MacConkey Agar (MAC): Composition, preparation, application and colony characteristics

MacConkey agar was developed in 20th century by Alfred Theodore MacConkey. It was the first formulated solid differential media. MacConkey Agar is a selective and differential culture media commonly used for the isolation of enteric Gram-negative bacteria. It is based on the bile salt-neutral red-lactose agar of MacConkey. Crystal violet and bile salts in incorporated in MacConkey Agar to prevent the growth of gram-positive bacteria and fastidious gram-negative bacteria, such as Neisseria and Pasteurella. Gram-negative enteric bacteria can tolerate to bile salt because of their bile-resistant outer membrane.

MacConkey Agar is selective for Gram negative organisms, and helps to differentiate lactose fermenting gram negative rods from Non lactose fermenting gram negative rods. It is primarily used for detection and isolation of members of family enterobacteriaceae and Pseudomonas spp.

Composition of MacConeky Agar:

Enzymatic Digest of Gelatin, Casein and Animal tissue: provides nitrogen, vitamins, minerals and amino acids essential for growth.

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MacConkey Agar (MAC): Composition, preparation, application and colony characteristics

LF and NLF colonies in MacConkey Agar

Source: microbeonline

Cardiovascular Disease Diagnostics and Testing

Current and emerging cardiac markers signal improved testing for better patient outcomes

Cardiovascular diseases continue to be the leading cause of death in the United States, responsible for nearly 800,000 deaths annually—or about one in every three deaths. Heart disease is the leading cause of death for both men and women, claiming the lives of about 610,000 Americans each year.1Coronary artery disease is the most common type of heart disease, killing more than 370,000 people annually.

In addition, about 5.1 million people in the United States have heart failure.2About half of the people who develop heart failure die within 5 years of diagnosis. In 2009, one out of every nine deaths included heart failure as a contributing cause. Heart failure costs the nation an estimated $32 billion each year.

In light of such dire statistics, it’s no wonder that achieving speedy diagnosis of acute myocardial infarction (AMI)—heart attack—remains a significant concern in emergency departments throughout the nation. Early triage of patients to rule-in or rule-out AMI is challenging. For many years, testing for the presence of the regulatory proteins troponin I or troponin T—both released into the bloodstream when the heart muscle has been damaged—has been the gold standard for diagnosing AMI. But recent reports have indicated that the latest generation of high-sensitivity troponin tests can increase diagnostic efficiency and improve early diagnosis of myocardial infarction.

Read more: Cardiovascular Disease Diagnostics and Testing

Alere’s troponin I test is a cartridge-based high-sensitivity immunoassay.

Source: clpmag

Emerging Blood-Borne Bacteria Detected in Blood Donors

Bartonella species cause chronic and intermittent intra-erythrocytic bacteremia and infect endothelial cells of both incidental and natural reservoir hosts. The establishment of chronic, stealth infection is achieved by evasion of innate immune responses.

In humans, Bartonella species have been detected from sick patients presented with diverse disease manifestations, including cat scratch disease, trench fever, bacillary angiomatosis, endocarditis, polyarthritis, or granulomatous inflammatory disease.

An international team of scientists, led by those at the Western University of Health Sciences, Pomona, CA, USA), collected blood from 500 apparently healthy Brazilian voluntary blood donors in a cross sectional study. Bartonella species infection from the bloodstream was detected based on enrichment blood culture in a liquid growth medium (Bartonella alpha-Proteobacteria growth medium-BAPGM), coupled with isolation in solid medium. Bartonella-specific DNA was amplified by polymerase chain reaction (PCR), followed by DNA sequencing to confirm species identification. Of the ten Bartonella species that are believed to produce infection in humans, the most commonly encountered are B. henselae, B. quintana, and B. bacilliformis. The latter causes Oroya fever and Verruga peruana.

Read more: Emerging Blood-Borne Bacteria Detected in Blood Donors

Electron micrograph of Bartonella henelae, Gram-negative bacteria that causes cat scratch fever

Source: Prokaryotes

Acid-Fast Stain Identifies Schistosoma Eggs

Schistosomiasis, also known as snail fever, is a disease caused by parasitic flatworms called schistosomes. The urinary tract or the intestines may be infected and signs and symptoms may include abdominal pain, diarrhea, bloody stool, or blood in the urine.

Microscopic identification of eggs in stool or urine is the most practical method for diagnosis. Stool examination is performed when infection with Schistosoma mansoni or S. japonicum is suspected, and urine examination should be performed if S. haematobium is suspected. Eggs can be present in the stool in infections with all Schistosoma species.

Scientists at the University of Lisbon examined whether the Ziehl–Neelsen (ZN) stain, also known as the acid- fast stain, would be helpful in detection and identification of Schistosoma eggs. In histological sections, S. mansoni eggshells appear as ZN positive and S. haematobium shells as ZN negative. The staining target of the responsible ZN component (carbolfuchsin) in the shell is unknown and because carbolfuchsin is supposed to stain mycolic acids in the mycobacterial cell wall, unidentified substances in the eggshell were proposed as target. Fuchsin is a known nucleic acid stain, and it was already shown that mycobacteria with insufficiently retained carbolfuchsin may be invisible in bright-field microscopy; yet, they can be easily detected because of a strong red fluorescence when excited with green light.

Read more: Acid-Fast Stain Identifies Schistosoma Eggs

Positive staining of Schistosoma mansoni eggs

Source: ganfyd

Novel Biomarker Predicts Breast Cancer Risk in Asymptomatic Women

A biomarker has been identified that may allow clinicians to predict the risk of an asymptomatic woman eventually developing breast cancer.

To identify this disease indicator, investigators at Harvard Medical School studied the association between breast cancer risk and the frequency of mammary epithelial cells expressing the proteins p27 (Cyclin-dependent kinase inhibitor 1B), estrogen receptor (ER), and Ki67 (Marker of proliferation Ki-67) in normal breast tissue from 302 women (69 breast cancer cases, 233 controls) who had been initially diagnosed with benign breast disease.

Immunofluorescence assays for p27, ER, and Ki67 were performed on tissue microarrays constructed from benign biopsies containing normal mammary epithelium and scored by computational image analysis.

Read more: Novel Biomarker Predicts Breast Cancer Risk in Asymptomatic Women

Source: gettyimages

Standardizing Immunoassays: The Benefits of Conformity

Interpreting results of immunoassay-based methods frequently presents a challenge for physicians, especially when caring for patients at multiple institutions that use different assay platforms. For many analytes including tumor markers, endocrine hormones, and cardiac biomarkers, results generated on different platforms are not directly comparable. This is due to the absence of a universally accepted reference material, which manufacturers need to calibrate their assays to a common standard.

Instead, test results must be interpreted using assay-specific reference intervals—a concept that comes naturally to clinical laboratorians but often is foreign to many physicians and patients. This lack of uniform results causes confusion that can adversely affect patient care, particularly when patients are diagnosed at one hospital but pursue follow-up care elsewhere. For example, does an increased CA-125 value at follow-up at a different institution reflect disease progression or simply differences in assay calibration? A lack of standardization also makes it impossible to transfer diagnostic cutoffs from one institution to another unless the assay platforms are identical.

Given the confusion associated with non-standardized assays, why haven’t all immunoassays already been standardized?

Read more: Standardizing Immunoassays: The Benefits of Conformity

Source: alfa

Laboratorians Working with Nurses to Make Lab Systems Safer

Both nurses and laboratorians get frustrated with each other’s behavior. For example, nurses may not understand or follow certain procedures as outlined by the laboratory.

In a recent article published in Clinical Laboratory News, James Hernandez, M.D., Associate Professor of Laboratory Medicine and Pathology, and Medical Director and Chair of the Division of Laboratory Medicine at Mayo Clinic in Scottsdale and Phoenix, Arizona, provides an overview of the working relationship between nurses and laboratory technicians.

Dr. Hernandez identifies fictional scenarios of nurses’ behavior that potentially could confound the laboratory and create conflict. He then analyzes each scenario to determine why nurse acted as he or she did and how to handles the situation effectively and gracefully.

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Source: mayomedicallaboratories

Diabetes Testing on High-Throughput Analyzer Files for FDA Approval

The cobas c513 analyzer has been submitted to the US Food and Drug Administration (FDA) for approval as a dedicated, high-throughput HbA1c testing solution to help laboratories meet increasing testing needs for people with diabetes.

The cobas c513 analyzer from Roche (Basil, Switzerland) is based on the proven, trusted cobas technology developed in cooperation with Hitachi High-Technologies (HHT). The HbA1c test is a longer term measurement of blood sugar levels used to determine if a person has or is at risk of developing diabetes. Set to run on the established Tina-Quant HbA1c A1cDx Gen.3 test, which is also used across the Roche laboratory HbA1c portfolio, the cobas c513 will ensure high-quality results and comply with current guidelines and recommendations for HbA1c testing and measures A1c as defined by the IFCC.

cobas c513 features direct results reporting, thereby minimizing risk of result misinterpretation and eliminating the need to perform time-consuming, manual result interpretation. This feature will help save valuable time and laboratory resources, while ensuring high-quality results. Furthermore, cobas c513 will provide a higher on-board test capacity, enabling laboratories to load the analyzer with more tests at a time, save lab space, minimize resources, and ensure a smooth workflow.

Read more: Diabetes Testing on High-Throughput Analyzer Files for FDA Approval

The cobas c513 analyzer provides throughput of up to 400 HbA1c patient results/hour, closed

tube sampling (CTS), and is standardized according to IFCC transferable to DCCT/NGSP

Source: Roche

Rapid Detection of Urinary Biomarkers with Novel Optical Device

A compact optical device has been developed that can rapidly and sensitively detect biomarkers in urine and has promise for developing simple point-of-care diagnostics of cancer and other diseases.

Micro ribonucleic acids (miRNAs) are a newly discovered class of short, about 19 to 24 nucleotides in length, fragments of noncoding RNAs that are useful biomarkers for diagnosing various diseases, including cardiac disease and some cancers. Since they are surprisingly well preserved in fluids such as urine and blood, their detection is well suited to a rapid, point-of-care method.

Bioengineers at the Agency for Science, Technology and Research (Singapore) have devised a silicon photonic biosensor that can detect tiny changes in the phase of a light beam caused by hybridization between an immobilized DNA probe and target miRNAs in a sample. A laser beam travels through a waveguide, which splits into two arms: a sensing arm in which the light interacts with the sample and a reference arm.

Read more: Rapid Detection of Urinary Biomarkers with Novel Optical Device

Image: Schematic diagram of the MZI biosensor system for miRNA detection.

(a) TEM image of the cross section of a silicon nitride slot wave guide; SEM images of

(b) a strip-slot wave guide mode converter and (c) a silicon nitride grating coupler.

(d) Image of MZI biosensor platform

Source: Agency for Science, Technology and Research

Colorectal cancer

Colorectal cancer had a low incidence several decades ago. However, it has become a predominant cancer and now accounts for approximately 10% of cancer-related mortality in western countries. The ‘rise’ of colorectal cancer in developed countries can be attributed to the increasingly ageing population, unfavourable modern dietary habits and an increase in risk factors, such as smoking, low physical exercise and obesity. New treatments for primary and metastatic colorectal cancer have emerged, providing additional options for patients; these treatments include laparoscopic surgery for primary disease, more-aggressive resection of metastatic disease (such as liver and pulmonary metastases), radiotherapy for rectal cancer, and neoadjuvant and palliative chemotherapies. However, these new treatment options have had limited impact on cure rates and long-term survival. For these reasons, and the recognition that colorectal cancer is long preceded by a polypoid precursor, screening programmes have gained momentum. This Primer provides an overview of the current state of the art of knowledge on the epidemiology and mechanisms of colorectal cancer, as well as on diagnosis and treatment.

Introduction

We live in an era with improved worldwide average living standards and increased access to adequate health care that has considerably improved the diagnosis and treatment of diseases. These measures have had an effect on the average life expectancy in most regions of the world. However, although death rates from communicable diseases have improved globally as a result of these medical improvements, cancer-related mortality has increased by almost 40% over the past 40 years. A further 60% increase is expected in the next 15 years, with 13 million people estimated to die of cancer in 2030. The main causes of cancer-related mortality have also changed, attributable to alterations in disease incidence, the introduction of screening programmes and therapeutic improvements. Colorectal cancer was rather rare in 1950, but has become a predominant cancer in western countries, now accounting for approximately 10% of cancer-related mortality. Reasons explaining this increased incidence include an ageing population and the preponderance of poor dietary habits, smoking, low physical activity and obesity in western countries. The change in incidence is not only apparent in the rates of sporadic disease but also in some familial cancer syndromes. Indeed, given that the rates of Helicobacter pyloriinfection (a causative factor of gastric cancer) have fallen dramatically, colorectal cancer is now the predominant presentation of Lynch syndrome (a hereditary non-polyposis type of colorectal cancer), whereas carriers of this syndrome used to be predominantly affected by gastric cancer.

Read more: Colorectal cancer

Source: krmc