A 19 year old male was admitted to the department of tuberculosis and chest diseases, with complaints of gradually progressive breathlessness of one week duration along with low grade fever and cough with foul smelling expectoration. Patient was not on any antimicrobial treatment. There was no history of trauma to the chest and his past medical history was unremarkable. He did not have pharyngitis or skin rashes. He was a non-smoker and non-alcoholic and was employed in a tea stall, wherein he handles unpasteurized milk.
Clinical examination and imaging studies revealed a right sided multi-loculated hydropneumothorax (Figure 1). Blood peripheral smear, total and differential leukocyte counts were normal. Routine serum biochemical parameters were also within normal limits. ELISA test for HIV was negative.
Therapeutic thoracocentesis yielded 500 ml of thick foul smelling pus and air. Empirical treatment with intravenous ceftriaxone and metronidazole was started. Patient was put on closed chest tube drainage with underwater seal which was removed after one month, in view of significant clinical and radiological improvement (Figure 2). Antimicrobial therapy was also continued for the same duration. Patient was then discharged and advised follow-up.
Microscopic observation of the Gram stained smear of the pus showed pleomorphic Gram positive coryneform bacteria. Aerobic culture after 48 hours at 37 C grew minute, translucent, non-pigmented colonies with a small zone of clear hemolysis on 5% sheep blood agar (Figure 3). Heavy growth was obtained in pure culture. Upon further incubating the culture plates the colonies increased in size and appeared opaque with enhanced hemolysis. Transmitted light revealed a small dark dot at the centre of each colony. When a colony was gently removed a tiny dark pit was seen in the agar. The isolate did not grow in MacConkey agar. It was non-motile, non-acid fast and did not show any volutin granules. Catalase and urease tests were negative. Glucose and maltose were fermented but not xylose and mannitol. Reverse CAMP (Figure 4) and DNAase tests were positive. Gelatin was not liquefied.
Based on the hemolytic pattern, catalase reaction and other biochemical tests the isolate was identified as Arcanobacterium haemolyticum. These tests also differentiate our isolate from the closely related Arcanobacterium pyogenes . The isolate was found to be sensitive to routinely used antibiotics (Ampicillin, 10 mcg/disc ; erythromycin, 15 mcg/disc ; ceftriaxone, 30 mcg/disc; gentamicin, 10 mcg/disc and ciprofloxacin, 5 mcg/disc) by Kirby-Bauer disc diffusion method done on Muller Hinton Agar supplemented with 5% sheep blood.