The Research Gap in Non-tuberculous Mycobacterium (NTM) and Reusable Medical Devices

Abstract

Intermediate-level disinfection is a microbicidal "process that kills viruses, mycobacteria, fungi, and vegetative bacteria, but not necessarily bacterial spores"; validated intermediate-level disinfection processes should demonstrate at least "6-log reduction of a mixed suspension of typical vegetative organisms, such as Pseudomonas aeruginosa, Staphylococcus aureus, Escherichia coli, and representatives of the Klebsiella-Enterobacter group, and a 3-log reduction of an appropriate Mycobacterium species" (18). High-level disinfection is a microbicidal process which has been demonstrated to kill "all microbial organisms but not necessarily large numbers of bacterial spores"; validated high-level disinfection processes should demonstrate at least "6-log reduction of an appropriate Mycobacterium species" (18). Disclaimer: The mention of commercial products, their sources, or their use in connection with material reported herein is not to be construed as either an actual or implied endorsement of such products by the Department of Health and Human Services. Additionally, this article is not a formal dissemination of information by the US Food and Drug Administration and does not represent agency position or policy.

A Methodology for Investigating Aerosolization of Nontuberculous Mycobacteria From Contaminated Heater Cooler Devices

“…In addition, the higher hydrophobicity (Phillips and von Reyn, 2001) and the larger cell size of M. smegmatis could either result in the individual cells aggregating in the water leaving fewer cells to aerosolize, and/or the large aggregates of M. smegmatis aerosols generated may settle under gravity leaving fewer ones to sample from the air. As a result, during device testing, the extent of aerosolization of M. smegmatis may not reflect the true risk of a device design to aerosolize M. chimaera (Weeks et al, 2020). Therefore, a comparative study was conducted with both organisms where the relative potential of both species was compared.…”

“…The mechanism of aerosolization has an impact on the quantity of aerosols generated as well as on the survivability and recovery of microorganisms (Heidelberg et al, 1997). While nebulization and humidification are the most popular means of aerosolization, bubbling has rarely been investigated (Weeks et al, 2020). Of the investigations reported, even fewer have used biological species, and have had complex set ups containing peristaltic pumps, multiple flow loops, and other complex parts (Heidelberg et al, 1997;Ulevicius et al, 1997;Maimelis et al, 2005;Simon et al, 2011).…”

“…However, in certain circumstances, such as addressing specific safety concerns related to HCDs, the significant inter-species variability in NTM (e.g., size, hydrophobicity) it is difficult to determine if M. smegmatis can be used for aerosolization potential studies in HCDs instead of slow growing M. chimaera (Weeks et al, 2020). To investigate this aspect under controlled circumstances, we performed a direct comparison of the number of aerosols generated by M. chimaera and M. smegmatis by our bubbler for the same bubbling flow rates, and inoculum concentrations.…”

“…This revealed that in the MDRs there were at least 300 patient infections and at least 64 patient deaths associated with HCDs. Nontuberculous mycobacteria (NTM) infections are difficult to diagnose and treat due to the late onset of non-specific symptoms, slow rates of bacterial growth and manifestation of disease, and high rates of antimicrobial resistance (Phillips and von Reyn, 2001;Falkinham, 2003;Brown-Elliott et al, 2012;Weeks et al, 2020). The prevalence of infections, and their severity has led to FDA intervention through several safety communications and interactions with manufacturers (U. S. Food and Drug Administration, 2021a,b), and collaboration with the CDC.…”

“…Addressing such questions using actual HCDs would not only be logistically challenging due to the required precautions necessary for work with risk group (RG-2) microorganisms, the logistics of using large volumes (heatercoolers often require 10-14 Liters of fluids), but also time consuming. Getting the answers to most of these questions would require a concerted community effort as pointed out elsewhere (Weeks et al, 2020).…”