Sickle Cell Disease Treatment

Presently, there is no proven cure for sickle cell disease. Bone marrow transplants are currently being considered as a potential cure, but research and experiments are still in progress. Treatment for sickle cell mainly involves the management and prevention of symptoms.

Various medications are often used for the treatment of sickle cell symptoms. Antibiotics, mainly penicillin, are prescribed for children between the ages of 2 months and 5 years to prevent pneumonia and other infections. Immunizations may also be effective in preventing infections in children. Pain relieving medications are prescribed as well as hydroxyurea to reduce the frequency of pain and may even reduce the need for blood transfusions. Hydroxyurea stimulates the production of fetal hemoglobin which in turn helps prevent the formation of sickle cells. This drug is no frequently used because it increases the risk for infections and may cause tumors or leukemia in certain situations.

Blood transfusions are also an option when helping to control sickle cell disease. Blood transfusions increase the number of normal red blood cells in the circulation and help to relieve anemia and decrease the risk of stroke. Although there are many benefits to blood transfusions, regularly transfused patients have a risk of heart, liver, and other organ damage due to the build up of excess iron in the body. Medication may be prescribed to reduce the excess levels of iron if the problem persists.

Bone marrow transplants are only recommended for patients with significant symptoms and problems from sickle cell disease. Healthy bone marrow from a donor replaces the marrow affected by sickle cell disease. The diseased marrow is first depleted by radiation or chemotherapy and the healthy stem cells are filtered from the blood of the donor and injected into the bloodstream of the patient with the disease. These healthy cells migrate to the bone marrow cavities where they begin producing new blood cells. This procedure is not used often due to the scarcity of donors, lengthy hospital stays, and possible rejection of the transplant.

This video shows a bone marrow aspiration.

See what's in you lens solution?

It is estimated that about 36 million Americans wear contact lenses. While contacts are effect at helping people see, there is also a chance that contacts and their cleaning solutions can lead to eye infections. The two most common eye infections are conjunctivitis and keratitis; which is caused by the bacteria Staphylococcus aureus and Pseudomonas aeruginosa.

Keratitis is an infection of the clear, round dome that covers the iris and pupil called the cornea. It causes pain, reduced vision, sensitivity to light and discharge from the eye. Bacterial keratitis usually develops very quickly and can cause blindness if left untreated. This type of infection may be superficial and only affect the top layers of the cornea, or deep and may leave scars. It is estimated that 30,000 people in the US are affected annually by bacterial keratitis. Contact lens wearers are at the greatest risk because contaminated lens solution and overnight contact wear are the biggest risk factors for acquiring the bacteria. 

For the diagnosis of keratitis, corneal ulcer scrapings are obtained and cultured onto chocolate, sheep blood, and Sabouraud agar. Samples of the eyelids, conjunctiva, contact lens cases, and lens solution may also be plated. Cotton swabs are not recommended because they contain fatty acids which may inhibit the growth of the bacteria. Once diagnosed, bacterial keratitis is treated with the antibiotics moxifloxacin and gatifloxacin.

Bacterial keratitis is easily preventable. Contact lens wearers should:

ALWAYS

• Wash hands properly with soap and water and dry them before handling contact lens, contact lens solutions or related accessories.
• Cleanse and disinfect your contact lens properly according to instruction.
• Have regular check-ups by your optometrist or ophthalmologist.
• Follow the professional advice from your optometrist or ophthalmologist.
• Take off the contact lens whenever you feel discomfort or redness and seek your optometrist's or ophthalmologist's advice.
• Seek medical advice from your doctor promptly if symptoms (redness, pain, blurring of vision or photophobia) persist despite removal of contact lens.

NEVER

• Wet your lens with saliva, tap water or bottled water.
• Wear your lens while swimming, taking shower, using hot tub or sauna.
• Sleep with your lens on.
• Wear them beyond the recommended period.  

Malarial Resistance

Each year, malaria affects about 400 million people, with a death rate of two to three million. Since the malarial parasite is constantly changing, and effective vaccine has yet to be developed. The sickle cell gene mutation has been shown to have an effective resistance to the malarial parasite for carriers of the gene. Carriers for the sickle cell trait have one sickle cell gene and one normal hemoglobin gene.

The sickle hemoglobin has been shown to impair malaria growth and development because of the change in the hemoglobin. Sickle cell trait does not provide complete protection against the parasite but those infected with P. falciparum are more likely to survive the acute illness. Most of this protection occurs between 2-16 months of life. This relationship was initially discovered when a correlation was found between the distribution of the gene for hemoglobin S and the distribution of malaria in Africa.

In a normal environment, the red cells of people with sickle cell remain normal and only sickle when venous oxygen levels are low. P. falciparum reduces the oxygen tension within the red cells to very low levels when it carries out its metabolism and causes the cells to sickle more readily. The deforming of these cells makes them a target for destruction by phagocytes and they are removed form the circulation and destroyed. The selective sickling of the infected cells reduces the parasite population in people with sickle cell and puts them at a greater chance to survive acute infections caused by malarial parasites. The CDC has determined that the sickle cell trait provides 60% protection against overall mortality caused by malaria.

Do You Want Flies With That?

The Fourth of July is coming up soon which means celebrations with fireworks and cookouts. While we all know to be careful with fireworks, eating outdoors may also be a cause for concern. Shigella sp is a bacteria that causes bacterial dysentery and is transmitted by feces, fingers, food, and even flies. Food left uncovered outdoors can be very enticing to flies. These flies may breed in infected feces and then contaminate the uncovered food.

Shigella spp are divided into four sup groups including S. dysenteriae, S. flexneri, S. boydii, and S. sonnei. S. sonnei is the most common group found in North America and causes around 14,000 cases of shigellosis each year.This bacteria is so potent that even the ingestion of as few as 10-100 organisms can cause an infection. Symptoms include high fever, chills, abdominal cramps, and pain and appear 1-2 days after ingestion while dysentery results after 1-3 days when the bacteria migrate from small intestine to the colon. Shigellosis is short lived with infections lasting from 5-7 days and most people affected are not hospitalized. Most patients that are hospitalized are elderly or children younger than two. Even if an infected person is asymptomatic, they can still spread Shigella sonnei to other persons.

S. sonnei is a gram negative, nonmotile, bacilli that closely resembles E. coli. Although it is resistant to many antibiotics, S. sonnei may be treated with ampicillin, trimethoprim/sulfamethoxazole , nalidixic acid, ciprofloxacin.

Prevention of Shigella sonnei can be easily resolved by hand washing, proper food preparation, and proper food storage. People should wash their hands before eating or preparing food and meat should be cooked at the proper temperature to ensure that any bacteria is killed. When outside, food should be covered so flies cannot come into contact and contaminate it. 

Commonly used methods for sickle cell disease screening

There are many different methods for screening for sickle cell disease. Then two most commonly used methods are isoelectric focusing and high performance liquid chromatography.

In isoelectric focusing, proteins are separated based on their specific isoelectric point. This point is determined by the pH in which the protein has no charge and does not migrate farther down the electric field. The specimen is added to a polyacrylamide gel attached to an electrical field and migrates from cathode to anode. The typical analytical run time for one test of ten samples to complete is 2.5 hours. The results are seen as sharp bands in their respective isoelectric points and are automatically calculated to show the percentages of each type of hemoglobin detected. Isoelectric focusing provides clearer banding patterns which are not affected by the analyte degrading in the blood spots. Because this method is not automated, the testing process is labor intensive and time consuming.

High performance liquid chromatography is ten times more expensive than isoelectric focusing. In this method, unknown hemoglobins are identified by comparing their retention times against a standard calibration curve. Test runs were considered normal with the presence of peaks in the zones representing HbF and HbA. Although variants are distinct, the presence of HbS in a specimen may interfere with the accurate HbA₂ measurement which identifies β-thalassemia. In a recent study, automated high performance liquid chromatography was calculated to have a coefficient of variation between 0.9-1.8% for the precision of retention times and a coefficient of variation of 4.4-17.5% for the precision of quantification. The retention times were shown to be within 0.01 minutes of the specified identification window. The results of this study showed this method to be an accurate and precise assay for the detection of abnormal hemoglobins.


Check out this journal article for more information

Confusing bacteria

Arcanobacterium haemolyticum is a gram positive rod with a matchbox or Chinese letter orientation. It was first discovered and described in 1946 in servicemen and people from the South Pacific. When plated out, the colony is small with a narrow zone of beta hemolysis and pits the agar. This organism has been a topic of controversy due to its resemblance to Corynebacterium pyogenes; because of this resemblance, A. haemolyticum was originally classified within the Corynebacterium genus with the subspecies hominis. Since this bacteria resembles Streptococcus pyogenes, the two are often confused and can be differentiated by the gram stain, inverse CAMP, and catalase reaction. This confusion was later resolved in 1982 when a new genus was created and this organism was renamed. The genus Arcanobacterium means secretive bacteria and is based on the characteristics of its fatty acid, peptidoglycan, and DNA.
Arcanobacterium haemolyticum typically infects teenagers and young adults aged 15 to 25 and is usually found in immunocompromised people. It is transmitted person to person through respiratory droplets and is found in the pharynx as well as the skin but there are no known risk factors. This bacteria causes pharyngitis, tonsillitis, and cellulitis. A rash believed to be caused by an exotoxin may be seen on the chest, abdomen, neck, and extremities in 20-25% of cases and can lead to diagnostic errors. The most common symptoms associated with A. haemolyticum are sore throat, pruritus, fever, pharyngeal erythema, and a nonproductive cough.

Arcanobacterium haemolyticum is usually treated with erythromycin, clindamycin, gentamicin, or cephalosporins. Serious infections may be treated with parenteral antimicrobial drugs.

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Introduction to Sickle Cell

Sickle cell disease is one of the most common monogenic diseases in the world with an approximated 7% of the world heterozygous carriers resulting in 300,000 newborns with severe hemoglobinopathies. It is an autosomal blood disease that causes the sickling of red blood cells. This sickle shape can lead to the development of cerebrovascular disease as well as cognitive impairment in children. If left untreated, it may also result in damage to organs such as the brain, kidneys, lungs, bones, and cardiovascular system. The sickling of red cells is caused at the sixth codon for the beta globin gene where glutamine is substituted for valine and has 900 different variants, most of which are not clinically significant. The sickling of these cells occurs due to a mutation in the hemoglobin gene and affects the ability of the hemoglobin to bind and release oxygen. This mutation results in crystallization that produces a polymer nucleus which grows and fills the cells, in turn disrupting the flexibility of the cell and causing dehydration. This can lead to a number of various complications, including a shortened life expectancy.

Sickle cell disease occurs in approximately 1 out of every 2500 newborns with black and Hispanic infants representing the majority. In infants, HbF is the major gene involved in determining the severity of the disease. Individuals who presented with a higher level of HbF generally had milder symptoms and fewer complications. Diagnosis of this disorder is based on the determination of variants of hemoglobin. Several newborn screening methods are currently being practiced; mainly isoelectric focusing and high performance liquid chromatography.

Check out this video for an animation of the sickle cell mutation in the blood.