Welcome! Welcome!

We're once again back for our weekly (maybe a little longer) article about a product! 

This week we're focusing on something new, our own bench reagents. We supply quite a few so there's a lot to cover, in total we have: 

• Catalase
• Kovacs reagent
• KOH
• Oxidase strips
• Neisseria PET
• Spot Indole
• Pyrazinamidase test
• Nitrate discs
• Ninhydrin
• Nitrate reagents
• Urease
• Nitrocefin discs

As you can see we have quite a few, so let's get into it! 

To observe the action of these enzymes, catalase reagent, a dilute solution of hydrogen peroxide is added to a pure bacterial culture. Any immediate observed bubbling is indicative of a positive result, since oxygen is a byproduct of hydrogen peroxide decomposition. This test can also be useful in the differentiation of Gram-positive bacilli. 

Catalse 15%

CK9810, 5 x 3ml Vials

The Wadsworth manual recommends 15% hydrogen peroxide for the catalase testing of anaerobes as being more sensitive than 3%. NB. Care is needed when performing catalase tests on colonies growing on blood agar, as the medium itself will give a positive reaction.

The test can be done by impregnating the reagent onto a filter paper, and touching a colony, they rubbing it onto the impregnated paper by touching the colony with the swab impregnated with the reagent. 

The developing reagent CK9801 Ferrous sulphate as a solution has a short shelf-life, to overcome this problem, the reagent is therefore supplied as a pellet in the dropper bottles, to be reconstituted before use. 

All Neisseria species are oxidase positive, and most fermenting Gram-negative rods are oxidase negative, with the exception of some Vibrios, Aermonads, Pasturella and Chromobacteriae. 

Most non-fermenting Gram-negative rods are oxidase positive. The test involves smearing a portion of the freshly cultured colony onto a moistened strip and observing. The development of a blue/ black colour within 30 seconds indicates a positive reaction. The test is being carried out using colonies picked from a blood containing medium, using either a plastic or platinum loop, a nichrome loop may generate false positives and should not be used. 

Kovacs Reagent

CK9020 5 x 3ml Vials 

Kovacs reagent is intended to be used for the detection of tryptophanase production, which can be used as an aid in the differentiation of the Enterobacterales and other genera. The active ingredient of Kovacs reagent, p-dimethlyaminobenzaldehyde, reacts with indole to form a pink/red compound. 

Potassium Hydroxide (KOH) 3%

CK9860 5 x 3ml Vials 

KOH is intended for use in the differentiation of Gram-positive, and Gram-negative, organism. Being simple and easy to use, while being rapid and inexpensive. KOH can be used in addition to a Gram-stain for primary differentiation of bacterial isolates. 

Other Reagents in our Catalogue 

For more information on each please contact us via our website, our email or telephone. 

• Nitrate Discs - CK9850
• Ninhydrin 3.5% - CK9058
• Nitrate Reagent A - CK9841
• Nitrate Reagent B - CK9842
• Urease (15 Minutes) - CK3650
• Urease/Indole - CK4651

Anaerobe Identification 

These reagents are required for first day 'Level one' identification, recommended in the Wadsworth Anaerobic Bacteriology Manual. 

• Catalase 15% - CK9810
• KOH 3% - CK9860

Neisseria Detection 

Neisseria PET (preformed enzyme test) presumptively identifies N. gonorrhoea, meningitis and Lactamaca in 32 minutes. 

• Neisseria PET - CK3025
• Nitrocefin Discs - CK2001
• Oxidase Strips - CK3520

Whilst the use of a single test method, and clinical findings, may be considered sufficient for a presumptive identification, we would advise the use of at least 2 test methods involving different principles (such as biochemical, antigenic or molecular) before issuing a definitive/confirmed identification for Neisseria gonorrhoea (advice from the UKHSA SMI (Chlamydia and Gonorrhoea infection - testing by nucleic amplification tests (NAATs) - Virology, V37, Issue 5, 12.12.24))