Legionnaire disease is an uncommon cause of pneumonia in children and an exceedingly rare entity in neonates.1 Only few cases of neonatal Legionella pneumophila pneumonia have been reported in the literature, with most cases being nosocomial in origin.1–5 Notably, there has been a preliminary report of a recent outbreak in a neonatal unit.6
The uncommon occurrence of Legionella pneumonia in children, may result in delay in both the diagnosis and in the initiation of appropriate antimicrobial therapy in young infants and immunocompromised hosts.1,2 There is probably an underestimation of the true number of Legionella cases in children with seroprevalence of 2% to 52% during childhood.1 Neil and Berkelman7 recently reported on the increasing incidence of legionellosis in the United States, with a total of 22,604 cases in 15 years (1990–2005), for whom the age was known (98% of the total cases); 209 cases were younger than 14 years old (0.93%). There was no mention of the disease in neonates in that report.
We describe a neonate with fatal hospital-acquired pneumonia caused by L. pneumophila, highlighting the importance of considering this diagnosis in neonates with late-onset respiratory distress syndrome.
An 11-day-old neonate was transferred to our pediatric intensive care unit (PICU) from another hospital, with pneumonia and impending respiratory failure. This male was the product of a 36- to 37-weeks gestation born by spontaneous vaginal delivery after prolonged premature rupture of membranes. The neonate's birth weight was 2295 g. Delivery did not take place in a water tub, but, as is customary at the birthing hospital's nursery, the neonate was rinsed in a sink within the first 24 hours of life. Initial blood and urine cultures were negative as were maternal vaginal cultures. The neonate did not receive antibiotics and was discharged after 6 days.
At home, on the day of his discharge, he was febrile to 38.2°C and the next day 39.5°C. On admission to the emergency room, the baby was ill-appearing with a high fever (39.5°C), hepatomegaly, and mild respiratory signs. There was no vomiting, diarrhea, or other signs of illness. Laboratory tests revealed normal blood count, but an elevated C-reactive protein of 255 mg/L (normal, 0.5–6 mg/L), normal serum electrolytes with metabolic acidosis. Gram-stain of CSF was negative. The neonate's chest radiograph showed multiple diffuse infiltrates. After blood, urine, and CSF cultures were obtained, ampicillin and gentamicin were initiated, and oxygen was administered. During the next few days, the neonate's fever resolved, but his respiratory condition deteriorated with dyspnea, respiratory acidosis, and apnea necessitating transfer to the PICU. In the PICU, he was intubated, and after repeat cultures, the antibiotic regimen was changed to cefotaxime, ampicillin, and azithromycin. Aspirated sputum for bacterial, viral, and fungal cultures yielded nontypeable Haemophilus influenzae. Indirect immune fluorescence for a panel of respiratory viruses (eg, respiratory syncytial virus, influenza, and adenovirus) was negative.
Two days after admission to the PICU, the neonate expired with multiorgan failure. Aspirated sputum and postmortem lung biopsy cultures grew L. pneumophila serotype 1 and a home-grown polymerase chain reaction assay targeting L. pneumophila specific sequence of the 16S rRNA was positive. Antigen detection for Legionella was not performed since the neonate was anuric.
Epidemiologic investigation at the birthing hospital, including environmental sampling of multiple water sources, revealed L. pneumophila serotypes 1 and 3, which were identified at several hospital water sources including the nursery and delivery room. Systemic disinfection measures including hyperchlorination and thermal eradication (superheat and flush) were conducted. Although neonates in the nursery were not actively tested for L. pneumophila, there have been no additional cases reported from the birthing hospital, or neonatal pneumonia cases that could be related to L. pneumophila. As for predisposing conditions in the neonate, besides mild prematurity, he did not have lymphopenia, abnormal serum immunoglobulins, or any obvious immunodeficiency.
Around 33 years have elapsed since the initial report incriminating Legionella as the cause of the severe pneumonia outbreak at the 1976 American Legion Convention in Philadelphia.8 Since then, there has been an increase in the number of cases of legionellosis reported among adults.7 In contrast, legionellosis in children is an uncommon cause of pneumonia and an even more unlikely pathogen in neonates.1–6 When neonatal legionellosis is diagnosed, however, it is typically hospital-acquired, although there is a report of a community-acquired case confirmed by molecular typing.3 Diagnosis can be established by specialized laboratory tests with variable sensitivities and specificities. Culture is regarded as the standard, but it requires special culture media, may take a few days to grow and its sensitivity is laboratory-dependent. Urinary antigen assay is highly specific and especially useful for L. pneumophila serotype 1. Other tests such as direct fluorescent-antibody stain of the sputum and serologic tests are less sensitive.9 The application of polymerase chain reaction-based methods on sputum samples reduces turn around time for detection of this pathogen to just a few hours, thereby facilitating the prompt initiation of appropriate antibiotics with a likely improvement in prognosis.
Predisposing factors for neonatal legionellosis include prematurity, congenital immunodeficiency, and congenital heart or lung disease.1–5 Of 12 cases reported in the literature, 11 were males (Table 1). They presented with severe pneumonia that was associated with a high mortality (50%) and L. pneumophila serotype 1 prevailed with its detection in 8 of the 12 cases. All but one of the 7 infants who received a macrolide antibiotic survived. While our male patient with L. pneumophila serotype 1 did receive azithromycin, it was administered late in the course of his illness, when he already had severe respiratory failure and impending multiorgan involvement (Table 1).
The temporal sequence of events strongly suggests that the neonate acquired his infection shortly after birth. Legionella pneumophila serotypes 1 and 3 were cultured from the water sources of the nursery and delivery room and serotype 1 was cultured from the postmortem lung biopsy thereby revealing the likely source of this nosocomial transmission. A limitation of our case report is that we did not perform PFGE or molecular studies to ascertain the identity of the strains from the patient and from the hospital water sources.
Awareness of L. pneumophila as a potential cause of pneumonia in neonates is essential, as the infection is usually severe, and empirical antibiotics for neonatal pneumonia do not include anti-legionella treatment. This rare case of neonatal L. pneumophila infection underscores its potential role as a nosocomial pathogen in the neonate and has potentially significant implications for neonatal sepsis management and infection control measures.
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