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BackgroundBooster vaccination is important because of waning immunity and variant immune evasion. We conducted a single-blinded, randomized trial to evaluate the safety, reactogenicity, and immunogenicity of heterologous booster vaccination in health care workers (HCW) who had received two doses of ChAdOx1 nCov-19.Methods and findingsHCW at least 90 days after the second dose were enrolled to receive one of the four vaccines: BNT162b2, half-dose mRNA-1273, mRNA-1273, and MVC-COV1901. The primary outcomes were humoral and cellular immunogenicity and the secondary outcomes safety and reactogenicity 28 days post-booster. 340 HCW were enrolled: 83 received BNT162b2 (2 excluded), 85 half-dose mRNA-1273, 85 mRNA-1273, and 85 MVC-COV1901. mRNA vaccines had more reactogenicity than protein vaccine.Anti-spike IgG increased by a fold of 8.4 for MCV-COV1901, 32.2 for BNT162b2, 47.6 for half-dose mRNA-1273 and 63.2 for mRNA1273. The live virus microneutralization assay (LVMNA) against the wild type, alpha and delta variants were consistent with anti-spike IgG for all booster vaccines. The LVMNA in the four groups against omicron variant were 6.4 to 13.5 times lower than those against the wild type. Serum neutralizing antibody against omicron variant was undetectable in 60% of the participants who received MCV-COV1901 as a booster by LVMNA. By using pseudovirus neutralizing assay, we found that neutralization activity in the four groups against omicron variant were 4.6 to 5.2 times lower than that against the D614G. All booster vaccines induced comparable T cell response.ConclusionsThird dose booster not only increases neutralizing antibody titer but also enhances antibody capacity against SARS-CoV-2 variants. mRNA vaccines are preferred booster vaccines for those after primary series of ChAdOx1 nCov-19.Trial registrationClinicalTrials.govNCT05132855

Background In 2012, we identified the dissemination of methicillin-resistant Staphylococcus aureus (MRSA) sequence type (ST)45 strain in 14 nursing homes in Taiwan and foreign nurse workers, a significant risk factor for MRSA carriage. We conducted this study to understand MRSA carriage and molecular characteristics among foreign workers recruited from Southeastern Asian countries. Methods A cross-sectional study involving a total of 1935 foreign workers—929 (arrival group) and 1006 (staying group)—from Vietnam (n = 843), Indonesia (n = 780), the Philippines (n = 239), and Thailand (n = 70) were conveniently recruited during upon-arrival and regular health examination in a regional hospital. A nasal swab was obtained from each participant for detection of MRSA. Results Overall, MRSA carriage rate was 2.72%, with 2.26% for arrival group and 3.18% for staying group, and 4.74% for Vietnamese, 1.28% for Indonesians, 1.26% for Filipino, and none for Thai workers. Pulsotype AK/ST45 (57%) and pulsotype AX/ST188 (14%) were the top 2 dominant clones for the arrival group, whereas pulsotype D/ST59 (41%) (an endemic community clone in Taiwan) and pulsotype AK/ST45 (19%) were predominant for the staying group. A significant decrease of pulsotype AK/ST45 from 57% to 19% (P = .007) and increase of pulsotype D/ST59 from 4.8% to 41% (P = .004) were found between the arrival and the staying groups. Conclusions Approximately 3% of foreign workers recruited from Southeastern Asian countries to Taiwan were colonized with MRSA, including the ST45 strain. However, the MRSA isolates from workers staying in Taiwan were mostly a locally endemic clone and genetically different from those identified from workers on arrival.

Background In 2012, we identified the dissemination of methicillin-resistant Staphylococcus aureus (MRSA) sequence type (ST)45 strain in 14 nursing homes in Taiwan and foreign nurse workers, a significant risk factor for MRSA carriage. We conducted this study to understand MRSA carriage and molecular characteristics among foreign workers recruited from Southeastern Asian countries. Methods A cross-sectional study involving a total of 1935 foreign workers—929 (arrival group) and 1006 (staying group)—from Vietnam (n = 843), Indonesia (n = 780), the Philippines (n = 239), and Thailand (n = 70) were conveniently recruited during upon-arrival and regular health examination in a regional hospital. A nasal swab was obtained from each participant for detection of MRSA. Results Overall, MRSA carriage rate was 2.72%, with 2.26% for arrival group and 3.18% for staying group, and 4.74% for Vietnamese, 1.28% for Indonesians, 1.26% for Filipino, and none for Thai workers. Pulsotype AK/ST45 (57%) and pulsotype AX/ST188 (14%) were the top 2 dominant clones for the arrival group, whereas pulsotype D/ST59 (41%) (an endemic community clone in Taiwan) and pulsotype AK/ST45 (19%) were predominant for the staying group. A significant decrease of pulsotype AK/ST45 from 57% to 19% (P = .007) and increase of pulsotype D/ST59 from 4.8% to 41% (P = .004) were found between the arrival and the staying groups. Conclusions Approximately 3% of foreign workers recruited from Southeastern Asian countries to Taiwan were colonized with MRSA, including the ST45 strain. However, the MRSA isolates from workers staying in Taiwan were mostly a locally endemic clone and genetically different from those identified from workers on arrival.

Variation in the genome of Pseudomonas aeruginosa, an important pathogen, can have dramatic impacts on the bacterium's ability to cause disease. We therefore asked whether it was possible to predict the virulence of P. aeruginosa isolates based on their genomic content. We applied a machine learning approach to a genetically and phenotypically diverse collection of 115 clinical P. aeruginosa isolates using genomic information and corresponding virulence phenotypes in a mouse model of bacteremia. We defined the accessory genome of these isolates through the presence or absence of accessory genomic elements (AGEs), sequences present in some strains but not others. Machine learning models trained using AGEs were predictive of virulence, with a mean nested cross-validation accuracy of 75% using the random forest algorithm. However, individual AGEs did not have a large influence on the algorithm's performance, suggesting instead that virulence predictions are derived from a diffuse genomic signature. These results were validated with an independent test set of 25 P. aeruginosa isolates whose virulence was predicted with 72% accuracy. Machine learning models trained using core genome single-nucleotide variants and whole-genome k-mers also predicted virulence. Our findings are a proof of concept for the use of bacterial genomes to predict pathogenicity in P. aeruginosa and highlight the potential of this approach for predicting patient outcomes. IMPORTANCE Pseudomonas aeruginosa is a clinically important Gram-negative opportunistic pathogen. P. aeruginosa shows a large degree of genomic heterogeneity both through variation in sequences found throughout the species (core genome) and through the presence or absence of sequences in different isolates (accessory genome). P. aeruginosa isolates also differ markedly in their ability to cause disease. In this study, we used machine learning to predict the virulence level of P. aeruginose isolates in a mouse bacteremia model based on genomic content. We show that both the accessory and core genomes are predictive of virulence. This study provides a machine learning framework to investigate relationships between bacterial genomes and complex phenotypes such as virulence., This work was supported by the National Institute of General Medical Sciences (grants T32 GM008061 and T32 GM008152 [N.B.P.]), by the American Cancer Society (grant MRSG-13-220-01-MPC [E.A.O.]), and by the National Institute of Allergy and Infectious Diseases (grants R01 AI118257, R21 129167, K24 AI104831, and U19 AI135964 [A.R.H.]). J.J.D. and M.N. are supported by the United States Defense Advanced Research Projects Agency Friend or Foe program iSENTRY award (contract HR0011937807 [J.J.D.]) and by the U.S. National Institute of Allergy and Infectious Diseases Bacterial and Viral Bioinformatics Resource Center award (contract 75N93019C00076 [principal investigator Rick Stevens]). A.O. is supported by Instituto de Salud Carlos III, Subdireccion General de Redes y Centros de Investigacion Cooperativa, Ministerio de Economia y Competitividad, Spanish Network for Research in Infectious Diseases (REIPI RD16/0016/0004), cofinanced by the European Development Regional Fund A way to achieve Europe and operative program Intelligent Growth 2014-2020.; This research was supported in part through the computational resources and staff contributions provided by the Genomics Compute Cluster, which is jointly supported by the Feinberg School of Medicine, the Center for Genetic Medicine, and Feinberg's Department of Biochemistry and Molecular Genetics, the Office of the Provost, the Office for Research, and Northwestern Information Technology. The Genomics Compute Cluster is part of Quest, Northwestern University's high-performance computing facility, with the purpose of advancing research in genomics. We acknowledge the University of Maryland School of Medicine Institute for Genome Sciences for performance of PacBio whole-genome sequencing.

FliA is known to be a sigma factor that regulates bacterial flagella gene expression. Accumulating evidence suggests that FliA is involved in bacterial behavior other than motility. To elucidate the contribution of FliA to Pseudomonas aeruginosa pathophysiology, we analyzed the biological properties and gene expression profiles of a ΔfliA mutant. Transcriptome analysis results demonstrated that the expression levels of flagella biogenesis genes decreased dramatically in the mutant; consequently, the Δ fliA mutant failed to synthesize flagella and exhibited reduced motility. The ΔfliA mutant displayed stronger hemolytic and caseinolytic activities, as well as pyocyanin production. The expression of type 6 secretion system-II genes and interbacterial competition activity was decreased in the ΔfliA mutant. Direct evidence of fliA participation in virulence was obtained from analysis of hypervirulent strain B136-33. Adhesion to and cytotoxicity toward mammalian cells and penetration through cell layers were noted; furthermore, the colonization ability of the fliA::Tn5 mutant in the intestines of laboratory mice was compromised. Notably, the fliA-overexpressing strain displayed phenotypes similar to that of the fliA -defective strain, indicating that optimal FliA levels are critical to bacterial physiology . Our findings indicate that FliA plays diverse roles in P. aeruginosa , not only in flagella biosynthesis, but also in pathophysiology.

Objectives Mycoplasma pneumoniae is currently the most commonly detected bacterial cause of childhood community-acquired pneumonia in several countries. Of note, clonal expansion of macrolide-resistant ST3 occurred in Japan and South Korea. An alarming surge in macrolide resistance complicates the treatment of pneumonia. We aimed to evaluate the clinical manifestation and clonal relatedness of M. pneumoniae circulating among children in Taiwan. Methods We prospectively enrolled 626 children with radiologically confirmed pneumonia between 2017 and 2019. An M. pneumoniae infection was suspected on clinical grounds, and tested by real-time PCR and oropharyngeal swab cultures. We used multilocus sequence typing and whole-genome sequencing to characterize the genetic features of M. pneumoniae. Results A total of 226 children with M. pneumoniae pneumonia were enrolled. Macrolide resistance was found in 77% (174/226) of patients. Multi-locus sequence typing revealed that ST3 (n = 93) and its single-locus variant ST17 (n = 84) were the predominant clones among macrolide-resistant strains. ST17 presented clinical characteristics comparable to its ancestor ST3. On multivariate analysis, macrolide resistance (OR 3.5; 95% CI 1.4–8.5; p 0.007) was independently associated with fever >72 hours after macrolide treatment. By whole-genome sequencing, prediction analysis of recombination sites revealed one recombination site in ST3 and ST17 compared with M29 (a macrolide-sensitive ST3 strain isolated from China in 2005) containing cytadhesin MgpC-like protein, RepMP4 and RepMP5. ST17 had another recombination site containing an adhesin and RepMP2/3. Conclusions In addition to macrolide resistance, ST3 and its ST17 variant might evolve through recombination between repetitive sequences and non-P1 cytadhesins for persistent circulation in Taiwan.

The gastrointestinal tract is not the common infection site of Pseudomonas aeruginosa. The role of P. aeruginosa as a causative agent for diarrhea in children without preexisting disease is controversial.From 2003 to 2012, we reviewed the records of 259 diarrheal patients less than 5 years of age whose stool culture grew P. aeruginosa. Virulence phenotypes of bacterial isolates were determined in vitro, including cytotoxicity, penetration and adherence to epithelial cells.The presence of P. aeruginosa in children with diarrhea less than 5 years old is 0.91%. P. aeruginosa-associated diarrheal diseases were classified into 4 groups: Shanghai fever (enteric infection and sepsis) (5%), P. aeruginosa enterocolitis (15%), P. aeruginosa-related diarrhea (19%) and antibiotic-associated diarrhea (43%). The remaining patients had coinfection with other pathogens (18%). Shanghai fever was the most severe enteric disease with invasive infection and complications. The clinical features of P. aeruginosa enterocolitis were prolonged fever with bloody or mucoid diarrhea mimicking bacterial enterocolitis. The clinical features of P. aeruginosa-related diarrhea and antibiotic-associated diarrhea were similar to viral or toxin-mediated diarrhea. Compared with other P. aeruginosa-associated diarrheal diseases, patients with Shanghai fever were younger, usually infants, and the characteristic laboratory findings included leukopenia, thrombocytopenia, high C-reactive protein, hyponatremia and hyperglycemia. Except for Shanghai fever, antibiotic treatment is not recommended. Isolates from Shanghai fever were more cytotoxic and adherent than isolates from uncomplicated diarrheal patients.P. aeruginosa could be an enteric pathogen even in healthy children. Young age and highly virulent bacterial strains were risk factors for Shanghai fever.

This paper develops an enhanced grey variable structure controlled DC-AC inverter in parallel, and is suitable for the application of ultra-precision machining (UPM). The enhanced grey variable structure control methodology consists of a nonlinear sliding function (NSF) and a grey model, GM(2,1). The NSF has finite system-state convergence time, and thus the AC output voltage regulation and balanced current-sharing among the parallel modules can be achieved. However, once the loading of the UPM is a highly nonlinear condition, the chatter still exists in NSF. The chatter may cause heat losses and high voltage harmonics in parallel-connected DC-AC inverter output, and thus deteriorates the stability and reliability of the UPM. To eliminate the chatter, the control gains of the NSF can be adjusted by the use of the GM(2,1) under system uncertainty bounds are overestimated. With the enhanced methodology, the parallel-connected DC-AC inverter yields a high-quality AC output voltage with low voltage harmonics and fast dynamic response under highly nonlinear loading, thus achieving the stability and reliability of the UPM. Experimental results are performed to demonstrate the enhanced methodology.

Objectives Clostridium innocuum can cause extraintestinal infection in patients with underlying diseases. The role of C. innocuum in antibiotic-associated diarrhoea (AAD) remains unknown. Methods Clinical information of 103 patients from whom C. innocuum was isolated was reviewed. We carried out cellular and animal experiments to examine the pathogenic potential of C. innocuum in AAD. Results Eighty-eight per cent (91/103) of the 103 patients received antibiotics within 2 weeks of diarrhoea onset. Patients were further classified into two groups, severe colitis and diarrhoea, according to clinical severity level. The mortality rate was 13.6% (14/103) among the patients from whom C. innocuum was isolated. The lowest concentrations at which 90% of the isolates were inhibited for metronidazole and vancomycin were 0.5 and 16 mg/L, respectively. All isolates tested were susceptible to metronidazole but resistant to vancomycin. Nineteen randomly selected isolates (ten from severe colitis group, nine from diarrhoea group) were subjected to further in vitro cellular examinations. The level of cytotoxicity to Vero cells was significantly higher in isolates from the severe colitis group at both 24 and 48 hours after inoculation (24 and 48 hours, p 0.042 and 0.033, respectively). We observed apoptotic changes that subsequently led to cell death in C. innocuum –infected Vero cells. Tissue damages, necrotic changes and oedema were observed in the mouse ileal loop infected by C. innocuum. Conclusions Vancomycin-resistant C. innocuum may play a potential role as a causative agent of AAD. The clinical manifestations of AAD caused by C. innocuum were diarrhoea or severe colitis, including pseudomembranous colitis.

Background Shanghai fever, a community-acquired enteric illness associated with sepsis caused by Pseudomonas aeruginosa, was first described in 1918. The understanding of Shanghai fever is incomplete. Objective To delineate the clinical features and to examine the host and microbial factors associated with Shanghai fever. Methods We prospectively enrolled 27 consecutive previously healthy children with community-acquired P aeruginosa enteritis and sepsis between July 2003 and June 2012. An immunological investigation, including measurement of serum immunoglobulin levels and lymphocyte subpopulations, was performed. The clonal relationship of bacterial isolates was determined by multilocus sequence typing (MLST) and the virulence of isolates was measured using cellular and animal models. Results The median age of the patients was 7 months; 24 (89%) were aged

Carbapenem resistance in Acinetobacter baumannii is a global problem. The purpose of this study was to elucidate current resistance mechanisms of imipenem-resistant A. baumannii (IRAB) in Taiwan and their correlation with patient outcomes. Acinetobacter baumannii clinical isolates from two teaching hospitals in Taiwan were collected in 2009 and were examined by Etest for determination of the minimum inhibitory concentrations (MICs) of imipenem, ceftazidime and ceftriaxone. Primers specific for carbapenemase genes and upstream regions were designed for PCR amplification. Bacterial isolates were genotyped by pulsed-field gel electrophoresis (PFGE). Clinical presentations of patients were analysed retrospectively. Upstream insertion sequence ISAba1 was found in 34 isolates that carried bla(OXA-23), including 28 with transposon Tn2006 (ISAba1-bla(OXA-23)-ISAba1) in an AbaR4-type resistance island and 6 with Tn2008 (ISAba1-bla(OXA-23)), as well as in 8 isolates carrying ISAba1-bla(OXA-51-like). All of these isolates expressed full resistance to imipenem (MIC>32 mg/L). Forty-one different PFGE genotypes were found among 62 isolates. Tn2006 was found in 19 genotypes (46.3%), which is more common than ISAba1-bla(OXA-51-like) (12.2%) (P=0.001). Prior use of carbapenems or extended-spectrum cephalosporins for ≥5 days was the only independent risk factor significantly associated with IRAB infection (odds ratio=361.175). Higher mortality was significantly associated with infection caused by IRAB and ISAba1-bla(OXA-23)-carrying strains compared with infection caused by imipenem-susceptible A. baumannii and ISAba1-bla(OXA-51-like)-carrying strains (P=0.009 and 0.027, respectively). Tn2006 is currently the most common imipenem resistance determinant, which showed a higher ability to spread among A. baumannii and was associated with a higher mortality in IRAB-infected patients.

The optimal age for administration of recently approved prophylactic human papillomavirus (HPV) vaccines remains undetermined.The aim of the study was to explore the age-specific seroprevalence of HPV 16 and 18 in the general population to design an HPV vaccination campaign for Taiwan.HPV seroprevalence was assessed by virus-like particle (VLP)-based ELISA in 1702 plasma samples collected in 1999.The sample population consisted of 1000 (58.8%) females and 702 (41.2%) males; age ranged from 17 days to 86 years. The age-specific distributions reveal a significant rise in HPV 16 seropositivity commencing at 19-25 years of age and peaking at60 years. The trend of seropositivity increase with age was also highly significant for HPV 18 (P(Trend)0.0001). Males had lower overall seroprevalence in gender comparison (7.6% versus 3.85% for HPV 16, 3.9% versus 2.71% for HPV 18), were older at seroconversion (19-25 years versus 26-30 years) with a more obvious seropositivity nadir in middle age.The age-specific seroprevalence of HPV 16 and 18 increases in young adults after the age of 18 years, with gender distribution varying. We conclude that the optimal age for universal HPV vaccination in Taiwan is 15 years or below.

Kawasaki disease (KD) is rare in infantsor =3 months of age. This study analyzed the features of KD in 25 infantsor =3 months of age treated from February 1994 to December 2004.Basic characteristics, clinical, laboratory, echocardiographic, therapeutic, and follow-up data of the infants were obtained from chart records.There were 19 male and 6 female infants in this cohort. The frequency of the 5 principal clinical features was as follows: changes in lips and oral cavity, 84%; bilateral bulbar conjunctival injection without exudates, 80%; polymorphous exanthem, 68%; cervical lymphadenopathy, 28%; and changes in extremities, 24%. Six infants (24%) fulfilled criteria for KD including fever which persists for 5 or more days with at least 4 of the principal clinical criteria, and the remaining infants were classified as having incomplete KD (all of whom showed coronary involvement). Coronary artery dilatation was found in 20 infants (80%). One infant developed a medium-size aneurysm (5.2 mm), while the others had only coronary arterial ectasia or small aneurysms. Coronary artery aneurysms regressed within 1-year follow-up in all but one infant. No fatal or recurrent case was observed during the study period.Infantsor =3 months of age with KD usually presented with incomplete clinical features. A high proportion of coronary artery involvement was observed in this series. Echocardiography should be considered in very young infants with unexplained prolonged fever who do not present all of the principal clinical features of KD.

OBJECTIVE. Among >2500 nontyphoid Salmonella serotypes, Salmonella enterica serotype Choleraesuis shows a high predilection to cause systemic infections in humans. The objective of this study was to delineate the clinical and microbiologic features of pediatric patients with Salmonella Choleraesuis infections. METHODS. Between May 1999 and February 2003, a total of 33 patients who were RESULTS. There were 24 males and 9 females with a mean age of 3 years. Fever (rectal temperature ≥38°C; 94%) was the most common clinical presentation. Sixteen (52%) had fever lasting >5 days before admission. Only 18 (54%) patients had diarrhea. The most common mode of infection is occult bacteremia without focal infection. Compared with data obtained from adult patients, the gastrointestinal manifestations appeared more frequently seen in pediatric patients. However, among the 18 who presented with diarrhea, 14 had concomitant bloodstream infection. Only 1 patient, who was a case of acute leukemia, died of S Choleraesuis sepsis. Resistance to ceftriaxone, ciprofloxacin, ampicillin, trimethoprim-sulfamethoxazole, and chloramphenicol was found in 6%, 28%, 88%, 76%, and 83% of the isolates, respectively. CONCLUSION. Children with S Choleraesuis infections usually presented with occult bacteremia with mild gastrointestinal involvement. The mortality of S Choleraesuis infections in previously healthy children is low. Ciprofloxacin resistance among S Choleraesuis isolates from pediatric patients was lower than that of isolates from adult patients. In view of the high rate of multidrug resistance, third-generation cephalosporins seem to be the drug of choice for treatment of invasive S Choleraesuis infections.

Background: Kikuchi's disease (KD) is characterized by cervical lymphadenopathy with or without fever. It has been recognized worldwide but seldom reported in pediatric patients. Methods: From January 1985 through December 2001, 64 patients younger than 18 years of age with pathologic proof of KD were enrolled in this study. The clinical manifestations, laboratory data and outcomes were reviewed. Results: There were 35 male patients and 29 female patients with age ranging from 2 to 18 years and a median age of 16. All patients had cervical lymphadenopathy except 1 who had generalized lymphadenopathy. Lymph nodes of 32 patients (50%) were painful or tender or both. Lymphadenopathy was unilateral in 52 patients (82.5%). Lymphadenopathy associated with fever was observed in 21 patients (32.8%). Other signs such as skin rash, hepatomegaly or body weight loss were less common. Twenty-six patients (40.6%) had leukopenia and 2 patients had leukocytosis. Nearly one-fourth of the patients had mild liver dysfunction. Virologic or immunologic studies were normal in most patients. Patients with prolonged fever were more likely to have leukopenia (P < 0.05). All patients recovered, but 1 developed systemic lupus erythematosus 5 years later, and the other had vasculitis syndrome 2 years later. Conclusions: The clinical presentation of KD in pediatric patients is similar to that of adults. KD is a benign, self-limiting disease; prolonged fever occurred only in 32.8% of pediatric patients in our cohort. Leukopenia was the only feature significantly associated with prolonged fever.

A 6-year-old girl with community-acquired disseminated infection caused by methicillin-resistant Staphylococcus aureus (MRSA) is described. She had sepsis, meningo-encephalitis, pyomyositis, osteomyelitis, pericarditis and pulmonary embolisation caused by a multi-resistant strain of MRSA. Vancomycin is not routinely recommended as the first-line antimicrobial agent for suspected Staphylococcus aureus infection; however, it should be considered pending susceptibility results in patients presenting with severe sepsis in areas where the prevalence of MRSA is high.

1Division of Pediatric Gastroenterology, Department of Pediatrics, Chang Gung Children’s Hospital, Chang Gung University College of Medicine, Taoyuan, Taiwan 2Graduate Institute of Clinical Medical Sciences, Chang Gung University College of Medicine, Taoyuan, Taiwan 3St Paul’s Hospital, Taoyuan, Taiwan 4Division of Pediatric Infectious Diseases, Department of Pediatrics, Chang Gung Children’s Hospital, Chang Gung University College of Medicine, Taoyuan, Taiwan

An experimental investigation of the twodimensional(2-D) flow normal to a flat plate at low to medium Reynolds numbers (ranging from 25 to 393 based on the breadth of the plate) is described. Both horizontal and vertical soap film tunnels are used to set up a truly 2-D experiment. The flow in the soap film is very thin and is a close approximation to 2-D flow. Momentum defect measurements are used to obtain the time averaged mean drag coefficient, cl, experienced by a normal flat plate via laser Doppler velocimetry. It is found that cl = 2.1 for the current Re range. The present data agree well with available nominally 2-D experimental results from previously published papers which were obtained in traditional towing tank, wind tunnel and water tunnel experiments with high plate aspect ratios. This measurement implies that the intrinsic 3-D motions in the previously nominally 2-D experiments are not significant on cl and the computational fluid dynamics results from previously published papers which are reviewed have overestimated cl. Introduction Bluff body flows are by nature very complex. Inevitably they involve boundary layer, free shear layer and wake flows, all accompanied by associated instabilities and non-linear interactions with each other and with the bluff body itself. Bluff body wake flows have direct engineering significance. The alternate shedding of vorticies in the near wake, in the classical vortex street configuration, leads to large fluctuating pressure forces in a direction some cases can trigger failure. A normal flat plate is in many ways the simp* Associate Professor, Department of Mechanical Engineering , Member AIAA ** Graduate Research Assistant, Department of Mechanical Engineering Copyright O 1998 by the American Institute of Aeronautics and Astronautics Inc . All right reserved. lest possible bluff body, since it has geometrically fixed separation points, and since the interaction between the body and the near wake formation region is minimized. However, in comparison to the bulk of contemporary literature dealing with circular cylinder flows, very few results have been published for normal flat plates. Of the normal flat plate results which are available, typically Strouhal shedding frequency, force and/or pressure coefficients are presented only as time averaged mean quantities. Lisoski' has reviewed published experimental and computational results for time averaged mean drag coefficient, cT, and Strouhal number, St, of nomianlly 2-D noraml flat plates extensively. The main thing to note about the reviewed results is the large difference in cT between the experimental results( typically c7 = 2.0 ) and the 2-D numerical models( typically c7 = 3.2 ),which in some cases have a drag of almost twice the experimental values. There has been a tendency to think of these truly 2-D computer models as being wrong, and to modify them by various means so that their results conform with "2-D" experiments which are indeed threedimensional. As has been noted by Lisoski, "this is the wrong approach." He then went on investigating the intrinsic( small scale ) and extrinsic( large scale ) 3-D motions in the towing tank and water channel experiments. A 2-D vortex element numerical model developed by Chua was also used for comparison with his experimental results. It is shown that agreement between normally 2-D experimental and 2-D numerical-model results is good at early times, indicating the experiments are 2-D until the breakdown of the closed wake bubble following the initial accerlation. The approach of this paper is different. A truly 2-D experiment is conducted to have a direct comparison with the previously 2-D numerical results on cl. Freely suspended flowing soap films are used to set up the truly 2-D flows. These films, which have a thickness of the order of a micron, offer an excellent opportunity for studying hydrodynamics American Institute of Aeronautics and Astronautics Copyright© 1997, American Institute of Aeronautics and Astronautics, Inc.