Mycobacterium chimaera Outbreak Management and Outcomes at a Large Pediatric Cardiac Surgery Center

Radiologic Manifestations of Mycobacterium chimaera Infection After Open Heart Surgery

PURPOSE

The objective of this study is to identify and detail the radiologic manifestations of surgical site and disseminated Mycobacterium chimaera ( MC) infection. The aim is to facilitate early identification and diagnosis of MC, considering its indolent nature and the challenges involved in clinically and pathologically establishing the diagnosis.

PATIENTS AND METHODS

This was a retrospective cohort study reviewing computed tomography (CT), positron emission tomography (PET)/CT, and magnetic resonance imaging examinations in patients over the age of 18 years with a history of open heart surgery and a clinical or pathologic diagnosis of MC. Two radiology residents, a fellowship-trained nuclear medicine radiologist, and a fellowship-trained cardiothoracic radiologist performed consensus reads to determine the imaging findings seen in MC infection.

RESULTS

Twenty-five patients were included. Localized, surgical site infection was more common than disseminated disease. Typical CT findings included peristernal soft tissue thickening, sinus tracts often extending to the cutaneous surface, slowly enlarging fluid collections, and sternal osteolysis. PET/CT findings demonstrated hypermetabolic activity in nearly all patients localized to sites of infection. Imaging findings for disseminated infection included hepatosplenomegaly, lymphadenopathy, involvement of the central nervous system, discitis/osteomyelitis, and distant abscesses.

CONCLUSIONS

Imaging plays a vital role in suggesting possible surgical sites and disseminated MC infection acquired from open heart surgery. Radiologists must keep a high index of suspicion given the indolent nature and subtle imaging change over time. PET/CT is most useful in diagnosis and helps in differentiating between a sterile postoperative fluid collection or scarring and active MC infection and helps provide a target for debridement.

Construction of a postoperative infection outbreak investigation form: A tool for early detection and control measures

BACKGROUND

To develop an investigation form for postoperative infection outbreak (PIO), and to identify sources of the outbreak in the early stage.

METHODS

After an exhaustive literature review, we used the Delphi method to determine the indicators and relative risk scores of the assessment tools through 2 rounds of specialist consultation and overall consideration of the opinions and suggestions of 20 specialists.

RESULTS

A total of 203 studies of PIO were eligible for inclusion. The mean authority coefficient (Cr) was 0.87. Kendall's W coefficient of the specialist consultation was 0.704 after 2 rounds of consultation (P < .005), suggesting that the specialists had similar opinions. Based on 4 primary items and 19 secondary items of the source of PIO, and tripartite distribution characteristics of infected patients, we constructed the PIO investigation form.

CONCLUSIONS

The PIO investigation form can be used in the investigation of the early-stage cluster of cases, it's a prerequisite for taking effective control measures, avoiding PIO occurrence. However, the effect of the investigation form needs to be further evaluated.

Epidemiological and Molecular Investigation of the Heater-Cooler Unit (HCU)-Related Outbreak of Invasive Mycobacterium chimaera Infection Occurred in Italy

BACKGROUND

From 2013 onwards, a large outbreak of Mycobacterium chimaera (MC) invasive infection, which was correlated with the use of contaminated heater-cooler units (HCUs) during open chest surgery, was reported from all over the world. Here, we report the results of the epidemiological and molecular investigations conducted in Italy after the alarm raised about this epidemic event.

METHODS

MC strains isolated from patients or from HCU devices were characterized by genomic sequencing and molecular epidemiological analysis.

RESULTS

Through retrospective epidemiological analysis conducted between January 2010 and December 2022, 40 possible cases of patients infected with MC were identified. Thirty-six strains isolated from these patients were analysed by whole genome sequencing (WGS) and were found to belong to the genotypes 1.1 or 1.8, which are the genotypes correlated with the outbreak. Most of the cases presented with prosthetic valve endocarditis, vascular graft infection or disseminated infection. Among the cases found, there were 21 deaths. The same analysis was carried out on HCU devices. A total of 251 HCUs were found to be contaminated by MC; genotypes 1.1 or 1.8 were identified in 28 of those HCUs.

CONCLUSIONS

To ensure patients' safety and adequate follow-up, clinicians and general practitioners were made aware of the results and public health measures, and recommendations were issued to prevent further cases in the healthcare settings. The Italian Society of Cardiac Surgery performed a national survey to assess the incidence of HCU-related MC prosthetic infections in cardiac surgery. No cases were reported after HCU replacement or structural modification and disinfection and possibly safe allocation outside surgical rooms.