Nitrocef Matchbook

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Rapid Detection of Beta-Lactamase.
Description

Hardy Diagnostics Nitrocef Matchbook™ sticks are intended for use in the rapid testing of isolated colonies of Neisseria gonorrhoeae, Moraxella (Branhamella) catarrhalis, Staphylococcus spp., Haemophilus influenzae, Enterococcus spp., and some anaerobic bacteria for the production of beta-lactamase.

SUMMARY

It has long been recognized that certain bacteria possess the ability to produce enzymes that inactivate beta-lactam antibiotics. Some hydrolyze penicillin class antimicrobics and are described as penicillinases. Others hydrolyze the cephalosporin class antimicrobics and are described as cephalosporinases. Some bacteria produce enzymes that hydrolyze both cephalosporins and penicillins.

 

Rapid beta-lactamase tests can yield clinically relevant information earlier than an MIC or disk diffusion test. Several clinical tests have been devised to detect beta-lactamases. These tests include the iodometric method, the acidometric method, and chromogenic substrates.(6) Iodometric methods are suitable for testing N. gonorrhoeae. Acidimetric methods produce acceptable results with Haemophilus spp., N. gonorrhoeae and staphylococci. Nitrocefin, a chromogenic cephalosporin, can be used to test Neisseria gonorrhoeae, Enterococcus spp., Moraxella (Branhamella) catarrhalis, Staphylococcus spp., Haemophilus influenzae and some anaerobic bacteria, and has been found effective in detecting all known beta-lactamases. Nitrocefin is the only reliable test for detecting beta-lactamase producing Enterococcus spp.

Hardy Diagnostics Nitrocef Matchbook™ sticks are impregnated with nitrocefin, a chromogenic cephalosporin. As the amide bond in a beta-lactam ring is hydrolyzed by a beta-lactamase, Nitrocefin changes color from yellow to red. Bacteria which produce beta-lactamase in significant amounts produce this rapid yellow to red color change on the tip of the Nitrocef Matchbook™ stick. These beta-lactamases are capable of inactivating "penicillinase-labile-penicillins", such as, amoxicillin, ampicillin, penicillin, carbenicillin, ticarcillin, mezlocillin and piperacillin.

 

Hardy Diagnostics Nitrocef Matchbook™ is intended for use in the rapid testing of isolated colonies of Neisseria gonorrhoeae, Enterococcus spp., Moraxella (Branhamella) catarrhalis, Staphylococcus spp., Haemophilus influenzae and anaerobic bacteria of the genera Bacteroides, Clostridium, Porphyromonas, Fusobacterium, and Prevotella.(11-13,19) The beta-lactamase test is of little value for many taxonomic organisms (e.g., Enterobacteriaceae). This is because organisms within a taxonomic group, or even a single strain, can produce a diversity of enzymes with different substrate specificities.

 

PROCEDURE

1. Prior to inoculation, allow Nitrocef Matchbook™ sticks to equilibrate to room temperature.

2. Using care not to touch the pointed tip of the Nitrocef Matchbook™ stick that is impregnated with reagent, detach a single Nitrocef Matchbook™ stick from the base. Immediately replace the remaining matchsticks into the Mylar bag, reseal and place into freezer.

3. Briefly dip the pointed tip of the Nitrocef Matchbook™ stick in sterile deionized water. Alternately, condensation on the lid of a petri dish can be used to hydrate the tip as well. Do not over saturate the tip, which could dilute the reagent.

4. Using the Nitrocef Matchbook™ stick, "sweep" up 1-3 well isolated colonies of similar morphology, ensuring that the reagent on the pointed tip of the Nitrocef Matchbook™ stick is exposed to the cell paste.

5. Observe the inoculated tip for the development of an orange/red color.

Note: Water is critical to the development of the color reaction, if the stick begins to dry out it may be necessary to rehydrate the reaction area of the Nitrocef Matchbook™ stick with a small amount of water.

 

INTERPRETATION OF RESULTS

A positive beta-lactamase result is denoted by a change in color of the tip of the Nitrocef Matchbook™ stick from its original yellow to orange or red. Most positive bacterial strains will produce a color change from yellow to orange or red within 5 minutes. Some staphylococci, however, may take up to 60 minutes for a positive result.

A positive beta-lactamase result predicts the following:

1. Resistance to penicillin, ampicillin and amoxicillin among Haemophilus spp., N. gonorrhoeae and M. catarrhalis.

2. Resistance to penicillin, as well as acylamino-, carboxy-, and uriedo-penicillins among staphylococci and enterococci. A negative beta-lactamase result is denoted by no color change (the tip of the Nitrocef Matchbook™ stick remains yellow). A negative result does not rule out resistance due to other mechanisms.

Cat No: HD Z108

Size: 10 tests

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