Bacteremia detection from complete blood count and differential leukocyte count with machine learning: complementary and competitive with C-reactive protein and procalcitonin tests.

BACKGROUND: Biomarkers, such as leukocyte count, C-reactive protein (CRP), and procalcitonin (PCT), have been commonly used to predict the occurrence of life-threatening bacteremia and provide prognostic information, given the need for prompt intervention. However, such diagnosis methods require much time and money. Therefore, we propose a method with a high prediction capability using machine learning (ML) models based on complete blood count (CBC) and differential leukocyte count (DC) and compare its performance with traditional CRP or PCT biomarker methods and those of models incorporating CRP or PCT biomarkers. METHODS: We collected 366,586 daily blood culture (BC) results, of which 350,775 (93.2%), 308,803 (82.1%), and 23,912 (6.4%) cases were issued CBC/DC (CBC/DC group), CRP with CBC/DC (CRP&CBC/DC group), and PCT with CBC/DC (PCT&CBC/DC group), respectively. For the ML methods, conventional logistic regression and random forest models were selected, trained, applied, and validated for each group. Fivefold validation and prediction capability were also evaluated and reported. RESULTS: Overall, the ML methods, such as the random forest model, demonstrated promising performances. When trained with CBC/DC data, it achieved an area under the ROC curve (AUC) of 0.802, which is superior to the prediction conventionally made with CRP/PCT levels (0.699/0.731). Upon evaluating the performance enhanced by incorporating CRP or PCT biomarkers, it reported no substantial AUC increase with the addition of either CRP or PCT to CBC/DC data, which suggests the predicting power and applicability of using only CBC/DC data. Moreover, it showed competitive prognostic capability compared to the PCT test with similar all-cause in-hospital mortality (45.10% vs. 47.40%) and overall median survival time (27 vs. 25 days). CONCLUSIONS: The ML models using only CBC/DC data yielded more accurate bacteremia predictions compared to those by methods using CRP and PCT data and reached similar prognostic performance as by PCT data. Thus, such models are potentially complementary and competitive with traditional CRP and PCT biomarkers for conducting and guiding antibiotic usage.

Predicting 2-Day Mortality of Thrombocytopenic Patients Based on Clinical Laboratory Data Using Machine Learning.

BACKGROUND: Clinical laboratories have traditionally used a single critical value for thrombocytopenic events. This system, however, could lead to inaccuracies and inefficiencies, causing alarm fatigue and compromised patient safety. OBJECTIVES: This study shows how machine learning (ML) models can provide auxiliary information for more accurate identification of critical thrombocytopenic patients when compared with the traditional notification system. RESEARCH DESIGN: A total of 50,505 patients' platelet count and other 26 additional laboratory datasets of each thrombocytopenic event were used to build prediction models. Conventional logistic regression and ML methods, including random forest (RF), artificial neural network, stochastic gradient descent (SGD), naive Bayes, support vector machine, and decision tree, were applied to build different models and evaluated. RESULTS: Models using logistic regression [area under the curve (AUC)=0.842], RF (AUC=0.859), artificial neural network (AUC=0.867), or SGD (AUC=0.826) achieved the desired average AUC>0.80. The highest positive predictive value was obtained by the SGD model in the testing data (72.2%), whereas overall, the RF model showed higher sensitivity and total positive predictions in both the training and testing data and outperformed other models. The positive 2-day mortality predictive rate of RF methods is as high as 46.1%-significantly higher than using the traditional notification system at only 14.8% [χ2(1)=81.66, P<0.001]. CONCLUSIONS: This study demonstrates a data-driven ML approach showing a significantly more accurate 2-day mortality prediction after a critical thrombocytopenic event, which can reinforce the accuracy of the traditional notification system.

Identification of a novel A2 allele through nt543 substitution.

BACKGROUND: ABO blood system has many subgroups. In A group, A1 phenotype and A2 phenotype are more common, and A2 is caused by deletion or substitution in A1 allele (ABO*A1.01). METHODS: Based on standard ABO serological test, the subject was identified as A2 phenotype. Direct sequencing and ABO gene cloning were performed to analyze the allele. RESULTS: The subject had one A1v allele (ABO*A1.02) and one O allele. The haplotype sequencing analysis of each allelic clone demonstrated that allele 1 was A1v (ABO*A1.02) allele with nt543 variation (543 G > C) and allele 2 was O1v allele (ABO*O.01.02) with nt261 deletion and nt220 variation. CONCLUSION: The 543 G > C nucleotide substitution of the present A1v allele (ABO*A1.02) shares the same sequence variation site with Ax allele (ABO*AW.33) (543 G > T), and both 543 G > C and 543 G > T nucleotide substitutions encode the same amino acid change of tryptophan to cysteine. Mechanism, such as allelic enhancement, has been proposed to explain this controversial phenotype-genotype relationship. But in present case, there has been no B allele to enhance the expression of Ax to that expected of A2, so there could be another novel underlying mechanism to be investigated.

Single amino acid substitution Gly186Val in AdeS restores tigecycline susceptibility of Acinetobacter baumannii.

OBJECTIVES: Amino acid substitutions within the AdeRS two-component system are believed to result in overexpression of the AdeABC efflux pump and extensive resistance to antibiotics in clinical Acinetobacter baumannii isolates. However, the exact amino acid substitutions in AdeRS that cause overexpression of the AdeABC efflux pump remain unclear. We elucidated the role of amino acid substitutions in AdeRS by a complementation assay in an adeRS knockout strain of A. baumannii. METHODS: Five types of adeRS operon from tigecycline-resistant XDR A. baumannii (XDRAB) were cloned and introduced into the adeRS knockout strain to reverse its tigecycline susceptibility. RESULTS: Through shuffling gene segments among those five adeRS operons and performing site-directed mutagenesis, we found that the specific amino acid substitution Gly186Val in AdeS is crucial for reducing tigecycline susceptibility of A. baumannii. CONCLUSIONS: Our result demonstrates that a critical amino acid substitution in AdeS alters the AdeABC efflux pump-mediated tigecycline resistance of A. baumannii.

Retrospective Analysis to Optimize the Detection of MET Exon 14 Skipping Mutations in Non-Small Cell Lung Cancer.

Our study optimized METex14 skipping mutation detection by analyzing 223 Oncomine™ Focus Assay-positive cases using Pan Lung Cancer PCR Panel and reverse transcription (RT)-PCR. Among the 11 METex14 skipping mutation-positive cases (average read counts: 1390), 2 with Oncomine™ Focus Assay read counts of 2540 and 10,177 were positive on all platforms. Those with Oncomine™ Focus Assay read counts ranging from 179 to 612 tested negative elsewhere. Specimens with low ratios (average ratio: 0.12% for nine cases) may yield false-positive results. Our results suggested that monitoring read counts and ratios and validating the results with RT-PCR are crucial to prevent false positives.

Objective indexes for comparing platelet usage among peer hospitals during the COVID-19 pandemic: A cross-sectional study.

Background and Aims: Besides hospital size, clinical diagnosis and severity of patient cases determine the total platelet usage. Therefore, the appropriateness of platelet usage could not be compared simply with the total units of platelet usage in each hospital. This study aimed to objectively monitor and analyze platelet usage after implementing a single-unit issuing policy for each platelet transfusion in our hospital in October 2020. Materials and Methods: We used three objective indices, X, Y, and Z, to monitor platelet usage and compared it with other hospitals. Three indices were generated by dividing the annual total units of platelet usage by the total annual reimbursement, total number of admissions, and average total reimbursement per admission for each hospital. Results: The new indices X and Y alleviated hospital size-dependent differences. Index Y was preferred over X because its value fluctuated less during the COVID-19 pandemic. The Z index was adjusted for the average total reimbursement per admission, and the results showed that more patients with higher disease complexity did not have increased platelet usage during the COVID-19 pandemic. In our hospital (H1), index Z decreased from 2019 to 2021 due to a policy of issuing a single unit for each platelet transfusion. Conclusion: These three objective indices are suitable for peer comparison and monitoring platelet usage in hospitals, irrespective of their size. They could be applied to promote patient blood management and provide an early response to the gradual shortage of blood resources owing to the aging population and declining birth rate in Taiwan.

Predominance of Enterobacteriaceae isolates in early positive anaerobic blood culture bottles in BacT/Alert system.

We collected and analyzed the time to detection (TTD) of blood cultures in the BacT/Alert automated system from 2002 to 2007. Among the 10,893 monomicrobial isolates from a total of 133,735 blood culture sets, the recoveries of aerobic bottles were compared with those of anaerobic bottles in this study. Significantly more Gram-positive cocci (except Staphylococcus aureus and enterococci), glucose nonfermentative Gram-negative bacteria, and yeast were recovered from aerobic bottles than from anaerobic bottles. The average TTD was 19.0 hr and 20.1 hr for the aerobic and anaerobic bottles, respectively, and 96.8% of the microorganisms were detected within the first 72 hr. Of the 5,489 microorganisms recovered from both of the blood culture bottle pair, microbial growth was significantly more often detected first in the anaerobic bottles than the aerobic bottles for Enterobacteriaceae except Serratia marcescens, while S. aureus, coagulase-negative staphylococci and Pseudomonas aeruginosa were more often detected first in the aerobic bottles. According to these data, we conclude that the earlier positivity of anaerobic bottles is a useful marker for rapid presumptive identification of Enterobacteriaceae infection.

Evaluation of Platelet Alloimmunization by Filtration Enzyme-Linked Immunosorbent Assay.

The current methods for detecting antiplatelet antibodies are mostly manual and labor-intensive. A convenient and rapid detection method is required for effectively detecting alloimmunization during platelet transfusion. In our study, to detect antiplatelet antibodies, positive and negative sera of random-donor antiplatelet antibodies were collected after completing a routine solid-phase red cell adherence test (SPRCA). Platelet concentrates from our random volunteer donors were also prepared using the ZZAP method and then used in a faster, significantly less labor-intensive process, a filtration enzyme-linked immunosorbent assay (fELISA), for detecting antibodies against platelet surface antigens. All fELISA chromogen intensities were processed using ImageJ software. By dividing the final chromogen intensity of each test serum with the background chromogen intensity of whole platelets, the reactivity ratios of fELISA can be used to differentiate positive SPRCA sera from negative sera. A sensitivity of 93.9% and a specificity of 93.3% were obtained for 50 µL of sera using fELISA. The area under the ROC curve reached 0.96 when comparing fELISA with the SPRCA test. We have successfully developed a rapid fELISA method for detecting antiplatelet antibodies.

Preservation of red blood cell antigenicity in a new storage solution in vitro.

INTRODUCTION: Red blood cell (RBC) storage solution is used for suspending and preserving RBCs for later use in in vitro immunohematology testing. Proper RBC preservation is crucial for obtaining accurate results in RBC phenotyping and pretransfusion antibody screening tests. Haemolysis or RBC antigen degradation during storage can result in inaccurate RBC phenotyping, thereby decreasing the sensitivity of pretransfusion antibody screening and identification assays. The conventional RBC storage solutions usually contain adenosine, adenine, and antibiotics. We designed an RBC storage solution and determined whether it could preserve RBC integrity for 70 days. MATERIALS AND METHODS: The new storage solution has a different formula from that of the conventional solution-in particular, it is strengthened with polyethylene glycol (PEG). The extent of haemolysis and hemagglutination reactivity of the RBC antigen systems, Rh, Duffy, Kidd, Lewis, MNS, P1, and the rare antigen Mia (which has a low prevalence antigen in most parts of the world but a higher prevalence in Taiwan), in the new RBC storage solution was compared with that of the conventionally preserved RBC storage solution. RESULTS: The RBCs preserved in the new solution for 70 days retained a similar haemolysis grade as those preserved in the control solution for 28 days. Although both solutions largely preserved RBC antigenicity, the decline in RBC hemagglutination scores in new solution often occurred later than that in the control solution in most antigen phenotyping assays, especially labile antigens such as D, P1, and M. CONCLUSION: The new solution reduces haemolysis more effectively and preserves antigenicity throughout the 70-day storage period. Moreover, Mia antigen is more stable in the experimental group.

Overexpression of the adeB gene in clinical isolates of tigecycline-nonsusceptible Acinetobacter baumannii without insertion mutations in adeRS.

Thirteen clinical isolates of multidrug-resistant Acinetobacter baumannii resistant to carbapenems (MRAB-C) with tigecycline nonsusceptibility were collected from individual patients in this study. None of the 13 isolates shared the same strain characteristics in molecular typing. All of them showed increased adeB transcription, as predicted. However, none of these tigecycline-nonsusceptible MRAB-C isolates were found to possess previously known adeRS mutations. Upregulation of adeB transcription may result from cross stimulation by other mechanisms.

Evaluation of the alkaline wash/lysis procedure for the molecular diagnosis of a positive bacterial blood culture in clinical routine practice.

Blood culture is commonly used to detect microorganisms in patients with a suspected blood infection. This study evaluated the alkaline wash/lysis procedure to extract DNA of microorganisms in a clinical blood culture. A multiplex polymerase chain reaction (PCR) targeting the 16S rDNA (ribosomal DNA) gene and the fungal ITS (internal transcribed spacer) gene was used as a reliable indicator for the presence of microorganism DNA in the extracts. A total of 535 BacT/ALERT positive blood culture bottles were evaluated. Multiplex PCR showed positive results in 530 DNA extracts, but 5 DNA extracts gave negative results. We conclude that the alkaline wash/lysis procedure in combination with the multiplex PCR is a simple and sensitive method, which can be used in a standard diagnostic laboratory to detect microorganisms in blood culture material.

The Influence of CD28 Gene Polymorphism in Transfusion Reaction after Transfusing Leukoreduced Blood Components.

CTLA-4 and CD28 belong to co-stimulation molecules, the abnormal expression of which can regulate the T cell activation and then affect the degree of immune response. Moreover, blood transfusion reaction (TR) is a kind of immune reaction. Consequently, the hypothesis of this study was that the TR still occurred after transfusing leukoreduced blood components as a result of the sensitivity of immune system, and a small number of immune stimulations were enough to induce an immune response in patients. There were 38 cases and 36 healthy controls included in this study. The selected CD28 gene were sequenced to search single nucleotide polymorphism (SNPs), and the correlation between TR and these SNPs was analyzed. According to our data, only the rs3181097 (promoter, -1059) of CD28 gene polymorphism was associated with TR. The p value of rs3181097 under the co-dominant model was 0.031. GG was used as a reference genotype, the p value of GG vs. AG was 0.010 (OR: 0.210, 95% CI: 0.062-0.712), and GG vs. AG + AA was 0.028 (OR: 0.292, 95% CI: 0.095-0.901). In addition to CTLA-4, CD28 gene was also a crucial SNP in TR, because there was a signification for the haplotype with Grs3181097 (p = 0.015). Consequently, we suggested that the TR was related to CD28 by regulating the degree of immune response.

Molecular and phenotypic characteristics of methicillin-resistant and vancomycin-intermediate staphylococcus aureus isolates from patients with septic arthritis.

Staphylococcus aureus is one of the most common pathogens in community- and hospital-associated infections and frequently causes severe and intractable infections in osteoarticular tissues. S. aureus isolates that are resistant to methicillin (meticillin) (MRSA isolates) and intermediately resistant to vancomycin (VISA isolates) have emerged. In this report, we described two patients, one female and one male, diagnosed with septic arthritis due to S. aureus infections. A total of 13 MRSA isolates were obtained from these two patients. All but one isolate belonged to the VISA group. All seven isolates from the female patient were determined to be community associated, multilocus sequence type (MLST) 59, and staphylococcal cassette chromosome mecA (SCCmec) type IV; had direct repeat units (DRUs) of nine repeats; were spa type t437; and were susceptible to sulfa and quinolone antibiotics. The other six isolates, from the male patient, were determined to be hospital associated, MLST 239, and SCCmec type III; had DRUs of 14 repeats; were spa type t037; and were resistant to sulfa and quinolone antibiotics. All 13 MRSA isolates were in agr group I, were pvl negative, and showed no evidence of any association between vancomycin resistance and autolysis.

Evaluation of Bruker Biotyper and Vitek MS for the identification of Candida tropicalis on different solid culture media.

BACKGROUND: The aim of this study was to investigate the performance of the Bruker Biotyper matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) and Vitek MS systems for identification of genetically-confirmed blood isolates of Candida tropicalis that had been grown on several types of culture media commonly used for primary fungal isolation. METHODS: Isolates included 105 from the National China Hospital Invasive Fungal Surveillance Net program (CHIF-NET) and 120 from National Taiwan University Hospital (NTUH). Culture media tested for CHIF-NET isolates included trypticase soy agar supplemented with 5% sheep blood (BAP), Sabouraud dextrose agar (SDA-C), CHROMagar, China blue agar (CBA), chocolate agar supplemented with vancomycin (CAP-VA), and MacConkey agar (MAC). Culture media used for NTUH isolates included BAP, SDA, CHROMagar, eosin methylene blue (EMB), inhibitory mold agar (IMA), Mycosel agar, and cornmeal agar (CMA). RESULTS: The Bruker Biotyper correctly identified all CHIF-NET isolates to the species level on all six agar media tested and correctly identified the majority of NTUH isolates with the exception of isolates grown on SDA (85.8%) and CMA (52.5%). The Vitek MS system correctly identified all CHIF-NET isolates to the species level with the exception of isolates grown on CHROMagar (84.8%), and correctly identified the majority of NTUH isolates with the exception of isolates grown on SDA (51.7%), Mycosel agar (57.5%), and CMA (9.2%) for NTUH isolates. CONCLUSION: Clinical microbiologists should be aware that different culture media can affect the performance of the Bruker Biotyper MALDI-TOF MS and Vitek MS systems in identifying C. tropicalis.

Association of CTLA4 Gene Polymorphism with Transfusion Reaction after Infusion of Leukoreduced Blood Component.

Leukocytes and cytokines in blood units have been known to be involved in febrile non-hemolytic transfusion reaction (FNHTR), and these adverse reactions still occur while using pre-storage leukoreduced blood products. Blood transfusion is similar to transplantation because both implant allogeneic cells or organs into the recipient. CTLA4 gene polymorphism was found to be associated with graft-versus-host disease in hematopoietic stem cell transplantation. We performed a prospective cohort study at a major tertiary care center to investigate the correlation of CTLA4 gene polymorphism and transfusion reactions. Selected CTLA4 gene SNPs were genotyped and compared between patients with transfusion-associated adverse reactions (TAARs) and healthy controls. Nineteen patients and 20 healthy subjects were enrolled. There were 4 SNPs showing differences in allele frequency between patients and controls, and the frequency of "A" allele of rs4553808, "G" allele of rs62182595, "G" allele of rs16840252, and "C" allele of rs5742909 were significantly higher in patients than in controls. Moreover, these alleles also showed significantly higher risk of TAARs (OR = 2.357, 95%CI: 1.584-3.508, p = 0.02; OR = 2.357, 95%CI: 1.584-3.508, p = 0.02; OR = 2.462, 95%CI: 1.619-3.742, p = 0.008; OR = 2.357, 95%CI: 1.584-3.508, p = 0.02; OR = 2.357, 95%CI: 1.584-3.508, p = 0.02, respectively). The present study demonstrated the correlation of CTLA4 gene polymorphism and transfusion reaction, and alleles of 4 CTLA4 SNPs with an increased risk of TAARs were found. It is important to explore the potential immune regulatory mechanism affected by SNPs of costimulatory molecules, and it could predict transfusion reaction occurrence and guide preventive actions.

Infection with Trichomonas vaginalis increases the risk of psychiatric disorders in women: a nationwide population-based cohort study.

BACKGROUND: Trichomonas vaginalis is a protozoan parasite that causes trichomoniasis and annually infects approximately 276 million people worldwide. We observed an ambiguously higher probability of trichomoniasis in patients from the psychiatric department of Tri-Service General Hospital. Herein, we aimed to investigate the association between trichomoniasis and the risk of developing psychiatric disorders. METHODS: The nationwide population-based study utilized the database of the National Health Insurance (NHI) programme in Taiwan. A total of 46,865 subjects were enrolled in this study from 2000-2013, comprising 9373 study subjects with trichomoniasis and 37,492 subjects without trichomoniasis as the control group. Cox proportional hazards regression analysis was performed to calculate the hazard ratio (HR) of psychiatric disorders during the 14 years of follow-up. RESULTS: Of the study subjects with trichomoniasis, 875 (9.34%) developed psychiatric disorders compared with 1988 (5.30%) in the control group (P < 0.001). The adjusted hazard ratio (aHR) of overall psychiatric disorders in the study subjects was 1.644 (95% confidence interval, CI: 1.514-1.766; P < 0.001). More specifically, the study subjects had a higher risk for developing an individual psychiatric disorder, including depression, anxiety, bipolar disorder, schizophrenia and substance abuse. Although metronidazole treatment reduced the risk for developing several subgroups of psychiatric disorders, significant reduction was detected for depression only. Furthermore, refractory trichomoniasis (trichomoniasis visits ≥ 2) enhanced the risk of psychiatric disorders. CONCLUSIONS: We show herein that T. vaginalis infection increases the overall risk for psychiatric disorders. The novel role of T. vaginalis in developing psychiatric disorders deserves more attention, and the control of such a neglected pathogen is of urgent public health importance.

Sustained or higher levels of growth factors in platelet-rich plasma during 7-day storage.

BACKGROUND: The effectiveness of platelet-rich plasma (PRP) for treating soft tissue injuries is still controversial. Most of PRPs were prepared simply by concentrating in volume and were injected right after preparation in physician offices. Neither platelet count nor growth factors were quantitated in advance. We prepared and stored leukocyte and platelet-rich plasma (L-PRP) by regular separation protocols for blood components in the blood bank. And we investigated the dynamic change of growth factors in the L-PRPs over the period of storage. METHODS: The L-PRPs were prepared by 2-step centrifugation and stored agitatedly at 22 °C for 7 days in the platelet incubator of blood bank. Levels of vascular endothelial growth factor (VEGF), fibroblast growth factor (FGF)-basic, hepatocyte growth factor (HGF), insulin-like growth factor (IGF)-1, platelet derived growth factor (PDGF)-AB, endothelial growth factor (EGF), and transforming growth factor (TGF) over the period of storage were evaluated daily after freeze-thawing to release growth factors from platelet. RESULTS: Compared to original whole blood, platelet concentration, VEGF, FGF-basic, PDGF-AB, EGF, and TGF-beta1 levels of L-PRPs significantly increased after PRP preparation. Both HGF and IGF-1 in L-PRPs remained the original plasma level. Platelet, FGF, and TGF-beta1 concentrations sustained during storage, and concentrations of VEGF, HGF, IGF-1, PDGF-AB, and EGF in L-PRPs increased over the period of storage. CONCLUSIONS: During the storage in blood bank, platelet counts and 7 growth factors sustained or reached higher level than L-PRP obtained on first day. Multiple injections of stored PRPs could become applicable by our protocol.

Long-term administration of ketamine induces erectile dysfunction by decreasing neuronal nitric oxide synthase on cavernous nerve and increasing corporal smooth muscle cell apoptosis in rats.

We investigated and evaluated the mechanisms of erectile dysfunction (ED) in a rat model of long-term ketamine administration. Adult male Sprague-Dawley rats (n = 32) were divided into four groups: namely the control group receiving intraperitoneal injection of saline, 1-month, 2-month and 3-month groups receiving daily intraperitoneal injection of ketamine (100 mg/kg/day) for 1, 2, and 3 month respectively. After treatment, animals underwent an erectile response protocol to assess intracavernosal pressure (ICP). Smooth muscle content was evaluated. Neuronal nitric oxide synthase (nNOS), inducible nitric oxide synthase (iNOS) and endothelial nitric oxide synthase (eNOS) expression were assessed using immunostaining assay. Ketamine-induced apoptosis was analyzed using TUNEL assay. Long-term ketamine administration caused significantly decreased erectile responses as measured by ICP. Smooth muscle content was significantly decreased in the ketamine-treated rats for 3 months. In the erectile tissue, ketamine administration significantly reduced nNOS expression and increased iNOS content compared with controls, whereas eNOS expression was not altered. Ketamine induced apoptosis in corpus cavernosum. The present study demonstrates that long-term ketamine administration led to erectile dysfunction in rat. The molecular mechanisms of ketamine-induced ED involved the increased apoptosis and up-regulated iNOS expression incorporating with loss of corporal smooth muscle content and reduced nNOS expression in cavernous nerve.

AdeR protein regulates adeABC expression by binding to a direct-repeat motif in the intercistronic spacer.

Overexpression of the efflux pump AdeABC is associated with tigecycline resistance of multi-drug resistant Acinetobacter baumannii (MDRAB). A two-component regulatory system, sensor AdeS and regulator AdeR proteins regulate the pump. However, the detailed mechanism of the AdeR protein to enhance the expression of adeABC operon is not well defined. We illustrated the biological characteristics of AdeR proteins by comparing a mutant AdeR protein of a tigecycline resistant MDRAB to the wild AdeR protein. By analyzing a series of deletion constructs, a minimal gene cassette of the intercistronic spacer DNA fragment specifically bound with the adeR protein and resulted in band shifting in electrophoresis mobility shifting assays (EMSA). A conserve direct repeat motif was observed in the intercistronic spacer DNA. We demonstrated the AdeR protein was a direct-repeat-binding protein. Two common residue mutations on the AdeR proteins of tigecycline resistant MDRAB isolates could reduce their binding affinity with the intercistronic spacer. The free intercistronic spacer may then more efficiently support the read-through of the adeABC operon during the co-transcriptional translation in tigecycline resistant MDRAB isolates.