Viability of selected microorganisms in parenteral preparations for novel systemic anti-cancer therapy

Risk factors for aseptic preparation of parenteral medicines encompass the growth-promoting nature of the preparation. Although many aqueous parenteral preparations do not have growth-promoting properties, inadvertently introduced microorganisms may remain viable. Knowledge about the viability of microorganisms in parenteral preparations can add useful information for assigning shelf life to preparations used to treat cancer patients.

The aim of the study was to assess the viability of four different facultative pathogenic microorganisms in 20 ready-to-administer parenteral preparations aseptically prepared in hospital pharmacies.

Samples of 20 different biologics and small molecules for systemic anti-cancer therapy were inoculated either with different bacteria (i.e., Staphylococcus aureus, Pseudomonas aeruginosa, Enterococcus faecium) or with Candida albicans suspension. The resulting test concentrations were 104-105 microorganisms per mL. Aliquots of inoculated test solutions were transferred in duplicate to tryptic soy agar plates at the time points 0, 4, 24, 48, 144 h. The plates were incubated for 24 h (bacterial strains) and 72 h (C. albicans) at 37 °C and colony forming units (CFUs) were counted.

In most test solutions, especially in monoclonal antibody solutions, increased CFU counts of P. aeruginosa and unchanged or increased CFU counts of E. faecium and S. aureus were registered. Pronounced nutritive properties of monoclonal antibodies and filgrastim were not registered. Azacitidine, pixantrone and vinflunine containing test solutions revealed species-specific bacteriostatic and even bactericidal activity. All test solutions, except nivolumab and pixantrone containing solutions, showed constant or increasing CFU counts of C. albicans after incubation.

Viability of the selected pathogenic microorganisms was retained in most of the tested biological and small molecule preparations used to treat cancer patients. Therefore, in pharmacy departments strict aseptic conditions should be regarded and the lack of antimicrobial activity should be considered when assigning shelf life to RTA parenteral preparations.