Diversity of nontuberculous mycobacteria in Heater-Cooler Devices - results from prospective surveillance

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.

A Case of Pericarditis and Pericardial Masses Associated With Mycobacterium Paragordonae

Tuberculosis is a common cause of pericarditis worldwide and has been associated with pericardial masses. Non-tuberculous mycobacteria are uncommonly associated with cardiac disease, having primarily been described in cases of endocarditis. Here we describe a case of an immunocompetent patient with Mycobacterium paragordonae infection causing pericarditis with a large effusion containing pericardial masses. The patient presented with chest pain, hypoxia and biochemical evidence of inflammation (CRP 216.1 mg/L). This report illustrates a rare case of pericarditis with pericardial masses associated with non-tuberculous mycobacteria and the first example of pericarditis associated with M. paragordonae.

Molecular epidemiology of nontuberculous mycobacteria isolated from tuberculosis-suspected patients

It is a growing problem around the world to deal with nontuberculous mycobacteria infection (NTM), but its clinical significance is still largely unknown. This study aims to investigate the epidemiology of NTM infections from various clinical samples and determine their clinical significance. From December 2020 to December 2021, 6125 clinical samples were collected. In addition to phenotypic detection, genotypic detection through multilocus sequence typing (hsp65, rpoB, and 16S rDNA genes) and sequencing was also conducted. Records of patients were consulted for clinical information, such as symptoms and radiological findings. Of the 6,125 patients, 351 (5.7%) were positive for acid-fast bacteria (AFB). Out of 351 AFB, 289 (82.3%) and 62 (17.7%) subjects were identified as M. tuberculosis complex (MTC) and NTM strains, respectively. Isolates of Mycobacterium simiae and M. fortuitum were the most frequent, followed by isolates of M. kansasii and M. marinum. We also isolated M. chelonae, M. canariasense, and M. jacuzzii, which are rarely reported. Symptoms (P = 0.048), radiographic findings (P = 0.013), and gender (P = 0.039) were associated with NTM isolates. M. Fortuitum, M. simiae, and M. kansasii presented with bronchiectasis, infiltration, and cavitary lesions most frequently, while cough was the most common symptom. In conclusion, Mycobacterium simiae and M. fortuitum were presented in seventeen and twelve NTM isolates from the collected samples. There is evidence that NTM infections in endemic settings may contribute to the dissemination of various diseases and the control of tuberculosis. In spite of this, further research is needed to evaluate the clinical significance of NTM isolates.

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

BACKGROUND

Colonization with Mycobacterium chimaera and other non-tuberculous mycobacteria (NTM) has been reported for heater-cooler devices (HCDs) produced by several manufacturers. Up until now, exclusively LivaNova (London, UK) HCDs have been associated with M. chimaera infections after cardiac surgery. The vast majority of studies on HCD colonization were cross-sectional.

AIM

We were interested in longitudinal dynamics of mycobacterial growth in HCD water samples and analysed data of a prospective mycobacterial surveillance of five LivaNova 3T HCDs.

METHODS

Five LivaNova HCDs were subjected to prospective mycobacterial surveillance. For each HCD and the total of HCDs, results of mycobacterial detection were analyzed. Logistic regression was applied to model the association between growth of any NTM or M. chimaera and duration of HCD use.

RESULTS

Non-tuberculous mycobacteria were isolated in 319 (48.0%, 21 water samples grew more than one mycobacterial species) of a total of 665 water samples. The most frequently detected species were M. chimaera (N = 247/319, 77.4%), Mycobacterium gordonae (46/319, 14.4%) and Mycobacterium paragordonae (34/319, 10.7%). Detection rates increased prospectively for any NTM (odds ratio (OR) per year in use: 1.60, 95% confidence interval (CI) 1.17-2.24, P<0.001) and for M. chimaera (OR per year in use: 1.67, 95% CI 1.11-2.57, P<0.01).

CONCLUSION

Longer duration of HCD use was associated with higher detection rates for any NTM and M. chimaera, respectively.

Mycobacterium paragordonae is an emerging pathogen in human pulmonary disease: clinical features, antimicrobial susceptibility testing and outcomes

Objectives: Mycobacterium paragordonae (MPG) is an emerging and less common type of Non-tuberculous mycobacteria (NTM) and we know little about its characteristics and prognosis, hence we constructed this retrospective cohort study. Methods: MPG was identified using MALD-TOF MS, multi-target combined gene sequencing and WGS. Clinical information was collected, antimicrobial susceptibility testing was measured using the SLOMYCO panel, and optimal growth temperature testing was measured using Lowenstein-Jensen medium. Results: Eight MPGs were isolated from 1730 NTMs (0.46%); the mean age of MPG pulmonary disease (MPG-PD) patients was 42.38 ± 9.92 years, 37.5% were male, and the average BMI was 18.4 ± 0.51 kg/m². All patients had the symptoms of cough and sputum and CT images mainly presented in patchy or streaky shadows, MPG grew at 25°C, 30°C and 37°C, and the optimal growth temperature is 37°C. MPGs were sensitive to clarithromycin, rifabutin, amikacin, linezolid, moxifloxacin, cotrimoxazole and ciprofloxacin, two isolates were resistant to rifampicin. Two patients had follow up information, their imaging remained stable during the follow-up. Conclusions: MPG-PD is a rare NTM disease and is more likely to develop in middle-aged, female, and low BMI patients. The patients present with no specific features within the symptoms as well as the CT imaging. The optimal growth temperature of MPG is at 37°C, MPG-PD has excellent sensitivity to drugs recommended by CLSI and presents with a stable disease.

Recovery of Mycobacteria from Heavily Contaminated Environmental Matrices

For epidemiology studies, a decontamination method using a solution containing 4.0% NaOH and 0.5% tetradecyltrimethylammonium bromide (TDAB) represents a relatively simple and universal procedure for processing heavily microbially contaminated matrices together with increase of mycobacteria yield and elimination of gross contamination. A contamination rate only averaging 7.3% (2.4% in Cluster S; 6.9% in Cluster R and 12.6% in Cluster E) was found in 787 examined environmental samples. Mycobacteria were cultured from 28.5% of 274 soil and water sediments samples (Cluster S), 60.2% of 251 samples of raw and processed peat and other horticultural substrates (Cluster R), and 29.4% of 262 faecal samples along with other samples of animal origin (Cluster E). A total of 38 species of slow and rapidly growing mycobacteria were isolated. M. avium ssp. hominissuis, M. fortuitum and M. malmoense were the species most often isolated. The parameters for the quantitative detection of mycobacteria by PCR can be significantly refined by treating the sample suspension before DNA isolation with PMA (propidium monoazide) solution. This effectively eliminates DNA residue from both dead mycobacterial cells and potentially interfering DNA segments present from other microbial flora. In terms of human exposure risk assessment, the potential exposure to live non-tuberculous mycobacteria can be more accurately determined.

The global outbreak of Mycobacterium chimaera infections in cardiac surgery-a systematic review of whole-genome sequencing studies and joint analysis

BACKGROUND

With the increasing dimensions of the international cardiac surgery-associated Mycobacterium chimaera outbreak the hypothesis of a point source arose.

OBJECTIVES

To review the published evidence of clonality among cardiac surgery-associated M. chimaera isolates evaluated by whole-genome sequencing (WGS) and to perform an integrative genomic analysis of available genome data.

DATA SOURCES

We searched PubMed and EMBASE for studies applying WGS on cardiac surgery-associated M. chimaera isolates.

STUDY ELIGIBILITY CRITERIA

We included studies that applied WGS on more than a single M. chimaera isolate.

METHODS

Two authors independently extracted data from included studies. Available genome data from published studies were subjected to a joint analysis.

RESULTS

Of 121 identified articles, nine studies were included. M. chimaera isolates from LivaNova heater-cooler devices (HCDs) had a high level of genetic similarity, but were genetically distant from isolates from HCDs produced by other manufacturers. With the exception of a single (11.1%) study, the remaining eight (89.9%) studies reported a high level of genetic proximity between the majority of M. chimaera isolates derived from cardiac surgery-associated patients and LivaNova HCDs. In-depth analysis revealed involvement of three distinct M. chimaera subgroups in the outbreak (1.1, 1.8, 2.1), with 1.1 suggested as causative of the outbreak. Samples taken at the LivaNova production site supported contamination with strains of subgroups 1.1 and 1.8. In the combined analysis of 526 publicly available WGS data sets, nearly all isolates from cardiac surgery-associated patients contained strain 1.1 (50/52, 96.2%), and at least one of the outbreak strains was found in almost all LivaNova HCDs (241/257, 93.8%), with strain 1.1 in particular present in 198/257 (77.0%).

CONCLUSIONS

HCD contamination during production seems plausible as the predominant point source for the global M. chimaera outbreak. Although HCDs can be contaminated with mixed populations, M. chimaera strains of the subgroup 1.1 caused most infections.

Heater-Cooler Devices and Risk of Contamination during Cardiac Surgery

BACKGROUND

 Heater-cooler devices (HCD) have been implicated in a cardiosurgical contamination scenario causing prosthetic valve endocarditis.

AIM

 We characterized contamination of new HCDs and assessed the risk of intraoperative microorganism transmission from the HCD to the operating field.

METHODS

 We initially acquired four new FlexTherm and then four new Maquet HCU40 HCDs and assessed occurrence and speed of microbial contamination (including mycobacteria) assessing swab and water samples from the device. In parallel, we collected repeated samples from different sites in the operating room either by swab sticks or by exposing different sample plates to room air. We also reviewed microbiological results from the hospital and compared them to cardiosurgical wound infections and endocarditis cases. Finally, we simulated cardiosurgical conditions and assessed the devices' ability to expel air to the operative field.

RESULTS

 All new HCDs were clean before first use. Despite authority-mandated decontamination procedures, microbial growth (Fusarium solani, Sphingomonas paucimobilis, Pseudomonas aeruginosa, Mycobacterium chelonae, and gordonae) was identified in all HCDs over time and could not be permanently eliminated. Four of these mircoorganisms were also found in tap water. However, none of the HCD-organisms were found inside the laminar airflow operating area. Importantly, except for P. aeruginosa, none of the HCD organisms were found in patients with surgical wound infections or endocarditis. HCD-expelled air did not rise more than 40 cm above ground.

CONCLUSION

 HCDs cannot be expected to remain sterile despite extensive decontamination procedures. However, airborne transmission of microorganisms directly from the HCD to the operating field appears unlikely.

Mycobacterium chimaera Genomics With Regard to Epidemiological and Clinical Investigations Conducted for an Open Chest Postsurgical Mycobacterium chimaera Infection Outbreak

Background

Postsurgical infections due to Mycobacterium chimaera appeared as a novel nosocomial threat in 2015, with a worldwide outbreak due to contaminated heater-cooler units used in open chest surgery. We report the results of investigations conducted in France including whole-genome sequencing comparison of patient and heater-cooler unit isolates.

Methods

We sought M. chimaera infection cases from 2010 onwards through national epidemiological investigations in health care facilities performing cardiopulmonary bypass, together with a survey on good practices and systematic heater-cooler unit microbial analyses. Clinical and heater-cooler unit isolates were subjected to whole-genome sequencing analyzed with regard to the reference outbreak strain Zuerich-1.

Results

Only 2 clinical cases were shown to be related to the outbreak, although 23% (41/175) of heater-cooler units were declared positive for M. avium complex. Specific measures to prevent infection were applied in 89% (50/56) of health care facilities, although only 14% (8/56) of them followed the manufacturer maintenance recommendations. Whole-genome sequencing comparison showed that the clinical isolates and 72% (26/36) of heater-cooler unit isolates belonged to the epidemic cluster. Within clinical isolates, 5–9 nonsynonymous single nucleotide polymorphisms were observed, among which an in vivo mutation in a putative efflux pump gene was observed in a clinical isolate obtained for 1 patient on antimicrobial treatment.

Conclusions

Cases of postsurgical M. chimaera infections have been declared to be rare in France, although heater-cooler units were contaminated, as in other countries. Genomic analyses confirmed the connection to the outbreak and identified specific single nucleotide polymorphisms, including 1 suggesting fitness evolution in vivo.

Contact Effect of a Methylobacterium sp. Extract on Biofilm of a Mycobacterium chimaera Strain Isolated from a 3T Heater-Cooler System

Mycobacterium chimaera is an opportunistic slowly growing non-tuberculous mycobacteriumof increasing importance due to the outbreak of cases associated with contaminated 3T heater-cooler device (HCD) extracorporeal membrane oxygenator (ECMO). The aim of this study was to evaluate the effect of pre-treating a surface with a Methylobacterium sp. CECT 7180 extract to inhibit the M. chimaera ECMO biofilm as well as of the treatment after different dehydration times. Surface adherence, biofilm formation and treatment effect were evaluated by estimating colony-forming units (CFU) per square centimeter and characterizing the amount of covered surface area, thickness, cell viability, and presence of intrinsic autofluorescence at different times using confocal laser scanning microscopy and image analysis. We found that exposing a surface to the Methylobacterium sp. CECT 7180 extract inhibited M. chimaera ECMO biofilm development. This effect could be result of the effect of Methylobacterium proteins, such as DNaK, trigger factor, and xanthine oxidase. In conclusion, exposing a surface to the Methylobacteriumsp. extract inhibits M. chimaera ECMO biofilm development. Furthermore, this extract could be used as a pre-treatment prior to disinfection protocols for equipment contaminated with mycobacteria after dehydration for at least 96 h.