Carriage With De Novo Macrolide-Resistance and Breakthrough Pneumonia.

pneumonia is prevalent in children and can be followed by upper airway carriage for months. Treatment of pneumonia with macrolides is widespread and can lead to the development of macrolide resistance. The clinical consequences of chronic carriage are unknown. In this article, we describe a child with acute lymphoblastic leukemia who developed macrolide-susceptible pneumonia confirmed by nasopharyngeal secretions polymerase chain reaction and culture with good response to azithromycin. Five months later, the patient developed another pneumonia that was diagnosed with positive macrolide-resistant polymerase chain reaction and culture from the bronchoalveolar lavage. The child responded well to fluoroquinolones and eventually was discharged from the hospital. The recovered from the second pneumonia is a novel strain and is genetically identical to the that caused the first pneumonia, apart from the macrolide-resistance 23S ribosomal RNA gene. Both isolates are identical in both P1 (subtype 2 with a novel variant, 2bv) and multiple-locus variable number tandem repeat analysis type (53662). This is indicative of chronic carriage with de novo macrolide-resistance mutation and subsequent breakthrough pneumonia that is reported for the first time here. Children with immunosuppression may be at increased risk of life-threatening macrolide-resistant pneumonia after carriage. Further studies are required to evaluate the impact of this phenomenon. This will then guide strategies to limit the associated morbidity, such as testing for macrolide resistance, treatment of pneumonia in high-risk children with bactericidal antibiotics (such as fluoroquinolones), and possibly eradication protocols of carriage to prevent subsequent life-threatening infections.