A 62-year-old female renal transplant recipient was admitted to hospital on 20 August 2021, with a 5 week history of recurrent fevers and progressive dry cough without haemoptysis or dyspnoea. She did not report any unintentional weight loss, night sweats, fatigue or altered mentation. She had no recent sick contact exposures (including no prior risk of exposure to tuberculosis) or significant travel history. Her past medical history included deceased donor renal transplant in October 2012, stable on tacrolimus and mycophenolate mofetil without any history of rejection. Other medical and surgical history included workup for chronic hypophosphataemia and hypocalcaemia requiring weekly electrolyte replacement infusions via Groshong line (inserted March 2021), prior hemicolectomy for diverticular disease and parathyroidectomy.
On examination, she was haemodynamically stable with blood pressure of 151/67, pulse rate of 69 beats min-1 and body temperature of 36.8  C. Lung auscultation was normal without any bilateral adventitious sounds, and cardiovascular examination did not reveal any murmurs or other stigmata of infective endocarditis. Groshong line site did not demonstrate purulent discharge or overlying cellulitis. Laboratory investigations showed a peripheral white blood cell count of 5.1x109 l-1 (normal range 4.5-11.0x109 l-1) with a neutrophil count of 3.4x109 l-1 (normal range 2.0-8.0 x 109 l-1). Inflammatory markers were elevated with C-reactive protein of 23.2 mg l-1 (normal <3.1 mg l-1).
Chest radiograph followed by whole-body computed tomography (CT) scan revealed multifocal ground-glass opacities suspicious for pulmonary septic emboli, without cavitary lesions (Fig. 1). Transthoracic and subsequent trans-oesophageal echocardiography were negative for vegetations or haemodynamically significant valvular dysfunction.
In the context of recurrent fevers occurring in temporal relation to weekly electrolyte infusions, outpatient blood cultures were initially obtained 2 weeks prior to admission and Gram-positive bacilli were only isolated from the aerobic bottle. The patient was initiated on intravenous (IV) vancomycin. Questions remained as to whether the positive blood culture was attributable to contamination and initially the organism was not identified using MALDI-TOF VITEK MS V3 (bioMerieux, Marcy L'Etoile, France). Subsequent repeat blood cultures collected both from peripheral draw and tunnelled Groshong line over a 2 week period continued to isolate Gram-positive bacilli only in aerobic bottles (Figs 2 and 3). The organism showed beige, non-haemolytic colonies that were mucoid in appearance and adherent to media, catalase-positive and partially acid-fast. In our local microbiology laboratory, API Coryne system (bioMerieux, Marcy L'Etoile, France) gave an identification of   Rhodococcus   spp.
Inoculum was prepared from blood agar after incubating the isolate for 3-5 days at 35  C (+/- 2  C), with suspension made to 0.5 McFarland standard. The minimum inhibitory concentrations (MICs) were determined using E-test gradient strip (bioMerieux, France) as part of non-standardized susceptibility testing for this isolate. Findings were interpreted as per Clinical and Laboratory Standards Institute (CLSI) M24. The results showed susceptibility to amoxicillin/clavulanate, azithromycin, ciprofloxacin, linezolid, penicillin and vancomycin; it was intermediate to doxycycline. Hence, oral ciprofloxacin 500 mg twice daily was added to the patient's regimen on the third day of admission as combination antimicrobial therapy. As her Groshong line was the suspected source of bacteraemia, it was subsequently removed and the catheter tip bacterial culture isolated Gram-positive bacilli after 4 days of incubation. Repeat blood cultures after 5 days of antibiotics (1 day post-line removal) were negative.