Investigating the Origin of Mycobacterium chimaera Contamination in Heater-Cooler Units: Integrated Analysis with Fourier Transform Infrared Spectroscopy and Whole-Genome Sequencing

Mycobacterium chimaera is ubiquitously spread in the environment, including factory and hospital water systems. Invasive cases of M. chimaera infection have been associated with aerosols produced by the use of heater-cooler units (HCU) during cardiac surgery. The aim of this study was to evaluate for the first time the performance of IR-Biotyper system on a large number of M. chimaera isolates collected from longitudinal environmental HCUs samples and water sources from hospitals located in three Italian provinces. In addition, IR-Biotyper results were compared with whole-genome sequencing (WGS) analysis, the reference method for molecular epidemiology, to investigate the origin of M. chimaera contamination of HCUs. From November 2018 to May 2021, 417 water samples from 52 HCUs (Stockert 3T, n = 41 and HCU40, n = 11) and 23 hospital taps (used to fill the HCU tanks) were concentrated, decontaminated, and cultured for M. chimaera. Positive cultures (n = 53) were purified by agar plate subcultures and analyzed by IR-Biotyper platform and Ion Torrent sequencing system. IR-Biotyper spectra results were analyzed using a statistical approach of dimensionality reduction by linear discriminant analysis (LDA), generating three separate clusters of M. chimaera, ascribable to each hospital. Furthermore, the only M. chimaera-positive sample from tap water clustered with the isolates from the HCUs of the same hospital, confirming that the plumbing system could represent the source of HCU contamination and, potentially, of patient infection. According to the genome-based phylogenies and following the classification proposed by van Ingen and collaborators in 2017, three distinct M. chimaera groups appear to have contaminated the HCU water systems: subgroups 1.1, 2.1, and branch 2. Most of the strains isolated from HCUs at the same hospital share a highly similar genetic profile. The nonrandom distribution obtained with WGS and IR-Biotyper leads to the hypothesis that M. chimaera subtypes circulating in the local plumbing colonize HCUs through the absolute filter, in addition with the current hypothesis that contamination occurs at the HCU production site. This opens the possibility that other medical equipment, such as endoscope reprocessing device or hemodialysis systems, could be contaminated by M. chimaera. IMPORTANCE Our manuscript focuses on interventions to reduce waterborne disease transmission, improve sanitation, and control infection. Sanitary water can be contaminated by nontuberculous Mycobacteria, including M. chimaera, a causative agent of invasive infections in immunocompromised patients. We found highly similar genetic and phenotypic profiles of M. chimaera isolated from heater-cooler units (HCU) used during surgery to thermo-regulate patients' body temperature, and from the same hospital tap water. These results lead to the hypothesis that M. chimaera subtypes circulating in the local plumbing colonize HCUs through the absolute filter, adding to the current hypothesis that contamination occurs at the HCU production site. In addition, this opens the possibility that other medical equipment using sanitized water, such as endoscope reprocessing devices or hemodialysis systems, could be contaminated by nontuberculous Mycobacteria, suggesting the need for environmental surveillance and associated control measures.

OR Air Quality: Is It Time to Consider Adjunctive Air Cleaning Technology?: 1.3 www.aornjournal.org/content/cme

Patients undergoing surgery may be at risk for infection from airborne particles such as dust, skin scales, respiratory aerosols, and hair fibers emanating from multiple sources in the OR, including personnel, heater-cooler devices, and surgical smoke. This risk is increased in surgical patients undergoing procedures involving implanted devices. Surgical personnel also are at risk from exposure to surgical smoke, which can contain viable viral particles including human papillomavirus infection. Air quality in the OR is improved by engineering controls (eg, maintaining positive pressure). During the past decade, innovations in the field of adjunctive technology designed to improve OR air quality include using ultraviolet disinfection and mobile ultraviolet disinfection plus high-efficiency particulate air filtration. Some of these technologies additionally provide continuous monitoring of circulating air particle counts. Additional research regarding the benefits of adjunctive air-cleaning technology in the OR is warranted.

Mycobacterium Chimaera Mimicking Sarcoidosis

Mycobacterium chimaera (M. chimaera) is a slow-growing nontuberculous mycobacteria usually associated with pulmonary infection in immunocompromised patients. Attributed to a specific brand of contaminated heater-cooler units used during cardiac surgery, M. chimaera has become a global public health concern due to disseminated infection affecting immunocompetent hosts. Given its nonspecific presenting symptoms and indolent course of infection, M. chimaera can mimic and be misdiagnosed as sarcoidosis. Increased awareness among the medical community and at-risk population should be maintained to facilitate more rapid diagnosis and prevent inappropriate treatment of this potentially devastating condition.

A novel wall water system for cardiopulmonary bypass may reduce the risk of aerosolized infection

OBJECTIVE

Oxygenators for cardiopulmonary bypass require water flow for their integral heat exchanger. Heater-cooler units are nearly universally used for this requirement. Heater-cooler units pose the risk of aerosolized infection. The Centers for Disease Control and Prevention recommended discontinuing use of Stöckert 3T heater-cooler units (LivaNova PLC, London, United Kingdom) in October 2016 because of this risk. We aimed to reduce the risk of aerosolized infection posed by heater-cooler units by eliminating those devices from our operating rooms.

METHODS

The cardiac surgery division collaborated with in-house specialties to engineer a novel wall water system. The design called for service to 4 operating rooms with the actual water mixing valve in an operating room closet. Remote temperature control was mounted next to the heart-lung machine. Primary safety systems built into the water system include 5 μm filtration, pressure regulating and relief valves, flow quantifiers, limits to the hot and chilled input temperatures, and a novel bridge near the heart-lung machine that allows the perfusionist to test the system before patient use and to quickly disconnect the patient in case of system malfunction. In addition, all water line connections can be made with the tubing drained and never under pressure.

RESULTS

This novel wall water system has successfully provided heat exchanger water flow on 625 patients undergoing congenital heart surgery requiring cardiopulmonary bypass during its first 9 months of use.

CONCLUSIONS

Wall water systems are an option for oxygenator heat exchangers that allow for improved heat exchange performance while reducing the risk of heater-cooler unit-associated infection during cardiac surgery.