Nocardia infections in solid organ transplantation: Guidelines from the Infectious Diseases Community of Practice of the American Society of Transplantation

Safety and Outcomes of Linezolid Use for Nocardiosis

Background

Tropical Australia has a high incidence of nocardiosis, with high rates of intrinsic antimicrobial resistance. Linezolid, the only antimicrobial to which all local Nocardia species are susceptible, has been recommended in empirical combination treatment regimens for moderate-severe Nocardia infections at Royal Darwin Hospital (RDH) since 2014. We report the safety and efficacy of linezolid use for nocardiosis in this setting.

Methods

We identified cases through a retrospective review of all RDH Nocardia isolates from December 2014 to August 2018 and included 5 linezolid-treated cases from a previous cohort. Laboratory, demographic, and clinical data were included in the primary analysis of safety and treatment outcomes.

Results

Between 2014 and 2018, Nocardia was isolated from 35 individuals; 28 (80%) had clinically significant infection and 23 (82%) received treatment. All isolates were linezolid-susceptible. Safety and efficacy were assessed for 20 patients receiving linezolid-containing regimens and 8 receiving nonlinezolid regimens. Median linezolid induction therapy duration was 28 days. Common adverse effects in those receiving linezolid were thrombocytopenia (45%) and anemia (40%). Adverse events prompted discontinuation of trimethoprim-sulfamethoxazole more often than linezolid (40% vs 20%). Linezolid therapeutic drug monitoring was used in 1 patient, with successful dose reduction and outcome. There was no difference in 30-day survival between those treated with linezolid (90%) vs no linezolid (87%). One Nocardia-attributed death occurred during linezolid therapy.

Conclusions

Linezolid is safe and efficacious in empirical treatment for moderate to severe nocardiosis in a monitored hospital setting, with 100% drug susceptibility and no difference in adverse events or outcomes compared with nonlinezolid regimens.

Management and prophylaxis of bacterial and mycobacterial infections among lung transplant recipients

Bacterial and mycobacterial infections are associated with morbidity and mortality in lung transplant recipients. Infectious complications are categorized by timing post-transplant: <1, 1–6, and >6 months. The first month post-transplant is associated with the highest risk of infection. During this period, infections are most commonly healthcare-associated, and include infections related to surgical complications. The lungs and bloodstream are common sites of infections. Common healthcare-associated organisms include methicillin-resistant Staphylococcus aureus (MRSA), Gram-negative bacilli such as Pseudomonas aeruginosa, and Clostridioides difficile. More than 1-month post-transplant, opportunistic infections can occur. Tuberculosis occurs in 0.8–10% of lung transplant recipients which reflects variation in background prevalence. The majority of post-transplant tuberculosis stems from reactivation of untreated or undiagnosed latent tuberculosis. Most post-transplant tuberculosis occurs in the lungs and develops within a year of transplant. Non-tuberculous mycobacteria commonly colonize the lungs of lung transplant candidates and are often hard to eradicate even with prolonged courses of antimycobacterial agents. Drug interactions between antimycobacterial agents and calcineurin and mTOR inhibitors also complicates treatment post-transplant. Given that infection adversely impacts outcomes after lung transplant, and that anti-infective therapy is often less effective after transplant, infection prevention is key to long-term success. A comprehensive approach that includes pre-transplant evaluation, perioperative prophylaxis, long-term antimicrobial prophylaxis, immunization, and safer living at home and in the community, should be employed to minimize the risk of infection.

Nocardiosis: A Neglected Disease

Nocardiosis is a neglected tropical disease. It has varied geographical presence and a spectrum of clinical presentations. This review aims to focus on the epidemiology of nocardial infections with a systematic approach to their diagnosis and treatment. Nocardiacauses chronic infections and ailments, and may remain cryptic but progressive in its course. Unless suspected, diagnosis can be easily missed resulting in increased morbidity and mortality. Thorough knowledge of local epidemiology, demography, clinical course and presentation, diagnostic modalities, and antibiotic susceptibility patterns of the prevalent Nocardia species is essential to curb spread of this infection. This is a systematic review in which internet search has been done for citation indices (Embase, PubMed, Ovid, and other individual journals) till March 2020 utilizing the following key words "Nocardia," "taxonomy," "prevalence," "clinical features," "diagnosis," "treatment," and "susceptibility." We selected a total of 87 review articles, case series, and case reports all in English language.

Nocardia infection in kidney transplant recipients: A single-center experience

BACKGROUND

Data on Nocardia infection in kidney transplant patients remain limited.

METHODS

A chart review of patients with a history of kidney transplant and one positive culture for Nocardia between 1999 and 2019 was performed.

RESULTS

Ten patients (0.1%) had a Nocardia infection. Eight were deceased donor kidney transplant recipients, and the mean age at the time of transplant was 56.0 ± 14.5 years. Nocardia infection occurred at a median of 12 months (range, 6-102) after transplant with half of the cases within 1 year. Breakthrough Nocardia infection occurred in five patients receiving daily double-strength (160/800 mg) TMP-SMX as prophylaxis. Half of the patients had comorbid CMV infection at diagnosis. The most common site involved was the lung. TMP-SMX was the most frequently used antimicrobial agent for treating Nocardia infection (9 of 10); it was administered as single-drug therapy (4 of 10) or as combination therapy with other antimicrobials (5 of 10). Overall mortality was 60% with 30% attributable mortality within a mean of 3.3 ± 7.7 weeks after a diagnosis of Nocardia.

DISCUSSION

TMP-SMX prophylaxis did not appear to protect against Nocardia but did appear to be associated with less severe disease. Overall outcomes remain poor, and infection can occur outside the traditional window.

Updates on Nocardia Skin and Soft Tissue Infections in Solid Organ Transplantation

PURPOSE OF REVIEW

Due to their immunocompromised status, solid organ transplant (SOT) recipients are at risk for Nocardia infections. These infections often necessitate early invasive diagnostics alongside prolonged, often combination antimicrobial therapy. This review summarizes the importance of this pathogen in skin and soft tissue infections (SSTIs) in SOT recipients inclusive of recently reported cases in the literature and an update on the epidemiology, diagnostics, and management.

RECENT FINDINGS

Six studies with 13 isolated SSTIs due to Nocardia have been published in the last 5 years in SOT recipients. The most common underlying type of transplant was kidney and time from transplantation to infection varied from 6 months to 16 years. Misdiagnosis was frequent. Available identified species included N. brasiliensis (2), N. farcinica (2), N. flavorosea (1), N. abscessus (1), N. anaemiae (1), N. asteroides (1), N. nova (1), and N. vinacea (1). Treatment choice and duration varied widely, and trimethoprim-sulfamethoxazole was utilized most often with no documented infection relapse. Nocardia SSTIs can occur both in isolation and as a component of a disseminated infection. Overall, isolated Nocardia SSTIs are uncommon in SOT recipients and are often initially misdiagnosed. They present multiple challenges to the clinician including evaluation for potential co-pathogens and/or non-infectious processes and ruling out the presence of disseminated infection. While trimethoprim-sulfamethoxazole remains the agent of choice for management of most isolated SSTIs, therapy must be tailored to the individual patient based on species-specific susceptibility patterns and formal susceptibility testing, site(s) of infection, and patient tolerability.