Biomedical Engineering Reference
In-Depth Information
species diversity is testament to the success of such adaptive survival strategy;
more than 1.5 x 10 6 species of microorganisms are believed to exist [40].
Only a small portion ( < 1%) of this total amount of microorganisms have been
successfully grown in axenic culture [41,42]. Microorganisms from all environ-
ments have frequently been demonstrated to be unculturable. Gao et al. [43]
identified that approximately 15% of all species recovered from the human fore-
arm are not currently culturable. Wade [44] similarly reports that only 50% of the
microorganisms in the buccal cavity are culturable. A recent study of classified
and controlled cleanrooms has identified that > 10 6 cells/m 2 nonculturable cells
exist, easily outnumbering culturable cells [45]. It is therefore likely that within
environments associated with aseptic manufacturing, admixing, and adminis-
tration, the actual magnitude of a microbial hazard significantly exceeds that
determinable by traditional microbiological culturing techniques. Quantitative
risk assessment incorporating such considerations, therefore, may well represent
a means of assuring product quality (in microbiological terms), which exceeds
that obtainable with currently available measurement technology.
10.5.3 Risk of Endotoxin
The adverse health effects elicited by endotoxins (the vestiges of bacterial cell
walls) within parenteral products are very well described; endotoxins are clearly
a hazard and need to be assessed within risk assessment. Endotoxins may realize
a risk to product quality either as an intrinsic or an extrinsic hazard. For example,
endotoxins existing as part of the “natural” load inherent in or originating from
a raw material or active pharmaceutical ingredient derived from a recombinant
gram-negative bacterial fermentation might be regarded as intrinsic. In contrast,
endotoxins contaminating a parenteral product presentation via, say, a container
closure (e.g., vial or stopper, sealing ring or plunger) originate externally and
therefore constitute an extrinsic hazard. Endotoxins within a parenteral product
presentation or derived from gram-negative bacteria entering the patient can sig-
nificantly and acutely jeopardize patient health. Lipopolysaccharide is regarded
as the main initiator of sepsis via the triggered release of inflammatory cytokines,
tumor necrosis factor alpha, and interlukin-6 (IL-6). Within the past 10-15 years,
peptidoglycan has also been recognized as a major contributor eliciting an IL-6
response and patient sepsis [46], warranting careful evaluation in any assessment
of risk to aseptic processes. Moreover, peptidoglycan appears to act synergisti-
cally with lipoteichoic acid and lipopolysaccharide to cause organ injury [47].
The complexity of synergism and likelihood of a wider variety of microbially
derived entities with the capability to agonistically elicit IL-6 response are some
of the reasons for introduction of the monocyte activation test [35]. This is a
clear acknowledgement that far more microbially derived molecules than those
we have detailed knowledge of or the ability to specifically test for may adversely
affect product quality. Any risk analysis and risk management strategies in aseptic
manufacturing must consider this and evaluate these risks derived from intrinsic
and extrinsic hazard ingress.
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