Laryngeal Swab for Mycobacterium Tuberculosis

As the name implied, the sample is usually collected from larynx for examination of mycobacterium tuberculosis. It has two method of culturing  the sample;

1. Is an absorbent wool swabs
2. Alginate wool swabs

Method 1. Absorbent wool swabs: The laryngeal swabs is immense into a 0.5ml of 6% sulphuric acid for 6 minute, after that discard the acid and replace it with 4% NaOH place the swab in it and left to stand inside the solution for 20 second, then remove it and inoculate two Lowenstein-Jensen slopes, incubate the culture at 35ºC , one in the aerobic and the second plate in an anaerobic jar for 8 weeks but with regular checking and record in change observed with the regular checking.

Method 2. Alginate wool swabs: the laryngeal swabs is immerse into 5ml of 15% Trisodium phosphate. Then shake the swab together with the solution until the swab dissolved in the solution. Centrifuge, after that discard the supernatant and then use the sediment to inoculate two Lowenstein-Jensen slopes. Examine as it is demonstrated in the method one above, film for microscopic examination is not important.

Gastric lavage

This is a sample obtained from stomach, the sample is often taken from the wards by washing of stomach, after that the washing liquid obtained is taken into a sterile universal container with 5ml of 15% trisodium phosphate and immediately send to laboratory for examination. On receiving the sample in the laboratory, the sample should be centrifuge, have the supernatant discarded to separate container, and the sediment should be treated as it were sputum specimen. The reason of placing the sample in a trisodium phosphate solution, is the ability of the solution to neutralized gastric juice of the stomach which is capable of killing tubercle bacilli.

Urine

Normal urine is sterile but contamination may take place either on the process of collection or the container used for collecting the urine. The urine can also be contaminated with normal flora bacterial in the genital organ when passing out true the urinary tracks.

These are several types of urine, depend on the way which they are collected, example of such types are mid-stream urine and clean catch urine catheter specimen urine, supra pubic aspiration and uretheric aspiration.

But the focus of this book will be limited to mid-stream urine  only because is the most frequently specimen required in routine laboratories.

Sterile mid-Stream Urine: this urine must be messaged to laboratories in a suitable sterile container with little or no delay. Urine is one of the good specimen that yield nice culture. In a urine specimen, any contaminant present will not hesitate to grow, so because of that urine should be store in the refrigerator at  a temperature of 2-8ºC if it will be delay over night before examination will be carried out on the urine sample, or better still boric acid can be added  to delay growth that may bound to occur during the process of overnight delay. The boric acid act as preservative to preserve the life span of the microorganism that might likely be found in the specimen. For detecting white cell, red cell, cast, and some other bacteria in the urine, direct microscopic examination is recommended. These examination is sometimes carried out by first centrifuge the urine, discard the supernatant, use the sediment in case number of cells present in the urine is required, then it is simple to achieved this task with urine that is not centrifuged. Staining film specimen urine with Gram staining method, it sometimes found important, because it reveal some pathogens causing infection to the patient. But with the advanced technology, automatic screening material is now available which will be discussed on new modern laboratory screening.

The screen reveal the negative urines depend on the particle of the red cells counted, the number of white cell and the number of bacteria present in the urine. But in case of culture, it is recommended that some of the lively count should be performed.

This phenomenon is achieved by using a loop and take quantity of known volume of urine and inoculate in an appropriate culture plate, and the next day the colonie growth is identify and counted. By following this step, lively number of organism per ml will be given. According to research it has been proven that 10⁵ of microorganism in urine culture is an indication of infection. It is very necessary that the urine specimen should be examine instantaneously when brought into the laboratories. Because organism will reproduce rapidly for any development made with the urine. And also is for isolation of mycobacterium tuberculosis, then it is recommended that three sample of early morning urine should be collected consecutively

Method of culturing Urine

The appearance of urine should be  noted. Use a loop and insert it vertically on the urine and inoculate MacConkey or CLED or blood agar plate make a film with the sample, and inoculate the plate at 35ºC, examine the plate the next day for any growth of colonies. If there is count of colonies up to 400 then that indicate infection on the particular patient.

The sample should be transfer to centrifuge tube and spin the sample at 3000rpm for 15 minute, discard the supernatant into a sterile container. From the deposit left, make a wet film preparation and examine for cast cells, crystals, etc and many microscopic particle that may present in the urine as result of contaminant of infection. Now if the sample is properly collected with a strictly adhere precaution, then the present of the following organism will be consider an infectious pathogenic organism;

Haemolytic streptococcus

Shigella species

Proteus species

Staphylococcus aureus

Salmonella species

Streptococcus feacalis

Coliform bacilli

For examination of mycobacterium tuberculosis, the following techniques should be followed;

The specimen of urine should be collected and allowed to stand overnight in a refrigerator, on the next day, discard the supernatant under a cover of inoculating cabinet. And the sediment should be transfer to universal containers.

Spin the sediment in centrifuge machine at 3000rpm for 20 minutes, discard the supernatant and treat the deposit as sputum specimen.

Prepared Lowenstein-Jensen slope medium, inoculate the medium with the sediment, on the next day examine any growth seen and report.