MALDI-TOF MS for identification of Tsukamurella species: Tsukamurella tyrosinosolvens as the predominant species associated with ocular infections.

Although Tsukamurella infections have been increasingly reported in Europe, Asia, America, and Africa, indicating that diseases caused by this group of bacteria are emerging in a global scale, species identification within this genus is difficult in most clinical microbiology laboratories. Recently, we showed that groEL gene sequencing is useful for identification of all existing Tsukamurella species. Nevertheless, PCR sequencing is still considered expensive, time-consuming, and technically demanding, and therefore is yet to be incorporated as a routine identification method in clinical laboratories. Using groEL gene sequencing as the reference method, 60 Tsukamurella isolates were identified as five different Tsukamurella species [T. tyrosinosolvens (n = 31), T. pulmonis (n = 25), T. hongkongensis (n = 2), T. strandjordii (n = 1), and T. sinensis (n = 1)]. The most common source of the patient isolates were the eye (n = 18), sputum (n = 6), and blood (n = 6). None of the 60 isolates were identified correctly to species level by MALDI-TOF MS with the original Bruker database V.6.0.0.0. Using the Bruker database extended with 15 type and reference strains which covered all the currently recognized 11 Tsukamurella species, 59 of the 60 isolates were correctly identified to the species level with score ≥2.0. MALDI-TOF MS should be useful for routine species identification of Tsukamurella in clinical microbiology laboratories after optimization of the database. T. tyrosinosolvens was the most common species observed in patients with Tsukamurella infections and the predominant species associated with ocular infections.

Novel selective medium for the isolation of corynebacterium kroppenstedtii from heavily colonised clinical specimens.

AIMS: Granulomatous mastitis due to Corynebacterium kroppenstedtii is an increasingly recognised cause of an indolent and distressing mastitis in non-lactating females. This slow-growing lipophilic organism is not reliably isolated using routine culture methods. A novel selective culture medium (CKSM) is designed to optimise the isolation of this organism from clinical specimens. METHODS: CKSM contains 10% galactose and Tween 80 (10%) to enhance the growth of C. kroppenstedtii, fosfomycin (100 µg/mL) to suppress the other bacteria, and differentiate C. kroppenstedtii from non-kroppenstedtii lipophilic corynebacteria by esculin hydrolysis. The medium was evaluated for its ability to support the growth of C. kroppenstedtii, selection and differentiation of C. kroppenstedtii from other bacteria in non-sterile clinical specimens. RESULTS: C. kroppenstedtii grew as 1-2 mm colonies with black halo on CKSM within 72 hours of incubation, compared with barely visible pinpoint colonies on routine blood agars. During the four-month period of evaluation with 8896 respiratory specimens, 103 breast specimens, 1903 female genital tract specimens, 617 newborn surface swabs and 10 011 miscellaneous specimens, 186 C. kroppenstedtii were isolated, including 127 (1.4%) respiratory and 59 (0.5%) miscellaneous specimens, 184 of them were found only on CKSM. Besides the three (2.9%) positive breast specimens, 27 (1.4%) high vaginal and endocervical swabs, and 11 (1.8%) surface swabs of newborns were positive for C. kroppenstedtii. CONCLUSIONS: CKSM is a useful addition to routine agar media for the isolation of C. kroppenstedtii, and will be helpful for studying the epidemiology and transmission of this unusual Corynebacterium causing granulomatous mastitis.

Rapid Differentiation of Haemophilus influenzae and Haemophilus haemolyticus by Use of Matrix-Assisted Laser Desorption Ionization-Time of Flight Mass Spectrometry with ClinProTools Mass Spectrum Analysis.

Haemophilus influenzae is associated with severe invasive disease, while Haemophilus haemolyticus is considered part of the commensal flora in the human respiratory tract. Although the addition of a custom mass spectrum library into the matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) system could improve identification of these two species, the establishment of such a custom database is technically complicated and requires a large amount of resources, which most clinical laboratories cannot afford. In this study, we developed a mass spectrum analysis model with 7 mass peak biomarkers for the identification of H. influenzae and H. haemolyticus using the ClinProTools software. We evaluated the diagnostic performance of this model using 408 H. influenzae and H. haemolyticus isolates from clinical respiratory specimens from 363 hospitalized patients and compared the identification results with those obtained with the Bruker IVD MALDI Biotyper. The IVD MALDI Biotyper identified only 86.9% of H. influenzae (311/358) and 98.0% of H. haemolyticus (49/50) clinical isolates to the species level. In comparison, the ClinProTools mass spectrum model could identify 100% of H. influenzae (358/358) and H. haemolyticus (50/50) clinical strains to the species level and significantly improved the species identification rate (McNemar's test, P < 0.0001). In conclusion, the use of ClinProTools demonstrated an alternative way for users lacking special expertise in mass spectrometry to handle closely related bacterial species when the proprietary spectrum library failed. This approach should be useful for the differentiation of other closely related bacterial species.

Coronary artery calcification across ethnic groups in Singapore.

INTRODUCTION: In Singapore, the age-standardised event rates of myocardial infarction (MI) are 2- and 3-fold higher for Malays and Indians respectively compared to the Chinese. The objectives of this study were to determine the prevalence and quantity of coronary artery calcification (CAC) and non-calcified plaques across these 3 ethnic groups. MATERIALS AND METHODS: This was a retrospective descriptive study. We identified 1041 patients (810 Chinese, 139 Malays, 92 Indians) without previous history of cardiovascular disease who underwent cardiac computed tomography for atypical chest pain evaluation. A cardiologist, who was blinded to the patients' clinical demographics, reviewed all scans. We retrospectively analysed all their case records. RESULTS: Overall, Malays were most likely to be active smokers (P = 0.02), Indians had the highest prevalence of diabetes mellitus (P = 0.01) and Chinese had the highest mean age (P <0.0001). The overall prevalence of patients with non-calcified plaques as the only manifestation of sub-clinical coronary artery disease was 2.1%. There was no significant difference in the prevalence of CAC, mean CAC score or prevalence of non-calcified plaques among the 3 ethnic groups. Active smoking, age and hypertension were independent predictors of CAC. Non-calcified plaques were positively associated with male gender, age, dyslipidaemia and diabetes mellitus. CONCLUSION: The higher MI rates in Malays and Indians in Singapore cannot be explained by any difference in CAC or non-calcified plaque. More research with prospective follow-up of larger patient populations is necessary to establish if ethnic-specific calibration of CAC measures is needed to adjust for differences among ethnic groups.

Acute myocardial infarction: Clinical features and outcomes in young adults in Singapore.

AIM: To investigate the clinical features and in-hospital outcomes of young adults with acute myocardial infarction (AMI) in Singapore. METHODS: Between January 2005 to September 2010, 333 consecutive patients aged ≤ 45 years old were diagnosed to have AMI at our institution. As Singapore is a multi-ethnic society, we also analysed whether ethnic differences exist between the three dominant ethnic groups, Malay, Chinese and Indian with regards to the clinical features. Clinical data was collected retrospectively on demographic characteristics, presenting signs and symptoms, blood investigation, angiographic findings and in-hospital clinical outcomes. RESULTS: The mean age at presentation was 40.2 ± 4.0 years with male predominance (94%). The majority of patients were Chinese (51%) followed by Indians (31%) and Malays (18%). The most common risk factor was smoking (74%) followed by hypertension (28.5%) and hyperlipidemia (20.0%). 37% of patients were obese. The majority of patients had single vessel disease (46%) on coronary angiography. The mean total cholesterol, low-density lipoprotein and high-density lipoprotein levels were 5.6 ± 1.2 mmol/L, 3.8 ± 1.1 mmol/L and 0.93 ± 0.25 mmol/L respectively. The mean left ventricular function was 44% ± 10% with the incidence of heart failure 3% and cardiogenic shock 4.5%. Overall in-hospital mortality was low with 4 deaths (1.2%). For ethnic subgroup analysis, Indians have a 3-fold risk of developing premature AMI when compared to other ethnic groups. CONCLUSION: Young AMI patients in Singapore are characterized by male predominance, high incidence of smoking and obesity. Overall in-hospital clinical outcomes are favourable. Among the 3 ethnic groups, Indians have the highest risk of developing premature AMI.

Rheolytic thrombectomy in patients with massive pulmonary embolism: a report of two cases and review of literature.

We present two cases of massive pulmonary embolism with persistent systolic hypotension but both have contraindications for thrombolysis. Therefore, rheolytic thrombectomy using AngioJet was performed and immediate haemodynamic improvement was achieved including blood pressure and symptoms. According to guidelines, catheter embolectomy or fragmentation may be considered as alternative to surgical treatment in massive pulmonary embolism patients when thrombolysis is absolutely contraindicated or has failed. Percutaneous catheter-based interventional techniques include thrombus fragmentation, rheolytic thrombectomy, suction thrombectomy and rotational thrombectomy. With the existing literature review and our case, rheolytic thrombectomy for treatment of massive pulmonary embolism using AngioJet achieves a high procedural success rate (approximately 90%) n terms of improvement of haemodynamics, pulmonary perfusion and angiographic result but low complication rate.

Intravascular ultrasound virtual histology imaging in acute ST-elevation myocardial infarction: A useful clinical tool during primary percutaneous coronary intervention.

We described the novel use of intravascular ultrasound-virtual histology (IVUS-VH) imaging in two young adult male patients who presented with acute inferior ST-elevation myocardial infarction (STEMI) and we highlight the usefulness of this new invasive coronary imaging technique. Both patients had thrombotic occlusion of the right coronary arteries but the underlying pathophysiological mechanisms leading to acute thrombosis were different. The in vivo information obtained by IVUS-VH imaging was invaluable in pinpointing the likely etiology of STEMI and thus, guided our primary percutaneous coronary intervention strategy appropriately.

Good visibility of TITAN-2 coronary stents demonstrable on cardiac computer tomographic angiography: a report of 2 cases.

Numerous studies have sought to assess stent patency by cardiac computer tomographic angiography (CCTA) in comparison with invasive coronary angiography in patients who had undergone percutaneous coronary stenting. Even with newer generation scanners, CCTA has been of limited value in the assessment of the revascularized patient. The main reason being blooming artifact from metallic stents often obscures stent luminal dimension, making the stented segment unassessable. We report on a novel finding of good visibility of TITAN-2 coronary stents demonstrable on CCTA for 2 patients and discuss the possible mechanism and potential implications of this observation.

Human antiquitin: structural and functional studies.

Antiquitin (ALDH7) is a member of the aldehyde dehydrogenase superfamily which oxidizes various aldehydes to form the corresponding carboxylic acids. Human antiquitin (ALDH7A1) is believed to play a role in detoxification, osmoregulation and more specifically, in lysine metabolism in which alpha-aminoadipic semialdehyde is identified as the specific, physiological substrate of the enzyme. In the present study, the structural basis for the substrate specificity was studied by site-directed mutagenesis. Kinetic analysis on wild-type human antiquitin and its mutants E121A and R301A demonstrated the importance of Glu121 and Arg301 in the binding as well as the turnover of alpha-aminoadipic semialdehyde. On the functional aspect, in addition to the already diversified physiological functions of antiquitin, the recent demonstration of its presence in the nucleus suggests that it may also play a role in cell growth and cell cycle progression. In this investigation, the expression level of antiquitin was monitored in synchronized WRL68 and HEK293 cell culture systems. It was found that the protein was up-regulated during G(1)-S phase transition. Immunofluorescence staining of the synchronized cells demonstrated an increased expression and accumulation of antiquitin in the nucleus during the G(1)-S phase transition. Knockdown of antiquitin using shRNA transfection also resulted in changes in the levels of several key cell cycle-regulating proteins.

Clinical implications of precordial ST-segment elevation in acute inferoposterior myocardial infarction caused by proximal right coronary artery occlusion.

BACKGROUND: The clinical significance of inferior wall acute myocardial infarction (MI) with combined ST-segment elevation in both anterior and inferior leads, compared with inferior leads alone, is unknown. HYPOTHESIS: Despite having more leads with precordial ST-segment elevation, these patients may have a better outcome due to less posterior involvement, which tends to drag down the precordial ST-segment. METHODS: A total of 158 postinferior MI patients with documented proximal right coronary artery occlusion were retrospectively studied. They were divided into three subgroups according to the magnitude of concurrent ST-segment deviation in lead V2: Group A (n = 19) had ST-segment elevation >/= 2.0 mm; Group B (n = 74) had ST-segment lay between + 2.0 mm and - 2.0 mm; and Group C (n = 65) had ST-segment depression >/= 2.0 mm. The clinical and electrocardiographic characteristics were then compared among these threes subgroups. RESULTS: The baseline demography, prevalence of risk factors, and treatment received were of no difference among the subgroups. However, Group A patients had significantly lower peak creatinine phosphokinase level and more preserved left ventricular function than Group B and C. Moreover, they had lower total sum of inferior ST-segment magnitude, less ST-segment depression in V4-6, and more ST-segment elevation in V(4R) than Group C. Group C patients had highest in-hospital and one-year mortality although it did not reach statistical significance. CONCLUSIONS: Precordial ST-segment elevation in inferior wall acute MI was associated with smaller infarct size and better left ventricular function, probably secondary to occlusion of a less dominant RCA, which did not result in a significant posterior infarction.

Zopiclone withdrawal: an unusual cause of delirium in the elderly.

We report a case of an elderly lady who was admitted for congestive heart failure. She developed delirium during the course of her hospital stay. Multiple investigations were performed but were unremarkable. Finally, a diagnosis of abrupt zopiclone withdrawal causing delirium was made. Zopiclone was resumed at a lower dose and delirium resolved completely.