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This portion of our website is devoted to keeping our customers
and other interested parties abreast of our current research
interests. Also, from time to time, we plan to use this site
to express our opinion on issues that concern us as microbiologists
involved in contamination control.
Mycobacteria
Mycobacteria are microorganisms that are
widely distributed in nature. They can be found in lakes,
streams, and ponds, as well as in soil environments.
They are different from many other bacteria in several
different ways. First
of all, they are relatively slow growing.
Whereas typical environmental and clinical organisms
can be cultured in a matter of a day or two, mycobacteria can
take up to two weeks or longer to grow in a laboratory. The cell wall of mycobacteria is also unique in the bacterial
world. It is very
waxy, and therefore difficult to penetrate by outside agents.
Some species of mycobacteria are pathogenic to man.
Mycobacterium tuberculosis is the causative
agent of tuberculosis and Mycobacterium leprae is the
organism responsible for leprosy.
The discovery of mycobacteria in
metalworking fluids is a relatively recent phenomenon.
Back in 1993, a Harvard University aerobiologist by the
name of Muilinberg reported an outbreak of a condition called
hypersensitivity pneumonitis in 10 patients.
These people were exposed to a semi-synthetic
metalworking fluid, a subsequent culture of which revealed
approximately one million mycobacteria per milliliter.
Another researcher named Bernstein reported similar
findings from a semi-synthetic fluid and termed the condition
“machine operators lung”.
Kay Kreiss, a worker with the National Institute of
Occupational Safety and Health (NIOSH), noted that by
1997 there were eight separate clusters of workers affected
with a total of 100 people.
She further investigated metalworking fluid as the
source.
In 1998, NIOSH issued a set of
recommendations to control worker exposure to metalworking
fluids. The
controls were based on health effects. The update by NIOSH went on to say that the “occupational
exposures to metalworking fluids may cause a variety of
respiratory conditions including hypersensitivity pneumonitis
(HP), chronic bronchitis, impaired lung function, and
asthma”. Brian
Shelton, a reasearcher from Pathcon Labs, did further
investigation on this organism in 1999.
Shelton, who specializes in the epidemiology of
environmental microbes, concluded that mycobacteria are very
likely the cause of HP in certain workers exposed to
metalworking fluids.
In 2001, Biosan Labs sent multiple
isolates of mycobacteria from metalworking fluids to the
Center for Pulmonary and Infectious Disease Control at the
University of Texas. There
were a total of 113 isolates, and the principal investigator
there, Rebecca Wilson, determined them to be a new species, Mycobacterium
immunogenum. A further study, this one in 2002, determined
all species of this organism were genetically identical,
regardless of the regional geography from which they came.
Okay, so that’s some of the history of
the microbe. But why should we care about it? Is it actually
dangerous? In the above history, several references were made to
hypersensitivity pneumonitis or HP. HP is an allergic type
illness caused by repeated exposures to bioaerosols, sometimes
taking years to develop.
The condition presents as a flu-like illness with
fatigue, cough, shortness of breath, and weight loss. Once the
individual’s immune system becomes allergic, symptoms can
develop within 4-12 hours of exposure.
The syndrome can last a few weeks to even a year or
two, depending on when exposure is terminated.
Although 100% proof has yet to be established, most
authorities in the field now believe that mycobacteria in
metalworking fluids are clearly responsible for this
condition. It is
estimated that approximately 1% of individuals exposed to
bioaerosols containing this organism will suffer from HP.
In order to protect workers from the
potentially harmful effects of these microbes, appropriate
biocide treatment of the fluids must be made.
Research in our laboratory has shown that one of the
more common families of biocides, the formaldehyde
condensates, are ineffective against mycobacteria. This would include hexahydro-triazine, commonly known as
Grotan. Our work
in the lab as well as in the field did yield some valuable
information about biocides that do work.
The phenolic biocides, including para-chloro metacresol
(PCMC), are very good agents for controlling these bacteria.
Isothiazolones such as Kathon can also work well provided they
remain stable in the particular field situation.
When testing for mycobacteria, it is
important to realize that both living and dead organisms play
a role in HP. Therefore,
samples from the field should be examined directly under the
microscope, looking for all cells.
The way this is done is by centrifuging the sample at
high speed (45-50,000rpm) to concentrate the organisms.
The resulting pellet is stained by acid fast staining
to look for the presence of total mycobacteria.
Living bacteria, as a separate entity, should also be
quantified. This
can be done using simple plate count media, provided there is
not a heavy overgrowth of other organisms.
If this is the case, a special media should be used
that inhibits the growth of non-mycobacteria.
At Biosan Laboratories, Inc., we offer a variety of microbiological
testing services and products. Please contact Lesley
Thomas at (800) 253-6800 x1229 or at lesley@biosan.com
for additional information.
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Biosan Laboratories, Inc.
1950 Tobsal Court, Warren, MI 48091-1351
Phone (586) 755-8970 / (800) 253-6800
Fax (586) 755-8978 e-mail lesley@biosan.com
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