Is there anyone who can give point me to a document other than the AAMI standard with regards to the guidelines for acid fast bacteria. I know that it is prudent to knck them down if they are found but in general what are the patient implications? What if any special treatment should be done in the RO system?

Here's a link to information on acid fast bacteria:

bugs.uah.ualberta.ca/mycob/afb.htm

Of the acid fast bacteria the mycobacteria family holds a significant interest as it is the family that includes m. tuberculosis, the pathogen responsible for tuberculosis. Also of interest are the non-tuberculous mycobacteria of which some species can be pathogenic in humans particularly those with compromised immunity.

The most infamous of this group relative to dialysis is M. chelonae, a member of the M. fortuitim complex, implicated in an infective outbreak amongst dialysis patients in Baton Rouge, La. in the early 80's.

Members of the fortuitum complex are associated with abscesses of injection sites and surgical wounds, and in pulmonary diseases.

While M. chelonae is not considered a water borne organism it was found to have infiltrated the dialysis unit's water system, possibly as a result of a break in the city water piping supplying the dialysis unit.

M. chelonae as with many other mycobacterium species can resist anti-turberculous drugs and disinfectants. As M. chelonae was also found in re-processed dialysers and in the 2 % formaldehyde solution used for disinfecting the dialyzers.

We do certain things today because of M. chelonae and its implication in the "Baton Rouge incident":

1) Mycobacteria in comparison to gram negative bacteria are relatively slow growers. Fast growers amongst the mycobacteria take 2 - 7 days and the true slow growers take 2 - 6 weeks to grow out in cultures. Up until the incident the standard culture was read at 24 hours. As a result we now read cultures at no less than 48 hrs.

2) Given that M. chelonae was found to survive in the 2% formaldehyde the percent of formaldehyde used to disinfect dialyzers was raised from 2% to 4%.

While mycobacteria are not usually found in dialysis water systems the Baton Rouge incident proved that anything can happen.

Becuase of this rarity, routine testing for mycobacteria is not usually done. A periodic test though is prudent. You need to specify to the lab to test for mycobacteria - longer incubation period, at 25 - 42 degrees C, with confirmation of suspecious colonies by acid fast testing.



[This message has been edited by Dennis Todaro (edited 05-04-2001).]

Thank you Dennis for a very helpfull reply. Interesting that AMMI has not set a maximum level for this type of organism other than to say that 200 colonies is too much.

When submitting samples for mycobacterial cultures, it is best to find a local lab to do the testing. A delay in testing will compromise the culture. Also the more sample, the better. I believe that the CDC filtered 500 ml of water in the Louisiana outbreak. It seems to me that the CDC estimated that at least 50% of dialysis clinics have myco present. It takes very careful and sensitive testing to demonstrate it.