OXA-23 carbapenemase Test Kit (LFIA)

Product Name

OXA-23 carbapenemase Test Kit (LFIA)

Intended Use

OXA-23 carbapenemase Test Kit (LFIA) is a colloidal gold immunochromatography for the rapid qualitative detection of OXA-23 carbapenemase in bacterial samples obtained after culture.

Summary

Infections caused by multidrug-resistant (MDR) and extensively drug-resistant (XDR) Gram-negative bacteria (GNB) have become major challenges for global health institutions because of the limited antibiotic options and high mortality rates.[1] The most widespread and threatening mechanism of antibiotic resistance in MDR A. baumannii is the production of different β-lactamase enzymes.[2] The first group of carbapenem-resistant OXA-type β-lactamases to be identified in A. baumannii was the OXA-23 group. The genes for this group of enzymes are frequently plasmid-borne and have been found in many Acinetobacter species as well as species belonging to the Enterobacteriaceae. The enzymes are able to hydrolyze oxyiminocephalosporins, aminopenicillins, piperacillin, oxacillin, and aztreonam in addition to the carbapenems.[3]

Test Principle

OXA-23 carbapenemase Test Kit (LFIA) detects OXA-23 carbapenemase with colloidal gold immunochromatography using a double antibody sandwich assay. When the appropriate amount of test samples treated with dilution buffer is added to the sample well of the test cassette, the sample will move forward along the test strip by capillary action. If the sample contains OXA-23 carbapenemase and the concentration is higher than the limit of detection, the antigen will form immune complexes with OXA-23 carbapenemase antibody labeled with colloidal gold. The immune complex was captured by a monoclonal antibody to the OXA-23 carbapenemase fixed on the nitrocellulose membrane, forming a red T line indicating a positive result for OXA-23 carbapenemase. Additionally, the test strip also contains a control line (C line). The C line should be formed to indicate that the sample has been transported properly through the membrane regardless of whether sample contains OXA-23 carbapenemase or not. If the C line does not appear, it indicates that the test result is invalid and the sample need to retest.

Test Kit Contents

Test cassette contains test strip, plastic cassette, desiccant. The test strip contains colloidal gold-labeled OXA-23 carbapenemase antibody, nitrocellulose membrane (C line fixed with goat-anti-mouse lgG polyclonal antibody, and T line fixed with OXA-23 carbapenemase antibody.)

Storage Instruct ions

The test kit should be stored away from direct sunlight at 2℃ to 30℃ with a shelf-life of 12 months. Do not freeze. After opening the aluminum foil bag, complete the test within 1 hour.

Sample Requ ire ments

The applicable sample type is the bacterial samples obtained after culture. Samples can be stored for 20 hours at 2~8℃, and for 10 hours at room temperature (14~30℃);The bacterial samples obtained after culture can be stored in dilution buffer for 1 month at -20℃± 5℃ and repeated freeze and thaw 3 times.

Test Procedure

1. Scrape one loop of bacteria with a 1uL inoculating loop, and the scraped bacteria should be full of inoculation loop hole as far as possible.

2. Dip the loop in the bottom of the tube containing the dilution buffer. Shake the inoculating loop in order to wash off the bacteria in the tube as much as possible. lf the bacteria are sticky and difficult to wash off, a vortex mixer can be used to fully wash the bacteria off the inoculation loop.

3. Remove the inoculating loop, cover the tube with the dropper and mix well on the vortex mixer. Attention: The normalization of sampling and the adequacy of processing samples into dilution buffer directly affect the test results.

4. Open the aluminum foil pouch, take out the test cassette and lay it on a clean flat surface. Add 4 drops (approximately 100 μL) processed sample extract into the sample well. The results should be observed within 15-20 minutes. Result observed after 20 minutes is invalid.

Remark: Additional required but not provided equipment: Timer, inoculating loop, culture dish and vortex mixer.

Display of Results/Expected Values

1. Positive result: If the quality control line (C line) and detection line (T line) appearat the same time, the color of T line can be deep or light, both are positive results,indicating that the sample contains OXA-23 carbapenemase.

2. Negative result: If only the quality control C line appears, and the T line is notvisible, the sample contains no OXA-23 carbapenemase or the OXA-23 carbapenemase concentration is lower than the limit of detection, and the result is negative.

3. Invalid result: If the C line does not appear, the result is invalid and a new testmust be performed.

Test Method Limitations

This product is only for qualitative testing and the specific concentration of the OXA-23 carbapenemase must be measured using other quantitative methodologies.

2. This test is used to qualitatively detect OXA-23 carbapenemase in bacterial samples. A positive or negative result does not rule out the existence of other antibiotic resistance mechanisms.

3. Improper handling and use will affect the test results of the samples.

Product Performance

• Limit of Detection-LoD

Limit of Detection (LoD) studies determined the lowest detectable concentration of the OXA-23 carbapenemase which ≥95% of all (true positive) replicates test positive.

The limit of OXA-23 carbapenemase is not more than 100 pg/mL.

• Cross Reactivity

The listed items in the following table may be present in the clinical samples. Each of the bacteria was tested in triplicate with no false positive results.

• Interfering Substances Effect

The concentration of common interfering substances is not higher than the concentration shown below and does not affect the test results of this product.

Clinical result

The clinical research was evaluated by comparing the OXA-23 Carbapenemase Test Kit (LFIA) manufactured by Jiangsu Medomics Medical Technology Co., Ltd with OXA-23 manufactured by Coris, to evaluate the clinical sensitivity and specificity of the Candidate Kit. The Clinical Test results of the test kit and the reference kit are summarized in the 2×2 table below:

Warnings and Precautions

1. Please read the manual carefully before operation, and please test in strict accordance with the requirements of the manual.

2. This test kit is used for in vitro diagnosis only.

3. This test kit should be used within 1 hour after opening the foil pouch.

4. When preparing the bacterial solution, pay attention to selecting a single colony to avoid contamination by miscellaneous bacteria.

5. The test results of this kit are for clinical reference only and are not the sole basis for clinical diagnosis. The clinical diagnosis and treatment of patients should be comprehensively considered in combination with their symptoms/signs, medical history, other laboratory tests and treatment response.

6. This product is for one-time use, please do not reuse.

7. Do not use if damaged.

8. After the test, the used test cards, etc. should be disposed of as medical waste.

Reference

1. Jean SS, Harnod D, Hsueh PR. Global Threat of Carbapenem-Resistant Gram-Negative Bacteria. Front Cell Infect Microbiol. 2022 Mar 15;12:823684. doi: 10.3389/fcimb.2022.823684. PMID: 35372099; PMCID: PMC8965008.

2. Colquhoun JM, Farokhyfar M, Hutcheson AR, Anderson A, Bethel CR, Bonomo RA, Clarke AJ, Rather PN. OXA-23 β-Lactamase Overexpression in Acinetobacter baumannii Drives Physiological Changes Resulting in New Genetic Vulnerabilities. mBio. 2021 Dec 21;12(6):e0313721. doi: 10.1128/mBio.03137-21. Epub 2021 Dec7. PMID: 34872351; PMCID: PMC8649759.

3. Evans BA, Amyes SG. OXA β-lactamases. Clin Microbiol Rev. 2014 Apr;27(2):241-63. doi: 10.1128/CMR.00117-13. PMID: 24696435; PMCID: PMC3993105.