Vol. 21, No. 9
THE JOHNS HOPKINS MICROBIOLOGY NEWSLETTER
Tuesday, March 12, 2002
10 outbreaks were reported to DHMH during MMWR
Week 10 (March 3 - March 9):
1 outbreak of influenza (lab-confirmed; type unknown)
at a nursing home in Frederick Co.
2 outbreaks of influenza-like illness at nursing homes
(1 in Garrett Co. & 1 in Allegany Co.)
1 outbreak of gastroenteritis at a nursing home in Garrett
Co.
1 outbreak of gastroenteritis/giardiasis at a private
home daycare in Harford Co.
1 outbreak of shigellosis at a private home in Anne Arundel
Co.
1 outbreak of rotavirus at a hospital in Baltimore City
3 outbreaks of foodborne gastroenteritis (2 associated
with fast food establishments [1 in Prince
George's Co. & 1 in Anne Arundel Co.]; 1 associated
with a restaurant in Montgomery Co.)
The patient is a 26-month-old white male residing in Maryland with past medical history limited to possible mild asthma accompanying upper respiratory infections, and managed with bronchodilator therapy. He attends daycare and has no exposure to pets. The patient presented with a 6-week history of right neck swelling, with mild progressive enlargement. Examination of the neck revealed a non-tender, well-circumscribed 2.5 x 1.5 cm mass along the inferior border of the right mandible, posterior to the right submandibular gland. The overlying skin was erythematous and bluish with a suggestion of early surface erosion. The remainder of the examination is unremarkable. There are no signs or symptoms of systemic illness. Magnetic resonance imaging of the lesion showed a heterogeneously enhancing mass with a cystic/necrotic component, local inflammatory changes, mass effect on the submandibular gland, and several sub-centimeter regional lymph nodes. An infectious/inflammatory process was favored. The patient was referred for surgical intervention. The initial incision released purulent material and revealed extensive necrotic tissue. Thorough curetting was performed with specimens sent to surgical pathology and for cultures. Mycobacterium avium intracellulare complex was isolated from culture. Tissue sections revealed necrotizing granulomatous inflammation, with mycobacterial organisms identified on auramine-rhodamine immunofluorescent stains.
Mycobacterium avium-intracellulare complex (MAC) cervical adenitis
Organism:
Although the most common cause of cervical adenitis worldwide remains M. tuberculosis, nontuberculous mycobacteria is responsible for nearly all cases in developed countries. Before the 1970’s, M. scrofulaceum was the most common agent. Currently the most frequent agents belong to the M. avium-intracellulare complex. Others include M. kansasii, M. fortuitum, M. haemophilum and M. genovense. MAC organisms are ubiquitous in the environment and distributed worldwide. Human exposure can occur through ingestion or inhalation. MAC organisms are short coccobacilli, although early in culture they may appear as long slender rods. They can be visualized using acid fast stains or auramine-rhodamine immunofluorescent stain. Histologic and cytologic preparations typically show necrotizing granulomatous inflammation, although the organisms may not be frequent enough to see even with the special stains.
Clinical manifestations:
MAC infections in children most commonly manifest as superficial lymphadenitis of the head and neck. Patients are typically 2-5 years of age, but rare cases occur in adults. The lesions are neither painful, nor tender to palpation. Fever, weight loss or other systemic symptoms are absent in this localized infection. The differential diagnosis includes abscess, duct obstruction or tumor of the salivary glands, thyroglossal duct or branchial cleft cysts, and reactive lymphoid hyperplasia. Other infectious agents such as M. tuberculosis, infectious mononucleosis, and Bartonella (cat-scratch disease) should be considered. Malignancy should be ruled out. Local tissue destruction can be significant, with sinus tract formation to the skin and scarring. Involvement of the deep soft tissues, however, is rare.
Diagnosis and treatment:
From the outset, it is critical to rule out M. tuberculosis infection in the patient and close contacts, in order to prevent unnecessary delays in chemotherapy. Tuberculin skin testing should be performed on the child and contacts. Chest radiograph is indicated for the child, however most children with M. tuberculosis cervical adenitis will have negative radiographs. The preferred diagnostic procedure is excisional biopsy and curettage of the involved lymph nodes. This is also treatment of choice. This technique is more likely than fine needle aspiration to yield adequate tissue for culture and microscopic examination. In addition, it prevents spread of the infection, shows more rapid healing and lowers rates of recurrence as compared to incision and drainage. Standard antituberculous drug therapy is significantly less effective. Anecdotal reports suggest that clarithromycin and azithromycin may be useful in combination with other standard antituberculous agents (to forestall resistance), however controlled clinical trials have not been performed. Since nontuberculous mycobacteria with excellent chemosensitivity, such as M. kansasii and M. fortuitum, may also cause cervical lymphadenitis, cultures and speciation should be performed.
References:
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