CTA sugars Neisseria
Bulls eye colonies Yersinia enterocolitica
CNA agar Staphylococcus
Sorbitol MacConkey E coli 0157H7
Alkaline peptone water Vibrio
Red colonies with black centres Salmonella
Coag neg MSA neg DNAse neg novobiocin R S saprophyticus
Kauffman White scheme Salmonella
Lancefield grouping Streptococcus
Impetigo S aureus
Bacitracin R halophile S aureus
MRSA S aureus
CAMP reaction with arrowhead haemolysis S agalactiae
Bacitracin S, Beta haemolytic GPC S pyogenes
Draughtsman colonies S pneumoniae
Increased haemolysis in CO2 Streptococcus
R to trimeth and sulphamethoxazole S pyogenes
GN diplococcic Neisseria
Opthalmia neonatorium N gonorrhoeae
Kidney shaped IC to neutrophils Neisseria
Growth on BA/CHOC at room temp, and NA at 37 degrees Non pathogenic Neisseria, i.e. commensals
Anorectal, conjunctival and oropharyngeal specimens N gonorrhoeae
MTM agar Neisseria
NYC agar Neisseria
HUS E coli 0157H7 or EHEC
CIN agar Y enterocolitica
Non motile at 37, motile at room temp Yesrsinia except pestis
Friday, March 4, 2011
Thursday, March 3, 2011
haemolytic disease of the newborn (HDN)
This is a disease of the newborn characterised by massive intravascular and extravascular lysis of red blood cells due to a Rhesus incompatibility.
This is what happens in HDN:
PS Please read Rhesus typing first, in order to appreciate this
a mom is Rhesus negative, pregnant with a baby from a Rhesus positive father. In most cases the baby will be Rhesus positive.
The situation i am going to describe is what happens in a normal pregnancy, no trauma, no placenta abruptio, etc
The mom's blood circulates through the baby, and never vice versa
So the D antigen in the baby never comes into contact with the mom'c immune system.
During delivery, when the placenta breaks, there is mixing of the baby's and mom's blood. D from the baby comes into contact with the mom's immune system and she, naturally, produces anti D.
If, at this stage, nothing is done, the antiD will remain in the mom, quietly waiting.....
In the next pregnancy from the same father, mom's blood is circulating through the baby. AntiD from the mom will now agglutinate the D of/in the baby, leading to HDN.
Can you imagine the consequences of this.....this tiny little baby, still in utero, having all or almost all its RBC haemolysed? so is there no hope for little Keith??????
weel if this situation was allowed to develop, doctors can do an exchange transfusion either in utero or after the baby is born. Basically quite dangerous but there have been some successes. The baby's blood is removed, a little at a time, and fresh blood from a donor is transfused into the baby. All sorts of possible transfusion reactions , but that will keep for another post. Ta Ta
This is what happens in HDN:
PS Please read Rhesus typing first, in order to appreciate this
a mom is Rhesus negative, pregnant with a baby from a Rhesus positive father. In most cases the baby will be Rhesus positive.
The situation i am going to describe is what happens in a normal pregnancy, no trauma, no placenta abruptio, etc
The mom's blood circulates through the baby, and never vice versa
So the D antigen in the baby never comes into contact with the mom'c immune system.
During delivery, when the placenta breaks, there is mixing of the baby's and mom's blood. D from the baby comes into contact with the mom's immune system and she, naturally, produces anti D.
If, at this stage, nothing is done, the antiD will remain in the mom, quietly waiting.....
In the next pregnancy from the same father, mom's blood is circulating through the baby. AntiD from the mom will now agglutinate the D of/in the baby, leading to HDN.
Can you imagine the consequences of this.....this tiny little baby, still in utero, having all or almost all its RBC haemolysed? so is there no hope for little Keith??????
weel if this situation was allowed to develop, doctors can do an exchange transfusion either in utero or after the baby is born. Basically quite dangerous but there have been some successes. The baby's blood is removed, a little at a time, and fresh blood from a donor is transfused into the baby. All sorts of possible transfusion reactions , but that will keep for another post. Ta Ta
Chempath test 3
1. Multiple choice: Choose the correct answer; showing how you obtained your answer
1.1 What is the molarity of a solution that contains 18.7g of KCl in 500 ml?
0.1
0.5
1.0
5.0
1.2 How much 95% alcohol is required to prepare 5 L 70% alcohol?
A. 2.4 L
B 3.5 L
3.7 L
4.4 L
How many milliliters of concentrated H2SO4 (100%) are required to prepare 10L of 0.1 M H2SO4?
A. 1.84
9.20
27.5
54.9
In a spectrophotometric procedure that follows Beer’s law, the absorbance of a standard solution of concentration 15 g/L is 0.50 in a 1 cm cell. The absorbance of the sample solution is 0.62. What is the concentration?
0.62 g/L
6.2 mol/L
12.1 g/L
18.6 g/L
1.5 How many grams of Na0H are required to prepare 2500 mL of a 4 M solution?
40
100
160
400
1.6 An isotonic saline solution contains 0.85% NaCl. How many grams of
NaCl are needed to 5 L of this solution?
4.25
8.5
42.5
170
How many milliliters of concentrated HN03 are required to prepare 2 L of 0.15 N HN03?
13.3
19.0
38.0
189.9
An analysis for sodium is performed on an aliquot of a 24- hour urine specimen. A sodium value of 122.5 mmol/l is read from the instrument. What is the amount of sodium in the 24hr urine specimen if 1540 mL of urine are collected?
79.5
188.6
1886.5
18,865
8 x 2 = 16
Additional information: Molar mass:
K 39 Cl 35.5 H 1 S 32 O 16 N 14 Na 23 C 12
2. Grace, a 49 year-old woman was admitted to the Inkosi Albert Luthuli Central Hospital for cataract extraction. Her eyesight was deteriorating but otherwise she was in good health. In 1990 Grace had undergone thyroidectomy for a multinodular goiter. Routine investigations were carried out using a blood sample from the patient.
Tests
Serum
Calcium 1.66 mmol/l
Phosphate 2.65 mmo/l
Albumin 42 g/l
Alkaline phosphatase 65 IU/L
2.1 Comment on the results. [6]
2.2 What was the main clue for the diagnosis apart from the patient’s results? [1]
3. After a phosphorous analysis using the molybdate method without a reducing agent, the following absorbance readings were obtained:-
Standard (1.6 mmol/l) 0.414
Standard 0.418
Normal control 0.380
Serum A 0.678
Serum B 0.350
Urine sample C (diluted 1 in 5) 0.204
(Volume 1567)
Calculate the phosphorus concentration for all specimens/controls.
If the mean target value for the normal control is 1.41 mmol/l and the SD is 0.10; is your batch of results within acceptable limits?
Which of the two serum samples gives an abnormal result? Can you give a possible cause for it?
Describe the principle of the method used.
Discuss all the precautions that must be taken when a serum sample is taken for phosphate determination. [20]
4. A 50-year-old man presented with weight loss and weakness. The time of the year was winter but his skin was noticeably bronzed. On examination, he was found to have hepatosplenomegaly.
Investigations
Urine positive for glucose
Blood sugar 12 mmol/l
Serum
Iron 58 µmol/l
Transferrin 2.15 g/l
Ferritin 3500 µg/ml
4.1 Predict the diagnosis of the patient. Justify your answer with explanations and show calculations. [8]
5. Provide an explanation / reasons for the following:
Tumor markers are processed in a batch.
Two – way traffic of samples and reports.
Receptions area should be free of clutter.
Bulk of the work is done in the first shift.
Transcription mistakes are not allowed.
[10]
6. Complete the following table.
Laboratory markers of iron status in Disease States
Conditions Serum Iron Transferrin Ferritin % Saturation
Malnutrition 6.1 Variable
Malignancy 6.2
Chronic infection 6.3
Viral hepatitis 6.4
Anaemia of chronic disease 6.5 Normal/
Sideroblastic anaemia Normal / 6.6
Iron deficiency 6.7 6.8
Iron poisoning / overdose 6.9
Haematochromatosis 6.10
[10]
7. Make recommendations of how space could be best utilized when designing a laboratory.
[4]
1.1 What is the molarity of a solution that contains 18.7g of KCl in 500 ml?
0.1
0.5
1.0
5.0
1.2 How much 95% alcohol is required to prepare 5 L 70% alcohol?
A. 2.4 L
B 3.5 L
3.7 L
4.4 L
How many milliliters of concentrated H2SO4 (100%) are required to prepare 10L of 0.1 M H2SO4?
A. 1.84
9.20
27.5
54.9
In a spectrophotometric procedure that follows Beer’s law, the absorbance of a standard solution of concentration 15 g/L is 0.50 in a 1 cm cell. The absorbance of the sample solution is 0.62. What is the concentration?
0.62 g/L
6.2 mol/L
12.1 g/L
18.6 g/L
1.5 How many grams of Na0H are required to prepare 2500 mL of a 4 M solution?
40
100
160
400
1.6 An isotonic saline solution contains 0.85% NaCl. How many grams of
NaCl are needed to 5 L of this solution?
4.25
8.5
42.5
170
How many milliliters of concentrated HN03 are required to prepare 2 L of 0.15 N HN03?
13.3
19.0
38.0
189.9
An analysis for sodium is performed on an aliquot of a 24- hour urine specimen. A sodium value of 122.5 mmol/l is read from the instrument. What is the amount of sodium in the 24hr urine specimen if 1540 mL of urine are collected?
79.5
188.6
1886.5
18,865
8 x 2 = 16
Additional information: Molar mass:
K 39 Cl 35.5 H 1 S 32 O 16 N 14 Na 23 C 12
2. Grace, a 49 year-old woman was admitted to the Inkosi Albert Luthuli Central Hospital for cataract extraction. Her eyesight was deteriorating but otherwise she was in good health. In 1990 Grace had undergone thyroidectomy for a multinodular goiter. Routine investigations were carried out using a blood sample from the patient.
Tests
Serum
Calcium 1.66 mmol/l
Phosphate 2.65 mmo/l
Albumin 42 g/l
Alkaline phosphatase 65 IU/L
2.1 Comment on the results. [6]
2.2 What was the main clue for the diagnosis apart from the patient’s results? [1]
3. After a phosphorous analysis using the molybdate method without a reducing agent, the following absorbance readings were obtained:-
Standard (1.6 mmol/l) 0.414
Standard 0.418
Normal control 0.380
Serum A 0.678
Serum B 0.350
Urine sample C (diluted 1 in 5) 0.204
(Volume 1567)
Calculate the phosphorus concentration for all specimens/controls.
If the mean target value for the normal control is 1.41 mmol/l and the SD is 0.10; is your batch of results within acceptable limits?
Which of the two serum samples gives an abnormal result? Can you give a possible cause for it?
Describe the principle of the method used.
Discuss all the precautions that must be taken when a serum sample is taken for phosphate determination. [20]
4. A 50-year-old man presented with weight loss and weakness. The time of the year was winter but his skin was noticeably bronzed. On examination, he was found to have hepatosplenomegaly.
Investigations
Urine positive for glucose
Blood sugar 12 mmol/l
Serum
Iron 58 µmol/l
Transferrin 2.15 g/l
Ferritin 3500 µg/ml
4.1 Predict the diagnosis of the patient. Justify your answer with explanations and show calculations. [8]
5. Provide an explanation / reasons for the following:
Tumor markers are processed in a batch.
Two – way traffic of samples and reports.
Receptions area should be free of clutter.
Bulk of the work is done in the first shift.
Transcription mistakes are not allowed.
[10]
6. Complete the following table.
Laboratory markers of iron status in Disease States
Conditions Serum Iron Transferrin Ferritin % Saturation
Malnutrition 6.1 Variable
Malignancy 6.2
Chronic infection 6.3
Viral hepatitis 6.4
Anaemia of chronic disease 6.5 Normal/
Sideroblastic anaemia Normal / 6.6
Iron deficiency 6.7 6.8
Iron poisoning / overdose 6.9
Haematochromatosis 6.10
[10]
7. Make recommendations of how space could be best utilized when designing a laboratory.
[4]
Chempath test 2
1. State whether the following statements are true or false. If false, correct the statement. [½ mark for True or False – 1 mark for an explanation of the incorrect statement]
In a work flow system, input refers to specimens, request forms and reagents.
For critical care patients, specimens are collected less frequently.
PTH is present in skin and from diet.
One of the causes of hyperphoshatemia is hypothyroidism.
EGTA binds to Mg so that one can measure the calcium content in the patient’s sample.
Aldosterone is antagonistic in that it increases serum Mg by promoting excretion by kidney.
Iron transport is via transferrin where each molecule binds two Fe 2+ ions.
A fetal lung maturity is when the LSAR may be 1.5, PG positive.
[10]
2. Calculate the recovery of the following Fe sample.
Sample 1: 1.0 ml serum + 0.2 ml H2O
Sample 2: 1.0 ml serum + 0.2 ml 10 µmol/l standard
Concentration:
Fe measured
Sample 1 31.0 µmol/l
Sample 2 32.5 µmol/l
[9]
3. Compare diagrams of LSAR in patients with lung maturity and lung immaturity. [6]
4. Write all the precautions of the globulin test for CSF measurement. [4]
5. Compare the laboratory findings of a patient with an exudate to that of another patient with a transudate effusion.
[9]
6. Explain all the factors to be taken when iron is measured. [8]
7. A 21 female with dizzy spells went the local clinic as this was affecting her work at the factory where she was employed. The doctor examined her and had blood samples taken and were sent to the laboratory. A report from the new automated analyser showed the following:
Serum iron: 0.007 mmol/l
7.1 Predict the doctor’s diagnosis based on the result obtained. [3]
7.2 Select the tests that may be done on the above patient. [3]
7.3 Comment on the units of the result. [1]
8. Make recommendations of how space could be best utilized when designing a laboratory. [10]
9. Determine the molarity of a bottle of glacial acetic acid, which has a specific gravity of 1.046 g/ml and a percent assay of 99.2%. [5]
10. A report on a male patient read as follows:
Calcium : 2.25 mmol/l
Phosphate : 0.90 mmol/l
Magnesium : 0.51 mmol/l
10.1 Explain the above results and give the possible diagnosis. [Give reasons for the abnormal result(s)] [7]
10.2 What would the treatment be for the above patient? [1]
[Additional Information: Mass C = 12 H =1 O =12]
In a work flow system, input refers to specimens, request forms and reagents.
For critical care patients, specimens are collected less frequently.
PTH is present in skin and from diet.
One of the causes of hyperphoshatemia is hypothyroidism.
EGTA binds to Mg so that one can measure the calcium content in the patient’s sample.
Aldosterone is antagonistic in that it increases serum Mg by promoting excretion by kidney.
Iron transport is via transferrin where each molecule binds two Fe 2+ ions.
A fetal lung maturity is when the LSAR may be 1.5, PG positive.
[10]
2. Calculate the recovery of the following Fe sample.
Sample 1: 1.0 ml serum + 0.2 ml H2O
Sample 2: 1.0 ml serum + 0.2 ml 10 µmol/l standard
Concentration:
Fe measured
Sample 1 31.0 µmol/l
Sample 2 32.5 µmol/l
[9]
3. Compare diagrams of LSAR in patients with lung maturity and lung immaturity. [6]
4. Write all the precautions of the globulin test for CSF measurement. [4]
5. Compare the laboratory findings of a patient with an exudate to that of another patient with a transudate effusion.
[9]
6. Explain all the factors to be taken when iron is measured. [8]
7. A 21 female with dizzy spells went the local clinic as this was affecting her work at the factory where she was employed. The doctor examined her and had blood samples taken and were sent to the laboratory. A report from the new automated analyser showed the following:
Serum iron: 0.007 mmol/l
7.1 Predict the doctor’s diagnosis based on the result obtained. [3]
7.2 Select the tests that may be done on the above patient. [3]
7.3 Comment on the units of the result. [1]
8. Make recommendations of how space could be best utilized when designing a laboratory. [10]
9. Determine the molarity of a bottle of glacial acetic acid, which has a specific gravity of 1.046 g/ml and a percent assay of 99.2%. [5]
10. A report on a male patient read as follows:
Calcium : 2.25 mmol/l
Phosphate : 0.90 mmol/l
Magnesium : 0.51 mmol/l
10.1 Explain the above results and give the possible diagnosis. [Give reasons for the abnormal result(s)] [7]
10.2 What would the treatment be for the above patient? [1]
[Additional Information: Mass C = 12 H =1 O =12]
chem path test1
Katie is a 35 year old woman with ulcerative colitis presented with diarrhoea and passing blood with her stools. Her HB level was 8.5 g/dl and there was moderate microcytosis and hypochromia. Her plasma iron and ferritin studies revealed:
Plasma
Iron 4 µmol/l
Transferrin 1.5 g/l
% saturation 11.89
Ferritin 33 µg/l
1.1 Comment on the diagnosis of Katie. [7]
Indicate treatment for Katie. [1]
2. The following sets of results were from a 65 year –old woman admitted to the coronary care unit because of chest pain. The ECG and plasma enzyme studies did not reveal a myocardial infarct:
Plasma:
Na 139 mmol/l
K 3.9 mmol/l
Cl 103 mmol/l
HCO3- 25 mmol/l
Urea 6.1 mmol/l
Creat 105 µmol/l
Ca 2.22 mmol/l
PO4 0.86 mmol/l
Mg 0.60 mmol/l
Alb 35 g/l
2.1 Comment on the patient’s results. [10]
Discuss the homeostasis of magnesium. [4]
3. Sharan is a Technologist – in - charge of a private lab. She reports to the lab manager, Tembe who in turn reports to the Pathologist Prof Mokoena. There are 3 qualified Med techs viz. Susan, Prinivan and Dorothy who reports to the QC officer Kinon, Senior med Tech Faizel and senior med Tech Sne’ respectively. Kinon, Faizel and Sne’ reports to Parvathy who is the 2IC. Prinivan’s subordinate is the student med Tech Jabu while the Technician Harry reports to Dorothy. The Technician handles all Peter’s day –to –day matters. Peter is a General assistant. Draw an organogram for this private lab, showing names and titles. [13]
Gives reasons/ explanation of the following:
Patients are bled in a quiet and pleasant area.
“Shute” or vacuum system for specimens.
Urgent specimens are distinguished in the lab
Treatment of Stat samples in a private lab.
Most work is done in the first shift.
Transcription errors are not allowed.[Give an example of an error of this type]
Laboratory staff are always rotated.
Most labs have a 3 way interface system
The two-way traffic in public hospitals has huge benefits.
Card board boxes are not stacked at lab exits.
[10]
Multiple choices. Show working / explanation and give the correct answer.
Calculate the coefficient of variation for a set of data where the mean = 89 mmol/l and the 2 standard deviations = 14.
7.8
7.9
15.7
15.8
A CSF specimen is sent to the lab @ 9 pm for glucose analysis. The specimen is cloudy and appears to contain red blood cells. Which of the following statements is true?
Glucose testing cannot be performed on the specimen
Specimen should be centrifuged and the glucose test run immediately.
Specimen can be refrigerated as received and the glucose run the next day.
Specimen can be frozen as received and the glucose run the next day.
Xanthrochromasia of cerebrospinal fluid may be due to increased levels of which of the following?
Chloride
Protein
Glucose
Magnesium
With the development of fetal lung maturity, which of the following phospholipid concentrations in amniotic fluid significantly and consistently increases?
Sphingomyelin
Phosphatidyl ethanolamine
Phosphatidyl inositol
Phosphatidyl choline
Which of the following is characteristic of an exudates effusion?
Leukocyte count greater than 1000 /µl
Cloudy appearance
Protein concentration less than 3.0 g/dl
Absence of fibrinogen
How many millilitres of concentrated H2SO4 ( sp gravity = 1.84g/ml; assay =97%) are required to prepare 10 L of a 0.1 N H2SO4
1.84
9.20
27.5
54.4
How many grams of NaOH are required to prepare 2500 ml of a 4 M solution?
40
100
160
400
Because of a malfunction, a spectrophotometer is able to show only the percent transmittance (%T) readings on the digital display. Convert 68.0%T to its corresponding absorbance.
0.109
0.168
0.320
0.495
How many grams of a NaOH are required to prepare 500ml of a 0.02N solution?
0.4
0.8
4.0
8.0
How much CaSO4 should be weighed out to prepare one litre of a 0.5 M solution of Ca SO4?
a. 6.8g
b. 0.68g
c. 6800g
d. 68 g
[10 x2 = 20]
6. A lumbar puncture is performed for suspected meningitis.
6.1 Explain the significance of the globulin test in CSF. [2]
6.2 Give the significance of a raised glucose level in CSF. [3]
7. Describe the interfering factors that may give false results in the occult blood test.
[3]
8. With the aid of a diagram show a LSAR chromatography plate indicating a possible
negative and a positive lung maturity. Show calculations of LSAR patterns. [7]
Plasma
Iron 4 µmol/l
Transferrin 1.5 g/l
% saturation 11.89
Ferritin 33 µg/l
1.1 Comment on the diagnosis of Katie. [7]
Indicate treatment for Katie. [1]
2. The following sets of results were from a 65 year –old woman admitted to the coronary care unit because of chest pain. The ECG and plasma enzyme studies did not reveal a myocardial infarct:
Plasma:
Na 139 mmol/l
K 3.9 mmol/l
Cl 103 mmol/l
HCO3- 25 mmol/l
Urea 6.1 mmol/l
Creat 105 µmol/l
Ca 2.22 mmol/l
PO4 0.86 mmol/l
Mg 0.60 mmol/l
Alb 35 g/l
2.1 Comment on the patient’s results. [10]
Discuss the homeostasis of magnesium. [4]
3. Sharan is a Technologist – in - charge of a private lab. She reports to the lab manager, Tembe who in turn reports to the Pathologist Prof Mokoena. There are 3 qualified Med techs viz. Susan, Prinivan and Dorothy who reports to the QC officer Kinon, Senior med Tech Faizel and senior med Tech Sne’ respectively. Kinon, Faizel and Sne’ reports to Parvathy who is the 2IC. Prinivan’s subordinate is the student med Tech Jabu while the Technician Harry reports to Dorothy. The Technician handles all Peter’s day –to –day matters. Peter is a General assistant. Draw an organogram for this private lab, showing names and titles. [13]
Gives reasons/ explanation of the following:
Patients are bled in a quiet and pleasant area.
“Shute” or vacuum system for specimens.
Urgent specimens are distinguished in the lab
Treatment of Stat samples in a private lab.
Most work is done in the first shift.
Transcription errors are not allowed.[Give an example of an error of this type]
Laboratory staff are always rotated.
Most labs have a 3 way interface system
The two-way traffic in public hospitals has huge benefits.
Card board boxes are not stacked at lab exits.
[10]
Multiple choices. Show working / explanation and give the correct answer.
Calculate the coefficient of variation for a set of data where the mean = 89 mmol/l and the 2 standard deviations = 14.
7.8
7.9
15.7
15.8
A CSF specimen is sent to the lab @ 9 pm for glucose analysis. The specimen is cloudy and appears to contain red blood cells. Which of the following statements is true?
Glucose testing cannot be performed on the specimen
Specimen should be centrifuged and the glucose test run immediately.
Specimen can be refrigerated as received and the glucose run the next day.
Specimen can be frozen as received and the glucose run the next day.
Xanthrochromasia of cerebrospinal fluid may be due to increased levels of which of the following?
Chloride
Protein
Glucose
Magnesium
With the development of fetal lung maturity, which of the following phospholipid concentrations in amniotic fluid significantly and consistently increases?
Sphingomyelin
Phosphatidyl ethanolamine
Phosphatidyl inositol
Phosphatidyl choline
Which of the following is characteristic of an exudates effusion?
Leukocyte count greater than 1000 /µl
Cloudy appearance
Protein concentration less than 3.0 g/dl
Absence of fibrinogen
How many millilitres of concentrated H2SO4 ( sp gravity = 1.84g/ml; assay =97%) are required to prepare 10 L of a 0.1 N H2SO4
1.84
9.20
27.5
54.4
How many grams of NaOH are required to prepare 2500 ml of a 4 M solution?
40
100
160
400
Because of a malfunction, a spectrophotometer is able to show only the percent transmittance (%T) readings on the digital display. Convert 68.0%T to its corresponding absorbance.
0.109
0.168
0.320
0.495
How many grams of a NaOH are required to prepare 500ml of a 0.02N solution?
0.4
0.8
4.0
8.0
How much CaSO4 should be weighed out to prepare one litre of a 0.5 M solution of Ca SO4?
a. 6.8g
b. 0.68g
c. 6800g
d. 68 g
[10 x2 = 20]
6. A lumbar puncture is performed for suspected meningitis.
6.1 Explain the significance of the globulin test in CSF. [2]
6.2 Give the significance of a raised glucose level in CSF. [3]
7. Describe the interfering factors that may give false results in the occult blood test.
[3]
8. With the aid of a diagram show a LSAR chromatography plate indicating a possible
negative and a positive lung maturity. Show calculations of LSAR patterns. [7]
Wednesday, March 2, 2011
Shigella identification
serotyping
S dysenteriae is group A with 13 serotypes
S flexneri is group B with 6 serptypes
S boydii is group C with 18 serotypes
S sonnei is group D with 1 serotype
group A is beg for mannitol fermentation
all others groups are pos
group D is late lactose fermenters and ONPG pos
serotyping is done using slide agglutination tests using specific antisera
S dysenteriae is group A with 13 serotypes
S flexneri is group B with 6 serptypes
S boydii is group C with 18 serotypes
S sonnei is group D with 1 serotype
group A is beg for mannitol fermentation
all others groups are pos
group D is late lactose fermenters and ONPG pos
serotyping is done using slide agglutination tests using specific antisera
Tuesday, March 1, 2011
this is getting weird
I am posting stuff on immunology and microbiology 3 to a site that already has microbiology1 stuff on it. Is it me or is it getting too busy here? Let me know
The ELEK test
This test is done to determine if Corynebacterium diphtheriae releases toxin. It is performed after the organism is identified as being C diphtheriae.
Add K tellurite and rabbit serum to molten agar. Dispense this agar to a sterile petri dish using aseptic technique. Place a filter paper strip impregnated with antitoxin across the middle of the plate. Allow the filter paper to sink to the bottom of the the plate. Wait till the plate solidifies and is dry.
do a line streak of the test organism, positive and negative controls at right angles to the filter paper. Incubate
Examine for lines of white precipitation at 45 degree angles a small distance away from the filter paper.
If the positive control is adjacent to the test, and the test is positive, you will see a wave like formation. Very very pretty, dont you think??? Nasty bug though
Add K tellurite and rabbit serum to molten agar. Dispense this agar to a sterile petri dish using aseptic technique. Place a filter paper strip impregnated with antitoxin across the middle of the plate. Allow the filter paper to sink to the bottom of the the plate. Wait till the plate solidifies and is dry.
do a line streak of the test organism, positive and negative controls at right angles to the filter paper. Incubate
Examine for lines of white precipitation at 45 degree angles a small distance away from the filter paper.
If the positive control is adjacent to the test, and the test is positive, you will see a wave like formation. Very very pretty, dont you think??? Nasty bug though
why do we wash the RBC?
Antigens are located on the surface of RBC. Ab are found in plasma
when you remove the RBC from the patients specimen, you have to go past the plasma to get to the RBC. Therefore you may remove some plasma as well as the RBC. Any Ag in the plasma will interfere with the expected agglutination
so we wash the RBC to get rid of all traces of plasma, and of Ab.
when you remove the RBC from the patients specimen, you have to go past the plasma to get to the RBC. Therefore you may remove some plasma as well as the RBC. Any Ag in the plasma will interfere with the expected agglutination
so we wash the RBC to get rid of all traces of plasma, and of Ab.
how to prepare a RBC suspension
dispense approx 0.5ml of RBC to a testtube
fill the tube up to 3/4 with saline
parafilm and mix by inverting tube once
centrifuge at 2000rpm or 0.5g for 5 minutes
remove parafilm, remove saline
repeat above steps twice more (total of 3 times)
at end of last centrifugation, remove as much saline without disturbing the RBC
add saline up to 1/2 tube, mix and note the colour
we are looking for a bright red/scarlet colour
if the suspension is too dark, add more saline and examine again
once the scarlet colour is achieved, use the suspension in your test
fill the tube up to 3/4 with saline
parafilm and mix by inverting tube once
centrifuge at 2000rpm or 0.5g for 5 minutes
remove parafilm, remove saline
repeat above steps twice more (total of 3 times)
at end of last centrifugation, remove as much saline without disturbing the RBC
add saline up to 1/2 tube, mix and note the colour
we are looking for a bright red/scarlet colour
if the suspension is too dark, add more saline and examine again
once the scarlet colour is achieved, use the suspension in your test
ABO blood typing, the test
take 5 testtubes and label as A, B, O, a and b.
A, B and O are the forward grouping tubes. Its purpose is to determine the identity of antigens present. Antigens are found on the surface of RBC, so the patients red cells are added to these tubes. The known is the antibodies, each of which is colour coded.
a and b is the reverse typing. Its purpose is to determine the identity of any antibodies present. Ab are found in serum/plasma, so the patients plasma are added to these tubes. The known are the antigens, which are red in colour.
dispense 1 drop of a 3% RBC suspension to tubes A, B,O
Dispense 1 drop of plasma to tubes a, b
add 1 drop of the relevant Ab and Ag to each tube (e.g.antiA to Tube A, etc)
mix well and incubate at room temperature for 15 minutes
examine each tube for agglutination
record your results and determine the ABO blood type
A, B and O are the forward grouping tubes. Its purpose is to determine the identity of antigens present. Antigens are found on the surface of RBC, so the patients red cells are added to these tubes. The known is the antibodies, each of which is colour coded.
a and b is the reverse typing. Its purpose is to determine the identity of any antibodies present. Ab are found in serum/plasma, so the patients plasma are added to these tubes. The known are the antigens, which are red in colour.
dispense 1 drop of a 3% RBC suspension to tubes A, B,O
Dispense 1 drop of plasma to tubes a, b
add 1 drop of the relevant Ab and Ag to each tube (e.g.antiA to Tube A, etc)
mix well and incubate at room temperature for 15 minutes
examine each tube for agglutination
record your results and determine the ABO blood type
ABO blood groups, the basics
This is just one blood type. The ABO blood type consists of both antigens and antibodies. These antibodies are not specific to the antigens.Ag and Ab are inherited as a set. There are only 2 Ag, antigen A and antigen B. The name of the blood type is taken from the antigen present in the blood. So blood type A has A antigens and antibody B. Blood type B has antigen B and antibody A. Blood type AB has antigens A and B, and no antibodies. Blood type O has no antigens and both antibody A and antibody B.
What I have just described takes place inside the patient, and is said to be in vivo. You need to fully understand this in order to read the agglutination reactions of the blood typing test, and interpret the results.
What I have just described takes place inside the patient, and is said to be in vivo. You need to fully understand this in order to read the agglutination reactions of the blood typing test, and interpret the results.
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