Characterization of Biofilm Formation by Mycobacterium chimaera on Medical Device Materials.

Archana D Siddam,Jayaleka J Amarasinghe,Matthew D Silverman,Patrick M Regan,Shari J Zaslow,K Scott Phillips,Yi Wang

doi:10.3389/fmicb.2020.586657

Abstract

Non-tuberculous mycobacteria (NTM) are widespread in the environment and are a public health concern due to their resistance to antimicrobial agents. The colonization of surgical heater-cooler devices (HCDs) by the slow-growing NTM species Mycobacterium chimaera has recently been linked to multiple invasive infections in patients worldwide. The resistance of M. chimaera to antimicrobials may be aided by a protective biofilm matrix of extracellular polymeric substances (EPS). This study explored the hypothesis that M. chimaera can form biofilms on medically relevant materials. Several M. chimaera strains, including two HCD isolates, were used to inoculate a panel of medical device materials. M. chimaera colonization of the surfaces was monitored for 6 weeks. M. chimaera formed a robust biofilm at the air-liquid interface of borosilicate glass tubes, which increased in mass over time. M. chimaera was observed by 3D Laser Scanning Microscopy to have motility during colonization, and form biofilms on stainless steel, titanium, silicone and polystyrene surfaces during the first week of inoculation. Scanning electron microscopy (SEM) of M. chimaera biofilms after 4 weeks of inoculation showed that M. chimaera cells were enclosed entirely in extracellular material, while cryo-preserved SEM samples further revealed that an ultrastructural component of the EPS matrix was a tangled mesh of 3D fiber-like projections connecting cells. Considering that slow-growing M. chimaera typically has culture times on the order of weeks, the microscopically observed ability to rapidly colonize stainless steel and titanium surfaces in as little as 24 h after inoculation is uncharacteristic. The insights that this study provides into M. chimaera colonization and biofilm formation of medical device materials are a significant advance in our fundamental understanding of M. chimaera surface interactions and have important implications for research into novel antimicrobial materials, designs and other approaches to help reduce the risk of infection.

Highlights

Mycobacterium chimaera is a slow-growing non-tuberculous mycobacterial (NTM) species ubiquitously found in the environment, including tap water (Falkinham, 2009; Wallace et al, 2013; Glickman et al, 2020)
It was determined that heater cooler devices (HCDs) used to thermoregulate patients’ body temperature during surgery were colonized with M. chimaera, and that bioaerosols containing M. chimaera released from HCD during surgery may have led to the airborn transmission of these emerging pathogens to the patient (FDA, 2015, 2016, 2020a; Sommerstein et al, 2016, 2017; Chand et al, 2017)
The optical density (OD) value for CV staining presented in Figure 1B is roughly proportional to the amount of biofilm extracted from the surface

Summary

Introduction

Mycobacterium chimaera is a slow-growing non-tuberculous mycobacterial (NTM) species ubiquitously found in the environment, including tap water (Falkinham, 2009; Wallace et al, 2013; Glickman et al, 2020). HCD’s operational temperature range is between 2 and 41◦C and standby units are kept at room temperature, a condition that may promote microbial buildup in both water tanks and connected tubes if maintenance and disinfection are performed poorly (FDA, 2016, 2020a; Sommerstein et al, 2016). Fans present in these devices may facilitate the movement of aerosolized bacteria into the sterile surgical field. A simulated operating room smoke test showed that air exhausted from an HCD can reach the patient if the device is oriented with the fan facing toward the surgical field and within a short distance of the operating table (Sommerstein et al, 2016)

Methods

Results

Discussion

Conclusion