late-onset pneumonias. The crude mortality of bacterial pneumonia in solid-organ trans-
plantation has exceeded 40% in most series (65,66). The clinical presentation and the
differential diagnosis are similar to those in other critical patients.
The incidence of bacterial pneumonia is highest in recipients of heart-lung (22%) and
liver transplants (17%), intermediate in recipients of heart transplants (5%), and lowest in renal
transplant patients (1–2%) (67–69). The crude mortality of bacterial pneumonia in solid-organ
transplantation has exceeded 40% in most series (66).
Pneumonias occur in 13% to 34% of liver transplant recipients. Singh has recently
analyzed 40 OLT patients who developed lung infiltrates in the ICU (41). The etiology was
pulmonary edema 40%, pneumonia 38%, atelectasias 10%, acute respiratory distress
syndrome (ARDS) 8%, contusion 3%, and unknown 3%. The signs that suggest an infectious
origin were Clinical Pulmonary Infection Score (CPIS) >6 (73% vs. 6%), abnormal
temperature (73% vs. 28%), and creatinine level>1.5 mg/dL (80% vs. 50%) (41). MRSA,P.
aeruginosa,andAspergilluscaused 70% of all pneumonias in the ICU (9). AllAspergillusand
75% of MRSA pneumonias but only 14% of the gram-negative pneumonias occurred within
30 days of transplantation.Legionella,Toxoplasma gondii, and CMV may also cause pneumonia
in this setting (7,70).
Pneumonia is the most common infection following HT. It occurs in 15% to 30% of
patients, with an attributable mortality of 23%. Risk factors include prolonged intubation,
CMV infection, and preoperative lung infarction. Gram-negative pneumonia in the early
posttransplant period is associated with significant mortality. In a recent multicentric
prospective study performed in Spain, the incidence of pneumonia after HT was 15.6
episodes/100 HT (65). Most cases occurred in the first month after transplantation. Etiology
could be established in 61% of the cases. Bacteria caused 91% of the cases, fungi 9%, and virus
6%. In another study, opportunistic microorganisms caused 60% of the pneumonias,
nosocomial pathogens 25%, and community-acquired bacteria and mycobacteria 15% (64).
Gram-negative rods caused early pneumonias (median 9 days), and gram-negative cocci,
fungi,Mycobacterium tuberculosisandNocardiaspp. and virus caused pneumonias in 11, 80, 145,
and 230 days, respectively.Legionellashould always be included in the differential diagnosis
(71–74). Pneumonia increases the risk of mortality after HT (OR 3.7; 95% CI 1.5–8.1;p<0.01).
Lung infections are very common in lung and heart-lung transplant recipients. These
patients have particular predisposing factors, since the allograft is in contact with the outside
environment, and have an impaired mucociliary clearance, ischemic lymphatic interruption,
and abolition of the cough reflex distal to the tracheal or bronchial anastomoses. In fact, the
anastomosis is especially vulnerable to invasion with opportunistic pathogens including gram-
negative bacilli (Pseudomonas), staphylococci, or fungus. Lung transplant recipients with
underlying cystic fibrosis may be prone to suffer infections caused by multiresistant
microorganisms such as Burkholderia cepacia. In this group of patients perioperative
antimicrobials are chosen on the basis of surveillance cultures. Pathogens transmitted from
the donor may also cause pneumonia in this setting, though it is not very frequent (75).
Pneumonia is less common after renal transplantation (8–16%), although it remains a
significant cause of morbidity (67–69).
Most Common Pathogens in Transplant Patients with Pneumonia
We have already mentioned some data on the etiology of pneumonia in SOT recipients, but we
will now review some of the most common pathogens in more detail.
Bacteria.Although bacterial pneumonia may occur any time after transplantation, the period
of greater risk is the first month after the procedure. Need for mechanical ventilation and
intensive care in this period are among the causes. The etiology will depend on the moment
after transplantation, length of previous hospital stay, the days on ventilation, previous use of
antimicrobial agents, and clinical and radiological manifestations (Table 3). Gram-negative
rods predominate (P. aeruginosa,Acinetobacterspp.,Enterobacteriaceae) but gram-positive cocci
(S. aureus, Streptococcus pneumoniae) account for a significant proportion of cases, as we
mentioned before.
392 Mun ̃oz et al.