Salmonella Latex Test

Latex particles are coated with polyvalent antisera raised against a wide range of Salmonella antigens. When mixed with a suspension of Salmonella organisms, the latex particles rapidly agglutinate to form visible clumps. The Salmonella Latex Test detects > 99% of motile Salmonella species and early investigations have indicated that specific non-motile species may also be detected.

Kit contents (50 tests)

• Salmonella Latex Reagent (F42a, 2.5 mL, blue cap): latex particles coated with rabbit antiserum against Salmonella antigens. Preserved with 0.099% sodium azide.
• Positive control (F42b, 0.5 mL, black cap): inactivated preparation of Salmonella antigens, preserved with 0.099% sodium azide.
• 0.85% isotonic saline (M40, 5.0 mL, white cap). Preserved with 0.099% sodium azide.
• Disposable agglutination slides (25 pcs).
• Disposable mixing sticks (2 x 25).

Additional materials required (not supplied in the kit)

• Bacteriological loops.

The Salmonella Latex Test should be stored at 2-8 °C. The kit should not be used after the expiry date printed on the box.

Before using this product, refer to Precautions and Limitations. The controls specified in the Quality control section should be performed each time the kit is used.

Specimens

Colonies grown on selective agar plates can be tested with the Salmonella Latex Test.

Test procedure

For the positive control protocol, see the Quality control section.

1. Dispense 1 drop of M40 isotonic saline into a circle of an agglutination slide.
2. Using an inoculating loop, remove a colony from the selective agar plate and emulsify the colony in the drop of saline to produce a heavy smooth suspension. Suspensions should only be made from colonies with morphologies resembling Salmonella spp.
3. Rock the slide gently for up to 2 minutes and observe for autoagglutination or clumping. If the suspension remains smooth, proceed to step 4 (see Limitations, note 1).
4. Mix the Salmonella Latex Reagent by gently inverting and add one drop next to the bacterial suspension. Do not allow the dropper to touch the suspension.
5. Mix the latex reagent and the bacterial suspension with a clean mixing stick and rock the slide gently two or three times. Excessive rocking of the slide is not necessary. Examine for agglutination within a maximum of 2 minutes.
6. After reading, discard the used mixing sticks and slides accordingly.

Interpretation of results

Agglutination within 2 minutes is a positive result and indicates the presence of Salmonella in the sample. Absence of agglutination indicates that Salmonella is not present in the test culture.

Safety

1. The kit and its reagents supplied are intended for professional use only, to be used for industrial diagnostics only and not for use in clinical testing.
2. Sodium azide, which is used as a preservative in the kit reagents, can react with lead or copper plumbing to form potentially explosive metal azides. Dispose by flushing with a large volume of water to prevent azide build-up.
3. Appropriate precautions should be taken when handling or disposing of potential pathogens. Decontamination of infectious material can be achieved with sodium hypochlorite at a final concentration of 3% for 30 minutes. Liquid waste containing acid must be neutralised before treatment.
4. The positive control has been inactivated during the manufacturing process. However, it should be handled as though potentially infectious.

Procedural

1. The Salmonella Latex Test should be used according to the kit instructions.
2. Allow all reagents to reach room temperature before use.
3. Do not dilute any of the kit reagents.
4. Do not intermix reagents from different batches of kits.
5. Do not freeze any of the kit reagents.
6. Do not allow the latex reagent dropper to touch the positive control or bacterial samples.
7. Be careful only to record agglutination. Reactions that are "curdy" or "stringy" may not be true agglutination.
8. Ensure the slide is clean and dry prior to use.

1. Results should be interpreted in the context of all available laboratory information.
2. Rough strains of Salmonella are known to cause non-specific autoagglutination in saline alone and therefore cannot be tested with the Salmonella Latex Test.
3. Some non-motile strains may not be detected by the Salmonella Latex Test.
4. Some oxidase-positive organisms may give false positive reactions.
5. Old stock cultures of Enterobacteriaceae on nutrient agar slopes may cause non-specific agglutination whereas old stocks of Salmonella may give false negative results. Fresh sub-cultures should be prepared for testing.
6. Identification with the Salmonella Latex Test is presumptive and all positive results should be confirmed by further identification tests and serotyping of pure cultures.

The following controls should be performed each time the kit is used.

1. Reagent control: Add one drop of Salmonella latex (F42a) to one drop of M40 saline solution in the same circle on a slide. Mix and spread the liquid over the entire area of the circle with a mixing stick. Rock the slide gently for 2 minutes and observe for agglutination. If any agglutination is seen, either the latex or the saline is contaminated and should be discarded.
2. Positive control: Add one drop of positive control (F42b) to one circle on the test slide. Add one drop of Salmonella latex to the same circle and mix. Do not allow the dropper to touch the positive control. Rock the slide gently. Within 2 minutes, agglutination, indicating a positive result, should be visible. If no agglutination is seen, a fresh kit should be used.

Dispose of according to any local, national, or regional regulations.