A biofilm model developed to investigate survival and disinfection of Mycobacterium mucogenicum in potable water

Abstract

Water in healthcare environments can be a source for healthcare-associated infections (HAI). However, information on the exposure risk to opportunistic pathogens in potable water distribution systems (PWDS) is lacking. Laboratory studies characterizing the interaction of opportunistic pathogens with biofilms are needed to understand their role in water systems within healthcare facilities. A stable, repeatable, PWDS multi-species biofilm model comprising Sphingomonas paucimobilis, Methylobacterium sp., Delftia acidovorans, and Mycobacterium mucogenicum was developed in the CDC Biofilm Reactor (CBR), reaching 6 log₁₀ CFU cm⁻² within 6 days. The model was used to investigate the interaction of the opportunistic pathogen M. mucogenicum with the other species, and to determine the efficacy of monochloramine (NH₂Cl) as a disinfectant against 2-week-old biofilms. Addition of 1 or 2 mg l⁻¹ NH₂Cl resulted in the same or an increased log density of viable M. mucogenicum in the biofilm while inactivating some of the Proteobacteria. Although M. mucogenicum preferentially resided in the biofilm, NH₂Cl exposure caused release of viable M. mucogenicum from the biofilm into the water. Additional studies with this model should determine if sodium hypochlorite has a comparative effect and if other nontuberculous mycobacteria (NTM) respond to NH₂Cl similarly.

Keywords:

• water distribution system biofilm
• Mycobacterium mucogenicum
• monochloramine
• nontuberculous mycobacteria

Acknowledgements

The authors thank Jody Shoemaker of DeKalb County Watershed Management for providing water quality data. Sarah Gilbert and Elizabeth Perez are also thanked for technical assistance. Funding for this work was provided by the National Center for Environmental Health in the Centers for Disease Control and Prevention (CDC). The findings and conclusions in this report are those of the authors and do not necessarily represent the official position of the US CDC.