Clinical features and treatment outcomes of Mycobacterium chimaera lung disease and antimicrobial susceptibility of the mycobacterial isolates

The State-of-the-Art of Mycobacterium chimaera Infections and the Causal Link with Health Settings: A Systematic Review

(1) Background. A definition of healthcare-associated infections is essential also for the attribution of the restorative burden to healthcare facilities in case of harm and for clinical risk management strategies. Regarding M. chimaera infections, there remains several issues on the ecosystem and pathogenesis. We aim to review the scientific evidence on M. chimaera beyond cardiac surgery, and thus discuss its relationship with healthcare facilities. (2) Methods. A systematic review was conducted on PubMed and Web of Science on 7 May 2024 according to PRISMA 2020 guidelines for reporting systematic reviews, including databases searches with the keyword "Mycobacterium chimaera". Article screening was conducted by tree authors independently. The criterion for inclusion was cases that were not, or were improperly, consistent with the in-situ deposition of aerosolised M. chimaera. (3) Results. The search yielded 290 eligible articles. After screening, 34 articles (377 patients) were included. In five articles, patients had undergone cardiac surgery and showed musculoskeletal involvement or disseminated infection without cardiac manifestations. In 11 articles, respiratory specimen reanalyses showed M. chimaera. Moreover, 10 articles reported lung involvement, 1 reported meninges involvement, 1 reported skin involvement, 1 reported kidney involvement after transplantation, 1 reported tendon involvement, and 1 reported the involvement of a central venous catheter; 3 articles reported disseminated cases with one concomitant spinal osteomyelitis. (4) Conclusions. The scarce data on environmental prevalence, the recent studies on M. chimaera ecology, and the medicalised sample selection bias, as well as the infrequent use of robust ascertainment of sub-species, need to be weighed up. The in-house aerosolization, inhalation, and haematogenous spread deserve experimental study, as M. chimaera cardiac localisation could depend to transient bacteraemia. Each case deserves specific ascertainment before tracing back to the facility, even if M. chimaera represents a core area for healthcare facilities within a framework of infection prevention and control policies.

Mycobacterium colombiense Pneumonia in HIV-Infected Patients: Three Case Reports and a Literature Review

Background

Mycobacterium colombiense pneumonia in HIV-infected patients is relatively unusual but is associated with a high mortality rate, as well as high rates of misdiagnosis and delayed diagnosis. Clinical metagenome next-generation sequencing (mNGS) may have potential for its accurate and timely diagnosis.

Case Presentation

We retrospectively reviewed the medical records of three HIV-infected patients who presented with M. colombiense pneumonia in Zhejiang Province between January 2019 and December 2020. No specific clinical presentations or radiological manifestations were found in any of the patients. The detection of M. colombiense is 28-55 days earlier using mNGS on bronchoalveolar lavage fluid (BALF) compared to traditional culture methods. A combined treatment of rifabutin, clarithromycin, or azithromycin, and ethambutol did not provide timely relief of symptoms in these three patients. In the early stage of treatment, moxifloxacin and linezolid were used for several weeks. The average course of treatment for all three patients was close to 17 months.

Conclusion

We recommend early BALF mNGS for fast and accurate diagnosis of M. colombiense pneumonia in HIV-infected patients with low CD4 counts and long duration of symptoms. Further, moxifloxacin and linezolid may be beneficial in the early stage of treatment.

Treatment of non-tuberculosis mycobacteria skin infections

Non-tuberculosis mycobacteria (NTM) skin infections have become increasingly prevalent in recent years, presenting a unique challenge in clinical management. This review explored the complexities of NTM infections localized to the superficial tissues and provided valuable insights into the optimal therapeutic strategies. The antibiotic selection should base on NTM species and their susceptibility profiles. It is recommended to adopt a comprehensive approach that considers the unique characteristics of superficial tissues to improve treatment effectiveness and reduce the incidence of adverse reactions, infection recurrence, and treatment failure. Infection control measures, patient education, and close monitoring should complement the treatment strategies to achieve favorable outcomes in managing NTM skin infections. Further efforts are warranted to elucidate factors and mechanisms contributing to treatment resistance and relapse. Future research should focus on exploring novel treatment options, innovative drug development/delivery platforms, and precise methodologies for determining therapeutic duration. Longitudinal studies are also needed to assess the long-term safety profiles of the integrated approaches.

Phages for the treatment of Mycobacterium species

Highly drug-resistant strains are not uncommon among the Mycobacterium genus, with patients requiring lengthy antibiotic treatment regimens with multiple drugs and harmful side effects. This alarming increase in antibiotic resistance globally has renewed the interest in mycobacteriophage therapy for both Mycobacterium tuberculosis complex and non-tuberculosis mycobacteria. With the increasing number of genetically well-characterized mycobacteriophages and robust engineering tools to convert temperate phages to obligate lytic phages, the phage cache against extensive drug-resistant mycobacteria is constantly expanding. Synergistic effects between phages and TB drugs are also a promising avenue to research, with mycobacteriophages having several additional advantages compared to traditional antibiotics due to their different modes of action. These advantages include less side effects, a narrow host spectrum, biofilm penetration, self-replication at the site of infection and the potential to be manufactured on a large scale. In addition, mycobacteriophage enzymes, not yet in clinical use, warrant further studies with their additional benefits for rupturing host bacteria thereby limiting resistance development as well as showing promise in vitro to act synergistically with TB drugs. Before mycobacteriophage therapy can be envisioned as part of routine care, several obstacles must be overcome to translate in vitro work into clinical practice. Strategies to target intracellular bacteria and selecting phage cocktails to limit cross-resistance remain important avenues to explore. However, insight into pathophysiological host-phage interactions on a molecular level and innovative solutions to transcend mycobacteriophage therapy impediments, offer sufficient encouragement to explore phage therapy. Recently, the first successful clinical studies were performed using a mycobacteriophage-constructed cocktail to treat non-tuberculosis mycobacteria, providing substantial insight into lessons learned and potential pitfalls to avoid in order to ensure favorable outcomes. However, due to mycobacterium strain variation, mycobacteriophage therapy remains personalized, only being utilized in compassionate care cases until there is further regulatory approval. Therefore, identifying the determinants that influence clinical outcomes that can expand the repertoire of mycobacteriophages for therapeutic benefit, remains key for their future application.

Phage Therapy for Nontuberculous Mycobacteria: Challenges and Opportunities

Non-tuberculous mycobacterium (NTM) infections are often clinically challenging, with lengthy antibiotic regimens that fail to resolve the infections with few good outcomes remaining. Mycobacteriophages-viruses that infect Mycobacterium hosts-show promise as therapeutic agents for NTM infections and have been used in 20 compassionate use cases. Favorable outcomes were observed in many but not all cases, although the phages show exceptional safety profiles and no evidence of phage resistance was observed, even when only a single phage was administered. Phage-specific antibodies are commonly present following intravenous administration and are often neutralizing for the phage in vitro. However, phage neutralization does not consistently correlate with poor treatment outcomes and may not be a therapeutic limitation in all patients, even when immunocompetent. Currently, the therapeutic potential of phages is substantially limited by the great variation in phage susceptibility and a relatively small repertoire of therapeutically useful phages. As many as 45% of clinical isolates can have a smooth colony morphotype, and phages that both efficiently infect and kill these strains have yet to be described. In contrast, ~ 75% of rough strains are susceptible to and killed by one or more phages and therapeutic options can be considered on a compassionate use basis. Although therapies must currently be personalized, elucidating the determinants of phage host specificity, expanding the useful phage repertoire, and identifying the key determinants of clinical outcomes will reveal their full therapeutic potential.

Disseminated Mycobacterium chimaera infection in a patient with adult-onset immunodeficiency syndrome: case report

BACKGROUND

Patients with adult-onset immunodeficiency syndrome due to anti-interferon-γ autoantibodies (AIGAs) are susceptible to disseminated Mycobacterium avium complex (MAC) infections. M. chimaera, a newly identified MAC species, is distinguished from the others due to the reduced virulence. Previous cases of disseminated M. chimaera infection have been linked to cardiothoracic surgery. Reports of disseminated M. chimaera in patients without a history of cardiothoracic surgery are rare.

CASE PRESENTATION

A 57-year-old Asian man, previously healthy, presented with fever, dry cough, exertional dyspnea, and decreased appetite. The delayed resolution of pneumonia despite antibiotic treatment prompted further imaging studies and biopsies from the lung and lymph node. The fluorodeoxyglucose positron emission tomography/computed tomography (FDG-PET/CT) demonstrated intense uptake in lung consolidations and diffuse lymphadenopathy. Cultures of the specimens obtained from sputum, blood, stool, lung tissue, and lymph node grew M. chimaera. Further immunological evaluation disclosed the presence of neutralizing AIGAs, which possibly led to acquired immunodeficiency and disseminated M. chimaera infection.

CONCLUSIONS

We herein present the first case of adult-onset immunodeficiency due to AIGAs complicated with disseminated M. chimaera infection. Further immunological evaluation, including AIGAs, may be warranted in otherwise healthy patients who present with disseminated mycobacterial infection.

Pharmacologic management of Mycobacterium chimaera Infections: A Primer for Clinicians

Mycobacterium chimaera, a member of the Mycobacterium avium complex, can cause infections in individuals after open heart surgery due to contaminated heater-cooler units. The diagnosis can be challenging, as the incubation period can be quite variable, and symptoms are nonspecific. In addition to aggressive surgical management, combination pharmacologic therapy is the cornerstone of therapy, which should consist of a macrolide, a rifamycin, ethambutol, and amikacin. Multiple second-line agents may be utilized in the setting of intolerances or toxicities. In vitro susceptibility of these agents is similar to activity against other species in the Mycobacterium avium complex. Drug–drug interactions are frequently encountered, as many individuals have chronic medical comorbidities and are prescribed medications that interact with the first-line agents used to treat M. chimaera. Recognition of these drug–drug interactions and appropriate management are essential for optimizing treatment outcomes.

Drug susceptibility distributions of Mycobacterium chimaera and other non-tuberculous mycobacteria

Recent outbreaks of cardiac surgery-associated Mycobacterium chimaera infections have highlighted the importance of species differentiation within the Mycobacterium avium complex and pointed to a lack of antibiotic susceptibility data for M. chimaera Using the MGIT 960/EpiCenter TB eXiST platform, we have determined antibiotic susceptibility patterns of 48 clinical M. chimaera isolates and 139 other non-tuberculous mycobacteria including 119 members of the M. avium complex and 20 Mycobacterium kansasii towards clofazimine and other drugs used to treat infections with slowly growing nontuberculous mycobacteria (NTM). MIC₅₀, MIC₉₀ and tentative epidemiological cutoff (ECOFF) values for clofazimine were 0.5 mg/L, 1 mg/L and 2 mg/L for M. chimaera. Comparable values were observed for other M. avium complex members, lower MIC₅₀ (≤0.25 mg/L), MIC₉₀ (0.5 mg/L) and ECOFF (1 mg/L) values were found for M. kansasii Susceptibility to clarithromycin, ethambutol, rifampin, rifabutin, amikacin, moxifloxacin and linezolid was in general similar for M. chimaera and other members of the M. avium complex but increased for M. kansasii The herein determined MIC distributions, MIC₉₀ and ECOFF values of clofazimine for M. chimaera and other NTM provide the basis for the definition of clinical breakpoints. Further studies are needed to establish correlation of in vitro susceptibility and clinical outcome.