Biomedical Engineering Reference
In-Depth Information
3.4 QUALITY ASSURANCE/QUALITY CONTROL
CONSIDERATIONS
Quality assurance and quality control (QA/QC) procedures play several important roles in
the commercial production of microbial inocula. They ensure that the growth process is
efficient, they confirm the integrity of the produced culture, and they provide customers
with assurance that the purchased culture is active, safe and functions as promised. QA/QC
procedures also assure regulatory authorities that a culture added to an environment is safe and
meets local regulatory requirements. Although no industry standards exist for production of
cultures used for bioaugmentation, most producers adopt their own procedures to meet their
own requirements and those of their clients. Below are some considerations for the develop-
ment of a QA/QC program for producing bacterial cultures for remediation of chlorinated
solvent-contaminated aquifers.
3.4.1 Pathogen Analysis
Pathogen analysis is commonly performed to assess the safety of bacterial cultures.
An early study suggested that some indicator organisms (e.g., coliforms and fecal coliforms)
may survive in early-stage enrichment cultures grown for bioaugmentation, especially if the
enrichment inoculum is derived from sewage sludge (Skramstad et al.,
2003
). Furthermore,
such analyses are sometimes required by regulatory authorities to evaluate the suitability of a
culture for injection into an aquifer.
Pathogen analysis is available through a number of commercial vendors. A common readily
available battery of pathogen tests includes assays for the following: (1)
Salmonella
spp
.
(enteric pathogens), (2)
Listeria monocytogenes
(food borne pathogen), (3)
Vibrio
spp
.
(enteric
pathogen, causative agent of cholera and other infections), (4)
Clostridium perfringens
(causa-
tive agent of gas gangrene; food poisoning and flesh-eating infections), (5)
Pseudomonas
spp.
(many plant and animal infections), (6) yeast (multiple infections), (7)
Escherichia coli
(enteric
pathogen; indicator of fecal contamination), total coliforms (indicators of fecal contamination
or enteric pathogens), (8)
Bacillus
spp. (causative agent of anthrax and some food poisonings),
(9)
Yersinia
spp. (causative agent of plague), (10)
Streptococci
(multiple infections), (11)
Campylobacter jejuni
(food poisoning agent usually associated with poultry) and mold (multi-
ple infections).
The cost of such a battery of tests is reasonable, but the actual utility of these tests for
assessing the safety of bioaugmentation cultures is questionable. For example, many of the
organisms identified are members of diverse bacterial families that contain multiple species,
strains or pathovars, many of which are non-pathogenic. Also, many strains in these families
are common soil bacteria that could reasonably be expected to test positively in a culture
isolated from an environmental sample (e.g.,
Pseudomonas, Bacillus, Yersinia,
mold and
yeast). Thus, a positive test for one of these potential pathogens could raise unnecessary
concerns about the safety of a culture. Furthermore, because all
Dhc
bioaugmentation cultures
are grown under strict anaerobic conditions, a greater focus on potential anaerobic pathogens
may be more suitable for assessing culture safety, but assays for such infective agents are less
readily available.
3.4.2
Dhc
Concentrations
Knowledge of the
Dhc
concentrations in bioaugmentation cultures is critical for planning
and for determining the relative value of commercially available cultures. Because the
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