Hot Tubs and Bioreactors

By Dr. Ray Nims

Contaminating organisms which most commonly are under the radar for biopharmaceutical manufacturing operations include bacteria, mollicutes (mycoplasmas and acholeplasmas), and viruses. Various in-process and lot-release detection assays are mandated by the FDA and the International Conference on Harmonisation to ensure that such contaminants are detected in bulk harvests and/or final products as part of assuring patient safety (specified in ICH Q5A R1 and the 1993 Points to Consider in the Characterization of Cell Lines used to Produce Biologics). There is, however, an additional group of organisms which may threaten biologics production (one which is not normally associated with such manufacturing activities) namely, the Mycobacterium fortuitum complex.

The what?? The fortuitum complex is a group of relatively rapid-growing (non-tuberculosis) mycobacteria which is more typically associated with hot tub disease, and the contamination of industrial cutting fluids and foot baths used for pedicures. The group includes M. fortuitum, M. chelonae, M. abscessus, M. immunogenum, M. mucogenicum, M. peregrinum, and a few others. These mycobacteria, as well as other groups of non-tuberculosis mycobacteria, can be pathogenic in humans, even those who are immuno-competent. The organisms of the fortuitum complex represent a potential risk to the biopharma industry due to their propensity for forming biofilms, their ability to proliferate in water under relatively low nutrient conditions, their resistance to typical water disinfection methods, and their relatively slow growth in nutrient media.

                    Mycobacteria growing at the liquid/air
                       interface of a growth medium.


These characteristics render the organisms capable of existing in water piping and other surfaces in contact with water or aqueous media. Their slow growth in nutrient media may result in these agents being overlooked in biopharmaceutical manufacturing operations, especially when surveillance methods such as short-term bioburden assays are employed. A few cases of contaminated vaccines and tissue extracts have been reported in the literature (Mycobacterium chelonei in abscesses after injection of diphtheria-pertussis-tetanus-polio vaccine. Am. Rev. Respir. Dis. 1973 Jan; 107:1-8; Abscesses due to Mycobacterium abscessus linked to injection of unapproved alternative medication. Emerg. Inf. Dis. 1999; 5: 681-687).

Are there other examples? It is, unfortunately, difficult to estimate the frequency of occurrence of mycobacterial contamination in biologics manufacturing, since many episodes may lead to premature bioreactor termination, with little evidence to implicate a mycobacterium. It is also likely that episodes may have occurred without being reported in the literature.