The spread of antimicrobial resistance among Enterobacteriaceae is a significant clinical threat. We report the first case of an Enterobacteriaceae strain harboring the NDM-1 metallo--lactamase in a pediatric patient in the United States. We describe strategies for the detection of this novel resistance mechanism encountered in an isolate of Klebsiella pneumoniae.
CASE REPORTA 13-month-old boy in severe respiratory distress was brought to the emergency department (ED) by his parents following a 3-day history of worsening cough and audible wheezing. At presentation, the patient was tachycardic and lethargic and had a low-grade fever of 38.1°C. The patient's past medical history was notable for episodes of reactive airway disease, managed with nebulized albuterol and short courses of corticosteroids, congenital skeletal abnormalities, multiple upper respiratory tract infections, hydrocele, hypotonia, and developmental delay. Also of note, the patient had returned from a 3-month visit to Pakistan with his family 4 months prior to presentation in the ED. While in Pakistan, the patient was hospitalized following an exacerbation of his lung disease and was intubated and mechanically ventilated for several days.The patient was intubated in the ED, started on empirical ceftriaxone (550 mg intravenously [i.v.] daily) for pneumonia, and admitted to the pediatric intensive care unit. On admission, a chest X-ray revealed right upper and lower lobe opacities, and azithromycin treatment (60 mg i.v. daily) was started. A urine specimen was sent to the microbiology laboratory for culture, and a Foley catheter was placed. Urinalysis revealed no pyuria, but nitrites were detected and less than 10,000 CFU of Klebsiella pneumoniae (strain KP1) and Proteus species grew in routine culture; these organisms were also isolated in similar quantities from a subsequent urine specimen obtained later that day. A nasal wash specimen was obtained for bacterial culture and respiratory virus detection by the Resplex II respiratory virus panel, version 2.0 (Qiagen, Valencia, CA). The respiratory virus panel detected the presence of an enterovirus. Following overnight incubation at 37°C in air supplemented with 5% CO 2 , bacterial culture grew normal oral flora and many K. pneumoniae organisms (strain KP2). Following identification of KP2, empirical antimicrobial coverage was switched from ceftriaxone to meropenem (MEM; 440 mg i.v. every 8 hours [q8h]) on hospital day 4. Also on hospital day 4, the patient's tracheal secretions increased in amount, requiring more-frequent suctioning to maintain a patent airway. A small right pleural effusion was detected by a computed tomography scan on hospital day 4, which subsequently resolved without drainage. On hospital day 5, respiratory secretions obtained by tracheal suction were submitted for bacterial culture, which also grew a K. pneumoniae isolate (KP3). No additional specimens were sent to the laboratory for culture.Antimicrobial susceptibility testing was performed on all three K. pneumoniae isolat...