Longitudinal increase in the detection rate of Mycobacterium chimaera in heater-cooler device-derived water samples

Emergence of Mycobacterium gordonae in heater-cooler units: a five-year prospective surveillance of devices frequently subjected to chloramine-T booster disinfection

BACKGROUND

Worldwide, the detection of Mycobacterium chimaera in LivaNova heater-cooler units (HCUs) has led to their replacement with other HCUs, although non-tuberculous mycobacteria (NTM) have been reported also for HCUs produced by other manufacturers. In almost all hospitals of our region, LivaNova HCUs have been replaced with Maquet HCU40s, regularly disinfected with chloramine-T.

AIM

To report the results of the surveillance over a 63-month operation period of the Maquet devices, and to provide a trend in NTM positivity over time.

METHODS

Twenty-nine Maquet devices (HCU40 and HU35) were monitored by two culture methods and propidium monoazide polymerase chain reaction (PMA-PCR) method. The trend in NTM positivity rate was evaluated through the Locally Estimated Scatterplot Smoothing regression and then modelled over time through segmented logistic regression.

FINDINGS

The data acquired during the study period demonstrate a remarkable increase in the positivity rate, especially after the third year (maximum slope change at 1280 days). Non-tuberculous mycobacteria were isolated in 150 water samples (37.2%); 100% and 62% of HCU40 and HU35 devices, respectively, were colonized with non-tuberculous mycobacteria. The most frequently detected species were Mycobacterium gordonae (73%) followed by Mycobacterium chelonae (41%) and Mycobacterium paragordonae (11%).

CONCLUSION

Preventive strategies by disinfection with chloramine-T did not effectively reduce non-tuberculous mycobacteria colonization of Maquet devices. Although, to date, no cases of postoperative invasive infections linked to Maquet devices have been reported, our microbiological results emphasize the need for (1) designing changes to increase safety of devices and (2) researching and developing new disinfection protocols including alternative molecules.

Mycobacterium chimaera Infections in a Unit of Cardio Surgery: Study at a General Hospital in Padua, Italy

Mycobacterium chimaera is a slow-growing non-tuberculous mycobacterium already known for being able to colonize cardio surgery heater-cooler units (HCUs). This study aims to describe the real magnitude of the phenomenon, providing a methodological protocol and the results of a longitudinal survey. In the period 1 January 2017-23 May 2022, over 1191 samples were collected on 35 HCUs of two different manufacturers. Among them, we identified 118 (10.3%) positive results for M. chimaera. We propose our 4-year biosurveillance experience as a practical model to minimize microbiological patients' risk, suggesting the need for new procedures and interventions for a safer and more ecological cardio surgery.