Background: Mycobacterium chelonae (MC) was isolated from an immunosuppressed four-year-old with Acute Myeloid Leukaemia. This was initially dismissed as gram positive bacilli diptheroid based on gram staining. Several more blood culture bottles flagged up positive in quick succession. A review of the gram stain with additional ZN staining revealed acid-fast bacilli and finally identified as Mycobacterium chelonae. Case presentation: A 4-year-old (now 5) male with acute myeloid leukaemia presented to Emergency department at Southend hospital with febrile non-neutropenia/low grade fever, loss of appetite, weight loss and general weakness. Suspected Sore and infected gastrostomy site, with percutaneous endoscopic gastrostomy (PEG). Blood cultures were collected and patient put-on broad-spectrum antibiotics and antifungal. 5 sets yielded Mycobacterium chelonae. The patient was kept on broad spectrum antibiotics with additional meropenem, removal of PEG and follow up blood cultures were negative. Conclusion: Nontuberculous mycobacteria, particularly fast growers, should be considered or excluded by ZN staining in positive cultures after 2-4 days from immunosuppressed patients with gram positive rods (GPRs) on gram staining, this is even more necessary if patients have lines insitu. Several multiple sets of blood culture will also be helpful to rule out contamination. Laboratories should attempt to identify NTM by Matrix Assisted Laser Desorption-Time of Flight (MALDI-TOF) by full extraction if available. If the isolate is considered clinically significant, a full antibiotic susceptibility should be sought to guide therapy.