Oxidase Test (odd results)

[Vert3X]

Hi,

 

I'm performing an oxidase test on a Gram (-) Rod that is Catalase +. I'm using 1% p-aminodimethylaniline oxalate (supposed to be colorless but is slight pink) as my oxidizing reagent. When I transfer colonies (from 4 degree storage plate) onto filter paper and subsequently add a drop of oxalate I get an immediate color change from clear to pink. However, the dark purple color either fails to appear, or appears after 30-60 seconds on the outer edges of the smear/colony. I've also poured oxalate over a nutrient agar plate containing my culture and I get the same results. The dark purple color appears after a while but accounts for a very small area % (rest of colony = light pink) and appears on the outer edges only. Would my culture be Oxidase + or - ?

 

I'm a student who's supposed to be identifying my species. The rest of the culture characteristics are as follows:

Motility (hanging drop as well as MTA inoculation): +

Catalase: +

Oxidase: +

Glucose oxidation: -

Glucose fermentation: -

I showed my instructor the above results and he said one of the above was wrong. I have strong confidence in my catalase and glucose results so either the oxidase or motility is wrong. I've performed a variety of other tests but won't get the results for those until next week. Any suggestions?