uncommon. Treatment requires control of interactions between antituberculous drugs and
immunosuppressive therapy. A high index of suspicion is recommended. If diagnosis of
pneumonia is uncertain in the first 24 to 48 hours, specific cultures and PCR forM. tuberculosis
should be considered.
Rhodococcus equi(89) andNocardia(90–94) are well-known causes of respiratory tract
infection in transplant recipients. However, they usually present in a subacute form and rarely
require ICU admission. These infections usually occur more than three months posttrans-
plantation. Radiologically, they may appear as multiple and bilateral nodules, possibly due to
their long-term silent presentation. The incidence of nocardiosis has been significantly reduced
since the widespread use of cotrimoxazole prophylaxis.Nocardia farcinicamay be resistant to
cotrimoxazole prophylaxis and cause particularly aggressive disease (90). In a retrospective
cohort study among 577 lung transplant recipients from 1991 to 2007, nocardiosis occurred in
1.9% of patients and was associated with a mean of nearly two weeks to diagnosis and
frequent adverse effects on therapy (95).
R. equiis an opportunistic pathogen that usually causes cavitated pneumonia in HIV-
positive patients, but SOT recipients may be affected as well. Infection occur usually late
(median of 49 months after transplantation) and the lungs are primarily involved in most
cases. Infection presents as a lung nodule in half of the patients. Clinicians should consider
R. equi when evaluating a solid-organ recipient with an asymptomatic lung nodule,
particularly when cultures fail to identify mycobacteria, Nocardia, or fungal organisms.
Clinical microbiology laboratories should be alerted when anR. equiinfection is suspected,
since it could be mistaken for a contaminant diphtheroid and will not respond to the standard
empirical therapy.
Fungi.Fungal infections have been reported to occur in 5% to 20% of SOT recipients, and
although they are decreasing proportionally, they increase in absolute figures as more
transplantation procedures are performed each year. Rates vary according to the type of
transplant recipient and are greatly influenced by the degree of immunosuppression, the use of
prophylaxis, the rate of surgical complications and of renal failure among the transplant
population. Fungal pathogens more likely to cause pneumonia in this population are
Aspergillus,P. jiroveci,Candidaspp., andCryptococcusspp.
Different types of transplantations imply differences in fungal infections (96). A recent
series prospectively collected in Spain reported incidence of invasive aspergillosis (IA) in SOT
recipients, which ranged from 0.3% in KT to 3.9% in pancreas recipients (97). In lung and
heart-lung transplantation, the incidence of fungal infections, most notably aspergillosis,
ranges from 14% to 35% if no prophylaxis is provided, but has significantly decreased since
aerosolized amphotericin B is provided to these patients (98,99). In single-lung transplant
patients, IA more commonly affects the native lung than the transplanted lung and may arise
immediately postoperatively due to preexistent disease in pretransplant immunosuppressed
patients. In lung and heart-lung transplant recipients, the types of disease presentation include
bronchial anastomosis dehiscence, vascular anastomosis erosion, bronchitis, tracheobronchitis,
invasive lung disease, aspergilloma, empyema, disseminated disease, endobronchial stent
obstruction, and mucoid bronchial impaction. Kramer et al. have described a distinct form of
IA after lung transplantation: ulcerative tracheobronchitis, a semi-invasive disease involving
the anastomosis site and the large airways (100). Risk factors include CMV infection,
obliterative bronchitis, rejection, and increased immunosuppression.
In HT,Aspergillusis the predominant fungal isolate and accounts for 38% of all lung
nodular lesions (101). It appears as a median of 5063 days after HT (102). We found that
postoperative hemodialysis, CMV disease, reoperation, and other episodes of aspergillosis in
the ward close to the transplantation date are the major risk factors for IA in this population.
The use of oral itraconazole is an effective way of preventing this infection.
In liver transplantation,Aspergillusinfection is less common when compared with lung
or heart-lung transplant recipients and is more commonly found than in KT recipients. In liver
transplant recipients, IA usually is an early event and most patients were still in the ICU with
evidence of organ dysfunction when the disease was diagnosed (87,103). Retransplantation is
also an independent risk factor (103,104), although aspergillosis may happen in low-risk
394 Mun ̃oz et al.