Retropharyngeal abscess coinfected with Staphylococcus aureus and Mycobacterium tuberculosis after rhinoviral infection in a 1-month-old infant
A 5-week-old boy was admitted to the hospital due to perioral cyanosis during crying, stridor, and refusal of feeds for three days. One week prior to admission, he developed rhinorrhea and sneezing, which continued to worsen after onset with the development of agitation and mild chest wall retractions. On admission, his blood pressure was 90/57 mmHg and pulse was 166 beats per minute. Although his mother perceived a tactile fever, he was afebrile. Though stridor was heard during inspiration and the respiratory rate was 60 breaths per minute, his oxygen saturation remained at 100% on room air. Due to his stridor, he was diagnosed with croup in addition to the common cold and was treated conservatively with budesonide and epinephrine nebulizer treatments. Initial laboratory testing displayed leukocytosis (white blood cell count 25,030/µL), thrombocytosis (platelet count 603,000/µL), and increased C-reactive protein (12.07 mg/dL, reference range <0.3 mg/dL). His electrolyte panel was within normal limits and chest radiograph did not show any lung abnormalities. Respiratory virus panel testing detected rhinovirus using multiplex polymerase chain reaction. As bacterial infection still could not be ruled out, ampicillin and gentamicin were administered. In spite of conservative treatment and administration of intravenous antibiotics, his stridor and head bobbing during respiration continued. Follow-up laboratory results revealed that his complete blood count was similar to the first results, but the C-reactive protein had decreased slightly (8.97 mg/dL). Because his symptoms and laboratory results had not improved as drastically as had been expected, we decided to pursue other causes of upper airway obstruction.\nOn hospital day 3, he had anteroposterior and lateral neck radiographs. The films showed a mass-like bulging lesion in the retropharyngeal area, complicated by severe narrowing of pharyngeal airway (). Multi-septated retropharyngeal abscesses and multifocal cervical lymphadenopathy with central necrosis were seen on computed tomography (CT) of the neck ().\nAfter making the diagnosing of a retropharyngeal abscess, screening tests for immunodeficiency were performed in light of this being such an uncommon diagnosis in this age range. Absolute neutrophil count, absolute lymphocyte count, lymphocyte subset analysis, respiratory burst assay, CH50, and immunoglobulin (Ig) levels were within normal limits with the exception of an increased IgE (29.3 IU/mL). At follow-up, the IgE level had normalized.\nOne day after the CT scan, incision and drainage of the right cervical lymph nodes, needle aspiration, and tissue biopsy from the bilateral retropharyngeal spaces were performed by otolaryngologists under general anesthesia. Gram stain and cultures for bacteria and tuberculosis were sent. Despite group B Streptococcus and S. aureus being the most common pathogens in retropharyngeal abscesses, there was no improvement after ampicillin administration. Intravenous antibiotics were changed empirically to vancomycin and imipenem to cover methicillin-resistant S. aureus, gram-negative bacteria, and anaerobes. Ultimately, methicillin-sensitive S. aureus was isolated from the exudate five days after the procedure. Tissue biopsy showed nonspecific chronic inflammation. After these results, cefazolin was administered for an additional two weeks. While he was receiving antibiotic therapy, his symptoms mostly improved except for the hoarseness and weakly audible stridor. Follow-up laboratory tests also normalized. To assess vocal cord injury after ventilator care, direct laryngoscopic examination was done by an otolaryngologist. The vocal cords were observed to move symmetrically, but there was a slight protrusion of a mass-like lesion on the posterior pharyngeal wall (). Follow-up CT scan showed that the abscesses, especially in the left pharyngeal space, still remained (). Surgery was performed to remove the abscess causing the mass-effect.\nAfterward, pansensitive M. tuberculosis was cultured from the pus of the first procedure using the automated BACTEC MGIT 960 system (BD, Franklin Lakes, NJ, USA). The patient had a history of Bacillus Calmette-Guerin (BCG) vaccination but we couldn't find any BCG scar on his deltoid. Mantoux testing of the patient and all acid-fast bacilli staining from the exudate, cerebrospinal fluid (CSF), and morning gastric aspirates were negative. Mantoux test and QuantiFERON-TB test were checked in the mother to determine the possibility of congenital tuberculosis infection and were negative. The antituberculosis drugs isoniazid, pyrazinamide, rifampin, and ethambutol were started. On hospital day 29, the infant was discharged without any respiratory symptoms. After three weeks, no mycobacteria were cultured from the exudate of the second procedure, CSF, or gastric aspirates. Ethambutol was discontinued one month after initiation of treatment because of difficulty to evaluate opthalmologic problems. After finishing 6 months antituberculosis therapy (2 months of pyrazinamide and 6 months of isoniazide and rifampin), he had no residual lesion on the neck CT scan ().