Surgical Antimicrobial Prophylaxis in Low-Risk Cholecystectomies is Associated with Fewer Surgical Site Infections: Nationwide Cohort Study in Switzerland.

OBJECTIVE: To assess whether administration of surgical antimicrobial prophylaxis (SAP) versus absence of SAP is associated with a decreased risk of surgical site infections (SSI) after low-risk cholecystectomies (LR-CCE). SUMMARY BACKGROUND DATA: Current guidelines do not recommend routine SAP administration prior to LR-CCE. METHODS: This cohort study included adult patients who underwent LR-CCE and were documented by the Swissnoso SSI surveillance system between 1/2009-12/2020 at 66 Swiss hospitals. LR-CCE was specified as elective endoscopic surgery, age <70, no active cholecystitis, ASA score <3, operating time <120 minutes without implantation of foreign material. Exposure was defined as the administration of cefuroxime or cefazoline ± metronidazole within 120 minutes prior to incision versus no SAP administration. Our main outcome was occurrence of SSI until day 30. Logistic regression models were used to adjust for institutional, patient, and perioperative variables. RESULTS: Of 44 682 surveilled adult cholecystectomy patients, 12 521 (8 726 women [69.7%]; median [IQR] age, 49.0 [38.1-58.2] years), fulfilled inclusion criteria. SSI was identified in 143 patients (1.1%). SAP was administered in 9 269 patients (74.0%) and was associated with a lower SSI rate (adjusted odds ratio [aOR], 0.50; 95% CI, 0.35-0.70; P < 0.001). The number needed to treat to prevent one SSI episode is 100. CONCLUSIONS: The overall LR-CCE SSI rate was 1.1%. SAP was associated with a 50% lower overall SSI rate. Patients undergoing LR-CCE may benefit from routine surgical antimicrobial prophylaxis.

Influence of patient characteristics on microbial composition in surgical-site infections: insights from national surveillance study.

BACKGROUND: Although the impact of surgery- and patient-dependent factors on surgical-site infections (SSIs) have been studied extensively, their influence on the microbial composition of SSI remains unexplored. The aim of this study was to identify patient-dependent predictors of the microbial composition of SSIs across different types of surgery. METHODS: This retrospective cohort study included 538 893 patients from the Swiss national infection surveillance programme. Multilabel classification methods, adaptive boosting and Gaussian Naive Bayes were employed to identify predictors of the microbial composition of SSIs using 20 features, including sex, age, BMI, duration of surgery, type of surgery, and surgical antimicrobial prophylaxis. RESULTS: Overall, SSIs were recorded in 18 642 patients (3.8%) and, of these, 10 632 had microbiological wound swabs available. The most common pathogens identified in SSIs were Enterobacterales (57%), Staphylococcus spp. (31%), and Enterococcus spp. (28%). Age (mean feature importance 0.260, 95% c.i. 0.209 to 0.309), BMI (0.224, 0.177 to 0.271), and duration of surgery (0.221, 0.180 to 0.269) were strong and independent predictors of the microbial composition of SSIs. Increasing age and duration of surgical procedure as well as decreasing BMI were associated with a shift from Staphylococcus spp. to Enterobacterales and Enterococcus spp. An online application of the machine learning model is available for validation in other healthcare systems. CONCLUSION: Age, BMI, and duration of surgery were key predictors of the microbial composition of SSI, irrespective of the type of surgery, demonstrating the relevance of patient-dependent factors to the pathogenesis of SSIs.

Local infections are a frequent problem after surgery. The risk factors for surgical infections have been identified, but it is unclear which factors predict the type of microorganisms found in such infections. The aim of the present study was to assess patient factors affecting the composition of microorganisms in surgical infections. Data from 538 893 patients were analysed using standard statistics and machine learning methods. The results showed that age, BMI, and the duration of surgery were important in determining the bacteria found in the surgical-site infections. With increasing age, longer operations, and lower BMI, more bacteria stemming from the intestine were found in the surgical site, as opposed to bacteria from the skin. This knowledge may help in developing more personalized treatments for patients undergoing surgery in the future.

Povidone Iodine vs Chlorhexidine Gluconate in Alcohol for Preoperative Skin Antisepsis: A Randomized Clinical Trial.

Importance: Preoperative skin antisepsis is an established procedure to prevent surgical site infections (SSIs). The choice of antiseptic agent, povidone iodine or chlorhexidine gluconate, remains debated. Objective: To determine whether povidone iodine in alcohol is noninferior to chlorhexidine gluconate in alcohol to prevent SSIs after cardiac or abdominal surgery. Design, Setting, and Participants: Multicenter, cluster-randomized, investigator-masked, crossover, noninferiority trial; 4403 patients undergoing cardiac or abdominal surgery in 3 tertiary care hospitals in Switzerland between September 2018 and March 2020 were assessed and 3360 patients were enrolled (cardiac, n = 2187 [65%]; abdominal, n = 1173 [35%]). The last follow-up was on July 1, 2020. Interventions: Over 18 consecutive months, study sites were randomly assigned each month to either use povidone iodine or chlorhexidine gluconate, each formulated in alcohol. Disinfectants and skin application processes were standardized and followed published protocols. Main Outcomes and Measures: Primary outcome was SSI within 30 days after abdominal surgery and within 1 year after cardiac surgery, using definitions from the US Centers for Disease Control and Prevention's National Healthcare Safety Network. A noninferiority margin of 2.5% was used. Secondary outcomes included SSIs stratified by depth of infection and type of surgery. Results: A total of 1598 patients (26 cluster periods) were randomly assigned to receive povidone iodine vs 1762 patients (26 cluster periods) to chlorhexidine gluconate. Mean (SD) age of patients was 65.0 years (39.0-79.0) in the povidone iodine group and 65.0 years (41.0-78.0) in the chlorhexidine gluconate group. Patients were 32.7% and 33.9% female in the povidone iodine and chlorhexidine gluconate groups, respectively. SSIs were identified in 80 patients (5.1%) in the povidone iodine group vs 97 (5.5%) in the chlorhexidine gluconate group, a difference of 0.4% (95% CI, -1.1% to 2.0%) with the lower limit of the CI not exceeding the predefined noninferiority margin of -2.5%; results were similar when corrected for clustering. The unadjusted relative risk for povidone iodine vs chlorhexidine gluconate was 0.92 (95% CI, 0.69-1.23). Nonsignificant differences were observed following stratification by type of surgical procedure. In cardiac surgery, SSIs were present in 4.2% of patients with povidone iodine vs 3.3% with chlorhexidine gluconate (relative risk, 1.26 [95% CI, 0.82-1.94]); in abdominal surgery, SSIs were present in 6.8% with povidone iodine vs 9.9% with chlorhexidine gluconate (relative risk, 0.69 [95% CI, 0.46-1.02]). Conclusions and Relevance: Povidone iodine in alcohol as preoperative skin antisepsis was noninferior to chlorhexidine gluconate in alcohol in preventing SSIs after cardiac or abdominal surgery. Trial Registration: ClinicalTrials.gov Identifier: NCT03685604.

[Surgical site infection after lower limb arterial reconstruction: can we improve prevention?] / Infections postchirurgie artérielle des membres inférieurs : peut-on mieux faire?

Infections associated with arterial reconstructions of the lower limbs are associated with high morbidity. This article reviews the risk factors for infection associated with this surgery and the preventive measures. These include smoking cessation and glycemic control preoperatively; avoiding unnecessary exposure to antibiotics or corticosteroids; optimal peripheral wound care; rigorous antisepsis and antibiotic prophylaxis in the operating theatre ; and finally, meticulous post-operative wound monitoring. The benefit of Staphylococcus aureus decolonization in vascular surgery is less clearly established than in cardiac and thoracic surgery, but it is still recommended in cases of implant placement or where there is a high risk of S. aureus infection, depending on the planned approach and type of surgery.

Les infections associées aux reconstructions artérielles des membres inférieurs sont grevées d'une morbidité élevée. Cet article revoit les facteurs de risque d'infection associés à cette chirurgie et les mesures de prévention. Ces dernières incluent l'arrêt du tabac et le contrôle glycémique en préopératoire ; l'absence d'exposition inutile aux antibiotiques ou aux corticostéroïdes ; les soins de plaies périphériques optimaux ; une antisepsie et une antibioprophylaxie au bloc opératoire rigoureuses et, finalement, un suivi de plaie postopératoire minutieux. Le bénéfice de la décolonisation à Staphylococcus aureus dans le cadre de la chirurgie vasculaire est moins clairement établi qu'en chirurgies cardiaque et thoracique, mais celle-ci reste recommandée en cas de mise en place d'implant ou de risque élevé d'infection à S. aureus, selon la voie d'abord et le type de chirurgie prévue.

Identifying the drivers of multidrug-resistant Klebsiella pneumoniae at a European level.

Beta-lactam- and in particular carbapenem-resistant Enterobacteriaceae represent a major public health threat. Despite strong variation of resistance across geographical settings, there is limited understanding of the underlying drivers. To assess these drivers, we developed a transmission model of cephalosporin- and carbapenem-resistant Klebsiella pneumoniae. The model is parameterized using antibiotic consumption and demographic data from eleven European countries and fitted to the resistance rates for Klebsiella pneumoniae for these settings. The impact of potential drivers of resistance is then assessed in counterfactual analyses. Based on reported consumption data, the model could simultaneously fit the prevalence of extended-spectrum beta-lactamase-producing and carbapenem-resistant Klebsiella pneumoniae (ESBL and CRK) across eleven European countries over eleven years. The fit could explain the large between-country variability of resistance in terms of consumption patterns and fitted differences in hospital transmission rates. Based on this fit, a counterfactual analysis found that reducing nosocomial transmission and antibiotic consumption in the hospital had the strongest impact on ESBL and CRK prevalence. Antibiotic consumption in the community also affected ESBL prevalence but its relative impact was weaker than inpatient consumption. Finally, we used the model to estimate a moderate fitness cost of CRK and ESBL at the population level. This work highlights the disproportionate role of antibiotic consumption in the hospital and of nosocomial transmission for resistance in gram-negative bacteria at a European level. This indicates that infection control and antibiotic stewardship measures should play a major role in limiting resistance even at the national or regional level.

The impact of public health interventions on the future prevalence of ESBL-producing Klebsiella pneumoniae: a population based mathematical modelling study.

BACKGROUND: Future prevalence of colonization with extended-spectrum betalactamase (ESBL-) producing K. pneumoniae in humans and the potential of public health interventions against the spread of these resistant bacteria remain uncertain. METHODS: Based on antimicrobial consumption and susceptibility data recorded during > 13 years in a Swiss region, we developed a mathematical model to assess the comparative effect of different interventions on the prevalence of colonization. RESULTS: Simulated prevalence stabilized in the near future when rates of antimicrobial consumption and in-hospital transmission were assumed to remain stable (2025 prevalence: 6.8% (95CI%:5.4-8.8%) in hospitals, 3.5% (2.5-5.0%) in the community versus 6.1% (5.0-7.5%) and 3.2% (2.3-4.2%) in 2019, respectively). When overall antimicrobial consumption was set to decrease by 50%, 2025 prevalence declined by 75% in hospitals and by 64% in the community. A 50% decline in in-hospital transmission rate led to a reduction in 2025 prevalence of 31% in hospitals and no reduction in the community. The best model fit estimated that 49% (6-100%) of observed colonizations could be attributable to sources other than human-to-human transmission within the geographical setting. CONCLUSIONS: Projections suggests that overall antimicrobial consumption will be, by far, the most powerful driver of prevalence and that a large fraction of colonizations could be attributed to non-local transmissions.

Nosocomial outbreak of vancomycin-resistant Enterococcus faecium (VRE) ST796, Switzerland, 2017 to 2020.

A large clonal outbreak caused by vancomycin-resistant Enterococcus faecium (VRE) affected the Bern University Hospital group from the end of December 2017 until July 2020. We describe the characteristics of the outbreak and the bundle of infection prevention and control (IPC) measures implemented. The outbreak was first recognised when two concomitant cases of VRE bloodstream infection were identified on the oncology ward. During 32 months, 518 patients in the 1,300-bed hospital group were identified as vanB VRE carriers. Eighteen (3.5%) patients developed an invasive infection, of whom seven had bacteraemia. In 2018, a subset of 328 isolates were analysed by whole genome sequencing, 312 of which were identified as sequence type (ST) 796. The initial IPC measures were implemented with a focus on the affected wards. However, in June 2018, ST796 caused another increase in cases, and the management strategy was intensified and escalated to a hospital-wide level. The clinical impact of this large nosocomial VRE outbreak with the emergent clone ST796 was modest. A hospital-wide approach with a multimodal IPC bundle was successful against this highly transmissible strain.

Hospital outcomes of community-acquired COVID-19 versus influenza: Insights from the Swiss hospital-based surveillance of influenza and COVID-19.

BackgroundSince the onset of the COVID-19 pandemic, the disease has frequently been compared with seasonal influenza, but this comparison is based on little empirical data.AimThis study compares in-hospital outcomes for patients with community-acquired COVID-19 and patients with community-acquired influenza in Switzerland.MethodsThis retrospective multi-centre cohort study includes patients > 18 years admitted for COVID-19 or influenza A/B infection determined by RT-PCR. Primary and secondary outcomes were in-hospital mortality and intensive care unit (ICU) admission for patients with COVID-19 or influenza. We used Cox regression (cause-specific and Fine-Gray subdistribution hazard models) to account for time-dependency and competing events with inverse probability weighting to adjust for confounders.ResultsIn 2020, 2,843 patients with COVID-19 from 14 centres were included. Between 2018 and 2020, 1,381 patients with influenza from seven centres were included; 1,722 (61%) of the patients with COVID-19 and 666 (48%) of the patients with influenza were male (p < 0.001). The patients with COVID-19 were younger (median 67 years; interquartile range (IQR): 54-78) than the patients with influenza (median 74 years; IQR: 61-84) (p < 0.001). A larger percentage of patients with COVID-19 (12.8%) than patients with influenza (4.4%) died in hospital (p < 0.001). The final adjusted subdistribution hazard ratio for mortality was 3.01 (95% CI: 2.22-4.09; p < 0.001) for COVID-19 compared with influenza and 2.44 (95% CI: 2.00-3.00, p < 0.001) for ICU admission.ConclusionCommunity-acquired COVID-19 was associated with worse outcomes compared with community-acquired influenza, as the hazards of ICU admission and in-hospital death were about two-fold to three-fold higher.

The effect of the COVID-19 pandemic on the epidemiology of positive blood cultures in Swiss intensive care units: a nationwide surveillance study.

BACKGROUND: Evidence about the impact of the pandemic of COVID-19 on the incidence rates of blood cultures contaminations and bloodstream infections in intensive care units (ICUs) remains scant. The objective of this study was to investigate the nationwide epidemiology of positive blood cultures drawn in ICUs during the first two pandemic waves of COVID-19 in Switzerland. METHODS: We analyzed data on positive blood cultures among ICU patients, prospectively collected through a nationwide surveillance system (ANRESIS), from March 30, 2020, to May 31, 2021, a 14-month timeframe that included a first wave of COVID-19, which affected the French and Italian-speaking regions, an interim period (summer 2020) and a second wave that affected the entire country. We used the number of ICU patient-days provided by the Swiss Federal Office of Public Health as denominator to calculate incidence rates of blood culture contaminations and bloodstream infections (ICU-BSI). Incidence rate ratios comparing the interim period with the second wave were determined by segmented Poisson regression models. RESULTS: A total of 1099 blood culture contaminations and 1616 ICU-BSIs were identified in 52 ICUs during the study. Overall, more episodes of blood culture contaminations and ICU-BSI were observed during the pandemic waves, compared to the interim period. The proportions of blood culture contaminations and ICU-BSI were positively associated with the ICU occupancy rate, which was higher during the COVID-19 waves. During the more representative second wave (versus interim period), we observed an increased incidence of blood culture contaminations (IRR 1.57, 95% CI 1.16-2.12) and ICU-BSI (IRR 1.20, 95% CI 1.03-1.39). CONCLUSIONS: An increase in blood culture contaminations and ICU-BSIs was observed during the second COVID-19 pandemic wave, especially in months when the ICU burden of COVID-19 patients was high.

Phenotypic and Genomic Analyses of Burkholderia stabilis Clinical Contamination, Switzerland.

A recent hospital outbreak related to premoistened gloves used to wash patients exposed the difficulties of defining Burkholderia species in clinical settings. The outbreak strain displayed key B. stabilis phenotypes, including the inability to grow at 42°C; we used whole-genome sequencing to confirm the pathogen was B. stabilis. The outbreak strain genome comprises 3 chromosomes and a plasmid, sharing an average nucleotide identity of 98.4% with B. stabilis ATCC27515 BAA-67, but with 13% novel coding sequences. The genome lacks identifiable virulence factors and has no apparent increase in encoded antimicrobial drug resistance, few insertion sequences, and few pseudogenes, suggesting this outbreak was an opportunistic infection by an environmental strain not adapted to human pathogenicity. The diversity among outbreak isolates (22 from patients and 16 from washing gloves) is only 6 single-nucleotide polymorphisms, although the genome remains plastic, with large elements stochastically lost from outbreak isolates.

Global Health Estimate of Invasive Mycobacterium chimaera Infections Associated with Heater-Cooler Devices in Cardiac Surgery.

Investigations of a worldwide epidemic of invasive Mycobacterium chimaera associated with heater-cooler devices in cardiac surgery have been hampered by low clinical awareness and challenging diagnoses. Using data from Switzerland, we estimated the burden of invasive M. chimaera to be 156-282 cases/year in 10 major cardiac valve replacement market countries.

Epidemiology of subsequent bloodstream infections in the ICU.

Subsequent bloodstream infections (sBSI) occur with a delay after removal of the intravascular catheter (IVC) whose tip revealed microbial growth. Here we describe the epidemiology of sBSI in the intensive care setting. Serratia marcescens, Staphylococcus aureus, Pseudomonas aeruginosa, and yeast were the pathogens most frequently associated with sBSI. In contrast, Enterococci were rarely found in sBSI.

Arenavirus Glycan Shield Promotes Neutralizing Antibody Evasion and Protracted Infection.

Arenaviruses such as Lassa virus (LASV) can cause severe hemorrhagic fever in humans. As a major impediment to vaccine development, delayed and weak neutralizing antibody (nAb) responses represent a unifying characteristic of both natural infection and all vaccine candidates tested to date. To investigate the mechanisms underlying arenavirus nAb evasion we engineered several arenavirus envelope-chimeric viruses and glycan-deficient variants thereof. We performed neutralization tests with sera from experimentally infected mice and from LASV-convalescent human patients. NAb response kinetics in mice correlated inversely with the N-linked glycan density in the arenavirus envelope protein's globular head. Additionally and most intriguingly, infection with fully glycosylated viruses elicited antibodies, which neutralized predominantly their glycan-deficient variants, both in mice and humans. Binding studies with monoclonal antibodies indicated that envelope glycans reduced nAb on-rate, occupancy and thereby counteracted virus neutralization. In infected mice, the envelope glycan shield promoted protracted viral infection by preventing its timely elimination by the ensuing antibody response. Thus, arenavirus envelope glycosylation impairs the protective efficacy rather than the induction of nAbs, and thereby prevents efficient antibody-mediated virus control. This immune evasion mechanism imposes limitations on antibody-based vaccination and convalescent serum therapy.

Burkholderia stabilis outbreak associated with contaminated commercially-available washing gloves, Switzerland, May 2015 to August 2016.

We describe an outbreak of Burkholderia stabilis associated with contaminated washing gloves, a commercially available Class I medical device. Triggered by an increase in Burkholderia cepacia complex (BCC) bacteremias and the detection of BCC in unopened packages of washing gloves, an ad hoc national outbreak committee comprising representatives of a public health organisation, a regulatory agency, and an expert association convened and commissioned an outbreak investigation. The investigation included retrospective case finding across Switzerland and whole genome sequencing (WGS) of isolates from cases and gloves. The investigation revealed that BCC were detected in clinical samples of 46 cases aged 17 to 91 years (33% females) from nine institutions between May 2015 and August 2016. Twenty-two isolates from case patients and 16 from washing gloves underwent WGS. All available outbreak isolates clustered within a span of < 19 differing alleles, while 13 unrelated clinical isolates differed by > 1,500 alleles. This BCC outbreak was rapidly identified, communicated, investigated and halted by an ad hoc collaboration of multiple stakeholders. WGS served as useful tool for confirming the source of the outbreak. This outbreak also highlights current regulatory limitations regarding Class I medical devices and the usefulness of a nationally coordinated outbreak response.

Transmission of Mycobacterium chimaera from Heater-Cooler Units during Cardiac Surgery despite an Ultraclean Air Ventilation System.

Heater-cooler units (HCUs) were recently identified as a source of Mycobacterium chimaera causing surgical site infections. We investigated transmission of this bacterium from HCUs to the surgical field by using a thermic anemometer and particle counter, videotape of an operating room equipped with an ultraclean laminar airflow ventilation system, and bacterial culture sedimentation plates in a nonventilated room. Smoke from the HCU reached the surgical field in 23 s by merging with ultraclean air. The HCU produced on average 5.2, 139, and 14.8 particles/min in the surgical field at positions Off, On/oriented toward, and On/oriented away, respectively. Culture plates were positive for M. chimaera <5 m from the HCU in the test room. These experiments confirm airborne transmission of M. chimaera aerosols from a contaminated HCU to an open surgical field despite ultraclean air ventilation. Efforts to mitigate infectious risks during surgery should consider contamination from water sources and airflow-generating devices.

Reemergence of Mycobacterium chimaera in Heater-Cooler Units despite Intensified Cleaning and Disinfection Protocol.

Invasive Mycobacterium chimaera infections after open-heart surgery have been reported internationally. These devastating infections result from aerosols generated by contaminated heater-cooler units used with extracorporeal circulation during surgery. Despite intensified cleaning and disinfection, surveillance samples from factory-new units acquired during 2014 grew nontuberculous mycobacteria after a median of 174 days.

Healthcare-associated prosthetic heart valve, aortic vascular graft, and disseminated Mycobacterium chimaera infections subsequent to open heart surgery.

AIMS: We identified 10 patients with disseminated Mycobacterium chimaera infections subsequent to open-heart surgery at three European Hospitals. Infections originated from the heater-cooler unit of the heart-lung machine. Here we describe clinical aspects and treatment course of this novel clinical entity. METHODS AND RESULTS: Interdisciplinary care and follow-up of all patients was documented by the study team. Patients' characteristics, clinical manifestations, microbiological findings, and therapeutic measures including surgical reinterventions were reviewed and treatment outcomes are described. The 10 patients comprise a 1-year-old child and nine adults with a median age of 61 years (range 36-76 years). The median duration from cardiac surgery to diagnosis was 21 (range 5-40) months. All patients had prosthetic material-associated infections with either prosthetic valve endocarditis, aortic graft infection, myocarditis, or infection of the prosthetic material following banding of the pulmonary artery. Extracardiac manifestations preceded cardiovascular disease in some cases. Despite targeted antimicrobial therapy, M. chimaera infection required cardiosurgical reinterventions in eight patients. Six out of 10 patients experienced breakthrough infections, of which four were fatal. Three patients are in a post-treatment monitoring period. CONCLUSION: Healthcare-associated infections due to M. chimaera occurred in patients subsequent to cardiac surgery with extracorporeal circulation and implantation of prosthetic material. Infections became clinically apparent after a time lag of months to years. Mycobacterium chimaera infections are easily missed by routine bacterial diagnostics and outcome is poor despite long-term antimycobacterial therapy, probably because biofilm formation hinders eradication of pathogens.

Prolonged Outbreak of Mycobacterium chimaera Infection After Open-Chest Heart Surgery.

BACKGROUND: Invasive Mycobacterium chimaera infections were diagnosed in 2012 in 2 heart surgery patients on extracorporeal circulation. We launched an outbreak investigation to identify the source and extent of the potential outbreak and to implement preventive measures. METHODS: We collected water samples from operating theaters, intensive care units, and wards, including air samples from operating theaters. Mycobacterium chimaera strains were characterized by randomly amplified polymorphic DNA polymerase chain reaction (RAPD-PCR). Case detection was performed based on archived histopathology samples and M. chimaera isolates since 2006, and the patient population at risk was prospectively surveyed. RESULTS: We identified 6 male patients aged between 49 and 64 years with prosthetic valve endocarditis or vascular graft infection due to M. chimaera, which became clinically manifest with a latency of between 1.5 and 3.6 years after surgery. Mycobacterium chimaera was isolated from cardiac tissue specimens, blood cultures, or other biopsy specimens. We were able also to culture M. chimaera from water circuits of heater-cooler units connected to the cardiopulmonary bypass, and air samples collected when the units were in use. RAPD-PCR demonstrated identical patterns among M. chimaera strains from heater-cooler unit water circuits and air samples, and strains in 2 patient clusters. CONCLUSIONS: The epidemiological and microbiological features of this prolonged outbreak provided evidence for the airborne transmission of M. chimaera from contaminated heater-cooler unit water tanks to patients during open-heart surgery.