Clinical Microbiology
Contributed by Vandana Baloda, MD & Tung Phan, MD, PhD, D (ABMM)
CASE REPORT
A fully immunized toddler boy presented with fever and right-sided neck swelling for few days. The investigations revealed elevated inflammatory markers and right level II lymphadenitis without abscess. He was given a 14-day course of augmentin for possible suppurative lymphadenitis.
Following which he was afebrile; however, his right-sided swelling remained enlarged. He had no difficulty breathing or feeding. He had good urine output and normal stooling. Family denied night sweats or weight loss. No reported erythema, color change, violaceous hue over his right neck swelling. Parents endorsed full range of horizontal neck movements. There was no previous history of lymph node swelling prior to this illness. No family history of methicillin resistant Staphylococcus aureus (MRSA) infection or recurrent boils.
Due to concern for atypical infectious process vs. non-infectious process, he subsequently underwent fine needle aspiration with intervention radiology. The aspirate was sent to microbiology laboratory for acid fast bacilli (AFB) culture/smear, aerobic and anaerobic culture. No microorganisms were isolated on aerobic and anaerobic cultures. The direct smear for AFB from the aspirate was reported as negative. The processed (digested and decontaminated) sample was inoculated on to Lowenstein-Jensen medium and into the BACTEC MGIT 960 system. Mycobacteria Growth Indicator Tube (MGIT) yielded a positive result as indicated by a high amount of fluorescence (bright orange color) following eight days of incubation at 370 C into the BACTEC system. The smear evaluation from the positive bottle revealed AFB by Ziehl-Neelsen stain (ZN stain) (100x oil immersion) (Fig. 1).
Differential diagnosis of the AFB included Mycobacterium tuberculosis and Nontuberculous mycobacterium. The identification of the AFB was performed using DNA probe on the culture isolates from the BACTEC MGIT.
The FNA cytology was reported as granulomatous lymphadenitis with acute inflammation and necrosis.