This article provides an overview on Containers and Swab for Collection of Specimens:- 1. Introduction to Containers and Swab 2. Disposable Specimen Containers 3. Wound Infection.
Introduction to Containers and Swab:
Containers used for microbiological investigations should be sterile, leak-proof and strong. Each container should bear the name of the patient, from whom the specimen was collected and his case register number.
The investigation requisition form should also accompany the specimen indicating the investigation required along with the probable clinical diagnosis and current chemotherapy. Details of previous immunization should be furnished for serological investigation.
Glass Tubes and Universal Containers:
Specimen of exudate, pus, blood, cerebrospinal fluid, urine and faeces should be collected in strong, sterile, corked glass test tubes (4×3/8 inch). Before collection of samples, tests tubes with loosely fitted from plug or bark corks can be sterilised in hot air oven and then the corks should be pressed in.
Universal container or screw-capped bottle is a strong moulded glass bottle (31/4 in height x 11/8) in diameter of one oz. (28 ml) capacity with a flat base and wide mouth. It is sterilised with loose cap and then tightened. It cannot be sterilised in the hot air oven as the rubber washer will not withstand the temperature.
The screw-capped universal container has many advantages over the glass test tubes. It is strong, the mouth of the container is sterile because of the screw cap, whereas in case of stoppered glass test tubes, the dust may collect at the rim of the test tube. The content of a container will not leak and will not be contaminated.
It is quite stable at the base of the container and it is very convenient for collection of the sample at the bed side and it is very suitable for the collection of serous fluids, e.g., Pleural or peritoneal fluids.
The collection of the fluids that may be coagulable on standing can be done in the container to which 0.3 ml. of a 20 per cent solution of sodium citrate is added prior to the autoclaving. This method of collecting fluid may be useful in performing cell count or centrifuging procedures.
Blood may be collected in a sterile universal screw-capped container or test tube fitted with cotton plug for serological investigation. The streptokinase digested or minced blood clot may be cultured in a selective medium e.g. for enteric organisms (Salmonella) or blood for culture may be collected and submitted to the bacteriological laboratory in a special blood cultures bottle containing bile salt broth.
Serum from clotted blood can be transmitted to the laboratory preserved in sodium azide or merthiolate (1:10,000) in a sterile polystyrene or polypropylene plastic container. Faeces may be collected in a small bottle of about 2 oz. capacity or in a glass specimen tube or by a rectal swab.
If the laboratory is situated at a far off place, the container may be transmitted with all precautions by post; the package should be labelled as “Pathological specimen“.
If there is a delay of some hours before laboratory cultivation can be performed, neutral glycerol saline should be added to the faeces. Rice water stool from cholera patient should be collected on a leaf or paper, but not in disinfected bedpan because disinfectants can kill Vibrio cholera. Specimen should be sent in transport medium, e.g., Alkaline peptone water or Venkataraman-Ramakrishnan (VR) medium.
Urine:
For the diagnosis of urinary tract infection, the urine, if required in small quantity, can be collected in a universal container; complete early morning specimens (large quantities of urine) can be collected in a 20 oz. screw capped bottles.
Disposable Specimen Containers:
Sterile screw-capped waxed cartoons of 2 oz. capacity (such as used for ice-cream) are suitable for the collection of sputum or faeces. These waxed cartoons cannot be sent through the post because of postal regulations.
Plastic polystyrene or polypropylene containers of variable size are suitable for urine, feces, pus, blood etc. Recently, disposable plastic specimen containers have become available from various manufacturers. All disposable containers should be destroyed in a furnace after use.
Swab:
A swab consists of a piece of wooden (bamboo or broom) stick of about 61/2 in long. A round one end of the stick a thin pledget of absorbent cotton wool is tightly wrapped for about 3/4 inch. The stick is placed in a test tube (5 in x 1/2) and the top of the tube is plugged with a cotton wool.
This has the advantage that the stick can be broken off short when the swab has to be placed in transport medium in a screw-capped container. Besides collection of specimens, the swab can also be useful in the laboratory for seeding of medium for antibiotic disk sensitivity tests.
A variety of disposable swabs (plain, serum coated, charcoal coated) in plastic tubes are available. They can be destroyed in a furnace after use or sterilised in autoclave before discarding.
Swabs are useful in collecting specimen from:
(i) Throat:
In cases of suspected diphtheria, tonsillitis;
(ii) Wound:
Specimen from surgical conditions (fistula, sinus) or discharging ears can be collected by swabs;
(iii) Post-nasal or Nasopharyngeal Space:
Specimens from suspected meningococcal carriers and whooping cough can be collected by using sterile post-nasal swab which is made from a flexible copper wire or nichrome (0.51 mm diameter), its terminal end (1/4 inch) bent back through an angle of 45 degrees is tightly wrapped with a thin pledget of absorbent cotton wool. For the diagnosis of whooping cough, a pre-nasal swab is preferable to the post-nasal swab.
(iv) Rectum:
Rectal swabs are very useful in bacillary dysentery in young children.
(v) Cervix Uteri:
A longer sterile stick or wire, 9 inch, is preferable for the specimens in gonorrhoea and purperal infections.
The conditions where delicate pathogens are concerned e.g. meningococcus, gonococcus or Bordetella pertussis, it is preferable to place the swab in sterile Bijou bottle containing transport medium, e.g., neutral glycerol saline.
Infection of Reproductive System:
Coliform bacilli, streptococci, Mycobacterium tuberculosis, Neisseria gonorrhoeae are pathogens responsible for the infection of female genital tract.
Puerperal sepsis or septic abortions which are acute infections in the female after delivery are caused by Streptococcus pyogenes, Clostridium welchii, Bacteroides, Coliform bacilli.
Cervical swabs should be taken with the help of a speculum under direct vision, put in to Stuart’s transport medium and sent to the diagnostic laboratory.
In acute vaginitis, due to Trichomonas vaginalis and vaginal thrush due to Candida albicans, exudates can be readily obtained by swabbing and direct smears can be made on slides for microscopic examination or exudates may be collected by pipette or spoon for wet films. Acute urethritis and prostatitis in male are due to N. gonorrhoeae., chlamydia or Mycoplasma hominis.
Wound Infection:
Wound Infection may be:
(a) Endogenous or
(b) Exogenous.
Endogenous infection (autoinfection) are caused by organisms that were commensals elsewhere in the host body, e.g., organisms from large intestine may infect the abdominal surgical wounds after an operation that has involved the incision of the skin.
Cross-infection is an example of exogenous infection where the causative organisms spread from person to person. Infection may occur after accidental or intentional trauma of the skin or other tissues: the latter type is known as “post-operative sepsis“.
Specimen Collection:
Swabs should be well soaked in pus or exudate from infected wounds. Syringe can be used to collect the pus or exudate specimens which can be used to collect the pus or exudate specimens which can be transferred into a sterile test tube.
Pieces of tissues removed at operation or curetting or other tissues can be sent immediately to the bacteriological laboratory and they should be homogenized in a tissue grinder before it is used for bacteriological examination. Delay in the transit of specimens to the laboratory must be avoided, particularly in cases of swabs where the exudate may dry in the cotton-wool.
Infection of the Conjunctiva:
Pseudomonas pyocyanea causes severe conjunctivitis due to the use of contaminated eye drops. Gonococcus (ophthalmia neonatorum), Staphylococcus aureus (sticky eye in new born babies), pneumococci, Moraxella lacunata and H. influenzae, certain viruses (herpes virus, adeno virus,) Trie agent (Trachoma, inclusion blennorrhoea) produce conjunctivitis.
Swabs coated with exudates can be sent to the laboratory in Stuart’s transport medium. Purulent exudate from inflamed conjunctiva can be considered as pus. Gonococcus can be shown by direct microscopy and can be grown on heated blood agar medium.