variables related to abscess recurrence by 90 days after diagnosis. Results: A total of 153 patients were included. Thirty (19.6%) patients underwent LD and 54 (35.3%) did not undergo drainage. Other than non-cystic appearance, LD/ND was associated with smaller size (adjusted odds ratio [aOR] 0.85, 95% confidence interval [CI] 0.73–0.98, p = 0.031) and culture-negativity (aOR 2.69, 95% CI 1.14–6.67, p = 0.027). Current hepatopancreaticobiliary malignancy was the only significant predictor of 90-day recurrence. Neither LD/ND (OR, 0.56; 95% CI, 0.13–2.41; p = 0.426) nor LD (OR, 1.26; 95% CI, 0.23–5.55; p = 0.719) was associated with recurrence by 90 days. The incidence of late complications was reduced by drainage, without a reduction in the duration of hospitalization. Conclusion: Several clinical features were associated with undrainable liver abscesses. Neither LD/ND nor ND had an adverse impact on clinical outcomes.

Objectives: Vancomycin and teicoplanin are glycopeptides with activity against Enterococcus faecium. However, studies on the clinical efficacy of teicoplanin are limited. This study aimed to compare the therapeutic efficacy of teicoplanin and vancomycin in E. faecium bacteremia. Methods: We identified patients with bloodstream infections prospectively from July 2015 to December 2016 in 14 hospitals as part of a multicenter nationwide surveillance. Patients with E. faecium monomicrobial bacteremia were selected. Teicoplanin and vancomycin groups included patients treated with either agent for ≥48 hours. The primary outcome was 30-day all-cause in-hospital mortality. The Cox proportional hazards model with inverse probability weighting was used to account for the imbalance in baseline characteristics between the two groups. Results: Among 97 patients with E. faecium bacteremia, 33 (34%) were treated with teicoplanin and 64 (66%) with vancomycin. There were no significant differences in 30-day in-hospital mortality (18.2% vs 26.6%, P = 0.358) and 7-day mortality (6.1% vs 15.6%, P = 0.212). Furthermore, multivariable analysis confirmed that the use of teicoplanin was not significantly associated with mortality (adjusted odds ratio, 0.72; 95% confidence interval, 0.28-1.86; P = 0.494). Conclusion: We found no significant differences in the clinical outcomes. These findings suggest teicoplanin as a useful alternative to vancomycin.

Abstract Purpose To find pharmacokinetic/pharmacodynamic parameters of vancomycin associated with the optimal outcome of severe infection due to Enterococcus species. Methods We retrospectively reviewed enterococcal bacteremia cases treated with vancomycin from January 2015 to December 2020. The primary outcome was 30-day mortality. We calculated cutoff values of the ratio of vancomycin area under the concentration–time curve over 24 h to the minimum inhibitory concentration (AUC24/MIC) and trough concentration (Ctrough) during the initial 72 h of treatment. The optimal cutoff value was determined using the Youden index. Binary variables created based on these cutoffs were further assessed using multivariable analysis. Results A total of 65 patients were included. The majority (87.7%) had solid or hematologic malignancies. Thirty-day mortality and nephrotoxicity occurred in nine (13.4%) and 14 (21.5%) patients, respectively. Both vancomycin AUC24/MIC and Ctrough showed fair performance in predicting 30-day mortality (AUC of receiver-operator curve for AUC24/MIC, 0.712; 95% confidence interval [CI] 0.539–0.886; AUC for Ctrough, 0.760; 95% CI 0.627–0.892; pairwise AUC comparison: p = 0.570). Ctrough ≥ 13.94 μg/mL, but not AUC24/MIC ≥ 504, had a significant association with 30-day mortality after adjusting for confounders (odds ratio, 8.40; 95% CI 1.60–86.62; p = 0.010). Conclusion Mean Ctrough ≥ 13.94 μg/mL during the initial 72 h was associated with higher 30-day mortality in enterococcal bacteremia. Further studies are warranted to elucidate optimal pharmacokinetic targets for enterococcal bacteremia.

Label-free rapid deep-learning-based identification of bacterial species that classifies 3D refractive index tomograms into the species.

BackgroundThe role of bacterial microbiota in the pathogenesis of nontuberculous mycobacterial pulmonary disease (NTM-PD) is unclear. We aimed to compare the bacterial microbiome of disease-invaded lesions and non-invaded lung tissue from NTM-PD patients.MethodsWe analyzed lung tissues from 23 NTM-PD patients who underwent surgical lung resection. Lung tissues were collected in pairs from each patient, with one sample from a disease-involved site and the other from a non-involved site. Lung tissue microbiome libraries were constructed using 16S rRNA gene sequences (V3-V4 regions).ResultsSixteen (70%) patients had Mycobacterium avium complex (MAC)-PD, and the remaining seven (30%) had Mycobacterium abscessus-PD. Compared to non-involved sites, involved sites showed greater species richness (ACE, Chao1, and Jackknife analyses, all p = 0.001); greater diversity on the Shannon index (p = 0.007); and genus-level differences (Jensen-Shannon, PERMANOVA p = 0.001). Analysis of taxonomic biomarkers using linear discriminant analysis (LDA) effect sizes (LEfSe) demonstrated that several genera, including Limnohabitans, Rahnella, Lachnospira, Flavobacterium, Megamonas, Gaiella, Subdoligranulum, Rheinheimera, Dorea, Collinsella, and Phascolarctobacterium, had significantly greater abundance in involved sites (LDA >3.00, p ConclusionsWe identified differential microbial distributions between disease-invaded and normal lung tissues from NTM-PD patients, and microbial diversity was significantly higher in disease-invaded tissues.Trial registrationClinical Trial registration number: NCT00970801.

Abstract We evaluated the association between 16S rRNA gene (rrs) mutations and susceptibility in clinical isolates of amikacin-resistant nontuberculous mycobacteria (NTM) in NTM-pulmonary disease (PD) patients. Susceptibility was retested for 134 amikacin-resistant isolates (minimum inhibitory concentration [MIC] ≥ 64 µg/ml) from 86 patients. Amikacin resistance was reconfirmed in 102 NTM isolates from 62 patients with either Mycobacterium avium complex-PD (MAC-PD) (n = 54) or M. abscessus-PD (n = 8). MICs and rrs mutations were evaluated for 318 single colonies from these isolates. For the 54 MAC-PD patients, rrs mutations were present in 34 isolates (63%), comprising all 31 isolates with amikacin MICs ≥ 128 µg/ml, but only three of 23 isolates with an MIC = 64 µg/ml. For the eight M. abscessus-PD patients, all amikacin-resistant (MIC ≥ 64 µg/ml) isolates had rrs mutations. In amikacin-resistant isolates, the A1408G mutation (n = 29) was most common. Two novel mutations, C1496T and T1498A, were also identified. The culture conversion rate did not differ by amikacin MIC. Overall, all high-level and 13% (3/23) of low-level amikacin-resistant MAC isolates had rrs mutations whereas mutations were present in all amikacin-resistant M. abscessus isolates. These findings are valuable for managing MAC- and M. abscessus-PD and suggest the importance of phenotypic and genotypic susceptibility testing.

Objectives: We evaluated the performance of the MicroIDSys Elite system, a newly developed matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) mass spectrometry system for identification of mycobacteria directly from positive MGIT liquid cultures. Methods: Analytical specificity was evaluated with 63 reference strains grown in mycobacteria growth indicator tube media. Prospective performance evaluation was conducted with primary liquid cultures of sputum samples for identification of mycobacteria, and results were compared to multigenerational sequencing as the reference method. Liquid media subcultures were also analyzed. Results: The accuracy for the 63 reference strains was 98.4% (62/63). A total of 167 paired mycobacterial primary cultures and subcultures in liquid media, comprised of seven Mycobacterium tuberculosis isolates, 109 slowly growing nontuberculous mycobacterial isolates, and 51 rapidly growing nontuberculous mycobacterial isolates, was identified by the MicroIDSys Elite system. Using primary liquid cultures, the MicroIDSys Elite system correctly identified 143 (85.6%) isolates; 21 (12.6%) resulted in “no identification”; and three (1.8%) isolates were misidentified. Using liquid media subcultures with this system, 159 (95.2%) isolates were correctly identified; seven (4.2%) resulted in “no identification”; and one (0.6%) isolate was misidentified. Conclusion: The MicroIDSys Elite system is a useful routine diagnostic tool for identification of mycobacterial species from liquid culture.

Objectives: The performance of the investigational-use-only version of the BioFire FilmArray Pneumonia Panel (FA-Pneumo), a high-order nested multiplex PCR, was evaluated for the detection of typical respiratory bacterial pathogens and antibiotic resistance genes in sputa and endotracheal aspirate (ETA) specimens. Methods: Thirty-one sputa and 69 ETA specimens were analyzed. The diagnostic performance of FA-Pneumo was assessed using routine microbiological methods as the reference standard. Results: Overall sensitivity and specificity for organism detection using FA-Pneumo were 98.5% and 76.5%, respectively. The sensitivity for each pathogen was 100%, except for Klebsiella aerogenes, and the range of specificity was 83.3–99.0%. FA-Pneumo detected antimicrobial resistance genes in 17 out of 18 specimens (94.4%) that were resistant by antimicrobial susceptibility testing. FA-Pneumo additionally detected 25 resistance genes in 22 specimens, and sequencing for the presence of resistance genes confirmed the majority of these results (20/25, 80%). Semi-quantitative analysis of bacterial nucleic acid amounts by FA-Pneumo revealed that 88.2% of the identified bacteria (67/76) with ≥106 copies/ml also gave culture-positive results with significant amounts of bacteria. Conclusions: FA-Pneumo is a rapid test with high sensitivity for the detection of bacteria and antimicrobial resistance genes in sputum and ETA specimens and could aid in determining antibiotic therapy.

BackgroundCo-circulation of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and other respiratory viruses, such as influenza and respiratory syncytial virus (RSV), can be a severe threat to public health. The accurate detection and differentiation of these viruses are essential for clinical laboratories. Herein, we comparatively evaluated the performance of the Kaira COVID-19/Flu/RSV Detection Kit (Kaira; Optolane, Seongnam, Korea) for detection of SARS-CoV-2, influenza A and B, and RSV in nasopharyngeal swab (NPS) specimens with that of the PowerChek SARS-CoV-2, Influenza A&B, RSV Multiplex Real-time PCR Kit (PowerChek; Kogene Biotech, Seoul, Korea).MethodsA total of 250 archived NPS specimens collected for routine clinical testing were tested in parallel by the Kaira and PowerChek assays. RNA standards were serially diluted and tested by the Kaira assay to calculate the limit of detection (LOD).ResultsThe positive and negative percent agreements between the Kaira and PowerChek assays were as follows: 100% (49/49) and 100% (201/201) for SARS-CoV-2; 100% (50/50) and 99.0% (198/200) for influenza A; 100% (50/50) and 100% (200/200) for influenza B; and 100% (51/51) and 100% (199/199) for RSV, respectively. The LODs of the Kaira assay for SARS-CoV-2, influenza A and B, and RSV were 106.1, 717.1, 287.3, and 442.9 copies/mL, respectively.ConclusionsThe Kaira assay showed comparable performance to the PowerChek assay for detection of SARS-CoV-2, influenza A and B, and RSV in NPS specimens, indicating that the Kaira assay could be a useful diagnostic tool when these viruses are co-circulating.

Background: A major complication of peritoneal dialysis (PD) is peritonitis, and bacterial culture of PD effluent in a blood culture bottle is the preferred technique for diagnosis of peritonitis. In this study, we compared dialysate inoculation and culture using the BacT/AlerTⓇ Fastidious Antimicrobial Neutralization Plus blood culture bottles (FAN Plus; bioMérieux, France) to the conventional centrifugation culture method.Methods: A total of 170 PD effluents were simultaneously processed by the conventional centrifugation culture method and by culture using FAN Plus media with two different inoculation procedures: inoculation after centrifugation and direct bedside inoculation.Results: Of the 52 cultures that were positive on at least one of the culture methods, 27 samples were positive on conventional centrifugation. However, 46 samples showed growth following inoculation into the FAN Plus media after centrifugation, and 47 samples were positive on the direct FAN Plus inoculation method. Using the case definition for PD peritonitis to classify samples, sensitivity of the conventional method was 50.0% (95% CI, 33.7-66.3%), whereas the sensitivity of the FAN Plus media was 78.9% (95% CI, 62.2-89.9%) by inoculation after centrifugation and 86.8% (95% CI, 71.1-95.1%) by direct inoculation. Use of both inoculation methods with FAN Plus media resulted in 92.1% sensitivity (95% CI, 89.2-99.9%).Conclusion: Culture using FAN Plus media demonstrated a superior bacterial recovery rate to the conventional centrifugation culture method. A combination of the two inoculation methods with FAN Plus media is recommended for the best diagnostic yield, while direct inoculation alone can be useful due to its simplicity and cost-effectiveness. (Ann Clin Microbiol 2019;22:90-95)

Abstract Background Although β-lactam monotherapy may be sufficient in non-critically ill patients with community-acquired pneumonia, the value of combination antibiotic regimens in community-onset neutropenic pneumonia remains unclear. Methods A retrospective cohort study was conducted to compare the effects of combination antibiotic regimens to those of β-lactam monotherapy in cancer patients with community-onset neutropenic pneumonia. Electronic medical records of patients diagnosed with community-onset neutropenic pneumonia between March 1995 and February 2015 at a tertiary care center were reviewed. Results During the study period, 165 cancer patients with community-onset neutropenic pneumonia were identified. Seventy-two patients received β-lactam monotherapy and 93 received combination therapy (β-lactam plus either a macrolide or fluoroquinolone). Causative pathogens were identified in 27.9% of the patients, and only two were positive for atypical pathogens. Although 30-day mortality was higher in the β-lactam group (15.3% versus 4.3%; P = 0.015), combination therapy was not associated with a statistically significant survival benefit in the multivariate analysis (hazard ratio 0.85, 95% confidence interval 0.20–3.67; P = 0.827). Duration of neutropenia, C-reactive protein level, and Multinational Association for Supportive Care in Cancer risk index were significant factors for 30-day mortality. In a subgroup analysis of patients treated with cefepime, the most frequently used β-lactam (63.0%), combination therapy also showed no significant survival benefit. Conclusions Combination antibiotic regimens were not associated with a survival benefit over β-lactam monotherapy in the treatment of community-onset neutropenic pneumonia. Unnecessary combination therapy should be reconsidered in cancer patients who are at high risk for adverse drug reactions and colonization with multi-drug resistant organisms.

Objectives: The aim of this study was to evaluate whether rifabutin can improve treatment outcomes in patients with rifabutin-sensitive MDR-TB. Methods: A retrospective cohort study was performed on 76 patients with rifabutin-sensitive MDR-TB who were treated with or without rifabutin between 2006 and 2011. Results: Overall, 75% (57/76) of patients achieved favorable outcomes, including cure (53/76, 70%) and treatment completion (4/76, 5%). In contrast, 25% (19/76) had unfavorable treatment outcomes, which included treatment failure (6/76, 8%), death (2/76, 3%), loss to follow-up (4/76. 5%), and no evaluation due to transfer to other institutions (7/76, 9%). Rifabutin was given to 52 (68%) of the 76 patients with rifabutin-sensitive MDR-TB. Although favorable treatment outcomes were more frequent in patients who received rifabutin [81% (42/52)] than in those who did not receive rifabutin [63% (15/24)], this difference was not statistically significant (P = 0.154). However, in multivariable regression logistic analysis, use of rifabutin was significantly associated with favorable treatment outcomes in patients with rifabutin-sensitive MDR-TB (adjusted odds ratio = 9.80, 95% confidence interval = 1.65â58.37, P = 0.012). Conclusions: These results suggest that the use of rifabutin can improve treatment outcomes in patients with rifabutin-sensitive MDR-TB. Keywords: Multidrug-resistant tuberculosis, Extensively drug-resistant tuberculosis, Rifabutin, Treatment outcome

Shiga toxin-encoding genes (stx) of enterohemorrhagic Escherichia coli (EHEC) can be lost during infection or in vitro cultivation, and in clinical practice, it is difficult to distinguish EHEC that have lost stx (EHEC-LST) from enteropathogenic E. coli (EPEC), as both are stx-negative and eae-positive. In this study, we performed whole-genome sequencing (WGS) of a stx-negative, eae-positive E. coli O63:H6 isolate from a child with hemolytic uremic syndrome and compared its genome with those of nine E. coli O63:H6 strains in public databases. Virulence gene profiles were analyzed and core-genome multilocus sequence typing (cgMLST) was conducted. The virulence gene profile of our isolate was consistent with EHEC, except for the absence of stx, and the isolate clustered with seven EHEC strains but was distant from two EPEC strains in cgMLST. In genome alignment, our isolate exhibited a high nucleotide identity with EHEC strain 377323_2f but displayed a gap corresponding to the stx-harboring prophage sequence. Overall, our isolate was genetically closely related to EHEC strains, consistent with this being an EHEC-LST strain. As EHEC-LST may be misdiagnosed as EPEC in routine laboratories, comparative genomic analysis using WGS can be useful to determine whether stx-negative and eae-positive isolates are EHEC-LST or EPEC.

Objective: To evaluate the performance of the Cobas TaqMan MTB assay (Cobas assay) with respect to its clinical application. Methods: This was a retrospective analysis of 1154 results from 1034 patients for whom mycobacterial cultures and the Cobas assay were performed simultaneously. Based on the patient medical records, two categories of clinical application were defined: (1) the diagnosis of patients with a high probability of pulmonary tuberculosis according to clinical and radiological features (n = 128), and (2) the exclusion of tuberculosis in clinically indeterminate patients (n = 1026). Standard culture was used as the reference method. Results: The sensitivity of the Cobas assay for the detection of Mycobacterium tuberculosis was 70.4% (95% confidence interval (CI) 49.7â85.5%) for category 1, but only 25.0% (95% CI 4.5â64.4%) for category 2. The specificity was â¥95.0% for both categories. The positive predictive value was 79.2% (95% CI 57.3â92.1%) for category 1 and 33.3% (95% CI 6.0â75.9%) for category 2, while the negative predictive value was 92.3% (95% CI 85.0â96.4%) for category 1 and 99.4% (95% CI 98.7â99.8%) for category 2. Conclusions: The results of this study indicate that Cobas assay results must be interpreted carefully according to the clinical purpose of the assay. Keywords: Mycobacterium tuberculosis, Pulmonary tuberculosis, Cobas TaqMan MTB assay, Korea

Introduction: During recent decades, the rates of multidrug resistance, including resistance to carbapenems, have increased dramatically among Acinetobacter species. Tigecycline has activity against multidrug-resistant Acinetobacter spp, including carbapenem-resistant isolates. However, reports of tigecycline-resistant Acinetobacter spp are emerging from different parts of the world. The purpose of this study was to evaluate potential risk factors associated with tigecycline non-susceptible Acinetobacter bacteremia. Methods: The medical records of 152 patients with Acinetobacter bacteremia attending Samsung Medical Center between January 2010 and December 2014 were reviewed. Non-susceptibility to tigecycline was defined as a minimum inhibitory concentration (MIC) of tigecycline ≥4 μg/ml. Cases were patients with tigecycline non-susceptible Acinetobacter bacteremia and controls were those with tigecycline-susceptible Acinetobacter bacteremia. Results: Of the 152 patients included in the study, 61 (40.1%) had tigecycline non-susceptible Acinetobacter bacteremia (case group). These patients were compared to 91 patients with tigecycline-susceptible Acinetobacter bacteremia (control group). The case group showed high resistance to other antibiotics (>90%) except colistin (6.6%) and minocycline (9.8%) when compared to the control group, which exhibited relatively low resistance to other antibiotics (

Objectives: The differentiation between Mycobacterium abscessus subspecies abscessus (M. abscessus) and Mycobacterium abscessus subspecies massiliense (M. massiliense) and determination of the presence of inducible resistance to macrolide antibiotics are important factors in the management of patients with Mycobacterium abscessus complex (MABC) infections. Unlike pulmonary MABC infections, little information on extrapulmonary MABC infections is available. Methods: The molecular identification of clinical isolates was performed, and the clinical characteristics and treatment outcomes of 20 consecutive patients with extrapulmonary MABC infections were assessed. Results: M. abscessus and M. massiliense each caused 10 (50%) of the cases. Eight (80%) M. abscessus isolates that had inducible resistance to clarithromycin harbored an intact erm(41) gene of the T28 variant, whereas two (20%) M. abscessus isolates had the C28 erm(41) variant and were susceptible to clarithromycin. All M. massiliense isolates had a truncated erm(41) gene and were susceptible to clarithromycin. The drug susceptibility profiles other than clarithromycin were similar for the M. abscessus and M. massiliense isolates. Of the 20 patients, 17 (85%) showed a favorable outcome, including all patients with M. massiliense infection and 70% (7/10) of patients with M. abscessus infection. Favorable outcomes were associated with M. massiliense and M. abscessus isolates with a non-functional erm(41) gene (p = 0.049). Conclusions: Precise species and subspecies identification and the determination of macrolide susceptibility are recommended for the optimal treatment of extrapulmonary MABC infections.

Purpose: We investigated trends in antibiotic resistance for gram-negative bacteria in infants with a urinary tract infection (UTI) over 15 years at a single institution. Methods: A retrospective chart review was conducted for children younger than 24 months who visited the emergency room and were diagnosed with a UTI between January 2000 and December 2014. We selected urine culture data that grew Escherichia coli and Klebsiella pneumoniae. Baseline clinical information and results of antimicrobial susceptibility tests were analyzed by dividing the 15-year study time frame into three periods (A: 2000-2004, B: 2005-2009, and C: 2010-2014). Results: During the study period, 478 applicable children were identified (E. coli, 89.7% and K. pneumoniae, 10.3%). Antibiotic resistance to third-generation cephalosporins was increased from period A to period C (A, 2.1%; B, 8.3%; C, 8.8%; P=0.025). Resistance to quinolones also showed a steady pattern during periods A to C, although it was not statistically significant (A, 7.9%; B, 9.7%; C, 12.4%; P=0.221). The incidence of Extended-spectrum β-lactamase (ESBL)-producing gram-negative bacteria increased from period A to period C (A, 1.4%; B, 7.6%; C, 8.2%; P=0.012). Conclusion: This study revealed that the common uropathogens E. coli and K. pneumoniae experienced increasing resistance rates against third-generation cephalosporins and a constant antibiotic resistance to quinolones in children younger than 24 months. We also showed a recent increased incidence of ESBL-producing gram-negative bacteria in patients with community-acquired UTIs. Therefore, it is necessary to actively surveil resistance in order to properly select empirical antibiotics.

Background and objectives: The objective of this study was to investigate the clinical significance of isolates from blood stream infection known to be blood culture contaminants in pediatric patients. Materials and Methods: Microbiological reports and medical records of all blood culture tests issued from 2002 to 2012 (n = 76,331) were retrospectively reviewed. Evaluation for potential contaminants were done by reviewing medical records of patients with the following isolates: coagulase-negative Staphylococcus, viridans group Streptococcus, Bacillus, Corynebacterium, Micrococcus, Aerococcus, and Proprionibacterium species. Repeated cultures with same isolates were considered as a single case. Cases were evaluated for their status as a pathogen. Results: Coagulase-negative Staphylococcus had clinical significance in 23.8% of all cases. Its rate of being a true pathogen was particularly high in patients with malignancy (43.7%). Viridans group Streptococcus showed clinical significance in 46.2% of all cases. Its rate of being a true pathogen was similar regardless of the underlying morbidity of the patient. The rate of being a true pathogens for remaining isolates was 27.7% for Bacillus and 19.0% for Corynebacterium species. Conclusions: Coagulase-negative Staphylococcus and viridans group Streptococcus isolates showed high probability of being true pathogens in the pediatric population, especially in patients with underlying malignancy.

To better understand extensively drug resistant Streptococcus pneumoniae, we assessed clinical and microbiological characteristics of 5 extensively drug-resistant pneumococcal isolates. We concluded that long-term care facility residents who had undergone tracheostomy might be reservoirs of these pneumococci; 13- and 23-valent pneumococcal vaccines should be considered for high-risk persons; and antimicrobial drugs should be used judiciously.

We compared two interferon gamma release assays (IGRAs), QuantiFERON-TB Gold In-Tube (QFT-GIT) and T-SPOT.TB, for diagnosis of latent tuberculosis infection (LTBI) in patients before and while receiving tumor necrosis factor (TNF)-α antagonist therapy. This study evaluated the significance of sensitive IGRAs for LTBI screening and monitoring.Before starting TNF-α antagonist therapy, 156 consecutive patients with rheumatic diseases were screened for LTBI using QFT-GIT and T-SPOT.TB tests. According to our study protocol, QFT-GIT-positive patients received LTBI treatment. Patients positive by any IGRAs were subjected to follow-up IGRA tests after completing LTBI-treatment and/or during TNF-α antagonist therapy.At the initial LTBI screening, 45 (28.9%) and 70 (44.9%) patients were positive by QFT-GIT and T-SPOT.TB, respectively. The agreement rate between IGRA results was 78.8% (k = 0.56; 95% confidence interval [95% CI] = 0.43 to 0.68). Of 29 patients who were positive only by T-SPOT.TB in the initial screening, 83% (19/23) were persistently positive by T-SPOT.TB, while QFT-GIT testing showed that 36% (9/25) had conversion during TNF-α antagonist therapy. By the end of the follow-up period (218 to 1,264 days), four patients (4/137, 2.9%) developed active tuberculosis (TB) diseases during receiving TNF-α antagonist therapy. Among them, one was Q-T+, one was Q+T-, and the remaining two were Q-T- at the initial screening (Q, QuantiFERON-TB Gold In-Tube; T, T-SPOT.TB; +, positive; -, negative). Two (2/4, 50%) patients with TB reactivation had at least one prior risk factor consistent with previous TB infection.This study demonstrated the need to capitalize on sensitive IGRAs to monitor for LTBI in at-risk patients for a more sensitive diagnosis in countries with an intermediate TB burden.

The clinical significance of Mycobacterium kansasii respiratory isolates is uncertain. The aims of this study were to determine the clinical relevance of M. kansasii isolates and to identify the clinical features and outcomes of M. kansasii lung disease. We reviewed the medical records of 104 patients from whom at least one respiratory M. kansasii isolate was obtained from January 2003 to July 2014 at Samsung Medical Center, South Korea. Of these 104 patients, 54 (52%) met the diagnostic criteria for nontuberculous mycobacterial lung disease; among them, 41 (76%) patients received antibiotic treatment for a median time of 15.0 months (interquartile range [IQR], 7.0-18.0 months). The remaining 13 (24%) without overt disease progression were observed for a median period of 24.0 months (IQR, 5.0-34.5 months). Patients with M. kansasii lung disease exhibited various radiographic findings of lung disease, including the fibrocavitary form (n = 24, 44%), the nodular bronchiectatic form (n = 17, 32%), and an unclassifiable form (n = 13, 24%). The fibrocavitary form was more common in patients who received treatment (n = 23, 56%), while the nodular bronchiectatic form was more common in patients with M. kansasii lung disease who did not receive treatment (n = 9, 70%). None of the patients with a single sputum isolate (n = 18) developed M. kansasii disease over a median follow-up period of 12.0 months (IQR, 4.0-26.5 months). In total, 52% of all patients with M. kansasii respiratory isolates exhibited clinically significant disease. Moreover, patients with M. kansasii lung disease displayed diverse radiographic findings in addition to the fibrocavitary form. The nodular bronchiectatic form was more common in patients with M. kansasii lung disease with an indolent clinical course. Thus, since the clinical significance of a single M. kansasii respiratory isolate is not definite, strict adherence to recommended diagnostic criteria is advised.

Internet of Things (IoT) platforms are the key for the development of scalable IoT applications and services that connect real and virtual worlds between objects, systems, and people. However, as the IoT platform market represents a truly new market segment that was almost non-existent a few years ago, the platforms are complex and changing quickly. These IoT platforms perform simple functions such as providing useful information, and others can provide services through collaborations with IoT devices. This situation needs a generic service interface, and results in a range of IoT architectures through not only the configuration setting of IoT devices and resources but also the varied environments of collaboration of each device. Due to these heterogeneities, it is quite challenging to develop applications working with diverse IoT services, and it is even more difficult to maintain such applications. Therefore, this paper presents a security generic service interface with the effective common characteristics of an IoT platform by defining a set of generic interfaces and adopting well-known design patterns. The generic interface solves the heterogeneity-driven problems and makes it possible to effectively adopt a platform-independent Generic Interface that could be operated in diverse IoT platforms.

This article evaluates a modified protocol for bacterial identification and antimicrobial susceptibility testing from positive blood culture bottles. The authors developed a modified protocol that includes an additional lysis step to improve accuracy. The study compared the modified protocol to the original and found that the modified protocol had a higher correct identification rate. The results suggest that the modified protocol may be a more effective method for direct identification and antimicrobial susceptibility testing. The study acknowledges limitations but highlights the potential benefits of the modified protocol. [Extracted from the article]

Background: CD14 recognizes lipopolysaccharide (LPS), and presepsin is a fragment of soluble CD14. Still, it remains uncertain whether Gram-negative bacteria induce higher presepsin levels than other microorganisms. To address this question, this study aimed to analyze presepsin levels based on microorganisms isolated in blood cultures. Materials and Methods: This study was a single-center study comprising suspected sepsis patients enrolled from July 2020 to September 2020. A total of 95 patients with a single isolate confirmed in blood culture were analyzed to evaluate if there are any differences in presepsin levels according to microbial isolates. Plasma presepsin level was measured using PATHFAST assay kit and analyzer (LSI Medience Corporation, Tokyo, Japan). Results: There were 26 Gram-positive bacteremia, 65 Gram-negative bacteremia, and 3 fungemia patients with median presepsin levels of 869, 1,439, and 11,951 pg/mL, respectively. Besides, one case of algaemia demonstrated a presepsin level of 1,231 pg/mL. Our results showed no statistically significant difference in presepsin levels among patients with Gram-positive bacteremia, Gram-negative bacteremia, and fungemia. Furthermore, presepsin levels did not differ significantly among bloodstream infections caused by bacteria that were isolated from at least three different patients. In particular, Gram-positive bacteria such as Staphylococcus aureus and Enterococcus faecalis were able to induce presepsin levels comparable to those induced by Gram-negative bacteria. Conclusion: We demonstrated that there were no significant differences in plasma presepsin levels according to microbial isolates in blood culture. The major cause of the variability in presepsin levels during bloodstream infection might be the immunogenicity of each microorganism rather than the presence of LPS in the microorganism. [ABSTRACT FROM AUTHOR]

This article discusses a study on severe lower respiratory tract infections (LRTIs) caused by human rhinovirus (HRV) in young children. The study analyzed medical records of children hospitalized for HRV LRTIs from 2016 to 2020 in Seoul, Korea. The findings show that HRV can cause severe LRTI in both previously healthy children and those with comorbidities, with chronic lung diseases being the most common underlying condition. The study emphasizes the importance of considering the potential for worsening clinical courses in children hospitalized with HRV LRTIs. [Extracted from the article]